碱金属对CO加氢制备低碳醇Cu-Fe-Co基催化剂的影响

考察了碱金属(Li、Na、K、Cs)对CO加氢制备低碳醇Cu-Fe-Co基催化剂反应性能的影响.研究发现:碱金属的添加能明显降低甲烷化反应,提高催化剂活性,使醇分布向碳链增长方向转移;碱金属Na的添加对催化剂活性的提高影响最大,与未添加碱金属的催化剂相比,液体产物中总醇质量分数提高45.98%,其中C2+醇和C5+醇在总醇中的摩尔分数分别提高了21.88%和22.89%,尾气中CH4摩尔分数下降42.83%.XRD结果表明,碱金属的加入使Cu、Fe、Co三种组分在载体上分散性加强,增加了CO与活性组分的接触位点从而使碳链增长;FE-SEM结果表明,碱金属Na的添加提高了催化剂孔隙结构和活性组分的均匀性和稳定性,同时减轻了催化剂积炭现象,提高了醇收率.

Effect of Alkali Metal Addition on Cu-Fe-Co Based Catalyst for Lower Alcohols Synthesis by CO Hydrogenation

Effects of the various alkali metals(Li,Na,K,Cs) on the catalytic performances of the Cu-Fe-Co co-impregnation catalyst for CO hydrogenation were investigated.Researches show that the addition of alkali metal can observely inhibit the methanation effect,improve the activity of catalyst and promote the transfer of alcohol distribution towards carbon chain growth.It was found that the Na is the best promoter for increasing the activity of catalyst,the mass fraction of total alcohols in liquid product is increased by 45.98%,the mole fractions of C2+ alcohols and C5+ alcohols are increased by 21.88% and 22.89% respectively,and the mole fraction of CH4 in exhaust gas is decreased by 42.83% compared with that without addition of alkali metals.XRD examinations show that Cu,Fe and Co are dispersed better after the addition of alkali metals,thus the contact point of CO and catalysis active center would be increase,which can promote the growth of carbon chain.Images of FE-SEM indicate that,adding Na could improve the dispersion and stability of catalysts and decrease the carbon deposition which would raise the space-time yield of alcohols.