Propane direct oxidation

Kaddouri, A., Mazzocchia, C. and Tempesti, E. (1999). The Synthesis of Acrolein and Acrylic Acid by Direct Propane Oxidation with Ni-Mo-Te-P-O Catalysts, Catal. A Gen., 180, pp. 271-275. 

Two reaction mechanisms for partial propane oxidation exist in the literature. One of them proposes that the reaction starts with catalytic combustion followed by reactions of a lower rate, namely steam reforming, C02 reforming and water-gas shift [54], Aartun et al. [55] investigated both reactions. The other mechanism proposes that the partial oxidation reaction occurs directly at very short residence times [56], which are easier to achieve in the micro channels. 

The mechanism of formation of the cracking products had not been resolved at the time of publication of Shtern s review [2]. Semenov [3], however, had pointed out that the direct decomposition of prop-l-yl and prop-2-yl radicals at 300 °C was most unlikely, due to the large activation energies involved (27—29 and 40 kcal. mole", respectively). He therefore suggested the following alkylperoxy radical isomerization and decomposition reactions to explain the formation of propene and ethylene in propane oxidation, viz. 

However, there are also very important limitations. As we mentioned above, even in oxidation of methane and ethane many elementary reactions are not accessible for direct and detailed investigation. When we shift from ethane to propane, not only the number of carbon atoms in the molecule increases, but also the complexity of the reaction network. In particular, one may assume that even in propane oxidation the formation of complex oxygenate intermediates, including bi-radicals and complex peroxides, may take place. Although such compounds can play a principal role in kinetically relevant steps (such as chain-branching), up to now our knowledge about such compounds is negligible. 

Steffan et al. [45] isolated a propane-oxidizing strain ENV 425 which was able to convert MTBE to CO2. This strain has been used to establish a biobarrier in an MTBE plume in New Jersey [49]. An air-sparging system at the site was tested, but was not successful in degrading MTBE. Therefore, propane was added to the sparge air for 10-minute periods at intervals of three hours each. Since natural microbial populations were low at the site (perhaps because of an unfavorable environment of about pH 3), one month later a culture of the propane-oxidizing strain ENV 425 was injected directly... 

Remarkably, almost no H2 was detected until all the added 02 was consumed, indicating that the two reactions occur in a sequence. Once again, it appears that the contribution of steam reforming to the overall HC removal might be significant only at rich conditions when insufficient amounts of 02 are present for the direct oxidation reaction. This was confirmed when the H2 production was monitored in propane oxidation as a function of the stoichiometry of the feed (Barbier and Duprez 1992). In the presence of H20 and 02, propane can be oxidised according to the following reactions ... 

Pt(lwt%)Rh(0.2wt%) catalysts supported on AI2O3 and Ce02-Al203, carbon monoxide and propane oxidation by oxygen (direct oxidation), by steam (water gas shift and steam reforming) and by a mixture of oxygen and steam (oxy-WGS and oxy-steam reforming). 

NO addition in propane and oxygen flow increases up to 68 % propane oxidation whereas NO reduction reaches 45 %. This result shows a positive effect of NO in propane oxidation in agreement with recent work on H-ZSM-5 reporting that addition of small amounts of NOx drastically increases tlie propane conversion [17]. This suggests a direct reaction between propane and NOx. One of tlie O2 roles would be to eliminate strongly chemisorbed species evidenced under propane and NO flow, without O2 such species could poison active... 

Accordingly, a direct formation of MA from -butane can be concluded for both VPO and MoVTeNbO catalysts (Fig. 24.8a), while acrylic acid is mainly formed from propane by consecutive reactions (in which propylene is initially formed) (Fig. 24.6a). The olefinic intermediate is also initially formed in -butane oxidation over VPO, although presenting a different reactivity than that proposed in the case of propene. Thus, although the nature and strength of acid sites between the VPO or MoVTe(Sb)NbO (Mo-based MMO) catalysts are considerably different, the difference in the reaction network between propane oxidation (Fig. 24.6) and -butane oxidation (Fig. 24.8) is not directly related to the catalytic system, but to the different reactivity of the corresponding olefin intermediate (propene and butenes). ... 

Another well-studied process, in which significant progress has been made, involves the oxidation of propane to acrylic acid. (See Table 9.3.) These results are quite impressive, with selectivity reported in excess of 80%. By contrast, direct catalytic oxidation of isobutane to methacrylic acid has been less developed. Sumitomo has reported that 42% methacrylic acid can be obtained at 25% conversion. 

Numerous patents have been issued disclosing catalysts and process schemes for manufacture of acrylonitrile from propane. These include the direct heterogeneously cataly2ed ammoxidation of propane to acrylonitrile using mixed metal oxide catalysts (61—64). 

Some more recent processes have been developed which involve direct hydrogenation of the oil to the fatty acid and 1,2-propane diol. These high-temperature (>230 °C) and high-pressure processes generally use a copper chromium oxide catalyst. 

