Batch Slurry Reactor Research Articles

Mechanistic analysis of ultrasound-assisted biodiesel synthesis with Cu2O catalyst and mixed oil feedstock using continuous (packed bed) and batch (slurry) reactors

This paper has investigated the mechanistic issues of ultrasound-assisted transesterification process using solid Cu2O catalyst and mixed feedstock of non-edible oils. The optimum conditions for transesterification have been determined using statistical experimental design in packed bed catalytic reactor. The kinetic constants of different steps of transesterification process have been determined using kinetic model based on Eley-Rideal mechanism coupled to time profiles of reactants and products of transesterification in batch slurry reactors. The batch experiments have been performed at optimum conditions predicted by statistical experimental design: alcohol/oil molar ratio=10.6, temperature=62.5°C, catalyst concentration=7.25wt% oil. It is revealed that adsorption of methanol is the slowest and rate determining step of transesterification process. Sonication enhanced the kinetics of reaction steps of transesterification process, but its effect on methanol adsorption on Cu2O catalyst was adverse. The activation energy of overall transesterification process was 90.14kJ/mol; while, the sum total of activation energies of the three reaction steps of triglyceride conversion was 40.98kJ/mol. These results essentially point to strong mass transfer influence on Cu2O-catalyzed transesterification process, even in presence of sonication. The adsorptive mass transfer of methanol to catalyst sites is not enhanced by microturbulence generated by sonication. Two probable causes leading to this effect are: discrete and intermittent nature of acoustic (or shock) waves generated by the transient cavitation, and secondly, the high temperature of reaction that offsets the methanol adsorption on catalyst websites.

Orange II Degradation by Wet Peroxide Oxidation Using Au Nanosized Catalysts: Effect of the Support

The degradation of Orange II was evaluated by wet peroxide oxidation using gold nanoparticles supported on Fe2O3, TiO2, ZnO, and Al2O3 as catalysts in a slurry batch reactor. Materials were prepared by the same deposition–precipitation method, which yielded well-dispersed nanosized gold particles (2.2–5.5 nm). For comparison, a commercial catalyst (Au/Fe2O3 supplied by the World Gold Council) was used as reference. It was demonstrated that the efficiency of wet peroxide oxidation for the Orange II removal and organics mineralization depends on the type of oxide used and the loading and diameter of gold. The Au/Al2O3 material, with the highest BET surface area, showed the highest turnover frequency value and also higher total organic carbon and Orange II removals. The catalysts were reused for consecutive cycles, with no Au leaching being detected into the solution, demonstrating their high stability. This stability was confirmed by textural and chemical characterization of the fresh and used materials.

Novel alkali-promoted hydrotalcite for selective synthesis of 2-methoxy phenyl benzoate from guaiacol and benzoic anhydride

Esters find several applications such as solvents, flavours and fragrants and intermediates in synthesis of drugs. In the present work, 2-methoxy phenyl benzoate was efficiently synthesized from guaiacol and benzoic anhydride by acylation. A variety of catalysts such as hydrotalcite and alkali-promoted hydrotalcite was synthesized. Potassium-promoted hydrotalcite (K/HT) calcined at 500 °C for 6 h was active, selective and reusable. It was characterized by different techniques. A slurry batch reactor was used to study reaction mechanism and kinetics. 2-Methoxy phenyl benzoate was efficiently obtained with 100% selectivity at guaiacol conversion of 98% over K/HT at 100 °C after 6 h. A power law model with second-order kinetics was fitted to obtain an apparent activation energy of reaction of 21.1 kcal mol−1. The process is clean and green.

