Silvana Mattedi

Protic ionic liquid as additive on lipase immobilization using silica sol-gel.

Ionic liquids (ILs) have evolved as a new type of non-aqueous solvents for biocatalysis, mainly due to their unique and tunable physical properties. A number of recent review papers have described a variety of enzymatic reactions conducted in IL solutions, on the other hand, to improve the enzymes activity and stability in ILs; major methods being explored include the enzyme immobilization (on solid support, sol-gel, etc.), protic ionic liquids used as an additive process. The immobilization of the lipase from Burkholderia cepacia by the sol-gel technique using protic ionic liquids (PIL) as additives to protect against inactivation of the lipase due to release of alcohol and shrinkage of the gel during the sol-gel process was investigated in this study. The influence of various factors such as the length of the alkyl chain of protic ionic liquids (monoethanolamine-based) and a concentration range between 0.5 and 3.0% (w/v) were evaluated. The resulting hydrophobic matrices and immobilized lipases were characterised with regard to specific surface area, adsorption-desorption isotherms, pore volume (V(p)) and size (d(p)) according to nitrogen adsorption and scanning electron microscopy (SEM), physico-chemical properties (thermogravimetric - TG, differential scanning calorimetry - DSC and Fourier transform infrared spectroscopy - FTIR) and the potential for ethyl ester and emulsifier production. The total activity yields (Y(a)) for matrices of immobilized lipase employing protic ionic liquids as additives always resulted in higher values compared with the sample absent the protic ionic liquids, which represents 35-fold increase in recovery of enzymatic activity using the more hydrophobic protic ionic liquids. Compared with arrays of the immobilized biocatalyst without additive, in general, the immobilized biocatalyst in the presence of protic ionic liquids showed increased values of surface area (143-245 m(2) g(-1)) and pore size (19-38 Å). Immobilization with protic ionic liquids also favoured reduced mass loss according to TG curves (always less than 42.9%) when compared to the immobilized matrix without protic ionic liquids (45.1%), except for the sample containing 3.0% protic ionic liquids (46.5%), verified by thermogravimetric analysis. Ionic liquids containing a more hydrophobic alkyl group in the cationic moiety were beneficial for recovery of the activity of the immobilized lipase. The physico-chemical characterization confirmed the presence of the enzyme and its immobilized derivatives obtained in this study by identifying the presence of amino groups, and profiling enthalpy changes of mass loss.

Thermodynamics of oxygenate fuel additives as a function of temperature

This article reports experimental data of density and ultrasonic velocity at the range from 278.15 to 323.15 K and atmospheric pressure of ethers used as additives in fuels (methyl tert-butyl ether ethyl tert-butyl ether, tert-amyl ether and diisopropyl ether). From the experimental data, temperature dependent polynomials were fitted and theoretical models were used to correlate these properties. The MTC Lattice Gas EOS is used to correlate simultaneously vapour pressures and volumetric properties. Free Length Theory is applied to estimate the ultrasonic velocity of the chemicals as a function of temperature, satisfactory predictions were obtained. The dependence of temperature showed by these magnitudes reveals a strong interaction at low values.

Experimental vapor-liquid equilibria data for binary mixtures of xylene isomers

Separation of aromatic C8 compounds by distillation is a difficult task due to the low relative volatilities of the compounds and to the high degree of purity required of the final commercial products. For rigorous simulation and optimization of this separation, the use of a model capable of describing vapor-liquid equilibria accurately is necessary. Nevertheless, experimental data are not available for all binaries at atmospheric pressure. Vapor-liquid equilibria data for binary mixtures were isobarically obtained with a modified Fischer cell at 100.65 kPa. The vapor and liquid phase compositions were analyzed with a gas chromatograph. The methodology was initially tested for cyclo-hexane+n-heptane data; results obtained are similar to other data in the literature. Data for xylene binary mixtures were then obtained, and after testing, were considered to be thermodynamically consistent. Experimental data were regressed with Aspen Plus® 10.1 and binary interaction parameters were reported for the most frequently used activity coefficient models and for the classic mixing rules of two cubic equations of state.

Phase equilibria of binary mixtures containing methyl acetate, water, methanol or ethanol at 101.3 kPa

Isobaric vapor–liquid equilibria data at 101.3 kPa were reported for the binary mixtures (methyl acetate + (water or methanol or ethanol), methanol + (water or ethanol) and (ethanol + water)). The experimental data were tested for thermodynamic consistency by means of the Wisniak method and were demonstrated to be consistent. The experimental data were correlated using Wilson, NRTL and UNIQUAC models for the activity coefficients and predicted using the UNIFAC and PSRK equation of state for testing theirs capability. The results show that the obtained data for the studied binary systems are more reliable than other published data.

Influence of temperature on thermodynamics of ethanol + hydrocarbon gasoline additives

The densities and ultrasonic velocity of the binary mixtures ethanol + (benzene, toluene, ethylbenzene, isooctane, tert-butyl alcohol and xylene isomers) at the range 288.15–323.15 K and atmospheric pressure, have been measured over the whole concentration range. The experimental excess volumes and deviation of isentropic compressibilities data have been correlated with a Redlich–Kister type polynomial accurately. The gathered data improve open literature related to gasoline additives, as the comparison has proved, and help to understand the ethanol volumetric and acoustic trend into different chemical environment.

