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The isomerization of glucose to fructose plays a crucial role in the food industry and the production of biomass‐derived chemicals in biorefineries. However, the catalyst used in this reaction suffers from low selectivity and catalyst deactivation due to carbon or by‐product deposition. In this study, MgSnO3 catalyst, synthesized via a facile two‐step process involving hydrothermal treatment and calcination, was used for glucose isomerization to fructose. The catalyst demonstrated outstanding catalytic performance, achieving a fructose equilibrium yield of 29.8 % with a selectivity exceeding 90 % under mild conditions owing to its acid‐base interaction. Notably, spent catalysts can be regenerated by photoirradiation to remove surface carbon, thereby avoiding the changes in properties and subsequent loss of activity associated with conventional calcination regeneration method. This novel approach eliminates the energy consumption and potential structural aggregation associated with traditional calcination regeneration methods. The acid‐base active sites of the catalyst, along with their corresponding catalytic reaction mechanism and photoregeneration mechanism were investigated. This study presents a demonstration of the comprehensive utilization of catalytic material properties, i. e. acid‐base and photocatalytic functionalities, for the development of a green and sustainable biomass thermochemical conversion system. [ABSTRACT FROM AUTHOR]

New results on the effect of TiO2 on Pd/La2O3-CeO2-Al2O3 systems for catalytic oxidation of methane in the presence of H2O and SO2 have been received. Low-temperature N2-adsorption, XRD, SEM, HRTEM, XPS, EPR and FTIR techniques were used to characterize the catalyst. The presence of Ce3+ on the catalytic surface and in the volume near the lantana was revealed by EPR and XPS. After aging, the following changes are observed: (i) agglomeration of the Pd-clusters (from 8 nm to 12 nm); (ii) transformation of part of the TiO2 from anatase to larger particles of rutile; and (iii)—the increase in PdO/Pd—ratio above its optimum. The modification by Ti of the La2O3-CeO2-Al2O3 system leads to higher resistance towards the presence of SO2 most likely due to the prevailing formation of unstable surface sulfites instead of thermally stable sulfates. Based on kinetic model calculations, the reaction pathway over the Pd/La2O3-CeO2-TiO2-Al2O3 catalyst follows the Mars–van Krevelen mechanism. For evaluation of the possible practical application of the obtained material, a sample of Pd/La2O3-CeO2-TiO2-Al2O3, supported on rolled aluminum-containing stainless steel (Aluchrom VDM®), was prepared and tested. Methane oxidation in an industrial-scale monolithic reactor was simulated using a two-dimensional heterogeneous reactor model. [ABSTRACT FROM AUTHOR]

Benzene and 1-dodecene are often alkylated to produce linear alkylbenzene (LAB). LAB is the raw material for the production of linear alkylbenzene sulfonate (LAS), a very important anionic surfactant used in both industrial cleaning and commercial laundry processes, as well as in household laundry detergents. In the present study, we investigated the use of [Et3NH]Cl–2AlCl3 modified with CuCl2 as a catalyst for the alkylation of benzene with 1-dodecene, specifically looking at the effect of reaction conditions on product activity. The results showed that a conversion of 1-dodecene of 100.0 % and a selectivity of LAB of 93.79 % could be obtained when the following ideal reaction conditions were present: molar ratio of benzene/1-dodecene = 6, reaction temperature = 25 °C, reaction time = 10 min, stirring speed of 1000 rpm and addition of 5.0 mol % CuCl2). The catalyst concentration was 7.0 mol %. FTIR and 31P-TMPO-NMR measurements were performed to characterise the ionic liquid before and after the addition of CuCl2. After the addition of CuCl2, it was found that the acidity of the ionic liquid had decreased. The regeneration of the catalyst was also investigated and the cause of inactivation of the catalyst was determined. The results showed that CuCl2 modified the ionic liquids and decreased the benzene/1-dodecene ratio, but the high product selectivity was maintained. [ABSTRACT FROM AUTHOR]

The increasing generation of plastic wastes forces us to search for final disposal technologies environmentally friendly such as pyrolysis, which becomes an interesting technique because it takes advantage of the wastes obtaining important products. In addition, catalytic pyrolysis by using commercial catalysts, e.g. such zeolites, alumina or recovered from other industrial processes, it allows decreases the activation energy and selectivity in the obtained products. In this study, we report the evaluation of the catalytic pyrolysis with a regenerated fluid catalytic cracking catalyst using thermogravimetry with polypropylene and a pyrolytic process carried out in a batch reactor with polypropylene in a 1:10 ratio (catalyst-plastic). The regeneration studies were carried using two solvents (ethanol and toluene) at different contact times, then a thermal regeneration at two heating ramps was performed and the best treatment was evaluated by scanning electron microscopy energy-dispersive X-ray spectroscopy and surface area analysis. The results showed a better action of the ethanol in the chemical treatment at 14 h of contact in the heat treatment due to longer gasification of the coke. The degradation process using recovered catalyst decreases the degradation temperature compared to the no-catalyst process. As a consequence, the yield of the liquid fraction decreases by 10% with greater orientation to aliphatic components. [ABSTRACT FROM AUTHOR]

