Search

The Special Issue "Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Catalytic Materials" contains 14 peer-reviewed research articles and 1 review paper. The articles focus on the field of homogeneous and heterogeneous catalysis, with an emphasis on synthesis, physico-chemical characterizations, and applications in environmental protection reactions. The studies provide detailed explanations of reactions in gas and liquid phases using different types of reactors and analyze reaction products using various techniques. The research papers also describe the synthesis and characterization of different types of catalytic materials, contributing to interdisciplinary knowledge in the field. The issue highlights ongoing efforts to develop more efficient and versatile catalysts for industrial and environmental applications. [Extracted from the article]

Those catalysts are engineered for conventional thermal oxidation catalysis but also sequential adsorption-catalytic, photocatalytic, and plasma-catalytic oxidation processes. This Special Issue collects three reviews, eight articles, and two communications related to the design of catalysts for environmental applications, such as the transformation of several pollutants into harmless or valuable products. The authors showed that the addition of Au improved the activity of the Al SB 2 sb O SB 3 sb -supported Cu and Pt catalysts and had a positive effect on SO SB 2 sb production by widening its production window, especially for the platinum-based catalyst. [Extracted from the article]

Abstract: Preparation of Pt–Ru electrocatalyst was successfully performed on carbon paper by one-step co-electrodeposition method. Particle size and density were controlled by deposition potential and time. Coverage of the catalysts deposited on the carbon paper was significantly related to the composition of the electrolyte. Catalyst particles were characterized by field emission scanning electron microscopy (FESEM), and the crystal structure was analyzed by X-ray diffraction (XRD). Bulk and surface compositions of the electrocatalysts were obtained by inductively coupled plasma mass spectroscopy (ICPMS) and X-ray photoelectron spectroscopy (XPS), respectively. The Pt–Ru electrocatalyst with a surface molar ratio of 51.7 Pt and 48.3 Ru showed the highest catalytic activity for methanol oxidation and the strongest tolerance against carbon monoxide poisoning. [Copyright &y& Elsevier]

Direct liquid fuel cells are very appealing alternatives for fighting climate change, particularly in the field of personal mobility solutions. This is especially true for direct methanol fuel cells (DMFCs) that use and burn safe fuels that are readily available from sustainable sources using well-established C1 chemistry. However, DMFCs also have some serious competitive disadvantages, like the high cost of the noble metal catalysts, the difficulties of the catalyst application, and the poisoning of the catalyst due to carbon monoxide formation. Here we demonstrate that depositing platinum on TiO2 by atomic layer deposition (ALD) is an easy, reproducible method for the synthesis of TiO2-supported platinum catalyst for methanol oxidation with superior anti-poisoning properties. [ABSTRACT FROM AUTHOR]

Hydrogenation of CO2 represents a promising pathway for converting it into valuable hydrocarbons and clean fuels like dimethyl ether (DME). Despite significant research, several challenges persist, including a limited understanding of reaction mechanisms, thermodynamics, the necessity for catalyst design to enhance DME selectivity, and issues related to catalyst deactivation. The paper provides a comprehensive overview of recent studies from 2012 to 2023, covering various aspects of CO2 hydrogenation to methanol and DME. This review primarily focuses on advancing the development of efficient, selective, and stable innovative catalysts for this purpose. Recent investigations that have extensively explored heterogeneous catalysts for CO2 hydrogenation were summarized. A notable focus is on Cu-based catalysts modified with promoters such as Zn, Zr, Fe, etc. Additionally, this context delves into thermodynamic considerations, the impact of reaction variables, reaction mechanisms, reactor configurations, and recent technological advancements, such as 3D-printed catalysts. Furthermore, the paper examines the influence of different parameters on catalyst deactivation. The review offers insights into direct CO2 hydrogenation to DME and proposes paths for future investigation, aiming to address current challenges and advance the field. [ABSTRACT FROM AUTHOR]

The document discusses the importance of heterogeneous catalysts in green chemistry and their role in driving molecular transformations to produce desired products in a sustainable and environmentally friendly manner. It highlights the significance of efficient catalysts in achieving sustainability goals, minimizing harmful emissions, and reducing production costs. The Special Issue covered various topics related to green chemistry, including pollution control, energy efficiency, CO2 conversion, and hydrogen production, through original articles and review papers, providing a comprehensive overview of the critical roles of catalysts in green processes. [Extracted from the article]

The sulfur poisoning mechanism of low-temperature SCR de-NOx catalyst has always been one of the hot spots in academic circles. By studying the surface sulfur poisoning mechanism, low-temperature catalysts can be developed pertinently. In this paper, the mechanism of sulfur poisoning on the surface of LaMnO3 catalyst was studied by DFT method, and the adsorption process of sulfur oxides on the surface and its influence on SCR reaction process, as well as the morphology and decomposition process of ammonium sulfate on the surface were calculated. The results show that sulfur oxides will be adsorbed on the surface and occupy the adsorption site, which will adversely affect the subsequent SCR reaction. At the same time, ammonium sulfate will accumulate on the catalyst surface, which will lead to sulfur poisoning. [ABSTRACT FROM AUTHOR]

