The kinetic and experimental study of the phenol steam reforming towards hydrogen production over Ni-Rh/MgO catalyst

Abstract

To study the kinetic implied on the Langmuir-Freundlich (LF) adsorption isotherm, the experimental tests of phenol steam reforming (PSR) reaction in the presence of Ni-Rh/MgO catalyst were performed in the temperature range of 500 °C-800 °C and flow rate of 10 mL/h to 30 mL/h in a fixed bed reactor. LF model accurately fitted the experimental responses with assuming CO and CO2 formation reactions as the kinetic limitations. By comparing two experimental and calculated values, the deviation of kinetic model in calculating experimental H2 yield was lower (2.58 %) compared to phenol conversion, CO and CO2 yields. The stability analysis revealed that conversion and yields were almost fixed without obvious deactivation up to 55 h initial time on stream, however, activity was declined over time on stream in the range of 55 h to 70 h because of coke deposition. The characterization results demonstrated that the deposited coke on the catalyst surface after the stability test was more aromatic and less aliphatic and included carboxylic group, methyl group and aromatic structure. The phenol conversion near to 90 % was attained at 800 °C and flow rate of 10 mL/h. The temperature had a positive effect on the catalytic activity regarding to phenol conversion, H2 and CO yields. However, temperature variable had a negative impact on CO2 yield. The changes of phenol conversion, H2 and CO2 yields showed descending trends with flow rate in the range of 10 mL/h to 30 mL/h. In the range of 500 °C-600 °C, CO yield was approximately constant by altering flow rate from 10 mL/h to 30 mL/h.