Lignin hydrogenolysis is a key step in the sustainable production of renewable bio‐based chemicals and fuels. Heterogeneous metal catalysts have led to high yields but they rapidly deactivate, notably due to nanoparticle sintering and carbonaceous deposit formation. While these deposits can be removed by regeneration, sintering is irreversible and a significant barrier to commercialization. Here, simple liquid phase atomic layer deposition is used to deposit an alumina layer to protect nickel particles from sintering. In the gas phase, it is proved that alumina can prevent sintering during reduction up to 600 °C. This catalyst for hydrogenolysis of extracted lignin in batch and continuous operation is used. In batch, the overcoated catalyst maintains high monomer yields with little sintering over four cycles of reuse while the yield obtained with the catalyst without an overcoat reduces to half and severe sintering occurs. In a continuous flow reactor, deactivation rates are three times lower for the catalyst with the alumina overcoat. Microscopy images confirm that the alumina overcoat largely preserves nickel particle sizes after ten days of operation. The results demonstrate that catalyst overcoating with metal oxides substantially slows irreversible deactivation during lignin hydrogenolysis, which could facilitate the development of continuous lignin upgrading. [ABSTRACT FROM AUTHOR]

Nanoporosity is clearly beneficial for the performance of heterogeneous catalysts. Although exsolution is a modern method to design innovative catalysts, thus far it is predominantly studied for sintered matrices. A quantitative description of the exsolution of Ni nanoparticles from nanoporous perovskite oxides and their effective application in the biogas dry reforming is here presented. The exsolution process is studied between 500 and 900 °C in nanoporous and sintered La0.52Sr0.28Ti0.94Ni0.06O3±δ. Using temperature‐programmed reduction (TPR) and X‐ray absorption spectroscopy (XAS), it is shown that the faster and larger oxygen release in the nanoporous material is responsible for twice as high Ni reduction than in the sintered system. For the nanoporous material, the nanoparticle formation mechanism, studied by in situ TEM and small‐angle X‐ray scattering (SAXS), follows the classical nucleation theory, while on sintered systems also small endogenous nanoparticles form despite the low Ni concentration. Biogas dry reforming tests demonstrate that nanoporous exsolved catalysts are up to 18 times more active than sintered ones with 90% of CO2 conversion at 800 °C. Time‐on‐stream tests exhibit superior long‐term stability (only 3% activity loss in 8 h) and full regenerability (over three cycles) of the nanoporous exsolved materials in comparison to a commercial Ni/Al2O3 catalyst. [ABSTRACT FROM AUTHOR]

Bifunctional composite catalysts are very intrigued to produce hydrogen via CO 2 sorption enhanced CH 4 /H 2 O reforming. However, their hydrogen production performance declined over multiple cycles, owing to the structure collapse and the sintering of active component under high-temperature regeneration. This work reported the facile synthesis of long-lasting Ni–Al 2 O 3 /CaO–CaZrO 3 composite catalysts with less inert components (36 wt%) for stable hydrogen production over the multiple cycles of CO 2 sorption enhanced CH 4 /H 2 O reforming. The effects of reaction and regeneration temperature on the hydrogen production performance of Ni–Al 2 O 3 /CaO–CaZrO 3 were explored. Ni–Al 2 O 3 /CaO–CaZrO 3 demonstrated high activity and stability while fixing reaction temperature as 600 °C and regeneration temperature as 750 °C. Of particular importance, H 2 concentration was 98 vol% even after 10 hydrogen production cycles due to the inert component CaZrO 3 having a cross-linked structure. The distribution of CaZrO 3 in the composite as a coral-like structure inhibited the sintering of CaO through high Taman temperature and physical separation. Moreover, it provided the skeleton support and pore volume for the repeated expansion and contraction process of CaO to CaCO 3 during the cycling process. Finally, the sintering of Ni slowed down in appropriate regeneration temperature to maintain the structure of the composite catalyst, which further improved the catalyst's stability over multiple cycles. [Display omitted] • Ni–Al 2 O 3 /CaO–CaZrO 3 catalysts obtained superior H 2 production performance. • CaZrO 3 inhibited CaO sintering through high Taman temperature and physical separation. • Ni sintering slowed down in a suitable regeneration environment. • Reaction temperature affected the activity matching of the catalytic and adsorptive components. [ABSTRACT FROM AUTHOR]

