Packed Bed Reactor Research Articles

Methane pyrolysis in packed bed reactors: Kinetic modeling, numerical simulations, and experimental insights

Pyrolysis of hydrocarbon feeds such as methane (CH4) and natural gas emerges as a pivotal carbon dioxide-free large-scale hydrogen (H2) production process combined with capturing the carbon as solid material. For fundamental understanding and upscaling, the complex kinetics and dynamics of this process in technically relevant reactors such as packed and moving beds still need to be explored, particularly concerning carbon formation and its impact on reactor performance. This study integrates kinetic modeling, numerical simulations, and experimental findings to comprehensively understand CH4 pyrolysis under industrially relevant conditions and its implications for efficient H2 production and carbon capture. The investigation covers temperatures from 1273 K to 1873 K, H2 addition with H2:CH4 ratios of 0 to 4, and hot zone residence time of 1 to 7 s. Two distinct pathways lead to carbon formation: soot formation and carbon deposition. Each pathway originates from different gas-phase precursors. An elementary-step-based gas-phase reaction mechanism is coupled with a soot formation model from polycyclic aromatic hydrocarbon and a newly developed deposition model from light hydrocarbons. Numerical simulations are performed in a packed bed reactor model, incorporating a method of moments for soot formation and a model for carbon deposition. The model is evaluated against experiments and predicts the effects of operating conditions on gas-phase product distribution and carbon formation. It also estimates the change in bed-voidage over operational time. The study reveals that at the temperature 1673 K, CH4 conversion exceeds 94 %, while both H2 and solid carbon yields surpass 96 %. The sophisticated modeling and simulation framework presented herein thus provides an enhanced understanding of the CH4 pyrolysis process and presents a valuable tool for optimizing this process.

Green chemistry and biocatalysis: Engineering a sustainable future

The increasing role of biocatalysis in the green and sustainable manufacture of chemicals is discussed. In the last two decades the breadth and scope of biocatalysis has increased enormously as a result of remarkable advances in metagenomics, protein engineering and bioinformatics. Moreover, the use of enzymes has become more cost-effective through advances in immobilization technologies and the application of the immobilized enzymes in continuous flow operation in packed bed reactors. Consequently, biocatalysis is already the method of choice for the synthesis of enantiopure chiral products for the pharmaceutical and fine chemical industries. Further applications in commodity chemicals manufacture are currently being stimulated by the increasing maturity of biocatalysis and the ongoing transition to a bio-based circular economy based on the valorization of organic waste on the road to net zero manufacturing.

Gypsum-derived CaO catalytic pyrolysis of palm oil in a continuously packed bed reactor

This study employed a Gypsum-derived CaO catalyst with 10 wt% MgCO3 to convert palm oil into biofuel via pyrolysis in a continuous packed-bed reactor at atmospheric pressure without purge gas. The reaction occurred within the 500–550 °C temperature range, with varying catalyst calcination temperatures. ASTM D86 distillation to separate the pyrolytic oil into biogasoline (75–150 °C), biokerosene (150–250 °C), and biodiesel (250–330 °C) was conducted. The physical and chemical properties of products and catalysts using various techniques were determined. Notably, calcination temperature changes minimally affected the final oxygen content in the product but significantly influenced the textural properties of the catalyst. At a reaction temperature of 525 °C, the 10% MgCO3 catalyst calcined at 850 °C yielded the highest volume of distilled product distilled from pyrolytic oil, accounting for 100% of pyrolytic oil (equivalent to 66.44 vol% of palm oil). It implies that 100% of pyrolytic oil could be converted to distilled oil completely by the distillation process. The primary constituents of the pyrolytic oil were aliphatic and olefinic compounds, with a notable presence of ketones, mainly in the C5 to C33 range. C17 ketones were prominent, constituting approximately 5 wt% of the pyrolytic oil (equivalent to 2.92 wt% of palm oil). These ketones likely resulted from the decarboxylation of carboxylic acids and aldol condensation reactions facilitated by CaO or MgO catalysts. CaO decarboxylation was confirmed by the presence of CaCO3 in the spent catalyst. Additionally, the pyrolytic oil exhibited an acidity of approximately 5.72 mg KOH/g, primarily attributed to phenolic compounds, confirmed through GCxGC-FID, GCxGC-TOFMS, and 1H NMR spectroscopy.

