Gopalakrishnan, R
1996
Effects of CaO, High-Temperature Treatment, Carbon Structure, and Coal Rank on Intrinsic Char Oxidation Rates
Gopalakrishnan, R. and Bartholomew, C.H.
Energy & Fuels, 10:689-695, 1996. Funded by ACERC.
The low temperature kinetics of oxidation of Dietz sub-bituminous coal char prepared in methane flat-flame burner (4% post-flame oxygen) was studied by TGA both in the presence and in the absence of calcium minerals. The reactivities of untreated and calcium-reloaded chars at 600 K are 5 and 2 times higher than acid-washed char, indicating a significant catalytic effect for CaO. The intrinsic reactivities of these chars after oxidation in a drop-tube reactor at a particle temperature of about 1900 K and 5% O2 also show a similar trend, although the reactivity of each char is lowered by about a factor of 10 due to this high-temperature oxidation. The physical properties of these chars are also significantly altered due to high-temperature oxidation treatment. Comparison of intrinsic oxidation rates of unloaded Spherocarb and demineralized (acid-washed) chars of Zap and Dietz coals based on available carbon mass shows a trend of increasing intrinsic rate with decreasing skeletal density suggesting that the intrinsic rate is a function of carbon structure. However, in the presence of CaO, the intrinsic oxidation rate based on CaO surface area is found to increase with decreasing coal rank. Dispersion of CaO is significantly higher for the original Dietz char prepared in a flat-flame burner (34%) than for the Ca-loaded char (12%), indicating that the Ca-reloading procedure could be improved.
1994
Catalysis of Char Oxidation by Calcium Minerals: Effects of Calcium Compound Chemistry on Intrinsic Reactivity of Doped Spherocarb and Zap Chars
Gopalakrishnan, R.; Fullwood, M. and Bartholomew, C.H.
Energy & Fuels, 8:984-989, 1994. Funded by ACERC.
Catalysis by CaO, CaCo3, and CaSO4 of the oxidation of a well-defined, high purity synthetic char, Spherocarb, was investigated at low reaction temperatures using thermogravimetric analysis. The results indicate significant catalytic effects-up to 160-fold increase for CaCO3 catalysis, 290-fold increase for CaSO4, and up to 2700 times for CaO. Oxidation rates were likewise measured for fresh, demineralized, and Ca-loaded chars prepared from Beulah-Zap lignite coal in a flat flame burner at 1473 K. The oxidation rates of CaO-catalyzed Spherocarb and Zap are the same within experimental error, suggesting that the high reactivity of the Zap char is due in large part to catalysis by CaO. It was also found that chlorine added to Ca-loaded char had a negligible effect on its low-temperature reactivity.
Catalysts for Cleanup of NH3, NOx and CO from a Nuclear Waste Processing Facility
Gopalakrishnan, R.; Davidson, J.E.; Stafford, P.R.; Hecker, W.C. and Bartholomew, C.H.
ACS Symposium Series, 552:74-88, 1994. Funded by Westinghouse Idaho Nuclear Company, Brigham Young University and ACERC.
Performance of Cu-ZSM-5, Pt/Al2O3 and Cu-ZSM-5 + Pt/Al2)3 for NH3 (425-750 ppm) and CO (~1%) oxidation in the presence of NO (250 ppm), O2 (14-15%) and H2O (~20%) was studied as a function of temperature. Pt/Al2O3 is more active for NH3 and CO oxidation, while Cu-ZSM-5 is more selective for conversion of NO and NH3 to N2. NH3 and CO are completely oxidized above 300°C on Pt/Al2O3, while on Cu-ZSM-5 about 99% of NH3 and NO are converted to N2 at 450-500°C, although only about 50% of CO is converted to CO2. The selectivity of Cu-ZSM-5 for conversion of NH3 and NO to N2 is about 100%, while selectivities of Pt/Al2O3 for N2 and N2O are 35-40% and 20-40% respectively. However, the activity and selectivity of a Cu-ZSM-5 + Pt/Al2O3 dual catalytic systems are very high, converting 99% of NH3, 94% of NO, and 100% of CO simultaneously at 485°C with a 100% selectivity to N2.
1993
Effects of CaO, CaSO4 and Coal Rank on Low- and High-Temperature Char Oxidation Rates
Gopalakrishnan, R.; Fullwood, M.; Moody, S.; Cope, R.F. and Bartholomew, C.H.
Proceedings of the 7th International Conference on Coal Science, Banff, Canada, September 1993. Funded by ACERC.
This study is part of an ongoing program to investigate (a) rates and mechanisms of Ca-catalyzed oxidation of synthetic char and chars prepared from representative U.S. coals and (b) the chemical nature of active catalytic sites for oxidation on those inorganic mineral phases present in coal chars.
