溶胶-凝胶法制备负载型磷钨酸催化剂及其催化合成蒽醌

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

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。

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 （H20） ： n （TEOS） 5, HPW loading 10% （mass fraction）, drying temperature 120 ~C and calcination temperature 250℃. Under the conditions structure parameters of the prepared catalyst are as follows： specific surface area 439 m^2/g, pore diameter 2. 301 6 nm and pore volume 0. 174 1 cm^3/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.