Kinetics,mass transfer,and thermodynamic and statistical modeling study for esterification of valeric acid with n‐butanol: Homogeneous and heterogeneous catalysis

The esterification of valeric acid with n‐butanol was studied with homogeneous and heterogeneous catalysts. The activity and performance of homogeneous p‐toluenesulfonic acid and heterogeneous cation exchange resin catalysts Amberlyst 36, Indion 190, and Amberlite IRC‐50 were evaluated. The pseudo‐homogeneous kinetic model was used to investigate the kinetic parameters of homogeneous‐ and heterogeneous‐catalyzed esterification. The UNIFAC (universal functional activity coefficient) approach was used to study the nonideality of the esterification reaction. The reaction was statistically modeled and optimized by the application of response surface methodology. The effects of independent variables such as reaction temperature, initial molar ratio, and catalyst loading on the conversion of valeric acid were investigated. The optimized conditions for the esterification reaction catalyzed by Amberlyst‐36 were found as temperature 360.4 K, initial molar ratio 3.8, and catalyst loading 6.7 wt%. The predicted conversion (89%) at these optimized conditions is in good agreement with the experimental conversion (87.3 ± 1.6%).     

New base‐soluble positive‐working photosensitive polyimides having o‐nitrobenzyl ester group

A new positive‐working polyimide having photosensitive o‐nitrobenzyl ester group as side substituent, poly{1,4‐phenyleneoxy‐1,4‐phenylene‐3,6‐di[4‐(o‐nitrobenzyloxy)carbonylphenyl]pyromellitimide} (ODA‐PI‐Nb), was prepared and its aqueous alkali‐developability and photosensitivity were investigated. ODA‐PI‐Nb was synthesized by the esterification reaction of poly[1,4‐phenyleneoxy‐1.4‐phenylene‐3,6‐di(4‐carboxylphenyl)pyromellit imide] (ODA‐PI) with o‐nitrobenzyl bromide in the presence of triethylamine (Et₃N). ODA‐PI‐Nb obtained was characterized by FT‐IR and ¹H‐NMR spectroscopy. The degree of esterification reaction was found from ¹H‐NMR absorption of CH₂ proton to be over 95 mol%. Upon photo‐irradiation ODA‐PI‐Nb transformed to the freely aqueous alkali‐soluble ODA‐PI under formation of o‐nitrosobenzaldehyde. The thickness loss of thin ODA‐PI‐Nb films upon post‐baking at 400°C was in the 10–15% range. ODA‐PI‐Nb showed positive‐tone behavior in characteristic sensitivity curve and positive patterns were obtained using a typical lithographic process using aqueous tetramethylammonium hydroxide developer. The patterns with excellent resolution were observed and evaluated by optical microscopy and scanning electron microscopy. Copyright © 2005 John Wiley & Sons, Ltd.     

Kinetic study on the dehydration of tert‐butyl alcohol catalyzed by ion exchange resins

The dehydration of tert‐butyl alcohol (TBA) in the liquid phase was studied by using an ion exchange resin, Amberlyst 15 (A15) in the H⁺ form. Experiments were carried out both in a semi‐batch reactor and in a continuous stirred tank reactor (CSTR) with wet or dry resins. The results with the dry resin in the semi‐batch reactor were different from those with the wet resin due to the swelling of resin in the presence of water. However, the results in CSTR agreed well with those in the semi‐batch reactor using the wet resin. A rate equation that considered the inhibition of water was formulated. The experimental results agreed well with the calculated ones. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 854–859, 1999     

Kinetics of liquid phase synthesis of tert-amyl methyl ether from tert-amyl alcohol and methanol catalyzed by ion exchange resin

Synthesis of tert-amyl methyl ether (TAME) from methanol (MeOH) and tert-amyl alcohol (TAA) in the liquid phase was studied by using an ion exchange resin, Amberlyst15 (A15) in the H⁺ form. Experiments were carried out in a stirred batch reactor under atmospheric pressure. The effects of catalyst size, agitation speed, temperatures, feed ratio and water on the reaction rate were investigated. Both of intraparticle and external diffusion effects could be neglected in this system. The dehydration of TAA could be decreased by increasing the ratio of MeOH/TAA and the reaction rates were greatly inhibited by water. A kinetic model which considered the inhibition of water was proposed. The experimental results agreed well with the model. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 137–143, 1998.     

