Co-N Co-doped Carbon Catalysts: Preparation And Application On Catalytic Hydrogenation Of Levulinic Acid

γ-Valerolactone（GVL）is an important biomass platform compound,which is favored by researchers for its high stability and unique physicochemical properties.It is generally synthesized by hydrogenation of levulinic acid（LA）.Although noble metal catalysts（such as Ru,Pt,etc.）can completely convert LA to GVL under mild conditions,their expensive price and low reserves are not conducive to industrial application.Non-precious metal catalysts（Cu,Co,Ni,etc.）have attracted the attention of researchers because of their cheap,easy availability and high reserves.In addition,the carrier is also very important to the activity and stability of the catalyst.Among many carriers,nitrogen-doped porous carbon materials have become one of the most commonly used carriers in the field of catalysis due to their unique chemical structure,high catalytic activity and stability.Combined with the previous research work of the research group on Co-N co-doped carbon catalysts,In this paper,Co-N co-doped porous carbon materials were synthesized by in-situ method with ZIF-67 as sacrificial template,one-step hydrothermal carbonization with bamboo shoot shell as carbon source,urea as nitrogen source,cobalt nitrate as metal source and using glucose as carbon source,hexamethylenetetramine as nitrogen source,and cobalt nitrate as metal active component by one-pot method and used for catalytic levulinic acid hydrogenation test.The main contents are summarized as follows:First,a Co-N co-doped carbon catalyst（Co@NCZ-T,T stands for the carbonization temperature）was prepared by direct carbonization at different temperatures using ZIF-67 as a precursor,and it was used for LA hydrogenation to GVL.The results show that,compared with similar catalysts,Co@NCZ-800 exhibits excellent catalytic performance,and LA can be completely converted into GVL under the conditions of 180℃,1.8 MPa hydrogen pressure,and 3 h.After five cycles,the yield of GVL can still remain above 98%,showing excellent catalytic activity and stability;Secondly,a Co-N co-doped carbon catalyst（Co@NCB-T,T stands for carbonization temperature）was prepared by a hydrothermal carbonization method using biomass waste bamboo shoot shells as the carbon source,urea as the nitrogen source,and Co（NO₃）₂·6H₂O as the metal active component.The hydrogenation reaction of levulinic acid shows that Co@NCB-700 has the best catalytic activity,and the GVL yield reaches more than 99%under the reaction conditions of 190℃,1.9MPa and 2 h hydrogen pressure.After five cycles,the GVL yield can still be maintained above 80%,the catalyst has excellent catalytic activity and stability;Third,using glucose as the carbon source,hexamethylenetetramine（HMT）as the nitrogen source,and Co（NO₃）₂ 6H₂O as the metal active component,on the basis of hydrothermal carbonization to prepare hydrothermal carbon,a high-temperature carbonization method was adopted.Co-N co-doped carbon catalysts（Co@NCH-T,T represent different carbonization temperatures）were prepared and used in LA hydrogenation.The results show that Co@NCH-700 has the best catalytic activity and stability.Under the reaction conditions of 180℃,1.8 MPa hydrogen pressure and 3 h,the yield of GVL was 100%,especially after five cycles of reaction,the catalytic stability did not change significantly,showing excellent catalytic stability.