Hydrogen production from bioethanol

Abstract

The world primary energy demand, currently dominated by fossil fuels with more than 80% of the total, is projected to expand by 45% from 2006 to 2030, so that global carbon dioxide emissions will increase by 1.8% per year, which would result in critical environmental problems all over the world. The use of hydrogen as a sustainable energy vector is an interesting and promising challenge. Hydrogen can be renewably produced in several ways and its utilization to obtain energy generates just water and no pollutant emission. In this Chapter, the current and future hydrogen production processes are described to focus in one of the most promising ones from the point of view of sustainability: bioethanol steam reforming. Ethanol is a good candidate as a hydrogen feedstock since it can be easily produced from several biomass sources (sugar and starchy crops, agricultural residues, wood and municipal solid wastes). Although bioethanol can be directly used as a fuel, the implementation of fuel cell systems where hydrogen can silently be converted to electricity, without the excessive thermal energy loss and the limit of the thermodynamic yield of the Carnot cycle observed in combustion engines, turns the use of bioethanol to produce hydrogen into a competent alternative. Besides, bioethanol steam reforming is a cost-effective and an efficient process which consists of a complex network of reactions generating hydrogen and several byproducts. The use of an appropriate catalyst may favour reaction pathways that minimize the formation of undesirable compounds, enhancing selectivity towards main products. In this Chapter, bioethanol steam reforming is detailed as regards industrial process, including future options such as autothermal reforming and membrane reactors. A review on commonly used and recently investigated catalysts is also provided, including active metals, auspicious supports and promoters which can minimize catalyst deactivation. © 2012 by Nova Science Publishers, Inc. All rights reserved.