The Effect of pH on Continuous Biohydrogen Production from Swine Wastewater Supplemented with Glucose

The effect of pH on hydrogen production from liquid swine manure supplemented with glucose by a mixed culture of fermentative bacteria in an anaerobic sequencing batch reactor was evaluated in this study. At 37 ± 1 °C, five pH values ranging from 4.7 to 5.9 at an increment of 0.3 were tested at a hydraulic retention time (HRT) of 16 h. The results showed that at this HRT, the optimal pH for hydrogen production was 5.0, under which the biogas comprised 33.57 ± 5.65% of hydrogen with a production rate of 8.88 ± 2.94 L-H₂/day and a yield of 1.48 ± 0.49 L-H₂/L liquid swine manure. The highest biomass concentration, highest butyric acid to acetic acid ratio, lowest propionic acid concentration, and the best stability were all found at pH 5.0, while the highest CH₄ productivity was found at pH 5.9. For efficient hydrogen production, oxygen content should be controlled under 2%, beyond which an inverse linear relationship (R ² = 0.986) was observed.     

The influence of dielectric layer on the thermal boundary resistance of GaN-on-diamond substrate

The cooling behavior of GaN-on-diamond substrate can be enhanced by reducing the thermal boundary resistance (TBR), which is mainly determined by the nature of interlayer. Although SiN film is considered as the primary candidate of dielectric layer, it is still needed to be optimized. In order to facilitate the understanding of the influence of dielectric layer on the TBR of GaN-on-Diamond substrate, aluminum nitride (AlN), and silicon nitride (SiN) film were compared systematically, both of which are 100 nm. The time-domain thermoreflectance (TDTR) measurements, adhesion evaluation, and microstructural analysis methods were adopted to analyse these two interlayers. The results show the TBR of SiN interlayer is as low as 38.5 ± 2.4 m²K GW⁻¹, comparing with the value of 56.4 ± 5.5 m²K GW⁻¹ for AlN interlayer. The difference of TBR between these two interlayers is elucidated by the diamond nucleation density, and the adhesion between the diamond film and GaN substrate, both of which are affected by the surface charge and chemical groups of the dielectric layer.     

Esterification reaction kinetics of acetic acid and n-pentanol catalyzed by sulfated zirconia

This study reports experimental data and kinetic modeling of acetic acid esterification with n-pentanol using sulfated zirconia as a catalyst. Reactions were carried out in an isothermal well-mixed batch reactor at different temperatures (50-80°C), n-pentanol to acid molar ratios (1:1-3:1), and catalyst loadings (5-10 wt% in relation to the total amount of acetic acid). The reaction mechanism regarding the heterogeneous catalysis was evaluated considering pseudo-homogeneous, Eley–Rideal, and Langmuir–Hinshelwood model approaches. The reaction mixture was considered a nonideal solution and the UNIQUAC thermodynamic model was used to take into account the nonidealities in the liquid phase. The results obtained indicated that increases in the temperature and catalyst loading increased the product formation, while changes in the n-pentanol to acetic acid molar ratio showed no significant effect. The estimated enthalpy of the reaction was −8.49 kJ mol⁻¹, suggesting a slightly exothermic reaction. The Eley–Rideal model, with acetic acid adsorbed on the catalyst as the limiting step, was found to be the most significant reaction mechanism.     

