Deactivation Process Research Articles

Highly loaded copper on mesoporous silica as catalysts for acetaldehyde production from ethanol: their synthesis, characteristics, and catalytic properties

AbstractBACKGROUNDThe present study investigates copper (Cu)/mesoporous catalysts supported on mesocellular foam silica (MCF‐Si) and Santa Barbara Amorphous‐15 (SBA‐15) for ethanol dehydrogenation, focusing on catalyst synthesis, performance, and stability. Cu catalysts were impregnated on the MCF‐Si and SBA‐15 supports with different pore morphologies – spherical and hexagonal structure, respectively – using the wetness impregnation method and incipient wetness impregnation (IW), with a Cu loading of 60 wt%. The synthesized catalysts underwent physical and chemical characterization via scanning electron microscopy combined with energy‐dispersive X‐ray spectroscopy, X‐ray fluorescence, X‐ray diffraction (XRD), transmission electron microscopy, N2 physisorption, X‐ray photoelectron spectroscopy, thermogravimetric analysis (TGA), carbon monoxide chemisorption, hydrogen temperature‐programmed reduction (H2 TPR), ammonia temperature‐programmed desorption, and carbon dioxide temperature‐programmed desorption.RESULTSIt was observed that copper impregnation of the support in either method did not alter the structural characteristics. Incipient wetness resulted in superior catalytic activity, particularly with Cu/MCF‐Si (IW), having pure ethanol conversion of 99.4% and acetaldehyde yield of 95.7%, attributed to effective Cu dispersion and a lower reduction temperature. Further investigation of time‐on‐stream (TOS) behavior revealed sustained ethanol conversion rates exceeding 95% with a 10% ethanol feed. However, catalyst deactivation due to coke formation occurred with 100% ethanol, highlighting the importance of understanding catalyst stability and deactivation mechanisms.CONCLUSIONIncipient wetness resulted in superior performance compared to wetness impregnation, with Cu/MCF‐Si (IW) achieving exceptional ethanol conversion rates due to effective Cu dispersion and a lower reduction temperature. TOS testing revealed sustained ethanol conversion; however, catalyst deactivation was observed with pure ethanol feed due to carbon deposition (coke formation). Characterization techniques, including XRD, TGA, and H2 TPR analyses, provided valuable insights into the deactivation processes, highlighting the need for strategies to mitigate oxidation‐induced deactivation. © 2025 Society of Chemical Industry (SCI).

Structural Transformation and Degradation of Cu Oxide Nanocatalysts during Electrochemical CO2 Reduction.

The electrochemical CO2 reduction reaction (CO2RR) holds enormous potential as a carbon-neutral route to the sustainable production of fuels and platform chemicals. The durability for long-term operation is currently inadequate for commercialization, however, and the underlying deactivation process remains elusive. A fundamental understanding of the degradation mechanism of electrocatalysts, which can dictate the overall device performance, is needed. In this work, we report the structural dynamics and degradation pathway of Cu oxide nanoparticles (CuOx NPs) during the CO2RR by using in situ small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS). The in situ SAXS reveals a reduction in the size of NPs when subjected to a potential at which no reaction products are detected. At potentials where the CO2RR starts to occur, CuOx NPs are agglomerated through a particle migration and coalescence process in the early stage of the reaction, followed by Ostwald ripening (OR) as the dominant degradation mechanism for the remainder of the reaction. As the applied potential becomes more negative, the OR process becomes more dominant, and for the most negative applied potential, OR dominates for the entire reaction time. The morphological changes are linked to a gradual decrease in the formation rate for multicarbon products (C2H4 and ethanol). Other reaction parameters, including reaction intermediates and local high pH, induce changes in the agglomeration process and final morphology of the CuOx NPs electrode, supported by post-mortem ex situ microscopic analysis. The in situ XAS analysis suggests that the CuOx NPs reduced into the metallic state before the structural transformation was observed. The introduction of high surface area carbon supports with ionomer coating mitigates the degree of structural transformation and detachment of the CuOx NPs electrode. These findings show the dynamic nature of Cu nanocatalysts during the CO2RR and can serve as a rational guideline toward a stable catalyst system under electrochemical conditions.

