Showing papers on "BET theory published in 1988"

The Corrosion of Carbon Black Anodes in Alkaline Electrolyte III . The Effect of Graphitization on the Corrosion Resistance of Furnace Blacks

Abstract: A selection of furnace black carbons of varying surface area and industry type were heat treated in purified helium at 2700°C and the corrosion resistance was measured under conditions of oxygen evolution in 30% at 55°C The extent of graphitization was determined qualitatively by x‐ray diffraction and by transmission electron microscopy (TEM) Separate linear correlations of the corrosion rate per unit mass with the BET surface area were observed for furnace blacks and for graphitized furnace blacks, with the rate for the graphitized blacks being a factor of ca 25 lower on a unit area basis The correlations had a relatively high standard deviation, however, indicating that BET area was probably not the only physical property affecting the corrosion rate TEM analysis of the carbons after extended corrosion indicated a strong preferential attack of the ungraphitized regions, ie, much greater selectivity than the factor of 25 indicated by the BET correlation A unifying correlation was observed for both the furnace blacks and their graphitized forms using the corrosion rate per unit mass and the iodine adsorption number It was concluded that there are specific sites on the carbon surface (titrated by iodide) that serve as the initiators for dissolution of carbon atoms from the bulk of the material One particular type of furnace black, SRF (N774), appears to be an especially good precursor for forming a highly graphitized and very corrosion resistant carbon black

Gel synthesis of glass powders in the BaOAl2O3SiO2 system

Abstract: Homogeneous glass powders were prepared from multicomponent silicate gels in the BaOAl2O3SiO2 system. Gels synthesized from TEOS, Al-sec-butoxide, and Ba-acetate were characterized by TGA, DSC, and single-point BET analysis. Amorphous oxide powders of controlled composition were obtained through an appropriate drying and heat treatment schedule. Inclusion-free clear oxynitride glasses were also prepared by co-melting gel synthesized oxide powders with silicon nitride powders.

Nickel/silica catalysts and their preparation

Abstract: The invention provides a nickel/silica catalyst optionally also containing cations of a lower Group II metal (X), which catalyst satisfies the following combination of features: 1) a molar ratio of SiO 2 /Ni=0.15-0.35 2) a molar ratio of X/Ni=0-0.15 3) an active nickel surface area above 120 m 2 /g 4) a BET surface area of which at least 40% is found with pores with a radius above 2.5 nm. Preferably the catalyst has an atomic X/Ni ratio between 0.05-0.10 and a BET surface area of which at least 45% is found in pores having a pore radius of above 2.5 nm. The group II metal X is preferably magnesium or barium.

Application of thin films to porous mineral oxides using two-dimensional solvents

Abstract: Thin polymeric films have been applied to the surface of a porous material in a novel process. Nitrogen sorption, a conventional tool for measuring surface areas and pore size distributions, can be employed for determining the thickness of such films through a comparison of the pore size distribution curves before and after film formation. The thickness of a polystyrene film on a porous alumina powder is determined and compared with the theoretical thickness for styrene polymerized inside a two-dimensional solvent, which consists of a partial bilayer of sodium dodecyl sulfate physically adsorbed from an aqueous solution onto the powder. Film thicknesses ranged from 1.8 to 0.4 nm while BET surface area decreased from 94.7 to 57.8 m2/g. The powder surface changes from hydrophilic to hydrophobic while retaining the basic pore structure.

Mössbauer studies of high surface area pillared-clays containing mixed metal complexes

Abstract: High surface area pillared-clays were prepared from naturally occurring montmorillonite by exchanging interlayer ions with polyoxocations containing: (i) iron, (ii) aluminum, (iii) discrete mixtures of (i) and (ii), or (iv) ironand aluminum located within the same complex. The valence state, solid-state properties and stability of these pillars were determined following reduction and oxidation using: Mossbauer spectroscopy, X-ray diffraction and BET surface area measurements. Mossbauer data suggested interlayer-formation of metallic iron domains following reduction of type (i) and (iii) pillared systems. The magnetic properties and the oxidation behavior deduced from Mossbauer, XRD and BET measurements indicated that these crystallites were in the form of thin-film/pancake-shape islands. Reduced domains remained accessible to the gas phase and resisted sintering during redox cycles. The expanded structure of the type (iii) pillared system was found to be stable following reduction up to 673K due to the irreducible nature of discrete aluminum pillars at these conditions. Based on these findings inteccalation of clays with mixtures of chemically distinct pillars appears to provide a unique method for preparing highly dispersed metallic or bimetallic systems possessing two-dimensional sieve-like behavior and high surface area.

