Packed Bed Reactor Research Articles

Experimental investigation on product and temperature distribution in a continuous flow packed-bed reactor for dodecahydro-N-ethylcarbazole dehydrogenation

The dehydrogenation of dodecahydro-N-ethylcarbazole (H12-NEC) generates enormous gas accompanied by intense heat absorption, affecting heat and mass transfer in porous catalysts. A packed-bed reactor equipped with a temperature measurement device was designed to investigate the continuous flow dehydrogenation of H12-NEC. The effects of weight hourly space velocity (WHSV), reaction temperature, catalyst particle size, and pressure were evaluated. The results reveal that the volume flow rate of hydrogen will increase with the increase of WHSV. And the reduction of gas–liquid ratio and catalyst particle size facilitates heat transfer causing a more uniform axial temperature distribution within the reactor. As the temperature rises, the hydrogen yield increases along with more by-products. 456 K and 2 mm of catalyst particle size are determined to be the optimal reaction conditions in the study, achieving the hydrogen production rate of 9.61 molH2·gPd-1·h-1. With pressure increasing, the hydrogen yield gradually decreases, but the decreased evaporation of H12-NEC results in a smaller temperature difference between the reactor and heating wall. A comparison with the thermodynamic equilibrium model reveals that the effect of pressure on chemical equilibrium may be more significant than the temperature.

Performance of single PN/A reactor under wide fluctuation of nitrogen load.

Partial nitritation-anammox (PN/A) is a cost-effective technology in high ammonia-nitrogen wastewater treatment. However, PN/A is prone to instability as the ammonia-nitrogen sharply fluctuates. In this study, a packed bed reactor is employed to construct a single-stage PN/A system to investigate the operational characteristics and explore the denitrification mechanism. The effluent NH4+-N concentration, ammonia nitrogen removal rate (ARE), and total nitrogen removal rate (TNR) could be sustained at about 60mg/L, 80%, and over 70%, respectively, when the influent nitrogen load rate (NLR) is changed from 0.733 to 0.879kg-N/m3/day. Both ARE and TNR are decreased when NLR continues increasing to 1.026kg-N/m3/day. The influent NLR decreases from 0.879 to 0.147kg-N/m3/day, and ARE and TNR reached 98% and 85.4%, respectively. Therefore, the denitrification effect of the reactor could be recovered, and the excellent nitrogen removal capacity could be obtained within a wide range of influent NLR. Moreover, the high-throughput sequencing and metagenomic testing indicate that the Proteobacteria and Planctomycetes that the PN/A functional strains (i.e., ammonia-oxidizing bacteria (AOB) and anammox bacteria (AnAOB)) account for 38.8% in the sludge. The relative abundance of Nitrospira containing the nitrite-oxidizing bacteria (NOB) has dropped to 0.01%, and the functional gene nxr of the nitrite oxidation process is also inhibited. The relative expression of the functional gene is dominated by the short-range nitritation and anammox oxidation, which demonstrates that the nitrogen removal is mainly dominated by nitritation-anammox.

Impact of the Channel- to Particle-Diameter Ratio on the Liquid–Liquid Mass Transfer and Pressure Drop in Micro Packed Bed Reactors

Impact of the Channel- to Particle-Diameter Ratio on the Liquid–Liquid Mass Transfer and Pressure Drop in Micro Packed Bed Reactors

Predicting nickel catalyst deactivation in biogas steam and dry reforming for hydrogen production using machine learning

