石油学报(石油加工) ›› 2019, Vol. 35 ›› Issue (3): 555-560.doi: 10.3969/j.issn.1001-8719.2019.03.025

• 研究报道 • 上一篇    下一篇

甲醇转化制丙烯反应机理研究

贺振富   

  1. 国家能源集团公司, 北京 100011
  • 收稿日期:2018-08-20 修回日期:2018-11-22 出版日期:2019-05-25 发布日期:2019-07-22
  • 通讯作者: 贺振富,男,教授级高级工程师,博士,从事石油化工、煤化工方面的研究;E-mail: zhenfu.he@chnenergy.com.cn E-mail:zhenfu.he@chnenergy.com.cn

Reaction Mechanism of Methanol to Propylene

HE Zhenfu   

  1. CHN Energy, Beijing 100011, China
  • Received:2018-08-20 Revised:2018-11-22 Online:2019-05-25 Published:2019-07-22

摘要: 以杂化轨道理论和关于含Si、Al元素催化剂酸中心的认识为理论依据和研究方法,从反应物与催化剂B酸中心相互作用为切入点,分析相互作用过程中甲醇与B酸中心分子结构变化,揭示甲醇制烯烃反应机理本质。研究结果表明甲醇转化制丙烯反应过程可分为3步:(1)B酸中心释放H+攻击甲醇分子中C-O键,C-O键断裂生成甲基碳正离子(CH+3)和H2O,CH+3中C原子外层有个空轨道,释放了H+后的B酸中心失去活性。(2)失活B酸中心从CH+3中获得H+,反应生成了一种新中间体H-form,H-form中C原子外层有1对孤对电子(e-)和1个空轨道,结构式为C↑↓〇H2;失活的B酸中心获得H+后恢复活性。第3步,有3个H-form结构的C原子,第1个C原子上的孤对e-占据第2个C原子上空轨道,第2个C原子上的孤对e-占据第1个C原子上空轨道,彼此共用2对e-,形成C=C键;第3个C原子上的空轨道与第1个C原子上C、H原子重叠轨道再次重叠,形成C、H和C三原子共用1对e-结构,结果是第1个C原子与第2个C原子形成C=C键,第1个C原子与第3个C原子形成C-C键,3个C原子形成C=C-C结构,即生成丙烯。

关键词: 甲醇;丙烯;甲基碳正离子CH3+;中间体C↑↓〇H2, H-form6配位B酸中心

Abstract: Based on the hybrid orbital theory, knowledge of acid center of Silicon and Aluminum-containing catalysts and the mutual interaction between the reactant and the catalyst B-acid center, the molecular structure of methanol and Bacid center in the interaction process are investigated. Through the above studies, the nature of reaction mechanisms of methanol to olefins are understood. It was found that the methanol-to-propylene (MTP) reaction process could be divided into three steps: At the first step, the B-acid center provides hydrogen proton (H+) to attack the C- bond in the methanol molecule, and the C-O bond breaks to form methyl carbocation (CH+3) and H2O. The outer layer of the carbon atom of the CH+3 has an empty orbit, but the B-acid center after the release of the hydrogen proton (H+) loses its activity. At the second step, the inactivated B-acid center obtains hydrogen proton (H+) from CH+3, and the reaction produces a new intermediate H-form. H-form has a pair of lone pairs of electrons (e-) and an empty orbit. The structural formula is C↑↓〇H2, where the double arrow represents the lone pair e-, and the circle represents the empty orbit. Thus, the inactive B-acid center recovers the activity after obtaining hydrogen proton (H+). At the third step, there are three carbon atoms of Hform structure, the lone pair e- on the first carbon atom occupies the an empty of the second carbon atom, and the lone pair e- on the second carbon atom occupies an empty orbit of first carbon atom, then first carbon and second carbon atoms share two pairs e- to form a C=C double bond;the empty orbit on the third carbon atom overlaps with the overlapping orbit of the carbon and hydrogen atoms on the first carbon atom, forming a pair e- structure which carbon, hydrogen and carbon atoms share with each other. As a result, the first carbon atom forms a C=C bond with the second carbon atom, and the first carbon atom forms a C-C bond with the third carbon atom. Then the three carbon atoms of H-form structure lead to a C=C-C structure, which is propylene.

Key words: methanol, propylene, methyl carbocation CH3+ ; H-form C↑↓〇H2, 6-Coordinatied B-acid center