Effect of ethylamines on the hydrogenation of toluene over supported

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Kinetics, Catalysis, and Reaction Engineering

Effect of ethylamines on the hydrogenation of toluene over supported nickel catalysts Jingxuan Cai, Li Zuo, Chang Hao, Yuchuan Fu, and Jianyi Shen Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b02565 • Publication Date (Web): 22 Oct 2018 Downloaded from http://pubs.acs.org on October 23, 2018

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Industrial & Engineering Chemistry Research

Effect of ethylamines on the hydrogenation of toluene over supported nickel catalysts Jingxuan Cai, Li Zuo, Chang Hao, Yuchuan Fu, Jianyi Shen* Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China

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ABSTRACT: Highly loaded and dispersed catalysts 60%Ni/Al2O3, 60%Ni/MgO and 60%Ni/MgAlO were used to study the effect of monoethylamine (MEA), diethylamine (DEA) and triethylamine (TEA) on the hydrogenation of toluene. It was found that the heats and coverages for the adsorption of toluene and hydrogen decreased greatly after the pre-adsorption of an ethylamine and thus the existence of ethylamines inhibited significantly the conversion of toluene on Ni. However, such effect was weakened over Ni supported on the basic supports (MgAlO and MgO). In addition, all the three ethylamines were strongly adsorbed on Ni, but with different coverages of MEA > DEA > TEA that was the same sequence as the effect of ethylamines on the hydrogenation of toluene. Particularly, the Ni/MgAlO was the most active among the catalysts studied for the hydrogenation of toluene with ethylamines and thus might be a good choice for the hydrogenation of aromatic rings in aromatic amines.

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1. INTRODUCTION Alicyclic amines are important intermediates in the chemical industry. 1 They are widely used for rubber ingredients, food additives, pharmacy, anticorrosion, plastic and textile. The hydrogenation of aromatic amines is the common method to synthesize alicyclic amines.1 However, the fundamental research of such reactions is not enough. Precious metal catalysts such as Pt,2-4 Pd,2, 3, 5 Ru1, 5-9 and Rh2, 10-12 were mainly studied for the reactions. Co and Ni catalysts were also reported13-16 for the reactions. Previously, we prepared three highly loaded (60%wt) and dispersed catalysts Ni/Al2O3, Ni/MgO and Ni/MgAlO displaying the different surface acidity and basicity17 and demonstrated that they were highly active for hydrogenation reactions.17-21 In this work, these catalysts were adopted to study the effect of ethylamines on the hydrogenation of toluene, i. e., the effect of amino group on the hydrogenation of aromatic rings over Ni. Aniline was not chosen as the probe molecule in this work owing to its low vapor pressure at room temperature (0.625 torr at 398 K) so that it is difficult to do the microcalorimetric adsorption. On the other hand, toluene contains an aromatic ring and ethylamines have amino groups so that the aromatic ring can be separated from the amino groups and the effects of amino groups on the adsorption of aromatic ring can be assessed. There are three ethylamines, mono- (MEA), di- (DEA) and triethylamine (TEA) that exhibit different gas phase basicities and geometrical effects. For example, the proton affinities (PA) of MEA, DEA and TEA are 921, 952 and 982 kJ/mol,22 respectively, indicating their gas phase basicities follow the order of TEA > DEA > MEA. In addition, the vapor pressures of ethylamines and toluene at room 3



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temperature are high enough for us to do the microcalorimetric adsorption so that the effects of ethylamines on the adsorption of toluene and hydrogen over the Ni catalysts were investigated. 2. EXPERIMENTAL 2.1

Catalysts

preparation.

