Co reaction rate

OH - - CO) Reaction Rate Coefficients (Reaction Time in Minutes)... 

Heating temperature (°C) 0HCOO- before heating Decomposition products (%) Hi CO Reaction rate a molec./cma sec... 

Although Chen et al. focused on CO oxidation in gas turbine exhausts with noble metal catalysts, much of the deactivation data that they presented is also relevant to oxidation of VOCs in other air pollution control applications. They reported that 100 to 200 ppm SO2 in the exhaust will require 150 to 200 C higher catalyst temperatures for the same CO conversion as that without SO2. However, above -350 C the effect of SO2 disappears with these catalysts because the CO reaction rate becomes mass-transfer controlled. The inhibition by SO2 is attributed to the strong adswption of the sulfur compounds on both the catalyst and carrier, limiting adsorption of CO. These adsorbed sulfur compounds can be removed with time and high temperatures in the absence of SO2, restoring catalyst activity. 

There is a clear inflection point at 500 K in the Arrhenius plot of NO reaction rate over the Rli/Ceo 4O2 catalyst prereduced at 673 K which is absent both in the CO reaction rate over the same catalyst and in the CO and NO reaction rates over the catalyst prereduced at 473 K. From the former plot an apparent activation energy for NO conversion of 64 kJ mol l is obtained for NO conversion below 500 K, while a value of approximately 120 kJ mol 1 is measured for all the other cases. This suggests that for NO conversion a complementary mechanism of lower activation energy is operating in the samples in which the support is initially reduced in the bulk, which is not observed when only rhodium and the surface have been reduced in the catalyst pretreatment. 

In our water effect experiment, a primarily reversible decrease in CO conversion was observed when up to 30 vol% of water was added to the feed for this catalyst [9], With the 0.5% Pt-15%Co/Al203 catalyst, a reversible water effect was obtained at a lower volume percent of water addition but irreversible deactivation occurred at > 25% vol. water addition [7], One possibility for the effect of water is that the amount of catalytic active sites (i.e., surface cobalt metal atoms) available for the FT reaction changes with partial pressure of water, perhaps by a temporary oxidation process for cobalt [9], Alternatively, competitive adsorption of water may decrease the surface concentration of CO and/or H2 [9], Thus, the following equation is proposed to described the reversible impact of water on the CO reaction rate ... 

To determine the order of the FT reaction for H2, constant CO inlet partial pressure was used at each H2/CO ratio. The CO reaction rate is calculated using the relation ... 

H2/CO ratio of the inlet gas). The regressed equations were obtained using a polynomial function and extrapolated to the origin. The regressed equations determined from the data in Figure 5 for different H2/CO ratios are summarized in Table 5. It is assumed that at very low CO conversion levels [i.e. (dXco/dt)-c=o], the partial pressure of water is zero so that the partial pressure of water did not affect the CO reaction rate (m = 0). Thus, equation (5) reduces to equation (6) ... 

SerH = the zwitterion of serine, is the anation rate constant, and is the ion-pair equilibrium constant between SerH and [Co]. Reaction rates in different ethanol-water mixtures reach a limit at high ligand concentrations and increases as the concentration of the organic component in the medium increases, while the reverse is true for k. The reaction is catalyzed by NOJ and the rate increases with pH within the quoted range. A mechanism involving ion-pair formation followed by dissociative interchange of the outer-sphere complex with the product is proposed. 

A striking feature of the images is the nonunifonnity of the distribution of the adsorbed species. The reaction between O and CO takes place at the boundaries between the surface domains and it was possible to detennine reaction rates by measuring the change in length L of the boundaries of the O islands. The kinetics is represented by the rate equation... 

As for the selectivity of DBO, the higher the reaction pressure and the lower the reaction temperature, the higher the selectivity. As for the reaction rate, the higher the reaction temperature, the larger the rate. Therefore, the industrial operation of the process is conducted at 10—11 MPa (1450—1595 psi) and 90—100°C. In addition, gas circulation is carried out in order to keep the oxygen concentration below the explosion limit during the reaction, and to improve the CO utili2ation rate and the gas—Hquid contact rate. 

Butylene isomers also can be expected to show significant differences in reaction rates for metaHation reactions such as hydroboration and hydroformylation (addition of HCo(CO). For example, the rate of addition of di(j -isoamyl)borane to cis-2-huX.en.e is about six times that for addition to trans-2-huX.en.e (15). For hydroformylation of typical 1-olefins, 2-olefins, and 2-methyl-l-olefins, specific rate constants are in the ratio 100 31 1, respectively. 

