Showing papers on "BET theory published in 1990"

Hydrodesulfurization Reactions of Residual Oils over CoMo/Alumina-Aluminum Phosphate Catalysts in a Trickle Bed Reactor

Abstract: Catalytic hydrodesulfurization (HDS) plays an important role in the conversion of sulfur-laden residual oils. Cobalt molybdate catalysts are commonly used for the process. In the present study, a series of alumina-aluminum phosphates (AAP) was prepared by a precipitation technique. These materials were used as a support of CoMo HDS catalysts. The samples were characterized by X-ray diffraction, BET surface area, and mercury-penetration pore volume measurements. The temperature-programmed reduction method was used to monitor the reducibility of MoO 2 . HDS of Kuwait atmospheric residuum over these catalysts was carried out in a cocurrent down-flow trickle bed reactor at 663 K and 7582 kPa. The reaction data can be fitted very well a pseudo-second-order rate equation

Methanol oxidation over nonprecious transition metal oxide catalysts

Abstract: This paper reports methanol oxidation over nonprecious transition metal oxide catalysts studied in a gradient less external recycle reactor. The catalysts (oxides of Cr, Mn, Fe, Co, Ni, Cu), which were prepared by using the incipient wetness technique, were supported on 1/8 in.{gamma}-Al{sub 2}O{sub 3} tablets. The catalysts were characterized by using BET surface area measurement, X-ray diffraction, laser Raman spectroscopy, scanning electron microscopy, and energy dispersive X-ray analysis techniques. All the catalysts exhibited similar activities for methanol conversion, but the Cu catalyst was found to be considerably more selective to CO{sub 2}. The order of the reaction was 1.2 with respect to methanol concentration and appeared to range between 0.5 and 0 with respect to oxygen concentration.

Silica beads, process for their preparation and their use for reinforcing elastomers

Abstract: Silica characterised in that it is in bead form and has a BET surface area of between 60 and 130 m /g, a relative density varying between 0.28 and 0.37 and a total pore volume of between 1.6 and 3.3 cm /g. This silica can be employed especially in the reinforcement of elastomers.

Catalyst material comprising platinum alloy supported on carbon

Abstract: An eloctrocatalytic material comprises an alloy of platinum with another element, supported on a conductive carbon support, the metal area of the alloy being greater than 75 m /gPt, and at a useful platinum loading, is especially suitable for use in phosphoric acid fuel cells, and demonstrates unexpectedly high stability at the high metal areas obtained. This material is produced by supplying a basic solution of compounds of platinum and one or more alloying elements onto the carbon support and reducing and heat treating the support carrying the compounds so as to form the platinum alloy. Suitable alloying elements are Ti, Or, Mn, Fe, 00, Ni, Cu, Zr and Mf. The catalyst may have a BET surface area of less than 1000m /gm. The reduction may be carried out in the liquid phase by adding a reducing agent to the slurry after deposition; drying the slurry and then reducing using a gas phase reducing agent. Alternatively reduction and heat treatment may take place in a single step.

Nickel/silica catalyst and the preparation and use thereof

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=015=035 2) a molar ratio of X/Ni=0-015 3) an active nickel surface area above 120 m 2 /g 4) a BET surface area of which at least 60% is found with pores with a radius below 15 nm Preferably the catalyst has an atomic X/Ni ratio between 05-010 and a BET surface area of which at least 60% is found in pores having a pore radius of below 14 nm The group II metal X is preferably magnesium or barium

Silica glass: preparation and characterization

Abstract: Silica glass with good optical quality and low OH content has been prepared by a sol-gel process. The sols have been prepared by mixing TMOS, methanol and water in acid condition, and 0.15 μm SiO 2 Stober microspheres or CabOSil M5 have been added to the sols in order to reinforce mechanically the gels and obtain monolithic samples. The gels were then dried at 60°C during 15 to 20 days. The gelation time and BET surface area have been determined as a function of the concentration of these additions and sol pH. The BET area shows an anomalous behavior with a narrow dip down to 300 m 2 /g for concentration of SiO 2 powder of the order of 1 wt%. The gelation time exhibits a maximum at a pH of 2.5 and a minimum at a pH of 4.5. Sintering into clear and bubble free amorphous silica has been obtained by heating under controlled atmospheres (CCL 4 , O 2 and vacuum) up to 1070°C. The OH content was measured by IR spectroscopy and found to decrease with the chlorination time.

