Compounds and methods for producing nylon 6

Methods and compounds for producing nylon 6 are disclosed. Di-substituted furanic compounds may be used as the raw material for producing precursor compounds for nylon 6, and the precursor compounds are convertible to nylon 6.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage filing under 35 U.S.C. § 371 of International Application No. PCT/US2013/066171 filed on Oct. 22, 2013 entitled “COMPOUNDS AND METHODS FOR PRODUCING NYLON 6,” which is incorporated herein by reference in its entirety.

BACKGROUND

Nylon is a designation for a family of synthetic polymers known as aliphatic polyamides, and is one of the most commonly used polymers. The chemical constituents of nylon include carbon, hydrogen, nitrogen, and oxygen. Nylons may include condensation copolymers, such as nylon 6,6, that may be formed by reacting a diamine and a dicarboxylic acid so that amides are formed at both ends of each monomer. Alternatively, type of nylons, such as nylon 6, may be made by a ring-opening polymerization of cyclic amides (lactams).

Types of nylons are distinguished by a numerical suffix that specifies the numbers of carbons donated by the monomers. For example, for nylons with a two-number designation, such as nylon 6,6 or nylon 6,12, the first number represents the number of carbons from the diamine monomer, and the second number represents the number of carbons from the diacid monomer. For nylons having a single number designation, such as nylon 4 or nylon 6, the number represents the number of carbon atoms in the repeating monomer units.

The 6 carbon commodity chemical caprolactam has global production on the order of 2 million metric tons per year. A major use of this commodity chemical is as a monomer in the manufacture of nylon 6. Current industrial processes for the manufacture of caprolactam use petrochemically derived benzene as the raw material. Efforts are being made to replace this petrochemically derived raw material with alternative raw materials, such as those that may be derived from biomass. Replacing current petrochemically derived caprolactam with biomass derived compounds may contribute to reducing greenhouse gas emissions. There remains a need to provide alternative scalable approaches for commercial production of nylon 6 from alternative raw materials.

SUMMARY

Nylon 6 may be produced from di-substituted furanic compounds as the raw material, wherein the furanic compounds may include furans or tetrahydrofurans. The di-substituted furanic compounds may be converted to amino carbonyl compounds, and the amino carbonyl compounds may be converted into nylon 6. In an embodiment, the di-substituted furanic compounds may be derived from biomass.

In an embodiment, a method for producing nylon 6 includes converting at least one furanic compound of formula

wherein M1 is

X is —F, —Cl, —Br, —I, —OH, —N3, an acetate, or sulfonate, and Y is —C(O)R or —C(O)OR, to an amino carbonyl compound of formula

wherein R is —H, alkyl, or substituted alkyl, and converting the amino carbonyl compound to nylon 6.

In an embodiment, a method for producing caprolactam includes converting at least one furanic compound of formula

wherein M1 is

X is —F, —Cl, —Br, —I, —OH, —N3, an acetate, or sulfonate, and Y is —C(O)R or —C(O)OR, to an amino carbonyl compound of formula

wherein R is —H, alkyl, or substituted alkyl, and converting the amino carbonyl compound to caprolactam.

In an embodiment, a method for producing a compound having a structure as represented by

wherein M1 is

R is —H, alkyl, or substituted alkyl, includes contacting at least one furanic compound having a structure

wherein X is —F, —Cl, —Br, —I, —OH, —N3, an acetate, or a sulfonate, with at least one of an alkali metal azide and tetraalkylammonium azide.

In an embodiment, a polyamide may have a structure as represented by

wherein M1 is

and R is —H, alkyl, or substituted alkyl.

In an embodiment, a method for producing a polyamide having a structure as represented by

wherein M1 is

and R is —H, alkyl, or substituted alkyl, includes converting at least one furanic compound having a structure

wherein X is —F, —Cl, —Br, —I, —OH, —N3, an acetate, or sulfonate, and Y comprises —C(O)R or —C(O)OR, to an amino carbonyl compound having a structure

wherein R is —H, an alkyl, or a substituted alkyl, and converting the amino carbonyl compound to the polyamide.

DETAILED DESCRIPTION

Nylon 6, as indicated above, receives its numerical designation from the number of carbon atoms in its monomer units, wherein each monomer unit has 6 carbons.

The 6-carbon monomers that form nylon 6 may be designated as derivatives of caprolactam.

