Study On Performance Of Ni-In Bimetallic Catalysts In Selective Hydrogenation Of Fatty Acid Methyl Ester To Fatty Alcohol

Selective hydrogenation of fatty acid methyl esters to fatty alcohols is an important method for producing fatty alcohols,and the structure and properties of the catalysts determines the reaction pathway of fatty acid methyl esters.The Ni catalyst is active for hydrogenation and low cost,however,it can lead to low alcohol yield because of the high activity for decarbonylation/decarboxylation and C-C hydrogenolysis.In this paper,the Ni-In intermetallic compounds（IMCs）were used to modify the geometric and electronic structure of Ni to inhibit decarbonylation/decarboxylation and C-C hydrogenolysis and to improve alcohol yield.First,the SiO₂-supported Ni-In bimetallic catalysts with different Ni/In atomic ratios were prepared by sol-gel method.Their structures were characterized by means of H₂-TPR,FT-IR,ICP-AES,N₂ adsorption-desorption,XRD,TEM,physical magnetism,XPS,CO chemisorption,TPD and TPSR.And their performance in selective hydrogenation was elevated on a fixed-bed reactor.The relationship between the catalyst structure and performance was analysized.It was found that the Ni phyllosilicate formed during the sol-gel process led to high metallic dispersion.Ni₂In,Ni In and Ni₂In₃ IMCs were syntheized in the catalysts with Ni/In atomic ratios of2:1～1:1,1:1.3 and 1:1.6～1:2,respectively.In Ni-In IMCs,the Ni atoms were homogeneously isolated by the In ones and the charge was transferred from In to Ni.Meanwhile,the electronic density of Ni increased with reducing the Ni/In atomic ratio.In the selective hydrogenation of fatty acid methyl esters,a synergetic effect between Ni and In favored the formation of fatty alcohols.The catalyst with Ni/In atomic ratio of 1:1.3（Ni In（1:1.3）/SiO₂）had better performance than others in selective hydrogenation.In the selective hydrogenation of methyl octanoate,at the condition of250～270°C,3.5 MPa,WHSV of 4 h^-1 and H₂/methyl octanoate molar ratio of 25,the yield of octanol can reach 94%on Ni In（1:1.3）/SiO₂;the conversion of methyl octanoate and the octanol selectivity decreased from 96.8%to 90.1%and 96.5%to 92.5%after reaction for 240 hours,respectively.The Ni In IMC remained unchangeable after the reaction,and the catalyst deactivation is mainly ascribed to the carbonaceous deposit.In the selective hydrogenation of methyl laurate and methyl palmitate,the yields of dodecanol and hexadecanol reached 86.2%and 94.8%,respectively.Afterward,the hexadecyl trimethyl ammonium bromide（CTAB）assisted sol-gel method was used to prepare the catalysts with the Ni/In atomic ratio of 1:1.3 and different CTAB/TEOS molar ratios.The results show that the IMCs particle size and the specific surface area,pore volume and pore size of the catalysts increased with raising CTAB/TEOS molar ratio.Unfortunately,the addition of CTAB only slightly improved the the catalyst performance in the selective hydrogenation of methyl palmitate.