Porous Ceramic Tube Research Articles

Auto-thermal reforming of biomass raw fuel gas to syngas in a novel reformer: Promotion of hot-electron

A novel reformer with porous ceramic oxygen distribution tube circled by electric wire for inspiring hot electron was designed for auto-thermal reforming of biomass raw fuel gas to produce syngas (H2+CO). The temperature of auto-thermal reformer was nearly uniform due to the excellent performance of partial oxygenation reaction in the reformer with porous ceramic tube for oxygen partitioning. The hot-electron inspired by electric wire promoted the cracking of biomass tar to form radical species, which were converted effectively to syngas over nickel based catalyst. The hot-electron also played an essential role in decreasing coke deposition on the surface of nickel based catalyst, which prolonged the lifetime of the reforming catalyst.

Elaboration of a new flat membrane support from Moroccan clay

The present paper is devoted to synthesis of porous ceramic support from local Moroccan clay (region of Agadir). This material has been dictated by their natural abundance (low price) and their beneficial properties. In this work, we were also interested in the development and the characterization of new mineral support for microfiltration and ultrafiltration membrane. The support, with flat configuration, was prepared from natural clay: the powder was crushed, sieved to 125μm and mixed with organic additives and water. The obtained paste was then extruded to elaborate a porous structure. The firing temperature of the support is 800°C. After firing, the elaborated support showed an average pore diameter of 11 μm and a porosity of 41%. The average support permeability determined using pure distilled water is 1,805 L/h m² bar. This porous ceramic tube was used as support to prepare microfiltration membrane which were tested for the filtration.

Fabrication and Cell Properties of Flattened Tube Segmented-in-Series Solid Oxide Fuel Cell-Stack Using Decalcomania Paper

In the segmented-in-series solid-oxide fuel cells (SIS-SOFCs), fabrication techniques which use decalcomania paper have many advantages, i.e., an increased active area of the electrode; better interfacial adhesion property between the anode, electrolyte and cathode; and improved layer thickness uniformity. In this work, a cell-stack was fabricated on porous ceramic flattened tube supports using decalcomania paper, which consists of an anode, electrolyte, and a cathode. The anode layer was <TEX>$40{\mu}m$</TEX> thick, and was porous. The electrolyte layers exhibited a uniform thickness of about <TEX>$20{\mu}m$</TEX> with a dense structure. Interfacial adhesion was improved due to the dense structure. The cathode layers was <TEX>$30{\mu}m$</TEX> thick with porous structure, good adhesion to the electrolyte. The ohmic resistance levels at 800, 750 and <TEX>$700^{\circ}C$</TEX> were measured, showing values of 1.49, 1.58 and <TEX>$1.65{\Omega}{\cdot}cm^2$</TEX>, respectively. The polarization resistances at 800, 750 and <TEX>$700^{\circ}C$</TEX> were measured to be 1.63, 2.61 and <TEX>$4.17cm^2$</TEX>, respectively. These lower resistance values originated from the excellent interfacial adhesion between the anode, electrolyte and cathode. In a two-cell-stack SOFC, open-circuit voltages(OCVs) of 1.915, 1.942 and 1.957 V and maximum power densities(MPD) of 289.9, 276.1 and <TEX>$220.4mW/cm^2$</TEX> were measured at 800, 750 and <TEX>$700^{\circ}C$</TEX>, respectively. The proposed fabrication technique using decalcomania paper was shown to be feasible for the easy fabrication of segmented-in-series flattened tube SOFCs.

Preparation of molecularly imprinted polypyrrole/Fe3O4 composite material and its application in recognition of tryptophan enantiomers

Ferrosoferric oxide (Fe(3)O(4)) magnetic material was first synthesized, and then the in-situ chemical polymerization of pyrrole was carried out on the surface of Fe(3)O(4) by using pyrole and L-tryptophan (L-Trp) as the functional monomer and templates, respectively. As a result, molecularly imprinted polypyrrole/Fe(3)O(4) composite material was obtained. This composite material was separated from the solution because of its magnetic property. Polypyrrole in the composite was overoxidized in 1 mol/L NaOH solution by applying a potential of 1.0 V, and thus L-Trp templates were de-deoped from the composite. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical methods were employed to characterize the composite. The solution containing L- or D-Trp was pumped through a porous ceramic tube packed with the composite, separately. High performance liquid chromatography (HPLC) was adopted for the detection of L- or D-Trp in the eluate, and the results indicated that the enrichment ability of the composite for L-Trp was almost 2 times that of D-Trp. Therefore, the electro-magnetic composite material has potential applications as chromatographic stationary phase for chiral recognition.

