Design And Synthesis On Ni-based Catalyst,Study On Active Site For CO Methanation

With the rapid developement of the global economic level,people's consumption and demand for natural gas are getting higher and higher.From 2007 to 2017,China's natural is in a state of gas supply is lower than demand.Most of China's natural gas is distributed in the western region,combined with the energy structure is rich coal,poor oil and short for gas of China,natural gas is one of the ways to solve the energy shortage.Xinjiang has rich coal resources,therefore,the development of clean coal natural gas technology has great advantages and inevitability in Xinjiang.CO methanation is the key step for SNG technology,and how to improve the conversion efficiency of CO and the selectivity of methane is the key step to this technology.Therefore,the mian purpose to the research is to study and develop of catalyst for methanation.Vermiculite resources are very abundant in Xinjiang,the vermiculite in Xinjiang Yuli is the largest ore deposits vermiculite,and the total geological reserves in Xinjiang ranked second in the world.Vermiculite is two-dimensional layer-structured clay mineral,contains Mg,Al,Si and other metal ion,has excellent adsorption and ion exchange properties.It has excellent mechanical properties,strong abrasion resistance,expansion performance,sound insulation and heat insulation and excellent high temperature resistance,and it is also an excellent catalyst carrier material.At the same time,expanded vermiculite,vermiculite-based hydrotalcite and vermiculite-based SiO₂ can be prepared by vermiculite.These materials are good catalyst supports materials.In the light of the above situation,the following studies have been researched.First,ultralow-weight loading Ni-based catalyst prepared by plasma method in the application of carbon monoxide reaction.The expanded can be used as the catalyst support in methanation reaction.Combined with the characteristics of the single atom catalyst,the load is 0.5 wt.%of Ni.It is easily aggregateactive for active components because of the surface is too smooth.The catalyst prepared by the traditional heat treatment has a large NiO particle,and poor catalytic performance.The PIM-Ni/PVMT treated 40 minutes at 160 W by the discharging electrode.The as-obtained catalyst shows the perfect performance of mathanation at 450°C,which achieve the CO conversion and TOF reaching achieved a maximum of 93%and 0.8537 s^-1,better than the catalyst prepared by the traditional heat treatment.Second,nickel-based catalyst for methanation prepared by flash nano-precipitation?FNP?method.Based on the preparation of hydrotalcite and application in methanation,the hydrotalcite supports was successfully prepared by coprecipitation and flash nano-preciphation technology,and prepared the catalyst for CO methanation.Compared with the Ni/MgAl-LDO?CP?prepared by the conventional coprecipitation technology,the Ni/MgAl LDO?FNP?prepared by flash nano-preciphation technology has better catalytic performance.The Ni/MgAl-LDO?FNP?catalyst achieved a CO conversion of 97%,at a temperature of350°C,a gas hourly space velocity of 20000 mLg^-1h^-1 and a pressure of 1 atm.The flash nano-preciphation technique greatly shortens the preparation period of the catalyst,and prepared thinner nanoscale layer.Third,the preparation of nickel based catalysts by the ammonia evaporation method and active sites research.We prepared the nickel based catalyst for methanation by the ammonia vapour method based on the SiO₂ nanomesh carry nichel has excellent catalytic performance.The catalyst Ni/Si O₂ also exhibited good catalytic activity,CO conversion of 96.7%,CH₄ selectivity of 93.6%and TOF of 1.619×10^-33 s^-1 at 623 K with a gas hour space velocity of 25000 mLg^-1h^-1.Excellent thermal stability was shown after the reaction of 150 h at 623 K.In-situ vacuum transmission infrared spectrum proves that the effective active sites is located at the interface between the metal Ni and the SiO₂.