Thermodynamic analysis of steam reforming and partial oxidation of acetic acid and acetone

Sustainability is crucial for modern industry. Biorefineries are one of the most important processes supporting sustainable technology. Bio based source feedstock is used as a raw material in biorefineries. Bio based feedstocks are converted to valuable chemicals by using thermochemical conversion technologies, which are, combustion, gasification and pyrolysis processes. Pyrolysis can produce solid, liquid and gas products. Liquid products are divided into two categories, which are bio-oil and aqueous phase. Bio-oils consist of chemical components, which are different amounts of hydrocarbons. These valuable chemical components can be converted to hydrogen rich gas mixture by steam reforming, partial oxidation reforming and adsorption enhanced reforming processes. In this thesis study, steam reforming, oxidative steam reforming and sorption enhanced reforming processes of acetic acid and acetone, the fundamental model components of bio-oil, have been investigated by changing temperature, pressure and feed composition. The thermodynamic analyzes of the processes were carried out with different feed components at a temperature range of 200-1000°C. Analysis are simulated by Gibbs free energy minimization method in R-Gibbs reactor by using Aspen Plus V8.8. All the components that can occur as a result of the reforming of acetic acid and acetone are defined in the simulation program. Under all reaction conditions, acetic acid and acetone were all depleted due to thermal decomposition reactions. In addition, all oxygen present in the input stream is exhausted to fulfill the energy requirement of the oxidative steam reforming reactions. The steam conversion and the yields of the products hydrogen, carbon monoxide, carbon dioxide, methane and coke are presented by tables and graphs. The effect of temperature, pressure and feed composition on the hydrogen yield was investigated. The reactions were carried out separately for both acetic acid and acetone and in different feed compositions as a mixture of acetic acid and acetone. H2, CO, CH4, coke yields and H2O conversion were affected negatively by H2O increase in feed stream, whereas CO2 production was affected positively. The increase of O2 in the feed stream had the same effect as the H2O increase. The presence of higher amounts of steam and oxygen in the feed stream as well as high temperature reduced the coke formation. It was observed that adsorption did not have an effect on product yield in the CaO sorption enhanced at temperatures above 700°C. CaO increase in the feed stream had a positive effect on the H2 and CO efficiency while decreased coke formation. According to thermodynamic analysis results, maximum hydrogen and CO yields were calculated as %98.5 for the ratio of C2H4O2/C3H6O/H2O/O2=0.5/0.5/1.0/0.0 at 1000oC and 1 bar pressure. H2/CO molar ratio of 2.0 obtained in steam reforming, oxidative reforming, sorption enhanced reforming processes is a requirement for Fischer-Tropsch synthesis and methanol production process. The presence of O2 in steam reforming process has either partially or totally compensated the energy requirement of the process via oxidation and combustion reactions. This energy benefit has varied according to the operational conditions. In recent studies, the effect of CaO adsorbent on reforming process of different bio-oil model components were investigated as a function of temperature and pressure. In this thesis, the conversion of two different bio-oil model components to H2 rich gas product in reforming processes has also been investigated. Generally, it has been observed that acetic acid and acetone reforming mechanisms are controlled by different reactions with regard to the operating temperature, pressure and varying feed compositions. It is possible to adjust the product composition by changing the temperature, pressure and the feed content, depending on the targeted downstream application.