Indium-mediated regioselective synthesis of ketones from arylstannanes under solvent-free ultrasound irradiation

The solvent-free indium-promoted reaction of alkanoyl chlorides with sterically and electronically diverse arylstannanes is a simple and direct method for the regioselective synthesis of primary, secondary and tertiary alkyl aryl ketones in good to excellent isolated yields (42–84%) under mild and neutral conditions. The protocol is also adequate for the synthesis of aryl vinyl ketones. Reaction times are drastically reduced (from 3–32 h to 10–70 min) under ultrasonic irradiation. Evidences for the involvement of a homolytic aromatic ipso-substitution mechanism, in which indium metal acts as radical initiator, are presented. It is possible the transference of two aryl groups from tin, thus improving effective mass yield, working with diarylstannanes as starting substrates.     

Biosynthesis of gold nanoparticles by Aspergillum sp. WL-Au for degradation of aromatic pollutants

A simple method for synthesis of gold nanoparticles (AuNPs) using Aspergillum sp. WL-Au was presented in this study. According to UV–vis spectra and transmission electron microscopy images, the shape and size of AuNPs were affected by different parameters, including buffer solution, pH, biomass and HAuCl₄ concentrations. Phosphate sodium buffer was more suitable for extracellular synthesis of AuNPs, and the optimal conditions for AuNPs synthesis were pH 7.0, biomass 100 mg/mL and HAuCl₄ 3 mM, leading to the production of spherical and pseudo-spherical nanoparticles. The biosynthesized AuNPs possessed excellent catalytic activities for the reduction of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, o-nitroaniline and m-nitroaniline in the presence of NaBH₄, and the catalytic rate constants were calculated to be 6.3×10⁻³ s⁻¹, 5.5×10⁻³ s⁻¹, 10.6×10⁻³ s⁻¹, 8.4×10⁻³ s⁻¹ and 13.8×10⁻³ s⁻¹, respectively. The AuNPs were also able to catalyze the decolorization of various azo dyes (e.g. Cationic Red X-GRL, Acid Orange II and Acid scarlet GR) using NaBH₄ as the reductant, and the decolorization rates reached 91.0–96.4% within 7 min. The present study should provide a potential candidate for green synthesis of AuNPs, which could serve as efficient catalysts for aromatic pollutants degradation.     

ZnO nanocubes with (1 0 1) basal plane photocatalyst prepared via a low-frequency ultrasonic assisted hydrolysis process

The crystallographic plane of the ZnO nanocrystals photocatalyst is considered as a key parameter for an effective photocatalysis, photoelectrochemical reaction and photosensitivity. In this paper, we report a simple method for the synthesis of a new (1 0 1) high-energy plane bounded ZnO nanocubes photocatalyst directly on the FTO surface, using a seed-mediated ultrasonic assisted hydrolysis process. In the typical procedure, high-density nanocubes and quasi-nanocubes can be grown on the substrate surface from a solution containing equimolar (0.04 M) zinc nitrate hydrate and hexamine. ZnO nanocubes, with average edge-length of ca. 50 nm, can be obtained on the surface in as quickly as 10 min. The heterogeneous photocatalytic property of the sample has been examined in the photodegradation of methyl orange (MO) by UV light irradiation. It was found that the ZnO nanocubes exhibit excellent catalytic and photocatalytic properties and demonstrate the photodegradation efficiency as high as 5.7 percent/μg mW. This is 200 times higher than those reported results using a relatively low-powered polychromatic UV light source (4 mW). The mechanism of ZnO nanocube formation using the present approach is discussed. The new-synthesized ZnO nanocubes with a unique (1 0 1) basal plane also find potential application in photoelectrochemical devices and sensing.     

