阅读说明：本技术 用于从乙醇醛生产单乙醇胺的方法和催化剂体系 (Process and catalyst system for the production of monoethanolamine from glycolaldehyde ) 是由 詹姆斯·布拉兹迪尔 马驰骋 于 2019-07-30 设计创作，主要内容包括：披露了用于将乙醇醛转化为单乙醇胺的催化剂体系和相关方法的改善。所述催化剂体系展现出对此所需产物的改善的选择性,并因此展现出对副产物如二乙醇胺和乙二醇的降低的选择性。通过使用酸、并且特别是路易斯酸作为还原胺化反应的助催化剂,结合氢化催化剂一起,实现了这些有益效果。(Improvements in catalyst systems and related methods for converting glycolaldehyde to monoethanolamine are disclosed. The catalyst system exhibits improved selectivity to this desired product and thus reduced selectivity to by-products such as diethanolamine and ethylene glycol. These benefits are achieved by using acids, and particularly lewis acids, as promoters for the reductive amination reaction in conjunction with a hydrogenation catalyst.)

1. A method for producing monoethanolamine, the method comprising:

reacting glycolaldehyde with an aminating agent in the presence of both a hydrogenation catalyst and an acid promoter under reductive amination conditions to produce the monoethanolamine.

2. The process of claim 1 wherein the reductive amination conditions comprise a temperature of from 20 ℃ to 200 ℃, a hydrogen partial pressure of from 3MPa to 20MPa and a residence time of from 0.5 hours to 10 hours.

3. The process of claim 1 or claim 2, wherein the glycolaldehyde is converted with a molar selectivity to monoethanolamine of at least 70%.

4. The process of any one of claims 1 to 3, wherein the glycolaldehyde is converted with a molar selectivity to diethanolamine of less than 10%.

5. The process of any one of claims 1 to 4, wherein the reaction takes place in an aqueous reaction mixture to which the glycolaldehyde and the aminating agent are added.

6. The method of claim 5, wherein the acid promoter is a solid in the aqueous reaction mixture.

7. The method of claim 6, wherein the acid promoter has a Lewis acid site density of from 200 to 1200 μmol/g.

8. The method of claim 6, wherein the acid promoter comprises a zeolitic molecular sieve or a non-zeolitic molecular sieve, a metal oxide, activated carbon, or a resin.

9. The process of claim 8 wherein the acid promoter is a zeolitic molecular sieve having a silica to alumina molar framework ratio of less than 200.

10. The process of claim 8 or claim 9, wherein the acid promoter is a zeolitic molecular sieve having a structure type selected from the group consisting of: FAU, FER, MEL, MTW, MWW, MOR, BEA, LTL, MFI, LTA, EMT, ERI, MAZ, MEI, and TON.

11. The method of claim 10, wherein the structure type is BEA or MFI.

12. The method of claim 5, wherein the acid promoter is dissolved in the aqueous reaction mixture.

13. The method of claim 12, wherein the acid promoter is a metal triflate.

14. The process of any one of claims 1 to 13, wherein glycolaldehyde is converted with a molar selectivity to monoethanolamine of at least 3% over a reference molar selectivity obtained in the absence of the acid promoter.

15. The process according to any one of claims 1 to 14, wherein the glycolaldehyde is obtained from the pyrolysis of an aldose or a ketose.

16. The method of any one of claims 1 to 15, further comprising:

sulfating at least a portion of the monoethanolamine to produce 2-aminoethylsulfuric acid; and

sulfonating at least a portion of the 2-aminoethylsulfuric acid to produce taurine.

17. A method for producing monoethanolamine, the method comprising:

contacting an aqueous feed comprising glycolaldehyde and an aminating agent with a hydrogenation catalyst and an acid promoter in a reactor providing an atmosphere comprising hydrogen to produce the monoethanolamine, wherein

The acid promoter is homogeneous or heterogeneous in the reaction mixture to which the aqueous feed is added.

18. The process of claim 17, wherein the acid promoter is heterogeneous in the reaction mixture, and wherein the process is carried out continuously.

19. A method for producing monoethanolamine, the method comprising:

reductive amination of glycolaldehyde added to an aqueous reaction mixture with aqueous ammonia as a reactant is carried out by contacting the aqueous reaction mixture and hydrogen with both a hydrogenation catalyst and an acid promoter under reductive amination conditions,

wherein the hydrogenation catalyst and the acid catalyst in combination catalyze the reductive amination such that the monoethanolamine is produced in a yield of at least 70% of theoretical yield.

20. The process of claim 19 wherein the hydrogenation catalyst and the acid catalyst are present together in the form of particles of a solid bifunctional catalyst.

Technical Field

From one perspective, the present invention relates to a process for the synthesis of biogenic amines, and more particularly to a process for the synthesis of such amines that are currently also made from non-renewable resources. Viewed from another perspective, the present invention relates to a process for producing monoethanolamine.

