Continuous Process For On Site And On Demand Production Of Aqueous Peracetic Acid

Abstract

Peracetic acid is prepared on-site and on-demand in a continuous process and at a controlled rate to meet the demand of a downstream operation. In one aspect, a continuous tank reactor is used to produce quantities of peracetic acid at a controlled rate in liquid or vapor form. In another aspect, the use of super acid catalysts enhances the production of peracetic acid under milder conditions, for example, than those typically encountered when using sulfuric acid catalysts alone.

1 . A continuous process for producing peracetic acid on-site and on-demand at a controlled rate compatible with the demand for peracetic acid in a downstream operation, the process comprising: 
 (a) feeding acetic acid, hydrogen peroxide, an acid catalyst, and water into a continuous tank reactor to form a reaction medium;    (b) feeding vapor from the reaction medium into the base of a distillation column, from which product is removed as distillate or effluent;    (c) determining the demand for peracetic acid in the downstream operation; and    (d) controlling the rate of peracetic acid discharged from the distillation column so that the rate is compatible with the demand for peracetic acid in the downstream operation;    wherein the rate of peracetic acid discharged from the distillation column is controlled by at least one of:    (i) increasing or decreasing catalyst concentration by purging a portion of the reaction medium from a recirculating line to the continuous tank reactor prior to introducing fresh acetic acid, hydrogen peroxide, catalyst, and water;    (ii) increasing or decreasing thermal energy input into the continuous tank reactor;    (iii) increasing or decreasing pressure in the continuous tank reactor to prevent the formation of a vapor phase; and    (iv) changing the temperature in the continuous tank reactor.    
   
   
       2 . The process of  claim 1  wherein the effluent stream comprises peracetic acid in an aqueous solution.  
   
   
       3 . The process of  claim 1  wherein the effluent stream comprises peracetic acid in a vapor phase.  
   
   
       4 . The process of  claim 1  wherein the hydrogen peroxide is pre-mixed with the acid catalyst, and thereafter contacted with the acetic acid to form peracetic acid.  
   
   
       5 . The process of  claim 1  wherein the acetic acid is pre-mixed with the acid catalyst, and thereafter contacted with the hydrogen peroxide to form peracetic acid.  
   
   
       6 . The process of  claim 1  wherein the deionized water is pre-mixed with the acid catalyst, and thereafter contacted with the hydrogen peroxide and acetic acid to form peracetic acid.  
   
   
       7 . The process of  claim 1  wherein a portion of the reaction medium is purged from a recirculating line prior to the introduction of fresh acetic acid, hydrogen peroxide, catalyst, and water to prevent buildup of trace metal contaminants.  
   
   
       8 . The process of  claim 7  wherein excess acids or impurities collected in the reactor are discharged to the downstream operation.  
   
   
       9 . The process of  claim 1  wherein vacuum in the system is created by a vacuum pump connected to the discharge end of the condenser in which the distillate is condensed.  
   
   
       10 . The process of  claim 9  wherein the vacuum pump is a liquid-ring vacuum pump and wherein seal liquid discharge and/or the vacuum discharge from the vacuum pump is captured and fed into the downstream operation.  
   
   
       11 . The process of  claim 1  wherein a plurality of continuous tank reactors and distillation columns are operated in parallel.  
   
   
       12 . The process of  claim 1  wherein the molar ratio of hydrogen peroxide to acetic acid fed to the reaction system is from about 0.5:1 to about 10:1.  
   
   
       13 . The process of  claim 12  wherein the molar ratio of hydrogen peroxide to acetic acid is from about 1:1 to about 5:1.  
   
   
       14 . The process of  claim 13  wherein the molar ratio of hydrogen peroxide to acetic acid is from about 1:1 to about 3:1.  
   
   
       15 . The process of  claim 1  wherein a mineral acid catalyst is premixed with acetic acid to achieve a concentration in the reactor of from about 1 to about 50 wt %.  
   
   
       16 . The process of  claim 15  wherein the mineral acid catalyst is premixed with acetic acid to achieve a concentration in the reactor of from about 5 to 20 wt %.  
   
   
       17 . The process of  claim 1  wherein the pressure in the distillation column is from about 3 to 27 KPa.  
   
   
       18 . The process of  claim 17  wherein the pressure in the distillation column is from about 5 to 17 KPa.  
   
