Abstract
Acetic acid (AA) hydroconversion was studied over various monometallic (Fe, Co, Ni, Cu, Zn, Pt) and bimetallic (doped with In as second, guest metal) catalysts loaded on a highly mesoporous, fumed silica support. The transformations were investigated in a fixed bed, flow-through reactor in temperature range of 240-380°C using hydrogen flow at 21bar total pressure. The catalyst precursors were activated in H2 flow at 21bar and 450°C as routine pre-treatment. Catalytic performances of the studied metal catalysts have nothing in common. Activities and the yields of main products contrast strikingly. Diversity of catalytic behaviour reflects the complexity of the surface reaction network. Contrary to the highly ethanol selective Co or Cu forms, over Ni catalyst mainly methane was produced. Indium doping can completely eliminate the hydrodecarbonylation activity and turn to the consecutive reduction route resulting in high ethanol yield. Metallic phases of different peculiarities can offer promising contacts for upgrading various oxygenates obtainable from biomass degradation.
Highlights
Both academia and industry are looking forward to utilize renewable, carbon neutral biomass to produce biofuels and value-added chemicals
There is a sore need of development alternative catalysts for more facile hydrogenation of organic acids than the conventional copper chromite (Adkins-type) catalysts [3]. Such catalysts should be active in the reduction of the carbonyl group to methylene group, but shows low activity in alcohol dehydration and hydrogenolysis of C-C bonds resulting in high selectivity for alcohol production
Their results showed that Cu/ SiO2 was active and quite selective for the production of ethanol, acetaldehyde and ethyl acetate through consecutive reduction of acetic acid, whereas Fe/SiO2 resulted in the production of acetone and CO2 following the ketonization reaction route
Summary
Both academia and industry are looking forward to utilize renewable, carbon neutral biomass to produce biofuels and value-added chemicals. The indium-additive doping of Ni host metal was found to suppress the total hydrogenation and hydrodecarbonylation reaction - both resulting in hydrocarbons - and promote selective alcohol formation [13, 14] The properties of such catalysts are determined by the type and the state of active metal phase the support can significantly influence the formation of active metal particles, the quality of the catalytically efficient surface. Et al studied acetic acid hydrogenation at atmospheric pressure over Fe, Co or Cu dispersed on an inert silica support [22], and Co loaded on various supports or using bimetallic combinations of the mentioned metals [23] Their results showed that Cu/ SiO2 was active and quite selective for the production of ethanol, acetaldehyde and ethyl acetate through consecutive reduction of acetic acid, whereas Fe/SiO2 resulted in the production of acetone and CO2 following the ketonization reaction route. Each catalyst precursor was reduced in hydrogen flow in situ in the reactor at 450°C for 1h in order to generate active supported metal prior to the catalytic test
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