Treatment of Dye Wastewater by Using a Hybrid Gas/Liquid Pulsed Discharge Plasma Reactor

A hybrid gas/liquid pulsed discharge plasma reactor using a porous ceramic tube is proposed for dye wastewater treatment. High voltage pulsed discharge plasma was generated in the gas phase and simultaneously the plasma channel was permeated through the tiny holes of the ceramic tube into the water phase accompanied by gas bubbles. The porous ceramic tube not only separated the gas phase and liquid phase but also offered an effective plasma spreading channel. The effects of the peak pulse voltage, additive gas varieties, gas bubbling rate, solution conductivity and TiO2 addition were investigated. The results showed that this reactor was effective for dye wastewater treatment. The decoloration efficiency of Acid Orange II was enhanced with an increase in the power supplied. Under the studied conditions, 97% of Acid Orange II in aqueous solution was effectively decolored with additive oxygen gas, which was 51% higher than that with argon gas, and the increasing O2 bubbling rate also benefited the decoloration of dye wastewater. Water conductivity had a small effect on the level of decoloration. Catalysis of TiO2 could be induced by the pulsed discharge plasma and addition of TiO2 aided the decoloration of Acid Orange II.

Use of anode barrier layers in tubular solid-oxide fuel cells for robust operation on hydrocarbon fuels

This paper presents a unique demonstration of anode barrier-layer technology in a tubular solid-oxide fuel cell (SOFC) architecture. The anode barrier layer is a chemically inert, porous ceramic tube that is positioned within the inside diameter of the tubular SOFC, separating the catalytically active anode from the hydrocarbon-carrying fuel stream. This porous tube reduces the respective diffusion rates of reactants and products into and out of the anode. This increases the local concentration of electrochemically produced steam and carbon dioxide throughout the anode, resulting in higher local steam-to-carbon ratios that enhance the selectivity of internal-reforming reactions toward hydrogen and carbon monoxide over the formation of deleterious carbon deposits. In this study, stable electrochemical performance is demonstrated under a simulated “biogas” fuel stream (63% CH4/34% CO2/3% H2O) over 12 days of continuous operation. The performance of the barrier layer-equipped SOFC is characterized under biogas and hydrogen fuels, and compared to the performance of an SOFC without a barrier layer. While some decrease in power density is evident with the presence of a barrier layer, the performance decrease at 0.7V is modest. Morphological characterization after performance testing reveals no evidence of carbon deposition within the anode or barrier layer. These results demonstrate the potential of barrier-layer technology in tubular solid-oxide fuel cell architectures.

Porous ceramic membrane with superhydrophobic and superoleophilic surface for reclaiming oil from oily water

A porous ceramic tube with superhydrophobic and superoleophilic surface was fabricated by sol-gel and then surface modification with polyurethane-polydimethysiloxane, and an oil-water separator based on the porous ceramic tube was erected to characterize superhydrophobic and superoleophilic surface's separation efficiency and velocity when being used to reclaim oil from oily water and complex oily water containing clay particle. The separator is fit for reclaiming oil from oily water.

Preparation of Pd/Ag Film on Porous Ceramic Tube by Osmosis Pressure–Assisted Electroless Plating

The osmosis pressure was introduced to improve the conventional electroless plating process for preparing porous ceramic supported Pd/Ag inorganic composite membrane. The effects of temperature (t), molar ratio of hydrazine to total metal ions(y), molar ratio of silver ions to palladium ions(x), concentrations of ethylene diamine tetraacetic acid (EDTA) and sucrose solution on the metal deposition rate, silver content in alloy film, surface morphology of film and permeation properties of the membrane were investigated and their optimal conditions were determined to be: [MET]=5mM, x = 20%, y = 1, [EDTA] = 40g•L-1, t = 40 °C, pH =11 and sucrose solution concentration of 6 M. Under these optimal conditions, the prepared Pd/Ag alloy film with thickness of 7.9 μm demonstrated good permeation properties with nitrogen free and hydrogen permeation rate of 8.8×10-3m3•m-2•s-1at 0.3 MPa and 473 K.

