Preparation and Characterization of Supported Vanadia Catalyst for the Selective Catalytic Reduction of NO with NH3

The structure characteristics and the catalytic behavior are analyzed on catalysts obtained by oxidative degradation of a planar VO complex on alumosilicate support (cordierite). By means of different techniques (FTIR, DRX, TGA), vanadium oxide formation was determined during the thermal decomposition of the organometallic precursor and the formation of NH₄ species during the reaction. Besides, the catalytic activity was also determined for the selective reduction of NO with ammonia.     

A First‐Principles Study on the Electronic,Vibrational, and Thermodynamic Properties of Jadeite and its Tentative Low‐Density Polymorph

The high‐pressure clinopyroxene mineral jadeite (chemical composition NaAlSi₂O₆) was studied by density‐functional theory with respect to its electronic, vibrational, and thermodynamic properties, correctly reproducing the available experimental data. At a larger‐than‐normal volume, however, a low‐density alumosilicate phase with tetrahedral instead of octahedral Al–O coordination was identified. This low‐density phase was investigated theoretically, too, and the results were compared to jadeite and experimentally observed properties of what has been dubbed jadeite glass. It turned out that the theoretically obtained properties of this hypothetical polymorph, such as the bulk modulus, the molar volume and the vibrational frequencies, agree well with the corresponding properties of the glass phase. Hence, from an inverse structure‐property relationship we propose to model jadeite glass with the aforementioned low‐density alumosilicate phase and tetrahedral Al–O motifs, as suggested from first principles and corroborated from experiment. The possibilities as well as the limitations of electronic, phonon and thermodynamic properties calculations applied to such a polymorph are also discussed.     

Direct contact free real-time acquisition of temperature profiles in adsorbent bed during vacuum swing adsorption

Real-time temperature co-axial profiles in a bed of mesoporous alumosilicate were recorded by means of FPA-based infrared thermography during air drying vacuum swing adsorption cycles. The good correlation between experimentally measured temperature profiles and profiles simulated on the basis of linear driving force model of mass and heat transfer in nonadiabatic regime is observed.     

Synthesis of pyrrolidine and other heterocycles from bu tane-1,4-diol and ethane-1,2-diol

The amination reactions of butane-1,4-diol and ethane-1,2-diol on seven different catalysts obtained by modifying a natural alumosilicate — gumbrin — and a natural zeolite — analcite -with iron and chromium salts, and also by activation with sulfuric acid, have been investigated. The maximum yield of pyrrolidine was obtained in the presence of a catalyst containing ferric oxide on gumbrin.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 937–941, July, 1973.     

Influence of water vapor on the spectral and kinetic characteristics of polyacene absorbates

Stationary and kinetic spectrofluorimetry has been used to investigate the influence of water vapor on the spectral characteristics of naphthalene and anthracene molecules adsorbed on alumosilicate and silica gel. The formation of complexes involving electron transfer has been observed in the ground state as well as after photo-excitation. The contact with water vapor leads to breaking up of the complex of the bound molecules and their transformation from the chemisorbed to the physically adsorbed state. The lifetimes of the molecules in the excited state have been assessed in the case of physical adsorption as well as in the complex.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 6, pp. 753–757, November–December, 1985.     

A study of composite membranes consisting of hydrargillite immobilized in a porous glass

Hydrargillite crystals were synthesized within the pores of a porous membrane (porous glass) from alumosilicate gel prepared by mixing solutions of sodium aluminate and sodium silicate diffusing from opposite sides. A study of the permeability of the composite membrane showed that virtually all the pores are sealed by the crystals grown within them. Dehydration above 200°C increases the permeability of the membrane by two orders of magnitude and subsequent rehydration does not restore the starting properties of the membrane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2842–2845, December, 1990.     

