Ethane and carbon monoxide

The simplest primary alkyl cations, CHJ and C2H, are formed from methane and ethane, respectively, by SbPs—PHSO3 (Olah and Schlosberg, 1968 Olah et al., 1969) and by SbPs (Lukas and Kramer, 1971). In these cases, intermolecular electrophilic substitution of these ions at the precursor alkanes leads to oligocondensation products, e.g. tertiary butyl and hexyl ions. In the presence of carbon monoxide it has been found possible to intercept the intermediate CHJ and C2H quantitatively as oxocarbonium ions (Hogeveen et al., 1969 Hogeveen and Roobeek, 1972). The competition between the reactions of the ethyl cation with ethane and carbon monoxide, respectively, is illustrated by the following equations ... 

In solution, diffusion apart of the radicals is inhibited by the solvent, resulting in the radicals recombining to form propanone. In the gas phase, however, the radicals do not combine and the acetyl radical breaks down to form carbon monoxide and another methyl radical. This elimination is known as decarbonylation. The methyl radicals then combine and the overall products are ethane and carbon monoxide (Scheme 9.1). 

If this reaction goes to completion, the principal reaction products are ethane and carbon monoxide ... 

Ethane and carbon monoxide yielded Hemptinne (1. c.) chiefly acetaldehyde, also some acetone ... 

According to Maquenne1 acetone vapor is decomposed by the electric discharge into hydrogen, ethane, and carbon monoxide, a small quantity of acetylene and carbon dioxide being also formed. The quantity ratios are less dependent upon the pressure than in the case of methyl and ethyl alcohol ... 

A fuel gas is known to con tain methane, ethane, and carbon monoxide. A sample of the gas is charged into an initially evacuated 2.000-liter vessel at 25 C and 2323 mm Hg absolute. The vessel is weighed before and after being charged, and the mass difference is found to be 4.929 g. Next, the higher heating value of the gas is determined in a calorimeter to be 841.9 kj/mol. Calculate the molar composition of the gas. 

Biacetyl. Photolysis of biacetyl was first reported in 1923 by Porter, Ramsperger, and Steel 121> who initiated the vapor at 100° and identified the products as ethane and carbon monoxide. Subsequently methane, acetone, ketene, and 2,3-pentanedione were also recognized as products. Considerable effort has been expended to achieve a full understanding of the details of the primary processes and progress was reviewed by Noyes, Porter and Jolley 113> in 1956. Irradiations have been performed over a wide range of pressure, temperature and wavelength (including the far ultraviolet 68> and mercury photosensitization 69>). Overall and individual quantum yields varied widely. 

Primary dissociation is followed by thermal dissociation of the acetyl radicals (secondary dissociation), so that ethane and carbon monoxide are the main products of the vapor phase photolyses. When the reaction is carried out at low temperature, with higher energy light filtered out, the acetyl radicals which are produced are sufficiently long lived so that their participation in coupling and disproportionation reaction competes with decarbonylation. Under such conditions formation of biacetyl, acetone, methane, and formaldehyde follow primary dissociation and the quantum yield of carbon monoxide decreases ( co = 1 at 2537 A and about 0.75 at 3130 A Noyes et al., 1956). 

The photochemical decarbonylation of ketones can be traced back to 1910 when acetone was photolysed in the gas phase to yield ethane and carbon monoxide. A radical process involving a-cleavage (Norrish type I reaction) and decarbonylation as two separate steps was proposed a few years later by Norrish and Appleyard (Scheme 1). Each of the two cleavage reactions has been the subject of numerous theoretical and mechanistic studies that have been covered in several reviews. 

Ethane. Ethane VPO occurs at lower temperatures than methane oxidation but requires higher temperatures than the higher hydrocarbons (121). This is a transition case with mixed characteristics. Low temperature VPO, cool flames, oscillations, and a NTC region do occur. At low temperatures and pressures, the main products are formaldehyde, acetaldehyde (HCHOiCH CHO ca 5) (121—123), and carbon monoxide. These products arise mainly through ethylperoxy and ethoxy radicals (see eqs. 2 and 12—16 and Fig. 1). 

