Cyclization of citronellal to p-menthane-3,8-diols in water and carbon dioxide

A clean process has been developed for the synthesis of p-menthane-3,8-diols from cyclization of citronellal in CO2-H2O medium without any additives. With the addition of CO2, the reaction rate could be enhanced about 6 times for the cyclization of citronellal in H2O, because CO2 dissolved into water and formed carbonic acid inducing an increase of the acidity. Although, the reaction conversion in CO2-H2O is slightly lower compared to that obtained with sulfuric acid as catalyst, CO2-H2O could replace the sulfuric acid at a relative higher reaction temperature. The reaction kinetics studies showed that the hydration of isopulegols to p-menthane-3,8-diols is a reversible reaction. The equilibrium constant and the maximum equilibrium yield obtained in CO2-H2O at a range of CO2 pressures are similar to that with sulfuric acid catalyst.

Effectiveness of the compound chlorpyrifos plus cypermethrin plus citronellal against Alphitobius diaperinus. Laboratory analysis and residue determination in carcasses

Biological security and the absence of residues in meat Effectiveness, and/or eggs must be considered when recommending options for the control Alphitobius diaperinus in poultry production environments. This research study evaluated the effectiveness of cypermethrin+chlorpyrifos+citronellal in the control of A. diaperinus, including analysis for the presence of residues of this compound in poultry carcasses (experimental farm). Two studies were carried out under laboratory conditions. One used paper filters a four dilutions of the compound, and the other used a container including with pulverized broiler litter and the compound. The analysis of carcasses for residues was conducted in broilers that raised in a broiler house treated (floor and/or litter) with the compound at a dilution of 1:800. Birds were regularly sacrificed, submitted to necropsy, and liver, muscle and fat fragments were collected. Gas chromatography was used to identify the possible presence of any chemical residue in these samples. High effectiveness rates against A.diaperinus were observed in the two laboratory studies, as well as the absence of residues in the carcasses. This compound, can be recommended as a valuable used in the studied concentrations, alternative for the control and treatment of A. diaperinus.

Influence of compressed carbon dioxide on hydrogenation reactions in cyclohexane with a Pd/C catalyst

The potential of CO2-expanded liquid media for chemical reactions has been examined in this work, using cyclohexane as a solvent and Pd/C as a heterogeneous catalyst for hydrogenation of styrene, citral, and nitrobenzene with H-2. The rate of hydrogenation reactions is increased, and the product selectivity is altered in the CO2-expanded cyclohexane phase. In the hydrogenation of citral, the selectivity to citronellal decreases with CO2 pressure, which changes from similar to 80% in the neat cyclohexane to similar to 65% at 16 MPa.

Selective hydrogenation of citral catalyzed with palladium nanoparticles in CO2-in-water emulsion

CO2-in-Water (C/W) emulsion was formed by using a nonionic surfactant of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (P123), and palladium nanoparticles were synthesized in situ in the present work. The catalytic performance of Pd nanoparticles in the C/W emulsion has been discussed for a selective hydrogenation of citral. Much higher activity with a turnover frequency (TOF) of 6313 h(-1) has been obtained in this unique C/W emulsion compared to that in the W/C microemulsion (TOF, 23 h(-1)), since the reaction was taking place not only in the surfactant shell but also on the inner surface of the CO2 core in the C/W emulsion. Moreover, citronellal was obtained with a higher selectivity for that it was extracted to a supercritical carbon dioxide (scCO(2)) phase as formed and thus its further hydrogenation was prohibited. The Pd nanoparticles could be recycled several times and still retain the same selectivity, but it showed a little aggregation leading to a slight decrease in conversion.

Selective hydrogenation of citral with transition metal complexes in supercritical carbon dioxide

The activity and selectivity of the transition metal complexes formed from Ru, Rh, Pd and Ni with triphenylphosphine (TPP) have been investigated for hydrogenation of citral in supercritical carbon dioxide (scCO(2)). High activities are obtained with Ru/TPP and Pd/TPP catalysts, and the overall activity is in the order of Pd approximate to Ru > Rh > Ni. The Ru/TPP complex is highly selective to the formation of unsaturated alcohols of geraniol and nerol. In contrast, the Pd/TPP catalyst is more selective to partially saturated aldehydes of citronellal. Furthermore, the influence of several parameters such as CO2 and H-2 pressures, N-2 pressure and reaction time has been discussed. CO2 pressure has a significant impact on the product distribution, and the selectivity for geraniol and nerol can be enhanced from 27% to 75% with increasing CO2 pressure from 6 to 16 MPa, while the selectivity for citronellol decreases from 70% to 20%. Striking changes in the conversion and product distribution in scCO(2) could be interpreted with variations in the phase behavior and the molecular interaction between CO2 and the substrate in the gas phase and in the liquid phase.

