CO2　methanation　suffers　from　the　problem　of　temperature　runaway　phenomenon　due　to　its　exothermic　nature.　To　mitigate　this　issue,　optimizing　catalyst　structure　becomes　crucial.　This　work　established　numerical　models　to　investigate　the　CO2　methanation　reaction　and　heat/mass　transfer　process　in　the　reactor　with　porous　pellet　and　monolithic　catalysts.　Results　show　that　the　reactor　with　porous　pellets　has　the　lowest　carbon　conversion　per　unit　pressure　drop　due　to　its　large　total　pressure　drop.　In　contrast,　the　reactor　with　monolith　exhibits　a　much　larger　carbon　conversion　per　unit　pressure　drop　but　a　smaller　absolute　carbon　conversion.　Based　on　this,　an　improved　＇CHESS＇　monolith　structure　was　proposed　and　improved,　which　not　only　maintains　a　high　absolute　carbon　conversion　(62.6　%)　but　also　enhances　the　heat　transfer　process　in　CO2　methanation.　Moreover,　compared　with　the　reactor　with　porous　pellets,　the　maximum　temperature　in　the　improved　＇CHESS＇　monolith　was　decreased　by　around　11.09　%.　©　2023　Elsevier　Ltd