Effect of Support Acidity on Liquid-Phase Hydrogenation of Benzene

Article pubs.acs.org/IECR

Effect of Support Acidity on Liquid-Phase Hydrogenation of Benzene to Cyclohexene over Ru−B/ZrO2 Catalysts Gongbing Zhou,† Jianliang Liu,† Xiaohe Tan,† Yan Pei,† Minghua Qiao,*,† Kangnian Fan,† and Baoning Zong*,‡ †

Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, People’s Republic of China ‡ The State Key Laboratory of Catalytic Materials and Reaction Engineering, Research Institute of Petroleum Processing, Beijing 100083, People’s Republic of China ABSTRACT: Ru−B/ZrO2 catalysts using monoclinic, amorphous, and tetragonal ZrO2 as supports were prepared and used for liquid-phase hydrogenation of benzene to cyclohexene. It is identified that both the Lewis acid sites and the Brønsted acid sites existed on monoclinic ZrO2 (ZrO2-M), while there were only Lewis acid sites on amorphous (ZrO2-A) and tetragonal ZrO2 (ZrO2-T). The amount of acid sites on ZrO2-T was the lowest. In liquid-phase hydrogenation of benzene to cyclohexene, the Ru−B/ZrO2-T catalyst exhibited the highest selectivity and yield of cyclohexene, with the maximum yield of cyclohexene being 47%. These results suggest that for ZrO2-supported Ru−B catalysts, the lower was the amount of acid sites on ZrO2, the higher was the selectivity to cyclohexene. Also, the presence of the Brønsted acid sites on ZrO2 is probably adverse to the selectivity toward cyclohexene.

■

INTRODUCTION Partial hydrogenation of benzene to cyclohexene has attracted much attention, because cyclohexene has wide applications in organic synthesis as the intermediate of adipic acid, nylon-6, nylon-66, polyamides, polyesters, and other fine chemicals.1 However, it is difficult to acquire a high yield of cyclohexene through this route, as the standard free energy change for cyclohexene formation from benzene hydrogenation is −23 kJ mol−1, while that for cyclohexane formation is −98 kJ mol−1. This is the reason that only cyclohexane was obtained in the hydrogenation of benzene for a long time.2 Catalytic hydrogenation of benzene to cyclohexene has been carried out in gas3 or liquid phase.4 The main advantage of the liquid-phase reaction is that it is accessible to a much higher selectivity to cyclohexene at a high conversion level of benzene.4 Among the various metals screened, Ru is the most selective, especially when in combination with ZnSO4 and other inorganic reaction modifiers such as NaOH5,6 and CdSO4.7 The properties of the support can exert a significant impact on the catalytic performance of the Ru catalyst, because the reducibility and dispersity of Ru are influenced by the interaction between the support and the metal.8 Many oxides, such as SBA-15,7 SiO2,9,10 Al2O3,11 AlOOH,12 ZrO2,13,14 bentonite,15 and ZnO-containing binary oxides,16−18 have been employed as supports for Ru, among which ZrO2 is the most effective. For instance, Wang et al. prepared a Ru−Zn/mZrO2 nanocomposite catalyst by coprecipitation of RuCl3 and ZrOCl2 with ammonia followed by reduction in an ZnSO4 aqueous solution and obtained a cyclohexene yield of 43.4%.13 Liu et al. performed the reaction with a Ru−La−B/ZrO2 catalyst and found that the selectivity to cyclohexene could amount to 66% at the conversion of 81% by further adding ZrO2 as the disperser and by finely tuning the acidity of the aqueous phase.14 However, to the best of our knowledge, the © 2012 American Chemical Society

function of the ZrO2 support in partial hydrogenation of benzene has not been explored, and hence scientific studies elucidating the support effects are desired. There are numerous examples showing that the surface acidic properties of the supports play important roles in determining the catalytic performance by affecting the adsorption and desorption behaviors of the reactants and products. For example, Venezia et al. found that the activities for toluene hydrogenation and dibenzothiophene hydrodesulfurization on Au−Pd/SiO2−Al2O3 catalysts increased with the concentration of the medium-strength acid sites on the support.19 This result is consistent with that of Grzechowiak et al., who found that the activity for toluene hydrogenation over the Ni/SiO2−TiO2 catalyst increased with the total number of weak- and medium-strength acid sites of the support.20 Chupin et al. reported that Pt and Pd supported on HFAU zeolite were more active for toluene hydrogenation than on Al2O3, because toluene molecules adsorbed on the acid sites of HFAU were easily hydrogenated by hydrogen spilled over from the metal sites.21 Yasuda et al. studied the acidity effect on the hydrogenation of aromatics over Pd−Pt/USY catalysts by varying the SiO2/Al2O3 ratio.22 The activity and the sulfur tolerance of the Pd−Pt/USY catalysts both decreased when increasing the SiO2/Al2O3 ratio, which was attributed to the decrease of the amount of electron-deficient Pd−Pt resulting from the decrease in the Lewis acidity of the supports. ZrO2 was claimed to display four polymorphs, monoclinic (m), amorphous (a), tetragonal (t), and cubic (c),23 which have different surface acidic features. Unlike m-ZrO2 on which both Received: Revised: Accepted: Published: 12205

