Study On Green Catalytic Synthesis Of 2-ethylanthraquinone

Hydrogen peroxide(H2O2)is one of important green fine chemical products.Its annual domestic production is about 12.5 million tons(27.5%).It has been widely used as green catalyst,oxidant,and disinfectant in many fields such as petrochemicals,fine chemicals,and environmental protection.Anthraquinone process is currently the only large-scale production of hydrogen peroxide at home and abroad.The domestic consumption of 2-ethylanthraquinone(2-EAQ)intermediates is tens of thousands of tons,and the direct economic benefits are several billion yuan.However,2-EAQ is produced in an oleum-catalyzed Friedel-Crafts route in China,resulting in the by-product of several hundred thousand tons of 30-50 wt%waste sulfuric acid containing organic compounds per year.So large amount of sulfuric acid severely corrodes equipment,pollutes the environment,and increases production costs,which have negative effect on the market competitiveness of 2-EAQ products and the rapid and healthy development of the entire hydrogen peroxide industry.Therefore,it is of great significance and practical application value to explore the novel high-efficiency green catalysis process for controllable production of 2-EAQ.In the Friedel-Crafts process,the BE acid(2-(4'-ethylbenzoyl)benzoic acid)cyclization reaction is a critical step and it is usually required that the strong acid species catalyze the dehydration of the carboxylic hydroxyl.Therefore,the fuming sulfuric acid must be replaced to promote the green catalytic process.One way is to look for superacids such as heteropolyacids,perfluorosulfonic acid resins(Nafion-H),etc.The other way is to change the reaction process based on the reaction mechanism.Based on the above ideas,firstly,this work investigated cyclization reaction of BE acid catalyzed by different heteropolyacids and Nafion-H concerning the possible catalytic conditions and the feasibility of industrial application;then systematically investigated the route of cyclization reaction in the two-step route involving acyl halide and then dehydrohalogenation to achieve cyclization synthesis of 2-EAQ.Speically,the main work has been done as follows:(1)2-EAQ was synthesized in a Friedel-Crafts acylation route of BE acid using a series of superacids as the catalysts such as phosphotungstic acid,silicotungstic acid,phosphomolybdic acid and Nafion-H.The catalytic activity and optimized process conditions of different heteropoly acids were investigated.The results show that the catalytic activity is consistent with the acid strength sequence,and the best catalytic activity among these three heteropolyacids is phosphotungstic acid.If chlorobenzene is used as the solvent,the conversion rate of BE acid arrives at 97.8%and the yield of 2-EAQ is 75.4%after refluxing at 135? for 3 h.This process is lower than the current oleum process yield(80-85%);Nafion-H produced 2-EAQ without a solvent at a high temperature of 200?.The BE conversion was 98.5%and the 2-EAQ yield was 73.8%.Nafion-H has slightly lower catalytic selectivity than phosphotungstic acid but good recovery performance.(2)Based on the consideration that the acid halide is easier to remove than the carboxyl hydroxyls,a new two-step process was designed and optimized to overcome the strong acid catalysis process,and new process parameters such as solvent and intermediate steps were systematically examined.The control and amplification effects was also investigated.The results show that using CH2Cl2 as the solvent and under the optimized reaction conditions,the conversion of BE acid reaches 99.7%,and the yield of 2-EAQ is as high as 97.9%,which is higher than the current oleum process with promising industrial application;Besides,after 20-fold amplification of the reaction system(2 L reactor),the conversion of BE acid still remains 99.5%and the yield of 2-EAQ is 95.1%;the purity of the crude 2-EAQ product is above 98.6%in the new amplification process,and the purity after purification is above 99.6%.Moreover,the hydrogenation efficiency of 2-EAQ prepared in the new green catalytic process is the similar with that of the commercial 2-EAQ produced in the sulfuric acid catalysis route.It is a new industrialized process for the green catalytic synthesis of 2-EAQ that replaces fuming sulfuric acid process.