Maximum Space Time Yield Research Articles

Synthesis of α-hydroxy ketones through novel one-pot multi-enzyme cascade system from racemic epoxides

α-Hydroxy ketones, highly versatile building blocks, present challenges for their green and efficient synthesis. Based on thermodynamic analysis, a novel in vitro one-pot multi-enzyme cascade system was designed for synthesizing 2-hydroxyacetophenone (1c) from racemic styrene oxide (1a). This system incorporated a Rhodotorula paludigena epoxide hydrolase (RpEHL360V) for the enantioconvergent hydrolysis of rac-1a to (R)-phenyl-1,2-ethanediol (1b), a Bacillus subtilis (2,3)-butanediol dehydrogenase (BsBDHAI49L/V266L/G292A) for the subsequent oxidation to 1c, and a Lactobacillus casei lactate dehydrogenase (LcLDH1) for the reduction of pyruvate to lactate, thereby facilitating coenzyme recycling and shifting the reaction's thermodynamic equilibrium. After optimizing the reaction conditions, the system reached its highest efficiency using cell-free extracts of RpEHL360V (4.0 U/mL), BsBDHAI49L/V266L/G292A (0.3 U/mL), and LcLDH1 (0.1 U/mL), along with 4 mM NADH and 200 mM sodium pyruvate as cofactor and cosubstrate, respectively, in a Na2HPO4-NaH2PO4 buffer (100 mM, pH 8.0) at 30 °C. Under these conditions, the system catalyzed the conversion of 50 mM rac-1a to 1c with a total yield of 73.1 % and a maximum space-time yield of 10.7 mmol/L/h within 24 h. Furthermore, this one-pot system was applied to catalyze 20 mM of rac-4-chlorostyrene oxide and 1,2-epoxyhexane, successfully synthesizing two corresponding α‑hydroxy ketones, each with a space-time yield of 0.7 mmol/L/h, demonstrating the system's efficacy for the production of α‑hydroxy ketones.

A Two-Stage Cascade for Increased High-Value Product Accumulation in Chlamydomonas asymmetrica

Cascade systems are used in the large-scale production of astaxanthin, facilitating a successful value-added process despite high accumulating costs. However, their application to other high-value products (HVPs), like lutein, β-carotene, chlorophylls, and fatty acids, remains unexplored. This study investigates Chlamydomonas asymmetica in chemostatic cultures, focusing on the impact of light and dilution rate. A two-stage cascade system is designed, combining high-light growth with low-light pigment accumulation. The results show potential for productivity improvement. Notably, the spacetime yield (STY) of Chlorophyll a increased by 20.96%, reaching 2.73 g·L−1·d−1 at the lowest dilution rate. Lutein maintains a consistent concentration of 22.34 mg·g−1, while β-carotene achieves a maximum STY of 3.60 mg·L·d−1. A cascade modification with a hollow fiber membrane significantly enhances HVP concentrations—Chlorophyll b, Lutein, Chlorophyll a, β-carotene, EPS, and GLA increase 27.23%, 38.95%, 31.88%, 86.19%, 128.7%, and 57.71%, respectively. STY improvements for these HVPs range from 1.78% to 82.96%. This study offers insights into C. asymmetica’s response and proposes a cascade modification for enhanced HVP production and downstream processing efficiency.

Continuous Fatty Acid Decarboxylation using an Immobilized Photodecarboxylase in a Membrane Reactor.

