Use of a supplemental promoter in conjunction with a carbon-supported noble-metal-containing catalyst in liquid phase oxidation reactions

A process for the preparation of N-(phosphonomethyl)glycine or a salt thereof, the process comprising:

• oxidizing N-(phosphonomethyl)iminodiacetic acid in an aqueous reaction medium in the presence of an oxidation catalyst comprising a noble metal on a carbon support, thereby producing an aqueous reaction mixture comprising N-(phosphonomethyl)glycine, formic acid or formaldehyde;
• separating oxidation catalyst from said reaction mixture to produce a filtrate comprising N-(phosphonomethyl)glycine, formic acid or formaldehyde;
• evaporating water, formic acid or formaldehyde from said filtrate to produce an overhead vapor stream;
• condensing water, formic acid or formaldehyde from said overhead vapor stream and forming an aqueous treatment mixture containing water, formic acid or formaldehyde obtained in the condensate;
• contacting said aqueous treatment mixture with an oxidizing agent in the presence of a noble metal catalyst on a carbon support and a promoter comprising a metal effective to promote oxidation of formic acid or formaldehyde, thereby oxidizing formic acid or formaldehyde contained in said treatment mixture;
• and
• recycling treated condensate incorporating it into an aqueous medium for N-(phosphonomethyl)iminodiacetic acid in the further oxidation thereof to glyphosate.

A process for making N-(phosphonomethyl)glycine, a salt of N-(phosphonomethyl)glycine, or an ester of N-(phosphonomethyl)glycine, the process comprising oxidizing N-(phosphonomethyl)iminodiacetic acid, a salt of N-(phosphonomethyl)iminodiacetic acid, or an ester of N-(phosphonomethyl)iminodiacetic acid in the presence of an oxidation catalyst and a supplemental promoter, wherein, before the oxidation, the oxidation catalyst:

• A. comprises a carbon support having a noble metal at a surface of the carbon support;
• and
• is identifiable as yielding no greater than about 1.2 mmole of carbon monoxide per gram of catalyst when a dry sample of the catalyst in a helium atmosphere is heated from about 20° to about 900° C. at a rate of about 10° C. per minute, and then at about 900° C. for about 30 minutes;
• or
• B. comprises a carbon support having a noble metal, carbon, and oxygen at a surface of the carbon support, the ratio of carbon atoms to oxygen atoms at the surface being at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• C. comprises a carbon support comprising:
• (i) a noble metal at a surface of the carbon support;
• and (ii) a surface layer having a thickness of about 50 Å as measured inwardly from the surface and comprising carbon and oxygen, the ratio of carbon atoms to oxygen atoms in the surface layer being at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• D. is formed by a process comprising depositing a noble metal at a surface of a carbon support, and then heating the surface at a temperature of at least about 400° C.;
• or
• E. is formed by a process comprising:
• depositing a noble metal at a surface of a carbon support, and then exposing the surface to a reducing environment, wherein, before the noble metal deposition, the carbon support has carbon atoms and oxygen atoms at the surface in amounts such that the ratio of carbon atoms to oxygen atoms at the surface is at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• F. comprises a carbon support having a noble metal, a promoter, carbon, and oxygen at a surface of the carbon support;
• or
• G. comprises a carbon support having:
• (i) a noble metal and a promoter at a surface of the carbon support;
• and (ii) a surface layer having a thickness of about 50 Å as measured inwardly from the surface and comprising carbon and oxygen, the catalyst being identifiable as having a ratio of carbon atoms to oxygen atoms in the surface layer which is at least about 20:1, as measured by x-ray photoelectron spectroscopy after the catalyst is heated at a temperature of about 500□C. for about 1 hour in a hydrogen atmosphere and before the catalyst is exposed to an oxidant following the heating in the hydrogen atmosphere.

A process for the catalytic oxidation of formic acid or formaldehyde, the process comprising:

• contacting formic acid or formaldehyde with an oxidizing agent, a catalyst and a supplemental promoter, wherein:
• said catalyst comprises a noble metal and a carbon support,
• said noble metal catalyst and supplemental promoter being introduced into a reaction medium in a mass ratio of the supplemental promoter to the catalyst of at least about 1:15,000;
• and
• said formic acid or formaldehyde is oxidized in said reaction medium.

A process for the catalytic oxidation of formic acid or formaldehyde, the process comprising:

• contacting formic acid or formaldehyde with an oxidizing agent in a reaction zone comprising a liquid reaction medium, a catalyst and a supplemental promoter wherein:
• the catalyst comprises a noble metal and a carbon support;
• and
• the mass ratio of the supplemental promoter to the catalyst in said reaction zone is at least about 1:200,000.

