| The development of green renewable energy is considered to be the main direction to solve the shortage of fossil resources.The use of biomass resources to prepare chemicals or fuels has become an important way.Among them,cellulose has attracted widespread attention due to its large output and wide distribution.The use of catalysts to catalyze conversion is an important method to achieve efficient application of cellulose.However,there are some disadvantages in the methods of effective cellulose degradation.Therefore,looking for a catalyst with high efficiency,mild reaction conditions,green,low cost,and recyclable catalyst will greatly promote the efficient use of cellulose and the development of renewable energy.Metal organic frameworks(MOFs)are emerging composite materials in recent years.They have become a research hotspot in the field of catalysis due to their large specific surface area,adjustable structure,and abundant unsaturated metal sites.However,MOFs are difficult to disperse and difficult to recycle,which limits their practical use.Based on the synthesis of a large number of relevant literatures,this paper synthesized a series of MOFs@3-dimensional graphene(MOFs@3D-rGO)composite catalyst,and it is used to efficiently catalyze the degradation of straw cellulose to small molecule acids.The main research contents are as follows:1.MIL-101(Cr)was grown in situ in a 3D-rGO matrix using a one-pot method,The MIL-101(Cr)@3 D-rGO(1:1)and MIL-101(Cr)@3D-rGO(1:2)composite catalysts were synthesized by controlling the ratio of MIL-101(Cr)to 3D-rGO.3D-rGO support ensures the dispersibility and acidic site density of MIL-101(Cr).MIL-101(Cr)@3D-rGO composite catalytic material has excellent catalytic activity,stability,and recyclability,and can effectively convert straw cellulose into formic acid(FA),acetic acid(AA),and oxalic acid(OA).By using MIL-101(Cr)@3D-rGO(1:1)as a catalyst and performing a hydrothermal reaction under mild conditions at 200?in an alkaline aqueous solution for 1 h,a maximum FA conversion rate of 95.36%can be obtained.MIL-101(Cr)@3D-rGO composite catalytic material is easy to recycle and the catalytic performance does not decrease significantly after 5 times of recycling.In addition,the addition of 3D-rGO reduces the leakage of Cr,and the leakage of Cr of the composite catalyst is lower than the national standard.2.In order to eliminate as much as possible the potential pollution to the environment during the use of the catalyst,MIL-101(Fe)with Fe metal as the center of the same structure was selected as the catalyst.However,the lack of Fe acid sites caused the defect of low cellulose conversion efficiency.To solve this problem,three different MOFs materials were used to construct the catalytic active center to modify MIL-101(Fe).MIL-101(Fe)-NH2@3D-rGO,Pt@MIL-101(Fe)@3D-rGO and MIL-101(Fe)@3D-rGO-SO3H composite catalytic materials were developed and used in catalytic conversion of straw cellulose.The results show that the catalytic effect of MIL-101(Fe)-NH2@3D-rGO is only slightly improved compared to MIL-101(Fe)@3D-rGO,and the maximum FA conversion rate at 200? for 1 h It is 63.27%;Pt@MIL-101(Fe)@3D-rGO has a very good catalytic effect on straw cellulose,the maximum FA conversion rate can reach 83.55%under the same catalytic conditions at 200? for 1 h,and it can obtain a very high formic acid conversion rate of 55.85%at a low temperature of 50 ?,but the expensive price of Pt is a factor limiting the widespread use of composite materials;Under the same conditions,MIL-101(Fe)@3D-rGO-SO3H can obtain an ultra-high FA conversion rate of 98.26%,with low cost,environmental protection,and is an ideal catalyst for the degradation of cellulose into small molecule acids. |
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