Carbon monoxide, 5.20

Carbon dioxide is usually marketed as the liquid under pressure. 

The toxicity of CO (and, in a sense, of the isoelectronic cyanide ion, CN ) is a direct consequence of this, as CO will compete effectively with O2 for the iron centers of the hemoglobin (Hb) in blood  

Quite small concentrations of the odorless, colorless CO in air can therefore lead to headache and extreme drowsiness, and eventually to death by preventing O2 from being delivered to tissues where it is required for metabolism. Fortunately, reaction 8.1 is readily reversible, so first aid for CO poisoning consists in moving the victim to fresh air and making the person breathe vigorously. The victim will recover completely if this is done soon enough. 

Carbon monoxide produced by the reactor will poison the fuel cell. This makes it necessary to include complex CO removal systems [8], Nation membranes are very sensitive to CO. The process of chemisorption (adherence to the surface via a chemical reaction) takes place, with CO competing with H2 on the platinum surface [4], 

Carbon monoxide is an important trace gas, which has a mean residence time of about two months and a mean concentration of the order of 0.1 ppm. The principal sources of CO are (1) oxidation of methane and other higher hydrocarbons, (2) biomass burning, (3) traffic, industry and domestic heating, (4) oceans, and (5) 

Carbon monoxide poisoning is a familiar situation in emergency medical practice, and the treatment depends on reversing the attachment of carbon monoxide to haemoglobin as carboxyhaemoglobin using free flow or hyperbaric oxygen therapy. The reader is referred to specialised texts for more details. 

Like CH4, carbon monoxide was first optically identified in the atmosphere by Migeotte (1949). It was believed at that time that atmospheric CO was wholly due to anthropogenic sources. However, more recent studies show that carbon monoxide is emitted into the air by many other sources. Furthermore, it became clear that the atmospheric cycle of this trace gas is much more complicated than was thought at the time of its discovery. 

Volume mixing ratio (ppm) of carbone monoxide in the troposphere (Seiler, 1974). (By courtesy of Tetha) 

The concentration of CO in the upper troposphere also varies in agreement with the latitudinal changes observed in surface air. However, the magnitude of upper air 

According to Seiler (1974) and Seiler et al. (1978) the atmospheric carbon dioxide is mostly produced by the following sources (see Table 7)  

According to the results of measurements carried out in the ocean (Seiler, 1974) the carbon monoxide concentration in near surface marine layers is 5 x 10 s mil 1 on an average. This water concentration would be in equilibrium with a surface air CO level of 2.5 ppm. However, the carbon monoxide concentration in air over the ocean surface is between 0.04 ppm and 0.20 ppm, which means that the ocean water is supersaturated with CO. It follows from these data that the ocean is a CO source, the global strength of which is about six times less than the total anthropogenic emission (Table 7). 

Most ofthe carbon monoxide (bpi.ou = 191.47 Qd at boSing point 0.787) consumed in the world is used in the form of gas mixtures containing hydrogen in particular. Small amotints, less than about 3 per cent volume, are used as the purified product 

Like hydrogen, carbon monoxide is mainly produced by steam reforming and partial oxidation of hydrocarbon or organic raw materials. However, it is also present in many industnal wastes from which it can be isolated (gases from blast furnaces, oxygen refining 

Its applicadons, which are usually capdve. in the form of synthesis gas, are discussed in the secdons concerning the manufacture of the major petrochemical imeimediates which it yields .  

However, other uses, including the prc ucdon of phosgen ablates, acedc acid, cenain oxo alcohols etc., require its use in purified form. 

Among the separadon tedmiques iodustrially implemented in this case are absorption and cryogenic separation. Adsorption according to the PSA process described above (see Secdon l.i.1.2) can also be applied, but is only economically viable for feedstock CO contents under 40 percent, or preferably 20 per cent This gives an effluent whose carbon monoxide concentration does not exceed or 80 per cent, althoi the yield of the operation is very hi (over 99 per cent). Cryogenic treatment is necessary for higher purities. 

