Fengqiu Chen

Catalyst design for methane oxidative coupling by using artificial neural network and hybrid genetic algorithm

Abstract A new method for catalyst design was discussed based on artificial neural network, which was developed to simulate the relations between catalyst components and catalytic performance in the previous research. For enhancing efficiency of catalyst design, a new hybrid GA tested by TSP was generated for global optimization to design the ‘optimal’ catalyst. A multi-turn design strategy was described. Based on the previous research, the design method was applied for designing multi-component catalyst for methane oxidative coupling, some better catalysts, in which C2 hydrocarbon yields were greater than 25% were designed. When reacting on the best catalyst, GHSV was 33313 cm 3 g −1 h −1 , CH4:O2 was 3, reaction temperature was 1069 K , methane conversion and C2 hydrocarbon selectivity were 37.79% and 73.50%, respectively (C2 hydrocarbon yield was 27.78%), which was higher than that of previous reported catalysts on no diluted gas condition, and showed a better prospect for industrialization of methane oxidative coupling. The research also showed that the new catalyst design method is highly efficient and universal.

Magnetic particle-based super-hydrophobic coatings with excellent anti-icing and thermoresponsive deicing performance

Magnetic nanoparticles (MNPs) were introduced as the heat mediators in a superhydrophobic coating for anti-icing and deicing performance in this article. The fluorinated copolymer tethered epoxy groups were synthesized and mixed with amino modified Fe3O4 nanoparticles, and then crosslinked with diethylenetriamine to obtain novel multifunctional magnetic hybrid coatings. The compositions, morphologies, surface microstructure and wettability performance of the hybrid coatings were systematically investigated by the scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and water contact angle (WCA) measurements. The target coatings exhibited excellent superhydrophobicity and wetting stability driven by the formation of micro–nano hierarchical surface roughness covered with fluorinated groups. The low temperature (−15 °C, RH: 50 ± 5%) WCA showed that the superhydrophobic surface could delay the freezing time from 50 s to 2878 s. And the ice adhesion strength was significantly lower than that of a pure copolymer coating. More importantly, the outstanding photothermy and magnetothermal effects of the magnetic particles endowed the coatings with long time icing delay and thermal deicing properties. The fabricated multifunctional superhydrophobic surfaces with excellent anti-icing and active deicing properties will be promising for practical applications.

Microphase Structure, Crystallization Behavior, and Wettability Properties of Novel Fluorinated Copolymers Poly(perfluoroalkyl acrylate-co-stearyl acrylate) Containing Short Perfluorohexyl Chains

Novel fluorinated copolymers of stearyl acrylate (SA) and (perfluorohexyl)ethyl acrylate (C6A), (perfluorohexyl)ethyl methacrylate (C6MA), 2-[[[[2-(perfluorohexyl)]-sulfonyl]methyl] amino]ethyl acrylate (C6SA), and methacrylate (C6SMA) were synthesized via miniemulsion copolymerization. The extremely hydrophobic monomers perfluoroalkyl acrylate (FA) and SA acted as the reactive costabilizer in the miniemulsion system. The microstructure and surface wetting properties of the copolymers were characterized by (1)H NMR, FT-IR, and dynamic contact angle test. The crystallization behaviors and fine surface structures of the copolymer films were determined by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) analysis. The self-assembled aggregation and roughness of the copolymer films were investigated by atomic force microscopy (AFM). The results showed that the fluorinated side chains interrupted and impeded the crystallizable side chains of SA from forming complete crystals. And the Tm and ΔHf of the copolymers were decreased as a consequence of this effect. The fluorinated side chains in P(C6A/SA) and P(C6MA/SA) arranged between the crystallizable hydrocarbon side chains of SA, while the crystallization structure of fluorinated and nonfluorinated pendant groups existed all at once in copolymers P(C6SA/SA) and P(C6SMA/SA). The four copolymers exhibited very low surface free energy and excellent dynamic water repellency attributed to the restriction of perfluoroalkyl groups combined with crystallization of stearyl pendant groups.

Ultralow Oil-Fouling Heterogeneous Poly(ether sulfone) Ultrafiltration Membrane via Blending with Novel Amphiphilic Fluorinated Gradient Copolymers

A novel amphiphilic fluorinated gradient copolymer was prepared by semibatch reversible addition-fragmentation chain transfer (RAFT) method using poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate (TFOA) as monomers. The resultant amphiphilic copolymers were then incorporated into the poly(ether sulfone) (PES) to fabricate PES blend membranes via the non-solvent-induced phase separation method (NIPS). During the phase inversion process, both hydrophilic (PEGMA) and low surface energy (TFOA) segments significantly enriched on the membrane surface by surface segregation to form an amphiphilic surface, which was demonstrated by surface wetting properties and X-ray photoelectron spectroscopy (XPS) measurements. According to the filtration experiments of oil-in-water emulsion, the heterogeneous membranes exhibited superior oil-fouling resistant properties, that is, low flux decay (as low as 15.4%) and high flux recovery (almost 100%), compared to the pure PES membrane. The synergistic effect of fouling-resistant and fouling-release mechanisms was found to be responsible for the excellent antifouling capacities. The findings of this study offer a facile and robust strategy for fabricating ultralow oil-fouling membranes that might be used for effective oil/water separation.

