Foam control in separation of hydrocarbons

Claim 1

IN A PROCESS FOR THE MANUFACTURE OF OLEFINS FROM NORMAL BUTANE WHICH COMPRISES, CATALYTICALLY DEHYDROGENATING NORMAL BUTANE TO SAID OLEFIN, SUBJECTING THE C4 HYDROCARBON CONTENT OF THE REACTION EFFUENT TO FRACTIONAL DISTILLATION SO AS TO REMOVE THE BUTENE-1 CONTENT THEREOF AS AN OVERHEAD PRODUCT AND PRODUCE A BOTTOMS PRODUCT CONTAINING PRINCIPALLY THE N-BUTANE AND BUTENE-2 CONTENT THEREOF, SUBJECTING THE RESULTING MIXTURE OF N-BUTANE AND BUTENE-2 TO EXTRACTIVE DISTILLATION WITH A SOLVENT COMPRISING ESSENTIALLY A MIXTURE OF FURFUURAL, 1 TO 60 WEIGHT PERCENT OF C5-C10 HYDROCARBONS FORMED IN SAID PROCESS AND COMPRISING PRINCIPALLY BUTADIENE DIMER, AND LIQUID POLYDIMETHYL SILOXANE OF THE FORMULA (CH3-)3-SI-(O-SI(-CH3)2)N-O-SI(-CH3)3 WHEREIN N IS AN INTEGER RESULTING IN A COMPOUND HAVING A VISCOSITY OF AT LEAST 40 CENTISTOKES AT 25*C. IN A CONCENTRATION OF ABOUT 1 TO 2 P.P.M. BY VOLUME PER PASS OF FURFURAL SO AS TO SELECTIVELY DISSOLVE BUTENE-2, AND STRIPPING THE DISSOLVED BUTENE-2 FROM THE RICH SOLVENT, THE IMPROVEMENT COMPRISING CONTINUOUSLY DETERMINING THE PRESSURE DROP ACROSS THE DISTILLATION, AND ADDING TO THE LOWER PART OF THE DISTILLATION A SINGLE INCREMENT OF SAID POLYDIMETHYL SILOXANE EQUIVALENT TO ABOUT 5 TO 10 P.P.M. BY VOLUME BASED ON THE PER PASS OF FURFURAL THROUGH SAID DISTILLATION WHEN THE PRESSURE DROP ACROSS THE DISTILLATION INDICATES A STATE OF UNBALANCE WHICH WILL RESULT IN FLOODING IN THE DISTILLATION.