The realm of photobiocatalytic alkane biofuel synthesis has burgeoned recently; however, the current dearth of well-established and scalable production methodologies in this domain remains conspicuous. In this investigation, we engineered a modified form of membrane-associated fatty acid photodecarboxylase sourced from Micractinium conductrix (McFAP). This endeavour resulted in creating an innovative assembled photoenzyme-membrane (protein load 5 mg cm-2 ), subsequently integrated into an illuminated flow apparatus to achieve uninterrupted generation of alkane biofuels. Through batch experiments, the photoenzyme-membrane exhibited its prowess in converting fatty acids spanning varying chain lengths (C6-C18). Following this, the membrane-flow mesoscale reactor attained a maximum space-time yield of 1.2 mmol L-1 h-1 (C8) and demonstrated commendable catalytic proficiency across eight consecutive cycles, culminating in a cumulative runtime of eight hours. These findings collectively underscored the photoenzyme-membrane's capability to facilitate the biotransformation of diverse fatty acids, furnishing valuable benchmarks for the conversion of biomass via photobiocatalysis.

Effect of glucose pretreatment on Cu-ZnO-Al2O3 catalyzed CO2 hydrogenation to methanol.

A series of Cu-ZnO-Al2O3 catalysts (CZA) were prepared by glucose pretreatment and applied for methanol synthesis from CO2 hydrogenation. The advantages of the glucose pretreatment and the effects of glucose content were investigated by XRD, N2 physisorption, SEM, N2O chemisorption, CO2-TPD, H2-TPR, TG, and XPS characterization techniques. The influence of glucose pretreatment on the average Cu particle size and the interaction between different components, as well as the effects of the amount of glucose on the Cu specific surface area, the ratio of Cu0/Cu+ and the performance of the catalysts were discussed. The results showed that the catalysts prepared by glucose pretreatment increased the number of basic sites and had a significant advantage in methanol yield. The optimum content of glucose was beneficial to improve the catalytic performance of the CZA catalyst. The maximum space-time yield of methanol was obtained by 2 wt% glucose pretreatments at 200 °C, which was 57.0 g kg-1 h-1.

Process Intensification of the Propane Dehydrogenation Considering Coke Formation, Catalyst Deactivation and Regeneration—Transient Modelling and Analysis of a Heat-Integrated Membrane Reactor

A heat-integrated packed-bed membrane reactor is studied based on detailed, transient 2D models for coupling oxidative and thermal propane dehydrogenation in one apparatus. The reactor is structured in two telescoped reaction zones to figure out the potential of mass and heat integration between the exothermic oxidative propane dehydrogenation (ODH) in the shell side, including membrane-assisted oxygen dosing and the endothermic, high selective thermal propane dehydrogenation (TDH) in the inner core. The developing complex concentration, temperature and velocity fields are studied, taking into account simultaneous coke growth corresponding with a loss of catalyst activity. Furthermore, the catalyst regeneration was included in the simulation in order to perform an analysis of a periodic operating system of deactivation and regeneration periods. The coupling of the two reaction chambers in a new type of membrane reactor offers potential at oxygen shortage and significantly improves the achievable propene yield in comparison with fixed bed and well-established membrane reactors in the distributor configuration without inner mass and heat integration. The methods developed allow an overall process optimization with respect to maximum spacetime yield as a function of production and regeneration times.

Large-scale synthesis of ionic liquid [BMIM]Br in a microbore tube

Large-scale continuous synthesis of ionic liquid [BMIM]Br in solvent-free mode is carried out in a 862 μm diameter microbore tube. A 750 μm diameter T-junction is used to mix the two reactant streams. The effects of reaction temperature, residence time and flow velocity on product yield, space-time-yield (STY), production rate (PR) and specific power consumption are studied. Product yield is observed to increase with an increase in residence time and reaction temperature. The conditions which maximize STY and PR while ensuring that the overall reaction is kinetically controlled and yield is close to 100% are obtained. Maximum STY of 213.1 g/min-L could be attained at reaction temperature of 90 °C and a residence time of 4.93 min. At the same conditions maximum PR of 7.1 kg/day could be attained with 100% yield, the specific power consumption being 27.67 W/kg. Plug flow reactor (PFR) model is found to reproduce experimental data better compared to a laminar flow reactor (LFR) model. Performance of a simple T-junction micromixer is compared with commercially available micromixers and is found to be at par with them.

