Glycerol Phase Research Articles

Liquid-liquid equilibrium of FAEs – glycerol phase – ethanol in the ethanol regeneration and FAE separation stage

Extraction and purification of biofuel components are as important as their synthesis. Synthesis of fatty acid esters in a molar excess of ethanol above 1:30 results in the formation of a homogeneous phase including the ester and glycerol phases dissolved in ethanol. It was observed that when excess ethanol was removed, the separation of the system into ester and glycerol phases did not always occur. To improve the biodiesel purification process the experimental binodal curve for the FAE-ethanol-glycerol phase system was obtained in the synthesis of biodiesel from rapeseed oil. The data was obtained from homogeneous alkaline synthesis of FAE with molar excess of ethanol 1:50. The pseudocomponent glycerol phase contains glycerol and unreacted oil (triglycerides (TGA)). The calculated liquid-liquid equilibrium (LLE) data for FAE – ethanol – glycerol and FAE – ethanol – TGA ternary mixtures were obtained by the UNIFAC (UNIQUAC Functional-group Activity Coefficients) model and compared with experimental diagram. It was found that glycerol and unreacted triglycerides affect the behavior of the system by preventing or promoting the mixing of immiscible components. The obtained results show that, depending on the conversion, the phase behavior of the FAE-ethanol-glycerol phase system will correspond to the ternary system FAE-ethanol-glycerol or FAE-ethanol-TGA. The obtained data help to predict the separation of glycerol and ester phases at the ethanol recovery stage knowing the degree of rapeseed oil conversion at the synthesis stage. Successful separation of the glycerol and FAE phases is possible at oil conversion above 53 %.

Beneficial synergetic effect of feedstock characteristics and reaction conditions on bio crude production from hydrothermal liquefaction of mixed residential waste

Hydrothermal Liquefaction (HTL) is a promising method for sustainable waste management and renewable energy production, converting mixed feedstocks into bio-crude, a precursor to various biofuels. A study focused on Mixed Residential Waste (MRW) as an HTL feedstock investigated temperature ranges (280 °C-360 °C) and residence times (30 min–90 min), achieving a maximum bio-crude yield of 39.16% at 340 °C and 75 min. Also, a thorough investigation of the synergistic relationships between all subcomponents of the MRW feedstock was conducted and concluded that the mixed waste (MW) feedstock samples containing a higher proportion of food and plastic wastes and MRW sample presented with a co-liquefaction percentage (CE%) of around 60% and 107% respectively for production of bio crude. Also, solvents such as ethanol, glycerol and aqueous phase (AQ) were tested for their potential as hydrothermal mediums and found that bio crude yield of 46.19% was obtained in case of AQ phase recirculation. Further, the quantitative and qualitative effect of usage of four different catalysts were tested individually and in combination with AQ phase recirculation and found that, although individually Nanoporous ZnO and Diatomaceous Earth (DE) yielded bio crude in the range of 46.86% and 42.68% respectively, when used in combination, DE cat–HTL with AQ resulted in maximum bio crude yield of 54.35%. Furthermore, qualitatively, the bio crude from DE cat–HTL with AQ presented with a high carbon and energy recovery percentage of 62.20% and 72.95% respectively and a high hydrocarbon content of 58.98%.

Production of biodiesel from Pistacia atlantica (PA) oil seeds using nano-catalyst of alumina/sludge of stone cutting factory (Al2O3/SSCF) and separation of biodiesel and glycerol phases by high voltage

Biodiesel is a renewable fuel and a suitable alternative to fossil fuels. However, the cost of its production and purification has prevented the commercialization and industrialization of this fuel. One economic solution for producing biodiesel fuel is the profit from the sale of glycerin, which is produced as a side product in various processes. In addition to the economic aspects, there are problems caused by the presence of glycerin residues in raw biodiesel before the purification process and the low speed of its separation from biodiesel. Biodiesel is produced by the transesterification method from Pistacia atlantica (PA) oil seeds of the Lorestan Mountains and methanol (1:6) using nano-catalysts of alumina/sludge from a stone cutting factory (Al2O3/SSCF). In this study, to investigate cost reduction and pure and quick separation of glycerin from biodiesel produced, a high-voltage electric method has been used. In this method, negative charges are absorbed by glycerin, separating it from biodiesel. The resulting biodiesel is produced in 10 min with 99% efficiency. The Fourier-transform infrared spectroscopy (FTIR) spectrum of biodiesel is investigated to ensure the formation of the reaction. This method can replace traditional methods.

