The Pore Size Effect Of Porous Zeolite Encapsulated Pd For The Direct Synthesis Of Hydrogen Peroxide

Hydrogen peroxide,as a clean and efficient oxidant,is widely used in the synthesis of fine chemicals,sewage purification and medical protection.With the acceleration of agricultural modernization,there is a strong demand for new environmental pesticides.The oxidants used in the oxidation reactions of pesticide synthesis are expected to be replaced by hydrogen peroxide.At the same time,hydrogen peroxide can also transform the organophosphorus and pyrethroid pesticides in wastewater into small molecule harmless substances.The traditional anthraquinone method with high energy consumption and high pollution is not suitable for the needs of social development.The direct synthesis of hydrogen peroxide from hydrogen and oxygen has attracted much attention because of its simplicity and no pollution.At the same time,the metal catalytic method is expected to be the best way to replace industrial anthraquinone process to realize green production of hydrogen peroxide because of its simple reactor structure and wide selection of catalyst materials.In this paper,the subnano Pd particles were encapsulated within titanium silicate voids via the mercaptosilane-assisted dry gel conversion synthesis method,and the valence state of Pd particles was controlled by continuous heat treatment.At the same time,the pore size of the synthesized TS-1 could be changed by adding different templates,the effect of pore size of porous materials on the direct synthesis of hydrogen peroxide was explored.Furthermore,the potential application of MOFs in the synthesis of hydrogen peroxide was explored.The main conclusions and results of this parper:?1?The anti sintering ability of encapsulated catalyst nanoparticles is outstanding.After high temperature heat treatments,the particle size?1.67 nm?1.79 nm?1.83nm?only slightly increases,and the average particle size is less than 2 nm.?2?In the in-situ oxidation of benzyl alcohol,the encapsulated Pd@HTS-1catalyst has excellent performance.After high temperature heat treatments,the yield of hydrogen peroxide reached 35705 mmol·g _Pd^-1·h^-1.Meanwhile,in the in-situ oxidation of benzyl alcohol,the benzaldehyde production over the Pd@HTS-1reached 4268.8 mmol h^-1kg^-1_cat,which is six times higher than that over the Pd/HTS-1(708.4 mmol h^-1kg^-1_cat).?3?The effect of HTS-1 with different pore sizes on the synthesis of hydrogen peroxide is different.With the increase of the pore size?2.2 nm?3.5 nm?5.8nm?7.2 nm?8.3 nm?12.3 nm?,the yield of hydrogen peroxide was climb up and then decline.The catalyst with a pore size of about 8 nm showed the best performance in the synthesis of hydrogen peroxide.?4?MOFs materials have large specific surface area and excellent performance in gas adsorption.Although its organic ligands are not resistant to oxidants,the experimental results show that MOFs have a good structure in high concentration?30wt%?of hydrogen peroxide at low temperature??30?C?.It has potential application value in the synthesis of hydrogen peroxide in situ and low temperature oxidation reaction.