GOALI: A Fundamental Study of Hydrocarbon Cracking on Acidic Zeolites

摘要 提案标题： GOALI：碳氢化合物的基础研究 酸性沸石上的裂化建议编号： CTS-9807333主要研究者：Harold H. Kung，Jeffrey米勒和Randall Q. Snurr机构： 西北大学 这个GOALI提案是西北大学（H。H. Kung和R. Q. Snurr）和Amoco Chemicals RD（Jeffrey米勒）。目的是确定HY分子筛水蒸气脱铝提高催化裂化活性的机理。在所提出的烷烃催化裂化模型中，三种反应机理是可操作的：涉及非经典碳正离子的单分子裂化，涉及氢化物转移和β-断裂的双分子裂化，以及涉及烷基化、低聚、氢化物转移和β-断裂的低聚裂化。虽然双分子和低聚物裂化都强烈依赖于烷烃分压，但单分子裂化强烈依赖于酸强度，并且低聚物裂化是扩散限制的。在实验上，主导机理表现在产物分布上，并受操作条件的控制。因此，将在对应于预定机制的条件下研究脱铝HY中活性增强的各种可能原因。新酸中心的形成将通过单分子裂化速率来测试。骨架外铝的作用将通过对比单分子和双分子低聚物裂化的速率来确定。通过对比单分子、双分子和低聚速率，阐明内扩散在介孔和缺陷中的作用。还需要研究的是酸性位点的选择性中毒的影响，例如，Na;结果表明，催化裂化反应的表观活化能与吸附热有关，吸附热对表观活化能的贡献，反应物烷烃的吸附对竞争裂化反应选择性的影响。实验吸附研究将得到理论计算和二元吸附等温线模拟的支持。

ABSTRACT Proposal Title: GOALI: A Fundamental Study of Hydrocarbon Cracking on Acidic Zeolites Proposal Number: CTS-9807333 Principal Investigators: Harold H. Kung, Jeffrey Miller and Randall Q. Snurr Institution: Northwestern University This GOALI proposal is a collaboration between Northwestern University (H. H. Kung and R. Q. Snurr) and Amoco Chemicals R&D (Jeffrey Miller). Its objective is the determination of the mechanisms responsible for the enhancement of catalytic cracking activity produced by the steam dealumination of HY zeolite. In the proposed model of catalytic cracking of alkanes, three reaction mechanisms are operative: monomolecular cracking involving a non-classical carbocation, bimolecular cracking involving hydride transfer and beta-scission, and oligomeric cracking involving alkylation, oligomerization, hydride transfer and beta-scission. While both the bimolecular and oligomeric cracking are strongly dependent on alkane partial pressure, the monomolecular cracking is strongly dependent on acidic strength, and the oligomeric cracking is diffusion limited. Experimentally, the dominant mechanism would be manifested in the product distribution, and could be controlled by the operating condition. Therefore, various possible causes of enhanced activity in dealuminated HY will be studied under conditions that correspond to a predetermined mechanism. The formation of new acid sites will be tested by means of the monomolecular cracking rate. The role of extra-framework Al will be determined by contrasting the rates of monomolecular and bimolecular-oligomeric cracking. The role of internal diffusion in mesopores and defects will be elucidated by contrasting monomolecular, bimolecular, and oligomeric rates. Also to be studied are the effects of selective poisoning of acid sites, e.g., Na; of zeolite type (Y, ZSM-5, ferrierite, mordenite); of adsorption heat contribution to apparent activation energy; of adsorption of reactant alkanes on the selectivity of c ompeting cracking reactions. The experimental adsorption study will be supported by theoretical calculations and simulations of binary adsorption isotherms.