Oxidation propane

Products obtained by propane-selective oxidation have been analyzed by gas sensor systems [19, 26]. Usually, several or multiple kinds of compounds are produced during the selective oxidation of propane. The formation of CO, C02, aldehydes such as acrolein, and ketone were observed over iron-silica catalysts [28, 29]. During the initial stage of catalyst investigation, the conversion of propane and the selectivity toward useful oxygenate products as chemical resources are of interest. Semiconductor-type gas sensors selective toward the oxygenate were employed to estimate the yield of oxygenate products, with a combination of the potentiometric CO sensor and the ND-IR C02 sensor [30]. 

194 I 8 Cos Sensor Technology for High-Throughput Screening in Catalysis 

Oxygenate sensor 2 (Sn02 with 13% Si02-Al203) 

40 s for the oxygenate, CO and C02 sensors, respectively. The slower response of the CO sensor is due to the presence of the active carbon filter. After 120 s, the output signal of each gas sensor reached 99% for the oxygenate sensors, 97% for the CO sensor and 100% for the C02 sensor. The response time of this gas sensor system is less than 2 min, even for a transient change in the products. This is much faster than the 40-50 min needed for precise gas analysis by conventional FID-GC. 

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Propane. The VPO of propane [74-98-6] is the classic case (66,89,131—137). The low temperature oxidation (beginning at ca 300°C) readily produces oxygenated products. A prominent NTC region is encountered on raising the temperature (see Fig. 4) and cool flames and oscillations are extensively reported as compHcated functions of composition, pressure, and temperature (see Fig. 6) (96,128,138—140). There can be a marked induction period. Product distributions for propane oxidation are given in Table 1. 

Wackett LP, GA Brusseau, SR Householder, RS Hanson (1989) Survey of microbial oxygenases trichloroethylene degradation by propane-oxidizing bacteria. Appl Environ Microbiol 55 2960-2964. 

Steffan RJ, K McClay, S Vainberg, CW Condee, D Zhang (1997) Biodegradation of the gasoline oxygenates methyl ferf-butyl ether, ethyl ferf-butyl ether, and amyl tcrt-butyl ether by propane-oxidizing bacteria. Appl Environ Microbiol 63 4216-4222. 

Streger SH, CW Condee, AP Togna, ME Deflaun (1999) Degradation of halohydrocarbons and brominated compounds by methane- and propane-oxidizing bacteria. Environ Sci Technol 33 4477-4482. 

Catalytic testings have been performed using the same rig and a conventional fixed-bed placed in the inner volume of the tubular membrane. The catalyst for isobutane dehydrogenation [9] was a Pt-based solid and sweep gas was used as indicated in Fig. 2. For propane oxidative dehydrogenation a V-Mg-0 mixed oxide [10] was used and the membrane separates oxygen and propane (the hydrocarbon being introduced in the inner part of the reactor). 

Most of the results have been already partly presented in [9] (isobutane dehydrogenation) and [10] (propane oxidative dehydrogenation). Let us recall that the membrane presented in this paper has been associated with a fixed bed catalyst placed within the tube. 

In the propane oxidative dehydrogenation, where the membrane separates the two reactants, a 20% increase in the yield was observed with respect to a conventional reactor working at isoconversion [10]... 

Steffan, R.J., Farhan, H.H., and Condee, C.W., Bioremediation at a New Jersey site using propane-oxidizing bacteria, in MTBE Remediation Handbook, Moyer, E.E. and Kostecki, P.T., Eds, Amherst Scientific Publishers, Amherst, MA, 2003. 

Ceria-based OSC compounds may have an impact on oxidation reactions especially when the catalysts are working around the stoichiometry (as this is the case under TW conditions). One of the first systematic studies was reported by Yu Yao [53,54], Most results were obtained in 02 excess (0.5% CO + O.5% 02 or 0.1% HC+ 1% 02). Several series of Pt, Pd and Rh/Al203 of various dispersion, as well as metal foils, were investigated in CO, alkane and alkene oxidation. The effect of metal dispersion in CO and the propane oxidation are shown in Figure 8.5. 

