Acid-base Sites Promoted Silver Catalyst For The Conversion Of Ethanol To N-butanol

Bio-ethanol is one of the most important biomass platform molecules.At present,the main purpose of bio-ethanol is only as biofuel.The downstream conversion capacity is insufficient,resulting in serious excess capacity.Therefore,it is imperative to efficiently convert bio-ethanol to produce high-value fine chemicals.Butanol is an important chemical raw material and product.It can be used as a platform molecule to prepare a large number of chemicals in the field of petrochemical,food and pharmaceutical industries.The preparation route of n-butanol from bio-ethanol has great strategic significance.The preparation route of n-butanol from ethanol involves several cascade steps:direct catalytic dehydrogenation,aldol condensation,and catalytic hydrogenation.The direct catalytic dehydrogenation of ethanol and the hydrogen transfer for the subsequent catalytic hydrogenation are the key step,which always results in low conversion and n-butanol selectivity in the reported publication up to now.How to design and control the structure of the supported metal catalyst to achieve high activity and high selectivity of this reaction is still a great challenge.In order to solve this scientific problem,a uniformly-dispersed supported Ag/MgAl-LDO catalyst has been prepared respectively by in-situ calcination and reduction Ag+ adsorbed layered double hydroxides(LDHs)and Ag3(S2O3)23-intercalated LDHs through the lattice-induced effect of LDH layer and the confinement effect of the two-dimensional space.It is found that the interfacial synergistic effect between acid-base sites and Ag nanoparticles contributes the enhancement of the conversion and selectivity in the reaction from ethanol to n-butanol.The main research work is displayed as follows:(1)Taking the advantages that the metal cations of the LDH layer are highly dispersed at an atomic level and the composition is adjustable,a uniformly-dispersed supported Ag/MgAl-LDO catalyst has been prepared respectively by in-situ calcination and reduction Agg adsorbed layered double hydroxides(LDHs).Applied in the production of n-butanol from ethanol,an ethanol conversion of 15.4%and n-butanol selectivity up to 73.4%were obtained.It is found that a strong interfacial interaction between the metal and the support metal oxides.FT-IR spectra reveal the efficient activation of the ethanol Ca-H bond on the Ag active site in the direct catalytic hydrogenation is promoted by the cooperation with the support metal oxides.While uniformly dispersed acid-base metal oxide is responsible for the condensation process with the assistance by the metal center in the C?-H activation of acetaldehyde.Moreover,incomplete hydrogenation products have not been detected indicating the sufficient H transfer and hydrogenation capability.(2)The particle size of the active site of Ag is further tailored by tailoring topological transformation condition.The interfacial interaction between the metal and the support metal oxides is therefore strengthened.With the decrease of the particle size of the Ag,the interface of Ag-O promotes the direct catalytic hydrogenation of ethanol.Moreover,the acidity and the alkalinity of the support are tailored by tailoring the M2+/M3+ ratio in LDH layer of the hydrotalcite.As the alkali density of the catalyst increases,the condensation ability intensified.(3)Taking the advantages that the 2D confined interlayer space of the LDH is adjustable,based on the two-dimensional space,Ag3(S2O3)23-intercalated LDHs has been prepared.Through in-situ topological transformation,a uniformly-dispersed supported Ag-MgAl-LDO catalyst with a particle size of(1.8 nm)has been prepared.Applied in the production of n-butanol from ethanol,an ethanol conversion of 22.0%and a n-butanol selectivity up to 75.6%were obtained.