This study employs Random Forests (RF) and Artificial Neural Networks (ANN) to model the transient behavior of Ni catalyst deactivation during steam and dry reforming of model biogas containing H2S, with a focus on hydrogen production. Deactivation, induced by carbon deposition and sulfur poisoning, is a complex and transient phenomenon demanding precise kinetic mechanisms for accurately predicting Ni catalyst behavior in biogas reforming. Black-box machine learning (ML) models are developed, incorporating catalyst properties, biogas composition, and operating conditions. Encompassing both dry and steam reforming, the ML models aim to predict catalyst behavior, expressed in terms of packed bed reactor exit mole fractions (H2, CO, CH4, and CO2) and conversions (CH4 and CO2). The ML models are trained and tested across a temperature range of 700–900 C with 0–145 ppm of H2S in model biogas (CH4/CO2 ratio varying from 1.0 to 2.0). RF outperforms the ANN across all performance metrics, including overall R2 and root mean squared error (RMSE). The RF achieves a mean overall R2 of 0.979, with training and testing RMSE equal to 6.7×10−3 and 1.47×10−2 respectively. In contrast, the ANN achieves a mean overall R2 of 0.939, with training and testing RMSE equal to 2.6×10−2 and 2.55×10−2 respectively. Moreover, pre-trained RF models are validated with unseen data of dry reforming of biogas containing 30 ppm of H2S (25 data points). It is suggested that 35 % of this unseen experimental data is required to train the RF model for it to predict catalyst deactivation, achieving a validation R sufficiently2> 0.9. The mean overall R2 values attained by the RF fine-tuned on 35 % of the unseen experiment data for both CH4 and CO2 conversions, as well as for all mole fraction predictions, are 0.952 and 0.948, respectively.

MoS2 sponge co-catalytic Fenton reaction for efficient degradation of antibiotics: Performance, mechanism and reactor operation

Levofloxacin (LEV) residue is one of the key issues with livestock wastewater, posing a threat to aquatic ecosystems and human health. Herein, MoS2 sponge (MS) co-catalyst was synthesized using a simple impregnation method to construct a MS/Fenton system. Under suitable conditions, MS/Fenton could achieve 95.8 % LEV degradation in 30 min, with a reaction rate constant 9.75 times higher than that of Fenton. The results of the reactive oxygen species identification and material characterization indicated that the massive decomposition of H2O2 generated ROS (•OH and 1O2) and accelerated Fe2+ regeneration were the main factors for pollutant removal. MS/Fenton performed well in various aqueous matrices, reflecting excellent adaptability and anti-interference performance. MS was structurally stable with minimal Mo leaching after the reaction. Furthermore, an external circulation packed-bed reactor was designed for application feasibility verification of the system. The system demonstrated excellent removal efficiency during 20 days of continued operation (without MS regeneration). In addition, MS/Fenton demonstrated a remarkable purification effect on real livestock wastewater. This study offered new insights for the large-scale preparation of recyclable co-catalysts, and the constructed long-acting and stable MS/Fenton system and reactor provide a reference for the green and efficient treatment of practical wastewater.

Evaluation of Bi‐reforming Performance of Bi‐disperse Catalyst in a Packed Bed Reactor

Evaluation of Bi‐reforming Performance of Bi‐disperse Catalyst in a Packed Bed Reactor

Optimization of diformylfuran production from 5-hydroxymethylfurfural via catalytic oxidation in a packed-bed continuous flow reactor.

DFF's diverse applications in pharmaceuticals, fungicides, and polymer synthesis motivate the development of efficient production methods. This study reports the continuous-flow synthesis of DFF from 5-HMF in a packed-bed reactor. The Box-Behnken design coupled with response surface methodology (RSM) was employed to optimize the reaction parameters (catalyst, solvent, temperature, oxygen flow rate, catalyst amount) for DFF yield. Ru/Al2O3 in toluene proved to be the most effective catalyst-solvent combination. The optimal conditions for DFF production were identified as: 140 °C reaction temperature, 10 ml min-1 oxygen flow rate, and 0.15 g catalyst loading. Under these conditions, a DFF yield of 84.2% was achieved.

Decoupling Charge Carrier Electroreduction and Enzymatic CO2 Conversion to Formate Using a Dual-Cell Flow Reactor System.

With an efficient atom economy, low activation energy, and valuable applications for fuel cells and hydrogen storage, formic acid (FA) is a useful fuel product to convert CO2 and reduce emissions. Although metal catalysts are typically used for this conversion, unwanted side reactions remain a concern, particularly when products are attempted to be recovered long-term. In this study, an enzymatic catalyst is used to enable the selective conversion of CO2 to FA, as a formate ion. A dual-cell flow reactor system is used to first reduce a charge mediator electrochemically (reduction cell), which then activates a catalyst to selectively convert CO2 to formate (production cell). This approach minimizes enzyme degradation by avoiding direct contact with increased voltages and improves the quantity of formate produced. The system produced 25 mM of formate and reached over 50% Coulombic efficiency. The larger volume of this dual-cell system increases the quantity of formate produced beyond that of a batch cell. Additional design configurations are employed, including a pH control pump to maintain catalyst activity and a packed bed reactor to improve contact of the charge carrier with the catalyst. Both configurations retained higher production and efficiency long-term (∼168 h). The results highlight the challenges of developing a system where many parameters play a role in optimizing performance. Nevertheless, the ability of the system to produce formate from CO2 demonstrates the potential to improve upon this configuration for a variety of electrochemical CO2 conversion applications.

