Glycerol-rich Phase Research Articles

Using a polar version of PC-SAFT to understand the impact of added CO2 on the phase behavior of biodiesel systems

Two obstacles to efficient transesterification of triglycerides to form biodiesel are the initial immiscibility of the reactants and the potential depletion of the short chain alcohol into the glycerol-rich phase formed as a result of the reaction. Consequently, co-solvents have been used to promote mixing and lower the energetic requirements of the process. Amongst the multiple proposed co-solvents in the literature carbon dioxide exhibits the highest vapor pressure, which provides multiple benefits in the downstream separation process of the biodiesel products and excess reactants. In previous work the presence of an optimal content of CO2 for each set of P-T conditions was demonstrated for a system containing CO2, methanol and triglycerides. In this work, that approach has been extended to the quaternary system of CO2, methanol, glycerol and biodiesel, with an aim towards understanding how added CO2 can reduce the loss of the reactant methanol to the glycerol-rich phase that forms during the transesterification reaction. Variation of the phase separation over a range of pressures (10–40 MPa) temperatures (40–200 °C) and different methanol to glycerol ratios (2–30:1) and the influence on the optimal conditions are reported using a polar version of PC-SAFT that can easily be extended to multiple substances and process conditions. In general, it has been found that adding CO2 promotes retention of methanol in the oil-rich phase until a very light third phase is formed; the appearance of this third phase is predicted by the PC-SAFT model.

Characterising the conversion of transesterification reaction by modelling of glycerol-rich phase

The preparation of fatty acid methyl esters (FAME) involves different phase changes which are not yet characterised. The reaction media in its initial and final stages form two phases; top phase being FAME/unreacted oil and bottom phase being glycerol/methanol. The exact point when the bottom phase starts forming is not well defined. Experimental data of the reaction media composition gives an understanding of the formation of the glycerol phase. A model built for its theoretical concurrence showed good agreement with experimental data. From experimentation, the density of the bottom glycerol/methanol phase showed to be a good and simple indicator of the reaction conversion.

Characterising the conversion of transesterification reaction by modelling of glycerol-rich phase

The preparation of fatty acid methyl esters (FAME) involves different phase changes which are not yet characterised. The reaction media in its initial and final stages form two phases; top phase being FAME/unreacted oil and bottom phase being glycerol/methanol. The exact point when the bottom phase starts forming is not well defined. Experimental data of the reaction media composition gives an understanding of the formation of the glycerol phase. A model built for its theoretical concurrence showed good agreement with experimental data. From experimentation, the density of the bottom glycerol/methanol phase showed to be a good and simple indicator of the reaction conversion.

Preparation and characterization of a novel starch–chestnut husk biocomposite

Biocomposites based on potato starch and reinforced with chestnut husks, a lignocellulosic agroforestry waste, were developed by incorporating 2.5 wt%, 5 wt% and 7.5 wt% of chestnut husks via an extrusion molding procedure. The effect of the filler on the morphology and thermos-mechanical properties were studied by scanning electron microscopy (SEM), infrared spectroscopy (FTIR) and dynamic mechanical analysis (DMA). Chestnut husks were homogeneously dispersed within the plasticized starch matrix as shown by SEM images. FTIR results shows that the peaks of pure starch samples in the 500–1500 cm−1 region vanished as chestnut husks was incorporated, suggesting an interaction between starch and chestnut. The glass transition temperature was found to decrease at higher filler content, which indicates an improvement in segmental mobility of starch molecules. DMA tests revealed the presence of two relaxation processes. The α relaxation was associated with the cooperative segmental motion of starch chains while the β relaxation was assigned to the segmental mobility of glycerol-rich phases.

UNIFAC correlated parameters for liquid-liquid equilibrium prediction of ternary systems related to biodiesel production process

Two phases liquid systems composed by vegetable oil, biodiesel, fatty acids (FAs), glycerol, low molecular weight alcohols, and water are present in most of the biodiesel production process stages, including oil refining, free FAs esterification, transesterification, biodiesel and glycerol-rich phases separation and biodiesel refining by water washing. For that reason, the correct prediction of the liquid-liquid equilibrium (LLE) is a key-factor for an accurate process understanding. In this work, a new set of group interaction parameters (GIP) for the UNIFAC model that describes the LLE for all the systems involved in biodiesel production was correlated and validated. A database including 1414 LLE tie lines from 97 references was constructed and employed to correlate the GIP using a genetic algorithm. These parameters describe the LLE involved in the correlation process with an average deviation up to 2.07%. Additionally, a sensitivity analysis using the proposed GIP was performed to understand the effect of the molecular structure on the LLE behavior for the studied systems. Results showed that composition of the distributed component (alcohol, fatty acid or biodiesel) in both phases depends on the number of carbon atoms, unsaturated bonds and hydroxyl groups in the oleochemicals conforming the system. The variable with the highest incidence in the sensibility analysis was the distributed component overall mass fraction, followed by the alcohol length chain.

