Catalyst and process for the preparation of sugar alcohols

Abstract

Provided herein is a catalyst for the reduction of saccharides to form sugar alcohols. The catalyst comprises a base anion exchange resin and ruthenium. Further provided herein is a method for reducing a saccharide to a sugar alcohol, in which a solution of a saccharide comprising from five to twenty carbon atoms is contacted with hydrogen gas and a catalyst. The catalyst is a base anion exchange resin comprising ruthenium.

Description

[0001] DI83915-WO-PCT PATENT

[0002] TITLE OF THE INVENTION CATALYST AND PROCESS FOR THE PREPARATION OF SUGAR ALCOHOLS

[0003] Cross-reference to Related Application

[0004] The present application claims priority under 35 U.S.C. § 365(c) to U.S. Provisional Appln. No. 63 / 714,803, filed on October 31, 2024, which is incorporated herein by reference in its entirety.

[0005] Field of the Invention

[0006] This invention relates generally to a method for the preparation of sugar alcohols by the reduction of sugar moieties using base anion exchange resin catalysts that comprise a metal, preferably metal-supported base anion exchange resin catalysts.

[0007] Background of the Invention

[0008] Several patents, patent applications and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains. The entire disclosure of each of these patents, patent applications, and publications is incorporated by reference herein.

[0009] Reduction of glucose to sorbitol by hydrogenation using several transition metals as heterogeneous catalysts is known. For example, V.N. Sapunov et al., J. Phys. Chem. A, 2013, 117, 4073-4083, discloses reduction of glucose to sorbitol with ruthenium embedded in a hyper-crosslinked polystyrene matrix. However, this reference reports low conversions of glucose and also uses special procedures to embed ruthenium in the hyper-crosslinked polymer matrix. Chinese Patent Appln. Publn. No. 115043705 describes a noble metal catalyst comprising a polystyrene maleic anhydride copolymer supported on an inorganic carrier.

[0010] Reduction of glucose to sorbitol by hydrogenation using ruthenium as heterogeneous catalyst is also known. See, for example ‘The Process for Preparation of a Sugar Alcohol’ WO 2022 / 026262 Al by J. A. Trejo et al. Nevertheless, expanding the availability of heterogeneous reduction systems for saccharides, in particular those systems having higher activity, selectivity, and longer life, would be economically and environmentally beneficial.

[0011] Summary of the Invention

[0012] Accordingly, provided herein is a catalyst for the reduction of saccharides to form sugar alcohols. The catalyst comprises a base anion exchange resin and ruthenium.

[0013] Further provided herein is a method for the reduction of saccharides to form sugar alcohols. The method comprises steps of: a) providing a solution of a saccharide comprising from five to twenty carbon atoms; and b) contacting said solution with hydrogen gas and a catalyst; wherein said catalyst comprises a base anion exchange resin comprising ruthenium.

[0014] Detailed Description

[0015] All percentages are weight percentages (wt%), and all temperatures are in °C, unless otherwise indicated. Averages are arithmetic averages unless indicated otherwise. All operations are performed at room temperature (from 18 to 25 °C) unless specified otherwise. Percentages of copolymerized monomer repeat units are based on the total weight of dry polymer, i.e., dry ion exchange resin beads. The terms “(meth)acrylate” and “(meth)acrylic” mean acrylate or methacrylate, and acrylic or methacrylic, respectively. References to transition metals by name alone, e.g., “ruthenium”, refer to the zero-valent, elemental metals. When a series of values is described as acceptable lower limits of a range, and a different series is described as acceptable upper limits of the same range, then every pair of a value in the series of lower limits with a value in the series of upper limits is acceptable as endpoints of the range.

[0016] Provided herein is a metal-containing, preferably metal-supported base anion exchange resin catalyst. It has now surprisingly been found that these catalysts are more resistant to metal leaching, compared to metal-containing or metal-supported acid cation exchange resin catalysts. Advantageously, one result of this property is that the reactivity of the base anion exchange catalyst degrades more slowly under reaction conditions. A further advantage of this property is that it is environmentally beneficial, in that the contamination of wastewater by heavy metals is reduced.

[0017] The base anion exchange resin catalyst is in the form of beads. Preferably, the harmonic mean diameter of the ion exchange resin beads is at least 200 microns, preferably at least 300 microns, preferably at least 400 microns; preferably no greater than 1100 microns, preferably no greater than 1000 microns, preferably no greater than 900 microns, preferably no greater than 800 microns, preferably no greater than 700 microns. A collection of particles has a harmonic mean diameter (HMD) defined as follows: where n is the number of particles, and di is the diameter of the i particle. The particle diameters may be measured by any suitable method, such as, for example, by a commercially available particle size analyzer. In one preferred method, the particle diameters are measured using optical microscopy, by suspending the particles in a liquid and thinning the liquid suspension to examine a single layer of particles, and then comparing the individual particles in the single layer with standard particles of known diameter.

[0018] Preferably, the particle size distribution has a Uniformity Coefficient of at least 1.01, not greater than 1.2 for Uniform Particle Size (UPS) resins and not greater than 1.6 for Normal Particle Size distribution resins. The Uniformity Coefficient is the 60th percentile diameter of a collection of beads on a volumetric basis divided by the 10th percentile diameter. Normal particle size distribution resins are synthesized by mixing aqueous and monomer phases in a stirred reactor and polymerizing. UPS resins may be produced in a manner described in U.S. Patent No. 4,444,961, for example.

[0019] Useful ion exchange resins include strong acid cation exchange resins, weak acid cation exchange resins, strong base anion exchange resins, and weak base anion exchange resins. Preferably, the ion exchange resin is a base anion exchange resin, i.e., one having primary, secondary, tertiary or quaternary amine groups.

