Methane Dehydroaromatization Reaction Research Articles

Direct conversion of methane to aromatics and hydrogen via a heterogeneous trimetallic synergistic catalyst

Non-oxidative methane dehydro-aromatization reaction can co-produce hydrogen and benzene effectively on a molybdenum-zeolite based thermochemical catalyst, which is a very promising approach for natural-gas upgrading. However, the low methane conversion and aromatics selectivity and weak durability restrain the realistic application for industry. Here, a mechanism for enhancing catalysis activity on methane activation and carbon-carbon bond coupling has been found to promote conversion and selectivity simultaneously by adding platinum–bismuth alloy cluster to form a trimetallic catalyst on zeolite (Pt-Bi/Mo/ZSM-5). This bimetallic alloy cluster has synergistic interaction with molybdenum: the formed CH3* from Mo2C on the external surface of zeolite can efficiently move on for C-C coupling on the surface of Pt-Bi particle to produce C2 compounds, which are the key intermediates of oligomerization. This pathway is parallel with the catalysis on Mo inside the cage. This catalyst demonstrated 18.7% methane conversion and 69.4% benzene selectivity at 710 °C. With 95% methane/5% nitrogen feedstock, it exhibited robust stability with slow deactivation rate of 9.3% after 2 h and instant recovery of 98.6% activity after regeneration in hydrogen. The enhanced catalytic activity is strongly associated with synergistic interaction with Mo and ligand effects of alloys by extensive mechanism studies and DFT calculation.

Methane dehydroaromatization (MDA) on VOx/HZSM-5 catalysts

In this study, the methane dehydroaromatization (MDA) on vanadium oxide (VOx)-based catalysts was investigated. Using various catalyst supports, VOx/HZSM-5 exhibited the highest MDA activity. In MDA using VOx/HZSM-5, an induction period was observed. Raman spectroscopy and XPS analysis indicated that V2O5 species result in the highly dispersed state by the contact with CH4. X-ray absorption fine structure analysis suggested the formation of VC species. Such structural changes lead to the induction period for the MDA reaction. Based on the effect of the catalyst support and the aromatization reaction of ethylene, we propose a mechanism in which methane forms ethylene on the vanadium catalyst, and ethylene is then aromatized with the aid of the acid sites and micropore structure of HZSM-5. Additionally, the effect of hydrogen co-feeding on the MDA reaction was investigated, which revealed that catalyst deactivation due to coke formation was suppressed in the presence of hydrogen.

Enhanced catalytic performance for methane dehydro‐aromatization on Mo/HMCM‐49 prepared with citric acid

AbstractA simple citric acid (CA)‐ammonium molybdate co‐impregnation method was applied to prepare the Mo‐based MCM‐49 catalyst to ameliorate the dispersion of metallic Mo for methane dehydro‐aromatization reaction (MDA). The newly prepared catalyst has higher crystallinity and maintains the original morphology of zeolite, which proves that the addition of citric acid will not destroy the basic structure of the catalyst. Based on H2‐TPR, UV‐vis, NH3‐TPD and XPS characterization results, it can be corroborated that the introduction of citric acid changes the coordination state of Mo element. Brønsted acid sites can stabilize the monomeric Mo oxide species by increasing MoOx migration into the MCM‐49 zeolite pores channel after calcination, which may affect the distribution of active sites MoCx and thus improve MDA catalytic activity. The experimental results show that the Mo‐based MCM‐49 catalyst with nCA : nMo ratios of 1.0 has higher methane conversion (14.5 %) and aromatics yield (9.8 %). The combination of XPS, TG and Raman tests of the spent catalyst confirms that the newly synthesized catalysts produce less carbon deposition, thus improving the catalytic durability during the MDA reaction.

