采用共沉淀包覆法制备了SAPO-34/CZA双功能复合催化剂,研究了复合相比例对催化剂晶体结构性质和CO2加氢制低碳烯烃催化性能的影响.采用XRD、FT-IR、SEM、BET、NH3-TPD和CO2-TPD等手段对不同催化剂的晶相组成、骨架结构、微观形貌、孔结构及表面酸碱性进行了分析表征.研究结果表明,复合相比例对SAPO-34/CZA双功能复合催化剂的结构性质和催化性能影响较大.质量比为1∶1时,制得复合催化剂具有明显微孔和介孔特征(微孔比表面积53.15 m2·g-1、介孔比表面积59.84 m2·g-1、总比表面积为113.00 m2·g-1、总孔容0.41 cm3·g-1、平均孔径14.57 nm),具有特殊包覆结构及存在复合相界面,构造了特殊反应路径,微介孔层级结构强化耦合反应,表现出较高催化性能.在还原温度285 ℃、反应温度325 ℃、压力3.0 MPa、V(H2)/V(CO2)=3.0、空速(SV)3500 mL·g-1·h-1的条件下,CO2转化率为64.80%,低碳烯烃选择性为49.68%.与物理共混催化剂SAPO-34/CZA-M相比,CO2转化率和低碳烯烃选择性分别提高了31.98%和2.43%.
Effects of various phase ratios on structure properties of SAPO-34/CZA composite crystal prepared via coprecipitation coating method and its catalytic performance on CO2 hydrogenation to light olefins were investigated in this paper.These obtained products were characterized by XRD, FT-IR, SEM, BET, NH3-TPD and CO2-TPD techniques to investigate their crystalline phase, skeletal structure, morphology, pore structure and surface acidity and alkalinity.The results indicate that composite phase ratio posed significant impact on the structure properties and catalytic performance of SAPO-34/CZA bifunctional composite catalyst.SAPO-34/CZA catalyst with composite phase ratio of 1∶1 has the distinct characteristics with micropore and mesopore (microporous specific surface area of 53.15 m2·g-1, mesoporous specific surface area of 59.84 m2·g-1, specific surface area of 113.00 m2·g-1, total pore volume 0.41 cm3·g-1, average pore size 14.57 nm) system, novel coating structure and composite interface, indicating the existence of a distinct reaction path and a coupling reaction.Accordingly, the CO2 conversion and light olefins selectivity are reach to 64.80% and 49.68% respectively under the condition of reduction temperature of 285 ℃, reaction temperature of 325 ℃, the reaction pressure of 3.0 MPa, V(H2)/V(CO2) of 3.0 and space velocity of 3500 mL·g-1·h-1.Compared with the blending catalyst SAPO-34/CZA-M, the CO2 conversion and light olefins selectivity of the sample with composite phase ratio of 1∶1 are increase by 31.98% and 2.43%, respectively.
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