Study On Enlarged Preparation Of Silica Supported Heteropoly Acids

It took H₃PW₁₂O₄₀ and H₃PW₁₂O₄₀/SiO₂ preparation craft enlargement as the main research contents based on the earlier optimization experiment,as well as the load stability.The influence of enlargement was separately inspected about H₃PW₁₂O₄₀ and H₃PW₁₂O₄₀/SiO₂ preparation craft condition to H₃PW₁₂O₄₀ receiving rate and the H₃PW₁₂O₄₀/SiO₂ catalyzed performance, thus discovered the best preparation craft of H₃PW₁₂O₄₀ and H₃PW₁₂O₄₀/SiO₂; Then determined the load stability with the ultraviolet spectrophotometer law.In this paper ,a conventional acidification method incorporated with an ether extraction technique was used to prepare H₃PW₁₂O₄₀ with Keggin structure,The experiment scale was enlarged 10 times in this article based on the earlier optimization experiment in order to study enlargement effect.Taking the charge proportion between Na₂WO₄ and Na₂HPO₄,the quantity of HCl,the reaction temperature and the reaction time as the influential factor and PW12 Heteropoly acid.receiving rate for the target to design orthogonal experiment,we found the best preparation craft condition.: Na₂WO₄250g,Na₂HPO₄40g,HCl160ml,the reaction temperature 85°C and the reaction time 2.5h,PW₁₂ Heteropoly acid.Receiving rate reached 89.3%.The infrared spectrum (IR),X beam diffraction (XRD),thermogravimetric -differential scanning calorimetry (TG-DSC) and the Hammett indicator were introduced into the structure characterization and the acidity characterization of the Keggin-type structure PW₁₂ Heteropoly acid.The results indicated the product was the Keggin structure and had six crystal water,as well as good heat stability and very strong acidity;Mixed dibasic acid (butane diacid,glutaric acid,adipic acid) with the normal butyl alcohol esterification responded for the probe,the esterification rate as the weight standard of the catalyst,finally the result indicated it had the very good catalytic activity to the esterification (the rate of conversion of mixed dibasic acid was 98.6%)and no obvious enlargement effect.H₃PW₁₂O₄₀/SiO₂ was prepared with the backflow-impregnation method, as the catalyst for esterification of mixed dibasic acid (butane diacid, glutaric acid, adipic acid) and the normal butyl alcohol. The experiment scale was enlarged 10 times by experience based on the earlier optimization experiment in order to study the best preparation craft condition and enlargement effect. With four factors three horizontal orthogonals experiments , the best preparation craft condition was: SiO₂100g, H₃PW₁₂O₄₀55g/500mlH₂O, the backflow temperature 85°C, backflow time 3.5h, drying temperature 120°C , activation temperature 180°C, activation time 3 hours.The rate of esterification was 97.8% as the use level of catalyst was 7% of mixed dibasic acid mass, charge number was 22.4%.The infrared spectrum (IR), X beam diffraction (XRD), thermogravimetric -differential scanning calorimetry (TG-DSC) and the Hammett indicator were introduced into the structure characterization and the acidity characterization of the Keggin-type structure PW₁₂ Heteropoly acid. Finally the result indicated H₃PW₁₂O₄₀ maintained the original Keggin structure well on the SiO₂ support, had the very good dispersivity and the very high acid strength, the thermostability also obtains the enhancement.The result indicated it had the very good catalytic activity and the repetition use to the esterification and no obvious enlargement effect.The impact was determined with ultraviolet spectrophotometer about preparation craft condition of H₃PW₁₂O₄₀/SiO₂ to load stability.the results showed: the loaded catalyst with preconditioning had good stability and high catalytic activity; The large charge number had higher desorption than that small one, the former had better stability than the later; The loaded catalyst with temperature programming drying had better stability and higher catalytic activity;The longer backflow time, the lower desorption rate, so it had better stability but worse catalytic activity.To study the redundant use of loaded PW12 Heteropoly acid as catalyst for mixed dibasic acid and the normal butyl alcohol esterification, and to attribute the used catalyst in order to explore the reason of the catalyst deactivation .The experiment indicated H₃PW₁₂O₄₀/SiO₂ could be duplicate used four times, the deactivation reason was the active constituent falling off from the carrier after several use, simultaneously other mass was on the carrier surface.