CO2 Dry Reforming Reaction over

Subscriber access provided by CORNELL UNIVERSITY LIBRARY

Article

Synergistic effect of CeO2 in CH4/CO2 dry reforming reaction over stable xCeO2 yNi/MCM-22 catalysts Roohul Amin, Xiaoqian Chang, and Bingsi Liu Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b01375 • Publication Date (Web): 12 Jun 2017 Downloaded from http://pubs.acs.org on June 17, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Industrial & Engineering Chemistry Research is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 30

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

Industrial & Engineering Chemistry Research

Synergistic Effect of CeO2 in CH4/CO2 Dry Reforming Reaction over Stable xCeO2 yNi/MCM-22 Catalysts Roohul Amina，Xiaoqian Chang, Bingsi Liu* Department of Chemistry, School of Science, Tianjin university, and The National Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, People’s Republic of China.

*

Corresponding author Tel.:+86-13072045829, Fax. 86-22-27403475, E-mail: [email protected] (B.S. Liu).

a

Current address: Institute of Chemical Sciences, University of Peshawar 25120, Pakistan. 1

ACS Paragon Plus Environment


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

ABSTRACT: Ceria supported Ni/MCM-22 catalysts with weight ratio of Ni:CeO2 (9:0, 9:4, 9:8, 9:12) were prepared by a sol-gel method. The effect of CeO2 on activity and stability of catalysts was evaluated at 700-750 oC with GHSV of 2.4× 104 mL g-1h-1. The presence of CeO2 in Ni/MCM-22 suppressed effectively the accumulation of coke on active Ni0 sites via the oxygen storage capacity on the interface between elemental nickel and CeO-Si groups of MCM-22. H2TPR results illustrated that CeO2 reduced the interaction between Ni and MCM-22 and increased high dispersion of Ni nanoparticles which is easily reducible. The 8CeO2 9Ni/MCM-22 catalyst performed the best at 750 oC with the lowest carbon deposition during time on stream of 60 h, plausible due to the presence CeO2, which promotes C-H activation. Moreover, the surface oxygen species on catalyst can interact with the coke generated during reaction to suppress the formation of coke.

Keywords: H2 and syngas production; xCeO2yNi/MCM-22 catalyst; CH4/CO2 dry reforming; Synergistic action; Coke removal.

2


Page 2 of 30

Page 3 of 30

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


1. INTRODUCTION

The CH4/CO2 and CH4/H2O reforming reactions are considered to be one of important industrial processes1-2 for the production of hydrogen and syngas, and the latter has been used industrially.

CH4 + CO2 = 2CO + 2H2

∆Ho = 247 kJ/mol

(1)

CH4 + H2O = CO + 3H2

∆Ho = 206 kJ/mol

(2)

Methane dry reforming in the presence of CO2 is considered better than CH4/H2O process. The suitable ratio of CO/H2 is obtained from CH4/CO2 reforming reaction (Eq.1) for the production of liquid hydrocarbons and other industrial products by means of Fischer-Tropsch (F-T) synthesis3. On the other hand, the utilization of CH4/CO2 can diminish effectively the emission of CO2, which has been studied extensively. CH4/CO2 reforming reaction is studied with noble metal based catalysts which are active for dry reforming reaction,4 however Ni-based catalysts were also considerably used for CH4/CO2 reforming reaction5-9 due to the high costs of noble metal. However, major problem associated with Ni-based catalysts is the carbon deposition, which impedes the catalytic activity and the long-term stability of Ni-based catalysts. Therefore, researchers hope to improve particle size,10, 11 metal dispersion12 and interaction between support and metal,13, 14 further to overcome on the carbon deposition problem. The addition of MgO improved catalytic activity and suppressed the formation of coke due to strong metal support interaction (SMSI) as a result of high dispersion of Ni particles, prevents metallic Ni species from sintering in Ni-based catalysts.15,16 It is reported that small amount of Ca can inhibit sintering of nickel17 and the catalyst with proper La/Al ratio presented high catalytic activity and 3



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

stability.18 Wang et al19 and Gallego et al 20-22 studied in detail the performance of LaNiO3/SBA15, LaNiO3/MCM-41 and LaNiO3/SiO2 perovskite catalysts and verified that specific surface area or thermal stability of support as well as the utilization of promoters3, 4 could improve effectively the activity of CH4/CO2 reforming reaction. In addition, the synergistic action between Ni sites and oxides, such as ZrO2, TiO2 and CeO2 will favor the resistance against sintering of Ni particles and removal of coke.8-9, 14, 23According to report of Lucredio et al,24 the addition of La2O3 and CeO2 as promoters can enhance the dispersion of nickel particles and minimize the formation of coke. It is well known that CeO2 doped Ni-based catalyst is promising for industrial applications in CH4/CO2 reforming reaction25 due to the behavior for coke resistance.26 Moreover, the presence of oxygen species like CeO2 accelerate the removal of surface carbon and responsible for high durability of catalysts. In this work, a series of 0-12% CeO2 9Ni/MCM-22 catalysts were prepared by a sol-gel method. The fresh and used catalysts were characterized by means of X-ray diffraction (XRD), temperature-programmed reduction of H2 (H2-TPR), N2 adsorption, temperature-programmed desorption or oxidation of oxygen (O2-TPD, O2-TPO), X-ray photoelectron spectroscopy (XPS), Fourier transform Infrared (FT-IR) spectroscopy and thermogravimetric/differential scanning calorimetry (TG/DSC) analysis. The role of CeO2 for CH4 dry reforming reaction was evaluated at different temperatures.

2. MATERIALS AND METHODS

2.1 Preparation of Catalysts. A series of xCeO2yNi/MCM-22 catalysts was prepared by a sol-gel method27 used commercial MCM-22 as support. Initially, for the preparation of 9%Ni/MCM-22 and 4 wt% CeO2 9%Ni/MCM-22, calculated amounts of 4


Page 4 of 30

Page 5 of 30

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


Ni(NO3)2·6H2O, Ce(NO3)3·6H2O, were dissolved in 25 mL of DW. After the addition of citric acid with molar amount 1.5 times that of total metal ions, 1 g of MCM-22 was added to the aforementioned solution. The obtained mixture was continuously stirred at 60 oC until the formation of gel which was aged at RT for 3 days. Finally the samples were heated to 550 oC at a rate of 2oC/min and calcined at 550 oC for 6 h. Similarly, 8wt% CeO2 9%Ni/MCM-22 and 12wt% CeO2 9%Ni/MCM-22 were also prepared by the same method. The obtained catalysts were denoted as 9Ni/MCM-22, 4CeO2 9Ni/MCM-22, 8CeO2 9Ni/MCM-22 and 12CeO2 9Ni/MCM-22, respectively hereinafter. The catalysts were then pressed and sieved through 40-60 meshes for the evaluation of catalytic activities.

