Production of multihollow polymer particles by the stepwise alkali/acid method IV. Acid treatment process

The effects of pH, temperature and time in the acid-treatment process on the multihollow structure formed within submicron-sized monodispersed polymer particles by the stepwise alkali/acid method proposed by the authors were examined in detail. The original particles were produced by emulsifier-free emulsion terpolymerization of styrene, butyl acrylate, and methacrylic acid. It was clarified that the number and the size of hollows per particle were drastically changed by the acid treatment conditions as well as those in the alkali treatment process.Part CXLV of the series Studies on Suspension and Emulsion     

Effect of ammonia on toluene ammoxidation over oxide catalysts

The increased activity of the catalyst for ammoxidation of toluene observed in the presence of ammonia is ascribed to its binding with the acidic centers. which leads to the formation of new active basic sites on the catalyst surface.

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, .

     

A new method to obtain supported oriented oxides: MoO3 graphite catalyst in propylene oxidation to acrolein

Oriented MoO₃-graphite catalysts were prepared by oxyhydrolysis of a MoCl₅-graphite intercalation compound and used in catalytic oxidation of propylene. Results show a correlation between the building of specific crystal faces of MoO₃ and a selectivity towards acrolein formation.

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MoO₃- -MoCl₅- - . MoO, - .

     

Production of submicron-sized multihollow polymer particles having high transition temperatures by the stepwise alkali/acid method

Submicron-sized multihollow styrene-methacrylic acid (92.6/7.4, molar ratio) copolymer particles having high transition temperature above 100°C were produced by using the stepwise alkali/acid method proposed by the authors. The original particles were prepared by emulsion copolymerization of styrene and methacrylic acid. The effects of pH, temperature and time in the alkali treatment process as the first step on the multihollow structure were clarified under the same acid treatment conditions.Part CLII of the series Studies on Suspension and Emulsion     

Alkylation of toluene with ethylene: An equilibrium approach

The equilibrium product of the toluene-ethylene system has been calculated at atmospheric pressure and 600, 700 and 800 K. Benzene and the xylenes are the principal products. If ethylene aromatization occurs, greater than 50 mol % of the feed toluene would be converted to benzene.

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- 600, 700 800 K . . , 50 . % .

     

A method for the construction of kinetic graph determinants

A new approach for the deduction of kinetic equations based on graph theory is suggested.

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, .

     

Studies of n-octane transformations on zeolites under hydrocracking conditions in a two-reactor flow-circulation system

Transformations of n-octane under hydrocracking conditions in a two-reactor flow-circulation system have been studied. It has been established that at high hydro-dehydrogenation activity of zeolite catalysts the reaction mechanism involves an initial step of paraffin dehydrogenation on a metal component and subsequent steps of cracking, isomerization and disproportionation of intermediate olefins on an acid component. Sodium content in zeolite determines the paraffin hydrocracking selectivity.

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- - . , - , . .

     

Li/MgO catalysts, I. Effect of precursor salts on their structural and surface properties

Li/MgO solids have been prepared from MgO, by thermal decomposition of Mg₅(OH)₂(CO₃)₄·4H₂O or by precipitation from aqueous solutions of magnesium nitrate, and then impregnating the solid thus obtained with aqueous solutions of lithium carbonate or nitrate. Non-porous solids are obtained in all cases. Specific surface area development depends on the nature of the precursors, the MgOMg(OH)₂MgO process being topotactic.

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Li/MgO MgO Mg₅(OH)₂(CO₃)₄·4H₂O . . , MgOMg(OH)₂MgO .

     

Quantum chemical calculations on the catalytic dehydration of 2-propanol

The charge on atoms and the bond strengths in CH₃CHOHCH₃, CH₃ CH₃, CH₃CHOHCH ₂ ^– , CH₃ CH ₂ ^– and CH₃ CH₃...O(H)CH(CH₃)₂ have been calculated by the CNDO/2 method. The results are in agreement with published experimental observations on catalytic dehydration. A modified mechanism of anti-elimination on solid catalysts is proposed.

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CH₃CHOHCH₃, CH₃ CH₃, CH₃CHOHCH ₂ ^– , CH₃ CH ₂ ^– CH₃ CH₃...O(H)CH(CH₃)₂, CNDO/2. . .

     

Binding energy of oxygen to the surface of promoted V?Mo?O catalysts for acrolein oxidation to acrylic acid

It has been established that P, Cs and Cu additives to V–Mo–O catalysts affect essentially both binding energy of surface oxygen and mobility of bulk oxygen.

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P, Cs Cu V–Mo–O .

     

Investigation of catalytic purification of gases from aromatic hydrocarbons

1,1- (AH) ([AH]=6,9 /, 50°C). AH W_i/W_{O 3}=0,40±0,16.

