Processes for making ethylene glycol and / or propylene glycol from aldose- and / or ketose-yielding carbohydrates with integrated tungsten catalyst recovery

Abstract

To provide integrated processes for catalytic conversion of carbohydrate to ethylene glycol and / or propylene glycol using a homogeneous, tungsten-containing retro-aldol catalyst.SOLUTION: A carbohydrate is subjected to retro-aldol conversion and hydrogenation. Ethylene glycol and propylene glycol are separated from the reaction product for purification, and at least a portion of the remaining fraction is subjected to ion exclusion chromatography to provide an eluant containing tungsten species and a subsequent eluant containing organic acids and a substantially reduced concentration of tungsten species. At least a portion of the eluant containing tungsten species can be recycled for reuse directly or with intervening unit operations to enhance the catalytic activity of the tungsten species. The organic-containing fraction can be subjected to unit operations to provide salable products or subjected to selective hydrogenolysis to lower glycols.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] FIELD OF THE INVENTION 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] Proposals have been made to produce ethylene glycol and propylene glycol from renewable resources, such as carbohydrates, e.g., sugars. One such route, commercially practiced, 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 route").

[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 desired initial 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 its hydrogenation to a polyol such as sorbitol.

[0007] The catalysts used for the retroaldol conversion are typically homogeneous and contain tungsten, which therefore exits the reaction system with the product. The monoethylene glycol and propylene glycol are separated from the reactor effluent, and at least the tungsten-containing remainder is removed. Various proposals have been made to recycle a portion of the tungsten to the reactor. See, for example, U.S. Patent Nos. 10,294,181 and 10,647,646 and U.S. Patent Application Publication No. 2021 / 0087128. While recycling can conserve tungsten, 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, which process is easy to operate, requires little energy, and provides recovered tungsten compounds with desirable catalytic activity for retro-aldol transformation. Summary of the Invention

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

[0011] The present invention provides an integrated process for the 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 a reaction product containing ethylene glycol and / or propylene glycol, and other reaction processes contain organic acids, thiols, and tungsten species. The ethylene glycol and propylene glycol are separated from the reaction product for purification, and at least a portion of the remaining fraction (the "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, either directly or with an intervening unit operation to enhance the catalytic activity of the tungsten species.

[0012] Although tungsten species constitute 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 separated into the subsequent eluent phase. Thus, the tungsten-containing eluent is suitable for recycle without excessive accumulation of non-reactive organic matter in the reaction zone, and any intervening treatment of the tungsten species in the recycled eluent involves reduced volume liquid treatment. Furthermore, when the organic acid content is reduced by intervening treatments such as pH adjustment, less pH adjuster is required for the desired pH change to convert the tungsten compounds into 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) adding at least one of the following to produce a reaction product containing lower glycols and one or more higher boiling by-products including sorbitol, erythritol, threitol, and glycerin; continuously or intermittently supplying 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, 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; (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, wherein the mass ratio of high-boiling by-products to tungsten compounds, calculated as metal, is 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 present in a 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 through step (a). Optionally, at least a portion of the tungsten compounds in the recycled first elution fraction are 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 total high boiling polyol to tungsten compound, calculated as metal, is less than about 5:1, preferably less than about 1:1, and sometimes between about 0.01:1 and 1:1. [Brief explanation of the drawings]

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

[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 apparent from the context of their use.

[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 appropriate intermediate values ​​and ranges between the recited endpoints can be selected. For example, if 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) n Non-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] An aldose-yielding carbohydrate refers to 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. By way of example and not limitation, a solution of 90 volume percent ethylene glycol and 10 volume percent water 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 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] Calculated as metal means calculated 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 that are 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, and for Hcats, includes supports, binders, and other auxiliary materials. A catalytic metal is a metal that is in an 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 that 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 with 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 does not require that every molecule of the fluid contact the catalyst.

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

[0030] The conversion of aldohexose to ethylene glycol is reported as a mass percent 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 aldohexose theoretically produced upon hydrolysis of any di- or polysaccharides contained in the carbohydrate feed.

