Process for making ethylene glycol and / or propylene glycol from aldose and / or ketose producing carbohydrates with integrated tungsten catalyst recovery - Patent Application 20070233633

Abstract

Disclosed are integrated processes for catalytic conversion of carbohydrates to ethylene glycol and / or propylene glycol using homogeneous tungsten-containing retro-aldol catalysts. In these processes, carbohydrates are subjected to retro-aldol conversion and hydrogenation to provide reaction products containing ethylene glycol and / or propylene glycol, and other reaction processes include organic acids, thiols, and tungsten species. Ethylene glycol and propylene glycol are separated from the reaction products for purification, and at least a portion of the remaining fraction is subjected to ion exclusion chromatography to provide an eluate containing tungsten species, and a subsequent eluate containing organic acids and a substantially reduced concentration of tungsten species. At least a portion of the eluate containing tungsten species can be recycled for reuse, either directly or with an intervening unit operation to enhance the catalytic activity of the tungsten species. The organic-containing fraction can be subjected to one or more unit operations to provide a saleable product, or can be subjected to selective hydrogenolysis to lower glycols.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 63 / 300,696, entitled "PROCESSES FOR MAKING ETHYLENE GLYCOL AND / OR PROPYLENE GLYCOL FROM ALDOSE- AND / OR KETOSE-YIELDING CARBOHYDRATES WITH INTEGRATED TUNGSTEN CATALYST RECOVERY," filed January 19, 2022, which is incorporated by reference in its entirety.

[0002] FIELD OF THEINVENTION The present invention relates to a process for the catalytic production of ethylene glycol and / or propylene glycol from aldose and / or ketose producing carbohydrates, particularly a process with integrated tungsten catalyst recovery. [Background technology]

[0003] Ethylene glycol and propylene glycol are valuable commodity chemicals, each with a wide range of uses. These chemicals are currently made from starting materials based on fossil hydrocarbons (petrochemical pathways).

[0004] There have been proposals to produce ethylene glycol and propylene glycol from renewable resources, such as carbohydrates, e.g., sugars. One such route is commercially practiced and involves fermentation of sugars to ethanol, catalytic dehydrogenation of the ethanol to ethylene, which is then catalytically converted to ethylene oxide, which can react with water to produce ethylene glycol. This route is economically unattractive because it requires three conversion steps and suffers from losses in conversion efficiency. For example, the theoretical yield of ethanol is 0.51 grams per gram of sugar, and theoretically, one mole of carbon dioxide is produced per mole of ethanol.

[0005] Therefore, there is a need for alternative processes for making ethylene glycol and propylene glycol from renewable resources. These alternative processes include catalytic routes, such as hydrogenolysis of sugars, and two-catalyst processes that use a retro-aldol catalyst to produce intermediates from sugars that can be hydrogenated over a hydrogenation catalyst to produce ethylene glycol and propylene glycol (the "retro-aldol pathway").

[0006] In the retro-aldol pathway, carbohydrates are converted to intermediates over a retro-aldol catalyst, and the intermediates are then catalytically converted to ethylene glycol and / or propylene glycol over a hydrogenation catalyst ("hydrogenation catalyst, Hcat"). The initial desired retro-aldol reaction is endothermic and requires high temperatures, e.g., often above 230°C, to provide sufficient reaction rates to preferentially favor the conversion of the carbohydrate to the intermediate over the hydrogenation of the carbohydrate to a polyol such as sorbitol.

[0007] The catalyst used for the reverse aldol conversion is typically homogeneous and contains tungsten, and therefore exits the reaction system with the product. Various proposals have been made to separate monoethylene glycol and propylene glycol from the reactor effluent and recycle at least a portion of the remainder containing tungsten to the reactor. See, for example, U.S. Pat. Nos. 10,294,181 and 10,647,646 and U.S. Patent Application Publication No. 2021 / 0087128. Recycling can preserve tungsten, but tungsten species that are catalytically inactive or have reduced or undesirable catalytic activity may be formed during use.

[0008] Tungsten can also be recovered, for example, by ion exchange or precipitation, and the recovered tungsten can be converted to a catalytically active species for the retro-aldol transformation, see U.S. Patent Application Publication No. 2021 / 0087128.

[0009] A process for making lower glycols from carbohydrates via the retro-aldol process is needed to recover tungsten compounds from processes involving purge streams that are easily operated, require little energy, and provide recovered tungsten compounds with desirable catalytic activity for retro-aldol conversion. Summary of the Invention

[0010] The process of the present invention includes an energy efficient and effective method for recovering tungsten from a process for making lower glycols from carbohydrates via a retro-aldol process, which includes the integration of ion exclusion chromatography for the selective recovery of tungsten compounds and, if desired, recycling of the tungsten compounds while providing a higher boiling organic phase that can be subjected to hydrocracking to enhance the conversion of carbohydrates to lower glycols, if desired.

[0011] The present invention provides an integrated process for catalytic conversion of carbohydrates to ethylene glycol and / or propylene glycol using a homogeneous tungsten-containing retro-aldol catalyst. In these processes, carbohydrates are subjected to retro-aldol conversion and hydrogenation to provide reaction products containing ethylene glycol and / or propylene glycol, and other reaction processes include organic acids, thiols, and tungsten species. Ethylene glycol and propylene glycol are separated from the reaction products for purification, and at least a portion of the remaining fraction ("retained fraction") is subjected to ion exclusion chromatography to provide an eluate containing tungsten species, and a subsequent eluate containing organic acids and a substantially reduced concentration of tungsten species. At least a portion of the eluate containing tungsten species can be recycled for reuse directly or with an intervening unit operation to enhance the catalytic activity of the tungsten species.

[0012] Although tungsten species are a very small portion of the retained fraction, it has been found that a significant portion of the tungsten, often at least about 60 percent, and sometimes about 70 or 80 percent (based on atomic tungsten), can be recovered by ion exclusion chromatography, with at least 90 percent by weight of the organic matter being separated into the subsequent eluent phase. Thus, the tungsten-containing eluent is suitable for recirculation without excessive accumulation of non-reactive organic matter in the reaction zone, and any intermediate treatment of the tungsten species in the recycled eluent includes treatment of a reduced volume of liquid. Also, with intermediate treatments such as pH adjustment, the content of organic acids is reduced, and less pH adjuster is required for the desired pH change to convert the tungsten compounds to those desired for recycle.

