(551f) Syngas Production from Methane Steam Reforming over Nickel Supported Hydroxyapatite Catalyst

Syngas is a very important intermediate in chemical industry for energy chemicals production through F–T synthesis. Methane steam reforming (MSR) is a well-established commercial process for syngas production. The produced syngas is in a high H₂/CO ratio close to 3 for MSR. The high endothermicity of the reforming reaction requires operating temperatures that are higher than 700°C and a H₂O/CH₄ ratio higher than 1 to reduce the coke formation. Among the various catalysts which have been used for MSR, Nickel catalyst is the most widely used for its high activity and low cost. However, coking formation and sintering of nickel particles are two main challenges for the catalyst performance.

The main objective of the present work is to study the performance and the stability of nickel supported on a sustainable bio-ceramic material which is hydroxyapatite (HAp), as a catalyst for methane steam reforming. Hydroxyapatite could be an efficient support for the MSR catalyst, due to its promising properties, which are it’s thermal stability, decomposing only at a temperature above 1000°C, and its basic character.

The influence of the temperature, gas hour space velocity (GHSV) and H₂O/CH₄ ratio were investigated for the performance of Ni/HAp catalyst with different %wt loadings. The catalysts were prepared by the incipient wetness impregnation method and were analyzed by the ICP, XRD, TGA-DTA and BET techniques. The reactions were performed in a fixed bed reactor at atmospheric pressure, in a GHSV between 12000 and 20000 ml.g_cat^-1.h^-1, a temperature between 700 and 800°C, using different ratio of H₂O/CH₄ (1,1.5,1.7,2).

Methane conversion and hydrogen yield conversion reached up to 88 and 80% at a ratio of H₂O/CH₄=1, respectively. The activity of the 10Ni/HAp was stable for a long reaction time of 100 h, at the reaction conditions of 800°C, GHSV=16000 ml.g_cat^-1.h^-1 and H₂O/CH₄=2. The thermal analysis revealed that HAp is a very stable material, a total weight loss of 4.5 % only was observed. The XRD patterns showed the presence of pics related to the nickel oxide phase (NiO) and the metallic phase (Ni°) for the fresh and used catalysts, respectively. The initial support presents the hexagonal closed packed phase structure of HAp. The BET results showed that the deposition of nickel particles on the support surface decreases slightly its initial specific surface area from 60 to 50m².g^-1, while after the reaction, the specific surface areas decrease to 4-8 m².g^-1 which can be a sign of the particles sintering.