金属前驱体和分散剂对CO偶联制草酸二甲酯Pd/α-Al_(2)O_(3)催化剂性能的影响  

Effects of metal precursors and dispersants on performance of Pd/α-Al_(2)O_(3) catalyst for CO coupling to dimethyl oxalate

作　　者：孙国方 郑修新 臧甲忠 李晨 田喜磊 乔宾 SUN Guo-fang;ZHENG Xiu-xin;ZANG Jia-zhong;LI Chen;TIAN Xi-lei;QIAO Bin(Tianjin Refining and Catalytic Technology Engineering Center,CenerTech Tianjin Chemical Research and Design Institute Co.,Ltd.,Tianjin 300131,China)

机构地区：[1]中海油天津化工研究设计院有限公司天津市炼化催化技术工程中心,天津300131

出　　处：《天然气化工—C1化学与化工》2021年第6期46-51,85,共7页Natural Gas Chemical Industry

摘　　要：以等体积浸渍法制备了Pd/α-Al_(2)O_(3)催化剂,研究了不同金属前驱体和有机酸分散剂对金属分散和催化剂性能的影响。采用CO脉冲吸附、TEM和BET等手段对催化剂进行了表征。结果表明,Pd金属前驱体影响催化剂的金属分散,以氯化钯和硝酸钯为前驱体所制备的催化剂中Pd含量由外向内逐渐递减;以醋酸钯为前驱体所制备的催化剂中Pd呈明显的蛋壳型分布,蛋壳厚度约0.5~1 mm,金属分散度24%,其草酸二甲酯时空收率为798 kg/(m^(3)·h)。不同有机酸分散剂对金属分散作用不同,以柠檬酸和马来酸作为分散剂有利于提高Pd的分散度,而草酸的作用不明显。由于马来酸和硝酸钯形成了大分子络合物改变Pd与载体间的相互作用,Pd呈蛋壳型分布,金属利用率高,草酸二甲酯时空收率由613 kg/(m^(3)·h)提高到826 kg/(m^(3)·h),且连续催化500 h未发现明显积炭;但反应过程中Pd金属颗粒由3~4 nm长大到6~8 nm,是初期催化剂活性下降的主要原因。Pd/α-Al_(2)O_(3) catalyst was prepared by incipient wetness impregnation.The effects of different metal precursors and organic acid dispersants on metal dispersion and catalyst performance were studied.The catalyst was characterized by CO pulse adsorption,TEM,BET and other methods.The results show that Pd precursor affects the metal dispersion and the content of Pd in the catalysts prepared with palladium chloride and palladium nitrate as precursors decreases from outside to inside.In the catalyst prepared with palladium acetate as precursor,Pd shows an obvious eggshell distribution with the eggshell thickness of about 0.5-1 mm,the metal dispersion is 24%,and the space-time yield of dimethyl oxalate is 798 kg/(m^(3)·h).Different organic acid dispersants have different effects on metal dispersion.Using citric acid and maleic acid as dispersants is conducive to improve the dispersion of Pd,but the effect of oxalic acid is not obvious.Due to the macromolecular complex formed by maleic acid and palladium nitrate,the interaction between Pd and carrier is changed.Pd is distributed in eggshell shape,and the metal utilization rate is high.The space-time yield of dimethyl oxalate increases from 613 kg/(m^(3)·h)to 826 kg/(m^(3)·h)and no obvious carbon deposition is found within 500 h,but Pd metal particles grow from 3-4 nm to 6-8 nm.It’s the main reason for the decline of catalyst activity in the initial stage.

关 键 词：CO 草酸二甲酯 偶联 金属分散 Pd/α-Al_(2)O_(3)催化剂 

分 类 号：TQ032[化学工程] O643.32[理学—物理化学]