Oilfield sludge is a kind of hazardous waste. In this study, supercritical water oxidation (SCWO) was used to treat oilfield sludge. The effect of operating parameters was investigated, including temperature (390–450 °C), reaction time (5–30 min), oxidation coefficients (OC, 1.0–5.0) and Ni/Al 2 O 3 catalyst. The experimental results showed that higher temperature and higher oxidation coefficient favored the degradation of oilfield sludge. Carbon in oilfield sludge was mainly converted to gas phase, for instance, 63.6% of carbon was converted to gas at 5.0 OC, 20 min and 450 °C without catalyst. The removal efficiency of total organic carbon (TRE) could be up to 96.0% at 450 °C, 20 min, and 4.0 OC without catalyst. Furthermore, the addition of Ni-based catalysts could also improve TRE. TRE and carbon conversion efficiency (CE) were 95.2% and 68.2% at 1.5 OC, 20 min and 450 °C with 20Ni/Al catalyst addition, respectively, which were higher than that of without catalyst (89.5% and 33.8%). The characterization and regeneration of catalyst were also carried out. Catalyst Ni/Al 2 O 3 had good reliability, the TRE of 92.5% and the catalytic recovery efficiency of 52.6% were observed after three cycles. [Display omitted] • Effect of operating parameters on SCWO of oilfield sludge was comprehensively studied. • COD, TOC and mass balance was measured to assess oilfield sludge degradation. • Ni/Al 2 O 3 and regenerated catalysts were tested for improving degradation efficiency. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pretreating catalysts at 800 °C in air impedes adverse sintering at 1000 °C. • Returning to 800 °C regenerates activity in sintered catalysts by redispersing Pd. • Mechanism for the sintering and redispersion of Pd explored. • Regeneration protocol can be repeatably used, due to persisting trap sites on CeO 2. • Regenerated catalysts effectively co-oxidize CO and C 3 H 8. Methods that can impede or reverse the effects of high-temperature sintering and deactivation are necessary to improve the utilization of catalytic materials. This work demonstrates that exposure to intermediate temperatures (800 °C) can effectively regenerate catalytic performance in sintered Pd-CeO 2 catalysts, through the disintegration and partial redispersion of agglomerated Pd, which increases the abundance of sites that interface strongly with the CeO 2 support. Pretreating the catalyst at 800 °C before sintering forms highly dispersed Pd species that slow the sintering of small, polycrystalline CeO 2 domains. This preserves the density of Ce3+ sites that trap mobile Pd, which improves the efficacy of regeneration. The regenerated catalyst is effective in the co-oxidation of CO and C 3 H 8 , two species which are known to competitively adsorb. The simplicity of this treatment makes it attractive for on-stream regeneration of catalyst performance. [ABSTRACT FROM AUTHOR]

MCM-41-type mesoporous silicas were modified with alumina by the impregnation, co-condensation, and template ion-exchange (TIE) methods. The obtained materials were characterized with respect to their chemical composition (ICP-OES), textural parameters (low-temperature N2 sorption), structure (XRD), and surface acidity (NH3-TPD) and tested as catalysts of methanol to dimethyl ether (DME) dehydration in a flow microreactor system. The catalytic performance of the studied materials was analyzed with respect to their porous structure, as well as their density and the strength of their acid sites. It was shown that the performance of the studied catalysts depends on the contribution of the surface exposed aluminum species, as well as their aggregation. For the most active catalyst, the study of its catalytic stability under rection conditions was performed. It was shown that the catalyst can be effectively regenerated by the incineration of carbon deposits under air flow at 550 °C for 1 h. [ABSTRACT FROM AUTHOR]

Soft matter catalyst system allowing controllable manipulation of the organized nanostructure and surface property holds the potential for renewable energy. Here we demonstrate the construction of a continuously regenerative hydrogel photocatalyst that confines the metal‐thiolate coordination induced nanocavity into robust micro‐sized spongy network for water splitting. Thanks to low vaporization enthalpy and fast proton mobility of water molecules confining in nanocavities, the composite delivers outstanding photocatalytic H2 production (TOF of 4568 H2 h−1), nearly 4.5 times higher than that on the catalyst without confinements. Incorporating with conductive polymers, the TOF is substantially improved to 7819 H2 h−1. Impressively, continuous regeneration is for the first time achieved with H2 production retention improved from 24 % to 72 % by regulating optically‐active catalyst surfaces. This optical regeneration method provides new avenues for sustainable solar energy conversion. [ABSTRACT FROM AUTHOR]

Electrocatalysts for boosting the conversion reactions of sulfur (S) have attracted increasing interest in achieving high S utilization and reaction kinetics in lithium-sulfur (Li-S) batteries. However, electrocatalysts may undergo complex changes in electrochemical conditions, especially for the liquid-solid conversion reactions, leading to an unsustainable electrocatalytic effect. Here, we present a functional separator modified with flower-like molybdenum sulfides grown on carbon nanofibers and reveal its real functional state and catalytic mechanism. The in-situ generated Mo 2 S 3 /MoS 2 @CNFs composite on the separator can enhance electron transfer between sulfur species and molybdenum sulfides, improving sulfur reduction kinetics. In addition, the highly electrochemical reactive Mo 2 S 3 located on the separator effectively avoids being covered by insulating sulfides, and provides a new reduction pathway for dissolved polysulfides, which significantly improve sulfur utilization and catalyst durability. As a result, the Li-S battery using MoS 2 @CNFs@PP separator achieved an areal capacity of 5.8 mAh cm−2 at high sulfur loading (∼4.5 mg s cm−2) and demonstrated stable long cycling performance at 1 C. This work provides valuable guidance for maintaining catalyst activity in lithium-sulfur batteries via in situ reconstruction of electrocatalysts. [Display omitted] • The MoS 2 @CNFs@PP separator enables a new S reduction pathway with fast kinetics and maintains good catalytic durability. • Reveal the interaction between MoS 2 @CNFs and sulfides, as well as the regeneration of the electrocatalyst during the cycle. • The Li-S battery with MoS 2 @CNFs@PP exhibits 5.8 mAh cm−2 areal capacity under high S loading and lean electrolyte condition. [ABSTRACT FROM AUTHOR]

