Studies on the Selection of Catalyst-Oxidant System for the Energy

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Fossil Fuels

Studies on the Selection of Catalyst-Oxidant System for the Energy Efficient Desulfurization and Denitrogenation of Fuel Oil at Mild Operating Conditions Sidra Subhan, Yaseen Muhammad, Maria Sahibzada, Fazle Subhan, and Zhangfa Tong Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.9b01950 • Publication Date (Web): 16 Aug 2019 Downloaded from pubs.acs.org on August 16, 2019

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Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11

Studies on the Selection of Catalyst-Oxidant System for the Energy Efficient Desulfurization and Denitrogenation of Fuel Oil at Mild Operating Conditions Sidra Subhan1, 2, Muhammad Yaseen*1, 2, Maria Sahibzada3, Fazle Subhan4, Zhangfa Tong*1 1 School

of Chemistry and Chemical Engineering, Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, Guangxi University, Nanning, China. 2 Institute

of Chemical Sciences, University of Peshawar, 25120, KP, Pakistan.

3 Department 4

of Chemistry, Umea University, Se-90187 Umea, Sweden.

Department of Chemistry, Abdul Wali Khan University Mardan, KP, Pakistan

12

Corresponding authors’ emails: Zhangfa Tong, [email protected]

13

Muhammad Yaseen: [email protected]

14 15

Abstract

16

This study reports the selection of ideal catalyst-oxidant system for the t5energy efficient

17

catalytic

18

denitrogenation (CODN) of pyridine over Mn-Co-Mo/Al2O3 and acid functionalized 1-

19

butyl, 3-methyl imidazolium chloride ([Bmim]Cl/ZnCl2) ionic liquid (IL) catalysts, using

20

H2O2 and NaClO as oxidants. NaClO-catalyst system realized 100 % CODS/CODN

21

activity within 15 min at 25 oC at comparatively low activation energies of 4.9 kJ/mol

22

and 5.4 kJ/mol for DBT and pyridine, respectively, under optimal conditions of oxidant

23

to sulfur ratio of 4, oxidant to nitrogen ratio of 8, ionic liquid to oil ratio of 1.5/5 and 0.1

24

g Mn-Co-Mo/Al2O3 catalyst for 15 mL of model fuel. Both, catalytic activity and kinetics

25

results revealed NaClO-catalyst system with greater efficiency and lesser energy

26

requirements than H2O2-catalyst system, and hence the former realized enhanced CODS

27

and CODN than the latter. Furthermore, Mn-Co-Mo/Al2O3 catalyst favored CODS while

28

[Bmim]Cl/ZnCl2 possessed greater affinity for CODN process, owing to the stronger

oxidative

desulfurization

(CODS)

of

dibenzothiophene

1 ACS Paragon Plus Environment

(DBT)

and

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nucleophilic interaction of the cationic species in IL towards hindered nitrogen

30

compounds. Further justification for the CODS and CODN activities and textural

31

characterization of the fresh and spent catalysts were provided by PXRD, XPS, SEM,

32

EDX elemental mapping and BET surface area characterizations. Based on the results,

33

this study is potentially viable endorsing to its environmental greenness, enhancement in

34

the calorific value of the final fuel and genially benignant in energy consumption via mild

35

operating conditions application, and hence can be envisaged as practicable alternative

36

approach in industrial processing of fuel oils.

37

Keywords: Catalytic oxidative desulfurization and denitrogenation; acid functionalized

38

IL; Mn promoted catalyst; sodium hypochlorite; activation energy; XRD and XPS.

39 40

1. Introduction

41

Technological advancements are greatly dependent on the continuous replenishment of

42

fossil fuels. Fossil fuels are contaminated with sulfur and nitrogen-bearing compounds

43

(SBCs and NBCs), which produce hazardous sulfur oxides (SOx) and nitrogen oxides

44

(NOx)

45

benzothiophenes (BT), dibenzothiophenes (DBT), and 4,6-dimethydibenzothiophenes (4,

46

6-DMDBT), while NBCs are either basic 6-membered ringed like pyridine and acridines

47

or neutral 5-membered ring structures like indole, carbazole etc. These SBCs and NBCs

48

are potential threats to the environment and hence many developed countries have

49

legislatively minimized the contamination levels of these compounds in fuel oils 3, 4.

50

Among

51

hydrodesulphurization and hydro-denitrogenation are widely adopted though are

1, 2.

Naturally occurring SBCs in fossil fuels are thiophenes and its derivatives i.e.

the

many

abatement

approaches

for


these

SBCs

and

NBCs,

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5-7.

52

objectionable owing to severity of operating conditions and costly nature

53

extractive desulfurization, adsorptive desulfurization, bio-desulfurization, ion exchange

54

and liquid-liquid extraction approaches have limited applications due to their dependence

55

on the use of polar compounds, active enzymes, choice of adsorbents, and convoluted

56

mechanistic

57

denitrogenation (CODN) processes are considered potentially efficient and genially

58

viable for the removal of SBCs and NBCs from fuel oils. In a typical CODS and CODN

59

process, sulfur (S) and nitrogen (N) compounds are oxidized by strong oxidant-catalyst

60

system, which both ionic liquids (ILs)

61

alumina along with many other polyoxometalates based catalysts

62

activity of these Mo/Al2O3, TiO2 and activated carbon supported catalysts for SBCs and

63

NBCs is further enhanced by decorating them with another promoter like Co, Ni, Fe, Pd,

64

and Ru etc. 7, 21-25. Among these promoters, Mn credited to its large intrinsic activity, high

65

stability, better selectivity, and high saturation on the surface sites, is getting much

66

attention recently

67

(NaClO) owing to their strong oxidizing power and ideal integration with Mn in a

68

catalysts-oxidant system and acidic ILs at room temperature have been proved highly

69

effective

70

CODS of SBCs due to their excellent thermal and chemical stability, low volatility and

71

promising reusability

72

owing to their non-stability towards air and moisture and the production of hydrogen

73

fluoride with fluorinated compounds

74

greatly dependent on the type of incorporated anion i.e. ILs composed of hydrophilic

8-10.

28-30.

Similarly,

On the contrary, catalytic-oxidative desulfurization (CODS) and

26, 27.

11-14

and solid i.e. molybdates supported over 15-20.

The removal

Similarly, among the oxidants, H2O2 and sodium hypochlorite

Large number of ILs have been reported with enhanced extraction and

13, 31-33.

For CODN, however ILs fail to earn their catalytic value

34.

The catalytic activity and stability of ILs is


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75

anions e.g. chloride and iodide are unstable, while those with hydrophobic anions are

76

considered more stable35. For a series of 1-alkyl-3-methylimidazolium cations, increasing

77

the alkyl chain length from butyl to hexyl to octyl correspondingly increases the

78

hydrophobicity and viscosities of the ILs, whereas density and surface tension values

79

decrease

80

imidazolium and pyridinium based ILs with acidic species such as chlorides in the

81

presence of H2O2, hence resulting in promising CODS and CODN activities 37, 38.

82

Taking full advantage of the strong oxidizing power of hypochlorite ions (ClO-) produced

83

from NaClO

84

catalysts

85

processing of DBT and pyridine as model fuel oil via CODS and CODN. Experiments

86

were conducted using Mn promoted Co and/or Ni-Mo/Al2O3 catalysts coupled with 1-

87

butyl, 3-methyl imidazolium chloride ([Bmim]Cl/ZnCl2), 1-ethyl-3-(4-sulfobutyl)

88

imidazolium bis (trifluoromethane sulfonyl) imide ([EimC4SO3H]NTF2), and 1-butyl, 3-

89

methyl imidazolium trifluoroaceticacid ([C4mim]TFA) ILs using H2O2 and NaClO as

90

oxidants at room temperature. Fresh and spent catalysts were characterized by powdered

91

X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), scanning electron

92

microscopy (SEM), energy dispersive X-ray analysis (EDX) elemental mapping, and

93

Brunauer–Emmett–Teller (BET) surface area techniques. Catalytic reactivity tests were

94

conducted to optimize reaction time, temperature, O/S and O/N ratio, IL:oil ratio, types

95

of oxidants, ILs and substrates. Dynamic studies were conducted to determine the

96

activation energies (Ea) for DBT and pyridine removal. This study is envisaged

97

potentially applicable for the processing of fuel oils attributed to minimizing

36.

However, these issues have been minimized by coupling aromatic cationic

27,

39,28, 29,

best coordination with acid functionalized ILs and Mn-promoted this study is designed to tune different catalyst-oxidant systems for the


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environmental hazards, increasing calorific value of processed fuel, lowering process cost

99

by employing milder operating conditions and simplified mechanized.

100

2. Experimental

101

2.1.

Materials

102

BT, DBT, 4, 6-DMDBT, pyridine, carbazole, indole, (> 99 %) were provided by

103

Sinopharm Chemical Reagents Co., Ltd. Manganese chloride MnCl2.6H2O, Al2O3

104

support, and Ammonium heptamolybdate ((NH4)6Mo7O24.4H2O) (> 98.2 %) were

105

purchased from Tianjin Guangfu Fine Chemical Research Institute, China. Sodium

106

hypochlorite NaClO (12.915 wt. %), Cobalt II Nitrate (Co (NO3)2.6H2O), Nickel II

107

Nitrate (Ni (NO3)2.6H2O), and n-Heptane (> 99 %)_were obtained from Guangdong

108

Guanhua Sci-Tech. Co. Ltd. H2O2 (30 wt. %), Formic acid, and sodium persulfate (>

109

99 %) were supplied by Merck Co., Darmstadt, Germany, while ([Bmim]Cl/ZnCl2),

110

([EimC4SO3H]NTF2), and ([C4mim]TFA) (> 99 %) were purchased from Shanghai

111

Chengjie Chemical Co,. Ltd. All the chemicals were of analytical grade and used without

112

further purification.

