Influence factors on activity of Ru-Zn catalysts in selective hydrogenation of benzene

doi:10.1016/j.cjche.2016.08.004

摘要/Abstract

摘要： Selective hydrogenation of benzene is an atom economic green route to produce cyclohexene. The control of Zn species is the key to the catalytic performance of Ru-Zn catalysts. The influences of ZnO crystals on selective hydrogenation of benzene were explored. A series of Ru-Zn catalysts with different Zn contents and ZnO morphologies were prepared by changing the amount of NaOH in the co-precipitation process. The catalysts were characterized by N₂ physisorption, X-ray powder diffraction (XRD), inductively coupled plasma optical emission spectrometer (ICP-OES), scanning electron microscope (SEM), temperature-programmed reduction (H₂-TPR) and Malvern laser particle size analyzer. It is found that with increasing the amount of NaOH, the Zn content first increased then decreased, and the ZnO crystals changed from relatively thicker pyramidal-shaped crystals to slimmer needle-shaped crystals. The catalyst had the highest Zn content (22.1%) and strongest interaction between ZnO crystals and Ru particles at pH 10.6 of the solution after reduction. As a result, it had the lowest activity. The activity of Ru-Zn catalysts is affected by both the Zn content and the interaction between ZnO crystals and Ru particles. The effect of reduction time was also investigated. Prolonging the reduction time caused no significant growth of ZnO crystals but the aggregation of catalyst particles and growth of Ru nanocrystals, thus resulting in the decrease of catalytic activity.

关键词: ZnO morphology, Benzene, Selective hydrogenation, Co-precipitation, Cyclohexene

Abstract: Selective hydrogenation of benzene is an atom economic green route to produce cyclohexene. The control of Zn species is the key to the catalytic performance of Ru-Zn catalysts. The influences of ZnO crystals on selective hydrogenation of benzene were explored. A series of Ru-Zn catalysts with different Zn contents and ZnO morphologies were prepared by changing the amount of NaOH in the co-precipitation process. The catalysts were characterized by N₂ physisorption, X-ray powder diffraction (XRD), inductively coupled plasma optical emission spectrometer (ICP-OES), scanning electron microscope (SEM), temperature-programmed reduction (H₂-TPR) and Malvern laser particle size analyzer. It is found that with increasing the amount of NaOH, the Zn content first increased then decreased, and the ZnO crystals changed from relatively thicker pyramidal-shaped crystals to slimmer needle-shaped crystals. The catalyst had the highest Zn content (22.1%) and strongest interaction between ZnO crystals and Ru particles at pH 10.6 of the solution after reduction. As a result, it had the lowest activity. The activity of Ru-Zn catalysts is affected by both the Zn content and the interaction between ZnO crystals and Ru particles. The effect of reduction time was also investigated. Prolonging the reduction time caused no significant growth of ZnO crystals but the aggregation of catalyst particles and growth of Ru nanocrystals, thus resulting in the decrease of catalytic activity.

Key words: ZnO morphology, Benzene, Selective hydrogenation, Co-precipitation, Cyclohexene

Qi Zhang, Xuhua Yan, Peng Zheng, Zhengbao Wang. Influence factors on activity of Ru-Zn catalysts in selective hydrogenation of benzene[J]. , 2017, 25(3): 294-300.