Liquid–Liquid Equilibrium Behavior of Ternary Systems Comprising Biodiesel + Glycerol and Triglyceride + Methanol: Experimental Data and Modeling

Having a comprehensive knowledge of phase equilibrium is advantageous for industrial simulation and design of chemical processes. For further acquisition of primary data to facilitate the separation and purification of waste oil biodiesel systems, a liquid–liquid equilibrium (LLE) tank is deployed for the ternary system of waste oil biodiesel + methanol + glycerin, thereby enhancing the precision and efficiency of the process. The phase equilibrium system was constructed under the influence of atmospheric pressure at precise temperatures of 303.15 K, 313.15 K, and 323.15 K. The equilibrium components of each substance were analyzed by employing high-temperature gas chromatography, a sophisticated analytical method that enables the identification and quantification of individual components of a sample. Moreover, the ternary liquid–liquid equilibrium data were correlated by implementing the NRTL and UNIQUAC activity coefficient models. Subsequently, the binary interaction parameters of the ternary system were derived by conducting regression analysis. The experimental data demonstrated that the presence of lower methanol content in the system resulted in nearly immiscible biodiesel and glycerol phases, which ultimately facilitated the separation of biodiesel and glycerol. Conversely, with the increase in methanol content, the mutual solubility of biodiesel and glycerol was observed to increase gradually. The results showed that the calculated values of the NRTL and UNIQUAC models aligned well with the experimental values. The root-mean-square deviations of the NRTL and UNIQUAC models at 313.15 K were 2.76% and 3.56%, respectively.

Application of Quaternary Ammonium-Based Deep Eutectic Solvents as Catalysts for the Glycerolysis of Free Fatty Acids

Nonedible waste sourced lipids such as fatty acid distillates, brown grease, and animal tallow, among many others, are excellent alternatives for expanding the feedstock inventory for biodiesel synthesis. A quaternary ammonium-based deep eutectic solvents (DESs) was used as a catalyst in the glycerolysis of free fatty acids (FFAs) in this study. Reaction optimization was carried out with oleic acid as the model molecule, followed by an in-depth examination of the reaction mechanism. Optimum conditions such as 130 °C and 10 wt % catalyst dosage with 10 min of reaction time gave an equilibrium conversion of 94%. The catalyst was found to remain in the glycerol phase allowing its reuse. Palm fatty acid distillate, brown grease, and crude glycerol were utilized for testing the novel DES at optimum conditions. FFA conversion was found to be 94% for both palm fatty acid distillate and brown grease. In the case of crude glycerol, FFA conversion decreased proportionally to the impurity level. Water was responsible for restricting equilibrium conversion and decreasing catalyst recyclability, necessitating further research into effective removal during the reaction. Aggressive nitrogen purging to remove water during the reaction pushed the reaction toward near-completion in 60 min. The catalyst reusability study showed a drop in equilibrium conversion to 62.5% at the end of the 5th cycle, even when water was removed.

Sterically Stabilized Diblock Copolymer Nanoparticles Enable Efficient Preparation of Non-Aqueous Pickering Nanoemulsions.

