Acid Molar Ratio Research Articles

Synthesis and Optimization of Methyl Laurate Using Sulfonated Pyrrolidonium Ionic Liquid as a Catalyst

Abstract Methyl laurate was synthesized from lauric acid and methanol using Brønsted acid ionic liquids as catalysts, by an esterification reaction. The efficiencies of four different catalysts, 1-methylimidazolium hydrogen sulfate ([Hmim]HSO4), 2-pyrrolidonium hydrogen sulfate ([Hnhp]HSO4), 1-(3-sulfonic acid) propyl-2-pyrrolidonium hydrogen sulfate ([C3SO3Hnhp]HSO4) and H2SO4 were compared. The effect of the methanol/lauric acid molar ratio, reaction temperature, reaction time, and catalyst dosage on the lauric acid conversion was investigated by single-factor experiments. On the basis of single-factor experiments, the esterification of lauric acid and methanol was optimized using response surface methodology (RSM) based on central composite design (CCD). The results showed that the most effective catalyst was the ionic liquid [C3SO3Hnhp]HSO4. The optimal conditions were as follows: [C3SO3Hnhp]HSO4 dosage of 10 % (based on the mass of lauric acid), methanol/lauric acid molar ratio of 9:1, reaction time of 1 h and reaction temperature of 70 °C. Under these conditions, the lauric acid conversion reached 95.33 %. The catalytic activity of [C3SO3Hnhp]HSO4 still remained high after 5 cycles.

A novel bulk-gas-to-atomized-liquid reactor for enhanced mass transfer efficiency and its application to syngas fermentation

Syngas fermentation for fuels and chemicals is limited by the low rate of gas-to-liquid mass transfer. In this work, a unique bulk-gas-to-atomized-liquid (BGAL) contactor was developed to enhance mass transfer. In the BGAL system, liquid is atomized into discrete droplets, which significantly increases the interface between the liquid and bulk gas. Using oxygen as a model gas, the BGAL contactor achieved an oxygen transfer rate (OTR) of 569 mg·L−1·min−1 and a mass transfer coefficient (KLa) of 2.28 sec−1, which are values as much as 100-fold greater than achieved in other kinds of reactors. The BGAL contactor was then combined with a packed bed to implement syngas fermentation, with packing material supporting a biofilm upon which gas saturated liquid is dispersed. This combination avoids dispersing these gas-saturated droplets into the bulk liquid, which would significantly dilute the dissolved gas concentration. Although this combination reduced overall KLa to 0.45–1.0 sec−1, it is still nearly 20 times higher than achieved in a stirred tank reactor. The BGAL contactor/packed bed bioreactor was also more energy efficient in transferring gas to the liquid phase, requiring 8.63–26.32 J mg−1 O2 dissolved, which is as much as four-fold reduction in energy requirement compared to a stirred tank reactor. Fermentation of syngas to ethanol was evaluated in the BGAL contactor/packed bed bioreactor using Clostridium carboxidivorans P7. Ethanol productivity reached 746 mg·L−1·h−1 with an ethanol/acetic acid molar ratio of 7.6. The ethanol productivity was two-fold high than the highest level previously reported. The exceptional capability of BGAL contactor to enhance mass transfer in these experiments suggests its utility in syngas fermentation as well as other gas-liquid contacting processes.

Studies on lauric acid conversion to methyl ester via catalytic esterification using ammonium ferric sulphate

Esterification of lauric acid with a new homogeneous acid catalyst, ammonium ferric sulphate (AFS), was used to get optimised reaction conditions in order to get the best methyl esters conversion by using the statistical modelling approach of response surface methodology (RSM). AFS acts as a new source of homogeneous acid catalyst and was optimised in this study to produce methyl ester. The Central Composite Design (CCD) and RSM were used to determine the relationship between reaction time, methanol to lauric acid molar ratio and catalyst loading to determine the optimum condition for the esterification process. This work reports the novel results of the optimum conditions obtained for esterification of lauric acid, which are 1.5 h of reaction time, 6:1 M ratio of methanol to lauric acid and 8 wt% loading of AFS catalyst to give the highest conversion rate of methyl esters at 99.8%. These reaction conditions were successfully applied and verified on the esterification of palm fatty acid distillate (PFAD) which demonstrated the ability of AFS to act as an acid catalyst in the esterification process with a conversion rate of 81.2% of methyl esters. Acid value of PFAD was also decreased from 185 to 41 mg KOH/g PFAD.

