Unraveling the effects of crystallization parameters on affordable semi-industrial scale synthesis of high-performance H-[B]-ZSM-5 for conversion of methanol to propylene (MTP)

Abstract

In light of the prohibitive expense associated with commercially available ZSM-5 catalysts, this investigation aimed to develop a cost-effective alternative exhibiting similar or superior catalytic activity compared to existing benchmarks. Unlike traditional synthesis optimization techniques, which typically employ isolated modification strategies, this study presents an innovative multiple-approach methodology, combining boron incorporation and application of a suspension form ball-milled silicalite-1 seed with adjusting the crystallization parameters, for the production of high-silica H-[B]-ZSM-5 (Si/Al = 200), the factors that have frequently been overlooked in the majority of studies. Through systematic variation of crystallization time and temperature, an integrated synthesis protocol was established, yielding enhanced catalytic performance beyond conventional optimization techniques. Building on extensive prior investigations, H-[B]-ZSM-5 catalysts were synthesized using ball-milled silicalite-1 seeds under various crystallization time and temperature (CtT) conditions (150–170 °C, 18–42 hours). The properties of the samples were characterized through XRD, FE-SEM, BET, NH₃-TPD, and FT-IR analyses. The catalytic performance in the MTP reaction was evaluated in a fixed-bed reactor under severe operating conditions (WHSV = 8 h⁻¹, MeOH/H₂O = 90/10). The optimal CtT conditions (170 °C, 18 h) at a semi-industrial scale (2.5 L) resulted in a H-[B]-ZSM-5 catalyst with high crystallinity, appropriate acidity, and superior catalytic activity (377 g_propylene g_cat⁻¹), accompanied by a reduction in preparation time and energy consumption (18 h vs. 48 h for the conventional catalyst with 10 °C less required temperature). Demonstrating a 47% enhancement in catalytic performance compared to the commercial benchmark (255 g_propylene g_cat⁻¹) under identical reaction conditions, this study establishes a scalable and cost-effective strategy for fabricating high-performance H-[B]-ZSM-5 tailored for industrial MTP applications.