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Molecular accessibility in solvent swelled coal

Description: Research continued on the swelling of coal. Changes in the size and number distribution of the accessible regions in five Argonne Premium Coal Samples (APCS No.3, No.4, No.5, No.6, and No.8) upon swelling with the solvents, cyclohexane, toluene, nitrobenzene and pyridine were examined by an EPR spin probe method. It was found that as the basicity of the solvent increased the number and length of the cylindrical pores increased with decreasing rank. The number of cylindrical pores also increased with oxygen content (with decreasing rank) suggesting a destruction of the hydrogen-bond network upon swelling with pyridine. 6 refs.
Date: November 1, 1990
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Magnetic resonance and optical spectroscopic studies of carotenoids. Progress report, December 1, 1994--November 30, 1995

Description: The fundamental goals of this project are (1) to understand the role of a host matrix in the formation and decay mechanisms of carotenoid cation radical and dication and (2) to determine the special properties of carotenoids that enable them to serve as photoprotective agents in photosynthesis and as possible components in electron transfer processes. Results to date are discussed briefly. Work will continue as outlined in the original proposal with emphasis on using simultaneous electrochemistry EPR, and optical methods, variable temperature electrochemistry using microelectrodes and fast scans to examine the more unstable intermediates formed upon electrochemical oxidation of synthetically prepared carotenoids.
Date: June 1, 1995
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in oxidized and dried coals. Quarterly report, July 1995--September 1995

Description: The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture loss both in the presence and absence of light using our newly developed EPR spin probe method. The proposed study will make it possible to deduce the molecular accessibility distribution in swelled, oxidized APCS coal for each rank as a function of (1) size (up to 6 nm) and shape, (2) the relative acidic/basic reactive site distributions, and (3) the role of hydrogen bonding as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecular accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering processes.
Date: February 1, 1996
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in oxidized and dried coals. Quarterly report, October--November 1994

Description: The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture loss both in the presence and absence of light using a newly developed EPR spin probe method. The proposed study will make it possible to deduce the molecular accessibility distribution in swelled, oxidized APCS coal for each rank as a function of (1) size (up to 6 nm) and shape, (2) the relative acidic/basic reactive site distributions, and (3) the role of hydrogen bonding as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecular accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering processes.
Date: December 1, 1994
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in oxidized and dried coals. Quarterly report

Description: The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture los both in the presence and absence of light using our newly developed EPR spin probe method. The proposed study will make it possible to deduce the molecular accessibility distribution swelled, {ital oxidized} APCS coal for each rank as a function of (1) size (up to 6 nm) and shape, (2) the relative acidic/basic reactive site distributions, and (3) the role of hydrogen bonding as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecular accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering process. This quarter we have continued to examine the effect of exposure of light before alkylation versus after O-alkylation of the coal structure. The variation in uptake of spin probe VII (amine group) is depicted in figure 1 for Wyodak-Anderson. Before O-alkylation, a significant decrease occurred in the uptake of VII with increasing exposure to ambient light. This suggests that partial break-up of the hydrogen bond network occurs, making it possible to wash out more of the spin probes. This effect was eliminated if the coal was O-alkylated after exposure to sunlight (Figure 2). The removal of the source of hydrogen bonding is responsible for the lack of spin probe up-take variation with time of exposure to light. Further experiments have shown that the data in Figures 1 and 2 is reproducible with a deviation of less than {+-} 10%. It has also been observed that ...
Date: December 1, 1995
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in oxidized and dried coals. Quarterly report, [January 1, 1996--March 31, 1996]

Description: The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture loss both in the presence and absence of light using our newly developed EPR spin probe method. The proposed study will make it possible to deduce the molecular accessibility distribution in swelled, oxidized Argonne Premium Coal Samples (APCS) for each rank as a function of (1) size (up to 6nm) and shape, (2) the relative acidic/basic reactive site distributions, and (3) the role of hydrogen bonding as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecular accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering processes. Results of current study on changes in molecular accessibility in APCS coal oxidized in presence of sunlight show that accessibility to spin probes upon O-alkylation of the oxidized coal depends on the percent oxygen present before alkylation. An increase in microporosity occurs upon alkylation and this increase is more pronounced in higher rank than lower ranked coals. It was also observed that the increase in microporosity depends on the structure of each coal.
Date: March 1, 1996
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in oxidized and dried coals. Quarterly report