A process for the catalytic oxidation of formic acid or formaldehyde, the process comprising:

• contacting formic acid or formaldehyde with an oxidizing agent in a reaction zone comprising a liquid reaction medium, a catalyst and a supplemental promoter wherein:
• the catalyst comprises a noble metal and a carbon support;
• and
• the mass ratio of the supplemental promoter to the noble metal component of said catalyst in said reaction zone is at least about 1:40,000.

A process for the catalytic oxidation of formic acid or formaldehyde, the process comprising:

• contacting formic acid or formaldehyde with an oxidizing agent in the presence of a supplemental promoter and a catalyst comprising a noble metal and a carbon support, wherein:
• said noble metal catalyst and supplemental promoter are introduced into a reaction medium in a mass ratio of the supplemental promoter to the noble metal component of at least about 1:3,000;
• and
• said formic acid or formaldehyde is oxidized in said reaction medium.

A process for oxidizing a substrate using a catalyst comprising a carbon support and noble metal, the process comprising contacting the substrate with oxygen in the presence of the catalyst and a supplemental promoter, wherein:

• the mass ratio of the supplemental promoter to the catalyst is at least about 1:15,000;
• and
• before the oxidation of the substrate, the catalyst:
• A. comprises a carbon support having a noble metal at a surface of the carbon support;
• and
• is identifiable as yielding no greater than about 1.2 mmole of carbon monoxide per gram of catalyst when a dry sample of the catalyst in a helium atmosphere is heated from about 20° to about 900° C. at a rate of about 10° C. per minute, and then at about 900° C. for about 30 minutes;
• or
• B. comprises a carbon support having a noble metal and a catalyst-surface promoter at a surface of the carbon support;
• and
• is identifiable as yielding no greater than about 1.2 mmole of carbon monoxide per gram of catalyst when a dry sample of the catalyst, after being heated at a temperature of about 500□C. for about 1 hour in a hydrogen atmosphere and before being exposed to an oxidant following the heating in the hydrogen atmosphere, is heated in a helium atmosphere from about 20° to about 900° C. at a rate of about 10° C. per minute, and then at about 900° C. for about 30 minutes;
• or
• C. comprises a carbon support having a noble metal, carbon, and oxygen at a surface of the carbon support, the ratio of carbon atoms to oxygen atoms at the surface being at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• D. comprises a carbon support having a noble metal, a catalyst-surface promoter, carbon, and oxygen at a surface of the carbon support;
• and
• is identifiable as having a ratio of carbon atoms to oxygen atoms at the surface which is at least about 20:1, as measured by x-ray photoelectron spectroscopy after the catalyst is heated at a temperature of about 500□C. for about 1 hour in a hydrogen atmosphere and before the catalyst is exposed to an oxidant following the heating in the hydrogen atmosphere;
• or
• E. comprises a carbon support having (i) a noble metal at a surface of the carbon support;
• and (ii) a surface layer having a thickness of about 50 Å as measured inwardly from the surface and comprising oxygen and carbon, the ratio of carbon atoms to oxygen atoms in the surface layer being at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• F. comprises a carbon support having:
• (a) a noble metal and a catalyst-surface promoter at a surface of the carbon support;
• and (b) a surface layer having a thickness of about 50 Å as measured inwardly from the surface and comprising carbon and oxygen;
• and
• is identifiable as having a ratio of carbon atoms to oxygen atoms in the surface layer of at least about 20:1, as measured by x-ray photoelectron spectroscopy after the catalyst is heated at a temperature of about 500□C. for about 1 hour in a hydrogen atmosphere and before the catalyst is exposed to an oxidant following the heating in the hydrogen atmosphere;
• G. is formed by a process comprising depositing a noble metal at a surface of a carbon support, and then heating the surface at a temperature of at least about 400° C., wherein, before the noble metal deposition, the ratio of carbon atoms to oxygen atoms at the surface of the carbon support is at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• H. is formed by a process comprising depositing a noble metal at a surface of a carbon support, and then exposing the surface to a reducing environment, wherein, before the noble metal deposition, the carbon support has carbon atoms and oxygen atoms at the surface of the carbon support in amounts such that the ratio of carbon atoms to oxygen atoms at the surface is at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• I. is formed by a process comprising depositing a noble metal at a surface of a carbon support, and then heating the surface at a temperature greater than about 500° C.