Methane dehydroaromatization (MDA) is a promising approach for direct methane transformation to aromatics and hydrogen. The benchmark catalyst Mo/H-ZSM-5 struggles to find commercial adoption because of thermodynamically-limited yields and rapid coking on Brønsted acid and molybdenum carbide species, especially on zeolite external surfaces. Here, gas-phase atomic layer deposition (ALD) overcoats H-ZSM-5 external surfaces with SiO 2 or Al 2 O 3. NH 3 -TPD, HRTEM, and textural properties show that these overcoats exclusively passivate zeolite external surfaces. Under MDA conditions, SiO 2 gives softer coke and increases cumulative benzene yields by 25 %, while Al 2 O 3 strongly decreases yields. H 2 -TPR and UV–visible and Raman spectroscopy show how the overcoats redisperse the MoO x precatalysts, especially over multiple deactivation and isothermal oxidative regeneration cycles. Combined with 27Al-MAS NMR, MoO x redistribution and dealumination are seen as the causes of long-term deactivation over multiple regeneration cycles, and this process continues to occur regardless of the overcoat. Overall, the deposition of a small amount of silica on the outer surface of Mo/H-ZSM-5 reduces the formation of hard coke, which could be regenerated by milder methods such as hydrogen treatment. [Display omitted] • Atomic layer deposition (ALD) of Al 2 O 3 and SiO 2 on zeolite external surfaces. • Their impact on MDA cumulative aromatic formation increases by 25 % for SiO 2 and decreases by 50 % for Al 2 O 3. • Oxide overcoats consume external acid sites and redistribute MoO x domains was key for improved C 6 H 6 yields. • A small amount of silica on the outer surface of Mo/H-ZSM-5 reduces the formation of hard coke. • Permanent deactivation under oxidative-regeneration driven by dealumination and further MoO x redistribution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu/BEA containing exclusively CuO x nanoparticles or ionic Cu+2 were synthesized. • Coke combustion was monitored with thermogravimetry and in situ spectroscopy. • Cu-containing catalysts outperformed BEA alone for all coke combustion. • CuO x nanoparticles were more active than Cu2+, especially for graphitic coke. Active site occlusion by carbon species, often referred to as coke, is a common deactivation mechanism for heterogeneous catalysts. While it is known that transition metals can lower the temperature required for oxidative coke removal, the roles of ionic species and metal nanoparticles in coke removal are not well understood. This work aims to differentiate how ionic and nanoparticle Cu sites catalyze oxidative regeneration of a coked beta (BEA) zeolite catalyst. This was accomplished by synthesizing catalysts containing exclusively CuO x nanoparticles (NPs) or Cu2+ ions supported on BEA, physically mixing Cu/BEA with a coked BEA catalyst, and monitoring coke removal using in situ spectroscopy. Our results point to an improved combustion activity for CuO x NPs relative to Cu2+ ions, especially in the combustion of graphitic-type coke species. This improved understanding of coke combustion in transition metal containing catalysts informs strategies to improve catalyst regeneration, thereby increasing operational lifetimes. [ABSTRACT FROM AUTHOR]

This study presents the CO2 reforming of CH4 over Ni coated monolith catalyst at 800°C and 101.325 kPa. The high CH4 to CO2 ratio employed in this study is similar to the CH4:CO2 ratio of >1 found in biogas. Cordierite monolith samples (0.258 channels per m2) washcoated with alumina are used for the experimental purpose. The study considers the combined deactivation effect due to sulphur poisoning and fouling due to carbon deposition. Four different cases with respect to the introduction and removal of H2S are considered. The rate of deactivation due to simultaneous carbon deposition and sulphur poisoning is much faster than the individual poisoning processes. The catalyst shows almost stable operation for 6 h without the presence of H2S in the feed stream. From the conversion studies, it appears that the pre‐treatment of catalyst samples with H2S leads to negligible sulphur coverage. The sulphur poisoning effect is also found to be reversible. [ABSTRACT FROM AUTHOR]

This study developed three activated CaO-based catalysts from chicken foot bone, catfish bone, and the mixed, employed for the synthesis of biodiesel from the blend of three (2 non-edible, 1 edible) vegetable oil. The catalysts were calcined at 1000 °C for 3 h and were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and BET isothermal adsorption. The blend of oil was achieved through the API gravity ratio, while the blended oil with high acid value was reduced with a strong acid (H2SO4). Process optimization of the reaction conditions was carried out using Central Composite Rotatable Design (CCRD) in the esterification step, while Box Behnken Experimental Design (BBED) was used in the transesterification of the esterified oil to biodiesel. The qualities of the biodiesel were determined using AOAC method.Results showed the oil blend ratio produced biodiesels of low viscosity and density. Catalysts’ characterization showed the amount of CaO-based found through XRD analysis in the catalysts was 93.52%, 91.24%, and 99.84%, respectively. Acid esterification through experimental design by CCRD produced a low blend oil acid number of 1.27 mg KOH/g oil. The maximum experimental biodiesel yields of 93.60, 92.47, and 97.12 (%wt.), but, the statistical optimization predicted values by BBED were 93.86, 92.7685, and 97.2566 (%wt.), which were validated as 93.5400, 91.87, and 96.88% (wt.), respectively, at the reaction time of 69.76 min, the catalyst amount of 4.16 g, the reaction temperature of 69.79 °C, and the CH3OH/OMR of 4.62:1. Catalyst regeneration and reusability showed that the derived catalyst has the potential to be reused in the 4th cycle. The qualities of the biodiesel were well within the limit recommended for biodiesel standard.