Thermodynamics of adsorption of organic liquids on Ni-modified solid obtained from collodal silica

Abstract: In order to reduce the well known silica surface inhomogeneity and to get a material suitable for selective chromatographic separations, a modified variety of the material was prepared by a controlled sorption of Ni2+ ions at the solid surface; its adsorption properties were then investigated using the GSC method. Since the starting material was of very high purity, it was possible to follow the influence of Ni2+ ion on the adsorption of various organic liquids, including n-alkanes, cyclohexane, benzene and halomethanes. Adsorption experiments, spanning zero surface coverage and the finite concentration region, were performed in the temperature range from 333 to 443 K. Both the surface activity change resulting from the modification and the possible interactions between the organic substances and the prepared adsorbent were examined using the standard free energy change of adsorption in zero coverage conditions. The adsorption isotherms of all the adsorbates listed were obtained using the Elution by Characteristic Point (ECP) technique and the data were fitted to the BET equation. To get a better insight into the adsorption process in the finite concentration region, the thermodynamic parameters of adsorption were determined and are discussed in terms of surface coverage.

Titania Coating of Alumina Powders

Abstract: TiO2 deposition on alumina powders by the hydrolysis of titanium isopropoxide (TIP) was investigated as a model experiment of the uniform addition of a sintering aid. The rate of hydrolysis increased with increasing TIP/Al2O3 and H2O/TIP molar ratios, and titania deposition occurred effectively at the H2O/TIP ratio larger than 10. Examination of the coated powders by SEM, TEM, BET surface area measurement and electrophoresis showed that fine titania deposits adhered loosely to the alumina particles before calcination, but that after calcination at 500°C the deposits spread over the surface of the alumina particles, resulting in the tight coating. The hydrolysis reaction was accelerated by the addition of diethylamine (DEA); however the titania powders had a tendency to deposit separately from the alumina particles.

Heat conductive catalytic body and production thereof

Abstract: PURPOSE:To enhance the heat conductivity of a heat conductive catalytic body and the catalytic activity per unit weight and to render heat exchange function by regulating the BET surface area of a catalyst on a heat conductive surface to >=3,000 times the heat conduction area to form the heat conductive catalytic body CONSTITUTION:A porous alumina layer is formed on the Al surface of a heat conductive carrier having an Al layer of >=10mum thickness and a metal having catalytic activity is supported on the above alumina layer after or during treat ment with hot water at 50-350 degC to obtain a heat conductive catalytic body In this catalytic body, the BET surface area of the catalyst on the heat conduc tive surface of the carrier is >=3,000 times the heat conduction area The shape of the catalytic body is a plate, tube, ribbon or honeycomb Pt, Pd, Ru, Mn or Zn is suitable for use as the metal having catalytic activity

Influence of thermal treatment on the surface characteristics of basic zirconium carbonate and oxalate

Abstract: Development of porosity and apparent BET surface area in samples of basic zirconium carbonate and oxalate on thermal treatment over the temperature range 25–650°C has been followed by nitrogen adsorption and mercury intrusion studies. As prepared, both salts exhibited a macroporosity which remained substantially unchanged irrespective of the temperature to which the solids were exposed. However, outgassing at temperatures above 400°C led to the generation of some mesoporosity, with the basic oxalate exhibiting both a greater porosity and surface area than the carbonate under such conditions. This has been attributed to the increased disruption to the structure caused by the elimination of oxalato ligands, which apparently dissociate into carbon dioxide and monoxide rather than evolving directly as the carbon dioxide derived from carbonato groups. The surface characteristics of the basic salts have been shown to be similar to those developed on thermal treatment of hydrous zirconia gels precipitated from aqueous solution through the agency of bicarbonates.

Characterization of Microporous Catalysts by N2 Adsorption : Empirical Correlations between Parameters Assessed by Different Methods.

Abstract: A wide class of solids, including modified and unmodified zeolites, aluminas, composite catalysts etc have been studied by N 2 adsorption at 77 K. Empirical correlations between parameters of different theoretical meanings such as the Dubinin micropore volume, the monolayer t volume, the BET surface area etc. have been established. Although these correlations can be rationalized on the basis of qualitative arguments, they remain to be explained quantitatively from the theories which are involved.

