Cellulose/Chitosan-Pd Catalyst For Selective Hydrogenation Of Acetylene:Catalytic Preparation And Performance Study

The utilization and development of agricultural,forestry and marine products wastes,as a significant measure,were used for the sustainable development of energy and environment.Chitosan and cellulose as natural biopolymer,with a plentiful hydroxyl,amino and hydroxy groups which are extremely a lot of polysaccharides stored in the world.Cellulose,chitosan and their derivatives have a huge ability to chelate metals to make catalysts used in various chemical reactions by connecting metal ions.In addition,they as excellent heterogeneous catalyst supporter,guarantees the high stability,easy to recycle and great catalytic activity and selectivity in the reaction.Therefore,macromolecule supported catalysts have attracted the attention of researchers in the field of catalysis.Enlightened by the development and utilization of forestry and marine products wastes,researehers promotes sustainable development.The utilization of cellulose and chitosan,the researching state about catalyst selection and reaction mechanism of selective hydrogenation of acetylene,which application of density functional theory were overviewed in this paper.By reviewing previous references,cellulose-metal or chitosan-metal complexes had been reported as heterogeneous catalysts.Cellulose,chitosan and their derivatives play special role in coordination between them and metal ions.As excellent heterogeneous catalyst supporter,the raw material of CMC and CS,preparated to catalyze the selective hydrogenation of acetylene after supporting metal Pd.The paper summarized synthesis highly dispersed of CMC/CS-Pd and applied scope of the selective hydrogenation of acetylene.Also,the present investigation also reported in detail the examination of the newly-designed catalysts for their performance for selectively hydrogenation of acetylene in four temperature range and different carriers.Besides,the surface catalytic performance and the structure-activity were also studied by using in DRIFTS,XRD,XPS,HRTEM and density functional theory?DFT?simulations.The findings in this work would highlight the dependence of catalytic behavior of materials on its structure-composition and thus can offer a new methodology for designing Pd-based catalysts for acetylene high-selective hydrogenation.We got the following conclusions:?1?We have synthesized carboxymethyl cellulose?CMC?or chitosan?CS?supported Pd catalysts to facilitate acetylene semi-hydrogenation toward ethylene.CS-Pd catalyst performs well in the selective hydrogenation of acetylene.Based on the co-existence of the large amounts of-OH,-NH₂,-COOH groups,some kinds of metal organic ligands could be formed by hydrogen bonding and the electrostatic attraction between Pd ions and CMC?or CS?.Highly dispersed Pd has a perfect catalytic effect in the reaction,and over Pd loading promotiover-hydrogenation to ethane.Pd loading of 0.25 wt%was selected as the better loading.?2?Four kinds of catalysts with different supports?i.e.,CMC-Pd,CS-Pd,CMC@CS-Pd,CS@CMC-Pd?have high acetylene conversion.The selectivity of ethylene over CMC@CS-Pd and CS@CMC-Pd catalysts higher than CMC-Pd and CS-Pd.And under the same conditions,the selectivity of CMC@CS-Pd catalyst for ethylene is better than that of CS@CMC-Pd catalyst.?3?The Pd is the main driving force f the selective hydrogenation of acetylene.And the effect of CMC and CS are weakly to the reaction activity.However,the actual adsorption energy of H₂,C₂H₂ and C₂H₄ molecules on the CS surface different to CMC.Activity and selectivity of four catalyst will be affected to the competitive process on the CS and CMC surface.?4?Compared the adsorption of C₂H₂ and C₂H₄ molecules on the Pd₂cluster surface,we found that the activation energie of C₂H₄on the Pd₂ surface was lower than C₂H₆ on the Pd₂ surface.The results demonstrated that the Pd₂ catalyst has a better selectivity for C₂H₄ molecule.