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论文类型：期刊论文

发表时间：2012-02-16

发表刊物：JOURNAL OF PHYSICAL CHEMISTRY C

收录刊物：SCIE、EI、Scopus

卷号：116

期号：6

页面范围：4071-4082

ISSN号：1932-7447

摘要：Methylation of 2-methylnaphthalene (2-MN) for synthesis of, 2,6-dimethylnaphthalene (2,6-DMN) is an industrially important reaction because 2,6-DMN is a key precursor for the advanced polymer material polyethylenenaphthalate. Shape-selective methylation of 2-MN with methanol in an H-ZSM-5 pore was studied using the ONIOM2 model and density functional theory. Two proposed reaction mechanisms, stepwise and concerted, were considered. Computational results reveal that the stepwise. path, with methanol dehydration to produce a methoxide intermediate as the rate-limiting step, is kinetically favored. Both the stepwise and concerted path indicated that methylation at the 6-position is favored over methylation at the 7-position; however, the concerted path shows a greater selectivity. 2-MN isomerization and methylation, which may occur on the catalyst external surface and decrease selectivity to the desired 2,6-DMN product were also examined. Isomerization of 2-MN to 1-MN proceeds faster on external surface sites than 2-MN methylation with methanol. Decreasing the external surface acid site concentration will restrict the extent of 2-MN isomerization, therefore increasing the beta,beta'-DMN selectivity inside the pore.