Sami H. Ali

Kinetic study of reactive absorption of some primary amines with carbon dioxide in ethanol solution

Abstract The observed pseudo-first-order rate constant ( k o ) values at 278, 283, 288 and 293 K for the reaction of aniline/cyclohexamine/hexamine with carbon dioxide in ethanol are determined using the stopped flow technique. The highest conversion to carbamate ion is detected with hexamine. The results favour the zwitterion intermediate mechanism proposed by Caplow and Danckwerts. The reaction order increases with the basicity of the amine (ranging from 1 to 2). The rate constants determined can predict the k o values accurately for the amine concentrations and temperatures studied. The basicity of the amine plays a very important role in the first step of the zwitterion formation while the bulkiness, resonance stabilisation of the zwitterion and temperature mainly affect the zwitterion deprotonation by the amine. Among the amines studied the role of the solvent (ethanol) as a base in the deprotonation step can only be ignored in the case of the cyclohexamine. For hexamine, the rate constant for the zwitterion formation step, is more temperature sensitive than for the other two amines.

Reaction kinetics of some secondary alkanolamines with carbon dioxide in aqueous solutions by stopped flow technique

Abstract The kinetics of the reaction between aqueous solutions of carbon dioxide and 2-(methylamino)ethanol (MMEA), 2-( n -butylamino)ethanol (NBAE) and 2-( tert -butylamino)ethanol (TBAE) was investigated over a temperature range of 283–308 K by using the direct stopped flow technique. These secondary alkanolamines differ only in the nature of the alkyl substituent on the amino group. At each of the temperatures studied, MMEA reacts faster than NBAE, which in turn, reacts faster than TBAE. Reactions of MMEA and NBAE can be explained by the zwitterion mechanism. However, the reaction mechanism of the TBAE, a severely hindered amine, is suggested to be similar to that for tertiary amines, but at a faster rate. The rate constants required to predict reaction rates of these three amines have been calculated and presented in this work. Water is found to stabilize and extensively deprotonate the zwitterion formed in the case of both MMEA and NBAE; the zwitterion of the former amine is found to be more stable than that of the latter one and the zwitterion stability for both amines decreases with temperature. At the temperatures studied, steric factors cause TBAE to react slower than its unhindered constitutional isomer, NBAE, but with increase in temperature, the detrimental effect of these steric factors on the reaction rates is found to decrease.

Characterization of iron hydroxide/oxide nanoparticles prepared in microemulsions stabilized with cationic/non-ionic surfactant mixtures

Iron oxide-hydroxide (α-Fe(2)O(3); Fe(OH)(3)) nanoparticles have been prepared by a microemulsion route using ammonia (NH(3)) solution or tetrabutylammonium hydroxide (TBAH) as precipitants. The iron oxide-hydroxide nanoparticles obtained were characterized by TGA, N(2) sorptiometry, XRD, IR, SEM, HR-TEM, and DLS techniques. Properties such as specific surface area (S(BET)), pore sizes and shapes, average particle size and distribution, crystallite structure, and thermal stability were determined. The properties of nanoparticles prepared using NH(3) and TBAH were compared after drying at 100°C and after being calcined in the temperature range 250-1100°C. It was found that the suspensions prepared using TBAH suffered immediate separation while those prepared using NH(3) resulted in very stable suspensions. Also, it was found that TBAH did not offer any advantage over NH(3) either in terms of specific surface area or in particle size of the prepared nanoparticles. Hence, the later part of the study was concentrated on the NH(3)-precipitated nanoparticles with particular emphasis on finding the most favorable, W (water-to-surfactant ratio) and/or surfactant concentration, S, to obtain the best conditions in terms of higher surface areas and narrower particle size distribution. It was found that the prepared suspension consisted of monodisperse nanoparticles (standard deviations <10%) and after separation and drying, high surface area powders were obtained. The highest surface area (315 m(2) g(-1)) was obtained when the smallest W (=20) and highest S (=0.20 mol L(-1)) were employed.