May 17, 2012 July 30, 2012 August 29, 2012 September 11, 2012 dx.doi.org/10.1021/ie301302x | Ind. Eng. Chem. Res. 2012, 51, 12205−12213

Industrial & Engineering Chemistry Research

Article

The black precipitates were washed thoroughly with deionized water. The obtained catalysts were denoted as Ru−B/ZrO2-M, Ru−B/ZrO2-A, and Ru−B/ZrO2-T depending on the crystallographic form of the ZrO2 employed. The Ru loading on these catalysts was ca. 8.0 wt % relative to ZrO2, and the atomic ratio of Ru to B in Ru−B is ca. 85: 15 as determined by inductively coupled plasma-atomic emission spectroscopy. Characterization. N2 physisorption was performed on a Micromeritics TriStar3000 apparatus at 77 K. Before measurement, the sample was transferred to the adsorption glass tube and heated at 423 K under N2 for 2 h. The pore size distribution was calculated from the desorption branch of the isotherm by the Barrett−Joyner−Halenda (BJH) algorithm. Powder X-ray diffraction patterns (XRD) were acquired on a Bruker AXS D8 Advance X-ray diffractometer using Ni-filtered Cu Kα radiation (λ = 0.15418 nm). The tube voltage was 40 kV, and the current was 40 mA. The 2θ angles were scanned from 10° to 70° at a speed of 2° min−1. The surface morphology and particle size were observed by transmission electron microscopy (TEM) (JEOL JEM2011) operating at 200 kV. Particle size distribution histograms were constructed by measuring at least 300 nanoparticles. X-ray photoelectron spectroscopy (XPS) was performed on a Perkin-Elmer PHI5000C instrument with Mg Kα radiation as the excitation source (hν = 1253.6 eV). The catalyst, protected by ethanol, was mounted on the sample plate, degassed in the pretreatment chamber at 393 K for 4 h in vacuo, and then transferred to the analyzing chamber where the background pressure was ZrO2-A > ZrO2-T (Table 2). Figure 4 shows the NH3-TPD profiles of the ZrO2 samples. ZrO2-M exhibited three desorption peaks at 444, 575, and 805 K. ZrO2-A also exhibited three peaks, but at 596, 897, and 980 K. Only an ill-defined broad peak can be seen with the peak maximum at about 422 K for ZrO2-T. The total amounts of the acid sites on the ZrO2 samples are displayed in Figure 5, which decrease in the order of ZrO2-M > ZrO2-A > ZrO2-T,

Figure 4. NH3-TPD profiles of (a) ZrO2-M, (b) ZrO2-A, and (c) ZrO2-T.

qualitatively consistent with the tendency of the total integral band intensities revealed by Py-IR (Table 2).

Figure 5. Total amount of acid sites on ZrO2-M, ZrO2-A, and ZrO2-T determined by NH3-TPD.

Taking into account of the results presented in Table 2 and Figures 2−5, it is clear that ZrO2-M, ZrO2-A, and ZrO2-T differ in the types of the acid sites, the amount of each type of acid site, and the total amount of acid sites. Such distinct differences in acidic property may exert a significant influence on the catalytic performance of the Ru−B/ZrO2 catalysts derived from 12208

dx.doi.org/10.1021/ie301302x | Ind. Eng. Chem. Res. 2012, 51, 12205−12213


Article

these supports in liquid-phase hydrogenation of benzene to cyclohexene. The textural properties of the Ru−B/ZrO2-M, Ru−B/ZrO2A, and Ru−B/ZrO2-T catalysts are summarized in Table 1. As compared to their corresponding ZrO2 supports, the Ru−B/ ZrO2 catalysts showed reduced specific surface areas and pore volumes, and increased average pore diameters, suggesting the incorporation of some Ru−B particles into the small pores. Table 1 also shows that the active surface area (SRu) and dispersion are the highest for the Ru−B/ZrO2-M catalyst, while they are the lowest for the Ru−B/ZrO2-A catalyst. Figure 6 reveals that the crystallographic forms of the supports were retained after the loading of Ru−B, although

Figure 6. XRD patterns of (a) Ru−B/ZrO2-M, (b) Ru−B/ZrO2-A, and (c) Ru−B/ZrO2-T catalysts.