2.2 Characterization of Catalysts. The N2 adsorption experiments of fresh and used xCeO2 yNi/MCM-22 catalysts were investigated at 77 K on a self-assembled BET apparatus.

27

The catalyst was dried overnight at 120 oC and weighted catalyst was charged into

the sample cell. Prior to measurement, the catalyst was degassed again in vacuum at 200 oC for 1 h. The volumes of micropores (Vmic) and mesopores (Vmeso) were determined by the volume of N2 adsorbed (Vm) at p/po = 0.10 and 0.95, respectively. Brunauer-Emmett-Teller (BET) and BarrettJoyner-Halenda (BJH) techniques were used to calculate specific surface area (SBET), pore size distribution and pore volume of catalysts. The X-ray diffraction patterns of catalysts were obtained on a PANalytical automatic diffractometer using Ni-filtered Cu Kα radiation (λ = 0.154 06 nm) at setting of 40 kV and 50 mA. The O2-TPO and H2-TPR of catalysts were conducted by gas chromatograph (GC) system 27, i.e, about 70 mg of catalyst was charged in U-shaped quartz reactor and treated at 150 oC in the flow of He or N2 (50 mL/min) for 30 min. After cooling to RT, the catalyst was heated to 850 oC 5



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

at a rate of 10 oC/min in 5% O2/He or 5% H2/N2 mixture (50 mL/min). The amount of O2 or H2 uptakes during the reaction was measured by a thermal conductivity detector (TCD). The structure and morphology of catalyst were investigated using a JP-S-4800 thermal field emission environmental scanning electron microscope at 200 kV. TG/DSC analysis was carried out in air on a STA 409 PC/PG model instrument in the temperature range 30-850 oC at a heating rate of 10oC/min. The X-ray photoelectron spectroscopy (XPS) signals were determined with a PHI-1600 ESCA spectrometer equipped with an Al Kα X-ray source (1486.6 eV). The binding energies (BEs) of the catalysts were calibrated using the Si 2p3/2 line (103.5 eV). The FT-IR spectra of MCM-22, fresh and used catalysts were observed on BIO-RAD FTS 3000 spectrophotometer. 2.3 Investigation on Catalytic Performance. CH4/CO2 reforming reaction was carried out on fixed-bed quartz reactor with a K-type thermocouple placed in the center of furnace to control the reaction temperature at atmospheric pressure. The amount of CH4 and CO2 was monitored using a mass flow controller (D07-7B/ZM, Beijing Seven-star Electronics Co. Ltd., China). Usually, 0.15 g catalyst was taken for CH4/CO2 reforming reaction, the catalyst was pre-reduced at 700 oC in H2 (40 mL/min) for 1 h prior to switching CO2 and CH4 mixture. The total flow rate of CH4 and CO2 (molar ratio of 1:1) was 60 mL/min with the gas hour space velocity (GHSV) of 2.4 × 104mLg-1h-1 at 700-750 oC at atmospheric pressure. The reactants and products were determined by gas chromatograph (GC) using TDX-01 packed column with a TCD. An ice-trap was used at the exit of the reactor to collect the water formed during reaction. The CH4/CO2 conversions, (XCH4 or XCO2), H2/CO selectivity (SH2or SCO), carbon yields (YC) and H2/CO molar ratio were calculated as follows: XCO2(%) = 100× ([ FCO2]in –[FCO2]out)/[FCO2]in 6


Page 6 of 30

Page 7 of 30

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


XCH4(%) = 100× ([FCH4]in–[FCH4]out)/[FCH4]in SH2(%) =100× [FH2]out/(2×([FCH4]in-[FCH4]out) SCO(%) =100× [FCO]out/([FCO2]in-[FCO2]out)+ ([FCH4]in-[FCH4]out) YC(%)=100×[(FCO2in+FCH4in)- (FCH4out+FCO2out+FCOout)]/(FCO2in+FCH4in) R FH2/FCO = SH2 out/SCO out Where, FCH4,in and FCO2,in were inlet flow rates (mL/min) of CH4 and CO2, and FCH4,out, FCO2, out,

FCOout, and FH2, out were outlet flow rates (mL/min) of CH4, CO2, CO and H2, respectively

and RFH2/FCO is the molar flow ratio of H2 and CO in the outlet.

3．．RESULTS AND DISCUSSION

3.1 BET, XRD, O2-TPD, H2-TPR, FT-IR, SEM Images and XPS Analysis of Catalysts. Nitrogen adsorption isotherms for MCM-22 and xCeO2yNi/MCM-22 catalysts are presented in Figure 1, resembling the type-II isotherms. The BET surface area (SBET) and micropore volumes (Vmic) for the supporting material MCM-22 and xCeO2 yNi/MCM-22 catalysts listed in Table 1, the N2 uptakes for catalysts decreased regularly compared to the N2 uptakes for MCM-22. The SBET and Vmic of MCM-22 are 498 m2/g and 0.145 cm3/g, respectively. The SBET, VT, Vmeso and Vmic of catalysts decreased regularly (Table 1) with excessive loadings of CeO2 and Ni due to occupation of more inner spaces via the interaction of metal oxide with the Si-OH groups of MCM-22. The adsorption isotherm over fresh catalysts revealed that the structure of MCM-22 remained intact with slight decrease in SBET after Ni-CeO2 loaded, indicating that Ni species are well dispersed on MCM-22 and occupied the part channels

7



of MCM-22 resulting in the decline in the SBET and Vmic of catalysts. After evaluation of catalytic activity via CO2 dry reforming reaction, the SBET, VT, Vmeso and Vmic of used catalysts further decreased due to coke formation on the surface of catalysts.

(A)

(B) a

a b

b

3

Adsorption Volume (cm /g)

c

c

e f g h i

0.2

0.4

0.6

0.8

e f g h i

j k 0.0

d

3

d

dV/dr (cm /Ag)

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 8 of 30

j k

1.0

10

Relative pressure (p/p0)

100

Pore diameter (angstrom)

Figure 1. (A) N2 adsorption isotherm and (B) pore size distribution of (a) MCM-22, fresh and used (700 oC ) (b, f ) 9Ni/MCM-22, (c, g ) 4CeO2 9Ni/MCM- 22, (d, h ) 8CeO2 9Ni/MCM-22, (e, i) 12CeO2 9 Ni/MCM-22 used at 750 oC for 10 h, (j) 8CeO2 9Ni/MCM-22 and (k) 8CeO2 9Ni/MCM-22 used at 750 oC for 60 h.