A convenient ultrasound-promoted regioselective synthesis of fused polycyclic 4-aryl-3-methyl-4,7-dihydro-1H-pyrazolo[3,4-b]pyridines

Fused polycyclic 4-aryl-3-methyl-4,7-dihydro-1H-pyrazolo[3,4-b]pyridines were obtained in a three-component regioselective reaction of 5-amino-3-methyl-1H-pyrazole, 2H-indene-1,3-dione and arylaldehydes in ethanol under ultrasound irradiation. This rapid method produced the products in short reaction times (4–5 min) and excellent yields (88–97%).     

Multi-species time-history measurements during high-temperature acetone and 2-butanone pyrolysis

High-temperature acetone and 2-butanone pyrolysis studies were conducted behind reflected shock waves using five species time-history measurements (ketone, CO, CH₃, CH₄ and C₂H₄). Experimental conditions covered temperatures of 1100–1600 K at 1.6 atm, for mixtures of 0.25–1.5% ketone in argon. During acetone pyrolysis, the CO concentration time-history was found to be strongly sensitive to the acetone dissociation rate constant k₁ (CH₃COCH₃ → CH₃ + CH₃CO), and this could be directly determined from the CO time-histories, yielding k₁(1.6 atm) = 2.46 × 10¹⁴ exp(?69.3 [kcal/mol]/RT) s^?1 with an uncertainty of ±25%. This rate constant is in good agreement with previous shock tube studies from Sato and Hidaka (2000) [3] and Saxena et al. (2009) [4] (within 30%) at temperatures above 1450 K, but is at least three times faster than the evaluation from Sato and Hidaka at temperatures below 1250 K. Using this revised k₁ value with the recent mechanism of Pichon et al. (2009) [5], the simulated profiles during acetone pyrolysis show excellent agreement with all five species time-history measurements. Similarly, the overall 2-butanone decomposition rate constant k_tot was inferred from measured 2-butanone time-histories, yielding k_tot(1.5 atm) = 6.08 × 10¹³ exp(?63.1 [kcal/mol]/RT) s^?1 with an uncertainty of ±35%. This rate constant is approximately 30% faster than that proposed by Serinyel et al. (2010) [11] at 1119 K, and approximately 100% faster at 1412 K. Using the measured 2-butanone and CO time-histories and an O-atom balance analysis, a missing removal pathway for methyl ketene was identified. The rate constant for the decomposition of methyl ketene was assumed to be the same as the value for the ketene decomposition reaction. Using the revised k_tot value and adding the methyl ketene decomposition reaction to the Serinyel et al. mechanism, the simulated profiles during 2-butanone pyrolysis show good agreement with the measurements for all five species.     

Effect of growth time of hydrothermally grown cobalt hydroxide carbonate on its supercapacitive performance

We present the time-dependent synthesis of cobalt hydroxide carbonate nanorods by hydrothermal method with a systematic increase of different parameters such as specific surface area and specific capacitance as a function of different synthesis time. Morphological characterization of the cobalt hydroxide carbonate nanorods were carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that variation of the time of reaction plays a crucial role in the transformation of samples’ morphology. Cobalt hydroxide carbonate nanorods synthesized with 12 h reaction time, which is the reaction just before the materials transforms into cobalt oxide under the same synthesis conditions exhibited the highest specific capacitance of 466 F g⁻¹ at a current density of 1 A g⁻¹ in 6 M KOH electrolyte and also showed excellent stability with ∼99% capacitance retention after 2000 cycles at a current density of 10 A g⁻¹. Based on the above results, the cobalt hydroxide carbonate nanorods show a considerable potential as electrodes materials for supercapacitor applications.     

