Nanping Xu

Polymer/Ceramic Composite Membranes and Their Application in Pervaporation Process

Pervaporation (PV), as an environmental friendly and energy-saving separation technology, has been received increasing attention in recent years. This article reviews the preparation and application of macroporous ceramic-supported polymer composite pervaporation membranes. The separation materials of polymer/ceramic composite membranes presented here include hydrophobic polydimethylsiloxane (PDMS) and hydrophilic poly(vinyl alcohol) (PVA), chitosan (CS) and polyelectrolytes. The effects of ceramic support treatment, polymer solution properties, interfacial adhesion and incorporating or blending modification on the membrane structure and PV performance are discussed. Two in-situ characterization methods developed for polymer/ceramic composite membranes are also covered in the discussion. The applications of these composite membranes in pervaporation process are summarized as well, which contain the bio-fuels recovery, gasoline desulfuration and PV coupled proc- ess using PDMS/ceramic composite membrane, and dehydration of alcohols and esters using ceramic-supported PVA or PVA-CS composite membrane. Finally, a brief conclusion remark on polymer/ceramic composite mem- branes is given and possible future research is outlined. Keywords polymer/ceramic composite membrane, pervaporation, bio-fuel recovery, solvent dehydration, PV cou- pled process

The Effect of Titania Structure on Ni/TiO2 Catalysts for p-Nitrophenol Hydrogenation

The catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/TiO2 catalysts prepared by a liquid-phase chemical reduction method. The catalysts were characterized by inductively coupled plasma (ICP), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). Results show that the titania structure has favorable influence on physio-chemical and catalytic properties of Ni/TiO2 catalysts. Compared to commercial Raney nickel, the catalytic activity of Ni/TiO2 catalyst is much superior, irrespective of the titania structure. The catalytic activity of anatase titania supported nickel catalyst Ni/TiO2(A) is higher than that of rutile titania supported nickel catalyst Ni/TiO2(R), possibly because the reduction of nickel oxide to metallic nickel for Ni/TiO2(A) is easier than that for Ni/TiO2(R) at similar reaction conditions.

Progress on Porous Ceramic Membrane Reactors for Heterogeneous Catalysis over Ultrafine and Nano-sized Catalysts

Abstract Heterogeneous catalysts with ultrafine or nano particle size have currently attracted considerable attentions in the chemical and petrochemical production processes, but their large-scale applications remain challenging because of difficulties associated with their efficient separation from the reaction slurry. A porous ceramic membrane reactor has emerged as a promising method to solve the problem concerning catalysts separation in situ from the reaction mixture and make the production process continuous in heterogeneous catalysis. This article presents a review of the present progress on porous ceramic membrane reactors for heterogeneous catalysis, which covers classification of configurations of porous ceramic membrane reactor, major considerations and some important industrial applications. A special emphasis is paid to major considerations in term of application-oriented ceramic membrane design, optimization of ceramic membrane reactor performance and membrane fouling mechanism. Finally, brief concluding remarks on porous ceramic membrane reactors are given and possible future research interests are also outlined.

Effect of Alumina Particle Size on Ni/Al2O3 Catalysts for p-Nitrophenol Hydrogenation*

Abstract The catalytic hydrogenation of p -nitrophenol to p -aminophenol was investigated over Ni/Al 2 O 3 catalyst on alumina support with different particle size. It is found that support particle size has significant influences on physiochemical properties and catalytic activity of the resulting Ni/Al 2 O 3 catalyst, but little influence on the selectivity. At a comparable amount of Ni loading, the catalytic activity of Ni/Al 2 O 3 prepared with alumina support of smaller particle size is lower. The reduction behavior of the catalyst is a key factor in determining the catalytic activity of Ni/Al 2 O 3 catalyst. The supported nickel catalyst 10.3Ni/Al 2 O 3 -3 improves the life span of the membrane by reducing fouling on the membrane surface compared to nano-sized nickel.

Effect of Ultrasound on the Treatment of Emulsification Wastewater by Ceramic Membranes

Abstract Ultrasonic field was applied in the treatment of oil emulsification wastewater by ZrO 2 ceramic membrane. The permeate flux, rejection ratio in the filtration process and recovery ratio of flux in the membrane cleaning process were measured. Great improvement in the permeate flux and rejection ratio have been observed for the membrane process enhanced by the ultrasonic field. The permeate flux of water through the membrane was about 210L·m -2 ·h -1 and the oil rejection ratio was over 99.9% under the optimal ultrasonic treatment conditions, which were 8W of ultrasonic power, 7cm of ultrasonic probe length introduced into the membrane channel and the same ultrasonic radiation direction as the wastewater flow. The resistance of the membrane process was compared between the cases with and without ultrasound, and the total resistance was reduced 68% by the use of ultrasound. Four methods including water cleaning, water cleaning under sonication, chemical cleaning and chemical cleaning under sonication were used to recover membrane flux. It was found that the flux recovery ratio increased with the increase of ultrasonic cleaning power. In addition, the use of chemical agents combining with ultrasonic irradiation showed a synergistic effect, which resulted in the highest cleaning efficiency and the shorter cleaning time.

