| As a kind of abundant and renewable energy source,vegetable oil is a new energy source with important potential use value.The main components of vegetable oils are high-grade fatty acids,which are characterized by relatively high molecular weight and high oxygen content.Vegetable oil undergoes hydrodeoxygenation to produce high-quality biodiesel.The hydrodeoxygenation reactions of vegetable oils mainly have two routes,namely direct hydrodehydration reaction and hydrodecarboxylation reaction/hydrodecarbonylation reaction.Hydrodeoxygenation needs to be carried out under the environment of hydrogen.The appropriate catalyst should be selected according to the local hydrogen resource conditions to achieve the able-controlling the hydrodeoxygenation route of vegetable oil,thereby achieving the rational using of resources and the reduction of biodiesel production costs.The key to this goal is the development of hydrodeoxygenation catalysts,in which the catalytic properties of the two routes are respectively predominant.In this thesis,the supported MoNi hydrodeoxygenation catalysts were preparated,and catalysts and supporters were characterized by XRD、Py-IR、NH3-TPD、SEM and so on.The catalytic performance of the catalyst was evaluated in a continuous fixed bed using n-octane solution containing 20%vegetable oil as feed.The influences of Mo/Ni moral ratio,type and amount of additives,support modification and reaction conditions on the catalytic performance of the catalyst were investigated.The effect of Mo/Ni molar ratio on catalyst performance showed that the selectivity of the decarbonylation/decarboxylation products of hydrodeoxygenation of vegetable oil can reach as high as 90.2%when Mo/Ni molar ratio of the catalyst is 0.4.The selectivity of the decarbonylation/decarboxylation product of hydro-deoxygenation of vegetable oil was the lowest,and the selectivity of the dehydration product of direct hydrodeoxygenation of vegetable oil was 49.8%when only the the Mo is used as the active component of the catalyst.The modified results of additives showed that the addition of additives B,F,W,Co,Fe,etc.could improve the catalytic performance of Mo/MgAl2O4 catalyst to varying degrees,among which non-metallic additives F and metal additives Fe have a good modification effect.When 1%F was added,the selectivity of the hydrodeoxygenated dehydration product of vegetable oil reached to 59.8%.With the addition of 10%Fe,the selectivity of the hydrodeoxygenated dehydration product of vegetable oil could reach the 91.8%.The characterization results showed that adding additives can increase the dispersion of active metals.The L acid amount was increased when the addition amount of nonmetallic additive F was increased,.The addition of the metal promoter Fe reduced the total acid amount of the catalyst,increased the amount of L acid and the amount of surface active hydrogen of the catalyst.The proper amount of L-acid is beneficial to the fracture of C-O bond,and more surface active hydrogen is beneficial to improve the direct hydrodeoxygenation performance of the catalyst.The results of the support modification showed that the additives La and Ce could improve the direct hydrodeoxygenation activity of the Mo/MgAl2O4 catalyst.When the 7%additive La was added,the dehydration product hydrodeoxygenation selectivity of vegetable oil reached to 71.8%.With the comprehensive action La,F and Fe,the selectivity of hydrodeoxygenated dehydration product products of vegetable oil was as high as 92.6%over the catalyst prepared under the optimal conditions of La 7%,F 0.5%,Fe 10%.The effect of reaction conditions on the distribution of hydrodeoxygenation products of vegetable oils showed that as the reaction temperature increasing,the reaction pressure decreases or the liquid hourly space velocity increasing,the hydrodeoxygenation reaction route of vegetable oil over the catalyst is transferred from the direct hydrodehydration reaction to the drodecarboxylation/decarbonylation reaction. |
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