Analysis of Carbon Dioxide Reforming of Methane via Thermodynamic Equilibrium Approach

Abstract

Pembentukan air melalui reverse watergas shift serta tindakbalas–tindakbalas sampingan lain dalam proses pembentukan semula metana menggunakan karbon dioksida (CORM) menjadi salah satu masalah utama yang menghadkan penghasilan maksima hidrogen and singas (campuran H₂–CO). Dengan ini, kajian ke atas keseimbangan termodinamik CORM seharusnya mengambil kira kesan pembentukan air dalam rangkaian tindakbalas CORM. Disebabkan oleh rangkaian tindakbalas CORM yang kompleks, kaedah Lagrange’s undetermined multiplier digunakan dalam kajian ini dan keberkesanannya telah dibuktikan. Prestasi equilibria CORM dipertingkatkan daripada 600K kepada lOOOK tetapi kesan suhu menjadi tidak bermakna pada suhu melebihi 1OOOK. Nisbah CO/H₂ menghampiri satu boleh dicapai dengan nisbah suapan CO2/CH₄ yang rendah tetapi nisbah suapan CO2/CH₄ yang sama diperlukan untuk memperoleh penghasilan H₂ dan CO yang tinggi pada suhu lOOOK ke atas. Keputusan ini disokong oleh keputusan eksperimen seperti yang dilaporkan dalam literatur. Kata kunci: Karbon dioksida, metana, singas, pembentukan air, Lagrange’s undetermined multiplier Water formation through reverse water gas shift and several other side reactions in carbon dioxide reforming of methane (CORM) have became one of the major process hurdles that limits maximum hydrogen and syngas (H₂–CO mixture) yields. Therefore, it is vital that the study on CORM thermodynamic equilibrium takes into consideration the formation of water in the CORM reaction network. Due to the complexity of the reaction network, Lagrange’s undetermined multiplier was employed in the present work and its applicability had been proven throughout this study. The equilibrium compositions improved drastically from 600–1OOOK, but the temperature effect becomes insignificant above 1OOOK. Furthermore, CO/H₂ ratio close to unity can be achieved at lower CO2/CH₄ feed ratios but equal CO2/CH₄ feed ratios is required to obtain higher H₂ and CO yields at temperature lOOOK and above. These findings are in strong agreement with laboratory experimental results reported in literature. Key words: Carbon dioxide, methane, syngas, water formation, Lagrange’s undetermined multiplier