| 1. |
- Li, Hongliang, et al.
(author)
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Catalytic performance and characterization of Al2O3-supported Pt-Co catalyst coatings for preferential CO oxidation in a micro-reactor
- 2010
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In: Applied Catalysis A. - : Elsevier BV. - 0926-860X .- 1873-3875. ; 387:1-2, s. 215-223
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Journal article (peer-reviewed)abstract
- Platinum-cobalt (Pt-Co) catalyst coatings are studied for preferential oxidation of carbon monoxide (PROX) ill hydrogen-rich gas streams. Experimental results show a role for cobalt in improving catalytic activity. The most active catalyst coating can decrease carbon monoxide concentrations from 1% to a value of less than 10 ppm for GHSV values ranging from 40,000 to 120,000 ml g(-1) h(-1). This catalyst coating can work at a wide window of operation ill terms of temperature. Transmission electron microscopy, selected-area electron diffraction, and diffuse reflectance infrared Fourier transform spectroscopy show that the addition of Co forms Pt3Co intermetallic compounds and slightly increases the average particle size. In situ laser Raman spectroscopy reveals the co-existence of Co metal and its oxides on the catalyst surface, due to gradual oxidation of Co by gas phase oxygen within the initial stage of the PROX reaction. The promotional effect of Co during PROX is confirmed and ascribed to this Pt3Co intermetallic compound and the synergetic effect of Co-0 and Co chi+. The high accessibility of the reactant to Pt3Co species appears favorable and crucial for PROX.
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| 2. |
- An, Lin, et al.
(author)
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CO2 capture using a superhydrophobic ceramic membrane contactor
- 2015
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In: CLEAN, EFFICIENT AND AFFORDABLE ENERGY FOR A SUSTAINABLE FUTURE. - : Elsevier. ; 75, s. 2287-2292
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Conference paper (peer-reviewed)abstract
- Wetting and fouling of membrane contactor result in performance deterioration of membrane gas absorption system for CO2 post-combustion capture of coal-fired power plants. To solve these problems, in this study, a superhydrophobic ceramic (SC) membrane contactor was fabricated by chemically modification using 1H, 1H, 2H, 2H-perfluorooctylethoxysilane (FAS) solution. The membrane contactor fabrication costs for both SC membrane and PP (polypropylene) membrane contactors per unit mass absorbed CO2 were roughly the same. However, by using the SC membrane, the detrimental effects of wetting can be alleviated by periodic drying to ensure a high CO2 removal efficiency (>90%), whereas the drying does not work for the PP membrane. The SC membrane contactor exhibited a better anti-fouling ability than the PP membrane contactor because the superhydrophobic surface featured a self-cleaning function. To ensure continuous CO2 removal with high efficiency, a method that two SC membrane contactors alternatively operate combined with periodic drying was proposed. (C) 2015 Published by Elsevier Ltd.
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| 3. |
- Lu, Yuexia, et al.
(author)
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CO2 capture by the absorption process in membrane contactors
- 2009
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In: The First International Conference on Applied Energy (ICAE09).
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Conference paper (peer-reviewed)abstract
- Membrane has a potential to improve the CO2 capture process. In this paper, experimentswere carried out to investigate the impact of amine absorbents on membrane surfaceproperties with polypropylene (PP) fibers immersed in monoethanolamine (MEA) andmethyldiethanolamine (MDEA) aqueous solutions with and without CO2 loading. The surfacemorphological changes of the membrane were examined by using scanning electronmicroscopy (SEM). The experimental results showed that the fibers immersed in the aqueoussolutions without CO2 loading underwent significant deformation than those with CO2 loading,which is mostly linked to the decrease of absorbent concentration with the reaction betweenCO2 and aqueous solutions. It was also found that the morphological changes of membraneimmersed in MDEA were severer than that in MEA due to the lower surface tension of theformer.
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| 4. |
- Lu, Yuexia, et al.
(author)
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INFLUENCE OF MEA AND MDEA SOLUTIONS ON SURFACE MORPHOLOGY OF MICROPOROUS POLYPROPYLENE MEMBRANES
- 2009
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In: The First International Conference on Applied Energy (ICAE09).
