Selective dehydrogenation of ethylbenzene from xylene solution for direct productionof polystyrene

Claim 1

IN THE PROCESS OF MAKING A MOLDING GRADE POLYSTYRENE FROM ETHYLBENZENE CONTAINED IN A C8 AROMATIC HYDROCARBON STREAM OBTIANED FROM HYDROFORMED NAPHTHA, THE IMPROVED METHOD OF OPERATION WHICH COMPRISES ADDING TO A C8 AROMATIC STREAM CONTAINING ABOUT 10 TO 40 PERCENT ETHYLBENZENE AT LEAST ABOUT 12 MOLS OF STREAM PER MOL OF C8 AROMATIC HYDROCATBON, PREHEATING THE MIXTURE TO A TEMPERATURE IN THE RANGE OF 430 TO 530*C., THEN INCREASING THE TEMPERATURE OF THE MIXTURE TO ABOUT 670 TO 730*C. IN A FRACTION OF A SECOND AND CONTACTING THE MIXTURE IN A REACTION ZONE AT A TEMPERATURE IN THE LAST NAMED RANGE AND AT A PRESSURE IN THE RANGE OF ABOUT 1 TO 10 P. S. I. G. WITH A STEAM-REGENERATIVE, ALKALI-PROMOTED IRON OXIDE DEHYDROGENATION CATALYST AT A SPACE VELOCITY IN THE RANGE OF ABOUT 4 TO 4 VOLUMES OF LIQUID CHARGE SOLUTION PER VOLUME OF CATALYST SPACE PER HOUR WITH A RESIDENCE TIME IN THE REACTION ZONE IN THE RANGE OF ABOUT .2 TO .6 SECOND, COOLING THE REACTION ZONE EFFLUENT BY HEAT EXCHANGE WITH AN INCOMING CHARGING STOCK, FURTHER COOLING THE REACTION ZONE EFFLUENT TO ABOUT 50*C., SEPARATING A FIRST GAS STREAM FROM A FIRST CONDENSATE STREAM, FURTHER COOLING THE FIRST GAS STREAM TO A TEMPERATURE OF ABOUT 30*C. TO OBTAIN A SECOND CONDENSATE AND A SECOND GAS STREAM, FURTHER COOLING SAID SECOND GAS STREAM TO A TEMPERATURE BELOW 0*C. TO OBTAIN A THIRD CONDENSATE AND UNCONDENSED GAS, VENTING SAID LAST NAMED UNCONDENSED GAS, COMBINING SAID THIRD CONDENSATE WITH THE COOLED FIRST GAS STREAM, COMBINING THE FIRST AND SECOND CONDENSATES, SEPARATING WATER FROM THE COMBINED CONDENSATES, SEPARATING GASES AND TAR FROM THE COOLED PRODUCT AFTER THE WATER-REMOVING STEP AND DRYING THE REMAINING PRODUCT WHEREBY THE STYRENE IN SAID DRIED REMAINING PRODUCT MAY BE POLYMERIZED TO MOLDING GRADE POLYSTYRENE WITHOUT SEPARATING OR PURIFYING THE STYRENE MONOMER.