Background

The long-standing trend of increasing the cost of many hydrocarbon feedstocks has created a major incentive to find alternative sources of petroleum-based carbon for the production of many important and valuable chemical products. Biomass (material derived from living or recently living organisms) is considered an easily available supply of inexpensive renewable, non-petroleum based carbon from which many such known high value chemicals can be derived. The ability to convert biomass into fuels, chemicals, energy and other materials is expected to enhance rural economy, reduce 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 release of carbon dioxide (greenhouse gases) into the environment from fossil-based sources that would otherwise "sequester" the carbon.

Nevertheless, developing sustainable technologies for producing those chemicals heretofore made from petroleum-based carbon from renewable resources remains a significant challenge. For example, in recent years, the biodiesel industry has provided large amounts of crude glycerol as a by-product of the refining of triglycerides in vegetable oils and animal fats. This glycerol can be purified for use as a feedstock for the production of propylene glycol (1, 2-propanediol), a known high value chemical from non-renewable resources having the same carbon number. However, the steps required to adequately purify glycerol for this purpose require significant expense, and the profitability of the biodiesel industry is heavily dependent on tax reimbursement and other forms of government subsidy.

As described in recent journal reviews (From novacux et al, "Biobased Amines: From Synthesis to Polymers; Present and Future [ biogenic Amines: From Synthesis to Polymer; Present and Future ]", chem. Rev. [ chemical review ]116(22):14181-14224(2016)), Amines represent a known useful class of chemical products From petroleum-based carbon-for example, as key monomers for the Synthesis of polyamides, polyureas, and polyepoxides (which are of increasing interest in automotive, aerospace, construction, and health applications) -they Present yet additional challenges because very few natural Amines (From which Biobased substitutes can be obtained) are available.

Ethanolamine (monoethanolamine or 2-aminoethanol (MEA), Diethanolamine (DEA) and Triethanolamine (TEA)) is a specific example of known commercially significant amines from petroleum based carbon (specifically, by reacting ethylene oxide with aqueous ammonia to provide MEA, DEA and TEA mixed with each other). Although the product distribution can be altered to some extent by various means, in particular by varying the stoichiometry of the reactants, the search to make MEAs for the following will generally also have to find advantageous uses or consumers of DEA and TEA: natural gas scrubbing, pharmaceuticals, detergents, emulsifiers, polishes, corrosion inhibition, or as intermediates. Ethylene oxide is also undesirable as a starting material, causing significant toxicological, reaction safety, and environmental concerns.

The review by Froidevaux et al does mention that bio-based monoethanolamine has been synthesized from the amino acid serine, but the amount of serine produced annually is orders of magnitude less than the amount required to synthesize and supply bio-based monoethanolamine to meet the annual MEA demand, and the necessity to produce serine involves additional costs, which ideally would be avoided.

Thus, the current state of the art would benefit significantly from additional improved processes for the production of bio-based monoethanolamine, particularly processes that proceed more directly from carbohydrates or through intermediates, at a more commensurate utility and manufacturing scale. Glycolaldehyde (C)₂H₄O₂) Is an example of such an intermediate that has significant utility as a reactive intermediate because it is the smallest molecule that has both reactive aldehyde and hydroxyl groups and is readily produced from biomass-derived carbohydrates (such as fructose or sucrose) through several conversion pathways. Also despite the small number of precedents from the previous years (describing methods for the production of 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 is still a need for considerable improvement in selectivity and yield for the commercial scale production of bio-based MEA from glycolaldehyde, which is considered reasonably economically predictable.

Summary of The Invention

Aspects of the invention are related to the improvement found in catalyst systems for converting glycolaldehyde to monoethanolamine that exhibit improved selectivity to this desired product, and thus reduced selectivity to diethanolamine and byproducts such as ethylene glycol. More specific aspects relate to the beneficial effects of acids, and particularly lewis acids, in performing the reductive amination of glycolaldehyde to selectively produce monoethanolamine. As a co-catalyst for this reaction, in conjunction with a hydrogenation catalyst, a lewis acid may be included in the reaction mixture to which glycolaldehyde and an aminating agent are added and from which monoethanolamine is produced. Suitable lewis acids may be homogeneous in the reaction mixture, typically such that both the cocatalyst and the reaction mixture are in the liquid phase (e.g., where the cocatalyst is dissolved). Alternatively, such lewis acids may be heterogeneous, typically such that the co-catalyst is present in the reaction mixture in solid form.