Recent Progress on the Involvement of Formaldehyde in the Methanol-To-Hydrocarbons Reaction.

This review summarized the recent research progress on the crucial role of formaldehyde during the methanol-to-hydrocarbons (MTH) reaction. As a reaction intermediate, formaldehyde participates in the formation of carbon-carbon, the establish of dual-cycle, and the coking process of MTH reaction. Different techniques for formaldehyde detection in the study of MTH are also introduced.The conversion of methanol-to-hydrocarbons (MTH) over zeolite catalysts has been the subject of intense research since its discovery. Great effort has been devoted to the investigation of four key topics: the initiation of C-C bonds, the establishment of hydrocarbon pool (HCP), the adjustment of product selectivity, and the deactivation process of catalysts. Despite 50 years of study, some mechanisms remain controversial. However, an intermediate species, formaldehyde (HCHO), has recently garnered considerable attention for its influence on the entire MTH process. The discovery of HCHO and its significant role in the MTH process has been facilitated by the application of in situ analytical techniques, such as synchrotron radiation photoionization mass spectrometry (SR-PIMS) and photoelectron photoion coincidence spectroscopy (PEPICO). It is now revealed that HCHO is involved in the initiation, propagation, and termination process of MTH reaction. Such mechanistic understanding of HCHO's involvement has provided valuable insights for optimizing the MTH process.

Reactive Brownian Dynamics of Chemically Fueled Droplets: Roles of Attraction and Deactivation Modes.

The self-assembly of biological membraneless organelles can be mimicked by active droplets resulting from chemically fueled microphase separation. However, how the nonequilibrium, transient structure of these active droplets can be controlled through the physicochemical input parameters is not yet well understood. In our work, a chemically fueled two-state chemical reaction and subsequent droplet growth and decay are modeled with a reactive Brownian dynamics simulation in two spatial dimensions. In our model, particles that are activated via the consumption of fuel become attractive and can accumulate into droplets. A local-density-dependent distinction of the droplet's 'internal' and 'external' particles allows for structural feedback by giving further control over the deactivation process. The simulation shows that the deactivation of only external particles slows down the decay and stabilizes the droplets, whereas the deactivation of only internal particles can lead to a temporary encapsulation of deactivated particles (in nonequilibrium 'core-shell' structures) where the chemically active particles serve as an outer shell. Additionally, the role of hydrophobicity resembled by the attraction energy ε and the dependency of the nonequilibrium droplet formation on the various parameters of the chemical reaction are investigated. For example, a high attraction energy can lead to transient finite-size crystalline droplets, while other parameter choices indicate bimodal droplet size distributions at specific times. Similarities and differences to related experiments are discussed.

Effect of Alkyl- vs Alkoxy-Arene Substituents on the Deactivation Processes and Fluorescence Quantum Yields of Exciplexes.

Decay processes of exciplexes of cyanoanthracenes with alkylbenzene donors were compared to those with alkoxybenzenes. For the three decay processes of exciplexes, the radiative rate constant (kf) of alkoxy derivatives is slightly lower than those of alkylbenzenes at the same average exciplex energy. However, the corresponding deactivation rate constants, intersystem crossing (kisc) and nonradiative decay (knr), are considerably higher. Consequently, the fluorescence quantum yields of the alkoxybenzene exciplexes are one-half to one-fifth of the corresponding alkylbenzenes at comparable emission energies. This trend is solvent-independent. The results can be rationalized in terms of the differing electronic character of the donor radical cation moieties in the alkoxy- vs alkylbenzene exciplexes and differences in their reorganization energies. The impact of these results for the design of exciplexes that emit more efficiently is discussed.

An Advanced Sensing Approach to Biological Toxins with Localized Surface Plasmon Resonance Spectroscopy Based on Their Unique Protein Quaternary Structures.

