Research On Preparation Of Alkylated Gasoline Catalyzed By Ployether-based Acidic Deep Eutectic Solvents

Alkylated gasoline is produced by catalytic alkylation of C₄ alkanes and alkenes under strong acid conditions.Compared with the gasoline produced by the traditional catalytic cracking process,alkylated gasoline has the advantages of high octane number,low steam,no sulfur,no aromatics and so on.These characteristics make it an excellent gasoline mixture.At present,liquid acid,solid acid,ionic liquid and other acidic catalysts are mainly used at home and abroad.However,these catalysts have a series of problems,such as high cost,high toxicity,environmental pollution,corrosion equipment and cumbersome post-treatment process,which is inconsistent with the country’s demand for green chemistry.Therefore,the development of green,non-toxic,economic,environmentally friendly new catalysts is very important.Deep eutectic solvent has broad application prospects in catalysis,organic synthesis,electrochemistry and biomass treatment due to its characteristics of cheap raw materials,simple preparation,high atomic utilization rate,non-toxicity and biodegradability.Current studies have shown that alkene dissolves in catalysts better than alkane to generate self-polymerization.In order to inhibit the self-polymerization of alkene,it is necessary to increase the alkane-to-alkene ratio so that the alkane in the catalyst can better contact with the alkene,but the increase of the alkane-to-alkene ratio also increases the cost.In previous studies,our research group found that polyether has a high solubility to isobutane,so we intend to use polyether as a component of deep eutectic catalyst to achieve the purpose of preparing high-quality alkylated gasoline at a low alkane-to-alkene ratio.In this paper,based on the determination of the solubility of isobutane and isooctane in different polyethers,some suitable polyethers were selected as the component of deep eutectic catalyst to synthesize polyether-based acidic deep eutectic catalysts for catalytic alkylation reaction,in order to achieve the catalytic preparation of high-quality alkylated gasoline at low alkane-to-alkene ratio.The structure and stability of the catalyst were studied by FT-IR,¹H NMR,pyridine IR and TG.The research content of this thesis is mainly divided into the following three parts:（1）On the one hand,by self-assembling a set of reactor and pipeline equipment,and using the supporting physical and chemical formula,the solubilities of isobutane in polyethers were determined,and the influence of temperature and pressure conditions on the solubility was explored.The combination of isobutane and polyether was simulated by DFT method and the result was compared with experiment.On the other hand,the solubilities of isoctane in different polyethers were determined by ultraviolet spectrophotometer and Langerber’s law.Then,based on the solubility ratio between isobutane and isoctane,suitable polyethers were selected as catalyst components,and a series of polyether-based deep eutectic catalysts were synthesized for the subsequent catalytic alkylation reaction.By comparing the data,it is more suitable to select small molecular weight polyethers（PEG200 and PPG200）as the DES component,which can realize the high solubility of alkylation raw materials and low solubility of alkylation products.（2）A series of polyether-based Br（?）nsted acidic deep eutectic solvents were synthesized by using the optimized polyether and trifluoromethanesulfonic acid（Tf OH）as two components of the deep eutectic solvent,and trichloroacetic acid,trifluoroacetic acid,salicylic acid,citric acid,tartaric acid,betaine,p-toluenesulfonic acid,oxalic acid and ice acetic acid as the third component,respectively.Alkylated gasoline was prepared catalytically at a low alkane-to-alkene ratio（5:1）.Betaine（BET）as the third component of deep eutectic solvent has the best catalytic performance,while the optimal molar composition ratio of catalyst is Tf OH:BET:PEG200=4.5:1:5.7.The optimum reaction conditions for the preparation of alkylated gasoline with the optimal composition of deep eutectic solvent are as follows:feed volume 15 m L,temperature60°C,rotation speed 600 rpm and reaction time 45 min.Under these conditions,the isobutene conversion rate reaches 80%,and the content of C₈ component in the obtained gasoline product is up to 82.4%.When the catalyst was recycled for 10 times,the content of C₈ component remained almost unchanged at 80%,and the conversion rate of isobutene also remained at 70-80%.（3）The optimized polyether and Tf OH were used as the two components of the deep eutectic solvent,in which Tf OH provided B acidity,and a series of Lewis acids（aluminum chloride,zinc chloride,indium chloride,cuprous chloride and zirconium chloride,etc.）were selected as the components providing L acidity to prepare B-L acidic deep eutectic catalysts.Alkylated gasoline was prepared catalytically at a low alkane-to-alkene ratio（5:1）.The results showed that only indium chloride（In Cl₃）could be combined with polyether and Tf OH to form InCl₃/PEG200/Tf OH eutectic system.The molar composition of catalyst was determined to be In Cl₃:PEG200:Tf OH=1.6:6.4:5.8 by proportional optimization.The optimum reaction conditions were determined as follows:feed volume 35 m L,temperature 80°C,reaction time 1 h,rotation speed 600 rpm.Under this condition,the conversion rate of isobutene was 89.1%and the selectivity of C₈ was 82.8%.The conversion and selectivity of catalyst remained almost unchanged within 7 cycles,and the conversion began to decrease after 7 cycles,while the selectivity of C₈ remained at a high level.In this paper,the solubility of isobutane in different polyethers under different temperature and pressure was determined,which laid the foundation for the subsequent experiments related to isobutane solubility.Both polyether-based B acidic and B-L acidic deep eutectic solvents can catalyze the alkylation for the preparation of high-quality alkylated gasoline at a low alkane-to-alkene ratio（5:1）.The catalyst has stable property and good recycling effect.This study provides a new economical and green method for the preparation of alkylated gasoline.