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

[0032] High shear mixing involves providing fluids moving at different velocities relative to adjacent regions, which can be accomplished by static or moving mechanical means to create 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 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 a residence time greater than 1 minute.

[0035] Intermittent means from time to time, which 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; because it is saturated, similar ions are repelled by the adsorbent material. Ion exclusion chromatography can use an ion exchange resin bed, which acts as a charged solid separation medium. Ion exclusion chromatography techniques using porous resin beds can be useful for achieving size exclusion separation, so that molecules can be separated by size and molecular weight, with larger, heavier molecules eluting first.

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

[0038] Ketose refers to a monosaccharide containing one ketone group per molecule. Non-limiting examples of ketoses include ketohexoses (all six-carbon ketone-containing sugars, including fructose, psicose, sorbose, and tagatose), ketopentoses (all five-carbon ketone-containing sugars, including xylulose and ribulose), ketotetroses (all four-carbon ketose-containing sugars, including erythrulose), and ketotrioses (all three-carbon ketose-containing sugars, including dihydroxyacetone).

[0039] By ketose-yielding carbohydrate is meant a ketose or disaccharide or polysaccharide or hemicellulose that can produce a ketose or ketose precursor 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-yielding carbohydrate, even though it also produces an aldose upon hydrolysis. For purposes herein, carbohydrates that produce both aldoses and ketoses are considered ketose-yielding 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 glycol is ethylene glycol or propylene glycol or a mixture 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 allowed to stand at ambient pressure and temperature for 2 hours, after which the pH is determined. If the aqueous solution contains less than about 50% by weight of water, for example, in a glycol-rich medium, water is added to the sample to provide a solution containing about 50% by weight of water. For consistency, the dilution of the solution is to the same weight percent of water.

[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, we mean 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 and 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, tank 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 chemical compounds, 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 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 present invention utilizes a carbohydrate feed containing either an aldohexose-yielding carbohydrate or a ketose-yielding 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 should be at least about 90 mass percent, preferably at least about 95 or 100 mass percent. 99 weight percent aldohexose-yielding carbohydrates. Often the carbohydrate feed comprises a carbohydrate polymer such as starch, cellulose, or a partially to essentially fully 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 gulose-fructose, psicose, sorbose, and tagatose. Most biogenic carbohydrate feedstocks produce glucose upon hydrolysis. Glucose precursors include, but are not limited to, maltose, trehalose, cellobiose, kojibiose, 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 a 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 be at least partially hydrated. Non-aqueous solvents include alkanols, diols and polyols, ethers, or other suitable carbon compounds having 1 to 6 carbon atoms. Solvents include mixed solvents, particularly 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 depletion. Preferred non-aqueous solvents are those that can 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 can 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, the volume of the feed must be balanced with the volume of the raw product being removed.

[0055] An additional consideration when feeding carbohydrates to the reaction zone is minimizing 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 must be separated to recover the desired glycol product.

[0056] Preferably, the feed is introduced into the reaction zone in a manner that avoids excessive concentrations of the feed, which can result in hydrogen deficiency. The use of more carbohydrate feed locations per unit volume of the reaction zone allows for a more concentrated carbohydrate feed. Generally, the water-to-carbohydrate mass ratio in the carbohydrate feed is preferably in the range of 4:1 to 1:4. Aqueous solutions of 600 grams per liter or more of certain carbohydrates, such as dextrose and sucrose, are sometimes commercially available.

