摘要
研究了液相沉淀包覆工艺终点pH值对SAPO-34/CZA复合催化剂物化性质和CO_2氢还原制低碳烯烃催化性能的影响。借助XRD、SEM、BET、NH3-TPD和CO_2-TPD等手段对不同复合催化剂的晶相组成、微观形貌、孔结构及表面酸碱性质进行了分析表征。研究结果表明,沉淀pH值对SAPO-34/CZA复合催化剂物化性质和CO_2加氢制低碳烯烃催化性能影响较大。过高或过低的沉淀pH值制得复合催化剂中SAPO-34分子筛结晶度、微孔比表面积及表面碱量均有所下降,呈现以介孔为主的孔结构特征;而当pH值为7时,制得复合催化剂形成了包覆相结构和微-介复合孔结构(微孔比表面积53.1 m2·g-1,介孔比表面积59.8 m2·g-1,总比表面积为112.9 m2·g-1,总孔容0.4cm3·g-1,平均孔径14.6 nm);在反应温度325℃,还原温度285℃,反应压力3.0 MPa,体积比H2∶CO_2=3.0,空速3500 m L·g-1·h-1反应条件下,CO_2转化率为64.8%,低碳烯烃选择性为49.8%。与pH=9制得催化剂比较,CO_2转化率和低碳烯烃选择性分别提高了26.2%和19.2%。
The SAPO-34/CZA composite catalysts were prepared via liquid deposition coating method,and effect of pH value on the physicochemical properties and CO 2 hydrogenation reaction performance of the SAPO-34/CZA composite catalyst was investigated in this paper.Crystalline phase,morphology,pore structure and surface acidity and alkalinity were extensively characterized by XRD,SEM,BET,NH 3-TPD and CO 2-TPD techniques.The results indicated that various pH value posed significant impact on the physicochemical properties and CO 2 hydrogenation reaction performance of the SAPO-34/CZA composite catalyst.The crystallinity,micropore specific surface area and surface alkalinity of the SAPO-34 molecular sieve in the composite catalyst were decreased when the precipitation pH was too high or too low,and the mesoporosity-dominated pore structure was observed.When the pH=7,the homogeneous continuous composite phase and hierarchical structure(microporous specific surface area of 53.1 m 2·g-1,mesoporous specific surface area of 59.8 m 2·g-1,total specific surface area of 112.9 m 2·g-1,the total pore volume of 0.4 cm 3·g-1,average pore size 14.6 nm).Accordingly,the CO 2 conversion and light olefins selectivity are reach to 64.8%and 49.8%respectively under the condition of reaction temperature of 325℃,reduction temperature 285℃,the reaction pressure of 3.0 MPa,the volume ratio of H 2/CO 2=3.0 and space velocity of 3500 mL·g-1·h-1.Compared with the SAPO-34/CZA composite catalyst prepared at pH=9,the CO 2 conversion rate increased by 26.2%and the selectivity to light olefins increased by 19.2%.
作者
王冠超
刘飞
倪丽萍
曹建新
WANG Guan-chao;LIU Fei;NI Li-ping;CAO Jian-xin(School of Chemistry and Chemical Engineering,Guizhou University,Guiyang 550025,China;Guizhou Key Laboratory for Green Chemical and Clean Energy Technology,Guiyang 550025,China;Guizhou Key Laboratory for Efficient Utilization of Mineral and Green Chemical Technology,Guiyang 550025,China)
出处
《人工晶体学报》
EI
CAS
CSCD
北大核心
2018年第8期1647-1653,共7页
Journal of Synthetic Crystals
基金
国家自然科学基金(21666007)
贵州省百层次创新型人才专项(黔科合平台人才[2016]5655)
贵州省科技创新人才团队(黔科合平台人才[2018]5607)
贵州省科技计划项目(黔科合平台人才[2017]5788号)
贵州省联合基金项目(黔科合LH字[2017]7260号)