Rate constant for the reaction of F-atoms with trichloroacetic acid

Kinetics of the reaction of F-atoms with trichloroacetic acid was studied at 293 K using a low-pressure flow reactor. Reactant concentrations were monitored by mass spectrometry combined with molecular beam sampling. The reaction rate constant obtained was k = (4.3 ± 0.8) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. This is an average value determined by the relative method employing four reference reactions of F-atoms: with 1,1,1-trichloroethane, ethanol, cyclohexane, and 2-fluoroethanol, for which rate constant ratios k/k_ref = 7.4 ± 1.2, 0.24 ± 0.02, 0.28 ± 0.02, and 0.34 ± 0.04, respectively, were obtained. The resultant rate constant is compared with the rate constants for the related fluoro-substituted acids.     

Temperature-dependent rate constant for the reaction of F atoms with HNO3

The kinetics of the reaction of F atom with HNO₃, source of NO₃ radicals widely used in laboratory studies, has been investigated at nearly 2.7 mbar total pressure of helium over a wide temperature range, T = 220-700 K, using a low-pressure discharge flow reactor combined with an electron impact ionization quadrupole mass spectrometer. The rate constant of the reaction F + HNO₃ → NO₃ + HF (1) was determined using both relative rate method and absolute measurements under pseudo–first-order conditions, monitoring the kinetics of F-atom consumption in excess of HNO₃, k₁ = (8.2 ± 0.4) × 10⁻¹² exp((315 ± 15)/T) cm³ molecule⁻¹ s⁻¹ (where the uncertainties represent precision at the 2σ level, the estimated total uncertainty on k₁ being 15% at all temperatures). The reaction rate constant was found to be in excellent agreement with the only previous temperature-dependent study. Experiments on detection of the reaction product, HF, have shown that NO₃ and HF forming channel of the title reaction is the dominant, if not unique, on the whole temperature range of the study.     

Kinetics of liquid-phase synthesis of ethyl tert-butyl ether from tert-butyl alcohol and ethanol catalyzed by ion exchange resin and heteropoly acid

Synthesis of ethyl tert-butyl ether (ETBE) from ethanol (EtOH) and tert-butyl alcohol (TBA) in the liquid phase was studied by using ion exchange resin, Amberlyst 15 (A15) in the H⁺ form and heteropoly acid, H_0.5Cs_3.5SiW₁₂O₄₀(HPA). Experiments were carried out in a stirred batch reactor with different temperatures under atmospheric pressure. It was found that water will inhibit the reaction rates greatly and the dehydration of TBA could not be neglected in this study. A kinetics model which considered the inhibition of water and the decrease of volume was proposed. The experimental results agreed well with the model. © 1995 John Wiley & Sons, Inc.     

Rate coefficients for the gas-phase OH + furan (C4H4O) reaction between 273 and 353 K

Rate coefficients, k₁, for the gas-phase OH radical reaction with the heterocyclic ether C₄H₄O (1,4-epoxybuta-1,3-diene, furan) were measured over the temperature range 273–353 K at 760 Torr (syn. air). Experiments were performed using: (i) the photochemical smog chamber THALAMOS (thermally regulated atmospheric simulation chamber, IMT NE, Douai-France) equipped with Fourier Transform Infrared (FTIR) and Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) detection methods and (ii) a photochemical reactor coupled with FTIR spectroscopy (PCR, University of Crete, Greece). k₁(273–353 K) was measured using a relative rate (RR) method, in which the loss of furan was measured relative to the loss of reference compounds with well-established OH reaction rate coefficients. k₁(273–353 K) was found to be well represented by the Arrhenius expression (1.30 ± 0.12) × 10⁻¹¹ exp[(336 ± 20)/T] cm³ molecule⁻¹ s⁻¹, with k₁(296 K) measured to be (4.07 ± 0.32) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The k₁(296 K) and pre-exponential quoted error limits are 2σ and include estimated systematic errors in the reference rate coefficients. The observed negative temperature dependence is consistent with a reaction mechanism involving the OH radical association to a furan double bond. Quantum mechanical molecular calculations show that OH addition to the α-carbon (ΔH_r(296 K) = −121.5 kJ mol⁻¹) is thermochemically favored over the β-carbon (ΔH_r(296 K) = −52.9 kJ mol⁻¹) addition. The OH-furan adduct was found to be stable over the temperature range of the present measurements. Maleic anhydride (C₄H₂O₃) was identified as a minor reaction product, 3% lower-limit yield, demonstrating a non-ring-opening active reaction channel. The present results are critically compared with results from previous studies of the OH + furan reaction rate coefficient. The infrared spectrum of furan was measured as part of this study and its estimated climate metrics are reported.     

