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Non-metallic Element Modified Palladium Nanocatalysts Are Used For The Selective Hydrogenation Reaction

Posted on:2019-06-07Degree:MasterType:Thesis
Country:ChinaCandidate:D Y ZhangFull Text:PDF
GTID:2351330548955539Subject:Physical chemistry
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The supported Pd catalyst has a wide range of applications in the selective hydrogenation reaction.The catalytic performance of supported Pd catalysts can be modulated by changing the size of Pd particles,morphology of Pd,modification of non-metallic elements,addition of second component metal,and carrier properties.In this dissertation,supported Pd catalysts were used as the research object,and the synthesis methods of ordered mesoporous carbon-supported Pd nanocatalysts with C,H,and N were developed.The effects of nonmetals on the structure,electronic properties and adsorption properties of the catalysts were investigated.Hydrogenation of ?-unsaturated aldehydes and acetylenes has found a way to increase the catalytic selectivity of Pd,which lays the foundation for the design of highly selective Pd catalysts.The main contents are as follows:Hydrothermal method and solvent volatilization self-assembly method,phenolic resin as carbon source,F127 as structure directing agent,aminopropyltrimethoxysilane/acetylacetone as coordination aid,chloropalladic acid as palladium source,successfully synthesized Sequential mesoporous carbon-supported carbon-modified palladium catalysts(Pd(C)/OMC),ordered mesoporous carbon-supported nitrogen-modified palladium catalysts(Pd(N)/OMC)and ordered mesoporous carbon-supported hydrogen-modified palladium catalysts(Pd(H)/OMC).The Pd(C)/OMC-1,2 and 3 catalysts have palladium particle sizes of 12.4,6.2 and 3.2 nm,respectively.It has a high specific surface area(about 400 m2/g),a uniform pore size(about 5 nm)and a high porosity,and palladium nanoparticles are confined to the carbon skeleton.The Pd(H)/OMC-1 and 2 catalysts have palladium particle sizes of 3.8 and 4.6 nm,respectively.The size of Pd(N)/OMC in different nitrogen species and different n(N)/n(Pd)Pd(N)/OMC is about 3.5 nm.XPS results showed that the Pd(0)3d5/2 band shifts to a high binding energy of 0.6 eV in Pd(N)/OMC-4,indicating that N forms a strong electron interaction with Pd.The Pd(0)3d5/2 band in Pd(C)/OMC did not shift,and there was no electron transfer between C and Pd.In the TPHD results,Pd(C)/OMC and Pd(N)/OMC showed no desorption peaks at all compared with Pd/FDU15,indicating that the subsurface C and N both promote the diffusion of the subsurface H.In order to eliminate the effect of size effect,a sample of Pd nanoparticle size was selected for selective hydrogenation of cinnamaldehyde and phenylacetylene in a series of catalysts.The cinnamaldehyde hydrogenation reaction conditions were as follows: the molar ratio of cinnamaldehyde to palladium was 1800:1,deionized water was the solvent,the temperature was 80°C,the pressure was 1 MPa,and the stirring speed was 800 r/min.The phenylacetylene hydrogenation conditions were as follows: the molar ratio of phenylacetylene to palladium was 1800:1,ethanol was the solvent,the temperature was 50 °C,the hydrogen balloon was used,and the stirring speed was 800 r/min.When the conversion rate is 100%,the selectivity of Pd(H)/OMC-2 to phenylpropanal and styrene is 60% and 84%,respectively.The choice of Pd(C)/OMC-8 for styrene propanal and styrene The levels were 80% and 95%,respectively.The selectivity of Pd(N)/OMC-4 to phenylpropanal and styrene were 95% and 100%,respectively.The selectivity of hydrogenation of cinnamaldehyde to styrene propionaldehyde and phenylacetylene to styrene was Pd(N)/OMC>Pd(C)/OMC>Pd(H)/OMC.The experimental results show that the improvement of the catalytic hydrogenation selectivity is the result of the superposition of the electron interaction and the suppression of the subsurface hydrogen.Either of the two effects disappears,and the selectivity will be reduced to some extent.
Keywords/Search Tags:ordered mesoporous carbon, palladium nanoparticles, carbon, hydrogen, nitrogen, hydrogenation of Cinnamaldehyde, hydrogenation of phenylacetylene
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