The direct methanol fuel cell (DMFC) represents a highly promising alternative power source for small electronics and automobiles due to its low operating temperatures, high efficiency, and energy density. The methanol oxidation process (MOR) constitutes a fundamental chemical reaction occurring at the positive electrode of a DMFC. Pt-based materials serve as widely utilized MOR electrocatalysts in DMFCs. Nevertheless, various challenges, such as sluggish reaction rates, high production costs primarily attributed to the expensive Pt-based catalyst, and the adverse effects of CO poisoning on the Pt catalysts, hinder the commercialization of DMFCs. Consequently, endeavors to identify an alternative catalyst to Pt-based catalysts that mitigate these drawbacks represent a critical focal point of DMFC research. In pursuit of this objective, researchers have developed diverse classes of MOR electrocatalysts, encompassing those derived from noble and non-noble metals. This review paper delves into the fundamental concept of MOR and its operational mechanisms, as well as the latest advancements in electrocatalysts derived from noble and non-noble metals, such as single-atom and molecule catalysts. Moreover, a comprehensive analysis of the constraints and prospects of MOR electrocatalysts, encompassing those based on noble metals and those based on non-noble metals, has been undertaken. [ABSTRACT FROM AUTHOR]

In recent years, the greenhouse effect has emerged as a major environmental concern. As a result, the utilization and capture of greenhouse gases have become urgent tasks. The dry reforming of methane (DRM) reaction is a technology that directly converts greenhouse gases (CH4 and CO2) into valuable products. Ni-based catalysts have gained significant attention and industrial prospects in DRM reactions due to their excellent performance and cost-effectiveness compared to noble metals. However, challenges such as metal sintering and carbon deposition hinder its industrialization. This paper provides a review of the recent advancements in catalyst design for DRM reactions, with a focus on the impact of additives, supports, and preparation methods on Ni-based catalysts. It also describes the reaction and deactivation mechanisms, as well as the thermodynamics and kinetics of DRM reactions. Furthermore, this paper envisions the main challenges and opportunities associated with Ni-based catalysts in DRM research. [ABSTRACT FROM AUTHOR]

Abstract: The present discussion paper deals with the Gyenge''s [E. Gyenge, Electrochim. Acta 49 (2004) 965] suggestion to add thiourea (H2N–CS–NH2) to the borohydride fuel of the direct borohydride fuel cell (DBFC). It is expected that thiourea inhibits the hydrogen evolution (stem from the borohydride hydrolysis, a side reaction) that occurs at the anode of the DBFC where in fact it is expected the direct oxidation of borohydride. However, thiourea is an organic sulphur compound and it is well known that the sulphur species are poisons for the metallic catalysts. Hence, the present discussion paper asks a question: may thiourea and the sulphur species stem from its decomposition act as poisons of metallic sites of catalysts used as DBFC anodes? [Copyright &y& Elsevier]

The direct conversion of methane to hydrogen and high-value hydrocarbons under mild conditions is an ideal, carbon-neutral method for utilizing natural gas resources. Compared with traditional high-temperature thermal catalytic methods, using clean light energy to activate inert C–H bonds in methane can not only significantly reduce the reaction temperature and avoid catalyst deactivation, but also surpass the limitations of thermodynamic equilibrium and provide new reaction pathways. This paper provides a comprehensive review of developments in the field of photocatalytic non-oxidative conversion of methane (PNOCM), while also highlighting our contributions, particularly focusing on catalyst design, product selectivity, and the underlying photophysical and chemical mechanisms. The challenges and potential solutions are also evaluated. The goal of this feature article is to establish a foundational understanding and stimulate further research in this emerging area. [ABSTRACT FROM AUTHOR]