The catalyst regeneration is still a challenge to make the ethanol steam reforming (ESR) process feasible for sustainable H2 production. NiAl2O4 spinel derived catalysts are highly active and selective for ESR, but they require avoiding irreversible deactivation to ensure their regeneration. Their stability depends on the catalyst structure, and herein we report different Ni/Al2O3-NiAl2O4 catalysts obtained upon reduction of a NiAl2O4 spinel at 700, 750, or 850 °C. The catalysts were tested in ESR reaction-regeneration cycles, with reaction at 600 °C and regeneration by coke combustion at 850 °C followed by reduction at the corresponding temperature. The fresh, spent, and regenerated catalysts were characterized using X-ray diffraction, N2 physisorption, temperature programmed reduction and oxidation, and scanning electron microscopy. The irreversible deactivation is due to Ni volatilization and catalyst particle fragmentation. These phenomena are prompted by a high filamentous carbon deposition favored by the Al2O3 content in the catalyst. The reduction in the 700–750 °C range is optimum for controlling the Al2O3 content, increasing the NiAl2O4/Al2O3 ratio in the resulting catalyst. These catalysts show a period of partial reversible deactivation by coke with a change in the H2 formation mechanism reaching a pseudo-stable state with a H2 yield of 40% and a reproducible performance in successive reaction-regeneration cycles. [ABSTRACT FROM AUTHOR]

Fluid catalytic cracking (FCC) is the workhorse of modern crude oil refinery. Its regenerator plays a critical role in optimizing the overall profitability by efficiently restoring the catalyst activity and enhancing the heat balance in the riser reactor. Improvement in the device metallurgy and process operations have enabled industrial regenerators to operate at high temperatures with a better coke burning rate and longer operating cycle. Today, the carbon content of regenerated catalyst has drastically reduced to less than 0.1 wt.%. However, the unit is still plagued with operational complexities and insufficient understanding of the underlying dynamic, multiscale intricacies. Recent process-intensification strategies provide insights into regenerator performance improvement potentials. In this review, the importance of the uniform distribution of spent catalysts through structural modification and operational manipulations of the catalyst distributor is discussed. The knowledge of the role of baffles in enhancing excellent gas–solid interaction has been increasing, but skepticism due to its complex hydrodynamic effects on gas–solid flows fends off operators from its application, a critical evaluation of its implication in the regenerators is covered. The understanding of the contribution of air/steam distributor design and feed gas injection techniques for even contact with spent catalyst leading to the improvement in FCC performance is also investigated. The reliability of FCC components is equally a big concern, as unplanned shutdown and enormous economic losses are being witnessed due to device failure. To this end, mitigation approaches to damaging afterburn and high-temperature erosion problems with respect to process control and geometric adjustment in the bed, freeboard, cyclone separators and collection ducts are explored. Emission limits for fluid catalytic cracking unit (FCCU) and products are consistently ratcheting downward; the commingled turnkey solutions to reducing pollutants generation are also reviewed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual fluidized bed methanol-to-olefins reactor-regenerator model was developed. • Lumped reaction kinetics was coupled with a generic 1D two-phase hydrodynamic model. • Bench-scale reactor and regenerator models were validated by literature data. • Pilot and demo-scale dual fluidized bed reactor–regenerator models were validated. • Coke formation and product distribution are well predicted over wide ranges. Based on a lumped methanol-to-olefins (MTO) reaction kinetic model over SAPO-34 catalyst particles, a one-dimensional two-phase model was developed for bubbling fluidized bed reactor and catalyst regenerator. Comparison of the model predictions with literature experimental data showed good agreement over wide ranges of operating conditions both on a bench-scale unsteady-state bubbling fluidized bed reactor as well as pilot and demo-scale steady-state dual fluidized bed reactor–regenerator. The two-phase reactor model was also applied for catalyst coke content combustion with diluted air to design the regenerator of the dual fluidized bed reactor. Finally, the heat duty required for cooling circulating catalyst particles is obtained from overall energy balances. This integrated reactor–regenerator simulation allows for seamless analysis of MTO process. The trade-off between the complexity and applicability of the model makes it a useful choice for conceptual process designs, scale-up, integration with simulation software, optimization, process control and economic analyses. [ABSTRACT FROM AUTHOR]

[Display omitted] • High bio-oil yield of low O content by cascade biomass catalytic fast pyrolysis (CFM). • Acid ZrO 2 /ZSM-5-attapulgite catalyzes CFP; base K-(USY-attapulgite) further upgrades. • Micro-spectroscopy to study deactivation modes and reversibility upon regeneration. • Coke in ZrO 2 /ZSM-5-attapulgite causes acid site poisoning. • K-(USY-attapulgite) deactivated irreversibly, damaging structure and basicity. The modes of deactivation -and the extent to which their properties can be restored- of two catalyst bodies used in cascade for bio-oil synthesis have been studied. These catalysts include a solid acid granulate (namely ZrO 2 /desilicated zeolite ZSM-5/attapulgite clay) employed in ex-situ catalytic fast pyrolysis of biomass, and a base extrudate (K-exchanged zeolite USY/attapulgite clay) for the subsequent bio-oil upgrading. Post-mortem analyses of both catalyst bodies with Raman spectroscopy and confocal fluorescence microscopy revealed the presence of highly poly-aromatic coke distributed in an egg-shell manner. Deactivation due to coke adsorption onto acid sites affected the zeolite ZSM-5-based catalyst, while for the base catalyst it is structural integrity loss, resulting from KOH-mediated zeolite framework collapse, the main deactivating factor. A hydrothermal regeneration process reversed the detrimental effects of coke in the acid catalyst, largely recovering catalyst acidity (∼80%) and textural properties (∼90%), but worsened the structural damage suffered by the base catalyst. [ABSTRACT FROM AUTHOR]

