Design of a Continuous Rotating Annular Bioreactor for Immobilized-Cell Fermentations

A novel continuous annular packed-bed bioreactor for immobilized-cell fermentation was developed. In the operation of this bioreactor, the non-growth medium was added to the immobilized-cell phase evenly and continuously through a stationary inlet. The nutrient medium, on the other hand, was fed to the bed through a rotating nozzle. Therefore, addition of the nutrient medium to every local point in the immobilized-cell phase was only intermittent whereas the whole process was continuous. For an α-amylase fermentation by κ-carrageenan gel-immobilized Bacillus amyloliquefaciens cells, this bioreactor was found to be suitable for the control of cell growth and maintenance of cell productivity. Moreover, the volumetric productivity of α-amylase obtained in this bioreactor could be much higher than in a shake flask, if the reactor was properly operated. © 1997 SCI.     

填充床反应器中酶法合成生物蜡酯

研究了填充床式反应器酶法合成生物蜡酯的生产工艺。以大豆油、十六醇为原料,在石油醚体系中,使用实验室自制的固定化Candida sp.99-125为催化剂。对操作参数,如填充高度、进料速度、固定化酶用量、底物摩尔比进行了研究。结果表明,固定化酶质量为47 g,填充高度40 cm（内径3.5 cm）,油醇摩尔比1∶2.4,以4 mL/min速度进料保留时间4 h,产率可达83%。固定化酶在使用16批时,产率仍保持在70%以上。同时,对于填充床的填充方式作了初步探索。     

A method for the evaluation of microbial growth in a trickling bed reactor

A method to evaluate microbial activity and growth in an eight-stage, trickling bed reactor, packed with peat particles, was developed. Steady-state measurements were made of the substrate degradation rate, based on the change in chemical oxygen demand (COD), and the biological rate of oxygen consumption based on the difference between inlet and outlet oxygen concentrations in the gas phase. From these values, a global yield coefficient (Yx/s) was evaluated in terms of g of total biomass produced per g of COD consumed. Using this method, Yx/s was 0.23 ± 0.03 from days 10 to 23. This correlated well with a Yx/s of 0.29 g of biomass produced per g of substrate consumed as determined in the first stage of an eight-stage reactor. This method could be applied to suspension culture and fixed bed bioreactors where obtaining a homogeneous, biomass sample is difficult.     

A study on the ethanol production by immobilized cells ofZymomonas mobilis

Cells ofZymomonas mobilis immobilized in Ca-alginate matrix were used for ethanol production under various conditions. Immobilized cells showed broad optimum pH profile and their operational optimum temperature shifted from 30‡C to 40‡C upon immobilization. As reportedlyZ. mobilis did get the substrate inhibition by glucose, but at high concentration level of glucose the reduction of activity for ethanol production was less severe than that for yeast. The used beads of the immobilizedZ. mobilis were reactivated by incubating them in the activation medium. The increase in cell number and the enhancement of the specific activity per each cell are considered the two major factors responsible for the overall activation. A packed-bed reactor with the feed glucose concentration of 20% (W/V) gave an ethanol productivity as high as 33.0 g/l.hr at the flow rate of 58.5 ml/hr. A comparison between the experimental results from the real packed-bed reactor and the simulation results of an ideal case showed a two-fold inferior performance by the real reactor and this is at least partly attributed to the CO₂ gas effect.     