Botulinum neurotoxins (BoNTs), ricin, and many other biological toxins are called AB toxins possessing heterogeneous A and B subunits. We propose herein a quick and safe sensing approach to AB toxins based on their unique quaternary structures. The proposed approach utilizes IgG antibodies against their A-subunits in combination with those human cell-membrane glycolipids that act as the natural ligands of B-subunits. In practice, an IgG antibody against the A-subunit of a target toxin is selected from commercially available sources and immobilized on the surface of Au nanoparticles to constitute a multivalent IgG/Au nanoconjugate. The derived IgG/Au conjugate is used in the pretreatment process of test samples for deactivating biological toxins in the form of a ternary toxin/antibody/Au complex. This process is implemented in advance to reduce the risk of handling biological toxins in laboratory work. On the other hand, the human glycolipid is immobilized on a tiny glass plate and used as a biosensor chip. The biosensor chip is set in the chamber of a flow sensing system using localized surface plasmon resonance (LSPR) spectrometry available in portable size at relatively low cost. In principle, the LSPR sensing system enables us to perform a rapid and selective detection for different kinds of biological toxins if the human glycolipid is correctly selected and installed in the sensing system. In the present LSPR sensing approach, a target AB toxin may have been deactivated during the pretreatment process. The test sample containing the deactivated AB toxin becomes a real target to be analyzed by the sensing system. In the present, we describe the concept of employing the commercially available IgG antibody in the pretreatment process followed by a typical procedure for converting it into the multivalent antibody/Au nanoconjugate and its preliminary applications in the LSPR detection of a ricin homologue (RCA120) and BoNTs in different serotypes. The tested LSPR sensing approach has worked very well for the ricin homologue and certain serotypes of botulinum neurotoxins like BoNT/A, indicating that the prior deactivation process at their A-domains causes no significant damage to the function of their B-domains with respect to determining the host cell-membrane glycolipid. The experimental results also indicated that LSPR responses from these pretreated AB toxins are significantly amplified. That is obviously thanks to the presence of Au nanoparticles in the multivalent IgG/Au nanoconjugate. We suggest in conclusion that the proposed LSPR sensing approach will provide us with a safe and useful tool for the study of biological AB toxins based on their unique quaternary protein structures.

Integrated inactivation of Microcystis aeruginosa and degradation of microcystin-LR by direct current glow discharge plasma in liquid-phase: Mechanisms and cell deactivation process

The frequent occurrence of blooms of Microcystis aeruginosa (M. aeruginosa) and the subsequent release of microcystin-LR (MC-LR) in eutrophic waters pose a serious threat to aquatic ecosystems. This study investigated the optimal conditions for inactivating M. aeruginosa and the degrading MC-LR using direct current glow discharge plasma in liquid phase (DC-LGDP), analyzed the potential inactivation mechanisms and the cell deactivation process of M. aeruginosa. The results showed that DC-LGDP generated reactive species (i.e., •OH, 1O2, and H2O2), active Cl and electroporation effect collectively contributed to inactivation of M. aeruginosa and degradation of MC-LR. The 97.07 % inactivation efficiency of M. aeruginosa and 94.98 % degradation rate of MC-LR were achieved with higher energy yield and without generating nitrogen oxides. Meanwhile, DC-LGDP destroyed the cell integrity, eliminated their antioxidant capacity and reduced the content of photosynthetic pigments. The transcriptome analysis indicated that the transcripts of genes related to photosynthesis, ribosome biosynthesis, ABC transporters, and nitrogen metabolism pathway in M. aeruginosa were altered by DC-LGDP. This study provides insights into the inactivation of M. aeruginosa by DC-LGDP, while elucidating the potential inactivation mechanisms and the cell deactivation process involved. It may be important for the eco-friendly inactivation of M. aeruginosa blooms in natural water bodies.

Gibbs states and Brownian models for coexisting haze and cloud droplets.

Cloud microphysics studies include how tiny cloud droplets grow and become rain. This is crucial for understanding cloud properties like size, life span, and impact on climate through radiative effects. Small weak-updraft clouds near the haze-to-cloud transition are especially difficult to measure and understand. They are abundant but hard to capture by satellites. Köhler's theory explains initial droplet growth but struggles with large particle groups. Here, we present a stochastic, analytical framework building on Köhler's theory to account for (monodisperse) aerosols and cloud droplet interaction through competitive growth in a limited water vapor field. These interactions are modeled by sink terms, while fluctuations in supersaturation affecting droplet growth are modeled by nonlinear white noise terms. Our results identify hysteresis mechanisms in the droplet activation and deactivation processes. Our approach allows for multimodal cloud's droplet size distributions supported by laboratory experiments, offering a different perspective on haze-to-cloud transition and small cloud formation.