In every case, large particles of metal are more active in oxidation than the smallest ones. CO oxidation is moderately structure-sensitive (less than one order of magnitude between metal foil and much dispersed catalysts). By contrast, propane oxidation (and in general oxidation of small alkanes) are strongly stmcture-sensitive (two orders of magnitude between large and small particles). Rate equations were also expressed as... 

Figure 8.5. Effect of metal dispersion on turnover frequencies in CO and propane oxidation (M/A1203 catalysts). Adapted from the data of Yu Yao [53,54].

Comparison of promoted alkaline-earth oxide catalysts prepared through evaporation and sol-gel methods by their catalytic performance in propane oxidative dehydrogenation... 

Alkaline earth oxides (AEO = MgO, CaO, and SrO) doped with 5 mol% Nd203 have been synthesised either by evaporation of nitrate solutions and decomposition, or by sol-gel method. The samples have been characterised by chemical analysis, specific surface area measurement, XRD, CO2-TPD, and FTIR spectroscopy. Their catalytic properties in propane oxidative dehydrogenation have been studied. According to detailed XRD analyses, solid solution formation took place, leading to structural defects which were agglomerated or dispersed, their relative amounts depending on the preparation procedure and on the alkaline-earth ion size match with Nd3+. Relationships between catalyst synthesis conditions, lattice defects, basicity of the solids and catalytic performance are discussed. 

To perform the dissociation of the hydrocarbon to alkyl radicals with C—C bond scission, a hydrocarbon molecule should absorb light with the wavelength 270-370 nm. However, alkanes do not absorb light with such wavelength. Therefore, photosensitizers are used for free radical initiation in hydrocarbons. Mercury vapor has been used as a sensitizer for the generation of free radicals in the oxidized hydrocarbon [206-212], Nalbandyan [212-214] was the first to study the photooxidation of methane, ethane, and propane using Hg vapor as photosensitizer. Hydroperoxide was isolated as the product of propane oxidation at room temperature. The quantum yield of hydroperoxide was found to be >2, that is, oxidation occurs with short chains. The following scheme of propane photoxidation was proposed [117] ... 

Jibril, B.Y. Propane oxidative dehydrogenation over chromium oxide-based catalysts. Appl. Catal. A General 2004, 264, 193-202. 

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. 

The reaction of propane in CaY appears to be an authentic thermal Frei oxidation [55], Propane is, itself, inert in CaY but slowly oxidizes at 21°C with complete selectivity for formation of acetone. In contrast, propane oxidation in BaY did not commence until the temperature was raised to 55°C, but even at this elevated temperature, the high regioselectivity for acetone formation argues for a thermal Frei oxidation mechanism,... 

Propane Oxidative Dehydrogenation on V-containing Silicalite. Reported in... 

Figure 1 is the catalytic behavior of VSU545 in propane oxidative dehydrogenation to propylene. Selectivities to propylene in the range of60-80% are obtained up to propane conversions of about 20-25% and reaction temperatures up to around 450- 500 C. For higher reaction temperatures and conversions the selectivity decreases due both to the formation of carbon oxides and of aromatics. As compared to pure silicalite, a significant increase in both the selectivity to propylene and the activity in propane conversion is observed. 

Figure 1. Propane oxidative dehydrogenation to propylene on VSil545. Exp. conditions flow reactor tests with 2.8% C3, 8.4% O2 in helium. 4.2 g of catalyst with a total flow rate of 3.1 L/h (STP conditions).

Figure 2. Comparison of the catalytic behavior of VSil samples in propane oxidative dehydrogenation to propylene. Conversion of propane and selectivity to propylene at 470 C. Exp. conditions as in Fig. 1.

Figure 4. Comparison of the behavior of VSil545 in propane oxidative dehydrogenation using N2O or O2 as oxidizing agents. Exp. conditions as in Fig. 1. The dotted lines represent the propane conversion and propylene selectivity observed in the absence of the catalyst (homogeneous gas phase). The activity of the catalyst in the absence of O2 or N2O is similar to that observed in the homogeneous gas phase, but the selectivity to propylene (around 50-60%) is lower.

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