Gas Phase Synthesis of Molybdenum and/or Iron Nitrides, Carbides and Sulfides

1994 ◽  
Vol 368 ◽  
Author(s):  
Michael R. Close ◽  
Jeffrey L. Petersen
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Lower Surface ◽  
Iron Nitrides ◽  
Ammonia Vapor ◽  
Surface Areas ◽  
Molybdenum Sulfides ◽  
Molybdenum Carbides ◽  
Increasing Temperature

ABSTRACTThe thermolytic decomposition of Mo(CO)6 with hydrogen sulfide or ammonia vapor (in a He carrier stream) at temperatures ranging from 300 to 1100 °C produces high surface area molybdenum sulfides (MoS2 or Mo2S3) or molybdenum carbides (hexagonal Mo2C) and carbonitrides, (hexagonal MoN(C) or cubic Mo2N(C)), respectively. The MoS2 surface areas range from 16.7 to 82.0 m2/g, while the surface areas of molybdenum carbides and carbonitrides vary from 14.9 to 21.1 m2/g. The maximum surface area for MoS2 is achieved at 500 °C and decreases with increasing or decreasing temperature. The surface area of the carbonitrides formed from 300 to 800 °C increases with increasing temperature up to 950 °C, where lower surface area Mo2C is formed. Crystallographically pure hexagonal MoN is prepared by decomposing Mo(CO) 6 in pure ammonia. Fe(CO) 5 decompositions in ammonia produce FexZ (where 5.8≥x≥1.6 and Z=C and N), and in some cases elemental Fe. Hexagonal Fe3 N(C) forms when Fe(CO) 5 is thermolyzed in ammonia from 300 to 600 °C, with surface areas ranging from 9.5 to 13.7 m2/g, whereas orthorhombic Fe3C and cubic Fe are produced at 700, 800, 900 and 1000 °C with surface areas of 6.7, 7.6, 2.2 and 2.0 m2/g, respectively. Within the same phase, the surface areas of the carbonitrides increase with increasing reaction temperature. These iron and molybdenum carbonitrides catalyze the conversion of CO/H2 to alkanes and methanol. Based on preliminary catalytic studies, the highest rate of methane (2850 g/kg/hr at 374 °C) and methanol (440 g/kg/hr at 284 °C) formation was accomplished with an FeMo carbonitride prepared by decomposing Mo(CO)6 and Fe(CO)5 in ammonia at 800 °C.

scholarly journals Fabrication of high surface area acid-treated activated carbon from pomegranate husk for 2,4-dichlorophenol adsorption

2021 ◽  
Author(s):  
Ensiyeh Taheri ◽  
Mohammad Mehdi Amin ◽  
Ali Fatehizadeh ◽  
Eder C. Lima
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Xrd Analysis ◽  
Absorption Capacity ◽  
Surface Areas ◽  
Adsorption Condition ◽  
Pomegranate Husk ◽  
Increasing Temperature

Abstract In the present study, zinc chloride followed by acid treating was employed for fabrication activated carbon with a high surface area from pomegranate husk (APHAC) for 2,4-dichlorophenol (2,4-DCP) adsorption. The APHAC was a well-developed pore and exhibiting specific surface areas of 1576 m2/g. Based on the XRD analysis, the diffraction peaks between 15 ° and 35 ° corresponded to amorphous carbon, and the pHpzc values of APHAC was 6.15 ± 0.15. According to batch experiments, the optimum adsorption condition of 2,4-DCP was pH of 3, contact time 60 min, and APHAC dose of 1.75. The absorption capacity of 2,4-DCP at the APHAC dose of 0.5 promptly decreased from 259.5 ± 12.9 mg/g at the initial concentration of 150 mg/L to 74.5 ± 3.7 mg/g dose of 2 g/L. With increasing temperature from 10°C to 50°C, the adsorption efficiency declined from 99.8 ± 0.5% to 75.6 ± 1.89%. The isotherm and kinetic of 2,4-DCP by APHAC revealed that Freundlich and Elovich satisfactorily fitted with experimental data.