In the case where both the hydrogenation catalyst and the cocatalyst are solids, a further advantage is obtained in terms of the ease of separating the product mixture from the catalyst and cocatalyst after the reaction. In the case of batch operation, this allows simple filtration of the catalyst from the product mixture. The solid catalyst system also allows the catalyst and cocatalyst to be formulated as particles of sufficient size to be contained in a reactor (e.g., a fixed bed reactor) with a sufficiently low pressure drop (as required for a continuous process) and thus in a manner more suitable for commercial operation. Continuous operation may involve, for example, continuous feeding of the reactant glycolaldehyde with an aminating agent such as ammonia or aqueous ammonia (ammonium hydroxide) and also hydrogen. These streams may be contacted with a hydrogenation catalyst and a co-catalyst contained in the reactor and operated under reductive amination conditions. Such operation may also involve continuously withdrawing a product mixture comprising monoethanolamine and then separating the monoethanolamine-containing product from the mixture. More specifically, the monoethanolamine-containing product may be separated from unconverted reactants and/or byproducts. At least a portion of any unconverted reactant (e.g., hydrogen) can be recycled to the reactor (e.g., hydrogen is returned to the reactor as a recycle gas stream using a recycle compressor). In the case of a solid catalyst, this also allows the hydrogenation catalyst and acid promoter to be formulated together in a solid particle, for example, a solid particle of a bifunctional catalyst having both hydrogenation activity and lewis acid sites.

These and other aspects, embodiments and related advantages will become apparent from the following detailed description.

Drawings

Figure 1 is a bar graph of the conversion and product selectivity values obtained in experiments in which reductive amination of glycolaldehyde was performed (i) in the absence of catalyst, (ii) in the presence of raney nickel alone and (iii) in the presence of both raney nickel and a metal triflate as a promoter.

FIG. 2 is a bar graph of monoethanolamine and diethanolamine yield values obtained in experiments in which reductive amination of glycolaldehyde was performed (i) in the presence of raney nickel alone, and (ii) in the presence of both raney nickel and various solid acid promoters.

Figure 3 is a bar graph of product selectivity values obtained in experiments in which reductive amination of glycolaldehyde was performed (i) in the presence of raney nickel alone, and (ii) in the presence of both raney nickel and various zeolites as solid acid promoters.

The figures are to be understood as presenting embodiments of the invention to aid understanding of the principles and chemical reactions involved, but not to limit the scope of the invention as defined in the appended claims. As will be apparent to those skilled in the art having the benefit of this disclosure, the reductive amination processes according to various other embodiments of the present invention will utilize specific catalysts, promoters, and reaction conditions determined, at least in part, according to the specific purpose.

Detailed Description

Embodiments of the invention relate to methods or processes for the production or synthesis of monoethanolamine from glycolaldehyde. The desired reductive amination reaction pathway can be depicted as:

the term "glycolaldehyde" is intended to include the compounds shown above as well as the various forms that such reactive compounds may take, such as in the aqueous environment of the 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 referred to as cyclic structure, 2, 5-dihydroxy-1, 4-dioxane. To determine the molar selectivity to monoethanolamine and the theoretical yield, it is believed that each mole of glycolaldehyde dimer corresponds to two moles of glycolaldehyde. Similar considerations apply to other glycolaldehyde oligomers.

"molar selectivity to monoethanolamine" is the mole-based percentage of converted glycolaldehyde that results in the formation of monoethanolamine. The yield of monoethanolamine is the amount obtained expressed as a percentage of the theoretical amount obtained by reacting glycolaldehyde with 100% conversion and 100% molar selectivity to monoethanolamine. The yield can be determined as the product of conversion and selectivity. Thus, if 10 moles of glycolaldehyde are reacted, 1 mole of glycolaldehyde remains in the product mixture (unreacted), and 7 moles of monoethanolamine are present in this mixture, (i) the conversion of glycolaldehyde is 90% (or 90 mole%), (ii) the molar selectivity to monoethanolamine is 78% (formation of 7 moles of monoethanolamine resulting from the conversion of 9 moles of glycolaldehyde), and (iii) the yield of monoethanolamine is 70%. Similar definitions of molar selectivity and yield apply to other reaction products.

Particular embodiments relate to a process for producing monoethanolamine comprising reacting glycolaldehyde (including the form of this compound as described above) with an aminating agent in the presence of both a hydrogenation catalyst and an acid promoter under reductive amination conditions to produce monoethanolamine (e.g., in a purified form after one or more separation steps in a product mixture from which monoethanolamine may be recovered). A representative hydrogenation catalyst is a sponge metal catalyst, which refers to a metal or metal alloy in particulate or powder form. A preferred hydrogenation catalyst is a sponge nickel catalyst, of which the material known as raney nickel is exemplary. This catalyst is a finely divided solid composed predominantly of nickel, which is present in the form of a nickel-aluminium alloy. The hydrogenation catalyst may more generally comprise one or more hydrogenation-active metals, such as one or more transition metals selected from the group consisting of: nickel (Ni), cobalt (Co), iron (Fe), and ruthenium (Ru). For example, a representative hydrogenation catalyst can comprise at least 5 weight percent (wt-%), typically at least 10 wt-%, and often at least 15 wt-%) of such metals. Such transition metals may be disposed or deposited on a solid support, which is intended to include catalysts in which the active metal is on the surface of the support and/or within the porous internal structure of the support. Thus, in addition to such hydrogenation-active metals, representative hydrogenation catalysts may further comprise a solid support, exemplary solid supports comprising one or more metal oxides, such as those selected from the group consisting of: alumina, silica, titania, zirconia, magnesia, strontium oxide, tin oxide, and the like. The solid support may comprise all or substantially all of one or more 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 wt.% of the solid support.