113

2.2. Catalyst synthesis

114

Incipient wetness impregnation technique was applied for catalyst synthesis

115

stoichiometric amount of powdered Al2O3 was impregnated with aqueous solution of

116

(NH4)6Mo7O24.4H2O) and stirred for 12 h at a speed of 600 rpm. The solution was dried

117

in an oven at 120 oC for 12 h and calcined in a muffle furnace at 500 oC for 7 h. The same

118

procedure was repeated for Co, Ni or Mn impregnated catalysts and the synthesized

119

catalysts were stored in inert N2 environment. Detailed elemental composition about

120

various catalysts is given in Table 1. 5 ACS Paragon Plus Environment

27, 40,

where

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121

2.3. Characterization of catalysts

122

PXRD analyses were performed on Rigaku Smart lab X-ray diffractometer (Japan),

123

operated at 9 KW with Cu-Kα radiation (λ=1.5406 Å) at a scan speed of 10°/min in 2θ

124

angular range of 10-80o. Surface morphologies of the catalysts were analyzed by SEM

125

coupled with EDX elemental mapping using Nova Nano SEM-450 [Model No: S3400N].

126

Prior to imaging, all the samples were gold coated under high vacuum. Brunauer–

127

Emmett–Teller (BET) surface area analysis was performed using surface area and

128

porosity analyzer (Micrometrics Gemini-VI Unit 1). Prior to each adsorption experiment,

129

the samples were dried at 393 K for 6 h under vacuum of < 0.05 Pa and degassed at 453

130

K for 12 h. Surface elemental compositions were achieved via XPS (Thermo Fisher

131

Scientific, USA [Model No: ESCALAB 250XI+]) with Al Kα radiation (hυ=1486.6 eV).

132

Reaction products were analyzed by high pressure liquid chromatography (HPLC)

133

equipped with Agilent 1100 Zorbax SB-C18 column (4.6 x 150 mm) using UV detector

134

at 320 nm and 270 nm for determination of concentration gradient of DBT and pyridine

135

respectively.

136

2.4. Catalytic activity evaluation

137

A model oil separately containing 800 ppm S (DBT, BT, 4,6- DMDBT) and N (pyridine,

138

indole, carbazole) compounds was prepared. CODS and CODN reactions were performed

139

employing 15 mL of the 800 ppm model oil (DBT or pyridine) in a 50 mL long-necked

140

flask, followed by the addition of 0.2 g/L catalyst and IL:oil ratio of 1.5:5 and 0.1 mL

141

H2O2 (30 %) or NaClO (12.915 wt. %). The flask containing model solution was then

142

stirred on a magnetic stirrer (500 rpm) for 60 min at 60 oC. The DBT and pyridine

143

removal (%) was calculated via Eq. 1 using calibration curve shown in Fig. S1. 6 ACS Paragon Plus Environment

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Energy & Fuels

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Removal (%) =

{𝐶𝑜𝐶𝑓― 𝐶𝑡} × 100

(Eq. 1)

145

Where, Co and Ct are the concentrations of initial and oxidized products after specific

146

time, respectively.

147

In dynamic experiments, change in DBT and pyridine concentration at different

148

temperatures (Ct) was investigated and time was plotted against ln(Co/Ct) (Co=800 ppm).

149

Activation energies for the catalytic oxidation of DBT and pyridine in the presence of

150

H2O2 and NaClO were determined using Arrhenius equation41.

151

3.

152

3.1. Characterization of catalysts

153

Fig. 1 shows the PXRD patterns of various catalysts, which suggest the corresponding

154

peaks for Al2O342, and participating metals in their respective oxidic phase i.e. NiO (37°,

155

44°, 63o)43, MnO2 (18o, 22o, 31o, 40o, 54o, 60o), Co3O4 (32°, 34°, 47°) and Mo (36°, 47°,

156

58°)

157

peaks in Fig. 1 could be concomitantly attributed to the highly powdered and ground

158

nature of the catalysts, and limitations of XRD instrument (< 5 wt.% loadings of Mn, Co

159

and Ni) 27, 47, 48. However, a uniform morphological trend for all the catalysts was shown

160

which was due to similar synthesis procedure, while the only difference arose in the

161

variation of metallic species in different samples.

162

Surface morphology and surface area analysis of fresh and spent catalysts via SEM and

163

BET techniques have been reported in our previous study 27, and also provided in Fig. S2.

164

SEM scans of fresh and spent catalysts at an average particle size of 2 μm showed

Results and discussion

44-46.

It is important to mention here that the vague and unclear nature of PRXD


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165

crammed structure with irregular distribution of support particles without any evident

166

conglomeration. Morphological differences were also sighted among the nascent support

167

and the impregnated samples, where Mn-decorated samples exhibited compact

168

morphology, high porosity with evenly dispersed surface particles, which could

169

contribute to their improved CODS and CODN activity

170

isotherms of the fresh and spent catalysts in Fig. S2 explicated the predominant presence

171

of both meso-pores and micro-pores

172

adsorbed N2 which suggested its largest specific surface area (SSA) (Table 2). A sharp

173

jump at higher relative pressure (P/P0 > 0.9) in all isotherms further revealed the

174

predominant presence of macropores 50-52. The high surface area of Al2O3 support (201.8

175

m2.g-1) could play active role in the effective and uniform distribution of active metal and

176

ultimately high catalytic activity of the catalysts 53. Significant decrease in the SSA and

177

pore volume of pure support in case of tri metallic catalysts (Mn–Co–Mo/Al2O3 and Mn–

178

Ni–Mo/Al2O3) than those of bi-metallic (Co–Mo/ Al2O3 and Ni–Mo/ Al2O3) was

179

attributed to the presence of extra metal thus blocking on the surface of the support 27, 42.

180

The decrease in the SSA of spent catalysts (tested in the CODS and CODN) could be

181

endorse to pore-fillings as compared to the fresh catalysts, which is more obvious in Mn

182

promoted catalysts, thus supporting the results of higher catalytic activity of later

183

catalysts (to be discussed in the proceeding sections) 44.

184

Fig. 2 shows the EDX spectra while Fig. S3 compiles elemental mappings of various

185

catalysts showing clear peaks for Al, Ni, Mo, Co and Mn along-with their relative

186

distribution data (%) provided in Table 3, where maximum abundance and distribution

187

density of Mo owes to the highest loading (wt.%) during catalyst synthesis. Fig. S3

27, 49.

27.

N2-adsorption type-II

Al2O3 support realized the highest amount of


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showing the concentration of active metals in various samples via EDX elemental

189

mapping suggests Co Fig. S3(a1-a2) possesses smaller pore size and higher dispersion

190

compared to its Ni counterpart Fig. S3(b1-b2), which could subsequently contribute to

191

the higher catalytic activity of the former. It is also obvious from the scans Fig. S3(c1-c2)

192

that promotion of Mn further dispersed the Co and Ni species, by making a strong contact

193

with Co, Ni, Mo and Al species without any conglomeration, which could be a reason for

194

the Mn promoted catalysts. Furthermore, high distribution densities of the alumina

195

support (Fig. S3(e)) could offer good base for the better impregnation and distribution of

196

metallic species 27.

197

Further insight about the electronic states of various metals in catalysts was obtained via

198

XPS analyses. The full survey spectra of four types of catalysts are shown in Fig. S4,

199

while high resolution XPS spectra for each metal in both, fresh and spent catalysts are

200

shown in Fig. 3(a-h). Fig. 3a and b (respectively representing fresh and spent catalysts)

201

show the two states for Co as 2p3/2 and 2p1/2 in Mn-Co-Mo/Al2O3 sample corresponding

202

to CoO species at respective binding energies (BE) of 780.30 eV and 796.5 eV

203

shift towards higher BE for Co, in both fresh and spent Mn-Co-Mo/Al2O3 catalysts could

204

be attributed to the stronger of interaction between Co and Mn species 55. The difference

205

in BE values of the two states is the result of inner core electronic attraction, high

206

population density and degeneracy in case of 2p3/2 54, 56. A minor decrease in BE for Co

207

2p1/2 in spent catalysts (Fig. 3b) as compared to fresh ones (Fig. 3a) could be due to the

208

isolation of Co species from Mn during the oxidation of DBT or pyridine. However,

209

closely similar peak positions for Co, in fresh and spent Mn-Co-Mo/Al2O3 catalysts

210

confirmed their stable nature under the current experimental conditions 9 ACS Paragon Plus Environment

57.

54, 55.

