GOALI: A Fundamental Study of Hydrocarbon Cracking on Acidic Zeolites

提案题目：GOALI：酸性沸石上烃类裂解的基础研究提案号：ccs -9807333主要研究人员：Harold H. Kung， Jeffrey Miller和Randall Q. Snurr机构：西北大学该GOALI提案由西北大学（h.h. Kung和R. Q. Snurr）和Amoco Chemicals R&amp；D （Jeffrey Miller）合作完成。其目的是确定HY沸石蒸汽脱铝提高催化裂化活性的机理。在提出的烷烃催化裂化模型中，有三种反应机制：涉及非经典碳正离子的单分子裂化，涉及氢化物转移和裂解的双分子裂化，以及涉及烷基化、低聚化、氢化物转移和裂解的低聚裂化。双分子裂解和低聚物裂解均强烈依赖于烷烃分压，单分子裂解强烈依赖于酸性强度，低聚物裂解受扩散限制。实验结果表明，主导机理表现在产品分布上，并可由操作条件控制。因此，在符合预定机制的条件下，将研究脱铝HY活性增强的各种可能原因。新酸位的形成将通过单分子裂解速率进行测试。框架外Al的作用将通过对比单分子和双分子低聚物的裂解速率来确定。内部扩散在介孔和缺陷中的作用将通过对比单分子、双分子和低聚物速率来阐明。还需要研究选择性中毒酸性部位的影响，例如Na；沸石型（Y型、ZSM-5型、铁素体、丝光沸石）；吸附热对表观活化能的贡献；吸附反应物烷烃对c竞争裂化反应选择性的影响。实验吸附研究将由理论计算和模拟二元吸附等温线来支持。

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.