Kinetic Modeling of Sorbitol Hydrogenolysis over Bimetallic RuRe/C Catalyst

Sorbitol hydrogenolysis kinetics using bimetallic RuRe catalyst is reported based on multiple experiments in parallel batch slurry reactors (H2 pressure: 1.0–6.5 MPa, temperature: 473–503 K) to obtain concentration–time profiles. It is observed that RuRe/C bimetallic catalysts with Ca(OH)2 as a base promoter show significantly higher activity and selectivity toward liquid phase products such as 1,2-propanediol, lactic acid, ethylene glycol, and linear alcohols compared with monometallic Ru/C catalysts and other base promoters. It is further found that sorbitol hydrogenolysis initiates with dehydrogenation and subsequent C–C cleavage via retro-aldolization to form smaller molecules (C2–C4). Those smaller intermediates undergo dehydration, reorganization, and C–O cleavage to form C2–C3 acids, glycols, and linear alcohols as products, which are very similar to glycerol conversion chemistry. For the kinetic modeling, experimental data on concentration–time profiles were obtained using RuRe/C catalysts with Ca...

Assessment of mechanisms for enhanced performance of Yb/Er/titania photocatalysts for organic degradation: Role of rare earth elements in the titania phase

The effect of doping titania with rare earth erbium and ytterbium ions on photocatalytic degradation of a real pollutant (phenol) and a model pollutant was studied under simulated solar radiation and using light of specific frequencies in the ultraviolet, green, red, and infrared regions via LEDs. The goal of this study was to quantify the effect of these dopants on photocatalytic degradation rates and critically assess the phenomena (upconversion, adsorption, recombination kinetics, etc) responsible for improved performance upon rare earth ion doping of titania. A hydrothermal process was modified to synthesize pure anatase and rare earth ion doped TiO2. The doped catalysts contained 2% Er and 0, 10, 15, or 20% Yb, on an elemental basis. These photocatalysts were characterized for structure, composition, surface area, particle size, bandgap, and band edge positions. The results indicated that the rare earth elements substituted in the titania phases, which were the crystalline anatase and amorphous titania phases. Aqueous-phase photocatalytic degradation rate constants for both organics under a variety of light irradiation conditions were quantified via slurry batch reactor studies in the liquid phase using pseudo first-order kinetics. On reactor volume and catalyst mass bases (same trends due to same catalyst loading), the 2% Er/TiO2 catalyst performed ∼3× better (compared to∼10× on surface area basis) and the 2% Er 10%Yb/TiO2 catalyst performed ∼1.7× (∼3.5× better on surface area basis) than the pure titania sample for phenol degradation under simulated solar irradiation. Though there were minor differences because the model pollutant (Rose Bengal) adsorbed during dark equilibration and phenol did not, similar enhancements were observed for photodegradation of Rose Bengal. Photodegradation was further studied using high-intensity LED irradiation at different narrow wavelengths (405, 530, 660, and 940nm) which matched the photon absorption energies related to upconversion of the doped samples. Phenol conversion was observed only for the UV (405nm) source. Similar observations were made for Rose Bengal degradation. A conclusion was reached that upconversion did not contribution to the photocatalytic performance under simulated solar insolation. Combined with the lack of phenol adsorption during dark equilibration for any of the samples, photon energy of the excitation source relative to the band gap and differences in defect chemistry on key kinetic steps are the only plausible explanations for the enhanced performance of these rare earth doped samples compared to pure titania.

Aqueous photocatalytic degradation of selected micropollutants by Pd-modified titanium dioxide in three photoreactor types

ABSTRACTThe goals of the present study were to synthesise highly efficient Pd-TiO2 photocatalyst, to characterise its performance in slurry in smaller scale and to investigate its performance in the aqueous photocatalytic oxidation of three antibiotics: doxycycline, sulphamethizole and amoxicillin. The performance of the photocatalyst was evaluated in an open batch slurry reactor equipped with a fluorescent long-wavelength ultraviolet (UVA) lamp (0.2 L). With the fastest degrading doxycycline, experimental research was continued in a fixed-bed continuous flow photoreactor (0.13 L), with the Pd-TiO2 photocatalyst attached to a glass plate, and a medium laboratory-scale three-phase fluidised-bed reactor (2 L) equipped with four fluorescent UVA lamps, with the photocatalyst attached to the surface of expanded clay granules employed as the bed material. While showing very high activity in the batch slurry reactor, far surpassing P25 Aeroxide, the performance of Pd-TiO2 with doxycycline was comparable to P25 in the semi-continuous reactors.

