Studies On Noble Metal-based Catalysts For Glycerol Hydrogenolysis To Propanediols

Biodiesel is a new kind of biomass-based energy and it could replacefossil-based energy. During the biodiesel production with the transesterificationreaction of vegetable oils or animal fats and methanol, glycerol is produced as aby-product. Converting this superfluous glycerol into high value addedpropanediols will decrease the manufacturing cost of biodiesel production. Theobjectives of this dissertation are to investigate the effect of acid additives onthe catalytic performance of Ru catalysts and the promoting effect of Re on theperformance of Pd catalysts in glycerol hydrogenolysis.From references, the acid additives could promote the glycerol dehydrationstep in glycerol hydrogenolysis and further increase the activity of the catalysts.In this dissertation, HZSM-5with different SiO2/Al2O3ratios were added into Rucatalyzed glycerol hydrogenolysis and the relationship between catalyticactivity, product distribution, especially the formation of CH4, and the acidproperties of the catalysts was investigated. The strong acid sites of HZSM-5could intensify the C-C bond cleavage. Al modified HZSM-5could change theacid property of HZSM-5, and this would decrease the C-C bond cleavagedegree and CH4formation.In glycerol hydrogenolysis, Ru had a relatively high activity, comparedwith other noble metal catalysts. However, Ru also showed activity for C-Cbond cleavage, which led to higher selectivity to CH4. In this dissertation, Pdwas also used as active component in glycerol hydrogenolysis. Re was addedinto Pd catalysts and the prepared bi-component Pd-Re/SBA-15catalyst hadrelatively high activities and selectivity to propanediols. XRD, TEM, H2-TPR,NH3-TPD, XPS and EXAFS were used to characterize the physical and chemicalproperties of Pd-Re catalysts. With the analysis, it was found that Pd and Re hadinteraction. The addition of Re could promote the particles of Pdhomogeneously dispersing along SBA-15channels. The existence of Pd madeRe maintain at higher chemical valence, and the electron might transfer from Pdto Re. Furthermore, the addition of Re could increase the acid property of Pd-Re catalysts.With mechanical mixing of mono-component Pd/SBA-15and Re/SBA-15,the catalyst (denoted as Pd+Re) was prepared and used in this reaction. It wasfound that the mechanical mixing Pd+Re catalyst had lower activity comparedwith co-impregnated Pd-Re catalyst, but higher than mono-component Pd or Recatalyst. From XRD and H2-TPR results, Pd and Re almost had no interaction.From these results, it was inferred that Pd-Re interaction was the main reason ofincreasing Pd-Re activity in glycerol hydrogenolysis. The possible reactionmechanism of Pd-Re in glycerol hydrogenolysis was also discussed.Different precursors of Pd and Re were used to prepare Pd-Rebi-component catalysts. The activities, physical and chemical properties of thecatalysts were investigated. It was found that the existence of Cl-could decreaseparticle sizes and change the reduction properties of the catalysts. These mightbe the reasons of high activity of Pd-Re catalysts with Cl-addition.