Triacetyl Glycerol Research Articles

Deep eutectic solvent incorporated AC/MIL-101 hybrid material catalysts for the production of fuel additives (acetins) from by-product glycerol

In this work, grafting of an AC/MIL-101(Cr) hybrid sample using acidic deep eutectic solvent (DES) was performed to enhance the acidity and catalytic activity for the acetylation reaction of glycerol. DESs are green solvents and have many advantages, such as easy preparation with the mixing of two or three components, high biodegradability, and an environmentally friendly nature. The synthesized hybrid materials, AC/MIL-101 and AC/MIL-101/DES, were characterized using different characterization methods such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), nitrogen (N2) adsorption, Fourier transform infrared (FTIR), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and potentiometric titration to elucidate the structure of the material. AC/MIL-101 and AC/MIL-101/DES composite catalysts were used in the acetylation of glycerol reactions as heterogeneous catalysts. The AC/MIL-101/DES sample gave higher triacetyl glycerol (TAG) selectivity and glycerol conversion in the acetylation reaction of glycerol. The catalytic activity was increased via the incorporation of deep eutectic solvent (DES) into the AC/MIL-101 structure. The acidity value increased after incorporation of DES into the AC/MIL-101 structure, so the TAG selectivity value increased from 1.20 to 3.31% at 90 °C. The maximum conversion of glycerol was found to be 100%, and TAG selectivity was increased up to 15.88% by changing the process conditions. In addition, the AC/MIL-101/DES sample could be regenerated and recycled without any decrement in TAG selectivity or glycerol conversion values.

Efficiently and directly produce triacetylglycerol from oils and fats over mesoporous polymeric solid acid catalysts

A series of mesoporous solid acid catalysts (PDS-x) with large BET surface area, superior thermal stability, strong sulfonic acid groups and tunable Brønsted acidity were synthesized by the copolymerization of divinylbenzene (DVB) and sodium p-styrenesulfonate (SPSS). The PDS-x catalysts showed high activity on the direct and efficient production of triacetylglycerol (TAG) via acyl exchange reaction of oils (fats) and acetic acid. The highest TAG yield of 93.0 mol% was obtained on the PDS-x catalysts at a mild condition of 200 °C. By combining SEM, TEM, FT-IR/DRIFTS, BET, XRD, XPS, EA, 31P MAS NMR and TG-DTG, the key factors that affected the TAG yield were clarified on the PDS-x catalysts. Moreover, the origin of the slow deactivation on these catalysts was elucidated. The large BET surface area and abundant mesopores of catalysts allowed the contact of large-sized oils (fats) with the strong sulfonic acid groups, accounting for the high TAG yield.

Determination of kinetic constants for glycerol acetylation by particle swarm optimization algorithm

The esterification of glycerol with acetic acid to produce mono-, di- and triacetyl glycerol was studied over several acid mesoporous materials. Adopting a pseudo-homogeneous second-order model, the kinetic constants could be determined by exploring the solution space with a particle swarm optimization algorithm in two stages. The error metric adopted was the sum of errors squared obtained comparing the experimental data with an approximation of the extent of the reaction by a numerical method. Different sulfonic-functionalized mesoporous silicas were evaluated (SBA-15, SBA-16, MCM-41 and MCM-48). The catalytic results were highly dependent on the structure, mainly due to the different acid sites density obtained with each support. In spite of an increase on the activity when the amount of acid sites per gram of catalyst increases, the productivity per site does not change significantly among the different catalysts.

Efficiently and Directly Produce Triacetylglycerol from Oils and Fats Over Mesoporous Polymer Solid Acid Catalysts

A series of mesoporous solid acid catalysts (PDS-x) with large BET surface area, superior thermal stability, strong sulfonic acid groups and tunable Bronsted acidity were synthesized by copolymerization of divinylbenzene (DVB) and p-styrenesulfonate hydrate (SPSS). The PDS-x catalysts showed high activity on the direct and efficient production of triacetylglycerol (TAG) by acyl exchange reaction of oils (fats) and acetic acid. The highest TAG yield of 92.2 mol% was obtained on the PDS-x catalysts at a mild condition of 200 o C. By combining SEM, TEM, FT-IR/DRIFT, BET, XRD, and TG-DTG, the key factors that affected the TAG yield were clarified on the PDS-x catalysts. Moreover, the origin of the slow deactivation on these catalysts was elucidated. The large BET surface area and abundant mesopores allowed the contact of large-sized glycerol tristearate with the strong sulfonic acid groups, accounting for the high TAG yield.