We report the first example of a non-aqueous Pickering nanoemulsion, which comprises glycerol droplets dispersed in mineral oil. The droplet phase is stabilized by hydrophobic sterically stabilized poly(lauryl methacrylate)-poly(benzyl methacrylate) nanoparticles which are prepared directly in mineral oil using polymerization-induced self-assembly. First, a glycerol-in-mineral oil Pickering macroemulsion with a mean droplet diameter of 2.1 ± 0.9 μm is prepared via high-shear homogenization using excess nanoparticles as an emulsifier. Then, this precursor macroemulsion is subjected to high-pressure microfluidization (a single pass at an applied pressure of 20,000 psi) to produce glycerol droplets of approximately 200-250 nm diameter. Transmission electron microscopy studies indicate preservation of the distinctive superstructure produced by nanoparticle adsorption at the glycerol/mineral oil interface, thus confirming the Pickering nature of the nanoemulsion. Glycerol is sparingly soluble in mineral oil, thus such nanoemulsions are rather susceptible to destabilization via Ostwald ripening. Indeed, substantial droplet growth occurs within 24 h at 20 °C, as judged by dynamic light scattering. However, this problem can be suppressed by dissolving a non-volatile solute (sodium iodide) in glycerol prior to formation of the nanoemulsion. This reduces diffusional loss of glycerol molecules from the droplets, with analytical centrifugation studies indicating much better long-term stability for such Pickering nanoemulsions (up to 21 weeks). Finally, the addition of just 5% water to the glycerol phase prior to emulsification enables the refractive index of the droplet phase to be matched to that of the continuous phase, leading to relatively transparent nanoemulsions.

Biodiesel Washing Machine From Esterification Process Equipped With A Cooling System

Biodiesel is a fuel that can be recycle, is easily obtained, and friendly to the environment. The production process of biodisesl is divided into four stages, they are the esterification process, cooling, washing and filtration. In this study, a biodiesel purifying machine was developed which is equipped with a cooling system. The cooling system uses a thermoelectric module attached to the delivery pipe from the esterification tank to the purifyer tank. The washing process begins with a pre-cooled hot oil deposition process for 20 minutes to obtain two phases of glycerol and crude biodiesel. The glycerol phase is removed by opening the valve at the bottom of the tank. After that the washing process takes place by mixing water and biodiesel. The mixture of water and distilled water was precipitated for 20 minutes and after that the dirty water was discharged through a valve driven by a servo motor. The purifying machine has been successfully developed and has been tested to perform the expected task. The test results show that the temperature sensor work well. Other tests were carried out on the accuracy of valves and flowmeters. The test results show that the test at low volume is relatively less accurate. Accurate results are obtained on testing volumes above 1500 ml. The purifying machine has been tested to perform the function of purifying crude biodiesel. The test results show that the washing process can take place well.

Synthesis of Ibuprofen Monoglyceride Using Novozym®435: Biocatalyst Activation and Stabilization in Multiphasic Systems

This work was focused on the enzymatic esterification of glycerol and ibuprofen at high concentrations in two triphasic systems composed of toluene+ibuprofene (apolar) and glycerol or glycerol–water (polar) liquid phases, and a solid phase with the industrial immobilized lipase B from Candida antarctica named Novozym®435 (N435) acting as the biocatalyst. Based on a preliminary study, the concentration of the enzyme was set at 30 g·L−1 and the stirring speed at 720 r.p.m to reduce external mass transfer limitations. To obtain more information on the reaction system, it was conducted at a wide range of temperatures (50 to 80 °C) and initial concentrations of ibuprofen (20–100 g·L−1, that is, 97 to 483 mM). Under these experimental conditions, the external mass transfer, according to the Mears criterion (Me = 1.47–3.33·10−4 << 0.15), was fast, presenting no limitation to the system productivity, regardless of the presence of water and from 50 to 80 °C. Considering that the enzyme is immobilized in a porous ion-exchange resin, limitations due to internal mass transfer can exist, depending on the values of the effectiveness factor (η). It varied from 0.14 to 0.23 at 50 to 80 °C and 0.32–1 mm particle diameter range in the absence of water, and in the same ranges, from 0.40 to 0.66 in the presence of 7.4% w/w water in the glycerol phase. Thus, it is evident that some limitation occurs due to mass transfer inside the pores, while the presence of water in the polar phase increases the productivity 3–4 fold. During the kinetic study, several kinetic models were proposed for both triphasic reacting systems, with and without first-order biocatalyst deactivation, and their fit to all relevant experimental data led to the observation that the best kinetic model was a reversible hyperbolic model with first-order deactivation in the anhydrous reaction system and a similar model, but without deactivation, for the system with added water at zero time. This fact is in sharp contrast to the use of N435 in a water-glycerol monophasic system, where progressive dissolution of ibuprofen in the reacting media, together with a notable enzyme deactivation, is observed.

