Synthesis and characterization of BZSM-5 and its catalytic performance in the methanol to hydrocarbons reaction

Five kinds of BZSM-5 molecular sieve with different Si/B ratio and a SiZSM-5 molecular sieve were pre-pared by hydrothermal synthesis method followed by acid exchange and pelletization.The samples were characterized by XRD,SEM,FT-IR,ICP,low temperature N2 physical adsorption and desorption,NH3-TPD and Py-IR.The catalytic performance in the reaction of methanol to hydrocarbons was evaluated in the fixed bed reactor.Compared with SiZSM-5,the amount and strength of Br(o)nsted (B) acid were enhanced by introducing skeleton boron and the activity of the catalyst was greatly improved.The characterization and evaluation results indicated that the BZSM-5 catalyst synthesized from the gel of SiO2/B2O320 with Si/B ratio 74.48 had modest acidity strength,acid amount of 0.18 mmol NH3·g-1 and large mesopore vol-ume of 0.23 cm3·g-1.The B acid ratio was higher and the acid strength of BZSM-5 was weaker than that of AlZSM-5,which could inhibit the deep coke formation and increase the activity stability.B-2 had the best lifetime which could reach 672 h under the same evaluation reaction conditions,due to the best match-ing of moderate acidity and good diffusion properties.