A kinetic study of the liquid-phase hydrogenation of citral on Au/TiO2 and Pt-Sn/TiO2 thin films in capillary microreactors

The kinetics of the liquid-phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) on Au/TiO2 and Pt-Sn/TiO2 thin films was studied in the temperature range 313-353 K and citral concentrations of 0.25-10.0 mol m(-3). The thin films were deposited onto the inner walls of silica capillaries with internal diameter of 250 mu m. First-order dependence on hydrogen pressure and near zero order dependence on citral concentration were observed for the initial rate of citral hydrogenation over the Pt-Sn/TiO2 and Au/TiO2 thin films. The Au/TiO2 catalyst prevents citronellal formation. The highest yield of unsaturated alcohols was obtained on the Pt-Sn/TiO2 film at a reaction temperature of 343 K, liquid residence time of 30 min and a citral conversion of 99%. (C) 2011 Elsevier B.V. All rights reserved.

Use of Short Time-on-Stream Attenuated Total Internal Reflection Infrared Spectroscopy To Probe Changes in Adsorption Geometry for Determination of Selectivity in the Hydrogenation of Citral

Abstract Image

A new experimental procedure based on attenuated total reflection infrared spectroscopy has been developed to investigate surface species under liquid phase reaction conditions. The technique has been tested by investigating the enhanced selectivity in the hydrogenation of α,β-unsaturated aldehyde citral over a 5% Pt/SiO2 catalyst toward unsaturated alcohols geraniol/nerol, which occurs when citronellal is added to the reaction. The change in selectivity is proposed to be the result of a change in the citral adsorption mode in the presence of citronellal. Short time on stream attenuated total internal reflection infrared spectroscopy has allowed identification of the adsorption modes of citral. With no citronellal, citral adsorbs through both the C═C and C═O groups; however, in the presence of citronellal, citral adsorption occurs through the C═O group only, which is proposed to be the cause of the altered reaction selectivity.

Micelle-hosted palladium nanoparticles catalyze citral molecule hydrogenation in supercritical carbon dioxide

A new approach of employing metal particles in micelles for the hydrogenation of organic molecules in the presence of fluorinated surfactant and water in supercritical carbon dioxide has very recently been introduced. This is allegedly to deliver many advantages for carrying out catalysis including the use of supercritical carbon dioxide (scCO(2)) as a greener solvent. Following this preliminary account, the present work aims to provide direct visual evidence on the formation of metal microemulsions and to investigate whether metal located in the soft micellar assemblies could affect reaction selectivity. Synthesis of Pd nanoparticles in perfluorohydrocarboxylate anionic micelles in scCO(2) is therefore carried out in a stainless steel batch reactor at 40 degreesC and in a 150 bar CO2/H-2 mixture. Homogeneous dispersion of the microemulsion containing Pd nanoparticles in scCO(2) is observed through a sapphire window reactor at W-0 ratios (molar water-to-surfactant ratios) ranging from 2 to 30. It is also evidenced that the use of micelle assemblies as new metal catalyst nanocarriers could indeed exert a great influence on product selectivity. The hydrogenation of a citral molecule that contains three reducible groups (aldehyde, double bonds at the 2,3-position and the 6,7-position) is studied. An unusually high selectivity toward citronellal (a high regioselectivity toward the reduction of the 2,3-unsaturation) is observed in supercritical carbon dioxide. On the other hand, when the catalysis is carried out in the conventional liquid or vapor phase over the same reaction time, total hydrogenation of the two double bonds is achieved. It is thought that the high kinetic reluctance for double bond hydrogenation of the citral molecule at the hydrophobic end (the 6,7-position) is due to the unique micelle environment that is in close proximity to the metal surface in supercritical carbon dioxide that guides a head-on attack of the molecule toward the core metal particle.

