Methane Aromatization in a Fluidized Bed Reactor: Parametric Study

Lasobras, Javier; Soler, J.; Herguido, J.; Menéndez, M.; Jimenez, Alonso; Silva, Mariana da; Franco, Marı́a José; Barrio, Izaskun; Lázaro, Jesús

doi:10.3389/fenrg.2019.00008

Cited by 5 publications

(4 citation statements)

References 36 publications

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“…The work of Lasobras et al. tested different parameters that influence the MDA reaction, which included a study on the reaction temperature [23] . The reaction took place in a fluidized bed, and the catalyst used is Mo/ZSM‐5/bentonite.…”

Section: Resultsmentioning

confidence: 99%

“…The third filter "F3" removes all of the experiments that are not performed under space velocities in the range (1500-2000) ml/g cat /h. The fourth filter "F4" removes all of the experiments that are not performed using a catalyst with a Si/Al ratio in the range (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). A slight trend can be seen after applying all the filters, which shows that the catalyst performance is better in terms of the methane conversion and the benzene yield at Mo content higher than 5 wt %.…”

Section: Effect Of Mo and Si/al Ratiomentioning

confidence: 99%

“…The work of Lasobras et al tested different parameters that influence the MDA reaction, which included a study on the reaction temperature. [23] The reaction took place in a fluidized bed, and the catalyst used is Mo/ZSM-5/bentonite. The temperature range chosen was 675-725 °C, and the optimum reaction temperature was selected based on maximizing the methane conversion and benzene selectivity.…”

Section: Effect Of Temperaturementioning

confidence: 99%

“…Studies done by Skutil & Taniewski, Abedin et al, and Jeong et al showed that a greater space velocity leads to a decrease in the maximum conversion that can be achieved by the catalyst, benzene selectivity, and total amount of coke formed along with a shorter induction period. [13,20,23] The range of space velocities that have been studied for the MDA reaction is very large. It can go as low as 750 ml/g/h up to 60,000 ml/g/ h. Nevertheless, at space velocities higher than 5000 ml/g/h, the maximum achievable methane conversion is very low.…”

Section: Effect Of Space Velocitymentioning

confidence: 99%

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Quantified Database for Methane Dehydroaromatization Reaction

et al. 2022

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Direct 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.

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Section: Resultsmentioning

confidence: 99%

Section: Effect Of Mo and Si/al Ratiomentioning

confidence: 99%

Section: Effect Of Temperaturementioning

confidence: 99%

Section: Effect Of Space Velocitymentioning

confidence: 99%

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Quantified Database for Methane Dehydroaromatization Reaction

et al. 2022

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Nature of the interactions between Fe and Zr for the methane dehydroaromatization reaction in ZSM-5

Denardin

Muniz

Perez‐Lopez

2020

Journal of Molecular Structure

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Methane is an abundant feedstock with steadily increasing availability due to recent technological developments. The methane dehydroaromatization reaction is a possible chemical route to convert methane into benzene, which has a higher energy density. This reaction presents thermodynamic limitations on benzene production, while coke formation is favored. In a previous work, the combination of Fe and Zr in ZSM-5 catalysts showed promising results regarding selective prevention of coke deposition, favoring benzene production. In this work, FeeZr/ZSM-5 catalysts were synthesized with varying Zr/Fe ratios and characterized with XRD, BET, TPR-H 2 , TPD-NH 3 , Raman and TEM in order to better understand the effects of Zr over Fe. DFT calculations were used to investigate the interactions between Zr and Fe within the ZSM-5 structure. Experimental and computational results show that mixed FeeZr oxides were not formed, and ZrO 2 and Fe 2 O 3 oxides were deposited on the ZSM-5. The Zr was found to promote Fe 2 O 3 reduction to Fe 0 and deposit in the Brønsted acid sites of the zeolite, which could explain the decreased induction period and coke deposition in FeeZr/ZSM-5 catalysts for methane dehydroaromatization observed in previous works.

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