Esterification Conditions Research Articles

Esterification and transesterification of palm fatty acid distillate in chitosan membrane reactor

Biodiesel from palm fatty acid distillate (PFAD) with FFAs of 87.1 ± 1.3 wt% was studied in a 2-litres chitosan membrane reactor. The reactor used in this study comprised of three parts; i.e., upstream side for reaction, membrane cell and downstream side connecting with a vacuum pump. The feed was operated under esterification reaction followed by transesterification reaction without intermediate washing. Flat sheet symmetric dense uncrosslinked chitosan membrane was used preferably in the laboratory 2-litres reactor. Operating the reactor under the pervaporation process, the optimum esterification condition was at 1:15 of PFAD to methanol ratio, 2.0 wt% H2SO4 and 20 ml/min methanol feed rate for 120 min. The FFA and methyl ester contents in the esterification product were 1.09 ± 0.03 and 85.9 ± 0.1 wt%, respectively. On the transesterification condition at 1:6 of PFAD to methanol ratio, 1.0 wt% NaOH and 20 ml/min methanol feed rate for 60 min, the methyl ester was increased to 97.9 ± 0.0 wt%. On performance and potential application, an 8-litres reactor installing a set of membrane modules was studied. Several membrane modules with flat sheet reinforced crosslinked composite chitosan membranes were installed in the pilot 8-litres reactor. Together with operating the reactor under the pervaporation process, the esterification was operated at 1:15 of PFAD to methanol ratio and 1.5 wt% H2SO4 for 180 min followed by the transesterification reaction at 1:6 of PFAD to methanol ratio and 1.0 wt% NaOH for 60 min without intermediate washing. The methyl ester yield of 96.6 ± 0.02 wt% was obtained.

Highly sulfonated chitosan-polyethersulfone mixed matrix membrane as an effective catalytic reactor for esterification of acetic acid

A new mixed matrix membrane (MMM) incorporating sulfonated polyethersulfone (SPES) and sulfonated crosslinked chitosan (SCCS) as a superior hydrophilic filler was synthesized and applied as a catalytic pervaporation membrane reactor (PMR) for the esterification of acetic acid with ethanol. The optimal conditions for esterification over SPES-SCCS were preliminarily studied using a batch reactor (BR). The synthesis of ethyl acetate was studied in the PMR based on experimental findings of BR esterification. The pervaporative separation of water in the PMR gave it better catalytic performance than the BR. More importantly, the newly developed PMR is permselective towards the ethyl acetate product.

One-Step Process of Mixed Oleic Acid Esters and Its High Temperature Lubrication Properties in Bentonite Gelling Suspension.

In recent years, with the increase in requirements for horizontal wells, ultra-high depth wells, small wells and branching wells, it has become increasingly important to deal with the conflict between drilling safety and bottomhole friction. In order to meet the requirements of complex boreholes and deepwater drilling processes, it is crucial to improve the performance of ester-based lubricants. Oleic acid esters are relatively stable and have high lubricity at low temperature, however, these can be hydrolyzed at high temperature. However, the structure of carboxylic acids and alcohols can significantly affect the performance of synthetic esters. In order to solve the problem of balancing the high-temperature performance and low temperature performance of oleic acid esters with different structures, we propose a new oleic acid esterification process. After mixing methanol and ethylene glycol, it is reacted with oleic acid, and the mixed oleate prepared is named MEO-21, and the optimal esterification conditions are obtained as follows: the reaction time is 3 h, the reaction temperature is 150 °C, and concentrated sulfuric acid is the catalyst. MEO-21 not only achieves an extreme pressure lubrication coefficient reduction rate (Δf) of 86.57% at room temperature, but maintains a stable performance after hot rolling at high temperatures. Hot rolling at 150 °C for 16 h, Δf was 85.25%, hot rolling at 180 °C for 16 h, Δf was 89.56%. MEO-21 was used as a base oil with other industrial by-product oils to compound and produce a high-temperature-resistant lubricant that was named L-541, L-541′s Δf was 90.39% at room temperature. L-541 was hot-rolling at 120 °C, 150 °C and 180 °C for 16 h, the Δf was stabled at 89%.

Revealing the Reactivity of Individual Chemical Entities in Complex Mixtures: the Chemistry Behind Bio-Oil Upgrading.