Description: The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture loss both in the presence and absence of light using the newly developed EPR spin probe method. The proposed study will make it possible to deduce the molecular accessibility distribution in swelled, oxidized APCS coal for each rank as a function of (1) size (up to 6 nm) and shape, (2) the relative acidic/basic reactive site distributions, and (3) the role of hydrogen bonding as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecular accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering processes.
Date: June 1, 1995
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in oxidized and dried coals. Quarterly report, January 1995--March 1995

Description: The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture loss both in the presence and absence of light using our newly developed EPR spin probe method. The proposed study will make it possible to deduce the molecular accessibility distribution in swelled, oxidized APCS coal for each rank as a function of (1) size (up to 6 nm) and shape, (2) the relative acidic/basic reactive site distributions, and (3) the role of hydrogen bonding as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecular accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering processes.
Date: March 1, 1995
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in solvent swelled coal

Description: Research continued on the determination of pore size and number distribution changes after swelling the coal samples with various solvents. A paper has just been submitted to the journal Fuel on the Low temperature Swelling of Argonne Premium Coal samples using solvents of varying polarity. The variation in the shape of the pore was followed as a function of temperature and swelling solvent polarity. This change in pore structure was attributed to break-up of the hydrogen bonding network in coal by polar solvents. The modification in pore shape from spherical to cylindrical was attributed to anisotropy in hydrogen bond densities. A copy of this paper has been attached to this report. Wojciech Sady has determine the structural changes in the pores that occur when APCS coal is dehydrated prior to swelling with polar solvents. These changes are different from those that occur in the absence of prior dehydration. He has also completed a study on the variation in the hydrogen bonding character of the pore wall as the coals are swelled with various polar solvents. A statistical analysis of the data is currently underway to determine important trends in his data. 9 refs.
Date: August 1, 1991
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in solvent swelled coal

Description: The EPR-spin probe method was used to study the swelling of covalently cross-linked 2%, 4%, 6%, 8% and 12% polystyrene-divinyl benzene copolymers, used as models of APCS coal structural elements. The results were compared with swelling studies on APCS coals and confirmed results showing that coal was polymeric, that it had covalent cross-links increasing with rank, that it was structurally anisotropic, and that its swelling was anisotropic. The low temperature swelling of Argonne Premium Coal Samples using solvents of varying polarity was investigated. The variation in the shape of the pore was followed as a function of temperature and swelling solvent polarity. This change in pore structure was attributed to break-up of the hydrogen bonding network in coal by polar solvents. The modification in pore shape from spherical to cylindrical was attributed to anisotropy in hydrogen bond densities. The structural changes in coal pores that occur when APCS coal is dehydrated prior to swelling with polar solvents has been determined. These changes are different from those that occur in the absence of prior dehydration. Most impressive is the huge change that occurs in lignite coal (Beulah-Zap). It appears that this coal has collapsed upon dehydration preventing any spin probe from being trapped in the dehydrated lignite upon swelling. Various sized probes have been studied. A study on the variation in the hydrogen bonding character of the pore wall as the coals are swelled with various polar solvents has also been completed. A statistical analysis of the data has been completed to determine important trends in the data. 9 refs.
Date: January 1, 1991
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in solvent swelled coal

Description: To expand the information base on molecular accessibility in solvent swelled coal, Argonne Premium Coal Samples (APCS) were swelled in polar, basic solvents before and after moisture loss and upon air oxidation. So far studies have been reported on the changes in pore size distribution as a function of temperature when polar basic swelling solvents are used. Additional studies employing EPR spin probe techniques performed on the breaking up of the hydrogen bonding between bedding planes were later confirmed by magnetic resonance imaging at Argonne National Lab and the University of Illinois.
Date: November 1, 1992
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in solvent swelled coal

Description: An EPR technique developed in this lab is being used to determine the pore size and number distribution changes after swelling the coal samples with various solvents. Stable nitroxide radical spin probes of different sizes, shapes and reactivity are dissolved in an appropriate solvent, the coal sample is added to the resulting solution, stirred over night at elevated temperature, filtered, washed with a nonswelling solvent to eliminate any spin probes that are not trapped in the pores and the spin concentration measured. Comparing these spin probe measurements to DRIFT data have shown that the relative number distribution of acidic functionalities can be accurately predicted by the spin probe method. The spin probe method has also been used to predict the increase in elongated voids in Pittsburgh No. 8 (APCS No. 4) upon swelling with pyridine in agreement with independent SANS data. NMR relaxation data show that it is possible to deduce the pore (accessibility) distribution as a function of size (up to 6 nm). It has also been possible by variable temperature and ENDOR measurements to determine the presence of hydrogen bonding as a function of pore shape and size. The advantage of EPR method is that it permits molecules of selected shape and size to be used as probes of accessible regions of the coal, thus providing information on the importance of molecular shape.
Date: May 29, 1992
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in solvent swelled coals