Process for eliminating nitrogen oxides from exhaust gases emanating from coal combustion.

Abstract: of EP0272620For the removal of nitrogen oxides by selective catalytic reduction with ammonia, catalysts are used which essentially contain titanium oxide and catalytically active quantities of oxides of vanadium, tungsten and/or molybdenum. The catalysts have a BET surface area from 5 to 60 m /g and a pore volume of 0.15 - 0.40 ml/g and contain at most 35 % of pores of diameters < 200 A.

Mixed Gels of Vanadia and Silica: Structural Properties and Catalytic Behavior in Selective Reduction of Nitric Oxide with Ammonia.

Abstract: Mixed gel catalysts of vanadia and silica containing 0.1, 1, 10, 20, and 50 wt% of vanadia were prepared from alkoxides of the constituents. The catalysts were investigated with regard to their physical and chemical properties, and their activity in the selective catalytic reduction (SCR) of nitric oxide. The textural properties (grain morphology, BET surface area, specific pore volume, pore size distribution) were found to depend on the composition of the mixed gels and varied most strongly in the composition range 1–20 wt% of vanadia. Bulk structural and chemical properties were investigated by means of X-ray diffraction (XRD), high-resolution electron microscopy (HREM), electron spin resonance, and temperature-programmed reduction and oxidation. XRD and HREM revealed that silica was existing in all catalysts as an amorphous phase only. Vanadia showed more complex behavior. At low concentrations (less than 10 wt%) it consisted of well-dispersed vanadium oxide species, whereas at higher concentrations small macrocrystalline domains were found in the amorphous V 2 O 5 matrix. Highest specific activities (molecules of NO converted to N 2 per V 5+ site per second) were measured for the catalysts containing 1 and 10 wt% of vanadia. Catalysts with higher vanadia contents exhibited a significant decrease in the activation energy around 430 K which is attributed to agglomeration of the well-dispersed vanadium oxide species under SCR conditions. The stability of the well-dispersed vanadium oxide species under SCR conditions was found to decrease with increasing temperature and vanadia content of the catalyst. In all mixed gel catalysts the well-dispersed vanadium oxide species were more stable than those in silica-supported vanadia layers.

Removal of trace sulfur compound in hydrocarbon

Abstract: PURPOSE: To remove trace sulfur compound in an aromatic hydrocarbon by contacting with a desulfurizing agent composed mainly of copper oxide having specific BET surface area and pore volume and reduced at a specific temperature in hydrogen stream. CONSTITUTION: An aromatic hydrocarbon is made to contact with a desulfurizing agent composed mainly of copper oxide at 150-179°C to remove trace sulfur compound contained in the hydrocarbon. The desulfurizing agent is composed mainly of copper oxide, has a BET surface area of 10-150m 2 /g and a pore volume of ≥0.1cc/g and is produced by supporting 20-60wt.% of copper oxide on a carrier and reducing the oxide at 150-200°C in hydrogen stream. The desulfurization can be carried out in high efficiency in the absence of hydrogen. COPYRIGHT: (C)1990,JPO&Japio

Die-formed articles based on parogenic aluminium oxide, process for their production and their use

Abstract: Die-formed articles based on pyrogenic alumina having the following physical-chemical data:… … external diameter 2 to 15 mm BET surface area 60 to 115 m /g pore volume 0.30 to 0.80 ml/g breaking strength 100 to 300 N pore distribution no pores of The die-formed articles can be used as a catalyst support and catalyst.

Studies of hydrous sodium titanate ion-exchange materials for use as catalyst supports

Abstract: Understanding how the activity of a catalyst is related to the concentration and dispersion of active metals on the catalyst support is critical to designing materials having the optimum catalytic properties. We have developed synthetic techniques for controlling both the concentration and dispersion of nickel on hydrous sodium titanate catalyst supports. The techniques require an understanding of the solution chemistry of both the support material and dissolved metal species (hydrolysis products). In this paper, we present the results of a study of three nickel-loaded samples of hydrous sodium titanate in which the scale of the nickel dispersion ranges from the atomic level to the scale of large (50 nm) clusters. The catalysts are characterized by transmission electron microscopy (TEM), hydrogen chemisorption, and BET surface area measurements. In addition, the activity and selectivity of the Ni catalysts for the n-butane hydrogenolysis reaction is used to monitor the surface structures of Ni in the catalysts. 8 refs., 7 figs., 1 tab.