Importantly, aspects of the present invention relate to the advantages that can be obtained when a hydrogenation catalyst (e.g., raney nickel or other catalysts described above) is promoted with a promoter that is acidic (e.g., has an acid site in the case of a solid promoter). The cocatalyst can in particular be a lewis acid or, in the case of a solid cocatalyst, have lewis acid sites. The density of lewis acid sites can be determined according to known analytical methods (e.g., Fourier Transform Infrared (FTIR) spectroscopy using pyridine adsorption, based at 1450cm^-1Integrated absorbance of the characteristic band of (b). For example, Takagaki et al, The Royal Society of Chemistry](RSC) Advances [ Advances](2014) It is described in volume 4: 43785-91. Representative solid acid cocatalysts, including those that are solid under reductive amination conditions (and thus in the presence of the reaction mixture), have a density of lewis acid sites generally from 50 to 2000 micromoles per gram (μmol/g), typically from 200 μmol/g to 1200 μmol/g, and often from 300 to 900 μmol/g. Unless otherwise indicated, the term "acid" or "acidic" when used in reference to a solid cocatalyst means that it has the property of having an acid site, or the ability to be titrated with a base (e.g., NaOH) in its "as-prepared" form (e.g., either in addition to or prior to introduction into the reaction mixture for reductive amination). This also applies with respect to the mention of specific ranges for the acid site density. Without being bound by theory, it is believed that a certain level of acidity that does not exceed the threshold level is beneficial for enhancing the selectivity to monoethanolamine in the reactions described herein. With the knowledge gained from the present disclosure, one skilled in the art can optimize the acidity level for a given set of reductive amination conditions.

Representative solid acid promoters may include zeolitic molecular sieves or non-zeolitic molecular sieves, metal oxides, activated carbon, or resins. In the case of zeolite molecular sieves, the acidity is silica with alumina (SiO)₂/Al₂O₃) A function of molar skeleton ratio, wherein lower ratios correspond to higher acid site densities. In embodiments in which the acid catalyst comprises a zeolitic molecular sieve (zeolite), its silica to alumina molar framework ratio may be less than 200 (e.g., from 5 to 200), or less than 100 (e.g., from 10 to 100). A particular solid acid catalyst may comprise one or more zeolitic molecular sieves (zeolites) having a structure type selected from the group consisting of: FAU, FER, MEL, MTW, MWW, MOR, BEA, LTL, MFI, LTA, EMT, ERI, MAZ, MEI, and TON, and is preferably selected from one or more of FAU, FER, MWW, MOR, BEA, LTL, and MFI. The Structure of zeolites having these and other Structure Types is described and in Meier, W.M et al, Atlas of Zeolite Structure type Atlas]Further references are provided in 4 th edition, Eschervier Boston (Elsevier: Boston) (1996). Specific examples include zeolite Y (FAU structure), zeolite X (FAU structure), MCM-22(MWW structure), ZSM-5(MFI structure), and zeolite beta (BEA structure). Preferred are the structure types BEA and MFI.

Non-zeolitic molecular sieves include ELAPO molecular sieves encompassed by an empirical chemical composition on an anhydrous basis represented by the formula:

(EL_xAl_yP_z)O₂，

wherein EL is an element selected from the group consisting of: silicon, magnesium, zinc, iron, cobalt, nickel, manganese, chromium and mixtures thereof, x is the mole fraction of EL and often is at least 0.005, y is the mole fraction of aluminum and is at least 0.01, z is the mole fraction of phosphorus and is at least 0.01, and x + y + z is 1. When EL is a mixture of metals, x represents the total amount of the mixture of elements present. The preparation of various ELAPO molecular sieves is well known in the art and can be found in US 5,191,141 (ELAPO); US 4,554,143 (FeAPO); US 4,440,871 (SAPO); US 4,853,197(MAPO, MnAPO, ZnAPO, CoAPO); US 4,793,984 (CAPO); US 4,752,651 and US 4,310,440. Representative ELAPO molecular sieves include ALPO and SAPO molecular sieves.