[0013] According to the present invention there is provided a catalytic process for producing lower glycols, including at least one of ethylene glycol and propylene glycol, from a carbohydrate-containing feed comprising at least one of aldose and ketose producing carbohydrates, the process comprising: (a) continuously or intermittently feeding a feed to a reaction zone having dissolved tungsten compounds therein, at least one of which is a homogeneous tungsten-containing retro-aldol catalyst, and at least one heterogeneous hydrogenation catalyst, to produce a reaction product containing lower glycols and one or more higher boiling by-products including sorbitol, erythritol, threitol, and glycerin, wherein the liquid medium is at catalytic conversion conditions including the presence of dissolved hydrogen; (b) continuously or intermittently removing a liquid medium containing the reaction products and dissolved tungsten compounds from the reaction zone; and (c) subjecting at least a portion of the removed liquid medium to one or more unit operations to remove at least a portion of the lower glycols in the separated fraction and to provide a retained liquid phase containing dissolved tungsten compounds and high-boiling by-products, the mass ratio of tungsten compounds, calculated as high-boiling by-products to metal, being greater than about 4:1; (d) contacting at least a portion of the retained liquid phase with an ionic resin for ion exclusion chromatography to provide a first elution fraction containing dissolved tungsten compounds and a mass ratio of tungsten compounds, calculated as high-boiling by-products to metals, of less than about 5:1, preferably less than about 1:1, and contacting the ionic resin with sufficient solvent to provide at least one subsequent elution fraction containing one or more high-boiling by-products and a lower concentration of tungsten compounds, calculated as metals, than in the retained liquid phase (often less than about 10 parts by weight of tungsten compounds, calculated as metals, per 100 parts by weight of high-boiling by-products).

[0014] In a preferred process of the present invention, at least about 90 weight percent of the tungsten compounds contained in the retained liquid phase contacting the ion exchange resin are in the first elution fraction. Preferably, at least a portion of the first elution fraction is recycled to step (a), and optionally the first elution fraction is provided at a pH of about 6.5 to 8 before being passed to step (a). Optionally, at least a portion of the tungsten compounds in the recycled first elution fraction is semi-neutralized tungstic acid. If desired, the subsequent elution fraction is subjected to hydrogenolysis conditions to convert isitol to lower glycols.

[0015] The present invention also relates to a product composition comprising a dissolved tungsten compound and one or more high boiling polyols, including sorbitol, erythritol, threitol, and glycerin, wherein the weight ratio of the total high boiling polyol to the tungsten compound, calculated as the metal, is less than about 5:1, preferably less than about 1:1, and sometimes between about 0.01:1 and 1:1. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of an apparatus for practicing the process of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] All patents, published patent applications and articles referenced herein are hereby incorporated by reference in their entirety.

[0018] definition As used herein, the following terms have the meanings indicated below, unless otherwise stated or clear from the context of their usage.

[0019] When ranges are used herein, only the endpoints of the range are recited to avoid the need to specify the length of each and every value included in the range. Any suitable intermediate values ​​and ranges between the recited endpoints can be selected. For example, when a range of 0.1 to 1.0 is recited, all intermediate values ​​(e.g., 0.2, 0.3, 0.63, 0.815, etc.) are included, as are all intermediate ranges (e.g., 0.2 to 0.5, 0.54 to 0.913, etc.).

[0020] The use of the terms "a" and "an" is intended to include one or more of the described elements.

[0021] Mixing or mixed means the formation of a physical combination of two or more elements that may have a uniform or heterogeneous composition throughout, including, but not limited to, solid mixtures, solutions, and suspensions.

[0022] Aldoses contain only a single aldehyde group (-CH=O) per molecule and have the general chemical formula C n (H2O) nNon-limiting examples of aldoses include aldohexoses (all six-carbon aldehyde-containing sugars, including glucose, mannose, galactose, allose, altrose, idose, talose, and gulose); aldopentoses (all five-carbon aldehyde-containing sugars, including xylose, lyxose, ribose, and arabinose); aldotetroses (all four-carbon aldehyde-containing sugars, including erythrose and threose); and aldotrioses (all three-carbon aldehyde-containing sugars, including glyceraldehyde).

[0023] By aldose-yielding carbohydrate is meant an aldose or a di- or polysaccharide that can produce an aldose upon hydrolysis. For example, sucrose is an aldose-yielding carbohydrate, even though it also produces a ketose upon hydrolysis.

[0024] Aqueous and aqueous medium or solution means that water is present, but does not necessarily have to be the major component. For purposes of illustration and not limitation, a solution of 90 percent ethylene glycol and 10 percent water by volume is an aqueous solution. Aqueous solutions include liquid media containing dissolved or dispersed components, such as, but not limited to, colloidal suspensions and slurries.

[0025] Biogenic carbohydrate feedstock means a carbohydrate-containing product that is derived in whole or in substantial part from or synthesized from biological products or renewable agricultural materials (including, but not limited to, plants, animals, and marine materials) or forestry materials.

[0026] By counted as metal, it is meant counting as elemental metal, regardless of the molecular structure of the metal-containing compound.

[0027] A catalyst for converting carbohydrates refers to one or more catalysts for catalytic conversion, both retro-aldol catalysts and hydrogenation catalysts ("Hcats"), each of which can contain one or a mixture of catalysts. The catalyst can contain one or more catalytic metals, including supports, binders, and other auxiliary materials for Hcats. A catalytic metal is a metal in the elemental state or ionically or covalently bound. The term catalytic metal refers to a metal that is not necessarily in a catalytically active state, but has the potential to become catalytically active when not in a catalytically active state. A catalytic metal can provide catalytic activity or modulate catalytic activity, such as a cocatalyst, selectivity modifier, etc.

[0028] Initiation of contact means that the fluid begins contacting the component, e.g., the homogeneous catalyst or the heterogeneous catalyst, e.g., the medium containing Hcat, but it is not necessary that every molecule of the fluid contacts the catalyst.

[0029] The composition of the aqueous solution is determined using gas chromatography for low boiling components, typically those with 3 carbons or less and normal boiling points below about 300° C., and using high performance liquid chromatography for high boiling components, typically those with 3 carbons or more and thermally unstable components.

[0030] The conversion of aldohexose to ethylene glycol is reported as a percentage by mass and is calculated as the mass of ethylene glycol contained in the product solution divided by the mass of aldohexose theoretically provided by the carbohydrate feed, and therefore includes any aldohexose itself contained in the carbohydrate feed and any aldohexose theoretically produced upon hydrolysis of any di- or polysaccharide contained in the carbohydrate feed.

[0031] Hexitols have one hydroxyl per carbon, CH 14 It refers to the six-carbon compound having the empirical formula O6.

[0032] High shear mixing involves providing fluids moving at different velocities relative to adjacent regions, which can be accomplished by stationary or moving mechanical means to create the shear to promote mixing. As used herein, the components subjected to high shear mixing may be immiscible, partially immiscible, or miscible.

[0033] By hydraulic distribution is meant the distribution of the aqueous solution in the vessel, including contact with any catalyst contained in the vessel.