Production of Oxygenated Fuel Additives from Residual Glycerine Using Biocatalysts Obtained from Heavy-Metal-Contaminated Jatropha curcas L. Roots

This work aims to shed light on the use of two biochars, obtained from the pyrolysis at 550 °C of heavy-metal-contaminated Jatropha curcas L. roots, as heterogeneous catalysts for glycerol esterification using residual glycerine. To do this, glycerine from biodiesel production was purified. In a first step, H3PO4 or H2SO4 was used to remove non-glycerol organic matter. The glycerol-rich phase was then extracted with ethanol or propanol, which increased the glycerol content from 43.2% to up to 100%. Subsequently, the esterification of both purified glycerine and commercial USP glycerine was assayed with acetic acid (AA) or with acetic anhydride (AH) at 9:1 molar ratio to glycerol using Amberlyst-15 as catalyst. Different reaction times (from 1.5 to 3 h) and temperatures (100–115 °C when using AA and 80–135 °C when using AH) were assessed. Results revealed that the most suitable conditions were 80 °C and 1.5 h reaction time using AH, achieving 100% yield and selectivity towards triacetylglycerol (TAG) almost with both glycerines. Finally, the performance and reuse of the two heterogeneous biocatalysts was assessed. Under these conditions, one of the biocatalysts also achieved 100% TAG yield.

Hansen solubility parameters and thermodynamic modeling for LLE description during glycerol-settling in ester production from coconut oil

The liquid–liquid equilibrium behavior is important when describing the separation of components involved in alkyl ester production during the glycerol-settling step. Therefore, this study presents original data on a liquid–liquid equilibrium system composed of glycerol + ethanol + ethyl esters from coconut oil at 298 K using an untapped approach based on the Hansen solubility parameters describing the individual ethyl ester distribution between the glycerol and ester rich phases. The difference in average molar masses of the ester mixtures in both phases when compared to fatty acid alkyl ester in overall composition reaches more than 10% depending on the ethanol content in the overall composition. The individual partition of ethyl esters in the glycerol-rich phase increases as result of the decrease in molecular size of this class of components. This behavior was shown based on the smaller difference in Hansen solubility parameters among esters with less carbon and the glycerol-rich phases as compared to esters with longer carbon chain atoms. Deviations between the experimental and calculated mass fractions were 0.83%, 4.07%, and 0.87% when using NRTL, UNIFAC-LLE, and UNIFAC-OHgly.

Biodiesel separation using ultrafiltration poly(ether sulfone) hollow fiber membranes: Improving biodiesel and glycerol rich phases settling

After alkali-catalyzed transesterification reaction for biodiesel production, the glycerol-rich phases have to be separated. These phases are traditionally separated by settling, requiring long residence time, especially when soaps and gels are formed. In this work, biodiesel, and glycerol rich phases separation was experimentally assessed using poly(ether sulfone) hollow fiber membranes (PES-HFM). Experimental data were obtained in a continuous bench scale system. The effect of pressure difference through the membrane (0–0.6bar), feed composition and biodiesel-rich phase mass fraction (0–0.8) on permeability and permeate composition were studied. In addition, a mathematical model adopting the Hagen–Poiseuille transport equation for membrane ultrafiltration, where permeate fluxes and compositions depend on the Liquid–Liquid Equilibrium (LLE), was proposed, correlated and experimentally validated. Experimental results demonstrated only glycerol-rich phase permeated through the membrane following the LLE. Glycerol-rich phase flux increased when pressure difference through the membrane augmented, and decreased when permeate viscosity increased. The highest experimental permeability (33.2kgbar−1h−1m−2) was obtained at the highest methanol content in the feed stream, 66%wt., equivalent to a molar ratio methanol to oil 18:1 fed to the reactor. The mathematical model predicts an increase in the glycerol-rich phase flux when temperature and methanol content augment. The transport mechanism coupled to the mathematical model explained accurately the membrane role in the separation of the compounds involved in transesterification of vegetable oils, as well as the membrane selectivity.

How the compatibility between polyethylene and thermoplastic starch can be improved by adding organic acids?