As generally represented inFIG. 1, Nylon 6 may be produced from furanic compounds of formula

where M1 is

X is —F, —Cl, —Br, —I, —OH, —N3, an acetate, or a sulfonate, and Y is —C(O)R or —C(O)OR, with R being —H, an alkyl, or a substituted alkyl. The furanic compounds may be converted to amino carbonyl compounds of formula

and the carbonyl compounds may be converted to nylon 6.

By using furanic compounds as raw materials for nylon 6, the use of petrochemically derived raw materials may be diminished or eliminated. Furanic compounds of the indicated formula may be derived from biomass. In an embodiment, when Y is —C(O)H and X is —OH (5-hydroxymethylfurfural, HMF) or —Cl (5-chloromethylmethylfurfural, CMF) the HMF or CMF may be directly derived from biomass or cellulose. In an alternative embodiment, hexoses may be isolated from biomass, and the hexoses converted to the furanic compounds. Hexoses may also be obtained from other sources.

As an example, as represented inFIG. 2, the furanic compound may be 5-chloromethylfurfural (where X is —Cl and Y is —C(O)H in the above formula). Hexoses may be converted to 5-chloromethylfurfural by heating the hexoses with HCl, and 1,2-dichloroethane, with or without an alkaline salt. The alkaline salt may be lithium halide, sodium halide, potassium halide, or any combination thereof.

The furanic compound may be converted to the amino carbonyl compound, as generally represented inFIG. 1, by an oxidation reaction (converting a portion of the molecule to a carboxylic acid) and an amination (introducing an amine group onto the molecule).

In an embodiment as generally depicted inFIG. 3A, a halogenated methyl furanic compound of structural formula

where M1 is

and X is a halogen, may be oxidized to form a halogenated methyl furanic compound of formula

where R is —H, alkyl, or substituted alkyl. The furanic compound may be treated with an azide to replace the halogen and produce 5-(azidomethyl) furanic compounds of formula

In an embodiment, the 5-(azidomethyl) furanic compounds may be produced and sold as a precursor for producing nylon 6, or for other uses.

In an embodiment, the 5-(azidomethyl) furanic compounds of formula

where R is —H, alkyl, or substituted alkyl, may be produced by contacting at least one furanic compound of structure

where M1 is

X is —F, —Cl, —Br, —I, —OH, an acetate, or a sulfonate, with a solvent and at least one of an alkali metal azide and tetraalkylammonium azide. The alkali metal azide may be sodium azide, and the tetraalkylammonium azide may be tetrabutylammonium azide. The solvent selected may be a function of the azide salt used. For example, if an alkali metal azide is used then the solvent may be dimethylformamide or dimethyl sulfoxide, whereas if tetraalkylammonium azide is used then the solvent may be less polar, such as tetrahydrofuran or 2-methyltetrahydrofuran.

Furanic compounds having the structure

may be produced by oxidizing furanic compounds having a structure

that may be derived directly from biomass, such as cellulose, or produced from biomass by isolating hexoses from the biomass, and converting the hexoses to the furfural compound. If X is —Cl, the hexoses may be converted by heating the hexoses with HCl and 1,2-dichloroethane to produce 5-chloromethylfurfural as the furfural compound.

In an embodiment, where X may be —Cl and R may be —H, the furfural compound having the structure

is 5-chloromethylfurfural as shown inFIG. 3B. While this example, and any examples below may be provided, illustrated and discussed for components having furan rings

the same may generally also apply for similarly structured components wherein the furan ring is replaced with a tetrahydrofuran ring

As shown inFIG. 3B, oxidation of the 5-chloromethylfurfural produces 5-(chloromethyl)-2-furoic acid. The 5-(chloromethyl)-2-furoic acid may then be contacted with a solvent, such as 2-methyltetrahydrofuran and at least one of an alkali metal azide and tetraalkylammonium azide to produce 5-(azidomethyl)-2-furoic acid. The 5-(azidomethyl)-2-furoic acid may be converted to an amino carbonyl compound 5-(aminomethyl)-2-furoic acid. In an embodiment, the 5-chloromethylfurfural may be oxidized with Jones reagent or chromic acid and at least one co-oxidant. In an embodiment, the co-oxidant may be periodic acid.