their intensities were attenuated to some extent. Furthermore, the diffractograms of the Ru−B/ZrO2 catalysts only contain the features of the supports, signifying the high dispersion of the amorphous Ru−B particles,40 which is directly confirmed by TEM. In the TEM images of the Ru−B/ZrO2-M, Ru−B/ZrO2A, and Ru−B/ZrO2-T catalysts (Figure 7), the Ru−B particles (marked by white arrows in Figure 7a−c) have narrow particle size distributions in the range of 1−4 nm. The average particle sizes of Ru−B are 2.1, 2.5, and 2.3 nm for Ru−B/ZrO2-M, Ru− B/ZrO2-A, and Ru−B/ZrO2-T, respectively, which are below the detection limit of the XRD technique. However, for the Ru−B/ZrO2-A catalyst, agglomeration of the Ru−B nanoparticles is observed, as highlighted by the circles drawn in Figure 7b, which explains its lowest SRu and dispersion in Table 1 derived from H2-TPD. Figure 8 shows the Ru 3d XPS spectra of the Ru−B/ZrO2 catalysts. Because the Ru 3d3/2 peak overlaps the C 1s peak of contaminant carbon, only the Ru 3d5/2 peak is employed to determine the chemical state of Ru. It is found that the Ru species in all three catalysts are mainly in the metallic state with the Ru 3d5/2 BE of 280.1 eV.41 In addition, the spectrum of the Ru−B/ZrO2-A catalyst is slightly broader than those of other two catalysts, which may be due to the formation of some RuO2 on the surface of the Ru−B/ZrO2-A catalyst during sample transfer. Nevertheless, the dominant Ru species on this catalyst is still metallic Ru. The surface chemical state of boron cannot be identified for these Ru−B/ZrO2 catalysts, because the B 1s peak is unfortunately totally superimposed by a broad Zr 3d5/2 feature of the supports. Catalytic Performance. The courses of the hydrogenation of benzene over these Ru−B/ZrO2 catalysts are displayed in Figure 9. Only cyclohexene and cyclohexane were detected as products under the present reaction conditions. In Figure 9, the

Figure 7. TEM images and the corresponding particle size distribution histograms of the Ru−B/ZrO2-M (a) and (d), Ru−B/ZrO2-A (b) and (e), and Ru−B/ZrO2-T (c) and (f) catalysts.

Figure 8. Ru 3d XPS spectra of (a) Ru−B/ZrO2-M, (b) Ru−B/ZrO2A, and (c) Ru−B/ZrO2-T catalysts.

12209



Article

Table 3. Results of the Hydrogenation of Benzene over the Ru−B/ZrO2-M, Ru−B/ZrO2-A, and Ru−B/ZrO2-T Catalystsa catalyst

vbenzene (mmol min−1 gcat−1)

TOF (s−1)

CBZb (%)

SHEb (%)

YHEb (%)

timeb (min)

Ru−B/ZrO2-M Ru−B/ZrO2-A Ru−B/ZrO2-T

51 19 47

4.4 4.9 4.5

72 73 83

42 53 56

30 39 47

11 30 15

a

Reaction conditions: 1.0 g of catalyst, 50 mL of benzene, 100 mL of H2O, temperature of 413 K, H2 pressure of 4.0 MPa, and CZnSO4 of 0.07 M. bValues recorded at the maximum yield of cyclohexene.

ZrO2-A catalyst in sequence. According to Table 1, it can be seen that the evolution of vbenzene is consistent with the change of SRu or dispersion. Higher SRu or dispersion means larger number of the exposed Ru atoms, thus leading to higher vbenzene, which is in line with the work by Wang et al.40 On the basis of the vbenzene and the dispersion values, the TOFs of benzene over these catalysts are calculated and listed in Table 3. It is interesting that the TOFs over all three Ru−B/ZrO2 catalysts are essentially the same, strongly suggesting that the active sites for the hydrogenation of benzene are situated on the Ru−B nanoparticles and identical in nature, as substantiated by the similar diameter and chemical state of the Ru−B nanoparticles on these catalysts shown above. As far as the close similarity of the Ru−B nanoparticles on these Ru−B/ZrO2 catalysts is concerned, it is reasonable to assume that the difference in the selectivity to cyclohexene is mainly determined by the ZrO2 supports. Researchers have evidenced that the product selectivity was influenced by the support acidity in many selective hydrogenation reactions.36,42,43 Volckmar et al. found that a high total amount of acid sites and a high amount of strong Lewis acid sites on the Ag/SiO2−Al2O3 catalysts induced a low selectivity to allyl alcohol in acrolein hydrogenation.36 Murzin and co-workers found a decrease in the selectivity to unsaturated alcohol with increasing support acidity in cinnamaldehyde hydrogenation over Pt-modified molecular sieves catalysts.42 Similar results were obtained over Ru/Al2O3 catalysts,43 inferring that the hydrogenation of the CC bond is promoted by the acid sites. Thus, it is rational to relate the selectivity patterns observed on the Ru−B/ZrO2-M, Ru−B/ZrO2-A, and Ru−B/ZrO2-T catalysts to the difference in the acidity of the ZrO2 supports. The effect of the acidic property of the support on the hydrogenation of benzene has been investigated on Pt catalysts. In general, both benzene and cyclohexene molecules can adsorb on the acid sites of the supported Pt catalysts and convert to final products by hydrogen spilled over from H2 dissociated on Pt sites.44−49 According to Ishikawa et al.,50 the spillover hydrogen also existed on the Ru/ZrO2 catalyst. FT-IR characterization revealed that when H2 (D2) was introduced to the Ru/ZrO2 catalyst, H2 (D2) dissociatively adsorbed on the Ru surface and spilled from Ru particles onto the ZrO2 support to form the H2O (D2O)-like species, which desorbs as H2 (D2) but not as H2O (D2O). Besides, Appay et al. found that on the acid sites of the Pt/ZrO2−SO4 catalyst, the hydrogenation of cyclohexene was always faster than that of benzene at various reaction temperatures,51 indicating the more facile hydrogenation of cyclohexene than benzene on acid sites. Considering the consecutive reaction mechanism of benzene hydrogenation on Ru-based catalysts52 and the virtually invariable TOFs on the Ru−B/ZrO2-M, Ru−B/ZrO2-A, and

