Synthesis and performance of surfactants based on epoxidized methyl oleate and glycerol

A small series of surfactants based on methyl oleate and glyceroe was synthesized. The synthesis utilizes an epoxidation reaction of methyl oleate followed by a simple esterification. The resultant products have between two and seven glyceride units, and their performance properties, including aqueous surface tensions and dynamic aqueous surface tensions, were studied. The droplet size of soybean oil/water emulsions made with each surfactant was also studied. The surfactants show properties similar to alcohol ethoxylates, such as the reduction of aquous surface tension to ∼34 mN m⁻¹. Additionally, because the synthesis leaves the epoxide functionality in the surfactant, further modification for performance optimization is possible.     

Estimation of mid‐distillates production rate in a low temperature Fischer–Tropsch process

BACKGROUND: The Fischer–Tropsch process is the most important path for converting natural gas to high quality liquid hydrocarbons. Low temperature Fischer–Tropsch synthesis in slurry bubble column reactors with cobalt‐based catalysts is used for mid‐distillates production. RESULTS: In this work the slurry bubble column reactor was simulated by applying the two‐bubble class mathematical model. In addition, the effect of operating parameters on synthesis gas conversion was studied. The distribution of products was also predicted from the simulation framework. CONCLUSIONS: The effect of synthesis gas inlet velocity on mid‐distillates production rate was studied in the present work. A maximum production rate for mid‐distillates of about 23 kg s^?1 was predicted from the simulation program. Copyright © 2011 Society of Chemical Industry     

Reactors for ethanol production using immobilised yeast cells

Ethanol production by immobilised yeast cells in packed-bed column reactors was significantly affected by the hold-up of CO₂ produced during the fermentation. Compartmentalisation of the reactor minimises CO₂ hold-up and prevents flotation of immobilised cell beads during operation and bead rupture during shut-down conditions. In a reactor of dimensions 2·2 × 60 cm, a rate of ethanol production of 5·11 g h^?1 at a dilution rate of 1·27 h^?1 was achieved, when 18% (w/v) glucose solution was fed at the bottom at pH 5·5 and temperature 33–35°C. In larger reactors of sizes 4 ×; 40 cm and 8 × 80 cm the rates of ethanol production and CO₂ hold-ups were 5·11 and 5·37 g h^?1 and 48·66% and 40·66% and 40·79% of the void volume at dilution rates of 1·27 h^?1 and 1·67 h¹, respectively. The CO₂ hold-ups in column reactors (4 × 40 cm) held in inclined (43° from horizontal) or horizontal positions were 41·33% and 46·67% of the void volume, respectively. Double and triple series reactors (each of dimensions 2·2 × 60 cm) showed better performance than a single verticle reactor (2·2 × 60 cm).     

Novel continuous process for methacrolein production in numerous droplet reactors

A continuous process for methacrolein production was constructed by filling w/o Pickering emulsions in a column reactor. Ionic liquid (IL-[HDEA]Ac) with secondary amine was designed to catalyze propionaldehyde condensation with formaldehyde through the Mannich reaction. Emulsion droplets encapsulated with IL aqueous solution were stabilized with modified SiO₂ nanoparticles and dispersed in cyclohexane, which could be observed as numerous reactors. The properties of SiO₂ stabilizer, such as wettability, surface groups, and the effect on interfacial tension were investigated. The characteristics of emulsion influenced by stabilizer properties and content were systematically studied. The droplet size, IL concentration and liquid hourly space velocity were optimized. The droplets were evaluated at 0.5 hr⁻¹ for 150 hr without IL leakage and obvious activity decreasing, indicating the excellent stability of the emulsion system. The continuous process showed a 1.25-fold enhancement in catalysis efficiency and less equipment compared to batch process.     

Intensification of organic reactions with hybrid flow reactors

The intensification of chemical processes, which means improving their efficiency and cutting down energy consumption, requires more automation and non-conventional energy sources, as well as new, efficient and scalable protocols which need to be implemented in continuous flow reactors. We showed that flowing systems are advantageous when using conductive heating or non-conventional energy sources such as microwave (MW) and ultrasound (US) irradiation. We developed several hybrid flow reactors suitable for organic reactions with the aim of optimizing heat and mass transfer and achieving process intensification. Here we present a series of applications of a simple flow reactor that uses an HPLC pump, a column heater and suitable columns filled with a supported catalyst. Using the same column packed with a commercially available derivatized acidic silica we efficiently performed two reaction types: the nucleophilic opening of epoxides with a series of alcohols and the Friedländer quinoline synthesis. In both cases we obtained pure products in excellent yield in a few minutes. The set of experiments on the epoxide opening could be repeated on a hybrid flow reactor under sequential MW/US irradiation, though at lower temperature. A suitable combination of 1D and 2D NMR experiments (i.e. ¹H–¹³C HMQC, ¹H–¹H COSY and ¹H–¹H NOESY) was applied to unambiguously assign the stereochemistry of hydroxyethers from the nuclephilic cleavage of limonene oxide.     

