A quasiclassical trajectory study of hydrogen atom + carbon dioxide .fwdarw. hydroxyl + carbon monoxide: bulk reaction dynamics and the effect of van der Waals precursor formation

1991 ◽  
Vol 95 (21) ◽  
pp. 8267-8273 ◽  
Author(s):  
Kathleen Kudla ◽  
George C. Schatz
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Hydrogen Atom ◽  
Van Der Waals ◽  
Reaction Dynamics ◽  
Bulk Reaction

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.

scholarly journals Controlled atmosphere GMAW welding of transportation vehicles and production machines parts made from 30MnB5 steel

2018 ◽  
Vol 216 ◽  
pp. 03001 ◽  
Author(s):  
Evgeny Ivanayskiy ◽  
Aleksei Ishkov ◽  
Aleksandr Ivanayskiy ◽  
Iakov Ochakovskii
Keyword(s):  
Mechanical Properties ◽  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Chemical Composition ◽  
Controlled Atmosphere ◽  
Shielding Gas ◽  
Reducing Atmosphere ◽  
Metal Composition ◽  
Gmaw Welding ◽  
Welding Materials

The paper studies the influence of shielding gas on the composition and the structure of weld joint metal of 30MnB5 steel applied in essential parts of automobiles and tractors. The welding was performed in inert, oxidizing and reducing atmospheres. It was established that TIG welding with argon used as shielding gas did not provide the required mechanical properties when using conventional welding materials. Carbon dioxide during MAG welding caused partial burning of alloying elements. Carbon monoxide used as shielding gas was proved to form reducing atmosphere enabling to obtain chemical composition close to the base metal composition. Metallographic examinations were carried out. The obtained results provided full-strength weld, as well as the required reliability and durability of welded components and joints.

Low-Carbon Monoxide Hydrogen by Sorption-Enhanced Reaction

2003 ◽  
Vol 1 (1) ◽  
Author(s):  
Douglas P Harrison ◽  
Zhiyong Peng
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Hydrogen Production ◽  
Proton Exchange Membrane ◽  
Primary Energy ◽  
Proton Exchange ◽  
Raw Material ◽  
Impurity Level ◽  
Low Carbon ◽  
Enhanced Production

Hydrogen is an increasingly important chemical raw material and a probable future primary energy carrier. In many current and anticipated applications the carbon monoxide impurity level must be reduced to low-ppmv levels to avoid poisoning catalysts in downstream processes. Methanation is currently used to remove carbon monoxide in petroleum refining operations while preferential oxidation (PROX) is being developed for carbon monoxide control in fuel cells. Both approaches add an additional step to the multi-step hydrogen production process, and both inevitably result in hydrogen loss. The sorption enhanced process for hydrogen production, in which steam-methane reforming, water-gas shift, and carbon dioxide removal reactions occur simultaneously in the presence of a nickel-based reforming catalyst and a calcium-based carbon dioxide sorbent, is capable of producing high purity hydrogen containing minimal carbon monoxide in a single processing step. The process also has the potential for producing pure CO2 that is suitable for subsequent use or sequestration during the sorbent regeneration step. The current research on sorption-enhanced production of low-carbon monoxide hydrogen is an extension of previous research in this laboratory that proved the feasibility of producing 95+% hydrogen (dry basis), but without concern for the carbon monoxide concentration. This paper describes sorption-enhanced reaction conditions – temperature, feed gas composition, and volumetric feed rate – required to produce 95+% hydrogen containing low carbon monoxide concentrations suitable for direct use in, for example, a proton exchange membrane fuel cell.

scholarly journals The flame spectrum of carbon monoxide

1940 ◽  
Vol 176 (967) ◽  
pp. 505-521 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Electronic State ◽  
Excited Electronic State ◽  
Combustion Process ◽  
Wave Number ◽  
Band Spectrum ◽  
Liquid Form ◽  
Triangular Form ◽  
Reduced Pressure

The spectrum of the flame of carbon monoxide burning in air and in oxygen at reduced pressure has been photographed on plates of high contrast which display the band spectrum clearly above the continuous background. Greater detail has been obtained than has been recorded previously and new measurements are given. The structure of the spectrum has been studied systematically. It is shown that the bands occur in pairs with a separation of about 60 cm. -1 , this separation being due probably to the rotational structure. Various wave-number differences are found to occur frequently, and many of the strong bands are arranged in arrays using intervals of 565 and 2065 cm. -1 . The possible origin of the spectrum is discussed. The choice of emitter is limited to a polyatomic oxide of carbon, of which carbon dioxide is the most likely. The spectrum of the suboxide C 3 O 2 shows some resemblance to the flame bands, but this molecule is improbable as the emitter on other grounds. A peroxide C0 3 is also a possibility, but no evidence for the presence of this has been obtained from experiments on the slow combustion of carbon monoxide. Carbon dioxide in gaseous or liquid form is transparent through the visible and quartz ultra-violet, and the flame bands are not obtained from CO 2 in discharge tubes. Comparison with the Schumann-Runge bands of oxygen shows that it is possible that the flame bands may form part of the absorption band system of CO 2 which is known to exist below 1700 A if there is a big change in shape or size of the molecule in the two electronic states. The electronic energy levels of CO 2 are discussed. Since normal CO 2 is not built up from normal CO and oxygen, an electronic rearrangement of the CO 2 must occur after the combustion process. Mulliken has suggested that the molecule in the first excited electronic state, corresponding to absorption below 1700 A, may have a triangular form. The frequencies obtained from the flame bands are compared with the infra-red frequencies of CO 2 . The 565 interval may be identified with the transverse vibration v 2 , indicating that the excited electronic state is probably triangular in shape. The 2065 interval cannot, however, be identified with the asymmetric vibration v 3 with any certainty. If the excited electronic state of CO 2 is triangular, then molecules formed during the combustion by transitions from this level to the ground state may be “vibrationally activated”. This is probably the reason for many of the peculiarities of the combustion of carbon monoxide.

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