Mechanism Of Catalyst Deactivation Research Articles

Electrocatalysis in Solid Oxide Fuel Cells and Electrolyzers.

Interest in energy-to-X and X-to-energy (where X represents green hydrogen, carbon-based fuels, or ammonia) technologies has expanded the field of electrochemical conversion and storage. Solid oxide electrochemical cells (SOCs) are among the most promising technologies for these processes. Their unmatched conversion efficiencies result from favorable thermodynamics and kinetics at elevated operating temperatures (400-900 °C). These solid-state electrochemical systems exhibit flexibility in reversible operation between fuel cell and electrolysis modes and can efficiently utilize a variety of fuels. However, electrocatalytic materials at SOC electrodes remain nonoptimal for facilitating reversible operation and fuel flexibility. In this Review, we explore the diverse range of electrocatalytic materials utilized in oxygen-ion-conducting SOCs (O-SOCs) and proton-conducting SOCs (H-SOCs). We examine their electrochemical activity as a function of composition and structure across different electrochemical reactions to highlight characteristics that lead to optimal catalytic performance. Catalyst deactivation mechanisms under different operating conditions are discussed to assess the bottlenecks in performance. We conclude by providing guidelines for evaluating the electrochemical performance of electrode catalysts in SOCs and for designing effective catalysts to achieve flexibility in fuel usage and mode of operation.

Recent progress in the deactivation mechanism of zeolite catalysts in methanol to olefins

Recent progress in the deactivation mechanism of zeolite catalysts in methanol to olefins

Ferric sludge derived pyrolyzed-hydrochar supported iron catalysts for catalytic cracking of toluene

Effective treatment of ferric sludge in an eco-friendly method is key to the feasibility of Fenton technology in pollution treatment, contributing to the realization of the “dual-carbon” strategic objectives. In this study, Fe-loaded pyrolyzed-hydrochar catalysts were prepared using simple one-pot hydrothermal carbonization (HTC) method with ferric sludge as the precursor, which greatly reduced the energy and time consumption on the preparation of the sludge derived catalyst. At 800 °C with a reaction time of 20 min, all catalysts showed high toluene removal performance (>60 %) and produced H2-rich syngas (H2 > 90 %). In particular, the catalyst prepared by HNO3-assisted HTC (HNC) presented the highest toluene removal efficiency and H2 yield, 77.52 ± 3.36 % and 11.12 ± 0.66 mol%, respectively. Additionally, the sources of carbon deposits and the interaction between the active site and carbon deposits were analyzed in detail by DFT to reveal the catalytic activity and deactivation mechanism of catalyst. The results showed that the adsorption energy of C generated from methyl on different Fe phases was lowest (the adsorption energy of C was −8.79 eV for Fe, −5.28 eV for Fe2O3, and −4.70 eV for Fe3O4), suggesting that the adsorption of C on catalyst was the main reason for the formation of carbon deposits. The lowest adsorption energy of the metallic Fe phase for C indicated that Fe0 was coated by carbon deposits during toluene catalytic cracking, which hampered catalytic activity. These results are of great significance for optimizing the preparation of Fe-loaded carbonaceous catalysts and the regulation of Fe active phase.

Study on performance and water deactivation mechanism of low-temperature denitrification catalyst in high-humidity flue gas