Synthesis of Biodiesel by Interesterification of Triglycerides with Methyl Formate

In the conventional synthesis of biodiesel, not only fatty acid esters (biodiesel) are formed, but also the by-product is the glycerol phase, which amounts to about 10 wt.%. Recently, the studies on the interesterification of oil using carboxylate esters have been launched. In this case, no glycerol is formed, and esters of glycerol and short-chain organic acids soluble in biodiesel are produced. The biodiesel yield is increased, and the biodiesel production process is more economically viable. The process of interesterification with methyl formate yields a mixture of biodiesel and triformylglycerol, which is not inferior in quality to biodiesel, but also has better low-temperature properties. The paper analyzes the application of chemical and enzymatic catalysis methods for the interesterification of triglycerides with methyl formate. The influence of catalyst amount, reagent molar ratio, temperature, and process time on the product yield is presented. The quality indicators of the obtained fuel and their compliance with the requirements of the biodiesel fuel standard are discussed.

Towards passive bioremediation of dye-bearing effluents using hydrous ferric oxide wastes: Mechanisms, products and microbiology

A novel, circular economy-inspired approach for the “passive” (non-powered and reagent-free) treatment of dye-bearing effluent is presented. The treatment utilises the biogeochemical interaction of dye-bearing wastewater with hydrous ferric oxide (HFO) bearing sludges. The work presented demonstrates for the first time the reuse of HFO-rich waste sludges from potable water and mine water treatment. The waste was used directly without modification or reagent addition, as media/substrate in simple flow-through reactors for the decolourisation and biodegradation of methyl orange (MO) and mixed dyes textile effluent. Three phases of exploratory proof of concept work were undertaken. Columns containing HFO sludges were challenged with solution of MO, and MO amended with glycerol (Phase I), MO in a synthetic textile effluent recipe (Phase II), and real mixed textile effluent containing a mixture of dyes (Phase III). After an initial lag period extensive decolourisation of dye was observed in all cases at rates comparable with pure strains and engineered bioreactor processes, with evidence of biodegradation beyond simple cleavage of the mono azo chromophore and mineralisation. The microbiology of the initial sludge samples in both cases exhibited a diverse range of iron oxidising and reducing bacteria. However, post experiment the microbiology of sludge evolved from being dominated by Proteobacteria to being dominated by Firmicutes. Distinct changes in the microbial community structure were observed in post-treatment MWTS and WTWS where genera capable of iron and sulphate reduction and/or aromatic amine degradation were identified. Average nitrogen removal rates for the columns ranged from 27.8 to 194 g/m3/day which is higher than engineered sequential anaerobic-aerobic bioreactor. Postulated mechanisms for the fast anaerobic decolourisation, biodegradation, and mineralisation of the dyes (as well nitrogen transformations) include various direct and indirect enzymatic and metabolic reactions, as well as reductive attack by continuously regenerated reductants such as Fe(II), HFO bound Fe(II), FeS, and HS−. The ability of iron reducers to degrade aromatic rings is also considered important in the further biodegradation and complete mineralisation of organic carbon. The study reveals that abundant and ubiquitous HFO-rich waste sludges, can be used without amendment, as a substrate in simple flow-through bioremediation system for the decolourisation and partial biodegradation of dyes in textile effluent.

Enhancement of biogas production from cattle manure using glycerine phase as a co-substrate in anaerobic digestion

This study investigated the effect of glycerine phase on the anaerobic digestion of cattle manure under mesophilic conditions. The process was carried out in semi-continuous stirred tank reactors at a constant organic loading rate of 2.3 g VS/L·d and a hydraulic retention time of 30 days. It was found that the addition of 10% (as volatile solids) glycerine phase to cattle manure produced 3.1-times more biogas than cattle manure alone (237.5 L vs. 76.4 L) and a 10% higher methane content (69% vs. 59%). Biogas formation during co-digestion was strongly correlated with the concentrations of ammonium nitrogen (r = 0.89, p < 0.05) and volatile fatty acids (r = −0.71, p < 0.05), which resulted in a decrease in biogas production over time despite a stable pH value. The proposed use of glycerine phase could provide an advanced anaerobic digestion system that is technologically simple, has a positive energy balance, and produces upgraded biogas, although additional monitoring of the concentration of volatile acids and ammonium nitrogen is needed to maintain stable biogas production. These findings will be useful for reducing demand for non-renewable energy resources, and more broadly, they will assist in the shift from a traditional economy to a circular bioeconomy.