[0020] More preferred ion exchange resins are weak base anion exchange resins comprising tertiary amine groups, quaternary amine groups, or both tertiary and quaternary amine groups. Preferred ion exchange resins may be acrylic (>70 wt% polymerized units of acrylic monomers, preferably >85wt%) or styrenic (>70 wt% polymerized units of styrene or a substituted styrene, preferably >85wt%), based on the total weight of the dry ion exchange resin. Preferred amine functionality is tertiary amine such as methylene dimethylamine (R-CH2-N(CH3)2, wherein “R” represents the polymer chain). The weak base anion exchange resins described herein comprise from about 90 % equivalents / liter to about 100% equivalents / liter of tertiary amine functionality, and optionally a complementary amount up to 10% equivalents / liter of strong base functionality, such as quaternary amine groups, based on the total number of equivalents of base functionality in one liter of dry ion exchange resin.

[0021] Preferably, the base anion exchange resin is a macroporous resin (surface area > 5 m2 / g dry resin as measured by the BET technique), preferably a macroporous resin having more than 8 wt% polymerized units of crosslinker, preferably no more than 20 wt%, preferably no more than 15 wt%, preferably no more than 10 wt%; preferably at least 5 wt%, preferably at least 8 wt%, preferably at least 10 wt%, preferably at least 12 wt%, based on the total weight of the dry ion exchange resin. The terms “macroporous” and “macroreticular” are synonymous and used interchangeably herein. The term “gel” refers to a resin that is substantially free of macropores, that is, pores having a diameter of at least 20 Angstroms.

[0022] Preferred macroreticular resins have a surface area from 10 to 100 m2 / g, more preferably from 10 to 100 m2 / g, and still more preferably from 20 to 50 m2 / g. Preferred macroreticular resins have a total porosity of 0.1 to 0.9 cm3 / g, more preferably 0.2 to 0.7 cm3 / g, and still more preferably 0.25 to 0.5 cm3 / g with an average pore diameter of 50 to 2500 Angstroms and preferably from 150 to 1000 Angstroms, which is also measured by the BET technique.

[0023] Surface area, pore volume, micropore volume, and pore diameter measurements are typically measured by removing solvent / water and / or gas under vacuum, cooling the sample to 77 K and then dosing in nitrogen gas. Based on the adsorption of the gas at different pressures, the BET formula can be applied to determine the surface area of a material. General methods are described in detail in the NIST recommended practice guide : porosity and specific surface area measurements for solid materials available at https: / / nylpubs.nist.gov / nistpubs / '-17. , for example.

[0024] The techniques used herein to determine the surface area, pore volume, micropore volume, and pore diameter measurements are set forth in detail in European Patent No. 2 859 021. Briefly, these measurements were obtained by BET theory; specifically, the test method is as follows: 0.20 to 025 g of resin previously dried at 105 °C were transferred into sample tubes and degassed and further dried at 105°C under vacuum (50 mm) for a minimum of 1 night. After reweighing, the degassed samples were placed on a Micromeritics Tri Star 3000 Surface Area and Porosity Analyzer porosimeter, available from the Micromeritics Instrument Corporation of Norcross, GA. The N2 isotherms were obtained using 53 points with relative pressures from 0.01 to 0.998 on the adsorption curve and 45 points with relative pressures from 0.998 to 0.05 on the desorption curve. The surface area using the BET technique was obtained for points with relative pressures from 0.06 to 0.20. The total pore volume was obtained from the maximum quantity of gas adsorbed at a relative pressure of 0.998. Relative pressures are dimensionless values (P / Po). The micropore volume was estimated from a t-plot analysis. The mean diameter as calculated by 4V / A is the diameter of a uniform cylinder which has the same total pore volume and surface area as the resin sample.

[0025] Preferred crosslinkers include divinylbenzene, trivinylcyclohexane, TMPTMA (trimethylol propane trimethacrylate) and DEGDVE (diethylene glycol divinyl ether); preferably divinylbenzene. Preferably, the dry ion exchange resin comprises from 80 to 99 wt% polymerized units of at least one monofunctional monomer. Preferred monofunctional monomers include vinyl aromatic monomers (e.g., styrene, methylstyrene, ethylstyrene, a-methyl styrene; preferably styrene) and acrylic monomers (alkyl (meth)acrylates, (meth)acrylic acid). The base anion exchange resin also comprises a complementary amount, that is, from 1 to 20 wt%, of at least one copolymerized crosslinker. As used herein, the terms “complementary” and “complementarily” refer to amounts whose sum is 100%. For example, in this instance the sum of the weight percentages of the copolymerized repeat units of monofunctional monomer and of crosslinkers is 100 wt%, based on the total weight of the dry ion exchange resin.

[0026] The counterions that may be bound ionically to the strong base anion functional groups are CT, SO4 , HCCh', NOs’, F’, SOs', or combinations of two or more of these anions. In the weak base anion exchange resins, there is no counterion for the tertiary amine groups, which are in free base form. Methods for introducing amine functionality into crosslinked styrene-divinylbenzene copolymers to form base anion exchange resins are well known and described in detail in Kunin, Robert. Ion Exchange Resins. United States: R.E. Krieger, 1990, for example.

[0027] When the base anion exchange resin comprises water (“wet resin”), the water content is preferably from 40 to 70 wt%; preferably at least 40 wt%, preferably no more than 70 wt%, based on the total weight of the wet resin. Complementarily, the remainder of the weight of the wet resin is the dry ion exchange resin. Also preferably, the base anion exchange resin consists of, or consists essentially of, the base ion exchange resin in weak base form and optionally water.

