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.     

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 degrees 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.     

Molecular distillation

Molecular distillation was studied for the separation of tocopherols from soya sludge, both experimentally and by simulation, under different operating conditions, with good agreement. Evaporator temperatures varied from 100°C to 160°C and feed flow rates ranged from 0.1 to 0.8 kg/h. The process pressure was maintained at 10⁻⁶ bar, the feed temperature at 50°C, the condenser temperature at 60°C, and the stirring at 350 rpm. For each process condition, samples of both streams (distillate and residue) were collected and stored at −18°C before tocopherols analyses. Owing to the differences between molecular weights and vapor pressures of free fatty acids and tocopherols, tocopherols preferentially remained in the residue at evaporator temperatures of 100°C and 120°C, whereas for higher temperatures (140°C and 160°C) and lower feed flow rate, tocopherols tended to migrate to the distillate stream.     

Monoglyceride and Diglyceride Production Through Lipase-Catalyzed Glycerolysis and Molecular Distillation

Distilled glycerides are obtained through distillation of the system mono-diglycerides which is produced from the esterification reaction between a triglyceride with glycerol. In this work, monoglycerides (MG) and diglycerides (DG) are produced through lipase-catalyzed glycerolysis of soybean oil using Candida antarctica B in a solvent-free system. To separate the products of the reaction in order to obtain essentially MG and an oil of DG, it is necessary to use a suitable process in order to preserve the stability of the components and to keep the products free of inappropriate solvents. So, after 24 h of enzymatic reaction, the mixture of acylglycerols and fatty acids was distilled into a centrifugal molecular distiller, since it provides a free solvent and lower temperature environment to increase the desired product concentration. Starting from a material with 25.06% of triglycerides (TG), 46.63% of DG, 21.72% of MG, 5.38% of free fatty acids (FFA), and 1.21% of glycerol, the MG purity in the distillate stream was 80% at evaporator temperature (T _E) equal to 250 °C and feed flow rate (Q) equal to 10.0 mL/min. At these conditions, the MG recovery was 35%. The material collected in the residue stream presented DG-enriched oil with TG unhydrolyzed, residual MG, and low acidity (29.83% of TG, 53.20% of DG, 15.64% of MG, and 1.33% of FFA), which is suitable to replace TG oil in the human diet.     

Steady state and dynamic simulation of a hybrid reactive separation process

Modelling and simulation of hybrid reactive separation system in steady state and in dynamic regime was carried out. The investigated hybrid process consisted of a reactive distillation column and a pervaporation membrane located in the distillate stream to remove water from the process. Heterogeneously catalysed esterification of propionic acid with propan-1-ol to propyl propionate and water was chosen as the model chemical reaction. Esterification reactions are a typical example of equilibrium-limited reactions producing water as a by-product. Using just a pervaporation membrane brings the biggest benefit in increasing the yield of one of the reactants due to the removal of water. To study reactive separation processes, a model of the hybrid system in steady state and in dynamic regime was developed. Steady state behaviour of the model was studied for different hybrid system configurations. The effect of catalyst amount doubling was also investigated. Dynamic behaviour of the system during the step changes of propionic acid feed flow rate and during the membrane module failure was investigated. For this reason, the conversion of propionic acid, purity of the product stream, mole fraction of water, and the temperature in three different parts of the reactive distillation column were monitored.     