Synthesis and Chemical Functionalization of Pseudo-Homogeneous Catalysts for Biodiesel Production-Oligocat.

With the increase in global demand for biodiesel, first generation feedstock has drawn the attention of governmental institutions due to the correlation with large land farming areas. The second and third feedstock generations are greener feedstock sources, nevertheless, they require different catalytic conditions if compared with first generation feedstock. In this work, we present the synthesis and characterization of oligoesters matrices and their functionalization to act as a pseudo-homogeneous acid catalyst for biodiesel production, named Oligocat. The main advantage of Oligocat is given due to its reactional medium interaction. Initially, oligocat is a solid catalyst soluble in the alcoholic phase, acting as a homogeneous catalyst, providing better mass transfer of the catalytic groups to the reaction medium, and as the course of the reaction happens, Oligocat migrates to the glycerol phase, also providing the advantage of easy separation of the biodiesel. Oligocat was synthesized through polymerization of aromatic hydroxy acids, followed by a chemical functionalization applying the sulfonation technique. Characterization of the catalysts was carried out by infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). The synthesized oligomers presented 5357 g·mol−1 (Mw) and 3909 g·mol−1 (Mn), with a moderate thermal resistance of approximately 175 °C. By sulfonation reaction, it was possible to obtain a high content of sulphonic groups of nearly 70 mol%, which provided the catalytic activity to the oligomeric matrix. With the mentioned physical–chemical properties, Oligocat is chemically designed to convert second generation feedstock to biodiesel efficiently. Preliminary investigation using Oligocat for biodiesel production resulted in conversion rates higher than 96.5 wt.%.

Facile synthesis of zein-based emulsion gels with adjustable texture, rheology and stability by adding β-carotene in different phases

The current study focused on the application of an agricultural byproduct, zein, to the formation of a novel type of emulsion gels. Zein based oil-in-glycerol emulsion gels (O/G ZEGs) were prepared by a facile one-step approach, and β-carotene was incorporated within the dispersed and continuous phases. β-Carotene could be interacted with zein, and thus the location of β-carotene significantly influenced the structures of O/G ZEGs. β-Carotene in the glycerol phase reduced the hardness of systems, but enhanced the viscosity, oil holding capacity and solvent binding capacity of the gels. Small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) rheological analysis revealed that β-carotene in the oil phase enhanced the elastic properties of ZEGs and strengthened gel stability upon deformation. The gels with stronger mechanical properties were more capable to protect β-carotene when subjected to UV-light, and simultaneous loading of β-carotene in the oil phase and glycerol phase resulted in much lower degradation rate. However, the degradation of β-carotene also led to the weakening of gel networks. Microstructural observation suggested that β-carotene in oil phase facilitated the formation of much denser gels networks and more uniform distribution of oil droplets. FTIR tests verified that there were hydrophobic interactions between β-carotene and zein, which modified the stacking of zein molecules. This study first reported the roles of β-carotene in modulating the structures of zein based emulsion gels, and also provided information to expand the application of prolamins as efficient delivery systems for bioactives.

Evaluating the Activity and Stability of Perovskite LaMO3-Based Pt Catalysts in the Aqueous Phase Reforming of Glycerol

