Hongfei Lin

Highly active and sinter-resistant Pd-nanoparticle catalysts encapsulated in silica

) that aresufficiently porous to allow unhindered mass transfer? 2) Howdoes the activity of the encapsulated catalysts compare totraditional supported Pd catalysts for CO oxidation andacetylene hydrogenation? 3) Do the shell structures providestability with respect to sintering at high temperatures?Nanoscale core/shell Pd@SiO

Advanced micro/nanocapsules for self-healing smart anticorrosion coatings

Smart self-healing coatings for corrosion protection of metallic substrates (steel, magnesium, and aluminium, and their alloys) have attracted tremendous interest due to their capability to prevent crack propagation in the protective coatings by releasing active agents from micro/nanocapsules, that is, micro/nano particles consisting of a coating layer or a shell (micro/nanocontainers) and core material (solids, droplets of liquids or gases), in a controllable manner. This paper aims to give a concise review on the most recent advances in preparing micro/nanocapsules based on different types of micro/nanocontainers, i.e., organic polymer coatings, inorganic clays, mesoporous silica nanoparticles, polyelectrolyte multilayers, etc. for smart coatings with self-healing properties. The state-of-the-art design and preparation of micro/nanocapsules are highlighted with detailed examples.

Profiles of particle velocity and solids fraction in a high-density riser

Abstract Radial profiles of particle velocity and solids fraction in a high density circulating fluidized bed (HDCFB) at average cross-sectional solids fraction up to 0.21 were measured by an improved optical fiber laser doppler velocimeter and an optical fiber density sensor. The axial development of these radial profiles and the influence of operating conditions on the profiles were examined. The results showed that similar radial profiles of solids fraction exist in the HDCFB. The following Boltzman function can correlate well the solids fraction profile: (1 − ɛ )/(1 − ɛ ) = 2.2 − (2)/(1 + exp(10· r / R −7.665)). The radial profiles of particle velocity in HDCFB can also be described by the Boltzman function, that is, ( V p )/ ( U g ) = (2.7)/(1 + exp(10· r / R −10· X o ) − 0.2). The Boltzman profiles of particle velocity in the high density operating regime was different with the parabolic shape operating in dilute phase regime. The local particle fluctuation velocity in the center of the riser increases with average solids concentration, while the fluctuation velocity decreases sharply as the radial position near the wall.

Reusable adsorbents for dilute solution separation. 6. Batch and continuous reactors for the adsorption and degradation of 1,2-dichlorobenzene from dilute wastewater streams using titania as a photocatalyst

Two types of external lamp reactors were investigated for the titania catalyzed photodegradation of 1,2-dichlorobenzene (DCB) from a dilute water stream. The first one was a batch mixed slurry reactor and the second one was a semi-batch reactor with continuous feed recycle with titania immobilized on inert supports (quartz and low density polyethylene, LDPE). The batch reactor was used to study the intermediates and reaction kinetics of DCB degradation. Four intermediate products were observed in the degradation of DCB; these being 2-chlorophenol (CP), 2,3-dichlorophenol (DCP), 1,2-dihydroxybenzene (catechol) and, o-benzoquinone. A mechanism based on these observations is proposed. Increasing the pH of the solution increased the intial rate of photodegradation of DCB. Added oxidant (hydrogen peroxide) did not have any appreciable effect on the degradation of DCB. The Langmuir–Hinshelwood kinetic parameters for DCB, DCP and CP were obtained. The steady state removals and apparent rate constants were obtained for the plug-flow reactor with different supports and compared under similar conditions. The titania supported on LDPE showed a better rate of photocatalysis than titania supported on quartz, although the titania film thickness on LDPE was five times lower than on quartz. The modification of titania surface by adsorption of a non-photodegradable polyfluorinated surfactant vastly improved the rate of DCB degradation on both LDPE and quartz. The rate of photodegradation in the immobilized tubular reactor was mass transfer controlled for the flow regimes investigated, viz., Reynolds numbers, Re<550. The steady state removal was directly proportional to the radiant flux within the range 4–16 mW cm−2.

High yield production of levulinic acid by catalytic partial oxidation of cellulose in aqueous media

A high yield of levulinic acid was produced by directly converting cellulose over a ZrO2 catalyst by a one-pot catalytic aqueous phase partial oxidation (APPO) process. Compared to conventional acid hydrolysis, APPO is a highly selective and environmentally benign process with merits of easy recovery and re-use of heterogeneous catalysts.

Magnetic and magnetoresistance behaviors of particulate iron/vinyl ester resin nanocomposites

Magnetoresistance (MR) behavior of vinyl ester monomer stabilized iron nanoparticles and heat-treated vinyl ester resin nanocomposites reinforced with iron nanoparticles were investigated. Vinyl ester monomer serves as a coupling agent with one side covalently bound onto the nanoparticle surface by a displacement reaction and the other end copolymerized with extra vinyl ester resin to form a robust entity. The particle loading and type of material (polymer or carbonized polymer) have a significant effect on the magnetic and MR properties. The heat-treated nanocomposites follow a tunneling conduction. After reduction annealing, the obtained nanocomposites possess a room temperature MR of 8.3 % at a field of 90 kOe.

