DIETHANOLAMINE FROM GLYCOLALDEHYDE

TECHNICAL FIELD

The present invention from one perspective relates to methods for the synthesis of biobased amines, and more particularly, to methods for the synthesis of such amines which are presently also made from non-renewable resources. From another perspective, the present invention relates to methods for the production of diethanolamine.

BACKGROUND ART

The long-term trend of increasing cost of many hydrocarbon feedstocks has created major incentives for seeking alternative sources to petroleum-based carbon for the production of many important and valuable chemical products. Biomass (material derived from living or recently living organisms) is viewed as a readily available, inexpensive supply of renewable, non-petroleum based carbon from which many such known, high value chemicals can be derived. The ability to convert biomass to fuels, chemicals, energy and other materials is expected to strengthen rural economies, decrease dependence on oil and gas resources, and reduce air and water pollution. The generation of energy and chemicals from renewable resources such as biomass also reduces the net liberation of carbon dioxide, a greenhouse gas, into the environment, from fossil-based sources of otherwise“sequestered” carbon.

Nonetheless, the development of sustainable technologies for the production from renewable resources of those chemicals that have heretofore only been made from petroleum-based carbon remains a significant challenge. For example, in recent years, the biodiesel industry has provided abundant crude glycerol as a byproduct of refining triglycerides in plant oils and animal fats. This glycerol can be purified to serve as a feedstock for producing propylene glycol (1, 2-propanediol), a same carbon- numbered, known high value chemical from non-renewable resources. However, significant expense resides in the steps needed to adequately purify glycerol for this purpose, and the biodiesel industry is heavily dependent on tax credits and other forms of governmental subsidies for its profitability.

As noted in a recent journal review, Froidevaux et al,“Biobased Amines: From Synthesis to Polymers; Present and Future”, CHEM. REV. 116 (22): 14181-14224 (2016), amines represent a class of known, useful chemical products from petroleum- based carbon-for example, as key monomers for the synthesis of polyamides, polyureas and polyepoxides, which are all of growing interest in automotive, aerospace, building and health applications-which present still an additional challenge in that very few natural amines are available from which biobased replacements might be obtained.

The ethanolamines - that is, monoethanolamine or 2-aminoethanol (MEA), diethanolamine (DEA) and triethanolamine (TEA) - are specific examples of known, commercially significant amines from petroleum-based carbon, specifically, through reacting ethylene oxide with aqueous ammonia to provide MEA, DEA, and TEA in admixture with one another. The product distribution can be altered to an extent by various means, in particular, by changing the stoichiometry of the reactants. Nevertheless one seeking to make DEA, for example, for use as an acid gas removal agent (e.g. , for sweetening of sour natural gas), or otherwise for the production of a chemical intermediate, such as in the manufacture of surfactants, corrosion inhibitors, or other end products, generally will also need to find profitable uses or consumers for MEA and TEA as well. Ethylene oxide as a starting material is also undesirable, posing significant toxicological, reactive safety and environmental concerns.

The present state of the art would thus benefit from methods for selectively producing biobased diethanolamine, particularly from methods proceeding directly from carbohydrates or via intermediates with a commensurate utility and scale of manufacture to that of DEA. Glycolaldehyde (C2H4O2) is an example of just such an intermediate, having significant utility as a reactive intermediate in that it is the smallest molecule having both reactive aldehyde and hydroxyl groups, and being susceptible of production by several conversion pathways from biomass-derived carbohydrates, such as fructose or sucrose. Yet while there are a handful of precedents from years prior to very recently which describe methods for producing MEA and DEA from glycolaldehyde by reductive amination in the presence of a catalyst, see, for example, US 6,534,441, US 8,772,548 and US 8,742,174, there remains a need for considerable improvements in selectivity and yield for the commercial scale production of a biobased DEA from glycolaldehyde. SUMMARY OF THE INVENTION

