Process for preparing and recovering lactams

Claim 1

A PROCESS FOR PREPARING LACTAMS WITHOUT REQUIRING THE SUBSTANTIAL ADDITION OF DISCHARGE OF SULPHURIC ACID OR OTHER SULFUR-CONTAINING COMPOUNDS TO THE PROCESS, SAID PROCESS COMPRISING THE FOLLOWING STEPS: A. REACTING A FIRST AMOUNT OF SO2, AMMONIUM HYDROXIDE AND AMMONIUM NITRITE TO FORM A SOLUTION OF AMMONIUM HYDROGEN SULFATE AND HYDROXYLAMMONIUM SULFATE, B. NEUTRALIZING THE REACTION MIXTURE IN STEP (A) ABOVE WITH AMMONIA TO FORM A SOLUTION OF AMMONIUM SULFATE AND HYDROXYLAMMONIUM SULFATE, C. REACTING THE NEUTRALIZED PRODUCT OBTAINED IN STEP (B) WITH A KETONE AND ADDITIONAL AMMONIA TO PRODUCE THE CORRESPONDING KETOXIME AND A SOLUTION OF AMMONIUM SULFATE, D. SEPARATING THE KETOXIME FROM THE AMMONIUM SULFATE SOLUTION OF STEP (C), E. MAKING OLEUM FROM A SECOND AMOUNT OF SO2, F. SUBJECTING THE OXIME SEPARATED IN STEP (D) TO THE BECKMANN REARRANGEMENT WITH THE OLEUM OF STEP (E) TO PRODUCE A SOLUTION OF LACTAM AND SULFURIC ACID, G. PARTIALLY NEUTRALIZING THE SULPHURIC ACID IN THE SOLUTION OBTAINED IN STEP (F) WITH THE AMMONIUM SULFATE SOLUTION OBTAINED IN STEP (D), WHEREIN THE RATIO OF AMMONIUM SULFATE TO THE SUM OF AMMONIUM SULFATE AND SULPHIRIC ACID IS ABOUT 0.45:1 TO ABOUT 0.63:1, TO PRODUCE A SOLUTION OF LACTAM IN AMMONIUM HYDROEN SULFATE, H. SEPARATING THE REACTION PRODUCT OF STEP (G) INTO LACTAM PRODUCT AND A SOLUTION OF AMMONIUM HYDROGEN SULFATE, I. THERMALLY DECOMPOSING THE SOLUTION OF AMMONIUM HYDROGEN SULFATE IN STEP (H) TO PRODUCE SO2 IN AN AMOUNT WHICH IS SUBSTANTIALLY THE SUM OF SAID FIRST AMOUNT AND SAID SECOND AMOUNT, J. RECYCLING SAID FIRST AMOUNT OF SO2 TO STEP (A), AND K. RECYCLING SAID SECOND AMOUNT OF SO2 TO STEP (E).