Partial oxidation of propane

The selective oxidation of propane is more difficult than that of propylene due to its low reactivity and there has been httle success in developing a viable process. 

Since then Centi has also examined catalysts based on vanadiitm antimo-nates. Conversion as high as 60-80%, but only 35 0% yields, were obtained with a VSbsWO catalyst supported on alumina. Bowker confirmed Centi s conclusion that the reaction proceeds in two steps. Propane is first dehydrogenated to propylene, which is then ammoxidized to acrylonitrile by the well-established reaction mechanism. 

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Figure 2.25 Product composition vs. product gas temperature for partial oxidation of propane in an Rh/AI203/FeCr alloy reactor [55] (by courtesy of ACS).

Chromium-containing mesoporous silica molecular sieves (Cr-HMS) with tetrahedrally coordinated isolated chromium oxide (chromate) moieties can operate as efficient photocatalysts for the decomposition of NO and the partial oxidation of propane with molecular oxygen under visible light irradiation (Yamashita et al., 2001). 

One-step partial oxidation of propane to acrylic acid (an essential chemical widely used for the production of esters, polyesters, amides, anilides, etc.) has been investigated so far on three types of catalysts, namely, vanadium phosphorus oxides, heteropolycompounds and, more successfully, on mixed metal oxides. The active catalysts generally consist of Mo and V elements, which are also found in catalysts used for the oxidation of propene to acrolein and that of acrolein to acrylic acid. 

Taylor SH, Hutchings GJ, Palacios ML, Lee DF (2003) The partial oxidation of propane to formaldehyde using uranium mixed oxide catalysts. Catal Today 81 171... 

Liu S, Xu L, Xie S, Wang Q, Xiong G (2001) Partial oxidation of propane to syngas over nickel supported catalysts modified by alkali metal oxides and rare-earth metal oxides. Appl Catal A-Gen 211 145-152... 

Under the differential reaction conditions used in this study [12], the concentrations of all products in the gas phase are small and therefore their respective surface coverages are small. Under these constraints, the following kinetic expressions apply for the partial oxidation of propane to propylene, and propylene to acrolein, respectively ... 

Partial oxidation of propane was investigated in the presence of molybdenum oxide based catalysts. We have shown the existence of a synergetic effect between the two phases aNiMo04 and aMoOs. Indeed activity and selectivity towards acetic acid and acrylic acid were maximal with a ratio aMo03 / (aNiMo04 + aMoOj) close to 0.25. These results could be explained by an interaction and a mutual covering of the two phases. The addition of bismuth to these mixed systems led to a total or a partial inhibition in the production of acetic acid and an increase in the formation of acrolein and acrylic acid. 

An important example of this kind is a contribution of cracking processes to partial oxidation of propane and higher hydrocarbons. In particular, in the case of catalytic propane ODH, the formation of lower hydrocarbons—first of all ethylene and methane—can substantially reduce propylene selectivity. The analysis of possible homogeneous and heterogeneous pathways of C-C bond breaking can provide valuable guidelines for further improvement of catalyst formulation and/or overall process design. 

If no commercial catalyst is available, it may still be advantageous to separate catalyst optimization from development of a coating procedure. Such an approach was pursued by Schwarz et al. [178] in the development of a catalytic microreactor for the partial oxidation of propane. In a first step, a VOY/ A1203 catalyst was developed. A commercially available Y-AI2O3 powder consisting of particles 3 pm in diameter was chosen as the support material, mixed with various amounts of vanadyl acetylace-tonate and suspended in methanol. After drying and calcination, the resultant material was characterized and its catalytic activity and selectivity for the partial oxidation of propane was determined. The optimized catalyst was resuspended in an alcoholic solution, mixed with binders, and coated onto a stainless steel MSR. 

Partial oxidation of propane (Coating characterization) Partial oxidation of propane Selective catalytic reduction of NOx (Coating characterization) Water gas shift Methane steam reforming Methanol steam reforming Schwarz et al. [178] Roumanie et al. [179] Pennemann et al. [183] Ercoli et al. [184] Stefanescu et al. [181] Germani et al. [177] Tonkovich et al. [182] Yu et al. [185]... 

Rh/Y-A1203 Pd/y-A1203 Stainless steel Partial oxidation of propane Pennemann et al. [183]... 

H. Pennemann, V. Hessel, G. Kolb, H. Lowe, R. Zapf, Partial oxidation of propane using micro structured reactors, Chem. Eng. J. 135 (2008) S66. 

The state of the art in partial oxidation of propane to propylene is assessed below. Unlike the preceding sections which dealt with commercially practical processes this section will concern itself with evaluating the promise of the partial oxidants—oxygen, halogens, and sulfur— that have been proposed for effecting the propane to propylene reaction. 

P-07 - Photocatalytic reactions on chromium containing mesoporous molecular sieves under visible light irradiation Decomposition of NO and partial oxidation of propane... 

M. Baems and M. Buyevskaya, Strategies in the Development of Heterogeneous Catal for the Partial Oxidation of Propane by Combinatorial and Evolutionary Methods, Ps er presented at the 2" Annual Conference on Combinatorial Approaches for New Materials Discovery, San Diego, CA, January 23-25,2000. 

