Research On Alkylation Of Benzene With Chlorinated Paraffins Catalyzed By Ionic Liquid

At present, most of researches on preparaing alkylbenzene focus onthe alkylation of benzene with olefin or monohydric alcohol, however, theakylation of benzene with chlorinated paraffins catalyzed by ionic liquidwas rarely reported. In this paper,2-chloropropane and tert-butyl chlorideare used as alkylating reagent to alkylate with benzene to prepare cumeneand tert-butyl benzene, and the mechanism of alkylation reactioncatalyzed by ionic liquid is also discussed.Firstly, we use pyridine and acetone as a probe molecular tocharacterize the acid activity of ionic liquids, the result showed that theacidity of the chloro-aluminated ionic liquids is mainly decided by theanion. In the process of preparing cumene, we investigate the effect ofionic liquids of different cation, mole ratio of AlCl3to [Et3NH]Cl, moleratio of benzene to2-chloropropane, amount of ionic liquid and thereaction temperature on alkylation of benzene with2-chloropropane. Inthe same time, and studied the influence ionic liquids of different cationon the activity and reusability of chloro-aluminate ionic liquids. The result showed that,[Et3NH]Cl-2AlCl3shows the better catalytic effect,and increasing the mole ratio of benzene to2-chloropropane, amount ofionic liquid, and reaction temperature can lead to the promotion of theselectivity of cumene. The ideal reaction condition is that, using[Et3NH]Cl2AlCl3as catalyst, the amount of catalyst was10%wt ofbenzene, mole ratio of benzene to2-chloropropan was3.3and thereaction temperature was55, under the ideal reaction condition, theconversion of benzene was29.3%, and the selectivity of cumene was90.1%.[Et3NH]Cl-2AlCl3can also show the best reusability, after fivetimes of reusing, the catalytic effect did not significantly change.In the process of preparing tert-butyl benzene, we investigate theeffect of ionic liquids with different cation, mole ratio of benzene totert-butyl chloride, and the reaction temperature on alkylation of benzenewith tert-butyl chloride, and also use both fresh benzene and benzene ofrecycling as material to study the reusability of chloro-aluminate ionicliquids. The result showed that,[Et3NH]Cl-2AlCl3shows the bestcatalytic effect, with the increasing of mole ratio of benzene to tert-butylbenzene and the reaction temperature, the selectivity of tert-butyl benzeneshows an upward trend. The ideal reaction condition is that, the amountof catalyst was10%wt of benzene, mole ratio of benzene to tert-butylchloride was2.9and the reaction temperature was55. Under the idealreaction condition, the conversion of benzene was32.5%, and the selectivity of tert-butyl benzene was91.2%. Only di-tert-butyl benzenewas detected in the byproduct. The catalyst of [Et3NH]Cl-2AlCl3can bereused for four times, and it shows no obvious influence on thereusability of ionic liquid with the recovery of benzene as a feedstock, theinactivation of ionic liquid can be regenerated via adding AlCl3. It alsoprovides a lot of reference data for2000t/a pilot in Heze and determinesthe pilot process.Alkylation of benzene with Chlorinated paraffins catalyzed by ionicliquid was the typical Friedel-Craft reaction, it obeys the mechanism ofcarbocations, the reaction activity mainly depends on the stability andactivity of carbocations, by comparing the process of synthesis of cumeneand tert-butyl benzene, we can see that, under the same reaction condition,the alkylation of benzene and chloro-tert-butane alkylation can be easierthan the reaction with2-chloropropane, this is due to the difference ofstability of carbocations.