Wet peroxide oxidation of dye-containing wastewaters using nanosized Au supported on Al2O3

The degradation of a model dye compound (Orange II) was evaluated by wet peroxide oxidation using gold supported on alumina (Au/Al2O3) as a catalyst, in a slurry batch reactor. The material was prepared by the deposition-precipitation method, which yielded nanosized gold particles well dispersed on the support, with a mean particle size of 3.6nm. It was concluded that both adsorption and catalyzed oxidation (via hydroxyl radical formation) contribute to the dye removal. The catalyst was reused for five consecutive cycles, with no Au leaching being detected into the solution (detection limit <0.5mg/L), showing its high stability. This was also confirmed by textural and chemical characterization of the fresh and used materials. A parametric study was carried out to assess the influence of the most important variables (hydrogen peroxide amount, catalyst concentration, reaction pH and temperature) in both dye and total organic carbon (TOC) removal. In all runs performed, gold leaching was not detected. In the best operating conditions found, high efficiencies were reached (i.e., ∼100% of dye removal, 50% of TOC reduction, 42% of chemical oxygen demand – COD – elimination). The treatment improved the biodegradability of the effluent and the obtained waste remained non-toxic (as inferred from the inhibition of Vibrio fischeri test).A simulated industrial acrylic dyeing effluent was also treated by wet peroxidation. It was found that the gold support on alumina catalyst was stable and achieved considerable removal of color (33%) and organic compounds (42% for TOC and 50% for COD) and improved the biodegradability of the wastewater.

Photocatalytic activity of Cu2O supported on multi layers graphene for CO2 reduction by water under batch and continuous flow

The photocatalytic activity of Cu2O supported on multi-layers graphene for CO2 reduction by water was studied under two hydrodynamic environments, in a slurry batch reactor and in a capillary reactor with the catalyst immobilized on the wall. Under both conditions, the major photoproduct was hydrogen observed in the gas phase, accompanied by lesser amounts of ethanol present in the aqueous solution. The maximum production rates were 2031 and 545μmolg−1h−1 for H2 and CH3CH2OH, respectively, and were found under the hydrodynamic mode attained in the capillary reactor.

Catalysts with Cerium in a Membrane Reactor for the Removal of Formaldehyde Pollutant from Water Effluents.

We report the synthesis of cerium oxide, cobalt oxide, mixed cerium, and cobalt oxides and a Ce–Co/Al2O3 membrane, which are employed as catalysts for the catalytic wet oxidation (CWO) reaction process and the removal of formaldehyde from industrial effluents. Formaldehyde is present in numerous waste streams from the chemical industry in a concentration low enough to make its recovery not economically justified but high enough to create an environmental hazard. Common biological degradation methods do not work for formaldehyde, a highly toxic but refractory, low biodegradability substance. The CWO reaction is a recent, promising alternative that also permits much lower temperature and pressure conditions than other oxidation processes, resulting in economic benefits. The CWO reaction employing Ce- and Co-containing catalysts was carried out inside a slurry batch reactor and a membrane reactor. Experimental results are reported. Next, a mixed Ce–Co oxide film was supported on an γ-alumina membrane used in a catalytic membrane reactor to compare formaldehyde removal between both types of systems. Catalytic materials with cerium and with a relatively large amount of cerium favored the transformation of formaldehyde. Cerium was present as cerianite in the catalytic materials, as indicated by X-ray diffraction patterns.