Co-ordinated carbon monoxide is activated towards nucleophilic attack. Through o-donation and Tt-back donation into the antibonding CO K orbitals the carbon atom has obtained a positive character. This makes the carbon atom not only more susceptible towards a migrating anion at the metal centre, but also for a nucleophile attacking from outside the co-ordination sphere. In this instance it is more difficult to differentiate between the two pathways. There are examples showing that the electrophilicity of the carbon atom can be further increased by the action of Lewis acids complexing to the oxygen atom of the co-ordinated CO. 

Insertion of carbon monoxide into the Zr—C cr-bond of [Zr(CHDCHDBu )(Cl)( 7-C6H6)2] to give the corresponding acyl complex proceeds with complete retention of configuration.  

Rate constants and activation parameters for the carbonyl migration reactions of fluoroacyl derivatives (13) to give six-co-ordinate fluoroalkyl complexes (14) are given in Table 2. The rates decrease in the order CFH2 CF3 CF2H, which does not 

In the majority of industrial processes where carbon dioxide capture can occur, the feed stream for separation is saturated with water vapour [42]. Therefore, competitive water sorption in the membrane, as well as plasticization and ageing effects, will have a much stronger influence on membrane performance compared to the previously mentioned 

Plasticization due to water sorption has been observed, with a polyelhersulfone membrane experiencing a dramatic flux increase of -250% upon exposure to water, with a corresponding decrease in selectivity [43], This is also of critical concern in membrane processing since it can permanently alter the membrane structure, meaning performance does not always return once the membrane is dried [44], 

1 Water Competitive Sorption into Polydimethylsiloxane (PDMS) 

Upon exposure to the wet feed, the permeabihty of both CO2 and N2 reduces, due to competition from water, with a trend of low permeability with increased humidity of the feed. 

2 Water Competitive Sorption into Polysulfone and Matrimid 5218 

The decomposition of carbon monoxide is a good example of a complex dissociation process for a diatomic molecule. The reaction has been studied over the temperature range 6000—15,000°K using pure CO [124] and dilute mixtures in argon [125—127] by the techniques of infrared emission [124—128] from CO, visible and ultraviolet emission [126] from C2 and C respectively, and vacuum-ultraviolet absorption [128] by CO. 

An incubation time was observed which occurred before appreciable dissociation and was 5—100 times longer than the vibrational relaxation process. It has been proposed that equilibrium concentrations of transient species such as CO in electronic excited state(s) and C2 are being produced during this period. The induction times t conform best to the expression 

The apparent dissociation rate in argon diluent was measured after the incubation period and the rate coefficients for the vacuum ultraviolet absorption experiments were fitted to the following equation 

Runs were also performed with O2 added to the CO—Ar mixture. The oxygen was completely dissociated shortly after shock arrival. The apparent decomposition was measured in the presence of oxygen atoms and it was observed that while the activation energy was not changed, the pre-exponential term was increased by a factor of 15. It has also been suggested that the molecular efficiency of CO is about twice that of argon. 

A four-step mechanism in which two electronic states of CO are involved has been advanced to explain the induction period behaviour, the low activation energy associated with the decomposition and the high efficiency of oxygen atoms [128]. The first two steps are the same as a mechanism in which dissociation takes place from CO  

The chemisorption of carbon monoxide is an established method for determining the surface area of dispersal metals, particularly in supported catalysts. The average area occupied by each molecule depends on whether attachment is on one or two sites, a state that can vary from metal to metal and with surface coverage [85]. The quantity of chemisorbed gases is commonly measured by volumetric methods with apparatus similar to that used for static BET gas adsorption measurements. 

This chapter is concerned with carbon monoxide as a ligand. By the end of the chapter you should be familiar with  

The discussion of typical reactions of coordinated CO should be seen as an introduction to the reactivity of other unsaturated molecules bound to, and activated by, transition metals. 

