Natural compounds obtained through centrifugal molecular distillation

Soybean oil deodorized distillate (SODD) is a byproduct from refining edible soybean oil; however, the deodorization process removes unsaponifiable materials, such as sterols and tocopherols. Tocopherols are highly added value materials. Molecular distillation has large potential to be used in order to concentrate tocopherols, because it uses very low levels of temperatures because of the high vacuum and short operating time for separation and, also, it does not use solvents. However, nowadays, the conventional way to recover tocopherols is carrying out chemical reactions prior to molecular distillation, making the process not so suitable to deal with natural products. The purpose of this work is to use only molecular distillation in order to recover tocopherols from SODD. Experiments were performed in the range of 140–220°C. The feed flow rate varied from 5 to 15 g/min. The objective of this study was to remove the maximum amount of free fatty acids (FFA) and, so, to increase the tocopherol concentration without add any extra component to the system. The percentage of FFA in the distillate stream of the molecular still is large at low feed flow rates and low evaporator temperatures, avoiding thermal decomposition effects.     

Optimization of tocopherol concentration process from soybean oil deodorized distillate using response surface methodology

Soybean oil deodorized distillate is a product derived from the refining process and it is rich in high value-added products. The recovery of these unsaponifiable fractions is of great commercial interest, because of the fact that in many cases, the "valuable products" have vitamin activities such as tocopherols (vitamin E), as well as anticarcinogenic properties such as sterols. Molecular distillation has large potential to be used in order to concentrate tocopherols, as it uses very low temperatures owing to the high vacuum and short operating time for separation, and also, it does not use solvents. Then, it can be used to separate and to purify thermosensitive material such as vitamins.In this work, the molecular distillation process was applied for tocopherol concentration, and the response surface methodology was used to optimize free fatty acids (FFA) elimination and tocopherol concentration in the residue and in the distillate streams, both of which are the products of the molecular distiller. The independent variables studied were feed flow rate (F) and evaporator temperature (T) because they are the very important process variables according to previous experience. The experimental range was 4-12 mL/min for F and 130-200 degrees C for T. It can be noted that feed flow rate and evaporator temperature are important operating variables in the FFA elimination. For decreasing the loss of FFA, in the residue stream, the operating range should be changed, increasing the evaporator temperature and decreasing the feed flow rate; D/F ratio increases, increasing evaporator temperature and decreasing feed flow rate. High concentration of tocopherols was obtained in the residue stream at low values of feed flow rate and high evaporator temperature. These results were obtained through experimental results based on experimental design.     

Kinetic study of pyrolysis of waste water treatment plant sludge

Activated sewage sludge samples obtained from two different waste water treatment plants were investigated by thermogravimetric analysis. Due to a very high content of water in the sludge samples, these had to be dried at 160°C in an electrical oven in order to remove all adsorbed water. To ensure pyrolysis conditions, nitrogen atmosphere was applied. The pyrolysis decomposition process was carried out in the temperature range from ambient temperature to 900°C at three different heating rates: 2 K min⁻¹, 5 K min⁻¹, 10 K min⁻¹. TGA and DTG curves of the decomposition processes were obtained. Temperature of onset decomposition, final temperature of decomposition, maximum decomposition rate, and decomposition temperature were determined by thermogravimetric analysis for both sludge samples used. The main decomposition process takes place at temperatures in the range from 230°C to 500°C. Above this temperature, there are only small changes in the mass loss which are often attributed to the decomposition of carbonates present in the sewage sludge samples. To determine the apparent kinetic parameters such as the activation energy and the preexponential factor, the so called Friedman isoconversional method was used. Because of the requirements of this method, initial and final parts of the decomposition process, where crossings of the decomposition lines occurred, were cut off. Obtained dependencies of the apparent activation energies and preexponential factors as a function of conversion were used backwards to calculate the modeled decomposition process of sewage sludge and the experimental data were in good accordance with the data obtained by simulation.     