Ultrasound-assisted butyl acetate synthesis catalyzed by Novozym 435: Enhanced activity and operational stability

The influence of low-frequency ultrasound (40 kHz) in the esterification reaction between acetic acid and butanol for flavor ester synthesis catalyzed by the commercial immobilized lipase B from Candida antarctica (Novozym 435) was evaluated. A central composite design and the response surface methodology were used to analyze the effects of the reaction parameters (temperature, substrate molar ratio, enzyme content and added water) and their response (yields of conversion in 2.5 h of reaction). The reaction was carried out using n-hexane as solvent. The optimal conditions for ultrasound-assisted butyl acetate synthesis were found to be: temperature of 46 °C; substrate molar ratio of 3.6:1 butanol:acetic acid; enzyme content of 7%; added water of 0.25%, conditions that are slightly different from those found using mechanical mixing. Over 94% of conversion was obtained in 2.5 h under these conditions. The optimal acid concentration for the reaction was determined to be 2.0 M, compared to 0.3 M without ultrasound treatment. Enzyme productivity was significantly improved to around 7.5-fold for each batch when comparing ultrasound and standard mechanical agitation. The biocatalyst could be directly reused for 14 reactions cycles keeping around 70% of its original activity, while activity was virtually zeroed in the third cycle using the standard mixing system. Thus, compared to the traditional mechanical agitation, ultrasound technology not only improves the process productivity, but also enhances enzyme recycling and stability in the presence of acetic acid, being a powerful tool to improve biocatalyst performance in this type of reaction.     

Ultrasound assisted co-precipitation synthesis and catalytic performance of mesoporous nanocrystalline NiO-Al2O3 powders

Mesoporous nanocrystalline NiO-Al₂O₃ powders with high surface area were synthesized via ultrasound assisted co-precipitation method and the potential of the selected samples as catalyst was investigated in dry reforming reaction for preparation of synthesis gas. The prepared samples were characterized by N₂ adsorption (BET), X-ray diffraction (XRD), Temperature programmed reduction and oxidation (TPR, TPO) and scanning electron microscopy (SEM) techniques. The effects of pH, power of ultrasound irradiation, aging time and calcination temperature on the textural properties of the catalysts were studied. The sample prepared under specified conditions (pH10, 70 W, without aging time and calcined at 600 °C) exhibited the highest surface area (249.7 m² g⁻¹). This catalyst was calcined at different temperature and employed in dry reforming of methane and the catalytic results were compared with those obtained over the catalysts prepared by impregnation and co-precipitation methods. The results showed that the catalyst prepared by ultrasound assisted co-precipitation method exhibited higher activity and stability with lower degree of carbon formation compared to catalysts prepared by co-precipitation and impregnation methods.     

Dependence of sonochemical parameters on the platinization of rutile titania – An observation of a pronounced increase in photocatalytic efficiencies

Using a standing wave sonochemical reactor (SWSR), the influences of parameters of ultrasonic power input, sonication time, sonication temperature and the amount of propanol (which generates the reducing radicals) were systemically investigated to ascertain and optimize the best conditions for the sonochemical reduction of Pt from its precursor hexachloroplatinic acid and then its deposition on rutile TiO₂ (platinization of rutile titania) catalysts. Catalytic activity of the prepared platinized catalysts was tested in the reaction of methyl orange degradation. The results of photocatalytic activity study in the degradation of methyl orange further demonstrate that sonochemically as-prepared Pt/TiO₂ catalysts show a pronounced increase (～2 times) in photodegradation, even with a deposition of small amounts of platinum (1.4 wt.%), as compared to the unsupported or naked rutile titania. Although there are various parameters that influence the sonochemical platinization of rutile titania, the present optimization results clearly indicate that the best photocatalytic degradation of methyl orange can be obtained when the experimental conditions of the preparation were with an input power of 50 W, an initial hexachloroplatinic acid volume of 70 ml (which results into 1.4 wt.% Pt on TiO₂), sonication time of 90 min, 0.18 g of propanol and a temperature of 10 °C were adopted. The method of ultrasound application to prepare metal supported semiconductors has many advantages such as convenience, safety and high efficiency. Furthermore, it is hopeful that this optimization study can also be extended to the generation of similar metal supported semiconductors.     