Jacquemin, J. et al.. Solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon, and carbon monoxide in l-butyl-3-methylimidazolium tetrafluoroborate between temperatures 283 K and 343 K and at pressures close to atmospheric, /. Chem. Thermodyn., 38, 490, 2006. 

Throughout these studies, no product other than propane was observed. However, subsequent studies by Sinfelt et al. [249—251] using silica-supported Group VIII metals (Co, Ni, Cu, Ru, Os, Rh, Ir, Pd and Pt) have shown that, in addition to hydrogenation, hydrocracking to ethane and methane occurs with cobalt, nickel, ruthenium and osmium, but not with the other metals studied. From the metal surface areas determined by hydrogen and carbon monoxide chemisorption, the specific activities of... 

Using an 800 mV applied voltage, the response of the sensor has been evaluated in the range of 12-100% CH4 in air (Fig. 7.18). Major interferences have been caused by the presence of nitrous oxide, ethane, hydrogen, and carbon monoxide. Other sensors of this type have been described, but they differ only in the details of the design and not significantly in the concept. 

Hydrogen, acetylene, and carbon monoxide are the primary products of the conversion of methane in the dc plasma system. In addition, small amounts of ethane, ethylene, and carbon dioxide are produced. Of the C2 products, acetylene accounts for 90%, while ethylene and ethane comprise 6% and 4%, respectively. Carbon dioxide is less than 0.2% of the effluent gas. No measurable amount of water is produced in the system. 

Hydrogen, acetylene, and carbon monoxide are still the major products of both systems, while carbon dioxide is still very low and water is negligible for both systems. However, the selectivity of the major products is different in the two systems. Acetylene still comprises 90% of the C2 s with ethylene and ethane around 6% and 4%, respectively. 

Before introducing the feed, a number of precautions must be observed to eliminate various impurities, such as ammonia, by prior washing with water. The process does not tolerate the presence of high contents of acetylene, H S, methanol, moisture, C3 hydrocarbons etc. However, it allows unlimited quantities of nitrogen, carbon monoxide, argon, methane, ethylene, ethane and carbon dioxide. 

Thus, acetaldehyde (ethanal) may be expected as a prominent molecular intermediate, which also readily undergoes further oxidation. An additional source of CH3CHO is from the oxidation of propene, formed as an intermediate by OH radicals (see Chapter 1). The oxidation of acetaldehyde is particularly well documented over a wide temperature range [152-156], an important feature being the generation of methyl radicals and carbon monoxide at temperatures in excess of 650 K, in the sequence of... 

In all experiments, the major products were ethane and carbon dioxide. Under some conditions, ethylene and carbon monoxide were also observed. In the following, Rj is the C] products (CO2 and CO) formation rate, and R2 is the C2 products (C2H6 and C2H4) formation rate. The methane conversion is defined as (Rj+2R2)/CH4 in feed. The selectivity to C2 products is defined as 2R2/(Ri+2R2), while the C2 yield is defined as the product of conversion and selectivity. Our experimental results indicate that methane does react with carbon dioxide to produce carbon monoxide and either hydrogen or water under reaction conditions, but if oxygen is present, most of the carbon monoxide will be further oxidized to... 

As an attempt in this direction, a hierarchy was recently developed for nickel catalysts (6). The basic idea is to monitor the chemical properties of a catalyst as probed by hydrogen chemisorption, ethane hydrogenolysis, and carbon monoxide hydrogenation. The hierarchy, originally developed for Ni/I O catalysts, was later extended to nickel supported on phosphate-containing materials and a niobia-silica surface phase oxide. In this paper the usefulness of the hierarchy will be illustrated by its ability to differentiate between support effects of niobia and phosphate, and to establish the intermediate degree of interaction of niboia-silica. 

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