Methane dehydroaromatization process in a carbon-neutral strategy

Methane dehydroaromatization (MDA) process is a “non-oxidative” technology for CH4 utilization, esteemed as a propitious substitution for fossil fuel-based counterparts in the synthesis of benzene, toluene, and xylene (BTX). However, the MDA process is less cost-effective than both commercial BTX production and “oxidative” CH4 conversion technologies, primarily due to its inherently low BTX yield and CH4 conversion rate. As the focus on attaining net-zero emissions escalates and concerns regarding the usage of abundant CH4 arise, the MDA process has emerged as an environmentally efficient alternative that can generate high-value products while decreasing direct CO2 emissions. In this study, we evaluate various MDA reaction systems, including MDA utilizing only pure CH4, additive co-feeding MDA, and hydrocarbons co-feeding MDA, employing a Mo/HZSM-5 catalyst. The proposed process design comprehensively analyzes the impact of MDA reaction systems on product distribution and energy consumption. Furthermore, we confirm the feasibility of the proposed MDA processes through an exhaustive environmental and economic assessment of “oxidative” CH4 conversion methods and commercial BTX production processes. By decentralizing some of the immense direct CO2 emissions from existing CH4 utilization to controllable indirect CO2 emissions, the MDA processes prove to be more advantageous under the net-zero strategy. The results of this analysis reinforce the potential of MDA reaction processes as a carbon-neutral technology that can effectively replace oxidative CH4 conversion while producing high-value products.

Conversion of fly-ash into pristine ZSM-5 and its application for methane dehydroaromatization reaction

Increasing Fly-Ash (FA) residues as a by-product in pulp/paper industries requires efficient routes for green and economical ash management. Converting FA into zeolite shows great potential for its efficient utilization. In this work, FA received from Indian paper mills was converted into pristine ZSM-5, support in methane dehydroaromatization (MDA). Following acid leaching, Fe and Al content were reduced to make ash residue, a precursor for ZSM-5 synthesis. Synthesized FA-derived ZSM-5 consisted of a highly crystalline structure (91 %) and high BET surface area (468 m2/g) comparable to commercial ZSM-5. Synthesized ZSM-5 (FA) possessed micropores/mesopores, with comparatively smaller particle size as confirmed by pore size distribution analysis/N2-sorption isotherms and SEM analysis. NH3-TPD study confirmed the acidity content (1.16 mmol/gcat) over ZSM-5 (FA) and was found to be compatible with that of commercial ZSM-5 (1.58 mmol/gcat). Further, the activity of ZSM-5 (FA) with 5 wt% Mo loading was evaluated towards MDA reaction and compared its activity with conventional Mo/HZSM-5. Higher activity was achieved with 5Mo/HZSM-5 (FA-derived) exhibiting a higher benzene production rate than the 5Mo/HZSM-5 due to effective textural properties and suitable acidity, which provides sites for dispersion of MoOx species in case of Mo/ZSM-5 (FA) thereby conferring improved activity.

Active Ensembles in Methane Dehydroaromatization over Molybdenum/ZSM-5 Zeolite Identified by 2D 1 H-95 Mo Magic Angle Spinning Nuclear Magnetic Resonance Correlation Spectroscopy.

Methane dehydroaromatization (MDA) over Mo-modified zeolite is a potential catalytic route for converting natural gas into valuable aromatics. However, the active species in this reaction are highly complex, involving diverse Mo species, acidic sites of zeolite, and organic molecules. Herein, we apply 1D 95 Mo NMR and 2D 1 H-95 Mo heteronuclear correlation solid-state NMR spectroscopy to directly observe the active ensembles in the confined channels of Mo/ZSM-5 zeolite during the MDA reaction. We monitor the evolution of the spatial correlations of Mo species with the Brønsted acid sites and organic products (olefins and aromatics) in the zeolite channels. We identified two kinds of MoOx Cy species, with the more carbidic one (MoOx Cy -II) exhibiting higher activity for methane activation and benzene formation. The strong spatial interactions between the active Mo species and the organic species in the Mo/ZSM-5 pores are related to the MDA activity.

Elucidating the roles of acid site on benzene production from methane dehydroaromatization over the supported Mo catalysts

Benzene production from methane dehydroaromatization (MDA) reaction is suffered by the low benzene yield and severe carbon deposition. In this work, the supported Mo/ZSM-5 catalysts were synthesized and the acid site was successfully regulated by Ga promoter. Benzene production was increased by adjusting the ratio of Brønsted acid to Lewis acid on ZSM-5. The Mo/ZSM-5 catalyst with 0.7 wt% of Ga showed the highest B/L acid of 1.2, which exhibited the highest benzene yield of 12.8% at 700 °C. The moderate amount of B acid enhanced the yield of benzene and suppressed the formation of carbon deposition effectively.