Droplet evaporation and solute precipitation during spray pyrolysis

The process of spray pyrolysis was investigated theoretically using a model that describes the evolution of the droplet size, solvent vapor concentration in the carrier gas, and both droplet and gas temperatures along the reactor axis. The model also accounts for solute concentration profiles and solute precipitation in the solution droplets. The model was used to describe the evaporation of sodium chloride aqueous solution droplets in diffusion dryers and hot-wall reactors as a function of reactor residence time, droplet size (a few microns), solution molality (up to 2 M), droplet concentration (10⁶–10⁷ cm⁻³), relative humidity of the carrier gas (0–50%) and reactor wall conditions. Decreasing initial droplet size and solution molality accelerated droplet evaporation and resulted in smaller droplets at the onset of solute nucleation. Decreasing droplet concentration and carrier gas inlet relative humidity as well as increasing wall temperature (up to 350°C) or axial wall temperature gradient (up to 100°C cm⁻¹) increased the droplet evaporation rate, but did not change appreciably the droplet size at the point of precipitation for a given droplet size and solute concentration. Thus, control of droplet size at the onset of solute nucleation by varying process parameters other than the solution concentration and initial droplet size is limited.     

Intensification principle of a new three-phase catalytic slurry reactor. Part I: Performance characterisation

This paper presents the concept and the performances of a mini horizontal stirred tank reactor, used for hydrogenation reaction. A simple analytical model based on characteristic times of heat and mass transfer illustrates the intensification principle and shows that the relevant intensification parameter is the mass to heat transfer characteristics times ratio. The proof of concept is made through a small scale reactor named RAPTOR^® (French acronym for Reactor with Polyvalent Rectilinear Stirred Reactor with Optimised Transfer). The mass transfer performances are measured and compared to conventional stirred tank reactor and other multiple impeller continuous reactors. In a following second paper, a comparative study is proposed to evaluate the eco-efficiency and the techno-economic advantages of a continuous process involving a RAPTOR^® versus a classical batch process based on a stirred reactor.     

Insight into the Interaction Between Carbopol® 940 and Ionic/Nonionic Surfactant

Mixtures of a cross‐linked polyacrylic acid (Carbopol^® 940) and two types of surfactants, namely anionic sodium dodecylsulfate (SDS) and nonionic Tween^® 80, were investigated by viscometry, conductometry, tensiometry, spectrophotometry, fluorimetry and scanning electron microscopy (SEM). The addition of nonionic surfactant decreased the reduced viscosity and the transmittance of the Carbopol^® polymer aqueous solutions. Furthermore, the interaction between Carbopol^® 940 and SDS was characterized by two significant concentration values: the critical aggregation concentration of SDS was particularly independent of Carbopol^® polymer concentration while the polymer saturation point of both surfactants increased with the increase in polymer content. The values of critical aggregation concentration and polymer saturation point obtained using various techniques confirmed the occurrence of Carbopol^® polymer–surfactant associations. The effect of different SDS and Tween^® 80 concentrations on the conformation of Carbopol^® 940 in aqueous solution could be explained through hydrophobic association between surfactant micelles and Carbopol^® polymer tails and through hydrogen bonding in the case of Tween^® 80. Additionally, the surfactant‐induced structural changes were confirmed in Carbopol^® 940–SDS and Carbopol^® 940–Tween^® 80 aqueous solutions by SEM measurements.     

Ultra‐selective epoxidation of styrene on pure Cu{111} and the effects of Cs promotion

Styrene undergoes efficient epoxidation to styrene epoxide on the Cu{111} surface. At the optimum condition (Θ_o = 0.03 ML) ∼20% of the styrene is converted to the epoxide with almost 100% selectivity. Comparison with Ag{111} shows that the epoxidation activity and selectivity of Cu greatly exceed those of Ag. Incipient oxidation of the Cu{111} surface does not suppress the adsorption of styrene, but the oxidised metal is catalytically inert. Submonolayer amounts of Cs enhance styrene uptake and increase conversion to the epoxide without adversely affecting epoxidation selectivity. This effect is due to inhibition of Cu oxidation by Cs. Our findings are discussed in the light of current understanding of Ag‐catalysed alkene epoxidation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hydrogen filter press electrolyser modelled by coupling Fluent<Superscript><Emphasis Type="Bold">®</Emphasis></Superscript> and Flux Expert<Superscript><Emphasis Type="Bold">®</Emphasis></Superscript> codes

