Reactions of carbon with atomic gases

1959 ◽  
Vol 12 (4) ◽  
pp. 533 ◽  
Author(s):  
JD Blackwood ◽  
FK McTaggart
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Water Vapour ◽  
Active Sites ◽  
Atmospheric Temperature ◽  
Carbon Surface ◽  
Hydrogen Atoms ◽  
Different Temperatures ◽  
Atomic Species ◽  
Oxygen Groups

Wood chars were reacted at atmospheric temperature with hydrogen atoms, oxygen atoms and carbon monoxide, hydrogen atoms and hydroxyl radicals, produced by the action of a radio frequency field on hydrogen, carbon dioxide, and water vapour respectively. The chars were prepared at different temperatures and contained different amounts of oxygen. The experimental results showed that the gases must be present in the atomic form before reaction with the carbon can take place and that such species react on the carbon-surface independently of active sites. In normal gasification processes the atomic species appear to be produced at active centres, which for the chars used could be correlated with specific oxygen groups remaining in the carbon. It is suggested that these groupings may have a pyran structure. An explanation has been put forward for the retardation of the carbon-water vapour reaction by hydrogen, and of the carbon-carbon dioxide reaction by carbon monoxide. These are considered as due to reverse mechanisms which decrease the concentration of the atomic species and not to the blocking of active sites by adsorption of the retardant.

The Reaction of Carbon with Carbon Dioxide at High Pressure

1960 ◽  
Vol 13 (2) ◽  
pp. 194 ◽  
Author(s):  
JD Blackwood ◽  
AJ Ingeme
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Active Sites ◽  
High Pressures ◽  
Carbon Dioxide Molecule ◽  
Partial Pressures ◽  
Different Temperatures ◽  
Adsorbed Carbon ◽  
Forward Process ◽  
High Carbon Dioxide

A study has been made of the reactions of purified carbon with carbon dioxide at pressures up to 40 atm and in the temperature range 790-870 �C. The effect of carbon monoxide has been examined by adding varying proportions of this gas to the carbon dioxide supplied to the reactor bed. At high carbon dioxide and carbon monoxide partial pressures, the rate of formation of carbon monoxide is greater than would be expected from the mechanism proposed by Gadsby et al. (1948). A mechanism has been proposed whereby the increased rate may be explained by additional steps involving the interaction of a carbon dioxide molecule with an adsorbed carbon monoxide to produce adsorbed oxygen, thus : ������������������ CO2 + (CO) → 2CO +(O) A general rate equation has been derived which includes this step and satisfies the experimental results. The reverse mechanism by which carbon monoxide can disappear is not the simple reverse of the forward process and at high pressures equilibrium cannot be expressed by the usual expression derived for the simple single-stage reversible process. The possible nature of active sites has been examined by studying the reactivity of a series of chars prepared at different temperatures. The reactivity appears to be related to the oxygen content of the chars and the type of active centres involved may be different from those which control the carbon-steam mechanism.

scholarly journals The mechanism of the steam-carbon reaction

1948 ◽  
Vol 193 (1034) ◽  
pp. 377-399 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Hydrogen Atom ◽  
Active Carbon ◽  
Active Sites ◽  
Adsorbed Oxygen ◽  
Adsorbed Hydrogen ◽  
Hydrogen Atoms ◽  
Exponential Factor ◽  
Gaseous Carbon Monoxide

The detailed mechanism of the reaction between steam and coconut shell charcoal has been studied by the method described in the preceding paper. The temperature has been varied in the range 680 to 800° C and the pressures of the gases from 10 to 760 mm. Steam first reacts with the carbon to give oxygen and hydrogen atoms separately adsorbed on neighbouring sites. An initial dissociation into an adsorbed hydrogen atom and an adsorbed hydroxyl radical is probably followed by the more rapid transfer of the second hydrogen atom to the carbon. Only about 2% of the total surface takes part in the reaction; these sites are distinct from the smaller group which reacts with carbon dioxide, but they are also thought to be atoms at the edges of lattice planes. The rate of the first stage can be accounted for by assuming that reaction occurs in those collisions in which the combined energy of the incident steam molecule and the two active carbon atoms exceeds 75 kcal. Adsorbed hydrogen evaporates rapidly, but in the steady state much remains on the surface. A close correlation has been observed between the fraction of the active sites occupied by hydrogen and the extent to which the reaction is retarded by that gas. Adsorbed oxygen reacts much more slowly to form gaseous carbon monoxide; the latter, which has no retarding effect, is not appreciably adsorbed by the sites accessible to steam. The activation energy for the conversion of an adsorbed oxygen atom into gaseous carbon monoxide is found to be 55 kcal., and the non- exponential factor to be 10 11±1.7 sec. -1 which may be compared with the value of 10 13 sec. -1 predicted by simple theory. As the active carbon atoms are thought to be exerting less than their maximum valency, it is suggested that the two types differ in the number of extra bonds which they can form. Energetic considerations show that whereas those which can form a single bond should react with steam, only the relatively few capable of forming a double bond should react with carbon dioxide. This theory also explains why hydrogen is strongly adsorbed by both the steam and the carbon dioxide sites, but carbon monoxide only by the latter type. The relation of these views to outstanding problems of the oxygen-carbon and nitrous oxide-carbon reactions is discussed, and an explanation of the main kinetic features of those processes is given.