Aspects of the invention are associated with the discovery of improvements in catalyst formulations for the conversion of glycolaldehyde to diethanolamine, which catalyst systems exhibit improved selectivity to this desired product and consequently reduced selectivity to monoethanol amine and byproducts such as ethylene glycol. More particular aspects relate to the beneficial effects of noble metal-containing hydrogenation catalysts in performing reductive ami nation of glycolaldehyde, to selectively produce diethanolamine· Such catalysts may be included in the reaction mixture, to which glycolaldehyde and an aminating agent are added, and from which diethanolamine is produced. Suitable hydrogenation catalysts may be heterogeneous in the reaction mixture, and suitably present as a solid in a liquid and/or gaseous reaction mixture under reductive ami nation conditions.

A heterogeneous hydrogenation catalyst allows for ease of separation of the product mixture, following reaction, from this catalyst. In the case of batchwise operation, this allows for simple filtration of the catalyst from the product mixture. A solid catalyst formulation also allows for catalyst particles to be made large enough, such that they may be contained in a reactor (e.g., fixed-bed reactor) with sufficiently low pressure drop as needed for the process to be performed continuously, and therefore in a manner that is more amenable to commercial operation. Continuous operation may involve continuous feeding of the reactant glycolaldehyde, for example with an aminating agent such as ammonia or aqueous ammonia (ammonium hydroxide), and also with hydrogen. These streams may be contacted with the noble metal-containing hydrogenation catalyst, contained in the reactor and operating under reductive ami nation conditions. Such operation may also involve the continuous withdrawal of a product mixture comprising diethanolamine, followed by the separation of a diethanolamine-containing product from this mixture. More particularly, the diethanolamine-containing product may be separated from unconverted reactants and/or byproducts. At least a portion of any unconverted reactants (e.g. , hydrogen) may be recycled to the reactor (e.g., using a recycle compressor to return hydrogen, in a recycle gas stream, back to the reactor). A solid catalyst also allows for the formulation to include other active constituents, such as one or more promoter metals.

These and other aspects, embodiments, and associated advantages will become apparent from the following Detailed Description. DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the invention are directed to methods or processes for producing or synthesizing diethanolamine from glycolaldehyde. The desired reductive amination reaction pathway can be depicted as:

The term“glycolaldehyde” is meant to encompass the compound shown above, as well as various forms that this reactive compound may undertake, such as in an aqueous environment of a reaction mixture as described herein. Such forms include glycolaldehyde dimer and oligomer forms, as well as hydrated forms. Glycolaldehyde dimer is a particularly prevalent form, and this form is also known as the ringed structure, 2, 5-dihydroxy- l,4-dioxane. For purposes of determining molar selectivity to, and theoretical yield of, diethanolamine, each mole of glycolaldehyde dimer is considered equivalent to two moles of glycolaldehyde. Similar considerations apply to other glycolaldehyde oligomers.

“Molar selectivity to diethanolamine” is the percentage, on a molar basis, of converted glycolaldehyde, which results in the formation of diethanolamine. The yield of diethanolamine is the amount obtained, expressed as a percentage of the theoretical amount that would be obtained by reacting glycolaldehyde with 100% conversion and 100% molar selectivity to diethanolamine. The yield can be determined as the product of conversion and selectivity. Therefore, if 10 moles of glycolaldehyde are reacted, 1 mole of glycolaldehyde remains (unreacted) in the product mixture, and 2 moles of diethanolamine are present in this mixture, then (i) the conversion of glycolaldehyde is 90% (or 90 mole-%), (ii) the molar selectivity to diethanolamine is 44%, (the formation of 2 moles of diethanolamine, requiring 4 moles of the 9 moles of converted glycolaldehyde (according to the reaction above)), and (iii) the yield of diethanolamine is 40%. Similar definitions of molar selectivity and yield apply to other reaction products.

