Kinetic Studies of Catalytic Oxidation of Cyclohexene Using Chromium VI Oxide in Acetic Acid Medium

Cyclohexene was oxidized using chromium (VI) oxide (CrO3) in pure acetic acid medium. The products of oxidation were analysed using simple qualitative analysis, IR spectroscopy and Gas chromatography-Mass spectrometry (GC/MS). Kinetics studies were carried out to determine the order of reaction, rate constant and the activation energy with respect to the oxidant using pseudo-order approximation method. The influence of Cu2+, Co2+ and Fe2+ as catalysts were also investigated. Qualitative analyses of the products revealed the presence alcohols and ketones while the GC/MS shows the presence of cyclohexanol (2.46%), cyclohexanone (5.05%), 2-cyclohexen-1-one (59.37%), 1,2-cyclohexanediol monoacetate (9.88%), 2-hydroxy-cyclohexanone (1.75%) and bi-2-cyclohexen-1-yl (5.16%). The reaction order was shown to be 2nd order with respect to the CrO3 with activation energy of 45.32 kJ mol-1 while Co2+ and Fe2+ indicated some catalytic activity on the reaction

Mechanism for partial oxidation of Cyclohexene by Chromium (VI) oxide in acetic acid

The oxidation of cyclohexene by chromium (VI) oxide in aqueous and acetic media has been studied. The reaction products were analysed using classical method, IR and GC/MS analyses. The major products of the oxidation reaction in acetic acid medium are cyclohexanol, cyclohexanone, cyclohex-2-en-1-one, cyclohexan-1,2-diol monoacetate and  Bi-2-cyclohexen-1-yl. However, no reaction was observed between cyclohexene and chromium (VI) oxide in aqueous medium. Based on the result a mechanism for the oxidation reactions has been proposed involving dissociation of acetic acid to form an acetate anion which attacks the chromium (VI) oxide to form an acetochromate ion. The latter then attacks cyclohexene to form an acetochromate cyclohexenyl ion intermediate which undergoes electron shift and rearrangement to produce cyclohexanone and chromium (IV) oxide, thereby regenerating the acid. The proposed mechanism suggests that the acetic acid serves both as homogeneous catalyst as well as medium for the reaction

Trace metal levels of drinking water sources in parts of Osun State, Nigeria

This study was carried out to investigate the portability of drinking water sources available to people in parts of Osun State, Nigeria, especially with respect to trace metal levels. The trace metal contents were determined over a period of six months covering both the rainy and dry seasons. Tap, well, stream and borehole water from five towns (Osogbo, Iwo, Ejigbo, Ile-Ife and Ilesha) in Osun State were analysed using Atomic Absorption Spectrophotometer. The concentrations of the metals analyzed range (µg/mL) as follows: Fe (0.18-0.30), Mn (0.33-0.37), Zn (0.11-0.14), Cu (0.05-1.0), Pb (0.01-0.03), Hg (Nd-0.03), As (Nd-0.03), Cd (Nd-0.04), Cr (0.02-0.05), and Ni (0.02-0.05) while the mean levels (ug/mL) were of the order: Hg (0.01) < Pb (0.02) = As (0.02) = Cd (0.02) < Ni (0.03) < Cr (0.04) < Cu (0.08) < Zn (0.13) < Fe (0.25) < Mn (0.36). The results indicated a significant correlation in the metal contents of the water samples from the various locations as well as the various water sources. The trace metals contents (Fe, Mn, Zn, Cu, Cr and Ni) were below or equal to the limits set by WHO for drinking and domestic water while the toxic metals (Pb, Hg, As and Cd), recorded values higher than the safe limits set by WHO hence, the water sources are capable of constituting serious health hazards. Key Words:     Trace Metals, Water, Borehole, Well, Stream, Tap, Toxicit

Cement stabilisation of crude-oil-contaminated soil

© 2016, Thomas Telford Services Ltd. All rights reserved. Crude-oil-contaminated soils are usually considered unsuitable construction materials for earthworks. This paper presents an experimental investigation of the effects of applying Portland cement on the plasticity, strength and permeability of a crude-oil-contaminated soil in order to ascertain its suitability for use as an earthworks construction material. Series of specific gravity, Atterberg limits, compaction, strength and permeability characteristics were determined for a natural soil, the soil after being artificially contaminated with crude oil and the contaminated soil with varying proportions of added cement. It was found that the geotechnical properties of the soil became less desirable after contamination with crude oil, but the application of cement to the contaminated soil improved its properties by way of cation exchange, agglomeration and cementation. Cement stabilisation of crude-oil-contaminated soil provides a stable supporting structure, as well as a capping layer, that prevents the crude oil from interacting with the construction materials above. Thus, instead of disposing of contaminated soils, creating unnecessary waste and incurring costs, stabilisation with cement – which is practically feasible to undertake on site – makes such soils useful for supporting structural foundations or road pavement structures