A titania thin film annular photocatalytic reactor for the degradation of polycyclic aromatic hydrocarbons in dilute water streams

An external lamp, annular photocatalytic reactor with titania immobilized on a quartz tube was used to degrade two polycyclic aromatic hydrocarbons (PAHs), viz. phenanthrene (PHE) and pyrene (PYR) from a dilute water stream. The thin film geometry was used to obtain both the mass transfer coefficients and intrinsic reaction rate constants for the two compounds on immobilized titania (Degussa P-25) particles. Beyond a feed velocity of 7 cmmin(-1), the conversion was solely reaction rate controlled and was not subjected to mass transfer limitations from the aqueous phase to the immobilized titania film. The overall reaction rate constant was independent of the feed concentration as large as the saturation aqueous solubility of the two compounds. However, the conversion was dependent on the ultraviolet (UV) light illumination intensity at the reactor. The quantum efficiency ranged from 3.7 x 10(-5) to 2.7 x 10(-4) which was somewhat low because of the very low aqueous concentrations of the chemicals. The overall reaction rate constant was 1.6 times larger for pyrene than for phenanthrene. Seven reaction intermediates were identified for the conversion of phenanthrene, while for the degradation of pyrene two intermediates were identified. The presence of the phthalate ester as an intermediate product in the degradation of both PAHs indicates the presence of a quinone in both cases which degrades to the products CO(2) and H(2)O, along with other stable intermediates. Mass balance in a batch reactor showed that only 28.6-40.1% of phenanthrene is mineralized to CO(2) in 1-3h of reaction although 35-67% of the parent compound has disappeared, confirming that a substantial fraction of the parent compound has been converted to stable intermediates that remain in the reactor. A plausible mechanism based on these observations is proposed.

High yield production of formate by hydrogenating CO2 derived ammonium carbamate/carbonate at room temperature

A sustainable economy is needed to recycle carbon rather than to irreversibly use stored carbon in fossil fuels. Instead of releasing CO2 into the atmosphere, its value can be recognized as a base C1 material for chemicals. In this study, a new CO2 utilization strategy is developed via the hydrogenation of CO2 derived ammonium carbamates/carbonates, which are the intermediates in industrial urea production or carbon capture processes, to produce value-added formate chemicals. A high yield of formate, ∼92%, was achieved after hydrogenating ammonium carbamates in the ethanol–water solution at room temperature with the carbon supported palladium nano-catalyst. The ethyl carbonate ions in the ammonium carbamate/carbonate solutions were speciated by 13C NMR and were attributed to the superior hydrogenation efficiency. Ammonium ions promote the formation of ethyl carbonate ions in the presence of ethanol. The solvent affects the distribution of the reactive intermediates.

Highly efficient hydrogen storage system based on ammonium bicarbonate/formate redox equilibrium over palladium nanocatalysts.

A highly efficient, reversible hydrogen storage-evolution process has been developed based on the ammonium bicarbonate/formate redox equilibrium over the same carbon-supported palladium nanocatalyst. This heterogeneously catalyzed hydrogen storage system is comparable to the counterpart homogeneous systems and has shown fast reaction kinetics of both the hydrogenation of ammonium bicarbonate and the dehydrogenation of ammonium formate under mild operating conditions. By adjusting temperature and pressure, the extent of hydrogen storage and evolution can be well controlled in the same catalytic system. Moreover, the hydrogen storage system based on aqueous-phase ammonium formate is advantageous owing to its high volumetric energy density.

Comprehensive and sustainable recycling of polymer nanocomposites

A coupled process to recycle the polystyrene (PS) polymer nanocomposites (PNCs) is introduced to synthesize ferromagnetic core@shell Ni@C nanoparticles (NPs) and simultaneously to produce useful chemical radicals or liquid fuels. The PNCs reinforced with core@shell Ni@NiO NPs are prepared by the solvent extraction method. The Ni@NiO NPs are found to have significant catalytic effects on the pyrolysis of PS. The pyrolysis pathway changes from radical generation and β-scission for PS to radical generation, recombination and hydrogenation for the PNCs. Gas chromatography/mass spectrometry (GC/MS) results confirm the same gas products from pure PS and its Ni@NiO PNCs. However, for the liquid products, more saturated products were obtained from the PNCs than those from pure PS due to the catalytic hydrogenation of the Ni NPs. A significantly large magnetization (25.0 emu g−1), anti-corrosion and high specific surface area (236.68 m2 g−1) were observed in the formed core–shell NPs.