Heqing Jiang

Simultaneous Production of Hydrogen and Synthesis Gas by Combining Water Splitting with Partial Oxidation of Methane in a Hollow-Fiber Membrane Reactor†

Hydrogen is gaining more and more attention because it is regarded as an important future fuel. Today, hydrogen is mainly produced from nonrenewable natural gas and petroleum. With concerns over worldwide energy demands and global climate change, alternative sources must be found. Obviously, water is recommended as the ideal source for the generation of large amounts of hydrogen. In addition to electrolysis, recently several new processes, such as photovoltaic–photoelectrochemical water splitting and one-step or multistep thermochemical water splitting 6] based on focused solar or nuclear heat, have been developed. Although water dissociation into oxygen and hydrogen is conceptually simple [Eq. (1)], efficient hydrogen production

Direct Decomposition of Nitrous Oxide to Nitrogen by In Situ Oxygen Removal with a Perovskite Membrane

Direct decomposition of N(2)O to N(2) using perovskite hollow fiber membranes is achieved by combination with in situ oxygen removal (see picture). A coupled partial methane oxidation allows N(2)-free synthesis gas to be obtained. This sustainable process combines N(2)O removal with the simultaneous production of valuable chemicals.

Natural Gas to Fuels and Chemicals: Improved Methane: Aromatization in an Oxygen-Permeable Membrane Reactor

Adding value with membranes: Improved methane aromatization was achieved by using an oxygen-permeable membrane. The resulting membrane reactor shows a superior methane conversion and a higher resistance towards catalyst deactivation.

A simple route to incorporate redox mediator into carbon nanotubes/ Nafion composite film and its application to determine NADH at low potential

Through a new and simple ion-exchange route, two-electron redox mediator thionine has been deliberately incorporated into the carbon nanotubes (CNTs)/Nafion composite film due to the fact that there is strong interaction between any of two among the three materials (ion-exchange process between thionine and Nafion, strong adsorption of thionine by CNTs, and wrapping and solubilizing of CNTs with Nafion). The good homogenization of electron conductor CNTs in the integrated films provides the possibility of three-dimensional electron conductive network. The resulting integrated films exhibited high and stable electrocatalytic activity toward NADH oxidation with the significant decrease of high overpotential, which responds more sensitively more than those modified by thionine or CNTs alone. Such high electrocatalytic activity facilitated the low potential determination of NADH (as low as -0.1 V), which eliminated the interferences from other easily oxidizable species. In a word, the immobilization approach is very simple, timesaving and effective, which could be extended to the immobilization of other cationic redox mediators into the CNTs/Nafion composite film. And these features may offer potential promise for the design of amperometric biosensors.

B-site La-doped BaFe0.95−xLaxZr0.05O3−δ perovskite-type membranes for oxygen separation

Partial La-substitution for Fe on the B-site of the perovskite BaFe0.95−xLaxZr0.05O3−δ (BFLZ) was achieved by applying a sol–gel synthesis method. The highest La content in BFLZ for the formation of a pure cubic perovskite structure without any detectable impurities is about x = 0.04. It is found for the first time that the introduction of La on the B-site of a mixed oxide stabilizes the cubic structure. Furthermore, the formation of the cubic structure of BFLZ increases significantly the oxygen permeability. The maximum oxygen permeation flux is found for a La-content of x = 0.04 with the largest volume of the cubic unit cell, reaching 0.63 and 1.24 cm3 (STP) min−1 cm−2 for a 1.1 mm thick membrane at 750 and 950 °C, respectively. This finding is in complete agreement with the XRD structure analysis, showing that the highest B-site La-substitution of BFLZ under conservation of the pure cubic perovskite phase without forming any foreign phase was about x = 0.04. For BFLZ with x > 0.04, the secondary phase Ba6La2Fe4O15 forms increasingly and the oxygen permeation flux decreases. The influence of the sweep gas flow rates on the oxygen permeation flux and the oxygen ionic conductivity were found to be in good agreement with the Wagner theory, indicating the oxygen ion bulk diffusion as a rate-limiting step of oxygen transport. Stable oxygen permeation fluxes were obtained during the long-term oxygen permeation operation of the BFLZ (x = 0.04) membrane over 170 h at 750 and 950 °C, respectively.