Mass production of hydrogen is a major issue for the coming decades particularly to decrease greenhouse gas production. The development of fourth-generation high-temperature nuclear reactors has led to renewed interest for hydrogen production. In France, the CEA is investigating new processes using nuclear reactors, such as the Westinghouse hybrid cycle. A recent study was devoted to electrical modeling of the hydrogen electrolyzer, which is the key unit of this process. In this electrochemical reactor, hydrogen is reduced at the cathode and SO₂ is oxidized at the anode with the advantage of a very low voltage cell. This paper describes an improved model coupling the electrical and thermal phenomena with hydrodynamics in the electrolyzer, designed for a priori computational optimization of our future pilot cell. The hydrogen electrolyzer chosen here is a filter press design comprising a stack of identical cathode and anode compartments separated by a membrane. In a complex reactor of this type the main coupled physical phenomena involved are forced convection of the electrolyte flows, the plume of evolving hydrogen bubbles that modifies the local electrolyte conductivity, and all the irreversible processes that contribute to local overheating (Joule effect, overpotentials, etc.). The secondary current distribution was modeled with a commercial FEM code, Flux Expert^®, which was customized with specific finite interfacial elements capable of describing the potential discontinuity associated with the electrochemical overpotential. Since the finite element method is not capable of properly describing the complex two-phase flows in the cathode compartment, the Fluent^® CFD code was used for thermohydraulic computations. In this way each physical phenomenon was modeled using the best numerical method. The coupling implements an iterative process in which each code computes the physical data it has to transmit to the other one: the two-phase thermohydraulic problem is solved by Fluent^® using the Flux-Expert^® current density and heat sources; the secondary distribution and heat losses are solved by Flux-Expert^® using the Fluent^® temperature field and flow velocities. A set of dedicated library routines was developed for process initiation, message passing, and synchronization of the two codes. The first results obtained with the two coupled commercial codes give realistic distributions for the electrical current density, gas fraction, and velocity in the electrolyzer. This approach allows us to optimize the design of a future experimental device.     

Behaviour of composites used in the confinement of nuclear wastes. 3. Diffusion of ions through epoxide networks

The diffusion of cesium and chloride ions through epoxide membranes was studied under a variety of conditions including self-diffusion, the presence of other salts in the aqueous solution, an excess of either reagent used in the manufacture of the membrane, the addition of various fillers in the epoxide network and two temperatures. At 23°C, the diffusion coefficient D was (2–6) × 10-¹³cm²s^?1 for most systems, except when the epoxide was prepared with an excess of the dioxirane component or when untreated glass beads were added to the network. In the latter instance D increased and most notably with glass beads. On the contrary, addition of sand to the epoxide resulted in a more effective barrier against diffusion as shown by a decrease in D. It is concluded that most of these materials should be suitable for the confinement of low and medium activity nuclear wastes.     

A NOVEL SPINNING DISC CONTINUOUS STIR TANK AND SETTLER REACTOR (SDCSTR) MODEL FOR CONTINUOUS SYNTHESIS OF TITANIA: A PHENOMENOLOGICAL MODEL

A novel phenomenological spinning disc continuous stir tank and settler reactor (SDCSTR) has been modeled for continuous synthesis of titania from its chloride precursor and water in which the desired polymorph, particle size, and distribution are controlled by the characteristics of the atomized inlet reagents, disc, and tank stir rate. This energy-efficient reactor generates seeding nuclei in the aerosol reacting volume that are then deployed for heterogeneous nucleation and particle growth in the metastable reacting volume of the aqueous (sol) process. Once at steady state, the enhanced TiO₂ nanoparticles due to the OH^?–H⁺ chemisorbed on the surface (with surface energy 0.5 < σ < 2.11 N/m) are continuously withdrawn at a rate equivalent to the particle settling rate from the settler. This reactor model eliminates the energy intensity required in traditional chemical vapor deposition (CVD) and aerosol reactors and provides better control for particle growth and size distribution by increasing particle residence time in the metastable zone of the aqueous (sol) reaction stage.     

