Modification of La on Cu/SiO2 catalyst for hydrogenation synthesis from methyl 3-hydroxypropionate to 1,3-propanediol
[Objective]1,3-Propanediol(1,3-PDO)is widely utilized as a raw material in industry,particularly as the key monomer for manufacturing polytrimethylene terephthalate(PTT),a well-known fiber resin,through a reaction with p-phthalic acid(PTA).Currently,the technology for production of 1,3-PDO is grasped by foreign companies,hindering the application and development of the advanced fiber resins.In this regard,it is necessary to develop technology for the production of 1,3-PDO.Recent progress has focused on the method involving epoxide hydroesterification that includes 3-hydroxypropionate methyl ester(3-HMP)as an intermediate,and hydrogenation to 1,3-PDO is of the current challenge.This study aims at preparing the La metal-promoted Cu/SiO2 catalyst and investigating its catalytic property.[Methods]Catalysts formulated as 20Cu-xLa/SiO2 were prepared using materials such as Cu(NO2)2·3H2O,La(NO3)3·6H2O,silica sol(containing 30％SiO2 by mass),ethanol,and NH3·H2O through the ammonia distillation method.The catalytic performance of 3-HMP hydrogenation to 1,3-PDO was tested over the catalysts using a fixed bed reactor.The catalysts were characterized using H2 temperature-programmed reduction(H2-TPR),H2 temperature-programmed desorption(H2-TPD),X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),and N2 physical adsorption desorption.[Results]It is found that the catalyst 20Cu-0.50La/SiO2 has the best catalytic performance,achieving a 3-HMP conversion of 91.8％at a high liquid space velocity(LHSV)of 0.10 h-1,along with 1,3-PDO selectivity and yield up to 85.2％and 78.2％.The doping of La metal produces a strong interaction with the Cu in the SiO2 support,which increases the dispersity of the Cu and the surface concentration of Cu+species.The surface area of the active Cu species is greatly enlarged,thereby improving the activity and stability of the catalysts in the hydrogenation reaction.Furthermore,the 20Cu-0.50La/SiO2 catalyst exhibits excellent stability as it maintains activity for over 100 h.H2-TPD results show that La addition promotes H2 activation,which increases the surface concentration of active H*.XPS characterization results further demonstrate the strong interaction between Cu and La species.This strong interaction between Cu-La not only increases the content of Cu+,but also prevents the thermal migration and agglomeration of Cu species on the catalyst surface,thereby inhibiting the sintering of the active components of the catalyst.[Conclusion]Under reaction conditions of a pressure of 6.0 MPa,temperature of 160 ℃,LHSV of 0.10 h-1,and hydrogen-ester ratio of 650,a 3-HMP conversion of 91.8％is achieved,while the selectivity and yield of 1,3-PDO are 85.2％and 78.2％,respectively.The reaction remains stable for over 100 h without significant deactivation,representing the best outcome obtained at a high LHSV of 0.10 h-1.Characterization via a series of spectroscopic means indicate that a strong interaction occurrs between La and Cu.This interaction enhances the dispersion of Cu particles on the SiO2 support,leading to an increase in the specific surface area of the catalyst,as well as the Cu+content of the active species in the H2-reduction process.The reactivity,selectivity,and stability of the catalyst are all improved for the hydrogenation of 3-HMP to 1,3-PDO.
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