RESUMO
Enzymatic synthesis of biodiesel showed advantageous characteristics in relation to other technologies once it works under bland conditions, no generation of wastewater, no occurrence of saponifications reactions and production of a biodiesel with high quality. Although many researches still apply immobilized lipases, the high costs associated with this biocatalyst hamper the economic viability of the process. Lipases in free/soluble/liquid formulation employed to biodiesel production via hydroesterification reaction have attracted interest from researchers because they are more cost effective than the immobilized form, making the enzymatic route more competitive. In addition, soluble lipases present higher reaction rates, reducing the time required to obtain a satisfactory biodiesel yield. Despite the fact that already exist industrial plants producing biodiesel with the assistance of lipases in liquid formulation, results of researches show that the process still needs to overcome some drawbacks. This paper is a comprehensive and critical discussion on the publications where soluble lipases were applied on biodiesel synthesis, as well as the challenges that the technology faces and its current status in pilot and industrial applications.
Assuntos
Biocombustíveis , Enzimas Imobilizadas/química , Lipase/química , Óleos de Plantas/química , EsterificaçãoRESUMO
The determination of organic sulfur compounds (OSC) in coal is of great interest. Technically and operationally these compounds are not easily removed and promote corrosion of equipment. Environmentally, the burning of sulfur compounds leads to the emission of SO(x) gases, which are major contributors to acid rain. Health-wise, it is well known that these compounds have mutagenic and carcinogenic properties. Bitumen can be extracted from coal by different techniques, and use of gas chromatography coupled to mass spectrometric detection enables identification of compounds present in coal extracts. The OSC from three different bitumens were tentatively identified by use of three different extraction techniques: accelerated solvent extraction (ASE), ultrasonic extraction (UE), and supercritical-fluid extraction (SFE). Results obtained from one-dimensional gas chromatography (1D GC) coupled to quadrupole mass spectrometric detection (GC-qMS) and from two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GC × GC-TOFMS) were compared. By use of 2D GC, a greater number of OSC were found in ASE bitumen than in SFE and UE bitumens. No OSC were identified with 1D GC-qMS, although some benzothiophenes and dibenzothiophenes were detected by use of EIM and SIM modes. GC × GC-TOFMS applied to investigation of OSC in bitumens resulted in analytical improvement, as more OSC classes and compounds were identified (thiols, sulfides, thiophenes, naphthothiophenes, benzothiophenes, and benzonaphthothiophenes). The roof-tile effect was observed for OSC and PAH in all bitumens. Several co-elutions among analytes and with matrix interferents were solved by use of GC × GC.
RESUMO
The objective of this work is to investigate the influence of process parameters on the pressurized liquid extraction (PLE) of Ilex paraguariensis leaves. A factorial 2(6-2) experimental design was employed using responses as the extraction yield and the chromatographic profile of the extracts. The extraction time, polarity of solvent, amount of sample, numbers of PLE cycles, flushing volume and extraction temperature were selected as independent variables (factors). Results obtained indicated that the solvent polarity was the most significant variable in the study, while the amount of sample and extraction temperature also showed significant effect. The other variables did not present significant influence in the yield of extraction. GC/MS analysis of the extract enabled the identification of saturated hydrocarbons, fatty acids, fatty acid methyl esters, phytosterols and theobromine in the extracts. Quantitative analysis of four compounds presented in the extracts (caffeine, phytol, vitamin E and squalene) was performed by the GC/MS in the SIM mode.
Assuntos
Bebidas/análise , Ilex paraguariensis/química , Extratos Vegetais/química , Folhas de Planta/química , Cromatografia Gasosa-Espectrometria de Massas , Pressão , Solventes/química , Temperatura , Fatores de TempoRESUMO
The main objective of this work was to compare the extraction of grape seed oil with compressed carbon dioxide and propane on the extraction yields and chemical characteristics of free glycerol compounds. The experiments were performed in a laboratory scale unit in the temperature range of 30 to 60 degrees C and pressures from 60 to 254 bar. The results showed that propane is a more suitable solvent for grape seed oil extraction than carbon dioxide, as higher extractions yields and a very fast kinetic of extraction were achieved with this solvent. In relation to compressed carbon dioxide extractions, both temperature and density presented a very pronounced and positive effect on the extraction yield. The oils extracted were analyzed qualitatively and quantitatively with regard to the free glycerol compounds, mainly fatty acids, ethyl, and methyl esters. The results showed that these compounds are present in low concentration in vegetable oil (<3%) and that, in general, samples extracted with propane present a smaller amount of peaks of free glycerol compounds in the oil than samples extracted with carbon dioxide.