Ni/Al2O3,

Ni/MgO

and

Ni/MgAlO

(m(Al2O3)/m(MgO)= 1:3) with the loading of about 60% (by weight) Ni as well as their supports were prepared by the co-precipitation method which has been described in detail elsewhere.21 2.2 Characterization. The X-ray diffractometer (XRD), X-ray fluorescence spectrometer (XRF), H2-O2 titration and N2 adsorption-desorption isotherms were used to characterize the samples. The procedures were also presented before.21 The H2-O2 titration was performed in a home-made volumetric apparatus. The samples were pretreated in H2 at 723 K. The H2 titration was carried out at 298 K. The O2 titration was performed at 673 K after the H2 titration and evacuation at 673 K for 1 h. The uptakes of H2 and O2 were acquired by extrapolating the coverages of corresponding isotherms to P = 0, according to which and the loading of nickel, the active nickel sites, dispersion of Ni and average particle size (= 101/dispersion of Ni (%)17) were calculated. Before these characterizations, the catalysts as well as their supports were treated in H2 for 2 h at 723 K and passivated overnight at 298 K in N2 with about 1% O2 (by volume).

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Microcalorimetric adsorption of hydrogen, toluene, and ethylamines were carried out at 308 K as described previously.18 Typically, the catalysts as well as their supports were treated and evacuated at 723 K. 2.3 Catalytic tests. The catalytic reaction was performed in a fixed-bed reactor with 10 mm inner diameter as described before.21 The samples were reduced in flowing H2 for 2 h at 723 K. The reaction solutions (10%wt toluene in n-hexane without and with 1%wt of an amine) were pumped into the reactor at the required liquid flow rates flowed downward with H2 through the packed bed. A GC SP-6890 was used to analyze the collected products, according to which the conversion of toluene was calculated. The turnover frequency (TOF) of toluene was obtained by dividing the amount of toluene molecules converted per second by the amount of surface Ni sites determined by H2 titration.

3. RESULTS AND DISCUSSIONS 3.1 Catalytic tests. Our previous work17 showed that the surface acidic and basic properties of Ni/Al2O3, Ni/MgO and Ni/MgAlO differed from each other. The Ni/MgO possessed the comparatively strong basicity and weak acidity while the Ni/Al2O3 displayed the comparatively weak basicity and strong acidity. Both the basic and acidic sites with moderate strengths were present on the surface of Ni/MgAlO.

Figure 1 shows the effect of WHSV (weight hourly space velocity) of toluene on the conversion of toluene at 423 K and 4 MPa. The only product was methylcyclohexane. All the catalysts were highly active without an ethylamine. For example, at the WHSV of 12 h-1, the conversion of toluene remained nearly 100% on 5



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the Ni/MgO, though it was less active than the other two catalysts. The conversion of toluene maintained 100% over the Ni/Al2O3 until WHSV higher than 50 h-1. The conversion of toluene decreased remarkably after the introduction of an ethylamine. The data are summarized in Table 1. The effect of ethylamines followed the order of MEA > DEA > TEA over all the catalysts. It is worth to note that among the catalysts studied the Ni/MgAlO displayed the highest activity for the hydrogenation of toluene with ethylamines. The conversion of toluene still remained at 90% with WHSV of 2 h-1 over the Ni/MgAlO even with MEA, indicating that the Ni/MgAlO could be a good choice for the hydrogenation of aromatic amines to alicyclic amines.

We also evaluated the TOF of toluene over the Ni catalysts, as shown in Figure 1. With the increase of WHSV, the TOF increased until a constant value was reached which represented the average activity of an active Ni atom of the corresponding catalyst. The TOF values were 0.11, 0.05 and 0.07 s-1 over the Ni/Al2O3, Ni/MgO and Ni/MgAlO, respectively, at 4 MPa and 423 K without an ethylamine. It is clear that the basic supports inhibited while the acidic support promoted the activity of Ni for the reaction.17 The introduction of ethylamines greatly decreased the TOF of toluene over the catalysts, implying that the hydrogenation of aromatic rings in aromatic amines must be much more difficult than that of toluene over Ni. The data given in Table 2 showed the following trends: (1) the inhibition effect of ethylamines on the TOF of converted toluene followed the order of MEA > DEA >> TEA over the catalysts, and (2) the catalysts affected by each ethylamine followed the order of Ni/Al2O3 > Ni/MgAlO > Ni/MgO. Thus, among ethylamines, MEA exhibited the 6


