Enhanced Nanao Catalytic Hydrogenation Of Cinnamaldehyde By Rotating Packed Bed

Nano-catalysis technology which has the advantages of high efficiency and selectivity,easy separation and recovery of catalysts,is a new frontier technology,and was widely applied in industrial catalysis.However,there is a mismatch between mixing/mass transfer and reaction to result in decreacing the catalytic effect of nano-catalysts in the nano-catalysis technology due to the small particle size and high activity of nano-catalyst.In the paper,a rotating packed bed(RPB),which has the advantages of intensified micromixing and mass transfer,was applied in the nano-catalysisprocess to intensify the mass transfer/mixing matching the reaction.The details are as follows:the liquid-solid mass transfer performance and effects of nanoparticles on the gas-liquid mass transfer performance was investigated in the RPB.the Ni-Pt nanoparitlces,which were controllably prepared by liquid phase reduction method in the PRB,were applied in the hydrogenation of cinnamaldehyde(CAL).The hydrogenation performance of CAL by Ni-Pt nanoparticles was investigated in the RPB.In addition,the kinetics of catalytic hydrogenation of CAL by Ni-Pt nanopartilces was investigated.The main coclusions are as follows:1.The effects of nanoparticles on gas-liquid mass transfer coefficient and the effective mass transfer area were investigated in the RPB by the method of dynamic measurement of dissolved oxygen in water and the method of sodium sulfite oxidation,respectively.The results indicated that the enhancement facor of gas-liquid mass transfer(E)and that of effective mass transfer area(Earea)decreased with an increase of rotation speed under the different nanoparticles.The liquid film thickness decreased with the increase of rotation speed in the RPB.When the particles size distribution of nanoparticles in the liquid phase was close to the liquid film thickness,the gas-liquid mass transfer coefficient and the effective mass transfer area was not intensified by nanoparticles.The Earea was greater than the E under different nanoparticles,which indictated that the enhancement of gas-liquid mass transfer performace by nanoparticles in the RPB was mainly intensified the effective mass transfer area.2.The liquid-solid mass transfer coefficient was investigated by the ion exchange reaction between cation exchange resin and sodium hydroxide solution in the RPB.The liquid-solid mass transfer coefficient increased with an increase of rotation speed.The liquid-solid mass transfer coefficient was not effect by the solid loading of cation exchange resin.The liquid-solid mass transfer coefficient increased with an incease of liquid volume rate,and the liquid-solid mass transfer coefficient generally remained a constant with a further incearse in liquid volume rate.In addition,a correlation to predict the liquid-solid mass transfer coefficient was established,and the predicted liquidsolid mass transfer fitted well to the experimental data with a deviation within 15%.Therefore,the correlation colud be used for the predicted the liquid-solid mass transfer coefficient of suspension in the RPB.3.The size-controlled synthesis of Ni-Pt nanoparticles without adding surfactant was carried out in the RPB.Furthermore,the prepared Ni-Pt nanoparticles without undergoing calcination and reduction process were directly used as nano-catalyst for the selective hydrogenation of CAL.The prepared Ni-Pt nanoparticles were characterized by XRD,TEM,TPR,TPD and XPS.The results of hydrogenation of CAL by Ni-Pt nanoparticles indicated that the conversion of CAL could be increased by doping a thin of Pt,while the selectivity of hydrocinnamaldehyde(HCAL)remained steady.The conversion of CAL increased with an increase of temperature and pressure.The conversion of CAL increase with an increase of stirring speed,and the conversion of CAL generally remained a constant with a further incearse in stirring speed.The conversion of CAL decreased while the selectivity of HCAL increased with an increase of the concentration of CAL.The catalytic activity of Ni-Pt nanoparticles decreased with the increase of reused times of Ni-Pt nanoparticles,and the activity of Ni-Pt nanoparticles generally remained a constant with a further incearse in reused times.The CAL conversion of 95.5%with the selectivity to hydrocinnamaldehyde(HCAL)of 92%were obtained in stirring tank bed under the operation conditions of Ni-Pt nanoparticles of 2 g,stirring speed of 1000 rpm,temperature of 100?,pressure of 2 MPa,reation time of 1 h.In addition,the kinetic parameter on the catalytic hydrogenation of CAL by Ni-Pt nanoparticles was obtained in this study.The pre-exponential factor value is 90.99 kJ/mol and activation energy is 3.22×1011.4.The hydrogrnation of CAL catalyized by Ni-Pt nanoparticles was carried out in the internal circulating rotating packed bed.Compared with the STR,the conversion of CAL was increased by nearly 2 times,wihle the selectivity of Hydrocinnamaldehyde(HCAL)decreased slightly,and the selectivity of hydrocinnamyl alcohol(HCOL)increased slightly.