Aromatics Alkylated with Olefins Utilizing Zeolites as Heterogeneous Catalysts: A Review

The alkylation reaction of aromatic compounds gains considerable attention because of its wide application in bulk and fine chemical production. Aromatics alkylated with olefins is a well-known process, particularly for linear alkylbenzene, phenyloctanes, and heptyltoluene production. As octane boosters and precursors for various petrochemical and bulk chemical products, a wide range of alkylated compounds are in high demand. Numerous unique structures have been proposed in addition to the usual zeolites (Y and beta) utilized in alkylation procedures. The inevitable deactivation of industrial catalysts over time on stream, which is followed by a decrease in catalytic activity and product selectivity, is one of their disadvantages. Therefore, careful consideration of catalyst deactivation regarding the setup and functioning of the process of catalysis is necessary. Although a lot of work has been carried out to date to prevent coke and increase catalyst lifespan, deactivation of the catalyst is still unavoidable. Coke deposition can lead to catalyst deactivation in industrial catalytic processes by obstructing pores and/or covering acid sites. It is very desirable to regenerate inactive catalysts in order to remove the coke and restore catalytic activity at the same time. Depending on the kind of catalyst, the deactivation processes, and the regeneration settings, each regeneration approach has pros and cons. In this comprehensive study, the focus was on discussing the reaction mechanism of 1-octene isomerization and toluene alkylation as an example of isomerization and alkylation reactions that occur simultaneously, shedding light in detail on the catalysts used for this type of complex reaction, taking into account the challenges facing the catalyst deactivation and reactivation procedures.

Identification of Deactivation Mechanisms by the Periodic Transient Kinetic Method

AbstractThe understanding of deactivation processes in heterogeneous catalysis is key for the development of new materials and exploration of new operation windows. In this contribution, the periodic transient kinetic method (PTK) is used to identify and separate catalyst deactivation processes for the first time. The PTK method is applied for a standard Ni/Al2O3 catalyst in CO and CO2 methanation for 24 h and compared to steady‐state experiments. For the example reactions, the study exhibits different deactivation behavior for CO and CO2 methanation. The results demonstrate that the PTK method delivers an insight into the deactivation process and furthermore gives evidence for the underlying mechanism.

Hydrothermal Valorization of Biosugars with Heterogeneous Catalysts: Advances, Catalyst Deactivation, Mitigation Strategies and Perspectives.

Sustainable production of valuable biochemicals and biofuels from lignocellulosic biomass necessitates the development of durable and high-performance catalysts. To assist the next-stage catalyst design for hydrothermal treatment of biosugars, this paper provides a critical review of (1) recent advances in biosugar hydrothermal valorization using heterogeneous catalysts, (2) the deactivation process of catalysts based on recycling tests of representative biosugar hydrothermal treatments, (3) state-of-the-art understandings of the deactivation mechanisms of heterogeneous catalysts, and (4) strategies for preparing durable catalysts and the regeneration of deactivated catalysts. Based on the review, challenges and perspectives are proposed. Some remarkable achievements in heterogeneous catalysis of biosugars are highlighted. The understanding of catalyst durability needs to be further enhanced based on full examination of the catalytic performance based on the conversion of substrates, the yield, and selectivity of products. Further, a full examination of the physiochemical changes based on multiple characterization techniques is required to eclucidate the relationships between treatment variables and catalyst durability. Collectively, a clear understanding of the relationships between chemical reaction pathways, treatment variables, and the physiochemistry of catalysts is encouraged to be gained to advise the development of heterogeneous catalysts for long-term and efficient hydrothermal upgrading of biosugars.