-
Conference paper (peer-reviewed)abstract
- Membrane has a potential to improve the CO2 capture process. In this paper, experimentswere carried out to investigate the impact of amine absorbents on membrane surfaceproperties with polypropylene (PP) fibers immersed in monoethanolamine (MEA) andmethyldiethanolamine (MDEA) aqueous solutions with and without CO2 loading. The surfacemorphological changes of the membrane were examined by using scanning electronmicroscopy (SEM). The experimental results showed that the fibers immersed in the aqueoussolutions without CO2 loading underwent significant deformation than those with CO2 loading,which is mostly linked to the decrease of absorbent concentration with the reaction betweenCO2 and aqueous solutions. It was also found that the morphological changes of membraneimmersed in MDEA were severer than that in MEA due to the lower surface tension of theformer.
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| 5. |
- Lv, Yuexia, et al.
(author)
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Experimental studies on simultaneous removal of CO2 and SO2 in a polypropylene hollow fiber membrane contactor
- 2012
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In: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 97, s. 283-288
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Journal article (peer-reviewed)abstract
- Membrane gas absorption technology is a promising alternative to conventional technologies for the mitigation of acid gases. In this study, simultaneous removal of SO2 and CO2 from coal-fired flue gas was carried out in a polypropylene hollow fiber membrane contactor using aqueous monoethanolamine as the absorbent. The influences of liquid and gas flow rates on the simultaneous absorption performance of CO2 and SO2 were investigated. The experimental results indicated that the membrane contactor could eliminate these two sour gases simultaneously and effectively. Absorption of SO2 and CO2 was enhanced by the increase in liquid flow rate and decrease in gas flow rate. It was observed that a small amount of SO2 in the flue gas had a slight influence on the absorption of CO2. In addition, the membrane contactor was operated continuously for two weeks to evaluate its duration performance. The results showed that the CO2 mass transfer rate was decreased significantly with the operating time due to partial wetting of membrane pores. After 14 days of continuous operation, the CO2 mass transfer rate of the wetted membrane contactor was decreased by 41% but could be retrieved to 86% of the fresh one by increasing the gas phase pressure.
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| 6. |
- Lv, Yuexia, et al.
(author)
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Fabrication and characterization of superhydrophobic polypropylene hollow fiber membranes for carbon dioxide absorption
- 2012
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In: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 90:1, s. 167-174
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Journal article (peer-reviewed)abstract
- The membrane wetting by amine absorbents results in performance deterioration of membrane gas absorption system for CO(2) post-combustion capture. To solve this problem, in this study, the polypropylene membrane fiber was modified by depositing a rough layer on the surface to improve its hydrophobicity. Weighing the coating homogeneity, hydrophobicity and modification process efficiency, the mixture of cyclohexanone and MEK system was considered as the best non-solvent. The contact angle increased dramatically from 122 to 158 by the modification, thereby obtaining superhydrophobic membrane surface. The membrane-absorbent interaction results demonstrated that the modification treatment effectively enhanced the stability and maintained the superhydrophobicity of fibers contacting with the absorbent. In addition, continuous CO(2) absorption experiments for up to 20 days were carried out in untreated and modified polypropylene hollow fiber membrane contactors, using 1 mol L(-1) MEA solution as the absorbent. The long-term system operation results indicated that, even though additional mass transfer resistance was introduced by the surface coating, the modified polypropylene hollow fiber membrane contactor was still technically feasible for CO(2) capture from the power stations.
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| 7. |
- Lv, Yuexia, et al.