Assuntos
Manipulação de Alimentos/métodos , Glicerol/análise , Óleos de Plantas/isolamento & purificação , Sementes/química , Vitis/química , Dióxido de Carbono , Óleos de Plantas/química , Propano , SolventesRESUMO
The objective of this work is to discuss the main parameters that influence the sonication extraction of Ilex paraguariensis leaves. For this purpose, the extraction time, solvent polarity, solvent volume, sample mass and particle size were evaluated. Results showed that the main variable affecting the extraction process was the solvent polarity. Though in a less extent, temperature and extraction time also demonstrated to be important parameters, while the other variables did not present a significant influence on the extraction yield. The extracts at the optimized condition were compared with those obtained by maceration, in terms of mass yield and chemical composition. The major compounds identified in the extracts were caffeine and palmitic acid. Some saturated hydrocarbons such as fatty acids, fatty acid methyl esters, phytosterols, and theobromine were also identified in the fractions.
Assuntos
Ilex paraguariensis/química , Ilex paraguariensis/efeitos da radiação , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Folhas de Planta/química , Folhas de Planta/efeitos da radiação , Sonicação , Fracionamento Químico/métodos , Extratos Vegetais/efeitos da radiaçãoRESUMO
The objective of this work was to investigate the extraction of Ilex paraguariensis leaves by means of three extraction techniques: pressurized liquid extraction (PLE, also called accelerated solvent extraction--ASE), maceration, and sonication. Samples of mate tea leaves were collected from an experiment conducted under agronomic control at Indfistria e Comércio de Erva-Mate Barão LTDA, Brazil. Six solvents with increasing polarities (n-hexane, toluene, dichloromethane, ethyl acetate, acetone, and methanol) were used in this investigation. Chemical analysis of the extracts was performed by GC coupled with a mass spectrometer detector. The identification and quantification were accomplished by coinjections of certified standards. The results showed that no significant differences in the qualities of the extracts were noticed regarding the extraction methods. On the other hand, the PLE technique was found to be more effective for the extractions of caffeine, phytol, palmitic, and stearic acid. The use of PLE led to a significant decrease in the total extraction time, amount of solvent consumption, and manipulation of samples compared to maceration and ultrasound-assisted extraction methods.
Assuntos
Cromatografia Gasosa/métodos , Ilex paraguariensis/química , Folhas de Planta/químicaRESUMO
This work investigated the production of fatty acid ethyl esters (FAEEs) from soybean oil using n-hexane as solvent and two commercial lipases as catalysts, Novozym 435 and Lipozyme IM. A Taguchi experimental design was adopted considering the variables temperature (35-65 degrees C), addition of water (0-10 wt/wt%), enzyme (5-20 wt/wt%) concentration, and oil-to-ethanol molar ratio (1:3-1:10). It is shown that complete conversion in FAEE is achieved for some experimental conditions. The effects of process variables on reaction conversion and kinetics of the enzymatic reactions are presented for all experimental conditions investigated in the factorial design.
Assuntos
Álcoois/química , Ácidos Graxos/síntese química , Hexanos/química , Lipase/química , Solventes/química , Óleo de Soja/química , Ativação Enzimática , Enzimas Imobilizadas/química , Ésteres , Proteínas Fúngicas , Hidrólise , Cinética , SoluçõesRESUMO
This article reports experimental data on the production of fatty acid ethyl esters from refined and degummed soybean oil and castor oil using NaOH as catalyst. The variables investigated were temperature (30-70 degrees C), reaction time (1-3 h), catalyst concentration (0.5-1.5 w/wt%), and oil-to-ethanol molar ratio (1:3-1:9). The effects of process variables on the reaction conversion as well as the optimum experimental conditions are presented. The results show that conversions >95% were achieved for all systems investigated. In general, an increase in reaction temperature, reaction time, and in oil-to-ethanol molar ratio led to an enhancement in reaction conversion, whereas an opposite trend was verified with respect to catalyst concentration.
Assuntos
Óleo de Rícino/química , Etanol/química , Ácidos Graxos/síntese química , Hidróxido de Sódio/química , Óleo de Soja/química , Álcalis/química , Catálise , Técnicas de Química Combinatória , Esterificação , Ésteres , Gasolina , Concentração de Íons de Hidrogênio , TemperaturaRESUMO
We studied the production of fatty acid ethyl esters from castor oil using n-hexane as solvent and two commercial lipases, Novozym 435 and Lipozyme IM, as catalysts. For this purpose, a Taguchi experimental design was adopted considering the following variables: temperature (35-65 degrees C), water (0-10 wt/wt%), and enzyme (5-20 wt/wt%) concentrations and oil-to-ethanol molar ratio (1:3 to 1:10). An empirical model was then built so as to assess the main and cross-variable effects on the reaction conversion and also to maximize biodiesel production for each enzyme. For the system containing Novozym 435 as catalyst the maximum conversion obtained was 81.4% at 65 degrees C, enzyme concentration of 20 wt/wt%, water concentration of 0 wt/wt%, and oil-to-ethanol molar ratio of 1:10. When the catalyst was Lipozyme IM, a conversion as high as 98% was obtained at 65 degrees C, enzyme concentration of 20 wt/wt%, water concentration of 0 wt/wt%, and oil-to-ethanol molar ratio of 1:3.