Study On The Reaction Of Glycerol Hydrogenolysis To Prepare 1,3-Propanediol

Biodiesel is a typical representative of green renewable energy and can be used as an ideal substitute for fossil fuels.However,a large amount of by-product glycerol is produced during the development of biodiesel.The accumulation of glycerol is bound to reduce the profitability of the biodiesel industry.Therefore,it is urgent to develop efficient catalysts to scientifically and green convert cheap glycerol into chemical products with high use value.In this paper,glycerol was used as a model compound to study the performance of glycerol selective catalysis of hydrolysis over Pt/WTi Zr catalyst.We discussed it in several parts:1.First,the effect of Pt loading on the performance of Pt/WTi Zr catalytic system for the selective hydrogenolysis of glycerol to 1,3-propanediol（1,3-PDO）was investigated.We selected Pt loadings as 1 wt%,2 wt%and 3 wt%.We found that with2 wt%Pt loading,the catalyst showed the highest glycerol conversion and the best1,3-propanediol selectivity,which were 32%and 47%respectively.In subsequent experiments,we controlled the loading of Pt to 2 wt%.We prepared a series of WO₃-Ti O₂/Zr O₂-Al₂O₃supports with mass ratio of Zr O₂and Al₂O₃by sol-gel method.And we obtained Pt/WTi Zr Al catalyst by impregnation method,to explore the effect of introducing appropriate amount of Al₂O₃on Pt/WTi Zr catalyst on the hydrogenolysis of glycerol.The reaction was carried out in a fixed bed.The catalyst dosage was 3.6 g.The H₂pressure and flow rate were 5 MPa and 30m L/min respectively.The reaction temperature was 140 ^oC,and the raw material was30%glycerol aqueous solution.Through experiments,we found that the introduction of an appropriate amount of Al₂O₃（the mass ratio of Zr O₂to Al₂O₃was 9:1）could inhibit the aggregation of the tetragonal Zr O₂carrier,improve the dispersion of Zr O₂,and then anchor the monoclinic WO₃and Pt nanoclusters on its surface cluster.The latter generates Bronsted acid centers in situ in H₂atmosphere,which is beneficial to promote the formation of the product 1,3-PDO.The glycerol conversion and 1,3-PDO selectivity were 38.6%and 49.1%respectively,and the catalyst could be operated stably for no less than 100 hours.2.By trying to introduce additives such as Re/Y/Nb/Mg/Li/Na/K into the Pt/WTi Zr Al catalyst of Zr-Al-9,we found that the promoters Li or Na can greatly improve the conversion of glycerol.And the yield of 1,3-PDO achieved a 2-fold increase.On this basis,by adjusting the Li₂O content,we found that when the Li₂O content in the Pt/Li WTi Zr Al catalyst was 1 wt%,the catalytic effect was the best,the glycerol conversion rate was 75%,and the 1,3-PDO selectivity was 43%.And the catalyst can be operated stably for no less than 170 hours.Finally,we adjusted the mass ratio of Zr O₂to Ti O₂and the mass ratio of Zr O₂to Al₂O₃with the Pt/Na WTi Zr Al catalyst as the optimization target.We found that when Zr-Ti-8.5 and Zr-Al-9,the catalyst has the best catalytic performance,the glycerol conversion rate is77%,the selectivity of 1,3-PDO is 42%,and the catalyst can be operated stably no less than 300 hours.