Potential biofuel additive from renewable sources – Kinetic study of formation of butyl acetate by heterogeneously catalyzed transesterification of ethyl acetate with butanol

Butyl acetate holds great potential as a sustainable biofuel additive. Heterogeneously catalyzed transesterification of biobutanol and bioethylacetate can produce butyl acetate. This route is eco-friendly and offers several advantages over the commonly used Fischer Esterification. The Amberlite IR 120- and Amberlyst 15-catalyzed transesterification is studied in a batch reactor over a range of catalyst loading (6-12 wt.%), alcohol to ester feed ratio (1:3 to 3:1), and temperature (303.15-333.15K). A butanol mole fraction of 0.2 in the feed is found to be optimum. Amberlite IR 120 promotes faster kinetics under these conditions. The transesterifications studied are slightly exothermic. The moles of solvent sorbed per gram of catalyst decreases (ethanol>butanol>ethyl acetate>butyl acetate) with decrease in solubility parameter. The dual site models, the Langmuir Hinshelwood and Popken models, are the most successful in correlating the kinetics over Amberlite IR 120 and Amberlyst 15, respectively.

Traffic contribution of volatile organic compounds to the air‐shed of Kuwait

Purpose – This study aims to evaluate the effects of volatile organic compounds (VOCs) on the indoor and outdoor air quality in Kuwait due to vehicular traffic.Design/methodology/approach – About 700 VOCs samples were collected from randomly selected residences within Kuwait. For simplicity, the study was divided into three areas: area A between the first and third ring roads, area B between the third and fifth ring roads and area C between the fifth and sixth ring roads. Hazardous Air Pollutants on Site (HAPSITE), a portable Gas Chromatograph/Mass Spectrometer (GC/MS), was used to gather air samples inside and outside of the residences selected in the study area for a period of three months during 2008.Findings – Median indoor air quality levels in the study area were similar to the outdoor levels. Indoor/outdoor ratios varied from 0.5 to 8 for most compounds, suggesting that the indoor air quality was less than the outdoor air quality. It was found that none of the indoor VOC concentrations measured exc...

A Carbon reaction pathway for dimethyl ether, methanol and methane from syngas on an alumina supported palladium catalyst

Abstract A novel modeling procedure was employed to identify a carbon pathway mechanism for the conversion of syngas to dimethyl ether over an alumina supported palladium catalyst. The concentration of adsorbed carbon monoxide, CO(a), and hydroxycarbon intermediates, CHO(a), CH 2 O(a) and CH 3 O(a), were estimated by comparing the model to the 13 CO tracing of the transient response of naturally occurring dimethyl ether, CH 3 OCH 3 . The path of methanation was identified by estimating the concentration of the adsorbed carbon, C(a), and the combined concentration of adsorbed hydrocarbonaceous species CH x (a), x= 1,2,3 from the isotope transient of methane. The results indicate that methane, methanol and dimethyl ether adsorb on the surface of the catalyst at high exchange rates and that the formation of the methoxy intermediate appears to be the rate controlling step in the synthesis of dimethyl ether. A comparison of the estimated concentrations of adsorbed carbon monoxide as estimated from the dimethyl ether and methanation data suggests that the amount of adsorbed carbon monoxide may not be equally accessible in its entirety to all reaction pathways.

Solubility of Sulfur Dioxide in Chlorine-Treated Wastewater

Abstract The solubility of sulfur dioxide in chlorine-treated wastewater was investigated. An experimental study was carried out to measure the solubility of sulfur dioxide in chlorine-treated wastewater over the temperature range of 10–40 °C. The highest solubility of sulfur dioxide was found to be equal to 1.098 × 10−3 mole/L at 10 °C, whereas the lowest value of 6.17 × 10−4 mole/L was obtained at 40 °C. The solubility of sulfur dioxide was correlated as a second-order dependence on temperature. The measured solubility data of sulfur dioxide in chlorine-treated wastewater were found in good agreement with that obtained using the solubility correlation.

Application of a Second-Order Kinetic Model to a Complex Melt Polymerization Reaction

A novel copolymer system has been synthesized using methyl hydroquinone diacetate (MHQDA), 1,4 naphthalene dicarboxylic acid (1,4 NDCA), and polybutylene terephthalate (PBT) using the melt polymerization technique. The optimum kinetic parameters pertinent to this system are reported in this study. A simple second-order reaction sequence summarizes catalyzed and uncatalyzed reactions between MHQDA, 1,4 NDCA, and PBT. The kinetic parameters for the copolymerization reaction were determined using a new second-order model. This technique was used to compute the moles of acetic acid generated in the polymerization process. The model was compared to that of the experimentally determined data. Close comparison (percentage error of less than 5%) was obtained between the experimental and theoretical data. The kinetic data support block copolyester formation. The thermal data also supports formation of block polymers.