Description: An EPR technique developed in this lab is being used to determine the pore size and number distribution changes after swelling the coal samples with various solvents. Stable nitroxide radical spin probes of different sizes, shapes and reactivity are dissolved in an appropriate solvent, the coal sample is added to the resulting solution, stirred over night at elevated temperature, filtered, washed with a non swelling solvent to eliminate any spin probes that are not trapped in the pores and the spin concentration is measured. Comparing these spin probe measurements to DRIFT data have shown that the relative number distribution of acidic functionalities can be accurately predicted by the spin probe method. The spin probe method had also been used to predict the increase in elongated voids in Pittsburgh No. 8 (APCS No. 4) upon swelling with pyridine in agreement with independent SANS data. NMR relaxation data show that it is possible to deduce the pore (accessibility) distribution as a function of size (up to 6 mn). It has also been possible by variable temperature and ENDOR measurements to determine the presence of hydrogen bonding as a function of pore shape and size. The advantage of the EPR method is that it permits molecules of selected shape and size to be used as probes of accessible regions of coal, thus providing information on the importance of molecular shape.
Date: February 1, 1993
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in oxidized and dried coals: Quarterly report, October 1996--December 1996

Description: The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture loss both in the presence and absence of light using our EPR spin probe method. The proposed study will make it possible to deduce the molecular accessibility distribution in swelled, oxidized APCS coal as a function of sunlight for each rank as a function of (1) size (up to 6 nm) and shape, (2) the relative acidic/basic reactive site distributions, and (3) the role of hydrogen bonding as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecular accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering processes.
Date: December 1, 1996
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in oxidized and dried coals. Quarterly report, 1996

Description: The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture loss both in the presence and absence of light using our newly developed EPR spin probe method. The proposed study will make it possible to deduce the molecular accessibility distribution in swelled, oxidized APCS coal for each rank as a function of (1) size (up to 6 nm) and shape, (2) the relative acidic/basic reactive site distributions, and (3) the role of hydrogen bonding as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecular accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering processes. It appears that the observed binary swelling data for the APCS coals studied to date can be explained in terms of four different processes: one, disruption of weak hydrogen bonds which protect or isolate the interconnected micropore system; two, disruption of weak hydrogen bonds which protect individual micropores; three, the competition of pyridine for the active sites capable of establishing hydrogen bonds or the `poisoning` of active sites; four, disruption of stronger hydrogen bonds within the macromolecular structure which cause an opening of the structure. The contributions of each of these factors to the spin probe retention with increasing concentrations of pyridine vary up to 5% pyridine. At concentrations above 5% pyridine, the first factor becomes less significant, and variations in the others require greater changes in pyridine concentration.
Date: June 1, 1996
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in oxidized and dried coals. Quarterly report

Description: The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture loss both in the presence and absence of light using the EPR spin pore method. The proposed study will make it possible to deduce the molecular accessibility distribution in swelled, oxidized APCS coal as a function of sunlight for each rank as a function of (1) size (up to 6 nm) and shape, (2) the relative acidic/basic reactive site distribution, and (3) the role of hydrogen bonding as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecular accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering processes.
Date: September 1, 1996
Creator: Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in solvent swelled coals. Quarterly report, [April--June 1993]

Description: The effect of weathering (oxidation and dehydration upon exposure to air) on the molecular accessibility of potential catalysts was studied by the EPR spin probe technique. Fresh samples of all 8 APCS coals were exposed to air for periods up to 36 days. Weathering produced significant effects on the retention of spin probes in most of the APCS coals under 91 % carbon (dmmf). It was determined that the lower ranked coal (Beulah Zap and Wyodak) under went a structural collapse which precluded retention of even spin probe VIII. However, medium ranked coals exhibited improved retention upon weathering when swelled in toluene. Swelling with pyridine opened up small pores for 81--86% carbon which is not observed for swelling with toluene. Changes in coal structure were successfully followed by the EPR spin probe method. A detailed analysis of the data collected from the swelling of coals oxidized in a moisture free environment was completed to differentiate between weathering and oxidation. Eight vacuum dried APCS coals were oxidized in an enclosed, pure oxygen, moisture free environment, and the effects of oxidation alone on coal structure were studied by the intercalation of EPR spin probes. The data shows a factor of 5 increase in spin probe retention for some coals oxidized in O{sub 2} versus air., suggesting a large increase in oxidized material. Particular care was taken during the swelling procedures to avoid exposure of the coal samples to air or moisture. EPR spectra were then obtained for these 300 samples.
Date: August 1, 1993
Creator: Kispert, L. D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in oxidized and dried coals. Quarterly report, October--December 1993