Particular embodiments are directed to methods for producing diethanolamine, comprising reacting glycolaldehyde (including forms of this compound as described above) with an aminating agent in the presence of a noble metal-containing hydrogenation catalyst under reductive ami nation conditions, to produce the diethanolamine (e.g. , in a product mixture from which the diethanolamine may be recovered, such as in a purified form following one or more separation steps). A representative hydrogenation catalyst is a noble metal-containing catalyst, meaning that it comprises at least one noble metal.

For example, the hydrogenation catalyst may comprise platinum or palladium as a noble metal or may comprise both of these noble metals. The hydrogenation catalyst may comprise either or both of these noble metals, or other noble metals, in an amount, or in a combined amount, generally from 0.1 wt-% to 15 wt-%, and typically from 0.5 wt-% to 10 wt-%, based on the weight of the catalyst. Regardless of the amount, the hydrogenation catalyst may be a solid supported noble metal-containing catalyst, meaning that the noble metals are disposed on a solid support, which may be substantially refractory (inert) under reductive ami nation conditions, or which may itself be functional (e.g., in the case of providing acidic or basic sites to provide or promote catalytic activity). Carbon, including activated carbon, is an exemplary solid support.

Noble metals are understood as referring to a class of metallic elements that are resistant to oxidation. In representative embodiments, the at least one noble metal of the hydrogenation catalyst may be selected from the group consisting of platinum (Pt), rhodium (Rh), ruthenium (Ru), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), and gold (Au), with the term“consisting of’ being used merely to denote group members, according to a specific embodiment, from which the noble metal(s) are selected, but not to preclude the addition of other noble metals and/or other metals generally. Accordingly, a hydrogenation catalyst comprising a noble metal embraces a catalyst comprising at least two noble metals, as well as a catalyst comprising at least three noble metals, and likewise a catalyst comprising two noble metals and a third, non-noble metal such as a promoter metal (e.g., a transition metal). According to preferred embodiments, the noble metal(s) is/are present in an amount, or combined amounts, within the ranges given above. Alternatively, in the case of at least two noble metals being present, they may each independently be present in amounts from 0.05 wt-% to 12 wt-%, from 0.3 wt-% to 10 wt-%, or from 1 wt-% to 7.5 wt-%, based on the weight of the catalyst. For example, a representative hydrogenation catalyst may comprise the two noble metals Pt and Pd, and the Pt and Pd may independently be present in an amount within any of these ranges (e.g., from 1 wt-% to 7.5 wt-%). That is, either the Pt may be present in such an amount, the Pd may be present in such an amount, or both Pt and Pd may be present in such amounts.

In representative embodiments, a single noble metal (e.g. , either Pt or Pd), or otherwise two noble metals (e.g., both Pt and Pd) may be substantially the only noble metals present in the hydrogenation catalyst, such that, for example, any other noble metal(s) is/are present in an amount or a combined amount of less than 0.1 wt-%, or less than 0.05 wt-%, based on the weight of the hydrogenation catalyst. In further representative embodiments, a single noble metal, or two noble metals, are substantially the only metals present in the hydrogenation catalyst, with the exception of metals that may be present in the solid support (e.g., such as aluminum being present in the solid support as aluminum oxide). Therefore, in the case of support comprising substantially all carbon, the single noble metal, or two noble metals, may be substantially the only metals present. For example, any other metal(s), besides the single noble metal, or two noble metals, and metals of the solid support (if any), may be present in an amount or a combined amount of less than 0.1 wt-%, or less than 0.05 wt-%, based on the weight of the hydrogenation catalyst. Any metals present in the catalyst, including noble metal(s), may have a metal particle size in the range generally from 0.3 nanometers (nm) to 20 nm, typically from 0.5 nm to 10 nm, and often from 1 nm to 5 nm.

