Triacetin Research Articles

Studies on the melt viscosity and physico-chemical properties of cellulose acetate propionate composites with lactic acid blends

Cellulose acetate has a high melting temperature due to intense intermolecular hydrogen bonding and is not significantly different from the deterioration temperature, so decomposition may occur during processing. Generally, in order to prevent pyrolysis of CA in the melting process, it is dissolved by using a solvent such as CS2 or H2SO4. However, it is not suitable for extrusion and injection process, and plasticized CA composition is prepared using plasticizer. In general, Dioctyl phthalate (DOP) is the most widely used plasticizer, and polyethylene glycol (PEG), glycerin (GC) triacetin (TA) and the like are partly used as environmentally friendly plasticizers. In this study, lactic acid was used as a compatibilizer and viscosity modifier in addition to plasticizer to prepare a composite. When the content of lactic acid is 5 wt% or more, phase separation occurs, so that the viscosity of the composition is controlled by blending in the range of 1 ∼ 5 wt%. The melting characteristics of the prepared compositions were confirmed by DSC and TGA, and specimens were prepared by injection molding. The effect of lactic acid content on the melt viscosity was measured and the yield stress, yield strain and elastic modulus were calculated by the evaluation of tensile properties. The composition of this study showed a viscosity change of about 10 ∼ 50% compared with the conventional one and the thermal properties were also different. The thermal properties were also different. In addition, the change of mechanical strength was observed depending on the degree of commercialization of additives.

Synergistic effect of functional groups in carbonaceous spheres on the formation of fuel enhancers from glycerol

Carbonaceous microspheres with tunable surface chemistry were prepared via sustainable hydrothermal carbonization combined with subsequent thermal treatment and/or SO3H-functionalization (with sulfuric acid or 4-benzenediazonium sulfonate). Various techniques (including SEM and TEM, elemental and textural analysis, potentiometric titration, TGA method, and XPS measurement) were used for determination of physico-chemical properties of the obtained materials. The results revealed that the effectiveness of applied acidic modifications was related to the structural features of the samples. Catalytic properties of the sulfonated carbons were further tested in glycerol acetylation with acetic acid performed in a batch mode at 80 °C. The experiments showed that the carbonaceous spheres treated with sulfuric acid were very active in the reaction, giving high glycerol conversion and high combined selectivity to diacetin (DA) and triacetin (TA), important fuel enhancers, after a relatively short time. Especially good results were achieved using SO3H-functionalized spheres richly decorated with oxygen groups such as carboxylic and hydroxyl/phenol ones. Finally, reusability measurements demonstrated good catalyst stability in subsequent reaction cycles. Additional investigations of the re-used system confirmed only small leaching of active sites from the tested material.

Scalable Green Approach Toward Fragrant Acetates.

The advantageous properties of ethylene glycol diacetate (EGDA) qualify it as a useful substitute for glycerol triacetate (GTA) for various green applications. We scrutinised the lipase-mediated acetylation of structurally diverse alcohols in neat EGDA furnishing the range of naturally occurring fragrant acetates. We found that such enzymatic system exhibits high reactivity and selectivity towards activated (homo) allylic and non-activated primary/secondary alcohols. This feature was utilised in the scalable multigram synthesis of fragrant (Z)-hex-3-en-1-yl acetate in 70% yield. In addition, the Lipozyme 435/EGDA system was also found to be applicable for the chemo-selective acetylation of (hydroxyalkyl) phenols as well as for the kinetic resolution of chiral secondary alcohols. Lastly, its discrimination power was demonstrated in competitive experiments of equimolar mixtures of two isomeric alcohols. This enabled the practical synthesis of 1-pentyl acetate isolated as a single product in 68% yield from the equimolar mixture of 1-pentanol and 3-pentanol.

Improvement in mechanical properties and biodegradability of PLA using poly(ethylene glycol) and triacetin for antibacterial wound dressing applications.