A

In a similar

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way, Fig. 3c and d compile the high resolution XPS spectra of Ni 2p3/2 and 2p1/2

212

oxidation levels in fresh and spent Ni in Mn-Ni-Mo/Al2O3 catalysts respectively

213

representing NiO species 54, 58. The peak positions of Ni of 2p3/2 and 2p1/2 oxidation states

214

were 856.5 eV and 873.9 eV, respectively, in both fresh and spent catalysts

215

relatively higher BE for the Ni doublet could be again attributed to their stronger

216

interaction with Mn species as compared to nascent Ni-Mo/Al2O3 catalysts, which

217

hinders the excitation of electrons, thus causing a shift towards higher BE 57. Fig. 3(e-h)

218

explicates the XPS spectra of fresh (e), (g) and spent (f), (h) Mo species in Mn-Co-

219

Mo/Al2O3 and Mn-Ni-Mo/Al2O3 catalysts respectively. The spin-orbit doublet of Mo 3d

220

core level further splits into 3d5/2 and 3d3/2 level at BE of 232.7 eV and 235.8 eV,

221

respectively, with the energy gap of 3.3 eV was ascribed to MoO3 type species

222

Spectral decomposition suggested that lower BE of 3d5/2 than 3d3/2 was due to the high j-

223

value of the former which facilitated the removal of electron at lower BE 49, 59, while the

224

oxidation states remained unchanged for the spent catalysts 57. Mn species though, were

225

not detected in XPS analysis due to low metal loading (Table 1) and its high dispersion.

226

However the shift in BE to higher values for Co and Ni species in Mn-Co-Mo/Al2O3 and

227

Mn-Ni-Mo/Al2O3 than those reported in literature indirectly justified the presence of Mn

228

species in the catalysts sample 55.

229

3.2. Catalytic activity evaluation

230

Fig. 4(a-d) and 5(a-d) compile the experimental results for the optimization of O/S and

231

O/N molar ratio (mol/mol), reaction time (min), reaction temperature (oC), and amount of

232

catalyst (g/mL) for the CODS and CODN of DBT and pyridine, respectively, over

233

different catalysts using H2O2 as oxidant. Fig. 4a and 5a show that increasing molar ratio 10 ACS Paragon Plus Environment

49.

The

49.

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234

of oxidant (H2O2) to S (O/S) and to N (O/N) from 2-16 mol/mol results in a

235

corresponding increase in DBT and pyridine conversion. DBT and pyridine removal

236

reached almost 100 % at O/S and O/N ratio of 12 mol/mol and 16 mol/mol, respectively.

237

Based on the stoichiometry, 2 moles of H2O2 are required to completely oxidize 1 mole of

238

DBT and pyridine, thus the desired O/S and O/N ratio is 2 (mol/mol). The much higher

239

stoichiometric ratio than the desired one is credited to the high consumption of H2O2

240

during the reaction without taking part in oxidation reaction60. Compared to CODN,

241

CODS required lower amount of oxidant which is because in case of sulfur compounds

242

interactions usually happen through CH---π bonds that experience stronger interaction

243

due to higher π-electron density on sulfur atom in DBT35, while the nitrogen compounds

244

interact via C-H---N (N-heterocycles) bonds where the π electron density is

245

comparatively lower on nitrogen atom in pyridine. Secondly, the quadruple moment

246

present in poly-aromatics is stronger than the mono-aromatics, which interacts more

247

strongly with the cations and solute molecules, showing more pronounced π-π stacking

248

and closer packings in DBT than the pyridine35. Additionally, the pKa values of

249

dibenzothiophenes are higher than the pyridine, explicating more dissociative nature of

250

the former than the later61. Thus, based on these facts, one can conclude that S

251

compounds (DBT) would require lower amount of oxidant to get oxidized as compared to

252

N compounds (Pyridine) due to high π electron density, pronounced π-π stacking and

253

closer packings and higher pKa values of the former than the later. Among the five

254

catalysts, activity of Mn promoted catalysts remained the highest due extra Mn active

255

phase and its interaction with other species as compared to nascent Co or Ni promoted

256

catalysts 26.


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257

Fig. 4b and 5b demonstrate the effect of reaction time on the CODS and CODN of DBT

258

and pyridine respectively. The acceleration of H2O2 molecules demands longer reaction

259

time in order to attain equilibrium, therefore, comparatively longer reaction time (60 min)

260

was provided to create greater chances of interaction between reacting species

261

60 min of reaction, DBT and pyridine were completely oxidized to respective sulfones

262

and nitrogen oxide. For both, CODS and CODN, various partaking catalysts followed an

263

activity order of: Mn-Co-Mo/Al2O3 > Mn-Ni-Mo/Al2O3 > [BMIM]Cl/ZnCl2 > Co-

264

Mo/Al2O3 > Ni-Mo/Al2O3. The superior activity of Mn based catalysts compared to

265

nascent Co or Ni loaded versions could be attributed to the extra Mn2+ active phase and

266

its better chemistry with Co2+ in the presence of H2O2 63. Credited to best performance in

267

both CODS and CODN, Mn-Co-Mo/Al2O3 was chosen for onward experimental studies.

268

Fig. 4c and 5c demonstrate the influence of reaction temperature on the CODS and

269

CODN for DBT and pyridine respectively. The decomposition of H2O2 speeds up at

270

higher temperature, thus a direct increase in the oxidation of DBT and pyridine with

271

increasing temperature was observed in these figures and reached to maximum at 45 oC 62.

272

Much lower reaction temperature value (45 oC) in this study than reported ones could be

273

accredited to the better synergism of the oxidant-catalyst system 11, 34.

274

Fig. 4d and 5d show that increasing catalyst dosage leads to a corresponding increase in

275

the conversion of DBT and pyridine. This could be accredited to the fact that higher

276

catalyst amount provides more active sites and greater chances of surface interactions for

277

the reacting species 64. From the data in Fig. 4d and 5d, 100 % conversion of DBT and

278

pyridine was achieved at a catalyst dose of 0.2 g. Higher DBT and pyridine conversion

279

by Mn promoted catalysts than pristine catalysts and IL is credited to the high intrinsic 12 ACS Paragon Plus Environment

62.

After

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280

behavior of Mn as promoter and its excellent surface saturation power. Another factor for

281

the better performance of Mn-Co-Mo/Al2O3 catalysts than the Mn-Ni-Mo/Al2O3 could be

282

the better pairing chemistry between Mn and Co than that between Mn and Ni over

283

Mo/Al2O3 surface 26, 42.

284

Fig. 6 shows the influence IL:Oil ratio for the CODS and CODN activity of DBT

285

pyridine over [Bmim]Cl/ZnCl2 catalyst in the presence of H2O2 at optimum experimental

286

conditions. It is obvious from Fig. 6 that CODS and CODN activity increases with

287

increase of IL:Oil ratio and reaches to 100 % at 1:5 IL:Oil (for CODS) and 1.5:5 (for

288

CODN). The increase in catalytic activity with increasing IL:Oil ratio is attributed to the

289

availability of more extraction sites which fascinates better S and N removal. The higher

290

IL:Oil ratio for CODN than CODS could be credited to the weaker IL-N interaction as

291

compared to IL-S35, 61. However, in both of these cases, the IL:Oil ratio was much lower

292

than previously reported studies

293

between oxidant-catalyst system, which could play a key role in the industrial

294

applications of the proposed study. Interestingly, ILs ranked higher at all experimental

295

condition in terms of DBT and pyridine conversion as compared to pristine Co-Mo/Al2O3

296

and Ni-Mo/Al2O3 catalysts which could be attributed to the strong extractive and catalytic

297

power of ILs than mere oxidative desulfurization activity of these catalysts. Mn decorated

298

catalysts (Mn-Co-Mo/Al2O3 and Mn-Ni-Mo/Al2O3) exhibited higher DBT and pyridine

299

conversion which could be accredited to the ideal chemistry between Mn active phase

300

and H2O265 than between IL and H2O2.

301

Further experiments were performed to test the effect of NaClO as oxidant for the CODS

302

and CODN of DBT and pyridine respectively. Fig. 7(a-c) and 8(a-c) respectively

34, 35, 61,

which was attributed to the better synergy


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Page 14 of 50

303

explicate the experimental data regarding O/S, O/N ratio (mol/mol), reaction time (min),

304

and reaction temperature (oC) for the CODS and CODN of DBT and pyridine over Mn-

305

Co-Mo/Al2O3 and [Bmim]Cl/ZnCl2 catalyst at optimized conditions. Fig. 7a and 8a

306

indicate that catalytic oxidation of both the species increases with the increasing O/S and

307

O/N ratio due to the providence of more oxidizing species. Comparatively, oxidative

308

conversion of DBT molecule reaches to 100 % at O/S ratio of 4 while a similar

309

conversion for pyridine was achieved at O/N ratio of 6. This lower amount of NaClO

310

required than that of H2O2 (Fig. 4 and 5) was due to the strong oxidizing power of the

311

hypochlorite ions resulting from the dissociation of NaClO and its excellent synergism

312

with Mn embossed catalytic species

313

the oxidation of pyridine than DBT could be again attributed to the stronger interaction of

314

S species in DBT with the oxidant than those of N species in pyridine. Fig. 7b and 8b

315

respectively encompassing the influence of reaction time on CODS and CODN of DBT

316

and pyridine at optimized conditions suggest a direct increase in conversion with reaction

317

time. 100 % DBT conversion as obtained from the saturation of the curves was recorded

318

after 15 min from the onset of the reaction

319

extended to 20 min, yet again owing to the inhibitory nature of N atom in pyridine and

320

weaker interaction with the oxidant than that of S of DBT

321

behavior of NaClO over H2O2 is awarded to the super active nature of oxidant and ideal

322

synergism with the catalyst that helps to decrease the total energy of the process 39. Fig.

323

7c and 8c illustrate that as the reaction temperature increases, a corresponding increase in

324

CODS and CODN activity is observed. At lower temperature, higher degree of resistance

325

is offered to the counter oxidative ions (OCl-) by DBT and pyridine molecules, thus

27, 39, 66.

