Study of nickel-molybdenum catalysts for methanation of carbon monoxide

1980 ◽  
Vol 45 (3) ◽  
pp. 783-790 ◽  
Author(s):  
Petr Taras ◽  
Milan Pospíšil
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Mixed Oxides ◽  
Minor Component ◽  
Fast Neutrons ◽  
Scanning Calorimetry ◽  
Low Concentrations ◽  
Γ Rays ◽  
Molybdenum Catalysts ◽  
Kinetics Of

Catalytic activity of nickel-molybdenum catalysts for methanation of carbon monoxide and hydrogen was studied by means of differential scanning calorimetry. The activity of NiMoOx systems exceeds that of carrier-free nickel if x < 2, and is conditioned by the oxidation degree of molybdenum, changing in dependence on the composition in the region Mo-MoO2. The activity of the catalysts is adversely affected by irradiation by fast neutrons, dose 28.1 Gy, or by γ rays using doses in the region 0.8-52 kGy. The system is most susceptible to irradiation in the region of low concentrations of the minor component (about 1 mol.%). The dependence of changes in catalytic activity of γ-irradiated samples on the dose exhibits a maximum in the range of 2-5 kGy. The changes in catalytic activity are stimulated by the change of reactivity of the starting mixed oxides, leading to different kinetics of their reduction and modification of their adsorption properties. The irradiation of the catalysts results in lowered concentration of the active centres for the methanation reaction.

Effect of the ionizing radiation on the catalytic activity of the BASF K-3-10 catalyst in the low-temperature conversion of carbon monoxide by water vapour. Stability of the radiation catalytic effects

1986 ◽  
Vol 51 (8) ◽  
pp. 1571-1578 ◽  
Author(s):  
Alois Motl
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Low Temperature ◽  
Catalytic Effect ◽  
Catalytic Properties ◽  
Beta Radiation ◽  
Fast Neutrons ◽  
Time Interval ◽  
The Stability ◽  
Catalytic Effects

The radiation catalytic properties of the BASF K-3-10 catalyst were studied, namely the dependence of these effects on the time interval between the catalyst irradiation and the reaction itself and also on the length of the catalyst use. The catalytic effects decrease exponentially with the interval between the irradiation and the reaction if the catalyst is kept in the presence of air. The stability of effects induced by various types of radiations increases in the sequence beta radiation - gamma radiation - fast neutrons. The radiation catalytic effect stability in the reaction increases in the same sequence.

Effect of the ionizing radiation on the kinetics of the reduction by hydrogen of NiO-Fe2O3 mixed oxides of various genesis

1986 ◽  
Vol 51 (8) ◽  
pp. 1561-1570 ◽  
Author(s):  
Milan Pospíšil ◽  
Jan Topinka
Keyword(s):  
Radiation Effects ◽  
Mixed Oxides ◽  
Chemical Properties ◽  
Fast Neutrons ◽  
Chemisorbed Oxygen ◽  
First Case ◽  
Different Temperatures ◽  
Negative Effect ◽  
Order Of Magnitude ◽  
Kinetics Of

The kinetics of the reduction by hydrogen of two series of NiO-Fe2O3 mixed oxides of different composition was studied in the temperature range 320 - 410 °C using thermogravimetry. Both series were prepared from different precursors that were thermally decomposed at different temperatures. The oxidizing ability of the surface ( the content of chemisorbed oxygen) is the only parameter from all physico-chemical properties studied that changed significantly during the pre-irridation of the system by 60Co gamma radiation (dose 505 kGy), by fast neutrons from the 252Cf source (dose Dn = 110 Gy) and by accelerated electrons (3 MeV, dose 500 kGy). A positive radiation effect was observed in the first case while the irritation by neutrons and electrons resulted in a negative effect. The magnitude of the effect depends on the composition and genesis of the system and it decreases in the sequence γ, e-, n. The radiation induced changes in the reduction kinetics of mixed oxides change their magnitude and sign in dependence on the composition and genesis. Not only the increase by an order of magnitude of the rate of the initial phase of the reduction which was ascribed to the partial reduction of hematite to magnetite but also the acceleration of the second step (reduction of Fe3O4 to Fe) was observed after the exposure to photons or fast neutrons. The radiation changes induced by electrons are limited only to the surface of the irradiated solid and they affect only the first step of the reduction. The maximum positive effect was observed in the region of high excess of hematite and its magnitude decreases with the increasing content of nickel oxide. The radiation effects decrease with the increasing temperature of the reduction and at about 400 °C the effect of irradiation is completely annealed.

scholarly journals Morphology of blends of self-assembling long-chain carbamate and stearic acid

2004 ◽  
Vol 76 (7-8) ◽  
pp. 1353-1363 ◽  
Author(s):  
M. Moniruzzaman ◽  
P. R. Sundararajan
Keyword(s):  
Hydrogen Bonding ◽  
Stearic Acid ◽  
Morphological Changes ◽  
Minor Component ◽  
Polymorphic Transition ◽  
Scanning Calorimetry ◽  
Self Assembling ◽  
Low Concentrations ◽  
Bonding Systems ◽  
Long Chain

The morphology of blends of two types of hydrogen-bonding systems was studied with a view to understanding the effect of blending on the extent of hydrogen bonding and changes in the morphology.One of them is the long-chain carbamate with a C18 alkyl side chain, and the other is stearic acid, which also has a C17 alkyl chain. At low concentrations, the C18 carbamate reduces the size of the crystals of stearic acid. However, the stearic acid has no effect on the morphology of the carbamate. The morphological changes are due to the disruptive packing of the alkyl chains, rather than a change in the extent of hydrogen bonding. The blends of homologous carbamates studied before [Moniruzzaman, Goodbrand, Sundararajan, J. Phys. Chem. Part B107, 8416 (2003)] are more effective in mutually controlling the spherulite size and imparting transparency than the carbamate/stearic acid blend. The presence of the carbamate as the minor component changes the ratio of the intensities of the X-ray reflections at 2 (theta)=21.6 and 2.21°. It is found that in the blends with the carbamates quenched from the melt, the stearic acid exhibits a polymorphic transition from the E to the C form in the differential scanning calorimetry (DSC) analysis.

