Methods for recovering and regenerating catalysts from ash

Abstract

A method for recovering and regenerating tungsten compounds suitable for use as promoters for converting carbohydrates and hydrogen into alkylene glycols and polyols from ash containing one or more tungsten oxygen components (e.g., containing tungstates and / or tungstic acid), which ash can be obtained by burning a liquid mixture containing alkylene glycols and / or polyols and sodium tungstate and / or tungstic acid.

Description

[0001] introduction

[0002] The present invention relates to a method for recovering and regenerating tungsten compounds from ash containing one or more tungsten oxygen components (e.g. containing tungstates and / or tungstic acid), which are suitable for use as promoters for converting carbohydrates with hydrogen into alkylene glycols and polyols. The ash can be obtained by burning a liquid mixture containing alkylene glycols and / or polyols and sodium tungstate and / or tungstic acid. The recovered and regenerated tungsten component catalyst can be fed into a reactor, where it is a promoter in the hydrogenolysis of carbohydrates. Background Art

[0003] WO 2016 / 114661 discloses a continuous method for producing ethylene glycol from a carbohydrate source. The method is carried out in a stirred tank reactor (CSTR) in which a catalyst system is present. The catalyst system comprises a tungsten compound and at least one hydrogenolysis metal. The hydrogenolysis metal is preferably present in the form of a catalyst supported on a carrier. The heterogeneous catalyst particles can be separated from the effluent stream quite easily, for example by separation by a sieve plate, and added back. On the other hand, tungsten compounds are generally dissolved or dispersed in a liquid reaction medium (i.e., present as a homogeneous catalyst compound) and are not so easily removed from the effluent stream. Therefore, when the method is operated in a CSTR, the tungsten compound is partially removed as part of the effluent. In order to maintain the desired concentration of tungsten compound, it is therefore necessary to add the desired tungsten compound to the reactor (following the carbohydrate source, diluent and hydrogen) in a continuous manner or in a periodic manner. This is accomplished in the method of WO2016 / 114661.

[0004] The tungsten compound to be added may be a freshly prepared tungsten compound, or may be a regenerated tungsten compound. In the long run, regenerated tungsten compounds are more attractive for a number of reasons, but they require the recovery of the tungsten compound dissolved or dispersed in the reactor effluent and subsequent regeneration. In this method, regeneration may be necessary because the tungsten compound found in the effluent may not necessarily have the same physical or chemical composition as that required for the most efficient and / or selective reaction. Therefore, it is desirable to recover the tungsten compound from the reaction effluent in WO2016 / 114661 and to regenerate it in a form suitable for feeding back to the reactor again.

[0005] WO2017 / 042125 discloses a discharge stream from a circulation loop, the discharge stream and the circulation loop comprising hydrocarbon heavies, and homogeneous catalyst compounds (containing metal compounds) can be burned at a temperature of 300-750°C to produce a solid residue. The discharge is to prevent the accumulation of heavy components that cannot be decomposed to provide glycols, and also to prevent the accumulation of contaminants present in the sugar feedstock. The discharge stream of the method can avoid the accumulation of pollutants of an organic nature because it is burned. WO2017 / 042125 states that the solid residue containing compounds derived from the homogeneous catalyst can be further processed. It also states that the metal compounds present in the (ash) residue may need to be reactivated. The only example is heating heavy hydrocarbons and a sodium metatungstate catalyst to 450°C in an oxygen-containing atmosphere to obtain a solid residue containing Na 2 W 2 O 7 and Na 2 WO 4 The catalyst is a white, water-soluble solid that is said to have comparable catalytic activity to fresh catalytic material fed into the reactor.

