Presence Of Sulphuric Acid Research Articles

Evolution of particle composition in CLOUD nucleation experiments

Abstract. Sulphuric acid, ammonia, amines, and oxidised organics play a crucial role in nanoparticle formation in the atmosphere. In this study, we investigate the composition of nucleated nanoparticles formed from these compounds in the CLOUD (Cosmics Leaving Outdoor Droplets) chamber experiments at CERN (Centre européen pour la recherche nucléaire). The investigation was carried out via analysis of the particle hygroscopicity, ethanol affinity, oxidation state, and ion composition. Hygroscopicity was studied by a hygroscopic tandem differential mobility analyser and a cloud condensation nuclei counter, ethanol affinity by an organic differential mobility analyser and particle oxidation level by a high-resolution time-of-flight aerosol mass spectrometer. The ion composition was studied by an atmospheric pressure interface time-of-flight mass spectrometer. The volume fraction of the organics in the particles during their growth from sizes of a few nanometers to tens of nanometers was derived from measured hygroscopicity assuming the Zdanovskii–Stokes–Robinson relationship, and compared to values gained from the spectrometers. The ZSR-relationship was also applied to obtain the measured ethanol affinities during the particle growth, which were used to derive the volume fractions of sulphuric acid and the other inorganics (e.g. ammonium salts). In the presence of sulphuric acid and ammonia, particles with a mobility diameter of 150 nm were chemically neutralised to ammonium sulphate. In the presence of oxidation products of pinanediol, the organic volume fraction of freshly nucleated particles increased from 0.4 to ~0.9, with an increase in diameter from 2 to 63 nm. Conversely, the sulphuric acid volume fraction decreased from 0.6 to 0.1 when the particle diameter increased from 2 to 50 nm. The results provide information on the composition of nucleated aerosol particles during their growth in the presence of various combinations of sulphuric acid, ammonia, dimethylamine and organic oxidation products.

Ethanol and biogas production after steam pretreatment of corn stover with or without the addition of sulphuric acid

BackgroundLignocellulosic biomass, such as corn stover, is a potential raw material for ethanol production. One step in the process of producing ethanol from lignocellulose is enzymatic hydrolysis, which produces fermentable sugars from carbohydrates present in the corn stover in the form of cellulose and hemicellulose. A pretreatment step is crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars, and later ethanol. This study has investigated steam pretreatment of corn stover, with and without sulphuric acid as catalyst, and examined the effect of residence time (5–10 min) and temperature (190–210°C) on glucose and xylose recovery. The pretreatment conditions with and without dilute acid that gave the highest glucose yield were then used in subsequent experiments. Materials pretreated at the optimal conditions were subjected to simultaneous saccharification and fermentation (SSF) to produce ethanol, and remaining organic compounds were used to produce biogas by anaerobic digestion (AD).ResultsThe highest glucose yield achieved was 86%, obtained after pretreatment at 210°C for 10 minutes in the absence of catalyst, followed by enzymatic hydrolysis. The highest yield using sulphuric acid, 78%, was achieved using pretreatment at 200°C for 10 minutes. These two pretreatment conditions were investigated using two different process configurations. The highest ethanol and methane yields were obtained from the material pretreated in the presence of sulphuric acid. The slurry in this case was split into a solid fraction and a liquid fraction, where the solid fraction was used to produce ethanol and the liquid fraction to produce biogas. The total energy recovery in this case was 86% of the enthalpy of combustion energy in corn stover.ConclusionsThe highest yield, comprising ethanol, methane and solids, was achieved using pretreatment in the presence of sulphuric acid followed by a process configuration in which the slurry from the pretreatment was divided into a solid fraction and a liquid fraction. The solid fraction was subjected to SSF, while the liquid fraction, together with the filtered residual from SSF, was used in AD. Using sulphuric acid in AD did not inhibit the reaction, which may be due to the low concentration of sulphuric acid used. In contrast, a pretreatment step without sulphuric acid resulted not only in higher concentrations of inhibitors, which affected the ethanol yield, but also in lower methane production.

