Catalytic Properties Of Metal-doped Heteropoly Acid Compounds In Olefin Isomerization

Heteropolyacid and their compounds have been widely used as catalysts in the fields of electrochemistry,food chemistry,catalytic chemistry and photochemistry due to their unique chemical and structural properties.Alkene is a kind of hydrocarbon containing unsaturated carbon-carbon double bond C=C,which is an important chemical raw material in organic synthesis and industrial production.Common olefins are usually chainα-olefins,mainly derived from oligomerization of short-chain olefins of petroleum and natural gas products.However,with the growing market demand,internal olefins are increasingly playing an important role in practical applications.In this paper,based on heteropoly acid as a photocatalyst to catalyze the isomerization of olefins under simulated sunlight irradiation,chainα-olefins were used to synthesize internal olefins and preliminary scale-up were carried out.The research contents and results are as follows:（1）The heteropoly acid is prepared by a conventional hydrothermal-ether extraction method and dried for several hours to remove the crystal water contained in the heteropoly acid,and then activated at a high temperature to obtain self-made heteropolyacids.Self-made heteropolyacid and commercial heteropolyacids as the photocatalyst,respectively,irradiated by ultraviolet light source at normal temperature and pressure,the photocatalytic experiments of isomerization of olefins were carried out,and the degree of carbon-carbon double bond C=C transfer was investigated.Photocatalytic isomerization experiments using synthetic heteropolyacids and terminal olefins,the migration degree of carbon-carbon double bonds of olefins was investigated.The experiments show that the commercial heteropoly acid transferred little olefin double bonds C=C,while self-made heteropoly acid had higher catalytic activity for olefin isomerization.Commercial heteropolyacid shows no catalytic activity.Industrial heteropoly acid is not activated by high temperature and contains a large amount of crystal water,which is different from the self-made heteropoly acid crystal form.In addition,different wavelength light has different catalytic activities,the ultraviolet band light source shows the largest catalytic activity in the experiment using the simulated solar light source on the photocatalytic activity of the olefin isomerization reaction.（2）The metal doping experiment was carried out on the self-made heteropoly acid.The metal atom in the heteropoly acid was substituted without changing the crystal form to increase the spectral absorption range of the heteropoly acid.The results show that the absorption spectrum of Cu²⁺and Mn²⁺heteropolyacids is not red-shifted by solid ultraviolet absorption analysis;the absorption spectrum of V⁵⁺heteropolyacid is extended to the visible region.In the photocatalytic experiment of olefin isomerization,vanadium-doped heteropoly acid has catalytic activity in both ultraviolet light source and visible light source.（3）The olefin isomerization photocatalytic experiment of the chainα-olefin was carried out,and the reaction product was analyzed.In the experiment,the reaction conditions were changed,and chromatographic analysis was carried out to obtain a comparison of the internal olefin yields,and the combination of the reaction conditions of the highest catalytic efficiency was explored to lay a foundation for the promotion and use of the catalyst.