Preperation And Modification Of Co₃Mo₃N Catalyst And Its Catalytic Performance For Syngas Conversion To Higher Alcohols

Conversion of syngas to higher alcohols is an important way to provide clean fuel,and it is also an important method to alleviate the energy supply shortage and improve environmental pollution.At present,the low-cost catalysts with excellent performance can be obtained by developing and optimizing the catalyst systems,which is a hot topic in the field of energy and chemical industry.Co₃Mo₃N,as a novel catalyst in the field of higher alcohols synthesis from syngas,has great research value.Therefore,this thesis optimized and studied the Co₃Mo₃N catalyst from the following aspects.?1?The surface modification of rod-shaped Co₃Mo₃N catalyst was carried out by low temperature radio-frequency cold plasma,and the products before and after plasma surface modification were characterized by XRD,Raman,TEM,XPS,H₂-TPR and CO-TPD in detail.Meanwhile,the effects of different plasma treatment conditions on the structure and performance of Co₃Mo₃N catalyst were also analyzed,The results demonstrate that the main phase and morphology of catalysts didn't change under different conditions of plasma generation power,but the surface oxide layer was etched,the degree of reduction was improved,and the surface defects were increased.Furthermore,plasma treatment could balance the content of bi-active sites(Co⁰ and Mo⁴⁺)in the catalysts and promote synergy effect of the active sites between dissociation and non-dissociation CO.Thus,at the optimal plasma power?300W?,the total alcohols selectivity can reach 58.1%,and the distribution of C₂₊OH and space time yield?STY?of total alcohols are 93.13%and 346.98mg/g/h,respectively.?2?In order to increase the active sites of the catalyst,the CA-Co₃Mo₃N catalyst with small particle size was prepared by sol-gel method,and the proportion of K promoter was optimized.The results show that compared with rod-like Co₃Mo₃N catalyst,the higher CO conversion of 92.22%is achieved at the optimal K/Mo molar ratio?K/Mo=0.6?,which could be attributed to higher dispersion and surface area,as well as more exposed CO adsorption active sites.Since the content of the bi-active sites in the CA-Co₃Mo₃N catalyst is reduced to some extent,the selectivity of the total alcohols is slightly decreased.Subsequently,the surface modification of CA-Co₃Mo₃N catalyst by cold plasma was carried out.The results suggest that the plasma treatment improved the total alcohols selectivity of CA-Co₃Mo₃N catalyst while the CO conversion rate is greatly reduced.Since the absorption of CO is enhanced after plasma treatment,most of the CO cannot be desorbed from the surface of the catalyst at the reaction temperature in time,resulting in a significant decrease in CO conversion.?3?Ca-montmorillonite from Xinghe County,Inner Mongolia was introduced,and the K-montmorillonite?M?carrier was obtained by cation exchange of Ca-montmorillonite with potassium acetate solution,and the cation exchange process did not destroy the structural characteristics of montmorillonite.Then X%-Co₃Mo₃N/M supported catalysts were prepared by the incipient wetness impregnation method,and their catalytic performance was investigated.The results indicated that K-montmorillonite as carrier was equivalent to the introduction of potassium promoter in situ,and the combination of a small amount of potassium ions and the active components of the catalyst could improve the adsorption capacity of non-dissociated CO.Subsequently,parts of the hydrocarbons could be converted into alcohols.However,most of the potassium ions were restricted to balance the positive charge defects in the layers of montmorillonite.Therefore,they could not sufficiently combine with the catalyst to improve the catalytic performance.