Isobutane Alkylation Catalyzed By Trifluoromethanesulfonic Acid In Acidic Deep Eutectic Solvents/Polyether System

Isobutane alkylation requires a strong acid as a catalyst,which has stringent requirements for the preparation of the catalyst.Br?nsted acid has better stability than Lewis acid in air.Trifluoromethanesulfonic acid?TfOH?is used as organic super Br?nsted acid.H₀=-14.6 meets the acidity need for C₄ alkylation and TfOH has high catalytic activity.Ionic liquids?ILs?and their analogues--deep eutectic solvents?DESs?are potential catalysts for isobutane alkylation because of their many unique advantages.In order to resolve the problem of the catalyst recycle and increase the selectivity of TfOH,this paper designed three major catalytic systems for the preparation of alkylate gasoline.?I?the catalytic system of TfOH-based DESs;?II?the catalytic system of TfOH in polyether ionic liquid;?III?the catalytic system of acidic DES in polyethylene glycol?PEG?.A series of DESs were designed and synthesized.It was found that the DES of ChCl/TfOH had the best catalytic performance for the C₄ alkylation reaction.When the acid content was 0.83,the best catalytic activity was achieved.The liquid nitrogen condensation method was used,and the melting point was determined to be-20 ^oC.ChCl/TfOH DES with the best acid content was characterized by nuclear magnetic resonance spectroscopy?¹H-NMR?,infrared spectroscopy?FT-IR?,and thermal gravimetric technique?TG?.The optimum reaction conditions for the preparation of alkylate gasoline were as follows:T=40 ^oC,t=40 min,V?raw material?=10 m L,RS=800 r/min.Under this condition,the conversion rate of isobutene reached 100%,and the content of C₈ component in the alkylation product was the highest at 43.62%.The DES of ChCl/TfOH was recycled for 5 times.The catalytic activity did not decrease significantly.A series of Br?nsted acidic polyether ionic liquids with different degree of polymerization?n value?were prepared by the reactions of tetramethylguanidine and different amount of epoxy ethane,followed by the successive reactions with 1,3-propane sultone and TfOH.The typical ionic liquid was characterized by ¹H-NMR and FT-IR,and its thermal stability was determined by TG.The synthesized ionic liquids were used for catalyzing alkylation reaction of isobutane and isobutene for the preparation of alkylate gasoline.By gas chromatographic analysis to determine isobutene conversion and C₈ selectivity,the best ionic liquid?n=94?was determined.The optimized alkylation reaction conditions were as follows:V_TfOH:V_IL=0.35,T=40 ^oC,t=50 min,RS=800 r/min.The conversion of isobutene was 92.4%,and the selectivity of C₈-product was 81.6%.Under the optimal conditions,the catalyst life was studied.The result showed that TfOH had better cyclic performance in guanidinium polyether ionic liquid.After eight times recycles,the catalytic activity of the catalyst was found without significant decline.Taurine?TAU?was mixed with Tf OH to prepare TAU/TfOH acidic DES.The structure of DES was characterized by ¹H-NMR,FT-IR and TG.The deep eutectic solvents was dissolved in PEG to obtain three components for the catalytic preparation of alkylate gasoline.Under the optimal reaction conditions(n_TAU:n_TfOH=1:3?V_{PEG 200}=10 mL?T=80 ^oC?t=60 min?RS=800 r/min),the maximum conversion rate of isobutene was 82.59%,and the maximum content of alkylate oil was 85.54%.Under this condition,the catalyst was recycled for 8 times and still had high catalytic activity.The three catalytic systems designed in this article have for the first time been applied to the preparation of alkylate gasoline.The first catalytic system of Br?nsted acidic DESs has showed excellent catalytic activity.The second catalytic system of the polyether ionic liquids has showed good product selectivity.The third catalytic system of the three-component catalytic system including DES and polyether has exhibited both excellent catalytic activity and good product selectivity.The paper provides a new thinking for the preparation of alkylate gasoline under the condition of low molar ratio of isobutene/butane?I/O=10:1?,and the novel catalytic system has potential industrial application value.