Understanding the role of surface basic sites of catalysts in CO2 activation in dry reforming of methane: a short review

The surface of basic sites in catalysts plays an important role in many catalytic applications, such as dry reforming of methane for generating renewable hydrogen energy. The reaction concept of methane dry reforming is initiated by an acid-base interaction, followed by catalytic cycles. For instance, the reactants of CO2 act as acids toward catalysts, which act as bases. The basic sites of catalysts are generated from a severe pre-treatment temperature by desorbing the surface species. The current consensus on the role of basic sites is to enhance the activation of acidic CO2 on the catalyst support's surface and to inhibit carbon deposition on the catalyst, thus enhancing the catalytic stability. This review elucidated the behaviour of surface basic sites towards CO2 activation in dry reforming of methane. The method for characterising the basicity of catalysts was also reviewed to strategically design catalysts, which could increase the catalytic activity

Optimisation of a sorption-enhanced chemical looping steam methane reforming process

An intensified hydrogen production steam reforming process named ‘Sorption-Enhanced Chemical Looping Steam Methane Reforming’ (SE-CL-SMR) was studied. Aspen Plus was used to carry out a thermodynamic investigation into the influence of various operating conditions on hydrogen production and process thermal efficiency. The steam to carbon molar ratio (S/C), the CaO to carbon molar ratio (CaO/C), the metal oxide to carbon molar ratio (MeO/C), the metal oxide composition (NiO:CuO), and the oxidising agent species were all shown to influence the process performance. The main findings were that; (1) the introduction of CaO reduces the potential for coke formation with predicted zero coke formation for CaO/C ratios > 0.4; (2) increasing amounts of metal oxide (MeO/C) and steam (S/C) enhance the hydrogen production yield and purity; (3) due to its involvement in an exothermic reaction, the presence of CuO allows for the reforming reactor to operate as an adiabatic reactor with an operating temperature within the range of 600 °C–700 °C; (4) an increase in the NiO:CuO ratio leads to an increase in methane conversion. With the operating conditions of S/C = 3, CaO/C = 1, MeO/C = 1, NiO:CuO = 0.9 and air as the oxidising agent, a hydrogen purity as high as 98% was predicted for the SE-CL-SMR process, along with the lowest observed CO2 production rate. Under the same conditions and using pinch analysis, the thermodynamic model prediction of the thermal process efficiency is reported as ca. 86%. This is significantly higher than the reported efficiency of 79% for the ‘Sorption-Enhanced Steam Methane Reforming’ (SE-SMR) process, predicted using similar thermodynamic models

High-performance bimetallic catalysts for low-temperature carbon dioxide reforming of methane

Catalytic dry reforming of methane (DRM) is a promising way for renewable syngas production due to the utilization of both CO2 and CH4 greenhouse gases. Current approaches were made to improve the catalytic activity and coke resistance by introducing a second metal into the Ni-based catalytic system. This bimetallic catalytic system showed a significant improvement in coke resistance due to the synergistic effect of both metals towards the reaction. This review summarizes recent developments in bimetallic catalysts in DRM which focused on the evaluation of catalysts, deactivation studies, and reaction mechanisms of developed bimetallic catalysts

Direct accessibility of mixed-metal (III/II) acid sites through the rational synthesis of porous metal carboxylates

Accessed by 06/2015International audienc