Thyroïdite d’Hashimoto sur hémiagénésie thyroïdienne

Pyrolysis of two representative solid humin samples using pyrolysis GC–MS (300–600 °C, 10 s, He atmosphere) and micro-pyrolysis (500 °C, 12 s, N2 atmosphere) are reported. The humins were obtained by treatment of aqueous solutions of d-glucose and d-fructose at 180 °C in the presence of sulphuric acid (0.1 M) and isolated as brown solids in 20–30% yield. The products were characterised with various techniques (SEM, elemental analysis, solid state CP-NMR, FTIR). Pyrolysis GC–MS showed the presence of furanics and organic acids, though the individual components were present in minor amounts (<1 wt%). Micro-pyrolysis yielded 30 wt% gaseous and liquid products, the remainder being a solid char. Gas–liquid yields are lower than obtained for a typical lignin sample (kraft lignin) under similar conditions.

A Mathematical Model for the Alkylation of Phenol with Octanol-1

A 3-factor 2-level Yates pattern experimental design was used to develop a mathematical model for the alkylation of phenol with octanol-1 in the presence of sulphuric acid. A set of trials was planned with two replicates and the centre point trial with 4 replicates. Main effects as well as two- and three- factor interaction effects were statistically significant. The highest experimental yield was 79.5%. The experimental settings were temperature, 160ºC; molar ratio of phenol to octanol-1, 10:1; amount of 94% sulphuric acid, 8% by wt. of phenol; addition time, 2h and stirring time, 2h. Adequacy of the suggested model was checked. The difference between the experimental and estimated yield was negligible.DOI: http://dx.doi.org/10.3329/dujs.v60i1.10339 Dhaka Univ. J. Sci. 60(1): 65-70 2012 (January)

COUMARINS VIA KNOEVENAGEL CONDENSATION REACTION (KCR) AND PECHMANN CONDENSATION REACTION

Knoevenagel condensation reaction (KCR) and Pechmann condensation reaction are the simplest and most widely used method to synthesize various substituted coumarins. The compounds such as 3–acetylcoumarin, 3–acetyl–7–(diethylamino)coumarin, and 7–(diethylamino)–3–(1–oxobutyl)coumarin were synthesized by KCR method which involved the condensation of salicylaldehyde or 4–(diethylamino)salicylaldehyde with ethyl acetoacetate, 4–(diethylamino)– salicylaldehyde with ethyl butyrylacetate in the presence of dimethylamine as a catalyst. Meanwhile, 7–hydroxy–4–methylcoumarin, 4–methyl–2H–benzo[h]chromen–2–one, 7–hydroxy–4,8–dimethyl– coumarin, 7–hydroxy–4–propylcoumarin, 4–propyl–2H–benzo[h]chromen–2–one, 7–hydroxy–8–methyl–4–propylcoumarin and 7,8–dihydroxy–4–propylcoumarin were synthesized through Pechmann condensation reaction by condensation of resorcinol, 1–napthol or 2–methylresorcinol with ethyl acetoacetate, and resorcinol, 1–napthol, 2–methylresorcinol or pyrogallol with ethyl butyrylacetate, respectively in the presence of sulphuric acid as a catalyst. All compounds were characterized by spectroscopic techniques using infrared (IR), proton and carbon nuclear magnetic resonance (1H and 13C NMR).

Removal of Chromium (VI) from wastewater using chemically activated Syzygium jambolanum nut carbon by batch studies

The chemically activated carbon prepared from Syzygium jambolanum nut, an agricultural waste, after activation with ammonium persulphate in the presence of sulphuric acid and then subjected to thermal activation by dolomite process, was successfully used to remove chromium (VI) from wastewater in batch studies by adsorption process. Effects of pH, carbon dose and equilibration time were determined. Desorption of Cr (VI) was done with 1M NaOH and 10% H2O2 mixture followed by 2 M HCl. Adsorption followed Freundlich, Langmuir and Temkin isotherms but was conformed to Freundlich adsorption isotherm predominantly. Kinetic studies indicated that the removal process followed pseudo second order predominantly rather than pseudo first order and reversible first order reaction. Removal of Cr (VI) followed the film diffusion process. Negative ΔG0 values indicated the feasibility and the spontaneous nature of the adsorption process. The performance of Chemically Activated High Temperature Syzygium jambolanum nut Carbon (CHSJC) was compared with a Commercial Activated Carbon (CAC).