In a variant of the above reaction procedure, the 5-(chloromethyl)furoic acid may be converted into an ester by reacting the 5-(chloromethyl)furoic acid with diazomethane to produce methyl 5-(chloromethyl)-2-furoate. The methyl 5-(chloromethyl)-2-furoate may then be contacted with a solvent, such as 2-methyltetrahydrofuran, and at least one of an alkali metal azide and tetraalkylammonium azide to produce methyl 5-(azidomethyl)-2-furoate.

The methyl 5-(azidomethyl)-2-furoate may be converted to the amino carbonyl compound methyl 5-(aminomethyl)-2-furoate. In an embodiment, the azide that is reacted with the methyl 5-(chloromethyl)-2-furoate may include at least one of an alkali metal azide and tetraalkylammonium azide. In an embodiment the alkali metal azide may be sodium azide. In an embodiment, the methyl 5-(azidomethyl)-2-furoate may be converted to methyl 5-(aminomethyl)-2-furoate by catalytic hydrogenation of methyl 5-(azidomethyl)-2-furoate at room temperature in the presence of a hydrogenation catalyst. In an embodiment, the hydrogenation catalyst may be palladium, platinum, rhodium, or combinations thereof.

In an embodiment, as shown inFIG. 3B, if the furanic compound is 5-hydroxymethylfurfural, the 5-hydroxymethylfurfural may be oxidized to produce 5-formyl-2-furoic acid (5-formylfuran-2-carboxylic acid) or methyl 5-(hydroxymethyl)-2-furoate. The methyl 5-(hydroxymethyl)-2-furoate may be converted to methyl 5-(formyl)-2-furoate. The 5-formyl-2-furoic acid or methyl 5-(formyl)-2-furoate may be reacted with an ammonia source to respectively produce 5-(aminomethyl)-2-furoic acid or methyl 5-(aminomethyl)-2-furoate. In an embodiment, the 5-hydroxymethylfurfural may be oxidized with 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl under phase transfer conditions to produce 5-formyl-2-furoic acid. In an embodiment, the ammonia source may include an ammonia equivalent in a solvent, and reacting the 5-formyl-2-furoic acid with the ammonia source may produce an intermediate imine that may be reduced with a reducing agent in a solvent to produce 5-(aminomethyl)-2-furoic acid. In an embodiment, the ammonia equivalent may be ammonia, ammonium acetate, hydroxylamine, or a combination thereof, and the reducing agent may be hydrogen, sodium borohydride, sodium cyanoborohydride, sodium acetoxyborohydride, or a combination thereof. In an embodiment, the reduction of the imine may be done in the presence of a reduction catalyst. The reduction catalyst may be nickel, palladium, platinum, rhodium, or a combination thereof. Alternatively, reductive amination of 5-formyl-2-furoic acid using a mixture of sodium cyanoborohydride, ammonium acetate, aqueous ammonium hydroxide and ethanol may also produce the amino carbonyl compound.

Referring back toFIG. 1, the amino carbonyl compounds produced from the furanic compounds may be converted to nylon 6. This conversion may be done by various routes as illustrated inFIG. 4. In an embodiment, nylon 6 may be produced by a series of reactions involving hydrogenation, hydrodeoxygenation, and polymerization. In a first reaction, the amino acid or ester may be hydrogenated to reduce the furan double bonds, if present, and hydrodeoxygenated to open the ring and produce an aminocaproic acid. The aminocaproic acid may be converted to caprolactam, and, via a ring-opening polymerization, the caprolactam may be polymerized to produce nylon 6. During polymerization, the amide bond within each caprolactam molecule is broken, with the active groups on each side re-forming two new bonds as the monomer becomes part of the polymer backbone.

The hydrogenation, hydrodeoxygenation, and polymerization may be done in a single-vessel reaction sequence. A mixture of the amino carbonyl compound (amino acid or amino ester), at least one metal catalyst, at least one halide source, and hydrogen gas may be heated in stages to conduct the various reactions. In a first stage, the mixture may be heated to a first temperature of about 140° C. to about 160° C. for a period of time sufficient to convert the aminocarbonyl compound to aminocaproic acid. The temperature may then be increased to a second temperature of about 190° C. to about 210° C. for an additional period of time sufficient to convert the aminocaproic acid to caprolactam. The temperature may then be increased to a third temperature of about 240° C. to about 270° C. for another period of time sufficient to convert the caprolactam to nylon 6.

