Kinetics of the catalytic esterification of castor oil with lauric acid using <Emphasis Type="Italic">n</Emphasis>-butyl benzene as a water entrainer

The esterification of castor oil with lauric acid was investigated using tetra n-butyl titanate (TBT), SnCl₂·2H₂O (stannous chloride), CoCl₂·6H₂O (cobalt chloride), and (CH₃COO)₂Zn·2H₂O (zinc acetate dihydrate) as catalysts. Effects of catalyst concentration and reaction temperature on the progress of the reaction were investigated. TBT was the best catalyst for the esterification of castor oil with lauric acid at temperatures lower than 200°C. The reaction was first order with respect to each reactant. The activation energy for the esterification reaction of castor oil with lauric acid using TBT was 26.69 kcal/mol. The rate constants obtained for the esterification of castor oil with decanoic, lauric, palmitic, and stearic acids were nearly the same (15.80, 15.44, 15.06, and 14.67 mL mol⁻¹ min⁻¹), as were the rate constants obtained for the reaction of castor oil and hydrogenated castor oil.     

Preparation and Characterization of a Magnetic Solid Acid for Esterification of Ammonium Lactate with n-Butanol

One kind of magnetic solid acid (MSA) was prepared by thermolysis of nickel sulfate with ferric hydroxide at 1,123 K. Its properties, such as magnetism and surface acidity, were investigated by PPMS, FTIR-NH₃, TPD-NH₃, XRF, XRD techniques. Its saturation magnetization is estimated to be 10.72 emu/g and a hysteretic feature with a remnant magnetization (2.76 emu/g) and coercivity (0.15 kOe) at 300 K is exhibited. The results also reveal that MSA solely possesses mild Lewis acid sites and four crystalline phases. Its catalytic activity for esterification of ammonium lactate with n-butanol was tested. The esterification yield (Ey) will be significantly enhanced when SnCl₂ · 2H₂O is added. The highest Ey will be up to 87.3% when the complex concentration is 5 wt% (mass ratio of SnCl₂ · 2H₂O to MSA = 4:1). The possible reasons correlating with the esterification performance of the complex system are discussed.     

Efficient Esterification of Fatty Acids with Alcohols Catalyzed by Zr(SO4)2 · 4H2O Under Solvent-Free Condition

Zirconium sulfate (Zr(SO₄)₂ · 4H₂O) was an efficient catalyst for the esterification of fatty acids and alcohols under solvent-free condition. The esterification of fatty acid with branched alcohols using Zr(SO₄)₂ · 4H₂O catalyst gave a good yield of the corresponding ester. The zirconium sulfate Bronsted acid site was suggested to be the catalytically active species in this reaction. In addition, Zr(SO₄)₂ · 4H₂O compound is a potential green catalyst due to its high catalytic activity and low toxicity. This compound is also cost effective, easy to handle, is easily recovered by simple filtration and can be recycled for further reactions.     

Synthesis of imine bond containing insoluble polymeric ligand and its transition metal complexes,structural characterization and catalytic activity on esterification reaction

In this study, synthesis of insoluble polymeric ligand (L) and its transition metal complexes [Cu(L)Cl₂]·2H₂O (1), [Co(L)Cl₂(H₂O)₂] (2) and [Ni(L)Cl₂(H₂O)₂] (3), having the azomethine groups, were synthesized by the condensation reactions of the diamines and dialdehydes. The structural properties were characterized by the analytical and spectroscopic methods using by elemental analysis, Fourier Transform Infrared, Thermo Gravimetric Analysis, Powder X-ray Diffraction, magnetic susceptibility and Inductively Coupled Plasma. The solubilities of the synthesized polymeric materials were also investigated and found as insoluble some organic and inorganic solvents. Additionally, their catalytic performance was carried out for the esterification reaction of acetic acid and butyl acetate. The highest conversion rate is 75.75% by using catalyst 1. The esterification of butanol gave butyl acetate with 100% selectivity.     

