Hydrocarbons oxidation processes

The detailed model was constructed as described by Carslaw et al. (1999, 2002). Briefly, measurements of NMHCs, CO and CH4 were used to define a reactivity index with OH, in order to determine which NMHCs, along with CO and CH4, to include in the overall mechanism. The product of the concentration of each hydrocarbon (and CO) measured on each day during the campaign and its rate coefficient for the reaction with OH was calculated. All NMHCs that are responsible for at least 0.1% of the OH loss due to total hydrocarbons and CO on any day during the campaign are included in the mechanism (Table 2). Reactions of OH with the secondary species formed in the hydrocarbon oxidation processes, as well as oxidation by the nitrate radical (NO3) and ozone are also included in the... 

The preceding discussion stresses the importance of properly handling rate expressions for thermal decomposition of polyatomic molecules, a condition that prevails in many hydrocarbon oxidation processes. For a detailed discussion on evaluation of low- and high-pressure rate constants, again refer to Ref. [16]. 

It is apparent that in any hydrocarbon oxidation process CO is the primary product and forms in substantial amounts. However, substantial experimental evidence indicates that the oxidation of CO to C02 comes late in the reaction scheme [13]. The conversion to C02 is retarded until all the original fuel and intermediate hydrocarbon fragments have been consumed [4, 13]. When these species have disappeared, the hydroxyl concentration rises to high levels and converts CO to C02. Further examination of Fig. 3.6 reveals that the rate of reaction (3.44) does not begin to rise appreciably until the reaction reaches temperatures above 1100K. Thus, in practical hydrocarbon combustion systems whose temperatures are of the order of 1100K and below, the complete conversion of CO to C02 may not take place. 

Thus methyl radicals are consumed by other methyl radicals to form ethane, which must then be oxidized. The characteristics of the oxidation of ethane and the higher-order aliphatics are substantially different from those of methane (see Section HI). For this reason, methane should not be used to typify hydrocarbon oxidation processes in combustion experiments. Generally, a third body is not written for reaction (3.85) since the ethane molecule s numerous internal degrees of freedom can redistribute the energy created by the formation of the new bond. 

The mechanism for oxidation of moist carbon monoxide is an extension of the H2-O2 mechanism. Carbon monoxide (CO) is an important intermediate in the oxidation of all hydrocarbons, and an accurate knowledge of the oxidation chemistry of this component is required to obtain a quantitative understanding of the more complex hydrocarbon oxidation processes. For this reason the detailed kinetics of CO oxidation has been the subject of a large number of studies. 

The statements of the possible role of HO radicals in saturated hydrocarbon oxidation processes is proved by experimentally determined formation of sufficient amounts of hydrogen peroxide and HO radicals during oxidation of propane [27] and paraffin dehydrogenation products [28-30],... 

In hydrocarbon oxidation processes to produce alcohol, there is always a degree of overoxidation. The alcohol is often further oxidized to waste carboxylic acids and carbon oxides. If boric acid is introduced to the reactor, the alcohol reacts to form a borate ester, which protects the alcohol from further oxidation. The introduction of boric acid terminates the by-product formation pathway and greatly increases the product yield. The borate ester of alcohol is then hydrolyzed, releasing boric acid for recycle back to the process. This kind of reaction pathway control has been applied to a commercial process, resulting in about a 50% reduction in waste generation once the process was optimized. 

The low-pressure acetic acid process was developed by Monsanto in the late 1960s and proved successful with commercialization of a plant producing 140 X 10 metric tons per year in 1970 at the Texas City (TX, USA) site [21]. The development of this technology occurred after the commercial implementation by BASF of the cobalt-catalyzed high-pressure methanol carbonylation process [22]. Both carbonylation processes were developed to utilize carbon monoxide and methanol as alternative raw materials, derived from synthesis gas, to compete with the ethylene-based acetaldehyde oxidation and saturated hydrocarbon oxidation processes (cf. Sections 2.4.1 and 2.8.1.1). Once the Monsanto process was commercialized, the cobalt-catalyzed process became noncom-... 

The large-scale production of sulfuric acid, overall one of the most important products in the chemical industry, exploits the redox activity of vanadium(V) oxide. Vanadia-, molybdena-, and tin oxide-based catalysts are used further for a host of selective hydrocarbon oxidation processes including dehydrogenation, oxidative coupling, and oxygenation (3,41. Much recent activity in this area has been aimed at the development of more active and more selective catalysts by dispersing oxides in the form of monolayers on bulk oxide supports. This approach has proven extremely successful for tailoring catalyst properties to... 

The reactions occurring at the sea surface and in the euphotic zone, photo-oxidation, oxidation processes and association of some hydrocarbons with orgemic complexes such as humic or fulvic acids (Khsm and Schnitzer, 1972 Gagosian and Stuermer, 1977), tend to reduce the concentration of more labile compounds, especially the unsaturated hydrocarbons. Oxidation processes lead to the formation of alcohols, acids, alkyl and arylethers, carbonyl compounds and sulfoxides (Kawahara, 1969 Hansen, 1977). 

The example considered here is again the hydrocarbon oxidation process with its simplified kinetic scheme used in Sec. 11. S.b. Suppose the reactor is at a temperature of 362 C and let the gas entering the bed be 362 C. How long will it take to... 

Moreover, gas-liquid reactors represent the simplest departure from reactors which involve purely homogeneous reactions, but nevertheless the interactions of the processes of simultaneous mass transfer and reaction in gas-liquid reactors have presented and continue to present a formidable challenge to the applied science of chemical reaction engineering. This is particularly true of the vigorous intense reactions which are involved in the production of many major chemical intermediates. For example, in many liquid phase hydrocarbon oxidation processes, partial oxidation competes with complete combustion to produce a wide range of oxidised hydrocarbons, where the kinetics may be summarised as... 

This design example is suggested from hydrocarbon oxidation processes such as benzene oxidation into maleic anhydride or the synthesis of phthalic anhydride from o-xylene. These strongly exothermic processes are carried out in multitubular reactors cooled by molten salt that is circulating around the tubes and that exchanges heat to an internal or external boiler. The length of the tubes is 3 m and their internal diameter is 2.54 cm. One reactor may contain 2500 tubes in parallel and even 10,000 or more in the latest versions. In German processes the... 

Acetic acid was originally produced by bacterial oxidation of ethanol, but from around 1914, synthetic acetic acid was produced by the oxidation of acetaldehyde. Hydrocarbon oxidation processes using butane or naphtha as feedstock were introduced in the 1950s. In a typical liquid phase oxidation process, a cobalt acetate catalyst operating at a temperature of 175°C, and a pressure of 54 bar was used, and by-products could be recycled. Conditions could be modified to produce methyl ethyl ketone. 

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