Hydrogen production from various alcohols using Pt/Al2O3 catalyst in supercritical water

Environmentally friendly and renewable energy technologies, which is one of the most important research area of the century, are gaining more importanceevery day. Since energy production from fossil sources causes environmental problems and increases external dependency for many countries, there is a needfor alternativeenergy sources. Hydrogen is an alternative energy source that it can be used in large areas and produced from renewable sources.Product or waste of hydrogen is only water compared with usage of hydrocarbon based fossil fuels. However, they produce carbon dioxide in large amounts, and cause acid rains due to NOx and SOx compounds. Hydrogen which is an important chemical in many industries such as chemical, petrochemical, food processing, semiconductor and metallurgy, is expected to be one of the most important fuels in future, since PEM fuel cells and hydrogen-blend gaseous fueled internal combustion engines (HBICE) are commercialized in near future. However, main subjects that scientists are focused, are searching of hydrogen production methods in high purity and development of hydrogen storage methods in safely. Main methods to produce hydrogen today are steam reforming natural gas and hydrocarbon mixtures, the electrolysis of water, biological conversion of organic containing wastes and wastewaters using microorganisms and hydrothermal gasification of biomass. Water which has critical temperature of 374oC and critical pressure of 22.1 MPa, has the unique physical properties in supercritical conditions. Compared with those of water in normal conditions, since it has lower density and dielectric constant, organics can solve completely in supercritical water. Its low viscosity and high diffusivity causes a rapid and efficient medium for reactions. Another advantage is able to change reaction conditions by changing supercritical water properties with temperature and pressure. Either water in supercritical conditions behaves as a reaction medium or an acid or base catalyst due to the self-dissociation to its ions. In this study, hydrogen production from 0.5 M solutions of methanol, ethanol and isobutanol was carried out using Pt/Al2O3 catalyst in supercritical water. Experiments for all alcohols used were proceed in the reaction time range of 10-30 s, in the temperature range of 400-600oC at constant pressure of 250 bar. The effects of kind of alcohol used, reaction temperature and time on the amount of hydrogen produced, gas product yield and TOC conversion were investigated.