Hydrocarbons noncatalytic oxidative

Homogeneous reactions. Homogeneous noncatalytic reactions are normally carried out in a fluidized bed to achieve mixing of the gases and temperature control. The sohds of the bed act as a heat sink or source and facihtate heat transfer from or to the gas or from or to heat-exchange surfaces. Reaclious of this type include chlorination of hydrocarbons or oxidation of gaseous fuels. 

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 individual hydrocarbons in the exhaust differ widely in the ease of both catalytic and noncatalytic oxidation. Thus, the poisoning effect may vary, and indeed does, with the hydrocarbon composition of the exhaust itself, and with the necessarily limited choice of particular hydrocarbons used in various laboratory tests. In many instances the hydrocarbons are... 

Synthesis gas may be prepared by a continuous, noncatalytic conversion of any hydrocarbon by means of controlled partial combustion in a fire-brick lined reactor. In the basic form of this process, the hydrocarbon and oxidant (oxygen or air) are separately preheated and charged to the reactor. Before entering the reaction zone, the two feed stocks are intimately mixed in a combustion chamber. The heat produced by combustion of part, of the hydrocarbon pyrolyzes the remaining hydrocarbons into gas and a small amount of carbon in the reaction zone. The reactor effluent then passes through a waste-heat boiler, a water-wash carbon-removal unit, and a water cooler-scrubber. Carbon is recovered in equipment of simple design in a form which can be used as fuel or in ordinary carbon products. 

C2 to Cg saturated hydrocarbons (LPG) Vapor phase noncatalytic oxidation Heterogeneous Butane, propane, or gas mixtures containing them are oxidized with air or O2, at —100 -450 C. 

An example of the controlled noncatalytic oxidation of low-molecular-weight paraffin hydrocarbons to form commercially practicable yields of oxidation products is given by a process devised by Bludworth In the oxidation of butane or other low-molecular-weight paraffin hydrocarbon, he... 

Noncatalytic oxidation of the aromatic hydrocarbons is slow at temperatures below 500 C. Benzene is not vigorously oxidized in glass apparatus until temperatures near 700°C are reached. Under similar conditions, toluene is noticeably oxidized at 650 0, and xjdene at 575 0. Even with an active catalyst such as vanadium pentoxide, a temperature of 400-450 0 is required for the commercial oxidation of naphthalene to phthalic anhydride by air. Furthermore, quantities of air from one to three times that theoretically necessary for the conversion must be used. This means that 20-60 moles of air must be used per mole of naphthalene in the reaction mixture. 

Another commercial example involving the use of a vessel-type PER is autothermal reforming (ATR) of natural gas. It is a key step in gas-to-liquid (GTL) processes and is used to produce synthesis gas (CO -1- H2) for FT synthesis in which a mixture of hydrocarbons in the C1-C30+ range is synthesized [6]. In ATR, noncatalytic oxidation (Reaction 1.4) and Ni-catalyzed steam reforming of natural gas (Reaction 1.2) are combined, and product distribution is affected by water-gas shift (Reaction 1.5), an important side reaction of steam reforming [3, 7] ... 

Partial oxidation processes rank next to steam-hydrocarbon processes in the amount of hydrogen made. They can use natural gas, refinery gas, or other hydrocarbon gas mixtures as feedstocks, but their chief advantage is that they can also accept liquid hydrocarbon feedstocks such as gas oil, diesel oil, and even heavy fuel oil. All processes employ noncatalytic partial combustion of the hydrocarbon feed with oxygen in the presence of steam in a combustion chamber at flame temperatures between 1300 and 1500°C. For example, with methane as the principal component of the feedstock ... 

Partial Oxidation. Noncatalytic partial oxidation processes (see Fig. 22.6) react hydrocarbons with gaseous oxygen at very high... 

The noncatalytic partial oxidation of hydrocarbons by the Shell gasification process (SGP) takes place in a refractory-lined reactor that uses a specially designed burner. The oxidant is preheated and then mixed with steam... 

The third strategy for minimizing NOx, known as posttreatment, involves removing NOx from the exhaust gases after the NOx has already been formed in the combustion chamber. Two of the most common methods of posttreatment are selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR).7 Wet techniques for posttreatment include oxidation/absorption, oxidation/absorption/reduc-tion, absorption/oxidation, and absorption/reduction. Dry techniques for posttreatment, besides SCR and SNCR, include activated carbon beds, electron beam radiation, and reaction with hydrocarbons. 

Several processes, including noncatalytic partial oxidation (POX), catalytic partial oxidation (CPO), and ATR may be used to perform partial oxidation of hydrocarbons. In all cases, some or all of the reactions listed in Table 4 are involved. Normally, these reactions are accompanied by the steam-reforming and shift reactions. The oxidation reactions are irreversible at all conditions of practical interest. 

The noncatalytic partial oxidation of fuel oil converts petroleum feedstock into synthesis gas, C02, CH4, and H2S if any sulfur is present. This process has the ability to handle sulfur compounds without pretreatment (sulfur removal). Eliminating a processing step from steam reforming techniques, however, requires additional equipment for oxygen addition in the reactor. The expected carbon deposition problem with hydrocarbon material containing low H C ratios is limited by the use of carbon recovery and extinction recycle schemes [28], The partial oxidation of fuel oil typically operates at a temperature range of 1200-1500°C and pressures of 30-80 bars in a refractory-lined reactor. 

A single plant operating in Texas, based on the noncatalytic controlled oxidation of propane-butane hydrocarbons, is reported to consume over 50 million gal annually of these light hydrocarbons together with large volumes of natural gas in the production of over 300 million lb of chemicals per year. Chemical products include formaldehyde purified to resin grade by means of ion-exchaiige resins, acetic acid, methanol, propanol, isobutanol, butanol, acetaldehyde, acetone, methyl ethyl ketone, mixtures of C4-C7 ketones, mixtures of C4-C7 alcohols, and propylene and butylene oxides. Catalytic liquid-phase oxidation of propane and butane is much more specific, and major yields of acetic acid are obtained. 

Fluidized beds aie used in both catalytic and noncatalytic systems. Typical examples of catalytic uses aie hydrocarbon cracking and reforming, oxidation of naphthalene to phthalic anhydride, and ammoxidation of propylene to acrylonitrile. Examples of noncatalytic uses are roasting of sulfide ores, coking of petroleum residues, calcination of ores, incineration of sewage sludge, and drying (Peiry and Gi een, 1999). 

At present, natural gas and light hydrocarbons are the predominant feedstocks for the production of synthesis gas. Synthesis gas can also be produced from heavy hydrocarbons or coal, but in that case noncatalytic partial oxidation processes will be used (see the section Hydrocarbon Steam Reforming). 

Supp, E. (1997) Noncatalytic partial oxidation and special gasification processes for higherboiling hydrocarbons, in UUmann s Encyclopedia of Industrial Chemistry, Fifth Edition on CD-ROM, Wiley-VCH Verlag GmbH, Wdnheim. 

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