Density and viscosity of mixtures of glycerol acetates saturated with CO2 for the design of a supercritical fractionation column

Supercritical CO2 technology has a great potential for the fractionation of glycerol acetates (mono, di, and triacetyl glycerol) according to the quality standards of the food and cosmeceutical sectors. The design of fractionation columns requires a robust thermodynamic model for phase-equilibrium and PVT predictions, as well as proper correlations for physical properties like viscosity. In this work, we measure volumetric and rheological properties of mixtures of glycerol acetates saturated with CO2 (up to 70 mol%) in the temperature range 298−323 K. The mixture molar volumes are between 75 mL/mol and 135 mL/mol, while the viscosities between 0.9 mPa.s and 20 mPa.s. Results show that assuming ideal solution behaviour to estimate the physical properties has a major impact on the design of the fractionation.

The driving effect of substituent size changes on reaction: a novel reaction for direct production of triacetylglycerol from oils and fats

A direct and efficient production of triacetylglycerol (TAG) from oils and fats was proposed based on the principle of driving effect of substituent size changes on reaction with a high TAG yield of 94.9%.

Glycerol acetylation considering competing dimerization

AbstractGlycerol acetylation is a very interesting reaction for studies of consecutive kinetics. In this short communication, we present a pseudo‐homogeneous model for the synthesis of triacetyl glycerol from the reaction of glycerol and acetic acid over strongly acidic Amberlyst‐15 and Amberlyst‐70 catalysts, considering a dimerization of diacetyl glycerol (DAG) into diglycerol tetraacetate as a parallel reaction and compare the results with a model without side reactions. The best fits were obtained for apparent zeroth‐order dimerization and first‐order consecutive reactions in the presence of acetic acid in excess and with removal of water. An adaptation was made for DAG. The proposed model shows that the formation of DAG is faster than the consumption of glycerol, which could be an explanation for the occurrence of DAG dimerization instead of other parallel reactions in acetylation.

Esterification of glycerol with acetic acid over Lewatit catalyst

Tri Acetyl Glycerol or triacetin is one of the glycerol derivative products which can be used as additives in liquid fuels (octane boosters) to reduce knocking on the machine. The use of triacetin as octane booster is considered very promising because it comes from renewable and environmentally friendly raw materials. The resulting glycerol-based additives are suitable for gasoline, biodiesel and diesel. In this study glycerol esterification with acetic acid over Lewatit catalyst was investigated. The effects of various parameters, such as reaction temperature, weight of catalyst and molar ratio of glycerol to acetic acid were studied and the optimum condition for the triacetin synthesis are 100°C, 1: 7 mole of ratio and 3% weight of catalys

Renewable glycerol esterification over sulfonic-modified mesoporous silicas

SO3H-functionalised mesoporous materials with different pore structures (SBA-15 and SBA-16) were prepared by the post-synthesis surface modification. The materials were thoroughly characterized by X-ray powder diffraction, nitrogen physisorption, temperature-gravimetric analysis, elemental analysis and solid state NMR spectroscopy. The acidic properties were investigated by the temperature-programed desorption of ammonia. The catalytic performance of SO3H-functionalised mesoporous materials was studied in glycerol esterification with acetic acid.The different amount of silanol groups in the initial SBA-15 and SBA-16 silicas predetermined the different amount of propylsulfonic groups which are formed in them and therefore significantly influenced the acidity and the catalytic performance in glycerol esterification. Much higher amount of Br?nsted acid sites was generated in SO3H modified SBA-15 catalyst, which exhibited higher activity to value-added triacetyl glycerol.