Contribution of Glycerol on Production of Poly(γ-Glutamic Acid) in <Emphasis Type="Italic">Bacillus subtilis</Emphasis> NX-2

Glycerol would stimulate the production of poly(γ-glutamic acid) (γ-PGA) and decrease its molecular weight in Bacillus subtilis NX-2. When 20 g/l glycerol was added in the medium, the yield of γ-PGA increased from 26.7 ± 1.0 to 31.7 ± 1.3 g/l, and molecular weight of γ-PGA decreased from 2.43 ± 0.07 × 10⁶ to 1.86 ± 0.06 × 10⁶ Da. In addition, it was found that the decrease of γ-PGA chain length by glycerol would lead to the decrease of broth viscosity during the fermentation and enhanced the uptake of substrates, which could not only improve cell growth but also stimulate γ-PGA production. Moreover, it was also found that glycerol could effectively regulate molecular weight between 2.43 ± 0.07 × 10⁶ and 1.42 ± 0.05 × 10⁶ Da with the concentration ranging from 0 to 60 g/l. This was the first time to discover such contribution of glycerol on γ-PGA production in Bacillus genus. And the effects of glycerol on molecular weight of γ-PGA would be developed to be an approach for the regulation of microbial γ-PGA chain length, which is of practical importance for future commercial development of this polymer.     

Unexpected Formation of A 4,6-O-Propylidene Derivative from Galactose and Allyl Alcohol in the Presence of AmberlystR15

Abstract

Allyl ethers are convenient and widely used protecting groups in synthetic carbohydrate chemistry.² One of the attractive reactions of the allyl ether group is its ready isomerization into a prop-1-enyl ether function under basic or metal-mediated conditions.^2-4 In our research projects to extend galactosyltransferase reactions to the enzymic syntheses of βGal 1,1-linked sugars,⁵ 1-O-allyl galactopyranoside was needed as a key synthetic intermediate. Anhydrous cation exchange resin (Amberlyst^R15:Rohm & Haas Co.) was chosen as the acidic catalyst owing to its ease of handling and removal. In this paper we report an unexpected result of this reaction which gave allyl 4,6-O-propylidene galactopyranoside from galactose and Amberlyst in refluxing allyl alcohol.

On treatment of galactose (200 mg) and Amberlyst (100 mg) in allyl alcohol (5 mL) at 100–110 °C, TLC analysis (silica gel, acetonitrile:water, 10:1) indicated that the allyl glycosylation was completed within 15 min, affording allyl D-galactopyranoside.     

Kinetics and mechanism of dissolved organic phosphorus (DOP) digestion by the UV/O3 process

In this study, the kinetics and mechanism of UV/O₃ synergistic oxidative digestion of dissolved organic phosphorus (DOP) were investigated, focusing on the ozone direct oxidation and hydroxyl radical oxidation parts of glufosinate and triphenyl phosphate (TPhP). The p-chlorobenzoic acid (p-CBA) was selected as the probe compound, and two kinds of reaction kinetic models were proposed by competitive kinetic method with R_ct according to the different scale of rate constants of hydroxyl radical oxidation. Under the condition of weakly alkaline (pH = 9.0) and weakly acidic environment (pH = 5.0), the second-order rate constants of glufosinate and TPhP was determined indirectly to be ko_{3/glufosinate} = (2.903 ± 0.247)M⁻¹s⁻¹ and ko_3/TPhP = (3.307 ± 0.204) M⁻¹s⁻¹ by ozone direct oxidation, and k_{·OH/glufosinate} = (1.257 ± 1.031) × 10⁹ M⁻¹s⁻¹ and k_·OH/TPhP = (7.120 × 10⁸ ± 0.963) M⁻¹s⁻¹ by hydroxyl radical oxidation, respectively. The comparison of the contribution levels of the two parts to the digestion process showed that the contribution levels in the digestion of glufosinate and TPhP processes both the contribution of ·OH were higher than those of ozone, 86.3% and 72.6%, respectively.     

