Packed Bed Reactor Research Articles

Preparative Isolation of N‐glycans from Natural Sources Mediated by a Deglycosylating Heterogeneous Biocatalyst in Flow

EEfficient methods for isolating N‐glycans are essential to understanding the functions and characteristics of the entire N‐glycome. Enzymatic release using PNGaseF is the most effective approach for releasing mammalian N‐glycans for analytical purposes. However, the use of PNGaseF for preparative N‐glycan isolation is precluded due to the enzyme's cost and limited stability. In this work, we develop a PNGaseF heterogeneous biocatalyst for the preparative isolation of N‐glycans from natural sources. By controlling the immobilization conditions, 100‐85% of offered PNGaseF is immobilized on aldehyde‐functionalized agarose porous microbeads through distinct protein orientations, achieving different performances. The enzyme orientation through the N‐terminus provides the best activity/operational stability balance, being 20% more efficient than that randomly oriented. This active and stable heterogeneous biocatalyst eases its application in a packed bed reactor (PBR) for continuous release of free N‐glycans from a model glycoprotein. This PBR processes 1g of ovalbumin from chicken egg white to isolate 95% of its N‐glycans upon operating the PBR for 7 days. Finally, by tuning the flow rate, we can control the profile of N‐glycans isolated due to different enzyme kinetics for the deglycosylation reactions. In‐line methodologies to isolate N‐glycans open new paths for more sustainable protocols to prepare relevant glycans.

Catalytic Screening for 1,2-Diol Protection: A Saccharose-Derived Hydrothermal Carbon Showcases Enhanced Performance

A benchmarking study is reported on a series of modified carbocatalysts to efficiently promote the acetalization of 1,2-diols under heterogeneous conditions. Among the catalysts surveyed, a hydrothermal carbon generated from saccharose, a cheap, abundant, and biobased material, showed excellent performance when tested on two representative diols. All catalysts have been thoroughly characterized, focusing on surface acidity and composition. Optimal working parameters such as temperature and catalyst loading could be established. Remarkably, sonication improved the diol protection, which proceeded faster at 25 °C. The catalyst could be easily recycled and reused several times. In addition, the protocol was successfully translated from batch to continuous flow operation using a packed-bed reactor.

Organocatalytic Packed-Bed Reactors for the Enantioselective Flow Synthesis of Quaternary Isotetronic Acids by Direct Aldol Reactions of Pyruvates

The utilization of the homogeneous (S)-2-pyrrolidine-tetrazole organocatalyst (Ley catalyst) in the self-condensation of ethyl pyruvate and cross-aldol reactions of ethyl pyruvate donor with non-enolizable pyruvate acceptors, namely the sterically hindered ethyl 3-methyl-2-oxobutyrate or the highly electrophilic methyl 3,3,3-trifluoropyruvate, is described as the key enantioselective step toward the synthesis of the corresponding biologically relevant isotetronic acids featuring a quaternary carbon functionalized with ester and alkyl groups. The transition from homogeneous to heterogeneous flow conditions is also investigated, detailing the fabrication and operation of packed-bed reactors filled with a silica-supported version of the pyrrolidine-tetrazole catalyst (SBA-15 as the matrix).

Mechanism, Performance, and Application of g-C3N5-Coupled TiO2 as an S-Scheme Heterojunction Photocatalyst for the Abatement of Gaseous Benzene.

In this research, S-scheme heterojunction photocatalysts are prepared through the hybridization of nitrogen-rich g-C3N5 with TiO2 (coded as TCN5-(x): x as the weight ratio of TiO2:g-C3N5). The photocatalytic potential of TCN5-(x) is evaluated against benzene (1-5 ppm) across varying humidity levels using a dynamic flow packed-bed photocatalytic reactor. Among the prepared composites, TCN5-(10) exhibits the highest synergy between g-C3N5 and TiO2 at "x" ratio of 10%, showing superior best benzene degradation performance (e.g., 93.9% removal efficiency, specific clean air delivery rate of 1126.9 L g-1 h-1, kinetic reaction rate of 46.1 nmol mg-1 min-1, quantum yield of 6.0 × 10-4 molec. photon-1, and space-time yield of 1.2 × 10-4 molec. photon-1 mg-1). The formation of an S-scheme heterojunction with a built-in internal electric field is supported by both theoretical (through the density functional theory calculations) and photoelectrochemical bases (e.g., improvement in the band potential and electrochemistry along with surface characteristics (e.g., reactive sites and charge migrations at the interface)). The results of the in situ DRIFTS analysis confirm that the oxidation of benzene molecules is accompanied by many reaction intermediates (e.g., phenolate, maleate, acetate, and methylene). The outcomes of this work will help us pursue the development of a state-of-the-art photocatalytic system for air quality management.