Other solid acid promoters include carbon black or activated carbon, which may optionally be acidified to introduce an acid of desired densityFunctional groups (e.g., by treatment with an appropriate reagent bearing functional groups (e.g., nitric acid, acetate, sulfonic acid, etc.)). As such, these promoters may be generally referred to as acidic carbon or acidic activated carbon. The term "activated carbon" refers to a form of carbon that has been treated according to known techniques (e.g., steaming) to increase its surface area and pore volume. Similarly, such co-catalysts may comprise resins, such as ion exchange resins having acid functional groups. For example, Amberlyst^TMThe resin in the polymeric catalyst set has sulfonic acid functional groups. The other resin comprisesThose in the group. If necessary, the acidity of any of the types of solid acid promoters described herein can be adjusted or reduced by treatment with a base such as ammonia or pyridine. For example, zeolite ZSM-5 may be prepared by reaction with NH₃Contact to at least partially convert to its ammonium form, thereby reducing acidity relative to the hydrogen form of ZSM-5 to the desired level for a given reductive amination reaction. Thus, in general, the ammonium form or ammonium exchanged zeolites (e.g. NH)₄-ZSM-5 or NH₄-BEA) may be used as acid co-catalyst, particularly those in which providing these forms of ammonia adsorption weakens the lewis acid strength such that the lewis acid site density is adjusted or reduced to a value within the range given above. Alternatively, such adjustment or reduction of acidity may occur in situ in the reaction mixture, and in particular in the presence of an aminating agent such as ammonium hydroxide. Still other solid acid promoters useful in the present invention may comprise metal oxides such as any one or more of silica, alumina, titania, zirconia, magnesia, calcia, strontia, tin oxide, and the like. In the case of tin oxide, it may be present in hydrated and/or acidic form, for example in the form of metastannic acid or stannous acid.

Metal oxides are also described above in the context of being useful as solid supports for hydrogenation-active metals. Thus, it will be more generally understood that the "hydrogenation catalyst" and the "acid promoter" need not be present as separate catalysts, but may be present together in the form of particles of a solid, bi-functional catalyst. In such a dual-function catalyst, (i) any "hydrogenation catalyst" or component thereof as described above may be present as the hydrogenation active component of such a dual-function catalyst, and (ii) any "acid promoter" or component thereof as described above may be present as the acidic component of such a dual-function catalyst. For example, the bifunctional catalyst may comprise any of the one or more hydrogenation-active metals described above (e.g., nickel) deposited on any of the solid acid promoters described above (e.g., zeolites or metal oxides). The hydrogenation-active metal may be present in such a dual-function catalyst in the amounts given above (e.g., at least 5 wt-%, based on the weight of the dual-function catalyst), or in a possibly lower amount (e.g., at least 2.5 wt-%, based on the weight of the dual-function catalyst) as a hydrogenation-active ingredient due to the integration of the two catalysts. The solid acid promoter, as the acidic component, may have a density of lewis acid sites in the range given above (e.g., from 50 to 2000 μmol/g), or possibly in a lower range (e.g., from 25 to 1000) due to the integration of the two catalysts.

The acid promoter, and in particular the lewis acid, may be homogeneous in the reaction mixture, typically such that both the promoter and the reaction mixture are in the liquid phase (e.g., where the promoter is dissolved). According to a specific embodiment, the cocatalyst is dissolved in an aqueous liquid reaction mixture comprising aqueous ammonia (ammonium hydroxide) as aminating agent. A representative soluble acid co-catalyst is the metal triflate, otherwise known as metal triflate. Specific examples include the triflates of 15 lanthanides, and the triflates of scandium and yttrium. According to particular embodiments, the triflate salt co-catalyst may be selected from the group consisting of: bismuth triflate (Bi), gallium triflate (Ga), copper triflate (Cu), europium triflate (Eu), silver triflate (Ag), indium triflate (In), cerium triflate (Ce), gadolinium triflate (Gd), erbium triflate (Er), aluminum triflate (Al), and mixtures of any two or more of these triflates. Other examples of co-catalysts that act as homogeneous lewis acids include ammonium compounds other than ammonium hydroxide when used as aminating agents. Ammonium acetate and ammonium chloride are exemplary.

Aspects of the invention relate to improvements in processes for reductive amination of glycolaldehyde resulting from the use of an acid promoter, whether the acid promoter is solid (heterogeneous) in the reaction mixture, liquid (homogeneous) in the reaction mixture, solid and separate from the hydrogenation catalyst, or solid and integral with the hydrogenation catalyst. Specific improvements are increased selectivity to the desired compound monoethanolamine, and/or decreased selectivity to undesired by-products such as the dimerization by-product diethanolamine and/or the hydrogenation by-product ethylene glycol. The amount of acid promoter used to achieve a given effect (e.g., selectivity improvement) depends on the particular acid promoter used and a given set of reductive amination conditions, and with the knowledge gained from this disclosure, one skilled in the art can determine the appropriate amount in each case. Generally, any of the above-described acid promoters or combinations of acid promoters may be present in the reaction mixture comprising the hydrogenation catalyst and a solvent such as water, typically in an amount or combination of amounts from 0.1 wt-% to 99 wt-%. More typically, the co-catalyst may be present in an amount of from 0.1 wt-% to 20 wt-%, such as from 0.3 wt-% to 15 wt-% or from 0.5 wt-% to 10 wt-%, or a combination. In the case of a continuous process, the acid promoter may be present in an amount necessary to achieve a Weight Hourly Space Velocity (WHSV) relative to the catalyst, as described below. The acid promoter, as well as the hydrogenation catalyst, and optionally the bifunctional catalyst having an integral component as described herein, can be prepared by any method known in the art, including, for example, impregnation/incipient wetness, co-precipitation, or hydrothermal methods.

