Arabian Journal of Chemistry (Dec 2023)
Oxidation characteristics and hazardous of α-pinene, β-pinene and turpentine
Abstract
α-Pinene, β-pinene and turpentine are renewable resources that are widely used in fine chemicals, fuels and other applications, and the safety of their production, transport and use should be considered. In this work, the characteristics and hazardous of the oxidation process of α-pinene, β-pinene and turpentine were investigated by using a novel mini closed pressure vessel testing system (MCPVT). The oxidation products were resolved by gas chromatography-mass spectrometry (GC–MS). The results showed that α-pinene, β-pinene and turpentine were stable under nitrogen atmosphere and very active chemically under oxygen atmosphere. The activation energies (Ea) of α-pinene, β-pinene and turpentine were calculated to be 78.87, 109.69 and 98.82 kJ/mol, respectively, using pressure–time (P-t) curves. So, the reaction activity sequence was α-pinene > turpentine > β-pinene. The peroxide concentrations of α-pinene (363 K), β-pinene (358 K) and turpentine (363 K) could reach 81.94, 84.70 and 75.76 mmol/kg, respectively, at relatively low temperatures. 0.6 g of α-pinene exploded at a system temperature of 369 K and an oxygen pressure of 1.23 MPa. 0.6 g of β-pinene also exploded at a system temperature of 373 K and an oxygen pressure of 1.27 MPa. 0.4 g of turpentine experienced thermal runaway at a system temperature of 384 K and an oxygen pressure of 0.81 MPa. The major oxidation products of α-pinene are α-campholenaldehyde, laevo-pinocarveol, verbenol, verbenone, bicyclo (3.1.1)heptane-2, 3-diol, 2, 6, 6-trimethyl, 2-cyclohexen-1-ol, 2-methyl-5-(1-methylethenyl)-, (1R,5R)-rel-, cyclobutaneacetic acid, 3-acetyl-2, 2-dimethyl, myrtenol and myrtenal. The major thermal runaway products are water, ethanol, acetone, acetic acid, 2-pentanone, propyl acetate, toluene, cymene and methylacetophenone. The major oxidation products of β-pinene are nopinone, laevo-pinocarveol, pinocarvone, myrtenol, myrtenal and perillyl alcohol. The major thermal runaway products are water, ethanol, acetone, n-ethyl propanoate, toluene, butyl acetate, cymene, apocamphor, nopinone, bornyl formate, methylacetophenone and dihydronopol. The oxidation products and thermal runaway products of pinene were significantly different. Possible reaction pathways for α-pinene and β-pinene are proposed.