Figure 9. Time courses of benzene hydrogenation over (a) Ru−B/ ZrO2-M, (b) Ru−B/ZrO2-A, and (c) Ru−B/ZrO2-T catalysts. Reaction conditions: 1.0 g of catalyst, 50 mL of benzene, 100 mL of H2O, temperature of 413 K, H2 pressure of 4.0 MPa, and CZnSO4 of 0.07 M. (■) Benzene, (▼) cyclohexene, and (▲) cyclohexane.

concentration of benzene decreased and the concentration of cyclohexane increased monotonically with the reaction time. For cyclohexene, there was a maximum concentration at a certain reaction time depending on the type of the Ru−B/ZrO2 catalyst. Among these catalysts, the Ru−B/ZrO2-T catalyst showed the best catalytic performance in terms of the selectivity and yield of cyclohexene. On this catalyst, the concentration of cyclohexene increased much faster than that of cyclohexane at the beginning of the reaction, and reached a maximum yield of 47% at benzene conversion of 83% at a reaction time of ca. 15 min. The yield of cyclohexene then declined gradually following the known behavior of consecutive reaction. On the Ru−B/ ZrO2-A catalyst, the maximum yield of cyclohexene was 39% at benzene conversion of 73% at a reaction time of 30 min. The Ru−B/ZrO2-M catalyst exhibited the lowest yield of cyclohexene of 30% at benzene conversion of 72%. However, the reaction proceeded so fast on this catalyst that within only 20 min benzene was completely consumed. Table 3 summarizes the catalytic results of benzene hydrogenation over these Ru−B/ZrO2 catalysts. It can be seen that the vbenzene over the Ru−B/ZrO2-M catalyst is the highest, followed by the Ru−B/ZrO2-T catalyst and the Ru−B/ 12210


Industrial & Engineering Chemistry Research Ru−B/ZrO2-T catalysts irrespective of the distinct differences in the acidic properties of the supports (Table 3), we suggest that successive hydrogenation of cyclohexene, produced by benzene hydrogenation on Ru−B nanoparticles, on the acid sites of the ZrO2 supports determines or at least strongly influences the selectivity to cyclohexene on these catalysts. Notably, Aboul-Gheit et al. observed that the hydrogenation of cyclohexene to cyclohexane was enhanced when the number of the acid sites was increased on the Pt/H-ZSM-5,53,54 Ir/HZSM-5,55 and Re/H-ZSM-5 catalysts.56 Thus, it is expected that the difference in the selectivity to cyclohexene can be observed over Ru−B catalysts supported on ZrO2 with different acidic properties, and the Ru−B/ZrO2 catalyst with the lowest amount of acid sites will exhibit the highest selectivity to cyclohexene. As can be seen from Tables 2, 3, and Figure 5, the changes in the amount of acid sites on the ZrO2 supports and the selectivity to cyclohexene over these Ru−B/ZrO2 catalysts follow an opposite trend. The amount of acid sites on the ZrO2 supports decreased in the sequence of ZrO2-M > ZrO2-A > ZrO2-T, while the selectivity to cyclohexene increased in the sequence of Ru−B/ZrO2-M < Ru−B/ZrO2-A < Ru−B/ZrO2T. It has been reported that the reactivity of cyclohexene on Brønsted acid sites or Lewis acid sites is at variance in reactions such as hydrogen transfer, isomerization, hydration, and alkylation, and higher reactivity of cyclohexene was observed on Brønsted acid sites.57−61 Although it can be qualitatively deduced that the lower amount of the Lewis acid sites is beneficial to the higher selectivity to cyclohexene based on the catalytic results of the Ru−B/ZrO2-A and Ru−B/ZrO2-T catalysts, further work is needed to differentiate the effects of the Brønsted acid sites and the Lewis acid sites on the selectivity to cyclohexene, which may be instructive for the design of Ru catalysts with improved selectivity to cyclohexene in partial hydrogenation of benzene.

