Preparation Of Nanosized Solid Acid And The Catalytic Performance On Esterification

The esterification reaction is an important acid catalytic reaction in chemical industy. And esters are very important chemical intermediates and materials. However the drawbacks traditional acid catalyst suffered are obvious, such as the difficulty for the separation of the catalyst from the reaction mixture, unreusable of catalyst and environmental pollutions. To research a new nanosized solid acid catalyst with high activity, low price, reusability and environmentalfriendly has become a hot topic. This paper adopts a new synthesis process to prepare a series of nanosized solid acid catalysts, and further studied the catalyst activity in the esterification of acetic acid with n-butanol.Nanosized sulfated zirconia has been synthesized by the incorporation method. And the amorphous zirconium hydroxide is an excellent supporter. Catalyst prepared with sulfamic acid gets higher content of sulfate group, bigger BET surface area and higher activity. The catalyst is amorphous phase and displays a disordered structure with a number of wormhole-like and interconnected channels. The presence of sulfate restrains the tetragonal crystal of zirconia. As the increase of the mole rateio of S:Zr, the BET surface area and the content of sulfate group of the catalyst present a first increases, then decreases trends. When S:Zr = 2, the catalytic activity get the highest point. The conversion of acetic acid reaches 92.73 % even with a reaction time of 30 min. The catalyst can be reused as there is no loss in catalytic activity during the five cycles.A series of nanosized tungtated zirconia was prepared by impregnation method with ammonium metatungstate and phosphotungstic acid. The catalysts displayed the nano flake structure, and catalyst prepared by phosphotungstic acid shows smaller diameter only about 10 nm. With the increase of calcination temperature, WO₃ crystals were separated out, and the BET surface area of the catalyst was reduced, and the W surface density was increased. The increasing of the WO₃ load transforms tetragonal phase to monoclinic phase, the W surface density was increased, and the BET surface area of the catalyst present a first increases, then decreases trends. Then we studied the catalyst activity in the esterification of acetic acid with n-butanol. The optimum preparation condition of catalyst is the calcination temperature at 750℃and the WO₃ load is 10 %. The catalyst can be reused as there is little loss in catalytic activity during the four cycles. And can be regeneration by oxidation charcoal burner method.