Continuous Production of Formic Acid from Biomass in a Three-Phase Liquid–Liquid–Gas Reaction Process

In this contribution, we present for the first time a continuous production of formic acid under industrially relevant conditions using real biomass as a feedstock. A scale up to 2 L of reaction volume including product separation and catalyst recycling in an automated continuous miniplant has been realized and demonstrated for 670 h time-on-stream using sucrose as a feedstock with space-time yields of 1.1 gFA L–1 h–1, a turnover number (TON) of 840, and an average turnover frequency (TOF) of 1.3 h–1. Very remarkably, by performing a sensitivity analysis, a maximum space-time yield of 1.7 gFA L–1 h–1 was achieved. Moreover, we could demonstrate that oxygen pressures of only 0.5 bar are sufficient for complete catalyst reoxidation in our miniplant. This shows great potential for simply using air as the oxidant in a large-scale application. Very importantly, an experiment with molasses as the substrate showed the use of a technically relevant biomass for a long-term economic application of the continuous OxFA process. By using optimized conditions from the sensitivity analysis, a total amount of 1.2 g h–1 of formic acid could be continuously produced by our miniplant.

Design of an Electrocatalytic Flow Reactor for the Electrosynthetic Aldol Reaction of Acetone

Organic electrosynthesis is a field within electrochemistry that concerns the synthesis of organic products using the electron as a redox agent instead of chemical reductants or oxidants. It offers several important advantages to conventional synthetic methods, such as less aggressive process conditions (reactions can be carried out at ambient temperature and pressure), higher selectivity (precise control of reaction by control of electrode potential), ability to produce unstable or hazardous reagents in situ and less generation of pollutants and waste streams. It is a versatile and inherently environmental-friendly technique, considered a “clean” and “green” process. Its advantages make it an interesting alternative for industrial applications. However, despite its potential, its implementation is limited. A major drawback is the lack of the necessary combined knowledge on organic synthesis, electrochemistry and engineering aspects. This work aims to bridge the gap between the engineering aspects and the fundamental electrochemical mechanistic insights of a reaction. One reaction that exhibits drawbacks to which electrosynthesis offers an answer, is the aldol condensation: an important reaction for the formation of carbon-carbon bonds. The often several possible reaction pathways between the various reactants and products of the aldol condensation make it difficult to promote the desired reaction. The homogeneous catalysts which are often used in industry require an intensive purification afterwards which often destroys the catalyst. Additionally the purification causes large waste streams. In this work, the potential-controlled electrochemical aldol reaction of acetone to diacetone alcohol is studied in a standard batch electrolysis set-up as well as in an electrochemical continuous flow microfluidic reactor. In the batch set-up the influence of a number of parameters such as electrolyte composition, electrode material and electrolysis potential is described. Starting with pure acetone and a quaternary ammonium salt as support electrolyte, a maximum concentration of 15 m% diacetone alcohol is obtained after 2 h electrolysis in a divided set-up with a platinum electrode at -2.5 V [1, 2]. These results are taken into account in the optimisation towards maximum space-time yield and diacetone alcohol selectivity in the electrochemical micro flow reactor. Employing a flow cell system has important benefits which allows for a more efficient reaction such as a high surface-to-volume ratio of the electrode area to the reaction volume and close proximity of the electrodes. In addition optimization of the flow rate and cell height allows high yields of product in continuous operation. Incorporating a membrane in the reactor prevents cross-over of products which is detrimental for the yield. [1] D. Pauwels, B. Geboes, J. Hereijgers, D. Choukroun, K. De Wael, T. Breugelmans, The application of an electrochemical microflow reactor for the electrosynthetic aldol reaction of acetone to diacetone alcohol, Chemical Engineering Research and Design, 128 (2017) 205-2013. [2] D. Pauwels, J. Hereijgers, K. Verhulst, K. De Wael, T. Breugelmans, Investigation of the electrosynthetic pathway of the aldol condensation of acetone, Chemical Engineering Journal, 289 (2016) 554-561. Figure 1: Exploded view of the electrochemical microreactor. 1: Electrode material 2: PEEK housing with hole for the electrode (2a: WE, 2b: CE), 3: POM spacer with serpentine reaction channel. 4: Aluminium parts with holes for the in- and outlet tubing, hole for the reference electrode (4a only) and holes for the electrode connections. Figure 1

