Hydrogen is considered to be the most viable energy carrier for the future. Producing hydrogen from ethanol steam reforming would not only be environmentally friendly but also would open new opportunities for utilization of renewable resources, which are globally available. This paper reviews the current state of the steam reforming process of ethanol, examines different catalysts, and, finally, makes a comparative analysis. Different catalysts have been used for the steam reforming of ethanol. Depending on the type of catalysts, reaction conditions, and the catalyst preparation method, ethanol conversion and hydrogen production vary greatly. It was observed that Co/ZnO, ZnO, Rh/Al 2 O 3 , Rh/CeO 2 , and Ni/La 2 O 3 -Al 2 O 3 performed the best, in regard to the steam reforming of ethanol. Currently, hydrogen production from ethanol steam reforming is still in the research and development stage.

Conventional resources mainly fossil fuels are becoming limited because of the rapid increase in energy demand. This imbalance in energy demand and supply has placed immense pressure not only on consumer prices but also on the environment, prompting mankind to look for sustainable energy resources. Biomass is one such environmentally friendly renewable resource from which various useful chemicals and fuels can be produced. A system similar to a petroleum refinery is required to produce fuels and useful chemicals from biomass and is known as a biorefinery. Biorefineries have been categorized in three phases based on the flexibility of input, processing capabilities, and product generation. Phase I has less or no flexibility in any of the three aforementioned categories. Phase II, while having fixed input and processing capabilities, allows flexibility in product generation. Phase III allows flexibility in all the three processes and is based on the concept of high-value low-volume (HVLV) and low-value high-volume (LVHV) outputs. This paper reviews the concept of biorefinery, its types, future directions, and associated technical challenges. An approach of streamlining biorefineries with conventional refineries in producing conventional fuels is also presented. Furthermore, twelve platform chemicals that could be major outputs from an integrated biorefinery are also discussed.

About 80% of the present world energy demand comes from fossil fuels. Unlike using fossil fuels, using hydrogen as an energy source produces water as the only byproduct. Use of hydrogen as an energy source could help to address issues related to energy security including global climate change and local air pollution. Moreover, hydrogen is abundantly available in the universe and possesses the highest energy content per unit of weight compared to any of the known fuels. Consequently, demand for hydrogen energy and production has been growing in the recent years. Membrane separation process is an attractive alternative compared to mature technologies such as pressure swing adsorption and cryogenic distillation. This paper reports different types of membranes used for hydrogen separation from hydrogen-rich mixtures. The study has found that much of the current research has been focused on nonpolymeric materials such as metal, molecular sieving carbon, zeolites, and ceramics. High purity of hydrogen is obtainable through dense metallic membranes and especially palladium and its alloys, which are highly selective to hydrogen. Thin membranes would not only reduce the cost of materials but also increase the hydrogen flux. Metal alloys or composite metal membranes have been used for hydrogen purification. However, metallic membranes are sensitive to some gases such as carbon monoxide and hydrogen sulfide. Therefore, ceramic membranes, inert to poisonous gases, are desirable. Inorganic microporous membranes offer many advantages over thin-film palladium membranes. More importantly, in microporous membranes, the flux is directly proportional to the pressure, whereas in palladium membranes, it is proportional to the square root of the pressure. The paper also discusses the advantages and disadvantages of different hydrogen separation membranes. Also, the paper reports performance of selected membranes in terms of hydrogen selectivity and permeability.

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