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Role of Nanocatalysts in Biofuel Production and Comparison with Traditional Catalysts
Published in Bhaskar Singh, Ramesh Oraon, Advanced Nanocatalysts for Biodiesel Production, 2023
Kamlesh Kumari, Ritu Yadav, Durgesh Kumar, Vijay Kumar Vishvakarma, Prashant Singh, Vinod Kumar, Indra Bahadur
The catalyst used in this method is a mineral acid such as sulphuric acid, and H+ of the mineral acid protonated the carbonyl group of the ester group as the ketonic group has a lone pair of electrons. Further, resonance takes place to obtain a more stable intermediate: a carbocation. also, a molecule of alcohol reacts to this carbocation and gives another reaction intermediate, finally producing the ester of interest with some by-products (Scheme 12.4).
Alkenes and Alkynes: Structure, Nomenclature, and Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
A carbocation is a trisubstituted positively charged carbon species. A carbocation is a transient product, an intermediate that is an electron-deficient carbon atom bearing a positive charge. What is the formal charge on a carbocation?
Fluid Catalytic Cracking
Published in Mark J. Kaiser, Arno de Klerk, James H. Gary, Glenn E. Hwerk, Petroleum Refining, 2019
Mark J. Kaiser, Arno de Klerk, James H. Gary, Glenn E. Hwerk
The first mechanism of initiating catalytic cracking, and by far the most common, is through classic carbocation chemistry (Figure 27.6). A carbocation is a trivalent carbon with a single positive charge. This is the carbocation chemistry that can be found in any standard organic chemistry text. The carbocation is commonly formed by the protonation of an olefin group. Olefins are not normally present in the feed but are initially formed by thermal cracking during the thermal “shock” at the reactor inlet, as well as by subsequent cracking reactions. Once the carbocation is formed, it can participate in all reactions that proceed through a carbocation intermediate. These reactions include isomerization of the position of the carbocation, skeletal isomerization, dimerization, cyclization, transalkylation, and cracking. Due to the high temperature, the reaction that is favored is cracking. Cracking takes place by β-scission, which means that the bond two positions from the carbocation breaks to produce an olefin and a carbocation. The olefin and carbocation formed by the cracking reaction are of lower molecular mass than the original molecule that was protonated. The acid catalysis involved in catalytic cracking is discussed in more detail in the chapter on hydrocracking (Chapter 28).
Polyethylene glycol-modified mesoporous zerovalent iron nanoparticle as potential catalyst for improved reductive degradation of Congo red from wastewater
Published in Journal of Environmental Science and Health, Part A, 2023
Ipsita Som, Mouni Roy, Rajnarayan Saha
Based on the m/z value obtained from the GCMS analysis degraded products, a plausible mechanistic pathway of CR degradation has been illustrated in Scheme 2. At first significant adsorption of CR molecule on the surface of synthesized nZVI-PEG6000 occur. Then, an electron-deficient reaction center (carbocation ion) is generated in the catalytic cavity of CR molecule. This carbocation ion is highly prone to react with nucleophile, i.e., BH4- ion which transfer electrons to nano catalyst. Later, this electrons attacked the carbocation ion, which leads to the cleavage of electronically unstable azo bond. The color of CR is due to the presence of azo bond along with chromophores.[74] Thus, cleavage of azo bond causes its decolorization gradually. Later, the various steps including demination (–NH2), desulphonation (–SO3H) and ring cleavage or rupturing process leads to the formation of several low molecular weight intermediate compounds. The obtained low molecular weight compounds (dicarboxylic acid, other organic acid) are finally mineralized to CO2 and H2O.
Probing radical versus proton migration in the aniline cation with IRMPD spectroscopy
Published in Molecular Physics, 2023
Laura Finazzi, Jonathan Martens, Giel Berden, Jos Oomens
An ion of composition CHNH is obtained via collision-induced dissociation (CID) of the protonated precursor 4-bromoaniline (Figures S1–S2). Precursor ions are mass-selectively accelerated by excitation at their secular frequency in the quadrupole trap, leading to higher-energy collisions with the He buffer gas and the formation of the product ions. An ion accumulation time of 30 ms is used and the CID amplitude is optimised to maximise the m/z 93 product ion signal. Upon IRMPD, this ion mainly produces a fragment ion at m/z 67, which likely corresponds to the cyclopentenyl carbocation (CH), produced by expulsion of a CN radical.
Non-emission hydrothermal low-temperature synthesis of carbon nanomaterials from poly (ethylene terephthalate) plastic waste for excellent supercapacitor applications
Published in Green Chemistry Letters and Reviews, 2023
Moses Kigozi, Gabriel N. Kasozi, Sachin Balaso Mohite, Sizwe Zamisa, Rajshekhar Karpoormath, John Baptist Kirabira, Emmanuel Tebandeke
The thermogravimetric analysis (TGA) was conducted on each material to ascertain the ideal temperature for thermal deterioration. At temperatures of 74 and 229°C, the PTTg materials exhibit different degradation behavior, with hydrocarbon weight rapidly losing mass, as shown in Figure 7. The material displayed a two-step decomposition process, with the first stage beginning at a lower temperature and the second beginning at a higher temperature. This could be because of volatile contaminants, like the additional filler used in manufacturing plastic (41). The PTTg material's highest deterioration was accomplished between 356 and 420°C. PTTg demonstrated a two-step breakdown and maintained 14% of its mass up to 1000°C. Under controlled circumstances, the PT-NANO material demonstrated a one-stage breakdown. With an increase in temperature, the carbon–carbon bond that causes the single-step decomposition supports the random scission mechanism (42). Compared to the PTTg sample, PT-NANO degradation began at a higher temperature (354°C). At temperatures between 354 and 698°C, the PT-NANO displayed a steady weight reduction that reduced the material by 60 percent. Tertiary carbon, a component of PT-NANO carbon production, facilitates the creation of carbocation throughout the material's thermal deterioration (43). PTTg showed a loss of more than 60% by 356°C, but PT-NANO showed a loss of less than 10%, and it took PT-NANO until 556°C to experience a loss of 60%. According to EDX examination, the PT-NANO material retained 23 percent at 1000°C, which the presence of silica and sulphur may have caused.