| 1. |
- Akhtar, Farid, et al.
(författare)
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Strong and binder free structured zeolite sorbents with very high CO2-over-N-2 selectivities and high capacities to adsorb CO2 rapidly
- 2012
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 5:6, s. 7664-7673
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Tidskriftsartikel (refereegranskat)abstract
- Mechanically strong monoliths of zeolite NaKA with a hierarchy of pores displayed very high CO2-over-N-2 selectivity. The zeolite monoliths were produced by pulsed current processing (PCP) without the use of added binders and with a preserved microporous crystal structure. Adsorption isotherms of CO2 and N-2 were determined and used to predict the co-adsorption of CO2 and N-2 using ideal adsorbed solution theory (IAST). The IAST predictions showed that monolithic adsorbents of NaKA could reach an extraordinarily high CO2-over-N-2 selectivity in a binary mixture with a composition similar to flue gas (15 mol% CO2 and 85 mol% N2 at 25 degrees C and 101 kPa). Structured NaKA monoliths with a K+ content of 9.9 at% combined a CO2-over-N-2 selectivity of >1100 with a high CO2 adsorption capacity (4 mmol g(-1)) and a fast adsorption kinetics (on the order of one minute). Estimates of a figure of merit (F) based on IAST CO2-over-N-2 selectivity, and time-dependent CO2 uptake capacity, suggest that PCP-produced structured NaKA with a K+ content of 9.9 at% offers a performance far superior to 13X adsorbents, in particular at short cycle times.
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| 2. |
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| 3. |
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| 4. |
- Cheung, Ocean, et al.
(författare)
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Adsorption kinetics for CO2 on highly selective zeolites NaKA and nano-NaKA
- 2013
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 112, s. 1326-1336
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Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide removal from flue gas via swing adsorption processes requires adsorbents with a high CO2 selectivity and capacity. These properties are particularly valuable to reduce the cost of carbon capture and storage (CCS). Zeolite NaKA was studied for its ability to selectively adsorb CO2 from flue gas, as we previously observed that zeolite NaKA, with a K+/(K+ + Na+) ratio of 17 atomic%, was highly selective towards CO2 over N-2 adsorption by tuning the size of the pore window apertures [1]. The reduced pore apertures may, however, retard the adsorption rate of CO2. Here, we studied the kinetics of CO2 adsorption on regularly sized zeolite NaKA and on nano-sized zeolite NaKA. We used in situ infrared (IR) spectroscopy and observed that CO2 physisorbed relatively rapidly. Density functional theory (DFT) was used for quantum chemical calculations, and the results indicated that CO2 molecules bridged across two or three Na+ ions in the samples with no or very small amount of K. When more K+ ions are present the CO2 molecules no longer bridged across multiple metal ions and adopted an end-on configuration. The calculation showed a shift in the stretching vibration frequency of physisorbed CO2 as observed by IR spectroscopy. Nano-sized zeolite NaKA were synthesised and studied to improve the rate of CO2 adsorption, as the diffusion rate typically increases quadratically with decreasing particle size. Still, the CO2 adsorption rate on nano-sized zeolites NaA and NaKA did not increase significantly. For nano-sized zeolite NaA, we speculate that the absence of such an increased rate is an effect from a skin layer that had formed on the nano-sized zeolite NaA, a layer that was possibly related to intergrowths with extremely small crystals on the surface. The apparently slow adsorption kinetics of CO2 on nano-sized zeolite NaKA was more difficult to explain because it could relate to imperfections within the small crystals, remaining water, or other effects. Overall, the CO2 adsorption rates on zeolite NaKA crystals of different sizes were fast and relevant for the time scales required for adsorption based CCS processes, such as vacuum and temperature swing adsorption (VSA/TSA).
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| 5. |
- Cheung, Ocean, et al.