The oxidation of Carbon with Atomic Oxygen

1959 ◽  
Vol 12 (2) ◽  
pp. 114 ◽  
Author(s):  
JD Blackwood ◽  
FK McTaggart
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Radio Frequency ◽  
Molecular Oxygen ◽  
Atomic Oxygen ◽  
Graphitic Carbon ◽  
Carbon Surface ◽  
Direct Oxidation ◽  
Radio Frequency Field ◽  
Frequency Field

Atomic oxygen, produced by dissociation of molecular oxygen in a radio frequency field, will react with amorphous or graphitic carbon at room temperatures and both carbon monoxide and carbon dioxide appear in the product gases. Carbon monoxide appears to be the primary product of oxidation of carbon, the carbon dioxide being produced by direct combination of carbon monoxide with oxygen which takes place mainly at the carbon surface. Atomic oxygen will also react with carbon dioxide to produce carbon monoxide and molecular oxygen but the quantity of carbon monoxide produced by this reaction is small compared to that produced by direct oxidation of the carbon.

scholarly journals The impact of orbital sampling, monthly averaging and vertical resolution on climate chemistry model evaluation with satellite observations

2011 ◽  
Vol 11 (3) ◽  
pp. 9705-9742
Author(s):  
A. M. Aghedo ◽  
K. W. Bowman ◽  
D. T. Shindell ◽  
G. Faluvegi
Keyword(s):  
Climate Change ◽  
Boundary Layer ◽  
Carbon Monoxide ◽  
Water Vapour ◽  
Climate Models ◽  
Atmospheric Temperature ◽  
Satellite Observations ◽  
Vertical Resolution ◽  
Upper Troposphere ◽  
The Impact

Abstract. Ensemble climate model simulations used for the Intergovernmental Panel on Climate Change (IPCC) assessments have become important tools for exploring the response of the Earth System to changes in anthropogenic and natural forcings. The systematic evaluation of these models through global satellite observations is a critical step in assessing the uncertainty of climate change projections. This paper presents the technical steps required for using nadir sun-synchronous infrared satellite observations for multi-model evaluation and the uncertainties associated with each step. This is motivated by need to use satellite observations to evaluate climate models. We quantified the implications of the effect of satellite orbit and spatial coverage, the effect of variations in vertical sensitivity as quantified by the observation operator and the impact of averaging the operators for use with monthly-mean model output. We calculated these biases in ozone, carbon monoxide, atmospheric temperature and water vapour by using the output from two global chemistry climate models (ECHAM5-MOZ and GISS-PUCCINI) and the observations from the Tropospheric Emission Spectrometer (TES) satellite from January 2005 to December 2008. The results show that sampling and monthly averaging of the observation operators produce biases of less than ±3% for ozone and carbon monoxide throughout the entire troposphere in both models. Water vapour sampling biases were also within the insignificant range of ±3% (that is ±0.14 g kg−1) in both models. Sampling led to a temperature bias of ±0.3 K over the tropical and mid-latitudes in both models, and up to −1.4 K over the boundary layer in the higher latitudes. Using the monthly average of temperature and water vapour operators lead to large biases over the boundary layer in the southern-hemispheric higher latitudes and in the upper troposphere, respectively. Up to 8% bias was calculated in the upper troposphere water vapour due to monthly-mean operators, which may impact the detection of water vapour feedback in response to global warming. Our results reveal the importance of using the averaging kernel and the a priori profiles to account for the limited vertical resolution of a nadir observation during model application. Neglecting the observation operators resulted in large biases, which are more than 60% for ozone, ±30% for carbon monoxide, and range between −1.5 K and 5 K for atmospheric temperature, and between −60% and 100% for water vapour.

scholarly journals The mechanism of the carbon dioxide-carbon reaction

1948 ◽  
Vol 193 (1034) ◽  
pp. 357-376 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Carbon Surface ◽  
General Nature ◽  
Exponential Factor ◽  
Carbon Dioxide Molecule ◽  
Partial Pressures ◽  
Rate Of Reaction ◽  
Order Of Magnitude ◽  
The Individual