[0057] In some cases, the recycled hydrogenation solution is substantially free of hydrogenation catalyst, or The recoat or separated portion 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 provides the carbohydrate at a rate sufficient to maintain a high conversion rate per unit volume of the reaction zone. The use of recycle, especially when the recycle is an aliquot portion of the raw product stream, allows for the feeding of a low concentration of carbohydrate to the reaction zone while maintaining a high conversion rate of carbohydrate to ethylene glycol. Additionally, the recycle stream can be maintained at or near the temperature within the reaction zone, and since the recycle stream contains a 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 added solvent is often in the range of about 0.05:1 to 0.4:1, and sometimes between about 0.1:1 and 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 retroaldol 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, which 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 before being introduced into the reaction zone, and the carbohydrate feed may or may not have been heated through a temperature zone between 170°C and 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, while in other cases, the retro-aldol reaction may have occurred at least partially before the carbohydrate feed is introduced into the liquid medium in the reaction zone. Rapid dispersion of the carbohydrate feed in the liquid medium is generally preferred, particularly when a hydrogenation medium is used to provide direct heat exchange to the carbohydrate feed. This dispersion can be achieved by any suitable procedure, including, but not limited to, the use of mechanical and static mixers and rapid diffusional 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, such as 90°C or as low as 150°C. 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 15,000 kPa). 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 heterogeneous and homogeneous catalysts, including catalysts supported on a support, including, but not limited to, tungsten and its oxides, sulfates, phosphides, nitrides, carbides, halides, acids, and the like. Also included are tungsten carbide, soluble tungsten phosphonates, and tungsten oxide supported on zirconia, alumina, and alumina-silica. Preferred catalysts are provided by soluble tungsten compounds and mixtures of tungsten compounds. Soluble tungsten Acid salts 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 lower glycol products. Without wishing to be bound by theory, the catalytically active species may or may not be the same as the soluble tungsten compound introduced as the catalyst. Rather, the catalytically active species may form 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 greater than 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 retroaldol catalysts include ammonium or alkali metal tungstates that are partially neutralized with an acid, preferably a 1-6 carbon organic acid, 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 can be carried out before the tungsten-containing compound is introduced into the reactor, or it can be carried out 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, as a separate feed to the liquid medium, with the recirculating liquid medium, or any combination thereof. When the retro aldol catalyst contains 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 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 a reaction zone containing a hydrogenation catalyst. Preferably, introduction into the aqueous hydrogenation medium occurs within less than 1 minute, and most often less than 10 seconds, from the start of subjecting the carbohydrate feed to retro-aldol conditions. Some or all of the retro-aldol reaction can occur within the reaction zone containing the hydrogenation catalyst. In any event, the most preferred processes are those with 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 a retro-aldol reaction, thereby enhancing 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. Therefore, the temperature for the hydrogenation reaction is often about 230°C to 300°C, e.g., about 240°C to 280°C. Typically, the retro-aldol reaction In the ethanol process, the pressure (absolute) is typically in the range of about 15 to 200 bar (1500 to 20,000 kPa), e.g., about 25 to 150 bar (2500 to 15,000 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, e.g., 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. Often, the hydrogenation catalyst is a supported, heterogeneous catalyst. It can be configured 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 capable of providing high hydrogen concentrations and rapid heating is a cavitation reactor, such as that disclosed in U.S. Pat. No. 8,981,135 (B2), the entire contents of which are incorporated herein by reference. Cavitation reactors generate heat in localized regions; 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 purposes of this invention. Cavitation reactors are interesting for this process because the retro-aldol transformation can be achieved very rapidly 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 can 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, of nickel (calculated as elemental nickel) per liter of liquid medium in the reactor. As noted above, not all nickel in the catalyst is in the zero-valent state, nor is all nickel in the zero-valent state readily accessible by glycolaldehyde or hydrogen. Therefore, 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 slurry reactors, 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; in packed-bed reactors, 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 carbohydrates in the feed. -1 Preferably, the residence time is sufficient so that glycolaldehyde and glucose are 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 process of the present invention, the combination of reaction conditions (e.g., temperature, hydrogen partial pressure, catalyst concentration, hydraulic distribution, and residence time) results in at least about 95 weight percent of the carbohydrates producing aldoses or ketoses, often at least about 98 or 99 weight percent, and sometimes It is sufficient to convert essentially all of the carbohydrates. 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 this disclosure.