Composite catalytic tubular membranes for selective hydrogenation in three-phase systems

Catalytic membrane contact reactors (CMCRs) were evaluated for the selective three-phase hydrogenation of the model reaction, the partial hydrogenation of soybean oil (PHSO). PHSO produces copious amounts of trans-fats when carried out in a batch slurry reactor due to hydrogen starvation at the catalyst, caused by inherent mass transfer limitations of the system. In this study composite ceramic/polymer membranes were rendered catalytically active by depositing a polymer-palladium complex, (poly(N-vinyl-2-pryyolidone) (PVP)-palladium (Pd)), onto the selective skin of the membrane. Hydrogen gas was supplied to the support side of the membrane, the hydrogen gas permeated from the support side to the skin side of the membrane, where it dissociated onto the catalyst surface. Liquid reactant was circulated over the skin side of the membrane, allowing the three components to come into contact and react. Our system is shown to be nearly zero order in hydrogen, indicating that the catalyst surface maintains high hydrogen coverage throughout. CMCRs produced 50% less trans-fat at equivalent levels of hydrogenation compared to slurry reactors. It was further demonstrated that an increase in temperature had minimal effects on trans-fat formation, while significantly increasing hydrogenation rates; allowing the system to capture higher reaction rates without adversely affecting product quality.

Kinetic modeling of Pt/C catalyzed aqueous phase glycerol conversion with in situ formed hydrogen

Detailed kinetic modeling of Pt/C catalyzed conversion of glycerol to lactic acid, glycols, and alcohols with in situ formed hydrogen is reported. Experimental concentration‐time profiles were obtained in a batch slurry reactor at different glycerol concentrations, nitrogen partial pressures, and NaOH concentrations in a temperature range of 130–160°C. Six different kinetic models were evaluated to describe the competing dehydrogenation, hydrogenolysis, dehydration, and CC cleavage reactions, and discriminated to fit the experimental data. It is found that a “dual‐similar‐site” mechanism involving alkali promoted dehydrogenation, on two adjacent Pt sites to affect CC and CO cleavage best describes the experimental data. The dehydrogenation reaction proceeds with a significantly lower activation barrier (Ea = 53 kJ/mol) compared with the noncatalytic hydrothermal conversion (Ea = 128 kJ/mol). The activation energy for glycerol hydrogenolysis on Pt/C catalyst without adding hydrogen is estimated to be 64 kJ/mol. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1162–1173, 2016

English

The liquid phase hydrogenation of 2-((1-benzyl-1, 2, 3, 6-tetrahydropyridin-4-yl)methylene)-5, 6-dimethoxy-2, 3-dihydroinden-1-one hydrochloride (1) over a 5 % Pt/C industrial catalyst was studied experimentally in a batch slurry reactor using methanol as a solvent. The catalyst was characterized by the adsorption techniques for specific surface area and pore volume, and by XRD for crystallinity. To investigate the intrinsic kinetics of the reaction, the effect of temperature, catalyst loading, hydrogen partial pressure and (1) concentration on the initial rate of hydrogenation was studied. The analysis of initial rate data showed that the gas-liquid, liquid-solid, and intraparticle mass-transfer resistances were not significant. The reaction scheme of (1) hydrogenation was proposed for the kinetic modelling. Apparent rate constants for all hydrogenation steps were calculated using a first order kinetic approach resulting in good agreement between the experimentally obtained and predicted concentrations. From the temperature dependence of rate constants, the activation energies of various reaction steps were calculated. The averaged activation energy of these steps was found to be 31.1 kJ mol-1.

