Carbon monoxide measurements

Unlike the carbon monoxide measuring instrument discussed above, the Lion Intoximeter 3000 uses an interference filter to produce monochromatic radiation... 

Figure 2.2. Thermal desorption spectra of carbon monoxide, measured mass spectrometically at mass 28 (atomic units, a.u.), on a platinum (100) surface upon which potassium has been pre-adsorbed to a surface coverage of 0K.7 Reprinted with permission from Elsevier Science.

Figure 2.27. Temperature programmed desorption (TPD) spectra of carbon monoxide (measured by Ap) as a function of temperature from nickel surfaces (a) Ni(l 11), (b) Ni(l 11) when the initially dosed surface has been subjected to an electron beam (150 pA for 10 minutes over an area of 1 mm2) and (c) a cleaved nickel surface.85 Reprinted with permission from Elsevier Science.

Connors, V.S., D.R. Caboon, H.G. Reichle Jr. and RE. Scheel (1991) Comparison between carbon monoxide measurements from spacebome and airborne platforms. Canadian Journal of Physics 69 1128-1137. 

Germani et al. [82] compared the performance of their catalyst coating developed for water-gas shift in a micro structured reactor with that of the same catalyst coated on a cordierite monolith under identical reaction conditions. Higher conversion was achieved in the micro channels at same modified residence time under all experimental conditions applied. Figure 2.88 shows the CO conversion vs. a modified residence time (catalyst weight/flow of carbon monoxide) measured at various reaction temperatures. 

Diffusing capacity for carbon monoxide (measurement of alveolar gas exchange)... 

What volume of carbon monoxide, measured at STP, is produced by the decomposition of 38 mg of tetraphenylcyclopentadienone ... 

The proper design of fuel reformer systems must pay careful attention to the minimization of carbon monoxide before the processed fuel stream enters the fuel cell stack. Many reformer systems use a secondary preferential oxidation reactor that selectively oxidizes the carbon monoxide present in reformate streams. In most transportation applications the steam reformer and the selective oxidation reactors do not operate under steady state conditions large transients may occur which produce relatively large amounts of carbon monoxide. It is highly desirable to have a low-cost real-time carbon monoxide measurement system that provides feedback control to the fuel processing system in order to protect the PEM fuel cells from performance degrading concentrations of carbon monoxide. 

The EPA Method 10 discusses measuring carbon monoxide emissions from stationary sources from continuous samples extracted from an exhaust stack where the sample is measured with nondispersive infrared (NDIR) analyzer. Possible interferences include water, carbon dioxide, and carbon monoxide. Method lOA tells how to make certified carbon monoxide measurements from continuous emission monitoring systems (CEMS) at petroleum refineries. 

The data on oxygen, carbon monoxide, and carbon dioxide content in extracted gases gives evidence that the in situ combustion process became effective in Experimental Section I from 1967 on, and in Experimental Section II from the end of February 1969. Content of oxygen in the gas sampled in the wells ranges essentially from zero percent to a fraction of one percent, that of carbon dioxide-from 12-17%, and that of carbon monoxide, measured in observation wells, from 1-2% during the first few months of the process, and then from a fraction of 1% to 1%. 

Cavanagh, L. A., C. F. Schadt, and E. Robinson. 1969. Atmospheric hydrocarbon and carbon monoxide measurements at Point Barrow, Alaska. Environ. Sci. Technol. 3 251-257. 

The most common method for the estimation of the surface area of a metallic phase in a supported catalyst is by measuring the extent of the hydrogen adsorption. With iron surfaces, however, the adsorption of hydrogen often does not proceed consistently. The free iron surface area is therefore usually calculated from the extent of adsorption of carbon monoxide, measured at 90 K. In contrast to adsorption of hydrogen, which has a low boiling point, physical adsorption of carbon monoxide by oxidic surfaces present in the catalysts is appreciable at 90 K. The extent of the adsorption is therefore measured twice after the first measurement, the catalyst is evacuated at 195 K and the extent of adsorption is determined again. The amount of carbon monoxide chemisorbed by the iron surface is assumed to be the difference between the values obtained from the two adsorption isotherms. ... 

Liquid Fuel Crossover Many DAFCs suffer large performance losses from crossover. In the case of liquid DAFCs, the crossover current can be determined from chemical species measurement of the cathode effluent gas. Since the product of oxidation of methanol or other fuel crossover is mostly carbon dioxide and carbon monoxide, measurement of these gases along with any residual crossover fuel vapor and minor species can be used to perform a carbon mass balance and deduce the crossover fuel current. 

The dynamics of fast processes such as electron and energy transfers and vibrational and electronic deexcitations can be probed by using short-pulsed lasers. The experimental developments that have made possible the direct probing of molecular dissociation steps and other ultrafast processes in real time (in the femtosecond time range) have, in a few cases, been extended to the study of surface phenomena. For instance, two-photon photoemission has been used to study the dynamics of electrons at interfaces [ ]. Vibrational relaxation times have also been measured for a number of modes such as the 0-Fl stretching m silica and the C-0 stretching in carbon monoxide adsorbed on transition metals [ ]. Pump-probe laser experiments such as these are difficult, but the field is still in its infancy, and much is expected in this direction m the near fiitiire. 