The optical properties of 3 + 3 macrocyclic Schiff base thin material obtained by the Molecular Beam Epitaxy method

3 + 3 optically active macrocyclic Schiff bases were synthesized in the reaction between 4-tert-butyl-2,6-diformylphenol with (1R,2R)-(+)-1,2-diphenylethylenediamine (S1) or (1S,2S)-(−)-1,2-diphenylethylenediamine (S1a). The new compounds were spectroscopically characterised by NMR, IR, X-ray (S1a), UV–Vis and fluorescence spectroscopy. The S1a molecule creates channels with distances between oxygen atoms ranging from 5.8-6.3 Å and sufficiently large to host acetonitrile molecule. Both compounds exhibit green-yellow emission in solution and solid state. Thin layers of the S1 compound obtained via Molecular Beam Epitaxy (MBE) were characterised by scanning electron microscopy with energy-dispersive X-ray spectroscopy SEM/EDS and atomic force microscopy (AFM). The optical properties of the S1/Si thin material were analysed using spectroscopic ellipsometry (SE), fluorescence spectroscopy and synchrotron radiation (SR). The time constant for the decay investigated under SR, denoted by τ1, was determined to be approximately 1.02 ns, suggesting a fast deactivation process of the excited electronic state in the S1/Si material. The ellipsometric analysis of the S1/Si layer showed semiconducting behaviour with pronounced absorption features in the UV range, attributed to π → π* and n → π* transitions, characteristic of Schiff bases. The band-gap energy, determined using the Tauc method, is 3.46 ± 0.01 eV. These analyses highlight the material’s potential in applications requiring precise control of optical properties. In the emission spectrum of S1a, a significant emission peak of approximately 561 nm indicates the presence of a prominent emissive process within this wavelength. The S1a compound is emissive in the yellow-green region of the spectrum and has a longer decay time, which suggests that it can be used in sensing optical technologies.

Synthesis and performance of PdAu/ITO electrocatalysts in urea oxidation reaction

PdAu electrocatalysts were prepared in different atomic compositions supported on ITO by sodium Borohydride process. XRD results show intense crystalline peaks related to ITO, which may mask the appearance of less crystalline Pd or Au phases. Transmission results indicate agglomeration of palladium and gold nanoparticles on the support, a phenomenon compatible with metal oxide supports. Cyclic voltammograms in the absence of urea display characteristics commonly observed for PdAu electrodes, with an increase in oxygenated species compared to pure Pd or Au. Voltammograms in the presence of urea showed oxidation processes and lower current values, indicating catalyst deactivation processes. PdAu 75:25 demonstrated higher power density values compared to other prepared electrocatalysts, suggesting a synergy between Pd and Au for urea oxidation reaction.

Theoretical Investigation on the Reversible Photoswitch Mechanism of Benzylidene-Oxazolone System.

The design and application of molecular photoswitches have attracted much attention. Herein, we performed a detailed computational study on the photoswitch benzylidene-oxazolone system based on static electronic structure calculations and on-the-fly excited-state dynamic simulations. For the Z and E isomer, we located six and four minimum energy conical intersections (MECIs) between the first excited state (S1) and the ground state (S0), respectively. Among them, the relaxation pathway driven by ring-puckering motion is the most competitive channel with the photoisomeization process, leading to the low photoisomerization quantum yield. In the dynamic simulations, about 88 % and 66 % trajectories decay from S1 to S0 for Z and E isomer, respectively, within the total simulation time of ~2 ps. The photoisomeization quantum yields obtained in our study (0.20 for Z→E and 0.12 for E→Z) agree well with the experimental measured values (0.25 and 0.11), even though the number of trajectories is limited to 50. Our study sheds light on the complexity of the benzylidene-oxazolone system 's deactivation process and the competitive mechanisms among different reaction channels, which provides theoretical guidance for further design and development of benzylidene-oxazolone based molecular photoswitches.