scholarly journals Photoreforming of Glucose over CuO/TiO2

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 477 ◽  
Author(s):  
Elnaz Bahadori ◽  
Gianguido Ramis ◽  
Danny Zanardo ◽  
Federica Menegazzo ◽  
Michela Signoretto ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Economic Analysis ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Lower Surface ◽  
Flame Synthesis ◽  
Biomass Hydrolysis ◽  
Model Molecule

Hydrogen production has been investigated through the photoreforming of glucose, as model molecule representative for biomass hydrolysis. Different copper- or nickel-loaded titania photocatalysts have been compared. The samples were prepared starting from three titania samples, prepared by precipitation and characterized by pure Anatase with high surface area, or prepared through flame synthesis, i.e., flame pyrolysis and the commercial P25, leading to mixed Rutile and Anatase phases with lower surface area. The metal was added in different loading up to 1 wt % following three procedures that induced different dispersion and reducibility to the catalyst. The highest activity among the bare semiconductors was exhibited by the commercial P25 titania, while the addition of 1 wt % CuO through precipitation with complexes led to the best hydrogen productivity, i.e., 9.7 mol H2/h kgcat. Finally, a basic economic analysis considering only the costs of the catalyst and testing was performed, suggesting CuO promoted samples as promising and almost feasible for this application.

Preparation of CuCrO2 Powders with High Surface Areas

2014 ◽  
Vol 617 ◽  
pp. 187-190 ◽  
Author(s):  
Te Wei Chiu ◽  
Yi Wei Feng
Keyword(s):  
Nitric Acid ◽  
Surface Area ◽  
Chemical Treatment ◽  
High Surface ◽  
High Surface Area ◽  
Phase Evolution ◽  
Surface Areas ◽  
Pure Phase ◽  
Cu Ions

In this study, the effects of glycine-nitrate ratios and postcombustion chemical treatment on the phase evolution and surface area of CuCrO2powders were investigated. The pure phase of CuCrO2powders was obtained at a glycine-nitrate ratio of 1.2–1.4. When the glycine-nitrate ratio was higher than 1.9, the Cu ions were reduced to Cu(0) and the phase of Cu metal and Cr2O3were observed. However, when the glycine-nitrate ratio was lower than 1.1, the Cu ions were partially maintained as Cu(2+), and a bluish residue was observed. As-combusted CuCrO2powder with a high surface area (50 m2/g) was obtained at a glycine-nitrate ratio of 1.2. Furthermore, a high surface area (> 60 m2/g) was obtained by leaching as-combusted CuCrO2powder with diluted nitric acid.

Pyrolysis of Organosilicon Gels to Silicon Carbide

1986 ◽  
Vol 73 ◽  
Author(s):  
Joseph R. Fox ◽  
Douglas A. White ◽  
Susan M. Oleff ◽  
Robert D. Boyer ◽  
Phyllis A. Budinger
Keyword(s):  
Silicon Carbide ◽  
Surface Area ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Carbon Chain ◽  
Carbon Chain Length ◽  
Pyrolysis Products ◽  
Surface Areas ◽  
Physical Measurements

AbstractSol-gel precursors to silicon carbide have been prepared using trifunctional chloro and alkoxysilanes which contain both the silicon and carbon necessary for SiC formation. Crosslinked gels having the ideal formula [RSiO1 5].]n have been synthesized by a hydrolysis/condensation scheme for a series of saturated and unsaturated R groups. The starting gels have been characterized by a variety of elemental analysis, spectroscopic and physical measurements including IR. XRD. TGA.. surface area and pore volume. A particularly powerful method for characterizing these gels is the combination of 13C and 29 Si solid state NMR which can provide information about the degree of crosslinking as well as residual hydroxy/alkoxy content.The controlled pyrolysis of these gels has been used to prepare silicon carbide-containing ceramic products with surface areas in excess of 600m2/gm. The pyrolysis products are best described as a partially crystalline, partially amorphous mixture of β-SiC, silica and carbon. The effect of carbon chain length and the degree of unsaturation in the R group on the composition and surface area of the product has been determined. The origin of the high surface area of the pyrolysis products has been identified and its implications on potential uses of these materials is discussed.

