Influence of Axial Temperature Profiles on Fe/SiO 2 Catalyzed Non‐oxidative Coupling of Methane

Effect of Hydrogen Addition on Coke Formation and Product Distribution in Catalytic Coupling of Methane

The effect of hydrogen addition on catalytic nonoxidative coupling of methane at 1000 °C was investigated. Experiments were performed at varying ratios between the catalyst and the postcatalytic volume to discern the effect of hydrogen on the catalytic reaction as well as on the gas-phase reaction. Adding 10% H2 decreases the methane conversion by a factor of 2, almost independent of the ratio between the catalyst and the postcatalytic residence time. The effect on the conversion is mostly determined by gas-phase chemistry. Hydrogen addition has no influence on the C2 hydrocarbon yield, whereas aromatic selectivity is significantly reduced. Changes in selectivity are attributed to changes in methane conversion. Quantitative determination of the amount of coke deposited on the catalyst reveals a decrease by 1 order of magnitude when dosing up to 10% H2, while carbon deposits-downstream of the catalyst bed are suppressed to a much lower extent. These results suggest a process in which the produced hydrogen is partly recycled, maximizing the carbon selectivity to C2 hydrocarbons while minimizing both aromatics and, most crucially, formation of coke on the catalyst as well as further deposits-downstream.

Technoeconomic Evaluation of the Industrial Implementation of Catalytic Direct Nonoxidative Methane Coupling

This paper presents a process design for catalytic nonoxidative natural gas conversion to olefins and aromatics, highlighting the opportunities and challenges concerning industrial implementation. The optimal reactor conditions are 5 bar and 1000 °C. Heat exchange over the reactor is challenging due to the high temperature and low gas pressure. Recovery of ethylene is economically unattractive due to the low ethylene concentration in the product stream, leading to a methane-to-aromatics process, recycling ethylene. Benzene is the most valuable product at an efficiency of 0.31 kgbenzene/kgmethane with hydrogen as a major valuable byproduct. Naphthalene, with a low value, is unfortunately the dominant product, at 0.52 kgnaphthalene/kgmethane. It is suggested to hydrocrack the naphthalene to more valuable BTX products in an additional downstream process. The process is calculated to result in a 107 $ profit per ton CH4.

Exploring the slow-light effect of Pt/TiO2-SiO2 inverse opal on photocatalytic nonoxidative coupling of methane

The slow-photon effect of Pt/TiO₂-SiO₂ inverse opal on photocatalytic nonoxidative coupling of methane was explored regarding the cavity size and filming treatment. The ethane production rate was maximized to 72 μmol g^-1 h^-1 on a filmed microarray with a macroporous diameter of 170 nm, demonstrating the significance of enhancing light-matter interaction for methane conversion.

Effect of ethane and ethylene on catalytic non oxidative coupling of methane

The effect of addition of ethane and ethylene (C2) on methane coupling at 1000 °C was investigated. A Fe/SiO2 catalyst was used to determine the contributions of catalytic as well as C2 initiated methane activation. The catalyst load as well as the residence times at 1000 °C downstream of the catalyst bed were varied. C2 addition significantly increases methane conversion rates, similarly for both ethane and ethylene, although ethylene is more effective when operating with long residence times in the post-catalytic volume. Methane activation via C2 addition proceeds dominantly in the gas-phase whereas catalytic C2 activation is negligible. The catalyst has no effect on methane conversion when the feed contains more than 2 vol% C2. Product selectivity distribution as well as total hydrocarbon yield at 10% conversion is not influenced by C2 addition, but is influenced by the amount of catalyst as well as residence time in the post-catalytic volume at high temperature. It is proposed that C2 impurities in natural gas change from a nuisance to an advantage by enhancing methane conversion and simplifying purification of the natural gas feed. A process is proposed in which ethylene is recycled back into the reactor to initiate methane coupling, leading to a process converting methane to aromatics.