Cationic Ring Opening Polymerization of Octamethylcyclotetrasiloxane Initiated by Acid Treated Bentonite

Cationic ring opening polymerization of octamethylcyclotetrasiloxane (D4) initiated by acid treated bentonite was investigated. The experimental conditions were chosen on the basis of preliminary experiments. Higher temperature was found beneficial for the reaction process while stirring intensity beyond a certain level showed no obvious effect on the reaction rate. Polymers were characterized by Fourier transform infrared, proton nuclear magnetic resonance ( 1 H-NMR) and gel permeation chromotography. The width of molecular mass distribu- tion was found ranging between 1.2 and 1.4, which is extraordinarily narrow compared with that of cationic polym- erizations reported elsewhere (>1.9). The results were believed due to the absence of free proton and counter ion which simplifies the polymerization process and the huge steric hindrance provided by bentonite particles which keeps the propagation of polysiloxane onto the surface of bentonite particles in a much more regular way. A feasible mechanism is proposed and seems to be supported well by experiments. Additionally, from the results of α, ω-dihydrogen terminated polysiloxanes prepared, the possibility of applying this potential environmentally friendly heterogeneous catalyst in industrial polymerization of cyclosiloxanes is anticipated. Keywords octamethylcyclotetrasiloxane, cationic polymerization, polysiloxane

Nickel–platinum nanoparticles immobilized on graphitic carbon nitride as highly efficient catalyst for hydrogen release from hydrous hydrazine

Here we demonstrate that the combination of NiPt alloy nanoparticles with a graphitic carbon nitride (g-C3N4) support facilitates H2 production from hydrous hydrazine in an alkaline solution under moderate conditions. Of all the heterogeneous catalysts tested, Ni37Pt63/g-C3N4 shows superior catalytic performance with a maximum initial turnover frequency (TOF) of 570 h−1 at 323 K.

Robust liquid-repellent coatings based on polymer nanoparticles with excellent self-cleaning and antibacterial performances

In this work, quaternary ammonium salt (QAS) functionalized fluorinated copolymer tethered hydroxyl groups were synthesized by free radical polymerization. And then novel liquid-repellent and antibacterial nanocomposite coatings were prepared via cross-linking the fluorinated copolymer and poly(urea-formaldehyde) nanoparticles (PUF NPs) containing active methylol groups with hexamethylene diisocyanate. The surface physical and chemical properties of the nanocomposite coating were systematically characterized by a series of measurements, demonstrating that the liquid-repellent surface with a dual hierarchical structure was obtained by the introduction of PUF NPs. The nanocomposite coating displayed superb self-cleaning and liquid-repellent properties, and could also maintain its superhydrophobicity even after 16 abrasion cycles and 20 cycles of cross-cut tape test. Moreover, the nanocomposite coating with over 0.11% surface concentration of N+ exhibited excellent antibacterial activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. These results conclusively indicated that nanocomposite coatings had great promise for potential application in a wide range of practical fields.

Reaction pathways of β-D-glucopyranose pyrolysis to syngas in hydrogen plasma: a density functional theory study.

In this work, density functional theory (DFT) was employed to investigate the reaction pathways of β-D-glucopyranose for better understanding the pyrolysis mechanism of cellulose in hydrogen plasma. Many possible reactions were considered, and the reaction enthalpies and activation energies of these reactions were calculated using density functional theory (DFT) with a Gaussian method of B3LYP and basic set of 6-31G(d,p). A most possible reaction pathway was brought up. According to this reaction pathway, the main products of cellulose pyrolysis in hydrogen plasma would be syngas, and few light hydrocarbons. CO mainly comes from the decomposition of aldehyde group, while H2 mainly comes from dehydrogenation processes. Active H in plasma are found to play a very important role in many reactions, and they can remarkably lower the energies needed for reactions.

Enhanced oil-fouling resistance of poly(ether sulfone) membranes by incorporation of novel amphiphilic zwitterionic copolymers

In this study, a novel amphiphilic copolymer, poly(carboxyl betain methyl acrylamide-co-3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate) P(CBMA-co-TFOA), with zwitterionic and fluorinated moieties was synthesized by free radical polymerization and a subsequent quaternization reaction. The synthesized copolymers acted as additives and were blended with poly(ether sulfone) (PES) to fabricate low oil-fouling PES membranes through nonsolvent induced phase separation (NIPS). The prominent surface enrichment of hydrophilic zwitterionic (CBMA) and low surface energy (TFOA) segments on the membrane surface was verified by X-ray photoelectron spectroscopy (XPS), water contact angle measurements and surface energy analysis. The excellent oil-fouling resistant capacity of these modified membranes was demonstrated by oil/water emulsion separation tests. In particular, membrane PES/P3, with the optimized hydrophilic and hydrophobic ratio, achieved the highest anti-oil-fouling properties with a total flux decay as low as 17.4% (nearly no irreversible flux-decline) and high flux recovery (99.3%) after simple water flushing. These desirable antifouling properties are believed to originate from the binary-cooperative effect of zwitterionic and low surface energy microdomains. Moreover, three-cycle oil/water separation tests and underwater immersion experiments further revealed that the as-prepared membranes have remarkable antifouling stability. The results of this study provide a new insight into the surface chemical heterogeneity–antifouling property relationships of membranes for efficient oil/water separation.

Efficient hydrogen generation from formic acid using AgPd nanoparticles immobilized on carbon nitride-functionalized SBA-15

Bimetallic AgPd nanoparticles were successfully immobilized on graphitic carbon nitride (g-C3N4) functionalized SBA-15 for the first time by a facile co-reduction method. These catalysts were applied in the decomposition of formic acid. The dehydrogenation of formic acid is dependent on the composition of AgPd and the content of carbon nitride (CN). Among all of the AgPd/mCND/SBA-15 catalysts tested, the Ag10Pd90/0.2CND/SBA-15 catalyst exhibits highly superior performance for the decomposition of formic acid into high-quality hydrogen at 323 K with 100% hydrogen selectivity and a turnover frequency of 893 h−1, which is among the maximum values obtained at 323 K in this paper. The improved performance is a promising step towards the utilization of formic acid as a hydrogen storage material.