【摘要】 采用Li NO3对γ-Al2O3进行改性,制备了以多孔锂铝尖晶石为载体,以Pd为活性组分的PdCl2-CuCl2/Li-Al-O负载型催化剂,并考察了催化剂对CO低压气相合成碳酸二乙酯(DEC)反应的催化性能,探讨了载体Li/Al比、改性浸渍方法、不同改性金属、Pd负载量和反应压力等因素对催化剂催化性能的影响.结果表明,当n(Li)/n(Al)=0.2,压力为0.3 MPa和温度为110℃时,DEC的时空收率可达到418 g/(L.h).用Li NO3对γ-Al2O3改性后的催化剂载体表层具有Li Al5O8尖晶石结构,不同Li/Al比的催化剂载体的晶胞参数、晶胞体积略有不同.采用双金属改性的催化剂载体表面由于结晶度较低不能形成"完全尖晶石结构",其催化活性较低.随着催化剂表面活性组分PdCl2含量的增加,可有效提高产物DEC的时空收率;锂铝尖晶石载体表面的酸性较低,有利于提高目标产物DEC的选择性.更多还原

【Abstract】 The catalytic performance of the PdCl2-CuCl2/Li-Al-O catalyst,with palladium as the active component and porous lithium alumina spinel(Li-Al-O) as the support,for vapor-phase synthesis of diethyl carbonate(DEC) from CO and ethyl nitrite was studied in a continuous fixed-bed reactor at low pressure.The Li-Al-O spinel support was synthesized by impregnation of γ-Al2O3(2-3 mm) with aqueous LiNO3 solution.Under the mild reaction conditions of 5%CO-20%EtONO-75%N2,GHSV=2 500 h-1,0.3 MPa,and 110 ℃,the CO conversion was 40% and the space time yield of DEC was 418 g/(L·h).The perfectly close-packed spinel structure could be obtained because of the lithium ions that entered the vacancy of γ-Al2O3.The Li-Al-O catalyst support had no strong acid sites,and the catalyst had stable palladium chloride,both of which were favorable for the DEC synthesis reaction.更多还原