Carbonaceous materials, reactivity

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials No reaction Stability During Transport If contaminated with carbonaceous materials, can become an explosive which is sensitive to shock and friction. Ready detonates or explodes Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

The physicochemical properties of carbonaceous materials can be altered in a predictable manner by different types of treatments. For example, heat treatment of soft carbons, depending on the temperature, leads to an increase in the crystallite parameters, La and Lc and a decrease in the d(0 0 2) spacing. Besides these physical changes in the carbon material, other properties such as the electrical conductivity and chemical reactivity are changed. A review of the electronic properties of graphite and other types of carbonaceous materials is presented by Spain [3],... 

This XPS investigation of small iron Fischer-Tropsch catalysts before and after the pretreatment and exposure to synthesis gas has yielded the following information. Relatively mild reduction conditions (350 C, 2 atm, Hg) are sufficient to totally reduce surface oxide on iron to metallic iron. Upon exposure to synthesis gas, the metallic iron surface is converted to iron carbide. During this transformation, the catalytic response of the material increases and finally reaches steady state after the surface is fully carbided. The addition of a potassium promoter appears to accelerate the carbidation of the material and steady state reactivity is achieved somewhat earlier. In addition, the potassium promoter causes a build up on carbonaceous material on the surface of the catalysts which is best characterized as polymethylene. 

The hydrogen sulfide adsorption on the HKUST-l/GO composites was only studied in moist conditions [44]. The choice was based on the presence of water in the ambient air and on the extensive studies of H2S reactive adsorption on carbonaceous materials where water was important for dissociation of hydrogen sulfide before its further reaction with surface active sites [5]. Here up to 20 wt% of H2S was adsorbed in the composite with the smallest content of GO. [44]. An increase in the GO content resulted in a decrease in the capacity but nevertheless it was higher than that on MOF... 

Bandosz TJ. Towards understanding reactive adsorption of small molecule toxic gases on carbonaceous materials, DOI 10.1016/j.cattod.20U. 08.017... 

Pt-Re Surface carbonaceous material determined and its reactivity studied. n-Hexane reforming. 

Presence of Re allows an increase in amount of reactive hydrogen available, and so lowers formation of carbonaceous material.87. ... 

Another phenomenon commonly observed in the analysis of catalysts is the deposition of carbon in the area of beam concentration (23). In many instances this can be associated with residual organic material left on the carbon coated grids. We have also found that the catalyst particles themselves may have organic debris on them which subsequently react in the electron beam creating carbonaceous material. Unfortunately, this may disrupt observation of small crystallites and/or the quantitative analysis of the particle. For example, STEM examination of a Fischer-Tropsch catalyst which had wax deposited on the alumina particles containing Ru crystallites was made. Due to the reactivity of the wax in the electron beam the particles turned progressively darker as a function of exposure time, until finally the Ru crystallites were not... 

In the laboratory, the study of the properties of pure polyynes and poly-cumulenes is inhibited because of their extreme reactivity with oxygen and the formation of cross linked chains. In space, refractory dust made of silicates or carbonaceous material are formed in the atmosphere of evolved stars and released into the interstellar medium (ISM). In dense molecular clouds ( Hydrogen > 10 cm, 10-20 K) atoms and molecules that... 

The rate of the oxidation process is determined by the reactivity of the starting carbon and oxidizer. The greater the reactivity of the substrates the lower the temperature of the process in which uniform formation of the pores in the granules is observed. In the case of carbonaceous materials the cokes of brown coals show the greatest reactivity, and the cokes of hard coals the smallest activity. The cokes of pit coals show an intermediate reactivity. This is connected with the earlier mentioned ordering of the crystallographic structure of carbon, which is of significant importance in the case of modification of carbon deposits contained in the carbon-mineral adsorbents in which the carbonaceous compound may be characterized by a differentiated chemical and physical structure. Thus the surface properties of hydrothermally modified complex adsorbents are defined by the course of three processes ... 

We now report on the reactivity of carbonaceous deposits which can be laid down on the Cu/ZSM-5 catalysts by exposure to the reaction mixture at low temperatures. As in our earlier study [16], carbonaceous material referred to for simplicity as coke was deposited by exposing the catalysts to the reaction mixture at 473 K. The reactivity of material deposited was then examined by exposing the catalyst at 473 K to the same concentration of NO and oxygen as present in the reaction mixture, (but no propene), and then heating to ca 920 K at 10 K min. The conversion of NO was monitored by the chemiluminescent detector, which has a response time of < 1 s. 

Vang et al. (289) used DTA to characterize the reactivities of three carbonaceous materials toward oxygen and carbon dioxide. A pseudo-third-order reaction can give a bifurcated peak in the DTA curve. The idea of the existence of two kinds of carbonaceous materials based on a bifurcated peak, as has often appeared in the literature, should be asserted with caution. 

Polynuclear AROMATIC HYDROCARBONS and heterocycles are quite abundant in fossil fuel materials such as coal and petroleum, and insights into new chemistry can potentially lead to developments in the areas of fuels, lubricants, chemicals, and carbonaceous materials. The study of large aromatic hydrocarbons is long-standing, and the symposium upon which this book is based was held on the 30th anniversary of a symposium, Polycyclic Hydrocarbons , held in Atlantic City in September 1956 and published in Volume 1 of the Preprints of the Petroleum Division. We are fortunate to have as one of the contributors to this book, Michael Szwarc, who was an author of one of the papers of the 1956 symposium ( Reactivities of Deformed Aromatic Hydrocarbons ). 

Although numerous reviews on the characteristics of carbonaceous materials have been published [51-54,59-63], in this chapter we focus on a detailed description of carbon surface chemistry and its importance for catalytic processes and those involving reactive adsorption. Thus, the classification of surface groups is followed by an overview of methods of surface modification and characterization, with a brief description and examples of their role in reactive adsorption and catalysis. 

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