Cacao shell-derived solid acid catalyst for esterification of oleic acid with methanol

Cacao shell-derived solid acid catalyst (CS-SAC) was successfully prepared by partial carbonization followed by sulfonation at various temperature (80, 100, 120 °C) and time (4, 6, 8 h) settings. The catalysts were analyzed for their acid densities and tested for their activity in the esterification of oleic acid with methanol at 45 °C for 4 h, with methanol to oleic acid molar ratio of 7:1 and a catalyst loading of 5 %w/w. It was found that increasing the sulfonation temperature at sulfonation times of 4 and 6 h increased the solid’s total acid density and sulfonic acid density thereby increasing its specific catalytic activity. Prolonging sulfonation time at any temperature, however, had no significant effect. The highest specific catalytic activity of 14.0 mmol FAME·g−1 CS-SAC·h−1, which corresponds to 79% conversion of oleic acid was observed for SAC sulfonated at 120 °C for 4–6 h. Prolonged esterification up to 24 h resulted in high conversion of ∼94% even at a low temperature of 45 °C. Although the catalyst was later found to decrease in its activity during reuse, its catalytic activity remained stable after the 3rd cycle at a conversion of 48% of the oleic acid.

Isopropyl Lactate Obtaining by Esterification in a Reactive Distillation System

The reactive distillation is a way for the intensification of chemical processes by thermal integration into a single process of chemical reactions with products separation. Isopropyl lactate is an important intermediate for drug synthesis what can be synthesized through reactive distillation. Based on scientific studies in literature, a preliminary study was performed in a reactive distillation laboratory system, in order to obtain isopropyl lactate by esterification of lactic acid with isopropyl alcohol. The independent variables studied are: the alcohol/lactic acid molar ratio (R), the catalyst concentration (CA) and the number of theoretical trays in the fractionation zone (NTT). The experimental matrix was established for a 23 factorial experiment, by considering two levels for each variable: R=1 and 3 mole/mole; CA= 3 %wt and 5 %wt; NTT=1.9 and 2.9. A linear mathematical model was proposed to correlate the lactic acid conversion with the molar ratio of reactants, catalyst concentration and the number of theoretical plates in the column. The model shows that R and NTT are the important variables of the process while the acid concentration is less important, in the studied range. The correlation coefficient is R2=0.9978 and the statistical analysis ANOVA of the model�s coefficients proved they are significant at a confidence level of 95%, so the model is reliable.

Influence of support on physicochemical properties of ZrO2 based solid acid heterogeneous catalysts for biodiesel production

Environmental pollution control is the challenge area of heterogeneous catalysts to avoid the use of harmful materials in chemical synthesis. So ZrO2-based solid acid catalysts were prepared and used in environmental applications like production of biodiesel. ZrO2 loading on different supports (Al2O3, Fe2O3, TiO2 and SiO2) prepared by a hybrid sol-gel auto combustion methods. The structural, surface and acidity properties are studied. The catalytic activity was evaluated by production of biodiesel through conversion of stearic acid to ester. ZrO2/ SiO2 has the highest conversion rate because of a high surface area and a high number of Lewis acid sites. Under the optimal reaction conditions of alcohol/ acid molar ratio 120:1, mass ratio of catalyst to acid 0.1, reaction time 3 h and reaction temperature 120 °C, the conversion rate reached 48.6%. Moreover, the catalysts reused over at least five runs without significant loss of activity.

Biocatalytic esterification of fatty acids using a low-cost fermented solid from solid-state fermentation with Yarrowia lipolytica.