■

CONCLUSION

■

AUTHOR INFORMATION

■

ACKNOWLEDGMENTS

■

REFERENCES

Article

This work was supported by the National Basic Research Program of China (2012CB224804), the NSF of China (21073043), the Science & Technology Commission of Shanghai Municipality (10JC1401800, 08DZ2270500), the Program of New Century Excellent Talents (NCET-080126), and SINOPEC.

(1) Nagahara, H.; Konishi, M. Process for Producing Cycloolefins. European Patent 86113578.8, 1986. (2) Haretog, F.; Zwietering, P. Olefins as Intermediates in the Hydrogenation of Aromatic Hydrocarbons. J. Catal. 1963, 2, 79. (3) Dietzsch, E.; Claus, P.; Hönicke, D. The Partial Gas-Phase Hydrogenation of Benzene to Cyclohexene on Supported and Coated Ruthenium Catalysts. Top. Catal. 2000, 10, 99. (4) Domínguez-Quintero, O.; Martínez, S.; Henríquez, Y.; D’Ornelas, L.; Krentzien, H.; Osuna, J. Silica-Supported Palladium Nanoparticles Show Remarkable Hydrogenation Catalytic Activity. J. Mol. Catal. A: Chem. 2003, 197, 185. (5) Liu, H. Z.; Liang, S. G.; Wang, W. T.; Jiang, T.; Han, B. X. The Partial Hydrogenation of Benzene to Cyclohexene over Ru−Cu Catalyst Supported on ZnO. J. Mol. Catal. A: Chem. 2011, 341, 35. (6) Hu, S. C.; Chen, Y. W. Effect of Preparation on Ru-Zn Ultrafine Catalysts in Partial Hydrogenation of Benzene. Ind. Eng. Chem. Res. 2001, 40, 3127. (7) Liu, J. L.; Zhu, Y.; Liu, J.; Pei, Y.; Li, Z. H.; Li, H.; Li, H. X.; Qiao, M. H.; Fan, K. N. Discrimination of the Roles of CdSO4 and ZnSO4 in Liquid Phase Hydrogenation of Benzene to Cyclohexene. J. Catal. 2009, 268, 100. (8) Ronchin, L.; Toniolo, L. Supported Ru Catalysts: a Study of the Influence of Supports, Promoters and Preparative Variables on the Catalytic Activity and Selectivity. React. Kinet. Catal. Lett. 2003, 78, 281. (9) Xie, S. H.; Qiao, M. H.; Li, H. X.; Wang, W. J.; Deng, J. F. A Novel Ru−B/SiO2 Amorphous Catalyst Used in Benzene-Selective Hydrogenation. Appl. Catal., A 1999, 176, 129. (10) Hu, S. C.; Chen, Y. W. Partial Hydrogenation of Benzene on Ru−Zn/SiO2 Catalysts. Ind. Eng. Chem. Res. 2001, 40, 6099. (11) Li, J.; Qiao, M. H.; Deng, J. F. Amorphous Ni−B/γ-Al2O3 Catalyst Prepared in a Modified Drying Approach and Its Excellent Activity in Benzene Hydrogenation. J. Mol. Catal. A: Chem. 2001, 169, 295. (12) Wang, J. Q.; Guo, P. J.; Qiao, M. H.; Yan, S. R.; Fan, K. N. Preparation, Characterization of Ru/AlOOH Catalyst and Its Benzene Partial Hydrogenation Behavior. Acta Chim. Sin. 2004, 62, 1765. (13) Wang, J. Q.; Wang, Y. Z.; Xie, S. H.; Qiao, M. H.; Li, H. X.; Fan, K. N. Partial Hydrogenation of Benzene to Cyclohexene on a Ru−Zn/ m-ZrO2 Nanocomposite Catalyst. Appl. Catal., A 2004, 272, 29. (14) Liu, S. C.; Liu, Z. Y.; Wang, Z.; Zhao, S. H.; Wu, Y. M. A Novel Amorphous Alloy Ru−La−B/ZrO2 Catalyst with High Activity and Selectivity for Benzene Selective Hydrogenation. Appl. Catal., A 2006, 313, 49. (15) Wang, W. T.; Liu, H. Z.; Wu, T. B.; Zhang, P.; Ding, G. D.; Liang, S. G.; Jiang, T.; Han, B. X. Ru Catalyst Supported on Bentonite for Partial Hydrogenation of Benzene to Cyclohexene. J. Mol. Catal. A: Chem. 2012, 355, 174. (16) Liu, H. Z.; Jiang, T.; Han, B. X.; Liang, S. G.; Wang, W. T.; Wu, T. B.; Yang, G. Y. Highly Selective Benzene Hydrogenation to Cyclohexene over Supported Ru Catalyst without Additives. Green Chem. 2011, 13, 1106. (17) Hu, S. C.; Chen, Y. W. Partial Hydrogenation of Benzene to Cyclohexene on Ruthenium Catalysts Supported on La2O3-ZnO Binary Oxides. Ind. Eng. Chem. Res. 1997, 36, 5153. (18) Hu, S. C.; Chen, Y. W. Liquid Phase Hydrogenation of Benzene to Cyclohexene on Ruthenium Catalysts Supported on Zinc OxideBased Binary Oxides. J. Chem. Technol. Biotechnol. 2001, 76, 954.

