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Lean NOx catalyst still a major challenge
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2nd World Congress on Environmental Catalysis as part of Topical Conference on Environmental Catalysis and Reaction Engineering The 2nd World Congress on Environmental Catalysis (Miami Beach, FL, 15-20 November 1998) had its beginning following the very successful first meeting in Pisa, Italy in May of 1995. At that time there was strong support to continue an international series of similar meetings with the next meeting to be held in the USA. The scope of the conference is aimed at promoting a global and interdisciplinary approach at using catalysis for a better environment and quality of life. A full five day program of oral and poster sessions in a single session format is planned. The Scientific Program will consist of a leadoff, keynote lecture each day given by a world leader in the field of environmental catalysis. Following this one hour presentation, there will be 30 minute oral presentations by other contributors throughout each of the five days of this meeting. There will also be at least two poster sessions jointly held with the parallel meeting on Environmental Reactor Engineering. Topics will include catalysts/catalysis reduction, removal, SO, for NO, VOC/N20/CFC or ozone emissions; mobile engine exhausts; CO:! utilization/abatement; waste minimization; replacements for liquid acids; fuel cells; and general/miscellaneous pollutants Accepted papers are to be published in a special issue of Catalysis Today to be edited by James J. Spivey. General Chairman of the meeting is John N. Armor of Air Products & Chemicals. Abstracts should be sent to the Program Chairwoman, Umit S. Ozkan, The
applied catalysis B: environmental
Ohio State Univ., Dept of Chem. Engn., Columbus, OH 43210. Further information may be obtained from R.M. Heck at the address given in the Calendar of Forthcoming Events. The World Congress on Environmental Catalysis will run concurrently at the same hotel with a technical program focused on Environmental Reactor Engineering. Both of these meetings will be offered as part of the Topical Conference on Environmental Catalysis and Reaction Engineering being sponsored by the AlChE during its 1998 November National meeting held in Miami Beach. J.N. Armor Lean NOx catalyst still a major challenge Some papers at the recent Society of Automotive Engineers (SAE) showed the continuing need for a technology breakthrough in lean NOx catalysis. One paper presented by Kobayashi-san (SAE 970745) concerned partial lean burn operation of the automobile engine and reviewed the use of thermodynamic calculations as a tool for selecting the NOx trapping compound. These calculations showed the trapping mechanism between the various carbonate and nitrate formation paths and indicated the trap performance depended on the added basic@ of the trap material. Equilibrium calculations followed by experimental studies confirmed this approach and showed Kand Ba to be the preferred trap materials. During the lean operation, the conversion of NO to NOz is critical for good trap performance. The effect of precious metal type and loading was studied and showed Pt = Rh > Pd. Increasing the precious metal loading improved performance up to a Volume 12 No. 2-3 -
12 June 1997
N13
point and thereafter was ineffective. Increasing the trapping component (e.g. Ba) was only effective at the higher precious metal loadings. Exhaust gas composition was also found to be important. Increasing the O2 and Hz0 content improved performance while increasing the COn content decreased performance. The authors concluded that the two step mechanism is as follows: - lean operation: NOp, formed by NO oxidation on Pt, attacks a M-carbonate component on the catalyst to form the corresponding M-nitrate. - rich operation: the M-nitrate decomposes to M-oxide and NOP. The released NOn is purified to N2 and the M-oxide is recovered to the M-carbonate by reaction with COn in the exhaust gas. Another paper presented by Martin Heimrich (SAE 970755) discussed experimental results for a lean NOx catalyst on a direct injection diesel engine. The catalysts were supplied by various catalyst manufacturers. The reductant for the lean NOx catalyst was supplied as diesel fuel. Steady state and transient federal procedure (FTP) tests were conducted The FTP tests showed that the NOx catalysts designed for lower operating temperature (225°C) performed better than those designed for higher operating temperatures (400°C) because of the low exhaust temperatures of the diesel engine. NOx conversion ranged from 5% to 17% for the FTP tests. Increasing the catalyst volume (decreasing the space velocity by a factor of 4.0) gave as high as 24% NOx removal. However, this large catalyst volume is not practical. Steady state tests gave a similar trend in results with a slightly higher maximum NOx removal. The majority of the NOx was converted to N20. SAE 970752 presented by Andre Boehman showed a
applied catalysis B: environmental
mathematical model of the lean NOx system. The peak NOx removal appeared to occurwhen the hydrocarbon was available at the catalyst surface for the entire length of the catalyst bed. At too high a temperature, all the hydrocarbons were consumed in the front of the catalyst bed. The rest of the reactor has no reductant left for further NOx reaction. New BASF process for reducing nitrous oxide emissions BASK will integrate this new process into its existing adipic acid production facilities at Ludwigshafen, Germany, where it will treat 64,000 m.t./yr of by-product nitrous oxide, a suspected greenhouse gas. This represents by-product nitrous oxide of about 12% of the 2 million m.t. of annual global adipic acid production. The new process used a catalyst based on aluminium, zinc and copper oxide to decompose more than 95% of the N20 and the company claims that the basic process would also have applications in any process which features NZO concentration above 5%. Source: Chemical Engineering, March 1997. VOC emission standards The European Commission has adopted a proposal which is aimed at cutting emissions of volatile organic compounds (VOC’s) from the solvent industry by two-thirds as part of its effort to reduce ground level ozone. Ground level ozone is produced when VOC’s react with oxides of nitrogen in the presence of bright sunlight and is damaging to both the environment and human health. For the summer months of 1994 Volume 12 No. 2-3-