This study aimed to evaluate the use of a lyophilized fermented solid (named solid enzymatic preparation, SEP), with lipase activity, as a low-cost biocatalyst for esterification reactions of fatty acids present in acid raw materials for biodiesel synthesis. The SEP was obtained by solid-state fermentation (SSF) of soybean bran using the strain of Yarrowia lipolytica IMUFRJ 50682 and contains the lipases secreted by this yeast. The esterification reaction of ethanol and the predominant fatty acids present in different acid oil sources for biodiesel production (oleic, linoleic, stearic and palmitic acids) was investigated. Oleic acid conversion of above 85% was obtained after 24h, using 30 wt% of SEP and ethanol/oleic acid molar ratio of 1, at 30°C, in a reaction medium with and without solvent (n-hexane). Similar results were achieved with stearic (79%), palmitic (82%) and linoleic (90%) acids. The reusability of SEP was investigated over ten successive batches by washing it with different solvents (ethanol, water or n-hexane) between the cycles of ethyl oleate synthesis. Washing with water allowed the SEP to be reused for six cycles maintaining over 80% of the conversion reached in the first cycle. These results show the potential of this biocatalyst to reduce the content of free fatty acids in acid oils for biodiesel synthesis with a potential to be applied in a broad plethora of raw materials.

Fabrication characterization of hafnium oxide thin films

Abstract Ferroelectric materials are commonly used in electronic devices such as memories, transistors, capacitors, sensors and actuators. Lead zirconate titanate (Pb(Zr1-xTix)O3 or PZT)-based ferroelectrics are a popular material for these applications due to their large dielectric constant, high polarization responses and superior piezoelectric properties. However, they contain toxic lead. Currently, the industry is looking for new ferroelectric materials with excellent electrical properties materials and that are also environmentally friendly. Hafnium oxide (Hafnai or HfO2)-based materials have become attractive candidates because they are a simple binary oxide (non-perovskite structure) but exhibit ferroelectric properties and do not pollute to the environment. Therefore, this work aims to fabricate HfO2 thin films by using a sol-gel method. The mole ratio of nitric acid (HNO3) and deionized water (DI) was varied between 0.03:0.05, 0.05:0.05, and 0.10:0.05. After the spin-coated, thin films were annealed at 700, 800, and 900 °C for 3 hours. In addition, phase formation and microstructure of HfO2 thin films were also investigated by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. XRD investigation suggested that the HfO2 thin films with 0.03:0.05 and 0.05:0.05 mole ratios exhibited a monoclinic phase. In addition, a homogenous surface was found in all compositions. The experimental results implied that the mole ratio of HNO3:DI water and annealing temperatures played a significant role in the formation of the HfO2 thin films.

Синтез и строение cольвата 2,6-пиридиндикарбоксилата бис(тетрафенилсурьмы) с толуолом

At interaction of pentaphenylantimony with 2,6-pyridinedicarboxylic acid (mole ratio 1:1 or 2:1) in a toluene solution, bis (tetraphenylantimony) 2,6-pyridinedicarboxylate toluene solvate (1) has been obtained for the first time (yield 72%, colorless crystals, m.p. 170 °C). The compound 1 has been characterized by IR-spectroscopy, elemental and X-ray analysis. The absorption band of a carbonyl group with the frequency 1620 cm –1 is present in the IR-spectrum, shifting towards the area of low-frequency oscillations in comparison with the spectrum of the acid (1701 cm –1 ). According to the data of X-ray analysis the unit cell crystallographic parameters of compound 1: triclinic syngony, the symmetry group P; a = 12.494(5), b = 13.788(5); c = 16.684(6) Å; V = 2550.5(16) Å3; Z = 2; ρ(calc.) = 1.455 g/сm 3 . The Sb(1) and Sb(2) atoms in a molecule have a distorted trigonal-bipyramidal coordination in different degrees. The CSb(1)O and CSb(2)O axial angles equal 178.41(10)° and 176.75(11)°, the CSb(1)C and CSb(2)C equatorial angles vary in the ranges 111.58(14)–125.24(13)°) and 103.44(13)−146.5(11)°. The Sb(1,2)−O bond lengths equal 2.301(2), 2.310(2) Å. The Sb(1,2)–Ceqv equatorial bonds (2.105(3)–2.112(3) Å and 2.140(3)–2.162(3) Å) are shorter than the Sb(1,2)–Cax axial one (2.177(3), 2.162(3) Å). The bidentate binding of carboxylate ligands is weak (the distance Sb(1)∙∙∙O(2) equals 3,263(4) Å) it has been proved by significant difference in the lengths of single (С–О 1.288(3), 1.261(4) Å) and double bonds (С=О 1.226(3), 1.236(4) Å) in the carboxylate groups. The pypidine ring nitrogen atom coordinates to the antimony atom (the distance Sb(2)∙∙∙N equals 2.947(3) Å).