Chemical catalytic conversion of biomass-derived sugars to lactic acid has attracted considerable attention due to the cheap, abundant and renewable nature of biomass and its huge potential application in the synthesis of biocompatible and biodegradable polylactic acid resins. However, this route is still a huge challenge in view of the transformation efficiency. This paper reports a series of Zn-based catalysts, which are facile and cheap to prepare and highly efficient for the conversion of biomass-derived carbohydrates to ethyl lactate (EL). The microstructure, active site composition and surface properties were characterized by TEM, HRTEM, XRD, NH3-TPD, CO2-TPD, Py-IR, and XPS. The catalytic performance of catalysts in the conversion of biomass-derived carbohydrates to ethyl lactate (EL) and the effect of water content were investigated. It was found that the Zn species played a decisive role in regulating the strengths of the acidic and basic sites to match the rate of each reaction in the tandem reactions. The basic sites are beneficial for isomerization and retro-aldol condensation, while the temperature-responsive released H+ protons are responsible for the dehydration of triose to methylglyoxal, a rate-determining step in the conversion of triose to EL. Addition of a small amount of water could enhance the release of the protons and thus accelerate the dehydration reaction, but excessive water would favor the formation of humins. Using ZnSi-2 as a catalyst under optimal conditions, yields as high as 74.5% of EL from glucose, 81.0% from fructose, 70.9% from mannose, and 80.3% from sucrose could be achieved with tens of times higher productivity than the previously reported values in the literature. DFT calculations revealed that Zn(OEt)Cl, Zn(OH)Cl, and Zn(OH)(OEt) were probably the active components. In addition, the stability of the catalyst as well as the deactivation and regeneration was also studied. The findings in this research provide new insights into the exploration of efficient catalysts for biomass conversion to value-added chemicals. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) system is considered to be the most effective control method for reducing NOx in exhaust gas post-treatment of the diesel engine. Catalysts are the main factors affecting de-NOx efficiency in SCR reactions. In recent years, due to the excellent characteristics of copper zeolite catalysts, they have been widely studied as low-temperature NH3-SCR catalysts. However, the development of low-temperature SCR catalysts with high removal efficiency still faces severe challenges. This paper reviewed the latest research progress with copper zeolite catalysts at low temperature and compared the action mechanism of various copper zeolite catalysts in NH3-SCR reactions. Copper zeolite catalysts were studied from the aspects of catalytic performance, preparation strategy, broadening the operating temperature window, hydrothermal deactivation and resistance to H2O and SO2. Several solutions to the problems existing in low-temperature NH3-SCR reactions were discussed. In addition, this paper also puts forward some views on the future research direction of copper zeolite catalysts. Finally, the summaries and prospects of the development of low-temperature SCR copper zeolite catalysts were presented. Hopefully, more researchers can understand the current research status of copper zeolite catalysts and obtain better research achievements from copper zeolite catalysts in the future. This review could pave the way for similar studies to enable a wider variety of copper zeolite catalysts to be commercially available. [ABSTRACT FROM AUTHOR]

ABSTRACT Exploring the relationship between the structure of active site and the activity in molecular level and investigating the reason for deactivation are extremely important in designing the highly active catalyst. In this paper, new self‐assembly Schiff‐base Pd/Cu nanosheets supported on the surface of graphene oxide (GO) (called as GO@Hpmaba‐Pd/Cu) were fabricated and characterized. Among them, GO@Hpmaba‐Pd0.2/Cu0.8 exhibited a high activity with a TOF value of up to 95,357 h−1 and substrate suitability in Suzuki cross‐coupling reaction. GO@Hpmaba‐Pd0.2/Cu0.8 could be reused at least 13 times. GO@Hpmaba‐Pd0.2/Cu0.8 was a heterogeneous catalyst and the catalysis occurred on the surface. The truly active sites included Pd/PdO/CuO/PdCu3 formed in situ on the surface of the hetero‐organometallic Pd/Cu nanosheet during catalysis. The synergistic effects among these active sites could be described as that the electrons transferred from GO to CuO (PdO) or to Pd via ligand (Hpmaba) and subsequently electrons transferred from CuO (PdO) to Pd. These made more electron negative palladium, enhancing the oxidation addition between palladium and aryl halide and prompting the activity. The deactivation of catalyst was mainly caused by some destroyed organometallic in the nanosheet, residues adsorbed on catalytic surface, loss of active Pd due to the leaching with increase of recycling, and the aggregation of active metals. [ABSTRACT FROM AUTHOR]

Methanol is considered a key and platform compound to produce high value‐added chemicals, and it could contribute to energy transition, decreasing the dependence of fossil fuels. This paper presents a methanol synthesis simulation over a commercial Cu/ZnO/Al2O3, which is used at industrial scale. With the aim of exploring renewable raw materials as alternative to synthesize this alcohol, synthesis gas was obtained as a starting mixture from gasification of residual coffee pulp, which is an agro‐industrial waste widely generated in coffee producing countries. Currently, the raw materials most used to obtain methanol are natural gas and coal, so the use of agro‐industrial waste as a raw material would achieve greener methanol production. Design of experiments and ANOVA were applied to obtain results with statistical significance. Residual coffee pulp gasification conditions and reaction temperature were the controlled variables, while methanol production was selected as a response one. The simulation runs and ANOVA were analyzed and compared with the literature reports, and it was observed that methanol production is possible avoiding the catalyst deactivation. For the best obtained conditions, the profiles along the reactor of chemical species molar fraction, stochiometric number, methanol production and pressure drop were shown. [ABSTRACT FROM AUTHOR]

In this paper, the effects of sulfuric acid treatment of a ZrO2 support (ZrO2-S) on the Ca resistance of CeO2 catalysts were investigated. The results showed that the CeO2/ZrO2-S catalyst exhibited much better SCR activity and Ca resistance compared with the CeO2/ZrO2 catalyst. To further reveal the Ca resistance mechanism, BET, XRD, Raman, XPS, H2-TPR, NH3-TPD and in situ DRIFTS were used to characterize the changes in structure and properties of the CeO2/ZrO2 and CeO2/ZrO2-S catalysts before and after the Ca deactivation tests. The Ca poisoning of the CeO2/ZrO2 catalysts was mainly due to the decrease in specific surface area and surface acidity, the loss of reducibility and the enhanced stabilization of adsorbed nitrate/nitrite species. The treatment of ZrO2 with sulfate acid led to an increased specific surface area and highly-dispersed Ce species at the catalyst surface. It was also beneficial to inhibiting the transformation of ZrO2 from the tetragonal to the monoclinic phase. Moreover, it also enhanced the redox properties, Ce3+ species ratio, total surface acidity (especially Brønsted acid sites), and adsorption of NH3 species. The SCR reactions via both Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) mechanisms could proceed well even after the CeO2/ZrO2-S catalysts were subjected to Ca poisoning. [ABSTRACT FROM AUTHOR]

