Conversion Of Glycerol Under The Catalytic Action Of Solid Bifunctional Catalysts

Propanediols (1,2-propanediol and1,3-propanediol) are valuable final products and also very important chemical intermediates. They are widely used in food, medicine and chemical industry. Recently, large amounts of surplus glycerol were produced in the process of biodiesel production. How to find out new outlets in order to make good use of this surplus glycerol and thereby promoting the development of whole biodiesel production is a serious problem. Hydrogenolysis of glycerol to1,2-PDO is considered as an effective method to make good use of surplus glycerol.Different methods to prepare solid base supported metal as a bifunctional catalyst for hydrogenolysis of glycerol to1,2-PDO were tried in this dissertation. The alkalinity of the support, the structure of the catalyst, metal species and their apparent configuration were characterized. The relationship between the activity and the structure of the catalyst were discussed. The main achievements gained as follows:Bi-functional catalysts Pt/HZSM5、Pt/HBeta、Pt/Al2O3、Pt/MgO and Pt/HLT(Mg:Al=3:1) were prepared via impregnation. The catalytic performances of these catalysts for hydrogenolysis of glycerol were examined. It was found that Pt/HLT performed the best activity for hydrogenolysis of glycerol among all the catalysts. Under the optimized conditions (220℃,3.0MPaH2,20h,0.5g catalyst,20wt.%glycerol solution,20.0g), the conversion of glycerol reached92.1%, the selectivity of1,2-PDO was93.0%. Characterization results indicated that the alkalinity of the catalyst and the particle size of Pt play a crucial role for this reaction; the alkalinity of support promoted the activity, and smaller Pt particle is more active on basic support than it on acidic support.Bi-functional Cu/MgO catalysts with different amounts of Cu were prepared by co-precipitation and impregnation. These results indicate that Cu/MgO prepared by co-precipitation shows better activity than that of Cu/MgO prepared by impregnation; Cu/MgO with copper loading amount15wt.%prepared by co-precipitation showed the best activity among all tesed catalysts, the conversion of glycerol reaches72.0%and the selectivity of1,2-PDO is97.6%; small amounts of NaOH further enhanced the activity of the catalyst. Characterization results indicated that the activity of the the catalyst mainly depends on the particle size of Cu and MgO, smaller particle sizes of Cu and MgO particles are, the more activity of the catalysts are.Hydrotalcite precursor as like Cu-Mg-Al with different copper loading amount was prepared by impregnation, ion-exchange and co-precipitation. The prepared precursors were converted into solid base supported copper bi-functional catalyst, and their activity for hydrogenolysis of glycerol was examined. The results indicate that Cu0.4Mg5.6Al2(OH)16CO3prepared by co-precipitation was changed into highly dispersed copper particles supported on solid base (Cu0.4/Mg5.6Al2O9). This highly dispersed Cu/solid-base catalyst was extremely active for glycerol hydrogenolysis. Characterization results indicated that prepared Cu0.4Mg5.6Al2(OH)]6CO3has the characteristic Mg-Al-hydrotalcite structure, after calcination, the copper particles dispersed highly in the lamellar structure of hydrotalcite. Due to the highly dispersed copper particles and alkalinity of hydrotalcite, the synthesized bi-functional catalyst (Cu0.4/Mg5.6Al2O9) shows extremely activity for glycerol hydrogenolysis to1,2-PDO.Super solid-base supported copper catalysts Cu/MgO/CaO and Cu/MgO/SrO were prepared via impregnation-combustion method, and the activity was examined. Characterization results indicated that CaO and SrO particles dispersed highly on precursor catalyst Cu/MgO prepared by impregnation-combustion method, and the high dispersion of copper remained. CO2-TPD and reaction results indicate that the alkalinity of the catalyst was enhanced obviously and the activity of catalyst increased. The detected glycerol conversion is88.0%with a93.0%selectivity of1,2-PDO. It was concluded that alkalinity strength of catalyst increased its activity.Cu/HPW catalyst was prepared and used for glycerol hydrogenolysis to1,2-PDO (ethanol as the solvent). But it was found that mainly etherification products of glycerol and ethanol were detected. Several solid/aqeous acids (H-ZSM5, H-Beta, HPW, HPW/SiO2, FeCl3, AlCl3and H2SO4) and solid bases (rare earth metal oxides, MgO) were tested for the etherification reaction. It was found that solid bases are inactive for this reaction, whereas HPW and HPW/SiO2exhibited the best activity for this reaction among all the tested catalysts, a97.1%glycerol conversion was obtained. The rection conditions were investigated such as reaction temperature, reation time, the mol ratio of ethanol to glycerol, and catalyst used amount.