Selective Catalytic Reduction of Nitric Oxide by Propane in Oxidizing Atmosphere over Copper-Exchanged Zeolites
Gopalakrishnan, R.; Stafford, P.R.; Davidson, J.E.; Hecker, W.C. and Bartholomew, C.H.
Applied Catalysis B: Environmental, 2: 165, 1993. (Presented at the Seventh Annual Symposium of the Western States Catalysis Club, Albuquerque, NM, March 1992; at the American Institute of Chemical Engineers Annual Meeting, Miami Beach, FL, November 1992 and at the 13th North American Meeting of the Catalysis Society, Pittsburgh, PA, May 1993). Funded by Shell, Brigham Young University and Winco.
Selective catalytic reduction of NO with propane and oxygen was investigated on Cu-exchanged ZSM-5, mordenite, X-type and Y-type zeolites at temperatures in the range of 200 to 600º C. Catalytic activities of Cu-X and Cu-Y are negligible, activity of Cu-mordenite moderate, and that of Cu-ZSM-5 very high, converting >90% of NO to N2 at 400ºC and a space velocity of 102,300/hr. Effects of space velocity, NO concentration, C3H8/NO ratio, oxygen concentration, and water vapor on the activities of Cu-ZSM-5 and Cu-mordenite were investigated. NO conversion decreases with increasing space velocity, decreasing propane and NO concentrations, and decreasing propane/NO ratio. Water vapor decreases the activity significantly at all temperatures. At temperatures above 400ºC, propane oxidation by oxygen is a significant competing reaction in decreasing the selectivity for NO reduction. The results indicate that Cu-ZSM-5 is a promising catalyst for SCR of NO by hydrocarbons.
1992
Selective Catalytic Reduction of Nitric Oxide by Propane in Oxidizing Atmosphere Over Copper-Exchanged Zeolites
Gopalakrishnan, R.; Stafford, P.R.; Davidson, J.E.; Hecker, W.C. and Bartholomew, C.H.
Applied Catalysis, 1992 (in press). (Also presented at the Seventh Annual Symposium of the Western States Catalysis Club, Albuquerque, NM, March 1992 and at the American Institute of Chemical Engineers Annual Meeting, Miami Beach, FL, November 1992). Funded by Shell and Brigham Young University.
Selective catalytic reduction of NO with propane and oxygen was investigated on Cu-exchanged ZSM-5, mordenite, X-type and Y-type zeolites at temperatures in the range of 200 to 600ºC. Catalytic activities of Cu-X and Cu-Y are negligible, activity of Cu-mordenite moderate, and that of Cu-ZSM-5 very high, converting >90% of NO to N2 at 400ºC and at a space velocity of 102,300/hr. Effects of space velocity, NO concentration, C3H8/NO ratio, oxygen concentration, and water vapor on the activities of Cu-ZSM-5 and Cu-mordenite were investigated. NO conversion decreases with increasing space velocity, decreasing propane and NO concentrations, and decreasing propane/NO ratio. Water vapor decreases the activity significantly at all temperatures. At temperatures above 400ºC, propane oxidation by oxygen is a significant competing reaction in decreasing the selectivity for NO reduction. The results indicate that Cu-ZSM-5 is a promising catalyst for SCR of NO by hydrocarbons.
1991
Catalysis of Char Gasification in O2 by CaO and CaCO3
Bartholomew, C.H.; Gopalakrishnan, R. and Fullwood, M.
ACS Fuel Division, 36(3):982-989, 1991 (4th Chemical Congress of North America, New York, NY, August 1991). Funded by ACERC.
Catalysis by CaO and CaCO3 of the oxidation of a well-defined, high purity synthetic char, Spherocarb, was investigated at low reaction temperatures using thermal gravimetric analysis (TGA). Oxidation rates were likewise measured for fresh, demineralized, and Ca-impregnated samples of a high temperature char prepared in a flat-flame burner at about 1300 K from Beulah Zap coal. Spherocarb and demineralized Zap char were impregnated with Ca using aqueous impregnation and ion-exchange techniques. The resulting kinetic parameters for Spherocarb indicate significant catalytic effects--up to a 100 fold increase in reaction rate for CaCO3 and 3,000 in the case of CaO. The oxidation rates of CaO-catalyzed Spherocarb and Beulah Zap char are the same within experimental error, suggesting that the high reactivity of the Zap char is due in large part to catalysis by CaO.
Calcium Oxide Catalysis of Char Oxidation
Bartholomew, C.H.; Gopalakrishnan, R. and Fullwood, M.