To address water poisoning issues of Selective Catalytic Reduction (SCR) denitrification catalysts in high-humidity flue gas, this study synthesized catalysts including Co–Mn/TiO2, Co–Mn–Ce/TiO2, Co–Mn–Ce/TiO2–Si, and Co–Mn–Ce/TiO2 (stearic acid). The activity of the catalysts at low temperatures and high humidity (140–180 °C, 0–35 vol%) was evaluated. Furthermore, the characterization of the most effective of these (the Co–Mn–Ce/TiO2 (stearic acid) catalyst) was performed. The results revealed distinct mechanisms of water poisoning under high- and low-humidity conditions. Under high humidity, the dissolution of water molecules affected the catalyst structure and thereby, resulted in reduced dispersibility of the active components. Conversely, at low humidity, the dissolution effect was relatively marginal, which resulted in a more stable catalyst structure. High-humidity flue gas reduced the catalyst acidity and thereby, hindered NH3 adsorption. Meanwhile, low-humidity flue gas had a lesser impact on the catalyst. High-humidity flue gas hinders the conversion of Co ions in Co–Mn–Ce/TiO2（stearic acid ) to higher oxidation states and reduced Ce4+ to Ce3+. This resulted in decreased Mn4+ on the catalyst surface and reduced chemisorbed oxygen (Oa). This, in turn, affected the adsorption and storage of oxygen by the catalyst.

Insights into Fischer–Tropsch catalysis: current perspectives, mechanisms, and emerging trends in energy research

Fischer–Tropsch (FT) synthesis is an important module for the production of clean and sustainable fuels and chemicals, making it a topic of considerable interest in energy research. This mini-review covers the current literature on FT catalysis and offers insights into the primary products, the nuances of the FT reaction, and the product distribution, with particular attention to the Anderson–Schulz–Flory distribution (ASFD) and known deviations from this fundamental concept. Conventional FT catalysts, particularly Fe- and Co-based catalysis systems, are reviewed, highlighting their central role and the influence of water and water–gas shift (WGS) activity on their catalytic behavior. Various mechanisms of catalyst deactivation are also investigated, and the high methanation activity of Co-based catalysts is illustrated. To make this complex field accessible to a broader audience, we explain conjectured reaction mechanisms, namely, the carbide mechanism and CO insertion. We discuss the complex formation of a wide range of products, including olefins, kerosenes, branched hydrocarbons, and by-products such as alcohols and oxygenates. The article goes beyond the traditional scope of FT catalysis by addressing topics of current interest, including the direct hydrogenation of CO2 for power-to-X applications and the use of bifunctional catalysts to produce tailored FT products, most notably for the production of sustainable aviation fuel (SAF). This mini-review provides a holistic overview of the evolving landscape of FT catalysts and is aimed at both experienced researchers and those new to the field while covering current and emerging trends in this important area of energy research.

Unraveling the deactivation mechanism of Co-LiH composite catalyst for ammonia synthesis at milder conditions

An efficient ammonia synthesis catalyst that operates under mild conditions has been a long-cherished goal in heterogeneous catalysis. The challenges associated with low-temperature ammonia synthesis arise from both the activation of inert N2 molecules and the presence of scaling relations between reactant dissociation and intermediate adsorption energies. Transition metals-metal hydride (TM-MH) composite catalysts have shown promise to overcome these challenges as both TM and MH actively participate in the reaction, enabling improved ammonia synthesis rates at lower temperatures (150 ºC). Considering this prospect, two types of Co-LiH catalyst were synthesized by ball-milling of precursors (CoCl2 and LiH- denoted as Co-LiH(rxn)) and pure components (Co and LiH- denoted as Co-LiH(pur)), and their catalytic activity was evaluated at several reaction conditions to investigate the stability for long-term operation. Co-LiH(rxn) was found to deactivate in less than 150 h whereas Co-LiH(pur) displayed a continuous production although the synthesis rate was 3 times lower than the former. Structural characterization techniques, such as XRD, SEM, and TEM were used, and it was found that Co metal in the FCC phase was primarily sintered due to its small particle size in the fresh catalyst. Temperature-programmed desorption (TPD) test on the spent Co-LiH(rxn) catalyst also displayed an ammonia release profile similar to that of LiNH2 decomposition, which confirms the presence of ammonia in the spent catalyst structure. Hence, another major finding is speculated that irreversible ammonia absorption by LiH at the target ammonia reaction conditions contributes to the deactivation of the catalyst and the formation of intermediate compounds that are required for continuous ammonia generation in this composite catalyst.

