Oxygenates are usually used as fuel additives. Recently, di-isopropyl ether (DIPE) has been considered as the potential fuel additive for the replacement of methyl tert-butyl ether (MTBE). So it is essential to research its thermophysical properties. In this paper, the speed of sound in DIPE was measured from 303.15 K to 673.15 K up to 10 MPa using Brillouin light scattering (BLS), including saturated liquid/vapour, and the liquid and supercritical regions. The saturated liquid/vapour and single phase liquid results were fitted as functions of temperature and pressure. The correlations represent the data with AADs of 0.62% for the saturated liquid, 0.44% for the saturated vapour and 0.73% for the liquid, respectively. Moreover, the variation of speed of sound with temperature and pressure was also analysed.
To explore the fuel isomeric effect on ether combustion characteristics, pyrolysis , and laminar flame propagation of di-n-propyl ether (DPE) and diisopropyl ether (DIPE) were investigated. A new kinetic model of DIPE was developed based on our recent DPE model [Fuel 298 (2021) 120797]. The pyrolysis experiments were carried out in two jet-stirred reactors at near-atmospheric pressure with good agreement on the measurements using synchrotron vacuum ultraviolet photoionization mass spectrometry and gas chromatography/mass spectrometry. The decomposition profile of DIPE showed a faster trend than that of DPE, which can be attributed to the faster alcohol elimination reaction of DIPE. The dominant roles of alcohol elimination reaction and H-abstraction reactions in fuel consumption explain the production of fuel-specific oxygenated species, i.e. n -propanol and propanal in DPE and i -propanol, acetaldehyde and acetone in DIPE. The laminar burning velocities of DPE and DIPE were also measured in a high-pressure constant-volume cylindrical combustion vessel at the initial temperature of 373 K and pressures of 1–10 atm. It was found that the linear DPE propagated faster than DIPE with the branched structure under all investigated conditions. Rate of production analysis and sensitivity analysis were also performed to elucidate the key radicals and reactions responsible for the remarkable reactivity of isomeric fuels. Fuel structures have a great influence on the distribution of radical pools, resulting in the easy formation of active radicals in DPE flames such as vinyl and ethyl and stable radicals in DIPE flames like methyl and allyl. The successive decomposition reactions of these dominant radicals promote the DPE flame and inhibit the DIPE flame propagation respectively, which explains the higher laminar burning velocities and reactivity of DPE than that of DIPE. Furthermore, the present model was also examined against the literature data, including pyrolysis and oxidation in the jet-stirred reactor and flow reactor.
Ruxing Zhao,Qingrun Meng,Guanchao Wang,Lin Xu,Weifeng Chu,Junjie Li
Intermolecular dehydration of 2-propanol (IPA) to di-isopropyl ether (DIPE) serves as an important process to produce the valuable chemical, however, developing advanced solid acid catalysts with high DIPE selectivity faces the great challenge of inhibiting the intramolecular dehydration reaction. In this context, we developed a highly selective intermolecular dehydration MFI nanosheet catalyst by synergistically modifying its diffusion and acid properties. We found that the DIPE selectivity over nanosheet ZSM-5 catalysts were obviously higher than that over the conventional ZSM-5 catalyst, benefited from the enhanced diffusion property over nanosheet catalysts that inhibited the further conversion of DIPE. However, the DIPE selectivity were still lower than 70 % over those catalysts attributed to their high acid strength that facilitated the intramolecular dehydration reaction. Thus, various heteroatoms (Fe, Ga, and B) substituted MFI zeolite nanosheet catalysts were prepared and employed in the dehydration reaction, Fe-MFI with a moderate acid strength exhibited the highest DIPE selectivity among those catalysts. Besides, the effects of acid amounts (Si/Fe ratio) and diffusion properties (thickness of b-axis) on the intermolecular dehydration selectivity and activities over nanosheet Fe-MFI catalysts were systematically investigated. An optimal Fe-MFI nanosheet catalyst with the b-axis thickness of ∼20 nm and Si/Fe ratio of ∼40 presented the stable high DIPE selectivity of ∼91 % in 360 h of time on stream, meanwhile the IPA conversions kept almost unchanged.
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