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The kinetics and oxidation products of 1,1-diethoxyethane (AH) ozonolysis have been investigated at [AH]=6.9 mol/l and 50 °C. The initiation efficiency of radical oxidation by ozone is W_i/W_{O 3}=0.40±0.16.

     

Formulation and Preliminary in vivo Testing of Rufloxacin-Cyclodextrin Ophthalmic Solutions

Aim of the present work was to investigate the effect of somecyclodextrins (CDs) on the solubility and ocular bioavailability of rufloxacin base (RUF), with theultimate goal of developing an ophthalmic formulation. Phase solubility studies of RUF inpH 7.4 buffer were carried out in the presence of -cyclodextrin (-CD),hydroxypropyl--cyclodextrin (HP--CD) and -cyclodextrin(-CD). The effect of hydroxypropyl methylcellulose (HPMC) on RUF solubility was evaluated after heating the solutionscontaining HP--CD at 120 °C.A significant enhancement of RUF solubility was achieved by associatingthe drug with CDs, particularly HP--CD. This CD formed with RUF a less stablecomplex than that formed by -CD, but did not suffer the solubility limitations ofthe parent CD, and showed a higher solubilizing capacity than -CD. Addition of 0.25%(w/v) HPMC to solutions containing HP--CD increased the solubilizing effect of this CD,thus allowing reduction of the amount necessary for solubilization of 0.3% (w/v) RUF.Preliminary pharmacokinetic data in rabbits indicated that theocular bioavailability of 0.3% (w/v) RUF solubilized by HP--CD was higher when compared witha 0.3% (w/v) RUF suspension used as reference.     

Electronic state of the active site of A V?P?O/SiO2 catalyst in oxidation of chlorine-containing hydrocarbons

V⁴⁺ ions in slightly associated states are supposed to play the role of V–P–O/SiO₂ active sites. V⁴⁺ ions are reduced to V³⁺ during deactivation of the V–P–O/SiO₂ catalyst.

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V–P–O/SiO₂ V⁴⁺ . V–P–O/SiO₂ V⁴⁺ V³⁺.

     

Temperature-programmed reduction of CuO?NiO/Al2O3 catalysts

Reducibility of NiO/Al₂O₃ and CuO–NiO/Al₂O₃ catalysts has been studied by the TPR method within the temperature range 293–873 K. The results suggest that the copper content essentially does not influence the reducibility of NiO/Al₂O₃.

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NiO/Al₂O₃ CuO–NiO/Al₂O₃ TPR 293–873 . , NiO/Al₂O₃.

     

Topological aspects of differential thermal analysis

The most important calorimetric methods have been reviewed: the differential thermal analysis (DTA) as basic disposition and the scanning calorimetry (DSC) as well as the adiabatic rate calorimetry (ARC). The thermal circuits of these are expressed by bond diagrams as conceived by topological thermodynamics. It has been stated that the heat flux associated with the process of transformation is virtually (uncompensated) transferred in the DTA system, really transferred (compensated) in the DSC and ARC systems, between the two containers through a transfer medium assumed to be purely dissipative.

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Zusammenfassung Eine Übersicht über die wichtigsten kalorimetrischen Methoden, sowie die Differentialthermoanalyse (DTA) als Grundverfahren, die Abtastkalorimetrie (DSC) und die adiabatische Geschwindigkeitskalorimetrie (ARC) wird gegeben. Die thermischen Kreise derselben werden durch Bindungsdiagramme, wie sie an Hand der topologischen Thermodynamik erhalten werden, ausgedrückt. Es wurde festgestellt, dass die Wärmeströmung mit dem Umwandlungsprozess assoziiert scheinbar (unkompensiert) in das DTA-System, wahrhaftig (kompensiert) in die Systeme DSC und ARC übertragen wird, undzwar zwischen den zwei Behältern durch ein als rein zerstreuend angenommenes Transfermedium.

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Résumé Mise au point sur les méthodes calorimétriques les plus importantes: l'analyse thermique différentielle (ATD) comme technique de base, l'analyse calorimétrique différentielle à compensation de puissance (DSC) et la calorimétrie à vitesse adiabatique (ARC). Les circuits thermiques de ces techniques s'expriment par des diagrammes de liaisons comme ceux conçus par la thermodynamique topologique. On établit que le flux de chaleur associé au processus de la transformation est virtuellement transferré (sans compensation) en ATD et réellement transferré (avec compensation) en DSC et ARC, entre les deux conteneurs par un milieu de transfert supposé être purement dissipatif.

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: ( ) , () (). , . , , , . , .

