Petal-Shaped Graphene Porous Films with Enhanced Absorption-Dominated Electromagnetic Shielding Performance and Mechanical Properties.

The absorption-dominated graphene porous materials, considered ideal for mitigating electromagnetic pollution, encounter challenges related to intricate structural design. Herein, petal-like graphene porous films with dendritic-like and honeycomb-like pores are prepared by controlling the phase inversion process. The theoretical simulation and experimental results show that PVP K30 modified on the graphene surface via van der Waals interactions promotes graphene to be uniformly enriched on the pore walls. Benefiting from the regulation of graphene distribution and the construction of honeycomb pore structure, when 15 wt % graphene is added, the porous film exhibits absorption-dominated electromagnetic shielding performance, compared with the absence of PVP K30 modification. The total electromagnetic shielding effectiveness is 24.1 dB, an increase of 170%; the electromagnetic reflection coefficient reduces to 2.82 dB; The thermal conductivity reaches 1.1 W/(m K), representing a 104% increase. In addition, the porous film exhibits improved mechanical properties, the tensile strength increases to 6.9 MPa, and the elongation at break increases by 131%. The method adopted in this paper to control the enrichment of graphene in the pore walls during the preparation of honeycomb porous films by the phase inversion method can avoid the agglomeration of graphene and improve the overall performance of the porous graphene porous films.

Study on the Hydroconversion Law of Coal-Based Heavy Fractions with Different Catalyst Contents Based on an Improved Separation Method.

Heavy fractions (e.g., asphaltene and resin) can easily be subjected to physical aggregation and chemical coking reaction through molecular force in the process of lightweight processing and use of coal tar (CT), such that the normal processing and use can be affected. In this study, hydrogenation experiments were performed by regulating the catalyst to oil ratio (COR), while the heavy fractions of the hydrogenated products were extracted based on a novel separation method (e.g., the resin with a poor separation effect and rare existing research). The samples were analyzed through Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. On that basis, the composition and structure characteristics of heavy fractions and the law of hydrogenation conversion were investigated. As indicated by the results, with the rise of the COR, the saturates, aromatics, resins, and asphaltenes (SARA) contents indicated the law of increasing the content of saturate, decreasing the content of other fractions, as well as sharply decreasing the content of asphaltene. Moreover, with the increase of the reaction condition, the relative molecular weight, the content of the hydrogen bonded functional groups and C-O groups, the carbon skeleton properties, the number of aromatic rings, and the stacking structure parameters were progressively reduced. In comparison with resin, asphaltene was characterized by large aromaticity and more aromatic rings, short and less alkyl side chains, as well as more complex heteroatoms on the surface of the heavy fractions. The results achieved in this study are expected to lay a solid basis for the relevant theoretical research and facilitate the industrial use process of CT processing.

Study on the Pretreatment Process and Removal Rules of Sulfur-Containing Compounds for Medium- and Low-Temperature Coal Tar.

The heteroatoms (sulfur and nitrogen) and metals (ferrum and calcium) in coal tar can easily cause the corrosion of hydrogenation equipment, catalyst poisoning, and environmental pollution. These should be removed before coal tar is hydrogenated. In this study, with the acid refining method, the effects of three polyether demulsifiers (i.e., PD1, PD2, and PD3), polyamine carboxylate demetallizers (i.e., PCD1, PCD2, and PCD3), and separation temperature on the removal of ferrum, calcium, sulfur, and nitrogen in medium- and low-temperature coal tar were determined. PD2 was selected, and the added amount was 200 µg·g-1. When the PD2 demulsifier was added alone or PD2 demulsifier with various demetallization agents was added, heteroatoms in coal tar could be effectively removed. For the experiments and analysis, the pretreatment conditions of coal tar were as follows: the addition amount of the PD2 demulsifier was 200 µg·g-1, the addition amount of the PCD3-type demetallization agent was 400 µg·g-1, and the stirring temperature was 80 °C. Before and after pretreatment, the methods of inductively coupled plasma-atomic emission spectrometer, gas chromatography-mass spectrometry (MS), and Fourier transform-ion cyclotron resonance MS were used in the present study to explore and analyze the distribution, occurrence form, and removal law of sulfur in coal tar. As revealed from the results, sulfur compounds in coal tar <360 °C fraction (light coal tar fraction, LF) before being pretreated had a lower content, which existed as benzothiophene and dibenzothiophene largely. Sulfur compounds S1 and S2 achieved the maximum relative abundance in >360 °C fraction (heavy coal tar fraction, HF). After the compounds were pretreated, the sulfur removal rate reached 40.0% in LF, and the sulfur compounds were primarily removed. For HF, the sulfur removal rate reached 20.1%. In addition, S1 compounds within the dibenzothiophene derivatives exhibiting more side chains and a larger condensation degree were basically removed. S2 compounds, mainly linked to several quinolines or more aromatic rings and thioether-aliphatic amine sulfur compounds exhibiting small molecular weight and simple structures, were relatively easy to remove. The SO class (e.g., the sulfones and thiophene-ketone group) was more difficult to remove.