Three kinds of ZrO2 (monoclinic, amorphous, and tetragonal) were prepared and used as supports for Ru−B catalysts. In liquid-phase partial hydrogenation of benzene to cyclohexene, Ru−B/ZrO2-M, Ru−B/ZrO2-A, and Ru−B/ZrO2-T catalysts exhibited similar TOFs, but the Ru−B/ZrO2-T catalyst exhibited better selectivity to cyclohexene than others, and the maximum yield of cyclohexene amounted to 47%. The lower amount of the acid sites on ZrO2-T is suggested as the main reason responsible for the superior selectivity of the Ru− B/ZrO2-T catalyst, and the absence of the Brønsted acid sites on ZrO2-T may be another possible reason. This finding opens a new avenue for the searching of supports capable of enhancing the selectivity to cyclohexene in liquid-phase hydrogenation of benzene.

Corresponding Author

*Tel.: +86-21-55664679 (M.Q.); +86-10-82368011 (B.Z.). Fax: +86-21-55665701 (M.Q.); (+86-10)-82368011 (B.Z.). Email: [email protected] (M.Q.); zongbn.ripp@sinopec. com (B.Z.). Notes

The authors declare no competing financial interest. 12211



Article

(19) Venezia, A. M.; Parola, V. L.; Pawelec, B.; Fierro, J. L. G. Hydrogenation of Aromatics over Au−Pd/SiO2−Al2O3 Catalysts; Support Acidity Effect. Appl. Catal., A 2004, 264, 43. (20) Grzechowiak, J. R.; Szyszka, I.; Rynkowski, J.; Rajski, D. Preparation, Characterisation and Activity of Nickel Supported on Silica-Titania. Appl. Catal., A 2003, 247, 193. (21) Chupin, J.; Gnep, N. S.; Lacombe, S.; Guisnet, M. Influence of the Metal and of the Support on the Activity and Stability of Bifunctional Catalysts for Toluene Hydrogenation. Appl. Catal., A 2001, 206, 43. (22) Yasuda, H.; Sato, T.; Yoshimura, Y. Influence of the Acidity of USY Zeolite on the Sulfur Tolerance of Pd−Pt Catalysts for Aromatic Hydrogenation. Catal. Today 1999, 50, 63. (23) Lu, F. Y.; Zhang, J. M.; Huang, M. B.; Namavar, F.; Ewing, R. C.; Lian, J. Phase Transformation of Nanosized ZrO2 upon Thermal Annealing and Intense Radiation. J. Phys. Chem. C 2011, 115, 7193. (24) Zhao, Y. B.; Li, W.; Zhang, M. H.; Tao, K. Y. A Comparison of Surface Acidic Features between Tetragonal and Monoclinic Nanostructured Zirconia. Catal. Commun. 2002, 3, 239. (25) Li, W. Z.; Huang, H.; Li, H. J.; Zhang, W.; Liu, H. C. Facile Synthesis of Pure Monoclinic and Tetragonal Zirconia Nanoparticles and Their Phase Effects on the Behavior of Supported Molybdena Catalysts for Methanol-Selective Oxidation. Langmuir 2008, 24, 8358. (26) Stichert, W.; Schuth, F.; Küba, S.; Knözinger, H. Monoclinic and Tetragonal High Surface Area Sulfated Zirconias in Butane Isomerization: CO Adsorption and Catalytic Results. J. Catal. 