The wide-angle XRD patterns of fresh and used catalysts were displayed in Figure 2. The characteristic peaks at 2θ = 14.2o and 25.9o [PDF65-5973] for all catalysts originated from diffraction of parent MCM-22.28 The diffraction peaks at 2θ = 37.3o 43.3o and 62.7o [PDF#656920] for fresh xCeO2 9Ni/MCM-22 were ascribed to NiO9 and no diffraction peak of CeO2 was detected due to high dispersion as well as synergistic action between Ce4+ and HO-Si(Al). While the diffraction peaks at 2θ = 43.9o and 51.8o (PDF65-2865)

29

8


were assigned to elemental Ni,

Page 9 of 30

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


meant the transformation of NiO to Nio over 9Ni/MCM-22 and 8CeO2 9Ni/MCM-22 catalysts (Figure 2(e,f)) after hydrogen reduction for 1 h and CH4/CO2 dry reforming reaction. Table 1. Specific Surface Area (SBET), Total Pore Volume (VT), Average Pore Size (Da), Microporous (Vmic) and Mesoporous (Vmeso) Volume of MCM-22, Fresh and Used xCeO2yNi/MCM-22 Catalysts with Different Weight Ratios. d

SBET (m2/g)

Catalysts

PSN (nm)

VT (mm3/g)

Vmic (mm3/g)

Vmeso (mm3/g)

Da (nm)

MCM-22

498

NA

248

145

103

1.99

9Ni/MCM-22

296

3.79

241

141

100

3.25

4CeO2 9Ni/MCM-22

279

NA

234

133

101

3.35

8CeO2 9Ni/MCM-22

261

3.16

216

117

99

3.31

12CeO2 9Ni/MCM-22

231

3.05

201

104

97

3.48

DR 700 9Ni/MCM-22 (10 h)

211

11.03

191

97

94

3.62

DR 700 4CeO2 9Ni/MCM-22

200

NA

168

89

79

3.36


186

8.08

151

79

72

3.24


171

NA

131

71

60

3.06

b

DR 750 8CeO2 9Ni/MCM-22 (10 h)

133

NA

119

65

54

3.57

c

DR 750 8CeO2 9Ni/MCM-22 (60 h)

129

NA

104

59

45

3.22

a

a

o

b

Notes: 9Ni/MCM-22 after dry reforming at 700 C for 10 h. 8CeO2 9Ni/MCM-22 after dry reforming at 750 o

C for 10 h. c 8CeO2 9Ni/MCM-22 after dry reforming at 750 oC for 60 h. dPSN- particle size of Nio (200) at

2θ = 43.9o or NiO (111) at 2θ = 43.3o estimated by Scherrer equation in Figure 2; NA—no detection.

9



NiO MCM-22

Ni a Intensity (a.u)

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 10 of 30

b c

d

e f

10

20

30

40

50

60

70

80

2θ (degree) Figure 2. XRD patterns of (a) MCM-22, (b) fresh 9Ni/MCM-22, (c) fresh 8CeO2 9Ni/MCM-22, (d) fresh 12CeO2 9Ni/MCM-22; (e) 9Ni/MCM-22 and (f) 8CeO2 9Ni/MCM-22 used at 700 oC.

The O2–TPD profiles of xCeO2 9Ni/MCM-22 catalysts are shown in Figure 3A. It can be seen that there is no O2-TPD peak to appear on 9Ni/MCM-22 (Figure 3A(a)) and there are three peaks of oxygen desorption over 4-12CeO2 9Ni/MCM-22 catalysts, which correlated closely with CeO2 loadings (or crystal structure of CeO2). According to reports of Chen et al.30 and Yao et al.31 the peaks at 209-226 oC can be assigned to the desorption of oxygen adsorbed physically, respectively and the desorption peaks in intensity increased with incremental CeO2 loadings. The peaks at 415-473 oC attributed to the desorption of chemisorption oxygen on the surface of 412CeO2 9Ni/MCM-22 while the ones at 637-651oC correlated with the desorption of lattice oxygen in CeO2 species. It is well known that addition of CeO2 can vary the oxygen storage 10


Page 11 of 30

capacity of catalysts to improve catalytic activity and inhibit the carbon deposition via the action of oxygen shifting.29, 32, 33

226

372

(A)

(B)

359

a

473 651 209

TCD signal

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


324

719

347

708

d

b

646 c

415 214

c

637

b

426 712

a

d 0

200

400

600

800

0

200

400

600

800

o

Temperature ( C )

Figure 3. (A) O2-TPD and (B) H2-TPR profiles of (a) 9Ni/MCM-22, (b) 4CeO2 9Ni/MCM-22, (c) 8CeO2 9Ni/MCM-22 and (d) 12CeO2 9Ni/MCM-22.

The H2-TPR profiles of xCeO2yNi/MCM-22 catalysts are shown in Figure 3B. It can be seen that there are two peaks over 4-12CeO2 9Ni/MCM-22 at 324-372 oC and 708-719 oC whereas only one strong peak appeared at 372 oC over 9Ni/MCM-22. The peaks at 324-372 oC for all catalysts are ascribed to the reduction of NiO to Nio 11 and the ones at 708-719 oC are accredited to the variation of Ce+4 to Ce+3 (2CeO2 + H2 = Ce2O3 + H2O).8,11,34 According to report of Amin et al,11 the reduction over Yb promoted Ni/Al2O3 occurred at 240-400 oC, similar to our results. The FT-IR spectra of MCM-22, fresh and used 8CeO2 9Ni/MCM-22 catalysts are shown in 11



Figure 4, it can be seen that the absorption peaks at 835 and 1245 cm-1can be ascribed to external linkage asymmetric stretching of T-O-T while the peaks at 445 and 1080 cm-1 are due to internal tetrahedral asymmetric stretching -O-T, in accordance with reports in literature.35

555 a

4000

3000

2000

507 610 445

1245

1120 1080

3671 3424

1629

c

835

b Transmittance (%)

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 12 of 30

1000

0

-1

Wavenumber (cm ) Figure 4. FT-IR spectra of (a) MCM-22, (b, c) fresh and used 8CeO2 9Ni/MCM-22 at 750 oC.

The peaks at 555 cm-1 and 610 cm- 1 are assigned to external linkage double ring. The broad band at near 3424-3671 cm−1 attributed to H-O stretching vibration of hydroxyl groups that related with the extra framework of aluminum species.36 The band at 507 cm-1 correlated with stretching vibration of NiO due to the interatomic vibrations (Figure 4(b,c)).37-38 The FT-IR spectrum at 1629 cm-1 is attributed to bending vibration of δSi-O-H.39 The strong peaks in Figure

12


Page 13 of 30

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


4(b, c) at 1120 cm-1 are assigned to stretching mode of Ce-O.38

Figure 5. SEM images of (A, B) fresh and (C, D) used 8CeO2 9Ni/MCM-22 at 750 oC.

