| Acrylic acid as an important raw material in modern chemical industry is widely used in the production of high absorbent resin?SAP?,coatings,textile auxiliaries,adhesives,and oilfield chemicals.The demand of acrylic acid has kept increasing rapidly with the development due to its wide application.Acrylic acid traditionally produced via propylene two-step oxidation,the raw material propylene is non-sustainable sources.As oil resource exhausting and environmental requirements,it has great significance that exploit new route to replace the petrochemical route to environmental protection and economic sustainable development.VPO catalyst has complex chemical composition,structure and properties,which active component are?VO?2P2O7 and VOPO4.It has been high catalytic activity and selectivity in synthesis of acrylic acid?methyl acrylate?by adol condensation catalyzed over VPO catalyst.The VPO catalyst has most potential value in many catalysts.This thesis focuses on the research about the preparation,characterization and catalytic performance of the new supported VPO catalyst.The main work and innovation are the following:1.Aldol condensation of acetic acid with formaldehyde to acrylic acid was catalysed by the SiO2-,SBA-15-,and HZSM-5-supported vanadium phosphorous oxide?VPO?catalysts prepared by the incipient wetness impregnation.The supports obviously increased the surface areas and changed the acid-base properties of the as-prepared catalysts.VPO/SBA-15 catalysts with high acid and alkali quantities exhibited high catalytic activities for the aldol condensation of acetic acid with formaldehyde to acrylic acid.When the VPO/SBA-15 catalyst with the P/V mole ratio of 2.0:1 catalyzed the reaction at 330-370°C,the acrylic acid selectivities were90.8%?70.2%,the formaldehyde conversions of 14.3?68.7%.2.Cs,Ce and Nd cation-modified VPO/SiO2 catalysts were prepared by the deposition method.Cs,Ce,Nd was used as an auxiliary agent to change the acidnity and alkalinity of the catalyst surface.Trioxymethylene as the soruces of formaldehyde to reduce the effect of water in the reaction.It is discussed that the effect of different alkaline metal types and contents on the catalytic performance of VPO/SiO2.The catalysts were characterized by XRD,XPS,Py-FTIR,CO2-TPD,NH3-TPD,and N2adsorption/desorption techniques.The Cs,Ce and Nd cation-modified VPO/SiO2catalysts exhibited higher catalytic activities for the aldol condensation reaction of acetic acid with formaldehyde,giving higher acrylic acid yield than the VPO/SiO2catalyst.The high acidity and basicity of the metallic cation-modified VPO/SiO2catalyst favored the aldol condensation reaction toward the formation of acrylic acid.Ce0.2-VPO/SiO2 catalyst showed the best catalytic effect in the reaction,the yields of acrylic acid reach 73.9%and the maximum formation rate of acrylic acid was 10.1mmolg-1cath-1.3.Aldol condensation of methyl acetate acid with trioxymethylene to methyl acrylate catalyzed by Cr?Mo,W?cation-modified VPO/SiO2 catalysts were prepared by the deposition method.It have very important valuable to synthesize methyl acrylate by methyl acetate the common by-product in chemical industry.It is found that Cr?Mo,W?cation-modified VPO/SiO2 has good catalytic activity catalysis menthyl aceate to methyl acrylate.The structure and chemical composition is discussed by XRD,XPS,Py-FTIR,BET,CO2-TPD and NH3-TPD.It is found that Cr?Mo,W?elements can change the active component structure,acidic and basic type,strength and relative content in VPO/SiO2,those changes have influence of catalytic activity.When W/P/V=0.2/2.6/1,370oC,the conversion rate of formaldehyde can reach 47.0%,and the selectivity of methyl acrylate can reach90.4%. |
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