Adsorption of SO2 on alumina

The adsorption of SO₂ on alumina used in the aluminium industry, the so-called smelter-grade alumina, was studied in the temperature range 15–120°C. It was found that at temperatures lower than 40°C, sulphur dioxide was bonded to alumina reversibly by physical forces, and the adsorption could be described satisfactorily by the Langmuir adsorption isotherm. The heat of adsorption was estimated to be −33 kJ mol⁻¹. At temperatures ranging from 80°C to 120°C, which prevail in dry scrubbers in the aluminium industry, the heat of adsorption was determined to be −56 kJ mol⁻¹. When SO₂ was adsorbed at temperatures higher than 80°C, about 30 % of the SO₂ could not be desorbed even if the samples were heated up to 250°C. In the presence of SO₂ and oxygen, the formation of sulphate was observed at temperatures above 90°C.     

Comparative study on uni-univalent and uni-bivalent ion-exchange reaction on Doulite A-116

Determination of ion-exchange equilibrium constant (K) for Cl⁻/I⁻ and Cl⁻/C₂O₄²⁻ system was studied at different temperatures from 25 to 45°C and by varying concentration of iodide and oxalate ion solution. For both uni-univalent and uni-bivalent exchange systems, using 0.5 g of ion-exchange resin DUOLITE A-116 (in chloride form), the value of K increases with rise in temperature i.e., from 13.0 at 25°C to 19.05 at 45°C for Cl⁻/I⁻ system and 33.0 at 25°C to 63.0 at 45°C for Cl⁻/C₂O₄²⁻ system indicating the endothermic ion-exchange reaction. The difference in K values at the same temperature for the two was related to the ionic charge of exchangeable ions in the solution.     

Study of temperature effect on uni-univalent and uni-bivalent ion exchange reaction

Ion exchange equilibrium constant (K) for Cl⁻/Br⁻ and Cl⁻/C₂O₄²⁻ system was studied at different temperatures from 30 to 45°C. For both uni-univalent and uni-bivalent exchange systems, the value of K increases with rise in temperature i.e., from 1.16 at 30°C to 2.95 at 45°C for Cl⁻/Br⁻ system and 19.5 at 30°C to 30.0 at 45°C for Cl⁻/C₂O₄²⁻ system indicating the endothermic ion exchange reaction. The difference in K values at the same temperature for the two was related to the ionic charge of exchangeable ions in the solution. The article is published in the original.     

Extraction of Co-Products from Biomass: Example of Thermal Degradation of Silymarin Compounds in Subcritical Water

In an effort to increase revenues from a given feedstock, valuable co-products could be extracted prior to biochemical or thermochemical conversion with subcritical water. Although subcritical water shows significant promise in replacing organic solvents as an extraction solvent, compound degradation has been observed at elevated extraction temperatures. First order thermal degradation kinetics from a model system, silymarin extracted from Silybum marianum, in water at pH 5.1 and 100, 120, 140, and 160 °C were investigated. Water pressure was maintained slightly above its vapor pressure. Silymarin is a mixture of taxifolin, silichristin, silidianin, silibinin, and isosilibinin. The degradation rate constants ranged from 0.0104 min⁻¹ at 100 °C for silichristin to a maximum of 0.0840 min⁻¹ at 160 °C for silybin B. Half-lives, calculated from the rate constants, ranged from a low of 6.2 min at 160 °C to a high of 58.3 min at 100 °C, both for silichristin. The respective activation energies for the compounds ranged from 37.2 kJ/gmole for silidianin to 45.2 kJ/gmole for silichristin. In extracting the silymarin with pure ethanol at 140 °C, no degradation was observed. However, when extracting with ethanol/water mixtures at and 140 °C, degradation increased exponentially as the concentration of water increased. An erratum to this article can be found at     

Kinetic study of wood chips decomposition by TGA

Pyrolysis of a wood chips mixture and main wood compounds such as hemicellulose, cellulose and lignin was investigated by thermogravimetry. The investigation was carried out in inert nitrogen atmosphere with temperatures ranging from 20°C to 900°C for four heating rates: 2 K min⁻¹, 5 K min⁻¹, 10 K min⁻¹, and 15 K min⁻¹. Hemicellulose, cellulose, and lignin were used as the main compounds of biomass. TGA and DTG temperature dependencies were evaluated. Decomposition processes proceed in three main stages: water evaporation, and active and passive pyrolysis. The decomposition of hemicellulose and cellulose takes place in the temperature range of 200–380°C and 250–380°C, while lignin decomposition seems to be ranging from 180°C up to 900°C. The isoconversional method was used to determine kinetic parameters such as activation energy and pre-exponential factor mainly in the stage of active pyrolysis and partially in the passive stage. It was found that, at the end of the decomposition process, the value of activation energy decreases. Reaction order does not have a significant influence on the process because of the high value of the pre-exponential factor. Obtained kinetic parameters were used to calculate simulated decompositions at different heating rates. Experimental data compared with the simulation ones were in good accordance at all heating rates. From the pyrolysis of hemicellulose, cellulose, and lignin it is clear that the decomposition process of wood is dependent on the composition and concentration of the main compounds.     

