Hongyan Wang,Xinyue Sun,Yurou Zhou,Bofeng Zhang,Jingpei Cao,Guozhu Liu
To further explore the decomposition behaviors of C5 cyclic hydrocarbons, important components in the transportation fuels and pivotal intermediates in high-density liquid fuels, the pyrolysis of cyclopentane, cyclopentene and cyclopentadiene with different unsaturation degrees were investigated. The experiments of cyclopentane and cyclopentene were performed at 1.0, 30.0 atm and 773–1173 K in a flow tube reactor. The mole fraction profiles of pyrolysis species, involving C1-C5 small hydrocarbons and monocyclic, bicyclic as well as polycyclic aromatic hydrocarbons (MAHs, BAHs and PAHs), were provided. A universal kinetic model for three C5 cyclic fuels pyrolysis chemistry was proposed and reasonably predicted the speciation profiles newly reported in this work and literature, where rate coefficients of the crucial reactions were compared and upgraded. The differences among three fuels specific pathways were evaluated and the effects of unsaturation on the pyrolysis characteristics of intrinsic reactivity and aromatics formation were revealed. Cyclopentene has the highest pyrolysis reactivity, followed by cyclopentane and cyclopentadiene. Simultaneously formed fuel radicals and key intermediates in three C5 cyclic fuels influence the formation channels of small products, MAHs and BAHs. The saturated cyclopentane is easily occur the ring-opening reaction to generate more C2 and C3 species, whereas the increase in unsaturation promotes MAHs and BAHs formation in cyclopentene and cyclopentadiene pyrolysis, especially the toluene, styrene, indene and naphthalene. The rate of production analysis shows the formations of these MAHs and BAHs are strongly dependent on the concentration levels of cyclopentadienyl resonance stabilized radical (RSR). Differently, the dominated growth pathways of three- and four-ring PAHs are barely influenced by the specific fuel chemistry and indenyl plays a crucial role via the typical RSR chain reactions at high pressures.
Hydrocarbons are well-known insoluble oils which are rarely considered as stimuli to trigger molecular self-assembly transition. We report in this work that hydrocarbons are a class of distinct stimuli for the self-assembly transition in the catanionic surfactant systems . Particularly, the cyclic hydrocarbons and chain-like ones has exactly opposite impact. By solubilizing in the palisade region of surfactant bilayers, the cyclic hydrocarbons would increase the volume of the hydrophobic part of the surfactant, thus increasing the packing parameter and leading to structures with smaller curvature. On the contrary, the chain-like hydrocarbons will be insolubilized in the interior of the hydrophobic domains formed by surfactant, which therefore swells the surfactant bilayers and increases the curvature of the outer layer. As a result, the self-assembly would change into structures with larger curvature. For this reason, addition of cyclic alkanes, such as ethylcyclohexane and ethylbenzene , leads to the transition from vesicles to lamellae, whereas addition of chain-like ones, such as octane, results in the transition from vesicles or lamellae to nanoemulsions . It is noticed that the saturation state of the hydrocarbons is not relevant to the self-assembly transition, and whether the alkanes are cyclic or chain-like is the determinative factor that decides which direction the self-assembly would transform to. We expect the current study is very promising in guiding enrichment and separation of organic matters.
Du Junjie,Zeng Lin,Yan Tao,Wang Chuanhao,Wang Menglin,Luo Lei,Wu Wenlong,Peng Zijun,Li Hongliang,Zeng Jie
Plastic pollution is a planetary threat that has been exacerbated by the COVID-19 pandemic due to the surge in medical waste, personal protective equipment and takeaway packaging. A socially sustainable and economically viable method for plastic recycling should not use consumable materials such as co-reactants or solvents. Here we report that Ru nanoparticles on zeolitic HZSM-5 catalyse the solvent- and hydrogen-free upcycling of high-density polyethylene into a separable distribution of linear (C 1 to C 6 ) and cyclic (C 7 to C 15 ) hydrocarbons. The valuable monocyclic hydrocarbons accounted for 60.3 mol% of the total yield. Based on mechanistic studies, the dehydrogenation of polymer chains to form C=C bonds occurs on both Ru sites and acid sites in HZSM-5, whereas carbenium ions are generated on the acid sites via the protonation of the C=C bonds. Accordingly, optimizing the Ru and acid sites promoted the cyclization process, which requires the simultaneous existence of a C=C bond and a carbenium ion on a molecular chain at an appropriate distance, providing high activity and cyclic hydrocarbon selectivity.
危险品化学品经营许可证（带存储）