The detailed mechanism of the reaction between carbon dioxide and coconut shell charcoal has been studied by both flow and static methods. The temperature has been varied in the range 700 to 830° C and the pressures of the gases from 10 to 760 mm. The static method has been used to investigate the adsorption of the gases on the carbon surface during the course of the reaction, and thus to illustrate in a very direct way the general nature of the mechanism. Accurate measurements of the rate of reaction have been made by the flow method. At a given temperature the rate of reaction can be represented in terms of the partial pressures of the gases by an expression of the form rate = k 1 pco 2 / 1+k 2 pco + k 3 pco 2 . The three separate constants have been evaluated and each has been found to vary exponentially with temperature. From these results the rates of the individual stages of the mechanism have been calculated. The first stage is the decomposition of the carbon dioxide molecule into an atom of oxygen which is adsorbed by the carbon and a molecule of carbon monoxide which passes into the gas phase. Only certain sites on the charcoal surface take part in the reaction; they represent about 0-5 % of the total area and probably consist of some of the less firmly bound carbon atoms situated at lattice discontinuities. The rate of the first stage can be accounted for by assuming that reaction occurs in those collisions in which the combined energy of the active carbon atom and the incident carbon dioxide molecule exceeds 68 kcal. The second stage is the evaporation of the adsorbed oxygen atom, together with an atom of carbon from the solid, to form gaseous carbon monoxide; the activation energy is thought to be 38 kcal., and the low value of 107 sec. -1 obtained for the non-exponential factor is discussed. The retarding effect of carbon monoxide is due to the adsorption of the gas on the reaction sites, the heat given out in the change being 46 kcal. On the basis of this value, which implies that the molecule is adsorbed chemically, it is possible to calculate theoretically the order of magnitude of the retardation constant, k 2 .

scholarly journals The impact of orbital sampling, monthly averaging and vertical resolution on climate chemistry model evaluation with satellite observations

2011 ◽  
Vol 11 (13) ◽  
pp. 6493-6514 ◽  
Author(s):  
A. M. Aghedo ◽  
K. W. Bowman ◽  
D. T. Shindell ◽  
G. Faluvegi
Keyword(s):  
Climate Change ◽  
Boundary Layer ◽  
Carbon Monoxide ◽  
Water Vapour ◽  
Climate Models ◽  
Atmospheric Temperature ◽  
Satellite Observations ◽  
Vertical Resolution ◽  
Upper Troposphere ◽  
The Impact

Abstract. Ensemble climate model simulations used for the Intergovernmental Panel on Climate Change (IPCC) assessments have become important tools for exploring the response of the Earth System to changes in anthropogenic and natural forcings. The systematic evaluation of these models through global satellite observations is a critical step in assessing the uncertainty of climate change projections. This paper presents the technical steps required for using nadir sun-synchronous infrared satellite observations for multi-model evaluation and the uncertainties associated with each step. This is motivated by need to use satellite observations to evaluate climate models. We quantified the implications of the effect of satellite orbit and spatial coverage, the effect of variations in vertical sensitivity as quantified by the observation operator and the impact of averaging the operators for use with monthly-mean model output. We calculated these biases in ozone, carbon monoxide, atmospheric temperature and water vapour by using the output from two global chemistry climate models (ECHAM5-MOZ and GISS-PUCCINI) and the observations from the Tropospheric Emission Spectrometer (TES) instrument on board the NASA-Aura satellite from January 2005 to December 2008. The results show that sampling and monthly averaging of the observation operators produce zonal-mean biases of less than ±3 % for ozone and carbon monoxide throughout the entire troposphere in both models. Water vapour sampling zonal-mean biases were also within the insignificant range of ±3 % (that is ±0.14 g kg−1) in both models. Sampling led to a temperature zonal-mean bias of ±0.3 K over the tropical and mid-latitudes in both models, and up to −1.4 K over the boundary layer in the higher latitudes. Using the monthly average of temperature and water vapour operators lead to large biases over the boundary layer in the southern-hemispheric higher latitudes and in the upper troposphere, respectively. Up to 8 % bias was calculated in the upper troposphere water vapour due to monthly-mean operators, which may impact the detection of water vapour feedback in response to global warming. Our results reveal the importance of using the averaging kernel and the a priori profiles to account for the limited vertical resolution and clouds of a nadir observation during model application. Neglecting the observation operators resulted in large biases, which are more than 60 % for ozone, ±30 % for carbon monoxide, and range between −1.5 K and 5 K for atmospheric temperature, and between −60 % and 100 % for water vapour.

