不同载体负载Pd双功能催化剂制备及其液相甲醇催化一步合成甲酸甲酯

以γ-Al_2O_3、ZrO_2、Bentonite(膨润土)、MIL-53(Al)和MIL-53(Fe)为载体,采用浸渍法制备负载Pd双功能催化剂,利用XRD、BET和NH3-TPD等表征催化剂结构,在微型高压反应器中评价催化剂的液相甲醇一步催化转化合成甲酸甲酯的反应性能,考察反应条件对催化剂性能的影响。结果表明,不同载体负载Pd催化剂未观察到Pd的XRD特征峰,表明催化剂表面的Pd是高分散状态。不同载体负载Pd催化剂的比表面积、酸强度和酸量差别较大,并且酸强度和酸量对甲醇转化率和产物选择性有较大影响。具有较多中强酸的2%Pd/Bentonite、2%Pd/MIL-53(Al)和2%Pd/MIL-53(Fe)催化剂比中强酸较少的2%Pd/γ-Al_2O_3和2%Pd/ZrO_2催化剂具有更高的甲醇转化率和甲酸甲酯选择性。2%Pd/Bentonite催化剂在每摩尔甲醇Pd用量为0. 030 mmol、反应温度150℃、O_2压力2 MPa和反应时间5 h条件下,液相甲醇一步催化转化合成甲酸甲酯反应中,甲醇转化率56. 08%,甲酸甲酯选择性55. 85%。

Preparation of Pd bifunctional catalysts with different supports and their catalytic performance for one-step liquid phase methanol to methyl formate

Pd-loaded bifunctional catalysts with γ-Al₂O₃,ZrO₂,bentonite,MIL-53(Al)and MIL-53(Fe) as supports were prepared by impregnation method and characterized by XRD,BET and NH₃-TPD techniques.Catalytic performance of the catalyst in one-step conversion of liquid phase methanol to methyl formate and the effect of reaction conditions on performance of the catalyst were evaluated in a micro-high-pressure reactor.The results showed that characteristic peaks of Pd were not observed in all XRD patterns of the catalysts,which might be due to high dispersion state of Pd on catalyst surface.Catalysts with different supports had large differences in specific surface area,acid strength and acid amount.Acid strength and acid amount of catalysts had a great influence on methanol conversion and product selectivity.2%Pd/Bentonite,2%Pd/MIL-53(Al) and 2%Pd/MIL-53(Fe)catalysts with more medium and strong acid sites had higher methanol conversion and methyl formate selectivity than 2%Pd/γ-Al₂O₃ and 2%Pd/ZrO₂ catalysts with less strong acid sites.Conversion of methanol was 56.08% and selectivity of methyl formate was 55.85% over 2%Pd/Bentonite catalyst under the conditions of amount of palladium per mole of methanol was 0.030 mmol,reaction temperature was 150 ℃,reaction pressure was 2 MPa,and reaction time was 5 h.