Thermodynamic analysis of hydrogen and synthesis gas production via reforming processes of propionic acid

The aim of thesis study is to investigate the effect of process conditions such as temperature, pressure, molar composition of the feed stream on product distribution for the production of synthesis gas and hydrogen from propionic acid selected as model component of bio-oil. For this purpose, thermodynamic analysis of steam reforming, oxidative steam reforming, sorption enhanced steam reforming and sorption enhanced oxidative steam reforming of propionic acid at 200-1000 °C temperature range and different feed stream molar compositions have been carried out. The product compositions at equilibrium conditions were determined by the Aspen Plus V8.8 simulation program and Gibbs free energy minimization method. All of the propionic acid was consumed in all thermodynamic analysis conditions. CO, CO2, CH4 and H2 as gaseous products and coke as solid product formation were observed. Simulation analysis results showed that the fundamental parameter affecting to H2 yield was the temperature. H2 and CO yields were decreased while CO2 yield was increased by increasing the number of moles of H2O in the feed stream. The increase of O2 in the feed stream enhanced the CO2 yield, while H2, CO and CH4 yields decreased. Coke formation was suppressed at high temperature, low pressure. Also, high content of H2O in feed stream caused a decline in coke formation. In the sorption enhanced refoming processes, up to 700-750 °C CaO adsorbent contributed to the H2 and CO product yields, and adsorption did not affect to product yields at higher temperature than 700-750 °C. According to thermodynamic analysis results, the process with the highest H2 yield is steam reforming reaction with a feed stream composition of C3H6O2/H2O=1/1 at 1000 oC temperature and 1 bar pressure. In this condition the yield of H2 was 98.58% and the yield of CO was 98.53%. The yield of H2 was 83.20%, the yield of CO was 89.03% in the oxidative steam reforming of propionic acid with a C3H6O2/H2O/O2=1/1/0.5 feed stream at 1000 oC temperature and 1 bar pressure. It is recommended that the H2/CO molar ratio should be 2 in Fischer-Tropsh synthesis and methanol production processes. The ideal H2/CO molar ratio (2.04) is belong to steam reforming process of propionic acid which has C3H6O2/H2O=1/3 molar ratio feed stream at 800 °C and 1 bar pressure. The H2/CO molar ratio decreases with the addition of O2 into the feed stream. Simulation results show that O2 addition to the feed stream significantly reduces the energy requirement of the reaction. For the low reaction enthaly, the most suitable process was found to oxidative steam reforming of propionic acid with C3H6O2/H2O=1/3 molar ratio feed stream at 800 °C and 1 bar pressure. It has been determined that product distribution can be changed accoding to temperature, pressure, feed stream compositions and type of reforming process.