Influence of acidic properties of different solid acid catalysts for glycerol acetylation

The glycerol esterification with acetic acid is studied in this work using propylsulfonic functionalized mesoporous silica (Pr-SO3H-SBA-15), and compared with H-ZSM-5 and H-Beta zeolites. The reaction was carried out in a batch reactor using a 6:1 molar ratio of acetic acid to glycerol. The initial TOF for the glycerol conversion was significantly higher in the propylsulfonic mesoporous silica, as compared to the two zeolites. These two catalysts have acid sites densities (μmolm−2) that are less than half than that displayed by the SBA-based catalyst. It was possible to obtain 96% conversion in 2.5h, with 87% selectivity to the products of interest diacetylglycerol (DAG) + triacetylglycerol (TAG), being the ratio DAG/TAG=1.7. The catalyst deactivates partly due to sulfonic groups loss and to coke deposition during the reaction, as observed when it was used in a second reaction cycle without any treatment in between cycles. The catalyst lost activity, but maintained the selectivity, associated to a non-selective site poisoning.

Fe4(SiW12O40)3-catalyzed glycerol acetylation: Synthesis of bioadditives by using highly active Lewis acid catalyst

In order to investigate the effect of Lewis acidic metals on the acid properties of Keggin heteropolyacids catalysts, a set of metal-exchanged HPAs (i.e. M3/nPW12O40, M3/nPMo12O40 and M4/nSiW12O40 (M=Cu, Co and Mn, n=2; M=Fe, n=3) were synthesized and their activity on glycerol esterification with acetic acid was evaluated. This procedure avoids the use of corrosive Brønsted acid catalysts. Regardless of the heteropoly anion, the activity of catalysts in terms of metal cations followed the sequence: Fe3+>Cu2+>Mn2+>Co2+. It has been found that among the HPAs, only H4SiW12O40 has the acidic protons that can be successfully exchanged with Fe3+ cations, resulting in Fe4(SiW12O40)3 salt, the most active and selective catalyst. The highest conversion (ca.99.9%) was achieved in Fe4(SiW12O40)3-catalyzed esterification reactions, along with the highest selectivity for di and triacetyl glycerol (ca.55 and 42%, respectively). Effects of temperature, stoichiometry of reactants, concentration and nature of catalysts were assessed. A kinetic study of Fe4(SiW12O40)3 or H4SiW12O40-catalyzed reactions was conducted and the activation energy determined.

Acetylation of glycerol over bimetallic Ag–Cu doped rice husk silica based biomass catalyst for bio-fuel additives application

Acetylation of glycerol with acetic acid was carried out over bimetallic silver and copper deposited rice husk silica-alumina like ecofriendly green catalyst. Bio-additive like mono, di and tri acetyl glycerol synthesis from raw glycerol (one of the main product of biodiesel), which are gaining attention as additives for improving petroleum fuel properties towards biofuel additive development applications. Advantage of using bimetallic catalyst for glycerol acetylation due to possible synergistic effect between the metals and it enhances the catalytic conversion and selectivity compared to single metal catalyst. The prepared catalysts were characterised by XRD, FT-IR and TEM. Silver and copper incorporated RHS (rice husk silica)-alumina catalysts are shown higher activity and selectivity towards diacetin (di acetyl glycerol) and triacetins (tri acetyl glycerol) formation by catalytic acetylation of glycerol. Higher conversion (98 %) and good selectivity (51 %) is achieved.

Glycerol Valorization as Biofuel Additives by Employing a Carbon-Based Solid Acid Catalyst Derived from Glycerol

A two-step process was developed for the preparation of triacetylglycerol (TAG), a biofuel additive employing a solid acid catalyst derived from glycerol. The first step involves esterification of glycerol with acetic acid (1:4 mol) at 115 °C for 1 h in the presence of catalyst (5 wt %) to obtain 100% conversion of glycerol with 22, 67, and 11% MAG, DAG, and TAG, respectively. In the second step, the esterified product mixture after removal of excess acetic acid and moisture was acetylated with acetic anhydride (1 mol with respect to glycerol) at 115 °C for 30 min to obtain 100% TAG. The recovered catalyst was reused for five cycles without any significant loss of its initial activity. The protocol is cost-effective due to the use of highly stable and recyclable SO3H-carbon catalyst for the production of TAG with minimum moles of acetic acid and acetic anhydride in shorter reaction time.