8th Annual International Pittsburgh Coal Conference, 1140, Pittsburgh, PA, October 1991. Funded by ACERC.
Catalysis by CaO and CaCO3 of the oxidation of a well-defined, high purity synthetic char, Spherocarb, was investigated at low reaction temperatures using thermal gravimetric analysis (TGA). Oxidation rates were likewise measured for fresh, demineralized, and Ca-impregnated samples of a high temperature char prepared in a flat-flame burner at about 1300 K from Beulah Zap coal. Spherocarb and demineralized Zap char were impregnated with Ca using aqueous impregnation and ion-exchange techniques. The resulting kinetic parameters for Spherocarb indicate significant catalytic effects--up to a 100 fold increase in reaction rate for CaCO3 and 3,000 in the case of CaO. The oxidation rates of CaO-catalyzed Spherocarb and Beulah Zap char are the same within experimental error, suggesting that the high reactivity of the Zap char is due in large part to catalysis by CaO.
1990
Calcium Oxide Catalysis of Char Oxidation
Bartholomew, C.H.; Gopalakrishnan, R. and Fullwood, M.
Proc. ASME Seminar on Fouling of Western Coals, Brigham Young University, Provo, UT, 1990. (Also presented at the National AlChE Meeting, Chicago, 1990). Funded by ACERC.
Catalysis by CaO of the oxidation of a well-defined, high purity synthetic char, Spherocarb, was investigated at low reaction temperatures using thermal gravimetric analysis (TGA). Spherocarb was impregnated with Ca using aqueous impregnation and ion-exchange techniques. The resulting kinetic parameters indicate a significant catalytic effect--10 to 100-fold increases in reaction rate. CO adsorption on CaO prepared by Ca(OH)2 decomposition was investigated using temperature-programmed desorption (TPD) of CO adsorbed at 298 K. Several high temperature peaks were observed consistent with heats of adsorption of 40-115 kJ/mal. These relatively large heats of adsorption are indicative of the presence of different, strongly adsorbed CO species on CaO and have significant implications for the catalysis of carbon oxidation and of CO oxidation to CO2 during char combustion. Experiments involving temperature-programmed reaction of hydrogen with adsorbed CO also indicate by the formation of methane that CO may adsorb dissociatively or at least dissociates in the presence of hydrogen to form methane.
Gopalakrishnan, R
1996
Effects of CaO, High-Temperature Treatment, Carbon Structure, and Coal Rank on Intrinsic Char Oxidation Rates
Gopalakrishnan, R. and Bartholomew, C.H.
Energy & Fuels, 10:689-695, 1996. Funded by ACERC.
The low temperature kinetics of oxidation of Dietz sub-bituminous coal char prepared in methane flat-flame burner (4% post-flame oxygen) was studied by TGA both in the presence and in the absence of calcium minerals. The reactivities of untreated and calcium-reloaded chars at 600 K are 5 and 2 times higher than acid-washed char, indicating a significant catalytic effect for CaO. The intrinsic reactivities of these chars after oxidation in a drop-tube reactor at a particle temperature of about 1900 K and 5% O2 also show a similar trend, although the reactivity of each char is lowered by about a factor of 10 due to this high-temperature oxidation. The physical properties of these chars are also significantly altered due to high-temperature oxidation treatment. Comparison of intrinsic oxidation rates of unloaded Spherocarb and demineralized (acid-washed) chars of Zap and Dietz coals based on available carbon mass shows a trend of increasing intrinsic rate with decreasing skeletal density suggesting that the intrinsic rate is a function of carbon structure. However, in the presence of CaO, the intrinsic oxidation rate based on CaO surface area is found to increase with decreasing coal rank. Dispersion of CaO is significantly higher for the original Dietz char prepared in a flat-flame burner (34%) than for the Ca-loaded char (12%), indicating that the Ca-reloading procedure could be improved.
1994
Catalysis of Char Oxidation by Calcium Minerals: Effects of Calcium Compound Chemistry on Intrinsic Reactivity of Doped Spherocarb and Zap Chars
Gopalakrishnan, R.; Fullwood, M. and Bartholomew, C.H.
Energy & Fuels, 8:984-989, 1994. Funded by ACERC.
Catalysis by CaO, CaCo3, and CaSO4 of the oxidation of a well-defined, high purity synthetic char, Spherocarb, was investigated at low reaction temperatures using thermogravimetric analysis. The results indicate significant catalytic effects-up to 160-fold increase for CaCO3 catalysis, 290-fold increase for CaSO4, and up to 2700 times for CaO. Oxidation rates were likewise measured for fresh, demineralized, and Ca-loaded chars prepared from Beulah-Zap lignite coal in a flat flame burner at 1473 K. The oxidation rates of CaO-catalyzed Spherocarb and Zap are the same within experimental error, suggesting that the high reactivity of the Zap char is due in large part to catalysis by CaO. It was also found that chlorine added to Ca-loaded char had a negligible effect on its low-temperature reactivity.