[0034] By immediately preceding, it is meant that there are no intervening unit operations requiring residence times greater than 1 minute.

[0035] Intermittent means from time to time, and may be at regular or irregular time intervals.

[0036] Ion exclusion chromatography involves an adsorbent material saturated with the same mobile ions (cations or anions) present in the feed, such that like ions are repelled by the adsorbent material because it is saturated. Ion exclusion chromatography can use ion exchange resin beds that act as charged solid separation media. Ion exclusion chromatography techniques using porous resin beds can be useful to achieve size exclusion separations, such that molecules can be separated by size and molecular weight, with larger and heavier molecules eluting first.

[0037] By itol is meant a carbon compound containing at least two hydroxyl groups with one hydroxyl on each carbon atom.

[0038] Ketose refers to a monosaccharide that contains one ketone group per molecule.Non-limiting examples of ketose include ketohexose (all 6-carbon ketone-containing sugars, including fructose, psicose, sorbose, and tagatose), ketopentose (all 5-carbon ketone-containing sugars, including xylulose and ribulose), ketotetrose (all 4-carbon ketose-containing sugars, including erythrulose), and ketotriose (all 3-carbon ketose-containing sugars, including dihydroxyacetone).

[0039] By ketose-producing carbohydrates is meant ketoses or disaccharides or polysaccharides or hemicelluloses that can produce ketoses or ketose precursors upon hydrolysis. Most sugars are ring structures under ambient conditions, and therefore the ketose form occurs under the conditions of the process of the present invention. For example, sucrose is a ketose-producing carbohydrate, even though it also produces aldoses upon hydrolysis. For purposes herein, carbohydrates that produce both aldoses and ketoses are considered ketose-producing carbohydrates, unless the context requires otherwise.

[0040] Liquid medium refers to the liquid in the reactor. The liquid is a solvent for the carbohydrates, intermediates, and products, and for the homogeneous tungsten-containing retro-aldol catalyst. Typically and preferably, the liquid contains at least some water, and is therefore referred to as an aqueous medium.

[0041] The lower glycols are ethylene glycol or propylene glycol or mixtures thereof.

[0042] The pH of the aqueous solution is determined at ambient pressure and temperature. For example, when determining the pH of an aqueous hydrogenation medium or product solution, the liquid is cooled and left at ambient pressure and temperature for 2 hours before determining the pH. If the aqueous solution contains less than about 50 percent water by weight, for example in a glycol-rich medium, water is added to the sample to provide a solution containing about 50 percent water by weight. For consistency purposes, the dilution of the solution is to the same percent water by weight.

[0043] By pH adjusting agent is meant one or more of a buffer and an acid or a base.

[0044] By pressure sufficient to maintain at least partial hydration of the carbohydrate, it is meant that the pressure is sufficient to maintain sufficient water of hydration on the carbohydrate to retard caramelization. At temperatures above the boiling point of water, the pressure is sufficient to allow the water of hydration to be retained on the carbohydrate.

[0045] Rapid diffusion mixing is mixing in which at least one of two or more fluids being mixed is finely divided to facilitate mass transfer to form a substantially homogeneous composition.

[0046] The reactor can be one or more vessels in series or parallel, and the vessel can contain one or more zones. The reactor can be of any suitable design for continuous operation, including but not limited to tanks and pipe or tubular reactors, and can have fluid mixing capabilities, if desired. Reactor types include, but are not limited to, laminar flow reactors, fixed bed reactors, slurry reactors, fluidized bed reactors, moving bed reactors, simulated moving bed reactors, trickle bed reactors, bubble columns, and loop reactors.

[0047] A separation unit operation is one or more operations for selectively separating chemicals, including, but not limited to, chromatographic separation, sorption, membrane separation, flash separation, distillation, rectification, and evaporation.

[0048] By soluble it is meant that it is capable of forming a single liquid phase or that it is capable of forming a colloidal suspension.

[0049] Solubilized tungsten compounds are dissolved or colloidally suspended tungsten compounds in the reaction medium.

[0050] Vapor / liquid separation is a separation that provides one or more vapor streams and one or more liquid streams and can be based on chromatographic separation, cyclic sorption, membrane separation, flash separation, distillation, rectification, and evaporation (e.g., thin film evaporators, falling film evaporators, and wiped film evaporators).

[0051] Carbohydrate Supply The process of the invention uses a carbohydrate feed containing an aldohexose-producing carbohydrate or a ketose-producing carbohydrate, the former providing an ethylene glycol-rich product under retro-aldol reaction conditions, and the latter providing a propylene glycol-rich product. When a product solution containing a high mass ratio of ethylene glycol to propylene glycol is desired, the carbohydrate in the feed comprises at least about 90 mass percent, preferably at least about 95 or 99 mass percent, of the aldohexose-producing carbohydrate. Often the carbohydrate feed comprises a carbohydrate polymer, such as starch, cellulose, or a partially to essentially completely hydrolyzed fraction of such a polymer, or a mixture of polymers, or a mixture of a polymer and a partially hydrolyzed fraction.

[0052] The carbohydrate feed is most often at least one of pentoses and hexoses, or compounds that produce pentoses or hexoses. Examples of pentoses and hexoses include xylose, lyxose, ribose, arabinose, xylulose, ribulose, glucose, mannose, galactose, allose, altrose, idose, talose, and glucose fructose, psicose, sorbose, and tagatose. Most biogenic carbohydrate feedstocks produce glucose when hydrolyzed. Glucose precursors include, but are not limited to, maltose, trehalose, cellobiose, kojibiose, nigerose, nigerose, isomaltose, β,β-trehalose, α,β-trehalose, sophorose, laminaribiose, gentiobiose, and mannobiose. Carbohydrate polymers and oligomers (such as hemicellulose, partially hydrolyzed forms of hemicellulose), disaccharides (such as sucrose, lactulose, lactose, turanose, maltulose, palatinose, gentiobiulose, melibiose, melibiulose, or combinations thereof) may be used.

[0053] If desired, the carbohydrate feed can be treated to remove one or more impurities, particularly impurities that may affect one or more of the catalysts, for example moieties that may oxidize or sulfidize one or more of the catalysts used in the process.