The hydrogenation-active, noble metal(s) of representative hydrogenation catalysts may be disposed or deposited on a solid support, which is intended to encompass catalysts in which the noble metal(s) is/are on the support surface and/or within a porous internal structure of the support. Therefore, in addition to such hydrogenation- active metal(s), representative hydrogenation catalysts may further comprise a solid support, with exemplary solid supports comprising carbon and/or one or more metal oxides. Exemplary metal oxides are selected from the group consisting of aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, strontium oxide, tin oxide, etc. The solid support may comprise all, or substantially all of the one or more of such metal oxides, for example such that the one or more metal oxides are present in an amount, or combined amount, of at least 95% by weight of the solid support. Alternatively, carbon, such as activated carbon, may be present in an amount of at least 95% by weight, or at least 99% by weight, of the solid support. Activated carbon refers to forms of carbon following any of a number of possible treatments (e.g. , high temperature steaming) to increase porosity. Activated carbon also refers to forms obtained by chemical treatment (e.g. , an acid or a base) to alter properties such as the concentration of acid sites.

The noble metal(s) may be incorporated in the solid support according to known techniques for catalyst preparation, including sublimation, impregnation, or dry mixing. In the case of impregnation, an impregnation solution of a soluble compound of one or more of the noble metals in a polar (aqueous) or non-polar (e.g., organic) solvent may be contacted with the solid support, preferably under an inert atmosphere. For example, this contacting may be carried out, preferably with stirring, in a surrounding atmosphere of nitrogen, argon, and/or helium, or otherwise in a non-inert atmosphere, such as air. The solvent may then be evaporated from the solid support, for example using heating, flowing gas, and/or vacuum conditions, leaving the dried, noble metal-impregnated support. The noble metal(s) may be impregnated in the solid support, such as in the case of two noble metals being impregnated simultaneously with both being dissolved in the same impregnation solution, or otherwise being impregnated separately using different impregnation solutions and contacting steps. In any event, the noble metal- impregnated support may be subjected to further preparation steps, such as washing with the solvent to remove excess noble metal(s) and impurities, further drying, calcination, etc. to provide the hydrogenation catalyst.

The solid support itself may be prepared according to known methods, such as extrusion to form cylindrical particles (extrudates) or oil dropping or spray drying to form spherical particles. Regardless of the specific shape of the solid support and resulting catalyst particles, the amounts of noble metal(s) being present in the hydrogenation catalyst, as described above, refer to the weight of such noble metal(s), on average, in a given catalyst particle (e.g., of any shape such as cylindrical or spherical), independent of the particular distribution of the noble metals within the particle. In this regard, it can be appreciated that different preparation methods can provide different distributions, such as deposition of the noble metal(s) primarily on or near the surface of the solid support or uniform distribution of the noble metal(s) throughout the solid support. In general, weight percentages described herein, being based on the weight of the solid support or otherwise based on the weight of hydrogenation catalyst, can refer to weight percentages in a single catalyst particle but more typically refer to average weight percentages over a large number of catalyst particles, such as the number in a reductive animation reactor that form a catalyst bed as used in processes described herein.

Aspects of the present invention relate to improvements in methods for the reductive amination of glycolaldehyde, resulting from the use of the noble metal- containing hydrogenation catalyst. Particular improvements are increased selectivity to the desired compound, diethanolamine, and/or decreased selectivity to monoethanolamine and/or the hydrogenated byproduct, ethylene glycol, which may be less desired for a given, overall synthesis (e.g., in the synthesis of glyphosate). The amount of hydrogenation catalyst for obtaining a given effect (e.g., selectivity improvement) is dependent on the particular catalyst used and given set of reductive amination conditions, and with the knowledge gained from the present disclosure, those skilled in the art can determine a suitable amount in each case. Generally, any hydrogenation catalyst described above, or combination of catalysts, may be present in the reaction mixture, including the solvent such as water, in an amount, or combined amount, from 0.1 wt-% to 10 wt-%, such as from 0.3 wt-% to 5 wt-% or from 0.5 wt- % to 3 wt-%. In the case of a continuous process, the hydrogenation catalyst may be present in an amount needed to achieve a weight hourly space velocity (WHSV) as described below.