Non-isothermal kinetic analysis and feasibilty study of medium grade crude oil field

In this research, non-isothermal kinetics and feasibility study of medium grade crude oil is studied in the presence of a limestone matrix. Experiments were performed at a heating rate of 10°C min⁻¹, whereas the air flow rate was kept constant at 50 mL min⁻¹ in the temperature range of 20 to 600°C (DSC) and 20 to 900°C (TG). In combustion with air, three distinct reaction regions were identified in all crude oil/limestone mixtures, known as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO). The activation energy values were in the order of 5–9 kJ mol⁻¹ in LTO region and 189–229 kJ mol⁻¹ in HTO region. It was concluded that the medium grade crude oil field was not feasible for a self-sustained combustion process.     

Influence of coagulation temperature on pore size and properties of cellulose membranes prepared from NaOH–urea aqueous solution

The morphology and structure of the regenerated cellulose membranes prepared from its NaOH–urea aqueous solution by coagulating with 5 wt% H₂SO₄–10 wt% Na₂SO₄ aqueous solution with different temperatures and times were investigated. The pore size, water permeability and physical properties of the membranes were measured with scanning electron micrograph (SEM), wide X-ray diffraction (WXRD), Fourier transfer infrared spectroscopy (FTIR), flow rate method, and tensile testing. The SEM observation revealed that the structure and pore size of the membranes changed drastically as a function of the coagulation temperature. The membranes coagulated at lower temperatures tended to form the relatively small pore size than those at higher temperatures. On the contrary, the membranes coagulated at different times exhibited similar pore size. Interestingly, the mean pore size and water permeability of the membranes increased from 110 nm with standard deviation (SD) of 25 nm and 12 ml h⁻¹ m⁻² mmHg⁻¹ respectively to 1,230 nm with SD of 180 nm and 43 ml h⁻¹ m⁻² mmHg⁻¹ with an increase in coagulation temperature from 10 to 60°C. However, the membranes regenerated below 20°C exhibited the dense structure as well as good tensile strength and elongation at break. The result from FTIR and ultraviolet-visible (UV-vis) spectroscopy indicated that the relatively strong intermolecular hydrogen bonds exist in the cellulose membranes prepared at lower coagulation temperatures. This work provided a promising way to prepare cellulose materials with different pore sizes and physical properties by controlling the coagulation temperature.     

The Thermal Expansion of Wood Cellulose Crystals

We have investigated tension wood cellulose obtained from Populus maximowiczii using X-ray diffraction at temperatures from room temperature to 250 °C. Three equatorial and one meridional d-spacings showed a gradual linear increase with increasing temperature. For temperatures above 180 °C, however, the equatorial d-spacing increased dramatically. Thus, the linear and volume thermal expansion coefficients (TECs) below 180 °C were determined from the d-spacings. The linear TECs of the a-, b-, and c-axes were: α _a = 13.6 × 10⁻⁵ °C⁻¹, α _b = −3.0× 10⁻⁵ °C⁻¹, and α _c =0.6× 10⁻⁵ °C⁻¹, respectively, and the volume TEC was β = 11.1× 10⁻⁵ °C⁻¹. The anisotropic thermal expansion in the three coordinate directions was closely related to the crystal structure of the wood cellulose, and it governed the macroscopic thermal behavior of solid wood.     

Drying dissipative structures of the thermosensitive gels of poly(N-isopropyl acrylamide) on a cover glass

Drying dissipative structural patterns of the thermosensitive gels of poly(N-isopropyl acrylamide) were studied on a cover glass. As the temperature of suspension and room rose from 25 to 50 °C, the small size of drying pattern area extended to the beautiful flickering spoke-like ones transitionally at the critical temperature ca. 35 °C. The principal patterns at 25 °C were the single or multiple broad rings of the hill accumulated with the gels. At 50 °C, on the other hand, the flickering spoke-like patterns were observed at the inner area of the broad ring especially at the gel concentrations higher than 1 × 10⁻³ g/ml. These observations support that the extended gels at low temperatures apt to associate weakly to each other, whereas the gels at high temperatures shrink and move rather freely with the convectional flow of water, though the very weak intergel attractions still remain. In the presence of sodium chloride at high temperatures, the cooperative patterns formed between the gel spheres and the salt. The gravitational and Marangoni convectional flow of the gels and the very weak interactions between the gels and substrate (cover glass) are important for the flickering spoke-like pattern formation.     