Carbon electrode material for electrolytic bath

Abstract: PURPOSE:To enhance energy efficiency and to lengthen charge-discharge cycle life by using a carbon material having pseudographite crystal structure, in which interplanar distance obtained by X-ray wide angle analysis is specified and the amount of total acidic functional groups, BET surface area, and the number of surface bonding nitrogen atoms are specified. CONSTITUTION:A carbon material having pseudographite crystal structure in which interplanar distance is 3.70Angstrom or less, and the amount of total acidic functional group, BET surface area, and the ratio of surface bonding nitrogen atoms to carbon atoms (N/C) are specified is used. The amount of total acidic functional group is 0.01meq/g or more, the BET surface area is 1m /g or more, and the ratio of nitrogen to carbon (N/C) is 1.0% or more. As the raw material of the carbon material, coal pitch, oil pitch, phenol family, acrylic family, aromatic polyamide family, or cellulose family material is used. The carbon material having high N/C ratio is obtained by carbonizing the raw material containing rich nitrogen atoms such as acrylic family and aromatic polyamide family material.

Adsorption of hydrogen on porous vycor glass

Abstract: Hydrogen adsorption isotherms have been measured at temperatures between 15 K and 20 K for porous Vycor glass. The intermediate adsorption data were analyzed using a modified Brunauer-Emmett-Teller method, which is based on the assumption that two layers are coadsorbed, the first layer being very strongly attached. Our results indicate that, relative to the adsorption energy of the free surface of the bulk liquid, the adsorption energy of the second layer is approximately 60 K, much smaller than the adsorption energy of the first layer but still significant at the low temperature of the experiments. Our results are compared to those for adsorption of4He on Vycor.

Determination of Surface Areas of Mineral Powders by Adsorption Calorimetry

Abstract: Adsorption calorimetry was used to develop a method for determining the surface area of low-surface-area materials (<1 m2/g), which required no pretreatment of the surface, such as outgassing at elevated temperatures. The method involved flowing heptane through a small amount of sample (0.15 to 1.0 g) in the flow cell of a commercial microcalorimeter. When thermal equilibrium was reached at the powder-heptane interface, pure heptane was replaced with a heptane carrier-solution containing 0.6 volume % n-butanol (n-BuOH) as the preferential adsorbate. The integral enthalpy of preferential saturation adsorption, ΔHsat, of n-BuOH on the surface was found to be a function of the BET surface area of the sample. An empirical relationship between ΔHsat and BET surface area was determined over a surface area range of about three orders of magnitude (0.095 to 81 m2/g) by performing adsorption experiments on five α-alumina standard reference powders. The technique was applied to the determination of surface areas of untreated rock and mineral powders.

Characterization of catalysts derived from oxidation of ruthenium-thorium intermetallics

Abstract: Ru methanation catalysts derived from oxidation of Ru{sub x}Th{sub y} intermetallics were characterized by X-ray photoelectron spectroscopy (ESCA), ion scattering spectroscopy (ISS), X-ray diffraction (XRD), BET surface area measurements, chemisorption, and gravimetric analysis. XRD measurements and gravimetric analysis indicated that all intermetallics were extensively decomposed by oxidation in air at 350{degree}C. ESCA and ISS Ru/Th intensity ratio measurements showed that surface segregation of ThO{sub 2} occurred for all catalysts. The structure of the intermetallic-derived (IM) catalysts can best be described as Ru particles embedded in a ThO{sub 2}-rich overlayer. Comparison of hydrogen and CO uptake with N{sub 2} BET surface area suggests that CO more accurately titrates surface Ru than does hydrogen. Extensive spillover of hydrogen from Ru to ThO{sub 2} was also observed for all IM catalysts. On the basis of CO chemisorption, the CO hydrogenation turnover frequency was comparable for all the IM catalysts.