Jet aeration as alternative to overcome mass transfer limitation of stirred bioreactors

In industrial biotechnology increasing reactor volumes have the potential to reduce production costs. Whenever the achievable space time yield is determined by the mass transfer performance of the reactor, energy efficiency plays an important role to meet the requirements regarding low investment and operating costs. Based on theoretical calculations, compared to bubble column, airlift reactor, and aerated stirred tank, the jet loop reactor shows the potential for an enhanced energetic efficiency at high mass transfer rates. Interestingly, its technical application in standard biotechnological production processes has not yet been realized. Compared to a stirred tank reactor powered by Rushton turbines, maximum oxygen transfer rates about 200% higher were achieved in a jet loop reactor at identical power input in a fed batch fermentation process. Moreover, a model-based analysis of yield coefficients and growth kinetics showed that E. coli can be cultivated in jet loop reactors without significant differences in biomass growth. Based on an aerobic fermentation process, the assessment of energetic oxygen transfer efficiency [kgO2 kW-1 h-1] for a jet loop reactor yielded an improvement of almost 100%. The jet loop reactor could be operated at mass transfer rates 67% higher compared to a stirred tank. Thus, an increase of 40% in maximum space time yield [kg m-3 h-1] could be observed.

Hierarchically porous metal-organic frameworks: rapid synthesis and enhanced gas storage.

Large pore sizes, high pore volumes, facile synthesis conditions, and high space-time yields are recognized as four crucial criteria in the fabrication of metal-organic frameworks (MOFs). However, these four objectives are rarely realized together. Herein, we have developed a simple and versatile method that employs 1,4-butanediamine (BTDM) as a template for rapidly fabricating four stable hierarchically porous MOFs (H-MOFs), including HKUST-1, ZIF-8, ZIF-67, and ZIF-90. The synthesis conditions are simple and facile at room temperature and ambient pressure, and the synthesis time can be shortened to 1 min. The resultant H-MOFs exhibit multimodal hierarchically porous structures with meso- and macropores interconnected with micropores, as well as high pore volumes (0.76 cm3 g-1). The maximum space-time yield for the hierarchically porous HKUST-1 reaches 7.4 × 104 kg m-3 d-1, at least one order of magnitude higher than previous reported yields. Notably, the additive BTDM not only facilitates crystal growth but also guides the formation of meso- and macropores. The synthesis route is highly versatile, as analogues (e.g., tetramethyl-1,3-diaminopropane and tetramethyldiaminomethane) can also be employed as templates to prepare diverse H-MOFs. Furthermore, the porosities of the H-MOFs are readily tuned by controlling the metal source, template amount and type of template. The as-synthesized H-MOFs act as adsorbents with significantly improved performances relative to those of microporous MOFs used for CH4 and CO2 gas storage. This strategy may aid in the large-scale industrial synthesis of desirable H-MOFs for gas storage.

Continuous Production of Biorenewable, Polymer-Grade Lactone Monomers through Sn-β-Catalyzed Baeyer-Villiger Oxidation with H2 O2.

