Epoxidation Of α-olefins Catalyzed By Metal Phosphates

Olefins epoxidation is one of the most extensive reactions,because the epoxides are important raw material intermediates,which can be used to synthesize drugs,flavors,resin coatings,lubricants,plastic additives,surfactants and other fine chemicals.In particular,epoxides can synthesize surfactants by ring-opening with hydrophilic groups such as glycerol.On the other hand,epoxides are hydrolyzed to produce vicinal diols with bases or acids.The ether alcohol surfactants and alkyl glycoside surfactants can be obtained via ethoxylation with ethylene oxide and glucosylation with glucose,respectively.The main purpose of this paper is to provide raw materials for ethoxylation or glycosidylation.At present,catalytic olefins epoxidation reactions with environmentally benign oxidants H₂O₂ and heterogeneous catalysts have attracted substantial attention of many researchers.The potential application of solid bases as catalysts of olefins epoxidation has aroused great interest.These catalysts not only are non-corrosive,environmentally friendly,reusable and easy to separate from liquid products but also exhibit a high activity in epoxidation.As a kind of solid base,magnesium phosphate-based material possessing the advantages of safety,non-toxicity,cheapness,and easy availability have not been reported in catalyzing olefins epoxidation.This paper is composed of two chapters.The magnesium pyrophosphate and farringtonite were obtained via calcination using magnesium hydrogen phosphate trihydrate and anhydrous magnesium phosphate as precursors respectively.A series of characterizations were conducted and,for the first time,the 1-olefin epoxidation as model reaction were systematically studied over magnesium pyrophosphate and farringtonite,and the corresponding optimal application conditions and stability of the catalysts also were studied respectively.Finally some valuable results were obtained.（1）The materials were determined as magnesium pyrophosphate and farringtonite via XRD and FT-IR spectra.The physical and chemical properties of magnesium pyrophosphate and farringtonite were characterized by N₂-physical adsorption,SEM-EDS and CO₂-TPD,respectively.N₂-physical adsorption results showed that both magnesium pyrophosphate and farringtonite possessed very small specific surface areas of 4.65 m²/g and 4.40 m²/g,respectively.SEM showed that the two precursors further aggregated into larger particles after the calcination process.It can be seen that the magnesium pyrophosphate and farringtonite had no other elements except for Mg,P,and O elements via EDS.CO₂-TPD characterization confirmed that magnesium pyrophosphate and farringtonite are solid base that coexist with weak,medium,and strong base sites,but the medium base is dominant.（2）To obtain the optimum conditions,the reaction parameters including solvent,reaction temperature,molar ratio of H₂O₂ to 1-octene,catalyst amount,reaction time,and so on were adjusted using 1-octene epoxidation as model reaction.Under the optimum conditions,magnesium pyrophosphate showed effective catalytic activity,indicating the conversion of 1-octene epoxidation was 35.7%and the selectivity of epoxide was 92.4%.For farringtonite,the conversion of 1-octene and selectivity of epoxide were 85.2%and 87.6%respectively.Both catalysts showed catalytic activity for 1-decene and 1-heptene,where the farringtonite showed efficient activity for1-decene and 1-heptene.In all,a convenient,scalable,environmentally friendly,and efficient method of olefins epoxidation,especially for acid-sensitive substances,was developed and a reference was provided in selecting other basic materials as catalyst.（3）The stability of magnesium pyrophosphate and farringtonite were investigated,respectively.The activity of magnesium pyrophosphate and farringtonite remained almost unchanged after four cycles.The XRD analyses and the IR spectra of the catalysts before and after the recycling reaction indicate the structure of both catalysts are stable.（4）The mechanism showed that the combination of magnesium pyrophosphate or farringtonite with acetonitrile and H₂O₂ in situ generation and consumption of Payne’s reagent is the main cause of olefin epoxidation reaction.