Protic Ionic Liquids Based on Oligomeric Anions [(HSO4)(H2SO4)x]− (x = 0, 1, or 2) for a Clean ϵ-Caprolactam Synthesis

Inexpensive Brønsted acidic ionic liquids, suitable for industrial-scale catalysis, are reported as reaction media and catalysts for the Beckmann rearrangement of cyclohexanone oxime to ϵ-caprolactam. A family of protic ionic liquids was synthesised from nitrogen bases (1-methylimidazole, N,N,N-triethylamine, N-methylpyrrolidine, 2-picoline) and sulfuric acid by proton transfer in a simple, inexpensive, solvent-free, one-step process. The density, viscosity, conductivity, and ionicity of the synthesised ionic liquids were determined. Variation in the molar ratio of sulfuric acid (χH2SO4=0.67 and 0.75) was used to tune the acidity of these protic ionic liquids, which showed extremely high catalytic activity in the Beckmann rearrangement of cyclohexanone oxime to ϵ-caprolactam. Both the structure of the cation and the sulfuric acid molar ratio strongly affect the rearrangement of cyclohexanone oxime. The most active ionic liquid, based on the 1-metyhylimidazolium cation, χH2SO4=0.75, afforded high conversion of oxime combined with very good selectivity under mild conditions (110°C, 15min). The product could be extracted from the reaction mixture, eliminating the need for the neutralisation step that exists in conventional processes. The combination of affordable catalyst and process advantages leads to a greener alternative, competitive against existent industrial applications.

Formulation and optimization of effervescent tablet containing bismuth sub-citrate

Objective: The objective of this study was to design, evaluate and optimize effervescent tablets containing bismuth sub-citrate with sufficient hardness and friability in treatment of peptic ulcer. Materials and Methods: Effervescent tablets were prepared by direct compression method and were optimized using irregular factorial design. Amount of citric acid, sodium bicarbonate to citric acid molar ratio, polyvinyl pyrrolidone K 30 (PVP k30), polyethylene glycol 6000 (PEG 6000) were selected as independent variables, whereas disintegration time, amount of carbon dioxide (CO2), friability, pH, and hardness were selected as dependent variables. All the batches were assessed for various pre and post compression characteristics such as flowability, hardness, friability, effervescent time, pH, and content uniformity. For the enhancement of tablets’ palatability, the components of optimized formulation were mixed with same amounts of different flavoring agents. Results: The best results obtained from effervescent tablets prepared by 500 mg citric acid, 5% PEG 6000 and 3% PVP k30 while the molar ratio of the sodium bicarbonate to citric acid was 3. The disintegration time, amount of CO2, friability, pH, and hardness of optimized formulation were confirmed to be 95.33 ± 1.15sec, 398.73 ± 1.46 mg, 0.73%, 6.0 ± 0.06 and 72.3 ± 5.5 N, respectively. The most pleasant taste according to volunteers’ acceptability was the taste of cherry. Conclusion: These results suggest that developed effervescent tablets may be promising for delivery of bismuth sub-citrate in peptic ulcers therapy.

