Presence Of Acid Catalyst Research Articles

Microporous phenol–formaldehyde resin-based adsorbents for pre-combustion CO 2 capture

Different types of phenolic resins were used as precursor materials to prepare adsorbents for the separation of CO 2 in pre-combustion processes. In order to obtain highly microporous carbons with suitable characteristics for the separation of CO 2 and H 2 under high pressure conditions, phenol–formaldehyde resins were synthesised under different conditions. Resol resins were obtained by using an alkaline environment while Novolac resins were synthesised in the presence of acid catalysts. In addition, two organic additives, ethylene glycol (E) and polyethylene glycol (PE) were included in the synthesis. The phenolic resins thus prepared were carbonised at different temperatures and then physically activated with CO 2. The carbons produced were characterised in terms of texture, chemical composition and surface chemistry. Maximum CO 2 adsorption capacities at atmospheric pressure were determined in a thermogravimetric analyser. Values of up to 10.8 wt.% were achieved. The high-pressure adsorption of CO 2 at room temperature was determined in a high-pressure magnetic suspension balance. The carbons tested showed enhanced CO 2 uptakes at high pressures (up to 44.7 wt.% at 25 bar). In addition, it was confirmed that capture capacities depend highly on the microporosity of the samples, the narrow micropores (pore widths of less than 0.7 nm) being the most active in CO 2 adsorption at atmospheric pressure. The results presented in this work suggest that phenol–formaldehyde resin-derived activated carbons, particularly those prepared with the addition of ethylene glycol, show great potential as adsorbents for pre-combustion CO 2 capture.

Glass fiber reinforced composites of phenolic–urea–epoxy resin blends

The present work aims to modify conventional epoxy resin by blending with four different phenolic–urea oligomers. These oligomers are similar to phenolic–urea resin matrix and simultaneously function as amino curing agent for epoxy matrix. In this context, phenolic–urea oligomers were prepared respectively by polycondensation reaction of four phenols namely phenol, m-cresol, resorcinol and 1,5-dihydroxy naphthalene, respectively with formaldehyde and urea in presence of acid catalyst. The resulting oligomers were characterized by elemental analysis, spectral studies (IR & NMR), number average molecular weight (M¯n) estimated by non-aqueous conductometric titration and thermal stability by thermogravimetric analysis (TGA). Each of these oligomers was used in resin matrix as a blending component for the modification of commercial epoxy resin for fabricating glass fiber reinforced laminates. Finally these laminates were evaluated for their synergetic thermal stability, mechanical properties and chemical resistance to different reagents.

Quantum-chemical study of nucleophilic substitution in protonated trisindolylmethane*

The total energies of reactants, products, and transition states of nucleophilic substitution reactions in protonated tris(indol-3-yl)methane have been assessed with the semiempirical AM1 method and the theory of functional density B3LYP/6-31(d) method. The results of calculations indicated that the reactions proceed by an SN1-like mechanism, since the activation barrier for it is significantly lower than in the case of the SN2-like mechanism. Tris(1-alkylindol-3-yl)methanes are the starting materials for obtaining tris(indol-3-yl)methylium salts possessing high cytotoxic activity. Tris(1-alkylindol-3-yl)methylium salts possess high cytotoxic activity and are inducers of apoptosis. The cytotoxic activity grows with increasing length of the alkyl substituent up to C(5) and then falls (1). The properties of unsymmetrically N-substituted tris(1-alkylindol-3-yl)methylium salts have not been studied, since on synthesis of the initial unsymmetrical tris(1-alkylindol-3-yl)methanes by known methods mixtures of compounds are formed. Thus, on interacting 3-formyl-1-methylindole with 1-ethylindole in the presence of acid catalysts a mixture of tris(1-methylindol-3-yl)methane, tris(1-ethylindol-3-yl)methane, bis-(1-ethylindol-3-yl)(1- methyl-indol-3-yl)methane, and (1-ethylindol-3-yl)bis(1-methylindol-3-yl) methane is formed. The ratio of these products is determined by the reaction conditions and the means of separating the mixtures. Analogous mixtures are formed on interacting tris(1-alkylindol-3-yl)methane with 1-alkylindoles in the presence of acid catalysts (Lewis acids) (Scheme 1). It may be proposed that under the action of Lewis acids an electrophilic center is induced in the trisindolylmethane molecule. This center is subject to attack by a nucleophile present in the reaction system (indole and its substituted derivatives). As quantum-chemical calculations of the partial Mulliken charges and Fukui indexes showed, the electron density on the C(3) atom of N-substituted derivatives of indole (possible

ChemInform Abstract: Stereoselective Syntheses of 22-Oxavitamin D3 D and CD Ring Synthones by Using Cleavage of Activated Cyclopropane.

