Study On Catalytic Conversion Of Bio-derived Glucose Into Lactic Acid

With the depletion of fossil resources and the increasing demand for energy in human society,it is urgent to find a new resource to replace fossil resources.As a renewable environment-friendly resource,biomass resources are abundant in nature and are the best alternative to fossil resources.As an important intermediate chemical,lactic acid has great potential to replace petroleum-based chemicals.Many liquid fuels and chemical products such as acrylic acid,propionic acid and 2,3-pentanedione can be synthesized by lactic acid.It makes great sense to discuss the conversion of biomass resources to lactic acid.In order to achieve high-valued utilization of biomass resources,this paper aims to develop efficient environmental catalysts for the conversion of bio-derived glucose to lactic acid.Firstly,several solid acid oxides?Ta₂O₅,Nb₂O₅,Al₂O₃ and ZrO₂?were selected to apply to the conversion of glucose to lactic acid.The catalytic performances of these catalysts were compared.The effects of different reaction conditions on the conversion of glucose to lactic acid catalyzed by Ta₂O₅ and the recycling performance of the catalysts were investigated.The structure and properties of Ta₂O₅ were characterized by XRD and SEM.The result shows that the best catalytic performance of the four metal oxide catalysts is Ta₂O₅.The glucose conversion of 92.3%and lactic acid yield of 71.9%could be obtained under the conditions of reaction temperature of 190?,glucose concentration of 6 mg/mL,reaction time of 4 h and catalyst dosage of 0.06 g.After the catalyst is recycled by five times,impurities adhere to the surface of the catalyst and the performance of the catalyst decreases.Secondly,the ZrO₂/Ta₂O₅ catalyst which was prepared by coprecipitation method will be used to the conversion of glucose to lactic acid.The glucose conversion of 96.4%and lactic acid yield of 73.3%could be obtained under the conditions of reaction temperature of 180?,glucose concentration of 4 mg/mL,reaction time of 4 h,and catalyst dosage of 0.1 g.ZrO₂/Ta₂O₅ showed excellent catalytic performance in the conversion of glucose to lactic acid.When the calcination temperature is over 700?,the acid amounts became smaller with the calcination temperature rising.XRD and SEM showed that impurities adhered to the surface of the catalyst after 5 times recycling of the catalyst and the catalytic performance decreased.Finally,in order to improve the selectivity of the catalyst,an Er₂O₃/Ta₂O₅ catalyst was prepared to the conversion of glucose to lactic acid.Compared with ZrO₂/Ta₂O₅ catalyst,the yield of lactic acid under the Er₂O₃/Ta₂O₅ was higher,but the conversion of glucose was decreased.The glucose conversion of 87.5%and lactic acid yield of 79.3%could be obtained under the conditions of reaction temperature of 170?,glucose concentration of 4 mg/mL,reaction time of 4 h,and catalyst dosage of 0.1 g.SEM showed that the surface of the catalyst agglomerated after five times recycling and the performance of the catalyst decreased significantly.