The addition of heteroatom compounds to alkynes and alkenes is an atom‐efficient method of carbon‐heteroatom bond formation and is widely used as a fundamental synthetic method for the construction of functional molecules. Nevertheless, examples of transition‐metal‐catalyzed addition reactions of group 16 heteroatom compounds to carbon‐carbon unsaturated bonds have been limited due to the widespread belief that organic sulfur and selenium compounds are representative catalyst poisons. In recent decades, however, several seminal catalytic reactions of sulfur compounds have been developed, providing important insights into catalysis and poisons. Therefore, this paper focuses on the transition‐metal‐catalyzed addition of organosulfur compounds to alkynes and alkenes, gains comprehensive insights into the catalysis and catalyst poisons, and proposes concepts for the development of transition‐metal‐catalyzed reactions of group 16 heteroatom compounds. [ABSTRACT FROM AUTHOR]

Fluid catalytic cracking (FCC) is one of the most important processes in gasoline/diesel oil production, but the strong endothermic effect accompanied by this reaction often results in the deactivation of the catalyst. In this paper, a novel multifunctional phase change material (PCM)@Catalyst composite was designed and constructed, in which the PCM could be used to store waste heat and regulate the temperature for enhancing the catalytic efficiency of the FCC catalyst. Firstly, a core/shell Al-12wt%Si@Al2O3 was prepared via subsequent vapor treatment and high-temperature calcination of an Al-12wt%Si sphere. The Al species in the Al-12wt%Si served as the source of metal ions and was transformed in situ into a well-defined Al2O3 shell, which greatly improved the thermal stability and prevented the leaking of the Al-12wt% Si core in the high-temperature situation. The PCMs@Catalyst composite was then fabricated by casting the mixed powder of Al-12wt%Si@Al2O3 and Y zeolite into a granulated structure. The FCC results demonstrate that Al-12wt%Si@Al2O3/Y zeolite can optimize product distribution and reduce coke yield. This design concept and synthesis strategy can be extended to the production of a wide variety of hierarchical PCM@Catalyst composites for other reactions. [ABSTRACT FROM AUTHOR]

The rising demand for portable energy conversion devices has spurred the advancement of direct liquid fuel cells (DLFCs) employing fuels such as alcohol, ammonia, hydrazine, and vitamin C. In these devices, various precious metal platforms have been explored to increase the de-electronation kinetics and reduce catalyst poisoning, but with substantial cost implications. We demonstrate the crucial role of ligands in non-precious organometallic complexes in influencing the de-electronation kinetics of fuel molecules through a unique substrate–ligand synergistic interaction. This unique chemistry imparts electron deficiency at the catalytic metal center while simultaneously populating the ligand with an extensive proton charge assembly. This distinct substrate–ligand interaction enhances the DLFC performance by coulombically dragging the substrate with a distinct amplification in its de-electronation kinetics. By integrating this approach with a ferricyanide/ferrocyanide half-cell reaction, a precious metal-free vitamin C fuel cell is developed, which is capable of generating an open circuit voltage of ∼950 mV, a peak power density of ∼97 mW cm−2 at a peak current density of ∼215 mA cm−2 with the performance metrics nearly 1.7 times higher than a precious metal based DLFC. This highlights the potential of the substrate–ligand synergy in the design of efficient molecular catalysts for energy conversion applications. [ABSTRACT FROM AUTHOR]

The epimerization of glucose into mannose is of great significance for high-value utilization of monosaccharides. Extensive studies on the epimerization of glucose into mannose have been conducted using molybdenum-based catalysts, owing to their good activities for the epimerization reaction. Nonetheless, a great challenge for this reaction is that molybdenum species are prone to leaching into solution, which is a primary reason for catalyst deactivation. Additionally, the reaction usually gives a very low mannose yield and poor selectivity because it is a thermodynamic equilibrium reaction with sugar prone to side reactions at high temperatures. Herein, a metal–organic framework (MOF) material incorporating Keggin-type phosphomolybdate was explored as the catalyst for the epimerization of glucose. Under optimal conditions, an excellent mannose yield of up to 32.5% with an impressive selectivity of 94% was achieved. When other aldoses such as arabinose were used as starting materials, the catalyst also afforded high yield and product selectivity in the epimerization reaction. This novel hybrid material, a polyoxometalate-based metal–organic framework (POMOF), has been introduced to catalyze the conversion of sugars for the first time. Notably, in contrast to most molybdenum-based catalysts, the target hybrid showed good stability after five successive cycles. Furthermore, the reaction mechanism of the glucose-to-mannose epimerization was proposed, confirming the intramolecular carbon-skeleton rearrangement pathway (involving C-1 and C-2 positions) by isotope-labeling trace experiments. [ABSTRACT FROM AUTHOR]