[0054] The carbohydrate feed may be solid or, preferably, in liquid suspension or dissolved in a solvent such as water. When the carbohydrate feed is in a non-aqueous environment, it is preferred that the carbohydrate is at least partially hydrated. Non-aqueous solvents include alkanols, diols and polyols, ethers, or other suitable carbon compounds of 1 to 6 carbon atoms. Solvents include mixed solvents, especially mixed solvents containing water and one of the non-aqueous solvents listed above. Certain mixed solvents may have a higher concentration of dissolved hydrogen under the conditions of the hydrogenation reaction, thus reducing the possibility of hydrogen starvation. Preferred non-aqueous solvents are those that may be hydrogen donors, such as isopropanol. Often these hydrogen donor solvents have hydroxyl groups that are converted to carbonyl groups when donating hydrogen atoms, and the carbonyls may be reduced under the conditions in the reaction zone. Most preferably, the carbohydrate feed is provided in an aqueous solution. In any case, to provide a continuous process, it is necessary to balance the volume of the feed with the volume of the raw product being removed.

[0055] An additional consideration when feeding carbohydrates to the reaction zone is to minimize energy and capital costs. For example, in steady state operation, the solvent contained in the feed exits the reaction zone with the raw product and needs to be separated to recover the desired glycol product.

[0056] Preferably, the feed is introduced into the reaction zone in such a manner that excessive concentration of the feed is avoided, which may result in hydrogen starvation. The use of more multiple locations for feeding carbohydrate per unit volume of the reaction zone allows for more concentration of carbohydrate in the feed. In general, the mass ratio of water to carbohydrate in the carbohydrate feed is preferably in the range of 4:1 to 1:4. Aqueous solutions of 600 grams / liter or more of certain carbohydrates, such as dextrose and sucrose, may be commercially available.

[0057] In some cases, the recycled hydrogenation solution, or an aliquot or separated portion thereof, substantially free of hydrogenation catalyst, is added as a component to the carbohydrate feed. The recycled hydrogenation solution can be one or more of a portion of the raw product stream, or an internal recycle from which the hydrogenation catalyst is removed. Suitable solids separation techniques include, but are not limited to, filtration and density separation (e.g., cyclone, vane separator, and centrifuge). This recycle reduces the amount of fresh solvent for the feed, but the carbohydrate is fed at a rate sufficient to maintain a high conversion rate per unit volume of the reaction zone. The use of recycle allows for a low concentration of carbohydrate to be fed to the reaction zone while maintaining a high conversion rate of carbohydrate to ethylene glycol, especially when the recycle is an aliquot portion of the raw product stream. Additionally, the recycle stream can be maintained at or near the temperature in the reaction zone, and since the recycle stream contains the tungsten-containing catalyst, the retro-aldol conversion can occur before the feed enters the reaction zone. When a recycled hydrogenation solution is used, the mass ratio of carbohydrate to total recycled product stream and additive solvent is often in the range of about 0.05:1 to 0.4:1, and sometimes between about 0.1:1 to 0.3:1. The recycled raw product stream is often about 20 to 80 volume percent of the product stream.

[0058] The carbohydrate contained in the carbohydrate feed is provided at a rate of at least 50 or 100, preferably about 150 to 500 grams per liter of reactor volume per hour. Optionally, a separate reaction zone containing a retro-aldol catalyst and essentially free of a hydrogenation catalyst can be used.

[0059] Conversion Process In this process, the carbohydrate feed is introduced into a solvent containing a catalyst for catalytic conversion and hydrogen. The solvent is often water, but can also be a lower alcohol or polyalcohol of 1 to 6 carbons, particularly methanol, ethanol, n-propanol, and isopropanol.

[0060] The carbohydrate feed may or may not have been subjected to retro-aldol conditions prior to being introduced into the reaction zone, and the carbohydrate feed may or may not have been heated through a temperature zone of 170°C to 230°C when contacting the liquid medium in the reaction zone. Thus, in some cases, the retro-aldol reaction may not occur until the carbohydrate feed is introduced into the liquid medium, and in other cases, the retro-aldol reaction may have occurred at least partially prior to the introduction of the carbohydrate feed into the liquid medium in the reaction zone. It is generally preferred to rapidly disperse the carbohydrate feed in the liquid medium, particularly when the hydrogenation medium is used to provide direct heat exchange to the carbohydrate feed. This dispersion may be achieved by any suitable procedure, including, but not limited to, the use of mechanical and static mixers and rapid diffusion mixing. The use of multiple ports for introducing the feed into the reactor also facilitates rapid dispersion.

[0061] The preferred temperature for the retro-aldol reaction is typically about 230°C to 300°C, more preferably about 240°C to 280°C, although the retro-aldol reaction can occur at lower temperatures, for example, as low as 90°C or 150°C. The pressure (absolute) typically ranges from about 15 to 200 bar (1500 to 20,000 kPa), for example, about 25 to 150 bar (2500 to 15000 kPa). The retro-aldol reaction conditions include the presence of a retro-aldol catalyst. A retro-aldol catalyst is a catalyst that catalyzes the retro-aldol reaction. Examples of tungsten compounds that can provide the retro-aldol catalyst include, but are not limited to, heterogeneous and homogeneous catalysts, including catalysts supported on a carrier, including tungsten and its oxides, sulfates, phosphides, nitrides, carbides, halides, acids, and the like. Also included are tungsten carbide, soluble tungsten phosphotungsten, and tungsten oxide supported on zirconia, alumina, and alumina-silica. Preferred catalysts are provided by soluble tungsten compounds and mixtures of tungsten compounds. Soluble tungstates include, but are not limited to, ammonium and alkali metal (e.g., sodium and potassium), paratungstates, partially neutralized tungstic acid, ammonium and alkali metal metatungstates, and ammonium and alkali metal tungstates. In many cases, the presence of ammonium cations results in the production of undesirable amine by-products in the lower glycol products. Without wishing to be limited by theory, the species exhibiting catalytic activity may or may not be the same as the soluble tungsten compound introduced as the catalyst. Rather, the catalytically active species may be formed as a result of exposure to retro-aldol reaction conditions. Tungsten-containing complexes are typically pH-dependent. For example, a solution containing sodium tungstate at a pH above 7 will produce sodium metatungstate as the pH is lowered. The form of the complexed tungstate anion is generally pH dependent. The rate at which the complexed anion formed from the condensation of the tungstate anion is formed is affected by the concentration of the tungsten-containing anion.Preferred retro-aldol catalysts include ammonium or alkali metal tungstates that are partially neutralized with an acid, preferably an organic acid of 1-6 carbons, such as, but not limited to, formic acid, acetic acid, glycolic acid, and lactic acid. The partial neutralization is often about 25-75%, i.e., an average of 25-75% of the tungstate cations are acid sites. The partial neutralization may be performed prior to introducing the tungsten-containing compound into the reactor, or may be performed with the acid contained in the reactor.

