Oxidation of propan

Historically, formaldehyde has been and continues to be manufactured from methanol. EoUowing World War II, however, as much as 20% of the formaldehyde produced in the United States was made by the vapor-phase, noncatalytic oxidation of propane and butanes (72). This nonselective oxidation process produces a broad spectmm of coproducts (73) which requites a complex cosdy separation system (74). Hence, the methanol process is preferred. The methanol raw material is normally produced from synthesis gas that is produced from methane. 

Other potential synthetic methods include fermentation (qv) of certain carbohydrates (qv), oxidation of propane, hydrogenation of acetone, and hydrolysis of isopropyl acetate. The hydrogenation of by-product acetone is the only method practiced commercially. 

Other Processes. Isopropyl alcohol can be prepared by the Hquid-phase oxidation of propane (118). It is produced iacidentaHy by the reductive condensation of acetone, and is pardy recovered from fermentation (119). Large-scale commercial biological production of isopropyl alcohol from carbohydrate raw materials has also been studied (120—123). 

Propanol has been manufactured by hydroformylation of ethylene (qv) (see Oxo process) followed by hydrogenation of propionaldehyde or propanal and as a by-product of vapor-phase oxidation of propane (see Hydrocarbon oxidation). Celanese operated the only commercial vapor-phase oxidation faciUty at Bishop, Texas. Since this faciUty was shut down ia 1973 (5,6), hydroformylation or 0x0 technology has been the principal process for commercial manufacture of 1-propanol ia the United States and Europe. Sasol ia South Africa makes 1-propanol by Fischer-Tropsch chemistry (7). Some attempts have been made to hydrate propylene ia an anti-Markovnikoff fashion to produce 1-propanol (8—10). However, these attempts have not been commercially successful. 

With the exception of acetic, acryUc, and benzoic all other acids in Table 1 are primarily produced using oxo chemistry (see Oxo process). Propionic acid is made by the Hquid-phase oxidation of propionaldehyde, which in turn is made by appHcation of the oxo synthesis to ethylene. Propionic acid can also be made by oxidation of propane or by hydrocarboxylation of ethylene with CO and presence of a rhodium (2) or iridium (3) catalyst. 

Some studies of potential commercial significance have been made. For instance, deposition of catalyst some distance away from the pore mouth extends the catalyst s hfe when pore mouth deactivation occui s. Oxidation of CO in automobile exhausts is sensitive to the catalyst profile. For oxidation of propane the activity is eggshell > uniform > egg white. Nonuniform distributions have been found superior for hydrodemetaUation of petroleum and hydrodesulfuriza-tion with molybdenum and cobalt sulfides. Whether any commercial processes with programmed pore distribution of catalysts are actually in use is not mentioned in the recent extensive review of GavriUidis et al. (in Becker and Pereira, eds., Computer-Aided Design of Catalysts, Dekker, 1993, pp. 137-198), with the exception of monohthic automobile exhaust cleanup where the catalyst may be deposited some distance from the mouth of the pore and where perhaps a 25-percent longer life thereby may be attained. 

The noncatalytic oxidation of propane in the vapor phase is nonselec-tive and produces a mixture of oxygenated products. Oxidation at temperatures below 400°C produces a mixture of aldehydes (acetaldehyde and formaldehyde) and alcohols (methyl and ethyl alcohols). At higher temperatures, propylene and ethylene are obtained in addition to hydrogen peroxide. Due to the nonselectivity of this reaction, separation of the products is complex, and the process is not industrially attractive. 

TPSR results are presented in Fig. 4. Propene is produced when the sample temperature is above 350 TC on both samples, which means converting of propane over CNF catalysts could occur without oxygm. The desorption products amounts are 0.35 and 0.26 mmol/g for CNF-RA and CNF-HA respectively while the percentages of propene in llie desorption substances over these two sample are 51.4% and 87.7%. These results imply that the propene selectivity may increase, at least partly, due to restriction of oxidation of propane to COx by heat treatment at the cost of catalytic activity. 

Al-Saeedi, J.N. and Guliants, V.V. (2002) High-throughput experimentation in multicomponent bulk mixed metal oxides Mo-V-Sb-Nb-O system for selective oxidation of propane to acrylic acid. Appl. Catal. A Gen, 237, 111. 

A catalytic system Mo-V-Nb-W supported on alumina was prepared by impregnation and investigated for the selective oxidation of propane. The effects of the variation of each metal and of the catalyst preparation were analysed. The results show that Mo and V species supported on alumina can lead to catalysts with high selectivity to propene and reasonable selectivity to acrolein. The presence of Nb and W seems to have little effect. The catalyst can be affected by the method of impregnation. 

The results presented in this paper therefore show that V and Mo species supported on alumina can give rise to a catalyst which has a high selectivity for the oxidation of propane to propene and a reasonable selectivity to acrolein and that both species are essential to give the optimal behaviour. Contrary to our previous observations and what observed for bulk catalysts [5], the presence of Nb and W seem to have little effect, perhaps because the methods used here restrict the active phase to a monolayer whereas previously prepared materials may have contained multilayer oxidic species. 

Sun, H., Blatter, F. and Frei, H. (1997). Oxidation of propane to acetone and of ethane to acetaldehyde by Oz in zeolites with complete selectivity. Catal. Lett. 44, 247-253... 

FIGURE 3.12 Oxidation of propane in a turbulent flow reactor (after [13]). 