For a molecule with such a low basicity (only protonated in super-acidic media), CO is a surprisingly versatile ligand. The homoleptic (or binary) carbonyls (i.e. in which CO is the only ligand) already span oxidation states from -IV to +III, and higher oxidation states are known for heteroleptic complexes (mixed ligand sets) which have good 71-donor co-ligands, e.g. RuIV(CO)(SR)4. 

G(-CO) is about 8. In the absence of oxygen, the main products are C02 (G = 2), a suboxide of carbon that is solid, and various gaseous compounds. In the presence of oxygen, the suboxide is inhibited but a chain reaction occurs, ultimately giving C02, probably through an ionic mechanism. 

To calculate the conventional entropy of crj stalline carbon monoxide in the limit as T - 0. 

We use the same notation as in problem 52. The following experimental data for carbon monoxide were obtained by Clayton and Giauque (J. Amer. Chem. Soc. 1932, 54, 2610). 

The molar mass of CO is 28.01 g mole-i. The rotational characteristic temperature Sr is 2.77 deg and the vibrational characteristic temperature 0, is 3.08 X 10 deg (calculated from data in Herzberg, Molecular spectra of diatomic molecules , Prentice-Hall, 1939). 

Inserting numerical values into formula (1) of problem 52 we obtain for T=Tt = 81.61 K audP = 1 atm 

There is strictly a correction for the difference of the vapour from a perfect gas which Clayton and Giauque estimate as 0.1 in SjR. This is only slightly greater than the experimental error and does not affect the conclusion. 

With the emergence of automobiles propelled by internal combustion engines, the CO emitted from the exhaust pipe has become the major source for human exposure. Serious problems exist with occupational exposure to increased ambient CO for firefighters, traffic police, toll booth attendants, coal miners, coke oven and smelter workers, and transportation mechanics. 

The oxidation by permanganate proceeds readily in acid and neutral solutions (to give MnOz) and in basic solution (to give MnO ). The rate law is  

By measuring the shifts of the various hydroxyl bands of the zeolite, a direct measure of the relative acid site strengths can be made without the need for thermal desorption. Table 4.6 lists the measured hydroxyl band shifts for a variety of hydroxyl groups on different zeolites using low temperature CO adsorption. This data indicates that there is indeed a difference in the intrinsic acid strength of the bridging hydroxyl groups in different zeolites as well as in the same zeolite structure with different framework aluminum content. 

The process is normally operated on a continuous basis, employing a high degree of automation. Owing to the toxicity of phosgene, extensive safety features are an integral part of the plant design. 

Carbon dioxide is removed from CO streams by amine (e.g. ethanolamine) scrubbing, and high concentration CO for COCl manufacture can be obtained from absorption of CO-containing streams into ammoniacal copper(I) solutions under pressure. The CO is 

In particular for liquid phosgene production, noncondensable impurities shouid be 

A typical specification analysis for carbon monoxide for use in a modern phosgene plant is given in Table 4.1 [311a]. 

A TYPICAL SPECIFICATION FOR CARBON MONOXIDE SUITABLE FOR PHOSGENE SYNTHESIS [311a] 

TABLE 2.13 Global Biogenic VOC Emission Rate Estimates by Source and Class of Compound, Tg yr-1 

TABLE 2.14 Estimates of Global Tropospheric CO Budget (in Tg(CO) yr ) and Values Adopted by I FIX (2001) 

1960 (Precontrol—no catalytic mufflers installed) 1993 (Catalytic mufflers required on all automobiles) 2004 Standards 

In 1988, William Chameides, of Georgia Tech in Allanla, published a report in Science magazine in which he stated that in some cities trees may account for more hydrocarbons in the atmosphere than those produced from human activities. The EPA has since found this to be true. 

Hydrocarbons enter the atmosphere from both natural sources and human activities. Certain natural hydrocarbons are produced in large quantities by both coniferous and deciduous trees. Methane gas (CH ) is produced by such diverse sources as rice growing, ruminant animals such as cows, termites, ants, and decay-causing bacteria acting on dead plants and animals. Human activities such as the use of industrial solvents, petroleum refining and distribution, and the release of unburned gasoline and diesel fuel components account for a lai e amount of hydrocarbons in the atmosphere. 

