摘要
采用连续共沉淀与喷雾干燥成型技术相结合的方法制备了微球形Fe- Cu- K- SiO2催化剂,并考察了焙烧温度对催化剂的结构和织构性质的影响.结果表明,催化剂具有较好的织构和结构热稳定性,粘结剂SiO2起到了分散和稳定α-Fe2O3晶相的作用.随着焙烧温度的升高,催化剂的比表面积逐渐减小,α-Fe2O3晶粒逐渐增大,催化剂体相中的Cu和K原子向表面富集,且Cu向表面的迁移更明显;同时,催化剂中的α-Fe2O3和CuO相发生了一定程度的离析,Cu的助剂作用减弱,使催化剂在合成气气氛下难于还原碳化.催化剂在n(H2)/n(CO)=0.67,GHSV=2.0L/(g·h),p=1.5MPa和θ=250℃下的浆态床F T合成反应评价结果表明,升高焙烧温度,催化剂的初活性和最高活性下降,但运行稳定性提高,而且有效地抑制了CH4的生成,明显促进了烃产物向高碳数方向移动.反应600h后卸载下的催化剂的形貌观测表明,催化剂的磨损主要是由化学磨损引起的,提高焙烧温度可明显改善其抗磨损性能,焙烧温度高于400℃时,催化剂具有较好的抗磨损性能.
The Fe-Cu-K-SiO2 catalyst for slurry Fischer-Tropsch synthesis (FTS) was prepared by the combination of continuous co-precipitation and spray-drying technology, and it exhibited good spherical morphology of about 23 μ m in average diameter. The catalyst was characterized by means of X-ray diffraction, Mossbauer effect spectroscopy, particle size distribution measurement, X-ray photoelectron spectroscopy, thermal gravity, H, temperature- programmed reduction and N-2 adsorption. The catalyst calcined at 320-550 ° C showed relatively good thermal textural and structural stability, and the surface area decreased but the pore size increased with the increase of calcination temperature. α-Fe2O3 was the main iron phase present in both the uncalcined and calcined catalysts, which was stabilized and dispersed by the addition of SiO2 binder. A large amount of superparamagnetic Fe3+ was found in the catalyst, and it was assigned to α-Fe2O3 crystallite with diameter smaller than 13.5 nm. More Cu and K, especially Cu, migrated to the catalyst surface with the increase of calcination temperature, which resulted in the separation of α-Fe2O3,03 and CuO phases to some extent. The CuO phase in the surface layer of the catalyst was easily reduced in H-2 atmosphere, while the bulk α-Fe2O3 was difficult to carbonize in syngas atmosphere due to the weakening of Cu promoter effect. The catalytic performance of the catalyst for FTS was evaluated in a slurry reactor under the industrial conditions of n(H-2) /n (CO) = 0. 67, GHSV 2. 0 L/(g • h), p = 1. 5 MPa and 0 = 250 ° C. The increase of calcination temperature decreased the FTS activity, improved the run stability, efficiently suppressed the formation of CH4 and shifted the hydrocarbon products to higher molecular weight. The attrition of the catalyst was mainly due to the chemical attrition. The morphology observation of the catalyst after FTS run for 600 h showed that the attrition resistance was enhanced by increasing the calcination temperature, and the catalyst calcined above 400 ° C exhibited robust attrition resistance.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2005年第4期340-348,共9页
基金
国家高技术研究发展计划(863计划)项目(2001AA523010)
中国科学院知识创新重大项目(KGCX1SW02)
国家自然科学基金重大项目(20590361).
