Abstract 1. A PROCESS OF TREATING AN INTERNAL COMBUSTION ENGINE EXHAUST GAS CONTAINING NITROGEN OXIDES AND CARBON MONOXIDE TO DECREASE THE CONTENT THEREOF BEFORE DISCHARGE INTO THE ATMOSPHERE, SAID PROCESS COMPRISING A START-U PHASE WHEREIN THE EXHAUST GAS AND ADDED AIR AR PASSED OVER A REFRACTORY CATALYST UNDER OXIDIZING CONDITIONS OF HEAT SAID CATALYST TO ITS OPERATING TEMPERATURE IN THE RANGE OF 750-900*C., A SUBSEQUENT RUNNING STAGE WHEREIN THE EXHAUST GAS IS PASSED OVER THE REFRACTORY CATALYST UNDER NET REDUCING CONDITIONS AT SAID OPERATING TE, TURE AND AT A SPACE VELOCITY OF 6000 TO 60,000 HOUR-1 WHEREBY AT LEAST 70% OF THE NITROGEN OXIDES IN SAID EXHAUST GAS IS DESTROYED WITH NOT MORE THAN 20% THEREOF BEING CONVERTED TO AMMONIA, AND AA FURTHER STAGE WHEREIN THE THUS TREATED EXHAUST GAS IS PASSED OVER AN OXIDATION CATALYST TO CONVERT THE CARBON MONOXIDE IN SAID GAS TO A NONTOXIC OR INNOCUOUS GAS, SAID REFRACTORY CATALYST CONSISTING ESSENTIALLY OF A HIGH TEMPERATURE STEAM REFORMING BASE METAL OR PRECIOUS METAL CATALYST HAVING AN ACTIVE METAL CRYSTALLITE SIZE OF AT LEAST 1000 A., AN ACTIVE METAL SPECIFIC SURFACE OF LESS THAN ABOUT 10 M.2/G. OF THE ACTIVE METAL, A TOTAL SPECIFIC SURFACE OF LESS THAN 150 M.2/G. AND HYDROTHERMAL STABILITY, THE CATALYST BEING SUPPORTED ON A STEAM-STABLE REFRACTORY OXIDE.
A PROCESS OF TREATING AN INTERNAL COMBUSTION ENGINE EXHAUST GAS CONTAINING NITROGEN OXIDES AND CARBON MONOXIDE TO DECREASE THE CONTENT THEREOF BEFORE DISCHARGE INTO THE ATMOSPHERE, SAID PROCESS COMPRISING A START-U PHASE WHEREIN THE EXHAUST GAS AND ADDED AIR AR PASSED OVER A REFRACTORY CATALYST UNDER OXIDIZING CONDITIONS OF HEAT SAID CATALYST TO ITS OPERATING TEMPERATURE IN THE RANGE OF 750-900*C., A SUBSEQUENT RUNNING STAGE WHEREIN THE EXHAUST GAS IS PASSED OVER THE REFRACTORY CATALYST UNDER NET REDUCING CONDITIONS AT SAID OPERATING TE, TURE AND AT A SPACE VELOCITY OF 6000 TO 60,000 HOUR-1 WHEREBY AT LEAST 70% OF THE NITROGEN OXIDES IN SAID EXHAUST GAS IS DESTROYED WITH NOT MORE THAN 20% THEREOF BEING CONVERTED TO AMMONIA, AND AA FURTHER STAGE WHEREIN THE THUS TREATED EXHAUST GAS IS PASSED OVER AN OXIDATION CATALYST TO CONVERT THE CARBON MONOXIDE IN SAID GAS TO A NONTOXIC OR INNOCUOUS GAS, SAID REFRACTORY CATALYST CONSISTING ESSENTIALLY OF A HIGH TEMPERATURE STEAM REFORMING BASE METAL OR PRECIOUS METAL CATALYST HAVING AN ACTIVE METAL CRYSTALLITE SIZE OF AT LEAST 1000 A., AN ACTIVE METAL SPECIFIC SURFACE OF LESS THAN ABOUT 10 M.2/G. OF THE ACTIVE METAL, A TOTAL SPECIFIC SURFACE OF LESS THAN 150 M.2/G. AND HYDROTHERMAL STABILITY, THE CATALYST BEING SUPPORTED ON A STEAM-STABLE REFRACTORY OXIDE.
Claim 2
Dependent Claim
212 words
A PROCESS OF TREATING AN INTERNAL COMBUSTION ENGINE EXHAUST GAS CONTAINING NITROGEN OXIDES AND CARBON MONOXIDE TO DECREASE THE CONTENT THEREOF BEFORE DISCHARGE INTO THE ATMOSPHERE, SAID PROCESS COMPRISING A START-U PHASE WHEREIN THE EXHAUST GAS AND ADDED AIR AR PASSED OVER A REFRACTORY CATALYST UNDER OXIDIZING CONDITIONS OF HEAT SAID CATALYST TO ITS OPERATING TEMPERATURE IN THE RANGE OF 750-900*C., A SUBSEQUENT RUNNING STAGE WHEREIN THE EXHAUST GAS IS PASSED OVER THE REFRACTORY CATALYST UNDER NET REDUCING CONDITIONS AT SAID OPERATING TE, TURE AND AT A SPACE VELOCITY OF 6000 TO 60,000 HOUR-1 WHEREBY AT LEAST 70% OF THE NITROGEN OXIDES IN SAID EXHAUST GAS IS DESTROYED WITH NOT MORE THAN 20% THEREOF BEING CONVERTED TO AMMONIA, AND AA FURTHER STAGE WHEREIN THE THUS TREATED EXHAUST GAS IS PASSED OVER AN OXIDATION CATALYST TO CONVERT THE CARBON MONOXIDE IN SAID GAS TO A NONTOXIC OR INNOCUOUS GAS, SAID REFRACTORY CATALYST CONSISTING ESSENTIALLY OF A HIGH TEMPERATURE STEAM REFORMING BASE METAL OR PRECIOUS METAL CATALYST HAVING AN ACTIVE METAL CRYSTALLITE SIZE OF AT LEAST 1000 A., AN ACTIVE METAL SPECIFIC SURFACE OF LESS THAN ABOUT 10 M.2/G. OF THE ACTIVE METAL, A TOTAL SPECIFIC SURFACE OF LESS THAN 150 M.2/G. AND HYDROTHERMAL STABILITY, THE CATALYST BEING SUPPORTED ON A STEAM-STABLE REFRACTORY OXIDE.