# Prospects and Technical Challenges in Hydrogen Production through Dry Reforming of Methane
## 5 Conclusions and Perspectives  
DRM has been extensively reported in the recent literature as a possible alternative pathway for sustainable H\({}_{2}\) production since it uses CH\({}_{4}\) and CO\({}_{2}\) (two main GHGs) as feedstock. However, this process still suffers from catalyst deactivation in the harsh reaction conditions, mainly due to coking and sintering of the active phase. Moreover, economic issues must also be taken into account, especially when H\({}_{2}\) production is considered, since this reaction also produces 1 mol of CO per mol of H\({}_{2}\) and side reactions (Equations (3)-(6)) may also occur, further decreasing the H\({}_{2}\)/CO ratio of the syngas produced. However, as presented in Section 2, the focus of catalyst development has been on improving the stability and activity of catalysts and the H\({}_{2}\)/CO ratio of the syngas produced is often secondary, even in papers that target DRM as a pathway for H\({}_{2}\) production. Some of the works cited in Section 2 suggested that low metal loadings could lead to small metal particles that would be more available to the reactants and could increase the H\({}_{2}\) production. High surface area of catalysts and high reducibility of the active phase would increase its activity and increase H\({}_{2}\) production. Finally, tuning process conditions, such as CH\({}_{4}\)/CO\({}_{2}\) feed ratio, can also improve CH\({}_{4}\) decomposition and increase the H\({}_{2}\)/CO ratio of the syngas produced. However, there is still a lack of detailed data on the literature dedicated to improving the catalyst design to favor higher H\({}_{2}\)/CO ratios via this reaction. Some of the technical and economic challenges in DRM for H\({}_{2}\) production could be partially overcome by either using a chemical looping process or by combining DRM with other technologies, such as steam reforming and partial oxidation. DRM operated in a chemical looping is an interesting process, since only CH\({}_{4}\) and CO\({}_{2}\) are used as feedstock, but the process produces syngas with H\({}_{2}\)/CO generally around 2.0, which is higher than the H\({}_{2}\)/CO obtained in classical DRM reactions. This is achieved by using oxidation and reduction cycles so the H\({}_{2}\) produced from CH\({}_{4}\) oxidation with the catalyst is not in contact with the CO\({}_{2}\), which prevents the RWGS reaction and assures a high H\({}_{2}\)/CO ratio. However, catalyst development is still required to improve their oxygen storage capacity before utilization at larger scales. Combined steam and dry reforming of methane (CSDRM) have also been considered as an alternative process to the classical DRM to improve the H\({}_{2}\)/CO ratio. Steam is added to the feed allowing the production of syngas with a flexible H\({}_{2}\)/CO ratio up to 8.0 depending on the amount of steam used. The addition of steam also contributes to preventing carbon depositions and catalyst deactivation. However, issues related to the endothermicity of this reaction must also be considered. Methane tri-reforming, which adds steams and oxygen to the feed mixture, has also been investigated, since it can produce syngas with a higher H\({}_{2}\)/CO of around 3.0. This process can also cope for the endothermicity of the reactions, since part of the CH\({}_{4}\) is combusted to generate heat for the reactions. However, there are issues related to catalyst deactivation via sintering and vapor-solid reactions that occur on the surface of catalysts. Due to these issues related to catalyst performance and thermodynamics, only very few industrial processes use DRM at large scale. However, none of them aim at the production of H\({}_{2}\) or of syngas with a high H\({}_{2}\)/CO ratio. The CALCOR(tm) process produces a CO-rich syngas while the SPARG(tm) process produces syngas with a H\({}_{2}\)/CO ratio lower than 1. Finally, the MIDREX(tm) process does not target H\({}_{2}\) or syngas as the final product. The syngas produced in this process is used as a reducing agent for metallic iron production.