The introduction of nitrogen‐containing functional groups to chiral polymer backbones enables the tailoring of physical properties and offers opportunities for further post‐polymerization modification. However, the substrate scope of such polymers is extremely limited because monomers having nitrogen‐containing groups can change coordination state with respect to the metal centers, thus decreasing the activity and enantioselectivity and even poisoning the catalyst completely. In this paper, we report our attempts to carry out the asymmetric copolymerization of meso‐epoxide with highly reactive isocyanates. In particular, we found that biphenol‐linked bimetallic Co(III) complexes with multiple chiral centers are very efficient in catalyzing this asymmetric copolymerization reaction, affording optically active polyurethanes with a completely alternating nature and a high enantioselectivity of up to 94 % ee. Crucially, we identified that the steric hindrance at the phenolate ortho position of the ligand strongly influences the catalytic activity and product enantioselectivity. In addition, density functional theory calculations revealed that the highly sterically bulky substituents change the mechanism from bimetallic to monometallic, and result in the unexpected inversion of the chiral induction direction. Moreover, the high stereoregularity of the produced polyurethanes enhances their thermal stability, and they can be selectively decomposed into oxazolidinones. This study offers a versatile methodology for the synthesis of chiral polymers containing nitrogen functionalities. [ABSTRACT FROM AUTHOR]

In this paper, room-temperature chemiresistive gas sensors for NO2 detection based on CVD-grown carbon nanofibers (CNFs) were investigated. Transmission electron microscopy, low-temperature nitrogen adsorption, and X-ray diffraction were used to investigate the carbon nanomaterials. CNFs were synthesized in a wide range of pressure (1–5 bar) by COx-free decomposition of methane over the Ni/Al2O3 catalyst. It was found that the increase in pressure during the synthesis of CNFs induced the later deactivation of the catalyst, and the yield of CNFs decreased when increasing pressure. Sensing properties were determined in a dynamic flow-through installation at NO2 concentrations ranging from 1 to 400 ppm. Ammonia detection was tested for comparison in a range of 100–500 ppm. The obtained sensors based on CNFs synthesized at 1 bar showed high responses of 1.7%, 5.0%, and 10.0% to 1 ppm, 5 ppm, and 10 ppm NO2 at 25 ± 2 °C, respectively. It was shown that the obtained non-modified carbon nanomaterials can be used successfully used for room temperature detection of nitrogen dioxide. It was found that the increase in relative humidity (RH) of air induced growth of response, and this effect was facilitated after reaching RH ~35% for CNFs synthesized at elevated pressures. [ABSTRACT FROM AUTHOR]

Transition metal radical‐type carbene transfer catalysis is a sustainable and atom‐efficient method to generate C−C bonds, especially to produce fine chemicals and pharmaceuticals. A significant amount of research has therefore been devoted to applying this methodology, which resulted in innovative routes toward otherwise synthetically challenging products and a detailed mechanistic understanding of the catalytic systems. Furthermore, combined experimental and theoretical efforts elucidated the reactivity of carbene radical complexes and their off‐cycle pathways. The latter can imply the formation of N‐enolate and bridging carbenes, and undesired hydrogen atom transfer by the carbene radical species from the reaction medium which can lead to catalyst deactivation. In this concept paper, we demonstrate that understanding off‐cycle and deactivation pathways not only affords solutions to circumvent them, but can also uncover novel reactivity for new applications. In particular, considering off‐cycle species involved in metalloradical catalysis can stimulate further development of radical‐type carbene transfer reactions. [ABSTRACT FROM AUTHOR]

Careless release of plastic waste is a pressing problem for marine and other eco‐environments, and materials recycling of this stream is an open problem. For this purpose, a new metal‐free acidic carbocatalyst with 8 wt % sulfur is constructed from a side product of the paper industry namely Na‐lignosulfonate. The catalyst shows an extraordinary performance for the fragmentation of polymer waste which smoothly occurs above the ceiling temperature of the polymers. The reaction is run without hydrogen and at ambient pressure with commercially available high‐density polyethylene (HDPE) as well as a real polymer waste mixture of high and low‐density polyethylene (HDPE, LDPE). In all cases, a homologous series of n‐alkanes and n‐alkenes are obtained. The unique sulfur‐rich carbonaceous structure (transfer hydrogenation functionality) and the metal‐free character of the acidic carbocatalyst makes it inert against many typical catalyst poisons, among them water, salt, polar functionalities, and sulfur species. The described performance in plastic recycling, as well as the low cost and large‐scale availability of lignosulfonate from the pulp industry, makes this metal‐free acidic carbocatalyst promising for real‐life environmental applications. [ABSTRACT FROM AUTHOR]

