Non-Oxidative Methane Conversion Using Lead- and Iron-Modified Albite Catalysts in Fixed-Bed Reactor

Nonoxidative Coupling of Methane to Produce C2 Hydrocarbons on FLPs of an Albite Surface

The characteristics of active sites on the surface of albite were theoretically analyzed by density functional theory, and the activation of the C-H bond of methane using an albite catalyst and the reaction mechanism of preparing C₂ hydrocarbons by nonoxidative coupling were studied. There are two frustrated Lewis pairs (FLPs) on the (001) and (010) surfaces of albite; they can dissociate H₂ under mild conditions and show high activity for the activation of methane C-H bonds. CH₄ molecules can undergo direct dissociative adsorption on the (010) surface, whereas a 50.07 kJ/mol activation barrier is needed on the (001) surface. The prepared albite catalyst has a double combination function of the (001) and (010) surfaces; these surfaces produce a spillover phenomenon in the process of CH₄ activation reactions, where CH₃ overflows from the (001) surface with CH₃ adsorbed on the (010) surface to achieve nonoxidative high efficiently C-C coupling with an activation energy of 18.51 kJ/mol. At the same time, this spillover phenomenon inhibits deep dehydrogenation, which is conducive to the selectivity of the C₂ hydrocarbons. The experimental results confirm that the selectivity of the C₂ hydrocarbons is maintained above 99% in the temperature range of 873 K to 1173 K.

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.