Harnessing Fermentation May Enhance the Performance of Biological Sulfate-Reducing Bioreactors.

Biological sulfate reduction (BSR) represents a promising strategy for bioremediation of sulfate-rich waste streams, yet the impact of metabolic interactions on performance is largely unexplored. Here, genome-resolved metagenomics was used to characterize 17 microbial communities in reactors treating synthetic sulfate-contaminated solutions. Reactors were supplemented with lactate or acetate and a small amount of fermentable substrate. Of the 163 genomes representing all the abundant bacteria, 130 encode 321 NiFe and FeFe hydrogenases and all genomes of the 22 sulfate-reducing microorganisms (SRM) encode genes for H2 uptake. We observed lactate oxidation solely in the first packed bed reactor zone, with propionate and acetate oxidation in the middle and predominantly acetate oxidation in the effluent zone. The energetics of these reactions are very different, yet sulfate reduction kinetics were unaffected by the type of electron donor available. We hypothesize that the comparable rates, despite the typically slow growth of SRM on acetate, are a result of the consumption of H2 generated by fermentation. This is supported by the sustained performance of a predominantly acetate-supplemented stirred tank reactor dominated by diverse fermentative bacteria encoding FeFe hydrogenase genes and SRM capable of acetate and hydrogen consumption and CO2 assimilation. Thus, addition of fermentable substrates to stimulate syntrophic relationships may improve the performance of BSR reactors supplemented with inexpensive acetate.

A Silica‐Supported Yttrium Triflate Packed Bed Reactor for Continuous Flow Michael Addition of Indoles to Benzylidene Malonates

AbstractThe catalytic properties of packed bed reactors filled with Y(OTf)3 immobilised onto functionalised silica have been tested in the Michael addition of indoles to benzylidene malonates under flow conditions, providing improved productivity over the batch conditions, a greater ease of recovery of the final products and a prolonged life of the catalyst. Noteworthy, the same catalytic reactor, after being used for five days, was employed to perform a different reaction, a stereoselective Diels Alder cycloaddition in flow, with a 24 times higher productivity compared to the in‐batch reaction.

A Eutectic Mixture of Calcium Chloride Hexahydrate and Bischofite with Promising Performance for Thermochemical Energy Storage

Thermochemical energy storage using salt hydrates is a promising method for the efficient use of energy. In this study, three host matrices, expanded vermiculite, expanded clay, and expanded natural graphite were impregnated with a eutectic mixture of CaCl2·6H2O and bischofite (MgCl2·6H2O). These composites were subjected to various humidity conditions (30–70% relative humidity) at 20 °C over an extended hydration period to investigate their cyclability. It was shown that only expanded natural graphite could contain the deliquescent salt at high humidity over 50 cycles. Hence, the expanded natural graphite composites containing either CaCl2·6H2O or CaCl2·6H2O/bischofite eutectic mixture were placed in a lab-scale open packed bed reactor, providing energy densities of 150 and 120 kWh/m3 over 20 h, respectively. The eutectic composite showed slightly lower temperature lift, water uptake rate, and power output but at reduced cost. Using the eutectic mixture also decreased the composite’s dehydration temperature at which the maximum mass loss rate occurred around 16.2 °C to 62.3 °C, allowing recharge using less energy-intensive heating methods. The cost of storing 1 kWh of energy with expanded natural graphite composites is only USD 0.08 due to its stability. This research leveraging cost-effective composites with enhanced stability, reaction kinetics, and high thermal energy storage capabilities benefits renewable energy, power generation, and the building construction research communities and industries by providing a competitive alternative to sensible heat storage technologies.

