Process for depositing noble metal catalysts

Claim 1

IN A PROCESS FOR THE DEPOSITION OF A NOBLE METAL CATALYST ON A REFRACTORY MONOLITHIC HONEYCOMB SUPPORT STRUCTURE WHICH COMPRISES THE STEPS OF PROVIDING AT LEAST THE INTERIOR CHANNEL WALLS OF THE STRUCTURE WITH AN OXIDE SUPPORT COATING, APPLYING A SOLUTION OF A NOBLE METAL COMPOUND TO THE OXIDECOATED STRUCTURE, DRYING THE STRUCTURE, AND TREATING THE STRUCTURE WITH A REDUCING AGENT TO REDUCE THE NOBLE METAL COMPOUND TO THE METALLIC STATE, THE IMPROVEMENT WHICH COMPRISES: A. PROVIDING IN SUBSTITUTION FOR SAID OXIDE SUPPORT COATING A COATING CONSISTING OF AT LEAST ONE AMPHOTERIC HYDROUS OXIDE, OXIHYDRATE OR HYDROXIDE SELECTED FROM THE GROUP CONSISTING OF HYDROUS CR2O3, MNO2, MN3O4, MN2O3, TIO2, ZRO2, SIO2, SNO2, THO2 AND AL2O3 ON THE INTERIOR CHANNEL WALLS OF SAID STRUCTURE, B. IMMERSING SAID STRUCTURE AND COATING INTO A CATALYST SOLUTION CONSISTING ESSENTIALLY OF WATER, AMMONIUM HYDROXIDE AND AT LEAST ONE NOBLE METAL COMPOUND SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS OF PLATINUM, PALLADIUM, RHODIUM, IRIDIUM AND RUTHENIUM WHICH FORM COMPLEX NOBLE METAL AMINE CATIONS IN AMMONIA ALKALINE SOLUTIONS, SAID CATALYST SOLUTION CONTAINING AMMONIUM HYDROXIDE IN AN AMOUNT SUFFICIENT TO BRING THE PH OF SAID CATALYST SOLUTION WITHIN THE RANGE OF ABOUT 10-11.5, C. REMOVING SAID STRUCTURE FROM SAID CATALYST SOLUTION AND REMOVING EXCESS CATALYST SOLUTION FROM SAID STRUCTURE BY RISING, D. DRYING SAID STRUCTURE, AND E. TREATING SAID STRUCTURE WITH A REDUCING AGENT TO REDUCE THE NOBLE METAL COMPOUNDS THEREON TO THE METALLIC STATE.