[0006] In a process for producing ethylene glycol and / or propylene glycol in a continuous manner from a feed to a reactor system, burning the exhaust stream is indeed a convenient way to avoid the accumulation of combustible pollutants (e.g., most organic pollutants, such as polyols or sugar alcohols). If the ash of the method of WO2017 / 042125 is discarded, pollutants of an inorganic nature are indeed removed (organic pollutants are removed by combustion). However, if, as in the example in WO2017 / 042125, the dissolved solid material is reused as a catalyst, then the method does not remove pollutants of an inorganic nature, such as sodium, calcium, magnesium or their salts. If too much accumulation is obtained, these ions may be detrimental to the desired reaction.

[0007] Therefore, there is a need for a method capable of recovering part or all of the tungsten compounds from ash, which can be obtained by burning (or thermally decomposing and / or oxidizing) the effluent or side stream of the process for producing ethylene glycol and / or propylene glycol and / or glycerol, and which can remove or reduce inorganic pollutants. More specifically, the method should preferably allow the removal or reduction of sodium, calcium or magnesium (salts or oxides). In addition, it is desired that the recovered tungsten compounds are in a form that can be reused in a process for producing ethylene glycol and / or propylene glycol and / or glycerol from carbohydrates using hydrogen and a catalyst system, the catalyst system comprising a tungsten compound and a hydrogenolysis metal selected from Groups 8, 9 or 10 of the periodic table. Preferably, the tungsten compounds in the ash can be recovered in a form that is conducive to the return of feed to the process. Summary of the invention

[0008] It has now been found that the above objects can be at least partially achieved by a process for recovering and regenerating a tungsten compound from an ash containing one or more tungsten oxide components, the tungsten compound being suitable for use as a catalyst for the conversion of carbohydrates with hydrogen into alkylene glycols and polyols, wherein the process comprises the steps of:

[0009] a. contacting the ash with an organic acid having a pH value below 2;

[0010] b. separating the mixture obtained from step a into a solid fraction and a liquid fraction;

[0011] c. washing the solid fraction obtained from step b with an aqueous liquid;

[0012] d. solubilizing the washed solid obtained in step d in an alkylene glycol composition and dissolving an alkali metal hydroxide in the alkylene glycol composition, wherein the amount of the alkali metal hydroxide is selected so that the molar ratio of alkali metal hydroxide to tungstic acid in the resulting composition is from 0.2 to 2.

[0013] In the above method, ash can be obtained by burning a reactor (e.g., operated in a continuous or semi-continuous manner) effluent stream (or part thereof) in which a carbohydrate (e.g., sugar) is hydrogenolyzed with hydrogen under pressure and in the presence of a catalyst system comprising a tungsten compound and a hydrogenolysis metal selected from Groups 8, 9, or 10 of the periodic table. This reaction is described in the prior art discussed herein. This effluent stream can be the effluent after valuable components (e.g., ethylene glycol and / or propylene glycol and / or glycerol and / or other components) are removed from the effluent, for example, by distillation. It can also be a discharge stream with or without the removal of the above valuable glycols.

[0014] Thus, the present invention also relates to a process for producing ethylene glycol and / or propylene glycol and / or glycerol in a continuous manner from a feed to a reactor system, the feed comprising a carbohydrate source and hydrogen in a diluent, the reactor system comprising a catalyst system comprising a tungsten compound and a hydrogenolysis metal selected from Groups 8, 9 or 10 of the Periodic Table of Elements, wherein the effluent of the reactor system comprises the diluent, the tungsten compound, one or more of ethylene glycol, propylene glycol, glycerol and one or more polyols having a boiling point higher than ethylene glycol, wherein the reactor system effluent undergoes the following process steps:

[0015] a. separating the reactor effluent into ethylene glycol and / or propylene glycol and / or

[0016] or glycerol and a bottoms stream comprising one or more polyols having a boiling point higher than ethylene glycol and one or more tungsten compounds;

[0017] b. subjecting the bottom stream of the distillation stage comprising a polyol having a boiling point higher than that of ethylene glycol and one or more tungsten compounds to a burner in which at least a portion of the polyol is burned and at least a portion of the ash is recovered;

[0018] a. contacting the recovered ash with an organic acid having a pH below 2;

[0019] d. separating the mixture obtained from step c into a solid fraction and a liquid fraction;

[0020] e. washing the solid fraction obtained by step d with an aqueous liquid;

[0021] f. solubilizing the washed solid obtained in step e in an alkylene glycol composition and dissolving an alkali metal hydroxide in the alkylene glycol composition, wherein the amount of the alkali metal hydroxide is selected so that the molar ratio of alkali metal hydroxide: tungstic acid in the resulting composition is from 0.2 to 2;

[0022] g. Feeding at least part of the mixture obtained in step f back into the reactor system.