Thus, the representative process is characterized by a higher selectivity to monoethanolamine relative to conventional processes in which the above-described acid co-catalyst is absent or, if present, not used in the manner described above and exemplified below. According to particular embodiments, glycolaldehyde may be converted to monoethanolamine with a molar selectivity of 45% or higher to 98% or lower, in other embodiments 55% or higher to 94% or lower, and in other embodiments 70% or higher to 90% or lower. In particular embodiments, the molar selectivity to MEA is at least 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, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, or 98 percent. Such selectivity may be associated with a lower selectivity to the dimeric by-product diethanolamine. According to particular embodiments, glycolaldehyde may be converted to diethanolamine with a molar selectivity of less than 20%, less than 10%, or less than 5%, such as less than 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8,7, 6, or 5%. Alternatively, the selectivity improvement can be characterized relative to a reference molar selectivity obtained from a reference process in which all reductive amination conditions (e.g., pressure, temperature, residence time, feed (including amine), catalyst, etc.) are the same except for the absence of an acid promoter. According to a specific embodiment, glycolaldehyde may be converted to monoethanolamine with a molar selectivity that exceeds a reference molar selectivity by at least 3%. That is, where the reference molar selectivity is 50%, the use of an acid co-catalyst results in an increase to a molar selectivity of at least 53%. In other embodiments, glycolaldehyde may be converted to monoethanolamine with a molar selectivity of at least 5%, or even at least 10%, such as at least 3, 4,5, 6, 7, 8, 9, or 10 percent over a reference molar selectivity. Those skilled in the art will appreciate that even modest increases in selectivity may result in substantial economic benefits on a commercial scale.

The above molar selectivity can be obtained at high conversion levels 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%, thus at least 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, or 99 percent. Thus, representative yields of monoethanolamine may be the same or substantially the same as the molar selectivity ranges given above, such as from 45% or more to 98% or less, in other embodiments from 55% or more to 94% or less, or in other embodiments from 70% or more to 90% or less of the theoretical yield that can be obtained, assuming the yield is determined as the product of conversion and selectivity.

Typical reductive amination conditions include an elevated hydrogen partial pressure, such as at least 3 megapascals (MPa) (435psi), which (in combination with a hydrogenation catalyst and an acid promoter) provides a reductive amination environment for effecting the selective conversion of glycolaldehyde to the product monoethanolamine. This hydrogen pressure may be contained in a reactor for contacting a feed (e.g., an aqueous feed comprising glycolaldehyde) and an aminating agent (e.g., aqueous ammonia) with a catalyst (or a bifunctional catalyst as described above) to obtain this product. The reaction mixture to which the feed and aminating agent are added and from which the product mixture is removed (e.g., after separation from the catalyst) is preferably aqueous and contains dissolved hydrogen under reductive amination conditions. As noted above, the acid promoter may be homogeneous or heterogeneous in the reaction mixture. In addition to or instead of aqueous ammonia, the aminating agent may additionally comprise gaseous ammonia which may be added to the reactor batchwise or continuously, for example, in the case of continuous operation, it may be added together with hydrogen or a recycle gas stream (comprising hydrogen). The addition of gaseous ammonia will typically result in the in situ formation of aqueous ammonia in the presence of the aqueous reaction mixture. Other possible aminating agents include those of the formula NHR¹R²Primary and secondary amines of (1), wherein R¹And R²At least one of them is C₁-C₃An alkyl group. Glycolaldehyde and the aminating agent may be charged to the reactor in batches or otherwise added continuously to the reactor with a molar excess of aminating agent, for example, wherein the molar ratio of aminating agent to glycolaldehyde is from 2:1 to 20:1 or from 5:1 to 15: 1.

Reductive amination conditions (the reaction mixture is kept at it during the production of monoethanolamine) include elevated pressures and hydrogen partial pressures. Representative absolute reactor pressures are in the range of typically 2.07MPa (300psi) to 24.1MPa (3500psi), typically 3.45MPa (500psi) to 20.7MPa (3000psi), and often 5.17MPa (750psi) to 10.3MPa (1500 psi). The reactor pressure may be primarily or substantially generated by 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 agents and other gaseous species vaporized from the reaction mixture may result in a reduction in hydrogen partial pressure relative to these total pressures, such that, for example, the hydrogen partial pressure may be generally in the range of 1.38MPa (200psi) to 22.4MPa (3250psi), typically 3.00MPa (435psi) to 20.0MPa (2901psi), and often 4.82MPa (700psi) to 9.31MPa (1350 psi).