Catalytic conversion of methane into benzene over ceria–zirconia‐promoted molybdenum‐supported zeolite for methane dehydroaromatization

The promotional effect of mixed ceria–zirconia oxides (CZO) over the Mo/HZSM‐5 catalyst for methane dehydroaromatization (MDA) reaction was studied. The surface and structural properties of the synthesized catalyst were thoroughly exemplified using various microscopic and spectroscopic tools, and the correlation between catalytic properties and its performance for MDA reaction is discussed. The impregnation of CZO solid solution on Mo/HZSM‐5 was monitored to give an excellent catalytic performance and improved benzene production rate (4.5 μmol/gcat.s) related to the conventionally prepared Mo/HZSM‐5 (3.1 μmol/gcat.s) catalyst. In addition, a significant reduction in coke formation was examined in the CZO‐modified Mo/HZSM‐5 catalyst. The prevailing comprehension for higher catalytic activity could be because of the redox properties of CZO‐deposited Mo/HZSM‐5, which acts as a selective oxygen supplier and performs hydrogen combustion during the reaction, which is indirectly probed by residual gas analysis‐mass spectroscopy, oxygen‐temperature programmed desorption, and hydrogen‐temperature programmed reduction analysis. The selective hydrogen combustion prevents the over‐oxidation of aromatic species formed during the reaction, whereas the generated steam helps in reducing the coke content deposition in the MDA reaction. Thus, the advantage of CZO‐incorporated Mo/HZSM‐5 is manifested as it promotes the reaction equilibrium to shift towards the formation of benzene which is favourable for MDA reaction.

Elucidation of quantitative effects of zeolitic pores in Mo-impregnated MWW type zeolites on catalytic activities and stabilities of methane dehydroaromatization reaction

The quantitative effects of the pores in Mo-impregnated zeolites on their catalytic activity and stability during methane dehydroaromatization (MDA) were investigated. For this, MCM-22 (Mobil Composition of Matter-22) and its derivatives (MCM-36, ITQ-2, and delaminated MCM-22 in this study), having MWW type zeolite topologies but different zeolite structures, were applied. Although Mo-impregnated catalysts exhibited different catalytic activities and stabilities, interestingly, all Mo-impregnated catalysts showed similar intrinsic benzene-toluene formation rates per zeolitic pore at the initial time-on-stream regardless of the different structures. Moreover, investigation of spent Mo-impregnated catalysts revealed that the coke deposited inside the zeolitic channels (viz., internal coke) was the cause of catalyst deactivation. In particular, the preferential deposition of internal coke in the 12-membered-ring supercage can retard zeolite channel blocking and, consequently, catalyst deactivation. Thus, the amount of zeolitic pore volumes in the catalyst structure is a crucial factor that determines the catalytic activity and stability during MDA.

Improved methane dehydroaromatization reaction over Mo and Cr co-doped ZSM-5 catalyst

We prepared Mo and Cr co-loaded ZSM-5 (Mo/Cr/ZSM-5) by a sequential impregnation method and applied it to methane dehydroaromatization (MDA) reaction.

Enhanced catalytic performance of the hollow Mo/HZSM-5 nanocrystal for methane dehydroaromatization

Although Mo/HZSM-5 catalyst is widely used in the methane dehydroaromatization (MDA) reaction, the conventional microporous HZSM-5 with long diffusion path often causes the blockage of channels and pores by coke. In this work, a series of hollow HZSM-5 zeolites with different cavity sizes and tunable shell thickness were prepared by varying the alkali treatment time. After being loaded with Mo, the catalytic performances of the hollow catalysts were investigated in MDA reaction. Compared with conventional solid Mo/Z5 catalyst, the hollow Mo/Z5(x) catalysts exhibit higher CH4 conversion and C6H6 selectivity, which show an increasing trend with the increase of inner cavity size and decrease of zeolite shell thickness. Specifically, the hollow Mo/Z5(24) catalyst achieves the maximum CH4 conversion of 13.8% and C6H6 selectivity of 72%. It suggests that the hollow structure is conducive to enhance the accessibility of feed or intermediates to the Brønsted acid sites within zeolites and facilitates the rapid diffusion of the C6H6 from the intraframework channels rather than further polymerization to the coke. Furthermore, this novel structure endows stronger interaction between the Mo species and the acid sites, resisting agglomeration of Mo-species on external zeolite surface at high temperature. This research provides a new insight into exploiting a candidate catalyst for the MDA reaction.