In embodiments, the metal catalyst may be platinum, palladium, rhodium, ruthenium, nickel, cobalt, iron, molybdenum, iridium, rhenium, gold, or any combination thereof. The metal catalyst may be mounted on a support. The halide source may be at least one hydrogen halide, which may be, for example, hydrogen iodide, hydrogen bromide, or a combination thereof.

In a variant of this reaction sequence, as depicted inFIG. 4, the aminocaproic acid or aminocaproic ester may be polymerized directly to nylon 6 via a polycondensation reaction.

In an embodiment, as also generally represented inFIG. 4, the amino acids or amino esters may be polymerized to produce polyamides of structure

where R is —H, alkyl, or substituted alkyl. Additional hydrogenation/hydrodeoxygenation of the polyamide may produce nylon 6.

In an embodiment, a polyamide may have a structure as represented by

wherein M1 is

and R is —H, alkyl, or substituted alkyl. In an embodiment R may be —H or —CH3. A polyamide having such a structure may be used as a precursor for producing nylon 6. The polyamide may be converted to nylon 6 by hydrogenating and hydrodeoxygenating the polyamide.

In a reaction based onFIG. 6, a polyamide having a structure as represented by

may be produced by converting at least one furanic compound having a structure

wherein X may be —F, —Cl, —Br, —I, —OH, —N3, an acetate, or sulfonate, and Y may be —C(O)R or —C(O)OR, to an amino acid or amino ester having a structure

where R may be —H, an alkyl, or a substituted alkyl. The amino acids or amino esters may then be converting to the polyamide. The amino acids or amino esters may be converted to polyamides by polymerization of the amino acids or amino esters. In an embodiment, Y may be —C(O)H and X may be —Cl or —OH.

As mentioned previously, the furanic compound may be derived directly from biomass, or may be produced from biomass by isolating hexoses or cellulose from the biomass, and converting the hexoses or cellulose to the furanic compound. In an embodiment, where X is —Cl and Y is —C(O)H, converting the hexoses or cellulose may be converted to the furanic compound by heating the hexoses or cellulose with HCl and 1,2-dichloroethane to produce 5-chloromethylfurfural as the furanic compound. In a variant, an alkaline salt may be heated with the hexoses, HCl and 1,2-dichloroethane to produce the 5-chloromethylfurfural. The alkaline salt may be lithium halide, sodium halide, potassium halide, or any combination thereof.

In an embodiment for furan compounds, which, as mentioned above, may also be applicable for tetrahydrofuran compounds, where X is —Cl and Y is —C(O)H, conversion of the at least one furan compound to the amino acid may include oxidizing 5-chloromethylfurfural to produce 5-(chloromethyl)-2-furoic acid, contacting the 5-(chloromethyl)-2-furoic acid with a solvent, such as 2-methyltetrahydrofuran, and at least one of an alkali metal azide and tetraalkylammonium azide to produce 5-(azidomethyl)-2-furoic acid, and converting the 5-(azidomethyl)-2-furoic acid to the amino acid 5-(aminomethyl)-2-furoic acid. In embodiments, the alkali metal azide may be sodium azide, and the tetraalkylammonium azide may be tetrabutylammonium azide.

The 5-(azidomethyl)-2-furoic acid may be converted to 5-(aminomethyl)-2-furoic acid by catalytic hydrogenation of 5-(azidomethyl)-2-furoic acid at room temperature in the presence of a hydrogenation catalyst. The hydrogenation catalyst may be palladium, platinum, rhodium, or any combination thereof. The 5-chloromethylfurfural may be oxidized with at least one of: Jones reagent, and chromic acid and at least one co-oxidant. The co-oxidant may be periodic acid.

For furanic compounds where X is —OH and Y is —C(O)H, converting hexoses or cellulose to the furanic compound may include heating the hexoses or cellulose with at least one of an acid and a metal salt catalyst to produce 5-hydroxymethylfurfural as the furanic compound. The step of converting the at least one furanic compound to the amino carbonyl compound may then include oxidizing the 5-hydroxymethylfurfural to produce 5-formyl-2-furoic acid or methyl 5-formyl-2-furoate, and contacting the 5-formyl-2-furoic acid or methyl 5-formyl-2-furoate with an ammonia source to produce the amino carbonyl compound 5-(aminomethyl)-2-furoic acid or the amino ester methyl 5-(aminomethyl)-2-furoate. In an embodiment, the 5-hydroxymethylfurfural may be oxidized with 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl under phase transfer conditions.