Operational stability of immobilised lipase/acyltransferase during interesterification of fat blends

The lipase/acyltransferase from Candida parapsilosis is an unusual enzyme that preferably catalyses alcoholysis over hydrolysis in biphasic aqueous/organic media. The aim of this study was to evaluate the operational stability of an immobilised form of this enzyme during the interesterification of fat blends containing n‐3 polyunsaturated fatty acids, in solvent‐free media, at 60 °C, carried out continuously and batchwise. When the interesterification was performed in a continuous fluidised‐bed reactor, an operational half‐life of 9 h was estimated. The biocatalyst was also reused in consecutive 23‐h batches, in a total of four batches, either using fresh medium with no water addition or adding water to rehydrate the biocatalyst. When no water and extra water was added to the reaction medium, the obtained half‐lives were 10 and 18 h, respectively. Thus, the loss of activity may be explained by a progressive dehydration occurring along the reaction rather than by product or substrate inhibition effects. The interesterification activity was accompanied by changes in the acylglycerol profile. An increase in compounds of low equivalent carbon number (ECN) and in triacylglycerols (TAG) of ECN 42 and 44 was observed. This increase was accompanied by the consumption of TAG of ECN 46, 48 and 50.     

The unsteady-state solution for a finite dispersion-type catalytic packed-bed tubular reactor

The unsteady-state solution is obtained by an operator theory in functional analysis setting for a general finite catalytic packed-bed tubular reactor model with axial dispersion in the bed, mass transfer between the catalyst particles and the flowing phase, and intraparticle diffusion and surface reaction in the catalyst particles.     

Optical resolution of 2-alkanol by lipase-catalyzed acetylation with vinyl acetate in packed-bed reactor with recycling system

The lipase-catalyzed acetylation of 2-alkanol with vinyl acetate was studied using Burkholderia cepacia lipase (BCL), three alcohol and three organic solvents in a packed-bet reactor with a recycling system (flow method). The optical resolution data were found in agreement with those of the batch method in which BCL was suspended in the substrate solution. Repeated reaction results clearly indicated BCL in the packed-bed to be quite stable and to be usable for at least 50 reaction runs or to remain effective for as long as two months in the water-insoluble solvents such as hexane and 1,2-dichloroethane. In the reaction using a water-soluble solvent such as acetonitrile, the catalytic power of BCL showed only a 1% decrease of conversion per run or solvent recycling possibly owing to compression of BCL in the bed although enantioselectivity was independent of the number of reaction repetitions. The present method showed thus be applicable to kinetic resolution by enzyme-catalyzed acylation in hydrophobic organic solvents with no waste of enzyme.     

Oxidative dehydrogenation of propane to propene, 2: Simulation of a commercial inert membrane reactor immersed in a fluidized bed

A novel reactor concept is proposed for partial oxidation reactions that combines membrane and fluid bed reactor technology in a single vessel. Air fluidizes the shell side in which both membrane tubes — charged with catalyst — and cooling coils are immersed. Oxygen transport through the membrane wall is controlled by pressure drop. Model simulations, based on the kinetics for the oxidative dehydrogenation of propane to propene, show improved performance compared to conventional fixed bed technology. The controlled oxygen addition along the axis improves propene selectivity and broadens the operating range with respect to hydrocarbon and oxygen feed rates.     

Improvement of biodiesel production through microstructural engineering of a heterogeneous catalyst

Biodiesel can be produced from ecological friendly processes using edible or waste vegetable oil. Actual production processes can be improved by using heterogeneous catalysts for transesterification reaction activation at low temperature. Few structured or particulated solids with high catalytic activity for biodiesel production reaction have been studied in bibliography. In this work, a microstructured catalyst based on catalytically active pumice material has been developed. Catalytic particles have been made with the shape of an organic template used as former. A novel methodology was used to control the fabrication of pumice-based heterogeneous catalysts as an effective way to improve their efficiency in the production of biodiesel in a continuous packed-bed industrial reactor. The catalytic packed bed reactor configuration studied shows high yields in biodiesel production, obtaining advantages from the microstructural engineering of the catalytic material.     

