Carbon monoxide conversion, rates

The catal5fsts were tested for CO oxidation in a flow reactor using a 2.5 % CO in dry air mixture at a fixed flow rate of 200 seem. Thirty milligrams of the catalyst were used for each experimental run. The reaction was conducted at 298, 323, 373 and 473 K with 75 minutes duration at each temperature. The carbon monoxide conversion to carbon dioxide was monitored by an online gas chromatogr h equipped with a CTR-1 column and a thermal conductivity... 

GP 9[ [R 16]The extent of internal transport limits was analysed for the wide fixed-bed reactor, using experimental data on carbon monoxide conversion and matter and process parameter data for the reactants [78]. The analysis was based on the Weisz modulus and the Anderson criterion for judging possible differences between observed and actual reaction rates. As a result, it was found that the small particles eliminate internal transport limitations. 

On Fe304 the rates of isotopic exchange reactions (356), (366), and (367) are close to the rate of carbon monoxide conversion, as should be expected from mechanism (343). 

If, after several manual trials, the calculations appear to be converging, it is reasonable to switch from manual to automatic iteration. It is strongly recommended that the calculations always be checked by a simple hand calculation. In this example, for instance, the user may add the feed and recycle carbon monoxide flow rates, multiply the sum by the conversion, and compare the result with the tabulated value for the methanol product rate c8. 

Summary data for different conversion/temperature conditions are provided in Tables 5-7. Rate constants were calculated from these data, and it was determined that although the operations at 140 kPa were influenced by mass transfer, this was not the rate-limiting step however, the reaction was mass transfer limited at 1000 kPa. The higher carbon monoxide conversion values and methane production observed for the monolith-supported nickel compared to pellets were explained to be due to the provision by the monoliths of smaller pore diffusion resistance and higher mass transfer rates at higher temperatures, primarily a result of shorter diffusion paths in thin alumina coatings on the monolith walls. 

Generally, in a conventional WGS system a two-step shift is used to obtain high CO conversion rates. In the first high-temperature shift reactor the major part of the CO is converted at high activity, whereas in the second shift reactor the rest of the CO (closely up to the thermodynamic equilibrium) is converted at low temperature and also low activity. Steam to carbon monoxide ratios above the stoichiometric ratio (higher than 2) are generally being used to attain the desired carbon monoxide conversion, but also to suppress carbon formation on certain catalysts. 

The gas-phase reaction of carbon monoxide and steam to produce carbon dioxide and hydrogen has been studied in the presence of a Siemens ozonizer discharge. A factorial design was used to determine the effect of input electrical power, pressure, space velocity, and temperature on the conversion of carbon monoxide. With the aid of an empirical equation, derived from the factorial design data, the region of maximum conversion of carbon monoxide within the limits of the factors was determined. The rate of approach to thermodynamic equilibrium was investigated for one set of experimental conditions and was compared with previous work. The effect of changing the surface-to-volume ratio of the reactor upon carbon monoxide conversion was also determined. 

Industrial practice has required the development of a usable equation so that workable reaction systems can be designed. Rate equations used commercially have been developed with little consideration being given to the theoretical aspects of the reaction kinetics. Thus information is developed about the action of a carbon monoxide conversion catalyst with little understanding of why it performs in the manner that it does. 

Catalysts were compared by measuring their rate of carbon monoxide conversion. Test variables were temperature, feed gas composition, and the feed rate/catalyst weight ratio. All tests were made at 1000 p.s.i.g. Three feed gases, covering a range of compositions typical of projected methanation feeds, were selected (Table I). 

The effect of space velocity is demonstrated by the example of 10%Co-M (9.25-0.75)/Al2O3. With rising space velocity from 90 to 300 hr, increase in temperature was required from 167 to 195°C to keep the constant degree of carbon monoxide conversion at 53%. At that rate, ceresin yield decreased from 23 to 10% (Table 2). The same behaviour was observed with all the catalysts studied in this woik. 

Productivity at high conversion Higher less significant efiect of water on the rate of carbon monoxide conversion Lower strong negative effect of water on the rate of carbon monoxide conversion... 

Results obtained with crushed catalyst particles showed that the first-order rate constant for carbon monoxide conversion (A co) calculated on the basis of equation (7) is fairly independent of space velocity and H2/CO feed ratio. This demonstrates the validity of the kinetic expression. 

