Hongyan Wang,Song Ma,Zhimao Zhou,Minjie Li,Hui Wang
The alkylation process of iso butane with butene is important in the petroleum industry. Ionic liquids (ILs) are considered as attractive alternative catalysts for iso butane alkylation besides strong liquid acids (H 2 SO 4 or HF) and solid superacids. In this study, ILs based on amides-aluminum chloride (AlCl 3 ) were synthesized and characterized, which exhibited both Lewis and Brønsted acidities. These deep eutectic ILs were found to be efficient catalysts for iso butane alkylation. The influences of the amide substrate, AlCl 3 /amide molar ratio, and metal additive on Lewis and Brønsted acidities were observed together with the synergetic effect of Lewis and Brønsted acid sites in the catalytic process. CuCl modified Urea-1.6AlCl 3 showed the best catalytic performance. The butene conversion was about 99.9% and C8 selectivity reached 57.6% under optimized reaction conditions (temperature of 15 °C, stirring rate of 1500 rpm, hydrocarbon feeding rate of 300 mL/h, iso butane/olefin molar ratio of 15:1, and reaction time of 15 min). In addition, Urea-1.6AlCl 3 -0.13CuCl could be recycled and reused for at least 20 times without obvious loss in catalytic activity.
Honghua Zhang,Ruixia Liu,Zhiqiang Yang,Feng Huo,Ruirui Zhang,Zihang Li,Suojiang Zhang,Yanji Wang
In this work, the alkylation of isobutane and butene, catalyzed by sulfuric acid in the presence of the fluoride–containing ionic liquids [Bmim][PF 6 ] and [Bmim][SbF 6 ], was investigated. The use of the binary mixture catalysts brought to a higher C 8 selectivity and longer catalyst lifetime, compared with the results obtained when working with sulfuric acid only. This was attributed to the formation of new species when [Bmim][PF 6 ] or [Bmim][SbF 6 ] are added to sulfuric acid. The acidolysis of [Bmim][PF 6 ] and [Bmim][SbF 6 ] was accompanied by the release of hydrogen fluoride (HF) and the decomposition of anions to [PF 6−x−2y (HSO 4 ) x (SO 4 ) y ] − and [SbF 6−x−2y (HSO 4 ) x (SO 4 ) y ] − , respectively. The presence of these new species after acidolysis was measured and confirmed by ion chromatography, 1 H–Nuclear Magnetic Resonance (NMR), 19 F–NMR and 31 P–NMR. The production of HF and the complexation of anions and carbenium ions both play an important role in stabilizing the carbenium ion and improving the catalytic performance.
To enhance the catalytic performance of H 2 SO 4 -catalyzed alkylation, various catalytic additives have drawn considerable attentions. Herein, the effects of deep eutectic solvent (DES) additives on catalytic performance and the interfacial properties of H 2 SO 4 alkylation were systematically investigated using experimental methods and molecular dynamics (MD) simulation. Experimental results indicate that DESs with the optimal concentration about 1.0 wt% can efficiently improve C 8 selectivity and research octane number of alkylate, especially at low temperature, but contribute less to the lifetime of H 2 SO 4 . MD results reveal that the phenyl molecules of DESs additives play a major role in enhancing interfacial properties of H 2 SO 4 alkylation, including enlargement of interfacial thickness, promotion of isobutane relative solubility and diffusion to butene, which is probably the main reason for the better quality of alkylate. This work gives a good guideline for the design of novel DESs for H 2 SO 4 alkylation.
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