Acid properties of solid acid from petroleum coke by chemical activation and sulfonation

A novel solid acid was prepared from petroleum coke by KOH chemical activation and concentrated H₂SO₄ sulfonation. The solid acid was characterized by XRD, FT-IR and solid-state NMR. The characterization results show that the chemical activation and sulfonation lead to three functional Brønsted acid sites: –OH, –COOH and –SO₃H on the solid acid. The probe molecules experimental reveal that the acid strength of the solid acid is stronger than that of SO₄²⁻ /ZrO₂, but slightly weaker than that of 100% H₂SO₄. The catalytic performance was evaluated by the esterification of oleic acid with methanol. The results indicate that this solid acid catalyst is very active, corresponding to high conversion (72%) of esterification reaction. In addition, the spent solid acid can be recovered by simple regeneration process.     

Producing biodiesel from high free fatty acids waste cooking oil assisted by radio frequency heating

Efficient biodiesel conversion from waste cooking oil with high free fatty acids (FFAs) was achieved via a two-stage procedure (an acid-catalyzed esterification followed by an alkali-catalyzed transesterification) assisted by radio frequency (RF) heating. In the first stage, with only 8-min RF heating the acid number of the waste cooking oil was reduced from 68.2 to 1.64 mg KOH/g by reacting with 3.0% H₂SO₄ (w/w, based on oil) and 0.8:1 methanol (weight ratio to waste oil). Then, in the second stage, the esterification product (primarily consisting of triglycerides and fatty acid methyl esters) reacted with 0.91% NaOH (w/w, based on triglycerides) and 14.2:1 methanol (molar ratio to triglycerides) under RF heating for 5 min, and an overall conversion rate of 98.8 ± 0.1% was achieved. Response surface methodology was employed to evaluate the effects of RF heating time, H₂SO₄ dose and methanol/oil weight ratio on the acid-catalyzed esterification. A significant positive interaction between RF heating time and H₂SO₄ concentration on the esterification was observed.     

Study of various catalysts in the synthesis of poly(propylene terephthalate) and mathematical modeling of the esterification reaction

Pure terephthalic acid (TPA) was esterified with 1,3-propanediol (1,3-PDO) in the presence of various catalysts, in order to find the most effective one for this esterification reaction. The prepared oligomers were polycondensated in a second step under high vacuum and using the same catalyst (Sb(OCOCH₃)₃, Ti(OC₄H₉)₄, GeO₂₎ as before, or the well known catalyst for poly(ethylene terephthalate) (PET) production technology Sb₂O₃. The esterification reaction was monitored by measuring the distilled water as a function of time and from these data the modeling of this process was carried out. The received poly(propylene terephthalate) (PPT) samples were characterized by viscometry, carboxyl end-group content and color measurement. From this study, tetrabutoxytitanium was proved to be the most effective catalyst for the esterification reaction. When this catalyst was used in the second step a PPT polymer with the highest molecular weight was received.     

Slow magnetic relaxation in a two-dimensional dysprosium(III) coordination polymer

A new two-dimensional (2D) dysprosium(III) coordination polymer, e.g. [Dy(HL)(NO₃)₂(H₂O)]_n (1, H₂L = 4-{[(2-hydroxy-3-methoxyphenyl)methylidene]amino}benzoic acid)), has been solvothermally synthesized and structurally characterized using single-crystal X-ray diffraction. The dysprosium ions in complex 1 display the capped trigonal prism geometry and are connected with each other through o-vanillin and carboxyl groups, generating an interesting 2D structure with a Shubnikov topological symbol of {3²4.3.4} (tts). Magnetic investigations indicate that the coordination polymer exhibits slow magnetic relaxation.     