Abstract Homoconjugate 1,5-addition of various alcohols to doubly activated cyclopropane in the presence of acid catalysts was investigated. 22-Oxavitamin D3 D and CD ring synthons were synthesized effectively in short steps using the above reaction.

Acid esterification of a high free fatty acid crude palm oil and crude rubber seed oil blend: Optimization and parametric analysis

Free fatty acids content plays an important role in selecting the appropriate route for biodiesel production. Oils with high content of free fatty acids can be treated by acid esterification where an alcohol reacts with the given oil in the presence of acid catalyst. In the current study, an equivolume blend of crude rubber seed oil and crude palm oil is fed to the reaction with methanol as the alcohol of choice and sulfuric acid. Selected reaction parameters were optimized, using Taguchi method for design of experiments, to yield the lowest free fatty acid content in the final product. The investigated parameters include alcohol to oil ratio, temperature and amount of catalyst. The effect and significance of each parameter were then studied based on the fractional factorial design and verified by additional experiments. The optimum conditions for acid esterification which could reduce the free fatty acid content in the feedstock to lower than 0.6% (95% reduction) were 65 °C, 15:1 methanol to oil ratio (by mole) and 0.5 wt% H 2SO 4 after 3 h of reaction time. Temperature had been found to have the most effect on the reduction of free fatty acids followed by reactants ratio while increasing catalyst amount had nominal effect.

Synthesis, characterization and comparison of group 14 pyrrolides and indolides Ph 3MX (M = Si, Ge, Sn; X = C 4H 4N, C 8H 6N)

The biologically important heterocycles pyrrole, C 4H 4N, and indole, C 8H 6N, ought to be useful as reagents in organic synthesis. Unfortunately, working with them has proved to be difficult because they tend to self-polymerize in solution, especially in the presence of acid catalysts. When the self-polymerization can be controlled, however, the pyrrole and indole units should provide an important route to selective N-metal binding, particularly when these ligands are activated by alkyl-lithium reagents. Using this approach, a general synthesis of the group 14 pyrrolides and indolides, Ph 3MX (M = Si, Ge, Sn; X = C 4H 4N, C 8H 6N), has been developed and the results are reported here. The compounds are formed as high-melting, white crystalline solids and have been characterized by 13C-, 29Si- and 119Sn-NMR, Raman and electron-impact mass spectroscopy as well as elemental analysis. A single-crystal X-ray study of Ph 3Si(C 4H 4N) has shown that the compound is disordered in the tetragonal lattice, even at low temperature (100 K).

Resins IV: Preparation and characterization of terpolymer resins prepared from biphenol, thiourea and formaldehyde

AbstractTerpolymer resins (BPhThF) were synthesized by the condensation of 2,2′‐dihydroxybiphenyl [BPh] and thiourea [Th] with formaldehyde [F] in the presence of acid catalyst and using varied molar ratios of reacting monomers. Terpolymer resin compositions have been determined on the basis of their elemental analysis, and the number average molecular weights of these resins were determined by conductometric titration in nonaqueous medium. Viscometric measurements in dimethyl formamide (DMF) have been carried out with a view to ascertain the characteristic functions and constants. UV–vis, FTIR, and NMR spectra were studied to elucidate the structure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Study of liquid-phase dehydration of d,l-1-(4-aminophenyl)ethanol in the presence of acid catalysts

Thermal acid-catalyzed liquid-phase dehydration of 1-(4-aminophenyl)ethanol at 250–260°C and 30–100 mm Hg was studied. In the presence of KHSO4 a 2:1 mixture of 1-amino-4-ethylbenzene with 4-aminostyrene is formed, the use of KHSO4/KH2PO4 causes the formation of polymers, and the use of H3BO3 (≤ 0.26 wt %) in a mixture with KHSO4 allows the preparation of pure 4-aminostyrene. The structure of the reaction products was confirmed by NMR spectroscopy and by authentic synthesis.