Production and characterization of two-step condensation bio-oil from pyrolysis

The goal of this project is to investigate the potential of fuel production directly from slow pyrolysis of straw pellets without further refining. A two-step condensation was used to separate liquids from the volatiles. The thermal process chosen is slow pyrolysis at 500°C to couple the fuel production with carbon capture by maximizing the char production alongside bio-oils collection. Condensation parameters were tuned to improve the pyrolysis oil quality. To assess the oil quality some requirements on marine fuels, bio-oils and boiler fuels were taken as reference. Three condensation conditions were inspected: the best pyrolysis overall process was repeated three times for a total of five pyrolysis processes (lately referred to as runs). As expected, the bio-oil characteristic changed with the condensation temperature. As a result of lowering the bio-oil condensation temperature, the bio-oil results less viscous, less dense, with lower heating value and with higher water content. The final bio-oil produced was almost compliant to ISO 8217:2017 for residual marine fuels K 380, apart from water content and acid number, while it was almost compliant for the standard EN 16900:2017 for industrial boilers fuels, apart for the kinematic viscosity. It was assessed that the char is produced with an average yield of 27 w% on dry basis, while bio-oil has a yield between 5 and 10 w%. It is possible to recover an average of 72 % of the total energy contained in the straw in the valuable products, gas, char and bio-oil. The carbon captured with charcoal was around 49 w% of the total present in straw. The pyrolysis experiments were performed using an innovative semi-batch, packed-bed reactor with gas re-circulation and a new two-fraction condensation appliance that is DTU patented. The innovation is both in the reactor, where the gas is directly heated and flushed back into the pyrolyser, and in the condensation section, where the bio-oil is separated from the water fraction during the pyrolysis. The company Stiesdal SkyClean A/S showed interest in further development and scale up of this pyrolysis and condensation system.

Bijel-based mesophotoreactor with integrated carbon nitride for continuous-flow photocatalysis

The integration of continuous-flow technologies with heterogeneous photocatalysis has recently emerged as a promising strategy for the development of sustainable processes. Although conventional packed bed reactors have been extensively utilized in industrial catalytic applications, they face challenges related to energy transfer in the photocatalytic systems. This study presents an innovative approach to address this issue by integrating heterogeneous photocatalysts with an organic polymer, leading to the fabrication of a mesophotoreactor featuring a bijel-based structural configuration. This novel strategy involves hybridizing polypentadecalactone and in situ confining of carbon nitride in a bicontinuous porous mesoarchitecture. The structural and physicochemical properties of the resulting catalytic composite material are evaluated through an array of characterization methods, affirming the successful integration of carbon nitride within the overall structure. The unique bicontinuous porous architecture of the composite and its suitability for industrial applications is verified, as exemplified by its exceptional efficiency in the photodegradation of methylene blue (>99 %) under flow conditions and remarkable stability up to three reaction cycles. A mathematical model is developed to describe continuous photocatalytic processes occurring in the novel tubular mesophotoreactor, with a specific focus on the degradation of the methylene blue dye. This model is successfully validated, leading to results in agreement with the experimental measurements. Additionally, fluid dynamics simulations demonstrate that the mesophotoreactor design allows for the effective diffusion of light through its channels, resulting in higher irradiation levels compared to conventional systems such as packed bed reactors. The innovative design of the catalytic reactor presented in this work offers a versatile and efficient alternative to the conventional heterogeneous systems, significantly broadening the range of applications for photocatalytic processes.