Recent Advances in Coke Management for Dry Reforming of Methane over Ni-Based Catalysts

The dry reforming of methane (DRM) is a promising method for controlling greenhouse gas emissions by converting CO2 and CH4 into syngas, a mixture of CO and H2. Ni-based catalysts have been intensively investigated for their use in the DRM. However, they are limited by the formation of carbonaceous materials on their surfaces. In this review, we explore carbon-induced catalyst deactivation mechanisms and summarize the recent research progress in controlling and mitigating carbon deposition by developing coke-resistant Ni-based catalysts. This review emphasizes the significance of support, alloy, and catalyst structural strategies, and the importance of comprehending the interactions between catalyst components to achieve improved catalytic performance and stability.

Influence of Impurities in the Chemical Processing Chain of Biomass on the Catalytic Valorisation of Cellulose towards γ-Valerolactone

The conversion of lignocellulosic biomass to valuable chemicals such as levulinic acid and γ-valerolactone is a promising approach for achieving a sustainable circular economy. However, the presence of impurities during the stepwise chemical processing chain of the biomass feedstock can significantly impact both the hydrolysis and hydrogenation steps implemented to convert the cellulosic feedstock to levulinic acid and further to γ-valerolactone, respectively. This review article explores the effects of those impurities by classifying them into two groups, namely endogenous and exogenous types, based on whether they originate directly from the raw lignocellulosic biomass or arise during its multi-step chemical processing. Endogenous impurities include heavy metals, alkali metals, alkaline earth metals, proteins, and side products from the downstream treatment of cellulose, while exogenous impurities are introduced during physical pre-treatments such as ball milling or during the hydrolysis step, or they might originate from the reactor setup. The specific catalyst deactivation by carbonaceous species such as humins and coke is considered. The mechanisms of impurity-induced catalyst deactivation and by-product formation are thoroughly discussed. Additionally, strategies for minimizing the detrimental effects of impurities on biomass conversion and enhancing catalytic efficiency and stability are also proposed.

Study on the deactivation and regeneration mechanism of Cu-Al catalyst in the hydrogenation of diethyl oxalate

The hydrotreating of dialkyl oxalate to ethylene glycol process as a representative technology pathway for the efficient and clean utilization of coal has gained wide attention in the context of carbon neutrality. The deactivation mechanism and catalyst regeneration mechanism of the hydrotreating process pathway of diethyl oxalate were systematically investigated by experimental techniques and kinetic simulations using a Cu-Al catalyst as a model catalyst in the hydrogenation reaction with diethyl oxalate as a probe molecule, and a reliable deactivation mechanism was obtained. The weaving properties of the fresh and used catalyst samples were systematically investigated by XRD, TEM, GC-MASS, BET, and O2-TPO. Characterization data indicate that the catalyst deactivation was not caused by an increase in the size of the Cu nanoparticles and a change in the physical structure of the catalyst. The deactivation was triggered by the polymer molecules produced by dehydration, polycondensation and aromatization of ethyl glycolate molecules in the acidic sites, which covered the active sites and blocked the catalyst pores. The regeneration behavior under different atmospheres showed that regeneration under H2 atmosphere is unable to restore the reaction performance of the deactivated catalyst to the original level, while the activity of the regenerated catalyst under air atmosphere significantly exceeds that of the fresh catalyst.

Recent progress on mechanisms, principles, and strategies for high‐activity and high‐stability non‐PGM fuel cell catalyst design