     

Investigation of surface phenomena on solid catalysts by thermogravimetry

Thermogravimetry was applied to the investigation of the phenomena of adsorption, chemisorption, desorption and surface reactions on solid catalysts. The measurements were carried out with 13 NaX and NaY type zeolites and with silica gels treated with sodium hydroxide, in the presence of cumene and methanol. On the basis of the quantitative results it is possible to give an interpretation of surface phenomena and to establish the existence of various active centres on the surface of the catalysts.

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Zusammenfassung Adsorptions-, Chemisorptions- und Desorptionserscheinungen, sowie Oberflächenreaktionen an festen Katalysatoren wurden thermogravimetrisch untersucht. Die Messungen wurden an Zeoliten der Typen 13 NaX und NaY und an mit Natriumhydroxid behandelten Silikagelen in Gegenwart von Cumol und Methanol durchgeführt. Aufgrund der quantitativen Ergebnisse war es möglich, die Oberflächenerscheinungen zu deuten und das Vorhandensein von verschiedenen aktiven Zentren an der Katalysatoroberfläche nachzuweisen.

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Résumé On a appliqué la méthode thermogravimétrique à l'étude des phénomènes d'adsorption, de chemisorption et de désorption ainsi qu'aux réactions de surface sur des catalyseurs solides. Les mesures ont été effectuées sur zéolites de type 13 NaX et NaY et sur des silicagels traités par la soude en présence de cumène et de méthanol. Des résultats quantitatifs permettent de donner une interprétation des phénomènes de surface et d'établir l'existence de divers centres actifs à la surface des catalyseurs.

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, , , . , , , , . 13 NaX NaY , . .

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The authors express their gratitude to Prof. S. Malinowski for help and discussion and to Mr. W. Dziklinski for his technical help.     

Chiral recognition of enantiomeric peptides in water at 25° by calorimetry

The heats of dilution in water of binary and ternary solutions of the two enantiomeric forms ofN-acetylalanineamide have been measured at 25°. The excess enthalpies, expressed as virial expansion series, permit evaluation of the pairwise self and cross enthalpic coefficients. As for the chiral forms of some monosaccharides, the cross coefficient for the interaction between theD andL forms ofN-acetylalanineamide is slightly but significantly different from the corresponding self coefficient. A weak, water-mediated chiral recognition can be assumed to exist between pairs of amide molecules.

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Zusammenfassung Die Verdünnungswärmen von binären und ternären wässrigen Lösungen der zwei enantiomeren Formen von N-Acetylalaninamid wurden bei 25 °C gemessen. Die in einer Virialexpansionsreihe entwickelten Überschußenthalpien ermöglichen die Berechnung der self und cross Enthalpiekoeffizientenpaare. Was die optisch aktiven Formen einiger Monosaccharide anbetrifft, so ist der cross Koeffizient für die Wechselwirkung zwischen der D- und L-Form von N-Acetylalaninamid etwas, aber signifikant verschieden von dem entsprechenden self Koeffizienten. Es kann angenommen werden, daß Paare von Amidmolekülen eine schwache, durch Wasser vermittelte Unterscheidungsfähigkeit hinsichtlich der optischen Aktivität zeigen.

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25° - N-. . L- N- , , , . .

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This work was carried out with the financial support from the italian C. N. R. (Rome) and from the Ministry of Public Education.     

Effect of reduction temperature and support on the surface electronic state of supported Pd catalysts

The effect of metal precursor, support and reduction temperature on the surface reduction of Pd on -Al₂O₃ and SiO₂ has been studied. For catalysts prepared from PdCl₂, temperatures as high as 450 °C are necessary to obtain surface Pd⁰.

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, Pd -Al₂O₃ SiO₂. , , PdCl₂, Pd^o - 450°C.

     

Studies of decomposition kinetics for ozone complexes with cumene and chlorobenzene

Kinetic regularities in decomposition of complexes of aromatic compounds with O₃ have been studied for ozone complexes with cumene and chlorobenzene. Oxidation effect of these complexes on both aromatic compounds and olefins has been established.

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O₃. .

     

Catalytic decomposition of N2O on La2CuO4 in the presence of LaNi5 alloy

Decomposition of N₂O has been studied on pure La₂CuO₄, La₂CuO₄ with 5 and 10 wt. % LaNi₅ and oxidized LaNi₅ in the temperature range of 240–490 °C at 50 and 200 Torr initial pressures of N₂O. The addition of LaNi₅ decreases the energy of activation compared to that of La₂CuO₄ which has been explained based on the dispersity of NiO over La₂CuO₄.

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N₂O La₂CuO₄ La₂CuO₄ LaNi₅ 5–10 .%, 240–490°C N₂O 50 200 . LaNi₅ , . NiO La₂CuO₄.