Application of electrophoretic deposition for inner surface coating of porous ceramic tubes

The direct coating of a nano-porous alumina layer on the inner surface of micro-porous alumina tubes was performed by electrophoretic deposition (EPD). A thin layer of polypyrrole (Ppy) was synthesized on the inside wall of the porous tubes by the chemical polymerization of pyrrole (Py) to give the wall electric conduction for the EPD electrode. The bimodal suspension of alumina powders with 0.6μm and 30nm average particle sizes was selected to control the nano-porous structure. The thickness of the coating layer was controlled by altering the applied voltage and deposition time. The interfacial connection of the coated layer and the substrate was observed by SEM before and after sintering. The pore size of the coated layer was characterized by its pore size distribution.

H 2O 2 synthesis over PdAu membranes

2–3 μm thick PdAu membranes have been prepared by sequential electroless plating on porous ceramic tubes followed by annealing at 823 K under H 2. Gas phase H 2 permeation rates had stabilized after 250 h annealing even though the alloy layers still remained inhomogeneous as evidenced by X-ray diffraction analyses after conclusion of all other experiments. The H 2 permeability of a Pd 90.5Au 9.5 membrane reached 1.2 × 10 −8 mol m −1 s −1 Pa −0.5 at 673 K. A marked discontinuity in the temperature dependence of the H 2 permeation rate at 573 K signals a change from diffusion to adsorption or desorption-limited H 2 transport through the membrane below that threshold. H 2O 2 was directly synthesized from the elements over these PdAu membranes in O 2-saturated, acidic water/ethanol mixtures while feeding H 2 through the membrane. The H 2O 2 formation rate increased from 19.5 to 97.5 mmol m −2 h −1 between 277 and 363 K in water at 300 kPa H 2 feed pressure even though the H 2O 2 selectivity decreased from 56% to 30% in parallel. H 2O 2 yield and selectivity improved both with H 2 feed pressure, however. H 2O 2 formation rate and selectivity increased also moderately with ethanol content, but the PdAu layer tended to delaminate from the ceramic support if the ethanol content was raised above 50%.

Photocatalytic degradation of Acid Red 4 using a titanium dioxide membrane supported on a porous ceramic tube

A photocatalytic membrane supported on a porous ceramic tube was described, in which permeation of solutes through the membrane and tube and photocatalytic reaction occur simultaneously. In this photocatalytic membrane reactor, TiO 2 catalyst was coated on the surface of a porous ceramic tube and all experiments were conducted in one pass dead-end system. The objectives of this study are to demonstrate the predominance of dead-end operation and to determine the reaction kinetics model of the photocatalytic reaction. Acid Red 4 (AR 4) dye was used as a model pollutant. A detailed study of physical parameters including flow configurations (dead-end and cross-flow), flow rate, initial dye concentration, light intensity and catalyst loading has been performed to obtain the reaction kinetics. The simultaneous effect of light intensity and catalyst loading was also determined experimentally. Experiments were also conducted to compare the photocatalytic degradation of AR 4 in the dead-end and cross-flow system. The major findings of this study are: (1) the decomposition ratios for dead-end system were three and five times higher than cross-flow system at flow rates of 6.67 × 10 −8 and 4.00 × 10 −7 m 3/s, respectively. (2) The decomposition ratio increased with increasing catalyst loading and light intensity, but remained constant at higher catalyst loading. (3) The decomposition ratio was found to be decreased with increasing flow rate.

Effects of Binary Mixture of Yb 2O 3-La 2O 3 on Pd/Ag Co-Deposition by Electroless Plating

The binary mixture of Yb 2O 3-La 2O 3 was used as an additive to improve the traditional electroless plating for Pd-Ag co-deposition on the inside surface of a porous ceramic tube. The main attention were paid to investigating the effects of Yb 2O 3-La 2O 3 on Pd-Ag co-deposition rate, plating temperature, Ag content in film and Pd/Ag reduction potentials. The experimental results show that the co-deposition rate is increased by 63%, the plating temperature is decreased by 10 ∼ 20 °C for obtaining the same co-deposition rate and the Ag content in film basically remains unchangeable when Yb 2O 3-La 2O 3 is added into the traditional electroless plating solution. The experiment also shows that Pd/Ag reduction potentials basically remain unchangeable with the binary rare earths based on the electrochemical mathematical models An inorganic composite membrane with alloy film of 76.8(mol)% Pd-23.2(mol)% Ag and the thickness of 7.7 μm on the porous ceramic tube was prepared and the permeation fluxes of hydrogen and nitrogen through the membrane are 8.65 × 10 −3 and 1.92 × 10 −6 m 3·m −2· s −1 at 350 °C and 0.3 MPa respectively.