Nanomagnet-Bound Imidazole as a Heterogeneous Axial Ligand for MnIII(salophen)Cl: An Efficient, Recoverable and Recyclable Catalyst for Epoxidation of Alkenes with Sodium Periodate

Efficient alkene epoxidation with sodium periodate catalyzed by manganese(III) salophen supported on nanomagnetic materials is reported. First, the iron nanomagnets were silica coated, functionalized with imidazole and then manganese salophen was successfully bonded to their surface. The catalyst, [Mn^III(salophen)Cl]@SiIm-Fe, was characterized by elemental analysis, FT-IR and UV/Vis spectroscopic techniques, SEM and ICP. The [Mn^III(salophen)Cl]@SiIm-Fe was used for alkene epoxidation with sodium periodate at room temperature. Different aromatic and aliphatic terminal alkenes were epoxidized efficiently using sodium periodate as an oxidant. The effect of reaction parameters such as solvent and oxidant in the epoxidation of cis-cyclooctene was investigated. This new heterogenized epoxidation catalyst is easily recovered with a magnet and showed no appreciable loss of activity even after four consecutive runs.     

On the feasibility of the microscale approach for a multistep biotransformation: sitosterol side chain cleavage

BACKGROUND: The millilitre/microlitre‐scale approach is widely used for screening purposes and one‐pot biotransformations, but it has seldom been applied to whole cell multistep biotransformations and two‐liquid biphasic processes. The present study aims to contribute to filling this gap by using 24‐well microtitre plates as reactors for the side chain cleavage of sitosterol with resting cells of Mycobacterium sp. NRRL B‐3805 and comparing results with other set‐ups. RESULTS: High catalytic activity in microtitre plates and aqueous medium was observed at 250 rpm shaking frequency and 25 mm shaking diameter with 80% headspace and a mixture of Mg²⁺, Zn²⁺, Mn²⁺ and Co²⁺ salts. Data obtained with microtitre plates were reproduced in other set‐ups when aqueous medium was used, whereas higher biotransformation rates were recorded in stirred reactors when biphasic systems were employed. CONCLUSION: Results suggest that microtitre plates may be used for the characterisation of complex bioconversion systems to establish representative screening systems, particularly if based in aqueous phase systems. Probing experiments also demonstrated the feasibility of using microlitre/millilitre shaken bioreactors to evaluate organic/aqueous two‐liquid bioconversion systems, although the enhanced mass transfer patterns resulting from the biphasic system hampered the translation of the data to the more common stirred reactor configuration. Copyright © 2007 Society of Chemical Industry     

Polyoxometalate-catalysed epoxidation of propylene with hydrogen peroxide: microemulsion versus biphasic process

Epoxidation of propylene with H₂O₂ catalysed by peroxo polytungstophosphates (P:W = 1:4), prepared by interaction of H₂WO₄, H₂O₂ and H₃PO₄ in the presence of Aliquat 336 as a surfactant, has been studied in chloride-free water-in-oil microemulsion (ME) Brij 30^® – n-octane – 30% aqueous H₂O₂ in comparison with the epoxidation in biphasic system 1,2-dichloroethane – H₂O. The epoxidation in ME occurs readily at 40–80 °C to give propylene oxide with 89–97% selectivity together with 3–11% propylene glycol. The catalyst can be reused but with a significant loss of activity. ³¹P NMR and chemical analysis indicate that the polyoxometalate catalyst is unstable in the ME system. In contrast, the epoxidation in the biphasic system occurs without catalyst decomposition, giving 83–86% epoxide and 14–17% glycol, and the catalyst can be easily reused without loss of activity and selectivity. The H₂O₂ utilisation in biphasic system (97–100%) has been found to be higher than in ME system (70–85%) at 60 °C.     

Epoxidation reactions of unsaturated fatty esters with potassium peroxomonosulfate

Epoxidation of the double bond in methyl oleate, octadec-11E-en-9-ynoate, ricinoleate (12-hydroxy-octadec-9Z-enoate), iso-ricinoleate (9-hydroxy-octadec-12Z-enoate), and 12-oxo-octadec-9Z-enoate with potassium peroxomonosulfate (oxone, 2 KHSO₅.K₂SO₄) in the presence of trifluoroacetone or methyl pyruvate gave the corresponding monoepoxy derivatives. Reaction of Oxone^® with methyl linoleate and octadeca-9Z,11E-dienoate furnished the corresponding diepoxystearate derivative. Methyl 9,12-dioxo-octadec-10Z-enoate was obtained when a C₁₈ furanoid fatty ester (methyl 9,12-epoxy-9,11-octadecadienoate) was treated with Oxone^®. The yield of these reactions was very high (85–99%), and the epoxy derivatives were readily isolated by solvent extraction. The products were identified by spectroscopic methods.     