[0028] As used herein, the term “water retention capacity” (“WRC”) refers to the amount of water held by a fully swollen and drained ion exchange resin, expressed as a percentage of its total wet weight. This capacity is influenced by the resin's porosity and its degree of cross-linking, which affects both its moisture content and its performance in water treatment. Suitable ion exchange resins have a WRC of from 20 to 80 wt%; preferably from 30 to 60 wt%; and more preferably from 40 to 50 wt%.

[0029] As used herein with respect to an ion exchange resin, the term “exchange capacity” refers to the number of acid or base equivalents per liter of the ion exchange resin. This quantity is normally determined after converting the resin by chemical regeneration techniques to a given ionic form. An ion exchange resin may be characterized by a number of exchange capacities. For example, in the basic ion exchange resins that are preferred for use in the compositions and processes described herein, the weak base exchange capacity is the number of equivalents of sites that interact with conjugate acids having a pH from 0 to 7 per liter of ion exchange resin, and the strong base exchange capacity is the number of equivalents of sites that interact with conjugate acids having a pH from 0 to 14 per liter of ion exchange resin. Preferably, a hydrated styrenic ion exchange resin has weak base sites, strong base sites, or both weak and strong base sites in an amount of from 0.7 to 2.0 eq / liter of resin; preferably at least 1.4 eq / liter; preferably no more than 2.0 eq / liter. Stated alternatively, the strong base exchange capacity, the weak base exchange capacity, or the total exchange capacity of a suitable ion exchange resin is from 0.7 to 2.0 eq / liter of resin; preferably at least 1.4 eq / liter; preferably no more than 2.0 eq / liter.

[0030] Preferably, the total loading of ruthenium in the base anion exchange resin catalyst is from 0.2 to 20 wt. %; preferably at least 0.5 wt. %, preferably at least 1 wt. %, preferably at least 2 wt. %, preferably no more than 20 wt. %, preferably no more than 10 wt. %, preferably no more than 7 wt. %, preferably no more than 5 wt. %, wherein the weight percentages are based on the total weight of the ruthenium -loaded dry resin. Alternatively, the total loading of ruthenium in the base anion exchange resin catalyst is 0.5 to 8wt%, 0.5 to 5.0 wt%, or 1.0 to 3.0 wt%, based on the total weight of the dry base anion exchange resin. Also preferably, the base ion exchange resin catalyst consists of, or consists essentially of, the base ion exchange resin in weak base form, the ruthenium, and optionally water.

[0031] Preferably, the catalyst is prepared by contacting the base anion exchange resin with an aqueous solution of the metal salt(s), followed by reduction of the metal ion(s) with a reducing agent. Preferred metal salts include salts of Ru(II), Ru(III), or Ru(IV), or combinations of two or more of these ruthenium oxidation states. More preferred salts include, without limitation, one or more of ruthenium(III) trichloride, hexaammineruthenium(III) chloride; ruthenium(III) acetylacetonate; dichloro(l,5- cyclooctadiene)ruthenium(II), potassium hexachlororuthenate(IV) and ruthenium(III) nitrosyl nitrate. Preferred reducing agents include sodium borohydride, hydrogen, hydrazine, formaldehyde, lithium aluminum hydride, and a combination of two or more of these reducing agents; preferably sodium borohydride, hydrogen, or both sodium borohydride and hydrogen. The metal ion(s) may be reduced to a lower positive valence state than they had in the original metal salt(s) in solution, or they may be reduced to zero-valent metal(s). Preferably, the catalyst comprises zero- valent metal.

[0032] Any form of association of the ruthenium with the base ion exchange resin is suitable to form the catalyst described herein. For example and without limitation, one or more of the following conditions may occur: the resin may be impregnated with the ruthenium; the ruthenium may be chemisorbed to the ion exchange resin support; the ruthenium may be coordinated with one or more base functional groups; the ruthenium and the resin may be subject to a charge-charge interaction; the ruthenium and the resin may be subject to a charge-induced charge interaction; particles of the ruthenium may be embedded on the surface or within the pores of the resin beads; or the particles of ruthenium may be physically confined, i.e. by their size, to the resin’s pores. The ruthenium is said to be supported on the base ion exchange resin, i.e., it is a ruthenium-supported base ion exchange resin catalyst, regardless of the means or mechanism by which the ruthenium and the base ion exchange resin are associated to form the catalyst. Preferably, the ruthenium is in the form of a uniformly dispersed, chemisorbed ruthenium cluster or clusters supported on the base ion exchange resin. The term “cluster” as used herein refers to a group of two or more metal atoms in which there are substantial and direct bonds between the metal atoms. See, e.g., Cotton and Wilkinson, Advanced Inorganic Chemistry, (digitized, 2008).

[0033] Further provided herein is a process for reducing a saccharide to form a sugar alcohol. In the process described herein, a saccharide solution or “feedstock” is contacted with the metal -containing base anion exchange resin catalyst. The saccharide solution is preferably an aqueous solution, i.e., a solution in which the primary solvent is water. Preferably, the aqueous solvent comprises at least 50 vol% water, preferably at least 75 vol%, preferably at least 90 vol%. The optional secondary solvent(s), which are present in a volume that is complementary to the volume of water, are selected from the group consisting of alkyl alcohols, preferably branched or unbranched Cl to C4 alkyl alcohols such as ethanol, methanol, propanol, isopropanol, butanol, sec-butanol, and t-butanol.

