Synthesis, Characterization Of The Supported Heteropolyacid Catalysts And Their Catalytic Activity In The Formation Reaction Of Acetals And/or Ketals

Heteroplyacids (HPAs) can be thought of a solid acid complex as made up of a central atom (e.g., P, Si, Ce or Fe) and some coordination atoms such as Mo, W, V or Ta, in which both two kinds of atoms are bonded together by an oxygen bridge.Heteropoly compounds used as catalysts have been studied widely because of their specific properties. However, the major disadvantages of HPAs, commonly, are lower surface area (1-10m²/g). Supporting the heteropolyacids on solids to widen their surface areas is a useful method. It was found that the supported heteropolyacid catalysts not only overcame the drawbacks of HPAs, such as low surface area, separation problem from reaction mixture and re-used, but also improved the catalytic performance in heterogeneous reaction.This paper consists of two parts.Part one A review on heteropolyacids1. The structure and character of heteropolyacids were introduced. Heteropolyacid compounds are of interest in catalysis because of their acidity, oxidation-reduction and pseudoliquid phase.2. The early syntheses methods and the advanced characterize by means of heteropoly compounds and supported heteropolyacid catalysts was describe.3. A review in brief on the application of heteropolyacid compounds in alkylation, esterification, condensation, nitration and oxidation.4. The relations between the catalytic activity and the supported carrier including the forming conditions such as lading, calcination temperature and time etc were reviewed.Part two ExperimentChapter 1 Preparation and characterization of three sorts of solid-acid catalysts1. Tungstophosphoric(HPW) supported on the neural alumina(H₃PW₁₂O₄₀/Al₂O₃) was prepared by an equilibrium and incipient wetness impregnation technique and characterized by FT-IR, XRD and TG-DTA.2. Tungstophosphoric (HPW) supported on the active carbon (H₃PW₁₂O₄₀/C) was prepared by an equilibrium and incipient wetness impregnation technique and characterized.3. A series of silver salts of 12-tungstophosphoric acid Ag_xH_3-xPW₁₂O₄₀ (Ag_x) (where 0x and AH_X type catalysts showed higher activity than that of the unique HPW under the optimal reaction conditions. It was found that the catalyst containing 30% PW by calcination at 500°C not only showed higher catalytic activity, but also could be recovered and reused easily as compared to Ag_x.