Wound is among the most common injuries. A suitable wound dressing has a significant effect on the healing process. In this study, a porous wound dressing was prepared using poly (lactic acid) (PLA) and two plasticizers, polyethylene glycol (PEG) and triacetin (TA), through solvent casting method. For antibacterial activities, metronidazole was incorporated in the structure. The morphology was investigated by scanning electron microscopy (SEM). In addition, the effect of plasticizers ratio on porosity growth was evaluated. It was also observed that each had a unique effect on the structure's porosity. The mechanical properties confirmed the effect of both plasticizers on increasing polymer softness and flexibility, and the most similar formulations to human skin in terms of mechanical properties were introduced. According to the results, TA had stronger effect on mechanical properties. The differential scanning calorimetry (DSC) showed the effect of increasing plasticizer concentration on crystalline structure and Tm reduction of PLA. The water contact angle measurement showed that both plasticizers enhanced hydrophilic characteristics of PLA, and this effect was weaker in PEG-containing formulations. The in vitro degradation study showed biodegradability, as a desirable property in wound dressing. Results suggested that higher degradation can be obtained by both plasticizers at the same time. The results also showed that PEG was more effective in enhancing water absorbency. In vitro drug release study indicated an explosive release and the highest amount was 85% over 186h. The antibacterial activity test confirmed the effectiveness of the drug in preventing bacterial growth in the drug-containing formulations, while it showed the antibacterial property of TA. MTT assay was performed and the cellular toxicity of the formulations was checked and those that revealed the least toxicity were introduced.

Interesterification of grease trap waste lipids using methyl acetate under supercritical conditions

The production of fatty acid methyl esters (FAMEs) and triacetin (TA) from the lipids of the grease trap waste (GTW) using methyl acetate (MA) under pressurized conditions was investigated. The experiments evaluating the effect of temperature (275–350 ºC), residence time (10–30 min), addition of water (2.5–10 wt% in relation to the MA), free fatty acid (FFA) content (25 and 50 wt% in the GTW) in the formation of FAMEs and TA. The results show that an increase in temperature favors the FAME production in the first 10 min of reaction and from 20 min onward the yield increases at 300 °C and decreases at 325 °C. The TA production was higher in 30 min at 300 ºC. The addition of up to 5 wt% water (in MA) showed a similar yield, while higher contents leads to a reduction in the FAME production after 30 min. The use of a feedstock with up to 50 wt% (by mass) of FFAs has little influence on the formation of FAMEs and leads to lower amounts of TA. The reaction with MA (5 wt% of water) provided a sample with 57 % of FAMEs and 1.4 wt% of TA.

Sulphuric acid-functionalized siliceous zirconia as an efficient and reusable catalyst for the synthesis of glycerol triacetate

In the present study, a sulphated siliceous zirconia catalyst (SSZ-550) has been prepared and characterized by XRD and FTIR analysis to indicate the incorporation of sulphate group over the matrix. X-ray photoelectron spectroscopy also revealed that sulphur group was incorporated over the matrix to impart the Bronsted acidity to the catalyst which is vital for the acetylation activity. To optimize the reaction parameters, viz. reagent molar ratios (3–12; glycerol/acetic acid), catalyst amount (1–5 wt%; catalyst/glycerol), reaction duration (20–50 min) and reaction temperature (30–100 °C) have been varied to obtain the optimum catalyst activity for the maximum glycerol triacetate yield. Finally, under the optimized reaction parameters of 9:1 glycerol/acetic acid molar ratio, 3 wt% catalyst, 80 °C reaction temperature and 40 min of reaction duration, a 93% glycerol triacetate yield was obtained. The catalyst was recovered from the reaction mixture and reused during six consecutive reaction runs while retaining 50% glycerol triacetate selectivity in the last cycle. A plausible mechanism suggests the heterogeneous catalyst-assisted protonation of carbonyl group of acetic acid to initiate the stepwise esterification of the hydroxyl groups of glycerol.

Hierarchical H-ZSM-5 zeolite and sulfonic SBA-15: The properties of acidic H and behavior in acetylation and alkylation reactions

