Fixed-bed Reactor Research Articles

Light-driven propane dehydrogenation by a single-atom catalyst under near-ambient conditions.

Propane dehydrogenation is an energy-intensive industrial reaction that requires high temperatures (550-750 °C) to overcome thermodynamic barriers. Here we overcome these limits and demonstrate that near-ambient propane dehydrogenation can be achieved through photo-thermo-catalysis in a water-vapour environment. We reduce the reaction temperature to 50-80 °C using a single-atom catalyst of copper supported on TiO2 and a continuous-flow fixed-bed reactor. The mechanism differs from conventional propane dehydrogenation in that hydrogen is produced from the photocatalytic splitting of water vapour, surface-bound hydroxyl radicals extract propane hydrogen atoms to form propylene without over-oxidation, and water serves as a catalyst. This route also works for the dehydrogenation of other small alkanes. Moreover, we demonstrate sunlight-driven water-catalysed propane dehydrogenation operating at reaction temperatures as low as 10 °C. We anticipate that this work will be a starting point for integrating solar energy usage into a wide range of high-temperature industrial reactions.

Silica‐Embedded Metal Oxide Nanoparticles as Epoxidation Catalysts: Batch and Continuous Flow Systems

AbstractCatalytic epoxidation of olefins gives epoxide chemicals for several end‐user products. With the technological advancements of these processes (especially for light olefins), which have importantly contributed to the epoxides market expansion, challenges remain in developing adequate heterogeneous catalysts for converting bulkier olefins, using simple catalyst synthesis procedures, and, on the other hand, studying the catalytic performances under different operation modes. Hence, heterogeneous epoxidation catalysts are prepared via simple one‐pot procedures, with the necessary versatility to tune the material properties for batch and continuous flow operation. Specifically, silica‐embedded nanoparticles of molybdenum oxide (Si/Mo(x), x = Mo loading) and silica‐embedded nanoparticles of binary transition metal oxides (Si/MoM, M = Ta, Nb or W) are synthesized, and promoted the epoxidation of cis‐cyclooctene with tert‐butylhydroperoxide as oxidant, at 70 °C. Epoxide yields in the range of 90%–100% are reached within 4 h, at 70 °C, under batch operation. Under continuous flow, steady state conditions (fixed bed reactor), catalyst Si/MoNb led to ca. 44% epoxide yield, at 70 °C. At 90 °C, Si/MoNb exhibited multifunctionality leading to 51% cyclooctanone yield. It represents the first fully inorganic heterogeneous Mo‐catalyst for continuous flow olefin epoxidation and the first heterogeneous Mo‐catalyst for integrated olefins‐to‐cycloalkanones with hydroperoxides.

Pyrolysis Characteristics of Empty Fruit Bunches at Different Temperatures and Heating Rates

EFB is a biomass waste primarily generated in Southeast Asia, and its pyrolysis enables both waste management and conversion into valuable products. In pyrolysis, the heating rate is a crucial factor; however, studies on its influence on EFB are extremely limited. This study investigates the pyrolysis characteristics of EFB by analyzing product properties based on reaction temperature and heating rate. TGA showed that the thermal decomposition of EFB begins at approximately 210 °C and is largely complete by 400 °C. Furthermore, kinetic analysis using TGA data, applying both differential and integral methods, revealed distinct trends. Through pyrolysis experiments using a fixed-bed reactor, the yield analysis of products under varying reaction temperatures and heating rates demonstrated that higher temperatures promote pyrolysis, leading to a decrease in biochar yield and an increase in gas product yield. For liquid products, a higher heating rate suppressed secondary reactions and led to an increase in the yield of the aqueous phase. Gas product characterization revealed that CO and CO2 formation began simultaneously at approximately 270 °C. GC-MS analysis of the liquid products recovered under different pyrolysis conditions showed that most compounds contained oxygen, originating from hemicellulose, cellulose, and lignin. Additionally, FT-IR analysis of the biochar confirmed that oxygen-containing functional groups decomposed as pyrolysis progressed, and the presence of turbostratic carbon and crystallinity influenced by trace inorganic elements was identified.

Modeling Fixed Bed Reactors of Open-Cell Foam Pellets as Porous Media

Modeling Fixed Bed Reactors of Open-Cell Foam Pellets as Porous Media

Facile Fabrication of Robust Supraparticles for Spatially Orthogonal Cascade Catalysis.

Macroscopically sized supraparticles (SPs) are emerging as cutting-edge materials for industrial applications because of their unique properties unachievable for their nano-building blocks, but their effective methods are lacking. Here, we develop a conceptually novel strategy to assemble binary or ternary nanoparticles (NPs) within compartments of droplets through electrostatic interactions, making it possible to facilely fabricate millimeter-sized multicomponent ionic supraparticles (ISPs). The assembled ISPs possess unexpectedly high mechanical strength (50 N per bead), being amenable to practical applications. The key factors governing the assembly behavior of nano-building blocks within water droplet compartments have been identified through regulating the size and charge density of NPs or ionic strength, providing key insights into multilevelled assembly of NPs beyond the conventional assembly. Our strategy is demonstrated to be versatile since a library of tailor-made ISPs containing multicomponent, diversely shaped and differently sized NPs can be facilely fabricated. As a proof of this concept, we showcase that this method enables to prepare spatially orthogonal cascade catalysts by co-assembling acidic, basic and metal sites in a single millimeter-scaled particles. The catalysts exhibited significantly enhanced catalytic efficiency in a one-pot cascade synthesis of α-alkylated nitriles and high operational stability (200 h) in industrially preferred fixed-bed reactors.