[0034] Preferably, the concentration of saccharide in the feedstock is from 10 to 90 wt%, from 10 to 75 wt%, from 10 to 60 wt%, preferably from 30 to 50 wt%, or from 2 to 55 wt%, based on the total weight of the saccharide solution. The weight of the solvent(s) is complementary to the weight of the saccharide in the saccharide solution. Preferably, the saccharide solution consists of or consists essentially of the saccharide(s) and the solvent(s), except when a portion of the reaction mixture or of the exit stream is recycled into the feed stream, in which case the saccharide solution may also comprise reaction products and by-products.

[0035] A saccharide is a chemical typically with a formula of (CH2O)m. Typically one end group of the carbon chain will have a ketone group when in an open chain form. Singular units can come together to form di-, tri-, oligo-, and polysaccharides depending on the number of saccharide units in the structure. Any saccharide that is capable of reduction by the catalyst described herein is suitable for use in the processes described herein. Preferably, the saccharide comprises from five to twenty carbon atoms; preferably at least six carbon atoms; preferably no more than 18 carbon atoms, preferably no more than 17, preferably no more than 16, preferably no more than 15, preferably no more than 12 carbon atoms.

[0036] Preferred saccharides include, without limitation, reducing sugars. More preferred reducing sugars and other more preferred saccharides include, without limitation, isomaltulose, erythrose, ribose, arabinose, xylose, lyxose, glucose, fructose, maltose, lactose, mannose, galactose, sedoheptulose, mannoheptulose, and sucrose; still more preferred are glucose, fructose, mannose, lactose, and xylose; still more preferred is glucose. Preferably, the saccharide is a monosaccharide or polysaccharide; more preferably a monosaccharide or disaccharide; still more preferably a monosaccharide.

[0037] The product of the catalytic reaction described herein is a sugar alcohol. Suitable sugar alcohols are the reduction product of the reaction of a saccharide and hydrogen to convert a ketone to an alcohol group. Preferred sugar alcohols include, without limitation, the reduction products of the preferred saccharides listed above. More preferred sugar alcohols are isomalt, erythritol, mannitol, lactitol, xylitol, sorbitol, and maltitol. Sorbitol is a particularly preferred sugar alcohol, which may be produced by the reduction of glucose.

[0038] In the processes described herein, the saccharide in solution is reduced by reaction with hydrogen in the presence of the catalyst. Preferably, the hydrogenation is carried out at a process temperature of from 25 to 180 °C; preferably at least 40 °C, preferably at least 60 °C, preferably at least 80 °C, preferably at least 100 °C; preferably no greater than 170 °C, preferably no greater than 160 °C, preferably no greater than 150 °C. The temperature of the reaction solution, of a slurry of the reaction solution with the catalyst beads, or of the reaction bed is measured.

[0039] Preferably, the hydrogenation is carried out at a hydrogen pressure from 40 to 1000 psi (275 kPa to 7 MPa); preferably at least 60 psi (410 kPa), preferably at least 100 psi (690 kPa), preferably at least 150 psi (1.0 MPa), preferably at least 200 psi (1.4 MPa); preferably no greater than 700 psi (4.8 MPa), preferably no greater than 600 psi (4.2 MPa), preferably no greater than 500 psi (3.5 MPa), preferably no greater than 400 psi (2.8 MPa). Preferred reaction times may vary from 0.25 to 15 hours, preferably 0.5 to 5 hours. Preferred reaction or residence times may vary from 0.25 to 15 hours, preferably 0.5 to 5 hours for batch and continuous stirred tank reactors. In addition, the Liquid Hourly Space Velocity (LHSV) of the feedstock is preferably from 0.1 to 10 h’1, preferably 1 to 7 h'1for fixed bed or trickle bed reactors. The term “LHSV” is defined as the volume of liquid feed at 60°F / hr) / volume of reactor or catalyst. Preferred pressures, times and temperatures as described above are not considered to be critical parameters (especially upper limits on time and pressure) and the combination of these parameters may be adjusted by one skilled in the art to achieve the desired conversion and reaction time efficiently.

[0040] The hydrogenation may be conducted in batch mode using a stirred tank reactor. When the batch reaction is judged to be sufficient or complete, the product solution comprising the solvent(s), the unreacted saccharide(s), and the sugar alcohol(s) is removed from the catalyst by one or more suitable means, including, for example, filtration, decanting, cannulation, or the like. The sugar alcohols may then be isolated from the product solution by one or more suitable means, such as crystallization, column chromatography, or the like.

[0041] Alternatively, the hydrogenation may be conducted in continuous mode using a single continuous stirred tank or a series of continuous stirred tank reactors, in a continuous slurry bubble column reactor, in a trickle bed reactor, in a continuous singular or multitubular reactor, loop reactor (BUSS-loop reactor), micro-fluidic reactor or in a fluidized bed reactor. Preferably, a continuous method for making a sugar alcohol, e.g. sorbitol, utilizes a mixing vessel and a fixed bed catalytic reactor containing a metal supported base anion exchange resin catalyst. An aqueous solution of a saccharide, as described above, here glucose, is introduced into the mixing vessel. Hydrogen is co-fed or sparged in the saccharide solution in the mixing vessel. Preferably, the saccharide (glucose) solution with the added hydrogen is pumped into the fixed bed catalytic reactor. The desired product (here sorbitol) generated in the fixed bed reactor in the aqueous solution exits the process as the product solution, optionally as part of an exit stream that may be recycled back into the process, for example by combining it with the saccharide solution.