V-Sb-oxide based catalysts show interesting catal)dic properties in the direct synthesis of acrylonitrile from propane [1,2], a new alternative option to the commercial process starting from propylene. However, further improvement of the selectivity to acrylonitrile would strengthen interest in the process. Optimization of the behavior of Sb-V-oxide catalysts requires a thorough analysis of the relationship between structural/surface characteristics and catalytic properties. Various studies have been reported on the analysis of this relationship [3-8] and on the reaction kinetics [9,10], but little attention has been given to the study of the surface reactivity of V-Sb-oxide in the transformation of possible intermediates and on the identification of the sxirface mechanism of reaction. 

The increasing volume of chemical production, insufficient capacity and high price of olefins stimulate the rising trend in the innovation of current processes. High attention has been devoted to the direct ammoxidation of propane to acrylonitrile. A number of mixed oxide catalysts were investigated in propane ammoxidation [1]. However, up to now no catalytic system achieved reaction parameters suitable for commercial application. Nowadays the attention in the field of activation and conversion of paraffins is turned to catalytic systems where atomically dispersed metal ions are responsible for the activity of the catalysts. Ones of appropriate candidates are Fe-zeolites. Very recently, an activity of Fe-silicalite in the ammoxidation of propane was reported [2, 3]. This catalytic system exhibited relatively low yield (maximally 10% for propane to acrylonitrile). Despite the low performance, Fe-silicalites are one of the few zeolitic systems, which reveal some catalytic activity in propane ammoxidation, and therefore, we believe that it has a potential to be improved. Up to this day, investigation of Fe-silicalite and Fe-MFI catalysts in the propane ammoxidation were only reported in the literature. In this study, we compare the catalytic activity of Fe-silicalite and Fe-MTW zeolites in direct ammoxidation of propane to acrylonitrile. 

In the direct ammoxidation of propane over Fe-zeolite catalysts the product mixture consisted of propene, acrylonitrile (AN), acetonitrile (AcN), and carbon oxides. Traces of methane, ethane, ethene and HCN were also detected with selectivity not exceeding 3%. The catalytic performances of the investigated catalysts are summarized in the Table 1. It must be noted that catalytic activity of MTW and silicalite matrix without iron (Fe concentration is lower than 50 ppm) was negligible. The propane conversion was below 1.5 % and no nitriles were detected. It is clearly seen from the Table 1 that the activity and selectivity of catalysts are influenced not only by the content of iron, but also by the zeolite framework structure. Typically, the Fe-MTW zeolites exhibit higher selectivity to propene (even at higher propane conversion than in the case of Fe-silicalite) and substantially lower selectivity to nitriles (both acrylonitrile and acetonitrile). The Fe-silicalite catalyst exhibits acrylonitrile selectivity 31.5 %, whereas the Fe-MTW catalysts with Fe concentration 1400 and 18900 ppm exhibit, at similar propane conversion, the AN selectivity 19.2 and 15.2 %, respectively. On the other hand, Fe-MTW zeolites exhibit higher AN/AcN ratio in comparison with Fe-silicalite catalyst (see Table 1). Fe-MTW-11500 catalyst reveals rather rare behavior. The concentration of Fe ions in the sample is comparable to Fe-sil-12900 catalyst, as well as... 

Alkyl and aryl C-nitroso compounds contain a nitroso group (-N=0) directly attached to an aliphatic or aromatic carbon. As compounds with a nitroso group attached to a primary or secondary carbon exist primarily as the oxime tautomer, the stable examples of C-nitroso compounds contain nitroso groups attached to tertiary carbons, such as 2-methyl-2-nitroso propane (1, Fig. 7.1) or nitroso groups attached to carbons bearing an electron-withdrawing group (-CN, -N02, -COR, -Cl, -OAc, Fig. 7.1). Oxidation of alkyl and aryl hydroxylamines provides the most direct route to alkyl and... 

This chapter will begin with a discussion of the role of chiral copper(I) and (II) complexes in group-transfer processes with an emphasis on alkene cyclo-propanation and aziridination. This discussion will be followed by a survey of enantioselective variants of the Kharasch-Sosnovsky reaction, an allylic oxidation process. Section II will review the extensive efforts that have been directed toward the development of enantioselective, Cu(I) catalyzed conjugate addition reactions and related processes. The discussion will finish with a survey of the recent advances that have been achieved by the use of cationic, chiral Cu(II) complexes as chiral Lewis acids for the catalysis of cycloaddition, aldol, Michael, and ene reactions. 

A possible economically attractive alternative would be the production of acrylic acid in a single step process starting from the cheaper base material propane. In the nineteen nineties the Mitsubishi Chemical cooperation published a MoVTeNb-oxide, which could directly oxidise propane to acrylic acid in one step [6], Own preparations of this material yielded a highly crystalline substance. Careful analysis of single crystal electron diffraction patterns revealed that the MoVTeNb-oxide consists of two crystalline phases- a hexagonal so called K-Phase and an orthorhombic I-phase, which is the actual active catalyst phase, as could be shown by preparing the pure phases and testing them separately. 

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