Performance of tobacco oil-based bio-diesel fuel in a single cylinder direct injection engine

In the present investigation, the high viscosity tobacco oil, which has been considered as non-edible oil as a potential alternative fuel for the Compression Ignition Engine (C. I.). Tobacco Methyl Ester (TME) was prepared by transesterification of raw tobacco oil. A two stage transestirification process was developed since tobacco is having higher acidic value. Transesterification was done using NaOH in the presence of sulphuric acid as catalyst and both acid transesterification and base transestirification was performed. Since TME has higher kinematic viscosity, its viscosity has been reduced by blending with neat diesel. The bio-diesel was blended with neat diesel at various volumetric proportions of B2, B5 (denoting 2, 5%) .The performance of this alternate fuel was tested by conducting a series of tests on 4 stroke single cylinder 5.2 kW direct injection diesel engine. The engine was run at different loads like full load, 3/4, 1/2, 1/4 and no load at various speeds and also at constant speed .The tests were conducted by using neat diesel and also diesel fuel blended with TME The combustion characteristics and exhaust emissions like hydrocarbon (HC), carbon (II) oxide (CO) and nitric oxides (NO) were measured. Torque, brake power, specific fuel consumption was also measured and the test was plotted in the graphs. The physical and chemical specifications like flash point, fire point, density, kinematic viscosity and acid number of TME were established. Significant improvement in engine performance was observed. The specific fuel consumption and the exhaust gas temperature reduced due to the decrease in viscosity of TME. From the properties and engine test results it has been established that at lower percentage of blending, TME has improved the engine performance but at higher percentages of blending, the performance and engine emissions were drastically effected. The results show that the TME can be used as an alternate fuel in diesel engines without any engine modifications. Key words: TME (Tobacco Methyl Ester), transesterification, diesel blend Bxx.

A simple spectrophotometric method for the determination of captopril in pharmaceutical preparations using ammonium molybdate

A simple, rapid and sensitive spectrophotometric method for the determination of captopril (CPT) in pharmaceutical formulations is proposed. This method is based on the reduction reaction of ammonium molybdate, in the presence of sulphuric acid, for the group thiol of CPT, producing a green compound (λmax 407 nm). Beer’s law is obeyed in a concentration range of 4.60 x 10-4 – 1.84 x 10-3 mol l-1 of CPT with an excellent correlation coefficient (r = 0.9995). The limit of detection and limit of quantification were 7.31 x 10-6 e 2.43 x 10-5 mol l-1 of CPT, respectively. The proposed method was successfully applied to the determination of CPT in commercial brands of pharmaceuticals. No interferences were observed from the common excipients in the formulations. The results obtained by the proposed method were favorably compared with those given by the official reported method at 95 % confidence level.

A simple spectrophotometric method for the determination of captopril in pharmaceutical preparations using ammonium molybdate

A simple, rapid and sensitive spectrophotometric method for the determination of captopril (CPT) in pharmaceutical formulations is proposed. This method is based on the reduction reaction of ammonium molybdate, in the presence of sulphuric acid, for the group thiol of CPT, producing a green compound (λ max 407 nm). Beer's law is obeyed in a concentration range of 4.60 x 10-4 - 1.84 x 10-3 mol l-1 of CPT with an excellent correlation coefficient (r = 0.9995). The limit of detection and limit of quantification were 7.31 x 10-6 e 2.43 x 10-5 mol l-1 of CPT, respectively. The proposed method was successfully applied to the determination of CPT in commercial brands of pharmaceuticals. No interferences were observed from the common excipients in the formulations. The results obtained by the proposed method were favorably compared with those given by the official reported method at 95 % confidence level.

ChemInform Abstract: Preparation and Characterization of 1,5-Diacyl-2,4-dioxohexahydro-1,3, 5-triazines with Higher Acyl Groups.

The title compounds were prepared from 2,4-dioxohexahydro-triazine (DHT) and the corresponding acid chlorides in the presence of sulphuric acid. They are active acylating agents against piperidine in dioxane as the solvent. Only the diacyl derivatives of DHT with acyl chain lengths up to C6 react with aqueous solutions of sodium perborate forming the corresponding peroxy acids.