Oxidative dehydrogenation of propane over V2O5-MgO/TiO2 catalyst: Effect of reactants contact mode

The performance of the active catalyst 5%V₂O₅-1.9%MgO/TiO₂ in propane oxidative dehydrogenation is investigated under various reactant contact modes: co-feed and redox decoupling using fixed bed and co-feed using fluid bed. Using fixed bed reactor under co-feed conditions, propane is activated easily on the catalyst surface with selectivities ranging from 30 to 75% depending on the degree of conversion. Under varying oxygen partial pressures, especially for higher than the stoichiometric ratio O₂/C₃H₈ = 1/2, nor the propane conversion or the selectivities to propene and COx are affected. The performance of the catalyst in the absence of gas phase oxygen was tested at 400 °C. It was confirmed that the catalyst surface oxygen participates to the activation of propane forming propene and oxidation products with similar selectivities as those obtained under co-feed conditions. The ability of the catalyst to fully restore its activity by oxygen treatment was checked in repetitive reduction–oxidation cycles. Fluid bed reactor using premixed propane–oxygen mixtures was also employed in the study. The catalyst was proved to be very active in the temperature range 300–450 °C attaining selectivities comparable to those of fixed bed.     

Investigation of OSN properties of PDMS membrane for the retention of dilute solutes with potential industrial applications

Few commercially available membranes can be used for organic solvent nanofiltration (OSN). Applying OSN in chemical industries is nevertheless of high interest to cut with energy consumption linked to solvent recycling and soluble catalysts recovery. A commercial membrane, PERVAP4060, was used to investigate the retention of dilute solutes in toluene feeds and to mimic metathesis medium. The studied solutes were R-BINAP a neutral polyaromatic molecule used in metathesis chemistry, tetraoctylammonium bromide (ToABr), a charged molecule used as a homogeneous catalyst and n-hexadecane. Retention of polar ToABr (95%) was higher than that of neutral R-BINAP (80%). The transfer mechanism, either pore flow or solution-diffusion, was discussed. All the results obtained suggested that the transport is governed by the solution-diffusion mechanism. The measured retentions could be explained in terms of solubility affinities and diffusion coefficients. The stability and performances of PERVAP4060 were well established, showing the strong potential for industrial applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48359.     

Effect of external mass transfer in a packed bed reactor system for a reversible enzyme reaction

A mathematical model was developed to describe the effect of external mass transfer for a packed-bed enzyme reactor in which a reversible, one-substrate, two-intermediate enzyme reaction took place. The model equation was applied to the analysis of an immobilized glucose isomerase reactor system. A Colburn-type mass transfer correlation was obtained from the Colburn j-factor versus Reynolds number plot: i.e., j_D = 0.045N_Re^−0.48. The values of mass transfer coefficient for the system under study ranged from 0.01 to 0.1 cm h⁻¹ depending on the substrate flow rate. Very good agreements were observed between the computer simulation using a plug flow reactor model with the derived mass transfer correlation and the experimental results obtained from the packed-bed reactor operation.     

Scale-up analysis of autothermal operation of methane oxidative coupling with La2O3/CaO catalyst

The exothermicity of oxidative coupling of methane (OCM) renders a cooled packed-bed reactor impractical or impossible. Recently, we proposed an adiabatic autothermal reactor as a solution to this problem and reported the first results for stable autothermal operation (AO) with feed at ambient temperature. AO on the ignited branch is possible only in the region of steady-state multiplicity. High per-pass conversion and productivity requirements demand a stable ignited branch at the lowest possible feed temperature and high flow rate. To achieve OCM scale-up, many conditions must be satisfied simultaneously. Using a kinetic model for La₂O₃/CaO catalyst, we examine the impact of space time, feed methane to oxygen ratio, feed temperature, particle size, inter-phase heat and mass transfer gradients, pore-diffusion, bed scale heat/mass dispersion on the region of AO for large scale adiabatic packed-bed reactors. We show that while it is possible to achieve CH₄ conversion of about 20% and C₂ selectivity of about 80% in scaled-up reactors, these values are sensitive to the design and operating parameters.     

