2,3-Dihydroimidazol-2-ylidene

A study has been performed on the production of high quality activated carbon from rice husk char obtained by flash pyrolysis in a conical spouted bed reactor. In order to enhance both the quality of the adsorbents obtained and the economy of the process, the amorphous silica contained in the char has been recovered with Na2CO3. Subsequently, the resulting carbonaceous material has been subjected to physical activation at 800 °C using steam and carbon dioxide as activating agents. Although the maximum BET surface areas obtained with carbon dioxide and steam are similar, 1514 and 1365 m2 g–1, respectively, significant differences are observed in the performance of the two oxidizers. Thus, steam gasification kinetics is faster than that of carbon dioxide. The carbons produced by activation using both steam and carbon dioxide have a wide pore size distribution, with microporous structure being more developed when the latter is used.

The purpose of this program is to study the conversion of biomass to liquid and gaseous hydrocarbon fuels and chemical feedstocks by a flash or rapid pyrolysis technique. During this period of study pine wood was flash pyrolyzed in atmospheres of methane and helium at a pressure of 50 psi and at temperatures up to 1050 C. The 1-inch I.D. entrained downflow tubular reactor was used in these experiments. Product yields of methane, ethane, ethylene, BTX, carbon monoxide and carbon dioxide were determined as a function of temperature and gas to wood ratio. Of particular interest were the ethylene and BTX yields. These represented as much as 29.6% and 24.6% of the carbon contained in the feed wood respectively when flash pyrolyzing in methane (flash methanolysls) and 14.7% and 9.7% when pyrolyzing in helium. In the case of flash methanolysis of wood the yields of ethylene and benzene increased with increasing methane to wood feed ratios. In the case of flash pyrolysis in helium the yields of ethylene and BTX decreased with increasing helium gas to wood feed ratios. These results indicate a mechanism by which a free radical reactive species originating from the wood interacts with the methane pyrolyzing gas to produce an enhanced yield of ethylene and benzene. The flash methanolysis of lignin extract from wood produced lower yields of ethylene, indicating the yields mainly originate from the cellulosic fractions of the wood. Some work was also performed on substituting wood ash for sillca flour (Cab-O-Sil) to allow free flow of wood particles through the entrained flow reactor. Preliminary process design and analysis indicates an economically competitive process for the flash methanolysis of wood for the production of methanol, benzene and ethylene. Future plans include completing the studies on obtaining the process chemistry of the flash methanolysis of woods, to obtain a better understanding of the enhanced ethylene and benzene yield and to investigate other biomass forms.

1-(2-Nitrophenyl)-5-phenyltetrazole (5b) decomposes when heated to give nitrogen, carbon dioxide, and 2-phenylbenzotriazole (6) in high yield. This new molecular rearrangement proceeds via 2-nitrophenyl(phenyl)carbodi-imide (8). Other precursors of this carbodi-imide, i.e. oxadiazolone (10), oxadiazolethione (11), oxathiadiazole 2-oxide (12), and the aminimide (16), and carbodi-imide itself, all give 2-phenylbenzotriazole (6) on thermolysis, the last three in high yield. This reaction is general for diarylcarbodi-imides with an ortho nitro group, and their precursors, and it provides a useful new route to 2-arylbenzotriazoles. A sequence of electrocyclic ring closing and opening reactions (Scheme 5) is proposed as the mechanism of this process. The key intermediate, 2-phenyl-1,2,4-benzotriazin-3-one 1-oxide (19), has been isolated from a careful thermolysis of (12) in toluene; in solution it is in reversible equilibrium with the ring-opened form (20). This new nitro-carbodi-imide group interaction has been extended to the more stable nitrobiphenyl(phenyl)carbodi-imide (25) and nitronaphthyl(phenyl)-carbodi-imide (24) which, on flash vacuum pyrolysis, give benzimidazo[1,2-f]phenanthridine (29) and benz[cd]indazole 1-oxide (32) respectively, in new rearrangements.

Irradiation of imidazole-2-carboxylic acid (3) – matrix-isolated in argon at 10 K – with a wavelength of 254 nm leads to decarboxylation and the formation of a complex between 2,3-dihydroimidazol-2-ylidene and carbon dioxide (1·CO2). Upon irradiation of 2,3-dihydroimidazol-2-ylidene (1) with λ = 254, 193, and 185 nm no imidazole can be detected. On the other hand flash vacuum pyrolysis of imidazole-2-carboxylic acid (3) produces imidazole and carbon dioxide. 2,3-Dihydroimidazol-2-ylidene (1) – the possible intermediate – cannot be trapped under these conditions.

On flash-vacuum pyrolysis, the oxazinone (3) is fragmented to diphenylacetylene, benzonitrile, and carbon dioxide; the oxazinones (4) and (6), on the other hand, undergo ring-opening to the isocyanates (5) and (7), respectively, which cyclise at room temperature.

