Preparation Of Nickel Based Catalyst For Methane Steam Reforming By Dielectric Barrier Discharge Plasma

The consumption of fossil fuels and the pollutants exhausted from theircombustion have caused severe energy and environmental problems. While hydrogen,a clean energy, is considered to be a promising alternatives to fossil fuels. The mainprocess in the hydrogen production industry is the steam reforming of natural gas.Nickel-based catalyst, which is commonly used in this process, can easily bedeactivated by coking during the reaction. To prevent coking, water to methane ratioof the feed gas has to be increased to much larger than the stoichiometric ratio of thereaction. The generation and recycle of the excess steam spend tremendous amountsof energy. Thus, it is significant to improve the coke resistance of the catalyst to lowerthe steam to methane ratio and reduce the cost of hydrogen production.In this paper, the dielectric barrier discharge plasma has been used to decomposenickel nitrate precursor during the preparation of Ni/SiO₂-DBD catalyst. The preparedcatalyst is used in methane steam reforming reaction. Ni/SiO₂-DBD catalyst showedhigh selectivity of carbon monoxide and low H₂/CO ratio. Analysis showed that theNi/SiO₂-DBD catalyst has a smaller Ni particle size and a lower intrinsic reaction rate,leading to a lower carbon deposition rate. While a high Ni dispersion and stronginteraction between Ni and SiO₂provide a high carbon gasification rate. A goodbalance between carbon formation and carbon gasification is then achieved. Thecarbon deposition is effectively inhibited at low steam to carbon ratio and theresistance to coking is improved.In order to study the effects of the dielectric barrier discharge plasma treatment,two control samples, Ni/SiO₂-C2and Ni/SiO₂-DBD2, are added and methanedecomposition reaction is taken as a ruler of the coking resistance. It was found thatthe rapid decomposition of nickel nitrate leads to small Ni particle sizes, and anenhanced performance of coking resistance. The redox sample with a released surfaceenergy and an increased ratio of Ni （111） surface shows better coking resistance. Sothe surface morphology of Ni/SiO₂-DBD plays an important role in coking resistance.It can be inferred that the instantaneous release of energy in DBD process can rapidlydecompose the nickel nitrate and form small particles. At the same time, electronics,charged atoms, electric and magnetic field, or other effects in the discharge can form the special surface morphology of nickel particles. Small nickel particle size andspecial surface structure are main reasons for Ni/SiO₂-DBD sample to perform goodcoking resistance.