Manganese(II) catalysed oxidation of glycerol by cerium(IV) in aqueous sulphuric acid medium: a kinetic and mechanistic study

The manganese(II) catalysed oxidation of glycerol by cerium(IV) in aqueous sulphuric acid has been studied spectrophotometrically at 25 °C and I = 1.60 mol dm⁻³. Stoichiometry analysis shows that one mole of glycerol reacts with two moles of cerium(IV) to give cerium(III) and glycolic aldehyde. The reaction is first order in both cerium(IV) and manganese(II), and the order with respect to glycerol concentration varies from first to zero order as the glycerol concentration increases. Increase in sulphuric acid concentration, added sulphate and bisulphate all decrease the rate. Added cerium(III) retards the rate of reaction, whereas glycolic aldehyde had no effect. The active species of oxidant and catalyst are Ce(SO₄)₂ and [Mn(H₂O)₄]²⁺. A mechanism is proposed, and the reaction constants and activation parameters have been determined.     

Kinetics of liquid phase synthesis of methyl tert-butyl ether from tert-butyl alcohol and methanol catalyzed by ion exchange resin

Synthesis of methyl tert-butyl ether (abbreviated as MTBE) from methanol (MeOH) and tert-butyl alcohol (TBA) in the liquid phase was studied by using Amberlyst 15 in the H⁺ form as an acid catalyst. Experiments were carried out in a stirred batch reactor at different temperatures (313, 318, and 323 K) under atmospheric pressure. It was found that catalyst sizes and rotation speeds had no significant effects on reaction rates. Mechanism studies showed that three reactions took place simultaneously. It was also found that dehydration of TBA could not be neglected. The experimental concentration profiles with time could be simulated well by simple kinetics. Finally, rate constants could be expressed by Arrhenius equations. © 1993 John Wiley & Sons, Inc.     

Temperature-dependent rate constants for the reactions of chlorine atom with methanol and Br2

Kinetics of the reaction of Cl atoms with methanol has been investigated at 2 Torr total pressure of helium and over a wide temperature range 225-950 K, using a discharge flow reactor combined with an electron impact ionization quadrupole mass spectrometer. The rate constant of the reaction Cl + CH₃OH → products (1) was determined using both absolute measurements under pseudo-first order conditions, monitoring the kinetics of Cl-atom consumption in excess of methanol and relative rate method, k₁ = (5.1 ± 0.8) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, and was found to be temperature independent over the range T = 225-950 K. The rate constant of the reaction Cl + Br₂ → BrCl + Br (3) was measured in an absolute way monitoring Cl-atom decays in excess of Br₂: k₃ = 1.64 × 10⁻¹⁰ exp(34/T) cm³ molecule⁻¹ s⁻¹ at T = 225-960 K (with conservative 15% uncertainty). The experimental data for k₃ can also be adequately represented by the temperature independent value of k₃ = (1.8 ± 0.3) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. The kinetic data from the present study are compared with previous measurements.     

Kinetics of reduction of hexavalent neptunium by nitrous acid in solutions of nitric acid

Nitrous acid is a key redox controlling factor, affecting the speciation of neptunium in the reprocessing of used nuclear fuel by solvent extraction. The kinetics of the reduction of neptunium(VI) by nitrous acid in solutions of nitric acid was investigated spectrophotometrically by the method of initial rates. The reaction is of first order with respect to Np(VI) while the order with respect to HNO₂ is 1.20 ± 0.04. The reaction rate is almost inversely proportional to the hydrogen ion concentration (reaction order −0.92 ± 0.06), indicating that the reaction proceeds primarily through the reaction of neptunium(VI) with the nitrate anion. The experimental value of the rate constant k for the rate law −d[Np(VI)]/dt = k·[Np(VI)]·[HNO₂]^1.2/[H⁺] is of (0.159 ± 0.014) M^−0.2 s⁻¹ in I = 4 M and at 20 °C. The activation energy is (−57.3 ± 1.6) kJ/mol, which is in agreement with previous data on this reaction in perchloric acid.     

