Catalyst characterization thermogravimetric analysis

Multiwall carbon nanotubes (MWCNTs) have been synthesized by catalytic chemical vapor deposition (CCVD) of ethylene on several mesoporous aluminosilicates impregnated with iron. The aluminosilicates were synthesized by sol-gel method optimizing the Si/Al ratios from 6 to 80. The catalysts are characterized by nitrogen adsorption, X-ray diffraction, 27A1 NMR, thermogravimetric analysis (TGA) and infrared. The MWCNTs are characterized by TGA and transmission and scanning electron microscope. 

For this purpose, all three catalyst supports were initially synthesized by a chemical vapor deposition (CVD) process and thereafter, using a wet impregnation method, loaded with cobalt as the active component for FTS. The as-synthesized Co/nanocatalysts were then characterized by applying electron microscopic analysis as well as temperature-programmed desorption, chemi- and physisorption measurements, thermogravimetric analysis, and inductively coupled plasma... 

Results of Carbon Nanomaterial Catalyst Characterization ICP, Chemisorption, Physisorption, Thermogravimetric Analysis (TG)... 

The fresh and spent catalysts were characterized with the physisorption/chemisorption instrument Sorptometer 1900 (Carlo Erba instruments) in order to detect loss of surface area and pore volume. The specific surface area was calculated based on Dubinin-Radushkevich equation. Furthermore thermogravimetric analysis (TGA) of the fresh and used catalysts were performed with a Mettler Toledo TGA/SDTA 851e instrument in synthetic air. The mean particle size and the metal dispersion was measured with a Malvern 2600 particle size analyzer and Autochem 2910 apparatus (by a CO chemisorption technique), respectively. 

The next stage of characterization focuses upon the different phases present within the catalyst particle and their nature. Bulk, component structural information is determined principally by x-ray powder diffraction (XRD). In FCC catalysts, for example, XRD is used to determine the unit cell size of the zeolite component within the catalyst particle. The zeolite unit cell size is a function of the number of aluminum atoms in the framework and has been related to the coke selectivity and octane performance of the catalyst in commercial operations. Scanning electron microscopy (SEM) can provide information about the distribution of crystalline and chemical phases greater than lOOnm within the catalyst particle. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) can be used to obtain information on crystal transformations, decomposition, or chemical reactions within the particles. Cotterman, et al describe how the generation of this information can be used to understand an FCC catalyst system. 

The precursor and the calcined catalyst were characterized by various techniques such as nitrogen adsorption, mercury porosimetry, X-ray diffraction (XRD), atomic emission spectrometry by inductively coupled plasma (ICP), thermogravimetric analysis, and temperature-programmed reduction (TPR). More details about the catalyst preparation and characterization can be found in a previous work (22). 

The other posibility for characterizing structural properties of inorganic sorbents deals with the thermogravimetric analysis. By means of this analysis the pore size distribution, pore volume and specific surface area of adsorbents and catalysts which are fundamental adsorption characteristics may be obtained. 

The catalysts were characterized by N2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), temperature-programmed desorption of ammonia (NH3-TPD), X-ray diffraction (XRD), Raman spectroscopy, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS). The procedures and experimental conditions have been detailed elsewhere [9]. 

Introduction of an aliphatic substituent (Scheme 12.2, R= Bu) solved the solubility problem. Deep red, stable to the atmosphere polymers soluble in benzene, CH2CI2, and tetrahydrofuran (THF) were obtained with a W-based catalyst. The molecular weight of the product increased qualitatively with the monomer/catalyst ratio, and polymers with M > 300,000 were obtained and characterized by thermogravimetric analysis, GPC, and UV/vis spectroscopy. The results were consistent with a moderate degree of conjugation in the polymer [7]. 

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