Industrial‐scale reforming of methane is typically carried out with an excess of oxidant to suppress coking of the catalyst. On the other hand, many academic studies on dry reforming employ a CO2/CH4 ratio of unity to quickly observe coking which can be reduced by adding a catalyst promoter. In this work, Ni/Al2O3 catalysts were tested for dry reforming of methane (CO2/CH4=1) with additional regeneration steps to test the resistance against an oxidation treatment. Thereby, we wanted to evaluate catalyst stability for industrial relevance. The effects of three promoters, Cr, Mn and Fe, that differ in their degree of CO2 interaction, are compared. A higher iron loading on Ni/Al2O3 leads to higher stability in dry reforming with lower coke formation. However, the higher the concentration of a promoter with high CO2 affinity, the quicker the catalyst is oxidized during regeneration with CO2. Subsequent reduction of a catalyst oxidized with CO2 leads to considerable sintering in all cases. This sintering induces formation of more coke during dry reforming. On such sintered samples only highly effective promoters in large concentrations still have a noticeable effect compared to unpromoted Ni/Al2O3. [ABSTRACT FROM AUTHOR]

The Modified Fischer-Tropsch process converts CO 2 to chemicals using a dual-function Fe-based catalyst composed typically of magnetite and iron carbides. However, catalyst deactivation limits its industrial application. In this study, we combined Density Functional Theory (DFT) calculations and experiments to provide insights into the underlying catalyst deactivation and regeneration mechanisms. The dynamic state of the catalyst was observed with time on stream, revealing the impact of the evolving reaction mixture along the reactor. Rapid CO 2 and H 2 O dissociation on the carbide phase creates persistent *O, causing Fe 5 C 2 deactivation through oxidation. On the other hand, the direct carburization of Fe 3 O 4 proves challenging due to significant energy barriers, underscoring the need for metallic Fe or a highly reduced surface as a precursor to effective catalyst activation. These insights into iron catalyst evolution during CO 2 reduction can guide the development of strategies for achieving efficient catalyst performance. [Display omitted] • Evolving reaction mixture drives catalyst's phase transformation and deactivation. • Persistent *O surface species from CO 2 and H 2 O dissociation oxidize the carbide phase to Fe 3 O 4 , causing deactivation. • Direct carburization of Fe 3 O 4 faces high energy barriers, highlighting the need for reduction before regeneration. [ABSTRACT FROM AUTHOR]

In this work, agricultural biomass waste was gasified in a two-zone tubular reactor in the presence of steam. Firstly, during preliminary experiments the effect of temperature in the 1st and 2nd reactor zone, as well as the influence of catalysts and steam/raw material ratio was investigated, then the reusability of catalysts was also studied during ten regeneration cycles. Based on the preliminary results, in the 1st reactor zone a lower temperature was used (400 °C), where the yield of carbon dioxide was ∼55 %, which has a positive effect on numerous reactions, also it can be converted to carbon monoxide with proper catalysts with in-situ process. Regarding the temperature, it is important to be mentioned that a significant difference was observed in the yield of synthesis gas at 700 °C thus, the experiments were carried out using 700 °C in the 2nd reactor zone. A natural (Clinoptilolite) and a synthetic zeolite (ZSM-5), a mesoporous alumina (Al 2 O 3) and a carbon dioxide capturing carrier (CaO) were selected and impregnated with nickel for further use and for enhancing the yield of synthesis gas and hydrogen during the gasification process. The utilization of catalysts helped the in-situ reduction of carbon dioxide while their performance in the gasification process during the regeneration cycles was also investigated. Henceforward, the tested Ni/ZSM-5, Ni/Al 2 O 3 and Ni/Clinoptilolite, reduced the amount of carbon monoxide from the 5th regeneration cycles, while the amount carbon dioxide with the four mentioned catalysts was decreased by 15–35 mmol/g raw material, compared to the results obtained during thermal degradation. • Nickel supported ZSM-5, Al 2 O 3 , CaO, Clinoptilolite were used for biomass pyrolysis-gasification. • Steam:biomass ratio was investigated between 0.2 and 1.8 value. • The amount of liquid product was increased with the steam:biomass ratio. • In case of Ni/ZSM-5, from the 4th, while that of Ni/CaO and Ni/Al 2 O 3 from the 6th regeneration cycle no significant change was observed. • H 2 /CO ratio was between 0.03 and 0.15 with zeolites. [ABSTRACT FROM AUTHOR]

Catalyst deactivation is a problem of great concern for many heterogeneous reactions. Here, an urchin‐like LaPO4 catalyst was easily developed for pentane‐2,3‐diol dehydration; it has an impressive ability to restore the activity in situ by itself during the reaction, accounting for its high stability. This facilitates the efficient production of renewable penta‐1,3‐diene from pentane‐2,3‐dione via a novel approach, where penta‐2,3‐diol was obtained as an intermediate in 95 % yield under mild conditions. [ABSTRACT FROM AUTHOR]