[0062] The concentration of the retro aldol catalyst used may vary widely and depends on the activity of the catalyst and other conditions of the retro aldol reaction, such as acidity, temperature, and carbohydrate concentration. Typically, the retro aldol catalyst is provided in an amount that provides about 0.01 or 0.05 to 100, e.g., about 0.02 or 0.1 to 50 grams of tungsten, calculated as elemental metal, per liter of aqueous hydrogenation medium. The retro aldol catalyst can be added as a mixture with all or a portion of the carbohydrate feed, or as a separate feed to the liquid medium, or with the recirculating liquid medium, or any combination of these. When the retro aldol catalyst includes two or more tungsten species, they can be fed separately or together to the reaction zone. In some preferred embodiments, the carbohydrate feed is mixed with the retro aldol catalyst before contacting it with the hydrogenation catalyst. The pH of the mixture is preferably greater than 4, often greater than 5.5, and in some cases is about 6 to 7.5, e.g., 6.5 to 6.8.

[0063] In many cases, the carbohydrate feed is subjected to retro-aldol conditions before being introduced into the hydrogenation medium in the reaction zone containing the hydrogenation catalyst. Preferably, the introduction into the aqueous hydrogenation medium is performed in less than 1 minute, and most often less than 10 seconds, from the start of subjecting the carbohydrate feed to retro-aldol conditions. Part or all of the retro-aldol reaction may occur in the reaction zone containing the hydrogenation catalyst. In any case, the most preferred processes are those that have a short time between the retro-aldol conversion and hydrogenation.

[0064] Under many process conditions useful in the process of the present invention, tungsten-containing precipitates may form and become suspended or deposited on surfaces, including the surfaces of the hydrogenation catalyst, where the activity of the hydrogenation catalyst may be affected.

[0065] Hydrogenation, i.e., the addition of hydrogen atoms to organic compounds without breaking carbon-carbon bonds, can be carried out at temperatures ranging from about 100°C or 120°C to 300°C or higher. Typically, the hydrogenation medium is maintained at a temperature of at least about 230°C until substantially all of the carbohydrate has reacted and broken the carbohydrate carbon-carbon bonds by the retro-aldol reaction, thereby enhancing the selectivity to ethylene and propylene glycol. Thereafter, if desired, the temperature of the hydrogenation medium can be reduced. However, hydrogenation proceeds rapidly at these higher temperatures. Thus, the temperature for the hydrogenation reaction is often about 230°C to 300°C, e.g., about 240°C to 280°C. Typically, in the retro-aldol process, the pressure (absolute) typically ranges from about 15 to 200 bar (1500 to 20,000 kPa), e.g., about 25 to 150 bar (2500 to 15000 kPa). The hydrogenation reaction requires the presence of hydrogen as well as a hydrogenation catalyst. Hydrogen has low solubility in aqueous solutions. The hydrogen concentration in the aqueous hydrogenation medium increases with increasing hydrogen partial pressure in the reaction zone. The pH of the aqueous hydrogenation medium is often at least about 2.5 or 3, for example, about 3 or 3.5 to 8, and in some cases, about 3.5 or 4 to 7.5.

[0066] The hydrogenation is carried out in the presence of a hydrogenation catalyst. In many cases, the hydrogenation catalyst is a supported heterogeneous catalyst. It can be arranged in any suitable manner, including but not limited to a fixed bed, a fluidized bed, a trickle bed, a moving bed, a slurry bed, a loop bed such as the Buss Loop® reactor available from BUSS ChemTech AG, and a structured bed. One type of reactor that can provide high hydrogen concentration and rapid heating is a cavitation reactor, as disclosed in U.S. Pat. No. 8,981,135 (B2), the entirety of which is incorporated herein by reference. Cavitation reactors generate heat in localized regions, and therefore the temperatures in these localized regions, rather than the bulk temperature of the liquid medium in the reaction zone, are the temperature process parameters for the purposes of this invention. Cavitation reactors are of interest for this process because the retro-aldol conversion can be very rapid at temperatures that can be achieved in cavitation reactors.

[0067] Nickel, ruthenium, palladium, and platinum are the more widely used reduction metal catalysts. However, many reduction catalysts will work in this application. The catalyst may be supported or unsupported, such as Raney nickel. The reduction catalyst can be selected from a wide variety of supported transition metal catalysts. One particularly preferred catalyst for the reduction catalyst in this process is a supported Ni-Re catalyst. Similar versions of Ni / Re or Ni / Ir can be used with good selectivity for the conversion of the formed glycolaldehyde to ethylene glycol. Nickel-rhenium is the preferred reduction metal catalyst and may be supported on alumina, alumina-silica, silica, or other supports. Supported Ni-Re catalysts with B as a promoter are useful. Generally, for slurry reactors, the supported hydrogenation catalyst is provided in an amount of less than 10 grams, sometimes less than about 5 grams, e.g., about 0.1 or 0.5 to 3 grams, per liter of nickel (calculated as elemental nickel) per liter of liquid medium in the reactor. As mentioned above, not all nickel in the catalyst is in the zero valence state, nor is all nickel in the zero valence state readily accessible by glycolaldehyde or hydrogen. Thus, the optimum mass of nickel per liter of liquid medium for a particular hydrogenation catalyst varies. For example, Raney nickel catalysts provide much higher concentrations of nickel per liter of liquid medium. Often, in a slurry reactor, the hydrogenation catalyst is provided in an amount of at least about 5 or 10 grams, more often about 10 to 70 or 100 grams, per liter of aqueous hydrogenation medium, and in a packed bed reactor, the hydrogenation catalyst comprises about 20 to 80 volume percent of the reactor. In some cases, the weight hourly space velocity is about 0.01 or 0.05 to 1 hr based on the total carbohydrate in the feed. -1 Preferably, the residence time is sufficient for glycolaldehyde and glucose to be less than 0.1 weight percent of the reaction product, and most preferably less than 0.001 weight percent of the reaction product.

[0068] The carbohydrate feed is at least 50 grams of carbohydrate per liter per hour, and often ranges from about 100 to 700 or 1000 grams of carbohydrate per liter per hour.

[0069] In the processes of the present invention, the combination of reaction conditions (e.g., temperature, hydrogen partial pressure, catalyst concentration, hydraulic distribution, and residence time) is sufficient to convert at least about 95 mass percent, often at least about 98 or 99 mass percent, and sometimes essentially all, of the carbohydrate to produce aldoses or ketoses. Determining the set or sets of conditions that provide the desired conversion of carbohydrates is well within the skill of one of ordinary skill in the art having the benefit of the disclosure herein.

[0070] Ion Exclusion Chromatography Separation The process of the present invention uses ion exclusion chromatographic separation to obtain a product composition enriched in dissolved tungsten compounds as the desired product, excluding the lower glycols and higher boiling by-products recovered in the subsequent eluent. The product composition has a substantially reduced ratio of lower glycols and higher boiling by-products to tungsten compounds compared to the ratio in the retained liquid phase. Thus, recovery of tungsten compounds can be performed without significant loss of lower glycols and higher boiling by-products, and the subsequent eluent can be purged and / or processed without undue loss of tungsten compounds.