scholarly journals Co-pyrolysis of rubberwood sawdust (RWS) and polypropylene (PP) in a fixed bed pyrolyzer

2019 ◽  
Vol 13 (1) ◽  
pp. 4636-4647 ◽  
Author(s):  
N. I. Izzatie ◽  
M. H. Basha ◽  
Y. Uemura ◽  
M. S. M. Hashim ◽  
M. Afendi ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Water Content ◽  
Fixed Bed ◽  
Oil Yield ◽  
Pyrolysis Oil ◽  
Pyrolysis Process ◽  
Increasing Trend ◽  
Different Temperatures

Co-pyrolysis of rubberwood sawdust (RWS) waste and polypropylene (PP) was carried out at different temperatures (450,500,550, and 600°C) with biomass to plastics ratio 1:1 by using fixed bed drop-type pyrolyzer. The yield of pyrolysis oil has an increasing trend as the temperature increased from 450°C to 550°C. However, the pyrolysis oil yield dropped at a temperature of 600°C. Co-pyrolysis of RWS and PP generated maximum pyrolysis oil with 36.47 wt.% at 550°C. The result is compared with the pyrolysis of RWS only without plastics, with the same feedstock, and the maximum pyrolysis oil yield obtained was 33.3 wt.%. The water content in pyrolysis oil of co-pyrolysis RWS with PP is lower than RWS only with 54.2 wt.% and 62 wt.% respectively. Hydrocarbons, acyclic olefin, alkyl, and aromatic groups are the major compound in the pyrolysis oil from the co-pyrolysis process. Carbon monoxide (52.2 vol.%) and carbon dioxide (38.2 vol.%) are the major gas components.

scholarly journals Supplementary table of wave-lengths of new lines in the secondary spectrum of hydrogen

1926 ◽  
Vol 113 (764) ◽  
pp. 420-432 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Water Vapour ◽  
Discharge Tube ◽  
Present Author ◽  
Pure Hydrogen ◽  
Coconut Charcoal ◽  
King's College ◽  
Pressure Discharge ◽  
Type Spectrum

During the course of the investigation of the secondary spectrum of hydrogen which is being carried out at King’s College, the present author had to take a number of spectrograms of a low potential and a low-pressure discharge of hydrogen known as the first-type discharge according to Prof. Richardson’s nomenclature. On measuring these first-type spectrum plates, it was found that each of them contained some eighty new lines not recorded in Merton and Barratt’s tables or in the table of additional lines recently published by Tanaka. At first it was suspected that these new lines might be due to some impurities in the discharge tube, but on carefully looking for impurities such as oxygen, nitrogen, carbon, mercury, barium, carbon monoxide, carbon dioxide, ammonia, water vapour, etc., it became evident that there were no impurity lines on our spectrum plates. It may be pointed out that before taking the first-type spectrogram of hydrogen, the discharge tube was being pumped out for a number of days, and it was then washed with hydrogen several times. The discharge tube was provided with a side tube containing coconut charcoal, which was surrounded by liquid air. This liquid-air trap was kept on during all exposures. Pure hydrogen was supplied by means of a palladium tube attached to the side of the discharge tube. This palladium tube was heated in a flame of commercial hydrogen.

Reaction Characteristics of Wastepaper Gasification With CO2 Catalyzed by Molten Carbonate Salts

2002 ◽  
Author(s):  
Hiroyuki Iwaki ◽  
Gong Jin ◽  
Tomohiko Furuhata ◽  
Norio Arai
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Critical Role ◽  
Boudouard Reaction ◽  
Low Carbon ◽  
Molten Carbonate ◽  
Steam Generation ◽  
Different Temperatures ◽  
Effective Use ◽  
Carbonate Salts

In this paper, wastepaper gasification with steam and carbon dioxide was tested in the presence of molten carbonate salt catalysts. Reactions with steam or carbon dioxide were first compared. Hydrogen was mainly produced by gasification with steam, but no carbon monoxide was generated. For the case where carbon dioxide was used as a reactant instead of steam, generation of carbon monoxide greatly increased via the Boudouard reaction. Different ratios of mixtures of lithium, sodium and potassium carbonates were examined. Lithium was found to play a critical role in the various catalyst combinations. The reaction rate with respect to carbon conversion was approximately first order for low carbon conversions. The rate constants were investigated at different temperatures (923–1023K) and the activation energies were determined. In addition, the flexibility of this technique was examined with three different types of wastepaper. These results suggest the applicability of this process for the effective use of wastepaper and recovery of carbon dioxide.

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