Representative processes are therefore characterized by comparatively high selectivities to diethanolamine, relative to conventional processes. According to particular embodiments, glycolaldehyde may be converted with a molar selectivity to diethanolamine of from 30% or more to 85% or less, in other embodiments with a molar selectivity of from 40% or more to 80% or less, and in still other embodiments from 50% or more to 75% or less, for example, a molar selectivity of at least 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68,69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84 up to 85%. Such selectivities may be associated with comparably low selectivities to monoethanolamine· According to particular embodiments, glycolaldehyde may be converted with a molar selectivity to monoethanolamine of less than 35%, less than 25%, or less than 15%, for example, less than 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16 or 15% to monoethanolamine· In yet other embodiments, the molar selectivity to diethanolamine may be at least 1.5 times, or at least two times, the molar selectivity to monoethanolamine. Alternatively, the selectivity improvement may be characterized with respect to a reference molar selectivity, obtained from a reference process in which all reductive ami nation conditions (e.g., pressure, temperature, residence time, feeds (including aminating agent), catalyst(s), etc.) are identical, except for the replacement of the noble metal- containing hydrogenation catalyst with an equal weight of the conventional catalyst, Raney nickel. This material is namely a type of sponge nickel catalyst that is further characterized by being a fine-grained solid composed mostly of nickel that is present as a nickel- aluminum alloy.

According to particular embodiments, glycolaldehyde may be converted with a molar selectivity to diethanolamine, which exceeds a reference molar selectivity by at least 15%. That is, in the case of a reference molar selectivity of 15%, the use of the hydrogenation catalyst compared to Raney nickel results in a molar selectivity that is increased to at least 30%. In other embodiments, glycolaldehyde may be converted with a molar selectivity to diethanolamine, which exceeds a reference molar selectivity by at least 20%, or even at least 30%. Those skilled in the art will appreciate that even modest increases in selectivity can potentially result in substantial economic benefits on the commercial scale.

The molar selectivities described above may be obtained at high levels of conversion of glycolaldehyde. According to particular embodiments, the glycolaldehyde conversion may be at least 85%, at least 90%, at least 95%, or even at least 99%. Accordingly, representative yields of diethanolamine may be the same or substantially the same as the molar selectivity ranges given above, such as at least 30% (e.g., from 30% to 85%), at least 40% (e.g., from 40% to 80%), or at least 50% (e.g. , from 50% to 75%), of the theoretical yield obtainable, given that yield is determined as the product of conversion and selectivity.

Typical reductive ami nation conditions include an elevated hydrogen partial pressure, such as at least 3 megapascals (MPa) (435 psi), which, in combination with the noble metal-containing hydrogenation catalyst, provide a reductive ami nation environment for carrying out the conversion of glycolaldehyde, selectively to the product diethanolamine. This hydrogen pressure may be contained in a reactor that is used for the contacting of the feed (e.g., an aqueous feed comprising glycolaldehyde) and an aminating agent (e.g., aqueous ammonia), with the noble metal-containing hydrogenation catalyst as described above, to obtain this product. The reaction mixture, to which the feed and aminating agent are added and from which a product mixture is withdrawn (e.g., following separation from the catalyst(s)) is preferably aqueous and comprises dissolved hydrogen under the reductive amination conditions. In addition, or alternatively, to aqueous ammonia, the aminating agent may otherwise comprise gaseous ammonia that may be added batchwise or continuously to the reactor, for example it may be added, in the case of continuous operation, with hydrogen or a recycle gas stream comprising hydrogen. The addition of gaseous ammonia will generally cause the in situ formation of aqueous ammonia in the presence of an aqueous reaction mixture. Other possible aminating agents include primary and secondary amines of the formula NHR ¹ R ² , wherein at least one of R ¹ and R ² is a C1-C3 alkyl group. The glycolaldehyde and aminating agent may be charged to the reactor batchwise, or otherwise continuously added to the reactor, with a molar excess of the aminating agent, for example, with an aminating agenkglycolaldehyde molar ratio of from 2: 1 to 20: 1 or from 5:1 to 15:1.