Candida sp. 99-125 lipase-catalyzed synthesis of ergosterol linolenate and its characterization

As a major sterol in edible mushroom, ergosterol has gained much attention owing to its potential bioactivities. However, ergosterol has a high melting point, poor oil solubility and stability, which restrict its scope of application. In this study, an ergosterol ester of α-linolenic acid was successfully and efficiently prepared using Candida sp. 99-125 lipase as a biocatalyst. The desired product was confirmed to be ergosterol linolenate using MS, FT-IR, and NMR analyses. Using Candida sp. 99-125 lipase, the product conversion exceeded 92% in 12 h under the following optimized parameters: 75 mmol/L ergosterol, 40 g/L lipase, 1:1.25 ergosterol-to-α-linolenic acid molar ratio, and 45 °C. The results confirmed that Candida sp. 99-125 lipase has good reusability and stability and is also relatively low cost, suggesting its great potential for large-scale production of ergosterol ester. Most importantly, the physiochemical properties (oil solubility and melting point) of ergosterol significantly improved after esterification with α-linolenic acid, thus facilitating its application in oil-based systems.

DFT analysis, reaction kinetics and mechanism of esterification using pyridinium nitrate as a green catalyst

The ionic liquid pyridinium nitrate ([H–Pyr]+[NO3]−) was synthesized and characterized theoretically and experimentally. Different quantum chemical analyses such as molecular electrostatic potential surface, natural bond orbital and frontier molecular orbital analyses were used for investigation of the electronic properties and chemical reactivity of the title compound. It was found the existence of an interaction between the nitrate anion and the pyridinium cation, expressed mainly by formation of the hydrogen bond O7⋯H11N1. The acetic acid esterification with 1-butanol was used as a model reaction in order to study the catalytic properties of the [H–Pyr]+[NO3]−. The influence of various process parameters (catalyst concentration, initial butanol-to-acetic acid molar ratio and reaction temperature) on the acetic acid conversion and reaction rate constant was discussed in details. The obtained experimental data were validated using a pseudo-homogeneous kinetic model. In addition, a plausible reaction mechanism of butyl acetate synthesis catalyzed by the ionic liquid pyridinium nitrate was offered.

The influence of the NCO/OH ratio and the 1,6-hexanediol/dimethylol propionic acid molar ratio on the properties of waterborne polyurethane dispersions based on 1,5-pentamethylene diisocyanate

1,5-Pentamethylene diisocyanate, a novel aliphatic diisocyanate formed from bio-based 1,5-pentamethylenediamine, has been used as a hard segmented material to synthesize polyurethane. In this study, several waterborne polyurethane (WPU) dispersions have been successfully prepared by a prepolymer process from 1,5- pentamethylene diisocyanate poly(polyether) with different NCO/OH ratios and 1,6-hexanediol (HDO)/dimethylol propionic acid (DMPA) molar ratios. The Fourier transform infrared (FTIR) spectra, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, and a mechanical tensile test were used to investigate the structures, thermal stability, phase separation, crystallinity, mechanical properties, and adhesive performance of the WPU dispersions. The FTIR results indicate that the degree of hydrogen bonding and the numbers of urea groups increase as the NCO/OH ratio and HDO/DMPA molar ratio increase. Furthermore, the phase separation increases and the thermal stability decreases as the NCO/OH ratio increases or the HDO/DMPA molar ratio decreases. Finally, WPU3.0-2.4 (NCO/OH = 3, HDO/DMPA = 2.4) exhibits a maximum tensile strength and shear strength, pointing to its possible use as an adhesive. These results could provide a very valuable reference for industrial applications of WPU.

