Vacuum Microbalance Techniques Research Articles

Evaluation of magnesium aluminate spinel as a sulfur dioxide transfer catalyst

Infrared spectroscopy and vacuum microbalance techniques have been used to study the sulfation of magnesium aluminate spinel, MgAl 2O 4, by oxidation of sulfur dioxide in excess oxygen at temperatures from 300 to 550°C. The results have been compared with those previously obtained for sulfated Al 2O 3, TiO 2, ZrO 2 and MgO with a view to evaluating which material would be a superior SO x transfer catalyst. For low doses of sulfur dioxide, surface sulfates on spinel are mainly formed which are covalently bonded to the surface but, at higher doses, ionic sulfates are incorporated into the bulk of the spinel. At least two types of surface sulfate species have been identified and that formed preferentially at low coverages has the probable structure (−0) 3SO, as was found previously for SO 2 oxidation on Al 2O 3 and TiO 2. All sulfate species are thermally stable to evacuation up to 800°C but are removed between about 800–900°C. They are also readily removed following reduction in excess hydrogen in a relatively narrow temperature range from about 550 to 640°C. On a very low surface area spinel, only bulk sulfate is formed. Relative to the other oxides studied, sulfated spinel has a high thermal stability, the sulfates are easily reduced in hydrogen and it has a high sorption capacity by virtue of its ability to form bulk sulfate species (not observed under the same conditions on Al 2O 3, TiO 2, or ZrO 2). These favorable characteristics account for the use of spinel as a transfer catalyst for reducing SO x emissions.

Some comments on the history of thermogravimetry

In a review of the authors about the history of vacuum microbalance techniques (including a chronology in table form), also published in Thermochimica Acta, (ref. 1) it uas pointed out, that also some corrections are to be made on the history of therinogravimetry. The first findings of balances are dated to about 3000 B.C. A gravimetric hygrometer is mentioned by Nicolaus Cusanus in 1450. In the 19th century chemical reactions at variable temperatures uere investigated using balances. The very beginning of the thermogravinietry is antedated to the work of Talabot who in 1833 at Lyon equipped a laboratory with thermobalances for quality control of Chinese silk.

Surface areas and porosities of particulate matter in turbid estuaries

A vacuum microbalance technique has been used to determine the specific surface areas and porosities of suspended solids and sediments from two turbid estuaries. In the Tamar Estuary, the suspended solids had specific surface areas in the range 8–20 m 2 g −1 whereas the sediments were in the range 5–15 m 2 g −1. Sediments from the iron-rich system of Restronguet Creek were in the range 5–26 m 2 g −1. The specific surface areas and porosities of the particles were influenced by the carbon and non-detrital iron contents. The results are relevant to sorption behaviour of dissolved trace constituents in the presence of natural particles.

Computer-controlled vacuum microbalance techniques for surface area and porosity measurements

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTComputer-controlled vacuum microbalance techniques for surface area and porosity measurementsK. A. Thompson and E. L. Fuller Jr.Cite this: Langmuir 1987, 3, 5, 699–703Publication Date (Print):September 1, 1987Publication History Published online1 May 2002Published inissue 1 September 1987https://doi.org/10.1021/la00077a021RIGHTS & PERMISSIONSArticle Views82Altmetric-Citations3LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (581 KB) Get e-Alerts Get e-Alerts

Mixed Solvents in gas-liquid chromatography : Activity coefficients for chloroform, dichloromethane and ehtyl acetate in squalane-dinonyl phthalate mixtures at 303°K

Activity and partition coefficients for the polar solutes chloroform, dichloromethane and ethyl acetate at infinite dilution in squalane—dinonyl phthalate mixtures have been determined at 303°K by the extrpolation of measurements made using a vacuum microbalance technique. The results are compared with predictions using the Purnell—Andrade and Tiley—Perry relationships. The effect of solvent—solid support ratios on the determined activity coefficients and the adsorption phenomena involved have been examined. Whereas 20% by weight of solvent yields true bulk liquid activity coefficients for chlorform and dichloromethane, a 40% loading is necessary for ethyl acetate.