(författare)
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Silicoaluminophosphates as CO2 sorbents
- 2012
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 156, s. 90-96
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Tidskriftsartikel (refereegranskat)abstract
- Silicoaluminophosphates (SAPO-17, SAPO-35, SAPO-56 and SAPO-RHO) synthesised via hydrothermal means are tested for their abilities to adsorb carbon dioxide. These 8-ring microporous phosphates show high capacities to adsorb CO2. SAPO-RHO has a high uptake of CO2 and a very low uptake of N-2 due to its narrow pore window aperture at 273 K. Its significant uptake of N-2 at 77 K is rationalised by a temperature induced shrinkage effect. SAPO-56 has a slightly higher CO2 capacity (5.42 mmol/g, 273 K, 101 kPa) and is less water sensitive than zeolite 13X. Cyclic adsorption and in situ infrared spectroscopy (IR) reveal that SAPOs retain 95% of their original CO2 capacity after six cycles and that adsorption occurs via physisorption. The calculated heat of adsorption for CO2 (at 0.2-0.7 mmol/g loading) on SAPO-56 and SAPO-RHO lies in the physisorption range (similar to 35 kJ/mol). SAPOs, in particular SAPO-56 and SAPO-RHO, possess many desirable properties and are potentially good adsorbents for CO2 capture in swing adsorption processes.
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| 6. |
- Hu, Wei, et al.
(författare)
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Transcriptome-wide association study reveals cholesterol metabolism gene Lpl is a key regulator of cognitive dysfunction
- 2022
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Ingår i: Frontiers in Molecular Neuroscience. - : Frontiers Media S.A.. - 1662-5099. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Cholesterol metabolism in the brain plays a crucial role in normal physiological function, and its aberrations are associated with cognitive dysfunction. The present study aimed to determine which cholesterol-related genes play a vital role in cognitive dysfunction and to dissect its underlying molecular mechanisms using a systems genetics approach in the BXD mice family. We first systematically analyzed the association of expression of 280 hippocampal genes related to cholesterol metabolism with cognition-related traits and identified lipoprotein lipase (Lpl) as a critical regulator. This was further confirmed by phenome-wide association studies that indicate Lpl associated with hippocampus volume residuals and anxiety-related traits. By performing expression quantitative trait locus mapping, we demonstrate that Lpl is strongly cis-regulated in the BXD hippocampus. We also identified ∼3,300 genes significantly (p < 0.05) correlated with the Lpl expression. Those genes are mainly involved in the regulation of neuron-related traits through the MAPK signaling pathway, axon guidance, synaptic vesicle cycle, and NF-kappa B signaling pathway. Furthermore, a protein–protein interaction network analysis identified several direct interactors of Lpl, including Rab3a, Akt1, Igf1, Crp, and Lrp1, which indicates that Lpl involves in the regulation of cognitive dysfunction through Rab3a-mediated synaptic vesicle cycle and Akt1/Igf1/Crp/Lrp1-mediated MAPK signaling pathway. Our findings demonstrate the importance of the Lpl, among the cholesterol-related genes, in regulating cognitive dysfunction and highlighting the potential signaling pathways, which may serve as novel therapeutic targets for the treatment of cognitive dysfunction.
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| 7. |
- Jiang, Bin, et al.
(författare)
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Zipf’s law for all the natural cities around the world
- 2015
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Ingår i: International Journal of Geographical Information Science. - : Informa UK Limited. - 1365-8816 .- 1365-8824 .- 1362-3087. ; 29:3, s. 498-522
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Tidskriftsartikel (refereegranskat)abstract
- Two fundamental issues surrounding research on Zipf’s law regarding city sizes are whether and why this law holds. This paper does not deal with the latter issue with respect to why, and instead investigates whether Zipf’s law holds in a global setting, thus involving all cities around the world. Unlike previous studies, which have mainly relied on conventional census data such as populations and census-bureau-imposed definitions of cities, we adopt naturally (in terms of data speak for itself) delineated cities, or natural cities, to be more precise, in order to examine Zipf’s law. We find that Zipf’s law holds remarkably well for all natural cities at the global level, and it remains almost valid at the continental level except for Africa at certain time instants. We further examine the law at the country level, and note that Zipf’s law is violated from country to country or from time to time. This violation is mainly due to our limitations; we are limited to individual countries, or to a static view on city-size distributions. The central argument of this paper is that Zipf’s law is universal, and we therefore must use the correct scope in order to observe it. We further find Zipf’s law applied to city numbers; the number of cities in the largest country is twice as many as that in the second largest country, three times as many as that in the third largest country, and so on. These findings have profound implications for big data and the science of cities.