Bio-oils are precursors for biofuels but are highly corrosive necessitating further upgrading. Furthermore, bio-oil samples are highly complex and represent a broad range of chemistries. They are complex mixtures not simply because of the large number of poly-oxygenated compounds but because each composition can comprise many isomers with multiple functional groups. The use of hyphenated ultrahigh-resolution mass spectrometry affords the ability to separate isomeric species of complex mixtures. Here, we present for the first time, the use of this powerful analytical technique combined with chemical reactivity to gain greater insights into the reactivity of the individual isomeric species of bio-oils. A pyrolysis bio-oils and its esterified bio-oil were analyzed using gas chromatography coupled to Fourier transform ion cyclotron resonance mass spectrometry, and in-house software (KairosMS) was used for fast comparison of the hyphenated data sets. The data revealed a total of 10,368 isomers in the pyrolysis bio-oil and an increase to 18,827 isomers after esterification conditions. Furthermore, the comparison of the isomeric distribution before and after esterification provide new light on the reactivities within these complex mixtures; these reactivities would be expected to correspond with carboxylic acid, aldehyde, and ketone functional groups. Using this approach, it was possible to reveal the increased chemical complexity of bio-oils after upgrading and target detection of valuable compounds within the bio-oils. The combination of chemical reactions alongside with in-depth molecular characterization opens a new window for the understanding of the chemistry and reactivity of complex mixtures.

Biodiesel Production of Palm Oil Mill Effluent by Using Hydrotalcite Catalyst

Biodiesel is currently preferred for consumption and has been widely used as a substitute for diesel. This study aimed to determine the effect of various methanol-to-oil ratios in the esterification process and also the effect of hydrotalcite catalyst weight on the transesterification product. The catalyst was characterized with SEM, XRD, FTIR, and TG-DTG-DTA. The esterification process was operated at various oil-to-methanol ratios, i.e., 1:12-1:36 and the transesterification was performed using several catalyst weights, 0.5%-2.5%. The results showed that the optimum conditions of esterification were at the 1:30 molar ratio of oil-to-methanol, which decreased the amount of acid number by 95.75%, while the optimum condition of transesterification was at 1.5% catalyst weight. The characteristics of biodiesel using 0.5-2% hydrotalcite catalyst (acid number, total glycerol, free glycerol, ester levels, viscosity, density, oxidation stability) have met the Indonesian biodiesel standard of SNI-04-7182-2012.

Features of the synthesis of pentaerythritol esters and carboxylic acids of aliphatic isomeric structure

Objectives. Due to their structures, pentaerythritol esters have a number of appealing properties such as high viscosity index when used as oils and excellent compatibility with polyvinyl chloride when used as plasticizers. For the production of pentaerythritol and carboxylic acids, natural gas can be used as a feedstock, which implies a strategic development of the petrochemical industry, a decrease in the amount of gas used for combustion, and its applications for the production of chemical products.Methods. The synthesis process was conducted in a self-catalysis mode with excess acids in a molar ratio of 8:1 and in the presence of a solvent (toluene) of ~30% per reaction mass. This ensures a uniform distillation of the reaction water at a constant temperature of 100–110 °C, a decrease in the side reaction products, and an increase in process selectivity. The products from the reaction mass were isolated by vacuum distillation, and identification of all the synthesized tetraesters was performed by chromatography–mass spectrometry analysis.Results. This work proposes options for optimizing the conditions of the thermal esterification of pentaerythritol with isomeric monocarboxylic acids (isobutyric, isovaleric, pivalic, and 2-ethylhexanoic acids) that have different reactivities due to their structures. Methods for isolating tetraesters of pentaerythritol and corresponding acids have been developed. The characteristics of the main series of ions of tetraesters of pentaerythritol and aliphatic isomeric acids C4–C8 in the mass spectra were obtained.Conclusions. The yields of tetraesters were at 95%–96% of the theoretical value, and product purity was >99.6%. The resulting target products (tetraesters) were characterized by relative color stability, where the maximum degree of color after cleaning was less than 20 units according to Hazen (180 units for tetra-2-ethylhexnoate), which corresponds to the standards in GOST 29131-91 (ISO 2211-73). The esterification rates were compared, and it was shown that the quantitative yields of isomeric tetraesters at 100–110 °C were achieved in 12–15 h for isobutyric and isovaleric acids, 25–27 h for 2-ethyl-hexanoic acid, and ~40 h for pivalic acid.