The higher amount of oxidant required for

27,

while in case of pyridine this time was


67.

This ultra-fast reaction

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326

leading to lower conversion values. However, upon increasing temperature, the oxidation

327

power of the counter ions increases due to higher dissociation power of the oxidant and

328

higher mobility of the reacting species, hence increasing the molecular energy of the

329

pyridine resulting in 100 % removal of pyridine at 35 oC. This effect was however,

330

marginal for DBT removal over Mn-Co-Mo/Al2O3 catalyst where 99 % removal was

331

observed at only 25 oC. This could also be better justified by the higher inertness of

332

pyridine towards the peroxometal species and reduces its penetration by the blocking

333

action, which resultantly demands high molecular energy for its oxidation than DBT 27, 29,

334

67, 68.

335

Mn-Co-Mo/Al2O3 and Mn-Ni-Mo/Al2O3 catalysts and NaClO as oxidant could be the

336

choice for the industrial applications of the proposed study attributed to their cost-

337

effective nature and superior activity at milder operating conditions.

338

Fig. 9a and b compare the influence of amount of Mn-Co-Mo/Al2O3 and acid

339

functionalized [BMIM]Cl/ZnCl2 catalysts on the CODS and CODN of DBT and pyridine.

340

Fig. 9a indicates that increasing Mn-Co-Mo/Al2O3 amount provides more active sites

341

with greater chances of interactions with the reacting species, which subsequently

342

increases the conversion of DBT and pyridine. A catalyst dose of 0.1 g/15 mL achieves

343

100 % DBT conversion 27, which for pyridine, due to its stringent nature, reached to 0.2

344

g/15 mL for 100 % conversion. This again proves that Mn promoted catalyst greatly

345

favors CODS reaction than CODN due to the resistance caused by NBCs

346

saturation curves in Fig. 9b against [Bmim]Cl/ZnCl2 show almost the same removal

347

efficiency. In case of DBT, 100 % removal was attained at IL:Oil of 1:5 whereas in case

348

of pyridine this value was 1.5:5. This ratio of IL:Oil was much lower than previously

Thus, from Fig. 7 and 8, one can conclude that among the ILs and solid catalyst,


67, 69.

The

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

349

reported one attributed to the best fitted catalyst-oxidant system proposed in the current

350

study 27, 29, 34.

351

Fig. 10(a-c) provides the data of catalytic performance of Mn-Co-Mo/Al2O3 and

352

[Bmim]Cl/ZnCl2 catalysts to accomplish CODS and CODN of DBT and pyridine by

353

varying the type of oxidants, ILs, and various SBCs and NBCs at optimized reaction

354

conditions. Fig. 10a and b show that among the various oxidants, sodium persulfate and

355

NaClO exhibited the highest CODS and CODN activity in the presence of Mn-Co-

356

Mo/Al2O3 and [Bmim]Cl/ZnCl2 owing to their high oxidizing power and better synergism

357

with the catalyst active sites

358

CODS (accredited to the ideal chemistry between the former with NaClO26, while acid

359

functionalized [Bmim]Cl/ZnCl2 favored CODN process due to its greater extraction

360

ability for pyridine 34. Fig. 10c summarizes the information about various S and N species

361

found in fuel oils having different electron density and steric hindrances. It is obvious

362

from Fig. 10c that sulfides and nitrides conversion in terms of various substrates follows

363

an order of: DBT > 4,6-DMDBT > BT and pyridine > carbazole > indole over both, Mn-

364

Co-Mo/Al2O3 and [Bmim]Cl/ZnCl2 IL as catalysts. DBT is closely related to BT and 4, 6-

365

DMDBT in chemical structure while its oxidation is highly susceptible due to the higher

366

electronic density over the S atom. Among the various S substrates, electronic densities

367

of DBT, 4, 6-DMDBT and BT were 5.758, 5.760 and 5.739 respectively, which

368

conclusively evidenced the lowest conversion of BT having the lowest electronic density.

369

The unexpected behavior of 4,6-DMDBT having greater density than the DBT molecule

370

but lower conversion could be attributed to its greater steric hindrance caused by two

371

methyl groups, which protected the S atom from oxidation and hence lower conversion

26, 29, 34.

Additionally, Mn-Co-Mo/Al2O3 catalyst favors


Page 16 of 50

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Energy & Fuels

70.

372

was recorded

Among the N compounds, the activity order was: pyridine > indole >

373

carbazole over both the types of catalysts. The electronic density is more inductive in

374

case of pyridine due to the electronegativity difference between N and carbon atoms.

375

Compared to DBT, pyridine is expected to induce all the electronic density on its part and

376

perform electrophilic substitutions more slowly, but readily accepts nucleophilic

377

substitutions, therefore, the acid functionalized IL catalyst was found more susceptible to

378

the CODN of pyridine than other N derivatives 71.

379

To get better interpretations of CODS and CODN of DBT and pyridine using H2O2 and

380

NaClO, a series of dynamic studies tests were conducted and the results are shown in Fig.

381

11-13(a-d). The reduction rates over Mn-Co-Mo/Al2O3 and [Bmim]Cl/ZnCl2 at different

382

temperatures were investigated at a constant stirring speed of 500 rpm. The oxidation of

383

DBT and pyridine followed first order kinetics by applying Eq. (2a) 70.

384

385 386

𝑟= ―

𝑑𝑐𝑡 𝑑𝑡

= 𝑘𝑐𝑡

(Eq. 2a)

𝐶𝑡

(Eq. 2b)

ln (𝐶𝑜) = ― 𝑘𝑡 𝑙𝑛𝑘 = 𝑙𝑛𝐴 ― 𝐸𝑎/𝑅𝑇

(Eq. 2c)

387

Where k is the first-order reaction rate constant and can be obtained from the slope of

388

linear plots (Eq. 2b) by plotting reaction time against ln Co/Ct

389

and c for DBT and pyridine, respectively, in the presence of H2O2. The values of k in

390

Table 4 indicate constant increase in reaction rate with rise in temperature. The activation

391

energy (Ea) for the catalytic oxidation of DBT and pyridine respectively over Mn-Co-

392

Mo/Al2O3 was calculated using Arrhenius equation (Eq. 2c) by plotting the inverse of


41,

and is shown in Fig. 11a

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Page 18 of 50

393

absolute temperatures (1/T) against the logarithms of apparent rate constant (lnk) as

394

shown in Fig. 11b and d. The calculated Ea for the oxidation of DBT and pyridine over

395

Mn-Co-Mo/Al2O3 in the presence of H2O2 are 13 kJ/ mol and 13.2 kJ/ mol, respectively.

396

Fig. 12a and c compare the rate constants (k) over Mn-Co-Mo/Al2O3 using NaClO while

397

the Ea values are filed in Fig. 12b and d for CODS of DBT and CODN of pyridine were

398

4.9 kJ/ mol and 5.4 kJ/ mol respectively. The substantially lower Ea values using NaClO

399

as oxidant than those of H2O2 and much lower than previously published report

400

be accredited to the excellent synergism between Mn based catalyst and NaClO 28.

401

As CODN was highly favored by [Bmim]Cl/ZnCl2 as catalyst, therefore, dynamic tests

402

were also conducted in its presence using NaClO as oxidant, and the results are compiled

403

in Fig. 13a and b for DBT, and in Fig. 13c and d for pyridine. The calculated Ea for DBT

404

and pyridine were 7.5 kJ/mol and 7.1 kJ/mol, respectively, which confirm the high

405

susceptibility of acid functionalized IL towards pyridine. Moreover, comparatively lower

406

Ea required for the oxidation of DBT and pyridine over both the catalysts in the presence

407

of NaClO confirmed their excellent catalytic activity and good compatibility with the

408

hypochlorite ions resulted from the dissociation of NaClO 15, 70, 73.

409

From industrial applications and energy conservation aspects, recycling of a catalyst is of

410

crucial importance as it can considerably decrease process cost. Fig. 14a shows the

411

recycling performance of Mn-Co-Mo/Al2O3 catalyst for five consecutive runs. After each

412

oxidation run, catalyst was recovered by filtration, washed with acetonitrile and methanol

413

to remove any left-over oxides, dried in oven for 12 h at 90 oC, and then subjected to

414

another oxidation run 15. After five consecutive cycles, minimal decrease (from 100 % to

415

94 %) was observed both for CODS of DBT and CODN of pyridine. Fig. 14b monitors


72

could

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Energy & Fuels

416

the regeneration of [Bmim]Cl/ZnCl2 after each oxidation cycle with the help of dilution,

417

owing to hydrophilic nature of IL and the hydrophobicity of S/N compounds. At the end

418

of each oxidation cycle, IL was diluted with water, followed by simple distillation

419

Results shown in Fig. 14b suggest excellent regeneration power of [Bmim]Cl/ZnCl2 after

420

five consecutive cycles, indicating a pragmatic notion for its industrial applications in

421

fuel oils processing.

