| Meta-diisopropylbenzene (m-DIPB) is an important raw material, which can mainly be oxidized to resorcinol. Recently, with the need of resorcinol increasing rapidly in industry, the need of m-DIPB is also increasing. DIPB will be formed as byproduct during manufacturing cumene by alkylation of benzene with propylene to in phenol-acetone plants. However, the boiling points of the three isomers of DIPB are very close, so it is difficult to separate m-DIPB from the other isomers using normal distillation. Due to limit of thermodynamic balance, isomerization reaction of DIPB is also hard to get high-concentration m-DIPB. In this paper, the certain zeolites which have the shape-selective function will be used as catalysts to crack DIPBs selectively. They have the appropriate pore diameter for para-DIPB go into the pores of molecular sieves and be cracking to benzene and cumene with the acid centers inside, but m-DIPB (larger diameter than para-) can not go inside and does not react. It will crack fully p-DIPB as far as possible to retain the full m-DIPB. So high-concentration m-DIPB can be producted though distillation using the obvious differences of boiling points of products (benzene 80.1℃, cumene 152.5℃).Shape-selective cracking of DIPB was investigated over nano-HZSM-5 with 35%SB in different reaction conditions. The results show that under the reaction conditions of 420℃, weight hourly space velocity (WHSV) 3 h-1, benzene reflux and without carrier gas, the cracking rate of p-DIPB (Cp) can reach to 89～97% in 8 h, selective cracking coefficient of m-DIPB (am) reaches to 1.7～4.5 and content of m-DIPB in product DIPB (Xm) reaches to 85-97% in 8 h. With the increase of reaction time, the activity of catalyst reduces rapidly. To 26 h, Cp reduces to 40%; am rises to 6.6 and Xm reduces to 66%.Nano-HZSM-5 was modified with citric acid.and low tempreture hydrothermal treatment for different time and in different medium under the temperature of 170℃, the results indicate the catalysts modified by 1mol/L citric acid,12h hydrothermal treatment and 0.6mol/L Mg(NO3)2 solution can effectively improve catalyst performance. Meantime, catalyst modified by boiled treatment for 12h can keep stability in 26 h, the Cp reaches over 70% in 26 h, am reaches to 7.7 on average result of 26 h and Xm reaches over80% in 26 h.Nano-HZSM-5 was modified by steam treatment at different temperature and time. Shape-selective cracking of DIPB was researched, the results show that under the treatment conditions of 500℃,4 h and water medium, selectivity and stability of catalyst are better than unmodified catalyst. The Cp reaches over 90% in 26 h and over 80% in 50 h; am reaches to 11.4 on average result of 26 h and 25.8 on average result of 50 h; Xm reaches over 92% in 26 h and over 86% in 50 h.In addition, catalyst modified by acid medium can also effectively improve catalyst performance, Cp reaches over 82% in 50 h; am reaches to 11.4 on average result of 50 h and Xm reaches over87% in 50 h.Catalyst modified by steam treatment was applied to shape-selective cracking of DIPB. It can get 90 kmol/h 99% m-DIPB by distillation with inputing quantity for 300 kmol/h, only with 70 theoretical plates in columns.
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