Effect of ionizing radiation on the kinetics of reduction of NiO-MgO mixed oxids with hydrogen

1979 ◽  
Vol 44 (4) ◽  
pp. 1023-1033 ◽  
Author(s):  
Milan Pospíšil ◽  
Miroslav Tvrzník
Keyword(s):  
Nickel Oxide ◽  
Magnesium Oxide ◽  
Reaction Rate ◽  
Mixed Oxides ◽  
Reduction Rate ◽  
Inert Atmosphere ◽  
Fast Neutrons ◽  
Mixed System ◽  
Degree Of Reduction ◽  
Kinetics Of

The low-temperature reduction of the mixed system nickel oxide-magnesium oxide with hydrogen was studied thermogravimetrically in the region 260-470 °C. The two oxides form in the whole composition region solid solutions, some physicochemical parameters of which vary nonmonotonically with the sample composition. The kinetics and degree of reduction of nickel oxide are appreciably affected by the presence of the unreduced magnesium oxide, in higher concentrations lowering the reaction rate. The kinetics of the reduction can be quantitatively described by the equation 1-(1-α)1/3 = kt, valid in dependence on the composition in differently wide ranges of the degree of reduction α. The reaction rate can be varied, particularly for samples with low contents of magnesium oxide, by heat treatment in inert atmosphere at 700 °C, and for all samples by irradiation by gamma rays or fast neutrons. The reduction rate grows with the increasing content of magnesium oxide up to a constant value. The positive effect increases with the increasing gamma dose and, according to the kind of radiation, in the order γ, n. The variation of the reactivity of irradiated or thermally treated mixed oxides is due predominantly to the shift of the equilibrium of the lattice defects, formation and stabilization of new centres, which affect the rate of nucleation of the forming metal phase.

Effect of the ionizing radiation on the catalytic activity of the BASF K-3-10 catalyst in the low-temperature conversion of carbon monoxide by water vapour. Catalytic activity of the pre-irradiated catalyst

1986 ◽  
Vol 51 (2) ◽  
pp. 279-287 ◽  
Author(s):  
Alois Motl
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Low Temperature ◽  
Ionizing Radiation ◽  
Water Vapour ◽  
Effective Activation Energy ◽  
Absorbed Dose ◽  
Beta Radiation ◽  
Fast Neutrons ◽  
Different Types

The catalytic activity of the BASF K-3-10 catalyst with regard to the low-temperature conversion of carbon monoxide by water vapour and its changes after irradiation of the contact area by gamma or beta radiation or by fast neutrons has been investigated. The irradiated samples exhibit a moderately or even substantially higher catalytic activity in comparison with the non-irradiated catalyst, the change being dependent on the absorbed dose; moreover, the effective activation energy of the reaction increases, too. Important differences in the action of different types of the ionizing radiation used have been observed and their probable explanation is offered. In course of these experiments the catalysts were analyzed and the specific surface of the catalyst was measured at various stages of their history. It has been found that at all stages the specific surfaces of the irradiated catalyst are equal to the respective specific surfaces of the non-irradiated contacts.

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

Submerged upflow biotower operation and computer simulation

1994 ◽  
Vol 30 (11) ◽  
pp. 143-146
Author(s):  
Ronald D. Neufeld ◽  
Christopher A. Badali ◽  
Dennis Powers ◽  
Christopher Carson
Keyword(s):  
Computer Simulation ◽  
Benzoic Acid ◽  
Computer Model ◽  
Rate Constants ◽  
Batch Mode ◽  
Operational Conditions ◽  
First Order ◽  
Low Concentrations ◽  
Biological Transformation ◽  
Kinetics Of

A two step operation is proposed for the biodegradation of low concentrations (&lt; 10 mg/L) of BETX substances in an up flow submerged biotower configuration. Step 1 involves growth of a lush biofilm using benzoic acid in a batch mode. Step 2 involves a longer term biological transformation of BETX. Kinetics of biotransformations are modeled using first order assumptions, with rate constants being a function of benzoic acid dosages used in Step 1. A calibrated computer model is developed and presented to predict the degree of transformation and biomass level throughout the tower under a variety of inlet and design operational conditions.

The effect of composition of cobalt-molybdenum catalysts on their surface acidity and isomerisation activity

1980 ◽  
Vol 45 (3) ◽  
pp. 697-702 ◽  
Author(s):  
Vlastimil Vyskočil ◽  
Miroslav Zdražil
Keyword(s):  
Chromatographic Method ◽  
Surface Acidity ◽  
Parallel Reaction ◽  
Molybdenum Catalysts ◽  
The Difference ◽  
Kinetics Of ◽  
Alumina Catalysts

Kinetics of isomerisation of cyclohexene to methylcyclopentene proceeding as parallel reaction to hydrogenation of cyclohexene to cyclohexane on cobalt-molybdenum catalysts of different composition has been measured. The surface acidity of these catalysts was estimated from the difference in the adsorption of toluene and heptane which was measured by chromatographic method. In a series of catalysts containing molybdenum the acidity parallels isomerisation activity. Cobalt on alumina catalysts and alumina itself have greater acidity but exhibit lower isomerisation activity compared to the catalysts containing molybdenum.

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