A process for making an oxidation catalyst system comprising a catalyst comprising a carbon support having carbon atoms and oxygen atoms at a surface thereof, the process comprising:

• depositing a noble metal at the surface of the carbon support to form a noble-metal-containing catalyst;
• removing oxygen-containing functional groups from the surface of the noble-metal-containing catalyst to form a noble-metal-containing catalyst comprising a deoxygenated surface, the removal of oxygen-containing functional groups comprising:
• (i) heating the surface of the noble-metal-containing catalyst at a temperature of greater than about 500° C.;
• or
• (ii) heating the surface of the noble-metal-containing catalyst at a temperature of at least about 400° C., wherein, before the noble metal deposition, the ratio of carbon atoms to oxygen atoms at the surface of the carbon support is at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• (iii) exposing the surface of the noble-metal-containing catalyst to a reducing environment, wherein, before the noble metal deposition, the ratio of carbon atoms to oxygen atoms at the surface of the carbon support is at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• (iv) exposing the surface of the noble-metal-containing catalyst to a reducing environment so that the ratio of carbon atoms to oxygen atoms at the deoxygenated surface of the noble-metal-containing catalyst comprising the deoxygenated surface is at least about 30:1, as measured by x-ray photoelectron spectroscopy;
• or
• (v) exposing the surface of the noble-metal-containing catalyst to a reducing environment so that no greater than about 1.2 mmole of carbon monoxide per gram of the noble-metal-containing catalyst comprising the deoxygenated surface desorb from the deoxygenated surface when a dry sample of the noble-metal-containing catalyst comprising the deoxygenated surface is heated in a helium atmosphere from about 20° to about 900° C. at a rate of about 10° C. per minute, and then at about 900° C. for about 30 minutes;
• and
• mixing a supplemental promoter with the noble-metal-containing catalyst after deoxygenation of the surface of the noble-metal-containing catalyst, wherein the mass ratio of the supplemental promoter to the noble-metal-containing catalyst is at least about 1:15,000.

An oxidation catalyst system prepared by a process comprising:

• depositing a noble metal onto a surface of a carbon support to form a noble-metal-containing catalyst;
• and
• removing oxygen-containing functional groups from the surface of the noble-metal-containing catalyst to form a noble-metal-containing catalyst comprising a deoxygenated surface, the removal of the oxygen-containing functional groups comprising:
• (i) heating the surface of the noble-metal-containing catalyst at a temperature of greater than about 500° C.;
• or
• (ii) heating the surface of the noble-metal-containing catalyst at a temperature of at least about 400° C., wherein, before the noble metal deposition, the carbon support has carbon atoms and oxygen atoms at the surface in amounts such that the ratio of carbon atoms to oxygen atoms at the surface is at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• (iii) exposing the surface of the noble-metal-containing catalyst to a reducing environment, wherein, before the noble metal deposition, the carbon support has carbon atoms and oxygen atoms at the surface in amounts such that the ratio of carbon atoms to oxygen atoms at the surface is at least about 20:1, as measured by x-ray photoelectron spectroscopy;
• or
• (iv) exposing the surface of the noble-metal-containing catalyst to a reducing environment so that the ratio of carbon atoms to oxygen atoms at the deoxygenated surface of the noble-metal-containing catalyst comprising the deoxygenated surface is at least about 30:1, as measured by x-ray photoelectron spectroscopy;
• or
• (v) exposing the surface of the noble-metal-containing catalyst to a reducing environment so that no greater than about 1.2 mmole of carbon monoxide per gram of the noble-metal-containing catalyst comprising the deoxygenated surface desorb from the deoxygenated surface when a dry sample of the noble-metal-containing catalyst comprising the deoxygenated surface is heated in a helium atmosphere from about 20° to about 900° C. at a rate of about 10° C. per minute, and then at about 900° C. for about 30 minutes;
• and
• mixing a supplemental promoter and the noble-metal-containing catalyst after deoxygenation of the surface of the noble-metal-containing catalyst, wherein the mass ratio of the supplemental promoter to the noble-metal-containing catalyst is at least about 1:15,000.

A promoted catalyst system comprising a noble metal on carbon catalyst having a supplemental promoter deposited on the surface thereof, said catalyst system being prepared by a process comprising:

• preparing a catalyst precursor by depositing said noble metal on a carbon support;
• reducing said catalyst precursor to produce said noble metal on carbon catalyst;
• and
• depositing said supplemental promoter on said catalyst.