Studies On Activity And Kinetics Of Ru/C Catalysts In Hydrogenation Of Glucose

In this article, Ru/C catalyst employed to produce sorbitol from hydrogenation of glucose was studied. The effects of reduction temperature and time on the catalytic activity were explored using the method of orthogonal design. The optimum reduction temperature of 400癈 and the most reasonable reduction time of 3 hrs were achieved. The choices of solvent, pH, soaking time and loading amount of ruthenium are important for the preparation of Ru/C with high catalytic activity. Among the solvents of water, alcohol, and acetone, it is found that water is the best. When water was used to be solvent, pH value of the solution should be adjusted to 3.3. Not enough soaking time would decrease catalytic activity, whereas the no significant effect of soaking time on the catalytic activity was observed when the soaking time is longer than 10 hrs. The catalytic activity is proportionally dependent on the ruthenium-loading amount when the ruthenium loading is smaller than 5%.The catalytic activities of bimetallic catalysts including Cu-Ru, Zn-Ru, and Ni-Ru were tested. The results indicated that the presence of second metal Cu, Zn, Ni in Ru/C catalyst decreases the catalyst's activity. Furthermore, comparison studies of Ru/C, Ni/C, Pd/C and Rh/C catalysts were done. For these catalysts, Ru/C catalyst showed the highest catalytic activity, followed by Ni/C catalyst, while the catalyst Pd/C, mostly used in hydrogenation processes, showed the worst activity. Different resources of carbon supported ruthenium catalysts were investigated, and found that the carbon from coconut shell was found to be the best support for the Ru/C catalyst.The catalyst prepared under the best conditions obtained the glucose conversion of 99%, and the greater than 97% selectivity to sorbitol, when the hydrogenation reaction was performed for 2 hrs reaction under 3 MPa, 120. Metal ruthenium can be uniformly dispersed on the surface of carbon, and no crystal was detected which approved via XRD results.Second, the kinetics of the reaction has been studied. The experimental results indicated that the reaction between the dissociated absorption hydrogen and glucose molecular on the surface of Ru/C catalyst is the reaction-rate-determining step in the-n-glucose hydrogenation for sorbitol. The kinetic equation can be expressed as follows:...