Temperature conversion elemental analyzers

Thermo Fisher Scientific, Waltham, MA (2001) ThermoFinnigan High Temperature Conversion Elemental Analyzer (TC/EA) Operating Manual. Ident. No. 112 76 01, Issue 11/2001. 

The bomb method for sulfur determination (ASTM D129) uses sample combustion in oxygen and conversion of the sulfur to barium sulfate, which is determined by mass. This method is suitable for samples containing 0.1 to 5.0% w/w sulfur and can be used for most low-volatility petroleum products. Elements that produce residues insoluble in hydrochloric acid interfere with this method this includes aluminum, calcium, iron, lead, and silicon, plus minerals such as asbestos, mica, and silica, and an alternative method (ASTM D1552) is preferred. This method describes three procedures the sample is first pyrolyzed in either an induction furnace or a resistance furnace the sulfur is then converted to sulfur dioxide, and the sulfur dioxide is either titrated with potassium iodate-starch reagent or is analyzed by infrared spectroscopy. This method is generally suitable for samples containing from 0.06 to 8.0% w/w sulfur that distill at temperatures above 177°C (351°F). 

In order to assess temperature limits for full conversion and syngas production and the possibility of carbon and carbonate formation, the thermodynamics of the CDS reaction with wustite have been analyzed in detail. Low temperatures (< 500 K) favor the formation of elemental carbon while at the same time guaranteeing complete reoxidation to magnetite. Increasing temperatures result in decreased conversion and higher amounts of the nonstoichiometric iron oxide Fei yO. Stable formation of CO is only expected for temperatures exceeding 800 K, at which a very limited degree of conversion is predicted for the static system [9]. 

This study focused on the deactivation of the Mn/Ce catalysts during reaction. The catalytic oxidation of phenol in aqueous solution to carbon dioxide, water and other side-products was selected as the test reaction. Catalysts were prepared from amorphous precursors using the citrate method and controlling the calcination temperature. Activity performance as a function of the time on stream was studied by simultaneously analyzing the conversion of phenol, the total organic carbon content of the catiyst, the cations eluted and the elemental composition of both cerium and manganese. Experimental conditions were widely varied. Fresh and used catalysts were also analyzed by BET surface area, X-Ray Diffraction and X-Ray Photoelectron Spectroscopy. 

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