Physicochemical properties of the products of basic aluminium-potassium sulfate decomposition in hydrogen atmosphere

Low-temperature modifications of aluminium oxide were obtained by thermal decomposition of basic aluminium-potassium sulfate at temperatures 550, 600, and 650°C. Physicochemical properties of the obtained oxides were studied with particular consideration to phase composition and porous structure. It has been shown how the decomposition parameters of the basic salt used determine the porous structure of the obtained oxides.

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Zusammenfassung Durch thermische Zersetzung von basischem Aluminiumkaliumsulfat bei Temperaturen von 550, 600 und 650°C wurden Niedrigtemperaturmodifizierungen von Aluminiumoxid hergestellt. Die physikochemischen Eigenschaften der erhaltenen Oxide wurden in besonderer Hinsicht auf Phasenzusammensetzung und Porenstruktur untersucht. Es wurde gezeigt, wie die Parameter der Zersetzung des eingesetzten basischen Salzes die Porenstruktur der erhaltenen Oxide beeinflussen.

     

Influence of carbon and water vapour on the thermal dissociation of a basic aluminium-potassium sulfate

The process of obtaining a special aluminium oxide by means of the thermal dissociation of a basic aluminium-potassium sulfate in the presence of carbon (soot) and water vapour was studied. Under these conditions, the dissociation of the basic salt occurs at a lower temperature than in presence of air. K₂O-Al₂O₃ and/or Al₂O₃ are formed as fine-grained reaction residues, depending on the final temperature. The technologically useful range of temperatures for the process was established.

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Zusammenfassung Der Herstellungsprozess eines speziellen Aluminiumoxids durch thermische Zersetzung von basischem Kalium-aluminium-sulfat in Gegenwart von Kohlenstoff (Russ) und Wasserdampf wurde untersucht. Unter diesen Bedingungen verläuft die Zersetzung bei tieferer Temperatur als in Gegenwart von Luft, und K₂O.Al₂O₃ und/oder Al₂O₃ werden als feinkörnige Endprodukte (abhängig von der Endtempeatur) erhalten. Der technologisch günstigste Temperaturbereich für den Prozess wurde ermittelt.

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Thermal transformations of the products of partial hydrolysis of hydrous aluminium nitrate

Thermal analysis, mass spectrometry, infrared spectrophotometry, X-ray phase analysis, scanning electron microscopy, and sorption methods were used in the study of thermal transformations of the products of partial hydrolysis of hydrous aluminium nitrate in ammonia medium. It has been found that the process of aluminium nitrate hydrolysis under the conditions applied and in the presence of ammonia gives boehmite as the main product, with some admixture of a basic salt.Aluminium oxide obtained from the products of partial hydrolysis of hydrous aluminium nitrate in ammonia medium at 550°C has a crystalline -Al₂O₃ structure. Its specific surface, as determined by low-temperature adsorption of nitrogen, exceeds 200 m²g^–1. Features of the products are well developed mesopore structure and considerable ability of benzene adsorption. Calcination of the obtained aluminium oxide for 2 h at 900°C reduces its specific surface to about 110 m² g^–1.This revised version was published online in November 2005 with corrections to the Cover Date.     

Mineral-carbon sorbents based on post-decarbonization lime and mixture of hydrocarbons

Summary An attempt was made to obtain mineral-carbon sorbents from waste products of petrochemical industry: lime from the decarbonization of river water to be used in technology and hydrocarbon wastes obtained in the treatment of industrial waste waters. The sorbents were prepared by thermal decomposition of mixtures of the mineral and carbon components. In order to optimize the preparation conditions, physicochemical studies were performed of both the mineral matrix and the mineral-carbon sorbents. Adsorption measurements involving nitrogen, water, and benzene as adsorbates were used for determining the parameters of porous structure of the obtained materials and their hydrophilic-hydrophobic properties. The properties influencing the sorptive properties of the organic compounds present in the petrochemical wastes were pointed out.     

Preface

Tin(II/IV) phosphate was prepared by various synthetic methods. The different methods resulted in tin phosphate with different properties, i.e., different crystalline form and behaviour during thermal treatment. The prepared materials have 3 mol water of crystallisation, which they lose in different ways. Total mass loss was between 20 and 30%. This could be connected with water loss, going generally in two steps in parallel with endothermic processes. At the end of thermal treatment, tin pyrophosphate is obtained, irrespective of the method of preparation used.     

