溶胶-凝胶法制备负载型磷钨酸催化剂及其催化合成蒽醌

采用溶胶-凝胶法制备了负载型磷钨酸催化剂,并将其用于催化邻苯甲酰苯甲酸(BBA)合成蒽醌。考察了溶剂种类、水与正硅酸乙酯的摩尔比(水硅比)、乙醇与正硅酸乙酯的摩尔比、水解温度、磷钨酸负载量、焙烧温度等制备条件对催化剂活性的影响,得到制备催化剂的适宜条件:以乙醇为溶剂,水解液pH为3.8,水解温度80℃,水硅比为5,乙醇与正硅酸乙酯的摩尔比为2,干燥温度120℃,在250℃下焙烧,磷钨酸负载量为10%(质量分数)。该条件下制备的负载型磷钨酸催化剂仍保持Keggin结构,比表面积为439m2/g,孔径为2.3016nm,孔体积为0.1741cm3/g。将该催化剂用于催化BBA合成蒽醌反应,在220℃、2.0h、m(催化剂)∶m(BBA)=1∶1的优化条件下,蒽醌收率达90.3%。但该催化剂易失活,初步推断积碳结焦是该催化剂失活的主要原因。

Preparation of Immobilized Phosphotungstic Acid by Sol-Gel Method and Catalytic Synthesis of Anthraquinone

Supported phosphotungstic acid(HPW)/SiO2 catalyst was prepared through sol-gel method and was used in synthesis of anthraquinone from o-benzoylbenzoic acid. Effects of the preparation conditions,namely solvent types,mole ratio of water to tetraethoxy-silicone(TEOS),mole ratio of alcohol to TEOS,hydrolysis temperature,HPW loading and calcination temperature,on the catalyst activity were investigated. Optimal preparation conditions are:hydrolysis temperature 80 ℃,pH 3.8,n(ethanol):n(TEOS) 2,n(H2O):n(TEOS) 5,HPW loading 10%(mass fraction),drying temperature 120 ℃ and calcination temperature 250 ℃. Under the conditions structure parameters of the prepared catalyst are as follows:specific surface area 439 m2/g,pore diameter 2.301 6 nm and pore volume 0.174 1 cm3/g. HPW/SiO2 catalyst remains the Keggin structure. The activity of HPW/SiO2 catalyst in synthesis of anthraquinone was studied. Under optimal reaction conditions:temperature 220 ℃,reaction time 2.0 h and m(HPW/SiO2):m(BBA) 1:1,AQ yield was 90.3%. HPW/SiO2 catalyst is easily deactivated because of coke deposition on the HPW/SiO2 catalyst.