The Baeyer–Villiger oxidation is a key transformation for sustainable chemical synthesis, especially when H2O2 and solid materials are employed as oxidant and catalyst, respectively. 4‐substituted cycloketones, which are readily available from renewables, present excellent platforms for Baeyer–Villiger upgrading. Such substrates exhibit substantially higher levels of activity and produce lactones at higher levels of lactone selectivity at all values of substrate conversion, relative to non‐substituted cyclohexanone. For 4‐isopropyl cyclohexanone, which is readily available from β‐pinene, continuous upgrading was evaluated in a plug‐flow reactor. Excellent selectivity (85 % at 65 % conversion), stability, and productivity were observed over 56 h, with over 1000 turnovers (mol product per mol Sn) being achieved with no loss of activity. A maximum space–time yield that was almost twice that for non‐substituted cyclohexanone was also obtained for this substrate [1173 vs. 607 g(product) kg(catalyst)−1 cm−3 h−1]. The lactone produced is also shown to be of suitable quality for ring opening polymerization. In addition to demonstrating the viability of the Sn‐β/H2O2 system to produce renewable lactone monomers suitable for polymer applications, the substituted alkyl cyclohexanones studied also help to elucidate steric, electronic, and thermodynamic elements of this transformation in greater detail than previously achieved.

CO2 hydrogenation to methanol over Cu/ZnO/ZrO2 catalysts prepared by precipitation-reduction method

A series of Cu/ZnO/ZrO2 catalysts were prepared by precipitation-reduction method and tested for the synthesis of methanol by CO2 hydrogenation. The advantages of precipitation-reduction method over conventional co-precipitation method, the effect of NaBH4 content were investigated by XRD, N2 physisorption, SEM, TEM, N2O chemisorption, XPS, TPR, CO2-TPD techniques. The influence of precipitation-reduction process on the average Cu particle size, aggregation state and interaction among different elements were discussed in detail. The content of NaBH4 had an effect on the exposed Cu surface area as well as the ratio of Cu0/Cu+ and thus influenced the catalytic performance. The catalysts prepared by precipitation-reduction method increased the number of basic sites and had a significant advantage in methanol selectivity in contrast with conventional precipitation method. A suitable NaBH4 content was beneficial to the catalytic performance in Cu/ZnO/ZrO2 catalysts and a maximum space time yield of CH3OH was obtained with B/Cu=5 at 543K.

Scalable continuous solvothermal synthesis of metal organic framework (MOF-5) crystals

Metal–organic frameworks (MOFs) are well suited as nanoporous materials for applications such as gas storage, catalysis and in medical devices. Literature predominantly covers information on the batch synthesis of MOF-5, however, for an industrially viable product to be formed, bridging the gap to scalable continuous processing is essential. Here, we show that crystals of MOF-5 can be formed in a scalable solvothermal continuous process with a maximum space time yield of nearly 1000kgm−3day−1. Analysis of the solid output as a function of time, in conjunction with variation of concentration of the feed supply, shows high purity MOF-5 is produced using a continuous system, with potentially high throughput on scale up. We also show that the output can be increased by increasing the concentration of reactants in the system, albeit resulting in a reduced surface area. The two most common solvents currently used for MOF-5 production are also compared to identify a more economically viable process.

Numerical optimization of a structured tubular reactor for Fischer–Tropsch synthesis

A performance comparison is made between a Random Packed Bed (RPB) and a Packed Closed Cross Flow Structure (CCFS) reactor model for the Fischer–Tropsch Synthesis. The model incorporates an earlier reported reaction–diffusion catalyst model with chain growth probability depending on the local conditions. 180,000 full reactor simulations have been performed for an extensive parameter space exploration to determine optimal sets of parameters at the maximum Space Time Yield of C5+ products. Results show that particles sizes tend to be minimized and the optimal inlet syngas ratio is relatively low (∼1). This study demonstrates the limitations of the RPB reactor at higher catalyst activities and shows the potential of the Packed CCFS reactor as an alternative. At catalyst activities of 3 times that reported by Yates–Satterfield the performance at optimal conditions of the Packed CCFS is 12% lower than RPB. At 10 times the YS activity the RPB takes relatively little advantage of the more active catalyst, productivity only increases by 24% compared to optimum conditions at 3 times YS activity. The Packed CCFS, on the other hand, is able to increase reactor productivity with 63% compared to its optimized benchmark conditions at 3 times YS activity. In spite of its lower catalyst inventory, the Packed CCFS can benefit from higher catalyst activities due to its improved heat transport properties and higher catalyst effectiveness at similar pressure drop over the reactor. Furthermore, larger reactor diameters can be applied with limited impact on the productivity per reactor volume.