   
       19 . The process of  claim 1  wherein the temperature in the reactor ranges from about 40 to about 100° C.  
   
   
       20 . The process of  claim 19  wherein the temperature in the reactor ranges from about 50 to about 80° C.  
   
   
       21 . The process of  claim 1  wherein the downstream operation is disinfection of municipal wastewater treatment plant effluent, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-wastewater effluent ratio of from about 0.5 to about 100 mg/L.  
   
   
       22 . The process of  claim 21  wherein the peracetic acid-to-wastewater effluent ratio is from about 3 to about 25 mg/L.  
   
   
       23 . The process of  claim 1  wherein the downstream operation is disinfection of combined sewer overflow, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-combined sewer overflow ratio of from about 0.1 to about 500 mg/L.  
   
   
       24 . The process of  claim 23  wherein the peracetic acid-to-combined sewer overflow ratio is from about 5 to about 100 mg/L.  
   
   
       25 . The process of  claim 1  wherein the downstream operation is reducing the concentration of undesirable organic and inorganic substances in an influent or effluent industrial wastewater stream, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-industrial wastewater ratio of from about 0.1 to about 100,000 mg/L.  
   
   
       26 . The process of  claim 25  wherein the peracetic acid-to-industrial wastewater ratio is from about 10 to about 1,000 mg/L.  
   
   
       27 . The process of  claim 1  wherein the downstream operation is treating petroleum products to oxidize sulfides, mercaptans, thiophenes, and similar analogues, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-petroleum products ratio of about 1 to about 5,000 mg/L.  
   
   
       28 . The process of  claim 27  wherein the peracetic acid-to-petroleum products ratio is from about 50 to about 500 mg/L.  
   
   
       29 . The process of  claim 1  wherein the downstream operation is disinfection of cooling waters, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-cooling water ratio of about 0.5 to 100 mg/L.  
   
   
       30 . The process of  claim 29  wherein the peracetic acid-to-cooling water ratio is from about 2 to about 25 mg/L.  
   
   
       31 . The process of  claim 1  wherein the downstream operation is deinking a medium containing recycled paper products, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-recycled paper products medium ratio of about 1 to about 5,000 mg/L.  
   
   
       32 . The process of  claim 31  wherein the peracetic acid-to-recycled paper products medium ratio is from about 50 to about 1,000 mg/L.  
   
   
       33 . The process of  claim 1  wherein the downstream operation is at least one of bleaching and delignifying a pulp or paper product stream, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-pulp or paper products stream ratio of from about 10 to about 100,000 mg/L.  
   
   
       34 . The process of  claim 33  wherein the peracetic acid-to-pulp or paper products stream ratio is from about 100 to about 10,000 mg/L.  
   
   
       35 . The process of  claim 1  wherein the downstream operation is bleaching a stream containing textiles, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-textile stream ratio of about 10 to about 10,000 mg/L.  
   
   
       36 . The process of  claim 35  wherein the peracetic acid-to-textile stream ratio is from about 50 to about 1,000 mg/L.  
   
   
       37 . The process of  claim 1  wherein the downstream operation is bleaching a stream containing institutional laundries, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-institutional laundries stream ratio of from about 50 to about 10,000 mg/L.  
   
   
       38 . The process of  claim 37  wherein the peracetic acid-to-institutional laundries stream ratio is from about 100 to about 1,000 mg/L.  
   
   
       39 . The process of  claim 1  wherein the downstream operation is treating and disinfecting potable water, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-potable water ratio of from about 0.5 to about 50 mg/L.  
   
   
       40 . The process of  claim 39  wherein the peracetic acid-to-potable water ratio is from about 3 to about 50 mg/L.  
   
   
       41 . The process of  claim 1  wherein the downstream operation is treating and disinfecting process water, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-process water ratio of from about 0.5 to about 1,000 mg/L.  
   
   
       42 . The process of  claim 41  wherein the peracetic acid-to-process water ratio is from about 3 to about 100 mg/L.  
   
   
       43 . The process of  claim 1  wherein the downstream operation is disinfecting and sanitizing food and beverage handling equipment, and wherein the controlled rate of peracetic acid discharge is defined by a peracetic acid-to-disinfecting and sanitizing stream ratio of from about 0.5 to about 1,000 mg/L.  
   