12 June 1997
2nd World Congress on Environmental Catalysis as part of Topical Conference on Environmental Catalysis and Reaction Engineering The 2nd World Congress on Environmental Catalysis (Miami Beach, FL, 15-20 November 1998) had its beginning following the very successful first meeting in Pisa, Italy in May of 1995. At that time there was strong support to continue an international series of similar meetings with the next meeting to be held in the USA. The scope of the conference is aimed at promoting a global and interdisciplinary approach at using catalysis for a better environment and quality of life. A full five day program of oral and poster sessions in a single session format is planned. The Scientific Program will consist of a leadoff, keynote lecture each day given by a world leader in the field of environmental catalysis. Following this one hour presentation, there will be 30 minute oral presentations by other contributors throughout each of the five days of this meeting. There will also be at least two poster sessions jointly held with the parallel meeting on Environmental Reactor Engineering. Topics will include catalysts/catalysis reduction, removal, SO, for NO, VOC/N20/CFC or ozone emissions; mobile engine exhausts; CO:! utilization/abatement; waste minimization; replacements for liquid acids; fuel cells; and general/miscellaneous pollutants Accepted papers are to be published in a special issue of Catalysis Today to be edited by James J. Spivey. General Chairman of the meeting is John N. Armor of Air Products & Chemicals. Abstracts should be sent to the Program Chairwoman, Umit S. Ozkan, The
applied catalysis B: environmental
Ohio State Univ., Dept of Chem. Engn., Columbus, OH 43210. Further information may be obtained from R.M. Heck at the address given in the Calendar of Forthcoming Events. The World Congress on Environmental Catalysis will run concurrently at the same hotel with a technical program focused on Environmental Reactor Engineering. Both of these meetings will be offered as part of the Topical Conference on Environmental Catalysis and Reaction Engineering being sponsored by the AlChE during its 1998 November National meeting held in Miami Beach. J.N. Armor Lean NOx catalyst still a major challenge Some papers at the recent Society of Automotive Engineers (SAE) showed the continuing need for a technology breakthrough in lean NOx catalysis. One paper presented by Kobayashi-san (SAE 970745) concerned partial lean burn operation of the automobile engine and reviewed the use of thermodynamic calculations as a tool for selecting the NOx trapping compound. These calculations showed the trapping mechanism between the various carbonate and nitrate formation paths and indicated the trap performance depended on the added basic@ of the trap material. Equilibrium calculations followed by experimental studies confirmed this approach and showed Kand Ba to be the preferred trap materials. During the lean operation, the conversion of NO to NOz is critical for good trap performance. The effect of precious metal type and loading was studied and showed Pt = Rh > Pd. Increasing the precious metal loading improved performance up to a Volume 12 No. 2-3 -
12 June 1997
N13
point and thereafter was ineffective. Increasing the trapping component (e.g. Ba) was only effective at the higher precious metal loadings. Exhaust gas composition was also found to be important. Increasing the O2 and Hz0 content improved performance while increasing the COn content decreased performance. The authors concluded that the two step mechanism is as follows: - lean operation: NOp, formed by NO oxidation on Pt, attacks a M-carbonate component on the catalyst to form the corresponding M-nitrate. - rich operation: the M-nitrate decomposes to M-oxide and NOP. The released NOn is purified to N2 and the M-oxide is recovered to the M-carbonate by reaction with COn in the exhaust gas. Another paper presented by Martin Heimrich (SAE 970755) discussed experimental results for a lean NOx catalyst on a direct injection diesel engine. The catalysts were supplied by various catalyst manufacturers. The reductant for the lean NOx catalyst was supplied as diesel fuel. Steady state and transient federal procedure (FTP) tests were conducted The FTP tests showed that the NOx catalysts designed for lower operating temperature (225°C) performed better than those designed for higher operating temperatures (400°C) because of the low exhaust temperatures of the diesel engine. NOx conversion ranged from 5% to 17% for the FTP tests. Increasing the catalyst volume (decreasing the space velocity by a factor of 4.0) gave as high as 24% NOx removal. However, this large catalyst volume is not practical. Steady state tests gave a similar trend in results with a slightly higher maximum NOx removal. The majority of the NOx was converted to N20. SAE 970752 presented by Andre Boehman showed a
applied catalysis B: environmental
mathematical model of the lean NOx system. The peak NOx removal appeared to occurwhen the hydrocarbon was available at the catalyst surface for the entire length of the catalyst bed. At too high a temperature, all the hydrocarbons were consumed in the front of the catalyst bed. The rest of the reactor has no reductant left for further NOx reaction. New BASF process for reducing nitrous oxide emissions BASK will integrate this new process into its existing adipic acid production facilities at Ludwigshafen, Germany, where it will treat 64,000 m.t./yr of by-product nitrous oxide, a suspected greenhouse gas. This represents by-product nitrous oxide of about 12% of the 2 million m.t. of annual global adipic acid production. The new process used a catalyst based on aluminium, zinc and copper oxide to decompose more than 95% of the N20 and the company claims that the basic process would also have applications in any process which features NZO concentration above 5%. Source: Chemical Engineering, March 1997. VOC emission standards The European Commission has adopted a proposal which is aimed at cutting emissions of volatile organic compounds (VOC’s) from the solvent industry by two-thirds as part of its effort to reduce ground level ozone. Ground level ozone is produced when VOC’s react with oxides of nitrogen in the presence of bright sunlight and is damaging to both the environment and human health. For the summer months of 1994 Volume 12 No. 2-3-
12 June 1997