Develop Nickel-Based Catalyst For Reversed Water-Gas Shift Reaction From Lignin-Derived Activated Carbon

The emission of carbon dioxide is a major issue in the 21st century which is related to the living environment of human beings.In today's world,the methods for reducing carbon dioxide in the atmosphere are mainly divided into three main methods:CO₂ capture,storage and utilization.At present,many researchers are devoted themselves towards carbon dioxide capture and storage,but they also encounter bottleneck and find it difficult to solve technical problems,such as high costs,storage effects,public acceptance,long-term instability,etc.This situation has forced scientists in related research to find other effective methods and techniques to reduce carbon dioxide emission.A useful approach is to convert carbon dioxide into value-added chemicals or fuel that is not only reduces emitted carbon dioxide,but also provides new ideas for converting to energy-value products.Hydrogenation of carbon dioxide is an effective way to reduce global greenhouse gas emissions and is a potential approach to producing fuels and high value-added chemicals.The carbon dioxide hydrogenation reaction can produce different products by controlling the reaction conditions,the feed ratio and so on.In this dissertation,a series of experimental procedures are conducted to produce lignin-based activated carbon?AC?supported nickel-based catalyst and explore its carbon dioxide hydrogenation reaction to produce carbon monoxide?the performance of the reverse water gas reaction?.The lignin-based activated carbon supporting nickel-based catalyst was prepared by pyrolysis-impregnation method.The performance of the water gas reaction was investigated with different pressure conditions during pyrolysis and the catalysts prepared by different activators.The catalytic test conditions were tested at 750°C on time stream for 1500 min.The results showed that the catalyst Ni/AC_KV prepared by pyrolysis of potassium hydroxide as an additive exhibited excellent CO₂ conversion and a high CO selectivity.The catalysts were characterized by using XRD,SEM,TEM,XPS,CO₂-TPD,FTIR,Raman,ICP-MS,BET and H₂-TPR techniques.These results showed that under vacuum conditions,it is beneficial to prepare activated carbon with large specific surface area and developed micropore and mesopores.Potassium hydroxide?KOH?is more suitable for using as an activator than that of zinc chloride?ZnCl₂?for developing larger specific surface area,and developed micropore and mesopores.The dispersion of Ni particles is better under vacuum condition.The results of CO₂-TPD and NH₃-TPD test indicate that under vacuum conditions,the nickel-loaded catalyst prepared by the activated carbon prepared by KOH activation has high basicity to that of the catalyst prepared under normal pressure conditions,and KOH activation is prior to that activated by ZnCl₂.In addition,CO₂-TPD and NH₃-TPD characterization implied that the basic site is more than the acidic site,thus facilitating the adsorption and catalysis of the catalyst for CO₂.Therefore,it can be concluded that the catalyst prepared under vacuum has a significant improvement in physical properties and catalytic performance compared to the catalyst prepared under normal pressure,thereby promoting its catalytic effects on reversed water-gas shift reaction.