Construction And Application Of Mo-Based Catalysts For Hydrodeoxygenation Of Biological Oxygenated Compounds At Atmospheric Pressure

As a renewable resource,biomass can be transformed into liquid fuel or high-quality chemicals by developing various effective methods,which is the active field currently.Hydrodeoxygenation is one of the most effective means to further deoxidize and improve the quality of small molecule compounds in the biomass conversion process.However,in the conventional hydrodeoxygenation process,there are some problems,such as excessive consumption of hydrogen,over-saturation of unsaturated bonds in bio-based materials and mismatching of reactivity between catalyst and feedstock.Atmospheric hydrodeoxygenation reaction has been widely concerned because it can achieve high efficiency deoxidation under the premise of low hydrogen consumption.The construction of effective catalysts for the hydrodeoxygenation of biological oxygenated compounds at atmospheric pressure is the most important task.The excellent performance of molybdenum catalysts in the hydrodeoxygenation of oxygenated compounds has been widely proved.Therefore,this paper constructed a series of molybdenum catalysts,and XRD,XPS,H₂-TPR,SEM and TEM were used for characterizing in detail the structure and morphology of different Mo-based catalysts.The catalytic mechanism of the active sites or oxygen vacancies of molybdenum oxide catalysts was also studied.Typical oxygen-containing model compounds and real bio-oils were selected,and Mo-based catalysts were applied to the hydrodeoxygenation of bio-based oxygen-containing compounds at atmospheric pressure.The catalytic performance of the catalysts in the hydrogenation reaction was evaluated.The main research contents and results are as follows.(1)The molybdenum catalyst system was constructed.Mo catalysts(Mo-ZSM-5)with Mo content of 15 wt%and 20 wt%were prepared by hydrothermal synthesis,MoO₃-based catalysts(MoO₃/ZSM-5 and MoO₃/meso ZSM-5)with 20 wt%MoO₃ and MoO₃/TiO₂ and MoO₃/ZrO₂ with loads of 15,20 and 25 wt%,respectively were prepared by overimpregnation method.The MoO₃ catalysts were prepared by calcination of commercial MoO₃.The catalysts were pre-reduced with hydrogen after preparation,and XRD,XPS,H₂-TPR,SEM and TEM were used for the anlysis of catalyts,etc.The results showed that various molybdenum oxide species were successfully attached to the surface or channels of the catalyst supports,and the Mo⁵⁺component,which was predicted to be the effective active site in the MoO₃ catalyst,increased after pre-reduction.(2)MoO₃,20 wt%MoO₃/TiO₂ and MoO₃/ZrO₂ catalysts were used for the hydrodeoxygenation of 4-propylphenol,2-cyclopentene-1-one and their mixtures at atmospheric pressure.Under the catalytic hydrogenation of three different catalysts,the conversion of 4-propylphenol was close to100%,and the selectivity of n-propylbenzene,the main product,was80%-100%.When 2-cyclopentene-1-one with the same mass concentration was added into 4-propylphenol,the hydrogenation reaction results showed that the conversion rate of 4-propylphenol was still maintained at about 100%,but the n-propylbenzene selectivity was improved under the catalysis of 20MT and 20MZ,and could be stabilized at about 100%during the whole reaction process.The hydrodeoxygenation of 1000 ppm and 3000 ppm 2-cyclopentene-1-one(dissolved in heptane)showed that the conversion of2-cyclopentene-1-one was the highest,when the mass concentration of the raw material was 1000 ppm,20 wt%MoO₃/TiO₂ was selected as catalyst,and the reaction temperature was 350?under atmospheric pressure.A long-period reaction of 1000 ppm 4-propylphenol and2-cyclopentene-1-one was carried out with 20MT catalyst,the conversion of 4-propylphenol can be completely converted within 100 h,and the reaction process can be carried out in a switched fixed-bed reactor.(3)MoO₃ catalyst was selected and used in the hydrodeoxygenation of eugenol and specific bio-oils at atmospheric pressure.The effects of light components acetone and 2-cyclopentene-1-one on the hydrogenation of eugenol were studied.First of all,conversion of eugenol in the reaction process was always maintained at about 100%,n-propylbenzene selectivity was over 80%.When different concentrations(1,3 and 5 wt%)of light components acetone,2-cyclopentene-1-one or a mixture of the two were added to eugenol feedstock,the conversion rate of eugenol and the selectivity of n-propylbenzene decreased with the increase of the mass concentration of the light components,which indicated that the light oxygen components were not conducive to the hydrodeoxygenation of high concentration phenol.At the same time,MoO₃ catalyst also has good catalytic activity for fractionated extraction of bio-oil and lignin oil,and the deoxidation rates of the two kinds of oil can reach 96%and 93%,respectively.(4)MoO₃/TiO₂ and MoO₃/ZrO₂ catalysts with MoO₃ loading of 15,20 and 25 wt%,respectively,were used for hydrodeoxygenation of 5 wt%real oil cardanol at atmospheric pressure.It was found that the catalytic activity sequence of the catalysts was as follows:20MT>25MT>25MZ>15MT>20MZ>15MZ.For 20 wt%MoO₃/TiO₂,the conversion rate of cardanol was the highest,which was 95.3%.However,these catalysts cannot maintain high catalytic activity and would be gradually deactivated as the hydrogenation continues.The possible reason was that the high molecular weight of cardanol was easy to coke on the surface area of the catalysts,which made the catalysts unable to contact with the raw materials for reduction reaction.Fluidized bed reactor can be used for this reaction process because the catalyst is easy to deactivate and can be regenerated.