镁物种二次改性ZSM-35分子筛及其催化正构烯烃异构化反应性能

Isomerization Performance of Secondary Modified ZSM-35 Molecular Sieves by Magnesium Species

采用不同的镁物种对适宜浓度盐酸处理的NaZSM-35分子筛进行二次改性处理,并考察了改性ZSM-35分子筛催化正构烯烃骨架异构化反应的性能。结果表明:草酸镁改性对ZSM-35分子筛的酸量改变及性能提高不明显;硝酸镁和氧化镁改性后,分子筛B酸和L酸的总酸量骤然降低,催化剂的活性快速下降;碱式碳酸镁改性可对分子筛B酸和L酸的酸量分布进行一定程度的调变,在反应物转化率不变的基础上,异己烯的收率明显增加。因此,碱式碳酸镁是最适宜的改性物种。进一步探究碱式碳酸镁负载量对分子筛催化正构烯烃异构化反应的影响,结果显示,当碱式碳酸镁质量分数为1.0%时,催化剂具有最佳催化骨架异构化反应性能。

In this paper,different magnesium salts were used to alter the NaZSM-35 molecular sieve treated with hydrochloric acid with suitable concentration by secondary modification.Moreover,the catalytic performance of modified ZSM-35 molecular sieves in alkene skeletal isomerization was investigated.Results show that after the modification by magnesium oxalate,the yield of isohexene does not increase obviously.After the modification by magnesium nitrate and magnesium oxide,the total acid amount of both B acid and L acid sites suddenly decrease,and the activity of the catalyst becomes lower rapidly.Basic magnesium carbonate is the most suitable modifier,which can adjust the acid amount distribution of the B acid and the L acid to some extent,hence the conversion of reactants and the yield of isohexene become significantly increased.The effects of different contents of magnesium carbonate were further explored.Results show that when the mass fraction of basic magnesium carbonate is 1.0%,the catalyst exhibits the highest catalytic performance in alkene skeletal isomerization.