Extração do óleo essencial de Cymbopogom winterianus J. com CO2 pressurizado

The extraction with pressurized fluids has become an attractive process for the extraction of essential oils, mainly due the specific characteristics of the fluids near the critical region. This work presents results of the extraction process of the essential oil of Cymbopogon winterianus J. with CO2 under high pressures. The effect of the following variables was evaluated: solvent flow rate (from 0.37 to 1.5 g CO2/min), pressure (66.7 and 75 bar) and temperature (8, 10, 15, 20 and 25 ºC) on the extraction kinetics and the total yield of the process, as well as in the solubility and composition of the C. winterianus essential oil. The experimental apparatus consisted of an extractor of fixed bed and the dynamic method was adopted for the calculation of the oil solubility. Extractions were also accomplished by conventional techniques (steam and organic solvent extraction). The determination and identification of extract composition were done by gas chromatography coupled with a mass spectrometer (GC-MS). The extract composition varied in function of the studied operational conditions and also related to the used extraction method. The main components obtained in the CO2 extraction were elemol, geraniol, citronellol and citronellal. For the steam extraction were the citronellal, citronellol and geraniol and for the organic solvent extraction were the azulene and the hexadecane. The most yield values (2.76%) and oil solubility (2.49x10-2 g oil/ g CO2) were obtained through the CO2 extraction in the operational conditions of T = 10°C, P = 66.7 bar and solvent flow rate 0.85 g CO2/min

Influência de cinco temperaturas de secagem no rendimento e composição do óleo essencial de citronela (Cymbopogon winterianus Jowitt)

The Influence of Drying Temperatures on the Yield Composition of Citronella (Cymbopogon winterianus Jowitt) essential oil. The studies were carried out to establish more precise parameters for citronella (C. winterianus Jowitt) post-harvest, and to optimize drying time and essential oil quantitative/qualitative yield. Five treatments were designed (30°C, 40°C, 50°C, 60°C and 70°C), with 14 repetitions of the drying process and 12 of the essential oil extraction. Drying at 60°C gave the best results for drying time (48 hours until weight stabilization), and also for extracted oil quantity (1.228 ± 0.127% over dry weight). Essential oil content showed high quantitative variations. The main compound found was neral, except in the 50°C treatment, where citronelal was the main compound.

In vitro and in vivo acaricide action of juvenoid analogs produced from the chemical modification of Cymbopogon spp. and Corymbia citriodora essential oil on the cattle tick Rhipicephalus (Boophilus) microplus

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Controle quimioterápico da mosca Stomoxys calcitrans (Insecta: Muscidae)

Pós-graduação em Medicina Veterinária - FCAV

Effects of Haematobia irritans infestation on weight gain of Nelore calves assessed with different antiparasitic treatment schemes

Effects of Haematobia irritans infestation on weight gain of 18 to 20 months old non-castrated Nelore calves, were investigated, under field conditions, using different antiparasitic treatments. Sixty animals were divided in three groups, with 20 bovines each: T01 (untreated control); T02 (treated with Cypermethrin 15 g + Chlorpyriphos 25 g + Citronellal 1 g, as a whole body spray, on days 0,30, 60, 90 and 120 post-treatment); and T03 (treated on day zero with an ear tag impregnated with Diazinon 6 g on the left ear). Counts of H. irritans were conducted on day 30, 60, 90, 120 and 150 post-treatment (DPT). On the same experimental dates, animals were individually weighed, seeking to evaluate the effects of parasitism on the development of animals in each group. From this study it is concluded that T03 had significantly higher efficacy (>90%, till 90 DPT), based on H. irritans fly counts, compared to T02 which showed little or no effect. At the specific conditions of the present study, an average of approximately 90 flies (mean difference of flycounts between groups T01 and T03) was associated with a difference of 20 kg/animal in 150 days. (C) 2014 Elsevier B.V. All rights reserved.

Effects of different spray formulations on the reproductive parameters of engorged Rhipicephalus (Boophilus) microplus females detached from experimentally infested cattle

This present study aimed to evaluate the deleterious effects of some commercially available spray formulations (15% Cypermethrin+25% Chlorpyriphos+1% Citronellal and 8% Cypermethrin+60% Ethion) on the reproductive parameters of engorged Rhipicephalus (Boophilus) microplus females that detached from experimentally infested cattle. The following reproductive parameters of engorged female ticks were analyzed: female weight, egg mass weight, percentage of hatchability, percentage of reduction in oviposition, percentage of reduction in hatchability, reproductive efficiency and percent control/efficacy of formulations for reproductive parameters. Our findings showed that although the strain R. (B.) microplus used in both experiments was thought to be sensitive to the test compounds because of the acaricidal efficacy observed throughout these trials, it was not possible to observe overall deleterious effects on the reproductive parameters of this tick species with both spray formulations. However, the 8% Cypermethrin+60% Ethion showed short-term significant effects on the weight of female ticks between the 14th and 16th days post-treatment and the weight of female and the egg mass weight between the 20th and 22nd days post-treatment. New studies should be conducted to show if these results regarding the reproductive parameters of fully engorged R. (B.) microplus females, combined with the acaricidal efficacy can be sufficient to reduce the number of chemical treatments administered to cattle.