Enzymatic Production of Monoacylglycerols with Camellia Oil by the Glycerolysis Reaction

Three commercial immobilized lipases, Lipozyme RM IM, Lipozyme TL IM and Novozym 435, were screened for the production of monoacylglycerols (MAG) by glycerolysis of camellia oil in a solvent medium of tert-butyl alcohol. Novozym 435 showed the best performance and was selected to catalyze the glycerolysis reaction. Different reaction conditions for the batch reaction, substrate mole ratio, substrate concentration and temperature, were investigated. The optimal reaction conditions were determined as 6:1 mole ratio of glycerol to camellia oil at 40% (w/v) of substrate concentration in tert-butyl alcohol at a reaction temperature of 50 °C. Under these optimal conditions, the conversion rate of camellia oil was 98.7% (10 h), and the mixture of acylglycerols contained 82.0% of MAG. A packed-bed reactor (PBR) system with 4.5 g Novozym 435 was employed in continuous production. The resulting product mixture of acylglycerols contained 80.74% of MAG and was obtained at a flow rate of 0.25 mL/min of substrates. The long-term operation of the PBR system gave an average productivity of 0.698 kg MAG/(kg enzyme h) after 38 days of operation.     

A computational method for determination of the mass-transfer coefficient in packed-bed immobilized enzyme reactors

A computational method was developed that determined the mass-transfer coefficient k_L or the volumetric mass-transfer coefficient k_La in packed-bed immobilized enzyme (IME) reactors. To study the performance of this method, two experimental systems were considered where an enzyme was immobilized on a non-porous support surface (surface-IME system) or within a porous support (pore-IME system). The values of k_L and k_La determined in these packed-bed IME reactor systems were successfully expressed in terms of the substrate concentration at the reactor inlet and the liquid flow rate. Furthermore, the correlations obtained for k_L and k_La were used to calculate the unconverted fractions of substrate at the reactor outlet. Comparison showed that the calculated results were in satisfactory agreement with the experimental values.     

Oxidative dehydrogenation of propane to propene, 1: Kinetic study on V/MgO

The reaction kinetics of the oxidative dehydrogenation of propane to propene over a V/MgO catalyst were studied. Both propane and propene oxidation kinetics were measured independently to quantify the rates of the parallel and consecutive reactions to propene and carbon oxides. Specific experiments to evaluate reaction products effects showed that water inhibited reaction rates but co‐feeding CO₂ or propene had no measurable effect on selectivity or conversion. Kinetic data generated under integral reactor conditions and over an inert membrane reactor have also been used to estimate the kinetic parameters. Selectivity decreased as the oxygen partial pressure increased; however, propene yield was relatively insensitive to oxygen concentration. A dual site Mars‐van Krevelen model characterizes the reaction kinetics well. The role of lattice oxygen was established by alternating pulses of propane and oxygen. This redox model is able to predict the experimental tendencies observed in the three types of reactor studied.     

Continuous Gas‐Phase Hydroformylation of 1‐Butene using Supported Ionic Liquid Phase (SILP) Catalysts

The concept of supported ionic liquid phase (SILP) catalysis has been extended to 1‐butene hydroformylation. A rhodium‐sulfoxantphos complex was dissolved in [BMIM][n‐C₈H₁₇OSO₃] and this solution was highly dispersed on silica. Continuous gas‐phase experiments in a fixed‐bed reactor revealed these SILP catalysts to be highly active, selective and long‐term stable. Kinetic data have been acquired by variation of temperature, pressure, syngas composition, substrate and catalyst concentration. A linear dependency in rhodium concentration could be established over a large concentration range giving another excellent hint for truly homogeneous catalysis in the SILP system. Compared to former studies using propene, the SILP system showed significantly higher activity and selectivity with 1‐butene as feedstock. These findings could be elucidated by solubility measurements using a magnetic microbalance.     