The SEM images of fresh and used 8CeO2 9Ni/MCM-22 for 60 h were shown in Figure 5. It can be observed that as catalyst support, structure of MCM-22 remained stable in the SEM images of fresh 8CeO2 9Ni/MCM-22 (Figure 5A-B) and appeared in the form of round, thin, and interpenetrating platelets. These individual platelets are in fact made up of stacks of much smaller and thinner hexagonal sheets and turned out to be a shape like rose, as shown in Figure 5A.40 The particles of Ni and CeO2 are dispersed highly on the inner surface of microporous channels of MCM-22. After CH4/CO2 reforming reaction, the structure of MCM-22 remained intact (Figure 5C-D). Although the size of active particles could not be distinguished clearly due 13



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 14 of 30

to low resolution of SEM images, a large amount of carbon nanotubes (CNTs) was observed in Figure 5C-D, which promoted further the dispersion of Nio nanoparticles.39 This meant that 8CeO2 9Ni/MCM-22 catalyst remained stable during CH4/CO2reforming reaction at 750 oC for time on stream of 60 h. The XPS spectra of fresh and used catalysts are shown in Figure 6 and 7. It can be seen that the Ni 2p3/2 binding energy (BE, 855.6 eV) of as-prepared 8CeO2 9Ni/MCM-22 (Figure 6A), together with two satellite peaks at 861.1 and 883.7 eV, respectively is higher than that (853.8eV) of isolate NiO41 and close to these (856.1 eV) of NiSiO342 or NiAl2O4 (855.8 eV),41 suggesting strong interaction of NiO nanoparticles with MCM-22 via Ni-O-Si(Al) bonding while Si 2s XPS spectra at 154.3 eV presented the character of SiO2 species (Figure 6A).

14


Page 15 of 30

(B)

872.8

855.5

(A)

Intensity (a.u)

u3

uu u2 1

ν3

ν

ν2

ν1

a

a b

Ni 2p

b 852.4

868.2

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


c

c

890 880 870 860 850 840

Ce 3d 930 920 910 900 890 880

Binding Energy (eV)

Figure 6. (A) Ni 2p and (B) Ce 3d XPS spectra of (a) fresh 8CeO2 9Ni/MCM-22, (b) fresh 12CeO2 9Ni/MCM-22 and (c) 8CeO2 9Ni/MCM-22 used in CH4/CO2 reforming reaction at 750 o

C.

However, with the increase of CeO2 loading, the Ni 2p3/2 peaks in intensity reduced and more dispersed (Figure 6A(b)), meaning that the more loadings of CeO2 will cover partially the active sites of surface NiO nanoparticles. After hydrogen reduction and CH4/CO2 reforming reaction over 8CeO2 9NiO/MCM-22 at 750 oC, the Ni 2p3/2 peaks at 852.4 eV became weak significantly in intensity or nearly disappeared due to a large amount of carbon deposition or the formation of CNTs. But it can still be observed that the NiO or NiSiO3 in 8CeO2 9Ni/MCM-22

15



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 16 of 30

was reduced to metallic nickel (Figure 6A(c)) accompanied with the disappearance of satellite peaks, similar to the XRD result of sample (Figure 2e).

As shown in Figure 7B, there are two sets of remarkable spin–orbit multiplets: µ and ν in the XPS spectra of Ce 3d, corresponding to the contributions of 3d3/2 and 3d5/2, respectively, indicating the co-existence of Ni2+ and CeO2 nanoparticles on the surface of 8CeO2 9Ni/MCM22 because there is attenuation of the signals from the under layer CeO2. According to report in literature,43 there are three main 3d5/2 features at ca. 882.5 (v), 889.4 (v2), and 898.7 (v3) eV and three main 3d3/2 features at ca. 900.6 (u), 907.7 (u2), and 916.6 (u3) eV in the Ce 3d spectrum. We observed u3 and v3 peaks which could be assigned to the 3d94f0 photoemission final state whereas the v2 and u2 peaks attributed to 3d94f2 configurations disappeared except for 3d5/2 (v, 882.8 eV) and 3d3/2 (u , 900.9 eV) XPS spectra.41 After hydrogen reduction and CH4/CO2 reforming reaction over 8CeO2 9NiO/MCM-22 at 750 oC, the states at 886.6 eV (v1) and 904.5 eV (u1) belonged to unique photoelectron features of the Ce3+state appeared due to reduction of CeO2 to Ce3+.44 As shown in Figure 7B, the peaks at 284.6 and 285.1 eV over fresh 8CeO2 9Ni/MCM-22 and 12CeO2 9Ni/MCM-22 can be ascribed to C1s signals of surface contaminant carbon due to pump oil. After the CH4/CO2 reforming reaction, the dominant C1s peak was shifted from 284.6 eV to 283.4 eV (Figure 7B(c)) due to the formation of graphitic carbon and/or carbon nanotubes.45, 46The main O1s peaks of all catalysts located at 532.7 eV, which originated from O1s signals of SiO2 (532.8 eV47 and the Si 2p3/2 XPS spectra are observed (Figure 7C). In addition, the shoulder or asymmetry peaks at nearly 530 eV appeared, which originated from the O 1s photoelectron signals of NiO (529.6 eV48, CeO2 (529.2 eV) 49 (Figure 7D) and Ce2O3 (530.3 eV).41

16


(A)

C 1s

3/2

O1s

Ni 2p

5/2

Si 2s Si 2P

Ce3d

a b c 1100 1000 900 C1s

284.6

800

700

600

(B)

Si 2p3/2

500

400 (C)

300

200

100

0

(D)

O1s

c

292 288 284 280 276

a b c

103.5

285.1

b

532.7

a 283.7

Intensity (a.u)

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


3/2

Page 17 of 30

a b c

108 104 100 96 92 545 540 535 530 525

Binding Energy (eV)

Figure 7. (A) Wide scanning spectra；(B) C1s (C) Si 2p3/2 and (D) O1s XPS spectra of (a) fresh 8CeO2 9Ni/MCM-22, (b) fresh 12CeO2 9Ni/MCM-22 and (c) 8CeO2 9Ni/MCM-22 used in CH4/CO2 reforming reaction at 750 oC.