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| 8. |
- Liu, Qingling, et al.
(författare)
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Aluminophosphates for CO2 Separation
- 2011
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631. ; 4:1, s. 91-97
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Tidskriftsartikel (refereegranskat)abstract
- The pressure-swing adsorption method for carbon dioxide capture would ideally be facilitated by adsorbents with a high capacity and a high selectivity for CO2. Several aluminophosphates with 8-ring window apertures (AlPO4-17, AlPO4-18, AlPO4-53, and AlPO4-25) were synthesized by hydrothermal crystallization, calcined, and their CO2 uptake and CO2/N-2 selectivity were studied. CO2 and N-2 uptake was determined for pressures up to 101 kPa at 273 and 293 K. Langmuir and Toth adsorption models were used to describe the adsorption isotherms. The CO2 and N-2 uptakes strongly indicated that the squeezed 8-ring windows of certain aluminophosphates can sieve CO2 from a CO2 and N-2 gas mixture. Both AlPO4-53 and AlPO4-25 exhibited a remarkably higher uptake of CO2 compared to N-2. The hydrophilicity of the AlPO4 materials was investigated by means of water adsorption, and the results showed that all of the tested aluminophosphates were less water sensitive than a benchmark zeolite (13X). In particular, AlPO4-53 and AlPO4-25 showed a very low degree of water uptake with up to 20-30% relative humidity. Determination of cyclic adsorption and desorption confirmed the relatively hydrophobic nature of the aluminophosphates, which render them less energy costly for the regeneration of adsorbents.
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| 9. |
- Liu, Qingling, et al.
(författare)
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NaKA sorbents with high CO2-over-N2 selectivity and high capacity to adsorb CO2
- 2010
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 46, s. 4502-4504
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Tidskriftsartikel (refereegranskat)abstract
- The uptake of carbon dioxide and nitrogen gas by zeolite NaKA was studied. A very high ideal CO2-over-N2 selectivity and a high CO2 capacity were observed at an optimal K+ content of 17 at.%. NaKA is a very promising adsorbent for CO2 separation from water-free flue gases.
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| 10. |
- Yao, Qingxia, et al.
(författare)
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Interpenetrated metal-organic frameworks and their uptake of CO2 at relatively low pressures
- 2012
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 22:20, s. 10345-10351
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption-driven separation of CO2 from flue gas has the potential to cut the cost for carbon capture and storage. Among the porous physisorbents, metal-organic frameworks (MOFs) are a class of promising candidates for gas separation and storage owing to their extraordinarily high specific surface areas and pore volumes, and predesigned pore structures. Here, we report three interpenetrated MOFs composed of Zn4O clusters and rigid dicarboxylate anions, namely SUMOF-n (SU StockholmUniversity; n = 2, 3, 4). All the interpenetrated MOFs possess small pores of two different types and high pore volumes. SUMOF-2 had a structure similar to interpenetrated MOF-5, but with an extra-framework cation present in one of the two types of pores. SUMOF-3 was an interpenetrated version of IRMOF-8 while SUMOF-4 crystallized with mixed linkers, biphenyl-4,4'-dicarboxylic acid and benzene-1,4-dicarboxylic acid. Among the three SUMOFs, SUMOF-4 had the largest specific surface area (1612 m(2) g(-1)) and pore volume. Single component adsorption of CO2 and N-2 was determined at 273 K. We showed that the interpenetrated SUMOF-2 adsorbedmore CO2 than non-interpenetrated MOF-5 under 273 K and 1 bar. This may be explained by the increased electric field gradients due to the interpenetration in the MOF. The uptake of CO2 for SUMOF-2 and SUMOF-4 was significant at somewhat higher pressure. Their CO2 isotherms were close to linear, which could be beneficial for separation of CO2 via pressure swing adsorption from biogas or natural gas. On the other hand, SUMOF-3 adsorbed most CO2 at pressures relevant for CO2 capture from flue gas.
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