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以4 甲基联苯(4 MBP)与甲醇的烷基化为探针反应,在固定床反应器上考察了MgO改性与水热处理的HZSM 5的催化性能。结果表明,MgO改性和水热处理均可显著提高目的产物4,4’ 二甲基联苯(4,4’ DMBP)的选择性,在MgO改性的HZSM 5上,4,4’ DMBP选择性可达80%;在水热处理的HZSM 5上,4,4’ DMBP选择性为70%;而在未改性的HZSM 5上仅为13%。水热处理HZSM 5再经HCl处理后,能改善其活性稳定性,反应1000min后4 MBP转化率仍有8%,而4,4’ DMBP选择性保持在65%。TPD数据表明,MgO改性和水热处理后,催化剂的酸性均有明显的下降;但氮气低温吸附数据表明,前者的微孔比表面积减小,而后者的中孔比表面积增加。4,4’ DMBP与甲醇在催化剂上的反应结果表明,MgO改性抑制了4,4’ DMBP的异构化、脱烷基化及进一步烷基化反应;而经水热处理后高的选择性是来源于4,4’ DMBP的异构化与脱烷基化反应受到抑制。
The catalytic performance of MgO-modified and hydrothermally-treated HZSM 5 was investigated on a fixed-bed reactor using alkylation of 4-methyl biphenyl (4 MBP) with methanol as a probe. The results showed that both MgO modification and hydrothermal treatment could significantly increase the selectivity of the 4,4 ’- dimethylbiphenyl (4,4’ - DMBP). On the MgO modified HZSM 5, 4,4 ’DMBP Up to 80%; 4,4’-DMBP selectivity at hydrothermally treated HZSM 5 was 70%; only 13% at unmodified HZSM 5. Hydrothermal treatment of HZSM 5 followed by HCl treatment improved its stability. The 4 MBP conversion was still 8% after 1000 min of reaction, while the selectivity of 4,4 ’DMBP remained at 65%. The TPD data showed that the acidity of the catalysts decreased obviously after MgO modification and hydrothermal treatment. However, the low temperature adsorption data of nitrogen showed that the former reduced the micropore specific surface area and the latter increased the mesopore specific surface area. The reaction of 4,4 ’DMBP with methanol on the catalyst showed that the modification of MgO inhibited the isomerization, dealkylation and further alkylation of 4,4’ DMBP, while the high selectivity after hydrothermal treatment Isomers derived from 4,4 ’DMBP isomerization and dealkylation reaction was inhibited.