A theoretical study of CO adsorption on FeCo(100) and the effect of alloying

FeCo catalysts are modeled for optimizing the Fischer–Tropsch synthesis process since they can be tuned to enhance CO activity and resist poisoning. The electronic properties associated with CO adsorption are studied using plane-wave density functional theory (DFT). The range of computed adsorption energies from this work falls between the CO adsorption energies on pure Fe and Co surfaces. It was found that CO prefers to adsorb on the top site of the Co surface of FeCo alloys, whereas CO has stronger adsorption on pure Fe rather than pure Co surface. The trend in adsorption energy is top-Co > hollow-Fe > top-Fe > hollow-Co > bridge-Co > bridge-Fe. This change in preferable metal for adsorption (i.e., from Fe in a pure system to Co in the FeCo alloy surface in the current investigation) is due to the shift in the d-band center of the alloyed material. It implies that alloying Fe with Co changes the properties of the pure metal and ultimately affects the CO adsorption energy; however, the mechanism of adsorption remains similar and can be explained using the Nilsson–Pettersson model. Additional CO configurations consisting of hollow-site adsorption with a tilted geometry, was also investigated. The corresponding adsorption energy was found to be slightly higher than the adsorption energy when CO is adsorbed on the top-Co site.     

Synthesis of alumina supported nickel nanoparticle catalysts and evaluation of nickel metal dispersions by temperature programmed desorption

The purpose of this study was to synthesize highly dispersed Ni/Al₂O₃ catalysts and to develop a suitable hydrogen-temperature programmed desorption (H₂-TPD) method for the determination of nickel metal surface area, dispersion, and crystallite sizes. Several highly dispersed Ni/Al₂O₃ catalysts with a Ni loading between 15 and 25 wt.% were synthesized. The reducibility of catalysts was determined by temperature programmed reduction (TPR) experiments. All catalysts exhibited a single reduction peak with a maximum rate of H₂ consumption (T_max in TPR) occurring below 450 °C. Three different H₂-TPD methods were employed to determine the amount of H₂ chemisorbed. In TPD-1, a 10% H₂/Ar mixture was used for catalyst pre-reduction and surface saturation by cooling down from T_max in TPR to room temperature. In TPD-2, the catalyst surface after pre-reduction was flushed with Ar at T_max in TPR + 10 °C. The TPD-3 was similar to the TPD-2, but used 100% H₂ instead of 10% H₂/Ar mixture. In all three TPD methods, the profiles exhibited 2 domains of H₂ desorption peaks, one below 450 °C, referred to as type-1 peaks, and attributed to H₂ desorbed from exposed fraction of Ni atoms, and the other above 450 °C, denoted as type-2 peaks, and assigned to the desorption of H₂ located in the subsurface layers and/or to spillover H₂. Flushing the reduced catalyst surface in Ar at T_max in TPR + 10 °C in TPD-2 and TPD-3 removed most of the H₂ located in the subsurface layers/ spillover H₂. The amount of H₂ chemisorbed to form a monolayer on the reduced Ni/Al₂O₃ catalysts was determined quantitatively from the TPD peak areas of type-1 peaks in TPD-1, and from both type-1 and type-2 peaks in TPD-2 and TPD-3. The Ni metal surface area, dispersions and crystallite sizes were calculated from the chemisorption data and the values were compared with those obtained using the static chemisorption method. Both TPD-2 and TPD-3 gave chemisorption results similar to that obtained from the static method.     