[0042] Advantageously, the catalysts described herein exhibit superior performance stability. In particular, after extended runs, there is little or no deactivation. For example, the amount of ruthenium that leaches away from the resin support or is sintered or deactivated by other means is small. Preferably, in continuous process, the amount of ruthenium in the accumulated product stream is less than 50 ppm, less than 30 ppm, less than 20 ppm, or less than 10 ppm, after processing 120g of glucose per gram of catalyst, where the catalyst comprises 5 wt% of ruthenium based on the total weight of the dry resin. The “accumulated product stream” is the total volume of liquid that was contacted with the catalyst, whether in a batch or continuous process. Also preferably, in a batch process, the amount of ruthenium in the product solution is less than less than 20 ppm, less than 10 ppm, less than 5 ppm, less than 2 ppm, or less than 1 ppm, after processing 6.25g of glucose per gram of catalyst, where the catalyst comprises 5 wt% of ruthenium based on the total weight of the dry resin.

[0043] The following examples are provided to describe the invention in further detail. These examples, which set forth specific embodiments and a preferred mode presently contemplated for carrying out the invention, are intended to illustrate and not to limit the invention.

[0044] EXAMPLES

[0045] I. Materials

[0046] Table 1. Properties of Polymeric Support

[0047] Notes for Table 1: a) These ion exchange resins are available from DuPont de Nemours, Inc., of

[0048] 5 Wilmington, DE. b) Acronyms: SAC- Strong Acid Cation, WAC - Weak Acid Cation, WBA - Weak Base Anion, and SBA - Strong Base Anion.

[0049] II. Methods a. Quantitative Analysis and Other Methods:

[0050] 10 Method 1 : HPLC Method

[0051] A sample was injected into the column under the following conditions:

[0052] Aminex™ HPX-87C column available from Bio-rad Laboratories, Inc., of Hercules, CA, temperature for column at 80 °C; Agilent 1260 RID HAS detector, temperature: 50 °C, flow rate: 0.4 mL / min; HPLC Grade H2O from Fisher Scientific of Waltham, 15 MA and injection volume: 2 pL. The instrument used was an Agilent technologies

[0053] 1260 Infinity II available from Agilent of Santa Clara, CA. Calibration of areas and concentrations were done using standards from Sigma Aldrich of St. Louis, MO for Sorbitol, Mannitol, Glucose, and Fructose and other peaks found as side products were reported as unknown. Reaction samples were typically diluted in a 4: 1 ratio (DI Water: Reaction Solution).

[0054] Calculations using HPLC data used the following equations:

[0055] • Conversion (%) = 100 - [ Glucose (at time x) / Glucose (at time 0) ] * 100

[0056] • Selectivity (%) = Sorbitol (peak integration) / (Sum of all peak integrations - Glucose peak integration ) *100

[0057] • Yield (%) = Conversion (%) * Selectivity (%) / l 00

[0058] Method 2. ICP for Ruthenium Quantification

[0059] Apparatus: Thermo ICAP 7600 Due ICP-OES, available from Thermo Fisher Scientific of Waltham, MA, and Milestone UltraWAVE microwave digestion system, available from Milestone, Inc., of Shelton, CT.

[0060] Procedure

[0061] 0.10 g sample was weighed by analytical balance. 2 ml Optima™ grade HNO3 + 1 ml Optima™ grade HC1, both available from Fisher Scientific, were added to each sample. Two replicates were prepared. High temperature digestion method and glass tube were used for microwave. Digested sample was diluted to 50 ml with deionized (DI) water. Samples were filtered and supernatant was measured if particulates were observed. Hps 68 A multi-element solution from Millipore Sigma of Burlington, MA, was used to prepare standards based on requested element list and concentration range. Rhodium was used as an internal standard. Ruthenium content of the catalysts and of the sugar solutions is reported as the average of three measurements obtained from the sample and the two replicates.

[0062] Calibration

[0063] Calibration curves for each element of interest were prepared by measuring the intensity of the signal vs. the known concentration of matrix matched standards. The detection limits (DL) for each element were calculated by the instrument software based on the calibration curve and a blank solution. The DL for different elements will vary based on instrument parameters and sample dilution factor. The correlation coefficient (R2) for all the measurements was determined to be greater than 0.998 for the calibration curve.

[0064] Calculation

[0065] The samples were analyzed by comparing the measured elemental intensities to the elemental calibration curves and multiplying by the dilution factor. The equation is shown below.

[0066] Concentration = calculated reading x dilution factor

[0067] Method 3. Catalyst Synthesis: Metal Loading and Reduction a. Preparation of Metal-supported Ion-Exchange Resin Catalysts Commercial ion exchange resins (e.g. AmberLite™ FPC88 UPS, Amberlyst™ A21, AmberLite™ MAC-3) and aqueous RuClrxlUO solutions were used to prepare supported metal ion-exchange resin catalysts. The weak and strong base anion exchange resins used as supports for the metal have a majority of functional groups in the free base form. The next general process, once the metal salt has been loaded on the resin, is the Ruthenium salt reduction to a lower oxidation state or to the zero valence state following one of the following procedures: a) Hydrogenation or b) NaBH4 solution. b. Metal Loading by Ion Exchange in Water:

[0068] An aqueous slurry solution containing ion exchange resin was made. An aqueous Ruthenium salt solution was prepared by solubilizing the salt in deionized water. Both solutions were put in contact for 24 h under agitation at room temperature. At the end of the process, the liquid was siphoned out from the reactor and the resin was then water washed with excess water (at least 10 BV), drained, dried on a Buchner funnel, and stored in a sealed container. The amount of Ru salt and ion exchange resin was calculated to achieve the loading in a range of 1 to 5 wt% Ru, based on the total weight of the dry ion exchange resin. c. Reduction of Ruthenium Salt Loaded Ion Exchange Resin: i. Reduction with Sodium Borohydride