(author)
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Wetting of polypropylene hollow fiber membrane contactors
- 2010
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In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 362:1-2, s. 444-452
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Journal article (peer-reviewed)abstract
- Membrane wetting by absorbents leads to an Increase in mass transfer resistance and a deterioration in CO2 absorption performance during the membrane gas absorption process In order to better understand the wetting mechanism of membrane pores during their prolonged contact with adsorbents, polypropylene (PP) hollow fibers were Immersed in three different absorbents for up to 90 days Monoethanolamine, methyldiethanolamine, and deionized water were applied as absorbent solutions The characterization results of membrane samples confirm that the absorbent molecules diffuse into PP polymers during the exposure process, resulting in the swelling of the membranes The absorption-swelling wetting mechanism is proposed to explain observations made during the wetting process The strong reduction of contact angles indicates that the membrane surface hydrophobicity decreases remarkably during immersion due to membrane-absorbent interaction Membrane surface morphologies and surface roughness suffer from significant and complicated changes after immersing the membrane fibers in the absorbents. Immersion in an absorbent with a high surface tension results in small changes in membrane surface morphology. As indicated by the experimental results, improving membrane surface hydrophobicity may be an effective way of overcoming wetting problems.
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| 8. |
- Wen, Zhenzhong, et al.
(author)
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Biodiesel production from waste cooking oil catalyzed by TiO2-MgO mixed oxides
- 2010
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 101:24, s. 9570-9576
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Journal article (peer-reviewed)abstract
- Mixed oxides of TiO2-MgO obtained by the sal-gel method were used to convert waste cooking oil into biodiesel. Titanium improved the stability of the catalyst because of the defects induced by the substitution of Ti ions for Mg ions in the magnesia lattice. The best catalyst was determined to be MT-1-923, which is comprised of an Mg/Ti molar ratio of 1 and calcined at 923 K, based on an assessment of the activity and stability of the catalyst. The main reaction parameters, including methanol/oil molar ratio, catalyst amount, and temperature, were investigated. The catalytic activity of MT-1-923 decreased slowly in the reuse process. After regeneration, the activity of MT-1-923 slightly increased compared with that of the fresh catalyst due to an increase in the specific surface area and average pore diameter. The mixed oxides catalyst. TiO2-MgO, showed good potential in large-scale biodiesel production from waste cooking oil.
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| 9. |
- Wen, Zhenzhong, et al.
(author)
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Intensification of biodiesel synthesis using zigzag micro-channel reactors
- 2009
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 100:12, s. 3054-3060
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Journal article (peer-reviewed)abstract
- Zigzag micro-channel reactors have been fabricated and used for continuous alkali-catalyzed biodiesel synthesis. The influences of the main geometric parameters on the performance of the micro-channel reactors were experimentally studied. it has been found that the zigzag micro-channel reactor with smaller channel size and more turns produces smaller droplets which result in higher efficiency of biodiesel synthesis. Compared to conventional stirred reactors, the time for high methyl ester conversion can be shortened significantly with the methyl ester yield of 99.5% at the residence time of only 28 s by using the optimized zigzag micro-channel reactor, which also exhibits less energy consumption for the same amount of biodiesel during biodiesel synthesis. The results indicate that zigzag micro-channel reactors can be designed as compact and mini-fuel processing plant for distributive applications.
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| 10. |
- Wen, Zhenzhong, et al.
(author)
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Synthesis of biodiesel from vegetable oil with methanol catalyzed by Li-doped magnesium oxide catalysts
- 2010
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In: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 87:3, s. 743-748
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Journal article (peer-reviewed)abstract
- The preparation of a Li-doped MgO for biodiesel synthesis has been investigated by optimizing the catalyst composition and calcination temperatures. The results show that the formation of strong base sites is particularly promoted by the addition of Li, thus resulting in an increase of the biodiesel synthesis. The catalyst with the Li/Mg molar ratio of 0.08 and calcination temperature of 823 K exhibits the best performance. The biodiesel conversion decreases with further increasing Lift molar ratio above 0.08, which is most likely attributed to the separated lithium hydroxide formed by excess Li ions and a concomitant decrease of BET values. In addition, the effects of methanol/oil molar ratio, reaction time, catalyst amount, and catalyst stability were also investigated for the optimized Li-doped MgO. The metal leaching from the Li-doped MgO catalysts was detected, indicating more studies are needed to stabilize the catalysts for its application in the large-scale biodiesel production facilities.
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