| The alkylation reaction is one of the important process of producing high-quality gasoline in refinery, and its product-alkylate is a good gasoline blending agent. The alkylate produced by the reaction of isobutane with isobutene is synthesized over the concentrated sulfuric acid or hydrofluoric acid in industry. Obviously, both catalysts have many disadvantages such as equipment corrosion, handling of hazards, high acid consumption, danger in case of an accidental release (HF), and environmental liability, etc. For this reason, this study introduced a new method to synthesize alkylate by the reaction of isobutane with isobutene using a designed green catalyst Br(?)nsted-Lewis acid ionic liquid. Because of this ionic liquid peculiar character of adjustable acid degeneration and the synergistic effect between Bronsted and Lewis acid sites, the high conversion rate and selectivity reaction-separation integration and the catalyst’s separation, recovery and recycling during alkylation process could be realized.Based on designability characteristic of the ionic liquid’s structure and throuth the allocating of anion-cation, a series of acid ionic liquids of quaternary ammonium salt type were systhesized and the acid type and acid strength of ionci liquid were charated. The resutls showed that ionic liquid (3-sulfonic acid)-propyltriethylammonium chlorozincinate [HO3S-(CH2)3-NEt3]Cl-ZnCl2 was suitable for synthesizing alkylated gasoline beacuse of its stability, and acid strength, etc. The process of synthesizing alkylation gasoline catalysized by ionic liquid was optimized. The results were followed:(1) When Br(?)nsted-Lewis acid ionic liquid [HO3S-(CH2)3-NEt3]Cl-ZnCl2 was used in the alkylation, the isobutylene conversion reached 100%, the selectivity of TMP, DMH and C9+ (the alkane more than 9 carbon in carbon chain) was 95.1%,1.2% and 3.7% under the following reaction conditions:[HO3S-(CH2)3-NEt3]Cl-ZnCl2 3.0 g, n([HO3S-(CH2)3-NEt3]Cl):n(ZnCl2)=1:5, water 1.3 g, HC (the mixture of isobutane and isobutylene) 11.5 g, n(isobutene):n(isobutylene) 10:1, reaction temperature 60℃, reaction time 2 h.(2) The alkylation was investigated by the camposite catalyst system composed by [HO3S-(CH2)3-NEt3]Cl-ZnCl2 and sulfuric acid. It was found that the catalytic performance of the system was enchanced when sulfuric acid was used. Under the following conditions:[HO3S-(CH2)3-NEt3]Cl-ZnCl23.0 g, n([HO3S-(CH2)3-NEt3]Cl): n(ZnCl2)=1:2, sulfuric acid 0.3 g, water 1.3 g, HC (the mixture of isobutane and isobutylene) 11.5 g, n(isobutene):n(isobutylene) 10:1, reaction temperature 40℃, reaction time 1 h, the isobutylene conversion reached 99.6%, the selectivity of TMP; DMH and C9+ was 84.8%,1.2% and 14.0%.(3) The catalystic performance of Br(?)nsted-Lewis acid ionic liquid loaded with phosphomolybdic acid was also investigated in the alkylation, and the optimal reaction conditions were obtained as following:[HO3S-(CH2)3-NEt3]Cl-ZnCl2 3.0 g, n([HO3S-(CH2)3-NEt3]Cl):n(ZnCl2)=1:3, phosphomolybdic acid 0.15 g, water 1.3 g, HC (the mixture of isobutane and isobutylene) 11.5 g, n(isobutene):n(isobutylene) 10:1, reaction temperature 50℃, reaction time 1.5 h. under the above reaction conditions, the isobutylene conversion reached 100%, the selectivity of TMP, DMH and C9+ was 95.3%,0.2% and 4.5%.(4) In addition, the results showed that the catalyst, reactant and products are not miscible and the catalyst could be recycled after simply separating. This indicated that the reaction-separation integration during alkylation reaction was successfully realized. The reusability of catalyst was studied. It was found that the conversion of isobutene and the selectivity of target components were almost the same when the catalyst was used 5 times.Compared with the traditional alkylation catalyst, the above catalytic systems showed better catalytic performance and some problems of traditional catslyst were solved, such as large consumption of acid, equipment corrosion, serious environmental pollution, catalyst’s non-recycling. Comparing the three catalytic systems, it was found. that the camposite catalyst system composed by [HO3S-(CH2)3-NEt3]Cl-ZnCl2 and sulfuric acid could obviously decrease the reaction temperature, shorten the reaction time. This was due to the strong acid of sulfuric acid. It was also found that the catalytic system of Br(?)nsted-Lewis acid ionic liquids and phosphomolybdic acid obtained the best results with high selectivity, short reaction time and low reaction temperature. The reason was that the high acidity of phosphomolybdic acid enhanced the catalytic system’s acidity and its anion’s unique structure could increase the alkylation reaction’s conversion rates and selectivity.Above all, the application of Br(?)nsted-Lewis acid ionic liquid in the alkylation was obtain high conversion and selectivity, realized the integration of reaction and separation of the catalyst, and solved some problems existed in the alkylation gasoline production. This study could provide effective and theoretical basis to the alkylation reaction. |
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