The saturation coverage during chemisorption on a clean transition-metal surface is controlled by the fonnation of a chemical bond at a specific site [5] and not necessarily by the area of the molecule. In addition, in this case, the heat of chemisorption of the first monolayer is substantially higher than for the second and subsequent layers where adsorption is via weaker van der Waals interactions. Chemisorption is often usefLil for measuring the area of a specific component of a multi-component surface, for example, the area of small metal particles adsorbed onto a high-surface-area support [6], but not for measuring the total area of the sample. Surface areas measured using this method are specific to the molecule that chemisorbs on the surface. Carbon monoxide titration is therefore often used to define the number of sites available on a supported metal catalyst. In order to measure the total surface area, adsorbates must be selected that interact relatively weakly with the substrate so that the area occupied by each adsorbent is dominated by intennolecular interactions and the area occupied by each molecule is approximately defined by van der Waals radii. This... 

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

Fuel economy is measured usiag a carbon balance method calculation. The carbon content of the exhaust is calculated by adding up the carbon monoxide (qv), carbon dioxide (qv), and unbumed hydrocarbons (qv) concentrations. Then usiag the percent carbon ia the fuel, a volumetric fuel economy is calculated. If the heating value of the fuel is known, an energy specific fuel economy ia units such as km/MJ can be calculated as well. 

Products of Incomplete Combustion Emission Limits. Products of iacomplete combustion typically are not directly measured duting the trial bum. Instead, levels of carbon monoxide (qv) emissions are used as an iadication of combustion efficiency. High combustion efficiencies are assumed to result ia acceptable levels of products of incomplete combustion. If carbon monoxide emissions are measured at less than 100 ppmv dry basis, the standard is met. However, if emissions are greater than 100 ppmv, no more than 20 ppmv of total hydrocarbons (qv) are allowed at the iaciaerator stack duting the trial bum. 

Nickel Carbonyl The extremely toxic gas nickel carbonyl can be detected at 0.01 ppb by measuring its chemiluminescent reaction with ozone in the presence of carbon monoxide. The reaction produces excited nickel(II) oxide by a chain process which generates many photons from each pollutant molecule to permit high sensitivity (315). 

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. 

The composition of the products of reactions involving intermediates formed by metaHation depends on whether the measured composition results from kinetic control or from thermodynamic control. Thus the addition of diborane to 2-butene initially yields tri-j iAbutylboraneTri-j -butylborane. If heated and allowed to react further, this product isomerizes about 93% to the tributylborane, the product initially obtained from 1-butene (15). Similar effects are observed during hydroformylation reactions however, interpretation is more compHcated because the relative rates of isomerization and of carbonylation of the reaction intermediate depend on temperature and on hydrogen and carbon monoxide pressures (16). 

A convenient method for assessing the extent of surface oxidation is the measurement of volatile content. This standard method measures the weight loss of the evolved gases on heating up to 950°C in an inert atmosphere. The composition of these gases consists of three principal components hydrogen, carbon monoxide, and carbon dioxide. The volatile content of normal furnace blacks is under 1.5%, and the volatile content of oxidized special grades is 2.0 to 9.5%. 

A variety of instmments are available to analyze carbon monoxide in gas streams from 1 ppm to 90%. One group of analyzers determines the concentration of carbon monoxide by measuring the intensity of its infrared stretching frequency at 2143 cm . Another group measures the oxidation of carbon monoxide to carbon dioxide electrochemically. Such instmments are generally lightweight and weU suited to appHcations requiring portable analyzers. Many analyzers are equipped with alarms and serve as work area monitors. 

Beyond the catalytic ignition point there is a rapid increase in catalytic performance with small increases in temperature. A measure of catalyst performance has been the temperature at which 50% conversion of reactant is achieved. For carbon monoxide this is often referred to as CO. The catalyst light-off property is important for exhaust emission control because the catalyst light-off must occur rehably every time the engine is started, even after extreme in-use engine operating conditions. 

The primary reference method used for measuring carbon monoxide in the United States is based on nondispersive infrared (NDIR) photometry (1, 2). The principle involved is the preferential absorption of infrared radiation by carbon monoxide. Figure 14-1 is a schematic representation of an NDIR analyzer. The analyzer has a hot filament source of infrared radiation, a chopper, a sample cell, reference cell, and a detector. The reference cell is filled with a non-infrared-absorbing gas, and the sample cell is continuously flushed with ambient air containing an unknown amount of CO. The detector cell is divided into two compartments by a flexible membrane, with each compartment filled with CO. Movement of the membrane causes a change in electrical capacitance in a control circuit whose signal is processed and fed to a recorder. 

Performance Specifications for Automated Analytical Methods for Measuring Carbon Monoxide... 

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