Electrocoagulation in wastewater containing arsenic: Comparing different process designs

Arsenic removal from wastewater is a key problem for copper smelters. This work shows results of electrocoagulation of aqueous solutions containing arsenic with three different process designs and operating parameters.Three types of electrocoagulation reactors were tested and compared: (a) a modified flow continuous reactor, (b) a turbulent flow reactor and (c) an airlift reactor. All used iron as sacrificial anodes. The results showed that the electrocoagulation process of a 100 mg/L As(V) solution could decrease the arsenic concentration to less than 2 mg/L in the effluent with a current density of 1.2 A/dm² with both the modified flow and the airlift reactor. The removal of arsenic with the turbulent flow reactor did not reach the same level but the Fe-to-As ratio (mol/mol) achieved in the coagulation process was in this case lower (approximately 7) than with the other two reactors.In addition, it seems that increasing the current density beyond a maximum value, the electrocoagulation process would not improve any further. This could probably be explained by passivation of the anode.     

Continuous lipase-catalyzed production of wax ester using silicone tubing

Enzymatic synthesis of cetyl palmitate was performed in a solvent-free system at 65°C using immobilized Candida antarctica lipase. Batch reactions at controlled water activity showed that the yield could be increased from 88.8 to 99.1% by decreasing the water activity from 1 to 0.05. A continuous reactor configuration was constructed, where two tubular reactors were run in sequence with a separation container in between, in which the water phase was separated from the wax ester phase. The reactor was run for 1 wk at low flow rate (0.005 g/min) with very good operational stability and a productivity of 7.2 g d⁻¹ using 0.4 g of biocatalyst. The activity of the individual preparations decreased during operation. The first reactor had only 30% activity left after 1 wk of operation whereas the second reactor showed only a 10% decrease. This difference in enzyme stability is a direct result of the different water activity in the two reactors.     

Continuous lipase‐catalyzed synthesis of hexyl laurate in a packed‐bed reactor: optimization of the reaction conditions in a solvent‐free system

BACKGROUND: Hexyl laurate has been applied widely in cosmetic industries and is synthesized by chemical methods with problems of cost, environmental pollution, and by‐products. In this study, Lipozyme^® IM77 (from Rhizomucor miehei) was used to catalyze the direct‐esterification of hexanol and lauric acid in a solvent‐free system by utilizing a continuous packed‐bed reactor, wherein the aforementioned difficulties could be overcome. Response surface methodology (RSM) and three‐level‐three‐factor Box‐Behnken design were employed to evaluate the effects of synthesis parameters, such as reaction temperature (45–65 °C), mixture flow rate (0.25–0.75 mL min^?1) and concentration of lauric acid (100–300 mmol L^?1) on the production rate (µmol min^?1) of hexyl laurate by direct esterification. RESULTS: The production rate was affected significantly by the mixture flow rate and lauric acid concentration. On the basis of ridge‐max analysis, the optimum synthesis conditions for hexyl laurate were as follows: 81.58 ± 1.76 µmol min^?1 at 55 °C, 0.5 mL min^?1 flow rate and 0.3 mol L^?1 lauric acid. CONCLUSION: The lipase‐catalyzed synthesis of hexyl laurate by Lipozyme^® IM‐77 in a continuous packed‐bed bioreactor and solvent‐free system was successfully developed; optimization of the reaction parameters was obtained by Box–Behnken design and RSM. Copyright © 2008 Society of Chemical Industry     

Epoxidation of Methanol-Soluble Kraft Lignin for Lignin-Derived Epoxy Resin and Its Usage in the Preparation of Biopolyester

Most commercial epoxy resins have been produced using toxic bisphenol A. Lignin can be utilized as green substitute for bisphenol A to produce bio-epoxy resins. Methanol-soluble kraft lignin was extracted by methanol fractionation for lignin epoxidation, and epoxidized into lignin-derived epoxy resin via two-step epoxidation consisting of epichlorohydrin addition and epoxide ring restructuring. Epoxidized lignin was selectively separated from non- or less-reacted lignin based on their solubility differences in organic solvents. The existence of epoxide groups in the lignin-derived epoxy resin was confirmed using FT-IR, ¹H-NMR, and TGA analyses. Epoxidized lignin was used as a reactive lignin macromonomer to prepare biopolyester. The characteristics of the synthesized biopolyester were analyzed using FT-IR, and the thermal properties were analyzed by TGA. The thermal decomposition temperature of 5% weight loss (T_d5) was determined to be 257.1°C, which is comparable to epoxy resins that are used in electronic applications.