Propane oxidation characteristics

In order to clarify the resistivity characteristics of the specimens, we obtained the relationship between an equilibrium oxygen partial pressure and the oxygen excess ratio from both theoretical calculations and measurements using the oxygen sensor. The complete propane oxidation can be described by the following reaction. 

To determine the characteristics of the electro-oxidation of propane, a series of half-cell experiments were conducted in 3 M sulfuric acid at 80 °C with various electrocatalytic materials, including R, Pt/Ru, and Pt/Sn catalyst materials. As illustrated in Fig. 1.5, both the Pt and Pt/Ru electrodes showed dramatically less polarization upon propane oxidation compared to the Pt/Sn... 

In addition to propane, the electro-oxidation characteristics of methane on R gas diffusion electrodes in half-cells was investigated. Methane displayed a much greater resistance to oxidation compared with propane, with large polarization occurring at low current densities (i.e., 0.1-0.3 mA/cm ). One factor contributing to the poor performance is the poor solubility of methane in the electrolyte, leading to mass transfer limitations at higher current densities. 

We must note that the acid characteristics of the latter three catalysts are different, and both the number and strength of Brpnsted acid sites decreases as follows MoVNbO (mainly Brpnsted acid sites) >V0x/Al203 (mainly Lewis acid sites) > MoVTeNbO. Accordingly, and in addition to the presence of an alkane activation site (V + sites), an a-hydrogen abstracting site (Te + or Sb +) and an 0-insertion site (Mo " ") are also present in a well-defined host structure, i.e. orthorhombic Te2M2oOs7 (Ml phase, with M = Mo, V, Nb). Therefore, the selective catalysts for propane oxidation to acrylic acid should have a low number of Brpnsted acid sites. Indeed, it has been reported that elimination of Brpnsted acid sites in both... 

As for the products of the gas-phase oxidation of butane, pentane, and heavier hydrocarbons at high pressures, only disembodied data can be foimd. The authors of [26] studied the oxidation of normal butane, pentane, and heptane. Among the products of the interaction of n-butane with oxygen at pressures from 33 to 160 atm, along with the products characteristic of propane oxidation, butyl alcohols were found, their fraction increasing with the pressme. In [93], the oxidation of isobutane was reported to produce acetone, ferf-butanol, and tert-butyl hydroperoxide. 

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. 

Lube oil solvent refining includes a collection of subprocesses improving the quality of lubricating oil stock. The raffinate or refined lube oils obtain improved viscosity, color, oxidation resistance, and temperature characteristics. A particular solvent is selected to obtain the desired quality raffinate. The solvents include furfural, phenol, sulfm dioxide, and propane. 

V-containing silicalite, for example, has been shown to have different catalytic properties than vanadium supported on silica in the conversion of methanol to hydrocarbons, NOx reduction with ammonia and ammoxidation of substituted aromatics, butadiene oxidation to furan and propane ammoxidation to acrylonitrile (7 and references therein). However, limited information is available about the characteristics of vanadium species in V-containing silicalite samples and especially regarding correlations with the catalytic behavior (7- 6). 

The reaction of propylene on ZrC>2 exhibits the same characteristics as on other oxides. Propane-d2, for example, is selectively formed in the deuteration process, with no hydrogen exchange in propylene215. New features appear, however, when zirconia is dispersed on other oxides (alumina, silica, titania)215,216. A considerable rate increase is observed and exchange in propylene proceeds simultaneously with addition via the associative mechanism through the common intermediate n-propyl and s-propyl species. 

Early studies of slow combustion and ignition characteristics of organic compounds showed that although methanol, ethanol and propanol are more readily oxidized than methane, ethane and propane, the situation is reversed with butanol and the higher homologues [1—4]. 

It seems that zeolite membranes may not be the best choice as catalytic contactors and oxygen distributors to enhance selectivity in oxidative dehydrogenation of propane. This may be due in part to the intrinsic catalytic activity of the zeolite material for this reaction, which probably exerts a nonselective contribution. Therefore, this specific application operates at conditions that do not make use of the most important properties, which are characteristic of zeolite membranes. More efficient approaches for selectivity enhancement can be obtained with zeolite membranes, as shown in the next section. 

Julbe A, Farmsseng D, Jalibert JC, Mirodatos C, and Guizard C. Characteristics and performance in the oxidative dehydrogenation of propane of MFI and V-MFI zeolite membranes. Catal Today 2000 56 199-209. 

NO (reactant) and CO (product) molecules were used as IR probes of the copper oxidation state in H-Cu-ZSM-5 catalysts. CO adsorption is specific to Cu sites. Its characteristic band at 2158 cm provides quantitative results on integrating its molar extinction-coefficient (e) NO decomposes oxidizing Cu to Cu. Propane and oxygen in a special IR reactor cell always yielded chemisorbed CO. Use of e indicates the NO influence on Cu state. 

---