Research On Shape-selective Synthesis Of P-Diisopropylbenzene Over Beta Zeolite

As an efficient way to produce p-isomers, shape-selective catalysts have been paid more and more attention by the chemical industry. Till now, lots of researchers dedicate to this field. ZSM series,Y,MOR and SAPO series are common p-selection zeolites to catalyze aromatics alkylation, but fewer records about zeoliteβ.In this paper, the alkylation of cumene (IPB) with isopropyl alcohol (IPA) for preparing p-DIPB on modified Hβzeolites was studied. The purpose is to discuss the chief factors of p-DIPB selectivity, then corresponding measures can be advanced. The catalysts were characterized by means of UV,XRD,FT-IR,NH₃-TPD,BET etc., and these results were related to their catalytic performances. Some conclusions were obtained as below:(1) When the alkylation of cumene with isopropyl alcohol proceeds in autoclave, the optimal reaction conditions are that, mole ratio of isopropyl alcohol to cumene 4:1, reaction temperature 250℃, catalyst dosage 10w%, and reaction time 5 hrs. Under this condition, a m/p=1.21 selective to m-DIPB/p-DIPB is achieved at a 57.2% cumene conversion.(2) By comparison of the physical and chemical properties between ZSM-5,MOR,HY and Hβ, it was found, Hβis the most suitable choice for cumene isopropylation to generate p-DIPB in zeolite catalysts, for it has more effective acids with high activity. But its selectivity has to be further enhanced.(3) When covered with silicone oxide, at 250℃, catalyst dosage 10w%, a m/p=1.00 selective is achieved at a 20% cumene conversion; and when loaded of copper,boron or phosphorus oxides, the cumene conversion increased to 70%, but the selectivity was unchanged or decreased. However, rare earth metal oxides (Ce₂O₃ and La₂O₃) modified zeolites had their conversion rate down to 30%, but the selectivity can improve to m/p=0.80.(4) This paper studied the alkylation of cumene on fixed bed micro-reactor to discuss the effect of product diffusion. A highly selective catalyst for cumene alkylation is obtained by previous carbon-covering treatment to sample 4%Ceβ. When IPA/IPB=4:1, catalyst dosage 10mL, reaction temperature 300℃, WHSV 5h^-1, reaction pressure 3MPa and H₂/materials=300 (volume ratio), a m/p=0.66 selective to m-DIPB/p-DIPB is achieved at a 23% cumene conversion.