Demulsification of water/sunflower oil emulsions by a tangential filtration process using chemically impregnated ceramic tubes

A tangential filtration process was implemented in this study using porous ceramic tubes made of α-alumina produced by the slip-casting technique. These tubes were sintered at 1450 °C and characterized by mercury intrusion porosimetry, which revealed a mean pore size of 0.5 μm. The tubes were chemically impregnated with a zirconium citrate solution, after which they were calcined and heat treated at temperatures of up to 600 and 900 °C to eliminate volatile organic compounds and transform the zirconium citrate into zirconium oxide impregnated in the alumina in the form of nanoparticle agglomerates. The microporous pipes were tested on a microfiltration hydraulic system to analyze their performance in the demulsification of sunflower oil and water mixtures. The fluid-dynamic parameters of Reynolds number and transmembrane pressure were varied in the process. The volume of permeate was analyzed by measuring the Total Organic Carbon concentration (TOC), which indicated 99% of oil phase retention. The emulsified mixture was characterized by optical microscopy, while the morphology and composition of the impregnated microporous tubes were analyzed by scanning electron microscopy (SEM). Quantification of the TOC values for the tube impregnated once at 600 °C showed the best demulsification performance, with the concentration on permeate smaller than 10 mg/L. The impregnated tube sintered once at 900 °C presented low carbon concentration (smaller than 20 mg/L), has the advantage of presenting the greatest trans-membrane flux in relation to the other microporous tube.

Study on Physical and Chemical Behaviors of Rare Earths in Preparing Ceramic Tube Supported Palladium Film by Electroless Plating

The rare earths of ytterbium, lanthanum, praseodymium, neodymium and their binary mixtures were respectively added into the traditional electroless plating solution to prepare thin palladium film on the inner surface of porous ceramic tube. The experimental results shows that the addition of rare earths increases palladium deposition rates and the binary mixtures are superior to the single rare earths and the mixture of ytterbium-lanthanum is the most efficient. Adding the mixture of ytterbium-lanthanum can also reduce the plating temperature by 10 ∼ 20 °C, shrink the metal crystal size and improve the film densification compared to those by traditional electroless plating. A thin palladium film with 5 μm was prepared and the film made a highly pure hydrogen with a molar fraction of more than 99.97% from a H 2-N 2 gas mixture. More attentions were paid to analyze the physical and chemical behaviors of the rare earths in palladium film preparation.

LTA zeolite composite membrane preparation, characterization and application in a zeolitic membrane reactor

Abstract An LTA membrane has been crystallized inside a porous ceramic tube and applied to synthesis of methanol from carbon dioxide and hydrogen in a zeolite membrane reactor (ZMR). The results obtained with the ZMR were compared with those gained from one traditional reactor (TR) used under the same operating conditions. CO 2 conversion obtained with the ZMR at 210 °C reached 17% under conditions where the equilibrium value without zeolite membrane (TR) is equal to about 6%.

Formation of Mg(OH)2 dynamic membranes for oily water separation: effects of operating conditions

Abstract Formation of a new type of Mg(OH)2 dynamic membrane on α-Al2O3 porous ceramic tubes was investigated. Attention was paid to the effects of operating conditions on the cake layer during formation of a dynamic membrane. The influence of operating parameters such as suspension concentration, cross-flow velocity and transmembrane pressure on the formation was different. It is difficult to form a satisfactory dynamic membrane under the conditions of shorter formation time, higher cross-flow velocity and lower suspension concentration. An increase in transmembrane pressure and suspension concentration resulted in an increase in the dynamic layer and an increase in TOC rejection. However, increasing the cross-flow velocity resulted in a decrease in the dynamic layer and TOC rejection. Under certain conditions, the prepared membrane had a uniform and compact structure. It showed good performance in separating oil from water using a model oil emulsion. A TOC rejection of more than 98% and a permeate flux of more than 1 L·m−2·h−1·kPa−1 were obtained in a batch concentration test.