Catalysts for Cleanup of NH3, NOx and CO from a Nuclear Waste Processing Facility
Gopalakrishnan, R.; Davidson, J.E.; Stafford, P.R.; Hecker, W.C. and Bartholomew, C.H.
ACS Symposium Series, 552:74-88, 1994. Funded by Westinghouse Idaho Nuclear Company, Brigham Young University and ACERC.
Performance of Cu-ZSM-5, Pt/Al2O3 and Cu-ZSM-5 + Pt/Al2)3 for NH3 (425-750 ppm) and CO (~1%) oxidation in the presence of NO (250 ppm), O2 (14-15%) and H2O (~20%) was studied as a function of temperature. Pt/Al2O3 is more active for NH3 and CO oxidation, while Cu-ZSM-5 is more selective for conversion of NO and NH3 to N2. NH3 and CO are completely oxidized above 300°C on Pt/Al2O3, while on Cu-ZSM-5 about 99% of NH3 and NO are converted to N2 at 450-500°C, although only about 50% of CO is converted to CO2. The selectivity of Cu-ZSM-5 for conversion of NH3 and NO to N2 is about 100%, while selectivities of Pt/Al2O3 for N2 and N2O are 35-40% and 20-40% respectively. However, the activity and selectivity of a Cu-ZSM-5 + Pt/Al2O3 dual catalytic systems are very high, converting 99% of NH3, 94% of NO, and 100% of CO simultaneously at 485°C with a 100% selectivity to N2.
1993
Effects of CaO, CaSO4 and Coal Rank on Low- and High-Temperature Char Oxidation Rates
Gopalakrishnan, R.; Fullwood, M.; Moody, S.; Cope, R.F. and Bartholomew, C.H.
Proceedings of the 7th International Conference on Coal Science, Banff, Canada, September 1993. Funded by ACERC.
This study is part of an ongoing program to investigate (a) rates and mechanisms of Ca-catalyzed oxidation of synthetic char and chars prepared from representative U.S. coals and (b) the chemical nature of active catalytic sites for oxidation on those inorganic mineral phases present in coal chars.
Selective Catalytic Reduction of Nitric Oxide by Propane in Oxidizing Atmosphere over Copper-Exchanged Zeolites
Gopalakrishnan, R.; Stafford, P.R.; Davidson, J.E.; Hecker, W.C. and Bartholomew, C.H.
Applied Catalysis B: Environmental, 2: 165, 1993. (Presented at the Seventh Annual Symposium of the Western States Catalysis Club, Albuquerque, NM, March 1992; at the American Institute of Chemical Engineers Annual Meeting, Miami Beach, FL, November 1992 and at the 13th North American Meeting of the Catalysis Society, Pittsburgh, PA, May 1993). Funded by Shell, Brigham Young University and Winco.
Selective catalytic reduction of NO with propane and oxygen was investigated on Cu-exchanged ZSM-5, mordenite, X-type and Y-type zeolites at temperatures in the range of 200 to 600º C. Catalytic activities of Cu-X and Cu-Y are negligible, activity of Cu-mordenite moderate, and that of Cu-ZSM-5 very high, converting >90% of NO to N2 at 400ºC and a space velocity of 102,300/hr. Effects of space velocity, NO concentration, C3H8/NO ratio, oxygen concentration, and water vapor on the activities of Cu-ZSM-5 and Cu-mordenite were investigated. NO conversion decreases with increasing space velocity, decreasing propane and NO concentrations, and decreasing propane/NO ratio. Water vapor decreases the activity significantly at all temperatures. At temperatures above 400ºC, propane oxidation by oxygen is a significant competing reaction in decreasing the selectivity for NO reduction. The results indicate that Cu-ZSM-5 is a promising catalyst for SCR of NO by hydrocarbons.
1992
Selective Catalytic Reduction of Nitric Oxide by Propane in Oxidizing Atmosphere Over Copper-Exchanged Zeolites
Gopalakrishnan, R.; Stafford, P.R.; Davidson, J.E.; Hecker, W.C. and Bartholomew, C.H.
Applied Catalysis, 1992 (in press). (Also presented at the Seventh Annual Symposium of the Western States Catalysis Club, Albuquerque, NM, March 1992 and at the American Institute of Chemical Engineers Annual Meeting, Miami Beach, FL, November 1992). Funded by Shell and Brigham Young University.
