Partial oxidation of hydrocarbons

In all three processes the reaction is performed in an empty pressure vessel lined with alumina. The reactants (oil and oxygen, along with a small amount of steam) are introduced through a nozzle at the top of the generator vessel. The nozzle consists of concentric pipes so that the reactants are fed separately and react only after mixing at the burner tip or in the space below. The temperature in the generator is between 1200 

Partial oxidation has practically no restrictions regarding the nature of the hydrocarbon and the sulfur content. Natural gas, refinery gases, LPG, naphtha, heavy fuel, vacuum residue, visbreaker oil, asphalt, and tar can be used as feedstock. As the investment costs for partial oxidation are higher than for steam reforming, mainly because of the cyrogenic air separation, it is usually not a choice for the lighter hydrocarbons, but heavy feedstocks from fuel oil to asphalt, when favorably priced, can be a competitive option for various locations and circumstances. In some special cases, where the primary reformer is a bottleneck for a capacity increase, a small parallel partial oxidation unit based on natural gas could be installed, if a surplus of 

After this the soot is removed from the product gas in two stages. About 95 % is removed by direct water-spray (quench type), the remainder by countercurrent waterscrubbing in a packed column. Older units used a gas-oil fraction to extract the carbon from the aqueous soot suspension. The pebbles formed in this operation were separated with vibrating sieves and either re-mixed with the generator feed or separately 

To prevent accumulation of ash and slag in the water circuit, some water is discharged continuously. In a combined chemical and physical treatment sulfides, cyanides and suspended solids (ash) are removed. A concentrated sludge has to be filtered off and disposed of. The run-off water from the filters is stripped of ammonia and after pH-adjustment sent to a biological treatment unit. Uhde [532] has developed an alternative route for soot treatment in which the soot is filtered off and subjected to combustion, and the filtered water is recycled to the quench and scrubbing circuits. Let down water is treated as described above. This soot treatment technique avoids not 

A recent development is the Uhde [532] three-stream burner with an adjustable tip. A portion of the of oxygen enters through the center nozzle, the remainder through the outer annulus, the oil is fed through the inner annulus. The center oxygen nozzle also accommodates the preheat burner. This combi-burner concept avoids the change from preheat burner to process burner in the start-up phase, a cumbersome procedure necessary when using the traditional two-stream Texaco burner. As tested in a demonstration plant the carbon conversion could be increased to better than 99.6%, which means a reduction soot formation by a factor better than 5. 

As mentioned above in Section 2.3, partial oxidation is an alternative process to steam reforming for producing hydrogen from methane. It is also applicable to a wide range of liquid hydrocarbons that include heavy oils found in low-value refinery residues (refinery bottoms ) and to the gasification of coal see Section 2.7. In general terms, the process may be expressed as  

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Acetaldehyde, first used extensively during World War I as a starting material for making acetone [67-64-1] from acetic acid [64-19-7] is currendy an important intermediate in the production of acetic acid, acetic anhydride [108-24-7] ethyl acetate [141-78-6] peracetic acid [79-21 -0] pentaerythritol [115-77-5] chloral [302-17-0], glyoxal [107-22-2], aLkylamines, and pyridines. Commercial processes for acetaldehyde production include the oxidation or dehydrogenation of ethanol, the addition of water to acetylene, the partial oxidation of hydrocarbons, and the direct oxidation of ethylene [74-85-1]. In 1989, it was estimated that 28 companies having more than 98% of the wodd s 2.5 megaton per year plant capacity used the Wacker-Hoechst processes for the direct oxidation of ethylene. 

Synthesis Gas Chemicals. Hydrocarbons are used to generate synthesis gas, a mixture of carbon monoxide and hydrogen, for conversion to other chemicals. The primary chemical made from synthesis gas is methanol, though acetic acid and acetic anhydride are also made by this route. Carbon monoxide (qv) is produced by partial oxidation of hydrocarbons or by the catalytic steam reforming of natural gas. About 96% of synthesis gas is made by steam reforming, followed by the water gas shift reaction to give the desired H2 /CO ratio. 

Ammonia production by partial oxidation of hydrocarbon feeds depends to some degree on the gasification step. The clean raw synthesis gas from a Shell partial oxidation system is first treated for sulfur removal, then passed through shift conversion. A Hquid nitrogen scmbbiag step follows. 

