Steam Reforming of Ethanol SRE

Similar to the methanol reforming methods discussed in Section 2.4.1, hydrogen can also be produced from ethanol by steam reforming (Eq. 2.79), partial oxidation (Eq. 2.80), and oxidative steam reforming or ATR (Eqs. 2.81 and 2.82). Among them, the SRE has been studied extensively. 

Rate Expression Catalyst Activation Energy (kJ/mol) Reference 

the thermodynamic analysis suggests that the SRE into H2 and C02 is thermodynamically favorable above 200 °C. A mixture of H2, C02, CO, and CH4 will be produced at lower temperatures, below 400 °C. The CH4 formed will be 

Recently, Comas et al.219 performed the thermodynamic analysis of the SRE reaction in the presence of CaO as a C02 sorbent. The equilibrium calculations indicate that the presence of CaO in the ethanol steam reforming reactor enhances the H2 yield while reducing the CO concentrations in the outlet of the reformer. Furthermore, the temperature range at which maximum H2 yield could be obtained also shifts from above 700 °C for the conventional steam reforming reaction without CaO to below 700 °C, typically around 500 °C in the presence of CaO. It appears that the presence of CaO along with ethanol reforming catalyst shift the WGS equilibrium in the forward direction and converts more CO into C02 that will be simultaneously removed by CaO by adsorption. 

The nature of support also plays a critical role in catalytic performance. Acidic supports such as A1203 favors the dehydration of ethanol to produce ethylene, which leads to carbon deposition on the catalyst surface.242,252,254,259 The carbon deposition can be minimized over basic supports such as Mg0.235, 241,258,259 However, these supports also favor condensation of alcohols to higher oxygenates.260 Interestingly, 

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Table 1 Non-noble metal-based catalysts employed in the steam reforming of ethanol (SRE) for hydrogen production... 

Table 4 Selected best performing catalysts for the middle-, and high-temperature steam reforming of ethanol (SRE) reaction"...

This review analyzed the chemistry involved, thermodynamics, catalysts used, reaction pathways and mechanisms of various reforming techniques reported for the conversion of ethanol into H2-rich gas. The known reforming processes are broadly classified into three categories, namely steam reforming of ethanol (SRE), partial oxidation of ethanol (POE) and oxidative steam reforming (OSR)/autothermal reforming of ethanol. All these reactions are thermodynamically favorable even at lower temperatures, above 200 °C. 

Ethanol can be converted directly to hydrogen through two main processes, steam reforming of ethanol (SRE) and partial oxidation of ethanol (POE). These two reforming techniques are described by the following equations ... 

Table 2.26. Non-Noble Metal-Based Catalysts Employed in the Steam Reforming of Ethanol (SRE) for Hydrogen Production... 

Table 2.28. Selected Best Performing Catalysts for the Low-Temperature Steam Reforming of Ethanol (SRE) Reaction1...

Carbon formation and catalyst deactivation have also been observed in the SRE. Approaches similar to those discussed above for the steam reforming of hydrocarbons are also employed to suppress the carbon formation in ethanol reforming as well.1 7... 

The thermodynamic analysis of loannides [193] on SRE in a solid polymer fuel cell indicated that the ethanol steam reforming reaction needs to be carried out in two steps a high-temperature endothermic step (steam reforming), in which ethanol is converted to a gaseous mixtures of H2, CO, CO2, CH4 and unreacted H2O, and a subsequent, low-temperature step (WGSR) in which CO reacts with water to form H2 and CO2. 

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