2001, 198, 277. (27) Li, W.; Yin, Y. Q.; Gao, R. X.; Hou, R. L. Comparison of CO Hydrogenation on Monoclinic and Tetragonal ZrO2 Catalysts. J. Mol. Catal. (China) 1999, 13, 186. (28) Rhodes, M. D.; Bell, A. T. The Effects of Zirconia Morphology on Methanol Synthesis from CO and H2 over Cu/ZrO2 Catalysts: Part I. Steady-State Studies. J. Catal. 2005, 233, 198. (29) He, D. P.; Ding, Y. J.; Luo, H. Y.; Li, C. Effects of Zirconia Phase on the Synthesis of Higher Alcohols over Zirconia and Modified Zirconia. J. Mol. Catal. A: Chem. 2004, 208, 267. (30) Jung, K. T.; Bell, A. T. The Effects of Synthesis and Pretreatment Conditions on the Bulk Structure and Surface Properties of Zirconia. J. Mol. Catal. A: Chem. 2000, 163, 27. (31) Mao, D. S.; Lu, G. Z.; Chen, Q. L. Influence of Calcination Temperature and Preparation Method of TiO2−ZrO2 on Conversion of Cyclohexanone Oxime to ε-caprolactam over B2O3/TiO2−ZrO2 Catalyst. Appl. Catal., A 2004, 263, 83. (32) Liu, J. L.; Zhu, L. J.; Pei, Y.; Zhuang, J. H.; Li, H.; Li, H. X.; Qiao, M. H.; Fan, K. N. Ce-Promoted Ru/SBA-15 Catalysts Prepared by a “Two Solvents” Impregnation Method for Selective Hydrogenation of Benzene to Cyclohexene. Appl. Catal., A 2009, 353, 282. (33) Shen, X. F.; Garces, L. J.; Ding, Y. S.; Laubernds, K.; Zerger, R. P.; Aindow, M.; Neth, E. J.; Suib, S. L. Behavior of H2 Chemisorption on Ru/TiO2 Surface and Its Application in Evaluation of Ru Particle Sizes Compared with TEM and XRD Analyses. Appl. Catal., A 2008, 335, 187. (34) Chuah, G. K.; Jaenicke, S.; Pong, B. K. The Preparation of HighSurface-Area Zirconia: II. Influence of Precipitating Agent and Digestion on the Morphology and Microstructure of Hydrous Zirconia. J. Catal. 1998, 175, 80. (35) Parry, E. P. An Infrared Study of Pyridine Adsorbed on Acidic Solids. Characterization of Surface Acidity. J. Catal. 1963, 2, 371. (36) Volckmar, C. E.; Bron, M.; Bentrup, U.; Martin, A.; Claus, P. Influence of the Support Composition on the Hydrogenation of Acrolein over Ag/SiO2−Al2O3 Catalysts. J. Catal. 2009, 261, 1. (37) Buzzoni, R.; Bordiga, S.; Ricchiardi, G.; Lamberti, C.; Zecchina, A.; Bellussi, G. Interaction of Pyridine with Acidic (H-ZSM5, H-β, HMORD Zeolites) and Superacidic (H-Nafion Membrane) Systems: An IR Investigation. Langmuir 1996, 12, 930. (38) Busca, G. The Surface Acidity of Solid Oxides and Its Characterization by IR Spectroscopic Methods. An Attempt at Systematization. Phys. Chem. Chem. Phys. 1999, 1, 723. (39) Kalevaru, V. N.; Benhmid, A.; Radnik, J.; Pohl, M. M.; Bentrup, U.; Martin, A. Marked Influence of Support on the Catalytic