The isomerization of glucose to fructose plays a crucial role in the food industry and the production of biomass-derived chemicals in biorefineries. However, the catalyst used in this reaction suffers from low selectivity and catalyst deactivation due to carbon or by-product deposition. In this study, MgSnO 3 catalyst, synthesized via a facile two-step process involving hydrothermal treatment and calcination, was used for glucose isomerization to fructose. The catalyst demonstrated outstanding catalytic performance, achieving a fructose equilibrium yield of 29.8 % with a selectivity exceeding 90 % under mild conditions owing to its acid-base interaction. Notably, spent catalysts can be regenerated by photoirradiation to remove surface carbon, thereby avoiding the changes in properties and subsequent loss of activity associated with conventional calcination regeneration method. This novel approach eliminates the energy consumption and potential structural aggregation associated with traditional calcination regeneration methods. The acid-base active sites of the catalyst, along with their corresponding catalytic reaction mechanism and photoregeneration mechanism were investigated. This study presents a demonstration of the comprehensive utilization of catalytic material properties, i. e., acid-base and photocatalytic functionalities, for the development of a green and sustainable biomass thermochemical conversion system., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

H 2 S and SO 2 poisoning during methane tri-reforming are the main degradation sources for nickel catalysts, especially when exhaust gases are used as reactants. To prolong the lifetime of such applications, it is of primary importance to find strategies which reduce the poisoning effects of sulphur or allow regeneration of poisoned catalysts. The specific feature of tri-reforming, oxygen addition to the reactants, offers possibilities for both of these objectives. This experimental study, based on a specific thermochemical recuperation process, thus scrutinizes three aspects of sulphur poisoning and regeneration during methane tri-reforming focusing on oxygen as key influencing factor: (I) Oxygen addition to the reactants is investigated. (II) A comparison between H 2 S and SO 2 poisoning is made. (III) Catalyst regeneration by oxygen treatment is performed. The conclusions derived from the results allow significant improvements in terms of catalyst stability and regeneration and thus contribute to expand application possibilities of reforming catalysts. Image 1 • H 2 S and SO 2 poisoning during methane tri-reforming was executed. • Sulphur poisoning experiments on a lab-scale sized test rig were performed. • The influence of oxygen on sulphur poisoning was investigated. • Catalyst poisoning was reduced by 71% due to the use of oxygen. • Full catalyst regeneration by oxygen treatment was achieved within 4.2 h. [ABSTRACT FROM AUTHOR]

Diesel particulate filter (DPF) is an advanced technology adopted in diesel vehicles to control particulate matter emissions. However, particulates get accumulated in the DPF and have to be regenerated periodically to reduce the backpressure. Passive regeneration can be done with the aid of catalytic coating on the DPF, for the oxidation of soot. In the present work, Ceria which is an excellent catalyst has been coated over the DPF as nanofibers to ensure passive regeneration at a lower temperature, which aids in the continuous regeneration without soot accumulation. The cerium oxide nanofibers were synthesized by hydrothermal synthesis and characterized. The ceria nanofibers were coated on FeCrAl alloy by dip-coating method, and the regeneration studies were done by Thermogravimetric analysis (TGA) and CO2 emission analysis. TGA analysis shows that the ceria nanofibers ignite the soot oxidation at a lower temperature of 300 °C. CO2 emission analysis shows that the onset temperature of regeneration for the coated sample is 60 °C lesser than that of the uncoated sample. The pressure drop across the DPF for the coated and non-coated sample was found to be almost the same. The prototype of the DPF was tested in a single-cylinder diesel engine. Emission studies show a reduction in opacity up to 10% for the coated DPF as compared to uncoated DPF. Thus the rate of accumulation of soot in the DPF will be decreased, resulting in the increased mileage as the interval of the post-injection for regeneration can be increased. [ABSTRACT FROM AUTHOR]

The application of secondary NOx control methods in medium to low-capacity furnaces is a relatively new topic on the energy market and thus requires further research. In this paper, the results of full-scale research of SNCR and hybrid SNCR + SCR methods applied into a 29 MWth solid fuel fired stoker boiler is presented. The tests were performed for a full range of boiler loads, from 33% (12 MWth) to 103% (30 MWth) of nominal load. A novel SNCR + SCR hybrid process was demonstrated based on an enhanced in-furnace SNCR installation coupled with TiO2-WO3-V2O5 catalyst, which provides extra NOx reduction and works as an excess NH3 “catcher” as well. The performance of a brand-new catalyst was evaluated in comparison to a recovered one. The emission of NOx was reduced below 180 mg NOx/Nm3 at 6% O2, with ammonia slip in flue gas below 10 mg/Nm3. Special attention was paid to the analysis of ammonia slip in combustion products: flue gas and fly ash. An innovative and cost-effective method of ammonia removal from fly ash was presented and tested. The main idea of this method is fly ash recirculation onto the grate. As a result, ammonia content in fly ash was reduced to a level below 6.1 mg/kg.