Ferric perchlorate hydrate as a new catalyst for highly efficient esterification of cellulose at room temperature

Ferric perchlorate was tested for the first time as a new catalyst to accelerate the esterification of microcrystalline cellulose (MCC) at room temperature in a less amount of acetic anhydride compared to the amount used in the conventional methods. It was possible to manufacture cellulose acetate (CA) with a high yield of up to 94%. The influence of changes in reaction time, catalyst amounts, and acetic anhydride on the characterization of cellulose acetate produced was investigated. The optimum condition for esterification of 2.0 g (12.34 mmol) MCC was found to be: 10 mL (105.98 mmol) AC2O, 200 mg (0.564 mmol, anhydrous basis) of Fe(ClO4)3·xH2O and 1 h reaction time at room temperature. The substitution degree of CA was investigated by FTIR and 1H-NMR spectroscopy. Thermal stability of CA was studied using TGA, DTA and DSC analyses. The degree of polymerization and the polydispersity index (PDI) were obtained using Gel permeation chromatography (GPC). This study verified the direct and efficient synthesis of di- and tri-cellulose acetate in one–pot reaction using Fe(ClO4)3·xH2O as a catalyst without using solvent.

Fuzzy Optimization of the Esterification Conditions of Biodiesel Production from Karanja Oil

Fuzzy Optimization of the Esterification Conditions of Biodiesel Production from Karanja Oil

Characterization and Conversion of Sludge Palm Oil (SPO) into Biodiesel

Sludge Palm Oil (SPO) is a potential low-cost feedstock for biodiesel production. The conversion efficiency and the quality of biodiesel produced is governed by the feedstock and the conversion reaction. To our knowledge, the potential of SPO produced by palm oil mills in Sarawak has yet to be explored. Hence, this paper aims to characterize the SPO obtained from Sarawak palm oil mills and to optimize the predominant conversion reaction. The SPO was converted into biodiesel via a sulphuric acid catalyzed esterification reaction, followed by transesterification using potassium hydroxide and methanol.  This SPO contained 1.30 - 10.15% moisture, 2.91 - 7.63% sediment and 47.05 – 87.86% free fatty acids (FFA). The optimum esterification conditions identified were: SPO:methanol ratio (1:10), sulphuric acid concentration (1.84%) and reaction time (3.25 hr). Under these conditions, the biodiesel yield was 74% with an FFA conversion efficiency of 79.87%. The water produced during the esterification process was found to hinder the reaction, reducing both conversion efficiency and biodiesel yield. The findings of this study offer important insights about the challenges and feasibility of biodiesel conversion from SPO, where esterification is inevitable due to its high FFA content. &nbsp

Synthesis and characterization of new bifunctional SnZrSi oxide catalysts for biodiesel production

A set of unprecedented (mesoporous SnO2/ZrSiO4) solids has been synthesized via the ultrasound-assisted co-precipitation path. The impact of silica dopant content (ranged between 0.05 and 0.4 mol%) on the characterization evolution of the sonicated ZrSnO4 interface and their biodiesel production efficiency were examined. Physio-chemical characteristics of the synthesized catalysts were analyzed by XRD, SEM-EDS, TEM, TGA-DTG, N2 adsorption–desorption analysis, NH3-TPD, UV–Visible/ DR, and FT-IR before and after pyridine adsorption. The obtained results revealed the formation of reconstructed rutile-SnO2 and zircon as new active phases by calcination at 500 °C, good morphology with mesoporous structure, and significant increase in the SBET, pore volume, interesting optical behavior, and exhibited different acidic properties. The impacts of reaction temperature, silica dopant content, fatty acid type and calcination temperature on the biodiesel % were examined. The tertiary oxide catalysts were gainful for the biodiesel production. The optimum catalyst (0.2 % SiO2/ZrSnO4) had the biggest number of both strong Brönsted and Lewis acid sites compared to the doped and undoped catalysts, so, its maximum yield at optimum conditions for esterification of palmitic acid reaction was 90.2 % and can be reused until the fifth run with giving excellent yield for biodiesel production. But, for the transesterification of soybean oil reaction with methanol was maxima at 88% for (0.4 % SiO2/ZrSnO4) sample. The kinetic, mechanism studies and thermodynamic parameters were estimated. The important role of the doped silica molecules in the mechanism of the esterification process was emphasized by the computational chemistry study.