High-purity CO x-free H 2 generation from NH 3 via the ultra permeable and highly selective Pd membranes

A compact H 2 generation system that coupled NH 3 decomposition with Pd membrane separation has been developed to provide high-purity CO x -free H 2 for the fuel cell uses. The ultra permeable and highly selective Pd membranes supported on porous ceramic tubes were successfully synthesized. Firstly, the NH 3 decomposition reaction over the Ni-based catalyst was carried out in a Pd membrane reactor, through which the in situ removal of H 2 product significantly enhanced the NH 3 conversion. It is further observed that the permeation performance was greatly limited by the low effective utilization of membrane in the NH 3-rich zone. When having integrated reaction with separation separately, we obtained a 54 m 3 m −2 h −1 99.96% H 2 stream with a H 2 recovery yield of 77%. Therefore, it is suggested that the combination of an NH 3 cracker with a followed Pd membrane separator is more preferable for on-site H 2 generation. Throughout a 500-h lifetime test, both the reaction and separation units showed a good stability. The residual NH 3 slightly inhibited the permeability of the Pd membrane. Nevertheless, the permeability of the used membrane could be recovered and finally increased by the air and followed H 2 treatments.

Experimental and simulation studies on concentration polarization in H 2 enrichment by highly permeable and selective Pd membranes

Highly efficient Pd membranes supported on porous ceramic tubes were synthesized by a modified electroless plating method and utilized in H 2 enrichment from the gas mixture that came from an NH 3 cracker. Two Pd membranes whose permeation properties varied widely had been evaluated at temperatures ranging from 623 to 773 K and under pressures up to 5.06625 × 10 5 Pa (5.0 atm). Experimental results revealed that the concentration polarization phenomenon played a determining role in the case of gas separation by the highly permeable and selective membranes. It caused a significant loss in both H 2 yield and purity; and therefore, the separation efficiency of H 2 generation system decreased greatly. A mathematical model was built to describe the concentration polarization phenomena in H 2 enrichment by highly permeable and selective Pd membranes under the conditions utilized. In line with the experimental observations, this model accurately predicated the dependency of permeation performance on the operation parameters such as pressure, temperature, feed gas flow rate and permeability.

Elaboration and characterization of microfiltration and ultrafiltration membranes deposited on raw support prepared from natural Moroccan clay: Application to filtration of solution containing dyes and salts

Different kinds of porous ceramic membranes deposited on a raw tubular support were prepared from a Moroccan clay. Clay powders mixed with some organic additives can be extruded to form a porous tubular support. After firing, the support showed an average pore diameter of 11 μm and a porosity of 43%. This porous ceramic tube was used as support to prepare microfiltration and ultrafiltration membranes which were tested for the filtration of electrolytes and dyes solutions.

An anti-corrosive reactor for the decomposition of halogenated hydrocarbons with supercritical water oxidation

An anti-corrosive reactor was studied, which decomposes halogenated organic compounds by way of supercritical water oxidation (SCWO). Two different types of SCWO reactor were used: a floating type reactor using a non-porous ceramic tube and a transpiring wall-type SCWO reactor using a porous ceramic tube. Reactor configurations were evaluated to protect a SCWO system from corrosion, due to halogenated hydrocarbon oxidation, and fouling, due to salt formation from the neutralizing agent. At various operating conditions (340–440 °C, 250–300 bar) and concentrations (300–3000 mg 2,4-dichloropenol/L), the system was operated to decompose 2,4-dichlorophenol (2,4-DCP) as a model compound with hydrogen peroxide (H 2O 2). Back-mixing led to corrosion of the injection part of the transpiring wall-type reactor. However, 2,4-DCP was successfully destroyed up to ≥99.99% without corrosion or fouling problems with a floating type SCWO system. As the range of the supercritical zone in the reactor was changed by the operating conditions, the conversion of 2,4-DCP increased with an increase in the reaction temperature and pressure. Therefore, residence time in the SCWO process played a key role in the decomposition efficiency of the developed system. Under the conditions of 420 °C, 250 bar and a 1 mL/min flow rate, 2,4-DCP at a concentration of 300 mg/L was completely converted using a stoichiometric amount of 100% of H 2O 2. In the case of 3000 mg/L of 2,4-DCP, complete conversion was observed under the conditions of 440 °C, 250 bar and with over 200% of H 2O 2 supply. The floating type reactor, consisted of one vertical double-wall reactor including neutralization and cooling, was successfully operated for more than 5 months for SCWO of 2,4-DCP without corrosion and fouling.