The Preparation Of Acid/base-modified Metal Nanocatalysts And The Study Of Their Structure And Catalytic Performance

Hydroxyapatite,as phosphate minerals,is widely used as green,substrate-tolerant,nearly water-insoluble,and easy to recover catalyst support with excellent ion exchange/adsorption ability and tunable surface acid-base property.Especially,many base-catalyzed reactions,as well as Guerbet reaction for the production of n-butanol from ethanol,can be efficiently promoted by HAP-based catalyst systems.In addition,the lattice oxygen in the structure of HAP may improve the oxidation activity of supported metal catalysts.Thus,it is probable that reasonably regulating the microstructure and surface acid-base property of HAP supports can greatly enhance catalytic performances of corresponding catalysts.In this paper,we prepared three different microstructures of hydroxyapatite load gold catalysts,implements the modulation of acid and alkaline catalysts and the high dispersion of the metal.Through the study of methylacrolein oxidative esterification,comprehensive research of the relationship between the structure and properties of catalysts.In addition,based on the calcium ion homologous,we prepared hydroxyapatite hydroxyapatite and calcium aluminum hydrotalcite composite and base promoted gold-palladium double metal catalysts.applied to 5-hydroxymethyl furfural oxidation reaction.(1)In this work,we first synthesize supported Au nanocatalysts based on three different types of needle-like,lamellar-like and rod-like HAP supports through the ultrasonic and solvent thermal method.The results demonstrate that small and uniform Au NPs can be tightly anchored onto the surface of HAP supports and even partially embedded into supports,thereby resulting in the SMSI and the formation of a large number of surface defects.The effects of the microstructures of HAP supports on metal-support interactions,surface acid-base properties,surface defects,electronic structures of Au species,and catalytic performance of catalysts are studied systemically.Compared with lamella-like and rod-like HPA supported ones,needle-like HAP supported Au catalyst displays much higher catalytic performance in the oxidative esterification of MA in terms of both the activity and the MMA selectivity under mild reaction conditions(i.e.,low methanol/MA ratio,low reaction temperature and ambient pressure).High catalytic efficiency is attributed to a cooperative effect between abundant surface acid-base sites and highly dispersed active Au species,thereby facilitating the chemisorption of reactants and the following activation.(2)Hydroxyapatite and hydrotalcite composite material of different calcium phosphorus ratio was synthesized by in situ growth method,in order to further enhance composites' alkaline,different concentration of lanthanum elements was joined in the synthesis,different series of gold palladium bimetallic catalyst were synthesized based on the composite materials.Compared the different series catalysts of BET,the distribution of gold palladium nanoparticles and electronic structure and surface alkaline.In 5-hydroxymethyl furfural oxidation reaction,obtained the best catalyst,inspected the influence factors of the conversion and selectivity including of time,temperature,pressure,catalyst and other conditions.The catalytic reaction mechanism are discussed.The results showed that the high specific surface area and the carrier's ion exchange properties of hydroxyapatite can get the high dispersion of gold palladium.Composite Materials has realized the basic ascension,especially the addition of lanthanum is conducive to the generation of strong alkaline,the catalyst is highly active by gold palladium bimetallic alloy and rich alkaline loci.