Cyclic alumosiloxanes and alumosilicates: exemplifying the Loewenstein rule at the molecular level

The cyclic alumosiloxane [{LAl(μ-O)(Ph(2)Si)(μ-O)}(2)] (3) and alumosilicate [{LAl(μ-O){((t)BuO)(2)Si}(μ-O)}(2)] (4) were obtained by reaction of the appropriate R(2)Si(OH)(2) precursor (R = Ph, O(t)Bu) with [{LAl(H)}(2)(μ-O)] (1), providing a nice illustration of the Loewenstein rule at work at the molecular level.     

Untersuchungen an oxidischen Katalysatoren. XXXVI. Struktur und thermisches Verhalten röntgenamorpher Al2O3–SiO2-Festkörper

Studies on Oxide Catalysts. XXXVI. Structure and Thermal Behaviour of Silica–Alumina The effect of thermal treatment up to 500°C on silica-alumina was studied by i.r. investigation in the lattice vibration region and the condensation degree of the silicate fragments in the silica-alumina was characterized using the molybdato method. The results of both methods demonstrate the proton form of the amorphous alumosilicates to be thermal instable and to undergo extraction of the aluminium from the alumosilicate lattice. The consequences resulting from this process on the catalytic efficiency of silica-alumina in the cracking reaction of cumene are discussed.     

Gamma-activation analysis of nitrogen solubility in alumosilicates at high pressure and temperature

A solubility of nitrogen in natural basalts and synthesized albite at 1250 °C and 3 kbar was studied by -activation method based on the reaction¹⁴N(,n)¹³N with radiochemical separation of nitrogen by high-temperature extraction at 1800 °C. Detection limit of 0.2 g in the samples of 15–20 mg weight is obtained. The investigation originated from the study of processes of accumulation and redistribution of nitrogen in rock-forming alumosilicate melt of the Earth mantle. The dependence of nitrogen solubility on the oxygen volatility and pressure were obtained (within 1–3 kbar in the presence of IW buffer [iron(Fe)-wustite(FeO)]) and NNO (Ni–NiO), and essential effect of the composition of the initial matrix was found. Special attention was given to standards, background, interference reactions, reliability and accuracy of the results.     

Reduction of copper in porous matrixes. Stepwise and autocatalytic reduction routes

The reduction of Cu(II) oxide species in siliceous matrixes of different porosity (MFI, FAU, MCM-48) and in alumosilicate MFI was studied by temperature-programmed reduction in hydrogen (TPR), by X-ray absorption fine structure (after stationary hydrogen treatments), and by transmission electron microscopy. It was found that the reduction may proceed in one or in two reduction steps. The two-step scheme known for zeolites was observed also for Cu(II) in siliceous microporous matrixes, with similar temperature of Cu(II) reduction onset as for the alumosilicate MFI. Therefore, the two-step scheme cannot be explained by the stabilization of Cu ions by intra-zeolite electrical fields. CuOx clusters in MCM-48 were reduced in a one-step scheme (similar to bulk CuO) at high Cu content (6 wt %) but in a two-step scheme at low Cu content (1 wt %). The two reduction steps observed with most samples cannot be identified with the transitions of all Cu(II) to Cu(I) and of Cu(I) to Cu(0). Instead, Cu(0) nuclei were observed already at low reduction temperatures and were found to coexist with Cu ions over temperature ranges of different extension. This coexistence range was narrow in materials that favor aggregation of the Cu nuclei into particles: Cu-MCM-48 of low Cu content and Cu-ZSM-5. In the latter, metal segregation from the pore system was found to be accompanied by an autocatalytic initiation of the second reduction step. In the siliceous microporous matrixes, the Cu(0) nuclei were observed to coexist with Cu ions over wide temperature ranges (100 K for MFI) at temperatures far above that of Cu reduction in the bulk oxide. These observations suggest that oligomeric Cu metal nuclei which may have been formed, e.g., at the intersections of the MFI channel system, may be unable to activate hydrogen, which would be required for rapid reduction of the coexisting Cu ions.     