Multiscale Free Energy Simulations: An Efficient Method for Connecting Classical MD Simulations to QM or QM/MM Free Energies Using Non-Boltzmann Bennett Reweighting Schemes.

The reliability of free energy simulations (FES) is limited by two factors: (a) the need for correct sampling and (b) the accuracy of the computational method employed. Classical methods (e.g., force fields) are typically used for FES and present a myriad of challenges, with parametrization being a principle one. On the other hand, parameter-free quantum mechanical (QM) methods tend to be too computationally expensive for adequate sampling. One widely used approach is a combination of methods, where the free energy difference between the two end states is computed by, e.g., molecular mechanics (MM), and the end states are corrected by more accurate methods, such as QM or hybrid QM/MM techniques. Here we report two new approaches that significantly improve the aforementioned scheme; with a focus on how to compute corrections between, e.g., the MM and the more accurate QM calculations. First, a molecular dynamics trajectory that properly samples relevant conformational degrees of freedom is generated. Next, potential energies of each trajectory frame are generated with a QM or QM/MM Hamiltonian. Free energy differences are then calculated based on the QM or QM/MM energies using either a non-Boltzmann Bennett approach (QM-NBB) or non-Boltzmann free energy perturbation (NB-FEP). Both approaches are applied to calculate relative and absolute solvation free energies in explicit and implicit solvent environments. Solvation free energy differences (relative and absolute) between ethane and methanol in explicit solvent are used as the initial test case for QM-NBB. Next, implicit solvent methods are employed in conjunction with both QM-NBB and NB-FEP to compute absolute solvation free energies for 21 compounds. These compounds range from small molecules such as ethane and methanol to fairly large, flexible solutes, such as triacetyl glycerol. Several technical aspects were investigated. Ultimately some best practices are suggested for improving methods that seek to connect MM to QM (or QM/MM) levels of theory in FES.

Improved production of fuel oxygenates via glycerol acetylation with acetic acid

The selective formation of fuel oxygenates via glycerol acetylation with acetic acid over a series of yttrium containing SBA-3 catalysts is reported. The products of glycerol acetylation are mono-, di- and triacetyl glycerol (MAG, DAG, and TAG, respectively) with TAG being the favored. The Y/SBA-3 was prepared by grafting yttrium into the framework of SBA-3. XRD, SAXS, FTIR, SEM–EDX, and surface area and porosity analyzer were used to confirm the properties of the catalysts. The 3%Y/SBA-3 presented unique catalytic performance achieving complete glycerol conversion with corresponding selectivity of 34% and 55% toward DAG and TAG. Over 0.05g of this catalyst, the reaction conditions were economized to reaction temperature of 110°C, molar ratio of glycerol to acetic acid of 1:4, and reaction time of 2.5h. The catalytic activity was mainly attributable to the catalyst’ strong acidity and its high surface area with large pore size that facilitate the diffusion of substrates and products. The reaction kinetics model over this catalyst has been developed using experimental data. The stability of the catalyst was examined via leaching and reusability tests through four consecutive batch runs.

Yttrium-grafted mesostructured SBA-3 catalyst for the transesterification of glycerol with methyl acetate to synthesize fuel oxygenates

The synthesis of di- and triacetyl glycerol (DAG and TAG) via the transesterification of glycerol with methyl acetate was investigated over series of solid acid catalysts prepared by grafting yttrium, 1–3.5wt.%, into the framework of SBA-3 support. The prepared catalysts were characterized for their intrinsic physicochemical and textural properties using BET surface area, surface acidity, XRD, SAXS, FT-IR, TEM, SEM and EDX. The catalyst 3%Y/SBA-3 exhibited superior catalytic performance achieving complete glycerol conversion with corresponding selectivity of 32% and 64% toward DAG and TAG. The best reaction conditions are: molar ratio of glycerol to methyl acetate of 1:12, reaction temperature of 110°C and reaction time of 3h. The effect of different operational parameters such as reaction temperature, the molar ratio of glycerol to methyl acetate, catalyst weight and reaction time on the transesterification reaction was investigated. The stability of the catalytic activity was examined via leaching and reusability tests through four consecutive batch runs.