Metal redispersion strategy for regeneration of sepiolite derived Co-phyllosilicate catalyst during glycerol steam reforming

Metal sintering and coke deposition have become main and irreversible obstacles for catalyst deactivation during H2 production from glycerol steam reforming (GSR). The regenerability of 15Co/SEP catalyst with a phyllosilicate derived strong metal-support interaction (SMSI) was probed by five successive GSR/regeneration cycles in order to evaluate the deactivation process and initial reactivity recovery. Two different regeneration methods were selected for the cycles: redox regeneration and combined regeneration. After the combined regeneration, reproducible GSR behaviors were obtained among the whole cycles. An almost recovery of initial activity (∼94 % of conversion and ∼ 73 % of H2 yield) and 50 h stability was noticed at 15Co/SEP-5 catalyst. By various characterizations analysis of fresh and spent catalysts, it was observed that irreversible metal sintering was aggravated by the redox regeneration, thus provoked initial activity loss and accelerated coking deactivation tendency. The combined regeneration achieved phyllosilicate recrystallization and metal exsolution/redispersion by a combination of NH4F-HNO3 assisted recrystallization and redox treatments, which ensured a small increase in Co0 nanoparticle size (13.2 nm vs. 15.3 nm) and coke deposition (23.9 wt% vs. 27.3 wt%) and inconspicuous change in the C1 species selectivity. The results suggested that 15Co/SEP catalyst is a promising candidate for commercialized GSR due to the favorable regenerability.

Coke formation and mineral accumulation on HZSM-5/Al2O3 catalysts during in-situ catalytic fast pyrolysis of microalgae over multiple regeneration cycles

Catalyst deactivation caused by coke formation and mineral accumulation occurs simultaneously and intensively during the catalytic pyrolysis of biomass. A comprehensive understanding of their distinction and interactions during the deactivation and regeneration process of shaped catalysts are essential for catalyst advancement and longevity in industrial application. In this study, we report the reversible and non-reversible catalyst deactivation caused by coke formation, mineral accumulation and the interactions thereof by a multi-technique characterization of a HZSM-5/Al2O3 catalyst (crushed extrudates; particle size 1–3 mm) in fast pyrolysis. A total of 5 cycles of catalyst reaction/regeneration were performed in a bench scale reactor (60 g/h feedstock feeding rate; pyrolysis temperature of 500°C) using both raw microalgae (Scenedesmus almeriensis, or SA) and citric acid treated microalgae (CA-SA). The measured properties of the fresh and used catalysts (SA-R5, 5th recycled and reacted catalyst mixed with SA) disclosed the anticorrelation of the metal contents (increased by a factor of 2.5 times) with surface area (-4.4 %) and Brønsted acid (-70.4 %). The presence of minerals in the feedstock might catalytically alter the pyrolysis chemistry, interfere with the shape selectivity and acidity of the catalysts, thus reduced the formation of coke. Additionally, metal species from the microalgae ash that ended up on the catalyst could promote coke combustion during the regeneration process. This work revealed the demineralization of the microalgae prior to fast pyrolysis minimized the rate of irreversible catalyst deactivation. Whereas, the trade-off between promoted coke formation after the ash removal of microalgae and accelerated minerals accumulation without microalgae demineralization should be evaluated.

The Heterogeneity of Turn-over Number in Electrocatalysis

Chemical catalysts dominate the multi-billion global revenue of the chemical industry because they accelerate the time it takes a particular reaction to reach equilibrium without altering the equilibrium constant. Electrocatalysis can provide significant benefits compared to other methods, as it has minimal purification and separation costs, is operational at low temperatures and pressures, replaces hazardous and toxic chemical sources with electric current, and can be integrated with renewable energy sources. From a techno-economical point of view, some considerations are critical during a catalyst design: cost, activity, and durability. One useful metric to quantify catalyst durability is turn-over number (TON), which represents the maximum yield of products attainable from a catalytic center. Mathematically speaking, the TON is defined as: TON = ∫0 ∞ TOF(t) dt, where TOF is the turn-over frequency, which is the rate of turn-overs (N) per active site. Currently, without any exception, the TON is given as a fixed number describing the total amount of substrate converted until the catalysts fully degrade. Our approach studies electrocatalytic deactivation processes at the single catalyst level using a technique entitled single-entity electrochemistry for freely diffusing catalysts. The hydrogen evolution reaction (HER) is investigated with platinum nanoparticles as the model catalyst because it deactivates at the nanoscale when the catalytic activity decreases over time. At specific applied potentials, the current measured when a single platinum nanoparticle impacts the electrode creates a transient spike and decay back to the baseline current. TON is quantified by fitting the current decay response and integrating above the fit to find the charge transferred to catalyze the reaction. Our results show that electrocatalyst degradation and TON have a distribution, where some catalysts are more stable than others, and depends on the applied potential and size of the nanoparticles. In order to study how the surface facets of platinum affect the TON, SECCM was coupled with scanning electron microscopy (SEM) to compare the deactivation of a polycrystalline platinum surface in the macro scale with immobilized platinum nanoparticles on a glassy carbon surface. Combining local structural, electrochemical activity, and durability will bridge our fundamental understanding of macro and nanoscale catalyst deactivation processes to assist in the bottom-up approach of material development and design of large-scale industrial electrocatalysts.