Soot. Emitted smoke from clean (ash-free) fuels consists of unoxidized and aggregated particles of soot, sometimes referred to as carbon though it is actually a hydrocarbon. Typically, the particles are of submicrometer size and are initially formed by pyrolysis or partial oxidation of hydrocarbons in very rich but hot regions of hydrocarbon flames conditions that cause smoke will usually also tend to produce unbumed hydrocarbons with thek potential contribution to smog formation. Both maybe objectionable, though for different reasons, at concentrations equivalent to only 0.01—0.1% of the initial fuel. Although thek effect on combustion efficiency would be negligible at these levels, it is nevertheless important to reduce such emissions. 

As the molecular weight of the hydrocarbon increases (lower H/C feed ratio), the H2/CO product ratio decreases. The H2/CO product ratio is approximately 3 for methane, 2.5 for ethane, 2.1 for heptane, and less than 2 for heavier hydrocarbons. Noncatalytic partial oxidation of hydrocarbons is also used to produce synthesis gas, but the H2/CO ratio is lower than from steam reforming ... 

The function 7(f) can be chosen for the whole reaction time interval, or two or three subsequent temperature-time data points 7(fi-i), 7(fi), and 7(fi+i) can be approximated by polynomials of second or third order 7,(f), respectively. These polynomials will then be used in a procedure for numerical integration in each integration step i. This method has been successfully applied in a kinetic study of the partial oxidation of hydrocarbons (Skrzypek et al., 1975, Krajewski etai, 1975, 1976, 1977). 

Sobacchi, M. et al., Experimental assessment of combined plasma/catalytic system for hydrogen production via partial oxidation of hydrocarbon fuels, Int.. Hydrogen Energ., 27, 635, 2002. 

The Role of Oxygen Ions in the Partial Oxidation of Hydrocarbons... 

Numerous chemical intermediates are oxygen rich. Methanol, acetic acid and ethylene glycol show a O/C atomic ratio of 1, as does biomass. Other major chemicals intermediates show a lower O/C ratio, typically between 1/3 and 2/3. This holds for instance for propene and butene glycols, ethanol, (meth)acrylic acids, adipic acid and many others. The presence of some oxygen atoms is required to confer the desired physical and chemicals properties to the product. Selective and partial deoxygenation of biomass may represent an attractive and competitive route compared with the selective and partial oxidation of hydrocarbon feedstock. 

Hydrogen production by catalytic steam reforming and partial oxidation of hydrocarbons has been the most efficient, economically and widely used process for the... 

Partial oxidation of hydrocarbons is the exothermic reaction with oxygen and steam. The amonnts of oxygen and water vapor are controlled so that the reaction proceeds without the need for external energy. An example reaction for this process is ... 

Vapor phase partial oxidation of hydrocarbons also yield H2O2. However, several by-products are generated, the separations of which make the process difficult and uneconomical. 

As mentioned earlier, Haber, et. al, have suggested that in the partial oxidation of hydrocarbons nucleophilic lattice oxygen (O ) is responsible for selective oxidation, while electrophilic ionic or radical oxygen species ( O2, 02, and 0-) cause deep oxidation to CO (6). This concept may be an oversimplification, since it is likely that a range of oxygen species exists at catalytic conditions. 

Selective partial oxidation of hydrocarbons poses considerable challenges to contemporary research. While by no means all, most catalytic oxidations are based on transition-metal oxides as active intermediates, and the oxidative dehydrogenation of ethylbenzene to styrene over potassium-promoted iron oxides at a scale of about 20 Mt/year may serve as an example [1]. Despite this... 

In the partial oxidation of hydrocarbons, the molecules are converted stepwise. Germain [134] remarks that a mechanism with the model of a rake applies... 

Production of ammonia requires large quantities of hydrogen, most of which comes from the partial oxidation of hydrocarbons with water or oxygen. A simple and important example is the so-called methane-steam gas reaction, which is favorable only at very high temperatures because of the entropy effect in the formation of H2 (see Section 4-4B) ... 

The gasification reaction is a partial oxidation of hydrocarbons to carbon monoxide and hydrogen ... 

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