Study On Cu-base Catalysts For Furfural Hydrogenation Reaction

As an important biomass platform product,furfural is an important intermediate for the synthesis of various chemical products.The total amount of furfural produced annually in the world is 350 million tons,of which more than 65%is used for hydrogenation to prepare furfural alcohol.Industrially,a Cu-Cr catalyst is generally used for gas phase hydrogenation of furfural to obtain furfural alcohol.However,this method has problems such as harsh hydrogenation conditions,high cost,and easy leap of heavy metals.The active metals used in furfural hydrogenation catalysts have always been a research hotspot.The research scope includes common noble metal catalysts such as palladium,platinum and rhodium,and non-precious metal catalysts such as nickel,copper and cobalt.Although the noble metal catalyst has high hydrogenation activity,it also faces disadvantages such as high cost and poor selectivity.In order to solve these problems,non-noble metal catalysts have received increasing attention from researchers.However,non-noble metal catalysts are difficult to achieve both in terms of activity and selectivity.For example,although nickel has high hydrogenation activity,it has poor selectivity to furfural alcohol;although copper has high selectivity,it is plagued by low activity.Therefore,it is necessary to develop a catalyst which has all advantages of low cost,high activity and high selectivity.In this work,copper-based catalyst supported by nitrogen-doped activated carbon was prepared by one-step calcined method using copper glycinate as the copper source and oxidized activated carbon as the support.The catalyst prepared by this method have been investigated of how different loading ratio,different N-doped ratio and different calcination temperatures effect on the activity of the catalyst.By TEM characterization and XPS characterization,it was found that the introduction of glycine not only made the dispersibility of copper very good,but also was doped into activated carbon in the form of nitrogen atoms after high temperature calcination,which improved the dissociation ability of copper to hydrogen.It can also be found by XRD characterization that the Cu~+and Cu~0 species of copper in the copper-based catalyst prepared by the one-step method both exist in catalyst,and the monovalent copper is favorable for the adsorption of furfural,which further improves the activity of the catalyst.In this work,a silica-coated copper-based catalyst was prepared by in-situ crystallization.The catalyst uses the copper ammonia solution as a copper source,and a highly active copper-based catalyst is prepared by a sol-gel method in combination with a hydrothermal method.Through the BET characterization,it is found that the introduction of ammonia can greatly improve the specific surface area of silica.The preparation by sol-gel method and hydrothermal method can obtain a catalyst with better pore uniformity and metal dispersion.Through experimental comparison,it was found that the catalyst with copper loading of 17%,crystallization at 100°C for12 hours,and nitrogen calcination at 550°C had the best catalytic performance.In order to continue to explore the ratio of copper valence in the catalyst,the work was carried out by using the silica-coated copper-based catalyst obtained above,and further controlled by different post-treatment reduction methods to obtain a series of catalysts having different copper valence ratios.It was found by experiments that the copper-based catalyst treated with hydrazine hydrate had the highest hydrogenation activity for furfural.It was found by XPS characterization that the ratio of Cu~+/Cu~0 in the catalyst was 1.15.