On the meaning of surface area measurements for microporous materials

Abstract: It is shown that the conventional BET surface area of a microporous solid is the sum of an external area (mesopores and macrostructure) and a term proportional to the micropore volume. The proportionality factor in the latter term is calculated from a simple model and found to depend upon the pressures used in the BET fit. A consistent methodology is presented for obtaining external areas and micropore volumes from the BET equation and t -plots.

Photochemical transformation of pyrene vapor deposited on eleven subfractions of a high-carbon coal stack ash

Abstract: A high-carbon coal stack ash has been separated by particle size and then by composition, into strongly magnetic, weakly magnetic, “nonmagnetic” mineral, heavy carbon and light carbon fractions. Eleven of these fractions have been characterized by bulk iron and carbon analyses and BET surface area determinations. The photochemical transformation of pyrene, deposited from the vapor phase onto these eleven ash fractions, has been studied. Appreciable phototransformation of adsorbed pyrene was observed for only three fractions; in those fractions, the bulk percentage of carbon (0.4–0.7%) and the specific surface area (0.50–0.68 m2/g) were both very low. For all fractions having bulk carbon percentages ≥ 4% and specific surface areas ≥ 2.85 m2/g, no detectable phototransformation of adsorbed pyrene was observed. There was no discernible correlation of photochemical reactivity of adsorbed pyrene with the iron content of the ash fractions. In general, the specific surface area of the fractions increased with increased carbon content; two different forms of carbon having different surface areas were observed.

Cooperation Between Phases in Mixed SnSbO Selective Oxidation Catalysts

Abstract: A synergy is observed in the oxidation of isobutene to methacrolein when a Sn-rich SnSbO oxide calcined at high temperature is mechanically mixed with an Sb-rich SnSbO oxide calcined at the same temperature (or if mixed with pure Sb 2 O 4 ). The catalysts were characterized by XRD, BET surface area measurements, Electron microscopy and XPS and it was found that i) the Sn-rich samples are either a pure Sb 5+ -SnO 2 solid solution or a solid solution with a small quantity of segregated antimony oxide; ii) the Sb-rich samples contain α-Sb 2 O 4 with a trace of solid solution and iii) mechanical mixtures are constituted of two separate phases: solid solution and α-Sb 2 O 4 . The observed synergy is explained by a remote control mechanism; α-Sb 2 O 4 controls the number of active sites on the surface of Sb 5+ -SnO 2 solid solution.

Carrier of a magnetic powder dispersed type

Abstract: A magnetic powder-dispersed carrier for use in electrophotography, electrostatic printing, and other reprographic methods, comprising a large number of magnetic particles dispersed in a binder resin, the particles having a BET surface area no greater than 5 m 2 /g, and an oil-absorbing capacity of no more than 25 ml/100 g.

Spherical silica, its production and use for reinforcement of elastomer

Abstract: Silica characterised in that it is in bead form and has a BET surface area of between 60 and 130 m /g, a relative density varying between 0.28 and 0.37 and a total pore volume of between 1.6 and 3.3 cm /g. This silica can be employed especially in the reinforcement of elastomers.

Impregnating grade sheet

Abstract: PURPOSE: To obtain the subject paper producible in a large amount at a low cost even in the case of the shortage of stock of titanium dioxide by using titanium dioxide and a specific amorphous precipitated silica as main fillers. CONSTITUTION: This paper comprises (A) titanium dioxide and (B) about 5-40 based on the component A of an amorphous precipitated silica having about 25-200 m /g BET surface area, pH of about 6-9.5, /g BET surface area, pH of about 6.5-7.5, about 3-10 μm medium value of particle size of aggregate and the paper has about 10-25 wt.% silica content based on titanium dioxide.

Silica, its preparation and its use in reinforcing elastomers

Abstract: Silica characterised in that it is in bead form and has a BET surface area of between 60 and 130 m /g, a relative density varying between 0.28 and 0.37 and a total pore volume of between 1.6 and 3.3 cm /g. This silica can be employed especially in the reinforcement of elastomers.