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strongest while TEA the lowest inhibition effect on the hydrogenation of toluene, and Ni atoms on the basic supports were less affected by ethylamines for the hydrogenation of aromatic rings. 3.2 Physical properties. All samples have been characterized previously.21 The Ni loadings in the reduced catalysts were 61, 64 and 63% by weight in the Ni/Al2O3, Ni/MgO and Ni/MgAlO, respectively, as measured by XRF, close to the values desired. The Ni/Al2O3, Ni/MgO and Ni/MgAlO possessed the surface areas of 341, 162 and 247 m2/g with the H2 uptakes of 764, 619 and 962 µmol/g, corresponding to the Ni dispersions of 22.5, 16.1 and 24.2 % with the average particle sizes of 4.5, 6.3 and 4.2 nm, respectively. It is seen that the nickel particles were highly dispersed and small in the catalysts, and the Ni/MgAlO displayed significantly higher density of active Ni sites than the Ni/Al2O3 and Ni/MgO. XRD patterns of the Ni/MgAlO before and after the hydrogenation reactions are shown in Figure 2. It is seen that ethylamines did not affect the metallic Ni phase and particle sizes in the catalysts during the short time we performed the reactions. The same XRD results were obtained (but not presented) for the Ni/MgO and Ni/Al2O3.

3.3 Microcalorimetric adsorption. Figures 3 and 4 show the results of microcalorimetric adsorption of ethylamines on the catalysts as well as on the supports. It is seen that the catalysts exhibited significantly higher heats than the corresponding supports for the adsorption of ethylamines, implying the significantly stronger interactions of ethylamines with Ni than with the supports. Table 3 summarizes the coverages and initial heats for the adsorption of ethylamines over the 7



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catalysts, from which we see the following trends: (1) the initial heat for the adsorption of ethylamines on each catalyst followed the order of TEA > DEA > MEA, (2) the coverage for the adsorption of ethylamines on each catalyst followed the order of MEA > DEA > TEA, and (3) both the coverage and initial heat for the adsorption of each ethylamine on the catalysts followed the order of Ni/MgO < Ni/MgAlO < Ni/Al2O3. It is clear that ethylamines as electron donors (from their N atoms) were more strongly adsorbed on the electron-deficient Ni atoms on the acidic support (Al2O3) than on the electron-enriched Ni atoms on the basic supports (MgAlO and MgO).17 This might be the reason why the Ni/MgO was lest affected by ethylamines in the catalysts studied for the hydrogenation of toluene. In addition, among ethylamines, the adsorption of TEA generated the highest heat owing to its strongest electron donating trend. On the other hand, MEA was also strongly adsorbed on Ni sites and owing to its small size it occupied more surface Ni atoms so that it affected more than DEA and TEA for the hydrogenation of toluene over the Ni catalysts. It should be pointed out that each ethylamine was adsorbed monolayerly on the catalysts according to our analysis of adsorption isotherms by Sips equation23. Figure 5 displays the effects of pre-adsorption of ethylamines on the adsorption of toluene over the catalysts. Table 4 summarizes the data. It is seen that the initial heats for the adsorption of toluene were 174, 162 and 140 kJ/mol, respectively, on the clean Ni/Al2O3, Ni/MgAlO and Ni/MgO, demonstrating that surface acidity promoted the adsorption of toluene on Ni. The initial heats for the adsorption of toluene on the catalysts were reduced remarkably after the pre-adsorption of ethylamines. This must

8


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be the main reason why ethylamines greatly inhibited the activity of Ni catalysts for the hydrogenation of toluene. Figure 6 shows the effects of pre-adsorption of ethylamines on the adsorption of H2 over the catalysts. The data were also given in Table 4. The initial heats for the adsorption of H2 were 87, 84 and 85 kJ/mol18 on the clean Ni/Al2O3, Ni/MgO and Ni/MgAlO, respectively. The initial heats for the adsorption of H2 on the catalysts were significantly reduced after the pre-adsorption of ethylamines, though less than that of toluene. Since it has been reported that the weakly adsorbed H atoms might be more active than the strongly adsorbed ones, 24 we speculate that the adsorption and activation of toluene must be more important than that of H2 for the hydrogenation of toluene over Ni. It is also seen from Table 4 that the initial heats for the adsorption of toluene and H2 following the pre-adsorption of ethylamines were higher on the Ni/MgAlO than on the Ni/Al2O3 and Ni/MgO, which might be attributed to its extremely high density of active Ni sites and quite strong surface basicity. This must be the important reason why the Ni/Al2O3 and Ni/MgO was less active than the Ni/MgAlO for the hydrogenation of toluene with the presence of ethylamines. According to the above results, we illustrate the competitive adsorption of ethylamines, toluene and H2 on the Ni catalysts schematically in Scheme 1. Although TEA is highly basic, its molecules could not occupy all the surface Ni atoms due to its steric hindrance of three ethyl groups. Thus, toluene and H could be still adsorbed on Ni atoms adjacent to the one with an adsorbed TEA. On the other hand, MEA molecules were also strongly adsorbed on Ni sites and could cover more surface Ni

