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

Abstract

Five kinds of BZSM-5 molecular sieve with different Si/B ratio and a SiZSM-5 molecular sieve were prepared by hydrothermal synthesis method followed by acid exchange and pelletization. The samples were characterized by XRD, SEM, FT-IR, ICP, low temperature N 2 physical adsorption and desorption, NH 3 -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 Brönsted (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 SiO 2 /B 2 O 3 20 with Si/B ratio 74.48 had modest acidity strength, acid amount of 0.18 mmol NH 3 ·g −1 and large mesopore volume of 0.23 cm 3 ·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 matching of moderate acidity and good diffusion properties. HBZSM-5 molecular sieve catalysts with different Si/B ratio were prepared by hydrothermal synthesis method followed by acid exchange and pelletization. The samples were characterized by XRD, SEM, FT-IR, ICP, low temperature N 2 physical adsorption and desorption, NH 3 -TPD and Py-IR. The catalytic performance in the reaction of methanol to hydrocarbons was evaluated in the fixed bed reactor. The results indicated that the BZSM-5 catalysts synthesized from gel of SiO 2 /B 2 O 3 20 with Si/B ratio 74.48 had modest acidity strength, acid amount of 0.12 mmol NH 3 ·g −1 , the ratio of B/L 3.27 and large mesopore volume of 0.23 cm 3 ·g −1 . It had the best lifetime, which could reach 672 h under the same evaluation reaction conditions. The B acid ratio was high and its strength of BZSM-5 was weaker than that of AlZSM-5, which could inhibit the deep coke formation and increase the activity stability.