Reductive amination conditions, under which the reaction mixture is maintained during the production of diethanolamine, include an elevated pressure and hydrogen partial pressure. Representative absolute reactor pressures are in the range generally from 2.07 MPa (300 psi) to 24.1 MPa (3500 psi), typically from 3.45 MPa (500 psi) to 20.7 MPa (3000 psi), and often from 5.17 MPa (750 psi) to 10.3 MPa (1500 psi). The reactor pressure may be generated predominantly or substantially from hydrogen, such that these ranges of total pressure may also correspond to ranges of hydrogen partial pressure. However, the presence of gaseous ammonia or other aminating agent, as well as other gaseous species vaporized from the reaction mixture, may result in the hydrogen partial pressure being reduced relative to these total pressures, such that, for example, the hydrogen partial pressure may range generally from 1.38 MPa (200 psi) to 22.4 MPa (3250 psi), typically from 3.00 MPa (435 psi) to 20.0 MPa (2901 psi), and often from 4.82 MPa (700 psi) to 9.31 MPa (1350 psi).

Other reductive amination conditions, present in the reactor, include a temperature generally from 20°C (68°F) to 200°C (392°F), and typically from 50°C (l22°F) to l50°C (302°F). The reaction time, i.e., time at which the reaction mixture is maintained under conditions of pressure and temperature at any target values or target sub-ranges within any of the ranges of pressure and temperature given above (e.g., a target, total pressure value of 8.27 MPa (1200 psi) and a target temperature of 85 °C (l85°F), is from 0.5 hours to 24 hours, and preferably from 1 hour to 5 hours, in the case of a batchwise reaction. For a continuous process, these reaction times correspond to reactor residence times. An additional parameter that is relevant for a continuous process is weight hourly space velocity (WHSV), which is understood in the art as the weight flow of the feed (e.g. aqueous feed comprising glycolaldehyde and NH ₄ OH) to a reactor, divided by the weight of the catalyst, in this case the noble metal-containing hydrogenation catalyst. This parameter therefore represents the equivalent catalyst bed weight of the feed processed every hour, and it is related to the inverse of the reactor residence time. According to representative embodiments, the reductive ami nation conditions include a WHSV generally from 0.01 hr ¹ to 20 hr ¹ , and typically from 0.05 hr ¹ to 5 hr ¹ .

A continuous process involving a heterogeneous (solid) hydrogenation catalyst may be performed by continuous feeding of glycolaldehyde, aminating agent, and hydrogen to the reaction mixture comprising the catalyst and contained within the reactor, and continuous withdrawal, from the reactor, of a product mixture comprising diethanolamine that is substantially free of the catalyst. This product mixture may then be further processed by separating portions of the product mixture to purify and recover the diethanolamine and optionally recycle unconverted reactants, such as the aminating agent and/or hydrogen. According to one embodiment, the product mixture may be subjected to flash separation to separate a primarily hydrogen-containing vapor phase, at least portion of which (e.g., following the removal of a purge stream to prevent excessive accumulation of unwanted impurities) may provide the recycle gas stream, described above. The liquid phase recovered from the flash separation and also comprising the desired diethanolamine, may be subjected to any of a number of possible separation steps, including one or more of phase separation, extraction (e.g., using an organic solvent having preferential affinity for monoethanolamine), and distillation, sequentially in any order. Extraction and distillation may alternatively be combined in a single, extractive distillation step. As with the recycle gas stream, any separated liquid products (e.g. , aminating agent and/or unconverted glycolaldehyde) may likewise be recycled to the reactor. Whether performed batchwise or continuously, particular embodiments relate to methods for producing diethanolamine, comprising performing a reductive amination of glycolaldehyde, added to an aqueous reaction mixture with aqueous ammonia as a reactant. This may be performed by contacting this reaction mixture and hydrogen with the noble metal-containing hydrogenation catalyst under reductive ami nation conditions as described above. Advantageously, the reductive ami nation selectively produces diethanolamine according to any of the conversion, selectivity, and yield performance criteria described above, such as a yield of at least about 40% of a theoretical yield.