[0070] Ion Exclusion Chromatography Separation The process of the present invention uses ion exclusion chromatography separation to obtain a product composition enriched in dissolved tungsten compounds as the desired product, while excluding the lower glycols and high-boiling by-products recovered in the subsequent eluent. The product composition has a substantially reduced ratio of lower glycols and high-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 high-boiling by-products, and the subsequent eluent can be purged and / or processed without excessive 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 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 removed reaction product is depressurized with the gas captured to recover hydrogen and remove 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 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, because most of the water and all of the ethylene glycol and propylene glycol are passed through to the vapor phase, the liquid phase is sometimes enriched in heavies, which can increase processing difficulties. Therefore, water is preferably added to the liquid phase from the gas-liquid separator to provide a liquid containing at least about 25 weight percent, 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 them; the conversion process operations and reaction product composition; the concentration of tungsten compounds in the reaction product; whether and, if so, the amount of water or other solvent added to the retained liquid phase. In most cases, 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 also 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, and paratungstates, 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 having widely varying concentrations of lower glycols, since both ethylene glycol and propylene glycol elute from the ion exclusion chromatography after most of the tungsten compounds have eluted. Thus, the lower glycols may comprise as much as about 50 or 60 weight percent of the organics in the retained liquid phase, e.g., about 10-50 weight percent. Because 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 compound (calculated as the 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] The entire retained liquid phase, or an aliquot or aliquot portion thereof, can be contacted with an ionic resin for ion exclusion chromatography separation. Contacting can be continuous, semi-continuous, intermittent, or batchwise. The retained liquid phase can be diluted, for example, with water, to reduce viscosity. Sometimes, the viscosity at the contact temperature 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 contacting the ionic resin is below a temperature that would adversely affect the resin, often in the range of about 0°C to 150°C, e.g., about 10°C to 100°C. The pressure of the feed can fall within a wide range, e.g., about 100 to 100,000 kPa (absolute). The liquid hourly space velocity of the feed to the ionic resin depends, among other factors, on the nature and composition of the feed, the degree of chromatographic separation desired, the properties of the ionic resin, and the design of the equipment used for ion exclusion chromatography. In most cases, the liquid hourly space velocity is approximately 0.1 to 50 h -1 The range is.

[0075] Contact with the ionic resin can be carried out in a moving bed or fixed bed and can be carried out in batch, semi-continuous, or continuous operation modes. 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 other components in the feed. Determining 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 valves and columns are arranged such that the points of addition of the feed and solvent, and the points of withdrawal of the desired product (product composition) enriched in tungsten compounds and organic products, are periodically moved from column to column in the series. The movement is opposite to the flow of liquid within the series of columns, creating the impression of a moving bed. For a general discussion of SMBs, see, e.g., U.S. Patent 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 crosslinking degree of at least about 3 percent, e.g., up to about 15 percent or more. Resins with a crosslinking degree of at least about 6 percent, preferably at least about 8 percent, are often used to enhance stability and provide more porosity. In some cases, the porosity is such that organics can be eluted without using excessive amounts of solvent. In these cases, the focus of the chromatographic separation is to achieve the desired tungsten compound-containing eluate, and it is not desirable to use the chromatographic separation to separate various organics. The effectiveness of an ionic resin for separating a tungsten-containing fraction from organics can be determined by comparing the total excluded volume to the total included volume. Generally, 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, such as tungstate, on the resin. 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 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. Preferred ionic resins are macroreticular cationic resins with carboxylic or sulfonic acid functionality for resin stability. Preferably, the cations associated with fresh cationic resins do not form precipitates with tungsten compounds, but after multiple cycles, any cations that form precipitates are eluted. Sodium cationic resins are preferred. In some cases, the cationic resin is a strong cation exchange resin with a crosslinking degree of at least about 4, e.g., at least about 6, e.g., about 6 to 15 percent.

[0078] drawing Reference is made to the drawings, which are provided to facilitate understanding of the invention and are not intended to limit the invention. 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, 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. A tungsten compound for the retro-aldol catalyst, as discussed below, is provided by at least lines 110 and 112. The reaction product is removed from reactor 102 via line 108.