[0069] A ruthenium salt loaded ion exchange resin catalyst was placed in a round bottom flask, and sufficient deionized (“DI”) water to create a suspension was added. The suspension while stirring was cooled to 2 °C using an ice bath with a nitrogen sweep through the system. A solution of 12 wt% sodium borohydride (20 equivalents) in 14 M sodium hydroxide was added to the mixture slowly over the course of 15 minutes and then left to react over 12 hours at room temperature. The resin was washed with excess deionized water (at least 10 BV of DI H2O) to a neutral pH. ii. Reduction with Flowing H2

[0070] A stainless-steel tube was packed with layers of material in the following order: glass beads, glass wool, ruthenium-loaded ion exchange resin, glass wool, glass beads, and glass wool, with a thermocouple in the middle of the tube. The tube was connected to an inlet and exit system. Dry nitrogen was flowed through the system using a mass flow controller set to 100 seem with a back pressure regulator set to 100 psig (586.1 kPa). The term “seem” refers to “standard cubic centimeters per minute,” that is, the volume of the gas, as measured at one atmosphere of pressure and 0°C, that is flowed into the reactor in one minute. The system was heated to 100 °C and held for 12 hours under nitrogen flow to dry the catalyst. For the length of the following 12 hours, the system was heated to 140 °C, nitrogen flow was stopped, and hydrogen was introduced for 4 hours at 100 seem using a mass flow controller. After 4 hours, the hydrogen flow was stopped, and dry nitrogen was flowed through the system at 100 seem to produce the active catalyst, which was cooled to room temperature under nitrogen flow and stored under dry nitrogen.

[0071] III. Experiments and Results

[0072] Comparative Example 1. Ruthenium loading on strong acid cation resin (AmberLite™ FPC88UPS Na).

[0073] In a 4-neck round bottom flask equipped with an overhead stirrer, 109 g of AmberLite™ FPC88 UPS H and 150 mL of DI water were added. In a separate flask, 7.8 g of ruthenium trichloride hydrate was added to 150 mL of DI water. The flask was heated to 40 °C and stirred to fully dissolve the ruthenium trichloride hydrate. The ruthenium trichloride solution was added slowly to the stirring resin mixture over the course of 5 minutes. The reactor was sealed and left to stir at 40 °C for 24 hours. After 24 h, the solution was removed and the resin was washed three times with 500 mL of DI water for 1 hour each time. Ruthenium content as measured by ICP was 5 wt% based on the total weight of the dry ion exchange resin.

[0074] Example 2.- Ruthenium loading into the Weak Base Ion Exchange Resin

[0075] In a 4-neck round bottom flask equipped with an overhead stirrer, 109 g of AmberLite™ FPA66 UPS and 150 mL of DI water were added. In a separate flask, 7.8 g of ruthenium trichloride hydrate was added to 150 mL of DI water. The flask was heated to 40 °C and stirred to fully dissolve the ruthenium trichloride hydrate. The ruthenium trichloride solution was added slowly to the stirring resin mixture over the course of 5 minutes. The reactor was sealed and left to stir for 24 hours at 40 °C. After 24 h the solution was removed and the resin was washed three times with 500 mL of DI water for 1 hour each time. Ruthenium content in the resin as measured by ICP was 5 wt% based on the total weight of the dry ion exchange resin.

[0076] Example 3. NaBELt Reduction of Ru(III) to Ru(0) on AmberLite™ FPA66UPS resin.

[0077] 36.1 g of AmberLyst™ or AmberLite™ ion exchange resins loaded with ruthenium salt (5 wt. % as (Ru(III) ions, based on the total weight of the ruthenium ions and the dry ion exchange resin) were added to a 4-neck round bottom flask with an overhead stirrer. 100 mL of DI water was added to the flask. The flask was put into an ice bath. 25 mL of 12 wt. % sodium borohydride in 14 M NaOH solution was added to the flask over the course of 15 minutes. After 12 hours, the solution was siphoned out of the reactor and the resin was washed three times with 250 mL of DI water for 1 hour to a final neutral pH.

[0078] Example 4. / / ? Reduction of Ru(III) to Ru(0) on AmberLite™ FPA66UPS resin.

[0079] Consistently with Method 3c(ii), above, 50 mL of Ru 5%-wt dry basis ion exchange resin was loaded into a stainless steel tube along with other materials in layers having the following order: glass beads, glass wool, catalyst, glass wool, glass beads, and glass wool with a multipoint thermocouple fixed in the middle of the resin bed. The tube was connected in series with the fixed bed reactor system. Dry nitrogen was flowed through the system using a mass flow controller set to 100 seem with a back pressure regulator set to 100 psig (586.1 kPa). The system was heated to 100 °C and held 12 hours to dry the catalyst. Following 12 hours, the system was heated to 140 °C, nitrogen flow was stopped and hydrogen was introduced for 4 hours at 100 seem using a mass flow controller. After 4 hours, the hydrogen flow was stopped and nitrogen flow recommenced at 100 seem. The active catalyst was then cooled to room temperature and stored under dry nitrogen.

[0080] Example 5. Glucose Hydrogenation Reactions - Batch Reaction

[0081] Glucose (25g) and DI water (25g) were weighed out and stirred together to form a 50 wt% solution. Ru(0) containing dry catalyst (2.9g) was weighed and then hydrated with DI water by slowly adding water until the resin no longer absorbed the water. The wet catalyst (5.8g) was charged into a 100 mL stainless steel Parr reactor and excess water was removed from the reactor. The 50 wt% glucose solution was added to the reactor and it was sealed. The solution was stirred at 200 to 300 rpm. The system was purged with nitrogen with 3 cycles of pressurizing to 500 psig (3.34 MPa) and venting. Following this, the sample was pressurized and vented twice with hydrogen at 500 psig (3.34 MPa), then filled a third time with hydrogen at 500 psig (3.34 MPa). The reaction mixture was heated to the desired temperature (as noted in Table 2) and held for 4 hours. After 4 hours, the reactor was removed from the heat source and placed into an ice bath to cool before the reactor was vented and opened. The catalyst was separated from the reaction solution by decanting. The reaction solution was then diluted with DI water in a 1 :4 ratio, filtered through a 250 pm syringe filter and analyzed by HPLC. The reaction conditions for each run are detailed in Table 2 and results are set forth in Table 3. The amount of ruthenium in the liquid reaction product was measured by ICP, and the results are reported in Table 4.

