The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Sophia E Hayes - One of the best experts on this subject based on the ideXlab platform.
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the missing Bicarbonate in co2 chemisorption reactions on solid amine sorbents
Journal of the American Chemical Society, 2018Co-Authors: Chiahsin Chen, Daphna Shimon, Frederic Mentinkvigier, Ivan Hung, Carsten Sievers, Christopher W Jones, Sophia E HayesAbstract:We have identified a hydrated Bicarbonate formed by chemisorption of 13CO2 on both dimethylaminopropylsilane (DMAPS) and aminopropylsilane (APS) pendant molecules grafted on SBA-15 mesoporous silica. The most commonly used sequence in solid-state NMR, 13C CPMAS, failed to detect Bicarbonate in these solid amine sorbent samples; here, we have employed a Bloch decay ("pulse-acquire") sequence (with 1H decoupling) to detect such species. The water that is present contributes to the dynamic motion of the Bicarbonate product, thwarting CPMAS but enabling direct 13C detection by shortening the spin-lattice relaxation time. Since solid-state NMR plays a major role in characterizing chemisorption reactions, these new insights that allow for the routine detection of previously elusive Bicarbonate species (which are also challenging to observe in IR spectroscopy) represent an important advance. We note that employing this straightforward NMR technique can reveal the presence of Bicarbonate that has often otherwise been overlooked, as demonstrated in APS, that has been thought to only contain adsorbed CO2 as carbamate and carbamic acid species. As in other systems (e.g., proteins), dynamic species that sample multiple environments tend to broaden as their motion is frozen out. Here, we show two distinct Bicarbonate species upon freezing, and coupling to different protons is shown through preliminary 13C-1H HETCOR measurements. This work demonstrates that Bicarbonates have likely been formed in the presence of water but have gone unobserved by NMR due to the nature of the experiments most routinely employed, a perspective that will transform the way the sorption community will view CO2 capture by amines.
Mcmahan L Gray - One of the best experts on this subject based on the ideXlab platform.
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thermal and chemical stability of regenerable solid amine sorbent for co2 capture
Energy & Fuels, 2006Co-Authors: Rajesh Khatri, Steven S C Chuang, Yee Soong, Mcmahan L GrayAbstract:The adsorption and desorption of CO2 and SO2 on an amine-grafted SBA-15 sorbent has been studied by in situ infrared spectroscopy coupled with mass spectrometry. CO2 adsorbed on an amine-grafted sorbent as carbonates and Bicarbonates, while SO2 adsorbed as sulfates and sulfites. The CO2 adsorption capacity of the amine-grafted sorbent was almost twice as much as that of a commercial sorbent. The adsorption of CO2 in the presence of H2O and D2O shows an isotopic shift in the IR frequency of adsorbed carbonate and Bicarbonate bands, revealing that water plays a role in the CO2 adsorption on amine-grafted sorbents. Although the rate of adsorption of SO2 was slower than that of CO2, the adsorbed S surface species is capable of blocking the active amine sites for CO2 adsorption. A temperature-programmed degradation study of the amine-grafted sorbent showed that the surface amine species are stable up to 250 °C in air.
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carbon dioxide capture by diamine grafted sba 15 a combined fourier transform infrared and mass spectrometry study
Industrial & Engineering Chemistry Research, 2005Co-Authors: Rajesh Khatri, Steven S C Chuang, Yee Soong, Mcmahan L GrayAbstract:The adsorption and desorption of CO2 on diamine-grafted SBA-15 have been studied by infrared spectroscopy coupled with mass spectrometry. Diamine was grafted onto the SBA-15 surface by the reaction of [N-(2-aminoethyl)-3-aminopropyl]trimethoxysilane with the surface OH. CO2 is adsorbed on the diamine-grafted SBA-15 as bidentate carbonate and bidentate and monodentate Bicarbonates at 25 °C. Bidentate carbonate and monodentate Bicarbonates are the major surface species formed and decomposed during the concentration-swing adsorption/desorption process at 25 °C. Temperature-programmed desorption revealed that the monodentate and bidentate Bicarbonates bound stronger to the diamine-grafted SBA-15 surface than the bidentate carbonate. The amount of CO2 desorbed from the carbonate and Bicarbonate between 30 and 120 °C is 2 times more than that of CO2 adsorbed/desorbed during each cycle of the concentration-swing adsorption/desorption. Desorption at 120 °C removes the majority of the captured CO2 and regenerates ...
Tong Ding - One of the best experts on this subject based on the ideXlab platform.
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hydroxyl promoted preferential and total oxidation of co over e mno2 catalyst
Catalysis Today, 2020Co-Authors: Zexin Zhang, Ye Tian, Wanyue Zhao, Jing Zhang, Lirong Zheng, Tong DingAbstract:Abstract Herein, we synthesize the hydroxyl-enriched e-MnO2 catalyst (MnO2-AT) by simple acid washing. Acid washing destroys the sphere structure into fragments with abundant structure defects and maintains the crystal and pore structure of e-MnO2. MnO2-AT exhibits the high activity and selectivity for preferential oxidation of CO in the H2-rich stream, as well as the high activity for CO total oxidation. It can completely converts CO in preferential and total oxidation of CO at 170 °C and 90 °C, respectively, with a good stability. The acid washing treatment highly increases the surface hydroxyl groups on MnO2-AT. Our results demonstrate that with the aid of surface hydroxyl groups CO can easily form Bicarbonate intermediates, which are more thermally unstable than carbonate intermediates. The faster CO2 desorption from Bicarbonates than carbonates promotes the CO oxidation process.