Green synthesis of methyl salicylate using novel sulfated iron oxide–zirconia catalyst

Esters of salicylic acid are in demand for the synthesis of drugs, food preservatives, pharmaceuticals, perfumes and solvents. A novel sulfated Fe2O3–ZrO2 catalyst with different iron loadings was prepared by the combustion technique and used in the preparation of methyl salicylate from salicylic acid and dimethyl carbonate. This process is a viable and safe substitute to other esterification processes, involving harmful alkylating agents and chemicals. The activity of sulfated Fe2O3–ZrO2 was evaluated for the esterification of salicylic acid with dimethyl carbonate. No solvent was used and hence the quality of the product was excellent. The product methyl salicylate is extensively used in the food and pharma industries. Catalysts with different loadings of iron on zirconia (5, 10, 15, 20 wt.%) were synthesized, and their activities evaluated vis-a-vis ZrO2 and sulfated zirconia. The catalysts were characterized using SEM, XRD, FTIR, TGA, NH3-TPD and BET surface area analysis. The activity of the catalysts increases after the loading of iron on zirconia and 10 wt.% sulfated Fe2O3–ZrO2 gave the highest acidity and activity for the synthesis of methyl salicylate. The effect of various kinetic parameters on the rate of esterification of salicylic acid was studied. The optimum conditions for 99% conversion of salicylic acid with 100% selectivity was 120 °C after 150 min at a 1:10 molar ratio of salicylic acid to dimethyl carbonate and catalyst loading of 0.03 g/cm3. The reaction mechanism and kinetics were studied. The activation energy for this reaction was found to be 13.82 kcal/mol.

In vitro antioxidant and immunostimulating activities of polysaccharides from Ginkgo biloba leaves

Ginkgo biloba leaves (GBLs) are used as herbal dietary supplements and medicine worldwide. In this study, crude GBL polysaccharides (GBPSs) were extracted and further purified on a DEAE (diethylaminoethanol) Sepharose Fast Flow column to obtain GBPS-2 and GBPS-3. The molecular weights of GBPS-2 and GBPS-3 were 672 and 723 kDa, respectively. GBPS-2 and GBPS-3 were typical acidic heteropolysaccharides, composed of mannose (Man), rhamnose (Rha), glucuronic acid (GlcA), galacturonic acid (GalA), glucose (Glc), galactose (Gal), and arabinose (Ara) (molar ratio: 0.08:0.12:0.16:0.06:0.11:1.00:0.32) and Man, Rha, GlcA, GalA, Gal, and Ara (molar ratio: 0.92:1.00:0.83:0.11:0.42:0.23), respectively. GBPS-2 and GBPS-3 exhibited limited scavenging abilities for the hydroxyl and 2,2‑diphenyl‑1‑picrylhydrazyl radicals as well as noticeable scavenging effects on superoxide radicals and 2,2′‑azino‑bis(3‑ethylbenzothiazoline‑6‑sulphonic acid) radicals. Furthermore, GBPS-2 and GBPS-3 significantly increased the phagocytosis of macrophages and promoted the production of NO, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. Thus, GBPS-2 and GBPS-3 exhibit potential application as functional food supplements.

Glycerol conversion towards valuable fuel blending compounds with the assistance of SO3H-functionalized carbon xerogels and spheres

The SO3H-functionalized carbon xerogels and carbon spheres were obtained via modification of the initial materials with sulfuric acid or in situ generated diazonium salt (4‑benzenediazonium sulfonate). The catalytic activity of the prepared samples was evaluated in glycerol acetylation leading to valuable fuel blending compounds. The process was conducted at 80 °C, at a glycerol/acetic acid molar ratio of 1:6. The catalysts tested in the reaction were characterized by texture and elemental analysis, potentiometric titration, FTIR measurement, and also using SEM. The catalytic data obtained demonstrate that oxygenated fuel additives can be produced with a combined selectivity of 75% to diacetin and triacetin (DA and TA, respectively), and a selectivity of 25% to monoacetin (MA), with the glycerol conversion of about 97%. These results are comparable to those obtained for a commercial ion exchange resin (Amberlyst 15), indicating a great potential of modified carbons in the glycerol esterification process and other acid-catalyzed reactions.