[0023] In this method, the temperature in the reactor is usually 120° C. to 300° C., and the hydrogen partial pressure is usually 1 to 6 MPa. DETAILED DESCRIPTION

[0024] "Continuous process" or "in a continuous manner" is understood herein as not being a batch process. It is carried out in a reactor system having at least one feed and one product stream and is intended to operate in a steady state (after startup). The duration (from reaction start to shutdown) is preferably at least 5 times the average residence time of the reactor system, more preferably at least 10 times the average residence time, most preferably at least 100 times the average residence time.

[0025] In the process according to the invention, the tungsten oxycomponent and the tungsten compound preferably comprise tungstic acid and / or alkali metal tungstates, and in the case of alkali metal tungstates, they preferably comprise sodium tungstate and / or potassium tungstate. "Comprise" is used because usually other tungsten oxycompounds (such as tungsten oxide) can be part of the tungsten promoter used, whether intentionally or because the components are converted to other tungsten oxycomponents.

[0026] In the method according to the invention, the pH of the inorganic acid with which the ash is treated is below 2, preferably below 1.5, more preferably below 1. The inorganic acid may be any inorganic acid capable of providing an aqueous solution with a pH below 2 in the presence of some water. Suitable examples include hydrochloric acid, sulphuric acid, phosphoric acid and nitric acid. Preferably, the inorganic acid used comprises hydrochloric acid. Preferably, the inorganic acid with which the ash is treated is an aqueous solution of hydrochloric acid, preferably the aqueous solution contains hydrochloric acid and has a molar concentration of 1 to 6 M, preferably 1.2 to 4 M, more preferably 1.5 to 3 M.

[0027] As for the amount of (aqueous) mineral acid used to treat the ash in the present invention, it is preferred that the weight ratio of mineral acid:ash is from 50:1 to 1:1. More preferably, the amount is from 30:1 to 2:1. Higher amounts are possible but may cause difficulties in handling and do not appear to provide further benefits.

[0028] In the process according to the invention, the step of separating the mixture obtained from the process step of the acid treatment step into a solid fraction and a liquid fraction can be carried out by methods known in the art for separating fine powders from (aqueous) liquids, such as centrifugation, decantation, filtration and other techniques.

[0029] In the method according to the invention, the washing step after the above-mentioned separation of solid matter and liquid matter is washing the solid matter. For example, this washing is carried out to remove most of the acid and dissolved salts and oxides. The washing can be carried out with an aqueous liquid, preferably with water, preferably with demineralized water. By adopting continuous washing steps, the pH value of the washing liquid is increased. The number of washing steps is at least 1 step, preferably at least 2 steps, preferably at least 3 steps. The amount of washing liquid used for each circulation is preferably 0.5 to 20 times the amount of acid used.