The effect of temperature on lithium intercalation into carbon materials

The effects of temperature on lithium intercalation into non-graphitized carbonized cloth from various electrolytes have been studied. The open-circuit potential (o.c.p.) of the intercalates shifts in the negative direction as the temperature is raised. The average temperature coefficient of the o.c.p. is equal to −0.04 mV·K⁻¹ in the range from −35 to +45 °C. Intercalation-deintercalation kinetics was studied by the galvanostatic technique. It was shown that this process is quasi-ohmic at room and higher temperatures and has activation-ohmic control at lower temperatures. The effective activation energy of intercalation-deintercalation is about 20kJ·mol⁻¹. Intercalates are corroded in all electrolytes, the corrosion rate being drastically increased as the temperature is raised. The apparent activation energy of corrosion is 120–150 kJ·mol⁻¹. The corrosion rate is suggested to be controlled by cathodic reduction of electrolyte components. Received: 11 April 1997 / Accepted: 8 September 1997     

Some thermal characteristics of a mineral mixture of palygorskite,metahalloysite, magnesite and dolomite

An industrial raw material taken from Sivrihisar (Eskişehir, Turkey) region was heat-treated at different temperatures in the range of 100–1000°C for 2 h. The volumetric percentage of the particles having a diameter below 2 μm after staying in an aqueous suspension of the material was determined as 67% by the particle size distribution analysis. The mineralogical composition of the material was obtained as mass% of 32% palygorskite, 10% metahalloysite, 35% magnesite, 20% dolomite and 3% interparticle water by using the acid treatment, X-ray diffraction and thermal analysis (TG, DTA) data. The temperature ranges were determined for the endothermic dehydrations for the interparticle water as 25–140°C, for the zeolitic water as 140–320°C, and for the bound water as 320–480°C, in the palygorskite. The temperature range for the endothermic dehydroxylation and exothermic recrystalization of the palygorskite is 780–840°C. The temperature range for the endothermic dehydroxylation of the metahalloysite and calcinations of magnesite are coincided at 480–600°C. Dolomite calcined in the temperature range of 600–1000°C by two steps. The zig-zag changes in the specific surface area (S/m² g⁻¹) and specific micro and mesopore volume (V/cm³ g⁻¹) as the temperature increases were discussed according to the dehydrations in the palygorkskite, dehydroxylation of palygorskite and metahalloysite, and calcinations in magnesite and dolomite.     

A new lidocaine-selective membrane electrode based on its sulfathiazole ion-pair

A novel lidocaine ion-selective electrode is prepared, characterized and used in pharmaceutical analysis. The electrode incorporates PVC-membrane with lidocaine-sulfathiazole ion pair complex. The influences of membrane composition, temperature, pH of the test solution, and foreign ions on the electrode performance were investigated. The electrode showed a Nernstian response over a lidocaine concentration range from 1.0 ×10⁻⁵ to 1.0 × 10⁻¹ mol L⁻¹ with a slope of 60.1 ± 0.2 mV per decade at 25°C and was found to be very selective, precise, and usable within the pH range 5–9.5. The standard electrode potentials, E ^o, were determined at 10, 15, 20, 25, 30, 35 and 40°C, and used to calculate the isothermal temperature coefficient (dE ^o/dT=−0.0003 V °C⁻¹) of the electrode. However, the electrode performance is significantly decreased at temperatures higher than 45°C. The electrode was successfully used for potentiometric determination of lidocaine hydrochloride in pharmaceutical products. The article is published in the original.     