Synthesis of hybrid SBA-15 functionalized with molybdophosphoric acid as efficient catalyst for glycerol esterification to fuel additives

Fibrous mesoporous hybrid silica (SBAH-15) with mesopore diameter of 70Å was synthesized using pluronic P123 (EO20PO70EO20) as surfactant, with Brij S100 as nonionic co-surfactant. Series of catalysts with different molybdophosphoric acid (MPA) loading (5–25%) were synthesized by the thermal decomposition of MPA species in the lattice of SBAH-15. Catalysts calcined at 560°C undergone a thermal decomposition of MPA resulted in the formation of β-MoO3 active species. The effectiveness of the hybrid support was evaluated by comparison with analogous catalyst prepared by incorporating MPA into the framework of classical SBA-15. The catalytic performance of the prepared acid catalysts was examined during glycerol esterification with acetic acid. Mono-, di- and triacetyl glycerol (MAG, DAG and TAG, respectively) were the esterification reaction products. SBAH-15(15) catalyst, with 15wt.% MPA loading, exhibited an excellent activity during this reaction, indicated by the complete glycerol conversion (after 1h) with a corresponding combined selectivity of 86% toward both DAG and TAG. The best reaction conditions are: reaction temperature of 110°C, glycerol to acetic acid molar ratio of 1:6 and reaction time of 3h. The SBAH-15(15) catalyst demonstrated good stability in activity upon recycling for four times.

Simultaneous enzymatic synthesis of FAME and triacetyl glycerol from triglycerides and methyl acetate

In the presence of methyl acetate triglycerides such as vegetable oils are transformed simultaneously into the corresponding fatty acid methyl esters and triacetyl glycerol (triacetin). The reaction, catalyzed by lipases, was studied as a function of some critical parameters, such as type of catalyst, enzyme hydration and immobilization support. The aim of the work was to achieve a conversion of the triglyceride as high as possible and to maximize the yield of the triacetin, the reaction end point. It was found that by using the immobilized lipase from Candida antarctica yields as high as 80% of both fatty acid esters and triacetin could be achieved. These results were obtained by carefully controlling the amount of water present in the reaction medium and the hydration level of the enzyme macromolecule.

Study of the influence of plasticizers on the thermal and mechanical properties of poly(3‐hydroxybutyrate) compounds

AbstractThe influence of four types of plasticizers, dioctyl phthalate (DOP), dioctyl adipate (DOA), triacetyl glycerol (TAG) and polyadipate (PA), in the thermal and mechanical properties of Poly(3‐hydroxybutyrate) (PHB), a highly crystalline biodegradable polyester, was evaluated in this work. The plasticizers were introduced alone or mixtures of them, using concentrations that varied from 5 to 30% wt. Their influence in some important polymer parameters as Tg, Tm and degree of crystallinity, and on its mechanical behavior, elongation and tensile strain were investigated. The best results were obtained for the sample with 30% TAG and that one using a binary mixture of plasticizers PA 20% and TAG 10%.

Purification and preliminary characterization of the extracellular lipase of Bacillus subtilis 168, an extremely basic pH-tolerant enzyme.

The extracellular lipase of Bacillus subtilis 168 was purified from the growth medium of an overproducing strain by ammonium sulfate precipitation followed by phenyl-Sepharose and hydroxyapatite column chromatography. The purified lipase had a strong tendency to aggregate. It exhibited a molecular mass of 19,000 Da by SDS-PAGE and a pI of 9.9 by chromatofocusing. The enzyme showed maximum stability at pH 12 and maximum activity at pH 10. The lipase was active toward p-nitrophenyl esters and triacylglycerides with a marked preference for esters with C8 acyl groups. Using trioleyl glycerol as substrate, the enzyme preferentially cleaved the 1(3)-position ester bond. No interfacial activation effect was observed with triacetyl glycerol as substrate.