Thermochemical Degradation Research Articles

96/03494 Macromolecular structure of brown coal and reactivity for thermochemical degradation

96/03494 Macromolecular structure of brown coal and reactivity for thermochemical degradation

Preparation and characterization of novel IR-transparent semiconducting carbonaceous materials

Infrared (IR) spectroscopy was used to study the solid products of the thermochemical degradation reaction of poly(vinylidene chloride) foils. Samples of foils heated at 200 °C in air and in the range of 300–650 °C in ammonia atmosphere. The degradation reaction produces new carbonaceous material with semiconducting properties.

Fade and wear characteristics of a glass-fiber-reinforced phenolic friction material

The fade and wear characteristics of a glass-fiber-reinforced friction material were studied using a Chase friction material testing machine. At low counterface temperatures, the friction material showed relatively high friction in the range 0.4–0.5. During fade tests, the coefficient of friction dropped to about 0.18 at 343 °C. Re-conditioning the wear surface at the end of a fade test altered the frictional behavior during a subsequent fade test. The wear tests showed that the specific weight loss per unit load and sliding distance decreases with increasing applied load and speed, but increases with increasing bulk drum temperature. At high temperatures, thermochemical degradation and fiber pull-out appear to contribute to higher specific wear rate. The worn surfaces of the specimens were observed by scanning electron microscopy and analyzed by energy-dispersive X-ray analysis. The results were consistent with low friction coefficients due to film formation on the worn surfaces of glass fiber at high temperatures. This film could be removed at lower temperatures by either sliding (application) or by sanding.

Thermal decomposition of α-tetralyl hydroperoxide under non-isothermal conditions, without solvents

The thermal decomposition of α-tetralyl hydroperoxide (THPO) has been investigated under a variety of conditions: in dynamic (argon and air) atmosphere, static air and self-generated atmosphere by employing DTA and TGA methods. The decomposition of THPO proceeds in two-stages during its thermochemical degradation under nonisothermal conditions in the temperature interval from room temperature to 500°C. It has been shown that the formation of associates resulting from the proton donor-acceptor interactions affects the initial temperature of hydroperoxide decomposition. Free-radical-induced decomposition proceeds in self-generated atmosphere at 165°C. 2,6-Di- tert-butyl-4-methyl phenol at some concentrations and phenyl-α-naphthylamine inhibit the induced radical decomposition. The products from the THPO decomposition are identical with those obtained during its decomposition in various solvents. The DTA and TGA methods show promise as useful techniques for the investigation of free-radical induced decomposition of hydroperoxides.

Structure and thermochemical reactivity of Cu(NH 3) 2CO 3

The structure and atmosphere-dependent thermochemical reactivity of diammine copper carbonate, Cu(NH 3) 2CO 3 has been investigated by means of combined thermoanalytical/mass spectrometric measurements, single crystal and powder X-ray diffraction studies as well as scanning electron microscopy. It could be shown that in reducing atmosphere a series of different organic volatile species as well as Cu° are formed. This observation is explained in terms of the structural vicinity of potential volatile agents in the parent material, i.e. NH 3 and CO 2, as well as the in situ formation of catalytically active solid products during the thermochemical degradation.

Progress on Nonlinear Optical Chromophores and Polymers with Useful Nonlinearity and Thermal Stability

ABSTRACTOrganic nonlinear optical (NLO) polymers must possess large and stable bulk nonlinear properties if they are to be of practical use. Numerous classes of NLO chromophores and polymers have already been evaluated but the selection process, particularly as related to stability issues, has been very stochastic in nature. If suitable chromophores are to be successfully identified their thermochemical degradation Mechanisms Must be elucidated and structural modifications introduced in a rational fashion. We have devised a protocol for the evaluation of NLO chromophores which involves initial screening by thermal analysis (DSC and TGA) and selected molecular hyperpolarizability (EFISH) analysis. The Most promising candidates are incorporated into thermoplastic polymer hosts where bulk nonlinear properties (dijand rij) and additional thermal stability properties are evaluated by spectroscopie Means (UV-VIS). Cyclicvoltammetry (CV) has been identified as a useful tool for evaluation of these chromophores; in the case of azobenzenes with aliphatic amine donor and a nitro acceptor a correlation between the thermal stability and oxidation potential has been found. The Most facile thermal degradation mechanism which occurs in these dyes has been identified and structural changes to the donor group have been introduced to avert the process.

