用Sc2O3作为促进剂,研发出一种Sc2O3掺杂的高效新型Ni—ZrO2基催化剂,该催化剂对CO和CO2共甲烷化制合成天然气(SNG)显示出高的活性和优异的热稳定性.在组成经优化的Ni5Zr3Sc1催化剂上,0.1MPa,573K,V(H2):V(CO):V(CO2):V(N2)=75:15:5:5,出口空速GHSV-40000mL/(h·g)的反应条件下,在反应开始之后的20~332h的反应过程中,CO和CO2的转化率一直分别保持在100%和85%的高水平,产物甲烷的选择性一直保持在100%,耐热试验结果显示,在973K下经历24h甲烷化反应、而后降至573K的Niszr3sc。催化剂试样上,(CO+CO2)的总转化率仍能稳定地保持在80.2%的水平;而不含Sc2O3。的原基质催化剂(NisZra)在经历相同耐热试验过程之后的(CO+CO2)总转化率骤降至2.7%,暗示其因烧结而失活.催化剂的表征结果证实,可观量的Sc^3+溶解入ZrO2晶格导致具有c—ZrO2结构的单一C-(Zr-Sc)Oy相的生成并使其稳定化,这类c-(Zr—Sc)O3相与Ni6Zr3Sc1催化剂的高活性,尤其与优良的热稳定性,密切相关.
A type of highly efficient Ni-ZrO2 catalysts doped with Sc2 O3 for co-methanation of CO and CO2 was developed, and dis played high activity and excellent thermal stability. Over a Ni6 Zr3 Sea catalyst under the reaction conditions of 0. 1 MPa, ,573 K, V( H2 ) : V(CO) : V(CO2 ) : V ( N2 ) = 75 : 15 : 5 = 5, GHSV = 40 000 mL/( h, g) ( outlet), the observed conversion of CO and CO2 maintained continuously at high levels of 100% and 85 %, respectively,during 20-332 h after the reaction started, with the corresponding selectivity of CH4 product being 100 %. The results of heat-resisting test showed that, over the Ni6 Zr3 Se1 catalyst after undergoing 24 h of the methanation operation at 973 K followed by going down to 573 K,the total conversion of (CO+CO2) still maintained stable at the level of 80.2%, whereas that of the Sc20a-free Ni6 Zr4 catalyst after undergoing the same heat-resisting test fell to 2.7 %, impl- ying that it was deactivated due to sintering. The results of the catalyst characterization demonstrated that solution of a considerable amount of Sca+ in the ZrO2 lattice resulted in the formation of (Zr-Sc)Oy composite oxide with simple c-ZrO2 phase-structure, which was closely associated with the high activity,especially the extremely high thermal stability,of the Ni6 Zr3 Sc1 catalyst.