Hydration of Cement Slurry in The Presence of Spent Cracking Catalyst

The physicochemical properties of spent fluidized bed cracking catalyst and its influence on hydration process of cement slurry were studied. The samples were cement slurries prepared with water/solid=0.5 and additions of used catalyst amounted to 0, 5, 10, 15, 20 and 25%with resp. to the solid. After definite time they were subjected to thermogravimetric analysis (TG, DTG, DTA) and, in order to determine the progress of reaction with water, the heat of hydration was measured by means of isotherm calorimetry. The studies disclosed that the spent cracking catalyst is not merely an inactive filler in cement slurries, but it modifies the course of the hydration process. The spent catalyst is a pozzolana additive and its presence leads to a decrease of calcium hydroxide contents in the system. The spent catalyst affect on the heat of cement hydration. Small amounts additive accelerate the process of binding. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of aluminium precursor on physico-chemical properties of aluminium hydroxides and oxides

An attempt to obtain aluminium hydroxide that could give aluminium oxides of increased thermal stability was made. Aluminium hydroxide was precipitated during a hydrolysis of aluminium chloride in ammonia medium. The influence of preparative conditions, such as a dosing rate of aluminium precursor, pH, duration of the precipitate refluxing and temperature of calcination, on the properties of obtained hydroxides and oxides was investigated. The materials were studied with the following methods: thermal analysis, IR spectroscopy, low-temperature nitrogen adsorption and adsorption–desorption of benzene vapours. Precipitated boehmites had high values of S _BET determined from nitrogen adsorption (220–300 m²g^–1), good sorption capacity for benzene vapours, developed mesoporous structure and hydrophilic character. It has been proved that a high pH value during the precipitation of aluminium hydroxide favoured better crystallisation of boehmite structure, higher temperature of its dehydroxylation into γ-Al₂O₃, and delayed transformation of γ phase into α-Al₂O₃. Aluminium oxides derived from the hydroxides precipitated at a high pH were the most stable at high temperatures, and were characterised with the best surface properties. The online version of the original article can be found at     

Investigation of thermal decomposition of hydrated aluminium oxide

The composition of a hydrated aluminium oxide was determined and the course of its thermal decomposition was investigated. The stages of the dissociation were established and all the solid and gaseous intermediates of the decomposition were identified. A correlation was observed between the peak temperatures for boehmite and the particle size and degree of crystallinity.

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Zusammenfassung Die Zusammensetzung eines hydratisierten Aluminiumoxids wurde bestimmt und der Verlauf der thermischen Zersetzung dieses Oxids untersucht. Die Dissoziationsstufen wurden ermittelt und alle gasförmigen und festen Zwischenprodukte der Zersetzung identifiziert. Es wurde eine Korrelation zwischen den Peak-Temperaturen für Böhmit und der Partikelgrö\e und dem Kristallisationsgrad beobachtet.

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Adsorption and Structural Properties of Mineral–Carbon Sorbents

In the present work an attempt was made to obtain mineral–carbon sorbents by thermal decompositon. The mineral matrix for the sorbents (aluminium hydroxide) was based on petrochemical waste stream containing considerable amounts of aluminium chloride. Reference tests were carried out with a model solution prepared with the use of analytical grade AlCl₃. Atactic polypropylene and hydrocarbon mixtures obtained in the flotation of petrochemical waste waters were used as carbon-containing raw materials. The aim of this work was to determine the adsorption and structural characteristics of the complex sorbents and to check the possibility of evaluation of their hydrophobic-hydrophilic properties. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition of basic aluminium-ammonium sulfate (BAAS) in hydrogen atmosphere

The stages of thermal decomposition of basic aluminium-ammonium sulfate (BAAS) in hydrogen atmosphere were studied with use of differential thermal analysis (DTA), thermogravimetric (TG), X-ray diffraction phase analysis (XRD), and chemical analyses. It has been found that hydrogen greatly influences the process of the desulfurization of the investigated compound: this process occurs at lower temperatures as compared to the desulfurization process in air. The final decomposition product of the basic salt at 1223 K is-Al₂O₃. The experimental part is preceded by the thermodynamic analysis of the desulfurization process of BAAS in hydrogen atmosphere, and its results have been correlated with experimental tests.

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Zusammenfassung Die Stufen der thermischen Zersetzung von basischem Aluminium Ammonium Sulfat (BAAS) in WasserstoffatmosphÄre wurden unter Verwendung von Differenzthermoanalyse (DTA), Thermogravimetrie (TG), röntgenographischer Phasenanalytik (XRD) und chemischer Analytik untersucht. Es wurde festgestellt, dass Wasserstoff den Desulfurierungsprozess der untersuchten Verbindung stark beeinflusst, indem dieser bei tieferer Temperatur ablÄuft als die Desulfurierung in Luft. Das Endprodukt der Zersetzung des basischen Salzes bei 1223 K ist-Al₂O₃. Die experimentellen Resultate wurden mit den Ergebnissen einer vorgÄngig durchgeführten thermodynamischen Betrachtung der Desulfurierung von BAAS in WasserstoffatmosphÄre korreliert.