Effect of Preparation Conditions on Visible Photocatalytic Activity of Titania Synthesized by Solution Combustion Method

Abstract Titania catalysts were synthesized by a solution combustion method (SCM). Photodegradation of 4-chlorophenol (4-CP) using the synthesized catalysts was studied under both visible light (λ ≥ 420nm) and sunlight irradiation. The effect of preparation conditions on photocatalytic activities of the synthesized catalysts was investigated. The optimal photocatalytic activity of the catalyst (denoted as A1) was obtained under the following synthesis conditions: ignition temperature of 350°C, fuel ratio (o) of 1 and calcination time of 1h. The degradation and mineralization ratio of 4-CP were 78.2% and 53.7% respectively under visible light irradiation for 3h using catalyst A1. And the catalyst A1 also showed high photocatalytic activity under sunlight irradiation.

A Comparative Study of the Performance of Symmetric and Asymmetric Mixed-conducting Membranes

According to the configuration, mixed-conducting membranes are classified as symmetric membranes and asymmetric membranes consisting of a thin dense layer and a porous support. In this study, these two kinds of SrCo0.4Fe0.5Zr0.1O(subscript 3-δ) oxide-based membranes were systematically compared in terms of oxygen permeability and chemical stability, and their differences were elucidated by means of the theoretical calculation. For the oxygen permeability, the asymmetric membrane was greater than the symmetric membrane due to the significant decrease of bulk diffusion resistance in the thin dense layer of the asymmetric membrane. In regard to the chemical stability, the increase of oxygen partial pressure on the asymmetric membrane surface at CH4 side produced the stable time of over 1032h in partial oxidation of methane at 1123K, while the symmetric membrane was only of 528h. This study demonstrated that the asymmetric membrane was a promising geometrical configuration for the practical application.

Nickel(II) complex anchored on MCM-41 for the epoxidation of styrene by oxygen

A heterogeneous catalyst, MCM-41-Ni, was synthesized by anchoring a nickel(II) Schiff base complex onto amino-modified MCM-41. The catalyst was characterized by small angle X-ray diffraction, nitrogen adsorption, infrared spectroscopy, thermal gravimetric analysis, inductively coupled plasma and C, H, N elemental analysis, and transmission electron microscopy. MCM-41-Ni showed excellent catalytic activity for the epoxidation of styrene with O2 as oxidant with high styrene conversion (95.2%) and epoxide selectivity (66.7%). The influence of reaction temperature, catalyst amount, solvent, and reaction time was studied. MCM-41-Ni showed good recyclability and can be reused four times.

Investigation of Mg2+/Li+ Separation by Nanofiltration

Abstract The Mg 2+ /Li + /Cl − solutions were filtrated with a commercially available DK nanofiltration membrane to investigate the possibility to enrich the lithium component. The investigation was significant as such an approach might be a competing substitute for the present lithium purification industry and the environmental protection purpose. The Donnan steric pore model (DSPM) was implemented for the prediction. The separation of Mg 2+ /Li + was mainly affected by the working pressure (or the permeation flux) and a limiting separation factor was found around 0.31. The effective membrane charge density was evaluated and its dependence on the permeation flux as well as the ion pattern was discussed. For predicting an actual separation of electrolytes, the experimental investigation seems necessary for the reliability and efficiency.

Preparation and Characterization of Alumina Membranes on Capillary Supports: Effect of Film-coating on Crack-free Membrane Preparation

Abstract Ceramic capillary membrane has received much attention due to its relatively high pack density and favorable mechanical strength. However, it is difficult to prepare capillary membrane on its thin support by a dip-coating method. In this study, alumina microfiltration membranes were prepared on the inner surface of alumina capillary support (outer diameter 4 mm, inner diameter 2.5 mm) by a dip-coating method. Scanning electron microscopy (SEM) observation, gas bubble pressure (GBP) method and membrane permeation test were carried out to evaluate membrane performance. Two major effects in preparation of crack-free membrane, capillary filtration and film-coating, upon the thin support were studied. The as-prepared crack-free membrane presents a narrow pore size distribution, a mean pore size of about 0.6 μm and a high pure water flux of 86000 L·m −2 ·h −1 ·MPa. It is proved that the membrane thickness should be sufficiently large to overcome the defects of support surface, but it is only one of the prerequisites for the formation of crack-free membrane. Furthermore, it is demonstrated that the capillary filtration effect is greatly restricted for thin capillary support with the dip-coating method and the film-coating effect plays a crucial role in the formation of crack-free membrane.