超临界条件下甲苯甲醇烷基化反应制对二甲苯的研究

【作者】 孙海；

【导师】 刘靖；

【作者基本信息】 大连理工大学 ， 催化化学与工程， 2002， 硕士

【摘要】 SCF能溶解某些导致固体催化剂失活的物质、抑制催化剂失活。我们以反应物(主要是甲苯)作为超临界反应介质，以改性的ZSM-5沸石分子筛为催化剂，探讨在超临界条件下甲苯甲醇烷基化制对二甲苯反应性能及特点。 首先在常压下进行甲苯甲醇烷基化的研究，以找到用于超临界反应的催化剂。研究中对HZSM-5进行了水热、载镁、载磷、硅处理等改性处理。发现在没有载气的条件下，800℃水热处理的催化剂甲苯转化率为11％，对二甲苯选择性为66％。载Mg催化剂甲苯转化率为7％，对二甲苯选择性为93％。 在超临界条件下，超临界流体能够抑制催化剂积炭，延长催化剂寿命。对于800℃水热处理SZ催化剂，在460℃，常压反应条件下，甲苯转化率在20h后就会下降，而在460℃，5.5MPa条件下，甲苯转化率在46h内保持稳定。另外，对所选择的催化剂体系，与常压气相反应相比，超临界条件下的反应中，甲苯转化率提高，对二甲苯的选择性下降，但是也具有一定的选择性。从而认为：在超临界条件下的反应中，超临界流体能萃取积炭前体、抑制催化剂失活；甲苯转化率提高，但对二甲苯选择性下降，催化剂的表面酸性和孔结构对催化性能有很大影响。更多还原

【Abstract】 The deactivation rate of catalyst can be reduced in supercritical reaction by SCFs’ situ extraction of coke precursors. It is investigated in this dissertation that the alkylation of toluene with methanol for para-xylene over modified ZSM-5 zeolite on the conditions of reactants (mainly toluene) as supercritical reaction media.The catalyst for alkylation is investigated at atmospheric pressure in order to find catalyst used in supercritical reaction. HZSM-5 is heated by steam and modified by Mg P and Si etc. It is found that conversion of toluene is 10% and selectivity of para-xylene is 68% on 800 hydrothermal catalyst without carrying gas when reaction temperature is 460. conversion of toluene is 7% and selectivity of para-xylene is 93% on Mg-modified catalyst.In supercritical reaction, coke deposition can be reduced by supercritical fluid and life of catalyst is prolonged. On 800 hydrothermal catalyst, when reaction is carried out at 460 and atmospheric pressure, conversion of -toluene decreases after 20 hours of continue reaction. But at 460 , 5. 5MPa, conversion of toluene is maintained for 46 hours. Furthermore, on the catalyst selected conversion of toluene increases and selectivity of para-xylene decreases-but there is still selectivity, in supercritical reaction compared to reaction at air pressure.It can be concluded that in supercritical reaction coke precursors can be extracted in situ and life of catalyst can be prolonged by supercritical fluids. Conversion of toluene increases while selectivity of para-xylene decreases in supercritical reaction. The catalysis character is greatly affected by acidity and pore structure of catalyst.更多还原