CatchyCFDEM: Open-source microkinetic modeling of heterogeneous catalysis in Eulerian-Lagrangian CFD applied to oxidative coupling of methane

This work introduces catchyCFDEM, an OpenFOAM-based open-source CFD-DEM framework designed for simulating reactive gas–solid fluidized beds with both gas-phase chemistry and heterogeneous catalytic chemistry. A convective gas–solid heat transfer model is implemented and validated using experimental data gathered in a non-reactive pseudo-2D fluidized bed. Catalytic chemistry including different levels of complexity are included: pseudo-homogeneous, heterogeneous without mass transfer, and heterogeneous with diffusive mass transfer. Verification studies are performed by simulating a packed bed reactor using catchyCFDEM and comparing mass fraction profiles to a 1D plug flow simulation in Cantera. To enhance the computational efficiency of the resource-intensive reactive CFD-DEM simulations, speed-up algorithms such as Particle Agglomeration (PA) and in-situ adaptive tabulation (ISAT) are integrated in catchyCFDEM. As a case study, a gas–solid vortex reactor (GSVR) is simulated using the validated framework. The applicability of the GSVR for the oxidative coupling of methane (OCM) is evaluated based on an isothermal analysis evaluating the influence of several operational and geometrical parameters on the process. Finally, a proof-of-concept adiabatic simulation of the GSVR is presented. The catchyCFDEM framework is made publicly available on GitHub.

Rapid fabrication of Ni supported MgO-ZrO2 catalysts via solution combustion synthesis for steam reforming of methane for hydrogen production

In this study, we introduced a solution combustion as a simple, efficient, and rapid technique for synthesis of a nanostructured Ni catalyst supported on MgO-ZrO2 for hydrogen production by steam reforming of methane. A series of Ni/MgO-ZrO2 catalysts with different Ni contents were prepared and investigated to observe a suitable Ni loading content. The evaluation of catalytic performance of the as-prepared catalysts was performed in a packed-bed reactor at 700 °C and atmospheric pressure at steam to carbon ratio (S/C) of 2. As a result, the 20Ni/20MgO-ZrO2 catalyst exhibited not only outstanding catalytic performances, but also minimized coke deposits, attributed to the presence of oxygen vacancies of MgO-ZrO2 solid solution. In addition, combustion synthesis could result in formation of NiO-MgO solid solution, boosting uniform dispersion of Ni particles. A durability test of the optimized 20Ni/20MgO-ZrO2 catalyst was conducted at 700 °C for 50 h, revealing a near constant methane conversion of approximately 92.9%. Although filamentous carbon and carbon encapsulation were observed on the surface of spent catalyst, there is no significant negative impact on the steam reforming performance. In conclusion, this present work highlights the efficacy of the solution combustion method for synthesis of nanostructured Ni/MgO-ZrO2 catalysts with superior catalytic performance and less coke deposits for hydrogen production from methane steam reforming.

Catalytic production of δ-valerolactone (DVL) from biobased 2-hydroxytetrahydropyran (HTHP) – Combined experimental and modeling study

δ-Valerolactone (DVL) is a five-carbon (C5) cyclic ester that can undergo ring-opening polymerization to yield high-performance, biocompatible polyesters. But current market prices of C5 chemicals like DVL are very high due to poor availability of C5 feedstock in petroleum. Herein, we demonstrate a novel route to DVL synthesis via dehydrogenation of biomass-derived 2-hydroxytetrahydropyran (HTHP) over Cu/SiO2 without the use of toxic reagents. Since HTHP exists in thermal equilibrium with 3,4-dihydropyran (DHP) via dehydration, and with 2,2’-oxybis(tetrahydropyran) and 5-(tetrahydropyran-2-yloxy)pentanal via acetalization, we have also determined the thermochemistry (ΔHrxn and ΔGrxn) of each competing reaction using density functional theory (DFT) calculations at the M06–2X/cc-pVTZ level. Lastly, by developing a kinetic model of all 8 reactions involved, we have achieved 84 % selectivity to DVL at 150°C in a packed bed reactor for over 72 hours of time on stream.