The aqueous phase reforming of glycerol, to hydrogen, alkanes and liquid phase dehydration/dehydrogenation products, was studied over a series of 1 wt% Pt/LaMO3 (where M = Al, Cr, Mn, Fe, Co, Ni) catalysts and compared to a standard 1 wt% Pt/γ-Al2O3 catalyst. The sol–gel combustion synthesis of lanthanum-based perovskites LaMO3 produced pure phase perovskites with surface areas of 8–18 m2g−1. Glycerol conversions were higher than the Pt/γ-Al2O3 (10%) for several perovskite supported catalysts, with the highest being for Pt/LaNiO3 (19%). Perovskite-based catalysts showed reduced alkane formation and significantly increased lactic acid formation compared to the standard catalyst. However, most of the perovskite materials undergo phase separation to LaCO3OH and respective M site oxides with Pt particle migration. The exception being the LaCrO3 support which was found to remain structurally stable. Catalytic performance remained stable over several cycles, for catalysts M = Al, Cr and Ni, despite phase separation of some of these materials. Materials where M site leaching into solution was observed (M = Mn and Co), were found to be catalytically unstable, which was hypothesised to be due to significant loss in support surface area and uncontrolled migration of Pt to the remaining support surface. In the case of Pt/LaNiO3 alloying between the exsoluted Ni and Pt was observed post reaction.

The influence of vegetable oils composition on separation of transesterification products, especially quality of glycerol

The paper describes the properties of glycerol produced by transesterification, especially the ester content in the glycerol phase (ester losses) including the distribution of esters according to higher fatty acids. Glycerol, produced by transesterification of oil as a side product – the polar glycerol phase, is an important chemical raw material. The decreasing of ester losses is important because it (i) increases the ester yield and especially (ii) decreases the cost of glycerol purification. The transesterification of oils (rapeseed, olive, palm, sunflower and Camelina Sativa) with various distributions of fatty acids was carried out by methanol, ethanol and butanol including different transesterification stopping. The losses of ethyl and butyl esters are much higher than losses of methyl ester (approximately 2–3x). The distribution of ethyl and butyl esters in the glycerol phase is the same as in the ester phase, whereas distribution of methyl ester is different and depends on the way of transesterification stopping. The reason is the different polarity of methyl esters, which depends on the type of fatty acid. The polarity increases with increasing of double bonds, i.e. the most soluble is methyl ester of linolenic acid in the glycerol phase.

Reusable TsOH-H2SO4 Mixed Catalysis for Tandem Synthesis of Biodiesel and Oxygenated Fuel Additives, tert-Butyl Glycerol Ethers.

A mixture of p-toluenesulfonic acid and sulfuric acid (TsOH-H2SO4) was used as a catalyst with a good performance in transesterification of palm oil (PO) with methanol and etherification of crude glycerol with isobutylene (tandem synthesis). For TsOH-H2SO4 catalyzed biodiesel production, the reaction noticeably ran faster in comparison with TsOH or H2SO4 alone and also gave up to 99.9% of the conversion using MeOH/PO molar ratio 9:1 at 80℃, in the period of 4 h. After the whole transesterification process, the crude glycerol phase was separated and then reacted with isobutylene in the etherification process using isobutylene/glycerol molar ratio 9:1 at 80℃, in the period of 5 h reaction time, to give DTBG and TTBG (91.14%). In the case of the etherification in biodiesel, higher selectivity of DTBG and TTBG (99.39%) was obtained in comparison with an absence of biodiesel as the solvent. Furthermore, the catalyst could be reused for 6 cycles of tandem synthesis (transesterification and etherification). The TsOH-H2SO4 catalyst showed a good catalytic performance in tandem synthesis similar to TsOH and it could be recovered for reuse while TsOH could not be recovered. This process offers an attractive route for reuse homogeneous catalyst of tandem synthesis, the main by-product of biodiesel, to tert-butyl glycerol ethers - a value-added in applications as a valuable fuel additive.

Component distribution associated with phase separation and purification of tropical almond biodiesel at different temperatures

Accurate knowledge of the components in the purification of biodiesel is important in achieving consistency in quality for the separation and purification process. In this paper, ternary phase diagrams were used to study the phase separation and purification of tropical almond biodiesel at temperatures of 20 °C, 30 °C and 40 °C. The biodiesel was produced using alkaline transesterification of the seed oil. The biodiesel was characterized using ASTM and EN standard methods. A modified cloud point titration procedure under constant temperature was used to determine the tie lines and binodal compositions. The phase mixture compositions were determined using gas chromatographic method. Distribution coefficient and selectivity analysis were performed and data accuracy, consistency and reliability were done using a first-order linear polynomial model. The result revealed free fatty acid values for the oil and the biodiesel as 0.63 and 0.23 respectively. The data quality and reliability showed a high coefficient of determination of 0.9998, adjusted coefficient of determination of 0.9887, a standard deviation of 0.0327, and a correlation coefficient of 0.8349 at the investigated temperatures. Methanol was prevalent in the glycerol phase. Ternary phase diagrams provided the visual means of estimating the distribution of the components.

