Study On Photocatalysis Of Converting Biomass Platform Molecular Levulinic Acid Into γ-valerolactone By Hydrogenating And Cyclizing

With the development of the human society, the traditional energy sources: coal, petroleum and nature gas are constantly consumed which bring huge damage to our environment. So, it is urgent to exploit and develop the new sources. Biomass energy-the only renewable organic carbon source-as one of new sources has drawn great attention due to its advantages, such as renewable, low pollution, large reserves. At the same time, the biomass could be converted into fuel, chemicals and carbon-based materials instead of petroleum.As the green and inexhaustible energy, the solar energy is exploited by people to develop a new technology called photocatalytic technology. It is very promising because of its outstanding characteristics such as green, environmental protection, mild reaction condition. Therefore, the conversion of biomass is very ideal and environment protection with photocatalysis technology which is using the solar energy as the power.Levulinic acid as one of the biomass platform molecules almost derives from cellulose hydrolysis and y-valerolactone as one of its important derivation chemicals has a widely application in flavor, food additive and so on. At present the conversion of levulinic acid into y-valerolactone almost using the thermal catalytic methods and the photocatalytic methods are seldom reported.Based on our research foundation, firstly we synthesize some kinds of TiO2 having different crystal structures and evaluate their performances by using photocatalytic technology to convert levulinic acid into y-valerolactone. In the next step, we add the noble metal co-catalyst into the reaction and find its better performance. Then we investigate the impact of all the factors in the reaction in details. Main contents are as follows:1. First, we use TiO2(P25) as the catalyst and isopropanol as the hydrogen source to prove that levulinic acid could be hydrogenated and cyclized to convert into the new chemical called y-valerolactone with high selectivity. Then, we analyze the production by GC and GC-MS;2. We prepare four different crystalline structures of TiO2 and select four noble metal co-catalysts which are used to hydrogenate and cyclize the levulinic acid into y-valerolactone. In the estimation, we can obtain the highest selectivity(70.34%) by using P25-600 loaded Pt;3. On the basis of P25(600)-Pt having the best performance, we also investigate the impacts of content of co-catalyst, reaction time and the content of water to the reaction in details;4. According to the experiment data, we give out the reasonable mechanism. The electron and hole separate from each other after the TiO2 photocatalyst actived by light illuminating. Then the hydrogen ions (mainly from the reaction of isopropanol and hole) obtain the electron to form the actived hydrogen which hydrogenate levulinic acid or isopropyl levulinate (generated in esterification reaction) into y-hydroxy valeric acid or y-hydroxy isopropyl valerate which could be converted into y-valerolactone by dehydration and cyclization;5. Based on above, we also investigate different solvents’ability of providing hydrogen radical and have a comparison with isopropanol. We could conclude that the ability of isopropanol is better than ethanol and butanol. The reasonable interpretation is that isopropanol radical generated after providing hydrogen is the most stablest among the three.