Abstract
Polyalkoxysilsesquiazanes ([ROSi(NH)1.5]n, ROSZ, R = Et, nPr, iPr, nBu, sBu, nHex, sHex, cHex, decahydronaphthyl (DHNp)) were synthesized by ammonolysis at −78 °C of alkoxytrichlorosilane (ROSiCl3), which was isolated by distillation as a reaction product of SiCl4 and ROH. The simultaneous thermogravimetric and mass spectrometry analyses of the ROSZs under helium revealed a common decomposition reaction, the cleavage of the oxygen–carbon bond of the RO group to evolve alkene as a main gaseous species formed in-situ, leading to the formation of microporous amorphous Si–O–N at 550 °C to 800 °C. The microporosity in terms of the peak of the pore size distribution curve located within the micropore size range (<2 nm) and the total micropore volume, as well as the specific surface area (SSA) of the Si–O–N, increased consistently with the molecular size estimated for the alkene formed in-situ during the pyrolysis. The CO2 capture capacity at 0 °C of the Si–O–N material increased consistently with its SSA, and an excellent CO2 capture capacity of 3.9 mmol·g−1 at 0 °C and CO2 1 atm was achieved for the Si–O–N derived from DHNpOSZ having an SSA of 750 m2·g−1. The CO2 capture properties were further discussed based on their temperature dependency, and a surface functional group of the Si–O–N formed in-situ during the polymer/ceramics thermal conversion.
Highlights
In the case of pressure swing adsorption (PSA), the adsorption process is operated at high pressures, typically ranging from 8 to 28 bar [36,37], and the PSA systems for pre-combustion CO2 capture are especially attractive for solid sorbents to adsorb CO2 efficiently since the partial pressure of CO2 in the pre-combustion streams such as steam-methane reforming (SMR) off-gas is high, in the order of several atmospheres [38,39]
To identify the chemical structure of the ROSZ in more detail, 13 C– and 29 Si–nuclear magnetic resonance (NMR) spectroscopic analyses were performed in solid state
ATR–IR, 13 C– and 29 Si–NMR spectroscopic analyses revealed that a series of polyalkoxysilsesquiazanes ([ROSi(NH)1.5 ]n, ROSZ, R = Et, nPr, iPr, nBu, sBu, nHex, sHex, cHex, DHNp) were successfully synthesized in a good yield via two simple steps: reaction of SiCl4 with ROH to afford ROSiCl3, followed by ammonolysis at −78 ◦ C
Summary
Micro and mesoporous structure formation through the polymer-derived ceramics (PDCs) [1,2]. In the case of PSA, the adsorption process is operated at high pressures, typically ranging from 8 to 28 bar [36,37], and the PSA systems for pre-combustion CO2 capture are especially attractive for solid sorbents to adsorb CO2 efficiently since the partial pressure of CO2 in the pre-combustion streams such as steam-methane reforming (SMR) off-gas is high, in the order of several atmospheres [38,39] For this system, zeolite 13X and NaY with large CO2 capture capacity at moderate temperatures have been used, but regeneration of the zeolites requires very low vacuum and/or high-temperature. CO2 capture capacities at 0 to 40 ◦ C of the present ROSZ-derived microporous amorphous Si–O–N materials were evaluated and briefly compared with those in literature, the capture behaviors under CO2 atmosphere were in-situ analyzed by using thermogravimetry and infrared spectroscopy
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