Catalytic dechlorination of 2,4-dichlorophenol by Ni/Fe nanoparticles prepared in the presence of ultrasonic irradiation

In this study, nickle/iron (Ni/Fe) nanoparticles were synthesized by liquid phase reductive method in the presence of 20 kHz ultrasonic irradiation to improve nanoparticles’ disparity and avoid agglomeration. The characterized results showed that this method has obviously modified most of the particles in term of sizes and specific surface areas. Meanwhile, the improved nanoscale Ni/Fe particles were employed for the reductive dechlorination of 2,4-dichlorophenol (2,4-DCP) as a function of some influential factors (Ni content, Ni/Fe nanoparticles dosage, reaction temperature and initial pH values) and degradation path. Experimental results showed that 2,4-DCP was first adsorbed by Ni/Fe nanoparticles, then quickly reduced to o-chlorophenol (o-CP), p-chlorophenol (p-CP), and finally to phenol (P). The application of ultrasonic irradiation for Ni/Fe nanoparticles synthesis was found to significantly enhance the removal efficiency of 2,4-DCP. Consequently, the phenol production rates increased from 68% (in the absence of ultrasonic irradiation) to 87% (in the presence of ultrasonic irradiation) within 180 min. Nearly 96% of 2,4-DCP was removed after 300 min reaction with these optimized conditions: Ni content over Fe⁰ 3 wt%, initial 2,4-DCP concentration 20 mg L⁻¹, Ni/Fe dosage 3 g L⁻¹, initial pH value 3.0, and reaction temperature 25 °C. The degradation of 2,4-DCP followed pseudo-first-order kinetics reaction and the apparent pseudo-first-order kinetics constant was 0.0737 min⁻¹. This study suggested that the presence of ultrasonic irradiation in the synthesis of nanoscale Ni/Fe particles could be a promising technique to enhance nanoparticle’s disparity and avoid agglomeration.     

Lipase catalyzed ultrasonic synthesis of poly-4-hydroxybutyrate-co-6-hydroxyhexanoate

Four different lipases were compared for ultrasound-mediated synthesis of the biodegradable copolymer poly-4-hydroxybutyrate-co-6-hydroxyhexanoate. The copolymerization was carried out in chloroform. Of the enzymes tested, Novozym 435 exhibited the highest copolymerization rate, in fact the reaction rate was observed to increase with about 26-fold from 30 to 50 °C (7.9 × 10^?3 M s^?1), sonic power intensity of 2.6 × 10³ W m^?2 and dissipated energy of 130.4 J ml^?1. Copolymerization rates with the Candida antarctica lipase A, Candida rugosa lipase, and Lecitase Ultra? were lower at 2.4 × 10^?4, 1.3 × 10^?4 and 3.5 × 10^?4 M s^?1, respectively. The catalytic efficiency depended on the enzyme. The efficiency ranged from 4.15 × 10^?3 s^?1 M^?1 for Novozym 435–1.48 × 10^?3 s^?1 M^?1 for C. rugosa lipase. Depending on the enzyme and sonication intensity, the monomer conversion ranged from 8.2% to 48.5%. The sonication power, time and temperature were found to affect the rate of copolymerization. Increasing sonication power intensity from 1.9 × 10³ to 4.5 × 10³ W m^?2 resulted in an increased in acoustic pressure (P_a) from 3.7 × 10⁸ to 5.7 × 10⁸ N m^?2 almost 2.4–3.7 times greater than the acoustic pressure (1.5 × 10⁸ N m^?2) that is required to cause cavitation in water. A corresponding acoustic particle acceleration (a) of 9.6 × 10³–1.5 × 10⁴ m s^?2 was calculated i.e. approximately 984–1500 times greater than under the action of gravity.     

Mechanistic insight into sonochemical biodiesel synthesis using heterogeneous base catalyst