Description: The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture loss both in the presence and absence of light using our newly developed EPR spin probe method. The proposed study will make it possible to deduce the molecular accessibility distribution in swelled, oxidized APCS coal for each rank as a function of (1) size (up to 6nm) and shape, (2) the relative acidic/basic reactive site distributions, (3) the role of hydrogen bonding and (4) the changes in the size and shape distribution of the accessible regions of the oxidized coal as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecularly accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering processes.
Date: December 1, 1993
Creator: Kispert, L. D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in solvent swelled coal. Quarterly report, November 1991

Description: The EPR-spin probe method was used to study the swelling of covalently cross-linked 2%, 4%, 6%, 8% and 12% polystyrene-divinyl benzene copolymers, used as models of APCS coal structural elements. The results were compared with swelling studies on APCS coals and confirmed results showing that coal was polymeric, that it had covalent cross-links increasing with rank, that it was structurally anisotropic, and that its swelling was anisotropic. The low temperature swelling of Argonne Premium Coal Samples using solvents of varying polarity was investigated. The variation in the shape of the pore was followed as a function of temperature and swelling solvent polarity. This change in pore structure was attributed to break-up of the hydrogen bonding network in coal by polar solvents. The modification in pore shape from spherical to cylindrical was attributed to anisotropy in hydrogen bond densities. The structural changes in coal pores that occur when APCS coal is dehydrated prior to swelling with polar solvents has been determined. These changes are different from those that occur in the absence of prior dehydration. Most impressive is the huge change that occurs in lignite coal (Beulah-Zap). It appears that this coal has collapsed upon dehydration preventing any spin probe from being trapped in the dehydrated lignite upon swelling. Various sized probes have been studied. A study on the variation in the hydrogen bonding character of the pore wall as the coals are swelled with various polar solvents has also been completed. A statistical analysis of the data has been completed to determine important trends in the data. 9 refs.
Date: December 31, 1991
Creator: Kispert, L. D.
Partner: UNT Libraries Government Documents Department

Molecular accessibility in solvent swelled coal. Quarterly report

Description: To expand the information base on molecular accessibility in solvent swelled coal, Argonne Premium Coal Samples (APCS) were swelled in polar, basic solvents before and after moisture loss and upon air oxidation. So far studies have been reported on the changes in pore size distribution as a function of temperature when polar basic swelling solvents are used. Additional studies employing EPR spin probe techniques performed on the breaking up of the hydrogen bonding between bedding planes were later confirmed by magnetic resonance imaging at Argonne National Lab and the University of Illinois.
Date: November 1, 1992
Creator: Kispert, L. D.
Partner: UNT Libraries Government Documents Department

Influence of binary swelling solvents: Mechanism of action

Description: This study addresses the dramatic up-take of a poor swelling solvent in Argonne Premium Coal Samples (APCS), Illinois No. 6, Beulah-Zap and Lewiston-Stockton when such a solvent is spiked with various amounts of the strong swelling solvent, pyridine. The unexpected up-take can be explained in terms of four different processes: (1) disruption of weak hydrogen bonds which isolate the interconnected micropore system; (2) disruption of weak hydrogen bonds which protect individual micropores; (3) competition of pyridine for the active sites involved in the hydrogen bonds or the {open_quotes}poisoning{close_quotes} of active sites; and (4) disruption of stronger hydrogen bonds within the macromolecules which causes an opening of the structure. When more than 5% pyridine is used, no additional disruption of the hydrogen-bonded network occurs. The structural changes were monitored by spin probe incorporation which was measured by EPR spectroscopy.
Date: December 31, 1995
Creator: Ding, R.; Tucker, D. & Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Swelling behavior of O-alkylated APCS coals as examined by the EPR spin probe method

Description: Known O-alkylation procedures have been used to derivatize the carboxyl and hydroxyl groups in the APCS coals Lewiston-Stockton, Wyodak-Anderson, Beulah-Zap, Illinois {number_sign}6, Upper Freeport, and Pittsburgh {number_sign}8. In general the resulting decrease in hydrogen bonding reduced the cyclical variation in nitroxide spin probe retention observed for nonalkylated coals when small amounts (<1%) of pyridine are present in the toluene swelling solvent. An increase in spin probe retention by the O-alkylated coals relative to the underivatized coals indicates a more open arrangement in the coal due to a decrease in attractive forces, confirming that microporosity increases with increasing rank.
Date: December 31, 1995
Creator: Ding, Ruisong; Tucker, D. & Kispert, L.D.
Partner: UNT Libraries Government Documents Department