On the use of the correlation coefficient r for testing the linearity of calibration functions

This paper criticises the use of the correlation coefficient r for testing the linearity of calibration functions and recommends better methods.

     

Liebig's Metamorphosis: From Organic Chemistry to the Chemistry of Agriculture

Abstract

In Oxford Street a collegemet the eyes

of those who breathe the smoke of London skies,

Grand was its structure, noble was the place

Framed for the training of the rising race.     

Application of HPLC to the Study of the Chloroplast Atpase Mg2+ Dependent Mechanism

Abstract

The determination by HPLC of released ADP from ATP by chloroplast ATPase (CF₁) is described.

The enzymatic rate measured by this method is well defined, over several minutes.

In the case of ? subunit-depleted CF₁ or activated CF₁, the rate is proportional to the enzyme concentration, the steady state theory is followed and the K_m and V_m constants have been calculated.

The enzymatic activity of CF₁ is inhibited by endogenous ? subunit and the inhibition constant has been measured.

The influences of ionic strength, pH, magnesium ion, phosphate and ADP concentrations have been studied and the results obtained by this method have been compared to previously reported data based on rate determination of released phosphate.     

On the Interpretation of Errors in Counting Experiments

Abstract

Digital experiments, such as the measurement of radioactivity, are usually governed by the Binomial or Poisson distribution. Three types of difficulty which commonly arise in the statistical treatment of such experiments include:

a) failure to recognize that the physical quantity of interest may be governed by a compound probability distribution, particularly, when dealing with short-lived radioactivity;

b) the improper use of the chi-squared statistic when making standard error estimates in least-squares calculations

c) selecting the correct number of degrees of freedom and choosing between the χ² dispersion test and the goodness-of-fit test for grouped data.

Examination of the nature of each of these difficulties has been followed by a recommended course of action.     

An Overview of Surfactant Applications in Drilling Fluids for the Petroleum Industry

Surfactants are increasingly being used in an ever-expanding variety of applications for drilling fluids. In oil-based drilling fluids, the most well-known applications of surfactants are as emulsifiers and wetting agents. In water-based drilling fluids, there is a continually-growing variety of applications that include:

• oil-in-water emulsification in base fluid formulations;

• shale-swelling inhibitors to prevent wellbore instabilities;

• detergency to prevent cuttings sticking to drill bit (adhesion of clay to metal parts);

• prevention of differential sticking;

• dispersants to inhibit flocculation of clay particles;

• foaming additives, to generate high gas/water ratio foam used as drilling fluids for low-pressure reservoirs and hard-rock drilling;

• defoaming additives to eliminate undesirable foam in water-based fluids;

• surfactant-polymer complexes for enhanced properties in fluids for low-pressure reservoirs.

This review describes historical and modern applications of surfactant technology in drilling fluids, and the impact of those molecules on drilling operations. Proper selection and application of surfactants in drilling fluids have a significant economic impact, in terms of reducing the amount of lost time and potential trouble, and have a direct consequence on overall drilling performance and results.     

Electrochromatography in the study of ions

Summary Bismuth can be quantitatively separated from Hg, Pb, Cu and Cd by paper electrophoresis and from the band on the filter paper, quantitative estimation of Bi is possible with the help of the photo-electric scanner. The error lies within ±5%.

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Zusammenfassung Die quantitative Bestimmung von Wismut und seine Abtrennung von Hg, Pb, Cu und Cd kann durch Papierelektrophorese und anschließende photoelektrische Auswertung der Papierstreifen erfolgen. Der Fehler ist kleiner als ±5%.

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Part IV: See H. G. Mukerjee: Z. analyt. Chem. 184, 170 (1061).

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The abstract of the paper has been communicated, for publication in the Proceedings of the 50th Indian Science Congress.     

Calculations of the enthalpies of combustion of organic compounds by the additive scheme

The enthalpies of combustion of more than 200 organic compounds were analyzed. Group contributions to Δ_c H ^o were calculated and used to estimate the enthalpies of combustion of a wide range of organic substances of various classes.