In addition to simpler hydrocarbons, some larger hydrocarbon molecules are released into the atmosphere, primarily from motor vehicle exhaust. The greatest danger of some of these pollutants and the organic derivatives formed from them is their toxicity. 

Although it is practically impossible to control hydrocarbon emissions from living plants and other natural sources, hydrocarbon emissions from automobiles can be controlled. Two means of control are in use at present. First, the spouts and hoses on gasoline pumps have been redesigned to prevent gasoline from entering the air. Second, catalytic converters that reduce emissions of hydrocarbons, GO, and NO are now part of every automobile s exhaust system. 

Lung capillary leakage was significantly increased 18 h after rats had been exposed to CO at concentrations of 50 ppm or more for 1 h (Thom et al. 

The reaction of [PtI(Me)(CO)(PPha)] with a number of tertiary-arsine and -stibine ligands has now been studied. The proposed mechanism of reaction proceeds as follows  

The rate-determining step involves neither the incoming ligand nor solvent and is considered to involve formation of a three-co-ordinate intermediate. The rate equation is 

Migration of para-substituted benzyl and trifluoromethyl groups in the complexes (7) occurs in the solid state and the enthalpy change is opposite in sign to that found 

Most refinery PM eomes from two sources - delayed coking units and the regenerators of fluid catalytic cracking (FCC) units. FCC regenerators also emit ammonia, which combines with SOx and NOx in the air to form ammonium sulfates and nitrates. According to the South Coast Air Quality Management District (AQMD) in Southern California, 1 ton of ammonia can generate 6 tons of PM 10 - airborne particulates with partiele diameters less than 10 microns. PM2.5 stands for airborne particulates with diameters less than 2.5 microns. 

In refineries, carbon monoxide (CO) is formed by incomplete combustion in boilers, process heaters, power plants, and FCC regenerators. CO is toxic because it binds strongly to the hemoglobin in blood, displacing oxygen. It is colorless and odorless, so without a special analyzer, it is hard to detect. This adds to its danger. 

---

Table 3 shows results obtained from a five-component, isothermal flash calculation. In this system there are two condensable components (acetone and benzene) and three noncondensable components (hydrogen, carbon monoxide, and methane). Henry s constants for each of the noncondensables were obtained from Equations (18-22) the simplifying assumption for dilute solutions [Equation (17)] was also used for each of the noncondensables. Activity coefficients for both condensable components were calculated with the UNIQUAC equation. For that calculation, all liquid-phase composition variables are on a solute-free basis the only required binary parameters are those for the acetone-benzene system. While no experimental data are available for comparison, the calculated results are probably reliable because all simplifying assumptions are reasonable the... 

System Hydrogen(1)-Carbon Monoxide(2)-Acetone(3)-Benzene(4)-Methane(5) at 25°C and 30 atm... 

An example of such recychng in a parallel reaction system is in the Oxo process for the production of C4 alcohols. Propylene and synthesis gas (a mixture of carbon monoxide and hydrogen) are first reacted to ra- and isobutyraldehydes using a cobalt-based catalyst. Two parallel reactions occur ... 

As an example of the application of a fixed-bed tubular reactor, consider the production of methanol. Synthesis gas (a mixture of hydrogen, carbon monoxide, and carbon dioxide) is reacted over a copper-based cat dyst. The main reactions are... 

CO. Alkynes will react with carbon monoxide in the presence of a metal carbonyl (e.g. Ni(CO)4) and water to give prop>enoic acids (R-CH = CH-C02H), with alcohols (R OH) to give propenoic esters, RCH CHC02R and with amines (R NH2) to give propenoic amides RCHrCHCONHR. Using alternative catalysts, e.g. Fe(CO)5, alkynes and carbon monoxide will produce cyclopentadienones or hydroquinols. A commercially important variation of this reaction is hydroformyiation (the 0x0 reaction ). 