Complete mechanisms for the high temperature oxidation of propane and larger hydrocarbons are available in the literature [e.g., Wamatz, J., Proc. Combust. Inst., 24, 553-579. (1992), and Ranzi, E., Sogaro, A., Gaffuri, R, Pennati, G., Westbrook, C. K., and Pitz, W. J., Combust. Flame, 99, 201 (1994)]. Because of the space limitations, only selected reactions for propane oxidation are presented in Table C7. 

Most industrially desirahle oxidation processes target products of partial, not total oxidation. Well-investigated examples are the oxidation of propane or propene to acrolein, hutane to maleic acid anhydride, benzene to phenol, or the ammoxidation of propene to acrylonitrile. The mechanism of many reactions of this type is adequately described in terms of the Mars and van Krevelen modeE A molecule is chemisorbed at the surface of the oxide and reacts with one or more oxygen ions, lowering the electrochemical oxidation state of the metal ions in the process. After desorption of the product, the oxide reacts with O2, re-oxidizing the metal ions to their original oxidation state. The selectivity of the process is determined by the relative chances of... 

H, Cl, Br, NO2, Me, MeO) by bromamine-B, catalysed in the presence of HCl in 30% aqueous methanol by RuCls have been smdied and a biphasic Hammett a-relationship derived. A kinetic study of the ruthenium(in)-catalysed oxidation of aliphatic primary amines by sodium A-bromo-j -toluenesulfonamide (bromamine-T, BAT) in hydrochloric acid medium has been undertaken and the mechanism of the reaction discussed. A concerted hydrogen-atom transfer one-electron transfer mechanism is proposed for the ruthenium(in)-catalysed oxidation of 2-methylpentane-2,4-diol by alkaline hexacyanoferrate(III). The kinetics of the oxidation of propane-... 

I) Oxidation of propan-l-ol with alkaline KMn04 solution. 

Table 8 Representative kinetic data for the oxidation of propan-2-ol by ruthenium oxo complexes.

One of the most important challenges in the modern chemical industry is represented by the development of new processes aimed at the exploitation of alternative raw materials, in replacement of technologies that make use of building blocks derived from oil (olefins and aromatics). This has led to a scientific activity devoted to the valorization of natural gas components, through catalytic, environmentally benign processes of transformation (1). Examples include the direct exoenthalpic transformation of methane to methanol, DME or formaldehyde, the oxidation of ethane to acetic acid or its oxychlorination to vinyl chloride, the oxidation of propane to acrylic acid or its ammoxidation to acrylonitrile, the oxidation of isobutane to... 

As to the method of preparation, it was found that V-Mg oxide catalysts prepared with a Mg(OH)2 precursor that was precipitated with KOH was less selective than one prepared with a MgC03 purecursor precipitated with (NH4)2C03 (25). Interestingly, unlike the butane reaction, there was no effect of preparation on the oxidative dehydrogenation of propane using the same catalysts, as mentioned earlier (25, 30). Unlike the oxidation of propane, Mg pyrovanadate was nonselective for butane (25, 26). Mg metavanadate was nonselective as well (26). 

Above 300°C. the effective reaction of an alkyl radical with oxygen may be Reaction 3 rather than 2 because of the reversibility of Reaction 2. If it is assumed that Reaction 3 is important at about 450°C., its rate can be estimated from the competition between pyrolysis and oxidation of alkyl radicals. Falconer and Knox (21) observed that the ratio of (pro-pene)/(ethylene) from the oxidation of propane between 435° and 475°C. increased with oxygen concentration and decreased with temperature—the apparent activation energy difference for the two reactions forming the olefins being 27 =t 5 kcal. per mole. They interpreted this result in terms of a competition between Reactions 1 and 3. The observed ratio (propene)/(ethylene) was 3.5 at 435°C. and 10 mm. of Hg pressure. If log ki(propyl) = 13.2 — 30,000/2.30RT, the value for the n-propyl radical (34), then log k3 = 8.0. If the A factor is 109-3, we derive the Arrhenius equation... 

Seakins (16) has reported that the low temperature oxidation of propane is promoted by chloroform but not by carbon tetrachloride. Our studies, however, show that chloroform and carbon tetrachloride have generally similar effects on all preflame stages (Figure 3) and that their patterns of oxidative degradation are also similar (Figure 8). Under the conditions of Seakins experiments the following reaction, which he suggested, probably initiates the sequence of reactions responsible for promotion. 

The chemistry in the high-temperature regime is known in more detail than that occurring at lower temperatures. This allows us to be a little more specific. As an example, consider oxidation of propane. Typically the initiation reaction is thermal dissociation of the fuel,... 

Satterfield, Reid, and Wilson (186-8) have suggested that Reaction 9" is the main olefin producing reaction in the low temperature oxidation of propane. [ 9" 20 kcal. E% 25 kcal. E9 40 kcal. per mole (204)]. As temperature increases Reaction 9 will become relatively more important. 

Oxyfunctionalization of lower paraffins such as methane, ethane, propane, and butanes has recently attracted much attention (5, 330, 331, 347-350). Oxidation of -butane to maleic anhydride is an industrial example (346, 351). The oxidation of propane and isobutane with heteropoly catalysts was first reported in 1979 (352). Ai (324a) and Centi et al. (324b, 324c) reported that heteropoly compounds catalyze the oxidation of lower paraffins, especially propane, isobutane, and pentane (324). 

The oxidation of propane into acrylic acid in the presence of heteropoly catalysts prepared from H3PM012O40 and antimony pentachloride gave rather low conversion and selectivity [10 and 19%, respectively (2% yield)] (352). Recently, a yield of ca. 9% was obtained with H5PV2M010O40 (353). The addition of Cr ion also enhanced the catalytic performance (354). 

---