An increase in total pressure would generally result in condensation of hydrocarbons, which are normally in the gaseous state at atmospheric pressure. Higher pressures and higher carbon monoxide conversions would probably lead to saturation of catalyst pores by liquid reaction products [49]. A different composition of the liquid phase in catalyst pores at high syngas pressures could affect the rate of elementary steps and carbon monoxide and hydrogen concentrations. A series... 

It was shown in laboratory studies that methanation activity increases with increasing nickel content of the catalyst but decreases with increasing catalyst particle size. Increasing the steam-to-gas ratio of the feed gas results in increased carbon monoxide shift conversion but does not affect the rate of methanation. Trace impurities in the process gas such as H2S and HCl poison the catalyst. The poisoning mechanism differs because the sulfur remains on the catalyst while the chloride does not. Hydrocarbons at low concentrations do not affect methanation activity significantly, and they reform into methane at higher levels, hydrocarbons inhibit methanation and can result in carbon deposition. A pore diffusion kinetic system was adopted which correlates the laboratory data and defines the rate of reaction. 

Kolbel et al. (K16) examined the conversion of carbon monoxide and hydrogen to methane catalyzed by a nickel-magnesium oxide catalyst suspended in a paraffinic hydrocarbon, as well as the oxidation of carbon monoxide catalyzed by a manganese-cupric oxide catalyst suspended in a silicone oil. The results are interpreted in terms of the theoretical model referred to in Section IV,B, in which gas-liquid mass transfer and chemical reaction are assumed to be rate-determining process steps. Conversion data for technical and pilot-scale reactors are also presented. 

GP 9] [R 16] The reaction rate and activation energy of metal catalysts (Rh, Pt or Pd) supported on alumina particles ( 3 mg 53-71 pm) were determined for conversions of 10% or less at steady state (1% carbon monoxide 1% oxygen, balance helium 20-60 seem up to 260 °C) [7, 78]. The catalyst particles were inserted into a meso-channel as a mini fixed bed, fed by a bifurcation cascade of micro-channels. For 0.3% Pd/Al203 (35% dispersion), TOF (about 0.5-5 molecules per site... 

At elevated temperatures, acetaldehyde (CH3CHO, A) undergoes gas-phase decomposition into methane and carbon monoxide. The reaction is second-order with respect to acetaldehyde, with kA = 22.2 L mol-1 min-1 at a certain T. Determine the fractional conversion of acetaldehyde that can be achieved in a 1500-L CSTR, given that the feed rate of acetaldehyde is 8.8 kg min-1, and the inlet volumetric flow rate is 2.5 m3 min-1. Assime T and P arc unchanged... 

Catalysts were tested for oxidations of carbon monoxide and toluene. The tests were carried out in a differential reactor shown in Fig. 12.7-1 and analyzed by an online gas chromatograph (HP 6890) equipped with thermal conductivity and flame ionization detectors. Gases including dry air and carbon monoxide were feed to the reactor by mass flow controllers, while the liquid reactant, toluene was delivered by a syringe pump. Thermocouple was used to monitor the catalyst temperature. Catalyst screening and optimization identified the best catalyst formulation with a conversion rate for carbon monoxide and toluene at room temperature of 1 and 0.25 mmolc g min1. Carbon monoxide and water were the only products of the reactions. 

As before, reaction (3.71) is slow. Reactions (3.72) and (3.73) are faster since they involve a radical and one of the initial reactants. The same is true for reactions (3.75M3.77). Reaction (3.75) represents the necessary chain branching step. Reactions (3.74) and (3.78) introduce the formyl radical known to exist in the low-temperature combustion scheme. Carbon monoxide is formed by reaction (3.76), and water by reaction (3.73) and the subsequent decay of the peroxides formed. A conversion step of CO to C02 is not considered because the rate of conversion by reaction (3.44) is too slow at the temperatures of concern here. 

Much of the work on the photoreduction of carbon dioxide centres on the use of transition metal catalysts to produce formic acid and carbon monoxide. A large number of these catalysts are metalloporphyrins and phthalocyanines. These include cobalt porphyrins and iron porphyrins, in which the metal in the porphyrin is first of all photochemically reduced from M(ii) to M(o), the latter reacting rapidly with CO to produce formic acid and CO. ° Because the M(o) is oxidised in the process to M(ii) the process is catalytic with high percentage conversion rates. However, there is a problem with light energy conversion and the major issue of porphyrin stability. 

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