Fischer-Tropsch reaction The catalytic reaction of hydrogen and carbon monoxide (synthesis gas ) to produce high-molecular weight hydrocarbons. 

Carbon monoxide and excess steam are normally passed over a cobalt catalyst at about 250-300 C resulting in greater than 99% conversion of CO to COj. This conversion reaction is widely used in oil or solid fuel gasification processes for the production of town gas or substitute natural gas. ... 

The material to be analyzed is pyrolyzed in an inert gas at 1100°C in the presence of carbon the carbon monoxide formed, if any, is either analyzed directly by chromatography or analyzed as carbon dioxide after oxidation by CuO. The CO2 is detected by infra-red spectrometry or by gas phase chromatography. 

However, such a level can still be considered too high for vehicles having 3-way catalytic converters. In fact, results observed in the United States (Benson et al., 1991) and given in Figure 5.20 show that exhaust pollutant emissions, carbon monoxide, hydrocarbons and nitrogen oxides, increase from 10 to 15% when the sulfur level passes from 50 ppm to about 450 ppm. This is explained by an inhibiting action of sulfur on the catalyst though... 

These are carbon monoxide, CO, unburned hydrocarbons (HC), and the nitrogen oxides, NO. In the U.S.A., a program called Auto/Oil (Burns et al., 1992), conducted by automotive manufacturers and petroleum companies, examined the effect of overall parameters of fuel composition on evaporative emissions and in the exhaust gases. The variables examined were the aromatics content between 20 and 45%, the olefins content between 5 and 20%, the MTBE content between 0 and 15% and finally the distillation end point between 138 and 182°C (more exactly, the 95% distilled point). 

Outside of carbon monoxide for which the toxicity is already well-known, five types of organic chemical compounds capable of being emitted by vehicles will be the focus of our particular attention these are benzene, 1-3 butadiene, formaldehyde, acetaldehyde and polynuclear aromatic hydrocarbons, PNA, taken as a whole. Among the latter, two, like benzo [a] pyrene, are viewed as carcinogens. Benzene is considered here not as a motor fuel component emitted by evaporation, but because of its presence in exhaust gas (see Figure 5.25). 

The basic conversion produces essentially carbon monoxide (CO) and hydrogen. 

We consider first some experimental observations. In general, the initial heats of adsorption on metals tend to follow a common pattern, similar for such common adsorbates as hydrogen, nitrogen, ammonia, carbon monoxide, and ethylene. The usual order of decreasing Q values is Ta > W > Cr > Fe > Ni > Rh > Cu > Au a traditional illustration may be found in Refs. 81, 84, and 165. It appears, first, that transition metals are the most active ones in chemisorption and, second, that the activity correlates with the percent of d character in the metallic bond. What appears to be involved is the ability of a metal to use d orbitals in forming an adsorption bond. An old but still illustrative example is shown in Fig. XVIII-17, for the case of ethylene hydrogenation. 

There has been a general updating of the material in all the chapters the treatment of films at the liquid-air and liquid-solid interfaces has been expanded, particularly in the area of contemporary techniques and that of macromolecular films. The scanning microscopies (tunneling and atomic force) now contribute more prominently. The topic of heterogeneous catalysis has been expanded to include the well-studied case of oxidation of carbon monoxide on metals, and there is now more emphasis on the flexible surface, that is, the restructuring of surfaces when adsorption occurs. New calculational methods are discussed. 

Engei T and Erti G 1978 Eiementary steps in the cataiytic oxidation of carbon monoxide on piatinum metaisTIdv. Catal. 28 1... 

Biyhoider G 1964 Moiecuiar orbitai view of chemisorbed carbon monoxide J. Phys. Chem. 68 2772... 

Varberg T D and Evenson K M 1992 Accurate far-infrared rotational frequencies of carbon monoxide Astrophys. J. 385 763-5... 

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... 

Yates J T and Garland C 1961 Infrared studies of carbon monoxide chemisorbed on nickel surfaces J. Catal. 65 617-24... 

---