Accelerated Diffusion of a Copper(I)-Functionalized COF Packed Bed Reactor for Efficient Continuous Flow Catalysis.

Flow chemistry provides a neo-orientation for the research and development of chemical technology, in which heterogeneous continuous catalysis based on packed beds can realize rapid separation and recycling. However, options for heterogeneous catalysts are still limited. In this work, we gradually grow covalent organic frameworks (COFs, TpBpy) on the surface of a silica gel (SiO2)-supported substrate to obtain a stable copper(I)-chelated high-loading heterogeneous catalyst (SiO2@CuI-TpBpy). SiO2@CuI-TpBpy shows high catalytic activity in three-component Huisgen 1,3-dipolar cycloaddition, giving the corresponding triazoles with excellent yields and reposeful recyclability under batch conditions. The structures of the catalysts remain steady, and the copper contents are basically unchanged after five cycles. Then, the catalysts are successfully applied for three-component heterogeneous catalysis in a one-pot continuous flow to prepare rufinamide in 89% yield for 24 h stably and efficiently with mere traces of copper ions remaining. More importantly, the catalytic system reveals a minuscule effect of catalyst particle size on internal diffusion. This COF encapsulation strategy presents a new possibility for the design of industrial heterogeneous catalysts with high metal loading and low internal diffusion resistance.

Construction of a continuous packed bed laccase reactor for the elimination of tetracyclines in seawater

Tetracycline antibiotics (TCs) are extensively present in the marine environment and have adverse effects on human health and aquatic ecosystems. Laccases are a type of green biocatalyst for TCs degradation. In this study, a continuous packed bed reactor based on the immobilized modified laccase was constructed to degrade TCs at environmentally relevant levels in seawater. Results showed that the chemical modification and immobilization of laccase had a synergistic effect on its activity and stability in seawater: after incubation in seawater for 12 h, the residual activity of free laccase was only 22.3%, while that of the immobilized modified laccase (A/PhA-Lac) was 79.3%. A laccase reactor was constructed based on A/PhA-Lac, and the response surface regression model was established to optimize the laccase reactor operating conditions. The laccase reactor under optimal conditions could continuously degrade TCs (5 μg/L each) in seawater within 10 h and reach the highest removal rate at 4 to 5 h (removal rates of tetracycline, oxytetracycline, and chlorotetracycline were 94.7%, 86.6% and 98.0%, respectively). The luminescent bacteria microtoxicity and seawater microbial community analysis revealed that the laccase reactor significantly mitigated the toxicity of TCs in seawater. This study provided an environmentally friendly and effective method for the elimination of antibiotics in seawater.

The Impact of Discrete Element Method Parameters on Realistic Representation of Spherical Particles in a Packed Bed

Packed bed reactors play a crucial role in various industrial applications. This paper utilizes the Discrete Element Method (DEM), an efficient numerical technique for simulating the behavior of packed beds of particles as discrete phases. The focus is on generating densely packed particle beds. To ensure the model accuracy, specific DEM parameters were studied, including sub-step and rolling resistance. The analysis of the packed bed model extended to a detailed exploration of void fraction distribution along radial and vertical directions, considering the impact of wall interactions. Three different samples, spanning particle sizes from 0.3 mm to 6 mm, were used. Results indicated that the number of sub-steps significantly influences void fraction precision, a key criterion for comparing simulations with experimental results. Additionally, the study found that both loosely and densely packed beds of particles could be accurately represented by incorporating appropriate values for rolling friction. This value serves as an indicator of both inter-particle friction and friction between particles and the walls. An optimal rolling friction coefficient has been thereby suggested for the precise representation for the densely packed bed of spherical char particles.