Beta zeolite, a crystal material with a three-dimensional twelve-ring cross-channel structure, has many advantages, such as high Brønsted acid concentration, high Si/Al ratio, thermal/hydrothermal stability, and large surface area. Due to these advantages, beta zeolite shows excellent catalytic performance in petroleum refining and petrochemical processes. However, traditionally microporous beta zeolite has strong steric hindrance and diffusion restrictions, which hinder large molecules from passing through its internal channels. In addition, carbon deposition occurs, resulting in catalyst deactivation. The main strategy to solve this problem is to prepare nanosized or hierarchical beta zeolites, which allow for large molecule conversion and shortening diffusion pathways. Therefore, researchers have explored different synthesis strategies to prepare beta zeolite with different particle sizes and porosities to obtain better zeolite catalysts. This paper briefly describes the recent research progress in the preparation of nanosized and hierarchical beta zeolite. Additionally, the mechanisms of various preparation methods, structural characteristics, and applications of the materials are introduced in detail. Furthermore, the main problems existing in its industrial application are describing by comparing the advantages and disadvantages of the different methods to prepare optimally nanosized and hierarchical zeolite to meet the requirements of industrial development. [ABSTRACT FROM AUTHOR]

A mechanistic model on catalyst deactivation by coke formation in a continuous stirred tank reactor (CSTR) has been developed in the paper. Catalyst deactivation by coke formation was treated as a surface reaction. Four reaction mechanisms representing coke formation through different routes were proposed. The evolved system of ordinary differential equations (ODEs) was solved numerically using MATLAB. This approach was validated by applying it to the skeletal isomerization of 1-pentene over ferrierite. Simulation results were compared qualitatively to those obtained from the literature. Simulation results indicated that coke formation is an extremely rapid process with fast formation of coke components on the strongest acid sites leading to final coke. The coke deposition is slower at higher residence times resulting in more stable product formation and weaker deactivation. The results obtained from this work revealed that the developed model is indeed able to successfully demonstrate the most essential features of catalyst deactivation by coke formation and are in agreement with the findings in the literature. Future work is aimed to extend the study to different reactors such as a plug flow reactor, in addition to analysis of the reaction system's sensitivity to variables such as temperature and pressure. [ABSTRACT FROM AUTHOR]

Vapor phase methylation of phenol with methanol is widely carried out to produce a variety of products such as anisole, cresols and xylenols due to their increasing application in industries. Numerous researches have been carried out to understand the mechanistic behavior of phenol methylation. Based on discussion of reaction mechanism, the present article covered methylation of phenol with methanol over various catalysts, including zeolites, metal oxides, spinel, phosphates, sulfates, hydrotalcites and others. Moreover, the influence of reaction conditions and catalyst deactivation behavior were described. Finally, this review paper gives useful insights for the future direction of phenol methylation with methanol. This review provides a summary for the process of phenol methylation with methanol: catalysts, reaction mechanism and deactivated behavior, etc. [ABSTRACT FROM AUTHOR]

This density functional theory (DFT) study explores the efficacy of cooperative catalytic systems in enabling the ionic hydrogenation of N2 with H2, leading to NH3 formation. A set of N-heterocyclic carbene-based pincer tungsten/molybdenum metal complexes of the form [(PCP)M1(H)2] (M1 = W/Mo) were chosen to bind N2 at the respective metal centres. Simultaneously, cationic rhodium/iridium complexes of type [Cp*M2{2-(2-pyridyl)phenyl}(CH3CN)]+ (Cp* = C5(CH3)5 and M2 = Rh/Ir), are employed as cooperative coordination partners for heterolytic H2 splitting. The stepwise transfer of protons and hydrides to the bound N2 and intermediate NxHy units results in the formation of NH3. Interestingly, the calculated results reveal an encouraging low range of energy spans ranging from ∼30 to 42 kcal mol−1 depending on different combinations of ligands and metal complexes. The optimal combination of pincer ligand and metal center allowed for an energy span of unprecedented 29.7 kcal mol−1 demonstrating significant potential for molecular catalysts for the N2/H2 reaction system. While exploring obvious potential off-cycle reactions leading to catalyst deactivation, the computed results indicate that no increase in energy span would need to be expected. [ABSTRACT FROM AUTHOR]

Promoting electrocatalytic ammonia oxidation reaction (AOR) holds the key to develop efficient direct ammonia fuel cells (DAFCs) and ammonia‐mediated hydrogen production (AMHP). Recent investigations indicated that Pt with the exposure of (100) facet has a moderate *N intermediate bonding strength, resulting in the highest AOR electrocatalytic activity among others. Therefore, maximizing the exposure of (100) planes with high active surface area is highly desired for efficient electrocatalysts. In this paper, Pt catalyst composed of directional alignment of nanoparticles around 50 nm (Pt‐100/C) were synthesized by hydrothermal method in the presence of KOH. The KOH concentration was found to modulate the one‐dimensional alignment of nanoparticles. The electrocatalyst showed the largest electrochemically active areas and the highest peak current density (3.14 mA cm−2), and the catalyst exhibited high stability after 500 cycles. A series of electrochemical tests and structural characterizations show that unique bead‐structured Pt combines the excellent activity of nanoparticles with the structural stability of nanowires. A scheme for "exchanging electrodes" has been proposed to solve the problem of catalyst poisoning caused by AOR in AMHP. [ABSTRACT FROM AUTHOR]

