Preparation Of Highly Dispersed Catalysts For Furfural Hydrogenation With Supercritical Fluid Deposition Technology

In view of the increasingly prominent environmental problems,increasing energy demand,and shortage of fossil resources,it is particularly important to seek new technologies to replace fossil resources.Furfural catalytic hydrogenation to high-value biomass derivatives is considered to be a promising technology.There has been extensive research on the furfural hydrogenation reaction,especially on optimizing the operating conditions and catalytic performances,including the effect of the support,metal components,and loading,etc.on the reaction performance.However,few reports have achieved both high loadings and high dispersion of the catalytically active components,although previous studies have shown that the dispersion and actual loading of supported catalysts are of critical importance to achieve desirable catalytic performance.Consequently,the development of new preparation technology to achieve both high dispersion and loading is critical for future advancement.The furfural hydrogenation reaction system is complex due to the presence of a series of parallel and tandem reactions.From a thermodynamic point of view,the feasibility,degree of progress and equilibrium conversion of these reactions were analyzed aiming to guide the catalyst design and the optimization of the reaction conditions for the gas phase hydrogenation of furfural.Thermodynamic analysis results show that between 300~550 K,the five reactions mainly involved in the hydrogenation of furfural can proceed thermodynamically;under high temperature conditions,the furfural decarbonylation to furan reaction is more advanced than the other four reactions;at temperatures lower than 500 K,and the hydrogen to furfural ratio is 3,the conversion rate of furfural hydrogenation is more than 95%,further increasing the ratio favors the deep dehydrogenation of furfural to other derivatives.In this thesis,Pd was selected as the catalytically active metal for furfural hydrogenation,and the supercritical fluid deposition technology was used to prepare highly dispersed supported Pd catalysts.Compared with the traditional catalyst preparation methods,this method is green and environmentally benign.Additionally,this method has adjustable process parameters,which can be adjusted to tune the dispersion and loading of the active components.The results show that the pressure,temperature and co-solvent dosage can change the solubility of the precursor salts in the supercritical fluid system,thereby affectingthe deposition process on the support surface.By adjusting these conditions,high loading and high dispersion were achieved simultaneously.Under the same conditions,the loading of the catalyst prepared by the supercritical fluid deposition method is higher than that of the catalyst prepared by the impregnation method,and the dispersion is good.Under the conditions of 480 K and a hydrogen to furfural molar ratio of 3,the furfural conversion on the catalyst prepared by the supercritical fluid deposition method is 1.5 times of that on the catalyst prepared by impregnation.