Study On The Catalytic Synthesis Reaction Of CO₂ With Glycerol And Olefin Epoxide

Carbon dioxide?CO₂?concentrations is increasing in the atmosphere,which have caused increasingly serious environmental problems.As a rich,cheap,non-toxic and renewable one-carbon resource,the chemical conversion of CO₂ is the current research focus.At present,the research focus of this work is:on the one hand,develop a cheap and easily available catalyst system to efficiently catalyze the reaction under mild conditions,and regulate the product to obtain one of the products with high selectivity;on the other hand,The substrate of high-energy activates CO₂ to promote the reaction.Therefore,this thesis mainly focuses on the following uses of CO₂resources:A series of Cu–Mn composite oxides were prepared by co-precipitation.Interestingly,catalysts with varied Cu/Mn molar ratios showed different catalytic performances for glycerol carbonylation.The physicochemical properties of the catalysts are characterized by X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,Fourier transform infrared?FT-IR?spectroscopy,temperature-programmed desorption?TPD?of CO₂ and NH₃.The results showed that the Cu_1.4Mn_1.6O₄ crystal phase is the active component of the catalysts for the carbonylation of glycerol,this phase can effectively provide Mn⁴⁺and lattice oxygen(O^2-),and the existence of the Mn⁴⁺-O^2-Lewis acid–base pair can promote the formation of glycerol carbonate.Various reaction parameters,such as reaction temperature,time,the molar ratio of glycerol to urea and the amount of catalysts,are studied.Under optimizing reaction conditions,the conversion of glycerol is 91.0%with 99.1%glycerol carbonate selectivity.A novel green method for synthesizing monoacetin was performed in which acetonitrile was hydrolyzed and then esterified with glycerol over Cu-Cr phosphates in CO₂ atmosphere.Up to now,it is the first time to synthesize monoacetin with high yield?87.6%glycerol conversion and 86.3%monoacetin selectivity?through this one-pot cascade method.In this process,acetonitrile can react with water to form acetamide and further esterify with glycerol.There are two main reasons for obtaining high-yield monoacetin:?1?the interaction of CO₂ with high-temperature liquid water enhances the acid strength of reaction system and then promote the activation of acetonitrile.?2?Two active centers of Lewis acid(Cu²⁺)and PO₄^3-on Cu-Cr phosphate are beneficial to improve reactivity.PO₄^3-interacted with water molecules to generate protons in situ as Br?nsted acid to further activate acetonitrile,and Lewis acid(Cu²⁺)can effectively activate acetamide to esterify with glycerol.Meanwhile,the introduction of Cr species inhibited the transformation of Cu²⁺ions to Cu⁺ones and results in smaller particles and larger specific surface area,which helps the catalyst to expose more active sites.A series of Mo-W composite oxides and the corresponding Mo O_x and WO_x were synthesized by co-precipitation method,and used to test the catalytic performance of CO₂ and epoxide to form cyclic carbonate.When the Mo/W molar ratio is 1:3,cycloaddition of styrene oxide with CO₂ can achieve the highest conversion?90.8%?and selectivity?91.9%?.At the same time,the cycloaddition of other epoxides can also achieve good results.These catalysts were characterized using a series of characterization techniques.Relevant characterizations indicate that the Mo/W molar ratio of 1:3 has excellent catalytic activity by replacing W⁶⁺in the WO₃ lattice with Mo⁶⁺to form a uniform W_0.79Mo_0.21O₃ crystal phase,which improves the mutual synergy of metals on the catalyst surface to further enhance the acidity and alkalinity of the catalyst.