Sulfated hafnia as a support for Mo oxide: A novel catalyst for methane dehydroaromatization

Abedin, Ashraful; Kanitkar, Swarom; Bhattar, Srikar; Spivey, James J.

doi:10.1016/j.cattod.2019.02.021

Cited by 15 publications

(8 citation statements)

References 40 publications

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“…The low-temperature peak could be described as amorphous and oxidized “soft” coke, the medium-temperature peak to polymeric aromatic carbon, and the high-temperature peak to the ordered, graphitic “hard” coke. The formation of diverse carbon species in the DNMC reaction has been observed in Mo/ZSM-5 ( Liu H. et al, 2002 ; Ma et al, 2002 ; Song et al, 2014 ) and metal/sulfated zirconia catalysts ( Abedin et al, 2019 ; Abedin et al, 2019 ; Kanitkar et al, 2019 ) as well as in methane pyrolysis in the absence of any catalyst ( Gueret et al, 1995 ; Vander Wal et al, 2018 ; Singh et al, 2019 ; Wang et al, 2019 ). The H 2 co-fed DNMC condition in the presence of SCZO oxide apparently leads to an obvious increase in the soft coke on the Fe/SiO 2 catalyst, resulting in active DNMC reaction without obvious methane conversion drop or high coke selectivity.…”

Section: Resultsmentioning

confidence: 98%

Understanding the Impact of Hydrogen Activation by SrCe0.8Zr0.2O3−δ Perovskite Membrane Material on Direct Non-Oxidative Methane Conversion

Cheng

Sakbodin

et al. 2022

Front. Chem.

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Direct non-oxidative methane conversion (DNMC) converts methane (CH4) in one step to olefin and aromatic hydrocarbons and hydrogen (H2) co-product. Membrane reactors comprising methane activation catalysts and H2-permeable membranes can enhance methane conversion by in situ H2 removal via Le Chatelier's principle. Rigorous description of H2 kinetic effects on both membrane and catalyst materials in the membrane reactor, however, has been rarely studied. In this work, we report the impact of hydrogen activation by hydrogen-permeable SrCe0.8Zr0.2O3−δ (SCZO) perovskite oxide material on DNMC over an iron/silica catalyst. The SCZO oxide has mixed ionic and electronic conductivity and is capable of H2 activation into protons and electrons for H2 permeation. In the fixed-bed reactor packed with a mixture of SCZO oxide and iron/silica catalyst, stable and high methane conversion and low coke selectivity in DNMC was achieved by co-feeding of H2 in methane stream. The characterizations show that SCZO activates H2 to favor “soft coke” formation on the catalyst. The SCZO could absorb H2in situ to lower its local concentration to mitigate the reverse reaction of DNMC in the tested conditions. The co-existence of H2 co-feed, SCZO oxide, and DNMC catalyst in the present study mimics the conditions of DNMC in the H2-permeable SCZO membrane reactor. The findings in this work offer the mechanistic understanding of and guidance for the design of H2-permeable membrane reactors for DNMC and other alkane dehydrogenation reactions.

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Section: Resultsmentioning

confidence: 98%

Understanding the Impact of Hydrogen Activation by SrCe0.8Zr0.2O3−δ Perovskite Membrane Material on Direct Non-Oxidative Methane Conversion

Cheng

Sakbodin

et al. 2022

Front. Chem.

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“…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 Abedin et al focused on testing the reaction over Mo-SH catalyst for a temperature range of 600-700 °C. [22] The reaction was tested for 15 hours, during which methane conversion decreased rapidly for the higher temperature in the testing range (700 °C) during the first 5 h of the reaction and then maintained its stability for the remaining 10 h. Whereas for 650 °C reaction temperature, the conversion gradually decreased for about 10 h but then became steady at low conversion for the last 5 h of reaction time. However, for a reaction temperature of 600 °Cthe conversion is maintained for ChemCatChem about 8 h of the reaction time, however, it was the lowest maximum conversion achieved.…”

Section: Effect Of Temperaturementioning

confidence: 99%

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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“…It has been reported that the sulfurized form of ZrO 2 known as sulfated zirconia (SZ), actively helps the active metal sites to stabilize on the oxide support at a greater degree [29,33]. SZ is a well-known solid acid possessing surface H + ions [29,34], which can react with some of the excess methyl radicals and remove these in the form of benzene and heavier hydrocarbons as valuable side products [15,35].…”

Section: Introductionmentioning

confidence: 99%

Direct conversion of methane to C2 hydrocarbons using W supported on sulfated zirconia solid acid catalyst

2020

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Sulfated hafnia as a support for Mo oxide: A novel catalyst for methane dehydroaromatization

Cited by 15 publications

References 40 publications

Understanding the Impact of Hydrogen Activation by SrCe0.8Zr0.2O3−δ Perovskite Membrane Material on Direct Non-Oxidative Methane Conversion

Understanding the Impact of Hydrogen Activation by SrCe0.8Zr0.2O3−δ Perovskite Membrane Material on Direct Non-Oxidative Methane Conversion

Quantified Database for Methane Dehydroaromatization Reaction

Direct conversion of methane to C2 hydrocarbons using W supported on sulfated zirconia solid acid catalyst

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