In an embodiment, the ammonia source may be an ammonia equivalent in an appropriate solvent, and upon contacting the 5-formyl-2-furoic acid or methyl 5-formyl-2-furoate with the ammonia source, an intermediate imine may be produced. The intermediate imine may be reduced with a reducing agent in a solvent to produce 5-(aminomethyl)-2-furoic acid or methyl 5-(aminomethyl)-2-furoate. In an embodiment, the intermediate imine may be reduced with the reducing agent in the presence of a reduction catalyst. In various embodiments, the ammonia equivalent may be ammonia, ammonium acetate, hydroxylamine, or a combination thereof, and the reducing agent may be hydrogen, sodium borohydride, sodium cyanoborohydride, sodium acetoxyborohydride, or a combination thereof.

EXAMPLES

Example 1: Method for Producing a Furanazido Acid or Furanazido Ester from 5-Chloromethylfurfural—and Conversion to an Amino Acid or Amino Ester

Furanazido acids or Furanazido esters are provided as precursor compounds for producing nylon 6.FIG. 3Bdepicts a representation of a method for producing 5-(azidomethyl)-2-furoic acid and methyl 5-(azidomethyl)-2-furoate from furanic compounds. One furanic compounds that is usable for producing 5-(azidomethyl)-2-furoic acid and methyl 5-(azidomethyl)-2-furoate is 5-chloromethylfurfural. As discussed previously, 5-chloromethylfurfural is commercially available (such as from Toronto Research Chemicals, Inc.; Toronto, Canada) or obtainable from biomass and other sources.

A solution of 5-(chloromethyl)furfural (1 equivalent) in isopropanol free acetone is cooled in an ice bath. Jones reagent is added slowly until the yellow color persists. The reaction is quenched with isopropanol, the mixture is concentrated under reduced pressure, and the residue is extracted with ethyl acetate. The extract is washed with 1 M hydrochloric acid, washed with water, dried over magnesium sulfate, and concentrated under reduced pressure to yield 5-(chloromethyl)-2-furoic acid.

A solution of 5-(chloromethyl)-2-furoic acid in diethyl ether is cooled in an ice bath. A diethyl ether solution of diazomethane is added slowly until the yellow color persists. After being stirred for about 10 minutes, the ether is removed under reduced pressure to yield methyl 5-(chloromethyl)-2-furoate.

A mixture of methyl 5-(chloromethyl)-2-furoate (1 equivalent), tetrabutylammonium azide (1 equivalent) and 2-methyltetrahydrofuran as solvent is stirred for about 1.5 hours. After being washed twice with a 1:1 mixture of brine and 1 M hydrochloric acid, the solution is dried over magnesium sulfate and concentrated under reduced pressure to yield methyl 5-(azidomethyl)-2-furoate.

In a similar manner, 5-(azidomethyl)-2-furoic acid is also synthesized from 5-(chloromethyl)-2-furoic acid.

Methyl 5-(azidomethyl)-2-furoate is converted to methyl 5-(aminomethyl)-2-furoate by treating a mixture of methyl 5-(azidomethyl)-2-furoate (1 equivalent), 10% palladium on carbon (0.03 equivalent palladium), concentrated hydrochloric acid (1.1 equivalents), and methanol as solvent, with hydrogen gas (about 30 psi) for about 3 hours. The catalyst is removed by filtration and rinsed with methanol. The combined filtrates are concentrated under reduced pressure. Trituration of the residue with diethyl ether yields methyl 5-(aminomethyl)-2-furoate hydrochloride salt.

Example 2: Method for Producing Furan Acid or Furan Ester from 5-Hydroxymethylfurfural—and Conversion to an Amino Acid or Amino Ester

Furan acids or furan esters are provided as precursor compounds for producing nylon 6.FIG. 3Bdepicts a representation of a method for producing 5-formyl-2-furoic acid and methyl 5-(hydroxymethyl)-2-furoate from furanic compounds. One furanic compound that is usable for producing 5-formyl-2-furoic acid and methyl 5-(hydroxymethyl)-2-furoate is 5-hydroxymethylfurfural.