Vacuum balance and related studies of green and red rusts

Green and red rusts are formed when iron is partially or completely oxidised. Analogues of the rusts may be precipitated from iron(II) and iron (III) salt solutions treated with alkali under reducing or oxidising conditions. Variations in surface area and porosity have been investigated by gravimetric nitrogen gas sorption, using vacuum microbalance techniques. Freshly-precipitated red rusts, hydrous iron (III) oxide, have surface areas of about 200–400 m 2g −1. When they are added to iron (II) hydroxide suspensions kept at pH 7, the green Fe (II)-Fe (III) rusts formed have lower surface areas of about 40–100 m 2g −1, depending on the initial iron(II) sulphate concentrations.

Bet nitrogen adsorption studies of iron oxides from natural and synthetic sources.

A vacuum microbalance technique has been used to obtain the surface areas and porosities of iron oxyhydroxides derived from Fe(III) and Fe(II) sources. The pore shape of the Fe(III)-derived material was of the wide-bodied, narrow-necked type, whereas the Fe(II)-derived precipitates were composed of parallel plates or slit-shaped pores. The surface area of the Fe(II)-derived material was found to be influenced by the temperature of the precipitate formation. These differences in surface character are discussed in relation to the adsorption of trace constituents at the iron oxyhydroxide-water interface.

The conferences on vacuum microbalance techniques

The conferences on vacuum microbalance techniques

Equilibrium sublimation and thermodynamic properties of SnSe and SnSe2

AbstractKnudsen effusion studies of the sublimation of polycrystalline SnSe and SnSe2, prepared by annealing and chemical vapor transport reactions, respectively, have been carried out using vacuum microbalance techniques in the temperature ranges 736–967 K and 608–760 K, respectively.From experimental mass‐loss data for the sublimation reaction SnSe(s) = SnSe(g), the recommended values for the heat of formation and absolute entropy of SnSe(s) were calculated to be ΔH°298,f = −86.4 ± 9.9 kJ · mol−1 and S°298 = 89.0 ± 7.1 J · K−1 · mol−1. From mass‐loss data for the decomposition reaction \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm SnSe}_{\rm 2} ({\rm s)} = {\rm SnSe(s)} + \frac{1}{{\rm x}}{\rm Se}_{\rm x} ({\rm g) (x} = 2 - 8) $\end{document}, the recommended values for the heat of formation and absolute entropy of SnSe2(s) were determined to be ΔH°298,f = −118.1 ± 15.1 kJ · mol−1 and S°298 = 111.8 ± 11.8 J · K−1 mol−1.

Mixed solvents in gas—liquid chromatography : Activity coefficients for diethyl ether in squalane and dinonyl phthalate mixtures at 303°K

Activity and partition coefficients for the polar solute diethyl ether at infinite dilution in squalane and dinonyl phthalate solvent mixtures have been determined at 303°K by the extrapolation of measurements made using a vacuum microbalance technique. The results are compared to predictions using the Purnell—Andrade and the Tiley—Perry relationships. The effect on the activity coefficients resulting from various solvent—solid support ratios has also been investigated.

Mixed solvents in gas-liquid chromatography : Activity coefficients for tetrachloromethane in squalane-dinonyl phthalate mixtures at 303°K

Activity and partition coefficients for tetrachloromethane at infinite dilution in squalane-dinonyl phthalate solvent mixture have been determined at 303°K by the extrapolation of measurements made using a vacuum microbalance technique. The deviation from solution ideality shown in the mixed solvents is greater than that shown in the separate solvents. This results in the activity and partition coefficients in the mixed solvents lying outside the range delinated by the coefficients for the separate solvents for a large part of the mixed solvent composition. The partition coefficients can be accounted for to within 0.2% by conventional solution theory but values predicted by the Purnell-Andrade relation differ by as much as 7%.