3.2 Evaluation of Catalytic Activity. The conversions of CH4 and CO2, selectivity of CO and H2 as well as carbon yields over xCeO2 9Ni/MCM-22 catalysts were shown in Figure 8, it can be observed that the conversions of CH4 and CO2 over 9Ni/MCM-22 are significantly low due to carbon deposition. More important factor is the dispersion of nickel particles. The XRD result of 9Ni/MCM-22 verified that the particle size of active nickel increased remarkably (from 3.79 nm to 11.03 nm, Table 1) after reforming reaction (Figure 2e). However, the conversions of CH4 (71-78%) and CO2 (83-98%) over 4-12CeO2 9Ni/MCM-22 are higher than these (60%, 72%) over 9Ni/MCM-22 catalyst at 700 oC and the same GHSV of 2.4× 17



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 18 of 30

104 mLg-1h-1, indicated that the introduction of CeO2 improved effectively the dispersion of Ni0 particles and the catalytic activity of CH4/CO2 dry reforming reaction, plausible due to the elimination of surficially active carbon before the formation of CNTs (Figure 5C-D) via the nonlattice or lattice oxygen in CeO2 species because a large amount of adsorbed oxygen is observed in O2-TPD profiles (Figure 3A) despite of that there are similar carbon yields over different catalysts (Figure 8). More interesting, we found that the change on SBET of 0-12CeO2 9Ni/MCM22 catalysts before and after CH4/CO2 reforming reaction decreased with incremental CeO2 loadings, i.e. the variation over 9Ni/MCM-22 is 85 m2/g whereas the one over 12CeO2 9Ni/MCM-22 is only 60 m2/g, which means that the formation and removal of coke on active Ni0 sites can remain a equilibrium via a shifting oxygen of CeO2. In other words, the catalytic activity of 4-12CeO2 9Ni/MCM-22 correlated closely with the dispersion of Ni0 nanoparticles. After CeO2 loadings, the decline on reduction temperature (324-359 oC) of nickel particles in H2TPR profiles meant that the size of NiO particles became small. Additionally, more loadings of CeO2 are unfavorable so that conversions CH4 and CO2 over 12CeO2 9Ni/MCM-22 declined (Figure 8D) due to the fact that the active Ni0 sites were partially covered or the SBET and VT decreased (Table 1). The Ni 2p3/2 XPS spectrum of 12CeO2 9Ni/MCM-22 in intensity reduced significantly (Figure 6A(b)) compared to that of 8CeO2 9Ni/MCM-22. As a result, 8CeO2 9Ni/MCM-22 catalyst exhibited the best catalytic activity and stability. In the meantime, the selectivity of CO is greater than that of H2 due to reverse water gas shift (RWGS) reaction (H2 + CO2 = H2O + CO). Therefore, the ratio of H2/CO is less than 1, which is more suitable for F-T synthesis50,51 to produce valuable oxygenated chemicals or long chain hydrocarbons.

18


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


Conversion, selectivity and C yield ( mol %)

Page 19 of 30

100 95 90 85 80 75 70 65 60

100

100

100

95

95

95

90

90

90

85

85

85

80

80

80

75

75

75

70

70

70

10

8

8

8

8

6

6

6

6

4

4

4

4

2

2

0

A

0

2 B 0 2 4 6 8 10

0 2 4 6 8 10

2 C

0

0 0 2 4 6 8 10

D 0 2 4 6 8 10

Time on stream (h)

Figure 8. Conversion of CH4 (□) and CO2 (○), selectivity of CO (△) and H2 (▽) as well as carbon yield (◇) over (A) 9Ni/MCM-22 (B) 4CeO2 9Ni/MCM-22 (C) 8CeO2 9Ni/MCM-22 (D) 12CeO2 9 Ni/MCM-22 at 700 o

C, GHSV = 24 L g-1h-1 , CH4/CO2 =1:1.

3.3 Effect of Reaction Temperature and Catalyst Stability. As shown in Figure 8C and Figure 9A, the conversions CO2 and CH4 over 8CeO2 9Ni/MCM-22 catalyst increased considerably with incremental reaction temperature, i.e. the CH4 conversion at 700 oC was 77 %, significantly higher than these (60-66%)52 over 1 or 3Mg 2Co 7Ni/MSU-S catalysts under the same conditions reported previously whereas the one at 750 oC is about 83% over 8CeO2 9Ni/MCM-22 catalyst with H2/CO ratios of lower than 1 due to RWGS reaction and carbon gasification. 53 Thermodynamically, the CH4/CO2 reforming reaction (CH4 + CO2 = 2H2 + 2CO, H298 = 247.3 kJ/mol) is endothermic54 and high temperature is advantageous for the 19



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 20 of 30

occurrence of reaction. In the meantime, anti-disproportionation reaction of CO (C + CO2 = 2CO) occurred easily under the condition of high temperature to remove coke on the surface of 8CeO2 9Ni/MCM-22 catalyst according to reaction mechanism as follows: C + 4CeO2 = 2Ce2O3 + CO2, Ce2O3 + CO2 = 2CeO2 + CO. Therefore, the carbon yield (ca. 1%) declined remarkably at 750 oC (Figure 9A), which will remain high activity and stability. In order to further investigate long term catalytic stability of 8CeO2 9Ni/MCM-22 catalyst, its performance was tested at 750 o

C for 60 h. The results (Figure 9B) indicated that 8CeO2 9Ni/MCM-22 catalyst almost remained

stable with approximately 1% of carbon yield and 83% of initial conversion of CH4 during time on stream of 60 h, which is lower than the theoretical value of CH4 (88.9%) estimated only by equation (1) based on thermodynamic equilibrium (rGmo (750 oC) = 230350-70.35TlnT + 5.04*10-2 T2 – 4.83*10-6 T3 + 185.4T (J/mol K) = -31.326 kJ/mol). However, the aforementioned result is slightly higher than that (80%)55 over 7Ni/M-Ce50Zr50 except that conversions of CH4 and CO2 decreased slightly after 40 h, plausible due to the aggregation of Ni particles (Figure 2e, Table 1) to lead catalyst deactivation. The FT-IR spectrum (Figure 4c) and SEM images (Figure 5C-D) of used 8CeO2 9Ni/MCM-22 illustrated that the structure of MCM-22 remained intact after CH4/CO2 dry reforming reaction at 750 oC for 60 h.

20


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


Conversion, selectivity and C yield ( mol %)

Page 21 of 30

100

100

95

95

90

90

85

85

80

80

75

75

70

70

65

65

CH4 Conversion CO2 Conversion

8 6

CO selectivity H2 Selectivity

4

Carbon yield

6

Carbon yield 2

0

0 2

4

6

8

CO selectivity H2 Selectivity

4

(A)

2

0

CH4 Conversion CO2 Conversion

8

10

0

10

20

30

40

50

(B)

60

Time on stream (h) Figure 9. Conversion of CH4 (□) and CO2 (○), selectivity of CO (△) and H2 (▽) as well as carbon yield (◇) over 8CeO2 9Ni/MCM-22 for (A) 10 h and (B) 60 h, respectively at 750 oC with GHSV = 24 L g-1 h-1, CH4/CO2 = 1:1.