Intensification of Sulfamethoxazole Degradation in a Submerged Rotating Packed Bed Reactor

Intensification of Sulfamethoxazole Degradation in a Submerged Rotating Packed Bed Reactor

Numerical simulation study on the mechanism of plasma dissociation of carbon dioxide in atmospheric pressure packed-bed reactors

The streamer propagation and electric field distribution in a two-dimensional fluid model of a packed bed reactor (PBR) filled with carbon dioxide are comprehensively studied by utilizing the PASSKEy simulation platform in this work. The spatiotemporal evolution of electron density, electric fields and key plasma species in the discharge process are studied in depth. The PBR with layered dielectric spheres is simulated by using the model, indicating that the inner sides of the first layer and the second layer of dielectric spheres are not the main 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 sphere. In this work, the propagation of streamers in an electric field is investigated, highlighting the influence of anode voltage rise and dielectric polarization on local electric field enhancement. This enhancement leads the electron density and temperature to increase, which facilitats streamer propagation and the formation of filamentary microdischarges and surface ionization waves. This work provides a detailed analysis of the local electric field evolution at specific points within the PBR, and a further investigation of the spatiotemporal dynamics of spatial and surface charges, revealing that negative charges concentrate in the streamer and on the dielectric surface, with density being significantly higher than that of positive charges. The positive charge distribution is closely related to the streamer path, and with time going by, the charge distribution becomes dominated in the discharge space. This work also explores the surface charge deposition on the dielectric spheres, and discusses the evolution trend of the distribution. Additionally, this work discusses the temporal and spatial evolution of key plasma species, including ions and radicals, and their contributions 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. Finally, the energy deposition within the PBR is examined by 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.

A General Strategy for Controllable Preparation of Nano-CaCO3.

Controllable preparation of inorganic nanomaterials with specific morphology and structure is very important for their applications in various fields. Herein, a general strategy was proposed to controllably synthesize nano-CaCO3 via a water-in-oil microemulsion method in the rotating packed bed reactor. By tuning key parameters, nano-CaCO3 with four primarily analyzed morphologies, including spherical, spindle-like, clustered, or linear formations, can be selectively obtained. The diameters of the nanospheres are adjustable within the range of 4-20 nm, and the lengths of the nanowires can be tuned from 100 to 800 nm. Notably, nano-CaCO3 with four crystal forms, amorphous, vaterite, aragonite, and calcite, can also be controllably synthesized. Importantly, these prepared nano-CaCO3 have excellent dispersity, which can be well-dispersed in dozens of types of liquid media to form transparent or semitransparent nanodispersions. This work provides a general method for producing nanomaterials, enabling precise control over the desired morphology and structure and ensuring commendable dispersibility, which can greatly foster broader preparations and applications of nanomaterials in the fields.

Riboflavin with H2‐Driven or Electrochemical Recycling: A Cheap Cofactor System for Supporting Biocatalytic Alkene Reduction

AbstractThis study shows that the organic cofactor riboflavin provides a cheap and atom‐efficient source of reducing equivalents to sustain biocatalytic alkene reductions by ene‐reductase enzymes, when coupled with a H2‐driven or electrochemical recycling system. We employ the robust NiFe hydrogenase, Escherichia coli Hyd1, for H2‐driven riboflavin reduction and show the feasibility of unmediated electrochemical recycling of reduced riboflavin at a simple carbon electrode. We show that H2‐driven reduction of riboflavin can be extended to continuous flow with a packed bed reactor comprising of Hyd1 immobilized on a carbon support. These findings demonstrate that there is scope for replacing the expensive nicotinamide cofactors—NADH or NADPH with riboflavin, for applications of ene‐reductases in biotechnology in either batch or continuous flow and in electrosynthesis.