Hydrogen Production by Water Dissociation in Surface‐Modified BaCoxFeyZr1−x−yO3−δ Hollow‐Fiber Membrane Reactor with Improved Oxygen Permeation

A porous perovskite BaCo(x)Fe(y)Zr(0.9-x-y)Pd(0.1)O(3-delta) (BCFZ-Pd) coating was deposited onto the outer surface of a BaCo(x)Fe(y)Zr(1-x-y)O(3-delta) (BCFZ) perovskite hollow-fiber membrane. The surface morphology of the modified BCFZ fiber was characterized by scanning electron microscopy (SEM), indicating the formation of a BCFZ-Pd porous layer on the outer surface of a dense BCFZ hollow-fiber membrane. The oxygen permeation flux of the BCFZ membrane with a BCFZ-Pd porous layer increased 3.5 times more than that of the blank BCFZ membrane when feeding reactive CH(4) onto the permeation side of the membrane. The blank BCFZ membrane and surface-modified BCFZ membrane were used as reactors to shift the equilibrium of thermal water dissociation for hydrogen production because they allow the selective removal of the produced oxygen from the water dissociation system. It was found that the hydrogen production rate increased from 0.7 to 2.1 mL H(2) min(-1) cm(-2) at 950 degrees C after depositing a BCFZ-Pd porous layer onto the BCFZ membrane.

A facile nanocomposite strategy to fabricate a rGO–MWCNT photothermal layer for efficient water evaporation

Solar-driven water evaporation assisted by photothermal membranes is considered as one of the sustainable and cost-effective strategies for pure water generation and wastewater treatment. Herein, we report a facile but effective approach to improve the photothermal performance by combining 2D reduced graphene oxide (rGO) and 1D multi-walled carbon nanotubes (MWCNTs), which have different nanomorphologies. The photothermal layer can be easily deposited on different substrate materials via simple vacuum assistance. Such a composite photothermal layer shows a rough surface with a controllable nano-structure, which can thus optimize solar light harvesting. On the other hand, the formation of a loose internal porous structure and suitable wettability ensure water transport inside the photothermal layer during evaporation. The surface temperature reaches as high as 78 °C even under one sun irradiation (1 kW m−2), which is 10 °C higher than the result of pure rGO membranes. When loaded on a PVDF substrate, the rGO–MWCNT based membrane is flexible and shows an obvious improvement in the evaporation rate, about 79.0% and 8.9% higher than those of pure rGO and MWCNT membranes, respectively. The solar thermal conversion efficiency can reach up to 80.4% without any extra accessory for thermal management. Based on our results, the nanocomposite strategy is facile and effective for the development of novel photothermal membranes for high-efficiency evaporation, and contributes to the widespread application in the fields of desalination and wastewater treatment.

An Efficient Oxygen Activation Route for Improved Ammonia Oxidation through an Oxygen-Permeable Catalytic Membrane

Upon using a reactant/oxygen mixture as co‐feed in partial oxidation, adsorbed surface molecular oxygen species can cause low selectivity. We propose a concept different from the conventional co‐feed partial oxidation process in packed‐bed reactors. In this new configuration, the activation of oxygen is separated from the catalytic oxidation by using an oxygen‐permeable membrane to suppress the formation of nonselective surface molecular oxygen species. A continuous flux of lattice oxygen through the membrane allows highly selective partial oxidation. In the oxidation of ammonia to NO, the NO selectivity was improved from 77 to 95 % if a La0.6Sr0.4Co0.2Fe0.8O3–δ oxygen‐permeable catalytically active membrane was used at 850 °C instead of a co‐feed fixed bed reactor.

Synthesis of DLC Films by Electrolysis of Dimethyl Sulfoxide

Amorphous diamond-like carbon (DLC) films were deposited on a silicon substrate by electrolysis of analytically pure dimethyl sulfoxide at relatively low voltage (150 V). Atomic force microscopy was used to investigate the surface morphology of the sample and indicated that the film was composed of small grains ∼100 nm in size. The composition and structure of the films were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. Results showed that the deposits were hydrogenated DLC films containing considerable sp 3 carbon, which could be transformed to sp 2 carbon through an annealing treatment.

Novel anaerobic membrane bioreactor (AnMBR) design for wastewater treatment at long HRT and high solid concentration

Performance of two novel designed anaerobic membrane bioreactor (AnMBRs) for wastewater treatment at long hydraulic retention time (HRT, 47 days) and high sludge concentration (22 g·L-1) was investigated. Results showed steady chemical oxygen demand (COD) removal (>98%) and mean biogas generation of 0.29 LCH4·g-1COD. Average permeates flux of 58.70 L·m-2·h-1 and 54.00 L·m-2·h-1 were achieved for reactors A and B, respectively. On top of reactor configuration, long HRT caused biofilm reduction by heterotrophic bacteria Chloroflexi resulting in high membrane flux. Mean total membrane resistances (2.23 × 109 m-1) and fouling rates (4.00 × 108 m-1·day-1) of both reactors were low suggesting better membrane fouling control ability of both AnMBRs. Effluent quality analysis showed the effluent soluble microbial products (SMP) were dominated by proteins compared to carbohydrates, and specific ultraviolet absorbance (SUVA) analysis revealed effluent from both reactors had low aromaticity with SUVA < 1 (L·mg-1·m-1) except for the first ten days.