Application of HZSM-5 Nanosheets in Biphenylmethylation
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采用晶种导向的方法合成了一系列具有不同硅/铝比、不同b轴厚度的纳米片状HZSM-5催化剂.利用XRD、SEM、NH3-TPD、N2吸附-脱附等手段对催化剂的物理和化学性质进行表征,并在反应温度为380 ℃、反应压力为0.1 MPa和进料速率为MHSV=1.0 h-1的反应条件下考察了硅/铝比和纳米片状HZSM-5 b轴厚度对于联苯甲基化反应性能的影响.研究结果表明,随着纳米片状HZSM-5硅/铝比降低,联苯转化率提高,同时4-甲基联苯(4-MBP)的选择性也小幅上升,4-MBP收率大幅提高;但催化剂失活严重,稳定性下降.在硅/铝摩尔比为20的条件下,通过提高晶种加入量,可将纳米片状HZSM-5的b轴厚度从100 nm降至20 nm.纳米片状HZSM-5的直孔道促进了反应物与产物分子在沸石微孔内的扩散,减缓了副反应的发生以及积炭的形成,提高了催化剂的稳定性;催化剂单程寿命从8 h延长到30 h.
A series of HZSM-5 nanosheets catalysts with different silicon/aluminum ratios and b-axis thicknesses were synthesized using seed oriented method.The physical and chemical properties of the catalysts were characterized by XRD,SEM,NH3-TPD,and N2 adsorption-desorption,and the effects of silicon/aluminum ratio and HZSM-5 nanosheets b-axis thickness on the performance of biphenylmethylation reaction were investigated.The research results indicate that as the silicon/aluminum ratio of HZSM-5 nanosheets decreases,the conversion rate of biphenyl increases,and the selectivity of 4-methylbiphenyl(4-MBP)also slightly increases,resulting in a significant increase in the yield of 4-MBP;however,the catalyst is severely deactivated and its stability decreases.At the silicon/aluminum molar ratio of 20,the b-axis thickness of HZSM-5 nanosheets was reduced from 100 nm to 20 nm by increasing the addition of seed.The straight pores of HZSM-5 nanosheets can promote the diffusion of reactants and product molecules in zeolite micropores,slow down the occurrence of side reactions and the formation of carbon deposits,and improve the stability of catalysts;the one-way lifespan of the catalysts has been extended from 8 h to 30 h.
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