Other reductive amination conditions present in the reactor include temperatures generally from 20 ℃ (68 ° F) to 200 ℃ (392 ° F) and typically from 50 ℃ (122 ° F) to 150 ℃ (302 ° F). The reaction time, i.e., the time under pressure and temperature conditions to maintain the reaction mixture at any target value or target subinterval within any range of pressures and temperatures given above (e.g., a target total pressure value of 8.27MPa (1200psi) and a target temperature of 85 ℃ (185 ° F)) is from 0.5 hours to 24 hours, and preferably from 1 hour to 5 hours, in the case of a batch reaction. For a continuous process, these reaction times correspond to the reactor residence time. Another parameter relevant for a continuous process is the Weight Hourly Space Velocity (WHSV), which is understood in the art as the feed to the reactor (e.g., comprising glycolaldehyde and NH₄An aqueous feed of OH) divided by the catalyst weight (e.g., the combined weight of the hydrogenation catalyst and the acid promoter, or the weight of the dual-function catalyst). Thus, this parameter represents the equivalent catalyst bed weight of feed processed per hour and is related to the inverse of the reactor residence time. According to representative embodiments, the reductive amination conditions include WHSV (typically from 0.01 hr)^-1To 20hr^-1And typically from 0.05hr^-1To 5hr^-1). However, with respect to the acid promoter alone, these ranges may be higher, e.g., typically from 0.02hr^-1To 40hr^-1And typically from 0.1hr^-1To 10hr^-1。

As noted above, a continuous process (e.g., a continuous fixed bed process) can be more compatible with heterogeneous acid promoters (e.g., comprising molecular sieves, activated carbon, metal oxides, or resins, having a desired Lewis acid site density). Such a continuous process may be carried out by continuously feeding glycolaldehyde, aminating agent and hydrogen to a reaction mixture comprising catalyst and contained in the reactor, and continuously withdrawing from the reactor a product mixture comprising monoethanolamine and substantially free of catalyst. This product mixture can then be further processed by separating portions of the product mixture to purify and recover monoethanolamine and optionally recycling unconverted reactants (e.g., aminating agent and/or hydrogen). According to one embodiment, the product mixture may be subjected to flash separation to separate a vapor phase comprising primarily hydrogen, at least a portion of which (e.g., after 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 containing the desired monoethanolamine may be subjected to any of a number of possible separation steps including one or more of the following: phase separation, extraction (e.g., using an organic solvent having a preferential affinity for monoethanolamine), and distillation, in any order, one after the other. Alternatively, the extraction and distillation may 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 batch-wise or continuously, particular embodiments relate to a method for producing monoethanolamine comprising performing a reductive amination of glycolaldehyde added to an aqueous reaction mixture with aqueous ammonia as a reactant. This can be done by contacting the reaction mixture and hydrogen with both the hydrogenation catalyst and the acid promoter (e.g., contacting both catalysts simultaneously) under reductive amination conditions as described above. Advantageously, the components of the combined catalyst or otherwise combined bifunctional catalyst catalyze reductive amination to produce monoethanolamine according to any of the above conversion, selectivity, and yield performance criteria, e.g., a yield of at least 70% of theoretical yield.

According to further embodiments, the production of monoethanolamine may be integrated with upstream and/or downstream processing steps in the overall production of biomass-derived chemicals, for example. In the case of integration with upstream processing, glycolaldehyde may be obtained from the pyrolysis of aldoses or ketoses (e.g., glucose, fructose, or sucrose). In the case of downstream processing, a representative process can further include sulfating at least a portion of the monoethanolamine (e.g., after it is recovered from the product mixture described above) to produce 2-aminoethylsulfuric acid. A convenient sulfating agent for this conversion is sulfuric acid, and the sulfuric acid ester of this first conversion step is advantageously prepared under conditions wherein the co-produced water is removed from the reaction mixture as quickly and completely as possible, driving the equilibrium toward 2-aminoethylsulfuric acid production. In such cases, representative methods can also include sulfonating at least a portion of the 2-aminoethylsulfuric acid (e.g., after its recovery from the product mixture obtained from sulfation) to produce taurine. A suitable agent for the sulfonation step, which is carried out under continuous heating in aqueous solution, is sodium sulfite. A representative two-step process (with details of the synthesis conditions for each step) is described, for example, by Bondareva et al, Pharmaceutical Chemistry Journal, 42(3), 142-144. In this way, a viable method for the synthesis of taurine from renewable carbon sources was established.

The following examples are presented as representative of the invention. These examples should not be construed as limiting the scope of the invention as other equivalent embodiments will be apparent in light of the disclosure and the appended claims.