Catalytic Routes for Direct Methane Conversion to Hydrocarbons and Hydrogen: Current State and Opportunities

Natural gas, the cleanest fossil fuel, is an abundant source of methane and expected to play an increasingly important role in powering the world’s economic growth over the energy transition of the coming decades. Methane has the potential to be a CO2-free feedstock to cogenerate hydrogen (H2) and added value “building-blocks” chemicals (e.g., olefins and aromatics) for petrochemistry. In this review, the two processes (i) the oxidative coupling of methane (OCM) for production of ethylene and (ii) the nonoxidative methane dehydroaromatization (MDA) producing hydrogen and benzene are discussed. Both routes convert methane directly into valuable products, an advantage over the several-steps syngas route. The performances of various a variety of catalysts reported during the last 25 years for OCM (MnNaW, La2O3, Li-MgO, etc.) and MDA (M/HZSM-5, M/TNU-9, M/IM-5, M/ITQ-2, M@SiO2, M@CeO2, TaH/SiO2, GaN/SBA15, single-site M@HZSM-5, bimetallic M-M′/HZSM-5, core–shell structures, M/Zr(SO4)2 with M = Mo, Fe, Pt) under similar reaction conditions are compared. The major drawbacks and the strategies used to mitigate the main challenges related with the performance of the catalysts in both OCM and MDA reactions are critically revealed. For instance, the overoxidation in the OCM is mitigated by optimizing of the operating conditions, using alternative oxidants, and the application of membrane reactor technology are discussed. In the MDA reaction, the major issue is the catalyst deactivation by coke formation and migration and sintering of metallic active phases. Strategies for robust catalysts, methods for mild coke removal, pretreatment under reductive atmosphere are presented. Approaches to improve aromatics yields over coke production by addition of promoters or co-feed reactants to the MDA catalysts are also discussed.

Acidity regulation for improved activity of Mo/HZSM-5 catalyst in methane dehydroaromatization

The Mo/HZSM-5 is a widely studied bifunctional methane dehydroaromatization (MDA) catalyst, and the acid site of zeolite is essential to the reaction process. In this study, the relationship between acid site control and MDA reaction performance is investigated. The Brønsted/Lewis acid sites have been toned by introducing promoters to the ZSM-5 zeolite. It shows that proper strong Brønsted acid sites are conducive to aromatic formation, while excessive Brønsted acid sites will lead to serious coke deposition. Thus, the MDA catalytic stability is further improved by passivation of partial Brønsted acid sites of Mo/HZSM-5 via coating Silicalite-1 on the catalyst surface. The optimized catalyst shows 95 % aromatic selectivity at initial with only 0.06 h−1 deactivation rate constant. The surface of HZSM-5 is reconstructed after hydrothermal treatment and the surface aluminum content is reduced. Moreover, the Silicalite-1 layer is beneficial to Mo species dispersion for preventing its aggregation and stabilizing the Mo-C active sites.