Multi-Objective Optimization and Multi-Criteria Decision-Making Approach to Design a Multi-Tubular Packed-Bed Membrane Reactor in Oxidative Dehydrogenation of Ethane

Multi-Objective Optimization and Multi-Criteria Decision-Making Approach to Design a Multi-Tubular Packed-Bed Membrane Reactor in Oxidative Dehydrogenation of Ethane

Thermodynamic and Kinetic Analysis of a CO2 Hydrogenation Pilot Scale Reactor for Efficient Methanol Production

Decarbonization of hard-to-abate industrial sectors, namely the extractive industries, has become an imperative, and thus, processes such as carbon capture and utilization (CCU) have been explored thoroughly and seem to be a promising solution. Carbon dioxide (CO2) catalytic hydrogenation employing green hydrogen (H2) to produce synthetic methanol (MeOH) aims to utilize industrial-captured carbon. A thermodynamic and kinetic analysis of a pilot scale methanol synthesis reactor was conducted by modeling the process using Aspen Plus V12 software. The methanol synthesis model consists mainly of a multi-tubular packed-bed reactor with a thermal oil heat recovery system, a product separator, and an internal recycle loop for optimal efficiency. The reactor has a 5 kg h−1 methanol production capacity, and its heat recovery system achieves an overall heat reduction of 64.1% and can retrieve 1.293 kWh per kg of methanol produced. The overall carbon conversion achieved is 80.6%. Valuable information concerning the design and profile of the reactor is provided in this study.

Synthesis of acylglycerols structured with n3 PUFA in a packed bed reactor with recirculation: Op-timization by response surface

The enzymatic esterification of n-3 PUFA and glycerol (G) catalyzed by a Candida antarctica lipase was studied in a recirculating packed-bed reactor for the synthesis of acylglycerols. An n-3 PUFA concentrate was prepared by chemical hydrolysis of Menhaden's oil followed by urea treatment. A rotatable central composition design was used to evaluate the effect of molar ratio (0.47 – 5.52 mol n-3 PUFA / mol G), temperature (28.14 – 71.86°C) and time (0.24 – 2.76 h) on the production structured acylglicerols. The analysis of variance shows that all principal factors have a significant effect in the different responses (p<0.05). It was determined through response surface methodology that around 80% of global esterification can be reached, by operating with a molar ratio of 0.5 mol PUFA/mol G, 70°C and 2.75 h. In general, models have had a good adjust to experimental data (R2>0.92) and the optimal operating conditions for the formation of the different acylglycerols produced during the esterification (MAG, DAG and TAG) can be established.

Gas–liquid upflow packed bed reactors: a comprehensive review focused on heat transport

Abstract A review of the available information about the packed bed reactors with cocurrent upflow of gas and liquid (UFRs), particularly focused on heat transfer with an external medium through the container wall, was undertaken in this contribution. The typical use of such reactors is summarized as well as some novel applications. A brief discussion about fluid-dynamics is also made due to its strong effect on the transport processes. Experimental setup, available data, and literature correlations of heat transfer parameters are thoroughly reviewed. From a critical analysis of the experimental data, a refined database has been built, which allows comparing the performance of the existing correlations for the two parameters of the extensively employed two-dimensional pseudo-homogeneous plug flow model (i.e., effective radial thermal conductivity and wall heat transfer coefficient). In addition, new correlations for these parameters have been developed, which allow improving the actual predictive capabilities. Finally, the global heat transfer between the bed and the wall was comparatively analyzed for upflow (UFRs) and downflow (TBRs) gas–liquid packed bed reactors.

Commercial Silica Materials Functionalized with a Versatile Organocatalyst for the Catalysis Of Acylation Reactions in Liquid Media.

Silica materials, natural and synthetic variants, represent a promising material for the application in heterogeneous organocatalysis due to their readily modifiable surface and chemical inertness. To achieve high catalyst loadings, usually, porous carriers with high surface areas are used, such as silica monoliths or spherical particles for packed bed reactors. While these commercial materials were shown to be efficient supports, their synthesis is elaborate, and thus less complex and cheaper alternatives are of interest, especially considering scaling up for potential applications. In this work, two commercial silica materials functionalized with the organocatalyst 4-(dimethylamino)pyridine (DMAP) were used in catalytic acylation reactions: a mesoporous silica gel (Siliabond-DMAP) and non-porous silica nanoparticles (Ludox). While both were successfully used in the acylation of phenylethanol, the latter required significantly longer reaction times, presumably due to the lack of mesopores and the associated spatial confinement, as well as agglomeration that limits the active amount of catalyst. Furthermore, we find that the influence of the linker molecule is negligible, since for two different linker motifs the reaction yields and activation energy remain largely similar. Lastly, as main result the commercial material Siliabond-DMAP, despite the non-uniform particles, were employed in a flow setup, thus demonstrating the potential as support material for application in heterogeneous organocatalysis.

