High efficient separation of olefin from fluid catalytic cracking naphtha: Separation mechanism and universal simulation method

The fluid catalytic cracking (FCC) naphtha critical component-oriented separation process is an efficient method to produce ultra-low-sulfur (<10 μg/g) gasoline with minimal loss of octane number (<1 RON). However, the product quality is highly dependent on the structure of the components of FCC naphtha. Aromatics and thiophene sulfides without a methyl side chain favor the separation of olefin. The major impulse of olefin separation is the solvent-induced dipole of aromatics or thiophene sulfides, leading to a “Plane-to-Plane” combination between the solvent and aromatics or thiophene sulfides, accompanied by a steric hindrance due to their side chains. This condition resulted in 2–3 times greater θ of benzene and thiophene compared with that of toluene and 3-methylthiophene. In addition, an improved non-random two-liquid model was proposed based on the above results, and a simulation method for FCC naphtha solvent extraction process was established. The calculation results accorded well with industry data.     

Roles of interaction between components in CZZA/HZSM-5 catalyst for dimethyl ether synthesis via CO2 hydrogenation

The roles of interaction between two catalyst components in CuO–ZnO–ZrO₂–Al₂O₃ (CZZA)/HZSM-5 bifunctional catalyst for dimethyl ether (DME) synthesis via carbon dioxide hydrogenation were investigated. It was found that CZZA catalyst showed excellent stability during methanol (MeOH) synthesis for 100 h, while there was a severe loss of catalytic activity in the bifunctional catalyst for DME synthesis. Hence, the effects of different degrees of intimacy of two catalyst components were studied for DME synthesis, including mixed and separated modes. For the mixed mode, the particle size of catalysts and the amount of reaction intermediates were proven to influence the catalyst deactivation. For the separated mode, the catalysts showed rapid deactivation within a short time. Various characterizations indicated that the remarkable deactivation of separated mode was mainly caused by the decrease of copper active centers (e.g., sintering and oxidation) and blockage of acid sites via increased coke deposition on HZSM-5.     

Simultaneously achieved high-energy storage density and efficiency in (K,Na)NbO3-based lead-free ferroelectric films

With the development of advanced electrical and electronic devices and the requirement of environmental protection, lead-free dielectric capacitors with excellent energy storage performance have aroused great attention. However, it is a great challenge to achieve both large energy storage density and high efficiency simultaneously in dielectric capacitors. This work investigates the energy storage performance of sol-gel-processed (K,Na)NbO₃-based lead-free ferroelectric films on silicon substrates with compositions of 0.95(K_0.49Na_0.49Li_0.02)(Nb_0.8Ta_0.2)O₃-0.05CaZrO₃-x mol% Mn (KNN-LT-CZ5-x mol% Mn). The appropriate amount of Mn-doping facilitates the coexistence of orthorhombic and tetragonal phases, suppresses the leakage current, and considerably enhances the breakdown strengths of KNN-LT-CZ5 films. Consequently, large recoverable energy storage density up to 64.6 J cm⁻³ with a high efficiency of 84.6% under an electric field of 3080 kV cm⁻¹ are achieved in KNN-LT-CZ5-5 mol% Mn film. This, to the best of our knowledge, is superior to the majority of both the lead-based and lead-free films on silicon substrates and thus demonstrates great potentials of (K,Na)NbO₃-based lead-free films as dielectric energy storage materials.     

Ti4+ modified MgZrNb2O8 microwave dielectric ceramics with an ultra-high quality factor

Ti⁴⁺-modified MgZrNb₂O₈ (MgZr_1-xTi_xNb₂O₈, x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were synthesized using the traditional solid-state reaction method. Pure MgZr_1–xTi_xNb₂O₈ was detected without any secondary phase via the X-ray diffraction patterns. According to the sintering behavior and the surface morphology results, the introduction of Ti⁴⁺ reduced the sintering temperature and promoted the grain growth. The correlations between the dielectric properties and the crystal structure were analyzed through the Rietveld refinement and Raman spectroscopy. The slight shifts of the Raman peaks, corresponding to different vibration modes, were induced by the substitution of Ti⁴⁺ for Zr⁴⁺ and related to the improved quality factor. In general, the sample of MgZr_0.9Ti_0.1Nb₂O₈ sintered at 1320°C for 4 h exhibited promising microwave dielectric properties with an ultra-high Q × f value of 130 123 GHz (at 7.308 GHz, 20°C), which is potential for 5G communication applications.     

High extinction-ratio microstructure fiber based on chalcogenide glasses

Extinction ratio (ER) is one of the important parameters to characterize the polarization-maintaining (PM) performance of the fiber. In this paper, we report the preparation and properties of a novel chalcogenide microstructure fiber with a high ER. We fabricate a preform using a peeled-off extrusion method. The core and cladding material of the fiber are Ge₉As₂₃Se₆₈ and Ge₁₀As₂₂Se₆₈. The preform was drawn into a fiber with an average ER of −17.08 dB. The loss of the fiber is less than 2 dB over 5.20–8.55 μm, and the minimum loss of the fiber is 0.57 dB/m at 6.2 μm. Moreover, a flat mid-infrared supercontinuum spectrum spanning from 1.53 to 12.50 μm is generated by pumping an 18-cm-long PM fiber for the first time.     

