High-pressure Hydrothermal Synthesis Of MoVTeNbO_x Complex Metal Oxides And Their Catalytic Performance For Selective Oxidation Of Propane And Propylene

Acrylic acid is an important intermediate in organic chemical industry,which has been widely studied and applied in medicine,environment,rare earth and other industries.In Industry,complex metal oxides are commonly used to catalyze the oxidation of propylene to prepare acrylic acid.Among many complex metal oxides,Mo VTe Nb O_xcomplex metal oxides show excellent activity in the selective oxidation of propane or propylene,so it is of great economic and social significance to the research of Mo VTe Nb O_x.In this paper,Mo VTe Nb O_xcomplex metal oxides were synthesized by high pressure hydrothermal method.The effects of high pressure hydrothermal condition,the molar ratio of precursor solution and oxalic acid treatment on the crystal phase,specific surface area,morphology and surface properties of Mo VTe Nb O_xsamples were investigated by XRD,SEM,BET,ICP,XPS and H₂-TPR,and explore the relationship between the structure and catalytic performance of Mo VTe Nb O_x.The experimental results show that M1Mo VTe Nb O_xcomposite metal oxides with typical rod morphology can be prepared in a short time（15～60 min）by high-pressure hydrothermal method.Compared with the synthesis time of 6～72 h by traditional hydrothermal method,the preparation time of the catalyst is greatly shortened.At the same time,the Mo VTe Nb O_xhas high surface V⁵⁺concentration（68.9%）and high content of M1 phase（94.5%）.With the increase of preparation temperature,the content of V element in Mo VTe Nb O_xcatalyst also showed an increasing trend,and the propane conversion increases with the increase of V element content.When propane was catalyzed,the selectivity of acrylic acid reached 74.1%.When propylene was catalyzed,the conversion of propylene was 78.7%and the yield of acrylic acid was 52.8%.When the reaction pressure increases with the increase of slurry volume,M1 phase is generated.on the contrary,when the pressure remains unchanged with the increase of slurry volume,M1 phase disappears.Reducing the V/Mo molar ratio of Mo/V/Te/Nb in the precursor will increase the conversion of propylene,but the selectivity of acrylic acid will decrease.When the molar ratio of Te/Mo is reduced,the conversion of propylene and the selectivity of acrylic acid decrease at the same time.Mo VTe Nb O_xtreated with oxalic acid increases the content of M1,specific surface area and pore volume,which increases the conversion of propylene by 4%～12%and the selectivity of acrylic acid by about 5%.