Preparation Of LaAlO₃ Perovskite Supported Ni-based Catalysts And Its Study In Methane Dry Reforming

CH₄and CO₂are greenhouse gases that have a significant impact on global warming.The methane dry reforming reaction is an important reaction to eliminate these two greenhouse gases.However,the catalyst is prone to sintering and carbon deposition during the reaction process.Perovskite is very suitable for methane dry reforming due to its good thermal stability,structural tunable denaturation and redox ability.But perovskite has a small specific surface area.The hard template method is an effective method to expand the specific surface area.Ni-based LaAlO₃perovskite catalysts with large specific surface area were prepared using SBA-15 as a hard template.Through the activity and stability test of the catalyst,as well as a series of characterizations such as XRD,BET,TG,etc.,the conclusions are as follows:（1）LaAlO₃-H perovskite supports were prepared using SBA-15 as a hard template and LaAlO₃-C perovskite supports were prepared by sol-gel method.The catalysts were prepared by supporting the two supports with Ni active components respectively.The prepared catalyst was used for methane dry reforming.During the reaction,the activity of Ni/LaAlO₃-H catalyst（CH₄conversion rate of 71.8%and CO₂conversion rate of 81.7%）was better than that of Ni/LaAlO₃-C catalyst（CH₄conversion rate of69.9%and CO₂conversion rate of 79.7%）.This is because the LaAlO₃-H perovskite support has both larger specific surface area and more surface oxygen vacancies than the LaAlO₃-C perovskite support.The Ni-Ca O/LaAlO₃-H catalyst prepared by adding basic oxide Ca O（CH₄conversion rate is 75.6%,CO₂conversion rate is 85.5%）has better activity than Ni/LaAlO₃-H catalyst.This is because Ca O can improve the adsorption capacity of Ni/LaAlO₃-H catalyst for CO₂,thereby further accelerating the reaction conversion rate of CH₄and CO₂of Ni/LaAlO₃-H catalyst.（2）LaAl_1-xNi_xO₃（x=0.3,0.5,0.7）perovskite catalysts with large specific surface area were prepared using SBA-15 as a hard template,which were used in the methane dry reforming reaction.The research results show that when the doping ratio is 0.5,La Al_0.5Ni_0.5O₃has the best activity（CH₄conversion rate69.8%,CO₂conversion rate 81.6%）and stability.The reason is that the catalyst can obtain more Ni active sites than the La Al_0.7Ni_0.3O₃perovskite catalyst after reduction.And this catalyst obtained Ni active components with smaller particle size than La Al_0.3Ni_0.7O₃perovskite catalysts after reduction.（3）In the 5X/La Al_0.5Ni_0.5O₃（X=Fe,Co,Cu）supported perovskite catalyst,5 represents a transition metal with a mass fraction of 5 wt%.Three different perovskite alloy catalysts were obtained by pretreatment,and the three catalysts were used in the methane dry reforming reaction.The results show that the 5Co/La Al_0.5Ni_0.5O₃perovskite alloy catalyst has the most excellent activity（CH₄conversion rate is71.6%,CO₂conversion rate is 82.8%）and stability（after 25 h of reaction,the activity of CH₄and CO₂is almost no decline）.The reason is compared with the 5Fe/La Al_0.5Ni_0.5O₃and 5Cu/La Al_0.5Ni_0.5O₃perovskite alloy catalysts,Co does not passivate the Ni active sites,and Co can improve the carbon resistance of the catalyst by enhancing CO₂adsorption.