Thermoplastic starch (TPS) can be added to a synthetic polymer, including linear low-density polyethylene (LLDPE), as a low-cost renewable and biodegradable source, to reduce the PE content. Nevertheless, this mixture leads to a mechanical performance decrease due to the immiscibility between both polymers. The aim of this work was to investigate the effect of three different organic acids (3% phr): citric, capric, and palmitic on LLDPE/TPS blends, with a mass ratio of 70/30. The introduction of capric or palmitic acid strengthened TPS and LLDPE interfacial adhesion and improved the mechanical properties of the blends. The glass transition of the glycerol-rich phase (measured by DMA) occurs at higher temperatures for LLDPE/TPS/CITRIC blends, suggesting a plasticizer effect of this acid. It also could be seen by SEM, the images showed that improvements in the compatibility between the immiscible components were achieved by capric or palmitic acid incorporation. TPS’s incorporation had increased the water absorption because of its hydrophilic characteristic; however, acid incorporation reduced this property. In relation to colorimetric aspects, all blends had loss of brightness, but the ones with citric acid were darker, presenting higher color change than the blends with others acids.

Morphology, transport characteristics and viscoelastic polymer chain confinement in nanocomposites based on thermoplastic potato starch and cellulose nanofibers from pineapple leaf

Eco-friendly “green” nano composites were fabricated from potato starch and cellulose nanofibers from pineapple leaf. Nanocomposites of starch/cellulose nanofibers were prepared by solution mixing followed by casting. The investigation of the viscoelastic properties confirms starch macromolecular chain confinement around the nano scale cellulose surface, superior dispersion and very good interaction between thermoplastic starch and cellulose nanofibers. The degree of chain confinement was quantified. The chain confinement was associated with the immobilization of the starch macromolecular chains in the network formed by the nano-scale cellulose fibers as a result of hydrogen boding interactions. From the results, it was assumed that the starch glycerol system exhibits a heterogenous nature and cellulose nanofibers tend to move towards glycerol rich starch phase. Barrier properties also improved with the addition of nanofiller up to 3wt.% but further addition depreciated properties due to possible fiber agglomeration. The kinetics of diffusion was investigated and typical kinetic parameters were determined and found that the nanocomposites follow pseudo fickian behaviour. The outcome of the work confirms that the prepared nanocomposites films can be used as a swap for packaging applications.

Interactions, structure and properties in PLA/plasticized starch blends

Abstract Blends were prepared from poly(lactic acid) (PLA) and thermoplastic starch (TPS) to study component interactions, structure and properties. Starch was plasticized with glycerol at two levels, at 36 and 47 wt%. The results unambiguously showed that the interaction of the two components is weak. The investigation of the possible partitioning of glycerol in the two phases indicated that most of the plasticizer is located in the TPS phase. Thermodynamic modeling predicted some dissolution of PLA in TPS which was assisted by the presence of the plasticizer, but TPS did not dissolve in PLA at all. No tangible proof was found for the formation of a glycerol rich phase in TPS, the relaxation transition assigned to this phase was rather explained with the movement of smaller structural units of starch molecules. Weak interfacial adhesion does not allow stress transfer through the interface resulting in poor strength and small deformation.

Talc Nanoparticles Influence on Thermoplastic Corn Starch Film Properties

Composite films of TPS with talc nanoparticles were obtained by thermo-compression in order to study the effect of this filler on structure, optical, and thermal properties. TPS-talc films showed good appearance and homogeneous thickness. Talc addition increased the amount of rigid phase in nanocomposite films, thus their cross-sections resulted more irregular than those of TPS ones. Talc preferential orientation within matrix and good compatibility between particles and TPS were evidenced. TEM observation showed scattered randomly dispersed individual talc platelets. Matrix crystallinity degree was not significantly affected by particles presence. Nanocomposite films were optically transparent due to the laminar morphology and nanosized particles. Materials microstructure presented glycerol- and starch-rich domains. Talc incorporation higher than 3% w/w increased softening resistance of nanocomposites as stated by DMA assays. TPS relaxation temperature of glycerol-rich phase was shifted to higher values since talc nanoparticles reduce starch chains mobility.