Facile Synthesis and In‐Vitro Antitumor Activity of Some Pyrazolo[3,4‐b]pyridines and Pyrazolo[1,5‐a]pyrimidines Linked to a Thiazolo[3,2‐a]benzimidazole Moiety

The key precursor E-3-(N,N-dimethylamino)-1-(3-methylthiazolo[3,2-a]benzimidazol-2-yl)prop-2-en-1-one 4 was synthesized in good yield using Gold's reagent. The reaction of enaminone 4 with 5-amino-3-aryl-1-phenylpyrazoles 5a, b in refluxing acetic acid in the presence of sulphuric acid, yielded pyrazolo[3,4-b]pyridines 7a, b. Similarly, pyrazolo[1,5-a]pyrimidines 10a, b and 14a-f were prepared by reaction of enaminone 4 with 5-amino-1H-pyrazoles 8a, b and 12a-f, respectively. The structure of pyrazolo[1,5-a]pyrimidine 10b was determined by X-ray diffraction. The synthesized compounds were tested for their in-vitro antitumor activity against the colon cancer cell line CaCo-2; their cytotoxicity against the normal fibroblast cell line BHK was explored as well. Some of the tested compounds exhibited cell growth inhibitory activity. The significant antitumor activity of compound 14f against the CaCo-2 cell line (IC(50 )= 0.5 microg/mL) was coupled with a lower toxicity against BHK (IC(50 )= 2.3 microg/mL).

Treatment of ink effluents from flexographic printing by lime precipitation and boron-doped diamond (BDD) electrochemical oxidation

Effluent treatment from flexographic printing was investigated by precipitation/coagulation and electrochemical oxidation over boron-doped diamond electrodes. Precipitation with 3 g/L of lime led to complete removal of effluent turbidity (initial value of about 410 NTU) but only about 20% chemical oxygen demand (COD) decrease (initial value of about 1,900 mg/L). Higher lime dosages (up to 15 g/L) had no effect on separation. On the other hand, coagulation with alum in the range 0.05-1 mM failed to enhance the extent of solids separation achieved by gravity settling alone (i.e. about 60%). Preliminary electrochemical oxidation experiments in the presence of sulphuric acid as supporting electrolyte showed that treatment performance (in terms of COD removal and decrease in sample absorbance at 300 nm) increased with increasing applied current. The latter was more efficiently utilized at shorter treatment times and lower currents with efficiency reaching 30%. Following lime precipitation, the effluent was electrochemically oxidized at alkaline conditions for 360 min yielding 64% absorbance reduction and 50% COD removal (this corresponds to 60% overall COD removal for the combined process). The rather low electrochemical treatment performance may be attributed to limestone deposition and fouling of electrodes and other electrochemical reactor components as evidenced by the gradual drop in conductivity/current throughout the operation.

Spectrofluorimetric Determination of the Hypertensive Drug Captopril Based on Its Oxidation with Cerium(IV)

AbstractA highly sensitive and specific spectrofluorimetric method for the analysis of captopril (CAP) in the pure form and in the tablet dosage forms has been described. The method was based on the oxidation of captopril by cerium(IV) in the presence of sulphuric acid and subsequent monitoring the fluorescence of the induced Ce(III) ion produced at λex = 256 nm and λem = 354 nm. All variables affecting the reaction conditions such as cerium(IV) concentration, type and concentration of acid medium, reaction time, diluting solvents, temperature and heating time were carefully studied and optimized. Under the experimental conditions used, an excellent linear relationship was obtained between fluorescence intensity and the concentration of CAP. A linear range of determination was verified for captopril concentrations between 0.1–1.3 μg mL−1 and the correlation coefficient of determination was 0.9997. Quantitation and detection limits were calculated. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 1.14%. No interference could be observed from the excipients and additives are commonly presented in dosage forms. The proposed method was applied successfully for the assay of the studied drug in pure form and in pharmaceutical dosage forms. Recovery experiments revealed recovery of 99.82–100.21%. The results of the analysis show a good agreement with those obtained by official method stated in the United State Pharmacopoeia.

Kinetics of oxidation of d-glucose by permanganate in aqueous solution of cetyltrimethylammonium bromide

The catalytic effect of cetyltrimethylammonium bromide (CTAB) on the permanganate oxidation of d-glucose has been studied spectrophotometrically in presence of sulphuric acid. It was observed that the reaction proceeds in two stages (a slow step followed by a relatively fast second step). The influence of different parameters was measured i.e., [reactants], [surfactant], [sulphuric acid] and temperature. The absorbance of the reaction mixture increases with [CTAB] which suggests the association of permanganate with the cationic head group of CTAB. The effect of [surfactant] on the rate constants was explained in terms of the pseudo phase model proposed by Menger and Portnoy and modified by Bunton et al. On the basis of observed kinetic results, a suitable mechanism has been proposed.