CO and H 2 S poisoning of Pt-based catalysts for hydrogen oxidation reaction (HOR) stands as one of the long-standing hindrances to the widespread commercialization of proton exchange membrane fuel cells. In this paper, a Ru/Ti 4 O 7 catalyst is successfully synthesized by the microwave-thermal method. This Ru/Ti 4 O 7 catalyst shows a much higher noble metal mass activity than those of commercial PtRu/C and conventional Ru/C catalysts. The performance of the Ru/Ti 4 O 7 catalyst under the exist of CO or H 2 S shows insignificant current decay, which is far superior to commercial PtRu/C and Pt/C catalysts. In this Ru/Ti 4 O 7 catalyst, the electron transfer between Ru and Ti to form d-p orbital hybridization is considered to be responsible for the favorable catalytic HOR performance and the corresponding CO and H 2 S tolerance. The interaction mechanism formed by electron transfer may open a promising way for the subsequent development of anti-poisoning catalysts for PEM fuel cell hydrogen oxidation reaction. [Display omitted] • Ru/Ti 4 O 7 catalyst shows a superior noble metal mass activity than those of commercial Pt–Ru/C based catalysts. • Ru/Ti 4 O 7 catalyst exhibits excellent resistance to CO poisoning. • The catalyst is extremely resistant to H 2 S while remaining CO-tolerant. • MSI of Ru/Ti 4 O 7 ensures catalytic activity and anti-poisoning properties. [ABSTRACT FROM AUTHOR]

The use of HZSM-5 and modified catalysts for the pyrolysis of lignin to produce aromatics has been extensively investigated. But certain limitations including catalyst deactivation and high-cost modifications still exist. A magnetic field (MF) was used to assist Fe and HZSM-5 catalytic lignin pyrolysis for aromatics production in this study. Product composition analysis revealed that the monocyclic aromatic hydrocarbon (MAH) and benzene, toluene, ethylbenzene, and xylene (BTEX) contents exhibited an upward trend in correlation with the MF intensity. The introduction of a MF significantly affects the improvement of the BTEX yield. Under the conditions of 80 mT MF intensity, 500 °C temperature and 50 mL min−1 carrier gas flow rate, the MAH and BTEX contents reach 32.94% and 27.19%, while the BTEX yield reaches roughly 19.55 mg g−1. Compared to no MF, these values rose by about 1.28, 1.36, and 1.94 times, respectively. Characterization results from XRD, XPS, TPO, N2 adsorption–desorption, and NH3–TPD tests showed that the MF facilitated the deoxidation and fragmentation of macromolecular oxygenates on the surface of Fe, promoting the ingress of smaller molecular compounds into the pores of HZSM-5 and boosting MAH production. Simultaneously, the MF impeded pore blockage in HZSM-5 and kept acidic sites from deactivating due to carbon deposition. This study lays a crucial groundwork for improving advanced technologies aimed at optimizing the utilization of organic solid waste. [ABSTRACT FROM AUTHOR]

Copyright of Tikrit Journal of Engineering Sciences is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The operating parameters of the active direct methanol fuel cell (DMFC) are essential factors affecting its power delivery performance. Different operating parameters lead to variations in the amount of methanol crossover in a DMFC, which might cause overpotential and cathode catalyst poisoning. Due to the complexity of the DMFC system, changes in operating conditions, and correlations among these parameters, it is challenging to maintain output power density while reducing the negative effects of methanol crossover. This paper proposes an adaptive joint optimization method for fuel cell operating parameters. The principle operating parameters are selected by the orthogonal tests, which include an adaptive numerical simulation and multiobjective optimization regarding cell output power density and methanol crossover. The selected parameter combinations are verified by an evaluation model that quantifies the influences of operating parameters on the active DMFC power density and its methanol crossover, where the nonlinear mapping function for the two optimization objectives is obtained. The nondominated sorting genetic algorithm‐II (NSGA‐II) is applied to rapidly obtain the optimal combination. The results show that with the optimal parameters, the maximum power density is increased by 16.7% and the methanol crossover is reduced by 35.1%. [ABSTRACT FROM AUTHOR]

To replace the noble metals used in hydrodeoxygenation (HDO) catalysts, guaiacol HDO was conducted using various transition metal-loaded catalysts. Co/TiO2 was highly active for guaiacol HDO, enabling a more economic removal of the methoxy groups compared to the Ru/TiO2 catalyst, resulting in superior cyclohexanol selectivity. When a WO3 promoter was added to the Co catalyst to enhance its oxygen removal ability, the conversion of guaiacol was severely reduced because the co-impregnated WOx species decreased the number of exposed Co sites. To avoid this phenomenon, Co and WO3 were isolated by physically mixing Co/TiO2 and WO3/TiO2, where 100% conversion and oxygen removal could be achieved under 10 bar H2 at 250 °C. The cause of the catalyst deactivation was systematically investigated by magnetic separation of the physical mixture of the catalysts after the reaction, followed by a series of characterization studies. Temperature-programmed-oxidation mass spectroscopy and Raman spectroscopy revealed that the deposition of carbonaceous species was the main contributor to the deactivation of WO3/TiO2, and the catalytic activity could be successfully recovered by simple calcination at 400 °C. This study provides insights into the development of economical and efficient physically mixed HDO catalysts using transition metals, and contributes to the understanding of the deactivation and regeneration of physically mixed HDO catalysts. [ABSTRACT FROM AUTHOR]