Sulfonated biochar catalyst derived from eucalyptus tree shed bark: synthesis, characterization and its evaluation in oleic acid esterification.

Herein, fatty acid (oleic acid, OA) was upgraded to fatty acid methyl ester (FAME) via esterification reaction using sulfonated biochar obtained from eucalyptus tree shed bark as solid acid catalyst. Under the optimal esterification conditions (i.e., at 65 °C for 2 h using a methanol/OA molar ratio of 10 : 1 with a catalyst dosage of 4 wt%), the FAME yield was 97.05 ± 0.28% when a solid acid catalyst prepared by loading 6 g of p-Toluenesulfonic acid (p-TSA) on 2 g of activated biochar (p-TSA3/ABC) was used. The remarkable performance of the p-TSA3/ABC could be attributed to its high acidity (468.8 μmol g−1) and dominance of the SO3H acid site on the catalyst surface. Experimental findings showed that the p-TSA3/ABC was relatively stable due to its highly functionalized structure. The catalyst was recycled for five successive cycles and exhibited no dramatic decrease in catalytic activity.

Syntheses of a Hyperbranched Polymer and Its Performance on Enhanced Oil Recovery.

A hyperbranched carboxylate-type polymer was synthesized through esterification and carboxymethylation, and its performance on enhanced oil recovery was experimentally evaluated. The optimum condition for esterification was 8 h at 120°C, where 3% PTSA as the catalyst and 9:1 mol ratio of the AB2 intermediate and trimethylolpropane were used. The optimum condition for carboxymethylation was 4 h at 80°C. The critical micelle concentration of the hyperbranched polymer was 433.63 mg/L, the Krafft point was 5°C, and the surface tension was lowered to 28 mN/m. In the range of 400–500 mg/L concentration, the adsorption onto the oil sand surface achieved equilibrium, and micellar solubilization reached 600 ml/mol. The interfacial tension can be lowered to a level of 10−2 mN/m by the single use of the hyperbranched polymer, and the value further decreased to a level of 10−3 mN/m while being formulated with sodium dodecylsulfate or NaOH. Oil recovery of water flooding was further enhanced by the single use of a hyperbranched polymer or the combination of hyperbranched polymer/sodium dodecylsulfate. The latter exhibited more prosperous advantages in low-permeability reservoirs.

Separation of squalene from olive oil deodorizer distillate using short‐path molecular distillation

AbstractSqualene was recovered from an olive oil deodorizer distillate (OODD) containing 40% of squalene by a two‐step process. The first step was to esterify the free fatty acids (FFAs) to make them less volatile. The second step was to separate the squalene by molecular distillation. The best esterification conditions were found to be 190°C and 360 min, where FFA content of the reaction mixture was reduced from 49.3% to 7.9%, however, an inevitable squalene loss (30%) was also observed due to a discontinuous operation. The remaining squalene (28%) in the esterified mixture was then distilled using a molecular distillation unit at elevated temperatures (190–230°C) and pressures (0.05–5 mmHg). When the temperature and vacuum during distillation increased, FFA content in the distillate reduced while distillate yield and squalene purity increased. The highest distillate yield (27.7%) and squalene purity (98.1%) were obtained at the highest applied temperature (230°C) under the lowest absolute pressure (0.05 mmHg), where FFA content of distillate was measured as 1.8%. High percentage of squalene (95%–98%) could be distilled at 230°C between 0.05 and 0.5 mmHg absolute pressures. The overall squalene recovery after all treatments was calculated as 68%.