Adsorption microcalorimetry characterization of K-doped MgAl mixed oxide catalysts for soybean oil transesterification synthesized by impregnation and ball milling techniques

Layered double hydroxides were prepared by pH-controlled co-precipitation method with a Mg/Al molar ratio between 1.5 and 4.0 and used as precursors for obtaining, through calcination, a series of MgAl mixed oxides, which were used as catalysts for soybean oil transesterification with methanol. The mixed oxide with the highest Mg/Al ratio was doped with potassium for obtaining highly basic catalysts. Three different potassium salts (K2CO3, KNO3, CH3COOK) were used for loading potassium on the support (K loading ca. 3 mass%) by two different techniques, namely conventional incipient wetness impregnation and innovative mechanical milling. All the catalysts were characterized as to their chemical composition, structure and texture by inductively coupled plasma atomic emission spectroscopy, X-ray diffraction and N2 physisorption, respectively. Their basic and acid features were assessed by adsorption microcalorimetry, using CO2 and NH3 as probe molecules, respectively. Catalytic testing was carried out in a slurry batch reactor operated at 343 K and atmospheric pressure. The occurrence of potassium leaching into the liquid phase was checked for the K-doped catalysts. The initial activity of the heterogeneous catalysts was interpreted in terms of surface basicity, by taking into account a possible role of acidity in determining the mechanism.

Enhanced photocatalytic activity of single-phase, nanocomposite and physically mixed TiO2 polymorphs

In this study, testing of TiO2 polymorphs (anatase, rutile, brookite) and their mixtures (anatase/rutile, anatase/TiO2-B) in heterogeneous photocatalytic oxidation process was conducted at ambient conditions in a batch slurry reactor. The efficiency of bare TiO2 catalysts was evaluated based on the degree of bisphenol A (BPA) removal, which is a well-known endocrine disrupting compound (EDC). The obtained results indisputably show that BPA removal is strongly affected by catalyst morphology, crystallite size, structure and specific surface area. Detailed interpretation of catalyst properties combined with BPA removal rates leads to the conclusion that photocatalytic oxidation is the most prominent either by using pure anatase particles or high surface area anatase/TiO2-B nanocomposite. However, the highest extent of mineralization was observed in the presence of high specific surface area nanotubular anatase/TiO2-B nanocomposite. Interestingly, when anatase and rutile particles were physically mixed, an additional beneficial effect on BPA degradation was observed. Interpretation of the obtained results shows that a synergistic effect between the respective phases takes place, and consequently enhances the overall activity. This phenomenon was explained by the proposed mechanism of overall hydroxyl radicals concentration increment due to transfer of OH formed on the surface of anatase particles (via H2O oxidation with photogenerated holes in the valence band) to rutile particles.

Residence time distribution and reaction rate in the horizontal rotating foam stirrer reactor

The performance of a multistage horizontal rotating foam stirrer reactor in semi-continuous operation was studied for the selective hydrogenation of functionalized alkynes to alkenes, an important process in the fine chemicals industry. This new type of multiphase reactor consists of a horizontal vessel compartmentalized by vertical baffles and equipped with an impeller in each compartment. The impeller is a donut-shaped foam block, which is also used as catalyst support. The advantage of this reactor configuration compared to batch slurry reactors is the better catalyst handling, since the catalyst is fixed on the stirrer. In addition, a higher selectivity towards the desired product is achieved as a result of a narrower residence time distribution. A reactor model consisting of stirred tanks in series with backflow and dead volume was used to describe the liquid flow behaviour. The effects of liquid flow rate, backmixing and number of stages for the hydrogenation reaction are discussed, and optimal operation conditions are suggested.

Remediation of Antiseptic Components in Wastewater by Photocatalysis Using TiO2 Nanoparticles

Environmental awareness in both the public and regulatory sectors has necessitated proper treatment of medicinal components-rich pharmaceutical effluents. Even the presence of trace antiseptic may cause adverse health effects including development of “product resistant microbes” in the aquatic environment. The present study involves photomineralization of chlorhexidine, which belongs to the class of antiseptic drug components. This study details investigations on photocatalytic degradation of chlorhexidine in a slurry batch reactor using titanium dioxide photocatalyst. Emphases were given to study the effects of operating parameters on the degradation behavior of the targeted compound and characterization of degraded products. About 68.14% removal of chlorhexidine digluconate (CHD) was found after 1 h at 25 °C with a substrate-to-catalyst ratio of 2.5:1 under UV intensity of 50 μW·cm–2 at pH 10.5. Though the product profile illustrates several degraded products, toxicological analysis on Bacillus subtilis exhibited no inhibition zone, suggesting the eco-friendly nature of the degraded products.

