氧化铝负载的钴基费托合成催化剂失活机理  

Deactivation on Co catalyst supported on alumina for Fischer-Tropsch synthesis

作　　者：秦绍东 李加波 何若南 杨霞 段雪成 孟祥堃 QIN Shaodong;LI Jiabo;HE Ruonan;YANG Xia;DUAN Xuecheng;MENG Xiangkun(National Institute of Clean-and-Low-Carbon Energy,Beijing 102211,China)

机构地区：[1]北京低碳清洁能源研究院,北京102211

出　　处：《煤炭学报》2020年第4期1244-1249,共6页Journal of China Coal Society

基　　金：国家重点研发计划资助项目(2017YFB0602500)。

摘　　要：Co/Al2O3催化剂在费托合成反应中具有良好的反应性能。采用浸渍法制备了Co/Al2O3催化剂,使用搅拌釜反应器在220℃,2.0 MPa,10000 h-1,H2/CO=2.0(体积比)合成气条件下对催化剂的费托合成反应性能进行了评价,评价结果表明随着反应的进行,催化剂的活性逐渐降低,CH4选择性逐渐升高。为研究Co/Al2O3催化剂在费托合成反应中的失活机理,采用N2物理吸附(BET)、X射线衍射(XRD)、透射电子显微镜(TEM)及程序升温加氢(TPH)对不同时间反应后的催化剂进行了表征。表征结果表明在费托合成反应过程中随着反应时间的延长,Co/Al2O3催化剂的孔结构没有发生显著变化,催化剂中部分CoO相被进一步还原为活性相金属Co。此外,在反应过程中活性相金属Co的晶粒尺寸逐渐发生烧结长大,催化剂表面的积碳量快速的增加。因此,活性相金属Co的烧结与催化剂表面的碳沉积应当是本研究中Co/Al2O3催化剂在费托合成反应过程中发生失活的主要原因。为改进催化剂抗烧结能力,对Al2O3载体的孔结构进行调控,进而控制催化剂中活性相金属Co的晶粒分布,减少易于发生烧结的小晶粒金属Co的生成。此外,通过进一步改进催化剂的配方,成功开发了具有高耐烧结性与抗积碳能力的Co基费托合成催化剂。在搅拌釜反应器中对改进后的催化剂进行了1800 h的费托合成性能测试,在整个反应过程中催化剂表现出高稳定性与低甲烷选择性。Co/Al2O3 catalyst demonstrates a high performance in Fischer-Tropsch synthesis.In this study,the Co/Al2O3 catalyst was prepared with impregnation method and the FTS performance of the catalyst was tested in a continually stirred tank reactor(CSTR)at 220℃,2.0 MPa,10000 h-1,and syngas H2/CO=2.0.With the increase of reaction time,the activity of the catalyst decreased continually while the selectivity to CH4 increased gradually.To understand the deactivation mechanism,spent catalysts with different reaction times were characterized with N2 adsorption(BET),X-ray photoelectron spectroscopy(XRD),transmission electron microscope(TEM)and temperature programmed hydrogenation(TPH).The characterization results show that the pore structure of the catalyst had no significant change during the reaction.With the increase of reaction time,the Co metal particle size and carbon deposition amount in the catalysts increased.It was evident that the Co metal sintering and carbon deposition should be the main reasons of Co/Al2O3 catalyst deactivation in this study.In order to improve the sintering resistance ability of the catalyst,the pore structure of the Al2O3 support was adjusted to control the Co metal particle size distribution,and to inhibit the formation of small Co particles that are easy to be sintered.Furthermore,by the modification of the catalyst recipe,a sintering and carbon deposition resistance Co catalyst was developed.The catalyst demonstrated high stability and low CH4 selectivity during a 1800 h test in the CSTR.

关 键 词：费托合成 钴基催化剂 氧化铝 失活机理 

分 类 号：TQ530[化学工程—煤化学工程]