A commercial H-ZSM-5 zeolite was modified by alkaline treatment using NaOH solutions in different concentrations, followed by consecutive ion exchanges with NH4NO3 solution in order to recover the acidic form of the material. According to the intensity of the treatment, mesoporosity with pore size ranged between 9 and 13 nm was generated in the zeolite. Also, the strength and number of acid sites were practically maintained, observing only a noticeable decrease for the more intense treatment. After testing in the glycerol acetylation reaction, some improvements in the activity were observed compared to the original zeolite, but no appreciable increment in the selectivity to diacetin (DA) and triacetin (TA) was reached. However, when a mesoporous SBA-15 functionalized with propylsulfonic acid groups was used as catalyst, the selectivities to DA and TA were noticeably enhanced. Moreover, the zeolites were tested in the isobutane/butene alkylation reaction in gas phase, and also in this case the modified materials did not favor the production of trimethylpentanes (TMPs) compared to the original zeolite. Characterization results allowed to conclude that the mesopores formed in the zeolite after the modification facilitated the accessibility of reactants and products to some acid sites, but these have not enough concentration, being most of them located in the micropores of the zeolite. H-D exchange in sulfonic SBA-15 prior to butene pulses demonstrated that its acidic H has not capacity for butenes adsorption. This explains the lack of activity of this catalyst in the isobutane/butene alkylation reaction.

Sequential process for obtaining methyl esters and triacetin from crambe oil using pressurized methyl acetate

The aim of this study was to investigate the application of a sequential process for the production of fatty acid methyl esters (FAME) and triacetin (TA) from crambe seeds using methyl acetate (MA) under pressurized conditions. In this process, methyl acetate acts as an extraction solvent and an acyl acceptor for the conversion of the oil to the products of interest. The initial step was pressurized liquid extraction (PLE) performed in a semi-continuous experiment (140 °C and 10 MPa) and material resulting from this step (oil+MA) was directed to a continuous reaction unit. The tests were performed with different pressures, temperatures and residence times. Reactions with commercial oil (CO) were evaluated for comparison. According to the data obtained, increasing the pressure to 20 MPa resulted in higher FAME yields (YFAME) and TA contents for both oils tested. In the reaction with the PLE mixture an increase in temperature favored the formation of FAME and a yield of 66.49 % was achieved at 375 °C after 15 min. The TA content was highest at 325 °C and 5.01 wt% of this coproduct was obtained after 35 min. At the other temperatures, an increase in the TA content was not observed after 15 min. The results obtained in the reactions with CO demonstrated lower than those for the oil obtained by PLE and the reduction of polyunsaturated esters was more evident in the reaction products of this oil. At 375 °C, the increase in residence time provided higher conversion of triglycerides and free fatty acids, as well as higher consumption of intermediate reaction compounds, and enhanced levels of thermal degradation. Thus, the results point to the benefits of using the sequential process to obtain FAME and TA in terms of yield and reduction of the decomposed fraction.

Acetate supplementation restores chromatin accessibility and promotes tumor cell differentiation under hypoxia

Despite the fact that Otto H. Warburg discovered the Warburg effect almost one hundred years ago, why cancer cells waste most of the glucose carbon as lactate remains an enigma. Warburg proposed a connection between the Warburg effect and cell dedifferentiation. Hypoxia is a common tumor microenvironmental stress that induces the Warburg effect and blocks tumor cell differentiation. The underlying mechanism by which this occurs is poorly understood, and no effective therapeutic strategy has been developed to overcome this resistance to differentiation. Using a neuroblastoma differentiation model, we discovered that hypoxia repressed cell differentiation through reducing cellular acetyl-CoA levels, leading to reduction of global histone acetylation and chromatin accessibility. The metabolic switch triggering this global histone hypoacetylation was the induction of pyruvate dehydrogenase kinases (PDK1 and PDK3). Inhibition of PDKs using dichloroacetate (DCA) restored acetyl-CoA generation and histone acetylation under hypoxia. Knocking down PDK1 induced neuroblastoma cell differentiation, highlighting the critical role of PDK1 in cell fate control. Importantly, acetate or glycerol triacetate (GTA) supplementation restored differentiation markers expression and neuron differentiation under hypoxia. Moreover, ATAC-Seq analysis demonstrated that hypoxia treatment significantly reduced chromatin accessibility at RAR/RXR binding sites, which can be restored by acetate supplementation. In addition, hypoxia-induced histone hypermethylation by increasing 2-hydroxyglutarate (2HG) and reducing α-ketoglutarate (αKG). αKG supplementation reduced histone hypermethylation upon hypoxia, but did not restore histone acetylation or differentiation markers expression. Together, these findings suggest that diverting pyruvate flux away from acetyl-CoA generation to lactate production is the key mechanism that Warburg effect drives dedifferentiation and tumorigenesis. We propose that combining differentiation therapy with acetate/GTA supplementation might represent an effective therapy against neuroblastoma.

