Study On Vermiculite-based Molecular Sieves And Their Derived Hydrotalcites In Dry Reforming Of Methane

Nowadays,countries around the world are vigorously advocating carbon peaking and carbon neutrality,and it has become very meaningful to produce clean energy while eliminating greenhouse gases.Dry reforming of methane（DRM）is a method to convert these two greenhouse gases into syngas,which is of great significance for solving the greenhouse effect and alleviating the energy crisis and promoting my country’s carbon peaking and carbon neutrality.However,dry reforming of methane catalysts are easily deactivated and sintered in high temperature reactions,and carbon deposition occurs,which limits their application in practical production.Therefore,it is very important to develop a high-performance catalyst.1.One-step preparation of vermiculite-based multilayer mesoporous Ni-based catalyst for dry reforming of methane.The multi-layer mesoporous catalyst Ni-VSiO₂ was prepared by precipitation method to load the active components in one step,and the mesoporous etching was enlarged,and the influence of additives Ca and Ce on its catalytic performance was studied,and Ni-5x-VSiO₂ was prepared.（x=Ce,Ca）catalyst and used in the dry reforming of methane reaction.The results show that the Ni-Ce-VSiO₂ has the best conversion rate stability,and the CH₄ conversion rate is maintained at about 78%and the CO₂ conversion rate is maintained at about 88%within 8 h.The reason may be that the pore size of the vermiculite-based molecular sieve becomes larger again due to the etching modification of the precipitant,and its layered mesoporous structure allows a part of the Ni nanoparticles to enter the pores of the catalyst support,thereby inhibiting the aggregation of the active component Ni and improving the efficiency of the catalyst.The sintering resistance is improved;CeO₂ and CaO are added to the catalyst Ni-VSiO₂ as co-agents respectively,and the addition of CeO₂ co-agent can strengthen the interaction between the active component Ni and the co-agent Ce,and the lattice oxygen-oxygen vacancies of CeO₂ In the reaction process,it can play a role in eliminating carbon deposits,and Ce element also has strong adsorption and dissociation effects.2.Research on vermiculite-based hydrotalcite Ni-based catalyst for methane dry reforming.The waste liquid after acid treatment of vermiculite contains a large amount of Mg and Al elements,as well as a small amount of Fe,Ca and other elements.The waste liquid is used to prepare a mesoporous multilayer magnesium-aluminum hydrotalcite precursor containing natural additives,and the precipitation is used.The catalyst Ni-VMT-LDO was prepared by loading the active components by the method,and it was used in the methane dry reforming reaction.It was found that the CH₄ conversion rate of the vermiculite-based hydrotalcite catalyst Ni-VMT-LDO was 77%and the CO₂ conversion rate was 87%.This is because the presence of the mesoporous structure of the carrier makes the catalyst better disperse the active components on the catalyst and further improves the sintering resistance.Has better sintering resistance than commercial magnesia-aluminum hydrotalcites.In addition,there are natural additives Fe and Ca in vermiculite-based hydrotalcite,which can be directly used as catalysts in the methane dry reforming reaction.Ca can improve the dispersion of active components,and Fe can reduce the particle size of active components.Further improve the anti-sintering and carbon deposition resistance of the catalyst.3.Study on Ni X-VMT-LDO（X=Co,Cu,Mn）bimetallic catalyst in methane dry reforming.Bimetallic catalysts were prepared by doping Co,Cu,and Mn transition metals in Ni-VMT-LDO catalysts.The research shows that the NiCo-VMT-LDO catalyst has the best catalytic activity and stability,the CH₄ conversion rate is 84%,the CO₂ conversion rate is 87%,and the stability is good.This is because,compared with single metal catalysts,bimetallic catalyst supports and active metals have stronger interaction force,which enhances the interaction force between support and metal,thereby inhibiting nickel sintering agglomeration and losing active sites,leading to catalyst deactivation.The Co particles in the catalyst contribute to the good dispersion of the Ni particles and further inhibit the agglomeration of the Ni particles,so that the anti-sintering performance of the NiCo-VMT-LDO catalyst is significantly improved.