Optimization And Research On The Green Acylation Reaction

Friedel-Crafts acylation is a crucial method for manufacturing aromatic ketones with high additive value.Traditionally,Broensted acids（e.g.H₂SO₄,HCl and HF）and Lewis acids（e.g.AlCl₃,FeCl₃,and BF₃）are often used as homogeneous catalysts,unfortunately,the commonly encountered defects of conventional acylation synthesis cover the excessive consumption of spent catalysts,equipment corrosion,products collection,the complicated handling of toxic wastes and environmental pollution.Thus,it is highly desirable to search for the ecofriendly and efficient processes by usage of heterogeneous catalysts.The study shows that some new catalysts such as MCM-41zeolites and Lewis acid ionic liquids were considered to be the most potential catalyst for acylation reaction due to their high catalytic activity,renewability and eco-friendly.In this work,the acylation experiment of 2-methylfuran and furan with acetic anhydride combined with the Box-Behnken design were carried out to study the effects of reaction factors on its acylated results in a batch reactor.The response surface methodology was applied to determine the optimal acylation conditions.Excellent catalytic activity was obtained in acylation of furan and 2-methylfuran catalyzed by Hβzeolite,whereas,a rapid catalyst deactivation occurred with a sharp decrease of the molar yield of product.Thus,deactivated Hβwere recovered and extracted in a soxhlet with dichloromethane,and the carbon deposit was proved the main reason for the deactivation of Hβby using GC/MS,SEM,¹³C NMR MAS,²⁷Al NMR MAS and TG-DTG characterization.To illustrate the effects of acid and chemical liquid deposition modification on the catalytic performances,we herein compared the continuous acylation results of 2-methylfuran over modified and parent Hβzeolites in fixed bed.According to the result of NH₃-TPD,Py-FTIR,the Broensted acids played a major role on catalytic activity,an increase in amounts ratio of B/L contributes to enhancing the catalytic stability.A close correlation between the catalytic stability and the ratio of the amount of strong to weak acids at 1:1 was highlighted.The solvents’effect on the catalytic performances was examined,and 1,2-dichloroethane with moderate polarity exerted a positive effect on catalytic stability.The deactivation of parent and modified Hβwere more severe in continuous liquid phase acylation of toluene.However,it was interesting to find that the higher catalytic stability can be acquired by MCM-41 zeolites and[Bmim]Cl-AlCl₃ ionic liquids.Nevertheless,low catalytic activity was obtained on MCM-41 zeolites,[Bmim]Cl-AlCl₃ can also show the better activity in acylation reaction of toluene with acetic anhydride,which need to keep on researching in future.