Multifunctionality of Cu–ZnO–ZrO2/H-ZSM5 catalysts for the one-step CO2-to-DME hydrogenation reaction

A series of Cu–ZnO–ZrO2/H-ZSM5 multifunctional catalysts for the one-step CO2-to-DME hydrogenation reaction was prepared via coprecipitation of methanol catalyst precursors by means of different precipitating agents (i.e., sodium bicarbonate, ammonium carbonate, oxalic acid and urea) in a slurry containing dispersed zeolite particles. The samples were characterized by XRF, XRD, N2 adsorption/desorption isotherms, SEM, N2O-titration, TPR and NH3/CO2 TPD techniques, while the catalytic testing was carried out in a fixed-bed reactor operating at 3.0MPa, in the TR range 473–513K and space velocity of 10,000h−1 (CO2/H2/N2, 3/9/1). The experiments revealed that the preparation methodology significantly affects catalyst properties and hence catalyst activity. The multifunctional catalyst prepared via ammonium carbonate precipitation resulted to be the most active in CO2 conversion, also accomplishing high DME selectivity, with a maximum space-time yield of 0.225kgDME/kgcat/h. Catalyst characterization disclosed that the strength of basic sites, the ratio between acid and basic sites along with the Cu particle sizes are crucial to achieve maximum catalytic performance, keeping CO selectivity to a minimum value.

Graphitic mesoporous carbon-supported molybdenum carbides for catalytic hydrogenation of carbon monoxide to mixed alcohols

Molybdenum carbide (β-Mo2C) nanoparticles were synthesized in situ on a soft-templated graphitic mesoporous carbon (GMC) and other commercial carbon materials (activated charcoal and carbon black) by carbothermal hydrogen reduction (i.e., carbon supports as carburizing agents). The catalytic activity of these carbon-supported and bulk carbides for carbon monoxide (CO) hydrogenation to mixed alcohols (mainly C1–C3) was investigated at 573K and 3.0MPa, showing that their areal specific rates for CO conversion increase with decreasing the carbide particle size, independent of the supports. GMC appears to be a preferable support of β-Mo2C to activated charcoal and carbon black because of its ability for the formation of smaller carbide particles resulting in higher catalytic activity. Addition of a minor amount of K2CO3 into β-Mo2C/GMC (molar K/Mo=0.05−0.5) promotes the formation of higher alcohols (C2+–OH) considerably, leading to a maximum space time yield (STY) for C2+–OH at medium K/Mo ratio of 0.1. Compared with typical Rh/GMC catalyst promoted triply with Mn, Li, and Fe oxides, the K2CO3-promoted β-Mo2C/GMC catalyst shows higher C2+–OH selectivity (30 vs. 25mol-C% on CO2-free basis) and STY (71 vs. 46mg(hgcat)−1) in spite of its suppressed formation of CH3OH.

Preferential CO oxidation over a platinum ceria alumina catalyst in a microchannel reactor

We have demonstrated the application of a Pt/Al 2O 3/CeO 2 catalyst into a microreactor to reduce the CO content by preferential oxidation in a H 2 rich model gas mixture. At temperatures between 120 °C and 260 °C and CO:O 2 ratios smaller than 0.7 CO conversion of up to 98% for CO 2-selectivities of 20%–35% were reached. The maximum space time yield was about 0.35 mmol g −1 min −1. To increase the CO conversion and CO 2-selectivity the concept of adding air or an air + N 2 mixture through microholes to the CO + H 2 mixture has been investigated with the design of an SSMR (staged supply microreactor). It was found that the CO 2 selectivity is higher compared to the case of feeding of all gases in one passage, but only for lower CO conversion rates. The best results for the preferential oxidation reaction were obtained at low reactant partial pressures. We found that the highest CO conversion rates are reached at reactant partial pressures in the range between 1 and 5 mbar. These values can be locally reached for total flows with 1–2 vol.-% CO and O 2 by feeding N 2 into the coated microchannels and the reactant gases into the uncoated microchannels. In this case, CO and H 2 are equally lowered and the CO oxidation may be favoured over the H 2 oxidation steps. A strong argument supporting this assumption is our measurements with varying the H 2 inlet stream.