Rates of Reaction. The rates of formation and dissociation of displacement reactions are important in the practical appHcations of chelation. Complexation of many metal ions, particulady the divalent ones, is almost instantaneous, but reaction rates of many higher valence ions are slow enough to measure by ordinary kinetic techniques. Rates with some ions, notably Cr(III) and Co (III), maybe very slow. Systems that equiUbrate rapidly are termed kinetically labile, and those that are slow are called kinetically inert. Inertness may give the appearance of stabiUty, but a complex that is apparentiy stable because of kinetic inertness maybe unstable in the thermodynamic equihbrium sense. 

FIG. 16 Variation of the steady-state rate of production, Pcoj, with Pco in the NO + CO lattice gas model with NO desorption (rate d o = 0.5), and CO desorption at various rates (shown). The inset shows the reaction rate measured experimentally at 410 K. (From Ref. 81.)... 

Bunnett and co-workers have shown that an or Ao-carboxy-late anion decreases the rate of reaction of 4-nitrochlorobenzene with methoxide ion but rather strongly increases the reaction rate with piperidine. This effect arises from an accelerative increase in the... 

Nucleophilic displacement reactions One of the most common reactions in organic synthesis is the nucleophilic displacement reaction. The first attempt at a nucleophilic substitution reaction in a molten salt was carried out by Ford and co-workers [47, 48, 49]. FFere, the rates of reaction between halide ion (in the form of its tri-ethylammonium salt) and methyl tosylate in the molten salt triethylhexylammoni-um triethylhexylborate were studied (Scheme 5.1-20) and compared with similar reactions in dimethylformamide (DMF) and methanol. The reaction rates in the molten salt appeared to be intermediate in rate between methanol and DMF (a dipolar aprotic solvent loiown to accelerate Sn2 substitution reactions). 

The report from Sheldon and co-workers was the second publication demonstrating the potential use of enzymes in ionic liquids and the first one for lipases (Entry 13) [43]. They compared the reactivity of Candida antarctica lipase in ionic liquids such as [BMIM][PFg] and [BMIM][BF4] with that in conventional organic solvents. In all cases the reaction rates were similar for all of the reactions investigated alcoholysis, ammoniolysis, and per hydrolysis. 

Logani and Smeltzer " have observed that, for Fe-1.5%Si at 1 000°C in CO/CO2, the initial slow reaction rate was followed by regions of linear behaviour due to the amorphous Si02 film being consumed by the growth of wustite-fayelite nodules during the early stages. These wustite-fayelite... 

Above 600 K, this reaction takes place as a direct result of collisions between CO and N02 molecules. When the concentration of CO doubles (Figure 11.6), the number of these collisions in a given time increases by a factor of 2 doubling the concentration of N02 has the same effect. Assuming that reaction rate is directly proportional to the collision rate, the following relation should hold ... 

The reaction rates depend on several factors the halide X, ligand L, even the solvent. Therefore, when Mel adds to IrX(CO)(PPh3)2 the rate increases in the order I < Br < Cl whereas for the addition of H2 or 02, the relative order is reversed. 

For the first assumption, the value of Kw for the shift appears to be too high. It must be this high because it is necessary to make C02 appear while both C02 and CO are being consumed rapidly by methanation. The data may be tested to see if the indicated rate appears unreasonable from the standpoint of mass transfer to the gross catalyst surface. Regardless of the rate of diffusion in catalyst pores or the surface reaction rate, it is unlikely that the reaction can proceed more rapidly than material can reach the gross pill surface unless the reaction is a homogeneous one that is catalyzed by free radicals strewn from the catalyst into the gas stream. 

It is concluded that a fully satisfactory system for calculating simultaneous reactions of CO and COo with H2 and H20 will require a schedule of the effect of CO on C02 methanation as a function of temperature. This effect will probably be different with different particle sizes. From a commercial standpoint, the particle size range may be too small to require much difference in the treatment of the data, but in the laboratory very small particle size may lower the CO methanation rate. A simple kinetics system such as that derived from Equation 3 may be satisfactory for all the reactions. It is unlikely that reliable data will be collected soon for the shift reaction (since it is of a somewhat secondary nature and difficult to study by itself), and therefore a more complicated treatment is not justified. 

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