| Friedel-Crafts alkylation of benzene with 1-dodecene is an important reaction of synthetic detergent, which is essential to human. LAB (linear alkyl benzene) world’s annual demand is more than 3 million tons, and it is expected to grow at 4% per year. The synthetic detergent industry started with AlCl3 homogeneous catalysis in 1940s. In 1980s, LAB synthesis process with HF homogeneous catalysis was industrialized. Today HF is still main catalyst in LAB synthesis. However, HF or AlCl3 catalysts showed serious problems including environment contamination, equipment corrosion, difficult separation, and low 2-LAB selectivity. Therefore, there are many intensive research activities on heterogeneous catalysis to find a better LAB process with improved product quality and better catalysts quality. The main contents of the dissertation are followings:This dissertation aims to the design of ionic liquid catalysts, to improve product quality, especially 2-LAB selectivity at acceptable reaction rate of Friedel-Crafts alkylation of benzene with 1-dodecene, and to improve catalyst stability, to simplify separate operation. The main foundation of catalysts design is "ionic liquid effect" in Friedel-Crafts alkylation, which containing 3 main effects.1. Change HF or AlCl3 homogeneous catalysis to ionic liquid heterogeneous catalysis.2. Change coordination structure of reactive sites via introducing "weak-coordinating anion", for controlling the Lewis acidity of ionic liquid catalysts and the result of reaction.3. Ionic liquid catalysts stabilize carbenium ion and inhibit the..its hydrogen shift reactions and isomerization via "weak-coordinating anion", resulting increase of 2-LAB selectivity from less than 30% to about 70%.Lewis acid ionic liquid catalysts based on Al were prepared, traditional AlCl3 homogeneous catalysis was changed into heterogeneous catalysis by "ionic liquid effect". Reusability of ionic liquid catalyst was improved significantly compared with homogeneous catalysts. Reactivity of ionic liquid catalyst was reserved after recycling 8 times. The Lewis acidity of catalysts could be controlled by regulating the ionic liquid content in ionic liquid catalysts. Meanwhile,2-LAB selectivity was increased substantially compared with homogeneous catalysts from about 30% to about 45%.In this work, aluminum impregnated silica molecular sieves were synthesized to change AlCl3 homogeneous catalysis into solid-liquid heterogeneous catalysis. The performances of these catalysts (immobilized on SiO2-gel, SBA-15, MCM-41 and so on) were investigated in Friedel-Crafts alkylation. Results showed that mass transport was the main factor in the catalysis. Catalysts with ordered and highly distribution uniformity channel network gave higher catalytic activity and selectivity.2-LAB selectivity was improved from about 30% at homogeneous catalyst to about 50% at heterogeneous catalyst based on the same active sites.Based on analysis of supporters, highly ordering mesoporous material SBA-15 has been synthesized. Aiming at declining in the ionic liquid catalyst amount and improving catalyst utilization, ionic liquid [bmim][TFSI]/AlCl3 was immobilized on SBA-15. Friedel-Crafts alkylation could not conduct with 0.5 mol% of ionic liquid in liquid-liquid heterogeneous catalysis, while could reach more than 60% 2-LAB selectivity and 98% conversion of 1-dodecene with immobilized ionic liquid catalyst, which contained 0.5 mol% of ionic liquid catalyst. And liquid-liquid heterogeneous catalysis was changed into solid-liquid catalysis.2-LAB selectivity was improved further after immobilization. Besides, the role of immobilized ionic liquid catalysts deactivation and performance of "ionic liquid effect" in solid-liquid heterogeneous were discussed.In this work, Lewis acid ionic liquid catalysts base on scandium(III) and indium(III) were synthesized. These metal salts do not decompose in water, based on it, the stability of ionic liquid catalyst was improved significantly. With introducing different "weak-coordinating anion", Lewis acidity of catalysts can be controlled. The mechanism of Lewis acidity controlling was discussion based on experiments. It proved that, anion with weaker coordinating ability declines more Lewis acidity of catalyst and reaches higher 2-LAB selectivity. Moreover, ionic liquid can stabilize carbenium ion via "ionic liquid effect", and increase 2-LAB selectivity. In ionic liquid catalyst, "ionic liquid effect" stabilized carbenium ion more, when anion with weaker electronegativity.This dissertation discusses and proves mechanism and effects of "ionic liquid effect", and analyzes the applicability of "ionic liquid effect" based on experiments. |
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