In one process, as shown inFIG. 7A, methyl 5-(hydroxymethyl)-2-furoate is synthesized from 5-(hydroxymethyl)furfural by treating a mixture of 5-(hydroxymethyl)furfural (1 equivalent), potassium methoxide (0.25 equivalent), gold on titanium oxide catalyst (0.005 equivalent gold) and methanol as solvent, with oxygen gas (1 atmosphere) for about 24 hours. The catalyst is removed by filtration and rinsed with methanol. The combined filtrates are concentrated under reduced pressure to yield methyl 5-(hydroxymethyl)-2-furoate. A mixture of methyl 5-(hydroxymethyl)-2-furoate (1 equivalent), o-iodoxybenzoic acid (3 equivalents), and ethyl acetate as solvent, is heated under reflux for about 3 hours. Byproducts are removed by filtration and the filtrate is concentrated under reduced pressure to yield methyl 5-formyl-2-furoate. A mixture of methyl 5-formyl-2-furoate (1 equivalent), hydroxylamine hydrochloride (1 equivalents), potassium acetate (1 equivalents) and 50% aqueous ethanol is heated at 50° C. for 1 hour. After cooling, the precipitate is filtered, washed with water and dried under reduced pressure to yield methyl 5-formyl-2-furoate oxime.

In an alternative process, as shown inFIG. 7B, 5-formyl-2-furoic acid is synthesized from 5-(hydroxymethyl)furfural by vigorously stirring a two phase mixture of 5-(hydroxymethyl)furfural (1 equivalent), 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (0.1 equivalent), acetylcholine chloride (0.1 equivalent), saturated aqueous sodium bicarbonate solution, and tetrahydropyran. Pyridinium tribromide (3 equivalents) is added to the mixture in portions. After being stirred for about 5 hours, the reaction is quenched by addition of 5% aqueous sodium thiosulfate solution, acidified by addition of aqueous tartaric acid, and extracted with tetrahydropyran. The extract is concentrated under reduced pressure to yield 5-formyl-2-furoic acid. A mixture of 5-formyl-2-furoic acid (1 equivalent), hydroxylamine hydrochloride (1 equivalent), 10% aqueous sodium hydroxide solution (2.1 equivalents sodium hydroxide) and ethanol is heated at 50° C. After 1 hour, the mixture is treated with 10% hydrochloric acid (1.2 equivalents) and the solid is filtered to yield 5-formyl-2-furoic acid oxime.

The oximes (FIGS. 7A, 7B) are then converted to amino acids or amino esters. For example, a mixture of 5-formyl-2-furoic acid oxime, Raney nickel catalyst, and tetrahydrofuran as solvent is treated with hydrogen gas (50 bar) in an autoclave for 1 hour. The catalyst is removed by filtration and rinsed with tetrahydrofuran under argon. The combined filtrates are concentrated under reduced pressure to yield 5-(aminomethyl)-2-furoic acid. Similarly, methyl 5-formyl-2-furoate oxime may yield methyl 5-(aminomethyl)-2-furoate.

Example 3: Methods for Producing Caprolactam

Any of the synthesized amino ester, amino acid, azido ester or azido acid monomers of Examples 1 and 2 may be used for producing caprolactam. A mixture of any, or a combination of, the monomers (1 equivalent), 5% palladium on silica (0.01 equivalent palladium) and acetic acid solvent is heated in an autoclave at 160° C. while treating with hydrogen gas (50 atmospheres) for about 3 hours. The mixture is cooled, hydrogen iodide (1 equivalent) is added, and the mixture is again heated at about 160° C. while treating with hydrogen gas (about 50 atmospheres) for about 3 additional hours. After cooling, the mixture is filtered to remove the catalyst. The solvent is removed by distillation under reduced pressure to yield 6-aminocaproic acid.

A mixture of 6-aminocaproic acid and ethanol as solvent is heated at about 200° C. while being stirred vigorously in an autoclave for about 20 minutes. Removal of the solvent under reduced pressure yields caprolactam.

Example 4: Method for Producing Nylon 6

Caprolactam is isolated and sold as a precursor for producing nylon 6 or other possible uses. Nylon 6 is also produced as a continuation of the method presented in Example 3 to provide a two-vessel conversion of 5-(aminomethyl)-2-furoic acid, methyl 5-(aminomethyl)-2-furoate, 5-(azidomethyl)-2-furoic acid or methyl 5-(azidomethyl)-2-furoate to nylon 6. After the formation of caprolactam in Example 3, the reaction mixture is heated to a third higher temperature of about 260° C. for a period of time of about 12 hours to open the caprolactam rings, whereby the amine ends of the molecules will react with the carboxyl end of other molecules to polymerize into nylon 6.