     

Contributions to the application of gel-chromatography in residue analysis

Summary A gel-chromatographic separation system using acetone in combination with cyclohexane and petroleum ether as elution solvent is discussed. The elution patterns of more than 100 pesticides and environmental chemicals are determined with this system.

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Beiträge zur Verwendung der Gel-Chromatographie in der RückstandsanalytikII. Ein neues gel-chromatographisches System, das Aceton zur Trennung von Pflanzenschutzmittel und Umweltchemikalien verwendet

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Dedicated to Dr. H. Brüne, Director of the Hessische Landwirtschaftliche Versuchsanstalt, on the occasion of his 60th birthday

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Part I see [1]     

Study of the Simultaneous Binding of ADP and ATP on Coupling Factor CF-1 by a Modification of the Hummel and Dreyer Method

Abstract

A modification of the Hummel and Dreyer method⁽¹⁾, based on anion exchange separation is used here for the study of the simultaneous binding of ADP and ATP on spinach coupling factor CF₁.

This method gives the same results as gel filtration (dissociation constant and number of sites) when ADP alone is present.

The extent of binding of ADP and ATP is approximately the same when mixed in equimolecular ratio, but since endogenous ADP is irreversible bound, this nucleotide is predominant on CF₁.

The binding of one nucleotide is partly prevented by prealable mixing of CF₁ with the other nucleotide. This phenomenon occurs likely at the level of high affinity sites, where binding would not be entirely reversible, contrarily to low affinity sites.

This method is of potential application for other ligands separable by anion exchange chromatography and for other types of chromatography (reversed phase).     

The influence of the dry grinding on the thermal behaviour of pyrophyllite

The differences of the thermal curves (DTA-TG) of pyrophyllite measured before and after grinding have been studied to obtain quantitative information about the alteration of the structure of this layer silicate.The mechanical treatment by dry grinding of pyrophyllite produces a decrease in the particle size of the original material. This strongly influences the thermal behaviour of weight losses on the TG curves decrease, and the endothermic DTA effects shift to lower temperatures, until the mechanochemical limit in particle size reduction is reached.Further grinding produces a disruption of the 21 aluminosilicate structure giving an exothermic DTA effect, and also reagglomeration processes of the amorphous and activated material accompanied by a decrease in specific surface area.

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Zusammenfassung Es wurden vergleichbare Änderungen an thermischen Kurven (DTA, TG) von Pyrophyllit vor und nach Zerkleinerung untersucht, um quantitative Angaben über die Änderung dieses Schichtensilikates zu erhalten.Durch die mechanische, trockene Zerkleinerung von Pyrophyllit kam es gegenüber dem Ausgangsmaterial zu einer Abnahme der Partikelgröße. Durch diesen Umstand wird das thermische Verhalten des erhaltenen Produktes stark beeinflußt. Bis zum Erreichen der mechanochemischen Grenze der Minderung der Partikelgröße nehmen in den TG-Kurven die Temperaturen für die Massenverluste ab, und die endothermen DTA-Effekte werden zu niedrigeren Temperaturen verschoben.Weiteres Zerkleinern führt zu einer Störung der 21-Aluminosilikatstruktur, was einen exothermen DTA-Effekt verursacht, sowie auch zu Reagglomeration des sehr amorphen und aktivierten Materiales, begleitet von einer Minderung des spezifischen Oberfläche.

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Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60^th birthday

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The authors thank Professors J. Sanz and J. M. Trillo for their valuable discussions of some aspects of this paper, and Mr. E. Gomez-Asensio for technical assistance in the SEM work.

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Thanks are extended to the Ministerio of Educacion y Ciencia for a grant to one of the authors (Pedro José Sánchez Soto) which enabled him to make this research.

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This paper was made possible through the financial support of the CICYT, research number GEO90-0060.