NMR and MD Analysis of the Bonding Interaction of Vancomycin with Muramyl Pentapeptide

The article describes an NMR spectroscopy study of interactions between vancomycin and a muramyl pentapeptide in two complexes: vancomycin and a native muramyl pentapeptide ended with D-alanine (MPP-D-Ala), and vancomycin and a modified muramyl pentapeptide ended with D-serine (MPP-D-Ser). The measurements were made in a 9:1 mixture of H₂O and D₂O. The obtained results confirmed the presence of hydrogen bonds previously described in the literature. At the same time, thanks to the pentapeptide model used, we were able to prove the presence of two more hydrogen bonds formed by the side chain amino group of L-lysine and oxygen atoms from the vancomycin carboxyl and amide groups. This type of interaction has not been described before. The existence of these hydrogen bonds was confirmed by the ¹H NMR and molecular modeling. The formation of these bonds incurs additional through-space interactions, visible in the NOESY spectrum, between the protons of the L-lysine amino group and a vancomycin-facing hydrogen atom in the benzylic position. The presence of such interactions was also confirmed by molecular dynamics trajectory analysis.     

Hydrothermal synthesis,crystal structure and fluorescent properties of a novel 1D polymer: VO2(C7H3O4N)Ag(C10H8N2)·H2O

The hydrothermal synthesis of V₂O₅, AgNO₃, pyridine-2,6-dicarboxylic acid (H₂pdc) and 2,2′-bipyridine (bpy) in water at 160 °C for 4 days yields a novel 1D coordination polymer VO₂(C₇H₃O₄N)Ag(C₁₀H₈N₂)·H₂O (1). Each V center chelates to a tridentate ligand pdc^2? and coordinates to two O atoms, while the square based pyramid conformation of Ag center consists of three O atoms and a bpy molecular. V and Ag polyhedra alternate by either carboxyl or oxo bridges to further form a unique 3d–4d heterometal-based 1D double-chain ribbon.     

A reactive distillation process with a sidedraw stream to enhance the production of isopropyl acetate

This paper designs an entrainer combined with a sidedraw to enhance the reactive distillation (RD) process of isopropyl acetate (IPAc). Acetic acid (HAc) reacts with isopropanol (IPOH) to generate IPAc and water (H₂O). The ratio of IPAc to H₂O in the products of esterification is smaller than that in the minimum boiling IPAc–IPOH–H₂O azeotrope, resulting in a mass of organic phase reflux to remove the surplus H₂O from the top of the RD column. This process consumes a high amount of energy. For better energy efficiency, a feasible design flowsheet includes an RD column, a stripper, a top decanter, a middle decanter, and a sidedraw stream to intensify the azeotropic separation where an entrainer is introduced to carry out the surplus water from the middle of the RD column in the form of a liquid phase. The key design variables in the proposed flowsheet are determined to obtain a minimal total annual cost (TAC). As a result, an optimal process design is drawn out while satisfying the stringent specifications for product purity. These results show that the energy requirements of the IPAc system can be decreased by 27.55%.     

Investigation on the Esterification of Fatty Acids Catalyzed by the H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> heteropolyacid

In this work, the H₃PW₁₂O₄₀ heteropolyacid (HPW) was employed as a homogeneous catalyst to promote the efficient esterification (ethanolysis) of a number of saturated and unsaturated fatty acids (myristic, palmitic, stearic, oleic, and linoleic) under mild reaction conditions. HPW showed a similar activity to those observed for p-toluene sulfonic acid (PTSA) and sulfuric acid (H₂SO₄), the other acidic catalysts we compared them with in this study. In the HPW-catalyzed esterification of stearic acid, the addition of water caused a remarkable decrease in the ethyl stearate yields. On the other hand, the increase in the HPW concentration (up to a maximum value) promoted a proportional improvement in the oleic acid to ethyl oleate conversion. Kinetic measurements using oleic acid as a prototype substrate revealed that the esterification reactions catalyzed by HPW, H₂SO₄, and PTSA are of first-order in relation to the fatty acid concentration. Finally, the catalytic activity of HPW remained unaltered even after several recovery/reutilization cycles whereas the tungsten content in the final product (biodiesel produced by the HPW-catalyzed esterification of oleic acid) was found to be at an acceptably low level (0.0095 mg of W per g of biodiesel).     