Improved methods to characterize the length and quantity of highly unstable PolySialic acids subject category: (Carbohydrates, chromatographic techniques)

Polysialic acid (polySia) is a linear homopolymer of α2-8-linked sialic acids that is highly expressed during early stages of mammalian brain development and modulates a multitude of cellular functions. While degree of polymerization (DP) can affect such functions, currently available methods do not accurately characterize this parameter, because of the instability of the polymer. We developed two improved methods to characterize the DP and total polySia content in biological samples. PolySia chains with exposed reducing termini can be derivatized with DMB for subsequent HPLC analysis. However, application to biological samples of polySia-glycoproteins requires release of polySia chains from the underlying glycan, which is difficult to achieve without concurrent partial hydrolysis of the α2-8-linkages of the polySia chain, affecting its accurate characterization. We report an approach to protect internal α2-8sia linkages of long polySia chains, using previously known esterification conditions that generate stable polylactone structures. Such polylactonized molecules are more stable during acid hydrolysis release and acidic DMB derivatization. Additionally, we used the highly specific Endoneuraminidase-NF enzyme to discriminate polysialic acid and other sialic acid and developed an approach to precisely measure the total content of polySia in a biological sample. These two methods provide improved quantification and characterization of polySia.

Surface modification with cholesteryl acetyl carnitine, a novel cationic agent, elevates cancer cell uptake of the PEGylated liposomes

The present study aimed to synthesize cholesteryl acetyl carnitine (CAC), and surface modify the PEGylated liposomes with the intention of enhanced cancer cell uptake. For this, CAC synthesis was performed in amine-free esterification conditions and then four liposomal formulations of unmodified, CAC/PEG, and CAC + PEG-modified were prepared by ethanol injection method. Cytotoxicity of the liposomes was investigated in A549 cells, followed by cellular uptake assessments of coumarin 6 (C6)-loaded liposomes. The results of ATR-FTIR, 1HNMR, and 13CNMR demonstrated successful formation of CAC. A molecular docking study showed efficient binding affinities rather than carnitine to the active site of four carnitine transporters. Liposomal formulations possessed spherical morphology with a mean particle size range of 112–138 nm, narrow size distribution, and negative surface charge. All formulations had low cytotoxicity at 0.5 mg/ml, but high cytotoxicity at around 2.5 mg/ml. The lowest IC50 was obtained for CAC modified liposomes. CAC + PEG-modified liposomes had the highest cellular uptake.In conclusion, CAC + PEG modification of liposomes is an effective approach for increasing A549 cellular uptake, with low cytotoxicity at commonly applied liposome concentrations. The elevated uptake may be due to the involvement of the organic cation transporter, cationic structure, and the metabolic preference of CAC in cancer cells.

Optimization of conditions for esterification of thiodiacetic acid in urine using mathematical planning for biological monitoring

Introduction. To assess the impact of the toxicants vinyl chloride (VC) and 1,2-dichloroethane (DCE) on humans, personalized biomonitoring of thiodiacetic acid (TDAA) is of most significant importance. Determination of TDAA in urine was carried out using the method of gas chromatography-mass spectrometry GC-MS. Materials and methods. Sample preparation consists of the analyte’s esterification in a biological matrix with methyl alcohol (with 10% boron trifluoride), extraction of the derivative by liquid extraction with ethyl acetate. We used an Agilent 7890A gas chromatograph with an HP-5MS capillary column and a mass-selective detector. TDAA was identified in the form of a dimethyl ester on a mass chromatogram according to the retention time and the ratio of the intensities of the registered ions. Results. To determine the rational parameters of the sample preparation process for the determination of TDAA in urine studies were carried out under the method of planning the experiment, which makes it possible to obtain the most accurate mathematical description of the processes. Optimization of the conditions for esterification of TDAA was carried out using mathematical planning, varying the temperature, process time, and the nature of the catalyst (BF3 or H2SO4). The scheduling matrix included eight experiments; the degree of conversion of TDAA served as an optimization parameter. Interpretation of the model showed that temperature makes more contribution to the formation of the degree of conversion than the processing time. The nature of the catalyst does not affect the degree of conversion. Conclusion. A mathematical model developed for optimizing the conditions for sample preparation of the biomarker of exposure to VC (TDAA) in urine, showed the contribution of three factors (reaction temperature, reaction time, catalyst nature) to the conversion rate, of which the reaction temperature makes the greatest contribution to the choice of optimal esterification conditions. The nature of the catalyst (BF3 or H2SO4) does not affect the conversion rate.

