High Silicon Hierarchical ZSM-5 Zeolite Prepared by Alkaline Treatment Catalyzed MTP Reaction
The parent boron-silicon zeolite was synthesized by hydrothermal method,and then treated with NaOH solution alone or NaOH and hexadecyl trimethyl ammonium bromide(CTAB)mixed solution;moreover,a series of high silicon hierarchical ZSM-5 samples(BHZ-A and BHZ-AB series samples)were prepared by adding Al source in the alkaline solution.The pore structure and acid properties of the samples are characterized by XRD,SEM,ICP,Ar adsorption-desorption,NH3-TPD and thermogravimetric analysis.The protective effect of CTAB is proposed as below:CTAB inhibits the desilication of NaOH to protect the zeolite from excessive etching during alkaline treatment.The performance of BHZ(H-type ZSM-5 containing B)molecular sieve sample in methanol to propylene(MTP)reaction for 72 hours was evaluated on a fixed bed reactor under pressure of 0.1 MPa,reaction temperature of 743 K,H2O/CH3OH molar ratio of 1/1,and methanol MHSV of 3 h-1.The results show that the strong acid content of the high silicon hierarchical ZSM-5 zeolite prepared by alkali treatment is the main factor affecting its performance in MTP reaction and coke deposition.Boasting of rich mesopores and suitable acidity,BHZ-0.1A and BHZ-0.1AB samples exhibit excellent performance in MTP reaction,with the propylene selectivity and carbon deposition of about 50％and 1.5％respectively.
alkaline treatmenthexadecyl trimethyl ammonium bromidemethanol to propyleneZSM-5 zeolite
万方数据
维普