[0082] Table 2: Batch Reaction Conditions

[0083]

[0084] Note for Table 2: “Ruthenium to Glucose %mol” = moles of ruthenium / moles of glucose * 100; Run Id. 27 and 28 were run with 750 psig (5.07 MPa) of H2 pressure and stirring speed of 600 RPM. Table 3: Batch Reaction Results of Catalysis

[0085]

[0086] Table 4a. Comparative Weak Base Results with Strong Acid catalysts.

[0087] Temperature 100C

[0088] Note for Table 4a: “Ruthenium to Glucose %-mol” = moles of ruthenium / moles of glucose * 100 Table 4b.- Ru content in the final solution as measured by ICP. Table 5. Comparative Weak Base Results Temperature 100° C

[0089] Table 6. Comparative Weak Base Results Temperature 70C Reduction process impact Example 5b. Saccharide Hydrogenation Reactions - Batch Reaction

[0090] In a typical reaction, 25 g of saccharide and 25 g of DI water were weighed out and stirred together to form a 50 wt% solution in all examples, except for lactose and isomaltulose where 8.76 wt% and 25 wt. % solutions were used, respectively. The 2.9 g of the Ru(0) containing dry catalyst (Catalyst used for this example is Catalyst identified from run 23 (AmberLite™ FPA66UPS Ru) listed in Table 3) was weighed and then hydrated with DI water by slowly adding water until the resin no longer absorbed the water. The catalyst amount was adjusted in the case of lactose and isomaltulose to maintain a similar ratio of moles of carbohydrate to moles of ruthenium. The wet catalyst was charged into the 100 mL stainless steel Parr reactor and excess water was removed from the reactor. The 50 wt% carbohydrate solution was added to the reactor and it was sealed. The solution was stirred at 200 to 300 rpm. The system was purged with nitrogen with 3 cycles of pressurizing to 500 psig (3.34 MPa) and venting. Following this, the sample was pressurized and vented twice with hydrogen at 500 psig (3.34 MPa), then filled a third time with hydrogen at 500 psig (3.34 MPa). The reaction was heated to the desired temperature (as noted in Table 7) and held for 4 hours. After 4 hours, the reactor was removed from the heat source and placed into an ice bath to cool before the reactor was vented and opened. The catalyst was separated from the reaction solution by decanting. The reaction solution was then diluted with DI water in a 1 :4 ratio, filtered through a 250 pm syringe filter and analyzed by HPLC. The reaction conditions, conversion, yield and selectivity for the desired sugar are detailed in Table 7.

[0091] Table 7. Hydrogenation of Carbohydrates (Batch process)

[0092] Example 6. Catalyst Performance in Fixed Bed Reactor. Glucose to Sorbitol

[0093] In the fixed bed reactor, 24 ml of wet, hydrogen reduced catalyst was loaded into the reactor. The system was heated to the desired reaction temperature set point (70° C - 120° C) with a hydrogen flow rate oflOO - 300 seem through the reactor and a system pressure of 100 to 300 psig (586.1 kPa to 1.97 MPa). Once the system was stable, aqueous glucose solution (10 - 20 wt% glucose, based on the total weight of the solution) was pumped into the system using two alternating ISCO syringe pumps available from Teledyne ISCO of Lincoln, NE. The liquid feed flow rate was set for 1 to 2 bed volume per hour (BV / hr). The condition of 70°C, 1 BV / h, 100 psig

[0094] (586.1 kPa), 100 seem, and 10 wt % glucose was used as a baseline to measure the life of the catalyst. The results of the control runs are summarized in Tables 8 to 13. Liquid effluent from the reactor after hydrogenation was collected and used for measurements by HPLC (%-conversion, %-selectivity, %-yield) and ICP (Ru leachables in effluent).

[0095] Table 8. Lifetime Testing of Catalyst

[0096] Performance of catalyst as a function of time at 70° C, 1 BV / h, 100 psig (586.1 kPa), 100 seem and 10 wt% glucose. Table 9. Effect of Flowrate

[0097] Test conditions: Temperature 90° C, Pressure at 100 psig (586.1 kPa), Glucose 10 wt% and Hydrogen mass flow controller set at 100 seem. Note: Glucose conversion, sorbitol selectivity and sorbitol yield were averaged over a 24 h period.

[0098] Table 10. Effect of System Pressure

[0099] Test conditions: Temperature 90 C, flow rate at 2 BV / hr, glucose 10 %-wt and hydrogen mass flow controller at 100 seem. Note: Glucose conversion, sorbitol conversion and sorbitol selectivity were averaged over a 24 h period.

[0100] Table 11. Effect of Glucose Weight Percentage in Solution

[0101] Test conditions: Temperature 90° C, flow rate at 1 BV / hr, Pressure at 100 psig (586.1 kPa) and hydrogen mass flow controller at 100 seem. Note: Glucose conversion, sorbitol selectivity and sorbitol yield were averaged over a 24 h period.