Anion-modified zirconia: effect of metal promotion and hydrogen reduction on hydroisomerization of n-hexadecane and Fischer–Tropsch waxes

The effect of metal promoters on the activity and selectivity of tungstated zirconia (8 wt.% W) for n-hexadecane isomerization in a trickle bed continuous reactor is studied by using different metals (Pt, Ni, and Pd) and, in one case, by varying metal loading. Platinum is found to be the best promoter. The effect of hydrogen reduction is investigated using platinum-promoted tungstated zirconia catalysts (Pt/WO₃/ZrO₂, 0.5 wt.% Pt and 6.5 wt.% W). Pretreatment at temperatures between 300 and 400°C for 3 h in hydrogen is found to be slightly beneficial for achieving high yields of isohexadecane. A platinum promoted sulfated zirconia (Pt/SO₄/ZrO₂) is compared with a Pt/WO₃/ZrO₂ catalyst for the hydroisomerization of n-hexadecane in the same reactor at the same n-hexadecane conversion. The former is a good cracking catalyst and the latter is suitable for use as a hydroisomerization catalyst. In a 27-ml microautoclave reactor, studies of the hydroisomerization and hydrocracking of two Fischer–Tropsch (F–T) wax samples are carried out. Severe cracking can be effectively suppressed using a Pt/WO₃/ZrO₂ catalyst so as to obtain branched isomers in the diesel fuel or lube-base oil range.     

Dehydrogenation of 11α‐hydroxy‐16α, 17‐epoxyprogesterone by encapsulated Arthrobacter simplex cells in an aqueous/organic solvent two‐liquid‐phase system

BACKGROUND: Arthrobacter simplex cells immobilised in sodium cellulose sulfate/poly‐dimethyl‐diallyl‐ammonium chloride microcapsules were used for the microbial dehydrogenation of 11α‐hydroxy‐16α,17‐epoxyprogesterone to 11α‐hydroxy‐16α,17α‐epoxypregn‐1,4‐diene‐3,20‐dione in an aqueous/organic solvent two‐liquid‐phase system, which is a key reaction in the production of glucocorticoid pharmaceuticals. The aim of the study was to establish a suitable aqueous/organic solvent two‐liquid‐phase system for performing semi‐continuous production in an airlift loop reactor by encapsulated A. simplex cells with the addition of suitable surfactants to achieve a higher yield of the product. RESULTS: n‐Hexane was selected as the most suitable organic solvent. In optimised Tween‐80 emulsion feed mode the conversion in the airlift loop reactor was as high as 97.54% when the time of reaction was 2 h, and the reaction time was greatly shortened. In semi‐continuous production the cultivation with immobilised cells was carried out for five batches in total. The conversion in each batch was above 95% and the enzymatic activity still remained quite high after five batches of biotransformation. CONCLUSION: The results showed that performing the conversion by this method shortened the reaction time and increased the productivity, thus demonstrating the great potential of the method for the dehydrogenation of 11α‐hydroxy‐16α,17‐epoxyprogesterone. Copyright © 2008 Society of Chemical Industry     

Kinetics and mass transfer in hydroformylation—bulk or film reaction?

The kinetics of a gas–liquid reaction, alkene hydroformylation was studied in the presence of a homogeneous catalyst in a pressurised laboratory‐scale semibatch reactor. Hydroformylation of propene to isobutyraldehyde and n‐butyraldehyde was carried out at 70–115°C and 1–15 bar pressure in 2,2,4‐trimethyl‐1,3‐pentanediol monoisobutyrate solvent with rhodium catalyst using the ligands cyclohexyl diphenylphosphine. In order to evaluate the influence of mass transfer, experiments were made using varied stirring rate from 100 to 1000 rpm at 100°C and 10 MPa syngas pressure. Only at higher stirrings rates, the reaction took place in the kinetic regime. A reactor model was developed comprising both complex kinetics and liquid‐phase mass transfer. The model was based on the theory of reactive films. The model is able to predict under which circumstances the hydroformylation process is affected by liquid‐phase diffusion of the reactants. Experimental data and model simulations are presented for the hydroformylation of propene in the presence of a homogeneous rhodium catalyst.