The thermochemical degradation of cork

The thermochemical degradation of cork from Quercus suber L. was studied in the temperature range 150°C–450°C in relation to mass loss, chemical composition and the influence on the cellular structure. The degradation of cork is strongly dependent on temperature and mass losses become significant at 200°C (15% of initial dry weight) and increase rapidly for higher temperatures (27% at 250 °C, 49% at 300 °C, 62% at 350 °C) until ashing at 450 °C. The polysaccharides are the most heat sensitive components: at 200 °C, hemicelluloses disappear and cellulose is degraded to a considerable extent. Suberin is more resistant and degradation starts at approx. 250 °C; 300 °C-treated samples only contain 7% suberin.

ChemInform Abstract: The Formation of Hydroxy Monocarboxylic Acids and Dicarboxylic Acids by Thermochemical Degradation of Cellulose

ChemInformVolume 21, Issue 28 Reviews ChemInform Abstract: The Formation of Hydroxy Monocarboxylic Acids and Dicarboxylic Acids by Thermochemical Degradation of Cellulose K. + NIEMELAE, K. + NIEMELAE Lab. Wood Chem., Helsinki Univ. Techn., 02150 Espoo, FinlandSearch for more papers by this author K. + NIEMELAE, K. + NIEMELAE Lab. Wood Chem., Helsinki Univ. Techn., 02150 Espoo, FinlandSearch for more papers by this author First published: July 10, 1990 https://doi.org/10.1002/chin.199028345Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume21, Issue28July 10, 1990 RelatedInformation

The formation of hydroxy monocarboxylic acids and dicarboxylic acids by alkaline thermochemical degradation of cellulose

AbstractTreatment of cotton cellulose with 3 M sodium hydroxide solution at 260°C and 280°C gave a mixture of carboxylic acids with a yield of > 95%. The identified 50 carboxylic acids included both hydroxy monocarboxylic acids and dicarboxylic acids; their routes of formation are discussed. Among the main compounds were lactic, glycolic, 2‐hydroxy‐2‐methylpropanoic, 2‐hydroxybutanoic, 3,4‐dideoxypentonic, anhydroisosaccharinic, 2,3‐dideoxypentaric, and 3,4‐dideoxyhexaric acids. Technical utilisation of this kind of acid mixture requires further studies.Investigations of the cyclic compounds, formed in small amounts only, resulted in identification of mainly alkyl‐substituted 2‐cyclopenten‐1‐ones.

Theoretical investigation of the thermochemical degradation of graphite in a high-enthalpy air flow

Theoretical investigation of the thermochemical degradation of graphite in a high-enthalpy air flow

Alkaline thermochemical degradation of rice straw to organic acids

The organic content of rice straw can be converted entirely to water-soluble products in aqueous, alkaline solutions. The amounts of total organic acids produced from rice straw are quite similar to those produced from pure cellulose at the same reaction conditions. Formic, acetic, glycolic and lactic acids are major products of alkaline degradation. The maximum total yield of these acids from the reaction of rice straw with 4% NaOH at 280°C for 40 min was 37%, based on the starting organic weight of rice straw. The corresponding maximum total yield from pure cellulose was 43%.

Alkaline Thermochemical Degradation of Rice Straw to Oxychemicals

ABSTRACT THERMAL degradation of rice straw in water produces more water solubles and acetone solubles and less insoluble residue than from pure cellulose. Addition of alkali can be adjusted to optimize acetone soluble oil or to produce only water-soluble products. Water solubles include alcohols, ketones and carboxylic acids.