Application of bio-based solvents for biocatalysed synthesis of amides with Pseudomonas stutzeri lipase (PSL)

Abstract Bio-based solvents were investigated for the biocatalysed amidation reactions of various ester-amine combinations by Pseudomonas stutzeri lipase (PSL). Reactions were undertaken in a range of green and potentially bio-based solvents including terpinolene, p-cymene, limonene, 2-methyl THF, ɣ-valerolactone, propylene carbonate, dimethyl isosorbide, glycerol triacetate and water. Solvent screenings demonstrated the importance and potential of using non-polar bio-based solvents for favouring aminolysis over hydrolysis; whilst substrate screenings highlighted the unfavourable impact of reactants bearing bulky para- or 4-substituents. Renewable terpene-based solvents (terpinolene, p-cymene, D-limonene) were demonstrated to be suitable bio-based media for PSL amidation reactions. Such solvents could provide a greener and more sustainable alternative to traditional petrochemical derived non-polar solvents. Importantly, once the enzyme (either PSL or CALB) binds with a bulky para-substituted substrate, only small reagents are able to access the active site. This therefore limits the possibility for aminolysis to take place, thereby promoting the hydrolysis. This mechanism of binding supports the widely accepted ‘Ping Pong – Bi Bi’ mechanism used to describe enzyme kinetics. The work highlights the need to further investigate enzyme activity in relation to para- or 4-substituted substrates. A priority in PSL chemistry remains a methodology to tackle the competing hydrolysis reaction.

Conversion of Crude Glycerol from by-Product Biodiesel into Bio-additive of Fuel through Acetylation Reaction based on Modified Zeolite Catalyst

<p class="BodyAbstract">Biodiesel is one of the alternative fuels produced from the transesterification reaction between triglycerides and alcohols with glycerol by-products. So far, the resulting crude glycerol has not been maximally utilized because of its low purity. So, it is necessary to purify glycerol before turning it into a more useful compound. The purified glycerol can be reacted with acetic acid within esterification reaction (acetylation process) using an acid catalyst to produce glycerol triacetate (triacetin). One of the uses of triacetin as an additive in gasoline and biodiesel. The purpose of this study is to utilize glycerol from by-products from biodiesel production to bio-additive materials that can improve fuel quality and are environmentally friendly. The method used in this study begins with the purification of crude glycerol, modification of zeolite catalyst with impregnated of nickel metal followed by an acetylation reaction which held on temperature of 100°C for 60 min. The experimental results are analyzed using base titration to determine the remaining unreacted acids and are applied as bio-additives by adding them to commercial fuels and measured the increasing octane numbers. The result shows that the reaction conversion increases with increasing mole ratio of reactants and catalysts with the best results in the mole ratio of acetic acid and glycerol is 9:1 and catalyst 5% by weight of acetic acid with a conversion of 66.02%. As bio-additives the reaction product could increase the octane number of commercial fuel by 6.5 up to 8.5%.</p><p> </p>Keywords: glycerol, acetylation reaction, mofified zeolite, bio-additive

Determinants of zero-order release kinetics from acetaminophen-layered Suglet® pellets, Wurster-coated with plasticized Aquacoat® ECD (ethyl cellulose dispersion).

The potential for zero-order drug-release was evaluated for ethyl cellulose (EC) coated, acetaminophen-layered sugar pellets (Suglets®) of mesh size 18/20 (850-1000μm). To determine optimal plasticizer/pore-former concentrations for EC films, solvent-cast Aquacoat® ECD (ethyl cellulose dispersion) films were prepared with 0-50% w/w ratios of two triethyl citrate (TEC) or triacetin (TA). Characterization studies showed that films with excipient concentrations ≥20% were homogenous, mechanically strong at room temperature (Young's modulus of 25-35MPa), and have a glass transition (Tg) in the range of 20-45°C. Based on these results, a working range of 20-50% weight concentrations was selected for drug release studies. Suglets® were layered with acetaminophen (APAP) using Wurster Glatt GPCG-3 to yield roughly 10% w/w coating (controls). The Controls were coated using the same Wurster process with Aquacoat® ECD containing 20-50% w/w of TEC or TA. Samples were removed periodically at 3-11% weight gain, to evaluate impact of weight gain, and consequently film-formation, on drug release. Dissolution was monitored over a period of 12h in a media consisting of simulated gastric fluid (first two hours), followed by simulated intestinal fluid. The controls showed near 100% release within the first 30min, indicating the value of EC-coating to achieve controlled release. Dissolution release profiles showed that TEC is more effective than TA as a plasticizer and pore-former, as linear profiles were apparent at lower concentrations and % weight gain. For a quantitative evaluation of these results, linear regression was fitted to all cumulative release profiles, and R-squared values examined as a function of excipient concentration and % weight gain. The corresponding response surface plots and the second order regression were shown to aid in optimization. The design space for zero-order release was represented as contour plots between excipient concentration and % weight gain.