[0102] Table 12. Effect of Hydrogen Flowrate

[0103] Test conditions: Temperature 90 C, flow rate at 1.5 BV / hr, system pressure at 100 psig (586.1 kPa) and glucose weight percentage at 10 wt%. Note: Glucose conversion, sorbitol selectivity and sorbitol yield were averaged over a 24 h period. Table 13. Testing Effect of Temperature system pressure at 100 psig (586.1 kPa) and 10 wt% aqueous glucose solution.

[0104] Glucose conversion, sorbitol selectivity and sorbitol yield were averaged over a 24 h time period.

[0105] It is well-known that functional groups in a polymer matrix can influence the stability of immobilized particles. In the present Examples, the ruthenium content in the reaction product solution was tested by ICP after a hydrogenation run to determine how the sulfonic acid and amine functional groups affected the ruthenium particles. The data in Table 4b demonstrate that the use of a strong acid cation resin results in much higher ruthenium leaching (56 ppm) than a weak base anion resin (0.04 ppm) while exhibiting similar catalytic performance. While certain of the preferred embodiments of this invention have been described and specifically exemplified above, it is not intended that the invention be limited to such embodiments. Various modifications may be made without departing from the scope and spirit of the invention, as set forth in the following claims.

Claims

Claims1. A method for the preparation of a sugar alcohol by the reduction of a saccharide using a base anion exchange resin catalyst, said catalyst comprising a base anion exchange resin and ruthenium.

2. The method of claim 1 that is a continuous process wherein a stream of saccharide solution is contacted with the catalyst to produce a product stream.

3. The method of claim 2, wherein the product stream is accumulated; wherein the amount of ruthenium in the accumulated product stream is less than 50 ppm, after reacting 120 g of glucose per gram of catalyst; and wherein the catalyst is a basic anion exchange resin catalyst comprising 5 wt% of ruthenium, based on the total weight of the dry base anion exchange resin.

4. The method of claim 2, wherein the product stream is accumulated; wherein the amount of ruthenium in the accumulated product stream is less than 10 ppm, after reacting 1435 g of glucose per gram of catalyst; and wherein the catalyst is a basic anion exchange resin catalyst comprising 1.5 wt% of ruthenium, based on the total weight of the dry base anion exchange resin.

5. The method of claim 1 that is a batch process wherein a saccharide solution is contacted with the catalyst to produce a product solution.

6. The method of claim 5, wherein the ruthenium concentration of the product solution upon separation from the catalyst is less than 20 ppm.

7. The method of any preceding claim, wherein one or more of the following conditions is met: the process temperature is between 25°C and 180°C; the pressure in the reaction vessel is between 275 kPa to 7.0 MPa; the flow rate of the feedstock is 0.1 to 6 LHSV (h-1); the hydrogen gas flow rate is from 50 to 400 seem; and the concentration of saccharide in the feedstock is from 2 to55 wt%, based on the total weight of the feedstock.

8. The method of any preceding claim, wherein the total loading of ruthenium in the base anion exchange resin catalyst is 0.5 to 8 wt% based on the total weight of the dry base anion exchange resin.

9. The method of any preceding claim, wherein the saccharide comprises 5 to 25 carbon atoms.

10. The method of any preceding claim, wherein the base anion exchange resin is a styrenic resin with basic sites, and preferably wherein the basic sites have a concentration of 0.3 to 1.8 equivalents / liter of resin.

11. The method of any preceding claim, wherein the base anion exchange resin is in the form of beads having a harmonic mean diameter from 200 to1100 microns.

12. The method of any preceding claim, wherein the saccharide comprises one or more reducing sugars; preferably one or more of isomaltulose, erythrose, ribose, arabinose, xylose, lyxose, glucose, fructose, maltose, lactose, mannose, galactose, sedoheptulose, mannoheptulose, and sucrose.

13. The method of any preceding claim, wherein the base anion exchange resin is a gel or a macroreticular resin.

14. The method of any preceding claim, wherein the base anion exchange resin has a water retention capacity of from 20 to 80 wt%; preferably from 30 to 60 wt%; and more preferably 40 to 50 wt%.

15. A base anion exchange resin catalyst comprising a base anion exchange resin and ruthenium.

16. The base anion exchange resin catalyst of claim 15, wherein the base anion exchange resin is a weak base anion exchange resin.

17. The base anion exchange resin catalyst of claim 15 or 16, comprising ruthenium in the amount of 0.5 to 5 wt% based on the total weight of the dry base anion exchange resin.

18. The base anion exchange resin catalyst of any of claims 15, 16, or 17, wherein the amount of copolymerized crosslinker in the base anion exchange resin is from 1 to 20 wt%, based on the total weight of the dry base anion exchange resin.

19. The base anion exchange resin catalyst of any of claims 15 through 8, wherein the copolymerized crosslinker is divinylbenzene.

20. The base anion exchange resin catalyst of any of claims 15 through 19, wherein the resin has one or both of a total exchange capacity of 1.1 to 1.7 eq / L and a weak base exchange capacity of 1 to 2 eq / L, based on the volume of the dry base anion exchange resin.

21. The base anion exchange resin catalyst of any of claims 15 through 20, wherein the base anion exchange resin comprises functional groups selected from the group consisting of tertiary amine groups, and quaternary amine groups, or both tertiary and quaternary amine groups.

22. The base anion exchange resin catalyst of any of claims 15 through 21, wherein the base anion exchange resin is a gel or a macroporous resin, preferably a macroporous resin.

23. The base anion exchange resin catalyst of any of claims 14 through 22, that has one or more properties selected from the group consisting of: a surface area of 30 to 50 m2 / g, a pore volume of 0.2 to 0.5 cm3 / g, a pore size of 150 to 350 A, a harmonic mean diameter of 300 to 1000 pm, a density of 1 to1.2 g / mL, and a uniformity coefficient of less than 1.6.

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