改性纳米HZSM-5催化剂上噻吩转化反应的研究

Catalytic Conversion of Thiophen over Nano-sized HZSM-5 Catalysts

采用脉冲微反色谱研究了噻吩在不同方法制备的四种纳米HZSM-5沸石催化剂上的催化转化,并利用色质联用技术对反应产物定性.结果表明,在370℃下,噻吩在各种催化剂上除了脱硫生成硫化氢以外,还生成少量2-甲基噻吩、3-甲基噻吩和苯并噻吩等新的硫化物.噻吩转化率和脱硫率受反应气氛和催化剂酸度影响很大.氢气气氛比氮气气氛有利于提高噻吩转化率和脱硫率.临氢作用的实质是气相中的分子氢被催化剂上的L酸活化向噻吩裂化脱硫反应供氢.通过改性适当降低催化剂上的B酸中心数量和强度,增加L酸的比例,有利于发挥临氢作用.

Pulsed micro-reactor-chromatography technique and GC-MS technique were used to investigate the conversion of thiophene over four kinds of modified nano-sized HZSM-5 catalysts. Results show that, in addition to the formation of H2S by desulphurization, new sulfur-containing compounds such as t-butyl sulfalcohol, 2-methyl-thiophene, 3-methylthiophene and benzothiophene are also produced during the conversion of thiophene over the different catalysts. Both atmosphere and the acidity of catalyst have significant influence on these reactions. Compared with nitrogen, the use of hydrogen as carrying gas can pronouncedly promote the conversion and desulphurization of thiophene even if under atmospheric condition. Such an effect of hydrogen drogen atoms for the cracking of thiophene via the activation of hydrogen carrier is connected to the supply of hymolecules on Lewis acid sites. It is observed that the effect of hydrogen carrier can be enhanced by decreasing the concentration and the strength of Bronsted acid site of the catalyst through suitable modifications.