The beneficial effect of ultrasound on transesterification reaction is well known. Heterogeneous (or solid) catalysts for biodiesel synthesis have merit that they do not contaminate the byproduct of glycerol. In this paper, we have attempted to identify the mechanistic features of ultrasound–enhanced biodiesel synthesis with the base–catalyst of CaO. A statistical design of experiments (Box–Behnken) was used to identify the influence of temperature, alcohol to oil molar ratio and catalyst loading on transesterification yield. The optimum values of these parameters for the highest yield were identified through Response Surface Method (with a quadratic model) and ANOVA. These values are: temperature = 62 °C, molar ratio = 10:1 and catalyst loading = 6 wt.%. The activation energy was determined as 82.3 kJ/mol, which is higher than that for homogeneous catalyzed system (for both acidic and basic catalyst). The experimental results have been analyzed vis–à–vis simulations of cavitation bubble dynamics. Due to 3–phase heterogeneity of the system, the yield was dominated by intrinsic kinetics, and the optimum temperature for the highest yield was close to boiling point of methanol. At this temperature, the influence of cavitation bubbles (in terms of both sonochemical and sonophysical effect) is negligible, and ultrasonic micro–streaming provided necessary convection in the system. The influence of all parameters on the reaction system was found to be strongly inter–dependent.     

Ultrasonic biodiesel synthesis from crude Jatropha curcas oil with heterogeneous base catalyst: Mechanistic insight and statistical optimization

This paper reports studies in ultrasound-assisted heterogeneous solid catalyzed (CaO) synthesis of biodiesel from crude Jatropha curcas oil. The synthesis has been carried out in two stages, viz. esterification and trans-esterification. The esterification process is not influenced by ultrasound. The transesterification process, however, shows marked enhancement with ultrasound. A statistical experimental design has been used to optimize the process conditions for the synthesis. XRD analysis confirms formation of Ca(OMe)₂, which is the active catalyst for transesterification reaction. The optimum values of parameters for the highest yield of transesterification have been determined as follows: alcohol to oil molar ratio ≈ 11, catalyst concentration ≈ 5.5 wt.%, and temperature ≈ 64 °C. The activation energy of the reaction is calculated as 133.5 kJ/mol. The heterogeneity of the system increases mass transfer constraints resulting in approx. 4× increase in activation energy as compared to homogeneous alkali catalyzed system. It is also revealed that intense micro-convection induced by ultrasound enhances the mass transfer characteristics of the system with ∼20% reduction in activation energy, as compared to mechanically agitated systems. Influence of catalyst concentration and alcohol to oil molar ratio on the transesterification yield is inter-linked through formation of methoxy ions and their diffusion to the oil–alcohol interface, which in turn is determined by the volume fractions of the two phases in the reaction mixture. As a result, the highest transesterification yield is obtained at the moderate values of catalyst concentration and alcohol to oil molar ratio.     

Propargylation of indene-1,3-dione under a new phase-transfer catalyst combined with ultrasonication – A kinetic study

In the present study, kinetics of synthesis of 2,2-di(prop-2-ynyl)-1H-indene-1,3(2H)-dione was successfully carried out by propargylation of indene-1,3-dione with propargyl bromide using aqueous potassium hydroxide and catalyzed by a newly synthesized phase-transfer catalyst viz., N-benzyl-N-ethyl-N-isopropylpropan-2-ammonium bromide, PTC under ultrasonic (40 kHz, 300 W) assisted organic solvent condition. The pseudo first-order kinetic equation was applied to describe the overall reaction. Under ultrasound irradiation (40 kHz, 300 W) in a batch reactor, it shows that the overall reaction rate can be greatly enhanced with ultrasound irradiation than without ultrasound.     

Environmental friendly cold-mechanical/sonic enzymatic assisted extraction of genipin from genipap (Genipa americana)

An efficient cold-mechanical/sonic-assisted extraction technique was developed for extraction of genipin from genipap (Genipa americana) peel. Ultrasound assisted extraction (285 W, 24 kHz) was performed at 5, 10 and 15 °C for 5, 10 and 15 min. After cold-extraction, genipin was separated from pectin and proteins by aid of fungal pectinesterase. The maximum yield of non-cross-linked genipin was 7.85 ± 0.33 mg/g, at 10 °C for 15 min by means of ultrasound extraction. The protein amount in extracts decreased in all samples. If mechanical process is combined with ultrasound assisted extraction the yield is increased by 8 times after the pectinesterase-assisted polyelectrolyte complex formation between pectic polysaccharides and proteins, avoiding the typical cross-linking of genipin. This novel process is viable to obtain non-cross-linked genipin, to be used as a natural colorant and cross-linker in the food and biotechnological industries.     