AbstractThe commercialization of a polymer membrane H2–O2 fuel cell and its widespread use call for the development of cost‐effective oxygen reduction reaction (ORR) nonplatinum group metal (NPGM) catalysts. Nevertheless, to meet the requests for the real‐world fuel cell application and replacing platinum catalysts, it still needs to address some challenges for NPGM catalysts regarding the sluggish ORR kinetics in the cathode and their poor durability in acidic environment. In response to these issues, numerous efforts have been made to study NPGM catalysts both theoretically and experimentally, developed these into the atomically dispersed coordinated metal–nitrogen–carbon (M–N–C) form over the past decades. In this review, we present a comprehensive summary of recent advancements on NPGM catalysts with high activity and durability. Catalyst design strategies in terms of optimizing active‐site density and enhancing catalyst stability against demetalization and carbon corrosion are highlighted. It is also emphasized the importance of understanding the mechanisms and principles behind those strategies through a combination of theoretical modeling and experimental work. Especially, further understanding the mechanisms related to the active‐site structure and the formation process of the single‐atom active site under pyrolysis conditions is critical for active‐site engineering. Optimizing the active‐site distance is the basic principle for improving catalyst activity through increasing the catalyst active‐site density. Theoretical studies for the catalyst deactivation mechanism and modeling stable active‐site structures provide both mechanisms and principles to improve the NPGM catalyst durability. Finally, currently remained challenges and perspectives in the future on designing high‐performance atomically dispersed NPGM catalysts toward fuel cell application are discussed.

Structure characterization of aged automobile exhaust catalysts using electron probe microanalysis

BackgroundDriven by emission regulations, the technology of emission control catalysts has been under increasing need for development. Understanding the deactivation mechanism of aged or spent automobile exhaust catalysts is the key to extending their service lifetime. However, the lack of comprehensive microstructural characterization results in an incomplete understanding of their physicochemical properties. Deactivation mechanism of automobile exhaust catalysts is a considerably complex phenomenon, it can be classified into three groups based on its origin: thermal sintering, chemical poisoning and mechanical deactivation. ResultsIn this study, an aged high-mileage automobile exhaust catalyst with Pd and Rh active phases supported on a cerium zirconium oxide doped alumina coating on cordierite was analysed; six consecutive monolithic blocks along the inlet to the outlet of the aged catalyst were extracted, and the corresponding metallographic samples were fabricated using the vacuum impregnation resin method. The purpose of this study was to accurately characterize the different regions of the monolith via electron probe microanalysis and to infer potential causes of catalyst deactivation. Two major causes of deactivation were found: (1) aggregation and alloying of precious-metal particles caused by thermal sintering and (2) chemical poisoning caused by sulphur and phosphorus. Other mechanisms, such as mechanical degradation, which mainly manifests as the loss or wear of the washed coating, were also found to be involved in deactivation. Additionally, the catalytic activity tests showed a considerable decrease in the aged catalyst. The poison concentration trends in the washcoat indicated that P is detrimental to CO oxidation, while S accumulation affects propane oxidation. SignificanceThis analysis method can be of substantial practical significance in developing advanced washcoat materials. Meanwhile, it has great potential in the washcoat analysis of honeycomb-shaped monolithic catalyst, such as natural gas catalyst, diesel vehicle oxidation catalyst and other honeycomb catalysts applied in chemical industry.

Functionalized Coal Fly Ash Is an Efficient Catalyst for Synthesizing Furfural from Xylose at a Low Catalyst Load

In this study, coal fly ash was functionalized, using a simple one-step process (loading with Al3+ and sulfonation), to yield a solid acid catalyst (S/Al-CFA) with strong acid sites. The catalyst was then used to produce furfural from xylose in a biphasic system (H2O(NaCl)/tetrahydrofuran). The furfural yield reached 82% at 180 °C–60 min with catalyst/xylose ratio of 0.2:1.0 (w/w). With the reaction completed, all of the components could be effectively separated, and the furfural was 97.6% pure. The cycle and regeneration of the catalyst were evaluated, and the catalyst deactivation mechanism was investigated.