Kinetic Study of Esterification of Free Fatty Acid in Low Grade Crude Palm Oil using Sulfuric Acid

The kinetics of the esterification of free fatty acids (FFA) in low grade crude palm oil (CPO) with methanol was studied. In this work, the effects of operational variables involved in the esterification process i.e. alcohol to oil molar ratio, reaction temperature, agitation speed and the initial amount of FFA of oil, were studied in the presence of sulphuric acid as catalyst at concentration of 1%-w. The experimental results show that the esterification process could lead to a practical and cost effective FFA removal unit in front of typical oil transesterification for biodiesel production. The experimental results were found to fit a first-order kinetic law. The influence of temperature on the kinetic constants was determined by fitting the results to the Arrhenius equation.

Enargite oxidation: A review

Enargite, Cu 3AsS 4, is common in some deposit types, e.g. porphyry systems and high sulphidation epithermal deposits. It is of environmental concern as a potential source of arsenic. In this communication, we review the current knowledge of enargite oxidation, based on the existing literature and our own original data. Explicit descriptions of enargite oxidation in natural environments are scarce. The most common oxidized alteration mineral of enargite is probably scorodite, FeAsO 4.2H 2O, with iron provided most likely by pyrite, a phase almost ubiquitously associated with enargite. Other secondary minerals after enargite include arsenates such as chenevixite, Cu 2Fe 2(AsO 4) 2(OH) 4.H 2O, and ceruleite, Cu 2Al 7(AsO 4) 4.11.5H 2O, and sulphates such as brochantite, Cu 4(SO 4)(OH) 6, and posnjakite, Cu 4(SO 4)(OH) 6·H 2O. Detailed studies of enargite field alteration at Furtei, Sardinia, suggest that most alteration occurs through dissolution, as testified by the appearance of etch pits at the surface of enargite crystals. However, apparent replacement by scorodite and cuprian melanterite was observed. Bulk oxidation of enargite in air is a very slow process. However, X-ray photoelectron spectroscopy (XPS) reveals subtle surface changes. From synchrotron-based XPS it was suggested that surface As atoms react very fast, presumably by forming bonds with oxygen. Conventional XPS shows the formation, on aged samples, of a nanometer-size alteration layer with an appreciably distinct composition with respect to the bulk. Mechanical activation considerably increases enargite reactivity. In laboratory experiments at acidic to neutral pH, enargite oxidation/dissolution is slow, although it is accelerated by the presence of ferric iron and/or bacteria such as Acidithiobacillus ferrooxidans and Sulfolobus BC. In the presence of sulphuric acid and ferric iron, the reaction involves dissolution of Cu and formation of native sulphur, subsequently partly oxidized to sulphate. At alkaline pH, the reactivity of enargite is apparently slightly greater. XPS spectra of surfaces conditioned at pH 11 have been interpreted as evidence of formation of a number of surface species, including cupric oxide and arsenic oxide. Treatment with hypochlorite solutions at pH 12.5 quickly produces a coating of cupric oxide. Electrochemical oxidation of enargite typically involves low current densities, confirming that the oxidation process is slow. Important surface changes occur only at high applied potentials, e.g. + 0.74 V vs. SHE. It is confirmed that, at acidic pH, the dominant process is Cu dissolution, accompanied (at + 0.56 V vs. SHE, pH = 1) by formation of native sulphur. At alkaline pH, a number of surface products have been suggested, including copper and arsenic oxides, and copper arsenates. XPS studies of the reacted surfaces demonstrate the evolution of Cu from the monovalent to the divalent state, the formation of As–O bonds, and the oxidation of sulphur to polysulphide, sulphite and eventually sulphate. In most natural and quasi-natural (mining) situations, it is expected that enargite reactivity will be slow. Moreover, it is likely that the release of arsenic will be further slowed down by at least temporary trapping in secondary phases. Therefore, an adequate management of exposed surfaces and wastes should minimize the environmental impact of enargite-bearing deposits. In spite of an increasing body of data, there are several gaps in our knowledge of enargite oxidation. The exact nature of most mechanisms and products remains poorly constrained, and there is a lack of quantitative data on the dependence on parameters such as pH and dissolved oxygen.