: 2,5-DIPHENYL-1,3,4-OXADIAZOLE AND 3,5-DIPHENYL-1,2,4-OXADIAZOLE WERE PYROLYSED IN DEALED AMPOULES AND THE VOLATILE DEGRADATION PRODUCTS EXAMINED EITHER BY GAS LIQUID CHROMATOGRAPHY OR BY MASS SPECTROMETRY. Good agreement was obtained between the results of the two analytical techniques. Despite a considerable difference in the thermal stability of the two compounds, the major breakdown products, benzonitrile and phenyl isocyanate, were the same in both cases. The penyl isocyanate further reacted to a certain extent to give diphenylcarbodiimide and carbon dioxide. As the 1,3,4-oxadiazole structure was the more thermally stable, poly(phenylene-1,3,4-oxadiazole) was prepared and its degradation studied by the sealed ampoule method and also by flash pyrolysis into a G.L.C. using either the tungsten filament technique, or that involving introduction of a small boat containing polymer into a previously heated furnace. The results obtained for the polymer by the three methods are compared and contrasted and the mechanism of decomposition compared with that of the model compounds. (Author)

Carbohydrate pyrolysis mechanisms from isotopic labeling. Part 5. The pyrolysis of D-glucose: The origin of the light gases from the D-glucose molecule

A new approach to study the mechanism of radiation-induced degradation of polymeric materials based on the combined analysis of radiolytic gases and pyrolytic products from preirradiated polymers is proposed. Bisphenol-A polycarbonate (PC) was γ-irradiated under vacuum in the dose range from 0.125 to 1.0 MGy followed by its flash pyrolysis under an inert atmosphere coupled to GC-FTIR-MS. Pyrolyzed PC at 750°C released mainly carbon dioxide, methane, benzene, toluene, phenol and 4-methylphenol. The yields of some of these products linearly decrease or increase with absorbed dose. On the basis of this behavior and combining our previous data on gas evolution, we infer two main pathways of PC radiation-induced scission with equal probabilities: (a) carbonate bond and (b) aliphatic-aromatic bond ruptures.

Quantitative flash pyrolysis Fourier transform infrared spectroscopy of organic materials

In this study, wood bark of neem tree (Azadirachta indica) is transformed into liquid (bio-oil), solid (char) and gaseous products via pyrolysis method. The main aim of this study is to analyze the effect of process parameters on pyrolysis yield, physical and chemical characterization of bio-oil, char, and gaseous products to find its feasibility as a commercial fuel as well as chemical feedstocks. The flash pyrolysis experiments were carried out in a laboratory scale fluidized bed reactor at a temperature ranging from 350 to 550°C, different particle sizes from 0.71 to 1.25 mm with a sweep gas flow rate of 1.25 to 2.25 m3/hr. The highest liquid product yield was obtained as 49.5 wt% at the pyrolysis temperature of 450°C, 1.0 mm particle size and at the sweep gas flow rate 2.0 m3/hr. The obtained bio-oil, char, and gaseous products were examined with FT-IR, GC-MS and Elemental analysis methods. Based on the elemental analysis of the bio-oil, the calorific value was found as 22.7 MJ/kg. GC-MS analysis of the bio-oil indicates that it mostly consists of phenolic and oxygenated compounds with alkanes, alkenes, ketones, and carboxylic acids. The pyrolysis gas fraction contains hydrogen, methane, oxygen, carbon dioxide, and carbon monoxide. The obtained bio-oil and gas can be used as a bio-fuel and bio-oil can be used as a valuable chemical feedstock. The char obtained are carbon-rich and are nearly equal to the standard fuel properties.

Gas chromatographic and capillary gas chromatographic-mass spectrometric analysis of thermal decomposition products of liquid crystal polymers

The production of activated carbons derived from waste tires has been carried out using steam and carbon dioxide as activation agents. The effect of temperature and activation time over the carbons prepared has been studied. The material subjected to activation has been char or residual carbon black obtained by continuous flash pyrolysis of waste tires carried out in a conical spouted bed reactor at 500 °C. The activation has been carried out at 850 and 900 °C using steam and only at 900 °C using carbon dioxide due to the slower kinetics of this process. The activation runs have been conducted in a fixed bed reactor. An essentially mesoporous structure is developed in the process, with BET surface areas above 500 m2/g for the carbons obtained with steam and above 370 m2/g in those obtained using carbon dioxide.

Betulin is the most popular of the known triterpenoids of the lupan series. It has valuable pharmacological properties. It exhibits antibacterial, antiviral, antitumor, hypolipidemic and other types of activity. The prospects of using betulin in medicine, pharmacology, and veterinary medicine require the development of effective methods for obtaining it from waste from the woodworking industry. Therefore, the question arises of the need to develop a technology for isolating and purifying triterpenoids from birch bark in large quantities. This review contains a variety of methods for the isolation of betulin. The advantages and disadvantages of the proposed methods are described. The following methods are considered: vacuum sublimation after preliminary alkaline; vacuum pyrolysis; supercritical extraction with carbon dioxide or mixtures of carbon dioxide with various solvents; extraction with organic solvents. Also, the method of microwave is described, it is activation on the example of the Kyrgyz birch (Betula kirghisorum), this is an endemic species that has not been studied before, growing on the territory of the Republic of Kazakhstan.

In previous research, carbon molecular sieve (CMS) membranes for gas separations have been produced using either a vacuum pyrolysis or an inert purge pyrolysis technique on a precursor which is often polymeric. This study compares both techniques using the same polyimide precursor material. Additional pyrolysis variables included the type of “inert” purge gas (argon, helium, and carbon dioxide), purge flow rate, and temperature. Vacuum pyrolysis produced more selective but less productive CMS membranes than the inert purge pyrolyzed membranes. “High” purge gas flow rates (i.e., 200 standard cubic centimeters per minute or cm3(STP)/min) produced a much higher permeability, but lower selectivity membrane compared to those produced in a “low” purge flow rate (20 cm3(STP)/min). By raising the pyrolysis temperature from 550 to 800 °C, the effective pore size was reduced, thereby making the CMS membranes more selective but less productive. Mixed gas tests using oxygen/nitrogen and hydrogen/nitrogen mixtures wer...

Influences of pyrolysis condition and acid treatment on properties of durian peel-based activated carbon