In the field of petrochemistry, the quantitative determination of trace elements in catalysts is crucial for optimizing various types of processes. Catalyst poisoning, resulting from the presence of contaminants, can lead to decreased performance and efficiency, even when these are present at trace level only. Inductively coupled plasma-mass spectrometry (ICP-MS) is a powerful technique for trace elemental analysis, but its application to catalysts is challenging due to their physicochemical characteristics challenging straightforward dissolution. Laser ablation (LA) coupled to ICP-MS (LA-ICP-MS) has emerged as a valuable approach for direct analysis of solid samples. However, developing an appropriate calibration strategy for reliable quantitative LA-ICP-MS analysis of catalyst samples remains a challenge. In this work, different calibration strategies for quantitative LA-ICP-MS analysis of fused catalyst samples were evaluated. The traditional strategy relied on external calibration against certified reference materials (CRMs) combined with internal standardization and was considered the reference approach. When using this approach, the relative bias with respect to the reference value was found to be <15%. Two novel calibration strategies were introduced and compared: a so-called multi-signal calibration approach and a solution-based calibration approach. The multi-signal calibration strategy involved varying the laser repetition rate (20, 30, 40 and 50 Hz) or laser beam diameter (10, 12, 15 and 20 μm), allowing a calibration curve to be constructed by comparing the analytical signal intensity for a single solid CRM with that for the sample, thus partially overcoming the shortage of CRMs for quantitative LA-ICP-MS analysis. The solution-based calibration approach was used for quantitative multi-element analysis without the need for any solid standard and required only minor hardware modifications to accommodate the introduction of aqueous standard solutions for calibration. Various glass certified reference materials were used for method development, calibration, and validation purposes. Furthermore, two fused alumina catalyst samples (used in the context of petroleum refining processes) were successfully analyzed as a proof-of-concept application. For both the multi-signal (matrix-matched conditions) and the solution-based calibration approaches, the average relative bias between the experimentally determined and certified/reference concentrations varied between −9% and +7%. [ABSTRACT FROM AUTHOR]

Ethyl mercaptan (Et‐SH) is a common sulfide in natural gas. It is toxic and can cause equipment corrosion and catalyst poisoning, which needs to be properly handled. In present paper, Zn−Ti layered double hydroxide and its nanosheets were prepared by hydrothermal method and solvothermal method using ethylene glycol (EG) as a reaction medium, respectively. The desulfurization capabilities of the as‐prepared samples were evaluated through the adsorption of Et‐SH from methane gas. The results show that the desulfurization performance of the samples prepared by solvothermal method is significantly elevated comparing that of sample prepared by hydrothermal method. The washing solvent in the post‐treatment of the samples obtained by solvothermal method has great influence on its desulfurization performance. Density Functional Theory (DFT) calculations indicate that the H atom of hydroxyl group on the surface of nanosheet is the main active site for adsorption of Et‐SH. The strong hybridization between S 3p orbitals and H 1s orbitals promote the formation of S⋅⋅⋅H bond. [ABSTRACT FROM AUTHOR]

In heterogeneous catalytic reactions, supported metal catalysts have attracted increasing attention for the environmental remediation and industrial manufacture due to their inherent catalytic capacity. However, leaching, agglomeration, and poisoning of active metal particles lead to catalyst deactivation, thereby limiting their applications. To avoid this, strategies to protect the active metals from such inactivating processes are major areas of research. Emerging encapsulation strategies, in which active species are coated by protective shells, have proven to be a powerful technology to enhance catalytic performance by creating a well-developed structure about the active catalytic sites. This review highlights the recent advances on preparation method and application of encapsulated catalysts since 2016. Building upon the traditional confinement effect, new categories and extended concepts of encapsulation are introduced. In parallel, effects of encapsulation structure on performance and key factors controlling the structure of encapsulated catalyst are discussed definitely in this review. Finally, future perspectives on opportunities and challenges for further research in the field are given at the end of this paper. [ABSTRACT FROM AUTHOR]

The paper considers the current state of research and development of composite structured catalysts for the oxidative conversion of liquid hydrocarbons into synthesis gas for fuel cell feeding and gives more detailed information about recent advances in the Boreskov Institute of Catalysis. The main factors affecting the progress of the target reaction and side reactions leading to catalyst deactivation are discussed. The properties of the Rh/Ce0.75Zr0.25O2/Al2O3/FeCrAl composite multifunctional catalyst for the conversion of diesel fuel into synthesis gas are described. The results of the catalyst testing and mathematical modeling of the process of diesel fuel steam–air conversion into synthesis gas are reported. [ABSTRACT FROM AUTHOR]