Reaction systems for making N-(phosphonomethyl) glycine compounds

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.

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.

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.

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.

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;
• dividing said evaporation product to provide an N-(phosphonomethyl)glycine product solids fraction that is relatively depleted in mother liquor and a mother liquor fraction that is relatively depleted in N-(phosphonomethyl)glycine product solids;
• and
• maintaining a ratio of particulate N-(phosphonomethyl)glycine product solids to mother liquor in said evaporation zone that exceeds the ratio of N-(phosphonomethyl)glycine product solids incrementally produced by the effects of evaporation to mother liquor incrementally produced thereby.