Carbon monoxide measurement techniques

The high degree of dispersion of platinum on alumina has also been confirmed by the hydrogen chemisorption measurements of Keavney and Adler (Kl), and by the chemisorption studies of Gruber (G2). In addition, high dispersion of platinum on silica-alumina has been observed by Hughes and associates, using a carbon monoxide chemisorption technique (H10). 

The methods of choice for beryUium oxide in beryUium metal are inert gas fusion and fast neutron activation. In the inert gas fusion technique, the sample is fused with nickel metal in a graphite cmcible under a stream of helium or argon. BeryUium oxide is reduced, and the evolved carbon monoxide is measured by infrared absorption spectrometry. BeryUium nitride decomposes under the same fusion conditions and may be determined by measurement of the evolved nitrogen. Oxygen may also be determined by activation with 14 MeV neutrons (20). The only significant interferents in the neutron activation technique are fluorine and boron, which are seldom encountered in beryUium metal samples. 

Carbon monoxide and carbon dioxide can be measured using the FTIR techniques (Fourier transform infrared techniques see the later section on the Fourier transform infrared analyzer). Electrochemical cells have also been used to measure CO, and miniaturized optical sensors are available for CO 2 monitoring. 

Continuous monitoring of the carbon monoxide and carbon dioxide evolved during thermal decomposition of brominated polyester resin samples, has been carried out using a simultaneous thermal analysis-mass spectrometry technique. In order to allow measurement of the carbon monoxide evolved, the atmosphere chosen for these runs was 21% oxygen in argon, since the peak at 28 atomic mass units (amu)... 

The present paper focuses on the interactions between iron and titania for samples prepared via the thermal decomposition of iron pentacarbonyl. (The results of ammonia synthesis studies over these samples have been reported elsewhere (4).) Since it has been reported that standard impregnation techniques cannot be used to prepare highly dispersed iron on titania (4), the use of iron carbonyl decomposition provides a potentially important catalyst preparation route. Studies of the decomposition process as a function of temperature are pertinent to the genesis of such Fe/Ti02 catalysts. For example, these studies are necessary to determine the state and dispersion of iron after the various activation or pretreatment steps. Moreover, such studies are required to understand the catalytic and adsorptive properties of these materials after partial decomposition, complete decarbonylation or hydrogen reduction. In short, Mossbauer spectroscopy was used in this study to monitor the state of iron in catalysts prepared by the decomposition of iron carbonyl. Complementary information about the amount of carbon monoxide associated with iron was provided by volumetric measurements. 

The increased throughput capahihty of the AutoAnalyzer and electronic balance, coupled with the reduction in staff time, substantially increased productivity. Further benefits accrued because implementation of the automatic techniques also coincided with a need for the LGC to measure the carbon monoxide yields of cigarettes because of the interest in the carbon monoxide dehveries of cigarettes hy epidemiologists working in the field of cardiovascular diseases. A development programme was initiated to find a method... 

Elemental composition Ni 34.38%, C 28.13%, O 37.48%. The compound may be identified and measured quantitatively by GC/MS. An appropriately diluted solution in benzene, acetone, or a suitable organic solvent may be analyzed. Alternatively, nickel tetracarbonyl may be decomposed thermally at 200°C, the liberated carbon monoxide purged with an inert gas, and transported onto the cryogenically cooled injector port of a GC followed by analysis with GC-TCD on a temperature-programmed column. Nickel may be analyzed by various instrumental techniques following digestion of the compound with nitric acid and diluting appropriately (See Nickel). 

Since enthalpy changes can be obtained directly from measurement of heat absorption at constant pressure, even small values of AH for chemical and biochemical reactions can be measured using a micro-calorimeter.1112 Using the technique of pulsed acoustic calorimetry, changes during biochemical processes can be followed on a timescale of fractions of a millisecond. An example is the laser-induced dissociation of a carbon monoxide-myoglobin complex.13... 

In the case of ethylene itself the cyclopentene technique is obviously inapplicable and the relative rate constants have in this case been obtained in other ways, for example, by measuring yield of carbon monoxide formed by fragmentation of the products of reaction of oxygen atoms with ethylene. In this case the total pressure has to be kept approximately constant although some variation is not too important in view of the relatively small effect of pressure on CO yield at pressures normally used. 

Alternative techniques do exist, however, for obtaining information regarding the distribution and number of catalytic components dispersed within or on the support. Selective gas adsorption, referred to as chemisorption, can be used to measure the accessible catalytic component on the surface indirectly by noting the amount of gas adsorbed per unit weight of catalyst. The stoichiometry of the chemisorption process must be known in order to estimate the available catalytic surface area. One assumes that the catalytic surface area is proportional to the number of active sites and thus reaction rate. This technique has found use predominantly for supported metals. A gas that will selectively adsorb only onto the metal and not the support is used under predetermined conditions. Hydrogen and carbon monoxide are most commonly used as selective adsorbates for many supported metals. There are reports in the literature of instances in which gases such as NO and O2 have been used to measure catalytic areas of metal oxides however, due to difficulty in interpretation they are of limited use. 

In Secs. 5-10 we present a series of selected examples of the use of the external reflectance technique to investigate some electrochemical systems of interest. Results from the electrochemical literature on the adsorption of hydrogen, carbon monoxide and alcohols are discussed and compared with the data from UHV measurements (Secs. 5-7). 

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