[0030] The effluent stream of the reactor that can be subjected to carbohydrate hydrogenolysis will contain polyols, such as sorbitol, glycerol and erythritol, optionally after removal / separation of desired products such as ethylene glycol and / or propylene glycol. Depending on the technology, intended use and market price, one or more of these polyols (such as glycerol) may also be worth separating. However, it may be feasible that the product value exceeds the cost of separation at the desired purity. This means that some polyols are usually retained, and it is not economical to separate these polyols. This effluent from the reactor usually contains a tungsten-based homogeneous promoter. . This tungsten compound can be separated first (before separating the desired diol), but it can also remain in the solution of the reactor product (containing the polyol / diol mixture). In particular, when the tungsten-based promoter comprises tungstic acid, it is found that tungstic acid remains well dissolved in the polyol. Therefore, in addition to the polyol and the desired diol, the effluent of this hydrogenolysis reaction when the reactor contains tungstic acid as part of the tungsten-based promoter can also contain tungstic acid. When these effluents are subjected to combustion, for example at temperatures above 900° C., organic molecules (such as polyols and glycols, etc.) are decomposed, leaving behind an ash containing various inorganic components (mainly oxides and salts). The oxides and salts may have tungsten, but may also have metals, such as sodium, potassium, calcium, magnesium, etc. The source of these (non-tungsten) components may be, for example, carbohydrates: some sugars contain some of these elements. It is generally preferred to avoid the accumulation of these non-tungsten salts and oxides, especially by continuous processing, which the method at least partially achieves.

[0031] Therefore, it can be preferred in the method according to the present invention that the ash content can be obtained (preferably obtained thereby) by burning a liquid mixture comprising alkylene glycols and / or polyols and sodium tungstate and / or tungstic acid. As mentioned above, this mixture can be obtained directly from a reactor in which hydrogen is being used to hydrogenate carbohydrates, for example, on a discharge stream or a portion of a product stream, for example, after obtaining required alkylene glycols such as ethylene glycol and / or propylene glycol and / or glycerine. In this case, polyols generally include one or more of glycerine, sorbitol, erythritol. In this case, glycerine can be used as required product processing, but does not need to remove all glycerine, and it can be suitable as a carrier to carry a used tungsten catalyst, leaving the reactor with the product stream.

[0032] According to the above, the effluent which is preferably subjected to combustion may be the exhaust stream or a portion thereof after removal of desired products such as ethylene glycol and / or propylene glycol, or may be the product stream (of the sugar hydrogenolysis reactor).

[0033] In the method according to the invention, it is preferred that the one or more tungsten oxide components of the ash include: alkali metal tungstates and / or tungstic acid. Other tungstated components may also be present, because under the processing conditions, tungstic acid or tungstates can be converted into another tungsten oxide-containing compound.

[0034] Without being limited by theory, according to the method of the present invention, after the ash is treated and washed with acid, a solid is obtained which is believed to contain tungstic acid (possibly in addition to other tungstate substances). This solid tungstic acid can be used as a co-catalyst compound in hydrogenolysis reactions, but such solids are generally not easy to administer or apply. Therefore, it is preferred to dissolve or solubilize the component in a liquid that can be fed to the reactor, such as immediately after the carbohydrate. It has been found that the acid-treated, washed ash can be well solubilized or dissolved in alkylene glycol. In this case, it is preferred that the alkylene glycol composition in which the acid-treated, washed ash (i.e., the regenerated tungsten component catalyst) is dissolved or solubilized contains at least 50% by weight of ethylene glycol or propylene glycol, preferably it contains at least 70% by weight of ethylene glycol. The advantage of this glycol is that it is also produced in the reaction, so there is no need to add an external solvent to the reaction mixture. This glycol does not need to be pure ethylene glycol or pure propylene glycol: it can also be a mixture of the two, optionally with the presence of other glycols. The alkylene glycol in which the regenerated catalyst is dissolved or solubilized may also be or comprise glycerol.

[0035] It has been found that in order to dissolve or solubilize the acid-treated, washed ash (i.e., the solid regenerated tungsten promoter) in the alkylene glycol, the presence of some alkali metal hydroxide, such as sodium hydroxide or potassium hydroxide, can facilitate dissolution or solubilization. This alkali metal hydroxide can be added to the alkylene glycol in dry form or in the form of a solution in water. In this case, the alkali metal hydroxide preferably added to the alkylene glycol and the acid-treated, washed ash includes sodium hydroxide, potassium hydroxide, or a mixture thereof. In this case, the preferred alkali metal hydroxide is sodium hydroxide.