According to further embodiments, the production of diethanolamine may be integrated with upstream and/or downstream processing steps in the overall production of chemicals, for example sourced from biomass. In the case of integration with upstream processing, the glycolaldehyde may be obtained from the pyrolysis of an aldose or a ketose (e.g. , glucose, fructose, or sucrose). In the case of downstream processing, representative methods may further comprise synthesizing glyphosate from at least a portion of the diethanolamine. Glyphosate is recognized as a valuable chemical for its use to kill weeds, and particularly annual broadleaf weeds and grasses that compete with crops. According to a synthesis method, diethanolamine may be oxidized using sodium hydroxide (NaOH) and a copper-based catalyst to produce disodium iminodiacetic acid (DSIDA). This intermediate is then reacted with phosphorous chloride (PCT) and formaldehyde (HCHO) to produce N- phosphonomethyliminodiacetic acid (PMIDA). The desired glyphosate is thereafter produced by oxidation of PMIDA using sodium molybdate, hydrogen peroxide, and iron (II) sulfate. These further processing steps, following DEA production, correspond to those of the“DEA process” for glyphosate production from ethylene oxide as a starting material and proceeding through DEA as an intermediate. These steps are described, for example, in the Electronic Supplementary Material (ESI) for Green Chemistry, published in 2012 by the Royal Society of Chemistry. In this manner, a viable alternative biobased (renewable) synthesis method for glyphosate, using DEA that has been obtained from carbohydrates, is established.

The following examples are set forth as representative of the present invention. These examples are not to be construed as limiting the scope of the invention as other equivalent embodiments will be apparent in view of the present disclosure and appended claims.

EXAMPLES

Hydrogenation Catalysts for Synthesis of Diethanolamine from Glycolaldehyde

A number of experiments were conducted to investigate the performance of various noble metal-containing hydrogenation catalysts in the reductive ami nation of glycolaldehyde. These catalysts were namely commercial, carbon-supported platinum and/or palladium catalysts, available from Evonik Industries, AG (Evonik) or Johnson Matthey Chemicals Company (JM), as indicated in Table 1 below. In each case, a feed comprising 5% glycolaldehyde dimer by weight in 28% aqueous ammonia solution was reacted, together with a fixed amount of noble metal-containing catalyst, in a high throughput screening batch reactor. A reference experiment was also performed with Raney nickel catalyst. The catalytic, reductive amination reactions were carried out in a sealed hydrogenolysis reactor at 85°C (l85°F) and under 8.27 MPa (1200 psi) hydrogen pressure for a 2-hour hold period. The reaction product, following separation from the solid catalyst, was analyzed by GC. The results demonstrated that yields and selectivities for diethanolamine could be enhanced significantly using noble metal- containing catalysts in place of Raney nickel. The yield results are shown in Table 1.

Table 1— Pt- and/or Pd-Supported Catalysts for Glycolaldehyde Reductive Amination

Overall, aspects of the invention relate to increases in reaction selectivity to diethanolamine, by reductive amination of glycolaldehyde, which can be achieved using noble metal-containing hydrogenation catalysts. Efficiencies and the associated economics of synthesis pathways from renewable feeds to high value chemicals are thereby improved. Those having skill in the art, with the knowledge gained from the present disclosure, will recognize that various changes can be made to the disclosed catalysts and processes in attaining these and other advantages, without departing from the scope of the present disclosure. As such, it should be understood that the features of the disclosure are susceptible to modifications and/or substitutions. The specific embodiments illustrated and described herein are for illustrative purposes only, and not limiting of the invention as set forth in the appended claims.