Purification of 3-hydroxypropionitrile by wiped molecular distillation

3-hydroxypropionitrile (HPN) is widely used asmaterials in many organic reactions such as synthe-sizing medicine, pesticide and polymeric compound.Since the 1970s, HPN has mostly been synthesizedwith the reaction of acrylonitrile and H2O catalyzed byNaOH aqueous solution, and the mole yield of HPN isabove 85%. However, the HPN must be separatedfrom the acrylonitrile hydration mixture and get rid ofwater, salt and other side products. The traditional separation method is evapora-tion…     

Development of multistage distillation in a microfluidic chip

Although there has been a lot of work on the development of microchemical processing systems such as micro-reactors and micro-sensors, little attention has been paid to micro-separation units, and in particular, microscale distillation. In this paper, various silicon-glass microscale distillation chips with different channel configurations were fabricated and tested. A temperature gradient was setup across the chip by heating and cooling the two ends. The feed was located at the middle of the microchannel. Arrays of micropillars were incorporated in order to guide the liquid flow. It was found that the separation performance was promoted by increasing the length of the microchannel. However, this created an imbalance of the liquid flows at the two sides of the microchannel and caused flooding. This hydrodynamic limitation was addressed by incorporating micropillars on both sides of the channel. The most efficient microdistillation chip consisted of a microchannel with 600 microns width and 40 cm length. Experimental results showed high efficiency for the separation of a 50 mol% acetone-water mixture when the heating and cooling temperature were 95 °C and 42 °C respectively. The concentrations of acetone were 3 mol% in the bottom stream and 95 mol% in the distillate, which was equivalent to at least 4 equilibrium stages at total reflux conditions. Furthermore, a 50 mol% methanol-toluene mixture was separated into nearly pure toluene in the bottom stream and 75 mol% methanol in the distillate. The performance of the microdistillation unit was reproducible in repeated tests.     

Effect of operating variables on the flux and selectivity in sweep gas membrane distillation for dilute aqueous isopropanol

Sweep gas membrane distillation was examined as a possible technique for isopropanol (IPA)–water separation using PTFE hollow fiber membrane module. The composition and flux of the permeate were monitored when feed concentration, operating temperature and flow rate were varied. The upper feed concentration tested was 10 wt.% IPA. Within the feed temperature range of about 20–50°C, IPA selectivity of 10–25 was achieved. Since the concentration near the surface on the membrane increased by the selective adsorption of IPA on the hydrophobic membrane, the selectivity increases. The permeate flux and IPA selectivity increase as feed temperature increase. The flux and selectivity increase at higher flow rates is mainly due to the reduced effects of concentration and temperature polarization. The effect of salt addition to the feed mixture was also examined.     

Fractional and component analysis of crude oils by the method of dynamic microdistillation—Differential scanning calorimetry coupled with thermogravimetry

High-resolution differential scanning calorimetry was used to accurately establish the temperature intervals of oxidation/distillation of the major components of crude oils. Some theoretical aspects of the method of dynamic microdistillation, enabling consecutive distillation (oxidation) of the main components of hydrocarbon mixtures, are discussed. The experimental TG-DSC curves show that the temperature scan of the run can be divided into six regions, of which the first belongs to simple distillation of the sample's liquid constituent (the distillate) and the others to oxidative cracking distillation of the solid (heavy) residue. The latter occur in the order paraffins + light oils, middle base oils, heavy base oils, condensed aromatics (resins) and asphaltenes. The probable oxidation mechanisms of different classes of petroleum hydrocarbons operating in different temperature regions are discussed. Full quantitative fractional and group component analysis of a number of crude oils of different chemical classes and geological age was carried out by the combined TG-DSC techniques under specially chosen experimental conditions (those of dynamic microdistillation).     

Influence of the reactive distillation column configuration on its performance: A computational study

Comparison of the performance of a reactive distillation column with three different hardware configurations is presented. As a reaction system the methyl tertiary-butyl ether (MTBE) synthesis has been chosen. The sieve tray columns with catalyst (encased inside wire gauze envelopes) placed along the liquid flow path differ in the number of reactive trays. The column simulations have been performed using the nonequilibrium model. The steady state behaviour of the three different hardware configurations was studied regarding the three input parameters; feed flow rate of methanol, feed flow rate of butenes, and reflux ratio. It has been shown that by varying the location of the methanol feed stage, the columns exhibit significantly different solution diagrams using the butenes feed flow rate as a continuation parameter. Using dynamic simulations, different perturbations of the manipulated variables were found to cause transitions between multiple steady states and these were also investigated. The major objective of this paper is to demonstrate the importance of the hardware choice in the performance of a reactive distillation column e.g. during the start-up or if occasional variations of the operating parameters occur. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