3.4 TG/DSC and O2-TPO Analysis of Used Catalysts. The coke properties of used catalysts were studied by means of TG/DSC and O2-TPO techniques (Figure 10A-B), it can be seen that the weight loss on TG profile of used 8CeO2 9Ni/MCM-22 at ca. 250 oC was attributed to the removal of amorphous carbon or water desorption56-57,5,59-60 with small exothermic peak appearing whereas the weight loss at 681 oC in the TG profile (Figure 10A (e1)) was due to the oxidation of graphitic carbon to CO2 or CO61-63 and there was a exothermic peak at 643 oC in DSC profiles (Figure 10A(e2)). As shown in Figure 10B, the peaks at 215-255 oC in O2-TPO profiles correlated with the oxidation of amorphous carbon,55-56, 5, 63 which is consistent 21



with TG result (Figure 10A) and the peaks at 548-593 oC were assigned to the oxidation of inert carbon (graphitic carbon) to CO and CO2.57, 5, 59-61

643

e1

100

(A)

18

255

1

548

(B)

e2

92 515

e3

88

6

EXO

0

-1

681 250

593

b c

248

583

241

d e

-2

DSC 0

215

569

TG 84

a

250 TCD Signal

12

Heat Flow (mW/mg)

DTG

Derived weight (%min)

577

96 TG Weight (%)

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 22 of 30

500

750

0 0

1000

300

600

900

o

o

Temperature ( C)

Temperature ( C)

Figure 10. (A) TG/DSC and (B) O2-TPO profiles of used catalysts (700 oC); (a) 9Ni/MCM-22 (b) 4CeO2 9Ni/MCM-22 (c) 8CeO2 9Ni/MCM-22 (d) 12CeO2 9Ni/MCM-22, (e, e1, e2, e3) 8CeO2 9Ni/MCM-22 used at 750 oC.

4. CONCLUSIONS CeO2 supported Ni-based MCM-22 catalysts with weight ratio (Ni: CeO2 9:0, 9:4, 9:8, 9:12) were prepared by a sol-gel method and 8CeO2 9Ni/MCM-22 catalyst performed the best at 750 o

C with high conversions of CH4 (83%) and CO2 (99%) during CH4/CO2 dry reforming reaction.

The results of BET and FT-IR revealed that the microporous structure of MCM-22 remained intact at 750 oC. The fresh and used catalysts were characterized by BET, XRD, O2-TPD, H2-

22


Page 23 of 30

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


TPR, TG/DSC, O2-TPO, XPS, SEM and FT-IR techniques. The synergistic effect between MCM-22 and CeO2 particles suppressed the sintering of Ni nanoparticles and the formation of coke. H2-TPR characterization illustrated high dispersion of Ni nanoparticles as a result of CeO2 segregation. ■ AUTHOR INFORMATION Corresponding author Tel.:+86-13072045829, Fax. 86-22-27403475, E-mail: [email protected] (B.S. Liu). a

Current address: Institute of Chemical Sciences, University of Peshawar 25120, Pakistan.

■ ACKNOWLEGEMENTS The authors thank the joint financial support of National Natural Science Foundation of China and BAOSTEEL Group Corporation (Grant 50876122), Chinese Government scholarship council, HEC Pakistan and the Ph. D innovation Program of Tianjin University.

■ REFERENCES (1) Eli, R.; Hu, Y. H. Carbon dioxide reforming of methane over Ni/alkaline earth metal oxide catalysts, Appl.Catal. A Gen. 1995, 133, 149-161. (2) Jeon, S. W.; Yoon, W. J.; Baek, C.; Kim, Y. C. Minimization of hot spot in a micro channel reactor for steam reforming of methane with the stripe combustion catalyst layer. Int. J. Hydrogen Energy 2013,38,13982-13990. (3) Djaidja, A.; Messaoudi, H.; Kaddeche, D.; Barama, A. Study of Ni-M/MgO and Ni-MMg/Al (M=Fe or Cu) catalysts in the CH4/CO2 and CH4/H2O reforming, Int. J. Hydrogen Energy 2015, 40, 4989 -4995. (4) Pakhare, D.; Spivey, J. A review of dry (CO2) reforming of methane over noble metal catalysts. Chem. Soc. Rev. 2014, 43, 7813-7838. (5) Rad, S. J. H.; Haghighi, M.; Eslami, A. A.; Rahmani, F.; Rahemi, N. Sol-gel vs. impregnation preparation of MgO and CeO2 doped Ni/Al2O3 nanocatalysts used in dry reforming of methane: Effect of process conditions, synthesis method and support composition Int. J. 23



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 24 of 30

hydrogen energy 2016, 41, 5335-5350. (6) Roh, H .S.; Jun, K.W.; Dong, W. S; Chang, J. S.; Park, S. E.; Joe, Y. I. Highly active and stable Ni/Ce-ZrO2 catalyst or H2 production from methane. J. Mol. Catal. A Chem 2002, 181, 137-142. (7) Rahemi, N.; Haghighi, M.; Babaluo, A. A.; Jafari, M. F.; Khorram, S. Non-thermal plasma assisted synthesis and physicochemical characterizations of Co and Cu doped Ni/Al2O3 nanocatalysts used for dry reforming of methane. Int. J. Hydrogen Energy 2013, 38, 1604816061. (8) Eltejaei, H.; Bozorgzadeh, H. R; Towfighi, J.; Omidkhah, M. R. et al. Methane dry reforming on Ni/Ce0.75Zr0.25O2-MgAl2O4 and Ni/Ce0.75Zr0.25O2 γ-alumina: Effects of support composition and water addition. Int. J. Hydrogen Energy 2012, 37, 4107-4118. (9) Albarazi, A. k.; Beaunier, P.; Costa, P. D. Hydrogen and syngas production by methane dry reforming on SBA-15 supported nickel catalysts: On the effect of promotion by Ce0.75Zr0.25 O2 mixed oxide. Int. J. Hydrogen Energy 2013, 38, 127-139. (10) Zheng, S. H.; Zhang, X. H.; Fu, X. J.; Zhang, L.; Su, H. Q.; Pan, H. Co/CexZr1−xO2 solid solution catalysts with cubic fluorite structure for carbon dioxide reforming of methane, Appl. Catal. B. Environ .2013, 136–137, 308–316. (11) Amin, M. H.; Mantri, K.; Newnham, J.; Tardio, J.; Bhargava, S. K. Highly stable ytterbium promoted Ni/Al2O3 catalysts for carbon dioxide reforming of methane. Appl. Catal. B Environ. 2012, 119–120, 217-226. (12) Liu, Z. C.; Zhou, J.; Cao, K.; Yang, W.; Gao, H. X.; Wang, Y. D.; Li, H. X. Highly dispersed nickel loaded on mesoporous silica: one-spot synthesis strategy and high performance as catalysts for methane reforming with carbon dioxide. Appl.Catal. B Environ .2012, 125, 324330. (13) Xu, L. L.; Song, H. L.; Chou, L. J. Carbon dioxide reforming of methane over ordered mesoporous NiO–MgO–Al2O3 composite oxides. Appl. Catal. B Environ. 2011, 108–109, 177– 190. (14) Rahmani, F.; Haghighi, M.; Vafaeian, Y.; Estifaee, P. Hydrogen production via CO2 reforming of methane over ZrO2 doped Ni/ZSM-5 nanostructured catalyst prepared by ultrasound assisted sequential impregnation method. J. Power Sources 2014, 272, 816-827. (15) Zhu, J. Q.; Peng, X. X.; Yao, L.; Tong, D. M.; Hu, C. W. CO2 reforming of methane over 24


