Study On The Shape-selective Cracking Of Diisopropylbenzenes

DIPB as byproduct during manufacturing cumene by alkylation of benzene with propylene in phenol-acetone plants.This method not only increases the production cost of phenol and acetone but also reduces the value of the mixed DIPB which is unfavorable to production and management.M-DIPB as an important chemical raw material is mainly used for the production of resorcinol. It is very difficult to separate m-DIPB completely from DIPB by conventional distillationfor boiling point of all the three isomers are near. Selective cracking of the mixed DIPB by nano-ZSM-5 molecular sieve is discussed in this paper which makes p-DIPB with a small molecular conformation migrate into molecular sieve channels break into benzene and cumin on acid site meanwhile m-DIPB with a big molecular conformation stay out of molecular sieve channels crack in a small quantity. In this way m-DIPB is retained while p-DIPB is fully cracked which is beneficial to the subsequent distillation.The cracking mainly includes two parts:one is the optimization of reaction conditions; and the other is the best conditions of hydrothermal treatment.First, the influence of temperature and space velocity for Cp, the m-DIPB content of products and o-DIPB/m-DIPB were studied under the condition of atmospheric reaction with benzene and without carrier gas. For the condition mentioned above, with the mixed DIPB as raw material, benzene as reagent, and nano-ZSM-5 molecular sieve as catalyst, the text confirmed the optimal temperature and space velocity(SV) were determined as 380℉ and 2.35 h-1, respectively.Second, nano-ZSM-5 zeolite was modified by hydrothermal treatment. The influence of temperature and time for Cp, the m-DIPB content and o-DIPB/m-DIPB were researched. Results revealed that the optimal temperature and time were 540℃and 4-5 h respectively for selective cracking under the optimum technological condition mentioned above.Besides, the effect of benzene on the catalyst performance was also observed. Depth cracking is restrained by benzene, which help to improve the content of m-DIPB.Finally, through the study of isomerization and distillation,we determined the best separation program after compared to the results which of isomerization and isomerization-cracking through distillation.