Performance of PdSb Acetoxylation Catalysts: Effects of Pd Particle Size, Valence States, and Acidity Characteristics. J. Catal. 2007, 246, 399. (40) Wang, J. Q.; Guo, P. J.; Yan, S. R.; Qiao, M. H.; Li, H. X.; Fan, K. N. Colloidal RuB/Al2O3·xH2O Catalyst for Liquid Phase Hydrogenation of Benzene to Cyclohexene. J. Mol. Catal. A: Chem. 2004, 222, 229. (41) Zahmakıran, M.; Tonbul, Y.; Ö zkar, S. Ruthenium(0) Nanoclusters Stabilized by a Nanozeolite Framework: Isolable, Reusable, and Green Catalyst for the Hydrogenation of Neat Aromatics under Mild Conditions with the Unprecedented Catalytic Activity and Lifetime. J. Am. Chem. Soc. 2010, 132, 6541. (42) Hájek, J.; Kumar, N.; Francová, D.; Paseka, I.; Mäki-Arvela, P.; Salmi, T.; Murzin, D. Y. Hydrogenation of Cinnamaldehyde over Ptmodified Molecular Sieve Catalysts. Chem. Eng. Technol. 2004, 27, 1290. (43) Mäki-Arvela, P.; Hájek, J.; Salmi, T.; Murzin, D. Y. Chemoselective Hydrogenation of Carbonyl Compounds over Heterogeneous Catalysts. Appl. Catal., A 2005, 292, 1. (44) Simon, L. J.; van Ommen, J. G.; Jentys, A.; Lercher, J. A. Sulfur Tolerance of Pt/mordenites for Benzene Hydrogenation. Do Brønsted Acid Sites Participate in Hydrogenation? Catal. Today 2002, 73, 105. (45) Lin, S. D.; Vannice, M. A. Hydrogenation of Aromatic Hydrocarbons over Supported Pt Catalysts. I. Benzene Hydrogenation. J. Catal. 1993, 143, 539. (46) Lin, S. D.; Vannice, M. A. Hydrogenation of Aromatic Hydrocarbons over Supported Pt Catalysts. III. Reaction Models for Metal Surfaces and Acidic Sites on Oxide Supports. J. Catal. 1993, 143, 563. (47) Wang, J.; Chen, H. Y.; Li, Q. Z. Influence of the Brönsted and Lewis Acid Sites in Platinum/Solid Acid Catalysts on the Hydrogenation of Benzene and Toluene. React. Kinet. Catal. Lett. 2000, 69, 277. (48) Wang, J.; Huang, L. M.; Li, Q. Z. Influence of Different Diluents in Pt/Al2O3 Catalyst on the Hydrogenation of Benzene, Toluene and o-xylene. Appl. Catal., A 1998, 175, 191. (49) Wang, J.; Huang, L. M.; Chen, H. Y.; Li, Q. Z. Acid Function of Al-MCM-41 Supported Platinum Catalysts in Hydrogenation of Benzene, Toluene and o-xylene. Catal. Lett. 1998, 55, 157. (50) Ishikawa, H.; Kondo, J. N.; Domen, K. Hydrogen Adsorption on Ru/ZrO2 Studied by FT-IR. J. Phys. Chem. B 1999, 103, 3229. (51) Appay, M. D.; Manoli, J. M.; Potvin, C.; Muhler, M.; Wild, U.; Pozdnyakova, O.; Paál, Z. High-Resolution Electron Microscopic, Spectroscopic, and Catalytic Studies of Intentionally Sulfided Pt/ ZrO2−SO4 Catalysts. J. Catal. 2004, 222, 419. (52) Nagahara, H.; Ono, M.; Konishi, M.; Fukuoka, Y. Partial Hydrogenation of Benzene to Cyclohexene. Appl. Surf. Sci. 1997, 121/ 122, 448. (53) Aboul-Gheit, A. K.; Aboul-Fotouh, S. M.; Abdel-Hamid, S. M.; Aboul-Gheit, N. A. K. Hydroconversion of Cyclohexene Using HZSM-5 Zeolite Catalysts Promoted via Hydrochlorination and/or Platinum Incorporation. J. Mol. Catal. A: Chem. 2006, 245, 167. (54) Aboul-Gheit, A. K.; Aboul-Fotouh, S. M.; Abdel-Hamid, S. M.; Aboul-Gheit, N. A. K. Effect of Hydrochlorination and Hydrofluorination of H-ZSM-5 on the Catalytic Hydroconversion Reactions of Cyclohexene. Appl. Catal., A 2006, 297, 102. (55) Aboul-Gheit, A. K.; Aboul-Gheit, N. A. K. Iridium/H-ZSM-5 Zeolite Catalyst Promoted via Hydrochlorination or Hydrofluorination for the Hydroconversion of Cyclohexene. Appl. Catal., A 2006, 303, 141. (56) Aboul-Gheit, A. K.; Aboul-Gheit, N. A. K.; Awadallah, A. E. Effect of Hydrohalogenation of Metal/Zeolite Catalysts for Cyclohexene Hydroconversion II. Rhenium/H-ZSM-5 Catalysts. Chin. J. Catal. 2008, 29, 113. (57) Rozwadowski, M.; Datka, J.; Lezanska, M.; Wloch, J.; Erdmanna, K.; Kornatowski, J. Al-MCM-41: Its Acidity and Activity in Cyclohexene Conversion. Phys. Chem. Chem. Phys. 2001, 3, 5082. (58) Bautista, F. M.; Campelo, J. M.; Garcia, A.; Luna, D.; Marinas, J. M.; Moreno, M. C.; Romero, A. A. Acidity and Catalytic Activity of 12212



Article

AlPO4−B2O3 and Al2O3−B2O3 (5−30 wt% B2O3) Systems Prepared by Impregnation. Appl. Catal., A 1998, 170, 159. (59) Yuan, P. Q.; Liu, Y.; Bai, F.; Xu, L.; Cheng, Z. M.; Yuan, W. K. Hydration of Cyclohexene in Sub-critical Water over WOx−ZrO2 Catalysts. Catal. Commun. 2011, 12, 753. (60) Luque, R.; Campelo, J. M.; Conesa, T. D.; Luna, D.; Marinas, J. M.; Romero, A. A. Catechol O-methylation with Dimethyl Carbonate over Different Acid-Base Catalysts. New J. Chem. 2006, 30, 1228. (61) Luque, R.; Budarin, V.; Clark, J. H.; Shuttleworth, P.; White, R. J. Starbon Acids in Alkylation and Acetylation Reactions: Effect of the Brönsted-Lewis Acidity. Catal. Commun. 2011, 12, 1471.

12213


Effect of Support Acidity on Liquid-Phase Hydrogenation of Benzene

Recommend Documents