高含量天然生育酚的提纯工艺研究及HPLC分析

以改性吸附树脂特异性吸附法对天然生育酚浓缩物进行提纯,以无水乙醇为溶剂,用静态吸附法测定了混合生育酚在改性吸附树脂上的平衡吸附容量;在树脂床层中测定了混合生育酚在特异性吸附树脂中的吸附穿透曲线和解吸曲线;利用HPLC测定了生育酚的含量。实验结果表明,柱温35℃,采用无水乙醇作溶剂、5%的乙酸?乙醇溶液作解吸剂进行解吸,提取的生育酚含量达到95.3%。     

Standing wave design of a four-zone thermal SMB fractionator and concentrator (4-zone TSMB-FC) for linear systems

For a dilute feed, a four-zone SMB with temperature gradient (4-zone TSMB-FC) can fractionate and simultaneously concentrate two solutes. Optimization of the operating parameters for this system, which include four zone flow rates and port switching time, is a major challenge because of the five variables. Initial choice of the variables using the triangle theory followed by a systematic search using rate model simulations is time-consuming. In this study, the SWD developed previously for isothermal systems is modified for the first time for a 4-zone TSMB-FC. The optimum operating parameters are determined with the new method. Only linear isotherm systems with significant mass transfer resistances are considered. For a dilute feed, a 4-zone SMB-FC can produce pure desorbent, in addition to extract and raffinate products with high purities. For the separation of p-xylene and toluene with silica gel in the temperature range from 0 to 80 °C, the enrichment factor in the linear region can be as high as 80 fold for an extract purity of 99.99 % and tenfold for raffinate purity of 99.8 %, while withdrawing the desorbent at a desorbent to feed flow rate ratio of 0.53 and 0.78, respectively.     

Innovation in a Continuous System of Distillation by Steam to Obtain Essential Oil from Persian Lime Juice (Citrus latifolia Tanaka)

The citrus industry is one of the most important economic areas within the global agricultural sector. Persian lime is commonly used to produce lime juice and essential oil, which are usually obtained by batch distillation. The aim of this work was to validate a patented continuous steam distillation process and to both physically and chemically characterize the volatile fractions of essential Persian lime oil. Prior to distillation, lime juice was obtained by pressing the lime fruit. Afterwards, the juice was subjected to a continuous steam distillation process by varying the ratio of distillate flow to feed flow (0.2, 0.4, and 0.6). The distillate oil fractions were characterized by measuring their density, optical rotation, and refractive index. Gas chromatography GC-FID was used to analyze the chemical compositions of the oil fractions. The process of continuous steam distillation presented high oil recovery efficiencies (up to 90%) and lower steam consumption compared to traditional batch process distillation since steam consumption ranged from 32 to 60% for different steam levels. Moreover, a reduction in process time was observed (from 8 to 4 h). The oil fractions obtained via continuous steam distillation differed significantly in their composition from the parent compounds and the fractions.     

Reactive Distillation: An Attractive Alternative for the Synthesis of Unsaturated Polyester

Summary: Unsaturated polyester is traditionally produced in a batch wise operating reaction vessel connected to a distillation unit. An attractive alternative for the synthesis of unsaturated polyester is a reactive distillation. To value such alternative synthesis route reliable process models need to be developed. In this paper, the strategy is described for the development of the reactive distillation model. Essential parts of the reactive distillation model are kinetic and thermodynamic which are subsequently validated with the experimental data of the traditional batch process such as acid value of the polyester, weight of the distillate and glycol concentration in the distillate. We find that the models predict these important variables reliably. Unsaturated polyester production time is around 12 hours in the traditional batch process. However, the simulation study of the reactive distillation process shows that the total production time of unsaturated polyester in a continuous reactive distillation system is between 1.5 hours to 2 hours for the same product quality as during batch production. The equilibrium conversion is raised by 7% compared to the traditional batch process. The model demonstrated that reactive distillation has the potential to intensify the process by factor of 6 to 8 in comparison to the batch reactor.     