422

Fig. 15 represents the proposed reaction mechanism for the CODS and CODN of DBT

423

and pyridine over Mn-Co-Mo/Al2O3 and [Bmim]Cl/ZnCl2 in the presence of NaClO and

424

H2O2. The reduced Mn2+ in Mn-Co-Mo/Al2O3 and Zn2+ species in [Bmim]Cl/ZnCl2

425

instigate the electrophilic nature of hypochlorite ions (ClO-) and active peroxide species,

426

which then readily attack the S and N atoms of DBT and pyridine respectively 60, 74. DBT

427

and pyridine are further oxidized to DBT sulfones and pyridine N-oxides respectively by

428

the nucleophilic attack from the reactive oxygen species. The CODS and CODN

429

reactions consist of four steps: i) Mn2+ in Mn-Co-Mo/Al2O3 and Zn2+ in [Bmim]Cl/ZnCl2

430

are converted to Mn4+ and Zn4+ respectively, by the action of H2O2 and NaClO; ii) Mn4+

431

and Zn4+ on the catalyst surface coordinate with DBT and pyridine molecules that are

432

adsorbed on the Lewis acid sites; iii) active oxygen species interacting with DBT and

433

pyridine molecules finally produce DBT-sulfones and pyridine N-oxides; iv) polar

434

sulfones and pyridine N-oxide from the catalyst surface are desorbed and then extracted

435

into a polar solvent. Strong coordination of Mn with Co and Mo metals as well as its

436

good synergism with ClO- ions accounted for the excellent performance of Mn based

437

catalysts

438

combination with acid functionalized ILs with excellent oxidizing ability

26, 28, 75.

34.

NaClO, due to its strong oxidizing power, has been reported in


29,

which is

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

439

explained in details in Fig. S5. In case of [Bmim]Cl/ZnCl2, acid functionalized cationic

440

IL possesses strong affinity towards electrophilic ClO- which readily attacks the S and N

441

atoms in DBT and pyridine respectively, producing green by-products such as NaCl and

442

H2O, and making CODS and CODN processes much safer and simpler 73.

443 444

Conclusions

445

In summary, this study reports the selection of H2O2-catalyst and NaClO-catalyst systems

446

for the energy efficient CODS and CODN of DBT and pyridine respectively, over Mn-

447

Co-Mo/Al2O3 and acid functionalized ([Bmim]Cl/ZnCl2) IL catalysts at milder operating

448

conditions. Catalytic activity and dynamic studies revealed good synergism between the

449

NaClO-catalyst system which achieved 100 % DBT and pyridine conversion in 15 min at

450

25 oC as compared to H2O2, where [Bmim]Cl/ZnCl2 exhibited greater affinity for N

451

compounds due to the nucleophilic behavior of cationic species. Textural

452

characterizations of fresh and spent catalysts greatly supported the catalytic activity

453

results. Dynamic studies revealed lower activation energy values for the removal of DBT

454

and pyridine in the presence of NaClO over Mn-Co-Mo/Al2O3 and [Bmim]Cl/ZnCl2 as

455

catalysts. Based on the excellent desulfurization and denitrogenation activity results, cost

456

effectiveness in terms of low energy consumption, simplified mechanization and

457

greenness, the proposed study can be envisaged of great help for fuel oil processing on

458

industrial level.

459

Acknowledgments


Page 20 of 50

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Energy & Fuels

460

The authors greatly acknowledge the financial support from Natural Science Foundation

461

of Guangxi (2017GXNSFDA198047), Dean Project of Guangxi Key Laboratory of

462

Petrochemical Resource Processing and Process Intensification Technology (2017Z001).

463

Conflict of interest

464

The authors declare no competing interest.

465

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552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600

Energy & Fuels

29. Yansheng, C.; Changping, L.; Qingzhu, J.; Qingshan, L.; Peifang, Y.; Xiumei, L.; WelzBiermann, U., Desulfurization by oxidation combined with extraction using acidic roomtemperature ionic liquids. Green Chemistry 2011, 13, (5), 1224-1229. 30. Andevary, H. H.; Akbari, A.; Omidkhah, M., High efficient and selective oxidative desulfurization of diesel fuel using dual-function [Omim]FeCl4 as catalyst/extractant. Fuel Processing Technology 2019, 185, 8-17. 31. Lo, W.-H.; Yang, H.-Y.; Wei, G.-T., One-pot desulfurization of light oils by chemical oxidation and solvent extraction with room temperature ionic liquids. Green Chemistry 2003, 5, (5), 639-642. 32. Song, H.; Gao, J.; Chen, X.; He, J.; Li, C., Catalytic oxidation-extractive desulfurization for model oil using inorganic oxysalts as oxidant and Lewis acid-organic acid mixture as catalyst and extractant. Applied Catalysis A: General 2013, 456, 67-74. 33. Hossain, M. N.; Park, H. C.; Choi, H. S. J. C., A Comprehensive Review on Catalytic Oxidative Desulfurization of Liquid Fuel Oil. 2019, 9, (3), 229. 34. Chen, X.; Yuan, S.; Abdeltawab, A. A.; Al-Deyab, S. S.; Zhang, J.; Yu, L.; Yu, G., Extractive desulfurization and denitrogenation of fuels using functional acidic ionic liquids. Separation and Purification Technology 2014, 133, 187-193. 35. Hansmeier, A. R.; Meindersma, G. W.; de Haan, A. B. J. G. C., Desulfurization and denitrogenation of gasoline and diesel fuels by means of ionic liquids. 2011, 13, (7), 1907-1913. 36. Fukaya, Y.; Ohno, H. J. P. C. C. P., Hydrophobic and polar ionic liquids. 2013, 15, (11), 4066-4072. 37. Chen, X.; Guan, Y.; Abdeltawab, A. A.; Al-Deyab, S. S.; Yuan, X.; Wang, C.; Yu, G., Using functional acidic ionic liquids as both extractant and catalyst in oxidative desulfurization of diesel fuel: An investigation of real feedstock. Fuel 2015, 146, 6-12. 38. Wang, H.; Xu, M.; Zhou, R., Mechanism of extractive/oxidative desulfurization using the ionic liquid inimidazole acetate: a computational study. Journal of molecular modeling 2017, 23, (2), 54. 39. Behin, J.; Akbari, A.; Mahmoudi, M.; Khajeh, M., Sodium hypochlorite as an alternative to hydrogen peroxide in Fenton process for industrial scale. Water Research 2017, 121, 120-128. 40. Sikarwar, P.; Kumar, U. K. A.; Gosu, V.; Subbaramaiah, V., Catalytic oxidative desulfurization of DBT using green catalyst (Mo/MCM-41) derived from coal fly ash. Journal of Environmental Chemical Engineering 2018, 6, (2), 1736-1744. 41. Liao, X.; Wu, D.; Geng, B.; Lu, S.; Yao, Y., Deep oxidative desulfurization catalyzed by (NH 4) x H 4− x PMo 11 VO 40 (x= 1, 2, 3, 4) using O 2 as an oxidant. RSC Advances 2017, 7, (76), 48454-48460. 42. Burger, T.; Koschany, F.; Thomys, O.; Köhler, K.; Hinrichsen, O., CO2 methanation over Fe- and Mn-promoted co-precipitated Ni-Al catalysts: Synthesis, characterization and catalysis study. Applied Catalysis A: General 2018, 558, 44-54. 43. Chen, X.; Ren, L.; Yaseen, M.; Wang, L.; Liang, J.; Liang, R.; Chen, X.; Guo, H. J. R. a., Synthesis, characterization and activity performance of nickel-loaded spent FCC catalyst for pine gum hydrogenation. 2019, 9, (12), 6515-6525. 44. Naboulsi, I.; Lebeau, B.; Aponte, C. F. L.; Brunet, S.; Mallet, M.; Michelin, L.; Bonne, M.; Carteret, C.; Blin, J.-L., Selective direct desulfurization way (DDS) with CoMoS supported over mesostructured titania for the deep hydrodesulfurization of 4,6-dimethydibenzothiophene. Applied Catalysis A: General 2018, 563, 91-97. 45. Muhammad, Y.; Rashid, H. U.; Subhan, S.; Rahman, A. U.; Sahibzada, M.; Tong, Z., Boosting the Hydrodesulfurization of Dibenzothiophene Efficiency of Mn decorated (Co/Ni)Mo/Al2O3 Catalysts at Mild Temperature and Pressure by Coupling with Phosphonium based Ionic Liquids. Chemical Engineering Journal 2019, 121957.