Modulating the properties of polylactic acid for packaging applications using biobased plasticizers and naturally obtained fillers

The properties of PLA films intended for packaging applications have been modulated by using bio-based platicizers and naturally obtained fillers. Triethyl citrate (TEC) and glycerol triacetate (GTA) have been used as platicizers and halloysite nanotubes (HNT) and chitosan have been used as fillers. The addition of 10 wt% TEC, 10 wt% GTA and 3 wt% HNT improves the ductility of PLA films, however, reduces the tensile modulus and tensile strength. Addition of chitosan (1 wt%), on the other hand, acts as a good reinforcing filler and improves the tensile strength and tensile modulus. PLA-HNT-chitosan film show comparable tensile strength, tensile modulus and ~12 times higher elongation at break compared to pure PLA. Besides, PLA-HNT-chitosan film demonstrates very good barrier properties against moisture and ultraviolet (UV) rays. Additionally, its antibacterial efficacy against E. coli and S. aureus are found to be around 80% and 70%, respectively. The study demonstrates the complementary effects of HNT and chitosan to modulate the properties of PLA film and indicates that the PLA-HNT-chitosan film can emerge as a very potent material for packaging applications.

Effect of Polymer Permeability and Solvent Removal Rate on In Situ Forming Implants: Drug Burst Release and Microstructure.

To explore the mechanism of drug release and depot formation of in situ forming implants (ISFIs), osthole-loaded ISFIs were prepared by dissolving polylactide, poly(lactide-co-glycolide), polycaprolactone, or poly(trimethylene carbonate) in different organic solvents, including N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), and triacetin (TA). Drug release, polymer degradation, solvent removal rate and depot microstructure were examined. The burst release effect could be reduced by using solvents exhibit slow forming phase inversion and less permeable polymers. Both the drug burst release and polymer depot microstructure were closely related to the removal rate of organic solvent. Polymers with higher permeability often displayed faster drug and solvent diffusion rates. Due to high polymer-solvent affinity, some of the organic solvent remained in the depot even after the implant was completely formed. The residual of organic solvent could be predicted by solubility parameters. The ISFI showed a lower initial release in vivo than that in vitro. In summary, the effects of different polymers and solvents on drug release and depot formation in ISFI systems were extensively investigated and discussed in this article. The two main factors, polymer permeability and solvent removal rate, were involved in different stages of drug release and depot formation in ISFI systems.

Control of Pore Size in Ordered Mesoporous Carbon-Silica by Hansen Solubility Parameters of Swelling Agent.