The conferences on vacuum microbalance techniques

The conferences on vacuum microbalance techniques

Precipitation and ageing of antimony (III) sulphide

Antimony (III) sulphide has been prepared by precipitation from aqueous solution, under different conditions of concentration, temperature, pH and ageing time. The phase composition, crystallinity and particle size of the precipitates have been studied by X-ray diffraction, electron microscopy and vacuum microbalance technique, and correlated with conditions of precipitation. The sulphide samples were prepared from 1 M, 0.5 M and 0.1 M antimony (III) chloride solutions through which hydrogen sulphide gas was passed at 20 °C and 85 °C. The precipitates were aged for different lengths of time, and examined by X-ray powder diffraction and electron microscopy. The surface area and porosity of selected samples were determined by the BET method from nitrogen adsorption isotherms recorded gravimetrically at −196 °C on a vacuum microbalance. However the above sulphide samples, precipitated at relatively low pH, contained impurities pure antimony sulphide was achieved best by precipitation from a dilute solution (0.015 M) of potassium antimonyl tartrate (tartar emetic) with hydrogen sulphide gas. Precipitation occurred then at the relatively higher pH of 4 – 5 in the presence of smaller concentrations of electrolytes, so that the product was very finely-divided and porous.

Vacuum balance and related studies of carbons used in zinc-lead production

The reduction of metal oxide to metal is an essential step in the extractive metallurgy of zinc and lead. The performance of metallurgical cokes in this reaction is governed by inter alia, their reactivity. In this research the reactivity of selected carbons, including some metallurgical cokes, is investigated as follows. The surface and solid state properties of the materials are examined by vacuum microbalance and microscopic techniques. Their oxidation is studied by thermogravimetry and differential thermal analysis. The extent of reaction is correlated with reaction conditions, for example, temperature and time of oxidation, flow rate and surrounding atmosphere, and particle size, porosity and crystallinity of the carbons. The nitrogen adsorption isotherms of the carbons were recorded at −196°C on a CI Mark II microbalance, specific surface areas were calculated by the BET method. The oxidations were carried out on a Stanton-Redcroft mass flow balance, model MF-H5; the TG and DTA curves were recorded simultaneously on the same sample. The crystallinity and particle size were characterised by scanning and transmission electron microscopy (Jeol SEM35 and Philips EM300 electron microscopes). Results are presented for a selection of charcoals, graphites and cokes.

Decomposition and Thermodynamic Properties of Sn2S3

AbstractKnudsen effusion studies of the decomposition of Sn2S3(s) have been performed employing mass spectrometry in the temperature range 669‐763 K and vacuum microbalance techniques in the range 677 ‐ 820 K yielding pressures from about 10−2 to 10 Pa. The results demonstrate that Sn2S3(s) decomposes under present experimental conditions according to the reaction Sn2S3(s) = 2SnS(s) + 1/2 S2(g). The mean values for the third‐law heat and second‐law entropy of reaction based on direct mass‐loss data are ΔH°298 = 114.0 ± 3.0 kJ/mol and ΔS°298 = 97.3 ± 3.5 J/ K · mol. From these data the standard heat of formation and absolute entropy of Sn2S3(s) are calculated to be −254.5 ± 6.0kJ/mol and 170.5 ± 6.0 J/K · mol, respectively.

Equilibrium sublimation and thermodynamic properties of SnS

Knudsen effusion studies of the sublimation of polycrystalline SnS, prepared by annealing and chemical vapor transport, have been performed employing vacuum micro-balance techniques in the temperature range 733–944 K and at pressures ranging from about 6 × 10 −3 to 11 Pa. The third-law heats of sublimation and second-law entropy of reaction SnS(s) = SnS(g) were determined to be Δ H 0 298 = 220.4 ± 3.0 kJ mole − and Δ S 0 298 = 162.4 ± 4.5 J K −1 mole −1. From these data the standard heat of formation and absolute entropy of SnS(s) were calculated to be −102.9 ± 4.0 kJ mole −1 and 79.9 ± 6.0 J K −1, respectively.