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46. Li, Q.; Shen, F.; Ji, J.; Zhang, Y.; Muhammad, Y.; Huang, Z.; Hu, H.; Zhu, Y.; Qin, Y. J. R. a., Fabrication of graphite/MgO-reinforced poly (vinyl chloride) composites by mechanical activation with enhanced thermal properties. 2019, 9, (4), 2116-2124. 47. Chen, K.; Zhang, X.-M.; Yang, X.-F.; Jiao, M.-G.; Zhou, Z.; Zhang, M.-H.; Wang, D.-H.; Bu, X.-H., Electronic structure of heterojunction MoO2/g-C3N4 catalyst for oxidative desulfurization. Applied Catalysis B: Environmental 2018. 48. Jiang, W.; Hu, X.; Yaseen, M.; Shi, L.; Zhang, D.; Zhang, J.; Huang, L. J. P. i. N. S. M. I., Template/surfactant free and UV light irradiation assisted fabrication of Mn-Co oxides composite nanorings: Structure and synthesis mechanism. 2019, 29, (2), 163-169. 49. Shi, Y.; Liu, G.; Zhang, B.; Zhang, X., Oxidation of refractory sulfur compounds with molecular oxygen over a Ce–Mo–O catalyst. Green Chemistry 2016, 18, (19), 5273-5279. 50. Ewald, S.; Standl, S.; Hinrichsen, O., Characterization of nickel catalysts with transient methods. Applied Catalysis A: General 2018, 549, 93-101. 51. Kubička, D.; Šimáček, P.; Žilková, N., Transformation of vegetable oils into hydrocarbons over mesoporous-alumina-supported CoMo catalysts. Topics in Catalysis 2009, 52, (1-2), 161-168. 52. Jiang, W.; Hu, X.; Yaseen, M.; Shi, L.; Zhang, D.; Zhang, J.; Huang, L., Template/surfactant free and UV light irradiation assisted fabrication of Mn-Co oxides composite nanorings: Structure and synthesis mechanism. Progress in Natural Science: Materials International 2019, 29, (2), 163-169. 53. Liu, Y.; Wang, H.; Zhao, J.; Liu, Y.; Liu, C., Ultra-deep desulfurization by reactive adsorption desulfurization on copper-based catalysts. Journal of Energy Chemistry 2018. 54. Biesinger, M. C.; Payne, B. P.; Grosvenor, A. P.; Lau, L. W.; Gerson, A. R.; Smart, R. S. C., Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni. Applied Surface Science 2011, 257, (7), 2717-2730. 55. Inturi, S. N. R.; Boningari, T.; Suidan, M.; Smirniotis, P. G., Visible-light-induced photodegradation of gas phase acetonitrile using aerosol-made transition metal (V, Cr, Fe, Co, Mn, Mo, Ni, Cu, Y, Ce, and Zr) doped TiO2. Applied Catalysis B: Environmental 2014, 144, 333-342. 56. Végh, J., On calculating intensity from XPS spectra. Journal of Electron Spectroscopy and Related Phenomena 2006, 151, (1), 24-30. 57. Hamoudi, S.; Larachi, F. ç.; Adnot, A.; Sayari, A., Characterization of Spent MnO2/CeO2 Wet Oxidation Catalyst by TPO–MS, XPS, and S-SIMS. Journal of Catalysis 1999, 185, (2), 333-344. 58. Shabaker, J.; Simonetti, D.; Cortright, R.; Dumesic, J., Sn-modified Ni catalysts for aqueous-phase reforming: Characterization and deactivation studies. Journal of Catalysis 2005, 231, (1), 67-76. 59. Xu, Y.-S.; Zhang, W.-D., Monodispersed Ag 3 PO 4 nanocrystals loaded on the surface of spherical Bi 2 MoO 6 with enhanced photocatalytic performance. Dalton Transactions 2013, 42, (4), 1094-1101. 60. Zhang, X.; Huang, P.; Liu, A.; Zhu, M., A metal–organic framework for oxidative desulfurization: UIO-66(Zr) as a catalyst. Fuel 2017, 209, 417-423. 61. Laredo, G. C.; Vega-Merino, P. M.; Trejo-Zárraga, F.; Castillo, J. J. F. p. t., Denitrogenation of middle distillates using adsorbent materials towards ULSD production: a review. 2013, 106, 21-32. 62. Ogunlaja, A. S.; Abdul-quadir, M. S.; Kleyi, P. E.; Ferg, E. E.; Watts, P.; Tshentu, Z. R., Towards oxidative denitrogenation of fuel oils: Vanadium oxide-catalysed oxidation of quinoline and adsorptive removal of quinoline-N-oxide using 2,6-pyridine-polybenzimidazole nanofibers. Arabian Journal of Chemistry 2017.


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Energy & Fuels

63. Sampanthar, J. T.; Xiao, H.; Dou, J.; Nah, T. Y.; Rong, X.; Kwan, W. P., A novel oxidative desulfurization process to remove refractory sulfur compounds from diesel fuel. Applied Catalysis B: Environmental 2006, 63, (1), 85-93. 64. Chen, L.; Guo, S.; Zhao, D., Oxidation of Thiophenes over Silica Gel in Hydrogen Peroxide/Formic Acid System11Supported by the National Natural Science Foundation of China (No.20276015) and the Natural Science Foundation of Hebei Province (No.203364). Chinese Journal of Chemical Engineering 2006, 14, (6), 835-838. 65. Qi, K.; Xie, J.; Hu, H.; Han, D.; Fang, D.; Gong, P.; Li, F.; He, F.; Liu, X., Facile synthesis of Mn-based nanobelts with high catalytic activity for selective catalytic reduction of nitrogen oxides. Chemical Engineering Journal 2018, 352, 39-44. 66. Liu, F.-J.; Wei, X.-Y.; Zhu, Y.; Wang, Y.-G.; Li, P.; Fan, X.; Zhao, Y.-P.; Zong, Z.-M.; Zhao, W.; Wei, Y.-B., Oxidation of Shengli lignite with aqueous sodium hypochlorite promoted by pretreatment with aqueous hydrogen peroxide. Fuel 2013, 111, 211-215. 67. Zhao, Y.; Wen, X.; Guo, T.; Zhou, J., Desulfurization and denitrogenation from flue gas using Fenton reagent. Fuel Processing Technology 2014, 128, 54-60. 68. Ogunlaja, A.; Abdul-quadir, M.; Kleyi, P.; Ferg, E.; Watts, P.; Tshentu, Z. J. A. J. o. C., Towards oxidative denitrogenation of fuel oils: Vanadium oxide-catalysed oxidation of quinoline and adsorptive removal of quinoline-N-oxide using 2, 6-pyridine-polybenzimidazole nanofibers. 2017. 69. Rodríguez-Cabo, B.; Rodríguez, H.; Rodil, E.; Arce, A.; Soto, A., Extractive and oxidative-extractive desulfurization of fuels with ionic liquids. Fuel 2014, 117, 882-889. 70. Abdelrahman, A. A.; Betiha, M. A.; Rabie, A. M.; Ahmed, H. S.; Elshahat, M. F., Removal of refractory Organo‑sulfur compounds using an efficient and recyclable {Mo132} nanoball supported graphene oxide. Journal of Molecular Liquids 2018, 252, 121-132. 71. Ja'fari, M.; Ebrahimi, S. L.; Khosravi-Nikou, M. R., Ultrasound-assisted oxidative desulfurization and denitrogenation of liquid hydrocarbon fuels: A critical review. Ultrasonics Sonochemistry 2018, 40, 955-968. 72. Liu, H.; Bao, S.; Cai, Z.; Xu, T.; Li, N.; Wang, L.; Chen, H.; Lu, W.; Chen, W., A novel method for ultra-deep desulfurization of liquid fuels at room temperature. Chemical Engineering Journal 2017, 317, 1092-1098. 73. Wang, F.; Xu, C.; Li, Z.; Xia, C.; Chen, J., Mechanism and origins of enantioselectivity for [BMIM] Cl ionic liquids and ZnCl2 co-catalyzed coupling reaction of CO2 with epoxides. Journal of Molecular Catalysis A: Chemical 2014, 385, 133-140. 74. Liu, C.; Shi, J.-W.; Gao, C.; Niu, C., Manganese oxide-based catalysts for lowtemperature selective catalytic reduction of NOx with NH3: A review. Applied Catalysis A: General 2016, 522, 54-69. 75. Sampanthar, J. T.; Xiao, H.; Dou, J.; Nah, T. Y.; Rong, X.; Kwan, W. P., A novel oxidative desulfurization process to remove refractory sulfur compounds from diesel fuel. Applied Catalysis B: Environmental 2006, 63, (1-2), 85-93.

689 690 691 692 693 25 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

694 695 696 697 698 699

Figure Captions

700

Figure 1: PXRD patterns of different Mo/Al2O3 catalysts

701

Figure 2: EDX scans for alumina supported catalysts

702

Figure 3: XPS spectra of fresh (a), and spent (b) Co in Mn-Co-Mo/Al2O3; fresh (c) and

703

spent (d) Ni in Mn-Ni-Mo/Al2O3; fresh (e) and spent (f) Mo in Mn-Co-Mo/Al2O3; fresh

704

(g) and spent (h) Mo in Mn-Ni-Mo/Al2O3 catalysts

705

Figure 4: Optimization of (a) O/S ratio, (b) Time, (c) Temperature, and (d) Catalyst

706

amount for the ODS of DBT using H2O2 as oxidant over (♦) Ni-Mo/Al2O3, (■) Co-

707

Mo/Al2O3, (▲) [Bmim]Cl/ZnCl2, (×) Mn-Ni-Mo/Al2O3, (ӝ) Mn-Co- Mo/Al2O3

708

catalysts.

709


710

amount for the ODN of pyridine using H2O2 as oxidant over (♦) Ni-Mo/Al2O3, (■) Co-

711

Mo/Al2O3, (▲) [Bmim]Cl/ZnCl2, (×) Mn-Ni-Mo/Al2O3, (ӝ) Mn-Co- Mo/Al2O3

712

catalysts.

