TEOM

W. T. TEom son, Agricultural Chemicals, Book III—Miscellaneous Agricultural Chemicals, 1991 —92 Revision, Thompson PubHcations, Eresno, Calif.,... 

The tapered-element oscillating microbalance (TEOM) sensor, as described by Patashnick and Rupprecht, consists of an oscillating tapered tube with a filter at its free end (Fig. 13.40). The mass of the filter increases due to the collected aerosol and produces a shift in the oscillation frequency of the tapered tube that is directly related to mass. 

The TEOM sampler draws air through a hollow tapered tube, the wide end of the tube being fixed, while the narrow end oscillates in response to an applied electric field. The narrow end of the tube contains the filter cartridge. The sampled air flows from the sampling inlet, through the filter and tube, to a flow controller. The tube-filter unit acts as a simple harmonic oscillator with ... 

TEOM series 7000 source parriculare monitor. Albany, NY Rupprecht Patashnick Co., Inc. (1998). 

Veenstra, T. D. Martinovic, S. Anderson, G. A. Pasa-Tolic, L. Smith, R. D. Pro-teome analysis using selective incorporation of isotopically labeled amino acids. /. Am. Soc. Mass Spectrom. 2000,11, 78-82. 

Jungblut PR et al. Comparative pro-teome analysis of Helicobacter pylori. Mol Microbiol 2000 36 710-725. 

King, A. M., Pless-Mulloli, T., Merefield, J. Stone, I. 2000. TEOMs and tire volatility of UK non-urban PM10 a regulatory dilemma Atmospheric Environment, 34, 3211-3212. 

Curwen, R.S., Ashton, P.D., Johnston, D.A. and Wilson, R.A. (2004) The Schistosoma mansoni soluble pro-teome a comparison across four life-cycle stages. Molecular and Biochemical Parasitology 138, 57-66. 

For the studies described in this chapter, a novel system was employed, namely the tapered element oscillation microbalance (TEOM), to monitor the dynamic process of carbon formation under real C02 reforming conditions. The use of TEOM enables carbon formation to be measured in situ, and kinetic studies of carbon formation to be performed at different partial pressures of CH4 and CO. 

TEOM Measurement of Carbon Formation in C02 Reforming of Methane... 

Figure 9.6 compares the weight percentages of carbon estimated by the TEOM and TPO-IR on the samples after reaction at CH4 C02 C0 H2 molar ratios of 1 1 0 0, 0.75 0.75 0.5 0.5, and 0.5 0.5 1 1. The good linear correlation between the weight of carbon measured by both methods confirmed that these results were consistent. Based on this comparison, it was concluded that the TEOM was effective for studying the dynamic process of carbon formation on catalysts. 

Figure 9.6 Comparison of the weight percentage of carbon formation measured by TEOM and TPO-IR (Carbon Analyzer) after reaction over 25 mg ICI R15513 catalysts at 0.1 MPa and 923 K at different feed gas compositions simulating (1) initial C02...

The TEOM results presented in Figure 9.4 showed that CO in the product stream of C02 reforming might represent another major component contributing to carbon formation. Consequently, in an effort to further elucidate the contribution of CH4 and CO to carbon formation, a kinetics study on the effect of the partial pressure of CH4 or CO (PCH4 or PCo) on the carbon formation rate was conducted under conditions of 0.1 MPa and 923 K. 

Kinetics studies on carbon formation, using the TEOM, have established that both CH4 in the reactants and CO in the products, may serve as the source of carbon formation in the C02 reforming reaction. In an equimolar C02-CH4 reforming condition, CO in the product stream is most likely the major source of carbon formation. However, carbon formed in C02 reforming from a feed without containing CO shows a more filamentous morphology, which is more difficult to be oxidized this contrasts with carbon formed from a feed containing CO, which mostly encapsulates metal particles in the catalyst and is relatively easily oxidized. Unfortunately, it is currently unclear as to whether these differences result from the presence of CO in the feed, or from the different times on-stream to accumulate similar amounts of carbon due to different carbon formation rates when the feeds contain CO or no CO. 

A Brief Description of the TEOM, TPO-IR, and TEM Experiments TEOM Measurements... 

The in situ measurement of carbon deposition by the TEOM provides more accurate information on carbon formation behavior than do ex situ approaches such as TPH and TPO, especially when the carbon formation rates change with the time on-stream. 

In the case when H20 addition was necessary, H20 was pumped into the TEOM through a separate line connected to the preheating zone of the TEOM. The gases and vaporized steam in the preheating zone were mixed and flowed into the TEOM. 

---