Torrefaction of tea brewing waste pellets and investigation of their pyrolysis properties under isothermal conditions by macro-TGA approach

This study examines the torrefaction of tea-brewing waste (TBW) in pellet form to assess its suitability as a biochar precursor. Torrefaction experiments were carried out over periods of 30 and 60 min. in a fixed-bed reactor under an inert nitrogen atmosphere, maintaining a flow rate of 100 ml.min−1 at temperatures of 200 °C, 250 °C, and 300 °C. We investigated the impact of torrefaction conditions on energy yield (EY), higher heating value (HHV), and the yield of the solid product. The pyrolysis of both raw TBW and torrefied samples (TS) was modeled using macro-TGA in a static atmosphere. Isothermal pyrolysis kinetics were analyzed through the Coast-Redfern (CR) method to elucidate the thermal degradation behavior and underlying reaction mechanisms. The HHV of torrefied samples varied between 23.29 MJ.kg−1 and 27.08 MJ.kg−1 under conditions of 250 °C for 30 min. and 300 °C for 60 min. Concurrently, the O/C and H/C atomic ratios diminished as both the temperature and duration of the process increased. The chemical kinetics F(3) model, indicative of a third-order reaction where the reaction rate is proportional to the cube of the remaining reactant concentration, yielded the most precise depiction of thermal degradation. The activation energy and frequency factor for raw TBW were established at 31.29 kJ.mol−1 and 17 s−1, respectively. Thermodynamic parameters ΔH, ΔG, and ΔS were calculated to be 25.27 kJ.mol−1, 62.75 kJ.mol−1, and −0.049 kJ.mol−1K−1, respectively, confirming the endothermic nature of the pyrolysis process. These values suggest a trend toward spontaneous occurrence and a reduction in product disorder relative to the reactants.

Ozone pretreatment and process optimization to improve fuel pellet production from sugarcane bagasse pith.

Ozone pretreatment and process optimization to improve fuel pellet production from sugarcane bagasse pith.

Aqueous-phase reforming of mannitol over Pt/C catalyst in a fixed-bed reactor

Aqueous-phase reforming of mannitol over Pt/C catalyst in a fixed-bed reactor

Intrinsic reaction and deactivation kinetics of Methanol-to-Propylene process (MTP) over an industrial ZSM-5 catalyst

Intrinsic reaction and deactivation kinetics of Methanol-to-Propylene process (MTP) over an industrial ZSM-5 catalyst

Maximizing CH4 yield by thermodynamically optimizing the temperature profile of fixed-bed CO2 methanation reactors

Maximizing CH4 yield by thermodynamically optimizing the temperature profile of fixed-bed CO2 methanation reactors

Improvement of heat transfer and reaction performance of a K2CO3 fixed-bed energy storage reactor using topology optimization

Improvement of heat transfer and reaction performance of a K2CO3 fixed-bed energy storage reactor using topology optimization

Process behavior analysis of a fixed-bed solar reactor for hydrogen generation via two-step thermochemical redox cycling

Process behavior analysis of a fixed-bed solar reactor for hydrogen generation via two-step thermochemical redox cycling

A novel multivariable optimization strategy for methanol to propylene fixed bed reactors using a hybrid algorithm

A novel multivariable optimization strategy for methanol to propylene fixed bed reactors using a hybrid algorithm

Scalable wastewater treatment: Performance of zeolite and bentonite in a fixed-bed reactor for textile effluents

Scalable wastewater treatment: Performance of zeolite and bentonite in a fixed-bed reactor for textile effluents

Optimizing operational strategies in a non-isothermal bench-scale fixed-bed reactor for CO2 hydrogenation to CH4 combining experimental and modeling and simulation approaches

Optimizing operational strategies in a non-isothermal bench-scale fixed-bed reactor for CO2 hydrogenation to CH4 combining experimental and modeling and simulation approaches

Continuous chemical looping combustion of CH4 in a parallel dual fixed-bed reactor using Fe-Cu oxygen carriers

Continuous chemical looping combustion of CH4 in a parallel dual fixed-bed reactor using Fe-Cu oxygen carriers

Olefin selectivity of K-Mn promoters on CoFe-ZSM-5 based catalyst in CO2 hydrogenation.