713

Figure 6: Optimization of IL:Oil ratio for the complete CODS and CODN of DBT and

714

pyridine using H2O2


Page 26 of 50

Page 27 of 50 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

715

Figure 7: Optimization of the reaction conditions for the complete CODS of DBT in the

716

presence of NaClO

717

Figure 8: Optimization of reaction conditions for the complete CODN of pyridine in the

718

presence of NaClO

719

Figure 9: Optimization of catalyst dose for the complete CODS and CODN of DBT and

720

pyridine in the presence of NaClO

721

Figure 10: Complete CODS and CODN in the presence of NaClO over catalysts: (♦)

722

[C4mim]TFA, (■) [EimC4SO3H]NTF2, (▲) [Bmim]Cl/ZnCl2, (×) Mn-Co- Mo/Al2O3

723

Figure 11: Dynamic study of DBT and pyridine in the presence of H2O2

724

Figure 12: Dynamic study of CODS and CODN of DBT and pyridine over Mn-Co-

725

Mo/Al2O3 in the presence of NaClO

726

Figure 13: Dynamic study of CODS and CODN of DBT and pyridine over

727

[Bmim]Cl/ZnCl2 in the presence of NaClO

728

Figure 14: Regeneration ability of: (a) Mn-Co-Mo/Al2O3 and (b) [Bmim]Cl/ZnCl2

729

employing 15 ml of 800 ppm NaClO / DBT/Pyridine solution (O/S-4, O/N-6), 0.2 g/mL,

730

IL: oil 1.5:5 (w/w) and 20 min at 25 oC

731

Figure 15: Proposed reaction mechanism for the catalytic oxidative desulfurization and

732

denitrogenation of DBT and Pyridine in the presence of H2O2 and NaClO as oxidant over

733

Mn-Co-Mo/Al2O3 and [Bmim]Cl/ZnCl2 as catalysts

734 27 ACS Paragon Plus Environment

Energy & Fuels

735 736 737 738 739 740 Mn-Ni-Mo/Al2O3Mo

Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 50

Al2O3

Ni

Mn

Mn-Co-Mo/Al2O3 Mn

Mn

Co

Co

Ni-Mo/Al2O3

Co-Mo/Al2O3

10

741 742

20

30

40

50

60

70



2   Figure 1: PXRD patterns of different Mo/Al2O3 supported catalysts

743 744 745 746 747


80

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Energy & Fuels

748 749 750 751

752

Co-Mo/Al2O3

Ni-Mo/Al2O3

Mn-Co-Mo/Al2O3

Mn-Ni -Mo/Al2O3

Figure 2: EDX spectra of alumina supported catalysts

753 754 755 756 757 758 29 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 50

759 760 761 781.5

(a)

Co 2p3/2

781.5

(b)

Co 2p1/2

Co 2p3/2 Co 2p1/2 Simulated ------ Raw

Simulated 797.3 ------- Raw

797.2

770

780

790

800

810

770

780

Binding energy (eV)

(c)

790

800

810

Binding energy (eV)

856.6

Ni 2p3/2

(d)

Ni 2p1/2 Simulated ------- Raw

Ni 2p3/2

856.5

Ni 2p1/2 Simulated ------- Raw

874.3

873.9

9

850

855

860

865

870

875

880

885

850

Binding energy (eV)

855

860

865

870

Binding energy (eV)


875

880

885

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Energy & Fuels

Mo 3d5/2

232.8

(e)

(f)

Mo 3d3/2

Mo 3d5/2

232.7

Mo 3d3/2 Simulated ------- Raw

Simulated ------- Raw

235.9

236.0

228

230

232

234

236

238

240

228

230

232

Binding energy (eV)

(g)

234

Mo 3d5/2

232.8

Mo 3d3/2

(h)

Simulated ------- Raw

232.7

230

232

234

236

238

240

Mo 3d5/2 Mo 3d3/2 Simulated ------- Raw

236.0

228

236

Binding energy (eV)

235.9

238

240

228

230

Binding energy (eV)

232

234

236

238

240

Binding energy (eV)

762

Figure 3: XPS spectra of fresh (a), and spent (b) Co in Mn-Co-Mo/Al2O3; fresh (c) and

763

spent (d) Ni in Mn-Ni-Mo/Al2O3; fresh (e) and spent (f) Mo in Mn-Co-Mo/Al2O3; and

764

fresh (g) and spent (h) Mo in Mn-Ni-Mo/Al2O3 catalysts

765 766 767 768 769 770 771 31 ACS Paragon Plus Environment

Energy & Fuels

772 773 100

100

(a)

90

(b)

DBT removal (%)

90

80

70

80

70

60 min, 45 oC, 0.2 g/15 mL, IL:Oil::1:5

45 oC, O/S 12, 0.2 g/15 mL, IL:Oil::1:5

60

60 4

8

12

20

30

40

100

50

Time (min)

H2O2 to sulfur molar ratio (O/S-mol/mol)

60

100

(d)

(c) 90

DBT removal (%)

DBT removal (%)

DBT removal (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 50

80

70

90

80

Mn-Ni-Mo/Al2O3

60

Mn-Co-Mo/Al2O3 60 min, O/S 12, 0.2 g/15 mL, IL:Oil::1:5

60 min, 45 oC, O/S 16.6 70

50

25

30

35 Temperature

40

0.08

45

0.1

0.2

Catalyst amount (g/15 mL)

(oC)

774 775


776

amount for the ODS of DBT using H2O2 as oxidant over (♦) Ni-Mo/Al2O3, ( ■ ) Co-

777

Mo/Al2O3, ( ▲ ) [Bmim]Cl/ZnCl2, (×) Mn-Ni-Mo/Al2O3, (ӝ) Mn-Co- Mo/Al2O3

778

catalysts. 32 ACS Paragon Plus Environment

0.3

Page 33 of 50

779 780 100

(a) Pyridine removal (%)

Pyridine removal (%)

100

90

80

(b)

90

80

70

60 min, 45 oC, CD 0.2 g/15 mL, IL:Oil::1.5:5

45 oC, O/N 16, 0.2 g/15 mL, IL:Oil::1.5:5 60

70 4

8

12

20

16

H2O2 to nitrogen ratio (O/N-mol/mol) 100

30

40

50

60

Time (min) 100

(c)

(d)

90



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

80

70

90

80 Mn-Ni-Mo/Al2O3

60

Mn-Co-Mo/Al2O3 60 min, O/N 16, 0.2 g/15 mL, IL:Oil::1.5:5

60 min, 45 oC, O/N 16 70

50 25

30

35

40

0.08

45

0.1

0.2

Catalyst amount (g/mL)

Temperature (oC)

781 782


783

amount for the ODN of pyridine using H2O2 as oxidant over (♦) Ni-Mo/Al2O3, (■) Co-

784

Mo/Al2O3, (▲) [Bmim]Cl/ZnCl2, (×) Mn-Ni-Mo/Al2O3, (ӝ) Mn-Co- Mo/Al2O3 catalysts.


0.3

Energy & Fuels

785 786 787 100

90

Removal (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 50

Pyridine

80

DBT

70

45 oC, 60 min, O/N 16, O/S 12 60 0.5/5

0.8/5

1/5.

1.5/5

IL/oil ratio

788 789

Figure 6: Optimization of IL:Oil ratio for the complete CODS and CODN of DBT and

790

pyridine using H2O2 as oxidant.

791 792 793 794 795 796 797 798 34 ACS Paragon Plus Environment

Page 35 of 50

799 800 110

110

(a)

[Bmim]Cl/ZnCl2

(b)

Mn-Co-Mo/Al2O3

[Bmim]Cl/ZnCl2

Mn-Co-Mo/Al2O3

100

DBT removal (%)

100

90

90

80

80

35 oC, O/S 4, 0.1 g/15 mL, IL:Oil::1:5

15 min, 35 oC, 0.1 g/mL, IL:Oil::1:5 70

70 2

4

5

6

10

15

Reaction time (min)

NaClO to sulfur rattio (O/S) 110

(c)

[Bmim]Cl/ZnCl2

Mn-Co-Mo/Al2O3

100

DBT removal (%)

DBT removal (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

90

80

15 min, O/S 4, 0.1 g/15 mL, IL:Oil::1:5 70 20

25

30

Reaction temperature

35

(oC)

801

Figure 7: Optimization of reaction conditions for the complete CODS of DBT in the

802

presence of NaClO as oxidant.

803 804 805 35 ACS Paragon Plus Environment

20

Energy & Fuels

806 807 808 110

110

(a)

[Bmim]Cl/ZnCl2

(b)

Mn-Co-Mo/Al2O3


100

90

80

[Bmim]Cl/ZnCl2

Mn-Co-Mo/Al2O3

100

90

80 70 35 oC, O/N 6, 0.2 g/15 mL, IL:Oil::1.5:5

20 min, 35 oC, 0.2 g/15 mL, IL:Oil::1.5:5 70

60

2

4 6 NaClO to N ratio (O/S)

100



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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5

8

10

15

Reaction time (min)

(c)

90

[Bmim]Cl/ZnCl2 Mn-Co-Mo/Al2O3

80

20 min, O/N 6, 0.2 g/15 mL, IL:Oil::1.5:5 70 20

25

30

35

Reaction temperature (oC)

809

Figure 8: Optimization of reaction conditions for the complete CODN of pyridine in the

810

presence of NaClO as oxidant. 36 ACS Paragon Plus Environment

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Page 37 of 50

811 812 813 110

110

(a)

Pyridine

(b)

DBT

DBT

Pyridine

100 100

Removal (%)

Removal (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

90

90 80

20 min, 35 oC, O/S 4, O/N 6

20 min, 35 oC, O/S 4, O/N 6 70

80 0.08

0.1

0.5/5

0.2

Mn-Co-Mo/Al2O3 amount (g/mL)

0.8/5

1/5.

[Bmim]Cl/ZnCl2:Oil

814 815

Figure 9: Optimization of catalyst dose for the complete CODS and CODN of DBT and

816

pyridine in the presence of NaClO as oxidant.