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atoms than DEA and TEA, leading to the stronger inhibition effect than DEA and TEA for the hydrogenation of toluene over the supported nickel catalysts. 4. CONCLUSIONS

The pre-adsorption of ethylamines significantly reduced the heats and coverages of toluene and hydrogen on nickel, leading to the significantly decreased activity of Ni for the hydrogenation of toluene with the presence of ethylamines.

In addition, the heat and coverage for the adsorption of toluene decreased much more than those of H2 upon the pre-adsorption of ethylamines, indicating that the adsorption and activation of toluene must be more important than that of H2 for the hydrogenation of toluene. In fact, it was evidenced that the weakly adsorbed H atoms were more active than the strongly adsorbed ones.24

Moreover, the decreases of coverages and heats for the adsorption of toluene and H2 were less upon the pre-adsorption of ethylamines over Ni supported on the basic supports, implying that basic supports must be more favorable for the hydrogenation of aromatic rings in aromatic amines over Ni.

All three ethylamines were strongly adsorbed on Ni, in which TEA exhibited the highest initial heat while MEA the highest coverage. The inhibition effect of ethylamines on the hydrogenation of toluene over Ni followed the order of MEA > DEA > TEA, revealing that MEA occupied more surface Ni sites so that it affected more than DEA and TEA for the hydrogenation of toluene over Ni.

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The Ni/MgAlO displayed the quite strong surface basicity and extremely high density of surface active Ni sites and thus it exhibited the highest activity among the catalysts studied for the hydrogenation of toluene over Ni with the presence of ethylamines. Hence, the Ni/MgAlO will be tried for the hydrogenation of aromatic rings in aromatic amines in our future work.

AUTHOR INFORMATION

Corresponding author. * Tel.: +86 25 89684305; E-mail address: [email protected]

ACKNOWLEDGEMENTS

We acknowledge the financial supports from the NSFC-DFG (21761132006), NSFC (21773108) and fundamental research funds for central universities.

REFERENCE

(1) Tomkins, P.; Müller, T. E. Enhanced selectivity in the hydrogenation of anilines to cyclo-aliphatic

primary

amines

over

lithium-modified

Ru/CNT

catalysts.

ChemCatChem 2018, 10, 1438. (2) Chatterjee, M.; Sato, M.; Kawanami, H.; Ishizaka, T.; Yokoyama, T; Suzuki T. Hydrogenation of aniline to cyclohexylamine in supercritical carbon dioxide: Significance of phase behaviour. Appl. Catal. A-Gen. 2011, 396, 186. (3) Greco, N. P. Hydrogenation of phenylprimary amines to cyclohexyl amines. US 3520928, 1970. (4) Greenfield, H. Hydrogenation of aniline to cyclohexylamine with platinum metal catalysts. J. Org. Chem. 1964, 29, 3082. (5) Otto, I.; Hans-Helmut, S. Ruthenium catalyst, process for its preparation and process for the preparation of a mixture of cyclohexylamine and dicyclohexylamine using the ruthenium catalyst. US 4952549, 1990.