Techno-economic and environmental assessment of hydrogen production through ammonia decomposition

Hydrogen is one of the potential candidates to replace fossil fuels to meet net zero emissions target. This study reports a detailed techno-economic and environmental assessment of hydrogen production through ammonia decomposition. The case study is based on a multiple catalytic packed bed reactor with intermediate heating system. Aspen plus® and MATLAB® were linked to evaluate economic and environmental impact of the process. The process parameter like furnace temperature, flue gas recirculation, ammonia decomposition temperature, market ammonia supply pressure, ammonia decomposition pressure, hydrogen purification unit's pressure and equivalence ratio, and economic parameters of capital expenditure (CAPEX) and operating expenditure (OPEX) were considered. The overall thermal efficiency of the developed process is found to be 79%. The levelized cost of hydrogen (LCOH) is estimated and found to be 6.05 USD/kg of H2 based on CAPEX and OPEX. A major contribution of up to 62.2% to LCOH comes from the price of feed Ammonia. Based on 25-year plant life with 10% discounted rate the plant is economically viable, with a return on investment of 23.7%, in a payback period of 3.58 years. Global warming potential of the process is also carried out.

Biodiesel Production from Jatropha Curcas Oil Using Li/Pumice as Catalyst in a Fixed-Bed Reactor

A packed-bed catalytic configuration reactor using pumice granules loaded with lithium (Li/Pumice) as a heterogeneous catalyst was developed for the continuous biodiesel production. For this purpose, Jatropha curcas oil was used as an alternative feedstock to edible oils and diethyl ether was used as a cosolvent to improve the mass transfer between the phases present in the transesterification reaction. The solid catalyst was characterized, and its catalytic activity was evaluated for the biodiesel production. Fatty acid methyl esters (FAME) yield of 100% was achieved under the conditions of 1.4 mL min-1, 20.0 methanol/oil molar ratio, 0.57:1 cosolvent/methanol molar ratio and 40ºC. Moreover, Li/Pumice catalyst shows high stability for the continuous biodiesel production.

Process simulation of methanol production via carbon dioxide hydrogenation

The performance of a packed bed reactor for CO2 conversion to methanol was investigated. Because of the exothermic reaction, temperature and concentration gradients happen along the reactor. A 2D packed-bed reactor model was applied for numerical investigations, coupled with detailed reaction kinetics and transport phenomena. The effect of feed inlet pressure and temperature on CO2 conversion and temperature profiles along the reactor was evaluated. The results showed that firstly increase in the temperature in the reactor because of the presence of exothermic reactions and then slight decrease in the temperature at top section of the reactor. Pressure was decrease from 55 bar to around 54 bar along the reactor. It was found that the CO2 conversion at outlet of reactor was 18.18 % at T = 475 K and it was increased to 23 % at temperature of 498 K and 555 K. The CO2 conversion was reached its maximum at short distance from the reactor entrance at T = 555 K. Also, the outlet temperature of gas mixture was increased from 522.53 K to 534.56 K with increasing feed inlet pressure from 35 bar to 55 bar. The CO2 conversion was 18.12 %, 20.77 %, and 22.96 % at pressures equal to 35, 45, and 55 bar respectively.

Numerical Simulation Study on the Mechanism of Plasma Dissociation of Carbon Dioxide in Atmospheric Pressure Packed-Bed Reactors

