Selective Hydrogenation Of Isophorone By Tris (M-sulfophenyl) Phosphine-Rh Catalysts

The selective hydrogenation of isophorone（IP）-3,3,5-trimethylclyclohexanone（TMCH）is a kind of high boiling-point solvent;and the chiral TMCH are very important fine chemicals and pharmaceutical intermediates.In this papaer,highly active and selective Rh nanoparticles catalyst were prepared to investigated the condition and kinetics of selective hydrogenation of IP.The asymmetric hydrogenation reaction were investigated preliminarily.Tris（m-sulfophenyl）phosphine（TPPTS）-stabilized Rh nanoparticles catalyst were prepared by transition metal salt reduction method and characterized by UV-vis,TEM and ³¹P NMR.The mechanism of the stabilization of TPPTS was investigated.The results showed that the pretreatment of Rh/TPPTS catalyst including pretreatment temperature,pretreatment time,stabilizer TPPTS and TPPTS/Rh ratio had great impact on the selective hydrogenation of C=C bond in isophorone whether in hydrogenation activity or selectivity.The condition of selective hydrogenation was investigated by Nano-Rh catalyst.Under the optimized reaction conditions:IP/Rh ratio=3000,T=70℃,p（H₂）=1.6MPa,t=30min,Stirring rate=800rpm,the conversion of IP can be as high as 99.8%and the selectivity of TMCH can be 97.4%.Reaction kinetic of selective hydrogenation of isophorone was studied.The conversion of isophorone and selectivity of TMCH were investigated in ranges of T=50¹10℃,p（H₂）=1.2².0 MPa and c_Rh=0.25².0 mmol?L^-1.Hydrogenation was zero order reaction with isophorone,2.36 order reaction with hydrogen pressure and 0.33 order reaction with catalyst concentration,the reaction rate equation was given.The Ea of the reaction is 6343.58 J?mol^-1.The results showed that the selective hydrogenation of C=C bond in isophorone on the Nano-Rh catalyst was an easy and quick reaction which is sensitive with hydrogen pressure but not with catalyst concentration and temperature.The asymmetric hydrogenation of IP（TMCH）and the intermediates of IP-Pro and TMCH-Pro were investigated by Rh/TPPTS in the presence of L-proline.The ee.of asymmetric hydrogenation were both low.The asymmetric hydrogenation of TMCH by Rh-TPP/Al₂O₃ catalyst generated chiral product（R-TMCH）.Asymmetric hydrogenation reaction of Nano-Rh catalysts needs further study..