Acetone, carbon deposition

Before pyrolysis silicas were dried at 200°C and cooled to room temperature. Different amounts of organic precursors were deposited on dry silica (weight 5 g) to obtain carbon-silica adsorbents (carbosils) with different amounts of carbon deposits. Samples based on acenaphthene (Tables 1 and 2), acetylacetone and glucose (Table 3), were pyrolysed under static conditions in a stainless steel autoclave (0.3 dm3) at 773 K for 6 h. After reaction, all the prepared carbosils were washed in a Soxhlet apparatus with N,N-dimethylformamide and acetone, and then dried at 200°C. 

Table III - The Effect of Sulphiding Upon Carbon Deposition from Acetone on Oxidised 20/25/Nb Stainless Steel...

TABLE IV - The Effect of Sulphiding by H S on Carbon Deposition frcm Acetone on Fe Cfy... 

TABLE VII - Influence of Continuous Addition of Thiophene to the Gas Phase upon Carbon Deposition from Acetone Decomposition on Fe O at 600°C... 

TABLE VIII - Influence of the Continuous Addition of Either Hydrogen Sulphide. Sulphur Dioxide or Carbonyl Sulphide to the Gas Phase upon Carbon Deposition f ran Acetone Decomposition on FeiO/. at 600°C... 

Two possible complementary mechanisms were responsible for the reduction, or in some circumstances complete inhibition, by sulphur of carbon deposition from acetone on Fe30. The first was operative on material sulphided before exposure to acetone, and possibly also when high partial pressures of hydrogen sulphide and sulphur dioxide were added continuously to the gas phase, as this also resulted in appreciable Fej-jjS formation. In these instances reduced deposition could be attributed, at least partly, to a slower rate of formation of the reaction intermediary, e.g. iron carbides, on Fej NS as compared with Fe30. ... 

With Cr203, neither sulphiding nor sulphur-containing gas phase additives, which also sulphided the surface, inhibited acetone deposition. This reflected the different mechanism involved in carbon deposition on this oxide such that whether the surface anion was either oxygen or sulphur, did not affect either acetone adsorption or the subsequent decomposition of the adsorbed molecules. 

Practically inso] in water. Sol in alcohol, acetone, carbon tetrachloride, chloroform, ether, and many other organic solvents. Dec upon exposure to light and air. Colorless solns in organic solvents oxidize upon exposure and become yellow, orange and then deep red and may deposit crystals of dehydrorotenone and rotenonone which are toxic to insects. LDm i.p. in mice 2.8 mg/kg (Fukami) in rats... 

The deactivation of Mg-Al mixed oxides during the gas-phase self-condensation of acetone was studied. Main aldol condensation reaction and secondary coke-forming reactions take place on both basic and acidic sites. Although deactivation is caused by carbon deposition, it was found that coke formed on basic sites rather than on acidic sites is responsible for the activity lost. 

The MgyAlOx activity declines in the acetone oligomerization reaction due to a blockage of both basic and acid active sites by a carbonaceous residue formed by secondary aldol condensation reactions. The key intermediate species for coke formation are highly unsaturated linear trimers that are formed by aldol condensation of mesityl oxide with acetone and remain strongly bound to the catalyst surface. The catalyst surface acid-base properties determine the preferential formation of a given trimeric intermediate, which in turn defines the chemical nature of the carbon deposit. Aromatic hydrocarbons are the main component of coke formed on acidic Al-rich MgyAlOx samples whereas heavy a,P-unsaturated ketones preferentially form on basic Mg-rich catalysts. 

After depositing the charged powder on the paper (see Fig. XII.S.c), the charges may leak off so that the powder adhesion will become weaker. Hence it is necessary to fix the deposited powder this can be done by heating, by applying pressure, or by using a solvent. When heating is used, the adherent powder particles are fused and thus fixed on the paper. A solvent vapor (acetone, carbon tetrachloride, diethyl ether, etc.) will partially dissolve and also fix the toner particles on the paper. 

Reamer et al ignited the microwave plasma after the solvent had been completely eluted, i.e. within 20 s after sample injection. It was necessary to delay ignition to minimize carbon deposits on the walls of the quartz capillary. In spite of this precaution, it was necessary to remove the quartz capillary weekly and clean it by rinsing with hydrofluoric acid, water and acetone. 

The carbon-containing catalyst was treated by ultra-sound (US) in acetone at different conditions. The power of US treatment, and the time and regime (constant or pulsed), were varied. Even the weakest treatments made it possible to extract the nanotubules from the catalyst. With the increase of the time and the power of treatment the amount of extracted carbon increased. However, we noticed limitations of this method of purification. The quantity of carbon species separated from the substrate was no more than 10% from all deposited carbon after the most powerful treatment. Moreover, the increase of power led to the partial destruction of silica grains, which were then extracted with the tubules. As a result, even in the optimal conditions the final product was never completely free of silica (Fig. 12). 

To a suspension of 3.0 g of 7-[D-(-)-a-amino-p-hydroxyphenylacetamido] -3-[5-(1-methyl-1,2,3,4-tetrazolyl)thiomethyl] -A3arboxylic acid in 29 ml of water was added 0.95 g of anhydrous potassium carbonate. After the solution was formed, 15 ml of ethyl acetate was added to the solution, and 1.35 g of 4-ethyl-2,3-dioxo-1 -piperazinocarbonyl chloride was added to the resulting solution at 0°C to 5°C over a period of 15 minutes, and then the mixture was reacted at 0°C to 5°C for 30 minutes. After the reaction, an aqueous layer was separated off, 40 ml of ethyl acetate and 10 ml of acetone were added to the aqueous layer, and then the resulting solution was adjusted to a pH of 2.0 by addition of dilute hydrochloric acid. Thereafter, an organic layer was separated off, the organic layer was washed two times with 10 ml of water, dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The residue was dissolved in 10 mi of acetone, and 60 ml of 2-propanol was added to the solution to deposit crystals. The deposited crystals were collected by filtration, washed with 2-propanol, and then dried to obtain 3.27 g of 7-[D-(-)-a-(4-ethyl-2,3-dioxo)-1 -piperazinocarbonylamino)-p-hydroxyphenylacetamido] -3-[5-(1 -methyl-1,2,3,4-tetrazolyl)thiomethyl]-A product forms crystals, MP 1BB°C to 190°C (with decomposition). 

The colloidal particles are often deposited on metallic electrodes in the form of adsorbed coatings. Rubber and graphite coatings can be formed in this way, using solvent mixtures (water-acetone) as the dispersion media. The advantage of this method is that additives can firmly be codeposited with, for example, rubber latex. Thermionic emitters for radio valves are produced in a similar manner. The colloidal suspensions of alkaline earth carbonates are deposited electrophoretically on the electrode and are later converted to oxides by using an ignition process. 

The influence of benzylidene acetone on the electrodeposition mechanism of Zn-Co alloy was investigated [436]. A relationship between corrosion resistance, microstructure, and cobalt content in Zn-Co alloys was investigated [437] using X-ray photoelectron spectroscopy (XPS) and Auger spectroscopy [438]. The role of vitreous carbon, copper, and nickel substrates in Zn-Co deposition from chloride bath was analyzed [439]. 

---