This article presents a comprehensive study on the streamer propagation and electric field distribution within a two-dimensional fluid model of a packed bed reactor (PBR) filled with carbon dioxide, utilizing the PASSKEy simulation platform. The research delves into the spatiotemporal evolution of electron density, electric fields and key plasma species in the discharge process. The model simulates a PBR with layered dielectric spheres, indicates that the inner sides of the first and second layers of dielectric spheres are not the primary regions for reactions such as CO<sub>2</sub> dissociation; instead, the main regions are along the streamer propagation path and the outer side of the first layer of dielectric spheres. The study by examining the propagation of streamers in the presence of an electric field, highlighting the influence of anode voltage rise and dielectric polarization on local electric field enhancement. This enhancement leads to increased electron density and temperature, facilitating streamer propagation and the formation of filamentary microdischarges and surface ionization waves. The article provides a detailed analysis of the local electric field evolution at specific points within the PBR. The research further investigates the spatiotemporal dynamics of spatial and surface charges, revealing that negative charges concentrate within the streamer and on the dielectric surface, with densities significantly higher than positive charges. The positive charges' distribution is closely related to the streamer's path, and over time, they come to dominate the charge distribution in the discharge space. The study also explores the surface charge deposition on the dielectric spheres, discusses the evolution trends of the distribution. Additionally, the article discusses the temporal and spatial evolution of key plasma species, including ions and radicals, and their contribution to the overall discharge characteristics. The production mechanisms of carbon monoxide particles, carbon dioxide ions, and oxygen ions are analyzed, with a focus on their spatial distribution and correlation with electron density. The study concludes with an examination of the energy deposition within the PBR, integrating the spatial energy deposition of electrons and major positive ions. The results indicate a total energy deposition value of approximately 1.428 mJ/m, with carbon dioxide ions accounting for 8.8% of this value.

Cross-linked whole cells for the sucrose transfructosylation reaction in a continuous reactor

Fructooligosaccharides (FOS) are fructose oligomers beneficial to human health and nutrition for prebiotic sugars. Their production occurs by a transfructosylation reaction in sucrose molecules catalyzed by fructosyltransferase enzymes (FTase, E.C.2.4.1.9) adhered to microbial cells. The purpose of this work was to study the preparation, enzymatic activity, and stability of glutaraldehyde-crosslinked Aspergillus oryzae IPT-301 cells used as a biocatalyst for the transfructosylation reaction of sucrose in a packed bed reactor (PBR), aiming at FOS production. The highest transfructosylation activity (AT) was presented by the biocatalyst prepared by cross-linking at 200 rpm and 45 min. The highest AT in the PBR was obtained at 50 ?C, with flow rates from 3 mL min-1 to 5 mL min-1 and sucrose concentrations of 473 g L-1 and 500 g L-1. The enzymatic kinetics was described using the Michaelis-Menten model. Finally, the biocatalyst showed constant AT of approximately 75 U g-1 and 300 U g-1 for 12 h of reaction in the PBR operating in continuous and discontinuous flow, respectively. These results demonstrate a high potential of glutaraldehyde-crosslinked A. oryzae IPT-301 cells as heterogeneous biocatalysts for the continuous production of FOS in PBR reactors.

Mechanistic insights into the oxidative coupling of methane over a Li/MgO catalyst: an experimental and microkinetic modeling study

This study investigates the oxidative coupling of methane (OCM) using a Li/MgO catalyst in a packed bed reactor.

Energy-efficient and eco-friendly continuous production of 5-CMF in a UV-ultrasound irradiated catalytic packed bed reactor: heterogeneous kinetics, reactor simulation and LCA analysis

An energy-efficient heterogeneous catalytic (Smopex-101 and TiO2) continuous flow packed bed reactor employing synergistic effects of UV-ultrasound (US) irradiations for the environmentally sustainable synthesis of high purity 5-CMF.

Selective vapor-phase formation of dimethylformamide via oxidative coupling of methanol and dimethylamine over bimetallic catalysts

Selective dimethylformamide formation occurs over PdAu; reactivity and selectivity are sensitive to Pd : Au ratio. Reaction kinetics suggest a crowded surface and that beneficial effects of surface hydroxyls are induced by co-feeding water.

