Kinetics of Oxidation of Benzyl Alcohol with Dilute Nitric Acid

Abstract

The oxidation of benzyl alcohol by dilute nitric acid has been selected for the study as a typical method for the manufacture of industrially important intermediate benzaldehyde. All the reactions have been performed in the absence of any solvent. A catalytic amount of sodium nitrite is essential for the generation of active state of nitrogen. Benzyl nitrite is formed in a substantial amount as an intermediate. The effects of various parameters such as the NaNO 2 loading, nitric acid concentration, temperature, and molar ratio have been investigated. The stoichiometric requirement of nitric acid for benzyl alcohol conversion has also been determined. The probable mechanism for the oxidation of benzyl alcohol using nitric acid is proposed, showing the reversible formation of benzyl nitrite and its irreversible decomposition to benzaldehyde. The mass-transfer resistance has been eliminated for the investigation of kinetics of all the reactions in the consecutive path. The influence of chloro substitution on the oxidation rates of 2-chlorobenzyl, 4-chlorobenzyl, and 2,4-dichlorobenzyl alcohols has been presented.

Probing the origin of in situ generated nanoparticles as sustainable oxidation catalysts

“…The reactor was charged with benzyl alcohol (1 g), diethylene glycol dimethyl ether (0.85 g) as an internal standard, tert-butanol (30 mL) as a 25 solvent and catalyst (50 mg). The reactor was pressurised with 20 bar of dry air, stirred and heated for the required amount of time.…”

“…The development of a novel design strategy for the "one-pot" in situ generation of metallic nanoparticle active sites, that could be 25 isolated and heterogenised within a porous copper chloropyrophosphate framework, has resulted in the generation of highly active and selective catalysts for the activation of molecular oxygen. The size, shape and morphology of the individual nanoparticles (Au, Pt or Pd) that could be effectively 30 confined within these novel anion-exchange host frameworks, opens up a new avenue of research for creating well-dispersed, single-sites that are stable and versatile in industrially-significant, selective catalytic oxidations, using benign oxidants such as air.…”

“…5,6 Heterogeneous nanoparticle catalysts have mostly been supported on porous carbon 10 impregnation, 15 deposition-precipitation 16 and polymer-stabilised colloidal deposition; 17 where precise control of nanoparticle size and distribution have been achieved employing polyvinylalcohol 10 (PVA) and polyvinylpyrrolidone (PVP) as polymer-stabilising agents. Catalytic studies for Au nanoparticles have revealed that the activity is inversely proportional to the particle size, especially below 10 nm, 18 thus highlighting the importance of -supported copper chloropyrophosphate with an analogous framework as 25 CU-2 was reported. 20,21 Herein, we adopt a modified approach for the generation of Pt ( Fig.…”

“…Current industrial processes involve the use of stoichiometric quantities of inorganic oxidants, largely homogeneous chromium(VI) based materials, 1 that result in the generation of excessive quantities of waste, notwithstanding the debilitating impacts on the environment 25 through use of caustic reagents and non-biodegradable solvents. From the point of view of sustainable chemistry, this sector of the chemical industry is faced with the particular challenge to utilise benign oxidants, such as molecular oxygen, to eliminate these toxic waste products and expensive reagents, whilst 30 simultaneously striving to achieve high degrees of activity and selectivity, through the deployment of heterogeneous catalysts.…”

“…Further structural characterisation is currently underway to probe the origin these isolated active sites and their implicit role in the catalytic process. It is also 25 noteworthy that larger faceted nanocrystals were detected with the Pd-based catalyst, which could well be responsible for the lower TON and selectivity associated with this catalyst. It is well known 22 that nanoparticle size and degree of siteisolation are crucial factors that lead to the generation of single-30 sites that are responsible for boosting the overall catalytic efficiency in nanoparticle-based catalysts that were previously studied 23 for catalytic oxidations and hydrogenations.…”