Effect of Cu addition

Andreev and coworkers—promoting effect of Cu addition on Fe-Cr shift catalysts, and Raney Cu/Zn catalysis described by an associative mechanism. Andreev and coworkers240 added promoters to traditional high temperature shift Fe-Cr catalyst, and found that Cu and Co moved the maximum in the CO conversion curve to lower temperatures. No explanation was provided for the effect. 

Dofour et al. [17] investigated the influence of synthesis method, precursor and effect of Cu addition on the WGS activity of Fe-Cr-Co catalysts. They prepared FeCr, FeCrCu, FeCrCo and FeCrCuCo formulations by oxidation precipitation method, using chloride (Cl) and sulphate (S) metal precursors. The catalytic activity results of FeCrCo and FeCrCuCo catalysts are presented in Figure 2.2. All the materials prepared from sulphate precursor showed higher carbon monoxide conversion than those synthesized with chloride. As expected Cu-promoted catalysts show better activity than Fe-Cr-Co catalysts. For the catalysts synthesized by chloride precursor, in the case of cobalt, incorporation of this metal into the magnetite lattice could improve the covalency of Fe and... 

Addition of cupric ion " greatly increases the relative amount of 4-equivalent oxidation, both by catalysis of (74) and by reducing the back-reaction in step (71). Analysis of the effect of Cu(II) confirms the importance of this reversibility" . 

The promotor effect of SO2 increases with the amount added to the reaction medium (Fig.3). An effect of the addition of sulfur dioxide has also been observed on the oxidation of decane with an increase of the activation energy expected for such a poisoning. This addition leads to a noticeable decrease of the rate of oxidation at low temperature, where Cu sulfate is stable, but the effect becomes negligible at about 600 K. At this temperature, the conversion of decane estimated by the evolution of the peak e/m = 57, characteristic of the hydrocarbon, is close to 100% with CufTi02 catalysts in presence or not of SO2 (Figure 4). With Cu/Zr02 SO2 inhibits decane oxidation below 640 K. At 640 K a conversion of about 60% is observed in both the presence or absence of additive and an acceleration of oxidation is noticed at higher temperatures. 

Between pH 4.S-6.3, Pb strongly reduced adsorption of Cu on hematite, whereas the effect of Cu on Pb uptake was less pronounced when the concentrations of both cations were the same (Christl and Kretsdimar, 1999). Palmquist et al. (1999) noted that uptake of Cu and Zn from equimolar solutions was additive. 

Copper and Ag salts have been found to be good cocatalysts. The effect of some additives and ligands on the cross-coupling of the stannylpyridine 336 has been studied [158]. However, it seems likely that these effects are observed case by case. Probably transmetallation of Cu(I) with tin reagents generates organocopper, which undergoes facile transmetallation with the Pd species. 

The addition of Cu, however, resulted in an outstanding effect as shown in Figure 7. The amount of Cu addition was limited to that corresponding to the solubility of about 1 wt-%. In this case, too, the behavior was considered to involve catalytic action, instead of the prior or simultaneous sulfurization. 

Fig. 55. Phololumiiiescence (a) and its excitation spectrum (b) of Cu(I)ZSM-5 aitalysl and the effect of CO addition on the photolumincscencc (1-4). Catalyst was prepared by evacuation of the original Cu(II)ZSM-5 sample (1.9 wt% as Cu metal) at 973 K. Addition of CO was carried out at 77 K. CO pressure (Pa) 1, 173 2, 306 3 and 3 (excitation spectrum of the photoluminescence spectrum 3), 372 4, 2660 [reproduced with permission from Yania-shita et al. (7iSd)].

Compared with the unpromoted catalysts the positive effect of the addition of ZnO on Cu-LaZr catalysts can be revealed by comparing the data of paragraph III to that of paragraph II... 

It was reported that the K/Cu-Zn-Fe oxides catalyst efficiently converted a mixture of COj and H2 into ethanol by Mitsubishi Gas Chemical and National Institute of Material and Chemical Research [1]. However, the catalyst was deactivated quickly during the reaction. To improve the catalytic life, an addition of various kinds of components was tried. It was found that the addition of Cr component to the catalyst prevented the deactivation of catalyst [2]. In this paper, we describe the effect of the addition of Cr component to the catalyst from the results of XRD analysis, transmission electron microscope observation (TEM), and energy-dispersive X-ray microanalysis (EDS) of the catalysts before and after the reaction. 

K/Cu-Zn-Fe oxides catalyst has good activity and selectivity in ethanol synthesis from COj/Hj as described above. However, its activity was found to decline quickly during the reaction. In order to prevent the deactivation of the catalyst, the additions of 5 th component to the catalyst were studied extensively and Cr was found to have a remarkable effect. The effects of Cr addition are shown in Figure 4. In the reaction over K/Cu-Zn-Fe-Cr oxides catalyst COj conversion as well as ethanol selectivity attained steady values after 40 hours. At the steady state,... 

Figure 7. Anaerobic reduction of the type 3 Cu of ascorbate oxidase by re-ductate. Conditions as in Figure 6. Curves 1—4 show the effect of stepwise addition of reductate to the enzyme prior to kinetic stopped-fhw runs. Curve 1 represents 6 fxM dioxygen, curves 2—4 demonstrate the successive removal of dioxygen and partial reduction of the enzyme.

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