Corrosion behaviour of Duplex stainless steels in organic acid aqueous solutions

This paper reports on mass loss and electrochemical polarization behaviour of two duplex stainless steels, SAF2205 and SAF2507, in aqueous solutions of acetic acid, formic acid and their mixtures, in the presence of specific contaminant, e.g. sulphuric acid. The effect of temperature and redox couples was also investigated. Both steels withstand corrosion in acetic acid solutions in a wide temperature and concentration range. The corrosion rate is higher in the more dissociated formic acid at the same concentration. Uniform corrosion with selective dissolution of the austenitic phase was observed in all tested solutions, being more pronounced with increasing solution aggressiveness. The presence of sulphuric acid is severely detrimental to the corrosion resistance. The corrosion rate increases almost linearly with H 2SO 4 concentration. The addition of few tens of ppm of oxidant species such as hydrogen peroxide and Fe 3+ or Cu 2+ improves the corrosion performance markedly, leading to corrosion rates close to zero. In particular, the addition of H 2O 2 increases the corrosion potential up to the passivity of the steels owing to the possible formation of peracids.

Biological Transformation of Kimberlite Ores

The weathering of kimberlite ores leads to the weakening of the kimberlite structure, which allows the use of less intensive comminution procedures during the liberation of diamonds from the ore, resulting in a decrease in potential damage to the diamonds. The possibility to use iron- and sulphur-oxidising chemolithotrophic microorganisms as a way to accelerate the weathering of kimberlite ores was evaluated. It was demonstrated that the presence of sulphuric acid as well as ferric iron could result in changes in the clay component of these ores. The results provided promising evidence that weathering can be successfully accelerated, but showed that the degree of transformation varies between different kimberlite types with different mineralogical characteristics.

Overall control strategy of a coupled reactor/columns process for the production of ethyl acrylate

Ethyl acrylate (EA) is widely used in industry as a precursor for varnishes, adhesive, and finishes of papers and textiles. This important ester can be produced directly from ethanol (EtOH) and acrylic acid (AA) via esterification reaction with the presence of sulphuric acid as homogeneous catalyst. The proposed design flowsheet of this process includes a CSTR reactor coupled with a rectifier and an overhead decanter. In order to further purify the final EA product, another stripper is needed with its top vapor recycled back to decanter. The simplest and industrial easily applicable overall control strategy will be investigated with only one tray temperature control loop in each of the two columns. The final proposed overall control strategy of this process is found to be different than another similar coupled reactor/columns process published earlier [I-L. Chien, Y.P. Teng, H.P. Huang, Y.T. Tang, Design and control of an ethyl acetate process: coupled reactor/column configuration, J. Proc. Cont. 15 (2005) 435–449]. Both EtOH and AA feed flow rates are used as manipulated variables in the overall control strategy with CSTR heat duty left as throughput manipulator for the overall process. The final EA product with stringent specifications of 0.1 wt% EtOH and 0.005 wt% AA impurities can be achieved with this proposed overall control strategy despite feed flow rate and feed composition disturbances.

A kinetic study of the esterification of free fatty acids (FFA) in sunflower oil

Abstract The kinetics of the esterification of free fatty acids (FFA) in sunflower oil with methanol in the presence of sulphuric acid at concentrations of 5 and 10 wt% relative to free acids as catalyst and methanol/oleic acid mole ratios from 10:1 to 80:1 was studied. The experimental results were found to fit a first-order kinetic law for the forward reaction and a second-order one for the reverse reaction. The influence of temperature on the kinetic constants was determined by fitting the results to the Arrhenius equation. The energy of activation for the forward reaction decreased with increasing catalyst concentration from 50 745 to 44 559 J/mol. Based on the experimental results, a methanol/oleic acid mole ratio of 60:1, a catalyst (sulphuric acid) concentration of 5 wt% and a temperature of 60 °C provided a final acid value for the oil lower than 1 mg KOH/g oil within 120 min. This is a widely endorsed limit for efficient separation of glycerin and biodiesel during production of the latter.