Lipase-Based Biocatalytic Flow Process in a Packed-Bed Microreactor

The transesterification of ethyl butyrate with 1-butanol to give butyl butyrate catalyzed by Novozym 435 was performed in a batch slurry reactor and in a packed-bed microreactor. The observed react...

Fractal analysis of catalyst surface morphologies on hydrogenation in process of 2-((1-benzylpiperidin-4-yl)methyl)-5,6-dimethoxy-2,3-dihydroinden-1-one hydrochloride synthesis

Catalytic hydrogenation of 2-((1-benzyl-1,2,3,6-tetrahydropyridin-4-yl)methylene)-5,6-dimethoxy-2,3-dihydroinden-1-one hydrochloride (1) to 2-((1-benzylpiperidin-4-yl)methyl)-5,6-dimethoxy-2,3-dihydroinden-1-one hydrochloride (2) was investigated in batch-slurry reactor. The 5% Pt/C catalysts were chosen for optimizing the catalytic activity. The catalyst activity has been changed by using the differently morphologically structured fractal catalysts. The kinetic terms of hydrogenation for (1) change with the fractal dimensions of the 5% Pt/C catalyst. The most active and selective (with the highest reaction rate for production of (2), and with the least impurities level) is the catalyst K3, and the worst the catalyst K4. This most active and selective catalyst has an intermediate fractal surface dimension, DF,ads=2.77, and the worst catalyst is represented by almost smooth surface with a high DF,ads=2.82. The interface D[BW] fractal indices (derived from the thresholded SEM images, at the magnifications in the range 600–2000×) are largest ones for the most suitable catalyst K3, and lowest for the catalyst K4.

Oxidative Degradation of Oxalic Acid in Aqueous Medium Using Manganese Oxide as Catalyst at Ambient Temperature and Pressure

Manganese oxide was prepared by mechano chemical process in solid phase and was characterized by physical (surface area, particle size, XRD and FTIR analyses) and chemical (surface and total oxygen content) techniques. Prepared manganese oxide was used as catalyst for oxidation/degradation of oxalic acid in aqueous medium in an agitated slurry batch reactor, where molecular oxygen was used as an oxidant. Influence of different reaction parameters like time of reaction, speed of agitation, initial concentration of oxalic acid, temperature and partial pressure of oxygen on oxidation/degradation of oxalic acid was investigated. About 71.5% of oxalic acid (20 mL of 0.017 M) was degraded with in 1 h. The oxidation/degradation reaction followed the Langmuir–Hinshelwood type of mechanism. Curve Expert software was used for kinetic analysis.

Surface properties of pillared acid-activated bentonite as catalyst for selective production of linear alkylbenzene

Acid-activated and pillared montmorillonite were prepared as novel catalysts for alkylation of benzene with 1-decene for production of linear alkylbenzene. The catalysts were characterized by X-ray diffraction, FT-IR spectroscopy, N2 adsorption isotherms, temperature programmed desorption of NH3, scanning electron microscopy and elemental and thermal analysis techniques. It was found that acid-activation of clays prior to pillaring increased the porosity, total specific surface area, total pore volume and surface acidity of the catalysts. Optimization of the reaction conditions was performed by varying catalyst concentration (0.25–1.75wt%), reactants ratio (benzene to 1-decene of 8.75, 12 and 15) and temperature (115–145°C) in a batch slurry reactor. Under optimized conditions more than 98% conversion of 1-decene, and complete selectivity for monoalkylbenzenes were achieved.