Nylon 6 may also be produced from any of the synthesized amino ester, amino acid, azido ester or azido acid monomers of Examples 1 and 2. A mixture of any, or a combination of, the synthesized amino ester, amino acid, azido ester or azido acid monomers (1 equivalent), 5% palladium on silica (0.01 equivalent palladium) and acetic acid solvent is heated in an autoclave at about 160° C. while treating with hydrogen gas (about 50 atmospheres) for about 3 hours. The mixture is cooled, hydrogen iodide (1 equivalent) is added and heated again at 160° C. while treating with hydrogen gas (50 atmospheres) for another 3 hours. The contents of the autoclave are pumped into a second autoclave with removal of the catalyst by filtration. After removal of acetic acid by distillation, ethanol is added to the autoclave. The mixture is heated at about 200° C. while being stirred vigorously for about 20 minutes. After removal of the solvent by distillation, water (5% by weight) is added to the autoclave and the mixture is heated at about 260° C. while maintaining the steam pressure at about 15 atmospheres for about 12 hours. Removal of water by distillation yields nylon 6.

Example 5: A Furan-Based Polyamide and Method for Producing

A furan based polyamide having the structure

is produced from furanic compounds according to a method as represented inFIG. 7A. Such a polyamide is usable as a precursor for the production of nylon 6. One furanic compound that is usable for producing the polyamide is 5-hydroxymethylfurfural. As discussed previously, 5-hydroxymethylfurfural is obtained from biomass or other sources. 5-hydroxymethylfurfural is oxidized to produce methyl 5-hydroxymethyl-2-furoate by reacting the 5-hydroxymethylfurfural with oxygen, potassium methoxide, gold on titanium oxide catalyst, and methanol as a solvent. The methyl 5-hydroxymethylfuroate is oxidized to produce methyl 5-formylfuroate with o-iodoxybenzoic acid. The methyl 5-formylfuroate is reacted with hydroxylamine to produce an intermediate oxime that is reduced with hydrogen in the presence of a nickel catalyst to produce methyl 5-(aminomethyl)-2-furoate. The methyl 5-(aminomethyl)-2-furoate is polymerized to produce the polyamide.

Example 6: A Tetrahydrofuran-Based Polyamide and Method for Producing

A tetrahydrofuran based polyamide having the structure

is produced from furanic compounds. Such a polyamide is usable as a precursor for the production of nylon 6. One furanic compound that is usable for producing the polyamide is 5-hydroxymethylfurfural. As discussed previously, 5-hydroxymethylfurfural is obtained from biomass or other sources. As shown in the upper portion ofFIG. 7A, 5-hydroxymethylfurfural is oxidized to produce methyl 5-hydroxymethyl-2-furoate by reacting the 5-hydroxymethylfurfural with oxygen, potassium methoxide, gold on titanium oxide catalyst, and methanol as a solvent. The methyl 5-hydroxymethyl-2-furoate is oxidized to produce methyl 5-formyl-2-furoate with o-iodoxybenzoic acid. The methyl 5-formyl-2-furoate is reacted with hydroxylamine to produce an intermediate oxime that is reduced with hydrogen in the presence of a nickel catalyst to produce methyl 5-(aminomethyl)-2-furoate.

As shown inFIG. 8, the methyl 5-(aminomethyl)-2-furoate is catalytically hydrogenated in the presence of a halide source (HI or HBr) to produce methyl 5-(aminomethyl)-2-tetrahydrofuroate. Via a polycondensation, the methyl 5-(aminomethyl)-2-tetrahydrofuroate is polymerized to form a polyamide.

Therefore, the Examples above demonstrate that nylon 6, and precursors for making nylon 6, such as caprolactam from Example 3 and polyamide from Example 5, can be produced from furanic compounds that are derived from biomass, thereby reducing the need for petrochemically derived raw materials.

While various compositions, methods, and devices are described in terms of “comprising” various components or steps (interpreted as meaning “including, but not limited to”), the compositions, methods, and devices can also “consist essentially of” or “consist of” the various components and steps, and such terminology should be interpreted as defining essentially closed-member groups.