Booming biodiesel production worldwide demands valorization of its byproduct of glycerol. Acrolein, an important intermediate chemical, can be produced by gas-phase glycerol dehydration catalyzed by solid acids. Because catalysts that lead to high acrolein selectivity usually deactivate rapidly due to the formation of coke that blocks the active sites on their surface, one major challenge of this method is how to extend the service life of the catalyst. Silica-supported silicotungstic acid (HSiW-Si) is a good example of such a catalyst that shows good activity in glycerol dehydration to acrolein initially, but deactivates quickly. In this study, HSiW-Si was selected to probe the potential of using non-thermal plasma with oxygen-containing gas as the discharge gas (NTP-O2) to solve the catalyst deactivation problem. NTP-O2 was found to be effective in coke removal and catalyst regeneration at low temperatures without damaging the Keggin structure of the HSiW-Si catalyst.

Results of a study of the synthesis of hydrocarbons (HC) from CO and H2 in the presence of a commercial Co–Al2O3/SiO2 catalyst at 6.0 MPa and a reaction gas recycle ratio of 2.2–6.0 for 1000 h have been described. Under these conditions, the catalyst deactivation rate depends on the selectivity for synthetic C35+ long-chain HCs (SLCHCs). An increase in the SLCHC content in the products from 27.6 to 39.8% leads to a threefold increase in the catalyst deactivation rate. With an increase in the recycle ratio from 2.2 to 6.0 at a pressure of 6.0 MPa, the olefin content in the synthesis products increases. An increase in temperature leads to a shift of the selectivity toward HCs with a shorter chain. The viscosity of LCHCs condensed in the pores decreases owing to their dilution with lighter HCs, which contributes to an increase in the number of accessible active sites of the catalyst and facilitates catalyst regeneration. [ABSTRACT FROM AUTHOR]

Catalytic methane decomposition was investigated over 40 wt% Fe/Al 2 O 3 catalyst in fluidized bed reactor (FLBR). After optimization of FLBR conditions in terms of catalyst bulk density, particle size, minimum fluidization velocity, and the catalyst bed height, the catalyst activity and stability tests were conducted by comparison with a fixed bed reactor (FBR). Although a similar stable methane conversion was obtained over both reactors, the pressure drop during 35 min operation of FBR was 9 times higher than that of FLBR, which indicated the possibility of continuous operation of methane decomposition process over FLBR. Further, the influence of the space velocity, feed dilution and regeneration on catalysts reactivity was studied in FLBR to conclude that a reaction condition of 12 L/g cat ∙h, feed of 20%H 2 –80%CH 4 and CO 2 -regeneration of deactivated catalysts may be favourable for operating methane decomposition in FLBR continually and effectively to provide stable hydrogen. Catalytic methane decomposition was investigated in a fluidized bed reactor over 40 wt% Fe–Al 2 O 3 catalysts, and optimized the reaction conditions of the fluidized bed reactor. Subsequently, the deactivated catalysts were regenerated by CO 2 oxidation at 750 ̊C. Image 1 • Comparison methane conversion and pressure drop between fluidized and fixed bed reactor. • Optimization of reaction parameters in fluidized bed reactor over 40 wt% Fe/Al 2 O 3 catalysts. • Improved performance of methane conversion over regenerated catalysts by CO 2 oxidation. • Producing bamboo shaped and straight carbon nanotubes over fresh and regenerated 40 wt% Fe/Al 2 O 3 catalysts. [ABSTRACT FROM AUTHOR]

Changes in the oxidation state and chemical environment of vanadium in poisoned and regenerated hydrotreatment (HDT) catalyst were followed by electron paramagnetic resonance (EPR). Oxovanadyltetraphenil porphyrin was used as model poison molecule on synthesized CoMo/Al2O3 HDT-UCV-1 catalyst. Unconventional methodologies of carbiding and nitriding were applied to the deactivated catalyst aiming at recovering its catalytic properties. The results showed that the vanadium incorporation method affected the metallic species on the catalyst surface, particularly the V-support interaction. This work represents an important contribution about the understanding of new phases formed in the spent catalysts after reactivation by means of nitriding and carbiding processes, which are expected to improve the catalytic HDT response. [ABSTRACT FROM AUTHOR]

ReaxFF molecular dynamics simulation has been employed to investigate the iron oxide-catalyzed supercritical water gasification (SCWG) of naphthalene (NAP), a common component of refractory polycyclic aromatic hydrocarbons. Simulation results showed that synergistic effects between SCW and iron oxide catalyst enormously promoted the degradation of NAP and the production of H 2 and CO. During the gasification process, SCW served not only as H source for H 2 generation but also as O source for CO generation and lattice oxygen recompense, while the major roles of iron oxide catalyst were to provide lattice oxygen with high hydrogen-abstraction ability, catalyze SCW to produce more active species, and weaken the C–C bonds. The effects of different parameters were subsequently revealed: increasing the use of H 2 O molecules raised H 2 and CO yields along with the lattice oxygen supplement but slowed the rate of CO generation, high hydrogen recovery was achieved at high NAP concentration accompanied by a low carbon gasification efficiency. Our simulated results further demonstrated that the deactivation of iron oxide catalyst was caused by carbon deposition, lattice oxygen exhaustion and iron loss. SCW media effectively inhibited the iron loss, while calcination in O 2 environment could successfully regenerate the iron oxide catalyst by cleaning up the carbon deposition and replenishing the lattice oxygen. Image 1 • SCW served not only as H source but also as O source. • Iron oxide provided lattice oxygen, catalyze SCW and C–C breaking. • Carbon deposition, lattice oxygen and iron loss caused catalyst deactivation. • Catalyst regeneration mechanism in O 2 environment was also revealed. [ABSTRACT FROM AUTHOR]