(Invited) Designing Photocatalytic Membrane to Direct Electron and Hole Transport

Surface interaction of chromophore or redox active molecule which dictate the efficiency of energy/electron transfer, plays an important role in realizing photocatalytic and optoelectronic applications. Metal halide perovskite nanocrystals are interesting in the sense that they can either transfer energy or selectively transfer electrons or holes to the adsorbed molecules.1,2 The presentation will focus on two specific scenarios of the flow of energy and electron processes in CsPbX3 (X= Br, I) nanocrystal-molecular hybrids. The energy transfer is probed through three moleculr acceptors – rhodamine B (RhB), rhodamine isothiocyanate (RhB-NCS), and rose Bengal (RoseB), which contain an increasing degree of heavy atom pendant groups. Electron and/or hole transfer from excited CsPbX3 nanocrystals to a molecular relay present near the interface offers another avenue to directly convert light energy into chemical energy. Such interfacial electron transfer of semiconductor nanocrystals has been widely explored in photocatalytic processes. A basic understanding of the fundamental differences between the two excited deactivation processes (energy and charge transfer) and ways to modulate them should enable design of more efficient light harvesting assemblies with semiconductor and molecular systems.

Factors affecting conversion of methane-hydrogen mixtures into nanostructured carbon and hydrogen

At the catalytic decomposition of methane, along with hydrogen, it is possible to obtain carbon nanofibers. The addition of hydrogen to the initial reaction mixture makes it possible to increase significantly the efficiency of the overall process by minimizing the contribution of the catalyst deactivation process caused by coking. As found, the maximum yields of hydrogen and nanostructured carbon over the NiO–CuO/Al2O3 catalyst is achieved at an inlet hydrogen concentration of 13 vol%. The accumulated carbon is represented by well-structured carbon nanofibers, which are resistant to the gasification reaction. The original stacked structure is preserved after the treatment of these fibers in a hydrogen medium. Using numerical methods, the hydrogen productivity at 610 °C was found to be 49.3 mL/(mgcat·h) at an optimal value of the residence time of 5 × 10−3 s.

Process of SCR Catalyst Deactivation by Dimethylsiloxanes Present in Marine Fuels

In recent years, there have been reports of the deactivation of selective catalytic reduction (SCR) exhaust gas catalysts after a short period of operation in marine applications. The trigger and the processes of this catalyst damage have now been investigated experimentally using a fuel burner test bench and various analysis techniques. It was found that organic silicon compounds (OSCs), which are present in marine fuels after use in mineral oil extraction and processing, cause the catalyst deactivation. In practice, these are predominantly dimethylsiloxanes. By the burner experiments, it was found that the OSCs were completely converted into combustion products, in particular SiO2. Measurements of particle size distributions and particle number concentrations up- and downstream of the catalyst showed that SiO2 particles < 20 nm in particular were retained in the catalyst. This filtration effect decreased until no further reduction was observed for particles > 50 nm. Other inorganic, particulate, SiO2-containing fuel impurities (catalyst fines) had no poisoning effect here, as these particles are mostly > 50 nm. The small particles formed a closed SiO2 layer with a thickness of approx. 5 µm on the catalyst surface which grew from the catalyst inlet to the outlet and blocked the catalyst as a diffusion barrier. As the SiO2 layer increased, the NO conversion rate decreased. The poisoning effects were observed experimentally at OSC concentrations of 5 to 60 mg Si kg−1 fuel. A field-aged catalyst that had been operated on board of a merchant ship revealed the same findings.