An efficient synthesis of 2-substituted benzothiazoles in the presence of FeCl3/Montmorillonite K-10 under ultrasound irradiation

2-Substituted benzothiazoles have been synthesized via one-pot reaction from aromatic aldehydes and o-aminothiophenol in the presence of FeCl₃/Montmorillonite K-10 in absolute methanol at 25–30 °C under ultrasound irradiation. The remarkable advantages are an inexpensive and easily available reagent, a simple procedure, mild conditions, short reaction times and moderate to good yields.     

Effect of reaction temperature on the size and morphology of scorodite synthesized using ultrasound irradiation

Synthesis of scorodite (FeAsO₄·2H₂O) using dynamic action agglomeration and the oxidation effect from ultrasound irradiation was investigated. The effect of different reaction temperatures (90, 70, 50, and 30 °C) on the size and morphology of scorodite particles synthesized under O₂ gas flow and ultrasound irradiation was explored because the generation of fine bubbles depends on the solution temperature. At 90 °C, the size of scorodite particles was non-homogeneous (from fine particles (<1 μm) to large particles (>10 μm)). The oxidation–reduction potential (ORP) and yield at 90 °C showed lower values than those at 70 °C. The scorodite particles, including fine and non-homogeneous particles, were generated by a decrease in the oxidation of Fe(II) to Fe(III) and promotion of dissolution caused by the generation of radicals and jet flow from ultrasound irradiation. Using ultrasound irradiation in the synthesis of scorodite at low temperature (30 °C) resulted in the appearance of scorodite peaks in the X-ray diffraction (XRD) pattern after a reaction time of 3 h. The peaks became more intense with a reaction temperature of 50 °C and crystalline scorodite was obtained. Therefore, ultrasound irradiation can enable the synthesis of scorodite at 30 °C as well as the synthesis of large particles (>10 μm) at higher temperature. Oxide radicals and jet flow generated by ultrasound irradiation contributed significantly to the synthesis and crystal growth of scorodite.     

Intensification of biodiesel production from soybean oil and waste cooking oil in the presence of heterogeneous catalyst using high speed homogenizer

In the present work, high speed homogenizer has been used for the intensification of biodiesel synthesis from soybean oil and waste cooking oil (WCO) used as a sustainable feedstock. High acid value waste cooking oil (27 mg of KOH/g of oil) was first esterified with methanol using sulphuric acid as catalyst in two stages to bring the acid value to desired value of 1.5 mg of KOH/g of oil. Transesterification of soybean oil (directly due to lower acid value) and esterified waste cooking oil was performed in the presence of heterogeneous catalyst (CaO) for the production of biodiesel. Various experiments were performed for understanding the effect of operating parameters viz. molar ratio, catalyst loading, reaction temperature and speed of rotation of the homogenizer. For soybean oil, the maximum biodiesel yield as 84% was obtained with catalyst loading of 3 wt% and molar ratio of oil to methanol of 1:10 at 50 °C with 12,000 rpm as the speed of rotation in 30 min. Similarly biodiesel yield of 88% was obtained from waste cooking oil under identical operating conditions except for the catalyst loading which was 1 wt%. Significant increase in the rate of biodiesel production with yields from soybean oil as 84% (in 30 min) and from WCO as 88% (30 min) was established due to the use of high speed homogenizer as compared to the conventional stirring method (requiring 2–3 h for obtaining similar biodiesel yield). The observed intensification was attributed to the turbulence caused at microscale and generation of fine emulsions due to the cavitational effects. Overall it can be concluded from this study that high speed homogenizer can be used as an alternate cavitating device to efficiently produce biodiesel in the presence of heterogeneous catalysts.