Production of toluene by decomposition of 2-hydroxy-6-methylbenzaldehyde: a DFT study

The fast pyrolysis of lignocellulosic biomass produces raw bio-oil that comprises of several oxygenated organic compounds which are disadvantageous and lower the quality of bio-oil as a fuel. In this numerical study, 2-hydroxy-6-methylbenzaldehyde (HMB) component, one such oxygenated compound which represents aromatic aldehyde category of bio-oil, is considered as model compound for its decomposition within the framework of density functional theory. The bond dissociation analysis of HMB component suggests that the dehydrogenation of methyl group is the least energy demanding amongst all nine possible bond scissions. Further, eight reaction pathways are investigated for the conversion of HMB into toluene as end product along with the analyses of their corresponding potential energy surfaces. Briefly, results indicate that the optimum reaction progress for the production of toluene from HMB requires an activation energy of 12.26 kcal/mol. It is further observed that the production of toluene from HMB includes m-cresol as an intermediate instead of 2-formyltoulene; and, the production of 2-hydroxybenzaldehyde is not favourable. Furthermore, the thermochemistry analyses for the production of toluene using optimum reaction pathway and for the production of 2-hydroxybenzaldehyde using reaction pathway 9 are performed over a wide range of temperature, i. e., 473–873 K at an interval of 100 K. The thermochemistry also suggests higher favourability for the production of toluene compared to the production of 2-hydroxybenzaldehdye by decomposing HMB

Quantum chemical study on gas phase pyrolysis of p-isopropenylphenol

In the pyrolysis of Sphagnum moss species, p-isopropenylphenol (p-IPP) is a major product which has been considered in this density functional theory based computational study for its conversion to various products such as benzene, phenol, 4-propenylphenol, indan-5-ol, 4-propylcyclohexanone, 4-cyclopropylphenol, etc. In order to achieve these products, eight different reaction schemes are performed using B3LYP/6–311 + g (d,p) level of theory. Further, thermodynamic properties such as reaction free energies and reaction enthalpies associated with these eight reaction schemes are developed in the temperature range of 298–898 K. The reaction schemes that include partial hydrogenation of the aromatic carbon followed by elimination of functional groups are found to demand low activation energy. The production of benzene from p-IPP with isopropenylbenzene as an intermediate product requiring only 19.83 kcal/mol of activation energy is the rate limiting reaction step. Indan-5-ol produced from p-IPP is validated with the literature results and found excellent agreement between two results. Furthermore, the temperature is found to have phenomenal effect in each reaction scheme

Quantum chemical study on gas phase decomposition of ferulic acid

<p>Ferulic acid, representing phenolic fraction of bio-oil, is considered to be a model compound in this study for its decomposition into various end products such as ethylbenzene, eugenol, <i>cis</i>-isoeugenol, vanillin, 4-ethylguaiacol, guaiacol, and acetovanillone using density functional theory approach. Results of bond dissociation energies indicate that cleavage of methyl group from ferulic acid is the lowest energy-demanding bond scission amongst all 14 bond cleavages. Primary end product by decomposition of ferulic acid is found to be ethylbenzene and its production occurs through the formation of intermediate products such as 4-hydroxycinnamic acid, cinnamic acid and styrene. Demethoxylation of ferulic acid gives rise to the production of 4-hydroxycinnamic acid which further undergoes the formation of cinnamic acid by dehydroxylation reaction route. The formation of cinnamic acid in this study is carried out using three reaction schemes 1–3 and its further reduction to ethylbenzene is performed using two reaction possibilities. Finally, favourable pathway is found to be decarboxylation of cinnamic acid to produce vinylbenzene followed by the production of ethylbenzene using hydrogenation of C=C chain double bond. Furthermore, thermochemistry of each reaction scheme is performed at atmospheric pressure and at a wide range of temperature of 598–898 K.</p