Crude glycerine characterization: analysis of free fatty acids, fatty acid methyl esters, and acylglycerides

Crude glycerine is a product obtained in a biodiesel production plant by processing the glycerine phase formed in the transesterification reactor. Crude glycerine contains approximately 80 wt% of glycerine, water, salts, and matter organic non-glycerol. This product is used mainly as a feedstock to obtain high-purity glycerine in a refining unit. Due to a large variability in biodiesel production processes and technologies, the crude glycerine has significant variations in its composition, making it difficult to run the latter process. Particularly, the content of saponifiable matter (free fatty acids, fatty acid methyl esters, and mono-, di-, and tri-acylglycerides) is relevant not only in the refining process, but also in other applications such as bioconversion processes to obtain value-added products. In this work, a method to quantify free fatty acids, fatty acid methyl esters, and mono-, di-, and tri-acylglycerides is presented. The method is based on a quantitative extraction with hexanes, and an analysis by GC with derivatization. It is possible to detect very low concentrations of these impurities. The confidence intervals for each of these impurities have been determined, being the highest for the quantification of the fatty acid methyl esters and mono-acylglycerides. In all cases, the 95% confidence intervals represent an error smaller than 20%.

Hydrophobic-hydrophilic balance of ZSM-5 zeolites on the two-phase ketalization of glycerol with acetone

Herein, ZSM-5 zeolites of several Si/Al mole ratios, and varying hydrophobicity were used as catalysts in the ketalization of glycerol. The water formed in the reaction adsorbs on acidic sites, hampering the catalytic conversion of glycerol. The conversion drops even more by adding water in the reaction mixture, intensifying the adsorption in hydrophilic zeolites. However, the samples with the higher Si/Al ratio and abundant hydrophobic ≡Si-O-Si≡ linkages had the uppermost turnover frequency. The reaction proceeds at the interface of the glycerol and acetone phases. Since the catalyst preferentially stays in the glycerol phase due to gravity action, the full catalytic action of the catalyst is hindered. Contact angle measurements with the glycerol/zeolite systems confirmed that the hydrophobic zeolite had the lowest affinity with glycerol, thus improving the interfacial solubilization of glycerol/acetone in the vicinity of active sites turning it much more efficient. The catalytic action was further enhanced by partially ion-exchanging external acid sites with minor quantities of bulky n-hexylammonium cations, turning the zeolite more hydrophobic and a strong candidate for other acid-catalyzed interfacial liquid-phase reactions.

Butanol as a co-solvent for transesterification of rapeseed oil by methanol under homogeneous and heterogeneous catalyst

The paper focuses on the use of methanol (M) together with butanol (B) in transesterification of rapeseed oil (O) under homogeneous (KOH) and heterogeneous catalysis (Mg-Fe mixed oxides with molar ratio of magnesium to iron of 2.9). The novelty lies in the use of these types of alcohols together under various reaction conditions and the determination of ternary plots for the reaction components. The advantage of using butanol consists of the formation of a homogenous reaction mixture and the slightly higher caloric value of the formed esters. For the homogeneous catalyst, the influences of the (i) molar ratios of reaction components, (ii) temperature, (iii) amount of catalyst and (iv) method of stopping the transesterification were studied in the course of transesterification. The properties of the ester and glycerol phases were determined, including ester loss in the glycerol phase. The ester yield was 97% after 10 min of reaction for 60 °C, and the O:M:B ratio was 1:6:2, representing a significant decrease in time compared with methanol only (90 min). However, the content of potassium ions was higher because butyl ester results in higher solubility of potassium ions. For the heterogeneous catalyst, the synthesized materials were characterized by the chosen method and tested in transesterification with methanol, butanol and their combination. The addition butanol caused the higher yield than only for methanol or butanol only.