Numerical Analysis of Spatial Distribution of Carbon in Methane Dry Reforming over Supported Nickel Catalyst in a Packed Bed Reactor

This study investigates carbon deposition during methane dry reforming over a nickel-based catalyst supported on alumina in a laboratory-scale fixed-bed reactor. Approximately 23.75 grams of catalyst were used, and simulations were performed using COMSOL 6.2 software. The reactor was simulated at isothermal wall conditions at four temperatures (650°C, 750°C, 850°C, and 950°C), with an equimolar CH₄ to CO₂ ratio in the feed. The results showed that while localized carbon deposition density increased with temperature, likely due to a higher local methane decomposition rate, the total amount of carbon deposited was inversely proportional to temperature. This suggests enhanced carbon gasification at higher temperatures. The total carbon deposited was estimated to be around 18 grams after 10,000 seconds of Time on Stream (TOS) at 650°C. As the temperature increased, the total carbon deposition decreased, although this reduction became negligible beyond 850°C. Furthermore, the hydrogen to carbon monoxide (H₂/CO) molar ratio peaked at over 1.1 at 650°C, dropped to approximately 0.76 at 750°C, and then rose back to 0.97 at 950°C. Steady-state operation was not achieved due to continuous carbon deposition and accumulation in the reactor. However, in the absence of carbon deposition, steady-state was reached around 100 seconds after the feed entered, at a velocity of 3 cm/s. Methane conversion reached 97% at 950°C.

The modelling of a multi-tubular packed-bed reactor for ammonia cracking and SOFC waste heat utilization

The modelling of a multi-tubular packed-bed reactor for ammonia cracking and SOFC waste heat utilization

Solid-state fermentation to produce biostimulant agents from green waste: A circular approach at bench-scale

This study aimed to develop a bench-scale process of solid-state fermentation (SSF) to produce biostimulants (indole-3-acetic acid-IAA) by Trichoderma harzianum CECT 2929, utilizing green waste as substrate. Additionally, biopesticide activity (in form of conidial spores) was also studied. The SSF was carried out in a 22-L packed bed reactor using grass clippings as the main substrate and pruning waste or wood chips as bulking agent. When using pruning waste, IAA production reached 62 µg/g dry matter, while the fermentation with wood chips resulted in a higher IAA concentration of 120 µg/g dry matter. Higher spore counts were reached using wood chips (9.5 × 108 and 1.3 × 109 spores g−1 dry matter, respectively). Further experiments showed that decreasing tryptophan as precursor for IAA production from 0.43 % to 0.2 % (w/w) significantly decreased IAA production from 120 to 25 µg/g dry matter while it did not alter spore production. In addition, a sequential batch operational strategy was explored, consisting of four consecutive batches as a strategy to scale-up the SSF process. The highest IAA and spore productions were achieved in the first batch, resulting in 119 µg/g dry matter and 1.1 × 109 spores g−1 dry matter, respectively. Subsequent batches showed a decline in production, particularly in batches 3 and 4, due to contamination issues. Summarizing, the strategies proposed in this study are a considerable advance to develop SSF to produce biostimulant and biopesticide agents in the context of circular bioeconomy, using green waste as raw material.

Open-loop response of Fischer–Tropsch reactions to manipulation of temperature and pressure

Abstract In the present work, the Fischer–Tropsch synthesis (FTS) is carried out through simulation. This reaction uses a gas mixture, called synthesis gas, composed of carbon monoxide rich in hydrogen (H2/CO > 2.5), to form medium and long chain hydrocarbons (C5 +). For the modeling of this system, a packed bed reactor with a cobalt-based catalyst has been considered, which promotes the polymerization of methylene species, selective to linear paraffins and 1-olefins. The objective of this work is evaluating the impact of operation variables, such as feed flows and temperature, coolant flow, system pressure, on the chain length distribution of the products. Current operating policies does not promote selectivity to the production of synthetic gasolines (C5–C12), because of the drastic increase in the temperature inside the reactor as consequence of the high exothermicity of the reactions (ΔH = −170 kJ mol−1). It has been impossible to maintain these reactions within the appropriate temperature range (475–520 K) without the presence of an external agent that manages the available heat, for this project molten sales have been proposed as a cooling medium (KNO3–NaNO3), based on its favorable heat transfer characteristics. By analyzing the system responses, the open loop model has allowed us to explore multiple hydrocarbon production scenarios, specifically highlighting the increasing of the yield of synthetic gasoline (48 wt%) in the products, from a defined molten salts (coolant) countercurrent flow range (7.05E-2 at 2.50E-1 m/h). It was noticed that this heat management allowed us to obtain a specific range of hydrocarbons, representing the opportunity to control the growth of the chain length. In conclusion, this analysis will lay the foundations for the design control policies, which help to increase current yields of synthetic gasoline, making it possible to achieve the desired quality for the immediate future.

