The effects of the structure and concentration of impurities on the alkylation of naphthalene with 1-octene catalyzed by chloroaluminate ionic liquid (IL) were investigated. The presence of impurities containing oxygen and nitrogen led to a decrease in the catalytic performance of chloroaluminate IL. As the water concentration increased to 65 mg·g –1 , the total selectivity of multi-octylnaphthalene gradually decreased to 42.33%, and the average friction coefficient of the multi-octylnaphthalene base oil gradually increased to 0.201. When the concentration of impurities increased to a critical value, the chloroaluminate IL began to deactivate, leading to a decrease in naphthalene conversion. The critical concentrations for ethanolamine, water, methanol, ether, and diisopentyl sulfide were 33 mg·g –1 , 65 mg·g –1 , 67 mg·g –1 , 87 mg·g –1 , and 123 mg·g –1 , respectively. Impurities with higher basicity resulted in an earlier onset of chloroaluminate IL deactivation. The changes of Lewis and Brønsted acids in chloroaluminate IL under the influence of impurities were investigated using in situ IR and 27 Al NMR spectroscopy. 2,6-dimethylpyridine as an indicator could detect the changes of Brønsted acid in chloroaluminate IL better, but the changes of Lewis acid were not obvious because of the overlap between the characteristic peaks. 2,6-dichloropyridine as an indicator could exclusively detect the changes of Lewis acid in chloroaluminate IL. With the increase in water concentration, the Lewis acid in chloroaluminate IL was continuously consumed and converted into Brønsted acid, and the Lewis acid gradually decreased, while the Brønsted acid showed a change of increasing first and then decreasing.
Yetong Li,Kailong He,Siyuan Zhao,Linyu Jiao,Huiyong Chen,Xiaoxun Ma,Chengyi Dai
Many researchers have extensively studied the alkylation of naphthalene with methanol for the preparation of high-value-added chemicals, especially methylnaphthalenes (MNs). Studies indicated that methanol generates a large number of methanol-to-olefin by-products on zeolites, resulting in low selectivity of the target product and poor stability of the catalyst, limiting its application in the industrial field. In this study, CO 2 hydrogenation was coupled with naphthalene alkylation, and the H 3 CO* active intermediate generated in situ was alkylated with naphthalene by using metal oxide-zeolite (OX-ZEO) bifunctional catalysts, which exhibited the ‘slow release’ phenomenon of the methylation reagent. It improved naphthalene conversion, suppressed deep alkylation and coke deposition side reactions and kept the catalyst stable for up to 500 h. A high-density and medium-strength Brønsted acid center facilitated the efficient migration of H 3 CO* active intermediates with the desorption of 2-methylnaphthalene (2-MN), which was particularly important for improving naphthalene conversion and 2-MN selectivity. The in situ IR showed that more Brønsted acid sites of Ga-S-1 effectively pulled the migration process of H 3 CO* species to the zeolitic acid center and increased the efficiency of C-C coupling compared to ZSM-5, which promoted the alkylation of H 3 CO* species with naphthalene. The results of chemisorption experiments showed that the medium-strength Brønsted acid site, which promoted the desorption of 2-MN, inhibited the deep alkylation reaction. The 2,6-dTBPy-IR results showed that the presence of fewer Brønsted centers on the outer surface of Ga-S-1 further optimized the product distribution and enhanced the selectivity of 2-MN in MNs to more than 90 %. Under optimal conditions, 80.1 % selectivity for MNs was obtained via ZnZrO x &Ga-S-1 bifunctional catalysts, with 97.4 % selectivity for 2-MN in MNs.
Using coal-based feedstocks to produce chemicals is of importance for the high value-added utilization of coal and the reduction of petroleum consumption. Alkyltetralins similar to naphthenic oil were successfully obtained through tetralin alkylation with various olefins. Various ionic liquids (ILs) were applied to catalyze alkylations, and Et 3 NHCl-AlCl 3 IL exhibited high catalytic activity under mild reaction temperature (80 °C), the selectivity of multi-alkyltetralins higher than 70% could be achieved at >99% tetralin conversion. Such catalyst was shown to be robust in the presence of trace water and oxygenated chemicals. COSMO-RS model was applied to predict the mutual solubility and interaction of tetralin, olefins and alkyltetralins in ILs. The experimental and calculated results demonstrated that the favorable interactions of shorter-chain olefins and ILs benefited to produce multi-alkyltetralins, and the low mutual solubility of reactants and products in ILs was helpful to the rapid separation of products in the system.
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