Oxidative Catalytic Decomposition of Toxic Gases Using Hydroxyapatite and Fluorhydroxyapatite

1994 ◽  
Vol 368 ◽  
Author(s):  
Timothy P. Palucka ◽  
Nicholas G. Eror ◽  
Thomas A. Mcnamara
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Catalytic Decomposition ◽  
Reaction Products ◽  
Fluorine Substitution ◽  
Dimethyl Methylphosphonate ◽  
Surface Areas ◽  
Percent Nitrogen ◽  
Protection Period

ABSTRACTAn oxidative catalytic route for the decomposition of nerve gases was investigated using hydroxyapatite (HA, chemical composition Ca10(PO4)6(OH)2) and its partially fluorinated analog fluorhydroxyapatite (FHA, Ca10(PO4)6Fx(OH)2−x). Samples were prepared with surface areas ranging from 34 to 238 m2/g to study surface area effects; 1.2 wt. % platinum was deposited on one substrate to investigate the effect of a transition metal on activity and selectivity. Reaction studies were performed using dimethyl methylphosphonate (DMMP), a nerve gas simulant, in a stream of 80 percent nitrogen and 20 percent oxygen at 573 K and atmospheric pressure. High surface area FHA samples showed an increase in the "protection period" (period of 100% conversion) with increasing fluorine substitution; such an increase was not seen for low surface area FHA samples. In the absence of platinum, the reaction products were methanol and dimethyl ether; with platinum, CO2 was also obtained.

Nitrogen and Water Sorption Properties of Ethyl-Substituted Silica Aerogels and Xerogels

1994 ◽  
Vol 371 ◽  
Author(s):  
Chunling Liu ◽  
Sridhar Komarneni
Keyword(s):  
Pore Structure ◽  
Surface Area ◽  
Water Sorption ◽  
Ph Value ◽  
High Surface ◽  
High Surface Area ◽  
Silica Aerogels ◽  
Modified Silica ◽  
Surface Areas ◽  
Water Sorption Properties

AbstractHigh surface area ethyltrimethoxysilane (ETMS) modified silica aerogels and xerogels were synthesized by cohydrolyzing the mixtures of ETMS and tetramethylorthosilicate (TMOS). The effects of ETMS content, pH value and solvent addition were investigated. The surface area, pore structure and hydrophobicity were studied using nitrogen and water sorption measurements. By ETMS modification of TMOS gels, high surface area, density and hydrophobicity were achieved. The 25 mole% ETMS-75 mole% TMOS was found to be the best composition for both aerogel and xerogel, which are hydrophobic and have surface areas of 1221 and 832 m2/g, respectively.

New ultrasonic assisted co-precipitation for high surface area oxide based nanostructured materials

2018 ◽  
Vol 3 (3) ◽  
pp. 244-250 ◽  
Author(s):  
Dereck N. F. Muche ◽  
Flavio L. Souza ◽  
Ricardo H. R. Castro
Keyword(s):  
Metal Oxide ◽  
Surface Area ◽  
Metal Oxide Nanoparticles ◽  
High Surface ◽  
High Surface Area ◽  
Oxide Nanoparticles ◽  
Specific Method ◽  
Surface Areas ◽  
Ultrasonic Assisted ◽  
Co Precipitation

A non-system specific method for the synthesis of metal oxide nanoparticles with high homogeneity, spherical morphology and high surface areas is proposed based on an aqueous precipitation.

scholarly journals High Surface Area Nanoporous Graphitic Carbon Materials Derived from Lapsi Seed with Enhanced Supercapacitance

