Research On The Hydroformylation Reaction Of 2-butene To Pentanal Catalyzed By Rh-P Complex

The hydroformylation of butene with synthetic gas to produce pentanal is recongnized as an atom economic reaction which gradually becomes a hot topic of green chemistry.There have been a lot of publications on 1-butene hydroformylation with well-known conclusions while the research on 2-butene hydroformylation still needs much effort due to its low conversion rate and low products yield.Herein,we deeply studied the reaction conditions,kinetics as well as olefin isomerization in the process of 2-butene hydroformylation,providing the theoretical basis for industrialization.Firstly,the catalyst system Rh(CO)2(acac)/BIPHEPHOS was employed in 2-butene hydroformylation in a 100 mL autoclave.The reaction conditions were optimized by single factor experiment in order to reach a best products yield and n/i(n-pentanal/i-pentanal)ratio.The reaults showed that under the conditions of 105?,0.8 MPa,[Rh]=0.3 mmol/L,P/Rh=4,reaction time 3 h,stirring rate 1200 r/min,2-butene amount 5.0 g,solvent amount 30 mL,the final pentanal yield,the n/i ratio and the turnover frequency(TOF)of catalyst could respectively reach 59.06%,36.38,and 1914.45 h-1.Next,the kinetics of 2-butene hydroformylation was studied on the basis of single factor experiment.Five factors(reaction temperature,pressure,catalyst concentration,ligand concentration and 2-butene amount)which influence the generation rate of pentanal greatly were investigated.It was found that pentanal yield could be improved by raising temperature,reducing pressure,increasing the catalyst concentration,ligand concentration and 2-butene amount.Based on the trend of the kinetic experiment,a model of pentanal generation rate was selected to do the non-linear fitting with Matlab function.Finally,the specific equation for pentanal generation was achieved and the theoretical data were tested to be in good agreement with experiment data.Furthermore,the butene isomerization in the process of 2-butene hydroformylation was studied.The results showed that when Rh/BIPHEPHOS was used as catalyst there were both isomerization of 2-butene to 1-butene and of trans-2-butene to cis-2-butene.However,when Rh/PPh3 was adopted,no isomerization of 2-butene was detected.This could be used to explain why Rh/PPh3 performs badly in the hydroformylation of 2-butene.