[0071] The feed to the ionic resin for ion exclusion chromatography separation is at least a portion (which may be an aliquot or aliquot portion) of the retained liquid phase from the separation of the lower glycols from the reaction product. Any suitable unit operation(s) can be used to separate the lower glycols, including, but not limited to, chromatographic separation, sorption, membrane separation, flash separation, distillation, rectification, and evaporation. Gas-liquid separation is typically used. In some examples, the withdrawn reaction product is depressurized with the gas captured for recovery of hydrogen and removal of unwanted gaseous by-products such as methane and carbon dioxide. Gas-liquid separation then provides a vapor overhead containing at least a portion of the lower glycols and other volatilized compounds such as acetic acid. The retained liquid phase often contains the lower glycols in addition to higher boiling by-products and tungsten compounds. When distillation, flashing, or evaporation is used, the bottom temperature is often in the range of about 120° C. to 200° C., and the vapor phase is at a pressure of about 500 to 10,000, e.g., 1000 to 5000 kPa (absolute). In these embodiments of the invention, since most of the water and all of the ethylene glycol and propylene glycol are passed to the vapor phase, the liquid phase is sometimes rich in heavies, and thus may increase processing difficulties. Thus, water is preferably added to the liquid phase from the gas-liquid separator to provide a liquid containing at least about 25 weight percent, and sometimes at least about 35 weight percent, water.

[0072] The composition of the retained liquid phase depends, among other things, on the unit operations used to separate the lower glycols and the extent to which these unit operations are used to remove the lower glycols; the conversion process operations and reaction product composition; the concentration of the tungsten compounds in the reaction products, and whether and, if so, the amount of water or other solvents added to the retained liquid phase. In most cases, the lower glycols are the most predominant organic species in the retained liquid phase, and the retained liquid phase also contains higher boiling by-products, i.e., sorbitol, erythritol, threitol, and glycerin, and potentially carboxylic acids or esters. The retained liquid phase also contains tungsten compounds. Tungsten compounds include soluble tungsten compounds and may include solid tungsten compounds such as tungsten bronzes and tungstic acid. Tungsten compounds are typically oxygenated tungsten anions such as tungstic acid, partially neutralized tungstic acid, tungstates, metatungstates, paratungstates, and the like, which may or may not have catalytic activity. The retained liquid phase can be subjected to one or more unit operations that can change its composition, such as the addition of water or other solvent, or further gas-liquid separation or sorption or chemical reaction.

[0073] The process of the present invention can be used with retained liquid phases in which the concentration of lower glycols varies widely, since both ethylene glycol and propylene glycol elute from the ion exclusion chromatography after most of the tungsten compounds have been eluted. Thus, the lower glycols may comprise as much as about 50 or 60 weight percent, e.g., about 10 to 50 weight percent, of the organics in the retained liquid phase. Since the higher boiling by-products are rarely separated from the reaction product along with the lower glycols, the weight ratio of the higher boiling by-products to the tungsten compounds (calculated as metal) is useful in describing the chromatographic separation. In most cases, this ratio is greater than about 4:1, and may be up to about 300:1 or 500:1, and in some cases may be about 25:1 to 100:1.

[0074] All of the retained liquid phase, or an aliquot or aliquot portion, can be contacted with the ionic resin for ion exclusion chromatographic separation. Contacting can be continuous, semi-continuous, intermittent, or batchwise. The retained liquid phase can be diluted, for example with water, to reduce the viscosity. Sometimes the viscosity at the temperature of contact with the ionic resin is less than about 100 Pascal seconds, and in some cases, about 0.1 to 50 Pascal seconds. The temperature of the retained liquid phase in contact with the ionic resin is below a temperature that would adversely affect the resin, and is often in the range of about 0° C. to 150° C., for example, about 10° C. to 100° C. The pressure of the feed can fall within a wide range, for example, about 100 to 100,000 kPa (absolute). The liquid hourly space velocity of the feed to the ionic resin depends, among other things, on the nature and composition of the feed, the degree of chromatographic separation desired, the nature of the ionic resin, and the design of the equipment used for ion exclusion chromatography. In most cases, the liquid hourly space velocity is about 0.1 to 50 h -1 The range is.

[0075] The contact with the ionic resin can be carried out in a moving bed or a fixed bed, and can be carried out in a batch, semi-continuous, or continuous operation mode. The ionic resin is typically packed in a column, and the feed is passed through the column to provide an eluate. A solvent is then passed through the column to elute the other components in the feed. The determination of the diameter and height of the column is well within the skill of one of ordinary skill in the art of ion exclusion chromatography separations with the benefit of the disclosure herein. In some cases, the process of the present invention uses a simulated moving bed (SMB). The SMB apparatus can be operated continuously, if desired. The SMB apparatus includes multiple columns containing ionic resins connected in series. The valve and column arrangement is such that in the series of columns, the addition points of the feed and the solvent, and the withdrawal points of the desired product (product composition) enriched in tungsten compounds and the organic product are periodically moved from column to column. The movement is opposite to the flow of liquid in the series of columns to give the impression of a moving bed. For a general discussion of SMBs, see, e.g., U.S. Pat. Nos. 2,985,589, 4,340,724, and 6,479,716.

[0076] Any suitable ionic resin can be used, including strong and weak anionic resins and strong and weak cationic resins. The resin can be a gel, or preferably a macroreticular resin. In some cases, the resin has a cross-linking degree of at least about 3 percent, such as up to about 15 percent or more. Often, resins with a cross-linking degree of at least about 6 percent, preferably at least about 8 percent, are used to enhance stability and provide more porosity. In some cases, the porosity is such that the organics are eluted without using excessive amounts of solvent. In these cases, the focus of the chromatographic separation is to achieve the desired tungsten compound-containing eluent, and it is not desired to use the chromatographic separation for the separation of various organics. The effectiveness of the ionic resin for separating the tungsten-containing fraction from the organics can be recognized by comparing the total excluded volume to the total included volume. In general, the greater the difference, the more effective the separation. The total excluded volume is the amount of solvent required to exclude an aliquot of an ionic compound on the resin, such as tungstate. The total volume contained is the amount of solvent required to elute an aliquot of a non-ionic compound, such as glycerin.