Phase–activity relationship of MnO2 nanomaterials in periodate oxidation for organic pollutant degradation

Manganese dioxide (MnO2), renowned for its abundant natural crystal phases, emerges as a leading catalyst candidate for the degradation of pollutants. The relationship between its crystal phase and catalytic activity, particularly for periodate activation, has remained both ambiguous and contentious. This study delineates the influence of various synthetic MnO2 phase structures on their capabilities in catalyzing periodate-assisted pollutant oxidation. Five distinct MnO2 phase structures (α-, β-, γ-, δ-, and ε-MnO₂) were prepared and evaluated to activate periodate and degrade pollutants, following the sequence: α-MnO₂ > γ-MnO₂ > β-MnO₂ > ε-MnO₂ > δ-MnO₂. Through quenching experiments, electron paramagnetic resonance tests, and in situ electrochemical studies, we found an electron transfer-mediated process drive pollutant degradation, facilitated by a highly reactive metastable intermediate complex (MnO₂/PI*). Quantitative structure-activity relationship analysis further indicated that degradation efficiency is strongly associated with both the crystal phase and the Mn (IV) content, highlighting it as a key active site. Moreover, the α-MnO₂ phase demonstrated exceptional recycling stability, enabling an effective pollutant removal in a continuous flow packed-bed reactor for 168 h. Thus, α-MnO₂/PI proved highly effective in mineralizing organic pollutants and reducing their toxicities, highlighting its significant potential for environmental remediation.

A feasibility study on the use of glycerol as a solution to waste renewable energy storage in the United Kingdom

This study has analysed to feasibility of incorporating a biologically derived liquid organic hydrogen carrier (LOHC) into the energy grid as a method of reducing waste renewable energy.With this goal in mind, a scenario has been devised in using glycerol to transport hydrogen for release at domestic homes for use in PEM fuel cells. Through this, a packed bed reactor can fulfil the average load with a glycerol conversion of 94 %. The peak load can be fulfilled by using 3 of these reactors at each home and reducing the temperature to decrease conversion when the energy is not needed. Through the dehydrogenation, many side products are formed, including methanol and ethanol which can be used to regenerate glycerol in a transesterification reaction. For a target conversion of 98 %, a 7.08 m3 reactor vessel would be required to handle the alcohol output of 100 houses.After these simulations, an economic analysis and life cycle assessment was performed. The economic showed operating costs to be around 76.5 $/h, and the capital cost per home to be $33,000. 60% of this investment is the cost of the catalyst used in the dehydrogenation of glycerol. An alternative catalyst is required to reduce this total cost. The life cycle assessment showed very high effectiveness in reducing carbon missions, however, the other pollutants severely damper its viability.

Enhanced CO2 Methanation over Nickel‐Based Unsupported Catalyst Synthesized by Chemical Precipitation Method

AbstractThis study investigated the catalytic CO2 methanation using nickel oxide (NiO) nanoparticles and nickel oxalate (NiC2O4) as catalysts. The NiC2O4 precursor was synthesized through a chemical precipitation reaction between nickel (II) nitrate hexahydrate (Ni(NO3)2.6H2O) and oxalic acid (H2C2O4.2H2O). Nickel oxide (NiO) nanoparticles were synthesized through thermal decomposition of NiC2O4 precursor at 450 °C in air. The samples were characterized by XRD, FTIR, BET, SEM, and EDX. The XRD and FTIR analyses revealed that the NiO nanoparticles were well‐crystallized having size 17.30 nm. The BET analysis of the NiO sample revealed mesoporous NiO nanoparticles with a specific surface area (SBET) of 29.08 m2/g and a narrow distribution of pore sizes. The catalytic performance of NiO and NiC2O4 catalysts studied for the CO2 methanation in tubular packed bed reactor at 150–550 °C and 1 atm. The reduced NiO nanoparticles exhibited more catalytic activity than the decomposed NiC2O4 catalyst. At 380 °C, 1 atm, and gas hourly space velocity (GHSV) of 9000 mL g−1 h−1, the reduced NiO nanoparticle catalyst showed high catalytic activity, with a maximum CO2 conversion of 85.54 %, 99 % CH4 selectivity, and 84.69 % CH4 yield. Furthermore, the NiO nanoparticle catalyst demonstrated excellent stability after 12 h of streaming at 380 °C.

Adsorption of extracellular lipase in a packed-bed reactor: an alternative immobilization approach.