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 728 ◽  
Author(s):  
Lok Kumar Shrestha ◽  
Rekha Goswami Shrestha ◽  
Subrata Maji ◽  
Bhadra P. Pokharel ◽  
Rinita Rajbhandari ◽  
...  
Keyword(s):  
Surface Area ◽  
Current Density ◽  
Electrode Materials ◽  
Carbon Materials ◽  
High Surface ◽  
High Surface Area ◽  
Graphitic Carbon ◽  
High Rate ◽  
Surface Areas ◽  
Nanoporous Carbon Materials

Nanoporous activated carbon materials derived from agro-wastes could be suitable low-cost electrode materials for high-rate performance electrochemical supercapacitors. Here we report high surface area nanoporous carbon materials derived from Lapsi seed agro-waste prepared by zinc chloride (ZnCl2) activation at 700 °C. Powder X-ray diffraction (pXRD) and Raman scattering confirmed the amorphous structure of the resulting carboniferous materials, which also incorporate oxygen-containing functional groups as confirmed by Fourier transform infrared (FTIR) spectroscopy. Scanning and transmission electron microscopy (SEM and TEM) analyses revealed the granular, nanoporous structures of the materials. High-resolution TEM (HR-TEM) confirmed a graphitic carbon structure containing interconnected mesopores. Surface areas and pore volumes of the materials were found, respectively, in the ranges from 931 to 2272 m2 g−1 and 0.998 to 2.845 cm3 g−1, and are thus superior to commercially available activated carbons. High surface areas, large pore volumes and interconnected mesopore structures of these Lapsi seed-derived nanoporous carbon materials lead to their excellent electrochemical supercapacitance performance in aqueous electrolyte (1 M H2SO4) with a maximum specific capacitance of 284 F g−1 at a current density of 1 A g−1. Furthermore, the electrodes showed high-rate capability sustaining 67.7% capacity retention even at high current density of 20 A g−1 with excellent cycle stability achieving 99% capacitance retention even after 10,000 charge–discharge cycles demonstrating the potential of Lapsi seed derived nanoporous carbons as suitable electrode materials in high-performance supercapacitor devices.

A theoretical morphologic analysis of convergently evolved erect helical colony form in the Bryozoa

Paleobiology ◽  
2000 ◽  
Vol 26 (4) ◽  
pp. 556-577 ◽  
Author(s):  
George R. McGhee ◽  
Frank K. McKinney
Keyword(s):  
Surface Area ◽  
Dimensional Space ◽  
High Surface ◽  
High Surface Area ◽  
Three Dimensional ◽  
Filter Feeding ◽  
Colony Form ◽  
Surface Areas ◽  
Morphologic Analysis ◽  
Intermediate Surface

Exploration of the theoretical morphospace of erect helical colony form in Bryozoa, created by McKinney and Raup (1982), reveals that only a small volume of the three-dimensional space of hypothetical form is occupied by actual colonies of the Paleozoic fenestrates (Class Stenolaemata) Archimedes and Helicopora, helical species of the cheilostome (Class Gymnolaemata) Bugula, and the cyclostome (Class Stenolaemata) Crisidmonea archimediformis. Actual helical-colony bryozoans are not found in regions of the morphospace characterized by colony geometries that possess the largest surface areas of filtration sheet. Examination of computer-simulated colonies in the theoretical morphospace reveals that, although possessing high surface areas, colonies in the empty region of high-surface-area morphospace possess other aspects of geometry that are unrealistic as filter-feeding geometries: the filtration-sheet whorls are held at small acute angles to the central colony axis and are deeply nested within one another, both of which are disadvantageous conditions for the system of filter feeding used by the extant cheilostome Bugula, and presumably by extinct helical-colony bryozoans as well.Even though actual bryozoans are found only in the low to intermediate surface-area regions of the theoretical morphospace, surface area of filtration sheet is a major determinant of form in these helical colonies, as is evidenced by a negative correlation in values of the parameters BWANG and ELEV exhibited by the colony data. Minimum values of BWANG are even further constrained by the apparent need of the Archimedes colonies to maintain filtration-sheet branching densities within the range of 20 to 50.

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