A Spectrophotometric Study on Uranyl Nitrate Complexation to 150 °C

The formation constant of the mononitratouranyl complex was studied spectrophotometrically at temperatures of 25, 40, 55, 70, 100 and 150 °C (298, 313, 328, 343, 373 and 423 K). The uranyl ion concentration was fixed at approximately 0.008 mol⋅kg⁻¹ and the ligand concentration was varied from 0.05 to 3.14 mol⋅kg⁻¹. The uranyl nitrate complex, UO₂NO₃⁺, is weak at 298 K but its equilibrium constant (at zero ionic strength) increases with temperature from log ₁₀ β ₁=−0.19±0.02 (298 K) to 0.78±0.04 (423 K).     

Thermal behavior of a mineral mixture of sepiolite and dolomite

An industrial raw material taken from Beypazarı (Ankara, Turkey) region was heated at different temperatures in the 100–1100°C interval for 2 h. The volumetric percentage of particles having diameter below 2 μm in an aqueous suspension of the material held 24 h were determined as 85% by the particle size distribution analysis. The mineralogical composition of the material was obtained as mass% of 81% sepiolite, 15% dolomite, and 4% interparticle water by using the X-ray diffraction (XRD) and thermal analysis (TG, DTA) data. The temperature ranges were determined for the dehydrations of the interparticle water and the zeolitic water as 25–340°C, for the dehydration of the bound water as 340–580°C, and for the dehydroxylation of the hydroxyls as 800–833°C in the sepiolite. The zig-zag changes in the specific surface area (S/m² g⁻¹) and specific micro-and mesopore volume (V/cm³ g⁻¹) with the temperature increases were discussed according to the dehydrations and dehydroxylation of the sepiolite.     

Application of Modulated Temperature DSC to Distillate Fuels and Lubricating Greases

In this work the usefulness of Modulated Temperature DSC (MTDSC) for characterizing petroleum products is illustrated with some typical examples of recent applications. Specifically, the reliability of the method is outlined on the basis of the freezing behaviour of distillate fuels and the thermal analytical characterization of lubricating greases. The results of experiments performed on the evaporation residue of distillate fuels, aimed at providing insights into the structure of degradation products, will also be presented. The experiments were carried out using a DSC 2910 module from TA Instruments Inc., upgraded with the MTDSC option. The samples were exposed to a cyclic heating profile which was generated by an underlying heating (or cooling) rate of 2°C min⁻¹ while superimposing a sinusoidally varying time-temperature wave with an amplitude of ±0.5°C and a period of 40 s. This revised version was published online in August 2006 with corrections to the Cover Date.     

Conductance of 1,1-electrolytes in acetonitrile solutions from −40° to 35°C

Conductance data for perchlorates of Li⁺, K⁺, Me₄N⁺, Et₄N⁺, Pr₄N⁺, Bu₄N⁺, iodides of K⁺, Me₄N⁺, i-Am₃BuN⁺, and tetraphenylborates of Na⁺, Bu₄N⁺ and i-Am₃BuN⁺ in acetonitrile solution in the temperature range −40° to 35°C are reported. Λ_° (limiting molar conductance) and K_A (association constant) are evaluated for several temperatures using a conductance equation based on the chemical model of electrolyte solutions including short range forces. Limiting molar ion conductances, λ _ΰ ⁱ , at −35°, −25°, −15°, −5°, 5°, 15° and 25°C are evaluated from temperature dependent limiting transference numbers. Enthalpies and entropies of association, obtained from the temperature dependence of the association constants, are also presented. Dedicated to the memory of Professor Raymond M. Fuoss.     

Temperature and Heat Flow Calibration of A DSC-instrument in the Temperature Range Between −100 and 160°C

Thermoanalytical instruments are extensively used in R&D as well as in industrial quality control. A quantitative analysis of the data of a thermoanalytical measurement requires a careful calibration of the instrument. In differential scanning calorimetry (DSC) the quantities that have to be calibrated are the temperature and the heat flow. These two quantities are usually calibrated by evaluating melting or solid-solid transitions of some reference materials with well known transition enthalpies and temperatures. In this contribution we investigate temperature and heat flow calibration in the temperature range between −100 and 160°C. We included 9 different samples for the analysis and established some general rules for the calibration process. As a result we found that with a well calibrated instrument the heat flow can be measured with 90% confidence to about ± 3% accuracy in this temperature range. With respect to temperature calibration we find that accuracies of ±0.8°C (90% confidence) may be expected. These values represent general accuracy limitations of DSC’s due to varying heat transfer conditions within the samples. This revised version was published online in July 2006 with corrections to the Cover Date.