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(6) Otto, I.; Hans-Helmut, S.; Reinhard, T. Supported ruthenium catalyst, its preparation and its use in the preparation of cyclohexyl amine and dicyclohexyl amine, substituted or not. EP 0324983, 1988. (7) Brake, L. D.; Stiles, A. B. Catalytic hydrogenation of nitrogen containing compounds over supported ruthenium catalysts. US 3644522, 1972. (8) Kim., H. S.; Seo, S. H.; Lee, H.; Lee, S. D.; Kwon, Y. S.; Lee, I. M. Ru-catalyzed hydrogenation of aromatic diamines: The effect of alkali metal salts. J. Mol. Catal. A-Chem. 1998, 132, 267. (9) Otto, I.; Gerhard, D.; Helmut, W.; Gerd-Michael, P. Process for the preparation of a mixture of cyclohexylamine and dicyclohexylamine using a supported noble metal catalyst. US 5322965, 1994. (10) Jenkins R. J.; Treskot R. A.; Vedage G. A.; White J. F. Hydrogenation of aromatic amines using rhodium on titania or zirconia support. US 5026914, 1991. (11) Amey, R. L. 1, 2-Diaminocyclohexane and chemical process. US 20100125151 A1, 2010. (12) Vedage, G. A. Hydrogenation of meta-toluenediamine. EP 0645367, 1994. (13) Narayanan, S.; Unnikrishnan, R. P. Comparison of hydrogen adsorption and aniline hydrogenation over co-precipitated Co/Al2O3 and Ni/Al2O3 catalysts. JCS Faraday Trans. 1997, 93, 2009. (14) Mink, G.; Horváth, L. Hydrogenation of aniline to cyclohexylamine on NaOH-promoted or lanthana supported nickel. React. Kinet. Catal. Lett. 1998, 65, 59. (15) Gray, T. J.; Masse, N. G.; Hagstrom, R. A. Raney nickel catalysis of aromatic amines. US 4503251, 1985. (16) Gerhard, D.; Wilfried, N.; Gerd-Michael, P. Process for the preparation of a mixture of cyclohexylamine and dicyclohexylamine. EP 0790232, 1997. (17) Hu, S.; Xue, M.; Chen, H.; Shen, J. The effect of surface acidic and basic properties on the hydrogenation of aromatic rings over the supported nickel catalysts. Chem. Eng. J. 2010, 162, 371. (18) Zhao, J.; Chen, H.; Xu, J.; Shen, J. Effect of surface acidic and basic properties of the supported nickel catalysts on the hydrogenation of pyridine to piperidine. J. Phys. Chem. C 2013, 117, 10573. (19) Zhao, J.; Xue, M.; Huang, Y.; Shen, J. Hydrogenation of dioctyl phthalate over supported Ni catalysts. Catal. Commun. 2011, 16, 30. 12


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(20) Chen, H.; Xue, M.; Hu., S.; Shen, J. The effect of surface acidic and basic properties on the hydrogenation of lauronitrile over the supported nickel catalysts. Chem. Eng. J. 2012, 181-182, 677. (21) Cai, J.; Zhu, J.; Zuo, L.; Fu, Y.; Shen, J. Effect of surface acidity/basicity on the selective hydrogenation of maleic anhydride to succinic anhydride over supported nickel catalysts. Catal. Commun. 2018, 110, 93. (22) Hunter, E. P. L.; Lias, S. G. Evaluated gas phase basicities and proton affinities of molecules: an update. J. Phys. Chem. Ref. Data 1998, 27, 413. (23) Damjanović, L.; Rakić, V.; Rac, V.; Stošić, D.; Auroux, A. The investigation of phenol removal from aqueous solutions by zeolites as solid adsorbents. J. Hazard. Mater., 2010, 184, 477. (24) Deng, L.; Zhu, J.; Chen, H.; Wang, H.; Shen, J. Microcalorimetric adsorption and infrared spectroscopic studies of supported nickel catalysts for the hydrogenation of diisopropylimine to diisopropylamine. J. Catal. 2018, 362, 35.

