Significance Statement
Man has started polluting the environment even since he has started using fire. Environmental pollution is a major issue that we are facing nowadays. It is a major threat to life and property. Awareness is created to promote smart technologies using chemical energy and materials, by utilizing our resources efficiently. Many countries have started using bio-ethanol in various applications. Hydrogen (H2) can be effectively made from renewable resources and it is eco-friendly.
A thermo-chemical technology known as endothermic Steam Reforming (SR) involves extraction of more hydrogen atoms to form a high hydrogen yield. A substantial amount of energy is required as input for SR. But this energy leads to carbon dioxide (CO2) imbalance. There is an alternative method, which uses oxygen as input to the feedstock. Nowadays, it has become more important to develop a new technology and alternative process that replaces CO2 emission fuels.
French scientists developed a successful, smart energy saving technology which uses nano oxyhydride catalysts to produce hydrogen from ethanol at only 50 °C of extra heating. The nano oxyhydride catalyst has the ability to store H2 and can effectively split the ethanol C-C bond. Hydrotalcites are treated as catalyst precursor in H2 production. Co-precipitation method is used to prepare catalytic precursors.
They used a fixed bed quartz reactor to perform catalytic reaction under atmospheric condition. The catalyst is first treated for 10 hours at 450 °C in pure H2. The temperature is then decreased to 150 °C and a purge in pure Helium is performed. A high performance liquid chromatographic pump is used to inject the reactant mixture into a chamber for heating. While adding the reactants, it should be noted that they are added in a particular order with oxygen being the last.
Gas chromatographic technique is used to analyze the outlet gases from the reactor. The temperature at which the reaction is performed varies depending on the catalyst and its ability to react with oxygen (O2). The reaction is usually started at an oven temperature of 200 degree Celsius. Within few minutes the reaction temperature increased quickly. When the reaction temperature started to increase extremely, the oven temperature was reduced to a temperature of 50 degree Celsius. The results were reported at this temperature. A thermocouple is used to measure the temperature. The Mg2AlNiXHZOY nano-oxyhydride is studied for the production of H2.
The authors clearly found that production of H2 can be achieved with different composition of oxyhydrides and with low energy input. It is noted that, there is no formation of carbon on a specific compound even if the reaction temperature cannot be fixed at 50 degree Celsius. In the gas phase, the products obtained are H2, CO2 and Carbon monoxide (CO) (obtained as by-product). Acetaldehyde and H2 are obtained when ethanol is subjected to dehydrogenation. CO, methane (CH4) and H2 are obtained when ethanol is decomposed. Depending on the conditions applied and the catalysts used, various reactions are obtained.
By varying the Ni content in the compound Mg2AlNiXHZOY and by varying the treatment temperature, hydride species’ concentration can be tuned. Different products are obtained from the conversion of ethanol. Hydroxyl groups are generated from the exothermic reaction between hydride species and oxygen. The generated hydroxyl groups transform ethanol to CO2 and H2. When the concentration of O2 in the gas phase is less, the reaction of hydride will lead to hydrogenation reaction with the formation of CH4, a greenhouse gas. But here the authors have increased the concentration of oxygen and found out no CH4 was released with the transformation of acetaldehyde in presence of oxygen and water.
This study demonstrated that H2 can be produced with low energy input from the ethanol water mixture by successful application of catalyst in the presence of O2. Future plans for Dr. Louise Jalowiecki-Duhamel and her colleagues are to replace various cations and thereby produce new nano-oxyhydride catalyst.
Journal Reference
- Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, 59000 Lille, France.
- Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, School of Chemical Science and Technology, Yunnan University, 650091 Kunming, China
- Institut Laue-Langevin (ILL), 38000 Grenoble, France.
- IRCELyon Institut de Recherches sur la Catalyse et I’Environnement de Lyon, 69626 Villeurbanne Cedex, France.
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