Preparation Of 3D Porous Fe-MoS₂/CMF Catalyst And Its Utilization In Microwave Catalytic Reforming Of Lignin

Lignin is the most abundant natural aromatic polymer in nature and is a renewable raw material with great potential for the preparation of biomass fuels and platform chemicals.Among the many lignin conversion technologies,microwave-assisted depolymerization has received much attention due to its fast heating without thermal inertia,low energy consumption and good selectivity of target products.In this paper,a 3D porous Fe-MoS2/CMF catalyst with good microwave absorption and catalytic properties was constructed for the microwave-catalyzed reforming of lignin vapor based on the unique heating mode and "non-thermal effect" of the microwave reaction,providing a new idea for the efficient preparation of phenols and aromatic hydrocarbons from lignin.In this paper,MoS2/CMF catalyst was prepared by hydrothermal method using 3D porous carbonized melamine foam as the skeleton,and the effect of different microwave parameters on the microwave absorption performance of the catalysts was investigated by multi-physical field simulation of the catalysts.On this basis,Fe-MoS2/CMF catalyst was prepared by Fe doping.The catalytic cracking effect of Fe-MoS2/CMF on the lignin β-O-4 model material was investigated,and the microwave-catalyzed reforming performance of lignin vapor under the action of the catalyst was studied.The conclusions are as follows:(1)MoS2/CMF catalyst with microwave absorption properties was prepared and a multi-physics field simulation model of MoS2/CMF was established.The results show that the microwave power significantly affects the electric field distribution in the cavity.In addition,the increase in microwave power and microwave radiation time,the decrease in nitrogen flow rate all promote the increase of catalyst surface temperature.Microwave-catalyzed reforming of lignin depolymerization vapor using MoS2/CMF was found to promote the generation of phenolic products with a high selectivity of 24.85 wt.%for phenol in the liquid product.(2)Fe-MoS2/CMF catalyst was prepared using a polyoxometalate(POM)as the molybdenum source,and the catalytic cracking of lignin β-O-4 model 2phenoxy-1-phenylethanol,guaiacylglycerol-β-guaiacyl ether and the G-type model polymer(GMP)were all carried out using Fe-MoS2/CMF catalysts.The results showed that Fe-MoS2/CMF converted the three model species up to 94.12%,98.71%and 86.88%,respectively,indicating that Fe-MoS2/CMF has a good catalytic cleavage ability for the β-O-4 ether bond of the lignin dimer model and the model polymer.Calculations of the reaction process using density functional theory simulations revealed that Fe doping not only increased the catalyst activity but also reduced the β-O-4 bond breaking energy barrier.(3)The microwave-catalyzed reforming effect of Fe-MoS2/CMF catalyst on lignin depolymerization vapor was investigated at 1000 W(2.45 GHz)microwave conditions.The results showed that the use of Fe-MoS2/CMF significantly reduce the molecular weight and content of oligomers in the lignin depolymerization liquid product and promoted the formation of phenolic and aromatic hydrocarbon compounds,especially showing high selectivity for phenol(30.01 wt.%)and styrene(16.34 wt.%).