Example 1

EXAMPLE 1 Al-triflate cocatalyst Synthesis of monoethanolamine from glycolaldehyde

The following were charged to a 100ml parr reactor made of hastelloy: at 20ml of NH₄1 g glycolaldehyde dimer in OH (28%), 1.5 g wet Raney nickel (Grace, W.R.Grace)&Co.)) and 0.18 g of aluminum tris (trifluoromethanesulfonate) (Al-trifluoromethanesulfonate). Using reactor N₂Purge twice, and then charge 6.2MPa (900psi) H₂. The reaction mixture was stirred at 85 ℃ (185 ° F) at 1100rpm for 2 hours. After this period of time, the reactor was cooled to room temperature and the reaction mixture was filtered to separate the nickel catalyst from the colorless product mixtureIs separated out. The calculated yield of this mixture was 93% monoethanolamine, 2% ethylene glycol and 0.5% diethanolamine based on Gas Chromatograph (GC) analysis.

EXAMPLE 2 Synthesis of monoethanolamine from glycolaldehyde with Metal-triflate cocatalyst

Numerous experiments were performed to investigate the performance of various metal triflates (triflates) as dissolved (homogeneous) promoters. In each case, a feed containing 5 wt% glycolaldehyde dimer in 28% aqueous ammonia was reacted with fixed amounts of raney nickel and metal triflate in a high throughput screening batch reactor. Reference experiments were also conducted without the raney nickel catalyst or the metal triflate promoter, and with the raney nickel catalyst alone (without the metal triflate promoter). The catalytic reductive amination reaction was carried out in a sealed hydrogenolysis reactor at 85 ℃ (185 ° F) and under a hydrogen pressure of 8.27MPa (1200psi) for a 2 hour hold period. After separation from the solid catalyst, the reaction product was analyzed by GC. The results demonstrate that the use of metal triflate as a promoter can improve the selectivity of monoethanolamine compared to raney nickel alone. The results (including glycolaldehyde conversion levels, selectivity to by-products propylene glycol and ethylene glycol, and selectivity to monoethanolamine) are shown in figure 1.

EXAMPLE 3 Synthesis of monoethanolamine from glycolaldehyde with solid acid cocatalyst

Numerous experiments were conducted to investigate the performance of various solid (heterogeneous) acid promoters. In each case, a feed containing 5 wt.% glycolaldehyde dimer in 28% aqueous ammonia was reacted with a fixed amount of raney nickel and a solid acid promoter in a high throughput screening batch reactor. Reference experiments were also conducted using raney nickel catalyst alone (in the absence of a solid acid promoter). The catalytic reductive amination reaction was carried out in a sealed hydrogenolysis reactor at 85 ℃ (185 ° F) and under a hydrogen pressure of 8.27MPa (1200psi) for a 2 hour hold period. After separation from the solid catalyst, the reaction product was analyzed by GC. The results demonstrate that the use of solid acid promoters (including zeolites and solid acids such as acidified activated carbon and hydrated or acidic forms of tin oxide) can improve the selectivity to monoethanolamine and thus the yield of monoethanolamine compared to the use of raney nickel alone. The results of ethanolamine and diethanolamine yields for various solid acid promoters are shown in figure 2.

EXAMPLE 4 Zeolite Co-catalyst Synthesis of monoethanolamine from glycolaldehyde

Numerous experiments were conducted to investigate the performance of various zeolites as solid (heterogeneous) acid promoters. In each case, a feed containing 5 wt% glycolaldehyde dimer in 28% aqueous ammonia was reacted with a fixed amount of raney nickel and zeolite in a high throughput screening batch reactor. Reference experiments were also conducted using raney nickel catalyst alone (in the absence of zeolite). Another experiment was performed with raney nickel and ammonium acetate as homogeneous promoters. The catalytic reductive amination reaction was carried out in a sealed hydrogenolysis reactor at 85 ℃ (185 ° F) and under a hydrogen pressure of 8.27MPa (1200psi) for a 2 hour hold period. After separation from the solid catalyst, the reaction product was analyzed by GC. The results demonstrate that the use of zeolite (as a solid (heterogeneous) acid promoter) can improve the selectivity of monoethanolamine compared to the use of raney nickel alone. The results, including selectivity to monoethanolamine and selectivity to by-products ethylene glycol, ethylenediamine and diethanolamine, are shown in figure 3.

In general, aspects of the invention relate to increasing the selectivity of the reaction to monoethanolamine by reductive amination of glycolaldehyde, which can be achieved using various acid promoters. The efficiency and associated economics of the synthetic route from renewable feeds to high value chemicals are thereby improved. Those skilled in the art, having the benefit of this disclosure, will appreciate that various modifications can be made to the disclosed catalysts and methods to achieve these and other advantages without departing from the scope of the present disclosure. As such, it should be understood that the features of the present disclosure are susceptible to modification and/or substitution. The specific embodiments shown and described herein are for illustrative purposes only and do not limit the invention, as described in the appended claims.