NaOH-TPAOH混合碱改性对ZSM-5沸石性能的影响

Effects of NaOH-TPAOH mixed alkali on ZSM-5 zeolite modification

为了进一步提高ZSM-5分子筛的烷基化性能,采用氢氧化钠(NaOH)-四丙基氢氧化铵(TPAOH)混合碱处理HZSM-5沸石分子筛,固定氢氧化钠和四丙基氢氧化铵量比n(NaOH)/n(TPAOH)=0.6不变,考察混合碱体系中OH-总量(即总碱量)对ZSM-5催化剂应用于苯-甲醇烷基化反应的性能的影响。结果表明,当处理的碱量浓度较低时,NaOH-TPAOH混合碱液不会破坏ZSM-5的骨架结构,且晶体表面会变得更光滑,同时出现一定量的介孔。随碱处理OH-总量的升高,催化剂的弱酸量增加,强酸强度逐渐下降。对于苯-甲醇烷基化反应,处理总碱量为6.4 mmol时,在液体积空速为85 h^-1条件下,运转10 h,苯转化率高达48%,积炭量相对较低,具有很好的稳定性。

In order to further improve alkylation performance of ZSM-5 molecular sieves,the HZSM-5 zeolite molecular sieve was treated with NaOH-TPAOH mixed alkali.The effects of total amount of OH □(total alkali amount) in the mixed alkali system on the performance of benzene-methanol alkylation reaction were studied at n(NaOH)/n(TPAOH)=0.6.The results show that when the alkaline concentration is low,it does not destroy the skeleton structure of ZSM-5,and the surface of ZSM-5 crystals become smooth with certain amount of mesopore appears.With the increase of alkaline concentration,the weak acid of the catalyst increases,and the strength of the strong acid gradually decreases.For the benzene-methanol alkylation reaction with total alkaline amount of 6.4 mmol,the benzene conversion rate is 48% and the carbon deposition amount is low under liquid volume space velocity of 85 h^-1 for 10 h.