Reaction systems for making n-(phosphonomethyl) glycine compounds

Abstract

This invention generally relates to liquid phase oxidation processes for making N-(phosphonomethyl)glycine (also known in the agricultural chemical industry as glyphosate) and related compounds. This invention, for example, particularly relates to processes wherein an N-(phosphonomethyl)iminodiacetic acid (NPMIDA) substrate (i.e., N-(phosphonomethyl)iminodiacetic acid, a salt of N-(phosphonomethyl)iminodiacetic acid, or an ester of N-(phosphonomethyl)iminodiacetic acid) is continuously oxidized to form an N-(phosphonomethyl)glycine product (i.e., N-(phosphonomethyl)glycine, a salt of N-(phosphonomethyl)glycine, or an ester of N-(phosphonomethyl)glycine). This invention also, for example, particularly relates to processes wherein an N-(phosphonomethyl)iminodiacetic acid substrate is oxidized to form an N-(phosphonomethyl)glycine product, which, in turn, is crystallized (at least in part) in an adiabatic crystallizer.

1 - 3 . (canceled) 
   
   
       4 . A process for preparing an N-(phosphonomethyl)glycine product by oxidizing an N-(phosphonomethyl)iminodiacetic acid substrate, the process comprising:
 introducing the N-(phosphonomethyl)iminodiacetic acid substrate into a liquid reaction medium within an oxidation reaction zone, the oxidation reaction zone being substantially back-mixed in the liquid phase and containing a catalyst for the oxidation reaction in contact with the liquid reaction medium, the liquid reaction medium comprising the N-(phosphonomethyl)glycine product;   introducing an oxidizing agent into the oxidation reaction zone;   continuously oxidizing the N-(phosphonomethyl)iminodiacetic acid substrate in the oxidation reaction zone to form the N-(phosphonomethyl)glycine product; and   continuously withdrawing a reaction mixture effluent comprising the N-(phosphonomethyl)glycine product from the oxidation reaction zone.   
   
   
       5 - 13 . (canceled) 
   
   
       14 . A process for preparing an N-(phosphonomethyl)glycine product by oxidizing an N-(phosphonomethyl)iminodiacetic acid substrate in a reactor system, the process comprising:
 introducing an aqueous feed stream comprising the N-(phosphonomethyl)iminodiacetic acid substrate into a first oxidation reaction zone;   introducing an oxidizing agent into the first oxidation reaction zone;   continuously oxidizing the N-(phosphonomethyl)iminodiacetic acid substrate in the first oxidation reaction zone to form the N-(phosphonomethyl)glycine product;   continuously withdrawing an intermediate reaction mixture effluent comprising the N-(phosphonomethyl)glycine product and unreacted N-(phosphonomethyl)iminodiacetic acid substrate from the first oxidation reaction zone;   continuously introducing an intermediate aqueous feed stream into a second oxidation reaction zone, the intermediate aqueous feed stream comprising N-(phosphonomethyl)glycine product and unreacted N-(phosphonomethyl)iminodiacetic acid substrate obtained in the intermediate reaction mixture effluent;   introducing an oxidizing agent into the second oxidation reaction zone;   continuously oxidizing the N-(phosphonomethyl)iminodiacetic acid substrate in the second oxidation reaction zone to form additional N-(phosphonomethyl)glycine product; and   continuously withdrawing a reaction mixture effluent comprising the N-(phosphonomethyl)glycine product from the second oxidation reaction zone.   
   
   
       15 . The process as set forth in  claim 14  wherein the first and second oxidation reaction zones contain a catalyst for the oxidation reaction. 
   
   
       16 . The process as set forth in  claim 15  wherein the catalyst in the first oxidation reaction zone is a heterogeneous particulate catalyst and is suspended in a liquid reaction medium comprising the N-(phosphonomethyl)iminodiacetic acid substrate. 
   
   
       17 . The process as set forth in  claim 16  wherein the first oxidation reaction zone is substantially back-mixed in the liquid phase. 
   
   
       18 . The process as set forth in  claim 17  wherein the first oxidation reaction zone is provided by a stirred tank reactor. 
   
   
       19 . The process as set forth in  claim 17  wherein the first oxidation reaction zone is provided by a fluidized bed reactor. 
   
   
       20 . The process as set forth in  claim 17  wherein the second oxidation reaction zone is provided by a fixed bed having the catalyst therein. 
   
   
       21 . The process as set forth in  claim 15  wherein the catalyst in the first and second oxidation reaction zones is a heterogeneous particulate catalyst and is suspended in a liquid reaction medium comprising the N-(phosphonomethyl)iminodiacetic acid substrate. 
   