Partial hydrogenation of 1,3-butadiene over nickel with alumina and niobium supported catalysts

The hydrogenation of 1,3 butadiene (BD) is an important industrial process that is generally used to generate butenes and aromatics, which are important petrochemicals and constituents of transportation fuels. Ni-based catalysts have gained increasing interest in the academic community and industry because of their superior hydrogenation activity, ability to exist in multiple oxidation states and most importantly, affordability compared to the less-abundant precious metal catalysts. In this work, we explore the ability of alumina (Al2O3) and niobia (Nb2O5) as catalytic supports for Ni as the active metal since they have shown excellent potential for hydrogenation of alkenes. Specifically, we compare the metal-support interactions, which disperse Ni effectively throughout the catalyst surface, textural and pore parameters, Ni crystallite size, surface morphology, elemental composition, coke formation and tendencies of both catalysts through extensive characterization techniques such as H2-temperature programmed reduction (H2-TPR), N2-adsorption–desorption, X-ray diffraction (XRD), scanning electron microscopy combined with electron-dispersive spectra (SEM-EDS), and thermal analysis of the spent catalysts. Limited reports on the use of niobium oxides and alumina as supports for Ni in the partial hydrogenation of BD prompted us to explore this literature gap. The catalytic reactions were conducted using a quartz tube reactor between a temperature range of 50 and 400 °C at regular intervals of 50 °C under operating pressures of 1 atm. A comprehensive analysis of the products from the reaction was carried out using gas-chromatography with mass spectrometry (GC–MS) detector and corroborated these results with those from infrared spectroscopy (FTIR). Reaction mechanisms of aliphatic and aromatic product formation were proposed and verified with literature and our own characterization results. The tests on the spent catalysts also helped to reveal the extent of deactivation of the catalysts due to carbon deposition. Mechanisms of catalyst deactivation and nature of carbonaceous deposits were explored and elaborate scientific reasoning was provided as to why Ni/alumina showed better performance in terms of product yields and BD conversion. Ways to mitigate the harmful effects of coke formation and its deposition are also discussed. The novelty of our work is that a comprehensive comparison of the performance of Ni/alumina and Ni/niobia for hydrogenation of BD along with extensive discussions on coke formation, its chemical nature and proposed reaction chemistry based on obtained characterization results of the catalysts and the products of BD hydrogenation has not been done before for this system. In this way, we show the low-temperature conversion of BD represents an economically efficient and relatively simple method to convert toxic, carcinogenic and environmentally hazardous BD into high-value products using low-cost and chemically efficient catalysts.

Manganese as a structural promoter in silica-supported cobalt Fischer-Tropsch catalysts under simulated high conversion conditions

Understanding the deactivation mechanism of cobalt-based Fischer-Tropsch catalysts is of significant practical importance. Herein, we explored the role of manganese as a structural promoter on silica-supported cobalt nanoparticles under simulated high CO conversion conditions, i.e., high relative humidity. The structural changes in cobalt dispersion and oxidation state were followed by in situ Mössbauer emission spectroscopy. Adding manganese oxide to silica-supported cobalt enhanced the dispersion of metallic cobalt in the reduced catalysts. This higher cobalt dispersion, however, led to a stronger tendency of cobalt silicate formation under humid conditions. Without manganese, the cobalt particles sintered, and the larger ones were prone to transformation into cobalt carbide under high conversion conditions. As such, silica is not preferred as a support for practical FTS.

Appraisal of agroforestry biomass wastes for hydrogen production by an integrated process of fast pyrolysis and in line steam reforming

The pyrolysis and in line steam reforming of different types of representative agroforestry biomass wastes (pine wood, citrus wastes and rice husk) was performed in a two-reactor system made up of a conical spouted bed and a fluidized bed. The pyrolysis step was carried out at 500 °C, and the steam reforming at 600 °C with a space time of 20 gcatalyst min gvolatiles−1 and a steam/biomass ratio (S/B) of 4. A study was conducted on the effect that the pyrolysis volatiles composition obtained with several biomasses has on the reforming conversion, product yields and H2 production. The different composition of the pyrolysis volatiles obtained with the three biomasses studied led to differences in the initial activity and, especially, in the catalyst deactivation rate. Initial conversions higher than 99% were obtained in all cases and the H2 production obtained varied in the 6.7–11.2 wt% range, depending on the feedstock used. The stability of the catalysts decreased depending on the feedstock as follows: pine wood ≫ citrus waste > rice husk. A detailed assessment of the mechanisms of catalyst deactivation revealed that coke deposition is the main cause of catalyst decay in all the runs. However, the volatile composition derived from the pyrolysis of citrus waste and rice husk involved the formation of an encapsulating coke, which severely blocked the catalyst pores, leading to catalyst deactivation during the first minutes of reaction.

