Design And Development Of The Cheap Metal Catalysts For Carboxylic Acid And Ester Hydrogenation

Recent years have witnessed the rapid development of the global economy,at the same time the demand for energy is speedily increasing year by year.Meanwhile,the dramatic increase in the consumption of fossil fuels and fossil-derived chemicals have led to serious environmental problems and exhaustion of energy resources.As a clean alternative energy,fuel ethanol has aroused widespread concern in many countries.In this paper,two strategies concentrated on several drawbacks among alcohol production were employed.Noble metal catalysts,such as Pt,Pd had been extensively investigated for the direct hydrogenation of carboxylic acid.Although noble catalysts showed high performance for carboxylic acids conversion,selectivity towards fatty alcohol is still unsatisfactory,which restricts its large-scale application.Thus,seeking for earth-abundant cheap alternatives to replace the scarce noble metals would be more appropriate when considering the cost and sustainability.The first part of this paper involves a cheap bimetallic carbon coating Fe-Ni catalyst,which adopted an in situ carbonization reduction,using the cheap melamine and oxalic acid as carbon source and nitrogen source.This Ni-Fe bimetallic catalyst showed outstanding catalytic activity in the hydrogenation of stearic acid and the yield of fatty alcohol was up to 98%.Characterizations confirmed that in the optimal Nil.8Fe1.5 catalyst,Ni3Fe alloy was formed,and the synergistic effect between Fe-Ni was responsible for the high performance.Furthermore,DFT calculation shown that Fe addition could significantly enhance the adsorption of carboxylic acid on the catalyst surface,and carboxylic acid dehydroxylation was identified to be the rate-determining step.The remarkable catalytic activity,long-term stability and easy separation make this carbon coated Ni-Fe catalyst a promising alternative for the production of fatty alcohols.In the second part of this paper,the co-precipitation strategy was utilized to design the Co-Fe doping MgAIOx-hydrotalcite-derived catalysts.As revealed by TEM characterization,CoFe nanoparticles were uniformly dispersed in the MgAlOx matrix,presenting a small average particle size of only 4.7 nm.This hydrotalcite-derived material has a well-developed mesoporous structure(mesopore volume of 0.5 cm2/g),large surface area(224 m2/g).Catalytic hydrogenation of ester was also explored on the Co-Fe doping materials.Co doping Co4-LDO catalyst was found to have the highest activity,but the alcohol selectivity was not high because of the decarbonylation side reaction.When Co and Fe were co-doped,the activity of the Co4Fel-LDO catalyst decreased slightly,but the selectivity of alcohol increased significantly.Combined with kinetics research,it was found that Fe could significantly inhibit the decarbonylation reaction and then increase the selectivity of alcohol.A new reaction pathway was also proposed on this Co-Fe doping catalyst.Besides,substrate scope experiments shown that this catalyst had an excellent adaptability in other ester hydrogenation.Generally speaking,two strategies were developed for the preparation of fatty alcohols with excellent catalytic performance,which can be effectively used for direct hydrogenation of fatty acids and carboxylic ester hydrogenation.These two strategies have significant guidance for the preparation of aliphatic alcohols and might be an promising alternative for industrial production.