Influence of asphaltene esterification conditions on product composition

The article is devoted to the study of reactivity and composition of oil asphaltene esterification products formed in reactions of various duration with and without solvent. As a result of the study, high reactivity of asphaltenes in reaction of esterification with isopropyl alcohol for 40 hours was first shown. Products contain 40 % wt. of fractions soluble in n-heptane and isopropyl alcohol. The increase in the duration of the reaction from 40 to 120 hours leads to counter reaction with the decrease in forming less polar substances by 5-6 % wt. Adding solvent (benzene) into the reaction mixture also negatively influences the effectiveness of asphaltene esterification for 40 hours. The results obtained show that the suggested approach is promising for chemical processing of asphaltene concentrates into less polar low-molecular products.

Effect of Esterification Conditions on the Physicochemical Properties of Phosphorylated Potato Starch.

The aim of this study was to evaluate the effect of the temperature (15 or 45 °C) and the duration (15–120 min) of the modification process on the selected physicochemical, thermal, and rheological properties of phosphorylated potato starch. The modified starches contained 93.6–98.2 mg P/100 g (dry weight basis, d.w.b.). Phosphorylation caused color changes with a total color difference between the starches below 0.55, but these changes were less than those that were recognizable by the human eye. The thermal analysis showed two opposite processes appearing during the modification: the loosening of the structure (dominant among starches obtained at 15 °C) and the strengthening of the structure (dominant among starches obtained at 45 °C). The higher phosphorylation temperature reduced native starch recovery from 140% to 87–116% and increased the hysteresis loop area from −169 to 1040. All of the pastes made from the modified starches showed a weaker tendency for retrogradation (during 21 days of storage) than native starches. The results of the regression analysis conducted between the properties of the starch pastes obtained at 45 °C indicated that the modification time appeared to be a better indicator of the rate of modification progress than the phosphorus content. The PCA (principal component analysis) results made it possible to distinguish starch phosphates obtained at 15 °C from those obtained at 45 °C and those from natural starch.

Systematic Studies of Sodium γ-Octyl Aspartate to evaluate its Biodegradation, Surface Parameters, Micellization Aspects and Thermodynamic Properties of its Binary Mixture using Electrolytes

γ-octyl aspartate has been synthesized with 46.2% yield. The optimized conditions for esterification of aspartic acid and n-octanol are 24 hours duration and 1:1 molar ratio of reactants (aspartic acid: n-octanol). FT-IR, 1H NMR and CHNS element analysis techniques are used for structure elucidation of γ -octyl aspartate. Surface/ interfacial studies, micellization aspects, thermodynamic parameters, biodegradability and binary salt behaviour of sodium γ-octyl aspartate have been studied. The CMC of synthesized surfactants was 0.0078 mol/L, whereas minimum surface area per surfactant molecule was calculated as 29.49 Å2m2; calculated aggregation number was 34 and micelle radius (r) found to be 1.40 nm. The degree of counter-ion dissociation (α) was determined to be 0.86. Thermodynamic parameter - standard free energy of adsorption (ΔG0ads) was calculated as -18.70 kJ/mol. The shape of micelle of synthesized surfactant was noticed to be spherical but during binary studies in some cases, it was found to be cylindrical. OECD and Winkler’s method were used to determine biodegradation of sodium γ-octyl aspartate found to be 95.1 %.

Biolubricant production under zero-waste Moringa oleifera Lam biorefinery approach for boosting circular economy

Here, we present a biorefinery perspective for biolubricant production with the valorisation of solid waste from Moringa oleifera Lam oil extraction (WMO). To achieve this, WMO, silica (SiO2), and a hybrid (SiO2–WMO) were prepared and employed as supports for the immobilisation of Candida rugosa lipase (CRL) via interfacial adsorption. The matrixes and immobilised biocatalysts were characterised by FTIR and AFM. The SiO2–WMO matrix was the most suitable, providing an immobilisation yield of 86 %. In the optimised conditions of esterification (40 °C, equimolar acid/alcohol ratio, and 22.6 mg/g of immobilised protein loading) in solvent-free medium, SiO2–WMO–CRL presented the best performance (94 % conversion) and retained its original activity after eight cycles. Furthermore, isoamyl esters exhibited physicochemical properties similar to those of commercial lubricants and could favourably be used as biolubricants in hydraulic machines and equipment. This pioneering work provides the opportunity for effective and cleaner production of biolubricants under a zero-waste Moringa oleifera Lam biorefinery approach.