Page 25 of 30

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


Mg promoted Ni/SiO2 catalysts: the influence of Mg precursors and impregnation sequences. Catal. Sci. Technol. 2012, 2, 529- 537. (16) Li, J. F.; Xia, C.; Au, C. T.; Liu, B. S. Y2O3-promoted NiO/SBA-15 catalysts highly active for CO2/CH4 reforming. Int. J. hydrogen energy 2014, 39, 10927-10940. (17) Hou, Z. Y.; Yokota, O.; Tanaka, T.; Yashima T. Characterization of Ca-promoted Ni/αAl2O3 catalyst for CH4 reforming with CO2. Appl. Catal. A Gen. 2003, 253, 381-387. (18) Liu, Z. W.; Roh, H. S.; Jun, K. W. Carbon dioxide reforming of Methane over Ni/ La2O3/Al2O3. J. Ind. Eng. Chem .2003, 9, 267-274. (19) Wang, N.; Yu, X. P.; Wang, Y.; Hua, W. C.; Liu, M. A. comparison study on methane dry reforming with carbon dioxide over LaNiO3 perovskite catalysts supported on mesoporous SBA15, MCM-41 and silica carrier. Catal Today 2013, 212, 98-107. (20) Gallego, G. S.; Batiot-Dupeyrat, C.; Barrault, J.; Florez, E.; Mondragon, F. Dry reforming of methane over LaNi1-y ByO3±δ (B = Mg, Co) perovskite used as catalyst precursor. Appl. Catal. A Gen.2008, 334, 251-258. (21) Gallego, G. S.; Batiot-Dupeyrat, C.; Barrault, J.; Florez, E.; Mondragon, F. Dual active site mechanism for dry methane reforming over Ni/La2O3 produced from LaNiO3 perovskite. Ind. Eng. Chem. Res. 2008, 47, 9272-9278. (22) Yang, N. T.; Kathiraser, Y.; Kawi, S. La0.6Sr0.4Co0.8Ni0.2O3Ld hollow fiber membrane reactor: Integrated oxygen separation CO2 reforming of methane reaction for hydrogen production. Int. J. Hydrogen Energy 2013, 38, 4483-4491. (23) Zhang, S. B.; Wang, J. K.; Wang, X. L. Effect of calcination temperature on structure and performance of Ni/TiO2-SiO2 catalyst for CO2 reforming of methane. J. Nat. Gas Chem. 2008, 17, 179-183. (24) Lucredio, A. F.; Jerkiewickz, G.; Assaf, E. M. Nickel catalysts promoted with cerium and lanthanum to reduce carbon formation in partial oxidation of methane reactions. Appl. Catal. A Gen .2007, 333, 90-95. (25) Trovarelli, A. Catalytic properties of ceria and CeO2 containing materials. Catal. Rev. 1996, 38, 439–520. (26) Zhang, S. H.; Muratsugu, S.; Ishiguro, N.; Tada, M. Ceria doped Ni/SBA-16 catalysts for dry reforming of methane. ACS Catal. 2013, 3, 1855-1864. (27) Guo, Y. H.; Xia, C.; Liu, B.S. Catalytic properties and stability of cubic mesoporous 25



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 26 of 30

LaxNiyOz/KIT-6 catalysts for CO2 reforming of CH4. Chem. Eng. J. 2014, 237,421–429. (28) Wang, J. S. B.; Tai, Y. L.; Dow, W. P.; Huang, T. J. Study of ceria supported nickel catalyst and effect of yttria doping on carbon dioxide reforming of methane. Appl. Catal. A Gen. 2001, 218, 69-79. (29) Pechimuthu N. A.; Pant, K. K.; Dhingra, S. C. Deactivation Studies over Ni−K/CeO2−Al2O3 catalyst for dry reforming of methane. Ind. Eng. Chem. Res. 2007, 46, 17311736. (30) Chen, P.; Shiowshyung, L.; Wang, C.; Chang, L.; Chang, J. S. Preparing and characterizing an optimal supported ceria catalyst for the catalytic wet air oxidation of phenol. Appl. Catal. B. Environ. 2004, 50, 49–58. (31) Yao, H.C.; Yao, Y. F. Ceria in automotive exhaust catalysts, oxygen storage. J. Catal. 1984, 86, 254-265. (32) Damyanova, S. B.; Pawelec, K.; Arishtirova, M. V. M. et al. The effect of CeO2 on the surface and catalytic properties of Pt/CeO2–ZrO2 catalysts for methane dry reforming. Appl. Catal. B. Environ. 2009, 89, 149-159. (33) Aneggi, E. M. D.; Boarode, L. C.; Dolcetti, G.; Trovarelli, A. J. Insights into the redox properties of ceria-based oxides and their implications in catalysis. J. Alloys Compd. 2006, 408, 1096-1102. (34) Fornasiero, Z. P.; Monte, R. D.; Rao, G. R.; Kaspar, J.; Meriani, S.; Trovarelli, A.; Graziani, M. Rh-loaded CeO2-ZrO2 solid-solutions as highly efficient oxygen exchangers: Dependence of the reduction behavior and the oxygen storage capacity on the structural properties. J. Catal. 1995, 151, 168-177. (35) Ravishankar, R.; Bhattacharya, D.; Jacob, N. E.; Sivasanker, S. Characterization and catalytic properties of zeolite MCM-22. Micro.Mater. 1995, 4, 83-93. (36) Wang, D. J.; Lunsford, J. H.; Rosynek, M. P. Characterization of a Mo/ZSM-5 catalyst for the conversion of methane to benzene. J. Catal. 1997, 169, 347-358. (37) Wang, R.; Li, Q.; Xie, D.; Xiao, H.; Lu, H. Synthesis of NiO using pine as template and adsorption performance for Pb (II) from aqueous solution. Appl. Surf. Sci. 2013, 279, 129-136. (38) Motahari, F.; Mozdianfard, M. R.; Niasari, M. S. Synthesis and adsorption studies of NiO nanoparticles in the presence of H2 acacen ligand for removing Rhodamine B in waste water 26