Interaction energies, structure, and dynamics at functionalized graphitic structure-liquid phase interfaces in an aqueous calcium sulfate solution by molecular dynamics simulation

Molecular dynamics simulations were performed to study the effect of surface functionalization of graphitic structures on the molecular-scale energetic, structure, and dynamics of water and ions at graphite surface-liquid phase interfaces. Three types of carbon surface structures were investigated: a pristine graphite plane and two graphite planes functionalized with hydroxyl (-OH) and carboxylate (-COO⁻, deprotonated carboxyl) groups. A divalent salt, calcium sulfate, was combined with water to simulate an electrolyte liquid phase. Results highlighted the ordering of H₂O molecules that occurs near graphite surfaces and revealed a subtle effect on the position of the H₂O layers associated with ions and functional group type. Surface functionalization of the graphitic structures affected the H-bond network and the orientation of near-surface H₂O molecules, decreased the ion hydration, and significantly restrained the mobility of near-surface H₂O molecules and bulk Ca²⁺ and ions.     

Esterification and transesterification of 9(10)-carboxystearic acid and its methyl esters. Kinetic studies

9(10)-Carboxystearic acid and its mono- and dimethyl esters were esterified and transesterified with 1-butanol, 2-methoxyethanol, 2-chloroethanol, 2,2-dimethylpentanol, 2-ethylhexanol and 1-octanol. Rate studies for the sulfuric acid-catalyzed esterification of 9(10)-carboxystearic acid to alkyl 9(10)-carboxystearate and alkyl 9(10)-carboalkoxystearate indicate than on an average the terminal carboxyl is approximately 26–27 times more reactive than the branched carboxyl group. Esterification is highly dependent on catalyst concentration. Steric hindrance in 2,2-dimethylpentanol and the electrophilic character of 2-methoxyethanol and 2-chloroethanol markedly retard the rate. In addition to the expected diesters, 2-chloroethanol yields esters containing extra-O-CH₂CH₂- groups. The rate of transesterification of the terminal ester group of mono- and dimethyl esters of 9(10)-carboxystearic acid is about two times faster than the rate of esterification of the branched carboxyl group. Transesterification of the branched 9(10)-ester group is extremely slow. Presented at the AOCS Meeting, Atlantic City, October 1971. N. Market. Nutr. Res. Div., ARS, USDA.     

An enzymatic method for the synthesis of mixed-acid phosphatidylcholine

The enzymatic synthesis of PC with decanoic acid in the sn-1 and hexanoic acid in the sn-2 position is described. The procedure comprises the following enzymatic steps: (i) treatment of egg yolk with phospholipase A₂ (PLA₂) to hydrolyze egg yolk PC to 1-acyl lysophosphatidylcholine (LPC); (ii) esterification of 1-acyl LPC with hexanoic acid catalyzed by PLA₂ to yield PC with hexanoic acid in the sn-2 position; (iii) removal of the FA in the sn-1 position by lipase-catalyzed ethanolysis to yield 2-hexanoyl LPC; and finally (iv) introduction of decanoic acid in this position by lipase-catalyzed esterification of 2-hexanoyl LPC to yield 1-decanoyl-2-hexanoyl-PC. Two egg yolks with a weight of 16 g were required to obtain 160 mg of the desired product. The chemical purity of the PC product and the positional purity of the FA were around 99%. The method is applicable for the synthesis of other mixed-acid PC species as well.     