Immobilization of graphene oxide into microbead for fluidized-bed adsorption of methylene blue

Graphene Oxide has shown outstanding performance in the application of adsorption, but these adsorbents are still limited due to some factors. Assembling 2-dimensional (2D) nanomaterials into 3-dimensional (3D) macrostructure (microbead, hydrogel, aerogel, sponge) is a promising alternative to solve the limitation. This paper embedded GO into the two natural polysaccharide polymers (agarose and sodium alginate) to form a 3D-adsorbent. GO-Alg and GO-Agar microbeads were synthesized using the crosslinking method. Analysis techniques such as FT-IR, FESEM-EDX, XRD, and zeta potential were used to characterize the GO-containing microbeads. Adsorption parameters such as adsorbent dosage, pH, contact time, initial ion concentration, and temperature were optimized. Langmuir isotherm and pseudo-first-order kinetic model well fit into the experiment data. The maximum adsorption capacity (qmax) obtained was 120.37 mg.g−1 for removing methylene blue solution. Thermodynamic parameters such as ∆G˚, ∆H˚, and ∆S˚ were determined, and the process was considered endothermic and spontaneous. Reusability results showed good regeneration of GO-Alg microbead up to eight consecutive adsorption-desorption cycles without a significant drop in removal efficiency (> 96%). The application of GO-Alg microbead for MB removal on a packed-bed reactor was investigated in different experimental conditions, and 1 mL.min−1 flow rate with 15 cm bed height revealed a better result. The application of fluidized-bed adsorption was performed to solve the limitation of packed-bed adsorption, and the result showed better adsorption performance than packed-bed using the same operating condition.

Green synthesis approach using deep eutectic solvents to enhance the surface functional groups on porous carbon for CO2 capture

This study explores the potential of green solvents using amino acids-based deep eutectic solvents to alter surface functionality of activated carbon thus enhancing the carbon dioxide (CO2) adsorption capacity. Green solvent is prepared by mixing an amino acid (L-Arginine) with ethylene glycol to form amino acid-based deep eutectic solvents. Amino acid-based deep eutectic solvents were used to modify the surface functionalities of activated carbon derived from palm shell waste. The change in surface functional groups and surface morphology of the modified activated carbon samples were characterized by Fourier-transform infrared spectroscopy and Scanning electron microscopy-energy dispersive X-ray analysis. Then, CO2 removal performance was performed using a packed-bed CO2 adsorption reactor to evaluate CO2 breakthrough time and adsorption capacity. CO2 adsorption experiments were measured at a certain temperature (25–45°C), at a fixed feed flow rate and CO2 concentration of 200 mL/min and 15%. It was observed that modified activated carbon showed the highest breakthrough time (15.2 min) compared to raw palm shell (5.2 min) at an adsorption temperature of 25°C. CO2 breakthrough times significantly decreased with increasing adsorption temperature because of physical adsorption.

Continuous reciprocating plate and packed bed multiphase reactors in biodiesel production: Advancements and challenges

Biodiesel, a renewable and environmentally friendly alternative to conventional fossil fuels, has gained significant attention over the last two decades. Continuous production of biodiesel offers efficiency, productivity, and scalability advantages. This paper provides a concise overview of continuous reactor systems for biodiesel production, focusing on two specific systems-the reciprocating plate reactor and the packed bed reactor-subjects of the authors' extensive research. A thorough comparison of these reactors, spanning biodiesel yield, reaction kinetics, and conversion efficiency, underscores their advantages. The reciprocating plate reactor demonstrates superior mixing characteristics, which improve mass transfer and reaction kinetics. Conversely, the packed bed reactor offers a higher catalyst-to-feedstock ratio and longer residence time, enhancing conversion efficiency. Both reactors exhibit favourable performance for continuous biodiesel production. This research can contribute to understanding continuous biodiesel production using innovative reactor designs. The comparative analysis between the reciprocating plate and packed bed reactors offers valuable insights for process optimization and reactor selection based on specific requirements such as feedstock availability, reaction kinetics, and economic considerations. These insights pave the way for the implementation of sustainable and efficient biodiesel production processes in the future.