Niobium Acid Catalyst In Organic Synthesis

Facing the more strict requirements of environmental protection and the arise of green chemistry, the most importance is laid in managing the fundamental sources besides developing the treatment technique of triwaste continually. The chemistry reactions in factories, mines etc. should produce less wastes as possibly as they can. The best things are to realize atomic economy reaction and nonemission. Due to the serious erosion, the arduous separation of catalyst with products and reactants and the severely environmental contamination of liquid acid catalysts, the research on new catalysts and catalytic technologies are emergent. Solid superacids, ion exchange resins, zeolite molecular sieves, polymer carriers-lewis acids, metal oxides and their compounds, inorganic acid salts and their hydrates, loaded heteropolyacids and their salts, are among typical solid acid catalysts which are widely and deeply studied and applied nowadays.Niobic acid(Nb₂0₃-5H2O)was a new kind of special solid-acid catalyst founded by F.Kurosawa in Japan in 1979, and maintained high catalytic activity and stability in aqeous systems such as gasphase esterification, hydration, dehydration, and so on. Lots of research was carried on in foreign countries, especially in Japan, but in our county, little work has been done about it by now, so exploring and exploiting the catalyst have theoretic significance and pragmatic value.Thesis studied some laws of liquid-solid esterification initially. The optimally synthetic conditions(including reaction temperature, reaction time, catalyst amount, catalyst particle sizes, ratio of reactants and water-removing reagents)of di-2-ethylhexyl phthalate, dhn-octyl phthalate,di-2-ethylhexyl maleate and di-n-octy maleate were explored elaborately. Secondly, the dehydration of cyclohexanol catalyzed by niobic acid in gas-phase was investigated. Compared with r-Al₂O₃, niobic acid is excellent in catalytic activity and stability. Experiments showed that niobic acid had prominent catalytic activity when loaded on silica gel(wt:2.5%),maybe due to the great dispersion of niobic acid, even the formation of monolayer structure of niobic acid. In order to improve the activity of niobic acid furthermore, we treated the niobic acid by different methods, including water-washing treatment, heat treatment, acid-dipping treatment, hydrothermal treatment, fusing treatment and adding assistant catalysts, companied with modern analysis technologies and ways. At last, the synthesis of di-2-ethylhexyl phthalate, as a probing reaction, was researched on the dynamics initially.