Thermal and ion-exchange studies on chelating terpolymer resins derived from o cresol urea formaldehyde

Terpolymers prepared by condensation of o cresol and urea with formaldehyde in presence of acid catalyst (2M HCl) proved to be selective chelating ion exchange resins for certain metal ions. The molecular weights of the synthesised terpolymers were determined by GPC Technique. TGA analysis was employed to study the thermal stability and the kinetic data like activation energy of the terpolymer resins. Chelation ion exchange properties of these terpolymers were studied for Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+ and Cd2+ ions. A batch equilibrium method was employed in the study of the selectivity of metal ion uptake involving the measurements of distribution of a given metal ion between the polymer samples. The study was carried out over a wide pH range and in media of various ionic strengths.

ChemInform Abstract: Optimizing the Synthesis of 5,10-Disubstituted Tripyrromethanes.

Abstract Condensation of aldehydes with pyrrole in the presence of acid catalyst gave the mixture of dipyrromethanes and tripyrromethanes. The major product was switched from dipyrromethanes to tripyrromethanes according to the sequence of adding the reactants and catalyst. Higher oligomers such as tetrapyrromethane and pentapyrromethane were isolated and characterized from the reaction of 4-methoxycarbonylbenzaldehyde with pyrrole.

Synthesis, characterization of Mannich base oligomers used with epoxy resin for glass fibre-reinforced laminates

This article aims to modify conventional epoxy resin by blending with four different Mannich base oligomers. These oligomers are similar to phenolic resin matrix and simultaneously function as amino curing agent for epoxy matrix. In this context, Mannich base oligomers were prepared, respectively, by Mannich polycondensation reaction of four phenols namely phenol, m-cresol, resorcinol and 1,5-dihydroxy naphthalene, respectively, with formaldehyde and piperazine in presence of acid catalyst. The resulting oligomers were characterized by elemental analysis, spectral studies (IR and NMR), number average molecular mass \( {\bar{M}}_{\rm n} \) estimated by non-aqueous conductometric titration and thermal stability by thermogravimetric analysis (TG). Each of these oligomers was used in resin matrix as a blending component for the modification of commercial epoxy resin for fabricating glass fibre reinforced laminates. Finally, these laminates were evaluated for their synergetic thermal stability, mechanical properties and chemical resistance to different reagents.

Molecular thermodynamics of biodiesel fuel compounds

Biodiesel fuel is a biodegradable clean energetic resource comprised by a mixture of monoalkyl esters of long chain fatty acids that can be obtained from a wide variety of raw materials. In terms of sulfur content, flash point, aromatic content, biodegradability and low emission of greenhouse-gases effect, biodiesel fuel is better than diesel fuel. In this paper we present a molecular-thermodynamic modeling of the phase equilibria of three very common long-chain alkylesters biodiesel compounds: methyl cis-9-octadecenoate (methyl oleate), methyl hexadecanoate (methyl palmitate) and methyl cis,cis,cis-9,12,15-octadecatrienoate (methyl linolenate). For all the cases, molecules are represented as chains of spherical segments that can associate due to the presence of short-ranged attractive sites. These attractive sites as well as the intermolecular interaction between monomer segments are modeled via square-well potentials of variable range (SW), following the Statistical Associating Fluid Theory for Potentials of Variable Range (SAFT-VR; A. Gil-Villegas, A. Galindo, P.J. Whitehead, S.J. Mills, G. Jackson, A.N. Burgess, J. Chem. Phys. 106(1997)4168–4186). The optimized values of the parameters for each pure component are obtained by fitting to vapor pressure and saturated liquid densities data, derived from the empirical Helmholtz free-energy reported recently by Huber et al. (M.L. Huber, E.W. Lemmon, A. Kazakov, L.S. Ott, T.J. Bruno, Energy Fuels 23(2009)3790–3797). Predictions are improved by the use of a discrete potential, instead of a SW potential, to represent segment–segment interactions, that can be tuned to give an optimized description of the liquid–vapor coexistence properties. The results obtained can be used to model reacting systems to produce biodiesel, based on esterification of fatty acids in presence of acid catalyst or on the transesterification with basic catalyst.