Phase Effects in Zirconia Catalysed Glucose Conversion to 5-(Hydroxymethyl)furfural.

5-(hydroxymethyl)furfural (HMF) is a key biomass derived platform chemical used to produce fuel precursors or additives and value-added chemicals, synthesised by the cascade isomerisation of glucose and subsequent dehydration of reactively formed fructose to HMF over Lewis and Bronsted acid catalysts, respectively. Zirconia is a promising catalyst for such reactions; however, the impact of acid properties of different zirconia phases is poorly understood. In this work, we unravel the role of the zirconia crystalline phase in glucose isomerisation and fructose dehydration to HMF. The Lewis acidic monoclinic phase of zirconia is revealed to preferentially facilitate glucose isomerisation, while the nanoparticulate tetragonal phase possesses Brønsted acid sites which favour fructose dehydration. Synergy between both zirconia phases facilitates cascade HMF production, with both catalysts investigated as physical mixtures in batch and flow reactor configurations. Using a physical mixture of only 15 wt % m-ZrO2 with 85 wt % t-ZrO2 in either batch or packed bed reactor configuration is sufficient to reach equilibrium conversion of glucose for subsequent dehydration by the t-ZrO2 component. Under continuous flow, a six-fold increase in HMF production was obtained when operating with a physical mixture of m- and t-ZrO2 compared to that from a single bed of t-ZrO2.

Investigation of microwave-based CO2 regeneration in a packed bed reactor for Direct Air Capture

This study investigates a microwave-assisted Direct Air Capture (DAC) application using Zeolite 13X to capture CO2 from the atmospheric air in Tuscaloosa, Alabama. For the regeneration process, a mono-mode solid state microwave generator with E orientation cavity was applied to desorb CO2 from the sorbent. The main purpose of this study is to explore microwave-based DAC system since there is no detailed parametric study which evaluates all desorption characteristics including temperature and microwave initial power effects on CO2 productivity, regeneration efficiency, desorption kinetics, energy consumption, temperature homogeneity, adsorption, and desorption capacities. In order to investigate all these desorption characteristics, sixteen non-cycling and ten cycling experiments were performed. In non-cycling experiments, regeneration temperature and microwave initial power changed from 45 ℃ to 100 ℃ and from 5 W to 60 W, respectively. The results illustrate that energy consumption to desorb a kg of CO2 can be as low as 60.37 MJ and 23.97 MJ for 100 % and 70 % regeneration, respectively. In cycling experiments, adsorption capacity of each experiment and the effects of 70 % desorption on the adsorption capacity of following experiments were analyzed at the lowest temperature and power conditions (45 ℃ and 5 W). It was found that 70 % desorption does not have significant effects on the adsorption capacity for the following cycles. This study also proves that complete CO2 regeneration can be achieved even at low temperature and initial power values in 3100 seconds.

Experimental investigation of La0.6Sr0.4FeO3 -δ pellets as oxygen carriers for chemical-looping applications

Lanthanum Strontium Ferrite (LSF), as an oxygen carrier, is used for chemical looping H2 production and CO2 utilization. In this work, the first attempt to upscale and understand the heat and mass transfer using 400 g of LSF pellets in a dynamically operated packed bed reactor is carried out.Experiments were conducted at 650–820 °C and 1–5 barg, evaluating the pellets' reactor heat management, phase stability, and mechanical integrity over 70 h for the high-temperature redox cycling in chemical looping water-gas shift (CL-WGS) and chemical looping reverse water-gas shift (CL-RWGS) reactions.Key results at the reactor scale indicate a maximum cyclic average H2O-to-H2 conversion of 31%, with a peak oxygen carrier capacity for CL-WGS of 0.38 mmol/gLSF. In the case of CL-RWGS, a peak CO2-to-CO conversion of 99.8% was achieved, with an oxygen carrier capacity of 0.57 mmol/gLSF.Reactor heat management for exothermic and endothermic redox reactions showed the ability to maintain a high temperature profile where the heat front lagged the reaction front over a 15 cm reactive bed length. A maximum ΔT of 45 °C and 35 °C were observed during the oxidation of the LSF bed with H2O and CO2, respectively. In the case of air oxidation, a maximum ΔT of 120 °C indicates that the reaction is more exothermic and can be used to raise the temperature of the bed especially if heat is required to sustain the process.No evidence of material performance degradation was recorded over 70 h of testing, maintaining the pellets' operational cyclability, phase stability, and mechanical integrity. The results demonstrate the robustness of the material, and they are encouraging versus the scalability of LSF for chemical looping applications, into H2 production and CO2 utilization processes.