[0036] It has been found that the regenerated tungsten catalyst (which may be obtained by burning part or all of the effluent of the reaction discussed herein, the acid-treated, washed ash) is most easily promoted to dissolve or solubilize in the alkylene glycol (and still give good results in the hydrogenolysis reaction) when the amount of alkali metal hydroxide in step d is such that the molar ratio of alkali metal oxide: tungstic acid in the resulting composition is from 0.3 to 1.5, preferably from 0.4 to 1.2, and more preferably from 0.5 to 1. Therefore, these are the preferred ratios of the molar ratio of alkali metal hydroxide: tungstic acid in the resulting composition when dissolved or solubilized in alkylene glycol.

[0037] It is preferred to filter the composition obtained after dissolving or solubilizing the acid treated washed ash in an alkylene glycol in the presence of some alkali metal hydroxide.

[0038] As an alternative, instead of dissolving the acid treated, washed ash in the presence of some alkali metal hydroxide in an alkylene glycol, the acid treated, washed ash can be dried for solid storage. At any suitable time, the dried regenerated catalyst can be dissolved or solubilized in an alkylene glycol in the presence of an alkali metal hydroxide.

[0039] In the process according to the invention, the tungsten compound or tungsten oxide component which is preferably produced by regeneration and is suitable for use as a promoter for the conversion of carbohydrates with hydrogen into alkylene glycols and polyols comprises tungstic acid. Preferably, it comprises at least 80% by weight of tungstic acid, based on the weight of the total tungsten-containing component.

[0040] Example

[0041] Waste stream preparation

[0042] A model waste stream containing various polyols, tungstic acid and some salts was prepared. The model waste stream was designed to look similar to the waste stream that can be obtained by experiments similar to the method recorded in WO2016 / 114661 to prepare ethylene glycol and propylene glycol. Such a waste stream can be obtained after removing water, lower alkanols such as methanol and ethanol, and after removing ethylene glycol and propylene glycol by distillation when performing the above method. The model waste stream has the composition as shown in Table 1.

[0043] Table 1: Waste stream composition

[0044] Components weight% glycerin 66 Sorbitol 14 Erythritol 10 <![CDATA[H 2 WHERE 4 ]]> 8 NaOH 1 KOH 0.042 <![CDATA[CaCl 2 ]]> 0.005 <![CDATA[Na 2 SO 4 ]]> 0.106 MgO 0.001

[0045] Ash preparation

[0046] The model waste stream was burned in a natural gas flame (in the presence of air) at a temperature of about 1200°C with a residence time of about 1 second, with the burner having a downward orientation to enable the collection of ash particles formed by the combustion. Three different runs were performed and the ash was collected at multiple points of the burner. In total, seven ash samples (varying in appearance from white to light grey, all fine particles) were assembled from these three runs and elemental analysis was performed using the ICP (Inductively Coupled Plasma) technique. The results are shown in Table 2, which lists the ranges for each of the seven samples.

[0047] Table 2: Ash element composition

[0048] element weight% W 66-73 O 18-22 Na 5.6-7.5 C 3.5-6.1 Ca 0.05-0.17 Mg 0.02-0.1

[0049] The elemental analysis (C, O not determined) of the ash (light grey) of one sample (third run, burner bottom) is shown in Table 3.

[0050] Table 3: Elemental composition of burner bottom ash sample 3

[0051] element weight% W 68.7 Na 5.8 Ca 0.055 Mg 0.025

[0052] Ash regeneration as catalyst

[0053] The ash samples of Table 3 were combined with samples (whitish) of the third run (run nr3) collected at different points of the burner equipment, and the rest of this experimental part was further carried out. A total of 9 g of this combined sample was mixed with 90 g of aqueous hydrochloric acid solution (2M) with a reflux device (set to about 10°C) and a magnetic stirrer (at 500 rpm) in a conical flask on a heating plate (Ace tube heating block) heated to 80°C. Duration after reaching the set temperature: 90 minutes. It is worth noting that although part of the ash was dissolved in the aqueous acid, most of the ash was not dissolved. After cooling, the mixture was centrifuged (Hettich Rotana 460, 4600 rpm, 5 minutes), the liquid was decanted, and ICP elemental analysis was performed. The results are listed in Table 4 (percentage of the amount of Table 3).

