Dehydrogenation process and catalysts therefor

Claim 2

A CHROMIA-ALUMINA DEHYDROGENATION CATALYST CONTAINING BETWEEN 25 AND 40 WEIGHT PERCENT CR2O3, HAVING AN ACTIVE CHROMIA SURFACE AREA AS MEASURED BY CO CHEMISORPTION OF LESS THAN 15 MICROMOLES CO PER GRAM AND AN ALUMINA SURFACE AREA AS MEASURED BY NITROGEN ADSORPTION OF AT LEAST 50 SQUARE METERS PER GRAM, SAID CATALYST HAVING BEEN PRODUCED BY A METHOD COMPRISING IMPREGNATING ALUMINA, WHICH WAS PREPARED BY HEAT TREATING A HIGH SURFACE AREA ALUMINA AT 1100-1600*F. FOR 2-24 HOURS TO REDUCE ITS SURFACE AREA TO BETWEEN ABOUT 60 AND ABOUT 100 SQUARE METERS PER GRAM AS MEASURED BY NITROGEN ADSORPTION, WITH A CHROMIUM COMPOUND DECOMPOSABLE TO CR2O3, AND THEN HEATING THE CHROMIUM-IMPREGNATED ALUMINA IN AN OXYGEN-FREE ATMOSPHERE AT 1100-1700RF. FOR 2-48 HOURS TO OBTAIN THE FIRST-MENTIONED CHROMIA AND ALUMINA SURFACE AREAS.

Claim 3

A PROCESS FOR THE DEHYDROGENATION OF BUTANE TO BUTENES AND BUTADIENE WHICH COMPRISES PASSING ALTERNATELY AND REPEATEDLY THROUGH A BED OF A CATALYST OF CLAIM 1, FIRST, BUTANE VAPORS AT 900-1100RF. AND 1-10 P.S.I.A. TO DEHYDROGENATE BUTANE AND TO DEPOSIT COKE ON THE CATALYST, AND SECOND, AND OXYGEN-CONTAINING GAS AT 900-1100*F. TO REMOVE DEPOSITE COKE BY COMBUSTION CAUSING ELEVATION OF THE BED TEMPERATURE, WHEREBY THE DEHYDROGENATION ACTIVITY OF SAID CATALYST INCREASES DURING AN INITIAL PERIOD OF USE, THEREAFTER REMAINS RELATIVELY STABLE, AND ULTIMATELY DECLINES SLOWLY, MAINTAINING THE TEMPERATURES OF BUTANE VAPORS AND OXYGEN-CONTAINING GAS BELOW ABOUT 1100*F. DURING SAID INITIAL PERIOD OF USE AND THEREAFTER FOR AT LEAST TEN WEEKS AND UNTIL SAID ACTIVITY HAS DECLINED SUBSTANTIALLY, THEN INCREASING SAID TEMPERATURES GRADUALLY TOWARDS 1200* F., AND CONTINUING ALTERNATELY AND REPEATEDLY PASSING BUTANE VAPORS AND OXYGEN-CONTAINING GAS FOR A PERIOD IN EXCESS OF FIVE MONTHS AT A PER PASS CONVERSION OF BUTANE TO BUTENES IN EXCESS OF 25%.