Coke Formation over Zeolite Catalysts in Light Alkanes Aromatization and Anti-Carbon-Deposition Strategies and Perspectives: A Review

Abstract

The price of light aromatics, which are important chemical intermediates, is greatly affected by fluctuations in the oil market, and there is a gap in the supply. It is urgent to expand the source of aromatics to match the market demand. Being highly accessible, oxygen-free aromatization of light alkanes (C1–C4), with high product selectivity and high cost-effectiveness, has attracted widespread interest from both academia and industry. However, the rapid deactivation of catalysts due to carbon deposition has seriously hindered the industrialization process. This Review presents the bifaciality of coke on catalysts and proposes a coke formation mechanism related to the dynamic migration of intermediates according to the type of catalyst active site. An emphasis is placed on creating a reaction microenvironment that resists carbon deposition by improving the mass-transfer efficiency, controlling the interaction between intermediates and active sites, adjusting silanol defects, and looking forward to future directions for development.

In-Depth Understanding of Highly Active Silicotungstic Acid Catalysts for Ethanol Dehydration to Ethylene under Industrially Favorable Conditions

“…The catalyst exhibits the maximum weight loss peak between 360 and 680 °C, accompanied by an exothermic phenomenon, indicating the decomposition of carbon deposition. According to the different decomposition temperatures, the carbon deposition is mainly divided into soft coke (composed mainly of aliphatic compounds) and hard coke (composed mainly of aromatic compounds) . Generally, the decomposition temperature of soft coke was between 300 and 480 °C, while that of hard coke was between 480 and 800 °C.…”

“…According to the different decomposition temperatures, the carbon deposition is mainly divided into soft coke (composed mainly of aliphatic compounds) and hard coke (composed mainly of aromatic compounds). 65 Generally, the decomposition temperature of soft coke was between 300 and 480 °C, while that of hard coke was between 480 and 800 °C. The main weight loss of the deactivated catalyst occurred above 480 °C (Figure 16), suggesting that the carbon deposition on the 36-STA/SiO 2 catalyst was mainly hard coke composed of aromatic compounds.…”

Smart Designs of Zeolite-Based Catalysts for Dry Reforming of Methane: A Review

“…The catalyst deactivation in DRM is mainly caused by carbon deposition, metal sintering, and poisoning. − The coke formation easily covers the metal sites and support pores, preventing the interaction between the reactants and catalysts . Two reactions are responsible for carbon formation: CH 4 cracking (eq ) and CO disproportionation (Boudouard reaction) (eq ).…”

Application of co‐feeds in the catalytic conversion of light alkanes to aromatics: A comprehensive review

“…Nevertheless, review articles on light alkane aromatization have been generally centered towards delivering a broad perspective of the reaction, often focusing on the conversion of individual alkane reactants. [17,[29][30][31][32][33] Only a few reviews have covered the addition of co-reactants in detail, [34,35] and thus, the literature lacks a comprehensive compilation of these studies. In this review, we gathered the substantial amount of work on the introduction of co-reactants in light alkane (C 1 -C 3 ) aromatization, within the past few decades.…”

“…Consequently, a vast amount of information has been accumulated regarding the pronounced effect of each co‐reactant and its underlying mechanism. Nevertheless, review articles on light alkane aromatization have been generally centered towards delivering a broad perspective of the reaction, often focusing on the conversion of individual alkane reactants [17,29–33] . Only a few reviews have covered the addition of co‐reactants in detail, [34,35] and thus, the literature lacks a comprehensive compilation of these studies.…”