Page 27 of 30

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


treatment. Process Saf. Environ. Prot. 2015, 93, 282–292. (39) Xia, C.; Liu, B. S.; Guo, Y. H. LaxNiyOz/MAS‑9 catalysts with high Nio dispersion and hydrothermal stability for CH4/CO2 reforming. Ind. Eng. Chem. Res. 2014, 53, 2189- 2196. (40) Wu, Y.; Ren, X.Q.; Wang, J. Facile synthesis and morphology control of zeolite MCM22 via a two-step sol–gel route with tetra-ethyl orthosilicate as silica source. Mater. Chem. Phys. 2009, 113, 773-779. (41) Moulder, J. F.; Stickle, W. F.; Sobol, P. E.;Bomben, K. D. Physical Electronics Ins. 1995. (42) Lorenz, P.; Finster, J.; Wendt, G.; Salyn, J. V.; Zumadilov, E. K. et al. Investigations of some NiO/SiO2 and NiO-Al2O3/SiO2 catalysts. J. Electron. Spect. Relat. Phenom. 1979, 16, 267276. (43) He, H.; Dai, H. X.; Ng, L. H.; Wong, K. W.; Au, C. T. Pd- Pt- and Rh-loaded Ce0.6Zr0.35Y0.05O2 three-way catalysts: An investigation on performance and redox properties. J. Catal. 2002, 206, 1–13. (44) Holgado, J. P.; Alvarez, R.; Munuera, G. Study of CeO2 XPS spectra by factor analysis: reduction of CeO2. Appl. Surf. Sci. 2000, 161, 301–315. (45) Nandini, A.; Pant, K. K.; Dhingra, S. C. Deactivation studies over Ni−K/CeO2-Al2O3 catalyst for dry reforming of methane. Ind. Eng. Chem. Res. 2007, 46, 1731-1736. (46) Fan, X. L.; Liu, Z. T.; Zhu, Y. A.; Tong, G. S.; Zhang, J.D. et al.Tuning the composition of metastable CoxNiyMg100-x-y(OH)(OCH3) nanoplates for optimizing robust methane dry reforming catalyst. J. Catal. 2015, 330, 106- 119. (47) Wagner, C. D.; Passoja, D. E.; Hillery, H. F.; Kinisky, I. G.; Six, H. A.; Jansen, W. I. et al. Sci. Technol.1982, 21, 933-944. (48) Nefedov, V. I.; Firsov, M. N.; Shaplygin, I. S. Electronic structures of MRhO2, MRh2O4, RhMO4 and Rh2MO6 on the basis of X-ray spectroscopy and ESCA data. J. Electron. Spect. Relat. Phenom. 1982, 26, 65- 78. (49) He, H.; Dai, H.X.; Au, C. T. Defective structure, oxygen mobility, oxygen storage capacity, and redox properties of RE-based (RE = Ce, Pr) solid solutions. Catal. Today 2004, 90, 245-254. (50) Subbaramaiah, V.; Vimal, C. S.; Indradeo, M. Catalytic wet per oxidation of pyridine bearing waste water by cerium supported SBA-15. J. Hazard. Mater. 2013, 248-249, 355-363. 27



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 30

(51) Son, I. H.; Lee, S. J.; Roh, H, S. Hydrogen production from carbon dioxide reforming of methane over highly active and stable MgO promoted Co-Ni/γ -Al2O3 catalyst. Int. J. hydrogen energy 2014, 39, 3762-3770. (52) Amin, R. H.; Liu, B. S.; Huang Z. B.; Zhao, Y. C. Hydrogen and syngas production via CO2 dry reforming of methane over Mg/La promoted Co-Ni/MSU-S catalyst. Int. J. hydrogen energy 2016, 41, 807-819. (53) Chu, W.; Wang, L. N.; Chernavskii, P. A.; Khodakov, A. Y. Glow discharge plasma assisted design of cobalt catalysts for Fischere-Tropsch synthesis. Angew. Chem. Int. Ed. 2008, 47, 5052- 5055. (54) Xu, L.; Song, H.; Chou, L. Ordered mesoporous MgO-Al2O3 composite oxides supported Ni based catalysts for CO2 reforming of CH4: Effects of basic modifier and mesopore structure. Int. J. Hydrogen Energy 2013, 38, 7307-7325. (55) Xu, L. L.; Song, H. L.; Chou L. J. Mesoporous nanocrystalline ceria-zirconia solid solutions supported nickel based catalysts for CO2 reforming of CH4. Int. J. Hydrogen Energy 2012, 37, 18001-18020. (56) Quek, X. Y.; Liu, D.; Cheo, W. N. E.; Wang, H.; Chen, Y.; Yang, Y. Nickel grafted TUD1 mesoporous catalysts for carbon dioxide reforming of methane. Appl. Catal. B Environ. 2010, 95, 374-382. (57) Chen, Y.; Guo, Z.; Chen, T.; Yang, Y. Surface-functionalized TUD-1 mesoporous molecular sieve supported palladium for solvent-free aerobic oxidation of benzyl alcohol. J. Catal. 2010, 275, 11-24. (58) Tsyganok, A. I.; Tsunoda, T.; Hamakawa, S.; Suzuki, K.; Takehira, K.; Hayakawa, T. Dry reforming of methane over catalysts derived from nickel-containing Mg-Al layered double hydroxides. J. Catal. 2003, 213, 191-203. (59) Perezlopez, O. W.; Senger, A.; Marcilio, N. R.; Lansarin, M. A. Effect of composition and thermal pretreatment on properties of Ni Mg Al catalysts for CO2 reforming of methane. Appl. Catal. A Gen. 2006, 303, 234-244. (60) Liu, B. S.; Au, C. T. Carbon deposition and catalyst stability over La2NiO4/γ-Al2O3 during CO2 reforming of methane to syngas. Appl. Catal. A Gen. 2003, 244, 181-195. (61) Xie, T.; Zhao, X.; Zhang, J.; Shi, L.; Zhang, D. Ni nano-particles immobilized Ce28


Page 29 of 30

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


modified mesoporous silica via a novel sublimation deposition strategy for catalytic reforming of methane with carbon dioxide. Int. J. Hydrogen Energy 2015, 40, 9685-9695. (62) Touahra, F.; Rabahi, A.; Chebout. R.; Boudjemaa,A.; Lerari, D.; Sehailia, M.; Bachari, K. Enhanced catalytic behaviour of surface dispersed nickel on LaCuO3 perovskite in the production of syngas: an expedient approach to carbon resistance during CO2 reforming of methane. Int. J. Hydrogen Energy 2016, 41, 2477-2486. (63) Therdthianwong, S.; Siangchin, C.; Therdthianwong, A. Improvement of coke resistance of Ni/Al2O3 catalyst in CH4/CO2 reforming by ZrO2 addition. Fuel Process Technol. 2008, 89, 160-168.

29



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

Graphical Abstract

Table of Contents (TOC) Graphic

30


Page 30 of 30

CO2 Dry Reforming Reaction over

Recommend Documents