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

摘要：

甲醇制烯烃（MTO）工业装置副产碳四（C₄）的高效利用是提升装置竞争力的关键。本文通过C₄预积炭工艺优化再生催化剂性能，以SAPO-34分子筛为核心催化剂，系统考察了不同温度下C₄裂解反应路径、双烯选择性及催化剂稳定性。实验采用工业级再生催化剂，通过固定流化床反应器模拟C₄预积炭过程，结合扫描电子显微镜（SEM）、X射线衍射（XRD）、N₂吸附-脱附等温线和热重分析（TGA）等多尺度表征手段，揭示了温度调控与孔道修饰的协同机制。研究结果表明，600℃为最优预积炭温度，C₄催化裂解转化率超80%，双烯选择性达40.50%；SAPO-34的择形催化作用优先裂解直链C₄组分（1-丁烯、顺/反-2-丁烯），同时抑制支链烃生成，其性能显著优于热裂解路径（双烯选择性差11.24百分点）。预积炭物种部分填充微孔并形成次级介孔通道，通过“孔道修饰”机制优化传质效率。尽管预积炭催化剂寿命略降，但可以缩短甲醇反应诱导期，维持高双烯选择性，且分子筛晶型与CHA拓扑结构保持完整，水热稳定性优异。

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