[0077] Many commercially available ionic resins include one of polystyrene, polymethacrylate, and polyacrylate, and are often crosslinked using agents such as divinylbenzene. The ionic functionality can be provided by amines in the case of anionic resins, or carboxylic, phosphonic, or sulfonic acid groups in the case of cationic resins. In some cases, the size of the ionic resin particles ranges from 100 to 10,000 microns or more in major dimensions. The preferred ionic resin is a macroreticular cationic resin having carboxylic or sulfonic acid functionality for resin stability. Preferably, the cations associated with fresh cationic resin are not those that form precipitates with tungsten compounds, but after multiple cycles, any cations that do form precipitates are eluted. Sodium cationic resins are preferred. In some cases, the cationic resin is a polystyrene sulfonic acid strong cation exchange resin having a degree of crosslinking of at least about 4, such as at least about 6, such as about 6 to 15 percent.

[0078] drawing Reference is made to the drawings, which are provided to facilitate understanding of the invention, but are not intended to be limiting thereof. The drawings omit small equipment such as pumps, compressors, valves, instruments, heat exchangers, and other devices whose arrangement and operation are familiar to those skilled in the art of chemical engineering. The drawings also omit auxiliary unit operations.

[0079] Referring to Figure 1, the apparatus 100 includes a catalytic conversion reactor 102 for converting carbohydrates to ethylene glycol and / or propylene glycol. The reactor may be a single vessel or two or more vessels of the same or different design in parallel or series. At least one vessel contains a heterogeneous hydrogenation catalyst. At least one vessel contains a retro-aldol catalyst, particularly a soluble retro-aldol catalyst.

[0080] As shown, a carbohydrate feed is passed to reactor 102 via line 104 and hydrogen for catalytic conversion is passed to reactor 102 via line 106. Tungsten compounds for retro-aldol catalysis are provided by at least lines 110 and 112, as will be discussed below. The reaction products are removed from reactor 102 via line 108.

[0081] The reaction products contain one or both of ethylene glycol and propylene glycol, and contain higher boiling by-products (sorbitol, erythritol, threitol, glycerol, and 1,2-butanediol). Because the catalytic conversion is carried out at high pressure in the presence of hydrogen, the reaction products contain dissolved hydrogen and dissolved tungsten compounds.

[0082] As depicted, the reaction product is passed to a gas-liquid separator 114. The gas-liquid separator may include, for example, one or more unit operations with recovery of hydrogen and light gases followed by one or more unit operations for recovery of water and ethylene glycol and propylene glycol from the reaction product. Hydrogen and other light gases such as carbon dioxide and methane are removed via line 116 for recovery of hydrogen for recycle. The liquid components may then be subjected to one or more unit operations for recovery of lower glycols, including additional gas-liquid or liquid-liquid separation (e.g., selective membrane permeation and selective sorption). In another embodiment, the gas-liquid separation provides a vaporous overhead containing a substantial portion of the ethylene glycol and propylene glycol in the reaction product. Often at least about 30 weight percent, more frequently at least about 50 weight percent, e.g., about 50 to 75 or 95 weight percent of the total ethylene glycol and propylene glycol is provided overhead. The overhead in line 118 is passed to unit operations for purification of ethylene glycol and propylene glycol and separation of the normal gaseous components not removed with the hydrogen and light gases.

[0083] All or a portion (aliquot or aliquot) of the retained liquid phase is removed from the gas-liquid separator 114 via line 120. An embodiment is shown in which the high boiling components in the retained liquid are subjected to catalytic conditions to convert at least a portion of the high boiling by-products to lower glycols, for example, by hydrocracking. A portion of the retained liquid phase, even if it contains tungsten compounds, can be withdrawn from line 120 by line 122 for such catalytic treatment. In this way, the volume of the retained liquid phase subjected to ion exclusion chromatography can be controlled, especially when plant production fluctuates. As discussed later, the organic phase from ion exclusion chromatography can also be subjected to such catalytic treatment.

[0084] All or a remaining portion of the retained liquid phase in line 120 is passed to a simulated moving bed unit 124 for ion exclusion chromatography to provide a separated tungsten compound-containing eluate phase and a separated organics-containing eluate phase. If desired, a portion of the retained liquid phase may be subjected to chemical and / or physical unit operations to reduce the presence of solids (e.g., filtration, oxidation, etc.).

[0085] For purposes of discussion and not to limit the invention, the simulated moving bed contains ten strong cation resin columns connected in series with valves for adding and removing liquid from each column. A quantity of retained liquid phase is introduced into one of the series of columns for a given time, and the liquid passing through that column is passed to the next column in the series, and so on for all ten columns. After a given time, the retained liquid phase feed is passed to the previous column in the series. This sequence is repeated continuously. The tungsten-containing eluate phase is removed from the subsequent column in the direction of liquid flow, for example, the fourth column from the column into which the retained liquid phase is introduced. The selection of columns is well within the skill of the art of ion exclusion chromatography in a simulated moving bed and depends in part on the portion of tungsten compounds to be recovered and the concentration of organic matter that can be tolerated in the tungsten compound-containing eluate phase. The ion exclusion chromatography can be operated so that the proportion of tungsten compounds toward the tungsten compound-containing elution phase is high, for example, at least about 90 atomic percent, preferably at least about 95 or 99 atomic percent tungsten. Alternatively, the ion exclusion chromatography can be operated so that contamination of the tungsten-containing elution phase with organic compounds is usually not significant, but minimization of organic acids is preferred to reduce the amount of base required for pH adjustment, especially when the tungsten compound-containing elution phase is subjected to pH adjustment to, for example, convert tungsten complexes to partially neutralized tungstates. In many cases, the mass ratio of total organics to tungsten compounds (calculated as elements) is less than about 10:1, and in some cases, less than about 1:1, for example, about 0.1:1. The tungsten compound-containing elution phase is removed from the simulated moving bed 124 via line 126. If desired, a portion of the eluate phase can be removed from line 126 via line 128 for tungsten purging or recovery.

[0086] The relative volume of the purge stream depends, among other things, on the portion of the tungsten species that is rendered catalytically inactive or relatively inactive during the reaction process, such as tungsten acid or tungsten bronze. Purging may be continuous or intermittent. When purging is used, often about 5-40 weight percent, e.g., about 10-25 weight percent, of the elution phase is purged. Tungsten may be recovered from the purge stream. Any suitable process or combination of processes may be used to recover tungsten, including, but not limited to, ion exchange and acidification to precipitate tungstic acid for separation.

[0087] All or a portion of the tungsten compound-containing eluate phase can be passed continuously or intermittently to treatment vessel 130 via line 126. Because the tungsten compound-containing eluate phase may contain several tungsten compounds, including but not limited to meta- and para-tungstates, tungstic acid, and partially neutralized tungstates, conversion of the species to partially neutralized tungstates facilitates providing more predictable retro-aldol catalytic activity for the recycled tungsten compounds. As shown, a base such as sodium hydroxide is added to treatment vessel 130 via line 132 in an amount sufficient to adjust the pH to about 6-8, often about 6.5-6.8. Treated effluent is removed from vessel 130 via line 134 for recycle to reactor 102.

