A Review of Methane Activation Reactions by Halogenation: Catalysis, Mechanism, Kinetics, Modeling, and Reactors

Abstract

Methane is the central component of natural gas, which is globally one of the most abundant feedstocks. Due to its strong C–H bond, methane activation is difficult, and its conversion into value-added chemicals and fuels has therefore been the pot of gold in the industry and academia for many years. Industrially, halogenation of methane is one of the most promising methane conversion routes, which is why this paper presents a comprehensive review of the literature on methane activation by halogenation. Homogeneous gas phase reactions and their pertinent reaction mechanisms and kinetics are presented as well as microkinetic models for methane reaction with chlorine, bromine, and iodine. The catalysts for non-oxidative and oxidative catalytic halogenation were reviewed for their activity and selectivity as well as their catalytic action. The highly reactive products of methane halogenation reactions are often converted to other chemicals in the same process, and these multi-step processes were reviewed in a separate section. Recent advances in the available computational power have made the use of the ab initio calculations (such as density functional theory) routine, allowing for in silico calculations of energy profiles, which include all stable intermediates and the transition states linking them. The available literature on this subject is presented. Lastly, green processes and the production of fuels as well as some unconventional methods for methane activation using ultrasound, plasma, superacids, and light are also reviewed.

Design and tailoring of advanced catalytic process for light alkanes upgrading

“…(d) Safety problems. [53][54][55] The co-feed of alkane and oxygen could form explosive reactive mixture. Giving these problems, the explorations of novel C H bond activation catalysts as well as advanced reaction processes emerge as the key to convert these light alkanes into target products in a direct and mild manner.…”

“…As a result, the metal catalysts have to be regenerated after a short period of operation. (d) Safety problems 53‐55 . The co‐feed of alkane and oxygen could form explosive reactive mixture.…”

Electrochemical collective synthesis of labeled pyrroloindoline alkaloids with Freon-type methanes as functional C1 synthons

“…1 Among functionalization of methane, halogenation is a facile and practical method with mild conditions to obtain various halomethanes (Scheme 1a). 2 Therefore, efficient transformations of halomethanes are significant to resource utilization of methane. For example, the Rochow-Mu ¨ller process has been an important method to produce silicone monomer from chloromethane, which is widely used in industrial production.…”

Conversão de metano em metanol usando complexos moleculares de metais de transição em um reator de eletrólito polimérico tipo célula a combustível

“…Atualmente, esforços estão sendo feitos para converter metano em produtos por uma única etapa, pois esta apresenta baixo consumo energético tornando a conversão economicamente atrativa [10][11][12][13][14] Na busca por utilizar eletrocatalisadores de metais abundantes e/ou reduzir a quantidade de metais nobres utilizada, é promissor o uso de uma nova variedade de materiais baseados em complexos moleculares, os quais podem apresentar propriedades catalisadoras. Formados por piridinas e diaminotriazina esses complexos moleculares apresentam a possibilidade de uso de diferentes átomos de metais de transição, com redução da quantidade em massa desses metais, podendo ser coordenados por metais de transição nobres e não nobres [21][22][23][24] .…”

“…Portanto, para a corversão do metano em produtos de alto valor agregado como o metanol, é necessária a escolha de um método que contemple a seletividade para favorecer essa formação e que seja energeticamente favorável. Para um melhor controle dos processos de conversão de metano em produtos e diminuição do gasto energético tem se adotado como base reatores com catalisadores heterogêneos [7][8][9] , homogêneos 8, 10 e 11 e biológicos [12][13][14] .…”