Kinetics and mechanism of oxidation of D-xylose and L-arabinose by chromium(VI) ions in perchloric acid medium

The kinetics of oxidation of D-Xylose and L-Arabinose by Cr(VI) ions in perchloric acid medium have been investigated spectrophotometrically under pseudo-first-order conditions. The reactions exhibit first-order rate dependence each on the substrate and oxidant. The order with respect to [H+] is unity while no effect on the reaction rate is found with respect to the ionic strength. The Arrhenius (Ea) and thermodynamic activation parameters (ΔH≠, ΔS≠ and ΔG≠) are evaluated and the reaction mechanism is interpreted in terms of formation of a 1:1 intermediate complex between a protonated chromic acid molecule and a neutral sugar molecule in sharp contrast to the results of our earlier studies on the C6 and C12 sugars

Proximate and nutritional composition of kola nut (Cola nitida), bitter cola (Garcinia cola) and alligator pepper (Afromomum melegueta)

The proximate composition and the mineral content of three (3) traditional ‘snacks’, kolanut (Cola nitida), bitter kola (Garcinia cola) and alligator pepper (Afromomum melegueta) were evaluated. The resultsshow that C. nitida has the highest moisture, crude fat and crude fibre contents of 66.4, 5.71 and 7.13%, respectively. Protein and ash contents were highest in A. melegueta (7.18 and 2.49%, respectively). G. cola has the least content of all nutrients considered except moisture. Generally, C. nitida and G. cola have relatively comparable nutrient compositions while the composition of A. melegueta is relatively different from those obtained for the other two samples. A. melegueta has non-detectable quantity of potassium and phosphorous but has the highest quantity of calcium (388 mg/Kg dry matter), magnesium (960 mg/Kg), iron (37.8 mg/Kg), zinc (32.93 mg/Kg) and manganese (68.53 mg/Kg). C. nitida has the highest content of potassium (3484.67 mg/Kg) and phosphorous (411.43 mg/Kg). G. cola also recorded the least content of all minerals except K and P which were absent in A. melegueta. Manganese was not detected in either of kola nut or bitter kola

Fuel–oxidizer mixtures: their stabilities and burn characteristics

Abstarct A survey of the stability and performance of eleven solid oxidizers and thirteen fuels was performed by differential scanning calorimetry, simultaneous differential thermolysis, and hot-wire ignition. Sugars, alcohols, hydrocarbons, benzoic acid, sulfur, charcoal, and aluminum were used as fuels; all fuels except charcoal and aluminum melted at or below 200 °C. It was found that the reaction between the oxidizer and the fuel was usually triggered by a thermal event, i.e., melt, phase change, or decomposition. Although the fuel usually underwent such a transition at a lower temperature than the oxidizer, the phase change of the fuel was not always the triggering event. When sugars or sulfur were the fuels, their phase change usually triggered their oxidation. However, three oxidizers, KNO3, KClO4, and NH4ClO4, tended to react only after they underwent a phase change or began to decompose, which meant that their oxidization reaction, regardless of the fuel, was usually above 400 °C. KClO4-fuel mixtures decomposed at the highest temperatures, often over 500 °C, with the ammonium salt decomposing almost 100 °C lower. Mixtures with ammonium nitrate (AN) also decomposed at much lower temperatures than those with the corresponding potassium salt. With the exception of the oxidizers triggered to react by the phase changes of the polyols and sulfur, the oxidizer-fuel mixtures generally decomposed between 230 and 300 °C, with AN formulations generally decomposing at the lowest temperature. In terms of heat release, potassium dichromate-fuel mixtures were the least energetic, generally releasing less than 200 J g-1. Most of the mixtures released 1000-1500 J g-1, with potassium chlorate, ammonium perchlorate, and AN releasing significantly more heat, around 2000 J g-1. When the fuel was aluminum, most of the oxidizers decomposed below 500 °C leaving the aluminum to oxidize at over 800 °C. Only two oxidizers reduced the temperature of the aluminum exotherm - chlorate and potassium nitrite. To go to temperatures above 500 °C, unsealed crucibles were necessary, and with these containers, the endothermic volatilization of reactants and products effectively competed against the exothermic decomposition so that heat release values were artificially low