Preparation And Application Of The Complex Oxide Solid Superacid Catalyst B₂O₃/WO₃-ZrO₂

Solid superacid catalyst is a new type of catalytic materials which have been developed in recent years. This catalyst has been proved to be very effective from the viewpoint of activity, selectivity and reusability in the preparation of various important chemicals which have a number of difficulties with homogeneous catalysts, and can overcome such as corrosion, pollution, more vice-reactions, difficult of separation, and low selectivity. The complex oxide solid superacid has such advantages as strong acidity, thermal stability, environmentally friendly and excellent catalytic activity. Solid superacid catalysts, e.g. WO₃/ZrO₂ have attracted much attention of the researchers.In this paper, the new type B₂O₃/WO₃-ZrO₂ solid superacid catalyst was prepared by co-precipitation and impregnation methods, The effects of preparation methods, catalyst component, pH value, calcination temperature on the physicochemical properties of the B₂O₃/WO₃-ZrO₂ catalysts were investigated, and the activity of the synthesis of ethyl acetate over the B₂O₃/WO₃-ZrO₂ catalyst was studied. Catalytic physical properties were investigated by some analytical methods, such as DSC-TG, XRD, BET and so on.The B₂O₃/WO₃-ZrO₂ catalysts prepared by co-precipitation and impregnation methods have superacid, the co-precipitation impregnation method is better than the stepwise impregnation method. When the catalyst was calcinated at the calcination temperature, the tetragonal ZrO₂ crystalline phase which is very important for the formation of acid center had formed, at 873K, the addition of the boric induced lattice distortion of ZrO₂ crystal ,the catalyst got into the amorphous ,the WO3 monolayer had nearly dispersed on ZrO₂.With the B₂O₃/WO₃-ZrO₂ catalyst prepared under the below preparation conditions : n(W: B: Zr)= 1.00:14.28:21.78, pH=10 Calcination at 873K for 3h in an air atmosphere, it exhibited excellent catalytic activity for the synthesis of ethyl acetate.Demethyl fumarate (DMF) is a new type of low poisonous, high performance, wide application and low price mildew inhibitor and fungicide. It is used in feed, fruits, vegetables leather textiles cosmetics and so on. The solid superacid catalyst B₂O₃/WO₃-ZrO₂ is used to synthesis demethyl fumarate. The best conditions of thesynthesis of demethyl fumarate are: molar ratio of fumaric acid to methanol is 1:15, the quantity of the major catalyst (B₂O₃/WO₃-ZrO₂) is 1.70% of the mass of fumaric acid, the quantity of the minor catalyst (98% H₂SO₄) is 3.17% of the mass of fumaric acid, reflux time is 5h.Under these conditions, the yield of DMF is above 85.0%.