Modelling of catalytic hydrocracking and fractionation of refinery vacuum residue

The main objective of this work was to create a kinetic model of refinery vacuum residue hydrocracking and to monitor the impact of the operating conditions on the product yields. Data and yield measurements were gathered from a residual hydrocracking unit (RHC). Reaction temperature ranged from 401°C to 412°C at the pressure of 18–20 MPa. A simplified kinetic yield model was applied; where the feed and each product fraction are represented by one lump (reactant or product of cracking) represented by the number of pseudo-components. The product fractions were determined by fractional distillation of the output mixture from the reactor. The kinetic model includes eight reaction steps and the following six fractions: vacuum residue, vacuum distillate, gas oil, kerosene, naphtha, and gas. In addition, a model for hydrodesulphurisation has been proposed. The average relative deviation between model and experimental yields was 5.36 %, and that for the sulphur conversion model was 1.04 %. An Excel file with the kinetic model was implemented in the Aspen Plus program using a user-defined model of the reactor. This model allows to input/output data between the Aspen Plus and Excel programs. The Excel subroutine calculates the reaction kinetics of cracking from the set temperature and residence time, and distributes the products into 30 pseudo-components created in the Aspen Plus program. The remaining part of the RHC unit was simulated in the Aspen Plus environment. The effects of the reaction conditions such as temperature and residence time on the conversion of the feed and on the distillation curves of the output mixture from the reactor were investigated. The model was verified by comparison of the distillation curves of simulated and real products.     

A novel study on CHEMCAD simulation of isopropyl alcohol dehydrogenation process development

Acetone is a product which is obtained via several processes. It is produced mainly by cumene hydroperoxide process. As an alternative process, acetone is obtained by isopropyl alcohol (IPA) dehydrogenation. The conversion of IPA to acetone is an endothermic gas-phase reaction which produces hydrogen as a byproduct. The process consists of an equilibrium reactor or kinetic reactor (EREA), a distillation column (SCDS), and a flash tank. As the fresh feed, liquid-phase IPA, combined with a recycle stream which contains slight amount of unseparated acetone, is vaporized and given into the equilibrium reactor. Reactor effluent is then cooled by two heat exchangers and pressurized by a compressor until unreacted IPA and formed acetone are liquidised. This stream is fed to a flash tank in order to separate the gas-phase hydrogen, which contains slight amount of acetone. The distillation column distinguishes the acetone from unreacted IPA. The distillate stream has an acetone purity over 99%. The bottoms stream, which consists of residual IPA and slight amount of acetone, is recycled back into the mixer. The purpose of this study is to improve the simulation of isopropyl alcohol (IPA) dehydrogenation process by using the ChemCad program in terms of industrial applications.     

Distillation of LiCl from the LiCl–Li2O molten salt of the electrolytic reduction process

Electrolytic reduction of the uranium oxide in LiCl–Li₂O molten salt for the treatment of spent nuclear fuel requires the separation of the residual salt from the reduced metal product, which contains about 20 wt% salt. In order to separate the residual salt and reuse it in the electrolytic reduction, a vacuum distillation process was developed. Lab-scale distillation equipment was designed and installed in an argon atmosphere glove box. The equipment consisted of an evaporator in which the reduced metal product was contained and exposed to a high temperature and reduced pressure; a receiver; and a vertically oriented condenser that operated at a temperature below the melting point of lithium chloride. We performed experiments with LiCl–Li₂O salt to evaluate the evaporation rate of LiCl salt and varied the operating temperature to discern its effect on the behavior of salt evaporation. Complete removal of the LiCl salt from the evaporator was accomplished by reducing the internal pressure to <100 mTorr and heating to 900 °C. We achieved evaporation efficiency as high as 100 %.     