Selective catalytic reduction of NO with propane and oxygen was investigated on Cu-exchanged ZSM-5, mordenite, X-type and Y-type zeolites at temperatures in the range of 200 to 600ºC. Catalytic activities of Cu-X and Cu-Y are negligible, activity of Cu-mordenite moderate, and that of Cu-ZSM-5 very high, converting >90% of NO to N2 at 400ºC and at a space velocity of 102,300/hr. Effects of space velocity, NO concentration, C3H8/NO ratio, oxygen concentration, and water vapor on the activities of Cu-ZSM-5 and Cu-mordenite were investigated. NO conversion decreases with increasing space velocity, decreasing propane and NO concentrations, and decreasing propane/NO ratio. Water vapor decreases the activity significantly at all temperatures. At temperatures above 400ºC, propane oxidation by oxygen is a significant competing reaction in decreasing the selectivity for NO reduction. The results indicate that Cu-ZSM-5 is a promising catalyst for SCR of NO by hydrocarbons.
1991
Catalysis of Char Gasification in O2 by CaO and CaCO3
Bartholomew, C.H.; Gopalakrishnan, R. and Fullwood, M.
ACS Fuel Division, 36(3):982-989, 1991 (4th Chemical Congress of North America, New York, NY, August 1991). Funded by ACERC.
Catalysis by CaO and CaCO3 of the oxidation of a well-defined, high purity synthetic char, Spherocarb, was investigated at low reaction temperatures using thermal gravimetric analysis (TGA). Oxidation rates were likewise measured for fresh, demineralized, and Ca-impregnated samples of a high temperature char prepared in a flat-flame burner at about 1300 K from Beulah Zap coal. Spherocarb and demineralized Zap char were impregnated with Ca using aqueous impregnation and ion-exchange techniques. The resulting kinetic parameters for Spherocarb indicate significant catalytic effects--up to a 100 fold increase in reaction rate for CaCO3 and 3,000 in the case of CaO. The oxidation rates of CaO-catalyzed Spherocarb and Beulah Zap char are the same within experimental error, suggesting that the high reactivity of the Zap char is due in large part to catalysis by CaO.
Calcium Oxide Catalysis of Char Oxidation
Bartholomew, C.H.; Gopalakrishnan, R. and Fullwood, M.
8th Annual International Pittsburgh Coal Conference, 1140, Pittsburgh, PA, October 1991. Funded by ACERC.
Catalysis by CaO and CaCO3 of the oxidation of a well-defined, high purity synthetic char, Spherocarb, was investigated at low reaction temperatures using thermal gravimetric analysis (TGA). Oxidation rates were likewise measured for fresh, demineralized, and Ca-impregnated samples of a high temperature char prepared in a flat-flame burner at about 1300 K from Beulah Zap coal. Spherocarb and demineralized Zap char were impregnated with Ca using aqueous impregnation and ion-exchange techniques. The resulting kinetic parameters for Spherocarb indicate significant catalytic effects--up to a 100 fold increase in reaction rate for CaCO3 and 3,000 in the case of CaO. The oxidation rates of CaO-catalyzed Spherocarb and Beulah Zap char are the same within experimental error, suggesting that the high reactivity of the Zap char is due in large part to catalysis by CaO.
1990
Calcium Oxide Catalysis of Char Oxidation
Bartholomew, C.H.; Gopalakrishnan, R. and Fullwood, M.
Proc. ASME Seminar on Fouling of Western Coals, Brigham Young University, Provo, UT, 1990. (Also presented at the National AlChE Meeting, Chicago, 1990). Funded by ACERC.
Catalysis by CaO of the oxidation of a well-defined, high purity synthetic char, Spherocarb, was investigated at low reaction temperatures using thermal gravimetric analysis (TGA). Spherocarb was impregnated with Ca using aqueous impregnation and ion-exchange techniques. The resulting kinetic parameters indicate a significant catalytic effect--10 to 100-fold increases in reaction rate. CO adsorption on CaO prepared by Ca(OH)2 decomposition was investigated using temperature-programmed desorption (TPD) of CO adsorbed at 298 K. Several high temperature peaks were observed consistent with heats of adsorption of 40-115 kJ/mal. These relatively large heats of adsorption are indicative of the presence of different, strongly adsorbed CO species on CaO and have significant implications for the catalysis of carbon oxidation and of CO oxidation to CO2 during char combustion. Experiments involving temperature-programmed reaction of hydrogen with adsorbed CO also indicate by the formation of methane that CO may adsorb dissociatively or at least dissociates in the presence of hydrogen to form methane.