High-­Performance Carbon Molecular Sieve Gas Separation Membranes Based on a Carbon-­Rich Intrinsically Microporous Polyimide Precursor

Handle URI:
http://hdl.handle.net/10754/627771
Title:
High-­Performance Carbon Molecular Sieve Gas Separation Membranes Based on a Carbon-­Rich Intrinsically Microporous Polyimide Precursor
Authors:
Hazazi, Khalid ( 0000-0001-9379-1507 )
Abstract:
The objective of this study was to investigate the transport properties and the microstructure of CMS membranes derived from a carbon-rich intrinsically microporous polyimide precursor. CMS membranes were prepared by a heat treatment of the polyimide precursor using a well-defined heating protocol in a horizontal tube furnace up to 1000 °C. A nitrogen purge was kept inside the furnace to remove all the evolved by-products as the precursor started to decompose and carbonize. The microstructures of the carbon molecular sieve membranes (CMSMs) were examined using wide-angle x-ray diffraction, Raman spectra, N2 adsorption and CO2 adsorption. The average interlayer spacing (d002) between the graphite plates was estimated using the data obtained by the WXRD. The average d002 decreased as a result of increasing the pyrolysis temperature; average d002 distances for CMS prepared at 700 and 1000 °C were estimated to be 0.40 to 0.38 nm, respectively. Raman spectra confirmed the progressive structural ordering as heat-treatment temperature increased. A substantial decrease in the intensity of the D band was observed as a function of pyrolysis temperature, indicating a decrease in the disordered structure. Graphitic structure and turbostratic carbon coexist in the as-prepared carbon membranes, of which the microcrystal size La and the stacking height Lc were increasing as a function of pyrolysis temperature. N2 adsorption showed a remarkable increase in the BET surface area as a function of pyrolysis temperature. BET surface areas for the pristine and CMSs prepared at 700 to 900 °C were in the range of 650 to 680 m2/g with a remarkable shift in the pore size distribution toward the ultra- microporous region. CO2 adsorption was used to estimate the surface area for pores with sizes of less than 1 nm. Surface areas were observed to increase from 350 m2/g at 500 °C to 857 m2/g at 800 °C, and then started dropping slightly from 857 to 650 m2/g at 800 to 1000 °C, respectively. This is believed to be caused by pore shrinkage effect being severe after 800 °C, which caused some pores to be hard to spot by the CO2 adsorption technique. The transport properties of the pristine and CMS membranes were tested using pure gases He, H2, N2, CH4, CO2, and O2. From the pristine to SBFDA-DMN-700°C, the selectivity increased significantly, with a massive loss in the permeability except for He and H2. From SBFDA-DMN- 700 °C to 900 °C, a substantial increase in selectivity with a moderate decline in permeability was observed. Beyond 900 °C, the permeability again decreased moderately, but a tremendous increase in the selectivity for N2/CH4, CO2/CH4, and H2/CH4 was observed.
Advisors:
Pinnau, Ingo ( 0000-0003-3040-9088 )
Committee Member:
Peinemann, Klaus-Viktor ( 0000-0003-0309-9598 ) ; Han, Yu ( 0000-0003-1462-1118 )
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Chemical and Biological Engineering
Issue Date:
Apr-2018
Type:
Thesis
Appears in Collections:
Theses

Full metadata record

DC FieldValue Language
dc.contributor.advisorPinnau, Ingoen
dc.contributor.authorHazazi, Khaliden
dc.date.accessioned2018-05-07T10:56:59Z-
dc.date.available2018-05-07T10:56:59Z-
dc.date.issued2018-04-
dc.identifier.urihttp://hdl.handle.net/10754/627771-
dc.description.abstractThe objective of this study was to investigate the transport properties and the microstructure of CMS membranes derived from a carbon-rich intrinsically microporous polyimide precursor. CMS membranes were prepared by a heat treatment of the polyimide precursor using a well-defined heating protocol in a horizontal tube furnace up to 1000 °C. A nitrogen purge was kept inside the furnace to remove all the evolved by-products as the precursor started to decompose and carbonize. The microstructures of the carbon molecular sieve membranes (CMSMs) were examined using wide-angle x-ray diffraction, Raman spectra, N2 adsorption and CO2 adsorption. The average interlayer spacing (d002) between the graphite plates was estimated using the data obtained by the WXRD. The average d002 decreased as a result of increasing the pyrolysis temperature; average d002 distances for CMS prepared at 700 and 1000 °C were estimated to be 0.40 to 0.38 nm, respectively. Raman spectra confirmed the progressive structural ordering as heat-treatment temperature increased. A substantial decrease in the intensity of the D band was observed as a function of pyrolysis temperature, indicating a decrease in the disordered structure. Graphitic structure and turbostratic carbon coexist in the as-prepared carbon membranes, of which the microcrystal size La and the stacking height Lc were increasing as a function of pyrolysis temperature. N2 adsorption showed a remarkable increase in the BET surface area as a function of pyrolysis temperature. BET surface areas for the pristine and CMSs prepared at 700 to 900 °C were in the range of 650 to 680 m2/g with a remarkable shift in the pore size distribution toward the ultra- microporous region. CO2 adsorption was used to estimate the surface area for pores with sizes of less than 1 nm. Surface areas were observed to increase from 350 m2/g at 500 °C to 857 m2/g at 800 °C, and then started dropping slightly from 857 to 650 m2/g at 800 to 1000 °C, respectively. This is believed to be caused by pore shrinkage effect being severe after 800 °C, which caused some pores to be hard to spot by the CO2 adsorption technique. The transport properties of the pristine and CMS membranes were tested using pure gases He, H2, N2, CH4, CO2, and O2. From the pristine to SBFDA-DMN-700°C, the selectivity increased significantly, with a massive loss in the permeability except for He and H2. From SBFDA-DMN- 700 °C to 900 °C, a substantial increase in selectivity with a moderate decline in permeability was observed. Beyond 900 °C, the permeability again decreased moderately, but a tremendous increase in the selectivity for N2/CH4, CO2/CH4, and H2/CH4 was observed.en
dc.language.isoenen
dc.subjectMembraneen
dc.subjectCarbon molecular sieveen
dc.subjectGas Separationen
dc.titleHigh-­Performance Carbon Molecular Sieve Gas Separation Membranes Based on a Carbon-­Rich Intrinsically Microporous Polyimide Precursoren
dc.typeThesisen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen
dc.contributor.committeememberPeinemann, Klaus-Viktoren
dc.contributor.committeememberHan, Yuen
thesis.degree.disciplineChemical and Biological Engineeringen
thesis.degree.nameMaster of Scienceen
dc.person.id142959en
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