Temperature Stable Ion Exchange Resins as Catalysts for the Manufacturing of Vitamin Precursors by Aldol Reaction.

This study explores the potential of robust, strongly basic type I ion exchange resins-specifically, Amberlyst® A26 OH and Lewatit® K 6465-as catalysts for the aldol condensation of citral and acetone, yielding pseudoionone. Emphasis is placed on their long-term stability and commendable performance in continuous operational settings. The aldol reaction, which traditionally is carried out using aqueous sodium hydroxide as the catalyst, holds the potential for enhanced sustainability and reduced waste production through the use of basic ion exchange resins in heterogeneous catalysis. Density Functional Theory (DFT) calculations are employed to investigate catalyst deactivation mechanisms. The result of these calculations indicates that the active sites of Amberlyst® A26 OH are cleaved more easily than the active sites of Lewatit® K 6465. However, the experimental data show a gradual decline in catalytic activity for both resins. Batch experiments reveal Amberlyst® A26 OH's active sites diminishing, while Lewatit® K 6465 maintains relative consistency. This points to distinct deactivation processes for each catalyst. The constant count of basic sites in Lewatit® K 6465 during the reaction suggests additional factors due to its unique polymer structure. This intriguing observation also highlights an exceptional temperature stability for Lewatit® K 6465 compared to Amberlyst® A26 OH, effectively surmounting one of the prominent challenges associated with the utilization of ion exchange resins in catalytic applications.

Electrochemical Ethylamine Dehydrogenation to Acetonitrile on Platinum-Based Catalysts

Hydrogen storage is a crucial link between green hydrogen generation by water electrolysis and hydrogen application in fuel cells. We very recently reported a new, electrochemical ethylamine/acetonitrile redox method for hydrogen storage [1]. This method realizes hydrogen uptake by pairing acetonitrile hydrogenation to ethylamine reaction (AHR) on cathode and hydrogen oxidation reaction (HOR) on anode, and realizes hydrogen release by pairing ethylamine dehydrogenation to acetonitrile reaction (EDR) on anode and hydrogen evolution reaction (HER) on cathode. With 8.9 wt.% theoretical storage capacity and ambient reaction conditions being demonstrated in the study, this method shows a great potential to advance hydrogen storage technology and meet the DOE target. One remaining challenge of this method was a rapid activity decay of the used commercial platinum catalyst (Pt/C) in the EDR, which caused a long-term durability issue.In this work, we report our fundamental study of Pt catalyst deactivation mechanism in EDR and the discovery of new Pt-based catalysts. Attenuated total reflection infrared spectroscopy (ATR-IR) was employed for characterizing working catalyst surface under reactive conditions. Partially dehydrogenated intermediate species were observed to generate on Pt surface, which strongly adsorbed and caused an accumulation and blockage of the active sites. Interestingly, the catalyst showed a self-cleaning property where the intermediates can be hydrogenated back to ethylamine and released from Pt surface below 0 V vs. RHE. A group of Pt-Ni alloy catalysts were prepared and investigated the composition effect in this reaction, among which Pt3Ni exhibited 75% higher activity and significantly improved stability compared to Pt. ATR-IR experiments showed that the accumulation of intermediates on the Pt3Ni surface was much slower than that on the Pt, attributed to weakened adsorption. This work provides mechanistic insights into EDR reaction pathways and the cause of Pt catalyst deactivation and offers a Pt alloy strategy for active and stable catalyst design.[1] Wu, D.; Li, J.; Yao, L.; Xie, R.; Peng, Z. ACS Appl. Mater. Interfaces 13, 55292 (2021).

