Study On Structural Catalysts Prepared By 3D Printing And Performance For Dry Reforming Of Methane

Methane dry reforming（DRM,CH₄+CO₂→2CO+2H₂）not only solves the problem of efficient and clean use of methane（CH₄）,but also consumes carbon dioxide（CO₂）,which is conducive to the mitigation of Greenhouse Effect,in line with the"carbon peaking and carbon neutrality goals"goal put forward by China,so DRM reaction has attracted much attention.In terms of catalysts,the stability of nickel-based catalysts with high activity and low cost is not ideal due to carbon deposition and Ni particle sintering,and most of the catalysts studied are powder or granular,in which the pressure drop is larger,coupled with the accumulation of carbon deposition will further increase the pressure drop and even block the reactor.To address issues associated with particulate or powder nickel-based catalysts in the DRM reaction,three types of catalyst carriers with different topological structures were manufactured using Stereolithography Appearance（SLA）3D printing technology,namely through-hole honeycomb,corrugated channel square-hole honeycomb,and pyramid-shaped diagonal framework.Three different structures of Ni/NiAl₂O₄（Ni-Al spinel）/Al₂O₃ and Ni/Al₂O₃ catalysts were obtained by loading nickel sources onto these carriers.The study investigated the effects of preparation processes on the morphology and mechanical strength of the catalyst carriers,the loading amount of active components,and the composition of the catalysts.The influence of different geometric configurations of the catalyst carriers on catalytic performance was explored,and the impact of the metal-carrier bonding strength on the stability of the catalysts was studied in depth.The specific research content and results include:（1）The study utilized SLA 3D printing technology to prepare three differentα-Al₂O₃ support structures,namely circular through-hole honeycomb,square corrugated channel honeycomb,and pyramid oblique frame topology.The pressure drop was compared with the powder catalyst,and the influence of the heat treatment procedure on the carrier morphology and mechanical strength were investigated.The results indicated that the macroscopic morphology of the support structures remained intact and without cracks or defects after heat treatment at 1400℃.The pressure drop was less than 1 Pa,which was significantly lower than the 1770 Pa observed in the same qualityα-Al₂O₃ powder.Additionally,the support structures exhibited good mechanical strength,as there was no obvious deformation or cracks after withstanding a pressure of 500 N.The pyramid oblique frame topology support achieved lightweight,high void fraction,and a large macroscopic surface area.Furthermore,Ni（NO₃ ）₂·6H₂O was used as a nickel source and impregnated onto the pyramid oblique frame topologyα-Al₂O₃ support.The study investigated the effect of calcination temperature on the composition of the catalyst.The results showed that when the calcination temperature was 650℃,the composition was Ni O/Al₂O₃ ,and Ni/Al₂O₃ structure catalyst was obtained after reduction.When the calcination temperature was 1400℃,the composition was NiAl₂O₄/Al₂O₃ ,and Ni/NiAl₂O₄/Al₂O₃ structure catalyst was obtained after reduction.In the DRM activity test at 750-950℃and 6600 m L·h^-1·g_cat^-1,the Ni/NiAl₂O₄/Al₂O₃ catalyst loaded on the pyramid oblique frame topology support achieved the highest CH₄conversion rate（950℃,97.5%）with the minimum amount of active component.This was due to its intricate fluid path,good radial mixing effect,and large macroscopic surface area.Compared with the powder catalyst,the CH₄conversion rate of the powder catalyst is similar to that of the powder catalyst,and the stability is better than that of the powder catalyst.（2）Investigated the influence of metal-support interaction on catalyst stability.In the Ni/NiAl₂O₄/Al₂O₃ structured catalyst,the active component was the strongly bound state Ni,while in the Ni/Al₂O₃ structured catalyst,the active component was the weakly bound state free Ni.The strongly bound state Ni effectively prevented Ni particles from sintering and promoted the reaction of carbon deposition and CO₂,which improved the anti-carbon deposition performance of the Ni/NiAl₂O₄/Al₂O₃ catalyst.After 750 h of reaction at 850℃and 6600 m L·h^-1·g_cat^-1,the carbon deposition amount of the Ni/NiAl₂O₄/Al₂O₃ catalyst was 21.82%,less than half of that of the Ni/Al₂O₃ catalyst.The conversion rate of CH₄in the Ni/Al₂O₃ catalyst decreased by 10%,while that in the Ni/NiAl₂O₄/Al₂O₃ catalyst only decreased by 3%.In the activity test,the conversion rates of CH₄and CO₂in Ni/NiAl₂O₄/Al₂O₃ were 97.5%and 99.1%,respectively,higher than those in Ni/Al₂O₃ of 94.0%and 95.3%.The above exploration and results show that the structural catalyst can improve the catalytic stability while solving the pressure drop of the powder catalyst,the 3D printing catalyst not only reduces the quality,reduces the material cost,but also improves the catalytic activity,proves the feasibility and advantages of 3D printing technology to the structural catalyst;Ni/NiAl₂O₄/Al₂O₃ catalyst compared with Ni/Al₂O₃ catalyst enhances the metal-carrier combination,thus improving the anti-sintering and carbon deposition capacity,and further enhancing the catalytic stability.Combining Ni/NiAl₂O₄/Al₂O₃ with the structural catalyst can improve the catalyst stability,reduce the pressure drop,and provide a new idea for the industrialization process of methane dry reforming.