Mixed solvents in gas-liquid chromatography : Activity coefficients for benzene, cyclohexane, pentane and heptane in squalane-dinonylphthalate mixtures at 303 °K

Activity coefficients at infinite dilution for benzene, cyclohexane, pentane and heptane in mixtures of squalane and dinonyl phthalate at 303 °K have been determined by the extrapolation of measurements made using a vacuum microbalance technique. Partition coefficients for the solutes at infinite dilution in the solvent mixtures have been derived and found to differ by as much as 6% from those calculated from the partition coefficients for the pure single solvents using the Purnell-Andrade equation, whereas those calculated on the basis of the Flory—Huggins solution theory differ from the experimentally derived values by no more than 1 %.

Studies on alumina-silica cracking catalysts II. Catalytic activity

In the present investigation, alumina-silica gels, as well as V 2O 5 doped samples of various pore structures, have been examined for cumene cracking activity in a fixed-bed catalytic reactor connected to a flame ionization detector. On estimating the catalytically active sites by adsorption of pyridine on the catalysts, using a vacuum microbalance technique, a correlation between acid sites and OH content was noted. An attempt was made to relate the activity towards cumene cracking with the chemistry as well as the pore structure of the substrate. Doping with V 2O 5 leads to poisoning of some active (acid) sites on the surface. The rate of cumene cracking is approximately proportional to the surface area, and the rate per unit area is roughly proportional to the surface density of acid sites. The activity of a site in the cumene reaction depends not only on whether it is a Brønsted or Lewis acid site but also on the energetic state of the site. The effect of the pore structure thus appears to be indirect in the sense that it is not the accessibility of the reacting molecules to the site, but rather the energetics of the site; this is different in micropores and wider pores.

スパッタ率測定へのマイクロバランスの応用

The torsion vacuum microbalance technique useful for the determination of the sputtering yield of wall materials for fusion reactors was developed. In order to measure the rate of weight change of the samples during sputtering continuously, it is very important to keep the null point drift of the microbalance as small as possible. The deflection angle of the balance beam was detected and amplified by optical lever, and was transformed to electrical output by linear photopotentiometer. The null point drift was mainly caused by temperature change in the laboratory, which induced relative displacement by thermal expansion between the balance system and the optical measuring system. The drift was reduced less than the equivalent weight of 4 × 10 -7 g/hr when the balance system wosset in the thermostat kept at 20 ± 0.5 °C. The sensitivity of the balance was 8.3 × 10 -7 g/mV.The microbalance technique developed was applied to the measurement of sputtering yield of Cu by Ar+. The measurement was carried out with Ar+ ion energy of 0.22 keV, beam current of 0.51.5 μA, and sputtering time of 2 hrs. The initial weight of Cu sample was 0.4g (15 mm × 15 mm sheet) and the sample temperature during sputtering was about 120 °C. The sputtering yields obtained show good agreement with the results reported by Wehner et al. [8] and Weijsenfeld [9].

Knudsen measurements of the sublimation and the heat of formation of GeSe2 [1

AbstractKnudsen effusion studies of the sublimation of polycrystalline GeSe2 have been performed employing mass spectrometry in a temperature range of about 610–750 K and vacuum microbalance techniques in the temperature range 614–801 K and at pressures ranging from about 10−7 − 10−4 atm. The results demonstrate that GeSe2 vaporizes congruently under present experimental conditions according to the predominant reaction (1) GeSe2(s) = GeSe(g) + 1/2 Se2(g) and a minor reaction (2) GeSe2(s) = GeSe2(g).The mean values for the third law heat and second law entropy of reaction (1) based on direct mass‐loss data are ΔH°298 = 70.4 ± 2 kcal/mole and ΔS°298 = 64.7 ± 2 eu. From these the standard heat of formation and absolute entropy of GeSe2(s) were calculated to be −21.7 ± 2 kcal/mole and 24.6 ± 2 eu, respectively.