参考文献

[1] H. Nagahara, M. Ono, M. Konishi, Y. Fukuoka, Partial hydrogenation of benzene to cyclohexene, Appl. Surf. Sci. 121-122(1997) 448-451.
[2] G.B. Zhou, Y. Pei, Z. Jiang, K.N. Fan, M.H. Qiao, B. Sun, B.N. Zong, Doping effects of B in ZrO₂ on structural and catalytic properties of Ru/B-ZrO₂ catalysts for benzene partial hydrogenation, J. Catal. 311(2014) 393-403.
[3] G.B. Zhou, X.H. Tan, Y. Pei, K.N. Fan, M.H. Qiao, B. Sun, B.N. Zong, Structural and catalytic properties of alkaline post-treated Ru/ZrO₂ catalysts for partial hydrogenation of benzene to cyclohexene, ChemCatChem 5(2013) 2425-2435.
[4] G.B. Zhou, J.L. Liu, X.H. Tan, Y. Pei, M.H. Qiao, K.N. Fan, B.N. Zong, Effect of support acidity on liquid-phase hydrogenation of benzene to cyclohexene over Ru-B/ZrO₂ catalysts, Ind. Eng. Chem. Res. 51(38) (2012) 12205-12213.
[5] J.Q. Wang, Y.Z. Wang, S.H. Xie, M.H. Qiao, H.X. Li, K.N. Fan, Partial hydrogenation of benzene to cyclohexene on a Ru-Zn/m-ZrO₂ nanocomposite catalyst, Appl. Catal. A Gen. 272(1-2) (2004) 29-36.
[6] P.Q. Yuan, B.Q. Wang, Y.M. Ma, H.M. He, Z.M. Cheng, W.K. Yuan, Partial hydrogenation of benzene over the metallic Zn modified Ru-based catalyst, J. Mol. Catal. A Chem. 309(1-2) (2009) 124-130.
[7] H.J. Sun, H.B. Jiang, S.H. Li, H.X. Wang, Y. Pan, Y.Y. Dong, S.C. Liu, Z.Y. Liu, Selective hydrogenation of benzene to cyclohexene over nanocomposite Ru-Mn/ZrO₂ catalysts, Chin. J. Catal. 34(2013) 684-694.
[8] S.C. Liu, Z.Y. Liu, S.H. Zhao, Y.M. Wu, Z.Wang, P. Yuan, Study on the nanosized amorphous Ru-Fe-B/ZrO₂ alloy catalyst for benzene selective hydrogenation to cyclohexene, J. Nat. Gas Chem. 15(4) (2006) 319-326.
[9] S.C. Liu, Z.Y. Liu, Z. Wang, S.H. Zhao, Y.M. Wu, A novel amorphous alloy Ru-La-B/ZrO₂ catalyst with high activity and selectivity for benzene selective hydrogenation, Appl. Catal. A Gen. 313(1) (2006) 49-57.
[10] J.Q. Wang, P.J. Guo, S.R. Yan, M.H. Qiao, H.X. Li, K.N. Fan, Colloidal RuB/Al₂O₃·xH₂O catalyst for liquid phase hydrogenation of benzene to cyclohexene, J. Mol. Catal. A Chem. 222(1) (2004) 229-234.
[11] Y.J. Zhao, J. Zhou, J.G. Zhang, S.D. Wang, Liquid-phase selective hydrogenation of benzene to cyclohexene on Ru/Al₂O₃-ZrO₂/cordierite monolithic catalysts, J. Mol. Catal. A Chem. 309(1-2) (2009) 35-39.
[12] J.L. Liu, L.J. Zhu, Y. Pei, J.H. Zhuang, H.X. Li,M.H. Qiao, K.N. Fan, Ce-promoted Ru/SBA-15 catalysts prepared by a "two solvents" impregnationmethod for selective hydrogenation of benzene to cyclohexene, Appl. Catal. A Gen. 353(2009) 282-287.
[13] J. Bu, J.L. Liu, X.Y. Chen, J.H. Zhuang, S.R. Yan, M.H. Qiao, H.Y. He, K.N. Fan, Ru/SBA-15 catalysts for partial hydrogenation of benzene to cyclohexene:Tuning the Ru crystallite size by Ba, Catal. Commun. 9(15) (2008) 2612-2615.
[14] H.Z. Liu, T. Jiang, B.X. Han, S.G. Liang, W.T. Wang, T. Wu, G.Y. Yang, Highly selective benzene hydrogenation to cyclohexene over supported Ru catalyst without additives, Green Chem. 13(5) (2011) 1106-1109.
[15] H.Z. Liu, S.G. Liang, W.T. Wang, T. Jiang, B.X. Han, The partial hydrogenation of benzene to cyclohexene over Ru-Cu catalyst supported on ZnO, J. Mol. Catal. A Chem. 341(1-2) (2011) 35-41.
[16] W. Xue, Y. Song, Y.J.Wang, D.D.Wang, F. Li, Effect of hydrazine hydrate on the Ru-Zn/SiO₂ catalysts performance for partial hydrogenation of benzene, Catal. Commun. 11(1) (2009) 29-33.
[17] H.G. Liao, D.H. Ouyang, J. Zhang, Y.J. Xiao, P.L. Liu, F. Hao, K.Y. You, H.A. Luo, Benzene hydrogenation over oxide-modified MCM-41 supported ruthenium-lanthanum catalyst:The influence of zirconia crystal form and surface hydrophilicity, Chem. Eng. J. 243(2014) 207-216.
[18] G.B. Zhou, R.F. Dou, H.Z. Bi, S.H. Xie, Y. Pei, K.N. Fan, M.H. Qiao, B. Sun, B.N. Zong, Ru nanoparticles on rutile/anatase junction of P25 TiO₂:Controlled deposition and synergy in partial hydrogenation of benzene to cyclohexene, J. Catal. 332(2015) 119-126.
[19] H.J. Sun, S.H. Li, Y.X. Zhang, H.B. Jiang, L.L. Qu, S.C. Liu, Z.Y. Liu, Selective hydrogenation of benzene to cyclohexene in continuous reaction device with two reaction reactors in serie over Ru-Co-B/ZrO₂ catalysts, Chin. J. Catal. 34(8) (2013) 1482-1488.