The performances of higher alcohol synthesis over nickel modified K 2CO 3/MoS 2 catalyst

Ni modified K 2CO 3/MoS 2 catalyst was prepared and the performance of higher alcohol synthesis catalyst was investigated under the conditions: T = 280–340 °C, H 2/CO (molar radio) = 2.0, GHSV = 3000 h − 1, and P = 10.0 MPa. Compared with conventional K 2CO 3/MoS 2 catalyst, Ni/K 2CO 3/MoS 2 catalyst showed higher activity and higher selectivity to C 2 +OH. The optimum temperature range was 320–340 °C and the maximum space-time yield (STY) of alcohol 0.30 g/ml h was obtained at 320 °C. The selectivity to hydrocarbons over Ni/K 2CO 3/MoS 2 was higher, however, it was close to that of K 2CO 3/MoS 2 catalyst as the temperature increased. The results indicated that nickel was an efficient promoter to improve the activity and selectivity of K 2CO 3/MoS 2 catalyst.

Gas phase partial oxidation of toluene over modified V2O5/TiO2 catalysts in a microreactor

The influence of different additives to V2O5/TiO2 catalyst for the gas phase partial oxidation of toluene was investigated in a microchannel reactor, where well-controlled reaction conditions were provided without heat and mass transfer influence. It was found that K-doping decreased the catalyst selectivity for benzaldehyde and benzoic acid. The addition of Sb promoted the selectivity but inhibited the catalyst activity greatly. The modification with Ag remarkably improved the catalyst performance in terms of increasing benzaldehyde and benzoic acid selectivity along with an increased activity. With Ag modified V2O5/TiO2 as catalyst and pure oxygen as oxidant, the total selectivity of benzaldehyde and benzoic acid reached over 80% with the toluene conversion above 10%. The maximum space–time yield of 4.82 kg h−1 L−1 has been achieved, calculated on the basis of the channel volume.

Compact Radial Reactor with a Structured Porous Metal Catalyst for the Conversion of Natural Gas to Synthesis Gas: Experiment and Modeling

To perform the catalytic conversion of natural gas to synthesis gas, a compact radial reactor supplied with a structured porous metal catalyst has been designed. The reactor was tested at normal pressure using natural gas and air. The reactor can operate without preheating of the inlet gas mixture. A novel structured porous metal catalyst was developed on the basis of the 7% Ni/α-Al2O3 commercial catalyst and Ni−Cr powders. The catalyst is characterized by a low hydraulic pressure drop and a high tortuosity coefficient of the regular structure. The coefficient of heat conductivity of the structured catalyst and the coefficient of mass transfer between a gas flow and the catalyst were determined in special experiments. The catalyst temperature and outlet gas concentrations were experimentally investigated with respect to the gas−air flow rate and methane concentration in the mixture. The catalyst temperature drop along the reactor radius was no higher than 230 °C. The maximum catalyst temperature does not exceed 1090 °C for all runs. At volumetric flow rates of the gas mixture of 4000−40 000 h-1 and O2/CH4 ratios of 0.6−0.9, methane is completely converted, and the maximum space time yield (STY) of the reactor is about 1 L of CH4 per second per liter of reactor. A mathematical model for this process was developed. The results of modeling agree well with the experimental data. One possible application of the developed syngas generator in internal combustion engines is discussed.