A customer-designed mini closed pressure vessel test (MCPVT) consisting of a pressure sensor and a temperature sensor connected to recorder was applied to evaluate the isothermal stability along with the formation of hydroperoxide in the ethyl t-butyl ether (ETBE) oxidation process at low temperatures. A new type of hydroperoxide, named 1-tert-butoxy-ethyl hydroperoxide (TBEHP), was separated from ETBE oxidation products via column chromatography, which was further characterized by mass spectrometry (MS), 1H and 13C nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR). The thermal characteristics of TBEHP were assessed via differential scanning calorimetry (DSC). Results showed that the exothermic onset temperature (T0) and thermal decomposition heat (QDSC) of TBEHP were 99.12 °C and 1523.89 J·g–1, respectively. Moreover, a jet-stirred reactor (vessel volume: 500 mL) was used to evaluate the explosive risk of ETBE oxidation. The corresponding result indicated that detonation would arise in conditions of reaching system temperature of 140.0 °C, sample mass of 5.0 g, and oxygen pressure of 1.0 MPa, respectively. Finally, it was confirmed that ETBE thermal oxidation was a three-step exothermic reaction including the formation of hydroperoxide by absorbing oxygen, followed by the thermal decomposition of hydroperoxide, and subsequently deep oxidation reactions or detonation caused by reactive free radicals.

•The crude polysaccharides from the leaves of Magnolia kwangsiensis Figlar & Noot. were extracted by hot water extraction.•Two homogeneous polysaccharides were obtained by DEAE-52 cellulose chromatography and Sephadex G-100 column chromatography.•P-2 and P-3 were characterized by IR, HPGPC and GC–MS.•The antitumor activities of P-2 and P-3 were evaluated.•P-3 with stronger antitumor activities was found.The crude polysaccharides from the leaves of Magnolia kwangsiensis Figlar & Noot. were extracted by hot water extraction, the yield was 5.09%. Two polysaccharide fractions (P-2 and P-3) were isolated by DEAE-52 cellulose chromatography and Sephadex G-100 column chromatography in order, respectively. P-2 and P-3 were characterized by IR, HPGPC and GC–MS. P-2 was comprised of only glucose. Its molecular weight was 11.2 × 103 Da and the formula was C414H690O345. P-3 was comprised of xylose and rhamnose in the ratio of 1:4. Its molecular weight was 7.8 × 103 Da, and the formula was C319H528O220. The antitumor activities of P-2 and P-3 on the growth of human lung cancer (A549) cells and human gastric carcinoma (SGC7901) cells in vitro were evaluated. The results indicated that P-3 exhibited marked antitumor activities with IC50 value of 8.48 and 5.66 μg/mL.

•Characteristics and products of ether oxidations were examined using accelerating rate calorimetry (ARC).•Three stages of ether oxidation with oxygen were identified.•Thermal decomposition kinetics were calculated.•Peroxides of DEE, DIPE, MTBE, and ETBE were quantified by iodimetry analysis.•The products of the oxidation of five ethers were analyzed and identified.The oxidation characteristics and products of five ethers – ethyl tert-butyl ether (ETBE), methyl tert-butyl ether (MTBE), dimethyl ether (DME), diethyl ether (DEE), and diisopropyl ether (DIPE) – were determined using an accelerating rate calorimeter (ARC) at low temperatures. Oxidation temperature and pressure were calculated using temperature–time (T–t) and pressure–time (P–t) plots, and reaction products were analyzed by gas chromatography–mass spectrometry (GC–MS). Results showed that the oxidation reaction pathway of ethers with oxygen occurred in three stages: (1) promotion of oxygen and peroxide absorption by ether; (2) generation of free radicals by thermal decomposition; and (3) complex oxidation caused by free radicals. Initial auto-oxidation temperatures of DME, DEE, DIPE, MTBE, and ETBE were approximately 393 K, 389 K, 359 K, 413 K, and 383 K, respectively, and the activation energies (Ea) for thermal decomposition were 167.3 kJ/mol, 126.7 kJ/mol, 111.6 kJ/mol, 236.7 kJ/mol, and 159.1 kJ/mol, respectively, for the first-order reaction. Peroxides of DEE, DIPE, MTBE, and ETBE were identified by iodimetry analysis when oxidation temperature was 333 K. Oxidation reaction products were complex and included alcohols, aldehydes, ketones, acids, esters, and carbon dioxide.

•A novel self-designed gas–solid reactor was used to conducted the oxidation of abietic acid, monitored by FT-IR spectroscopy.•Molecular mechanism of abietic acid oxidation process in the nature environment was investigated.•2D-IR was shown as a suitable measurement to study reaction mechanism and was firstly applied to analyze mechanism of abietic acid oxidation process.The oxidation behavior of abietic acid was monitored by FT-IR and UV spectroscopy, using a novel, self-designed, gas–solid reactor, and the data was analyzed by 2D-IR. The hetero-spectral two-dimensional correlation of the FTIR data allowed the use of well-established band assignments to interpret less clearly assigned spectral features. Characteristic changes in the conjugated bond and the active methylene in abietic acid were revealed, and a mechanism was proposed. We concluded that the methylene at C7 was first transformed to a hydroxyl, thereby inducing the isomerization of the conjugated band. Meanwhile, the methylene at C12 was converted by an oxygen atom to a hydroxyl intermediate. Hydrogen continued to react with oxygen to form CO and water. Finally, the conjugated band was converted into a peroxide before transforming into an oxidant.

The thermal stability and decomposition of dimethyl ether (DME) and DME hydrate were studied using a self-designed instrument. The Raman spectra of DME, a solution mixture of DME and water (DME–water) and DME hydrate were measured. The result showed that the decomposition temperature of DME hydrate was dependent on the ambient pressure and H2O/DME molar ratio; DME hydrate tended to decompose at a higher temperature under a higher ambient pressure. The decomposition temperature of DME hydrate was −13.8 °C when the molar ratio of H2O/DME was 12.0, and the stoichiometric composition of DME hydrate was inferred to be DME·13H2O. Raman spectroscopy analysis showed that the vibration of DME hydrate shifted toward lower wave numbers in comparison with that of DME-water and DME. Moreover, the spectrum of DME hydrate showed a vibration band at 3151 cm−1, which was not observed for DME-water or DME.Highlights► The thermal stability and decomposition of dimethyl ether (DME) and DME hydrate were studied using a self-designed instrument. ► The thermal stability and decomposition of DME hydrate was studied. ► Raman spectroscopy analysis showed that the vibration of DME hydrate shifted toward lower wave numbers in comparison with that of DME-water and DME. ► The stoichiometric composition of DME hydrate was inferred to be DME·13H2O.

The Mo–Fe/HZSM-5 catalyst was prepared by the impregnation method using citric acid to form Fe3+ and Mo6+ chelates in the impregnation solution. The structure, acidity and the catalytic performance for the macrolactonization of methyl 15-hydroxypentadecanoate to cyclopentadecanolide over Mo–Fe/HZSM-5 catalyst in comparison with unmodified HZSM-5, Fe/HZSM-5 and Mo/HZSM-5 catalysts were studied. The results indicate that the optimum ratio of Mo/Fe is 2.5. The Fe2(MoO4)3 and Al2(MoO4)3 species are formed on the Mo–Fe/HZSM-5 catalyst, with an increase of strength and slight diminution of the amount of acid sites. The Mo–Fe/HZSM-5 catalyst exhibited high activity for the selective macrolactonization of methyl 15-hydroxypentadecanoate to cyclopentadecanolide.