Oxidation system with sidedraw secondary reactor

Abstract

Disclosed is an optimized process and apparatus for more efficiently and economically carrying out the liquid-phase oxidation of an oxidizable compound. Such liquid-phase oxidation is carried out in a bubble column reactor that provides for a highly efficient reaction at relatively low temperatures. When the oxidized compound is para-xylene and the product from the oxidation reaction is crude terephthalic acid (CTA), such CTA product can be purified and separated by more economical techniques than could be employed if the CTA were formed by a conventional high-temperature oxidation process.

1 . A process for making a polycarboxylic acid composition, said process comprising: 
 (a) subjecting a multi-phase reaction medium to oxidation in a primary oxidation reactor to thereby produce a first slurry;    (b) subjecting at least a portion of said first slurry to further oxidation in a secondary oxidation reactor, wherein said secondary oxidation reactor is a bubble column reactor.    
     
     
         2 . The process of  claim 1  further comprising introducing an aromatic compound into said primary oxidation reactor, wherein at least about 80 weight of said aromatic compound introduced into said primary oxidation reactor is oxidized in said primary oxidation reactor.  
     
     
         3 . The process of  claim 2  wherein said aromatic compound is para-xylene.  
     
     
         4 . The process of  claim 1  wherein step (b) includes oxidizing para-toluic acid present in said first slurry.  
     
     
         5 . The process of  claim 4  further comprising withdrawing a second slurry from said secondary oxidation reactor, wherein the time-averaged concentration of para-toluic acid in the liquid phase of said second slurry is less than about 50 percent of the time-averaged concentration of para-toluic acid in the liquid phase of said first slurry.  
     
     
         6 . The process of  claim 5  wherein the time-averaged concentration of para-toluic acid in the liquid phase of said first slurry is at least about 500 ppmw, wherein the time-averaged concentration of para-toluic acid in the liquid phase of said second slurry is less than about 250 ppmw.  
     
     
         7 . The process of  claim 1  wherein said primary oxidation reactor is a bubble column reactor.  
     
     
         8 . The process of  claim 1  wherein said secondary oxidation reactor is located outside of said primary oxidation reactor.  
     
     
         9 . The process of  claim 8  wherein at least a portion of said secondary oxidation reactor is located alongside said primary oxidation reactor.  
     
     
         10 . The process of  claim 1  wherein said secondary oxidation reactor is not a piston flow reactor.  
     
     
         11 . The process of  claim 1  further comprising removing said first slurry from said primary oxidation reactor via a slurry outlet located between the top and bottom ends of said primary oxidation reactor.  
     
     
         12 . The process of  claim 11  wherein said primary oxidation reactor defines therein a primary reaction zone having a maximum height (Hp), wherein said slurry outlet is space at least about 0.1 H p  from the bottom and top ends of said primary reaction zone.  
     
     
         13 . The process of  claim 12  wherein said slurry outlet is spaced at least about 0.25 H i  from the bottom and top ends of said primary reaction zone.  
     
     
         14 . The process of  claim 1  wherein said primary oxidation reactor defines therein a primary reaction zone, wherein said secondary oxidation reactor defines therein a secondary reaction zone, wherein the ratio of the volume of said primary reaction zone to said secondary reaction zone is in the range of from about 4:1 to about 50:1.  
     
     
         15 . The process of  claim 14  wherein said primary reaction zone has a ratio of maximum vertical height to maximum horizontal diameter in the range of from about 3:1 to about 30:1, wherein said secondary reaction zone has a ratio of maximum vertical height to maximum horizontal diameter in the range of from about 1:1 to about 50:1.  
     
     
         16 . The process of  claim 14  wherein the ratio of the maximum horizontal diameter of said primary reaction zone to the maximum horizontal diameter of said secondary reaction zone is in the range of from about 0.1:1′ to about 0.6:1, wherein the ratio of the maximum vertical height of said primary reaction zone to the maximum vertical height of said secondary reaction zone is in the range of from about 0.1:1 to about 0.9:1.  
     
     
         17 . The process of  claim 14  wherein said primary reaction zone has a maximum diameter (D p ), wherein the volumetric centroid of said secondary reaction zone is horizontally spaced at least about 0.5 D p  from the volumetric centroid of said primary reaction zone.  
     
     
         18 . The process of  claim 17  wherein said primary reaction zone has a maximum height (H p ), wherein the volumetric centroid of said secondary reaction zone is vertically spaced less than 0.5 H p  from the volumetric centroid of said primary reaction zone.  
     
     
         19 . A reactor system comprising: 
 a primary oxidation reactor defining a first inlet and a first outlet; and    a secondary oxidation reactor defining a second inlet and a second outlet, wherein said first outlet is coupled in fluid flow communication with said second inlet, wherein said secondary oxidation reactor is a bubble column reactor.    
     
     
         20 . The reactor system of  claim 19  wherein said primary oxidation reactor is a bubble column reactor.  
     
     
         21 . The reactor system of  claim 19  wherein said secondary oxidation reactor is located outside of said primary oxidation reactor.  
     
     
         22 . The reactor system of  claim 21  wherein at least a portion of said secondary oxidation reactor is located alongside said primary oxidation reactor.  
     
     
         23 . The reactor system of  claim 19  wherein said second reactor is not a piston flow reactor.  
     
     
         24 . The reactor system of  claim 19  wherein said primary oxidation reactor via defines a slurry outlet connected in fluid flow communication with said secondary oxidation reactor, wherein said slurry outlet is located between the top and bottom ends of said primary oxidation reactor.  
     
     
         25 . The reactor system of  claim 24  wherein said primary oxidation reactor defines therein a primary reaction zone, wherein said slurry outlet is space at least about 0.1 H i  from the bottom and top ends of said primary reaction zone.  
     
     
         26 . The reactor system of  claim 25 , wherein said slurry outlet is spaced at least about 0.25 H i  from the bottom and top ends of said primary reaction zone.  
     
     
         27 . The reactor system of  claim 19  wherein said primary oxidation reactor defines therein a primary reaction zone, wherein said secondary oxidation reactor defines therein a secondary reaction zone, wherein the ratio of the volume of said primary reaction zone to said secondary reaction zone is in the range of from about 4:1 to about 50:1.  
     
     
         28 . The reactor system of  claim 27  wherein said primary reaction zone has a ratio of maximum vertical height to maximum horizontal diameter in the range of from about 3:1 to about 30:1, wherein said secondary reaction zone has a ratio of maximum vertical height to maximum horizontal diameter in the range of from about 1:1 to about 50:1.  
     
     
         29 . The reactor system of  claim 27  wherein the ratio of the maximum horizontal diameter of said primary oxidation zone to the maximum horizontal diameter of said secondary oxidation zone is in the range of from about 0.1:1 to about 0.6:1, wherein the ratio of the maximum vertical height of said primary oxidation zone to the maximum vertical height of said secondary oxidation zone is in the range of from about 0.1:1 to about 0.9:1.  
     
     
         30 . The reactor system of  claim 27  wherein said primary reaction zone has a maximum diameter (D p ), wherein the volumetric centroid of said secondary reaction zone is horizontally spaced at least about 0.5 D p  from the volumetric centroid of said primary reaction zone.  
     
     
         31 . The reactor system of  claim 30  wherein said primary reaction zone has a maximum height (H p ), wherein the volumetric centroid of said secondary reaction zone is vertically spaced less than 0.5 H p  from the volumetric centroid of said primary reaction zone.