Transesterification of canola oil catalyzed by nanopowder calcium oxide

Two types of commercial nanopowder calcium oxides, a higher surface area (HSA nano-CaO) and moderate surface area (nano-CaO) were studied for the transesterification of canola oil. The effect of reaction temperature, catalyst/oil weight ratio, and methanol/oil molar ratio on the reaction performance was investigated. The results show that nanopowder CaOs possess high activity due to their larger BET surface areas. At 65°C, 99.85% biodiesel yield was obtained at 2h when 3wt.% of the nano-CaO catalyst was used with 9:1 methanol/oil molar ratio. The required catalyst/oil weight ratio to achieve the same yield under the same conditions was 10 times less for the HSA-nano-CaO catalyst. In contrast, only 88.59% and 16.23% yield were obtained for calcium methoxide (Ca(OCH3)2) and laboratory-grade CaO, respectively. A Langmuir–Hinshelwood model-based reaction mechanism was proposed for nano-CaO catalyzed transesterification reaction. The reaction was assumed to be first order with respect to triglyceride. The apparent reaction constants, apparent activation energy and pre-exponential factors have been calculated based on experimental data. Nanopowder CaOs were capable of being used without significant deactivation for 10cycles. A slight drop in activity was ascribed to a combination of surface area loss from particle aggregation, the formation of Ca(OCH3)2, CaCO3, a Ca-glycerin complex, and adsorbed CO2 on the catalyst surface. Particle size did not have any effect on the amount of Ca leaching but leaching did increase with longer reaction time especially at higher catalyst loadings. Increasing the methanol/oil molar ratio increased Ca leaching in the glycerol-rich phase and decreased Ca leaching in the biodiesel-rich phase.

Thermoplastic starch films reinforced with talc nanoparticles

Nanocomposite films of thermoplastic corn starch (TPS) with talc particles were obtained by thermo-compression in order to study the effect of filler on structure, optical, and thermal properties. Talc increased the films rigid phase, thus their cross-sections resulted more irregular. Talc preferential orientation within matrix and good compatibility between particles and TPS was observed by SEM. Slight crystalline structure changes in TPS matrix were measured by XRD and DSC, due to talc nucleating effect. Randomly dispersed talc nanoagglomerates and individual platelets were assessed by TEM. Laminar morphology and nano-sized particles allowed that nanocomposite films were optically transparent. TPS–talc films resulted heterogeneous materials, presenting domains rich in glycerol and others rich in starch. Talc incorporation higher than 3%, w/w increased softening resistance of the nanocomposites as stated by DMA. Relaxation temperatures of glycerol-rich phase shifted to higher values since talc reduces the mobility of starch chains.

LLE experimental data, thermodynamic modeling and sensitivity analysis in the ethyl biodiesel from macauba pulp oil settling step

The aim of this study was to obtain experimental data related to liquid–liquid equilibrium (LLE) of systems containing glycerol+ethanol+ethyl biodiesel from macauba pulp oil, perform thermodynamic modeling and simulate the settling step of this biodiesel using simulation software. Binary interaction parameters were adjusted for NRTL and UNIQUAC models. The UNIFAC-LLE and UNIFAC-Dortmund models were used to predict the LLE of the systems. A sensitivity analysis was applied to the settling step to describe the composition of the output streams as a function of ethanol in the feed stream. Ethanol had greater affinity for the glycerol-rich phase. The deviations between experimental data and calculated values were 0.44%, 1.07%, 3.52% and 2.82%, respectively, using the NRTL, UNIQUAC, UNIFAC-LLE and UNIFAC-Dortmund models. Excess ethanol in the feed stream causes losses of ethyl ester in the glycerol-rich stream and high concentration of glycerol in the ester-rich stream.

Phase equilibrium of the CO2/glycerol system: Experimental data by in situ FT-IR spectroscopy and thermodynamic modeling

Phase equilibrium experimental data for the CO2/glycerol system are reported in this paper. The measurements were performed using an in situ FT-IR method for temperatures ranging from 40°C to 200°C and pressures up to 35.0MPa, allowing determination of the mutual solubility of both compounds. Concerning the CO2 rich phase, it was observed that the glycerol solubility in CO2 was extremely low (in the range of 10−5 in mole fraction) in the pressure and temperature domains investigated here. Conversely, the glycerol rich phase dissolved CO2 at mole fractions up to 0.13. Negligible swelling of the glycerol rich phase has been observed. Modeling of the phase equilibrium has been performed using the Peng–Robinson equation of state (PR EoS) with classical van der Waals one fluid and EoS/GE based mixing rules (PSRK and MHV2). Satisfactory agreement was observed between modeling results and experimental measurements when PSRK mixing rules are used in combination with UNIQUAC model, although UNIFAC predictive approach gives unsatisfactory representation of experimental behavior.