Quantified Database for Methane Dehydroaromatization Reaction

AbstractDirect conversion of methane to aromatics, known as methane dehydroaromatization (MDA) is a very promising one‐step conversion route that could significantly reduce CO2 emissions and simplify the process. There is an increasing interest in this reaction evident by a large number of literature and patents published so far. Although this review examined 500 scientific articles studying the MDA reaction, the ones considered to be suitable to create a quantified database did not exceed 150 articles. This resulted in more than 300 experimental studies carried out at different combinations of catalyst compositions, and operating conditions for the reaction and the regeneration phases. This work provides a quantitative database in a unified manner, which sets it apart from other literature reviews in the field. A set of definitions are used to quantify the cyclic operation of this complex reaction that included deactivation and regeneration. Most of the studies in this work utilize the commonly used Mo/ZSM‐5 based catalyst. Other zeolites such as Mo/IM‐5, Mo/MCM‐22, and Mo/SiO2 are also included in this database with different metal compositions. This database is limited to experiments carried out using fixed‐bed reactors to allow a fair comparison. The quantified database generated many valuable results. The validity of different proposed research claims is tested against all collected experimental studies to verify the effect of Mo content, reaction temperature, reaction space velocity, and particle size. Most of the reported claims aligned with the reported data; however, they were only satisfied within a very narrow range of conditions which demonstrates how critical the correlation between the parameters is on the catalytic performance. This work proposed a simple decay model to quantify the rate of deactivation for the different studies. Additionally, figures of merit were generated from the quantified database to guide future experiments in this field, map out the performances achieved so far, as well as create a benchmark to identify best‐performing catalysts and operating conditions. A global yield is defined by taking into account the effect of deactivation and regeneration. This factor proved to be valuable as a benchmark of the enhancement in the catalyst stability and productivity. Some of the studies achieved high values for both the initial yield and the global yield. One study used a continuous feeding of CO2 in the feed and added Mg to the Mo/ZSM‐5 catalyst. Another study added minor amounts of C2H4 and C2H6 to the feed which help reduce regeneration and increase the yield. Studies that used periodic‐switch feeding with H2, showed promising results as they maintained the performance for a longer time on stream for the same initial yield; thus, maximizing the global yield. A correlation analysis was performed on the MDA database to further statistically investigate the existence of correlations between input operating conditions (reaction temperature, reaction space velocity, and Mo. content) and the outputs (methane conversion, benzene yield, and decay factor). The absolute values of the correlation coefficients were categorized as weak [0–0.3], moderate [0.3–0.7], and strong [0.7–1]. The main highlights from this analysis are: (i) the conversion and yield are strongly correlated; (ii) Mo content has a nonlinear relation to the CH4 conversion. It has a positive moderate correlation for Mo content within the range of 1 to 3 wt % while a negative moderate correlation within the range of 4 to 6 wt %; (iii) space velocity and yield are strongly and negatively correlated; and (iv) there is a weak correlation between temperature and decay rate. The correlation analysis is efficient to analyze available data and provided similar conclusions as that of the knowledge‐based approach. However, much more valuable as it quantifies the strength of the correlation. Besides, it imposes the need to study the operating conditions space more comprehensively. The correlation matrix, on its own, does not always provide decisive conclusions as shown by the effect of Mo content on CH4 conversion due to the nonlinear relationship between the variables. The real value is reached when the correlation matrix analysis is combined with the prior expert knowledge.

Improved benzene selectivity for methane dehydroaromatization via modifying the zeolitic pores by dual-templating approach

Catalytic upgradation of methane into benzene and valuable chemicals over Mo/HZSM-5 has a great economic potential, yet it has serious drawback due to the obstacles in the micropores because of extensive coking at an elevated temperature during methane dehydroaromatization (MDA). Under such circumstances, it requires the design of micro/mesoporous ZSM-5, which has the advantages viz. enhanced product formation due to uniform Mo distribution inside the pores and lower carbon deposition because of improved mass transfer rate within the hierarchical pores. We infer herein a unique strategy to control the porous structures of ZSM-5 through a dual templating approach, employing both C6 and C12 -surfactants as porogen. The structural and morphological parameters of the synthesized ZSM-5 catalysts were investigated in detailed to ascertain the crystallinity, porosity, particle shape, size, Si/Al ratio, and acid strength which were further correlated with the physicochemical and catalytic properties of Mo modified HZSM-5 catalysts. After Mo impregnation, all the catalysts were evaluated for methane dehydroaromatization reaction. Compared with the conventional Mo/HZSM-5(C), C6 surfactant-treated hierarchically porous Mo/HZSM-5(H) showed the highest benzene formation rate (1.5 μmol/gcat. s) and longer stability of 270 min in TOS analysis. In contrary, C12 surfactant modified Mo/HZSM-5(D) is inferior towards MDA reaction (benzene formation rate: 0.5 μmol/gcat. s). We attribute to the difference in MDA reaction could be due to the hierarchically mesoporous feature of Mo/HZSM-5(H) with interconnected topology that precludes secondary reaction of coking from benzene and hence, contributing significant stability towards MDA reaction.

MoO3 Nanobelt-Modified HMCM-49 Zeolite with Enhanced Dispersion of Mo Species and Catalytic Performance for Methane Dehydro-Aromatization.

The methane dehydro-aromatization reaction (MDA) is a promising methane valorization process due to the conversion of methane to value-added aromatics (benzene, toluene and naphthalene). However, one of the major disadvantages of utilizing zeolite in MDA is that the catalyst is rapidly inactivated due to coke formation, which eventually causes the activity and aromatic selectivity to decrease. Consequently, the process is not conducive to large-scale industrial applications. The reasonable control of Mo site distribution on the zeolite surface is the key factor for partially inhibiting the coking of the catalyst and improving stability. Here, MoO3 nanobelts can be used for alternative Mo precursors to prepare MDA catalysts. Catalysts modified with MoO3 nanobelts present higher activity (13.4%) and benzene yield (9.2%) than those catalysts loaded with commercial MoO3.