In light of the growing demand for novel biocatalysts and enzyme production methods, this study aimed to evaluate the potential of Aspergillus tubingensis for producing lipase under submerged culture investigating the influence of culture time and inducer treatment. Moreover, this study also investigated conditions for the immobilization of A. tubingensis lipase by physical adsorption on styrene-divinylbenzene beads (Diaion HP-20), for these conditions to be applied to an alternative immobilization system with a packed-bed reactor. Furthermore, A. tubingensis lipase and its immobilized derivative were characterized in terms of their optimal ranges of pH and temperature. A. tubingensis was shown to be a good producer of lipase, obviating the need for inducer addition. The enzyme extract had a hydrolytic activity of 23 U mL-1 and achieved better performance in the pH range of 7.5 to 9.0 and in the temperature range of 20 to 50°C. The proposed immobilization system was effective, yielding an immobilized derivative with enhanced hydrolytic activity (35 U g-1), optimum activity over a broader pH range (5.6 to 8.4), and increased tolerance to high temperatures (40 to 60 ℃). This research represents a first step toward lipase production from A. tubingensis under a submerged culture and the development of an alternative immobilization system with a packed-bed reactor. The proposed system holds promise for saving time and resources in future industrial applications.

Comparative analysis of hydrogen production from ammonia decomposition in membrane and packed bed reactors using diluted NH3 streams

Ammonia decomposition is a key technology for its use as a hydrogen carrier and in the recovery of H2 from waste streams containing ammonia. The coupling of the catalytic decomposition of ammonia with an H2 permeoselective membrane improves the process by mitigating thermodynamic constraints and producing a flux of high-purity hydrogen, not requiring further separation/purification. In this study, we compare the behaviour of an eggshell catalyst 1.3 wt % Ru/Al2O3 catalyst in a packed bed reactor (PBR) and a packed bed membrane reactor (PBMR) using an ultrathin Pd membrane (3.4 μm). Tests were made at 11 bar(a) with a weight hourly space velocity of NH3 in the 0.560–1.68 Lꞏg−1ꞏh−1 range and temperatures of 350–400 °C, e.g. milder conditions than the conventional ammonia cracking catalysts. Under optimised conditions (0.56 Lꞏg−1ꞏh−1, 400 °C, sweep gas flow 0.55 L min−1), the PBMR shows excellent performance, achieving NH3 conversion, H2 productivity and recovery factor of 99%, 47 mmolH2·gRu−1·min−1, and 94.9%, respectively. PBMR increases by ∼50% the conversion rate compared to PBR. Without a sweep gas, PBMR performances are lower, even still higher than in PBR. For the first time, superior or comparable performance was demonstrated compared to similar systems using pure ammonia in terms of conversion, hydrogen recovery, H2 productivity, and Ru utilisation. These results can be further enhanced with vacuum systems to convert diluted ammonia streams into high-purity hydrogen for small-scale distributed systems and can be extended to other reactions.

An efficient technology for dye intermediate production: Process intensification of catalytic hydrogenation of aromatic nitrocompounds in a rotating packed bed reactor

AbstractThe rotating packed bed (RPB) is suitable for catalytic hydrogenation of aromatic nitrocompounds whose reaction rate is limited by the mass transfer rate. However, the matching mechanism between the mass transfer rate and intrinsic reaction rate in the RPB reactor is still unclear. In this work, the matching relationship in the RPB reactor is studied by combining the characteristics of mass transfer and reaction in detail. Effects of various operating conditions on the gas–liquid mass transfer coefficient up to 0.31/s, under working conditions were studied and the mass transfer correlation was proposed. The hydrogenation of p‐nitroanisole was used as a probe reaction to analyze the matching mechanism. Various aromatic nitrocompounds in the RPB and stirred tank reactors were investigated. The reaction efficiency of the former is 5–20 times that of the latter, which further explained the universality of the matching mechanism in the RPB reactor.

Local Gas Holdup, Bubble Size Distribution, and Bubble Velocity in a Submerged Rotating Packed Bed Reactor

Local Gas Holdup, Bubble Size Distribution, and Bubble Velocity in a Submerged Rotating Packed Bed Reactor