Chelation ion‐exchange study of copolymer resin derived from 8‐hydroxyquinoline 5‐sulphonic acid, oxamide, and formaldehyde

AbstractCopolymers (8‐HQ5‐SAOF) were synthesized by the condensation of 8‐hydroxyquinoline 5‐sulphonic acid (8‐HQ5‐SA) and oxamide (O) with formaldehyde (F) in the presence of acid catalyst. Four different copolymers were synthesized by using varied molar proportion of the reacting monomers. Copolymer resin composition has been determined on the basis of their elemental analysis and average molecular weights of these resins were determined by conductometric titration in nonaqueous medium. Viscometric measurement in dimethyl sulphoxide (DMSO) has been carried out with a view to ascertain the characteristic functions and constants. Electronic spectra, FTIR, and proton nuclear magnetic resonance spectra were studied to elucidate the structures. The newly synthesized copolymer proved to be a selective chelating ion‐exchange copolymer for certain metals. The chelating ion‐exchange properties of this synthesized copolymer was studied for different metal ions such as Fe3+, Cu2+, Ni2+, Co2+, Zn2+, Cd2+, and Pb2+. A batch equilibrium method was used in the study of the selectivity of metal ion uptake involving the measurements of the distribution of a given metal ion between the copolymer sample and a solution containing the metal ion only for representative copolymer 8‐HQ5‐SAOF‐I due to economy of space. The study was carried out over a wide pH range, shaking time, and in media of various ionic strengths. The copolymer showed a higher selectivity for Fe3+, Cu2+, and Ni2+ ions than for Co2+, Zn2+, Cd2+, and Pb2+ ions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Thermogravimetric study of 8-hydroxyquinoline 5-sulfonic acid–melamine–formaldehyde terpolymer resins-II

The title terpolymer (8-HQ5-SAMF-II) is synthesized by the condensation of 8-hydroxyquinoline 5-sulfonic acid (8-HQ5-SA) and melamine (M) with formaldehyde (F) in the presence of acid catalyst and using 2:1:3 M proportions of the reacting monomers. The synthesized terpolymer resin is then characterized by different physicochemical techniques viz. number average molecular mass determination, intrinsic viscosity determination, and spectral studies like UV–Visible, IR, 1H NMR, and 13C NMR spectra. The morphology of synthesized terpolymer was studied by scanning electron microscopy (SEM). The thermogravimetry of the terpolymer resin prepared in this study has been carried out by non-isothermal thermogravimetry technique in which sample is subjected to condition of continuous increase in temperature at linear rate. Thermal study of the resin was carried out to determine their mode of decomposition and relative thermal stabilities. Thermal decomposition curves were studied carefully with minute details. The Freeman-Carroll and Sharp-Wentworth methods have been used in the present investigation to calculate thermal activation energy and different kinetic parameter of the terpolymer resins. Thermal activation energy E a calculated with the two above-mentioned methods are in close agreement. The advantage of Freeman-Carroll method is to calculate both the order of reaction n and energy of activation in one single stage by keeping heating rate constant. By using data of thermogravimetry, various thermodynamic parameters like frequency factor Z, entropy change ΔS, free energy change ΔF, and apparent entropy S* have been determined using Freeman-Carroll method.

Oxidative Desulfurization of Naphtha with Hydrogen Peroxide in Presence of Acid Catalyst in Naphtha/Acetic Acid Biphasic System

Oxidative desulfurization of naphtha with H2O2 in the presence of H2SO4 in the naphtha/acetic acid (AcOH) biphasic system was investigated. All organosulfur compounds examined were smoothly oxidized in AcOH by peracetic acid effectively formed from AcOH and H2O2 in the presence of H2SO4. The order of the oxidation reactivities was sulfides, disulfides > benzothiophenes > thiophenes. The organosulfur compounds in octane were also oxidized with H2O2 in the presence of H2SO4 in the octane/AcOH biphasic system. The oxidation proceeded in the AcOH phase and most of the oxidized sulfur compounds resided in this phase, resulting in the successive removal of the sulfur compounds from the octane phase. This oxidative treatment effectively reduced the sulfur content of naphtha, and adsorption with silica gel further reduced the sulfur content to below 0.5 mass ppm. In addition, hydrodesulfurization is an effective pretreatment for this oxidative desulfurization of naphtha, resulting in further reduction of the sulfur content to below 0.1 mass ppm.

Study of Non‐Isothermal Decomposition and Kinetic Analysis of 2,4‐Dihydroxybenzoic Acid‐ Melamine‐Formaldehyde Copolymer

A copolymer (2,4‐DHBAMF) synthesized by the condensation of 2,4‐dihydroxybenzoic acid and melamine with formaldehyde in the presence of acid catalyst using varied molar proportions of the reactants. A composition of the copolymer has been determined by elemental analysis. The number average molecular weight has been determined by conductometric titration in non‐aqueous medium. The copolymer has been characterized by UV‐Visible, IR and 1H NMR spectral analysis. Thermogravimetric analysis was carried out to study the decomposition and various kinetic parameters. Freeman Carroll and Sharp Wentworth methods have been applied for the calculation of kinetic parameters while the data from Freeman Carroll method have been used to determine various thermodynamic parameters such as order of reaction, energy of activation, frequency factor, entropy change, free energy change and apparent entropy change. The results indicate that given copolymer have potential as matrix resin for long term applications at temperature up to 350 °C.