Intrinsic ratios of glucose, fructose, glycerol and ethanol 13C/12C isotopic ratio determined by HPLC-co-IRMS: toward determining constants for wine authentication

High-performance liquid chromatography linked to isotope ratio mass spectrometry (HPLC-co-IRMS) via a Liquiface? interface has been used to simultaneously determine ¹³C isotope ratios of glucose (G), fructose (F), glycerol (Gly) and ethanol (Eth) in sweet and semi-sweet wines. The data has been used the study of wine authenticity. For this purpose, 20 authentic wines from various French production areas and various vintages have been analyzed after dilution in pure water from 20 to 200 times according to sugar content. If the ¹³C isotope ratios vary according to the production area and the vintage, it appears that internal ratios of ¹³C isotope ratios ( R_¹³\textC {R_{{{}^{{13}}{\text{C}}}}} ) of the four compounds studied can be considered as a constant. Thus, ratios of isotope ratios are found to be 1.00 ± 0.04 and 1.02 ± 0.08 for R_{¹³\textC\textG/F} {R_{{{}^{{13}}{{\text{C}}_{{{\text{G/F}}}}}}}} and R_{¹³\textC\textGly/Eth} {R_{{{}^{{13}}{{\text{C}}_{{{\text{Gly/Eth}}}}}}}} , respectively. Moreover, R_{¹³\textC\textEth/Sugar} {R_{{{}^{{13}}{{\text{C}}_{{{\text{Eth/Sugar}}}}}}}} is found to be 1.15 ± 0.10 and 1.16 ± 0.08 for R_{¹³\textC\textGly/Sugar} {R_{{{}^{{13}}{{\text{C}}_{{{\text{Gly/Sugar}}}}}}}} . Additions of glucose, fructose and glycerol to a reference wine show a variation of the R_¹³\textC {R_{{{}^{{13}}{\text{C}}}}} value for a single product addition as low as 2.5 g/L⁻¹. Eighteen commercial wines and 17 concentrated musts have been analyzed. Three wine samples are suspicious as the R_¹³\textC {R_{{{}^{{13}}{\text{C}}}}} values are out of range indicating a sweetening treatment. Moreover, concentrated must analysis shows that ¹³C isotope ratio can be also used directly to determine the authenticity of the matrix.     

Kinetics study of propyl acetate synthesis reaction catalyzed by Amberlyst 15

The reaction kinetics of esterification of acetic acid with n‐propanol was investigated. The reaction was catalyzed by the commercial cation‐exchange resin Amberlyst 15, and the kinetic data were obtained in a batch reactor within the temperature range 338–368 K. The chemical equilibrium constant, K_eq, was first determined experimentally; the result shows that K_eq is about 20 and slightly temperature dependent. Altogether 14 sets of kinetic data were then measured. The influences of operating parameters such as temperatures, initial molar ratios, and catalyst concentrations were checked. The pseudo‐homogeneous (PH), Rideal–Eley (RE), and Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic models were developed to interpret the obtained kinetic data. The parameters of the kinetic models were identified by the software DIVA, and the confidence interval of each parameter was also estimated. Both the chemical equilibrium constant and kinetic models were formulated in terms of the liquid phase activity, which was described by the nonrandom two‐liquid (NRTL) model. The LHHW model gives the best fitting result, followed by the RE model and the PH model, whereas the confidence intervals rank in the reverse order. In addition, an effective solution was proposed to overcome a convergence problem occurring in the LHHW model parameter identification, which has been reported several times in the literature. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 245–253, 2007