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Biomass Chemistry
Published in Jay J. Cheng, Biomass to Renewable Energy Processes, 2017
Structural isomers of alkenes are obtained by changing the position of the double bonds or by changing the way the carbon atoms are joined to each other. The presence of double bonds can lead to another type of isomerism: geometric isomerism (cis–trans isomerism). However, the presence of a double bond is not a guarantee for such geometric isomerism. In order for such isomerism to be exhibited, each carbon atom involved in the double bond must be attached to different functional groups. For example, Figure 2.5 shows the structural isomers with the empirical formula C4H8: 1-butene, 2-butene, and 2-methyl propene. However, 2-butene exhibits geometric isomerism as well. The cis isomer of 2-butene has the methyl (CH3) substituent groups oriented on the same side of the double bond and the trans isomer has the methyl groups on opposite sides of the double bond.
Chemicals from Olefin Hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Butylenes (butene derivatives) are byproducts of refinery cracking processes and steam cracking units for ethylene production. Dehydrogenation of butanes is a second source of butylenes. However, this source is becoming more important because isobutylene (a butylene isomer) is currently highly demanded for the production of oxygenates as gasoline additives.
Speciation and Heat Release Studies during n-Heptane Oxidation in a Motored Engine
Published in Combustion Science and Technology, 2022
Elyasa Al-Gharibeh, Steven Beyerlein, Kamal Kumar
The speciation analysis in this research detected fifty-six stable intermediate species across a wide range of chemical classes such as alkenes, aldehydes, ketones, ethers, alcohols, and acids. This work also provides quantitative measurements for eleven intermediate species and compares them to results from an existing detailed chemical kinetic mechanism in the literature. Species of the same chemical group show similar trends for variation with compression ratios, although there were differences in their relative concentrations. The NTC effect was apparent in nearly all species detected in this work. This NTC effect was not as strong in the computed results, which, however, did show a diminished reactivity, but not a reduction in the region of interest (6.5 < CR < 6.75). The model predictions were found to be in good agreement with the experiments for alkene and alcohol production but were unable to account for the generation of acetone. A noticeable feature in the experimental results was the relative lack of straight-chain carbonyl compounds with six carbon atoms in the oxidation products. The incipient second stage heat release was associated with a preference for the formation of small carbon number alkenes, especially the butene isomers. This work provides benchmark data for the validation of chemical kinetic mechanisms using both global and detailed responses. It fills in the gap for speciation studies existing in the literature, especially under high-pressure conditions.
A review on solid base heterogeneous catalysts: preparation, characterization and applications
Published in Chemical Engineering Communications, 2022
Diksha K. Jambhulkar, Rajendra P. Ugwekar, Bharat A. Bhanvase, Divya P. Barai
Isomerization of alkenes and complex structure of alkenes extended to double bond migration was done by using solid base catalysts. In order to explain the reaction mechanism and properties, 1-butene was widely studied over several solid base catalysts. Isomerization occurs without cleavage of C-C bond, since the feature of C-C bond cleavage was absent in basic catalyst. Industrial processes, such as olefin conversion, require isomerization of 1-butene. But, 1-butene remains unreacted when treated with ethylene. Thus, solid base catalysts are used to conduct the double bond isomerization of such unsaturated hydrocarbons. The reaction starts with the loss of H+ ion from third carbon atom of 1-butene with the aid of basic sites of catalysts to form trans or cis allylic anion as shown in Figure 21 (Hattori 2015). The concentration of formation of cis allylic anion was higher due to higher stability than that of trans. Further addition of H+ ion to trans and cis allylic anion resulted in formation of trans-2-butene and cis-2-butene, respectively. Here, intramolecular H transfer took place. The H+ ion which was initially released by 1-butene molecule returns to the same molecule in order to form isomerized molecule of 1-butene.
Carbon nanotube-zeolite composite catalyst - characterization and application
Published in Journal of Dispersion Science and Technology, 2021
Ádám Prekob, Viktória Hajdu, Béla Fiser, Ferenc Kristály, Béla Viskolcz, László Vanyorek
Using scanning electron microscopy (SEM, Hitachi S 4800) have been used to analyze the surface of the catalyst. The samples were fixed with carbon tape rubber. Energy dispersive X-ray (EDX) spectroscopy was used for elemental analysis. The carbon content of the SoS composite was determined by thermogravimetric analysis (TG, Tarsus TG 209, Netzsch). The type nitrogen atom incorporations were characterized by X-ray photoelectron spectroscopy (XPS, SPECS spectroscope with a Phoibos 150 MCD 9 analyser). The hydrogenation reactions were followed by Fourier-transform infrared spectroscopy (FTIR, Bruker Vortex 70). The vibration of the C = C double bond in olefins like 1-butene can be easily located at 1642 cm−1 (Figure 1A). During hydrogenation, the intensity of the corresponding peaks decreases, beacuse of the disappearance of double bond. Consequently the area below the peaks also decreasing, and thus, the conversion could be calculated throughout the hydrogenation.