Liquid–liquid equilibrium of pseudoternary systems containing glycerol + ethanol + ethylic biodiesel from crambe oil (Crambe abyssinica) at T/K = (298.2, 318.2, 338.2) and thermodynamic modeling

In the present work liquid–liquid equilibrium (LLE) data were obtained for systems composed of glycerol+ethanol+distilled fatty acid ethyl esters from crambe oil at T/K=298.2, 318.2 and 338.2. The experimental data measured for these systems were used to adjust the binary interaction parameters between their components for NRTL model treating the mixture of ester as a single ethyl ester, with the average molar mass of the mixture of esters. Two sets of UNIFAC binary interaction parameters were also tested to predict the LLE of the systems. Ethanol, which is distributed in the glycerol-rich and ester-rich phases, showed a greater affinity to the glycerol rich phase. Glycerol and FAEE presented very low miscibility. The average deviations related to mass fraction composition between experimental and calculated values by the NRTL model were less than 0.82% and by the UNIFAC model were between 2.27% and 3.97%, considering the two different sets of binary interaction parameters.

Bioplastics from Blends of Cassava and Rice Flours: The Effect of Blend Composition

Abstract Bioplastics from melt-mixing of cassava flour, rice flour and their blends with compositions of between 0/100 and 100/0 %wt were successfully obtained using twin-screw extrusion and compression molding processes. The influence of blend composition on the bioplastic's properties was studied. It was found that the flour blends were uniformly mixed. The tensile properties and dynamic properties of the flour bioplastics were examined. The tensile strength and storage modulus of compression molded bioplastics based on rice flour was greater than those of the cassava flour, but their flexibility was lower. The tensile strength and storage modulus of the flour blend bioplastics increased with increasing rice flour content. The flour bioplastics showed two glass transitions, one corresponding to glycerol rich phase and the other corresponding to plasticized starch. For plasticized flour blends, the glass transitions were not affected by the blend composition. The improvement in the mechanical properties of the bioplastics produced from the cassava/rice flour blend could be explained by an increase in the crystallinity level resulting from the higher concentration of rice flour. Using flour blends derived from cassava and rice flours, the bioplastics developed in this study offer a greater performance while maintaining environmental compatibility and sustainability, which allows for a substitution of tradition bioplastics from cassava starch.

Glycerol removal from biodiesel using membrane separation technology

Membrane separation technology was used to remove free glycerol from biodiesel in order to meet the ASTM D6751 and EN 14214 standards. Fatty acid methyl esters (FAME) produced from canola oil and methanol were purified using ultra-filtration. The effect of different materials present in the transesterification reaction, such as water, soap, and methanol, on the final free glycerol separation was studied. A modified polyacrylonitrile (PAN) membrane, with 100 kD molecular weight cut-off was used in all runs. Tests were performed at 25 °C and 552 kPa operating pressure. The free glycerol content in the feed, retentate and permeate of the membrane system was analyzed using gas chromatography according to ASTM D6584. Results showed low concentrations of water had a considerable effect in removing glycerol from the FAME even at approx. 0.08 mass%. This is four orders of magnitude less than the amount of water required in a conventional biodiesel purification process using water washing. It is suggested that the mechanism of separation of free glycerol from FAME was due to the removal of an ultrafine dispersed glycerol-rich phase present in the untreated FAME. This was confirmed by the presence of particulates in the untreated FAME. The size of the particles and the free glycerol separation both increased with increasing water content of the FAME. The trends of separation and particle size vs. water content in the FAME phase were very similar and exhibited a sudden increase at 0.08 mass% water in the untreated FAME. This supports the conclusion that water increased the size of the distributed glycerol phase in the untreated FAME leading to its separation by the ultra-filtration membrane. The technology for the removal of free glycerol from biodiesel was found to use 2.0 g of water per L of treated FAME (0.225 mass% water) vs. the current 10 L of water per L of treated FAME.

Effect of glycerol and short sisal fibers on the viscoelastic behavior of wheat flour based thermoplastic

Wheat flour based thermoplastic having glycerol content (20%, 23%, 25%, 30% and 35% w/w) were fabricated using extrusion followed by compression molding. Dynamic mechanical analysis (DMA) has been done with reference to the amount of glycerol, sisal fiber loading, frequency and temperature. Two transitions peaks were observed for the, matrix, one at low temperature, due to the molecular dynamics associated to glycerol rich phase, and another at high temperature attributed to the molecular relaxation of starch rich phase. By changing the amount of glycerol, it has been observed that, at all temperature ranges, a plasticization effect which concerns mainly in the starch rich phase. Introduction of sisal fiber (up to 10% w/w) increases the storage modulus of the thermoplastic matrix. The peak height of damping curves (tan δ) was lowered as the fiber content. The activation energy was calculated from the maximum temperature ( T max) of damping curves.