Effect of plasma treatments on the steam‐sour gas resistance and lubricity of elastomers

AbstractElastomers are widely used in drilling and logging applications as static seals such as casing packers and dynamic seals such as o‐rings for drill bits. Static seals often fail in service because of thermochemical degradation due to the combined effects of steam and sour gas at elevated temperatures that are characteristic of deep wells. Dynamic seals frequently fail because of abrasive wear that occurs even at the low temperatures that prevail in shallow wells. We have shown that improved steam–sour gas resistance of a fully formulated ethylene–propylene rubber at elevated temperatures can be achieved by coating the rubber with a thin film of plasma polymerized tetrafluoroethylene. Thus, no change in the mechanical properties of the coated rubber was observed after exposure to steam and sour gas at 275°C for 48 h. In contrast, the shear modulus of the uncoated rubber increased by 96% after the same exposure. While the effectiveness of the fluorocarbon coating decreased at longer exposure times, short‐term protection of elastomers could be beneficial in certain logging operations. It was also found that the coefficient of friction of a nitrile rubber (Buna N) was reduced by 20% after treatment with a carbon tetrafluoride plasma. This enhanced lubricity could lead to better wear characteristics in conventional drill bits where the seal is in contact with a moving metal surface. The surfaces of the plasma treated elastomers were characterized by water contact angle, scanning electron microscopy, and electron spectroscopy for chemical analysis.

Evidence for Two Major Cycles of Petroleum Generation in Mississippian Chainman Shale of East-Central Nevada: ABSTRACT

Marine Chainman Shale from drill cores in Railroad Valley and from outcrops in several mountain ranges of east-central Nevada contains a mixture of marine-sapropel and detrital terrestrial-plant organic matter. The organic matter ranges from immature to supermature in thermochemical evolution as indicated by organic geochemical data on kerogen and on hydrocarbon extracts and oil, by vitrinite reflectance, and by alteration colors of palynomorphs and conodonts. Hydrocarbon contents (< 30 to 2,000 ppm) and organic-carbon contents (< 0.1 to 7 weight %) vary widely. A discontinuity in thermochemical maturity has been identified between Paleozoic and Paleogene rocks in uplifted terranes, whereas a more continuous kerogen-maturation profile exists across the Paleozoic and Paleogene boundary where deeply buried beneath Neogene rocks. A two-cycle model of petroleum generation is proposed to account for these variations. The first cycle of petroleum generation began probably in early Mesozoic time when the Chainman was buried beneath upper Paleozoic and lower Mesozoic rocks. Depth of burial and hence the degree of thermochemical maturation varied with late Paleozoic and Mesozoic folding, faulting, and erosion. Organic matter in the Chainman is supermature in many localities where higher paleotemperatures were related to subcrustal hotspots or deeper burial. Analyses of surface and subsurface data indicate that although Chainman rocks were subjected to thermochemical degradation and generated some hydrocarbons in Mesozoic time--as evidenced by oil of varying viscosities trapped in fractures, voids, and invertebrate-fossil cavities in dense limestone concretions and beds--organic matter was not completely transformed into petroleum where buried at moderate depths. Uplift of buried Chainman Shale prior to the late Mesozoic arrested the first cycle of petroleum generation in thermochemically immature and mature rocks. Many organically immature and mature Chainman rocks in this region are now undergoing a second cycle of thermochemical degradation and renewed oil generation in Neogene basins where adequate fill and temperature increase have occurred. Rocks of the Chainman Shale probably are a major source of petroleum in Railroad Valley where oil has accumulated in fractured, welded ash-flow tuffs of Oligocene age. Oil accumulations are inferred to occur in other valleys in eastern Nevada where similar geologic conditions exist. End_of_Article - Last_Page 838------------