   
       44 . The process of  claim 43  wherein the peracetic acid-to-disinfecting and sanitizing stream ratio is from about 3 to about 100 mg/L.  
   
   
       45 . The process of  claim 1  wherein the downstream operation is epoxidizing and hydroxylating at least one of alkyls, oils, and fats in a chemical processing stream, and wherein the controlled rate of peracetic acid discharge is defined by a molar ratio of about 0.5:1 to about 5:1 of peracetic acid to alkyl, oils and fats.  
   
   
       46 . The process of  claim 45  wherein the molar ratio is from about 1:1 to about 2:1 of peracetic acid to alkyl, oils and fats.  
   
   
       47 . A continuous process for producing peracetic acid on-site and on-demand at a controlled rate compatible with the demand for peracetic acid in a downstream operation, the process comprising: 
 (a) preparing a superacid reaction intermediate by combining an acid catalyst and hydrogen peroxide, wherein the acid catalyst is selected from the group consisting of strong mineral acids, sulfonic acids, phosphotungstic acids, phosphomolybdic acids, phosphonic acids, silicic acids, zirconium phosphates, sulfated zirconias, sulfonated polystyrenes, and sulfonated tetrafluoroethylene ethers;    (b) contacting the superacid reaction intermediate with acetic acid and water in a reactor to form a reaction medium;    (c) feeding vapor from the reaction medium into the base of a distillation column, from which product is removed as distillate or effluent; and    (d) controlling the rate of peracetic acid discharged from the distillation column so that the rate is compatible with the demand for peracetic acid in the downstream operation.    
   
   
       48 . The process of  claim 47  wherein the acid catalyst is calcined into a support containing at least one of solid silica and zirconia, and wherein said support is placed into a column through which the hydrogen peroxide, a mixture of peroxyacid precursors, or both, are passed.  
   
   
       49 . The process of  claim 47  wherein the acid catalyst comprises a strong mineral acid selected from the group consisting of sulfuric acid and a phosphoric acid.  
   
   
       50 . The process of  claim 49  wherein the acid catalyst comprises a phosphoric acid selected from the group consisting of orthophosphoric acid, monohydrogenphosphoric acid, dihydrogenphosphoric acid, and respective phosphate salt analogues thereof.  
   
   
       51 . The process of  claim 47  wherein the acid catalyst comprises a sulfonic acid selected from the group consisting of sulfonic acid and an organosulfonic acid of formula R—S(═O) 2 OH where R is an organic or organosulfonate analogue of formula R—S(═O) 2 O − X +  where X +  is the conjugate salt ion.  
   
   
       52 . The process of  claim 47  wherein the acid catalyst comprises a phosphotungstic acid selected from the group consisting of phosphotungstic acid, tungstophosphoric acid, and tungsten hydrogen oxide phosphate.  
   
   
       53 . The process of  claim 47  wherein the acid catalyst comprises a phosphomolybdic acid selected from the group consisting of phosphomolybdic acid and analogue salts thereof.  
   
   
       54 . The process of  claim 47  wherein the acid catalyst comprises a phosphonic acid of formula R 1 P(═O)OR 2 OR 3 , where R 1 , R 2 , and R 3  represent organic molecules, and analogue salts thereof.  
   
   
       55 . The process of  claim 47  wherein the acid catalyst is selected from the group consisting of silicic acid of formula SiO x (OH) 4-2x , metasilicic acid (H 2 SiO 3 ), orthosilicic acid (H 4 SiO 4 ), disilicic acid (H 2 Si 2 O 5 ), and pyrosilicic acid (H 6 Si 2 O 7 ).  
   
   
       56 . The process of  claim 47  wherein the acid catalyst comprises zirconium phosphate.  
   
   
       57 . The process of  claim 47  wherein the acid catalyst is a sulfonated polystyrene divinylbenzene copolymer.  
   
   
       58 . The process of  claim 47  wherein the acid catalyst is a tetrafluoroethylene-perfluoro[2-(fluorosulfonylethoxy)-propyl]vinylether polymer.  
   
   
       59 . The process of  claim 47  wherein a purge stream from the reactor is further reacted to form a stream containing a peroxycarboxylic acid.  
   
   
       60 . The process of  claim 59  wherein the peroxycarboxylic acid is at least one of peroctanoic acid and peroxymonosulfuric acid.