[0081] The reaction products contain one or both of ethylene glycol and propylene glycol, and 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 involving the recovery of hydrogen and light gases, followed by one or more unit operations for the 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 the recovery of hydrogen for recycle. The liquid component may then be subjected to one or more unit operations for the 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 often 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 the purification of ethylene glycol and propylene glycol and the separation of the usual gaseous components not removed with hydrogen and light gases.

[0083] All or a portion (aliquot or aliquant) of the retained liquid phase is removed from gas-liquid separator 114 via line 120. In one embodiment, 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, e.g., by hydrocracking. A portion of the retained liquid phase, even if it contains tungsten compounds, can be withdrawn from line 120 via line 122 for such catalytic treatment. In this manner, the volume of the retained liquid phase subjected to ion exclusion chromatography can be controlled, particularly when plant production fluctuates. As discussed below, 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, but not limitation, a simulated moving bed system contains ten strong cation resin columns connected in series with valves for adding and removing liquid from each column. A certain amount of retained liquid phase is introduced into one of the columns in the series for a predetermined 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 predetermined time, the retained liquid phase feed is passed to the previous column in the series. This sequence is repeated continuously. A tungsten-containing eluate phase is removed from a subsequent column in the direction of liquid flow, e.g., the fourth column from the column into which the retained liquid phase is introduced. The selection of columns is well within the skill of simulated moving bed ion exclusion chromatography 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 to achieve a high proportion of tungsten compounds in the tungsten compound-containing eluate phase, e.g., 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 eluate phase with organic compounds is generally less significant, although minimizing organic acids is preferred to reduce the amount of base required for pH adjustment, particularly when the tungsten compound-containing eluate phase is subjected to pH adjustment, e.g., to 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, e.g., about 0.1:1. The tungsten compound-containing eluate 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 tungsten species that are rendered catalytically inactive or relatively inactive during the reaction process, such as tungsten acid or tungsten bronze. Purging can be continuous or intermittent. When purging is used, often about 5 to 40 weight percent, e.g., about 10 to 25 weight percent, of the eluate phase is purged. Tungsten can be recovered from the purge stream. Any suitable process or combination of processes can 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, converting 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 continuously or intermittently sent to line 136 for recycle to reactor 102, bypassing treatment vessel 130. When bypassing is performed, typically about 20 to 100 weight percent, and sometimes about 25 to 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 to 8, sometimes about 5.5 to 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 that 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 via line 125 to the fifth column to elute the organics from the sorption media in the simulated moving bed 124, providing an eluate containing the organics in the last column of the series. With simulated moving bed sequencing, the organic eluate is removed via line 140. A portion of this eluate is typically purged via line 142 to ensure steady-state operation of the composition within reactor 102. The purge is often in the range of 1 to 30 weight percent of the eluate, with larger percentages often being used if a significant portion of the retained liquid phase is bypassed via line 122. All or a portion of the organic eluate and bypassed retained liquid phase can be passed directly to reactor 102 or, as shown, can be subjected to unit operations to enhance the conversion efficiency of the feed to monoethylene glycol. In the figure, the organic eluate 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 the organics provided via line 122 under hydrocracking conditions to provide a hydrocracking product containing, among other things, 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 may be the 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 Nickel, cobalt, ruthenium, rhodium Any suitable hydrocracking catalyst may be used, such as one containing one or more of platinum and palladium. Conveniently, the hydrocracking catalyst may be Hcat, which is used for hydrogenation.

[0091] The hydrocracking product is removed from the hydrocracking reactor 144 via line 146, and the gases are removed for recovery and purification via line 148. All or a portion of the hydrocracking product 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 supplying 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 high-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 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, wherein the mass ratio of high-boiling by-products to tungsten compounds, calculated as metal, is 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, of 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 cation 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. 10. 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. 10. The process of claim 1, wherein the ionic resin has a degree of cross-linking of at least 6 percent. Process.

11. 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) comprise 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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