The cooperative assembly of functional precursors with block copolymers (BCPs) is a powerful, general route to fabricate ordered mesoporous materials, but the precise tuning of the mesopore size generally requires trial and error to obtain the correct BCP template or appropriate swelling agent. Here, we demonstrate the ability to effectively modulate both expansion and contraction of the ordered cylindrical mesopores relative to those obtained from cooperatively assembled Pluronic F127, resol, and tetraethylorthosilicate. The two key physical parameters for the swelling agents are their hydrophobicity, as quantified by the octanol-water partition coefficient (Kow), and Hansen solubility parameters that describe the interactions of the solvent with the different components of the BCP template. Four low volatility solvents are examined that span a wide Kow with up to 90 wt % solvent relative to the Pluronic F127. Glycerol triacetate (Kow < 1) can decrease the average mesopore size from 5.9 to 4.8 nm due to segmental screening of the interactions in the Pluronic F127 to decrease chain stretching at intermediate loadings. A modest increase in mesopore size to 8.1 nm can be achieved with trimethylbenzene (TMB, Kow = 3.42). Dioctyl phthalate (DOP), which is slightly more hydrophobic (Kow = 8.1), is more effective than TMB at expanding the pore size (maximum: 13.5 nm) without loss of ordered structure. A more hydrophobic solvent, tris (2-ethylhexyl) trimellitate (Kow = 12.5), is less effective at increasing the pore size (maximum: 8.2 nm). The Hansen solubility parameters for DOP most closely match those of the hydrophobic segment in the Pluronic F217 template. We attribute this similarity, which is related to the solvent quality, to the improved efficacy of DOP in increasing the pore size. These results illustrate that both the Hansen solubility parameters (relative to the hydrophobic segment of the template) and relative hydrophobicity of the swelling agent determine the obtainable pore sizes in cooperatively assembled ordered mesoporous materials.

P: 73 Acetate Attenuates the Astrocyte Swelling and Brain Edema in Severe Liver Failure

BACKGROUND: Astrocyte swelling and brain edema are major complications of severe liver failure. Ammonia plays a major role in the development of astrocyte swelling/brain edema in this condition. However, current therapies have not thus far improved the outcome of liver failure induced astrocyte swelling/brain edema. Since acetate has been shown to have neuroprotective effect in other neurological conditions, likely though increased energy production, we examined whether acetate similarly protect cell swelling in cultured astrocytes post-ammonia exposure. We also examined whether treatment of rats with glyceryl triacetate (GTA), an acetate precursor, which is known to increase circulating, as well as tissue levels of acetate, alleviates the brain edema induced by the liver toxin thioacetamide (TAA). METHODS: Astrocyte cell volume was estimated by measuring the intracellular water space using 3-O-methylglucose. Brain water content was measured by using the gravimetric method. RESULTS: Exposure of astrocyte cultures to pathological concentrations of ammonia (NH4Cl; 5 mM) for 24 h significantly increased cell swelling. Co-treatment of ammonia with acetate reduced such swelling in a dose-dependent manner. Further, treatment of rats with TAA (250 mg/kg bw) for 3 days increased the brain water content, and that pretreatment of (intragastrically) TAA-treated rats with GTA (7.5 g/kg bw), attenuated brain edema. CONCLUSIONS: These findings strongly suggest that acetate supplementation will exert salutary effects in reducing brain edema in patients with severe liver failure.

Combustion of CL-20 cocrystals

Combustion behavior, flame structure, and thermal decomposition of bimolecular crystals of hexanitrohexaazaisowurtzitane (CL-20) with glycerol triacetate (GTA), tris[1,2,5]oxadiazolo[3,4-b:3′,4′-d:3″,4″-f]azepine-7-amine (ATFAz), 4,4′′-dinitro-ter-furazan (BNTF), oxepino[2,3-c:4,5-c′:6,7-c′′]trisfurazan (OTF), oxepino[2,3-c:4,5-c′:6,7-c′′]trisfurazan-1-oxide (OTFO) have been studied by using a constant-pressure bomb, microthermocouple technique, and TG/DSC analysis. It has been found that the introduction of volatile and thermally stable compounds into the composition with CL-20 brought about unexpected results: first, the thermally stable component decreased the thermal stability of CL-20, and second, even twofold dilution of rapidly-burning CL-20 with slow-burning compound may practically does not change the burning rate of the former. It was suggested that a reason for the observed phenomena might be amorphous CL-20 which remains after evaporation of the volatile component in the combustion wave. The above assumption was confirmed by combustion modeling of bimolecular crystals in a wide pressure interval. It has been found that the combustion mechanism of the CL-20 cocrystals depends both on the burning rate of the second component and its volatility. Depending on these parameters, several combustion models of cocrystals are implemented: the burning rate is determined by (1) the CL-20 heat release kinetics at its boiling temperature, (2) the CL-20 heat release kinetics at the boiling point of the second component and (3) by the heat flow from the gas phase. It is abundantly clear that all these combustion mechanisms can be realized in real CL-20-based propellants.

