浸渍溶液pH值对Co/SiO_2催化剂催化F-T合成反应的影响  

Effect of pH Value of Impregnating Solution on Co/SiO_2 Catalyst for Fischer-Tropsch Synthesis

作　　者：赵红霞[1] 朱柘权[1] 陈建刚[1] 孙予罕[1] 

机构地区：[1]中国科学院山西煤炭化学研究所煤转化国家重点实验室,山西太原030001

出　　处：《催化学报》2004年第4期289-292,共4页

基　　金：国家重点基础研究发展规划项目 (G19990 2 2 40 2 )资助

摘　　要：以硅胶为载体 ,利用硝酸和尿素调节浸渍液的 pH值 ,采用等体积浸渍法制得钴质量分数为 10 0 %的Co/SiO2 催化剂 ,结合XRD ,TPR和原位IR等表征手段 ,考察了浸渍溶液 pH值对催化剂物化性质和催化性能的影响 .结果表明 ,浸渍溶液 pH值大于硅胶载体的等电点有利于活性组分钴在硅胶表面的吸附和分散 ,促进了钴与硅的相互作用 ,降低了催化剂的还原度 ,使催化活性降低 ,甲烷选择性增大 .浸渍溶液pH值小于硅胶载体的等电点则减弱了钴在硅胶表面的吸附 ,降低钴的分散 ,削弱了钴与硅的相互作用 。Co-based catalysts have been paid much attention due to their high activity, selectivity for heavier hydrocarbons, and low activity for water-gas shift reaction. Co/SiO 2 catalyst samples were prepared by incipient wetness impregnation, and the pH value of the impregnating solution was regulated with nitric acid and urea. The physico-chemical properties of the samples were characterized by XRD, TPR and in-situ IR. Fischer-Tropsch (F-T) reaction was carried out in a fixed-bed reactor under the conditions of n(H 2)/ n(CO)=2.0, GHSV=500 h -1, p=2.0 MPa and θ=200～230 ℃. The results showed that the dispersion of cobalt oxide (Co 3O 4) species increased and their reduction degree decreased with the increase of pH, hence, the catalytic activity for F-T synthesis decreased. It is suggested that the silica surface was negatively charged when the pH of the impregnation solution was above the isoelectric point of silica. In this case, adsorption of cobalt was enhanced and the interaction between cobalt and silica was promoted, thus the catalytic activity decreased. On the contrary, samples prepared at pH below the isoelectric point of silica, adsorption of cobalt was suppressed, the interaction between cobalt and silica was weakened, and the catalytic activity increased.

关 键 词：PH值 费托合成 钴 二氧化硅 甲烷 CO/SiO2催化剂 催化F-T合成反应 

分 类 号：O643[理学—物理化学]