Membrane Reactor, Methane Partial Conversion Of Synthesis Gas

Exploring the using of natural gas has become a hotspot because of the exhaustion of petroleum. Partial oxidation of methane to syngas in membrane reactors is a new research way in recent years. Dense mixed-conducting ceramic membranes which have a higher oxygen permeability can be used to separate oxygen from air directly, therefore, it can make the separation of oxygen and catalytic oxidation in one process. It not only simplifies the process of operation and reduces the production cost, but also improve the safety and selectivity in the reaction process. Therefore, it is a promising way to use it in the conversion of methane to syngas. In this paper, we investigated partial oxidation of methane to syngas in YBCO and doped Co membrane reactor. The reacted catalysts were investigated with TG SEM and its specific surface, the reacted membranes were also investigated with SEM.The performance of YBCO membrane reactor in the process of partial oxidation of methane (POM) to syngas was investigated. The results show that when Ni/ZrO₂ catalyst is used the CH₄ conversion and CO selectivity can reach almost 100% and 95% respectively and the oxygen permeation fluxes can reach 1.5ml·min^-1·cm^-2 at 900℃. The YBCO membranes reactor also show self-catalytic properties; without any catalysts the CH₄ conversion and CO selectivity can reach about 28% and 90% at 900℃respectively. The reaction mechanism of POM in YBCO reactor was also discussed based on the influence of space velocity (SV) on CO selectivity. The indirect partial oxidation mechanism may be the dominant mechanism of POM process in the YBCO membrane reactor. The suitable CH₄/O₂ radio of methane partial oxidation is 2/1. The excessive methane will result in deposition of carbon on catalyst and lower CH₄/O₂ radio will decrease the CO selectivity.The reaction performance of YBCO membrane reactor is determined by the stability of membrane and catalyst. However, SEM pictures show the stability of YBCO membrane is not desirable in reduced atmosphere at high temperature. The deactivation of catalyst is caused mainly by the deposition of carbon on catalyst in methane partial oxidation reaction. The deposition of carbon is mainly influenced by the decomposition reaction of methane. TG curves show that the higher the temperature is, the greater the carbon deposits. SEM pictures of the catalysts indicate that the deposited carbon is tubular carbon when used in the temperature range 850⁸75°C and the deposited carbon is mainly contained carbon when used at 900℃. The contained carbon will affect the activity of catalyst and even lead to deactivation.Ru/ ZrO₂ and Ni-Ru/ZrO₂ catalytic performance were investigated in this methane partial oxidation membrane reactor. Results show that RU/ZiO₂ has good resistance to carbon deposition and selectivity of CO, Ru can increase the resistance to carbon deposition of Ni/ZrO₂ obviously. After reaction, the specific surface of Ru/ZrO₂ decreases because of sintering, while the specific surface of Ni/ ZrO₂ and Ni-Ru/ ZrO₂ catalysts increases which should be attributed to the deposition of carbon.