Effect of DAPBO segment on the structure and performance enhancement of powder foamed BTDA-ODA polyimide

Achieving excellent thermal stability, good mechanical strength, and low-density in one product, is a big challenge in the design and synthesis of polyimide (PI) foams. We selected a rigid diamine monomer, 2-(4-aminophenyl)-5-aminobenzoxazole (DAPBO) to partially replace 4,4′-oxydianiline (ODA) in BTDA-ODA system, and studied the effect on properties of foamed PI products. With various molar ratio between DABPO and ODA (0:5, 1:4, 2:3, 3:2, 4:1, 5:0), the diamine(s) polymerized with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and produced six PI precursors (PAE-0 ~ PAE-5). After foaming and thermal imidization, corresponding PI foams (PI-0 ~ PI-5) prepared. Among them, PI-3 has a glass transition temperature of 386°C, which is 95°C higher than PI-0, and its compressive strength reaches 1.32 MPa. Moreover, PI-3 has a uniform cell structure with an average pore size of ~200 μm. The analysis results show that PI-3 is in a transition state from amorphous to partial crystalline, maintaining a balance between flexibility and rigidity. The addition of DABPO not only increases the rigidity of polymer molecular segments, but also introduces N and O atoms that can form intermolecular hydrogen bonds between molecules, which increases the packing density and arrangement regularity of polymer molecules.     

Effects of thickness and hydrophobicity of double microporous layer on the performance in proton exchange membrane fuel cells

In this paper, a multi-layer gas diffusion layer (GDL) is designed. The GDL consists of a single carbon paper backing layer and dual microporous layers (MPLs). Moreover, the effects of thickness and hydrophobicity of double MPL on the performance of proton exchange membrane fuel cells are investigated. From the test results of the water contact angle, conductivity, pore size distribution, and the polarization curve, it is found that the thickness adjustment increases the number of 0.5 to 7 μm and 20 to 100 μm pores in GDL, which is more conducive to water discharge. Therefore, the thickness adjustment is more favorable to the cell performance under high humidity. While the gradient hydrophobic design makes the MPL of the modified intermediate layer have a certain water-retaining capacity to humidify the reaction gas, which has better effect under low humidity. At last, the results show that the optimized GDL meets a limit power density of 1.772 W/cm² under 60% humidification and 1.600 W/cm² under 100% humidification.     

Hierarchically porous N-doped carbon nanofibers derived from ZIF-8/PAN composites for benzene adsorption

Coupling with electrospinning technique, metal–organic-frameworks (MOFs)-derived porous carbon fibers exhibit a great potential application in the adsorption of volatile organic compounds (VOCs) because of their huge surface area, high porosity, as well as sufficient heteroatom-doped active sites. In this work, the hierarchically porous N-doped carbon nanofibers are obtained after the pyrolysis of zeolite imidazole framework-8 and polyacrylonitrile (ZIF-8/PAN) composite fibers synthesized by electrospinning method. The N-doped carbon nanofibers fabricated in N₂ atmosphere (N-CF-N₂) present an enhanced adsorption capacity of 694 mg/g for benzene because of the synergistic effect of the hierarchically porous structure and the abundant N-species-containing active sites. It is also interesting that the N-doped hierarchical carbon nanofibers fabricated in Ar atmosphere (N-CF-Ar) exhibit a low benzene adsorption as compared with the N-CF-N₂, which can be attributed to the porous structure damage caused by the bombardment of heavy Ar atoms on the pore shells during the pyrolysis. These results not only show a promising application of the as-fabricated N-CF-N₂ in adsorption of VOCs for air purification due to its merit of cost-efficient, large-scale production, and excellent adsorption capacity, but also expand the potential of electrospinning technology and composite fibers in volatile organic gas adsorption.     

Preparation and tribological behavior of polytetrafluoroethylene/metal mesh composites with sandwich structure

Polytetrafluoroethylene (PTFE) owns an excellent self-lubricating performance, but its wear rate is very high due to the large-scale spalling of the matrix in the friction. In this paper, A new kind of PTFE composites with sandwich structure was prepared by layer-press technology, whose middle layer is filled with metal mesh. The influence of the mesh structure and mesh density of middle metal layer on tribological properties of composites were researched in detail. The results revealled that the metal mesh located in the composites can efficiently prevent the large-scale spalling of PTFE, which induces the sample of PTFE/500# plain woven dutch metal mesh (PTFE-500#PWD) to have a lower wear rate (9 × 10⁻⁵ mm³/Nm) and COF (0.106) under the fixed experimental condition. The prepared PTFE/metal mesh composites reveal excellent anti-friction and anti-wear performance, which can be used to fabricate a new kind of self-lubricating materials.     

Achieving superiorly high heat-dimensional stability,high strength,and good electrochemical performance for electrospun separators in power lithium-ion battery through building unique condensed structure based on polyimide and poly (m-phenylene isophthalamide)

It is still a challenge for simultaneously achieving high heat resistance, high strength and outstanding electrochemical performance for separators in power lithium-ion battery (PLB). Herein, new high performance electrospun separators are developed through building unique structure based on polyimide (PI) and poly (m-phenylene isophthalamide) (PMIA). Orthogonal tests (4⁴) show that the magnitude order of electrospinning factors on the morphology of membrane is concentration>injection rate>receiving distance>voltage. With the optimum factors, the electrospun membrane (PI/PMIA) was prepared, which was further pressed at 100°C for 10 min to get treated membrane (H-PI/PMIA). Interestingly, the comprehensive performance of PI/PMIA is not a simple combination of those of PI and PMIA; instead, PI/PMIA has much better thermal and mechanical properties than both PI and PMIA, proving that PI/PMIA has a synergistic effect. PI/PMIA and H-PI/PMIA not only have good ionic conductivity and electrochemical stability, but also have superiorly high properties including dimensional stability (thermal shrinkage temperature>300°C), tensile strengths (24.1 MPa for PI/PMIA, 34.3 MPa for H-PI/PMIA) and capacity retentions (97.9%, 99.2%) compared with electrospun membranes for PLBs reported in the literature so far (SCI database). The mechanism behind these attractive performances is discussed from condensed structure of membranes.