Influence of oxidative conditions on the deactivation of an equilibrium FCC catalyst in the fast pyrolysis of HDPE in a conical spouted bed reactor

This study approaches the continuous catalytic fast pyrolysis of plastics in a flexible and original technology, i.e., a conical spouted bed reactor equipped with fountain confiner and draft tube. The catalyst is an inexpensive equilibrium fluid catalytic cracking (FCC) one. Moreover, operation under oxidative conditions is proposed to solve heat supply to the pyrolysis reactor, as a previous study revealed a remarkable difference in the performance of the cracking catalyst when pyrolysis was carried out under inert (conventional) and oxidative conditions. Therefore, the aim of this paper is to assess the role played in the catalyst stability and deactivation mechanism by the presence of air in the reaction environment. A comparative study has been conducted by operating in long continuous runs under the same conditions (550 °C and a space time of 15 gcatalyst min gHDPE−1) in inert and oxidative atmospheres, i.e., equivalence ratios (ER) of 0 and 0.2, respectively. The evolution of product distribution with time on stream was evaluated. Moreover, samples of catalysts were taken from the reactor at different reaction times to correlate catalyst performance with the deactivated catalyst properties, and therefore progress in the understanding of the deactivation mechanism. The amount and nature of the coke deposited on the catalyst and its influence on catalyst properties was ascertained using thermogravimetry (TG-TPO), Raman spectroscopy, and NH3 and N2 adsorption–desorption techniques. The operation under oxidative conditions improved product distribution, with higher yields of light olefins. Moreover, catalysts activity and stability were also enhanced under oxidative conditions. Therefore, the results obtained involve a step forward towards the scaling up of plastics continuous catalytic pyrolysis.

Shifts in catalyst deactivation mechanisms as a function of surface coverage during Friedel-Crafts acylation in zeolites

The production of commodity chemicals from renewable resources is often accompanied by rapid catalyst deactivation rates. An important example is direct Friedel Crafts acylation, which can yield a range of valuable products from surfactants to renewable transportation fuels. Furanic acyl acceptors are among the most intriguing and promising possible acceptors; however, they undergo self-coupling reactions in the presence of Brønsted acid surface sites leading to rapid catalyst deactivation. In this contribution, we study 2-methylfuran acylation with acetic acid over HZSM-5 catalysts at temperatures ranging from 160 to 240 °C, revealing the remarkable shift in deactivation behavior as a function of surface coverage of acetic acid. We reveal that a surface saturated with acetic acid lowers the deactivation rate by blocking the direct access of furanic species to surface sites. However, on surfaces fully saturated with carboxylic acids, deactivation is revealed to proceed via reactions between adsorbed products with gas phase methylfuran reactants.

The properties of ethylamine dehydrogenation and electrolysis using platinum catalyst for efficient, ambient hydrogen production

Hydrogen serves as an important, clean energy carrier, which, however, has a challenge for its storage. Herein, we report the properties of ethylamine dehydrogenation (EDH) to acetonitrile under half-cell conditions and ethylamine electrolysis under full-cell conditions for fast, energy-efficient, ambient hydrogen release, which would couple with spontaneous acetonitrile hydrogenation to ethylamine for hydrogen uptake to realize hydrogen storage cycles under mild conditions. The influences of different reaction parameters on the EDH and ethylamine electrolysis properties are examined. The catalyst deactivation and regeneration mechanisms are investigated with aid of in situ ATR-FTIR characterizations. As fast as 309 μmol/h H2 production rate with 97% faradaic efficiency (FE) from cathode and acetonitrile production with 100% FE from anode are achieved with a low 0.6 V cell voltage, demonstrating a great potential of this new electrochemical approach for hydrogen storage application.