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TABLES Table 1 Conversion of toluene over the catalysts with and without an ethylamine (reaction conditions: P= 4 MPa, T= 423 K, n (H2)/n (toluene)= 5 and WHSV= 20 h-1). Catalysts

Ni/Al2O3

Ni/MgAlO

Ni/MgO

Without an ethylamine

99.6%

99.2%

86.5%

With 1%MEAa

6.3%

11%

8.2%

(Decrease (%))

(94%)

(89%)

(91%)

With 1%DEA

15.8%

25.3%

12.3%

(Decrease (%))

(84%)

(74%)

(86%)

With 1%TEA

85.7%

96.6%

48.2%

(Decrease (%))

(14%)

(3%)

(44%)

With 1.63%DEAa

7.8%

12.2%

(Decrease (%))

(92%)

(88%)

With 2.25%TEAa

36.8%

55.1%

(Decrease (%))

(63%)

(44%)

a

Note: With same moles (0.033 mol/L) of ethylamines.

14


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Table 2 TOF values (s-1) over the catalysts with and without an ethylamine. (reaction conditions: P= 4 MPa, T= 423 K, and n (H2)/n (toluene)= 5). Catalysts

Ni/Al2O3

Ni/MgAlO

Ni/MgO

Without ethylamines

0.11

0.07

0.05

With 1%MEAa

0.0025

0.003

0.004

(Decrease (%))

(98%)

(96%)

(92%)

With 1%DEA

0.0063

0.0077

0.006

(Decrease (%))

(94%)

(89%)

(88%)

With 1%TEA

0.033

0.03

0.024

(Decrease (%))

(70%)

(57%)

(52%)

With 1.63%DEAa

0.003

0.004

(Decrease (%))

(97%)

(94%)

With 2.25%TEAa

0.015

0.023

(Decrease (%))

(86%)

(67%)

a

Note: With the same moles (0.033 mol/L) of ethylamines.

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Table 3 Coverages and initial heats for the adsorption of ethylamines over the catalysts. Ethylamine Ni/Al2O3 Ni/MgAlO

Ni/MgO

MEA

DEA

TEA

Heat (kJ/mol)

134

172

187

Coverage (µmol/g)

1387

1112

924

Heat (kJ/mol)

122

145

177

Coverage (µmol/g)

1074

826

664

Heat (kJ/mol)

99

106

122

Coverage (µmol/g)

772

540

463

Table 4 Initial heats for the adsorption of toluene and H2 (kJ/mol) over the catalysts without and with the pre-adsorption of ethylamines. (Reprinted in part with permission from [Zhao, J.; Chen, H.; Xu, J.; Shen, J. Effect of surface acidic and basic properties of the supported nickel catalysts on the hydrogenation of pyridine to piperidine. J. Phys. Chem. C 2013, 117, 10573.]. Copyright [2013] American Chemical Society) Catalyst

Adsorbate

Without an

MEA

DEA

TEA

174

59

64

66

162

65

68

77

Ni/MgO

140

48

54

59

Ni/Al2O3

8718

56

57

65

8518

58

63

75

8418

39

43

53

Ni/Al2O3 Ni/MgAlO

Ni/MgAlO Ni/MgO

Toluene

H2

ethylamine

16


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FIGURE CAPTIONS

Figure 1. Conversion and TOF of toluene versus WHSV (toluene) on the catalysts (a) Ni/Al2O3, (b) Ni/MgAlO and (c) Ni/MgO reduced at 723 K in H2. Reaction conditions: mcat = 0.2 g, P = 4 MPa, T = 423 K and n (H2)/n (toluene) = 5. Figure 2. XRD patterns of the Ni/MgAlO reduced at 723 K in H2 before (a) and after the reaction without an ethylamine (b) as well as after the reaction with MEA (c), DEA (d) and TEA (e). Figure 3. Differential heat versus coverage for the adsorption of ethylamines at 308 K on the (a) Ni/Al2O3, (b) Ni/MgAlO and (c) Ni/MgO reduced at 723 K in H2. Figure 4. Differential heat versus coverage for the adsorption of ethylamines at 308 K on the (a) Al2O3, (b) MgAlO and (c) MgO treated at 723 K in H2. Figure 5. Differential heat versus coverage for the adsorption of toluene at 308 K on the (a) Ni/Al2O3, (b) Ni/MgAlO and (c) Ni/MgO reduced at 723 K in H2 before and after the pre-adsorption of ethylamines at 308 K. Figure 6. Differential heat versus coverage for the adsorption of H2 at 308 K on the (a) Ni/Al2O3, (b) Ni/MgAlO and (c) Ni/MgO reduced at 723 K in H2 before18 and after the pre-adsorption of ethylamines at 308 K. (Reprinted in part with permission from [Zhao, J.; Chen, H.; Xu, J.; Shen, J. Effect of surface acidic and basic properties of the supported nickel catalysts on the hydrogenation of pyridine to piperidine. J. Phys. Chem. C 2013, 117, 10573.]. Copyright [2013] American Chemical Society)