Synthesis and Studies of Novel Optically Active Schiff’s Base Derivatives and their Antimicrobial Activities

Several new Schiff’s base derivatives were prepared by condensing various substituted benzaldehyde with 1‐(4‐aminophenyl)‐2‐{4‐[(S)‐(4‐chlorophenyl)(phenyl) methyl]‐1‐piperazinyl}ethanone in presence of acid catalyst under reflux condition. All the compounds were characterized by elemental analysis and spectral studies. The newly synthesized compounds were evaluated for their antibacterial and antifungal activity.

Catalytic conversion of glycerol to value added liquid products

Catalytic conversion of glycerol was performed for production of value-added liquid chemicals. In this work, a systematic study has been conducted to evaluate the effects of operating conditions such as glycerol conversion to liquid chemical products in the presence of acid catalysts. Experiments were performed in a fixed-bed reactor using HZSM-5, HY, silica-alumina and γ-alumina catalysts. The temperature, carrier gas flow rate and weight hourly space velocity (WHSV) were maintained in the range of 350–500 °C, 20–50 mL/min and 5.40–21.60 h −1, respectively. The main liquid chemicals detected in liquid product were acetaldehyde, acrolein, formaldehyde and hydroxyacetone. Under all experimental conditions complete glycerol conversion was obtained over silica-alumina and γ-alumina. A maximum liquid product yield of approximately 83 g/100 g feed was obtained with these two catalysts when the operating conditions were maintained at 380 °C, 26 mL/min and 8.68 h −1. Maximum glycerol conversions of 100 wt% and 78.8 wt% were obtained in the presence of HY and HZSM-5 at temperature, carrier gas flow rate and WHSV of 470 °C, 26 mL/min and 8.68 h −1. HY and HZSM-5 produced maximum liquid product of 80.9 and 59.0 g/100 g feed at temperature of 425 and 470 °C, respectively. Silica-alumina produced the maximum acetaldehyde (∼24.5 g/100 g feed) whereas γ-alumina produced the maximum acrolein (∼25 g/100 g feed). Also, silica-alumina produced highest formaldehyde yield of 9 g/100 g feed whereas HY produced highest acetol yield of 14.7 g/100 g feed. The effect of pore size of these catalysts was studied on optimum glycerol conversion and liquid product yield.

Terpolymer resin–III: Synthesis and characterization of 8‐hydroxyquinoline–dithiooxamide–formaldehyde terpolymer resins

AbstractTerpolymer resins (8‐HQDF) were synthesized by the condensation of 8‐hydroxyquinoline (8‐HQ) and dithiooxamide (D) with formaldehyde (F) in the presence of acid catalyst and using varied molar ratios of reacting monomers. Terpolymer resins compositions have been determined on the basis of their elemental analysis and the number average molecular weights of these resins were determined by conductometric titration in non‐aqueous medium. Viscometric measurements in dimethyl formamide (DMF) have been carried out with a view to ascertain the characteristic functions and constants. The UV‐visible, FTIR, and proton nuclear magnetic resonance (H+ NMR) spectra were studied to elucidate the structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Terpolymer resin VIII: Chelation ion‐exchange properties of 2,4‐dihydroxybenzophenone‐oxamide‐formaldehyde terpolymer resins

AbstractTerpolymer resins (2,4‐DHBPOF) were synthesized by the condensation of 2,4‐dihydroxybenzophenone and oxamide with formaldehyde in the presence of acid catalyst and using varied molar ratios of reacting monomers. Terpolymer resins composition has been determined on the basis of elemental analysis and the number average molecular weight of these resins was determined by conductometric titration in nonaqueous medium. Viscometric measurements in N,N‐dimethyl formamide have been carried out with view to ascertain the characteristic functions and constants. UV–visible, IR and NMR spectra were studied to elucidate the structure. The ion‐exchange study of the prepared resin was checked by batch equilibrium method with selected metal ions, Cu2+, Hg2+, Cd2+, Co2+, Zn2+, Ni2+, Pb2+, and Fe3+ at varying electrolyte concentration, pH and time. It is found that, resin can be used as ion exchanger. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009