[20] H.J. Sun, X.D. Zhang, Z.H. Chen, X.L. Zhou, W. Guo, Z.Y. Liu, S.C. Liu, Monolayer dispersed Ru-Zn catalyst and its performance in the selective hydrogenation of benzene to cyclohexene, Chin. J. Catal. 32(2011) 224-230.
[21] H.J. Sun, H.X.Wang, H.B. Jiang, S.H. Li, S.C. Liu, Z.Y. Liu, X.M. Yuan, K.J. Yang, Effect of (Zn (OH)₂)₃(ZnSO₄)(H₂O)₅ on the performance of Ru-Zn catalyst for benzene selective hydrogenation to cyclohexene, Appl. Catal. A Gen. 450(2013) 160-168.
[22] H.Z. Qin, Z.X. Huang, S.C. Liu, Study on the unsupported Ru-Zn-B catalysts for selective hydrogenation of benzene to cyclohexene, J. Xinyang Norm. Univ. 20(3) (2007) 350-352(in Chinese).
[23] S.C. Liu, Z.Y. Liu, G. Luo, M.L. Han, Characterization of Ru-Zn catalysts prepared by precipitation method for selective hydrogenation of benzene to cyclohexene, Pet. Technol. 31(2002) 720-724(in Chinese).
[24] Z.X. Huang, Z.Y. Liu, Y.M. Wu, S.C. Liu, Selective hydrogenation of benzene to cyclohexene by a novel Ru-Zn catalyst, J. Mol. Catal. 20(2006) 226-229(in Chinese).
[25] S.C. Liu, Z.X. Huang, Y.M.Wu, Influence of Zn on property of Ru catalyst for selective hydrogenation of benzene to cyclohexene, J. Zhengzhou Univ. 38(2006) 72-75(in Chinese).
[26] Z.B.Wang, Q. Zhang, X.F. Lu, S.J. Chen, C.J. Liu, Ru-Zn catalysts for selective hydrogenation of benzene using co-precipitation in low alkalinity, Chin. J. Catal. 36(3) (2015) 400-407.
[27] R. Narayanan, M.A. El-Sayed, Catalysis with transition metal nanoparticles in colloidal solution:Nanoparticle shape dependence and stability, J. Phys. Chem. B 109(26) (2005) 12663-12676.
[28] F.L. Liao, Y.Q. Huang, J.W. Ge,W.R. Zheng, K. Tedsree, P. Collier, X.L. Hong, S.C. Tsang, Morphology-dependent interactions of ZnO with Cu nanoparticles at the materials' interface in selective hydrogenation of CO₂ to CH₃OH, Angew. Chem. Int. Ed. 50(9) (2011) 2162-2165.
[29] H. Lei, R.F. Nie, G.Q.Wu, Z.Y. Hou, Hydrogenation of CO₂ to CH₃OH over Cu/ZnO catalysts with different ZnO morphology, Fuel 154(2015) 161-166.
[30] H.Y. Xu, H.Wang, Y.C. Zhang, W.L. He,M.K. Zhu, B.Wang, H. Yan, Hydrothermal synthesis of zinc oxide powders with controllable morphology, Ceram. Int. 30(2004) 93-97.
[31] D. Vernardou, G. Kenanakis, S. Couris, E. Koudoumas, E. Kymakis, N. Katsarakis, pH effect on the morphology of ZnO nanostructures grown with aqueous chemical growth, Thin Solid Films 515(24) (2007) 8764-8767.
[32] J. Li, S. Srinivasan, G.N. He, J.Y. Kang, S.T.Wu, F.A. Ponce, Synthesis and luminescence properties of ZnO nanostructures produced by the sol-gel method, J. Cryst. Growth 310(3) (2008) 599-603.
[33] J.H. Kim, E.M. Kim, D. Andeen, D. Thomson, S.P. DenBaars, F.F. Lange, Growth of heteroepitaxial ZnO thin films on GaN-buffered Al₂O₃(0001) substrates by lowtemperature hydrothermal synthesis at 90℃, Adv. Funct. Mater. 17(3) (2007) 463-471.
[34] W.J. Li, E.W. Shi, W.Z. Zhong, Z.W. Yin, Growth mechanism and growth habit of oxide crystals, J. Cryst. Growth 203(1) (1999) 186-196.
[35] R.Wahab, S.G. Ansari, Y.S. Kim, M.W. Song, H.S. Shin, The role of pH variation on the growth of zinc oxide nanostructures, Appl. Surf. Sci. 255(9) (2009) 4891-4896.
[36] W. Huang, J.G. Jia, X.W. Zhou, Y. Lin, Morphology controllable synthesis of ZnO crystals-pH-dependent growth, Mater. Chem. Phys. 123(1) (2010) 104-108.
[37] O. Singh, M.P. Singh, N. Kohli, R.C. Singh, Effect of pH on the morphology and gas sensing properties of ZnO nanostructures, Sensors Actuators B Chem. 166(2012) 438-443.
[38] S.S. Alias, A.B. Ismail, A.A. Mohamad, Effect of pH on ZnO nanoparticle properties synthesized by sol-gel centrifugation, J. Alloys Compd. 499(2) (2010) 231-237.
[39] X.H. Yan, Q. Zhang, M.Q. Zhu, Z.B. Wang, Selective hydrogenation of benzene to cyclohexene over Ru-Zn/ZrO₂ catalysts prepared by a two-step impregnationmethod, J. Mol. Catal. A Chem. 413(2016) 85-93.
[40] C.H. Lu, C.H. Yeh, Influence of hydrothermal conditions on themorphology and particle size of zinc oxide powder, Ceram. Int. 26(2000) 351-357.