Dardin, V. J. Albright, L. N. Partial Oxidation of Propane Initiated by Ozone. Ind. Eng. Chem. Proc. Des. Dev. 1965, 4(61), Pullabhotla, V. S. R. R. Southway, C. Jon-nalagadda, S. B. Oxidation of n-hexadecane with uranyl loaded/anchored microporous zeolites and ozone. Catalysis Communications 200S, 9, 1902-1912 Grewer, T. H. Chapter IV. 4.3. Oxidation of Hydrocarbons by Ozone in Low Temperature Oxidation (Ed. W. Jost) 1964, 1, 186-188... 

Permemann et al. performed partial oxidation of propane and identified the Boudouart reaction to be responsible for significant coke formation, which was observed in particular downstream of the catalyst on the steel surface of their microchannel test reactors [59]. The nickel contained in the stainless steel clearly served as the active species. Coating the steel with a-alumina suppressed the coke formation. 

These experiments confirmed once again that pure noble metal surfaces are not suitable catalysts, even at reaction temperatures exceeding 1000 °C. Even though low surface area carrier materials such as a-alumina probably provide insufficient surface area to achieve satisfactory catalyst selectivity, fine dispersion of noble metals on carrier materials of substantial surface area improves the catalytic performance of noble metals considerably. In Section 4.2.5 results of catalyst optimisation for partial oxidation of propane performed by Pennemann et al. [59] were discussed, which always revealed full propane conversion over rhodium catalysts above a reaction temperature of 750 °C and short contact time, because catalysts of sufficient surface area were applied. 

Pennemann, H., Hessel, V., Kolb, G Lowe, H. and Zapf, R. (2008) Washcoat-based catalysts for the partial oxidation of propane using a micro structured reactor. Chem. Eng. J. 135, 66-73. 

Li, D., Shigara, M Atake, L, ShiShido, T, Omni, Y., Sano, T. and Takehira, K. (2007) Partial oxidation of propane over Ru promoted Ni/Mg(Al)0 catalysts. Selfactivation and prominent effect of reduction-oxidation treatment of the catalyst Appl. Catal. A, 321, 155—164. 

In general, mixed-metal oxides are at present the most important catalytic system for the partial oxidation of C2-C5 alkanes into 0-containing partial oxidation products. However, different characteristics should be considered among the several catalysts within this group. For instance, VPO- and MoVO-based catalysts are the most effective systems for -butane (or -butene) oxidation to MA and propane (or propene) oxidation to acrylic acid, respectively. It must be indicated that, although some similarities are observed for the ammoxidation " over MoVO- or SbVO-based catalyts, the latter show very low selectivity during the partial oxidation of propane and no results with other alkanes have been reported. " Therefore, SbVO-based catalysts will not be explicitly included in the following discussion. 

Figure 24.6 shows the variation of the main partial oxidation products during the oxidation of propane (Fig. 24.6a) and propylene (Fig. 24.6b) over a MoVTeNbO catalyst. It can be observed that propane is initially transformed into propylene (unstable primary product), which is then selectively oxidized into acrylic acid (a secondary reaction product). The formation of the olefin is clear, since the initial selectivity to propylene of ca. 90% is observed in effective catalysts for the partial oxidation of propane.A similar reaction network has been proposed for propane oxidation with modified VPO catalysts,but also in the propane... 

At this point it is interesting to compare the evolution of propylene adsorption over catalysts with different surface acid characteristics, i.e. a MoVTeNbO catalyst (active and selective in the partial oxidation of propane to acrylic acid), an alumina-supported vanadium oxide (active in the ODH of propane to propylene), or a MoVNbO mixed oxide (active in the oxidative transformation of propane to propylene and acetic acid). The final products observed in each case were related to the characteristics of the adsorbed intermediates (Fig. 24.7) (i) a ir-allylic compound, interacting with a redox site intermediate in the selective oxidation of... 

Finally, the results for the partial oxidation of propane are rather frustrating, as after two decades of intense study, the yields to acrylic acid have not been enhanced. In fact, the highest yield to acryUc acid in both the open and patent literature indicates a limit to the maximum yield which can he obtained, as specifically reported by Muller. This is a consequence of the Umitations of the reaction network in consecutive steps, with propylene as the primary reaction product, as indicated in Fig. 24.6. Accordingly, mayhe we should design catalysts by considering the model of -butane selective oxidation over VPO catalysts (Fig. 24.8), in which the olefinic intermediate was not desorhed and acrylic acid was directly formed as the primary reaction product. In this sense, new crystalline strucmres could be required in which active sites for propane activation and those for propylene oxidation were near enough to directly transform the propylene intermediate into acrylic... 

Landi, G., Lisi, L. and Volta, J. (2004). Role of Water in the Partial Oxidation of Propane to Acrylic Acid, Catal. Today, 91-92, pp. 275-279. 

Lintz, H. and Muller, S. (2009). The Partial Oxidation of Propane on Mixed Metal Oxides A Short Overview, Appl. Catal. A Gen., 357, pp. 178-183. 

Partial oxidation of propane with air in CO2 up to 400" C and 113 bar, over supported metal oxide catalysts in a flow reactor, revealed an increase in total... 

Kerler, B., Martin, A., Pohl, M., etal (2002). (VO)2P207 catalysed partial oxidation of propane in dense carbon dioxide, Catal. Lett., 78, pp. 259-265. 

Kerler, B. and Martin, A. (2001). Partial oxidation of propane using dense carbon dioxide, Chem. Eng. Technol, 24, pp. 41-44. 

Bettahar, M.M., Costentin, G., Savary, L., and Lavalley, J.C. On the partial oxidation of propane and propylene on mixed metal oxide catalysts. Appl. Catal. A Gen. 1996,145, 1-48. 

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