Improved synthetic method and conformation studies of polymers and copolymers of l-β-3,4-dihydroxyphenyl-α-alanine with l-glutamic acid

Eight different copolymers of l-β-3,4-dihydroxyphenyl-α-alanine (l-Dopa) and l-glutamic acid with high degrees of polymerization have been synthesized by the treatment of a series of $\text{copoly}\text{(O,O′-}\text{dimethyl-}\text{l}\text{-Dopa}$, γ-benzyl-l-glutamate) with boron tribromide in chloroform. The conformation of poly(l-Dopa) has been established to be a right-handed helix in trimethyl phosphate on the basis of the following observations. The [θ]₂₂₂ and b₀ values of the copolymers were almost linear with composition in trimethyl phosphate. The linear relationship between the rotation properties and composition indicates that poly(l-Dopa) has the same helical sense as that of poly(l-glutamic acid) which is a right-handed α-helix.     

Solvothermal syntheses,characterizations and properties of two new NiII-PMIDA phosphonates

Two new nickel(II) phosphonates (H₄PMIDA = N-(phosphonomethyl)iminodiacetic acid, H₄L), one-dimensional zigzag chain (NH₄)₂[Ni(PMIDA)(H₂O)] (1) and tetramer (H₃O)₈[Ni₄O₂(HPMIDA)₄(H₂O)₂] (2), have been solvothermally synthesized and characterized by elemental analyses, IR, TGA and X-ray single-crystal diffraction, and their magnetic and fluorescent properties are also reported.Compound 1 is the first chain phosphonate linked by carboxyl group in anti–anti mode based on Ni(II) and H₄PMIDA ligand, and compound 2 with tetranuclear units is the first example of showing the spin-canting antiferromagnetic coupling between Ni(II) centers.     

Novel Esterification of Glycerol Catalysed by Tin Chloride (II): A Recyclable and Less Corrosive Process for Production of Bio-Additives

Abstract  

In this work, a novel process based on use of a SnCl₂·2H₂O catalyst which is less corrosive, inexpensive, and a water tolerant Lewis acid was employed for synthesis of fuel bio-additives from glycerol. High yields and selectivities were achieved for glycerol esterification with acetic acid under mild reaction conditions. The SnCl₂ catalyst showed to be as active as p-toluene sulfonic and sulfuric acid, catalysts commonly used in acid-catalysed esterification reactions. However, its use has significant advantages in comparison to these Br?nsted acid catalysts, including lower reactor corrosion and unnecessary neutralization at the end reaction. The SnCl₂ catalyst can also be recovered and reused without loss of catalytic activity. Additionally, effects of reaction temperature, HOAc:glycerol molar ratio and catalyst concentration on both selectivity and yield of glycerol acetates were also investigated. The lower corrosiveness, facilitated handling, as well as potential for reuse without activity loss after simple recycle protocols are positive aspects of SnCl₂ catalysts.     

A new 3D Cd(II) metal–organic framework with discrete (H2O)6 clusters based on flexible cyclohexane-1,2,4,5-tetracarboxylic acid ligand

A 3D metal–organic framework (MOF), {[Cd₂(CTA)(bpp)₂(H₂O)₂] (H₂O)₃}_n (1) (H₄CTA = cyclohexane-1,2,4,5-tetracarboxylic acid, bpp = 1,3-bis(4-pyridyl)propane), has been synthesized and structurally characterized by elemental analysis, IR and powder X-ray diffraction. Single-crystal X-ray measurement reveals that the complex presents three-dimensional frameworks with 1D channels which are filled by unique (H₂O)₆ clusters. Noteworthily, the H₄CTA ligands keep exclusive conformation, where the carboxyl groups adopt different coordination modes, and the bpp ligands perform two different conformations. Thermogravimetric analysis demonstrates that 1 features favorable thermal stability. Photoluminescence property of 1 is investigated in the solid state at room temperature as well.     

The kinetics of the esterification reaction between castor oil and oleic acid

In this study, esterification of castor oil with oleic acid was investigated in view of the reaction kinetics under various conditions. Potassium hydroxide,p-toluenesulfonic acid and tin chloride (SnCl₂2H₂O) were used as catalysts. Reaction was carried out at 200°C, 225°C and 250° C by using equivalent proportions of the reactants. For tin chloride, experimental data fitted the second-order rate equation, while for the other catalysts the obtained data fitted the third-order rate equation.