BIOFUEL VIA INTERESTERIFICATION OF RAPESEED OIL WITH METHYL ACETATE IN PRESENCE OF POTASSIUM t-BUTOXIDE/THF

Transesterification does not allow to make full conversion of oil to biodiesel because the by-product glycerol cannot be included in the composition of biofuel. Interesterification constitutes a full conversion process with production of triacetin (TA) instead of glycerol, which can be included in the composition of biofuel and allows to increase its yield. Both interesterification and transesterification effectively occur only in presence of catalysts. Results of the investigation of heterogeneous and homogeneous catalysts indicate the superior importance of catalyst solubility in starting reaction mixture. Partial solubility can remarkably lower the activity of homogeneous catalyst and extremely increase that of formally heterogeneous one. The reaction mixture of interesterification reaction is less polar than that of transesterification, and potassium tert-butoxide (t-BuOK) should be more appropriate catalyst for interesterification than sodium methoxide which is used in most cases. The catalytic system t-BuOK/t-BuOH substantially increases the yield of TA and changes the properties of obtained biofuel. Whereas the content of the TA in the interesterification reaction mixture does not achieve the same level from the theoretically predicted as the FAME, the occurrence of side reaction between t-BuOH and TA cannot be excluded. This paper presents a study of the interesterification of rapeseed oil in presence of catalytic system t-BuOK/THF (catalytic system without alcohols) with the aim of establishing the influence of aprotic tetrahydrofuran to the proceeding the reaction, composition of reaction mixtures and their fuel properties. Obtained results show that the absence of alcoholic hydroxyl groups in the catalytic system insufficiently increases the activity of catalytic system but fails to increase the yield of FAME.

Fabrication and Optimization of a Lipase Immobilized Enzymatic Membrane Bioreactor based on Polysulfone Gradient-Pore Hollow Fiber Membrane

Enzymatic membrane bioreactors (EMBRs) possess the characteristic of combining catalysis with separation, and therefore have promising application potentials. In order to achieve a high-performance EMBR, membrane property, as well as operating parameters, should give special cause for concerns. In this work, an EMBR based on hollow fiber polysulfone microfiltration membranes with radial gradient pore structure was fabricated and enzyme immobilization was achieved through pressure-driven filtration. Lipase from Candida rugosa was used for immobilization and EMBR performance was studied with the enzymatic hydrolysis of glycerol triacetate as a model reaction. The influences of membrane pore diameter, substrate feed direction as well as operational parameters of operation pressure, substrate concentration, and temperature on the EMBR activity were investigated with the production of hydrolysates kinetically fitted. The complete EMBR system showed the highest activity of 1.07 × 104 U⋅g−1. The results in this work indicate future efforts for improvement in EMBR.

Investigation of the PES microfiltration membrane fouling characteristics for five substances

This article proposes two new concepts, adsorption and rejection accumulation and the membrane fouling efficiency per unit accumulation to quantitatively characterize the membrane fouling capacity of different single substances. The membrane fouling caused by bovine serum albumin (BSA), sucrose, glycerol triacetate, l-glutathione and maltodextrin on a polyethersulfone (PES) microfiltration membrane was studied. The real-time variations in filtrate concentration and transmembrane pressure were measured with an ultraviolet (UV) detector and pressure sensor during constant-flux filtration. The results showed that the PES membrane had rejection effects for the five substances. However, adsorption phenomena on the PES membrane were observed only for BSA and l-glutathione filtration. The membrane fouling capacity depended on the accumulation and fouling coefficient of the fouling component. The adsorption and rejection accumulation over 40 min followed the order of BSA (1441.39 µg·cm−2) > sucrose (908.53 µg·cm−2) > glycerol triacetate (290.29 µg·cm−2) > l-glutathione (145.18 µg·cm−2), while the membrane fouling efficiency per unit accumulation followed the order of l-glutathione (6.06 × 108 m−1·µg−1·cm2)>BSA (2.44 × 108 m−1·µg−1·cm2) > glycerol triacetate (2.08 × 108 m−1·µg−1·cm2) > sucrose (8.41 × 107m−1·µg−1·cm2). Based on these two factors, the membrane fouling was the most severe with BSA, followed by sucrose, l-glutathione and glycerol triacetate. The membrane fouling caused by maltodextrin was severe in the early stage and weakened in the later period due to the periodic formation and collapse of the maltodextrin cake layer on the membrane surface.