17



FIGURES

-1

Conversion of toluene (%)

(a)

80

TOF of toluene (s )

0.12

100

Conversion of toluene

0.08

with TEA

60

with DEA with MEA without an ethylamine

40

0.04

TOF of toluene with TEA

20


0.00

0 0

10

20

30 40 50 WHSV (h-1)

60

70

80

0.06 Conversion of toluene with TEA

60

with DEA

0.04

with MEA

40

without an ethylamine TOF of toluene

0.02

with TEA

20

-1


(b)

80

TOF of toluene (s )

0.08

100


0 0

10

20

30 40 -1 WHSV (h )

50

60

0.00

70

0.06

100

(c) 80 0.04

Conversion of toluene

60

with TEA with DEA with MEA

40


0.02

with TEA

20

TOF of toluene (s-1)


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 25


0 0

5

10

15 20 25 -1 WHSV (h )

30

35

0.00 40

Figure 1

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


■ -Ni

▼ -MgO

▼■

Intensity (a. u.)

Page 19 of 25

▼

(e)

▼■ ▼

(d)

▼■

(c)

▼

(b)

▼

(a)

▼

15

▼■ ▼■

30

■

▼

■

■

▼

■

■

▼

■

■

▼

■

■

▼

■

45

60

75

2 θ (°)

Figure 2

19



Differential heat (kJ/mol)

200 160

TEA DEA MEA

120 80 40

(a)

0 0

200

400 600 800 1000 1200 1400 Coverage (µmol/g)


180 TEA DEA MEA

150 120 90 60

(b)

30 0 0

200

400 600 800 Coverage (µmol/g)

1000

1200

120 Differential heat (kJ/mol)

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 25

TEA DEA MEA

80

40

(c) 0 0

200

400 600 Coverage (µmol/g)

800

Figure 3

20


120 TEA DEA MEA

80

40

(a) 0 0

200 400 600 800 1000 1200 1400 1600 1800 Coverage (µmol/g)


120 TEA DEA MEA

80

40

(b) 0 0


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 21 of 25

200

400 600 800 1000 Coverage (µmol/g)

80

1200

TEA DEA MEA

40

(c) 0 0

100 200 300 400 500 600 700 800 900 Coverage (µmol/g)

Figure 4

21


160

(a)

Page 22 of 25

with TEA with DEA with MEA without an ethylamine

120 80 40 0 0

200


160

(b) 120

400 600 800 1000 Coverage (µmol/g)

1200


80

40

0 0


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



200

(c)

120

400 600 800 1000 1200 1400 Coverage (µmol/g)


80

40

0 0

200


1000

1200

Figure 5

22




80 60 40

(a)

20

0

100

200

300 400 500 600 Coverage (µmol/g)


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


700

800


80 60 40

(b)

20 0 0

100

200

300 400 500 600 Coverage (µmol/g)


Page 23 of 25

700

800


60

30

(c) 0 0

100


500

Figure 6

23



Page 24 of 25

SCHEMES

Scheme 1. Schematic expression of co-adsorbed toluene, H, MEA and TEA on the Ni surfaces.

24


Page 25 of 25


120

Toluene adsorption on Ni/MgAlO 80

40

0 0

200

400 600 800 1000 1200 1400 Coverage (µmol/g)

0.08

100 80

0.06 Conversion of toluene with TEA

60

with DEA

0.04

with MEA

40


0.02

with TEA

20


0 0

10

20

30 40 WHSV (h-1)

50

60

0.00

70

25


TOF of toluene on Ni/MgAlO (s-1)

160

Conversion of toluene on Ni/MgAlO (%)

For Table of Contents Only


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Effect of ethylamines on the hydrogenation of toluene over supported

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