   
       22 . The process as set forth in  claim 21  wherein the first and second oxidation reaction zones are substantially back-mixed in the liquid phase. 
   
   
       23 . The process as set forth in  claim 22  wherein the oxidizing agent introduced into the first and second oxidation reaction zones is an O 2 -containing gas and the second oxidation reaction zone is substantially back-mixed in the gas phase. 
   
   
       24 . The process as set forth in  claim 23  wherein the first and second oxidation reaction zones are provided by first and second continuous stirred tank reactors respectively, the stirred tank reactors containing a headspace above the liquid reaction medium and the second stirred tank reactor being provided with an impeller system adapted to draw gas from the headspace into the liquid reaction medium. 
   
   
       25 . The process as set forth in  claim 24  wherein the O 2 -containing gas is introduced into the headspace above the liquid reaction medium within the second stirred tank reactor. 
   
   
       26 . The process as set forth in  claim 22  wherein the first and second oxidation reaction zones are provided by first and second continuous stirred tank reactors respectively. 
   
   
       27 . The process as set forth in  claim 26  wherein the heterogeneous particulate catalyst comprises a noble metal deposited on a particulate carbon support. 
   
   
       28 . The process as set forth in  claim 27  wherein the particulate carbon support exhibits a particle size distribution such that about 95% of the catalyst particles are from about 3 to about 100 μm in their largest dimension. 
   
   
       29 . The process as set forth in  claim 28  wherein the average particle size of the particulate catalyst is from about 15 to about 40 μm. 
   
   
       30 . The process as set forth in  claim 28  wherein the concentration of the particulate catalyst within the first and second oxidation reaction zones is from about 0.1 to about 10 wt. % based on the total weight of catalyst and the liquid reaction medium in the oxidation reaction zones. 
   
   
       31 - 69 . (canceled) 
   
   
       70 . A process for removal of water from an aqueous starting solution comprising N-(phosphonomethyl)glycine product and crystallization N-(phosphonomethyl)glycine product therefrom, the process comprising:
 introducing an aqueous evaporation feed mixture into an evaporation zone, said feed mixture comprising said aqueous starting solution;   evaporating water from said feed mixture in said evaporation zone in the presence of solid particulate N-(phosphonomethyl)glycine product, thereby producing a vapor phase comprising water vapor, precipitating N-(phosphonomethyl)glycine product from the aqueous liquid phase, and producing an evaporation product comprising N-(phosphonomethyl)glycine product solids and a mother liquor that is substantially saturated or supersaturated in N-(phosphonomethyl)glycine product; and   maintaining a ratio of particulate N-(phosphonomethyl)glycine product solids to mother liquor in said evaporation zone which exceeds the ratio of N-(phosphonomethyl)glycine product solids incrementally produced by the effects of evaporation to mother liquor incrementally produced thereby.   
   
   
       71 - 97 . (canceled) 
   
   
       98 . A method for removal of water from an aqueous starting solution comprising N-(phosphonomethyl)glycine product and crystallization of N-(phosphonomethyl)glycine product therefrom, the process comprising:
 introducing an evaporation feed mixture comprising said aqueous starting solution into a vapor/liquid separation zone wherein the pressure is below the vapor pressure of said mixture, thereby allowing water to flash from the evaporation feed mixture, producing a vapor phase comprising water vapor and increasing the concentration of N-(phosphonomethyl)glycine product in the remaining liquid phase to a concentration in excess of the solubility of N-(phosphonomethyl)glycine product, whereby N-(phosphonomethyl)glycine product precipitates from the liquid phase to produce a first slurry stream comprising particulate N-(phosphonomethyl)glycine product in a saturated or supersaturated mother liquor;   separating said vapor phase from said first slurry stream;   introducing said first slurry stream into a decantation zone in which a supernatant liquid comprising a fraction of said mother liquor is separated from a second slurry stream comprising precipitated N-(phosphonomethyl)glycine product and mother liquor, said decantation zone having an inlet for said first slurry, a decantation liquid exit for said supernatant liquid spaced above said inlet, and an exit for said second slurry vertically spaced above said inlet but below said supernatant liquid exit; and   maintaining the relative rates at which said first slurry is introduced into said decantation zone, said second slurry is drawn off through said second slurry exit and said supernatant liquid is drawn off through said decantation liquid exit such that the upward flow velocity in a lower region of said decantation zone below said second slurry exit is sufficient to maintain precipitated N-(phosphonomethyl)glycine product in suspension in the liquid phase while the upward flow velocity in an upper region of said decantation zone above said second slurry exit is below the sedimentation velocity of at least 80% by weight of the N-(phosphonomethyl)glycine product particles in said lower region.   
   
   
       99 . (canceled)