Abstract
Activity improvement of Ru-based catalysts is needed for efficient production of valuable chemicals from glycerol hydrogenolysis. In this work, a series of Re promoted Ru catalysts encapuslated in porous silica nanoparticles (denoted as Re-Ru@SiO2) were prepared by coating silica onto the surface of chemically reduced Ru-polyvinylpyrrolidone colloids, and were used to catalyze the conversion of glycerol to diols and alcohols in water. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) were used to characterize these nanoparticles. Effects of Ru/Si atomic ratio, Re addition, glycerol and catalyst concentrations, reaction time, temperature, and hydrogen pressure were investigated. Re addition retarded the reduction of ruthenium oxide, but increased the catalyst reactivity for glycerol hydrogenolysis. Due to its greater Ru content, Re-Ru@ SiO2 showed much better activity (reacted at much lower temperature) and more yields of 1,2-propanediol and overall liquid-phase products than Re-Ru/SiO2 (prepared by conventional impregnation method) reported before. The rate of glycerol disappearance exhibited first-order dependence on glycerol concentration and hydrogen pressure, with an activation energy of 107.8 kJ/mol. The rate constant increased linearly with increasing Ru/Si atomic ratio and catalyst amount. The yield of overall liquid-phase products correlated well with glycerol conversion.
Highlights
Glycerol is the co-product of biodiesel manufacturing and has become one of the top 12 building blocks of biorefinery [1,2]
Several useful C1–C3 diols and alcohols can be produced from glycerol hydrogenolysis, via the reaction scheme shown in Figure 1 [5,6]
The results suggest that the activation energies for PDO conversion to alcohols are higher than those for PDO formation from glycerol
Summary
Glycerol is the co-product of biodiesel manufacturing and has become one of the top 12 building blocks of biorefinery [1,2]. It is interesting to note that k increases linearly with the increase of Ru/Si atomic ratio and with the increase of Re-08RuSi catalyst amount, suggesting that most Ru sites have identical activity for catalyzing glycerol hydrogenolysis. For the Re-08RuSi catalyst, frequency factor A and activation energy E were 1.06 × 1013/h and Nan1o0m7a.t8erkiaJls/m20o18l,, 8r,e1s5p3ectively, which were obtained from an Arrhenius plot of lnk versus 1000/1T0.oIfn14the region of pressure ≥800 psig, rate constant increased linearly with hydrogen pressure (a straight line witphasthsienignctrheraosuegohf Rzuer/oSiwataosmoibctraaitnioedanbdywpiltohtttihneginkcrveearsseuosf pRree-0ss8uRrueS),i cwahtailcyhstsaumggoeusntts, sthuagtgegsltyincegrol thahtynderaorglyenaolllyRsuissiistefsirhstavoerdiedrenwtiitchalraecstpievcittytofohrycdartoalgyezninpgregslsyucreer.ol hydrogenolysis. Reduce the particles in a gas of 5% hydrogen in 95% argon at a heating rate of 1 ◦C/min to 200 ◦C, and maintain at 200 ◦C for 4 h
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