关键词: 甲醇制烯烃, C₄烃副产物, 预积炭, 再生催化剂, 乙烯丙烯选择性

Abstract:

The efficient utilization of C₄ by-product from methanol-to-olefins (MTO) plants is crucial for enhancing their competitiveness. In this study the performance of regenerated catalysts was optimized by C₄ pre-carbonization, and SAPO-34 molecular sieves were used as the core catalyst. The C₄ cracking reaction pathway, diene selectivity, and catalyst stability were systematically investigated at different temperatures. Industrial-grade regenerated catalysts were used in the experiment, and the C₄ pre-carbonization process was simulated using a fixed fluidized bed reactor. Combined with multi-scale characterization methods such as SEM, XRD, N₂ adsorption/desorption, and TGA, the synergistic mechanism of temperature regulation and pore modification was explored. The results showed that 600℃ was the optimal pre-carbonization temperature, with a C₄ catalytic cracking conversion rate exceeding 80% and a diene selectivity of 40.5%. The shape-selective catalysis of SAPO-34 preferentially cracked straight-chain C₄ components (1-butene, cis/trans-2-butene) while inhibiting the formation of branched hydrocarbons, demonstrating significantly superior performance compared to that in the thermal cracking pathway (with a 11.24% lower diene selectivity). The pre-carbonized species partially filled the micropores and formed secondary mesoporous channels, optimizing mass transfer efficiency through the "pore modification" mechanism. Although the lifespan of the pre-carbonized catalyst was slightly decreased, C₄ pre-carbonization had shortened the methanol reaction induction period, maintained high diene yield, retained the integrity of the molecular sieve crystal form and CHA topology, and exhibited excellent hydrothermal stability.

Key words: methanol to olefins, C₄ hydrocarbon by-product, pre-deposited carbon, regeneration catalyst, ethylene-propylene selectivity