Determination of surface areas of mineral powders by adsorption calorimetry 1

Abstract: Adsorp tion calorimetry was used to develop a method for determining the surface area of low- surface-area materials (< 1 m2/g), which required no pretreatment of the surface, such as outgassing at elevated temperatures The method involved flowing heptane through a small amount of sample (015 to 10 g) in the flow cell of a commercial microcalorimeter When thermal equilibrium was reached at the powder-heptane interface, pure heptane was replaced with a heptane carrier-solution containing 06 volume % n-butanol (n-BuOH) as the preferential adsorbate The integral enthalpy of preferential satu- ration adsorption, AH,~, of n-BuOH on the surface was found to be a function of the BET surface area of the sample An empirical relationship between AH,, and BET surface area was determined over a surface area range of about three orders of magnitude (0095 to 81 mE/g) by performing adsorption experiments on five a-alumina standard reference powders The technique was applied to the determi- nation of surface areas of untreated rock and mineral powders

Mixed Titanium and Phosphorus Oxides. II. — The Effect of pH Values of Solutions on Surface Acidity

Abstract: A series at mixed oxides of titanium and phosphorus were prepared by co-precipitation method accompanying refluxing treatment. The effect of the pH values of the solutions on the structures, compositions, and surface acidities of the resultants compounds was determined. The samples were characterized by BET surface area measurement, X-ray powder diffraction (XRD) for structural analysis and amine-titration for surface acidities. After calcinating the oxides at 773 K, the surface acidities were attributed mainly to Ti(OH)PO4 structure. Elemental analysis revealed that the P/Ti ratios in the samples decreased with increasing the pH value of the preparative solution. When the mixed oxides were used as catalysts for 2-propanol decomposition reaction, the highest activities were obtained over the samples prepared in the solutions with the pH values being 2 or 3. That result was in agreement with the variation in surface area and acid amount of the catalysts.

Chemisorption studies of Pt/SnO2 catalysts

Abstract: The low temperature CO oxidation catalysts that are being developed and tested at NASA-Langley are fairly unique in their ability to efficiently oxidize CO at low temperatures (approx. 303 K). The bulk of the reaction data that has been collected in the laboratory has been determined using plug flow reactors with a low mass of Pt/SnO2/SiO2 catalyst (approx. 0.1 g) and a modest flow rate (5 to 10 sc sm). The researchers have previously characterized the surface solely in terms of N2 BET surface areas. These surface areas have not been that indicative of reaction rate. Indeed, some of the formulations with high BET surface area have yielded lower reaction rates than those with lower BET surface areas. As a result researchers began a program of determining the chemisorption of the various species involved in the reaction; CO, O2 and CO2. Such a determination of will lead to a better understanding of the mechanism and overall kinetics of the reaction. The pulsed-reactor technique, initially described by Freel, is used to determine the amount of a particular molecule that is adsorbed on the catalyst. Since there is some reaction of CO with the surface to produce CO2, the pulsed reactor had to be coupled with a gas chromatograph in order to distinguish between the loss of CO that is due to adsorption by the surface and the loss that is due to reaction with the surface.

Magnetic recording carrier

Abstract: The invention relates to a magnetic recording carrier having improved conductivity and improved magnetic properties It comprises finely divided magnetic particles, preferably metal powders, which are dispersed in a polymeric binder The improvement has been achieved by means of a conductive black having a BET surface area of greater than from 900 to 1200 m /g, and conductive black having a dibutyl phthalate adsorption of from 350 to 450 ml/100 g, which is treated with a dispersant known from the prior art before introduction into the magnetic dispersion

Magnetic information carrier.

Abstract: The magnetic recording medium, consisting of a substrate, a binder- containing and a carbon black-containing adhesion-promoting layer and a magnetic layer present thereon and having improved adhesive strength, surface conductivity and running properties is obtained by a method in which the adhesion-promoting layer contains a conductive carbon black having a BET surface area of 200 - 700 m /g and a DBP number of not more than 300 ml/100 g and one or more binders, which are also used in the magnetic layer. The carbon black is advantageously coated with a dispersant or with a fatty acid, and binders which have been found to be particularly advantageous are polyurethane, polyesters and polyvinylidene chloride.