The conversion of carbon dioxide (CO2), a major greenhouse gas, into light olefins is crucial for mitigating environmental impacts and utilizing non-petroleum-based feedstocks. Thermo-catalytic CO2 transformation into valuable chemicals offers a promising solution to this challenge. This study investigates the effect of potassium (K) and manganese (Mn) promoters on CO2 conversion and C2H4 selectivity over CoFe-ZSM-5 zeolites. Structural characterization via FTIR, pyridine-FTIR, and PXRD confirmed the successful incorporation of K and Mn into CoFe-ZSM-5 at 80°C without significant structural changes to the zeolite framework. BET analysis revealed that metal incorporation did not substantially alter the surface area, while SEM and TEM analyses confirmed the preservation of ZSM-5 spherical morphology. Fixed-bed reactor experiments conducted at 350°C and 20bar demonstrated that K and Mn synergistically enhanced CO2 conversion efficiency and selectivity toward C2H4. The K-Mn/4Fe4Co-ZSM-5 catalyst (modified with 4% Co and 4% Fe) exhibited the highest performance, achieving 97% olefin selectivity. Furthermore, Mn and K promoters reduce the CO selectivity on the Co-Fe-ZSM-5 catalyst. These findings underscore the critical role of K and Mn in facilitating efficient CO2 activation and directing the reaction pathway toward valuable olefin products.

Enhancement of Bio-H2 Purification Performance in a Multi-Stage Desulfurization Process Using Mining Waste and LaNi5

The fuel-cell (FC) power system, utilizing biohydrogen from biomass resources, is a promising alternative to fossil fuels. However, hydrogen sulfide (H2S) in bio-syngas can severely degrade FC performance and increase environmental impact, necessitating impurity removal. This study investigates a multi-stage desulfurization process using neutralized sediment (NS) and a metal hydride (LaNi5) as H2S adsorbents. NS, a mining waste material, can potentially reduce environmental impact when repurposed as an adsorbent, with its performance influenced by pore configuration and Fe content. However, the purified gas does not fully meet FC fuel specifications. To address this, LaNi5, which selectively absorbs and releases hydrogen, was incorporated to achieve higher purification levels. In our study, H2S adsorption tests were conducted using two fixed-bed flow reactors heated to 250 °C, where a gas mixture containing 196 ppm of H2S flowed through the system. The proposed multi-stage system achieved a breakthrough time of 182.5 h with purified gas remaining under 0.1 ppm and an adsorption capacity of 16.4 g/g-sorbent. These results demonstrate the high desulfurization performance achieved using NS and LaNi₅.

Valorization of Municipal Solid Wastes and Paper Mill Sludge Through Their Steam Co-Gasification for the Production of Energy Carriers Rich in H<sub>2</sub> and Lean in Greenhouse Gas Emissions

This study aimed to explore the valorization of municipal solid wastes and paper mill sludge through their steam co-gasification, for the production of energy carriers rich in H2 and lean in CO2 greenhouse gas emissions. Waste concrete fines and paper sludge ash were investigated as CO2 sorbents and Na2CO3 as a catalyst. The experiments were carried out in a fixed bed reactor coupled with a thermal analysis-mass spectrometer unit. The analysis encompassed various aspects including the composition of the resulting gas and its heating value, H2 and syngas yield, fuel conversion and energy recovery, under different operating conditions. When quarry dust was used to capture CO2 at a calcium-to-carbon molar ratio of unity and 750 °C, H2 in the product gas was 75.7 mol%, molar ratio H2/CO was 7.19 and syngas yield was 0.65 m3/kg. When the Na2CO3 catalyst was added at a loading of 20%, H2 in the gas mixture was increased to 81%, the syngas yield to 2.82 m3/kg and conversion of fuel was complete. When paper sludge ash was used as CO2 sorbent a higher amount of CO2 was captured, however the selectivity towards H2 production was lower. The performance of Na2CO3 catalyst was better in the presence of quarry dust sorbent.

New Insights into the Key Role of Thermal Treatment in V/P/O Catalysts for the Selective Oxidation of n-Butane to Maleic Anhydride.

This work explores the thermal treatment of V/P/O catalyst precursors to achieve active and selective catalysts for the oxidation of n-butane to maleic anhydride (MA) in a continuous-flow fixed-bed reactor. Vanadyl pyrophosphate (V4+, VPP), the key catalyst component, is produced together with suitable V5+ vanadium orthophosphate (VOPO4) allotropic forms by thermally treating vanadyl hydrogen phosphate hemihydrate (VHP) under various atmospheres and temperature ramps. The characterization conducted by using X-ray diffraction, Raman spectroscopy, and reaction testing allowed the identification of optimal conditions for active and selective catalysts. Oxygen is necessary for obtaining VPP and affects the vanadium oxidation state, which is a crucial parameter for selectivity. Water enhances the crystallinity and conversion of VHP to VPP. An optimized calcination atmosphere (6:10:84 mol % O2/H2O/N2) ensures 70% MA selectivity at 50% butane conversion at 400 °C. VHP precursors characterized by higher P/V ratios allow us to obtain higher MA selectivity when treated under the same calcination conditions. This study provides valuable insights into the VPP production steps, representing the starting point for fine-tuning the calcination conditions based on the VHP properties (i.e., P/V ratio and carbon content).