Carbonyls formation

Wm. Haynes There may also be problems with carbonyl formation if you try to handle medium Btu gas in the present high pressure gas transmission system. 

Dr. Moeller In our plant, we investigated our catalyst after 4000 and 5000 hrs of operation and we found no trace of iron on our catalysts. But we know that if you take no precautions against iron carbonyl formation, then you will destroy some part of your activity by iron deposition on your catalyst. And we found that the iron carbonyl is formed mainly at the mild steel tube walls or at the tube in the temperature range of 150°-200°C. So, if you enter this range and you have to heat up your gas, which has a high CO content and steam in it, you have to... 

There is little data available to quantify these factors. The loss of catalyst surface area with high temperatures is well-known (136). One hundred hours of dry heat at 900°C are usually sufficient to reduce alumina surface area from 120 to 40 m2/g. Platinum crystallites can grow from 30 A to 600 A in diameter, and metal surface area declines from 20 m2/g to 1 m2/g. Crystal growth and microstructure changes are thermodynamically favored (137). Alumina can react with copper oxide and nickel oxide to form aluminates, with great loss of surface area and catalytic activity. The loss of metals by carbonyl formation and the loss of ruthenium by oxide formation have been mentioned before. 

The gases used were purchased premixed in aluminum cylinders to avoid carbonyl formation. The high purity gas mixture was further purified by a zeolite water trap and a copper carbonyl trap. The gas pressure in the reactor was measured with a capci-tance manometer and the fTow monitored with a mass fTow controT-ler. The typical gas flow rates were 15 cc/min (STP) and the maximum conversion was 1% based on integration of hydrocarbon products. The hydrocarbon products were analyzed by gas chromatography (temperature programmed chromosorb 102, FID). 

Some data on the adsorption stoichiometry of various gases on relevant transition metals have been collected in Table 3.7, which illustrates the usefulness of certain molecules for catalyst characterization by chemisorption. Note that Cu as active phase can be measured well with N2O and CO, but not with H2. It is not wise to determine Ni dispersion with CO, due to the possibility of carbonyl formation Ni carbonyls are volatile and poisonous. Note that in Table 3.7, for Rh the H/Me ratio is size dependent. This phenomenon is not restricted to Rh it is common in the chemisorption of metals. 

Induction Period to Number of days to Carbonyl Formation (h) craze formation... 

ESCA spectra, 190,192/ kinetic curves of carbonyl formation, 190,191/ wettability, 193/... 

In the early stages of reaction, HC1 has been found to accelerate carbonyl formation during the photooxidation of PVC (59). This result has been attributed to an unprecedented HC1-catalyzed conversion of sec-peroxy radicals into hydroxy radicals and carbonyl groups (59). 

This reaction Is not a widely known text book reaction. In fact. It was only found In the patent literature (4 ). However, this reaction explains the evidence of free hydrochloric acid. Since a carbonyl group, e.g., aldehyde, was generated by the above reaction, this group should be observable In the IR. Subsequent IR scans of the aged polyol revealed formation of a carbonyl at about 5.8 microns. Unaged polyol shows negligible carbonyl formation. 

Godinho, M. and Fox, P. F. (1981). Ripening of Blue cheese Influence of salting rate on lipolysis and carbonyl formation. Milckwissenschaft 36,476-478. 

The stoichiometric hydroformylation of olefins with cobalt hydrocarbonyl is also inhibited by an atmosphere of carbon monoxide (62, 73) (Section II, A) and this has been shown to involve a CO inhibition of alkylcobalt carbonyl formation (Eq. (18)). 

Rooney et al (45) reported that the rate of carbonyl formation varied with the molecular structure of sugar. Xylose was most reactive as it produced the greatest quantity of carbonyls, followed by glucose, then maltose. In the presence of these sugars isoleucine was more reactive than phenylalanine. In a study on the Strecker degradation of valine-carbonyl, diacetyl showed the greatest reactivity followed by sorbose> arabinose>xylose>fructose>glucose>sucrose>rhamnose, Self(46). 

Reiney (12) attributed this to conjugated carbonyl products. Mathe-son and Boyer (10), who also observed carbonyl formation, reported that the yellow discoloration occurs only in the presence of air or oxygen and is primarily a surface phenomenon. 

Figure 17. Relationship between discoloration and carbonyl formation...

Figure 19. Inhibition of carbonyl formation of polystyrene films...

Figures 18 and 19 show that inhibition of discoloration by these additives under Fade-ometer exposure was also accompanied by inhibition of carbonyl formation.

Figure 20 illustrates that a similar reduction in the rate of carbonyl formation also occurs under fluorescent blacklamp exposure. These results suggest that the antioxidant acts as a free radical inhibitor, reducing the over-all rate of photooxidation. The similarity in the relationship between the change in absorbance at 365 m/i, and carbonyl formation observed in the presence of the additives also lends further support to the previous conclusion that under exposures of this type, discoloration is caused by carbonyl products. 

In contrast to the above, Figure 21 shows that the antioxidant did not inhibit the rate of either discoloration or carbonyl formation under mercury-arc exposure. Grassie and Weir (5) also reported that under 2537-A. irradiation the antioxidant, 2,6-di-tert-butyl-p-cresol, had no effect on the rate of polystyrene photooxidation. It may be concluded,... 

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