Hierarchically modified Mo/HZSM-5 via alkali treatment for improved activity in methane dehydroaromatization

Considering direct utilization of natural gas, methane dehydroaromatization (MDA) is a promising alternative to produce valuable aromatic hydrocarbons. However, the major limitation of the process is the low catalyst stability and durability due to simultaneous coking. This contribution depicts the modifications of HZSM-5 support via controlled desilication approach using two different kinds of alkaline reagents at two different concentrations. The physicochemical characterizations revealed that after the alkaline treatment, morphological features are modified e.g., pore size distribution, Si/Al ratio, and acidity of HZSM-5. In the catalytic activity results, it was observed that among all the alkali modified catalysts, 0.1 M NaOH modified Mo/HZSM-5 exhibited highest benzene formation rate (2 μmol/gcat.s) as compared to pristine Mo/HZSM-5 (0.4 μmol/gcat.s) in MDA reaction over 90 min of time on stream. The exceptional catalytic performance was attributed to the incorporation of secondary mesopores which in turn facilitated the effective diffusion of Mo species in the pore interiors and subsequently cause the formation of higher number of Mo-anchored active sites. Further, the coke tolerance ability was enhanced, which might be due to the entrapment of coke species in the generated mesopores, thus leaving higher amount of accessible active sites for aromatization.

How does the balance of metal and acid functions on the benchmark Mo/ZSM-5 catalyst drive the Methane dehydroaromatization reaction?

Among all the proposed catalytic systems (new supports, synthesis post-treatment, change of transition metal, multi-metallic catalysts, etc.) for the methane dehydroaromatization, the initial Mo/ZSM-5 has remained one of the best suitable catalysts, despite its lack of deep understanding. The catalyst evolves throughout four successive stages: calcination, activation, induction, and deactivation. By studying the balance influence between the acid and metal functions throughout its lifetime, the molybdenum and carbon species could be localized, quantified, and identified as well as their roles. An optimal compromise was then established where the catalyst is composed of 4 wt% Mo with the highest possible acidity. Below these targets, the catalysts with minimal Mo content and low Brønsted acidity display poor catalytic performances, whereas zeolite amorphization occurs during the early stages of the reaction independently of the zeolite acidity once the Mo loading exceeds the optimal value.

Unraveling the Mo/HZSM-5 reduction pre-treatment effect on methane dehydroaromatization reaction

Reduction pre-treatment at different temperatures were performed over Mo/HZSM-5 system before methane dehydroaromatiztion reaction. We have shown the crucial effect of reduction temperature on the final catalytic performance. Outstanding improvement in the aromatics conversion has been attained. Thus, H2 formation form methane cracking reaction seems to be hindered for pre-treated catalysts. As a consequence, the deposition of coke in these samples appeared also notably suppressed. The optimum performance has been achieved for reduction pre-treatment at 550 ºC. For this temperature, we have observed that the fraction of reduced Mo species is higher.

How do the products in methane dehydroaromatization impact the distinct stages of the reaction?

Methane dehydroaromatization reaction at 700 °C over Mo/ZSM-5 involves numerous modifications of the molybdenum species from the catalyst preparation and throughout the catalyst lifetime, composed of 4 successive steps: calcination, activation, induction, and deactivation. A thorough kinetic study was undertaken with the aim to understand the transformation phenomena occurring on the catalyst during each stage of the reaction, using methane gas hourly space velocity per gram of catalyst (M-GHSV) from 1 to 29 LCH4 h−1 gcat−1. Here from, unexpected behaviors were observed, supported by molecular modeling results. MoO3 firstly reacts stoichiometrically during the calcination (ΔrH =0.86 eV) with bridged hydroxyl pairs yielding [Mo2O5]2+ species (calcination). Thereafter, [Mo2O5]2+ slowly reduces by methane to form [Mo2C2]2+ (activation). The latter converts methane to ethylene (EA= 1.49 eV), which dimerizes two times faster to butene through hydrocarbon pool catalysis rather than through Brønsted acid sites (induction). The catalyst deactivates through an inhibition effect of aromatics, which adsorb strongly onto [Mo2C2]2+ (ΔHads ~ 0.7 eV) (deactivation). The large amount of autogenous hydrogen produced at lower space velocity allows preventing the active species poisoning, leading to slower deactivation rate.