Mineralization of pentachlorophenol by ferrioxalate-assisted solar photo-Fenton process at mild pH

This work reports the use of ferrioxalate complexes to assist solar photo-Fenton treatment of pentachlorophenol (PCP) in aqueous medium at mild pH, which inhibits the precipitation of iron hydroxides and allows working at a low iron dosage. The experimental parameters were optimized by assessing the effect of initial concentrations of H2O2 (0–2.5 mM) and Fe(II) (2–10 mg/L), pH (3.0–9.0) and iron/oxalic acid molar ratios (1:0–1:13.5) on total organic carbon (TOC) removal. Ferrioxalate-assisted solar photo-Fenton achieved 97.5% mineralization in 120 min, clearly outperforming conventional Fenton and solar photo-Fenton. The presence of photosensitive ferrioxalate complexes accounted for the enhancement, as a result of Fe(II) regeneration that accelerated the hydroxyl radical (OH) production. The time course of H2O2 and Fe(II) concentrations was evaluated under different iron/oxalic acid ratios. The five carboxylic acids determined by ion-exclusion HPLC and the eight aromatic by-products identified by GC-MS allowed the proposal of a degradation pathway that included hydroxylation, dechlorination and dimerization steps. Complete chloride ion release was achieved after 90 min of treatment.

Production of value-added chemicals from esterification of waste glycerol over MCM-41 supported catalysts

Abstract A series of active and selective MCM-41 supported catalysts have been successfully prepared and used for bioderived glycerol esterification with acetic acid to produce fuel additives. In the synthesis of MCM-41, an acidic hydrothermal synthesis route was used, and silicotungstic acid (STA) and zirconia (ZrO2) were added to the catalyst structure by wet impregnation. X-ray diffraction, nitrogen adsorption-desorption methods, scanning electron microscopy with energy-dispersive spectroscopy, and inductively coupled plasma-mass spectrometry analysis were used for characterizations of the catalysts. Diffuse reflectance infrared Fourier transform spectroscopy analyses of pyridine-adsorbed catalysts owns Lewis and Brønsted acidity hosting in one, which promotes the esterification reaction of glycerol into glycerol esters with high selectivity. Esterification of glycerol reactions were performed at temperature intervals of 105°C–200°C, with an amount of catalyst equal to 0.5 g, and glycerol/acetic acid molar ratio of 1:6 in a stirred autoclave reactor operated batchwise. STA and ZrO2-impregnated MCM-41 catalysts showed better performance with a complete glycerol conversion and high selectivity to triacetin.

Evaluation of commercially available styrene-co-maleic acid polymers for the extraction of membrane proteins from spinach chloroplast thylakoids

Solubilization of membrane proteins by poly(styrene-co-maleic acid) salts (pSMA-S) has significant potential for membrane protein studies. This approach provides an opportunity to overcome many disadvantages associated with a traditional detergent-based technique including protein denaturation and displacement of boundary lipids which may offer both structural and functional stability to membrane proteins. Thylakoid membranes (TMs) from photosynthetic organisms are well studied protein-rich membranes that host several multi-subunit protein complexes associated with oxygenic photosynthesis. These protein complexes are important for applied photosynthesis and by being extracted and purified they can be used in the near future for direct energy conversion. In this study, we used spinach TMs isolated from purified intact chloroplasts to systematically test the solubilization efficacy of 12 commercially available styrene-maleic acid (SMA) copolymers that vary in size, styrene-to-maleic acid molar ratio, and type of ester group. The efficacy of these pSMA-S to solubilize protein-containing biomembranes was evaluated via quantification of protein and chlorophyll content in the resulting SMA Lipid Particles (SMALPs). In addition, the extracted polymer-lipid-protein complexes were studied by low temperature fluorescence, sodium dodecyl sulfate and clear native polyacrylamide gel electrophoresis (SDS- and CN-PAGE), and immunoblot analysis. Our results indicate considerable variability in the solubilization efficacy of commercially available pSMA-S with at least 5 polymer formulations being able to efficiently extract membrane proteins from TMs. These 5 SMA copolymers may also be effective in extraction of membrane proteins from other biomembranes.