Solid-liquid equilibrium data of amoxicillin and hydroxyphenylglycine in aqueous media

The enzymatic synthesis of amoxicillin is catalyzed by Penicillin G Acylase (PGA). As byproducts, hydroxyphenylglycine and alcohol are also formed from hydrolytic reactions and antibiotic synthesis, respectively. The design of this process should be directed to promote the synthesis reaction. At the same time, it is necessary to reduce the hydrolytic reaction of amoxicillin through its crystallization or separation from the reaction medium. This work presents measurements of solid-liquid equilibrium data for amoxicillin and hydroxyphenylglycine in water at different temperatures (283.15 - 298.15 K), pH (5.5 - 7.5) and ethanol composition (0 - 70 wt.%). This information is relevant to determine the conditions that offer the lowest solubility for the antibiotic, favoring its separation and purification. All solubility data were obtained using an analytical method with indirect determination by UV spectroscopy. Ideal thermodynamic modeling was applied to describe the experimental solubility data sets.

Influence of temperature on thermodynamic properties of substituted aromatic compounds

This work presents experimental liquid densities and ultrasonic velocities for a collection of substituted aromatic compounds (isobutylbenzene, 1,3,5-trimethylbenzene, butylbenzene, isopropylbenzene, p-xylene, m-xylene and o-xylene) at the range of temperature 278.15–323.15 K and atmospheric pressure of a collection of halogenated and aromatic hydrocarbons. Fitting equations were applied to data in order to correlate for later computer-based design. The estimation of the studied properties was made by the application of different theoretical procedures. An equation of state based on the generalised Van der Waals theory which combines the Staverman–Guggenheim combinatorial term of lattice statistics with an attractive lattice gas expression and the free length theory (FLT) showed a good response at the studied conditions.

The novel mesoporous silica aerogel modified with protic ionic liquid for lipase immobilization

Mesoporous silica supports (aerogels) were used to immobilize Burkholderia cepacia lipase (BC) by encapsulation (EN or ENIL), physical adsorption (ADS or ADSIL) and covalent binding (CB or CBIL) into or onto the aerogel modified with protic ionic liquid (PIL). Yield immobilization (Ya) and operational stability were determined by the hydrolytic reaction of olive oil. Ya (37% to 83% by physical adsorption) and operational stability (2 to 23 batches by encapsulation) increased when the support was modified with PIL. For immobilized derivates observed by the BET method, in this case ADS and CB for ADSIL and CBIL, increased pores size was observed, possibly due to the higher amount of BC immobilized conferring Ya and operational stability. This effect was probably attributed to the entry of the enzyme into the pores of the silica aerogel structure. SEM images showed a change in the structure and properties of immobilized lipase derived with PIL. A characteristic FTIR band was obtained for the silanol groups and amides I, IV and V, demonstrating the efficiency of immobilization of BC. The most efficient biocatalysts were ADSIL with regard to yield immobilization and ENIL for operational stability.

Influence of anion chain length of protic ionic liquids on the corrosion resistance of API X70 steel

The objective of this paper is to evaluate the corrosion resistance of API X70 steel in three different protic ionic liquids (PILs). Protic ionic liquids cation was 2-hydroxiethylammonium, and their anion was a carboxylate where the carbon chain length was varied. The synthetised PILs were characterised by nuclear magnetic resonance. The corrosion resistance of API X70 steel was evaluated on the hand of the monitoring of the open circuit potential and electrochemical impedance spectroscopy. Results showed that PIL adsorption on the substrate surface occurs to form a film that enhances corrosion inhibition effects. However, the adsorbed film can break due to desorption that exposes the substrate surface and promotes corrosion of the substrate. In addition, it was observed that corrosion inhibition effects improve with the increase in the anion carbon chain length, since the longer is the anion the larger is the substrate coverage.

Imobilização de lipase por encapsulação em sílica aerogel

Lipase from Burkholderia cepacia was immobilized in a silica matrix and dried in high pressure carbon dioxide media (aerogel). The protic ionic liquid (PIL) was used in the immobilization process by encapsulation. The objective of this work was to evaluate the influence of the drying technique using supercritical carbon dioxide in biocatalysts obtained through the sol-gel technique by evaluating temperature and pressure and, after selecting the best drying conditions, to investigate the application of the technique for the biocatalyst using ionic liquid as an additive in the immobilization process. The results for immobilized biocatalysts showed that the best conditions of pressure and temperature were 100 bar and 25 oC, respectively, giving a total activity recovery yield of 37.27% without PIL (EN) and 44.23% with PIL (ENLI). The operational stability of the biocatalysts showed a half-life of 11.4 h for ENLI and 6 h for EN. Therefore, solvent extraction using supercritical CO2, besides shortening drying time, offers little resistance to the immobilization of lipases, since their macropores provide ample room for their molecules. The use of the ionic liquid as an additive in the process studied for the immobilization of enzymes produced attractive yields for immobilization and therefore has potential for industrial applications in the hydrolysis of vegetable oils.