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Hydroxyl promoted preferential and total oxidation of CO over ε-MnO2 catalyst
Catalysis Today, 2020Co-Authors: Zexin Zhang, Ye Tian, Wanyue Zhao, Jing Zhang, Lirong Zheng, Tong DingAbstract:Abstract Herein, we synthesize the hydroxyl-enriched e-MnO2 catalyst (MnO2-AT) by simple acid washing. Acid washing destroys the sphere structure into fragments with abundant structure defects and maintains the crystal and pore structure of e-MnO2. MnO2-AT exhibits the high activity and selectivity for preferential oxidation of CO in the H2-rich stream, as well as the high activity for CO total oxidation. It can completely converts CO in preferential and total oxidation of CO at 170 °C and 90 °C, respectively, with a good stability. The acid washing treatment highly increases the surface hydroxyl groups on MnO2-AT. Our results demonstrate that with the aid of surface hydroxyl groups CO can easily form Bicarbonate intermediates, which are more thermally unstable than carbonate intermediates. The faster CO2 desorption from Bicarbonates than carbonates promotes the CO oxidation process.
Chiahsin Chen - One of the best experts on this subject based on the ideXlab platform.
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the missing Bicarbonate in co2 chemisorption reactions on solid amine sorbents
Journal of the American Chemical Society, 2018Co-Authors: Chiahsin Chen, Daphna Shimon, Frederic Mentinkvigier, Ivan Hung, Carsten Sievers, Christopher W Jones, Sophia E HayesAbstract:We have identified a hydrated Bicarbonate formed by chemisorption of 13CO2 on both dimethylaminopropylsilane (DMAPS) and aminopropylsilane (APS) pendant molecules grafted on SBA-15 mesoporous silica. The most commonly used sequence in solid-state NMR, 13C CPMAS, failed to detect Bicarbonate in these solid amine sorbent samples; here, we have employed a Bloch decay ("pulse-acquire") sequence (with 1H decoupling) to detect such species. The water that is present contributes to the dynamic motion of the Bicarbonate product, thwarting CPMAS but enabling direct 13C detection by shortening the spin-lattice relaxation time. Since solid-state NMR plays a major role in characterizing chemisorption reactions, these new insights that allow for the routine detection of previously elusive Bicarbonate species (which are also challenging to observe in IR spectroscopy) represent an important advance. We note that employing this straightforward NMR technique can reveal the presence of Bicarbonate that has often otherwise been overlooked, as demonstrated in APS, that has been thought to only contain adsorbed CO2 as carbamate and carbamic acid species. As in other systems (e.g., proteins), dynamic species that sample multiple environments tend to broaden as their motion is frozen out. Here, we show two distinct Bicarbonate species upon freezing, and coupling to different protons is shown through preliminary 13C-1H HETCOR measurements. This work demonstrates that Bicarbonates have likely been formed in the presence of water but have gone unobserved by NMR due to the nature of the experiments most routinely employed, a perspective that will transform the way the sorption community will view CO2 capture by amines.
Rajesh Khatri - One of the best experts on this subject based on the ideXlab platform.
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thermal and chemical stability of regenerable solid amine sorbent for co2 capture
Energy & Fuels, 2006Co-Authors: Rajesh Khatri, Steven S C Chuang, Yee Soong, Mcmahan L GrayAbstract:The adsorption and desorption of CO2 and SO2 on an amine-grafted SBA-15 sorbent has been studied by in situ infrared spectroscopy coupled with mass spectrometry. CO2 adsorbed on an amine-grafted sorbent as carbonates and Bicarbonates, while SO2 adsorbed as sulfates and sulfites. The CO2 adsorption capacity of the amine-grafted sorbent was almost twice as much as that of a commercial sorbent. The adsorption of CO2 in the presence of H2O and D2O shows an isotopic shift in the IR frequency of adsorbed carbonate and Bicarbonate bands, revealing that water plays a role in the CO2 adsorption on amine-grafted sorbents. Although the rate of adsorption of SO2 was slower than that of CO2, the adsorbed S surface species is capable of blocking the active amine sites for CO2 adsorption. A temperature-programmed degradation study of the amine-grafted sorbent showed that the surface amine species are stable up to 250 °C in air.
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carbon dioxide capture by diamine grafted sba 15 a combined fourier transform infrared and mass spectrometry study
Industrial & Engineering Chemistry Research, 2005Co-Authors: Rajesh Khatri, Steven S C Chuang, Yee Soong, Mcmahan L GrayAbstract:The adsorption and desorption of CO2 on diamine-grafted SBA-15 have been studied by infrared spectroscopy coupled with mass spectrometry. Diamine was grafted onto the SBA-15 surface by the reaction of [N-(2-aminoethyl)-3-aminopropyl]trimethoxysilane with the surface OH. CO2 is adsorbed on the diamine-grafted SBA-15 as bidentate carbonate and bidentate and monodentate Bicarbonates at 25 °C. Bidentate carbonate and monodentate Bicarbonates are the major surface species formed and decomposed during the concentration-swing adsorption/desorption process at 25 °C. Temperature-programmed desorption revealed that the monodentate and bidentate Bicarbonates bound stronger to the diamine-grafted SBA-15 surface than the bidentate carbonate. The amount of CO2 desorbed from the carbonate and Bicarbonate between 30 and 120 °C is 2 times more than that of CO2 adsorbed/desorbed during each cycle of the concentration-swing adsorption/desorption. Desorption at 120 °C removes the majority of the captured CO2 and regenerates ...