Gas chromatographic characterization of vegetable oil deodorization distillate

Because of its complex nature, the analysis of deodorizer distillate is a challenging problem. Deodorizer distillate obtained from the deodorization process of vegetable oils consists of many components including free fatty acids, tocopherols, sterols, squalene and neutral oil. A gas chromatographic method for the analysis of deodorizer distillate without saponification of the sample is described. After a concise sample preparation including derivatization and silylation, distillate samples were injected on column at 60 degrees C followed by a gradual increase of the oven temperature towards 340 degrees C. The temperature profile of the oven was optimized in order to obtain a baseline separation of the different distillate components including free fatty acids, tocopherols, sterols, squalene and neutral oil. Good recoveries for delta-tocopherol, alpha-tocopherol, stigmasterol and cholesteryl palmitate of 97, 94.4, 95.6 and 92%, respectively were obtained. Repeatability of the described gas chromatographic method was evaluated by analyzing five replicates of a soybean distillate. Tocopherols and sterols had low relative standard deviations ranging between 1.67 and 2.25%. Squalene, mono- and diacylglycerides had higher relative standard deviations ranging between 3.33 and 4.12%. Several industrial deodorizer distillates obtained from chemical and physical refining of corn, canola, sunflower and soybean have been analyzed for their composition.     

Why is the order reversed? peroxyl‐scavenging activity and fats‐and‐oils protecting activity of vitamin E

The orders of relative tocopherol biopotency, scavenging activity of lipid peroxyl radicals, and quenching activity of singlet oxygen are as follows: jalpha‐tocopherol > β‐tocopherol ? γ‐tocopherol > δ‐tocopherol. However, the reverse is the case for the activity to protect fats and oils from oxidation: jalpha‐tocopherol < β‐tocopherol < γ‐tocopherol δ‐tocopherol. The reason for this reverse has been studied by measuring weight gains of solutions including methyl linoleate and various antioxidants at daily intervals. Antioxidant activity is expressed as an induction period in days. Induction periods are compared with the second‐order rate constants for scavenging of an aroxyl radical by the antioxidants. A plot of the logarithm of the second‐order rate constant vs. the induction period is found to give a good linear fit, and the slope is negative. From these results, it is considered that the larger the peroxyl‐radical‐scavenging activity of a tocopherol, the more favorable the production of the tocopheroxyl radical, and thus the more efficient the oxidation of fats and oils by the tocopheroxyl radical. This is not the case for tocopherols in vivo, because vitamin C and ubiquinol reduce tocopheroxyl radicals formed from tocopherols. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 605–610, 2005     

Impact of α-, γ-, and δ-tocopherol on the radiation induced oxidation of rapeseed oil triacylglycerols

Gamma-irradiation (doses: 2, 4, 7, and 10 kGy) was used as oxidation tool to study the antioxidant effects of α-, γ-, and δ-tocopherol (enrichments 500–5000 ppm) in purified rapeseed oil triacylglycerols (RSOTG). Fatty acid composition, tocopherol degradation, primary (conjugated dienes (CD) and peroxide value (POV)) and secondary (p-anisidine value) oxidation products were chosen as test parameters. Fatty acid composition did not change. While secondary oxidation products could not be found in the irradiated samples, the POVs and CDs showed a significant, dose-dependent increase. α-Tocopherol did not inhibit the formation of peroxides, whereas γ- and δ-tocopherol reduced the POVs by more than 30%. No uniform effect of the different tocopherol concentrations at the particular doses could be established. The influence of the individual tocopherols on the CD formation was not pronounced. The degradation of the tocopherols decreased with increasing concentration. None of the tocopherols showed a prooxidant effect.