[0088] Returning to line 126, if desired, all or a portion of the tungsten compound-containing eluate phase can be sent continuously or intermittently to line 136 for recycle to reactor 102, bypassing treatment vessel 130. When bypassing is performed, typically about 20-100 weight percent, sometimes about 25-80 weight percent, of the tungsten compound-containing eluate phase is passed from line 126 to line 136. In some cases, the bypass tungsten compound-containing eluate phase is such that the pH of the mixture of feed, organic recycle, and retro-aldol catalyst in line 104 is at least about 4.5, preferably at least about 5, e.g., 5.5-8, sometimes about 5.5-6.8.

[0089] The treated effluent in line 134 from treatment vessel 130 is depicted as being combined with an optional bypass in line 136 for recycle to reactor 102. All or a portion of the recycled tungsten compound in line 136 can be sent to line 104 via line 112 for mixing with the feed, and all or a portion of the recycled tungsten compound in line 136 can be passed directly to reactor 102 via line 138. If the recycled tungsten compound is added directly to reactor 102, it is particularly beneficial if it has passed through treatment vessel 130 and has a pH in the higher range, e.g., about 6.5 to 8, so it can be used in part to control the pH in the reactor.

[0090] Returning to the simulated moving bed 124, a solvent such as water is added to the fifth column via line 125 to elute the organics from the sorption media in the simulated moving bed 124 to provide an eluent containing the organics in the last column of the series of columns. With simulated moving bed sequencing, the organic eluent is removed via line 140. A portion of this eluent is typically purged via line 142 to ensure steady state operation of the composition in the reactor 102. The purge is often in the range of 1 to 30 weight percent of the eluent, with larger percentages often being used when a significant portion of the retained liquid phase is bypassed via line 122. All or a portion of the organic eluent and the bypassed retained liquid phase can be passed directly to the reactor 102 or, as shown, can be subjected to unit operations to enhance the efficiency of the conversion of the feed to monoethylene glycol. In the figure, the organic eluent in line 140 is combined with the retained liquid phase in line 122 and passed to the hydrocracking reactor. In hydrocracking reactor 144, hydrogen provided via line 150 and a hydrocracking catalyst are contacted with organics provided via line 122 under hydrocracking conditions to provide a hydrocracking product containing, inter alia, monoethylene glycol and propylene glycol and reduced concentrations of carboxylic acids and higher boiling by-products. It should be understood that the hydrogen for hydrocracking can be an off-gas removed from reactor 102 via line 150. Hydrocracking conditions often include a temperature of about 150° C. or 200° C. to 240° C., preferably about 200° C. to 230° C. The hydrogen partial pressure is about 2500 to 12,000, e.g., about 5000 to 10,000 kPa, and the liquid hourly space velocity is about 0.01 to 20 hr -1 Any suitable hydrocracking catalyst can be used, such as those containing one or more of nickel, cobalt, ruthenium, rhodium, platinum, and palladium. Conveniently, the hydrocracking catalyst can be Hcat, which is used in hydrogenation.

[0091] Hydrocracking products are removed from hydrocracking reactor 144 via line 146 and gases are removed via line 148 for recovery and purification. All or a portion of the hydrocracking products in line 146 can be sent to line 108 for recovery of ethylene glycol and propylene glycol in gas-liquid separator 114.

Claims

1. 1. A catalytic process for producing lower glycols, including at least one of ethylene glycol and propylene glycol, from a carbohydrate-containing feed comprising at least one of aldose and ketose producing carbohydrates, said process comprising: (a) continuously or intermittently feeding said feed to a reaction zone having dissolved tungsten compounds therein, at least one of which is a homogeneous tungsten-containing retro-aldol catalyst, and at least one heterogeneous hydrogenation catalyst, to produce a reaction product containing said lower glycols and one or more higher boiling by-products including sorbitol, erythritol, threitol, and glycerin, wherein said liquid medium is at catalytic conversion conditions including the presence of dissolved hydrogen; (b) continuously or intermittently removing a liquid medium containing the reaction products and dissolved tungsten compounds from said reaction zone; (c) subjecting at least a portion of the removed liquid medium to one or more unit operations to remove at least a portion of the lower glycols in the separated fraction and to provide a retained liquid phase containing dissolved tungsten compounds and high-boiling by-products, the mass ratio of tungsten compounds, calculated as high-boiling by-products to metals, being greater than about 4:1; (d) contacting at least a portion of the retained liquid phase with an ionic resin for ion exclusion chromatography to provide a first elution fraction containing dissolved tungsten compounds and a mass ratio of tungsten compounds calculated as high boiling by-products to metal that is less than about 1:1, and contacting the ionic resin with sufficient solvent to provide at least one subsequent elution fraction containing one or more high boiling by-products and a lower concentration of tungsten compounds than in the retained liquid phase.

2. 2. The process of claim 1, wherein at least about 90 weight percent of the tungsten compounds contained in the retained liquid phase contacting the ionic resin is in the first elution fraction.

3. 10. The process of claim 1, wherein the portion of the retained liquid phase that contacts the cationic resin is a purge stream.

4. 2. The process of claim 1, wherein at least a portion of the first elution fraction is recycled to step (a).

5. 5. The process of claim 4, wherein the pH of the recycled first elution fraction is provided at about 6.5 to 8 before being passed to step (a).

6. 6. The process of claim 5, wherein at least a portion of the tungsten compounds in the recycled first elution fraction is semi-neutralized tungstic acid.

7. 2. The process of claim 1, wherein at least a portion of the at least one subsequent elution fraction containing one or more high boiling by-products is subjected to hydrocracking conditions to provide at least one of ethylene glycol and propylene glycol.

8. The process of claim 1 , wherein the ionic resin comprises a cationic resin.

9. 9. The process of claim 8, wherein the cationic resin comprises a polystyrene sulfonate strong cation exchange resin.

10. The process of claim 1 , wherein the ionic resin has a degree of cross-linking of at least 6 percent.

11. The process of claim 10, wherein the ionic resin has a degree of cross-linking of at least 8 percent.

12. 10. The process of claim 1, wherein step (d) is carried out as a simulated moving bed.

13. 10. The process of claim 1, wherein the one or more unit operations of step (c) comprises gas-liquid separation.

14. 1. A product composition comprising a dissolved tungsten compound and one or more high boiling polyols including sorbitol, erythritol, threitol, and glycerin, wherein the mass ratio of total high boiling polyol to tungsten compound, calculated as metal, is less than about 5:

1.

15. 15. The product composition of claim 14, wherein the weight ratio of total high boiling polyol to tungsten compound, calculated as metal, is from about 0.01:1 to 1:1.

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