1.5/5

Energy & Fuels

100

100

(a)

(b) Pyridine removal (%)

90

80

70

90

80

70

60

60

20 min, 35 oC, O/N 6, IL:oil-1.5:5, 0.2 g/15 mL

15 min, 35 oC, O/S 6, IL:Oil-1:5, 0.1 g/15 mL 50

50 Formic Acid

H2O2

Sodium Persulfate

Formic Acid

NaClO

Type of oxidant

H2O2

Sodium Persulfate

Type of oxidants

110

(c)

[Bmim]Cl/ZnCl2

Mn-Co-Mo/Al2O3

100

Removal (%)

DBT removal (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 50

90

80

70 20 min, 35 oC, O/S 4, O/N 6, IL:oil-1.5:5, 0.2 g/15 mL 60 BT

Indole

Carbazole

4,6-DMDBT

Pyridine

DBT

Type of substrate

824 825

Figure 10: Complete CODS and CODN in the presence of NaClO over: (♦)

826

[C4mim]TFA, (■) [EimC4SO3H]NTF2, (▲) [Bmim]Cl/ZnCl2, (×) Mn-Co- Mo/Al2O3

827

catalysts 38 ACS Paragon Plus Environment

NaClO

Page 39 of 50

(a)

5

298K 303K 308K 313K 318K

4 ln Co/Ct

-2.5

3

(b)

DBT over Mn-Co-Mo/Al2O3 (H2O2)

-3.0

lnk

6

-3.5

Ea= 13 kJ/mol

-4.0

2

-4.5

1

-5.0

0 20

30

40

50

0.00300 0.00305 0.00310 0.00315 0.00320 0.00325 0.00330

60

1/T

Time (min)

5 4

(c)

-2.5

298K 303K 308K 313K 318K

(d)

Pyridine over Mn-Co-Mo/Al2O3 (H2O2)

-3.0

lnk

6

ln Co/Ct

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

3

Ea= 13.2 kJ/mol

-3.5

-4.0

2

-4.5

1

-5.0

0 20

30

40

50

0.0030

60

0.0031

0.0032

0.0033

1/T

Time (min)

828 829

Figure 11: Dynamic study of DBT and pyridine in the presence of H2O2 as oxidant.

830


0.0034

Energy & Fuels

7

DBT over Mn-Co-Mo/Al2O3 (NaClO)

-1.4

lnk

Ea= 4.9 kJ/mol

4

-1.6

3

-1.8

2

-2.0

1

-2.2 4

(b)

-1.2

293K 298K 303K 308K

5

lnCo/Ct

-1.0

(a)

6

8

12

16

20

0.00325

0.00330

Time (min)

7

-1.2 293K 298K 303K 308K

5

0.00335

0.00340

1/T

(c)

6

(d)

Pyridine over Mn-Co-Mo/Al2O3 (NaClO)

-1.4

4

lnk

lnCo/Ct

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 40 of 50

Ea= 5.4 kJ/mol -1.6

3

-1.8

2 1 4

8

12

16

20

-2.0 0.00320

Time (min)

0.00325

0.00330

0.00335

0.00340

1/T

831

Figure 12: Dynamic study of CODS and CODN of DBT and pyridine over Mn-Co-

832

Mo/Al2O3 in the presence of NaClO as oxidant.

833 834 835


Page 41 of 50

7

(b)

(b)

DBT over [Bmim]Cl/ZnCl2 using NaClO

-2.4

Ea= 7.5 kJ/mol

5

lnk

lnCo/Ct

-2.2 293 K 298 K 303 K 308 K

6

-2.6

4

-2.8

3

2 4

8

12

16

-3.0

20

0.00320

0.00325

Time (min)

8

-2.3

293 K 298 K 303 K 308 K

6

0.00330

0.00335

0.00340

0.00345

1/T

(a)

7

(d)

Pyridine over [Bmim]Cl/ZnCl2 (NaClO)

-2.4

5

-2.5

Ea= 7.1 kJ/mol

lnk

lnCo/Ct

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

4

-2.6

3 -2.7

2 -2.8

1 4

8

12

16

0.00320

20

0.00325

0.00330

0.00335

0.00340

1/T

Time (min)

836

Figure 13: Dynamic study of CODS and CODN of DBT and pyridine over

837

[Bmim]Cl/ZnCl2 in the presence of NaClO as oxidant.

838 839 840


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

841

Figure 14: Regeneration performance of: (a) Mn-Co-Mo/Al2O3 and (b) [Bmim]Cl/ZnCl2

842

employing 15 ml of 800 ppm NaClO / DBT/Pyridine solution (O/S-4, O/N-6), 0.2 g/mL,

843

IL: oil 1.5:5 (w/w) and 20 min at 25 oC

844 845 846 847 848 849 850 851


Page 42 of 50

Page 43 of 50 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

S

H2O2/NaClO OH

Na+

OH Mn Mo

OClDibenzothiophene sulfone

Mo Co Mo

Mo N

O O S

Al2O3 Mo Co Mo

Mo

N

+

O-

Mn-Co-Mo/Al2O3 Pyridine oxide

S

O

H2O2/NaClO Na+

OH

HO

O S

OClDibenzothiophene sulfone

H3C N

N

+

N

CH3

ZnCl3

N+

O-

Pyridine oxide

852 853

Figure 15: Proposed reaction mechanism for the CODS and CODN of DBT and pyridine

854

in the presence of H2O2 and NaClO as oxidants over Mn-Co-Mo/Al2O3 and

855

[Bmim]Cl/ZnCl2 as catalysts.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

863

Table Captions

864

Table 1: Composition of various partaking alumina supported catalysts

865

Table 2: BET surface area and porosity data of various catalysts

866

Table 3: EDX elemental compositions of various alumina supported catalysts

867

Table 4: Dynamic study results of CODS of DBT and CODN of pyridine.

868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 44 ACS Paragon Plus Environment

Page 44 of 50

Page 45 of 50 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

885 886

Table 1: Composition of various partaking alumina supported catalysts

Type of catalyst

Metal loading (wt. %) Co

Mo

Mn

Ni

Al2O3

Co-Mo/Al2O3

2

5

-

-

12

Ni-Mo/Al2O3

-

5

-

2

12

Mn-Co-Mo/Al2O3

2

5

1

-

12

Mn-Ni-Mo/Al2O3

-

5

1

2

12

887 888 889 890 891 892 893 894 895 896 897 898 899 900 45 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 46 of 50

901 902 903

Table 2: BET surface area and porosity data of alumina support and various catalysts Sample

Surface area

Pore Size

Pore Volume

(m2.g-1)

(nm)

(cm3.g-1)

Fresh

Spent

Fresh

Spent

Fresh

Spent

Al2O3

201.8

-

6.02

-

0.3

-

Ni-Mo/Al2O3

71.7

63.6

8.1

6.7

0.14

0.08

Co-Mo/Al2O3

71.4

50.07

8.01

5.2

0.14

0.08

Mn-Ni-Mo/Al2O3

52.7

45.5

9.1

5.3

0.13

0.07

Mn-Co-Mo/Al2O3

49.1

40.6

8.8

6.2

0.13

0.08

904 905 906 907 908 909 910 911 912 913 914 915 46 ACS Paragon Plus Environment

Page 47 of 50 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

916 917 918

Table 3: EDX Elemental compositions of various alumina supported catalysts Catalyst type

Active element

Co-Mo/Al2O3

Ni-Mo/Al2O3

Mn-Co-Mo/Al2O3

Mn-Ni-Mo/Al2O3

Elemental composition Wt. %

At. %

Co

03.14

05.02

Mo

96.86

94.98

Ni

04.07

06.49

Mo

95.93

93.51

Mn

14.49

18.55

Co

40.74

48.63

Mo

44.76

32.82

Mn

08.44

13.57

Ni

04.06

06.10

Mo

87.47

80.33

919 920 921 922 923 924 925 926 927 928 47 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 48 of 50

929 930 931

Table 4: Dynamic study results of CODS of DBT and CODN of pyridine. Catalyst type

Temperature

Rate constant

Correlation

Activation

(oC)

K (min)

factor (R2)

energy (KJ/mol)

Desulfurization of DBT using H2O2

Mn-Co-Mo/Al2O3

25

0.0077

0.87527

30

0.00898

0.97427

35

0.01334

0.9845

40

0.0255

0.98974

45

0.0788

0.89722

13

Denitrogenation of pyridine using H2O2

Mn-Co-Mo/Al2O3

25

0.0084

0.96819

30

0.01092

0.96086

35

0.01747

0.87409

40

0.0304

0.8124

45

0.0802

0.89567

13.2

Desulfurization of DBT using NaClO

Mn-Co-Mo/Al2O3

[Bmim]Cl/ZnCl2

15

0.1168

0.99285

20

0.1644

0.99314

25

0.286

0.98563

30

0.3254

0.99047

20

0.05344

0.98302


4.9

7.5

Page 49 of 50 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

25

0.0682

0.9858

30

0.087

0.99081

35

0.107

0.99615

Denitrogenation of pyridine using NaClO

Mn-Co-Mo/Al2O3

[Bmim]Cl/ZnCl2

20

0.1488

0.96940

25

0.1736

0.99130

30

0.206

0.96038

35

0.2982

0.99691

20

0.0628

0.99185

25

0.0682

0.9960

30

0.087

0.99061

35

0.100

0.99614

932


5.4

7.1

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

Page 50 of 50

Green Fuel

15 min, 25 oC

Studies on the Selection of Catalyst-Oxidant System for the Energy Efficient Desulfurization and Denitrogenation of Fuel Oil at ACS Mild Operating Paragon Plus EnvironmentConditions

Studies on the Selection of Catalyst-Oxidant System for the Energy

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