Rui Cai

Investigation of ideal zirconium-doped perovskite-type ceramic membrane materials for oxygen separation

Zirconium-doped perovskite-type membrane materials of BaCo0.4Fe0.6−x Zrx O3−δ (x = 0–0.4) with mixed oxygen ion and electron conductivity were synthesized through a method of combining citric and EDTA acid complexes. The results of X-ray diffraction (XRD), oxygen temperature-programmed desorption (O2-TPD) and hydrogen temperature-programmed reduction (H2-TPR) showed that the incorporation of proper amount of zirconium into BaCo0.4Fe0.6O3−δ could stabilize the ideal and cubic structure of perovskite. Studies on the oxygen permeability of the as-synthesized membrane disks under air/He gradient indicated that the content of zirconium in these materials had great effects on oxygen permeation flux, activation energy for oxygen permeation and operation stability. The high oxygen permeation flux of 0.90 ml cm −2 min −1 at 950 ◦ C, the single activation energy for oxygen permeation in the range of 600–950 ◦ C and the long-term operation stability at a relatively lower operational temperature of 800 ◦ C under air/He gradient were achieved for the BaCo0.4Fe0.4Zr0.2O3−δ material. Meanwhile, the effect of carbon dioxide on structural stability and oxygen permeability of this material was also studied in detail, which revealed that the reversible stability could be attained for it.

Novel and ideal zirconium-based dense membrane reactors for partial oxidation of methane to syngas

A novel and ideal dense catalytic membrane reactor for the reaction of partial oxidation of methane to syngas (POM) was constructed from the stable mixed conducting perovskite material of BaCo0.4Fe0.4Zr0.2O3−δ and the catalyst of LiLaNiO/γ-Al2O3. The POM reaction was performed successfully. Not only was a short induction period of 2 h obtained, but also a high catalytic performance of 96–98% CH4 conversion, 98–99% CO selectivity and an oxygen permeation flux of 5.4–5.8 ml cm−2 min−1 (1.9–2.0 μmol m−2 S−1 Pa−1) at 850 °C were achieved. Moreover, the reaction has been steadily carried out for more than 2200 h, and no interaction between the membrane material and the catalyst took place.

Investigation on the structure stability and oxygen permeability of titanium-doped perovskite-type oxides of BaTi0.2CoxFe0.8−xO3−δ (x=0.2–0.6)

Titanium-doped perovskite-type ceramic oxides of BaTi 0.2 Co x Fe 0.8-x O 3-δ (x=0.2-0.6) were synthesized by a combined citrate-EDTA complexing method. The results of XRD, TG-DTA, O 2 -TPD and H 2 -TPR indicated that the oxide of BaTi 0.2 Co 0.5 Fe 0.3 O 3-δ was more stable than other compositions and the famous membrane material of SrCo 0.8 Fe 0.2 O 3-δ . The oxygen permeation experiments showed that the contents of Co and Fe had a great effect on the oxygen permeability. The oxygen permeation flux of 0.90 ml/cm 2 .min at 950°C under air/He was obtained for the composition of BaTi 0.2 Co 0.5 Fe 0.3 O 3-δ .

Titanium-based perovskite-type mixed conducting ceramic membranes for oxygen permeation

A titanium-based perovskite-type oxide was synthesized by an improved method of combining EDTA acid and citric acid complexes. High structural stability, good sintering ability, and relatively high oxygen permeation flux were obtained simultaneously for disks synthesized from this ceramic oxide.

One-pot synthesis of NiAl–CO3 LDH anti-corrosion coatings from CO2-saturated precursors

Anti-corrosive coatings based on layered double hydroxides (LDHs) have been considered as promising alternatives to conventional chromate-containing conversion coatings. Among various LDHs, carbonate-intercalated LDH coatings with a c-axis preferred orientation should be the optimum structure for protecting metals against corrosion. Herein we successfully prepared NiAl–CO3 LDH coatings on aluminium plates in one step. Particularly it was found that CO2 dissolved in the precursor solution exerted great influence on the microstructure and anti-corrosion capacity of prepared LDH coatings. Trace amounts of CO2 in the precursor solution led to the formation of ab-oriented 7 μm-thick LDH coatings, while preferentially c-oriented LDH coatings with an average thickness of 12 μm were formed from CO2-saturated precursor solutions. A DC polarization test demonstrated that preferentially c-oriented LDH coatings exhibited much higher anti-corrosion performance than ab-oriented LDH coatings possibly due to the decreased density of mesoscopic defects. Simultaneously, CO2, the green gas, was also positively utilized.

Suppression of twins in b-oriented MFI molecular sieve films under microwave irradiation.

Twin growth in the synthesis of b-oriented MFI films is successfully suppressed by applying microwave irradiation on a b-oriented MFI seed layer, relying on the nucleation-related bottleneck effect. Electrochemical oxidation experiments demonstrated the importance of twin suppression in enhancing the diffusion of guest molecules in MFI films.

In Situ Electrochemical Synthesis of Oriented and Defect-Free AEL Molecular-Sieve Films Using Ionic Liquids

Simply preparing oriented and defect-free molecular-sieve films have been a long-standing challenge both in academia and industry. Most of the early works focus on the careful and multiple controls of the seeds layer or synthesis conditions. Herein, we report a one-step in situ electrochemical ionothermal method that combines a controllable electric field with ionic liquids. We demonstrate that an in-plane oriented and defect-free AEL (one molecular-sieve framework type) molecular-sieve film was obtained using an Al electrode as the Al source. The excellent corrosion-resistant performance of the film makes this technology promising in multiple applications, such as anti-corrosion coatings.

Bi4Cu0.2V1.8O11-δ based membrane electrochemical reactors for propane oxidation at moderate temperatures

Bi4Cu0.2V1.8O11–δ membrane material was synthesized by following the solid-state method. The oxygen permeation flux at 673 K was found to be 0.5 ml/cm2 by the use of an external electric power source. The oxidation of propane was selected as the probe reaction using the Bi4Cu0.2V1.8O11–δ electrochemical membrane reactor. It was found that such electrochemical membrane reactors could have potential application in the area of alkanes selective oxidation at moderate temperatures.Bi4Cu0.2V1.8O11–δ membrane material was synthesized by following the solid-state method. The oxygen permeation flux at 673 K was found to be 0.5 ml/cm2 by the use of an external electric power source. The oxidation of propane was selected as the probe reaction using the Bi4Cu0.2V1.8O11–δ electrochemical membrane reactor. It was found that such electrochemical membrane reactors could have potential application in the area of alkanes selective oxidation at moderate temperatures.

Highly Efficient Removal of CO in Effluent Streams from Real‐Life Propane Oxidation Process over CuO−CeO2−Based Catalysts

Selective removal of CO from the effluent streams in real‐life chemical processes is of great importance in many different fields of industry. Until now it remains challenging to use non‐precious metal oxides to selectively remove CO at low temperatures from real‐life chemical effluent with complex compositions. Herein, a series of binary and ternary transition metal oxide catalysts were prepared by co‐precipitation method and employed for the preferential removal of CO in the effluent stream (off‐gas) of propane selective oxidation. It was found that the CuO−CeO2−based mixed oxide catalyst exhibited the best CO removal performance, wider operating temperature window and higher resistance to the inhibition of hydrocarbons, H2O and CO2. The presented catalyst showed high potential for selective removal of CO in the off‐gas stream containing CO2, H2O and various hydrocarbons.