Institutional Repository of Institute of Process Engineering, CAS (IPE-IR）
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Independent Research Project of State Key Laboratory of Coal Resources and Safe Mining, CUMT
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Pyrolytic stage evolution mechanism of Zhundong coal based on reaction consistency analysis of mono/multi molecular models
No full textZhundong coalfield is the largest coalfield in China and the unclear stage evolution mechanism of Zhundong coal pyrolysis is the key factor restricting its coal fire control. Here, the monomolecular model (299 atoms) and large-scale multimolecular model (5083 atoms) were constructed for Liu huanggou (LHG) coal from Zhundong coalfield. The pyrolysis processes of the two models were calculated by ReaxFF MD method. Based on the re-action consistency analysis, the reaction paths tracing on pyrolysis stage evolution and toxic gases formation mechanisms were obtained. The LHG coal pyrolysis process is mainly because of the breakages of the ether oxygen bridge bonds, thioether bridge bonds and aliphatic hydrocarbon bridge bonds. It begins with the shed-ding of small molecules and then undergoes the thermal decomposition of the main structure and pyrolytic fragments. During the pyrolysis process, the LHG coal has constantly broken out tars, gases and other key products, accompanied by a large number of free radicals and intermediates produced. The main sources of CO are the active reaction sites where the carbonyl group and the carboxyl group located; H2S is directly produced from the sulfhydryl group. The research results will guide the staged control and directional transformation of coal fire
Controlled alcoholysis of PET to obtain oligomers for the preparation of PET-PLA copolymer
No full textControlled degradation of macromolecules or natural macromolecules is important for their subsequent utilization. Normally, it is easier to degrade them to monomers than to oligomers in designated molecular weight range, the controlled degradation is much difficult to achieve and has been challenge for the utilization of macromolecules. Here, we proposed a strategy for simultaneous degradation of the inner and outer layers of PET, which avoid the degradation of polymers from the outside to the inside and achieved the controlled degradation. Under high temperature and micro-pressure conditions, PET is transformed from dense to flocculent structure by the swelling effect, which satisfies the need for simultaneous degradation of the inner and outer layers. In addition, a stable "Dawson" type Polyoxometalates (POMs) alpha(2)-K8P2W17O61X(H2O)center dot 16H(2)O (X = Zn, Mn, Co, Ni, Cu) with limited number of catalytic activity center was synthesized and applied to PET alcoholysis to obtain oligomer with given molecular weight range. Under the optimal conditions, PET: EG: POM catalyst = 1.0: 4.0: 0.02 (wt%), 240 degrees C, 10 min, PET was completely degraded and obtained the oligomer products (Mn < 2000 g/mol) with 72.1 % yield. By investigating the mechanism of the controlled alcoholysis, the formation of flocculent PET was be the key factor in achieving controlled degradation; hydrogen bonding and coordination of POMs are the key interactions to achieve rapid alcoholysis. Finally, oligomers were applied in the preparation of PET-PLA copolymers to follow sustainable route. The incorporation of bio-based polymers demonstrates better inclusiveness to the environment and contributes to harmonious development
Revealing the wetting mechanism of Li plus -doped ionic liquids on the TiO2 surface
No full textThe sensible design of ionic liquid (IL)-based application relies on a thorough knowledge of the structure and characteristics of electrolyte-electrode interfaces. Here, the wetting processes of the Li+-doped ILs droplets on the TiO2-B(10 0) surface are investigated by molecular dynamics simulation. According to the spatial distributions of components, doped Li+ prefers to substitute the ILs and adsorb to the sub-strate, causing the orientation changes of the ILs, weakening the ILs-substrate interaction, and slowing down the wetting process significantly. As Li+ concentration rises from 0 to 80 %, the contact angle increases from 86.97 to 131.18 degrees, inducing the hydrophilic-to-hydrophobic transition. On the contrary, heating up would reduce the contact angle by extending the contact length and enhancing the maximum density of Li+-doped ILs at the interface. These quantitative results prove that the dense adjacent layer in the interface induced by the strong adsorption of Li+ dominates the wetting process of Li+-doped ILs. (c) 2022 Elsevier Ltd. All rights reserved
High temperature oxidation behavior and mechanism of SiC-TaB2 composites
No full textIn order to improve the oxidation resistance of SiC in its ceramic matrix composites (CMCs), monolithic SiC ceramics doped with various proportions of TaB2 were prepared, isothermal and non-isothermal oxidation was investigated in detail as well. It was found that even a small proportion addition of TaB2 can effectively alleviate the intense oxidation of SiC between 1200 degrees C to 1600 degrees C, i.e., an oxidation degree of SiC can be reduced by 37% in the case with 10 wt% TaB2 under non-isothermal oxidation from room temperature to 1600 degrees C. The oxidation resistance mechanism was also studied via analyzing the composition and micro-structure of the formed oxide layer, it was found that the transformation of Ta2O5 in the multiphase oxide layer from grainy to flaky shape at about 1500 degrees C plays the most important role in the excellent high temperature oxidation resistance of composites.(c) 2022 Published by Elsevier B.V