Propane partial oxidation

Hazbum [2.129] in a U.S. patent, reported ethane and propane partial oxidation to ethylene and propylene oxides using a TiYSZ mixed O Velectron conducting membrane with silver deposited on the hydrocarbon side of the membrane as a catalyst. For the ethane partial oxidation reaction catalyst at 250-400 C, the ethylene oxide selectivity was (>75 %) but the ethane conversion was low (<10 %), limited by the low membrane oxygen flux at these temperatures. For the partial oxidation reaction to propylene oxide yields close to 5 % were reported. Using porous membranes Santamaria and coworkers (Mallada et al. [2.252, 2.253, 2.254, 2.255]), Mota et al. [2.256], and Xue and Ross [2.257] recently studied the oxidation of butane into maleic anhydride. 

The interested reader is referred to surveys of research in the thermal reaction by Medley and Cooly (38) and by Rovertson (49), who cover the field of propane partial oxidation before 1960. Process variables are reported by Satterfield et al (50, 51), Mitchell (40), and Newitt (42). Mechanism, surface effects, and theoretical considerations are given in papers by Albright et al (1, 2), Ferguson and Yokley (21), and Knox et al (33, 34). 

Zhan Z, Barnett SA (2005) Use of a catalyst layer for propane partial oxidation in solid oxide fuel cells. Solid State Ionics 176 871... 

Godefroy, A., G.S. Patience, T. Tzakova, D. Garrait and J.-L. Dubois (2009). Reactor technologies for propane partial oxidation to acrylic acid, Chem. Eng. TechnoL, 32, pp. 1-8. 

Considering the nature of the reactants, the interactions between reactants in gas phase, reactants with catalyst, and the subsequent reactions on the catalyst surface, three main classes of catalysts have been proposed for propane partial oxidation ... 

Propane is a homologue of -butane with one less CH2 group and therefore, the same mechanism of catalyst operation may apply. Unfortunately, VPO catalysts are not particularly effective in propane selective oxidation (<15% yield to acrylic acid) due to lesser reactivity of propane (higher reaction temperatures) and lesser stability of acrylic acid compared with maleic anhydride (enhanced total combustion) [29]. At the higher reaction temperatures, coke is also formed in some cases on the catalyst surface [30]. Typical catalytic results for propane partial oxidation over VPO catalysts, reported in the literature, are summarized in Table 13.2. 

Deoxygenation can oxidize the metal surfaces. It was found that the partially oxidized Cu surface was the most active in the isomerization of methy-loxirane to propanal.288 The same is true for Ni. Therefore, it is very likely that the metal ions produced by the oxidation of copper or nickel surfaces during deoxygenation play an important role in isomerization to aldehyde. 

Vanadia catalysts exhibit high activity and selectivity for numerous oxidation reactions. The reactions are partial oxidation of methane and methanol to formaldehyde, and oxidative dehydrogenation of propane to propene and ethane to ethcnc.62 62 The catalytic activity and selectivity of... 

The partial oxidation method is normally used for heavier feedstocks, everything from naphtha to residual fuel, in those places where natural gas or light hydrocarbons (ethane, propane, or butane) are not readily available. 

More recently, it was demonstrated that 80 is a catalyst for the partial oxidation of olefins using dioxygen (230). For example, dry propene was oxidized to acetone when water vapor was present in the catalyst stream, some propanal could also be detected. Other reactions reported included the conversion of styrene to acetophenone and phenylacetaldehyde in an 80 20 product ratio, and 2-norbornene to 2-norbomanone and cyclohexene-4-carboxyaldehyde in a 70 30 product ratio. 

A prototype study for this issue was performed for the conversion of ethane to acetic acid [71] and the same group highlighted in an earlier comparative study of C3 oxidation [54] that, although initial propane activation is a difficult step, subsequent reactions associated with either excessive residence times of intermediates or with branching of reaction sequences into total oxidation may interfere with the overall selectivity to partial oxidation products. 

The synthesis of intermediates and monomers from alkanes by means of oxidative processes, in part replacing alkenes and aromatics as the traditional building blocks for the chemical industry [2]. Besides the well-known oxidation of n-butane to maleic anhydride, examples of processes implemented at the industrial level are (i) the direct oxidation of ethane to acetic acid, developed by Sabic (ii) the ammoxidation of propane to acrylonitrile, developed by INEOS (former BP) and by Mitsubishi, and recently announced by Asahi to soon become commercial (iii) the partial oxidation of methane to syngas (a demonstration unit is being built by ENI). Many other reactions are currently being investigated, for example, (i) the... 

When X is above unity and propane is oxidized completely, the equilibrium oxygen partial pressure can be given by the combination of eqs. (6) and (7)... 

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. 

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).

Flego [1] recommends the use of micro devices for automated measurement and microanalysis of high-throughput in situ characterization of catalyst properties. Murphy et al. [5] stress the importance of the development of new reactor designs. Micro reactors at Dow were described for rapid serial screening of polyolefin catalysts. De Bellefon ete al. used a similar approach in combination with a micro mixer [6], Bergh et al. [7] presented a micro fluidic 256-fold flow reactor manufactured from a silicon wafer for the ethane partial oxidation and propane ammoxidation. 

Several profound theoretical and experimental studies performed on the laboratory scale have been reported which focus on the use of various configurations of membrane reactors as a reactant distributor in order to improve selectivity-conversion performances. In particular, several industrially relevant partial oxidations have been investigated, including the oxidative coupling of methane [56], the oxidative dehydrogenations of propane [57], butane [58], methanol [59, 60], the epoxidation of ethylene [61], and the oxidation of butane to maleic anhydride [62]. 

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). 

Reduction of by-products can be achieved by only partially oxidizing the propan-2-ol, and by carrying out the oxidation in several consecutive steps, at decreasing temperatures.26 The hydrogen peroxide yield is typically 90-94% with respect to the propan-2-ol, and the acetone yield is 92-94%. 

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. 

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