The tribological behaviours of a steel-on-steel contact lubricated by three different fl uids: (i) tetrakis(3-trifl uoromethylphenoxy)-bis(4-fl uorophenoxy)-cyclotriphosphazene (X-1P), (ii) a synthetic bridged cyclotriphosphazene, and (iii) linear phosphazene derivative as base fl uids were comparatively investigated on an Optimol SRV oscillating friction and wear tester. The results show that X-1P records the lowest friction coeffi cient, and linear phosphazene oligomer gives the lowest wear volume loss of the steel among the investigated lubricants. Moreover, the bridged cyclotriphosphazene shows much better anti-wear ability than cyclotriphosphazene (X-1P) at both room and elevated temperatures. The worn surfaces were analysed by means of scanning electron microscopy, energy dispersive spectrometry and X-ray photoelectron spectroscopy. The results demonstrate that the protective layer originated from the tribochemical reaction together with the adsorbed boundary lubricating layer containing organic F-containing compounds; nitrogen oxide and FeF 2 played an important role in improving the friction and wear behavior of the steel-on-steel system.
In this study, we investigated the structure–absorption relationship of common surface modifiers of chitosan (CTS), polyvinyl acetate (PVA), and titanium dioxide (TiO2) with α-quartz surface using molecular dynamics simulation. And the orientations and combinations derived from structures between modified α-quartz and ZSM-5 crystallites were also investigated. The results show that PVA is a non-linear organic macromolecule with a large amount of hydroxyl groups on its surface, which easily adhere to the surface of the substrate and agglomerate. CTS is a straight-chain structure containing a large number of hydroxyl and amino groups, which easily accumulate and spread on the surface of the substrate. TiO2 not only forms hydrogen bonds and complexes with the substrate but also interacts with each other to form a dense modifier layer. We observed that a large number of stable Ti–O–Si chemical bonds formed between the modified layer of inorganic small-molecule TiO2 and the surface of α-quartz, which compacted and stabilized the attached ZSM-5 film. Moreover, the orientation angle of the ZSM-5 nanocrystalline nucleus on the modified α-quartz was computed, which confirmed that the b-axis orientation of the ZSM-5 nanocrystalline nucleus was the highest on the surface of the substrate modified by TiO2. We discussed the influence of the modified temperature of modifiers in the constructed materials, and we have observed the adsorption state differences of TiO2 at different modified temperatures. We also discussed the catalytic properties of the materials prepared by the corresponding methods in conversion of methanol-to-aromatics (MTA) reaction. These results agree with our previous experimental data. By employing molecular dynamics simulation, we have obtained more precise conclusive information of the b-oriented growth of ZSM-5 crystallites, which highly depends on the surface modifiers.
In this study, all‐atom model of Pd/ZSM‐5/γ‐Al2O3 was developed and validated by comparing the experimental results of nitrogen adsorption isotherm, pore structure parameters, and powder X‐ray diffraction to our simulation results. Coal tar was simulated using dibenzothiophene (DBT), and tetralin (THN) in our study, and the product of coal tar hydrodesulfurization was modeled by H2S and n‐hexane (Hex). The adsorption and diffusion of the DBT, THN, and Hex on Pd/ZSM‐5/γ‐Al2O3 were investigated, and the simulation results were verified by differential thermogravimetric and X‐ray photoelectron spectroscopy results. The results demonstrated that DBT and THN mainly adsorbed to mesopores, and part of THN could also adsorb to micropores. Note that the mesopores allow the reactions of DBT, THN, and Hex to take place as they have large enough size, and micropores limit those reactions as those model molecules hardly adsorbed to micropores. In addition the acidity of the carrier weakens the heat of adsorption of H2S, making it easier to diffuse out of the catalyst and protect the active site. And our simulation results also show that the diffusion coefficient of H2S was much higher than other chemicals. As a consequence, the multichannel design and the choice of acidic carrier improved the sulfur tolerance of the catalyst.
Abstract.A series of ZSM-5/Ȗ-Al 2 O 3 composite materials were prepared under various pretreatment method; The physicochemical properties of composite materials were investigated by XRD, SEM, FTIR to find out optimal pretreatment method. The results showed that the composite materials performance better structure property when Ȗ-Al 2 O 3 was firstly immersed in TPAOH solution under reflux condensation for a period of time and then immersed into anhydrous alcohol before mixed with ZSM-5 precursor solution. The result of infrared spectrum indicated that the formation of Al-OH bond played a key role in the synthesis of micro-mesoporous ZSM-5/Ȗ-Al 2 O 3 composite materials.
Porous polymer based on copolymer of acrylonitrile and the ionic liquid 1-allyl-3-methylimidazolium can be prepared by free radical polymerisation and then turned into porous particle by a two-step swelling method. The CO 2 absorption of the product was investigated.
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