[0054] Table 4: Elemental analysis results of decanted acid

[0055] element Dissolved % W 3.34％ Na 83.5％ Ca 80.5％ Mg 86.6％

[0056] The elemental analysis of the acid means that most of the components containing sodium, calcium and magnesium in the ash of the model solution are well dissolved in the acid after reflux, and only a small part of the tungsten-containing components in the ash of the model solution is lost with the acid.

[0057] The solid from the centrifugation was washed with demineralized water (about 30 g of water) and centrifuged again (4600 rpm, 5 minutes), decanted and the pH of the liquid was measured. This wash was repeated a total of 6 times. The pH of the wash liquid increased from about 0.75 in the first wash to about 3.4 in the last wash.

[0058] The washing water from the last washing was subjected to ICP elemental analysis of tungsten, and the result was a dissolution percentage of 0.17%, which means that the tungsten compounds in the ash are almost not lost with the washing water.

[0059] The ash thus obtained (acid treated and washed) was oven dried at a temperature of about 80°C for 14 hours and stored for later use.

[0060] The combined results of ICP elemental analysis of the aqueous hydrochloric acid solution and the washing water used above are listed in Table 5 (percentages of the amounts in Table 3).

[0061] Table 5: Elemental analysis results of decanted acid and wash water

[0062] element Dissolution by acid treatment % Water washing dissolution % Total dissolved % W 3.35％ 0.17％ 3.5％ Na 83.5％ - 86.9％ Ca 80.5％ - 88.9％ Mg 86.6％ - 92.8％

[0063] The results in Table 5 show that most of the non-tungsten metals in the ash are lost due to the acid treatment and subsequent washing, while most of the tungsten is retained as tungsten compounds.

[0064] The acid-treated, washed and dried tungsten component from the ash was dissolved in ethylene glycol in the presence of some sodium hydroxide. To this end, 6.7 g of the acid-treated, washed and dried ash obtained was mixed with 292.9 g of ethylene glycol and 1.41 g of sodium hydroxide solution (51 wt. % sodium hydroxide in water) to give a NaOH / H 2 WO 4 Mole ratio. This was performed in a glassware flask on a hot plate at 500 rpm, using a reflux column (open to atmosphere), heated to about 150°C, and once at set temperature, held for 120 minutes.

[0065] After cooling, the resulting mixture was filtered using vacuum filtration to remove a small amount of undissolved residues. ICP elemental analysis of tungsten gave a solubility of 84.2% as a percentage of boiler ash. The filtrate thus prepared was used directly as a co-catalyst in the conversion of sugars to glycols using hydrogen. The tungsten concentration in the solution thus obtained was also measured by ICP elemental analysis and was found to be 1.26% (calculated as pure tungsten).

[0066] Use of regenerated catalysts in sugar hydrogenolysis

[0067] The ethylene glycol solution containing the tungsten compound thus prepared (also containing sodium hydroxide and a small amount of water) was used as a co-catalyst in hydrogenolysis experiments.

[0068] To this end, two experiments were conducted: one experiment using the tungsten compound contained in ethylene glycol obtained as described above and a control experiment using 5 wt % fresh tungstic acid (H 2 WO 4 ) solution. Both experiments were performed using sucrose as the carbohydrate.

[0069] The experiments were conducted using the following reactor system.

[0070] The reactor was a 200 ml Hastelloy autoclave which was modified to a CSTR (continuous stirred tank reactor). Liquid feed (sugar water, ethylene glycol, ethylene glycol containing tungstic acid and sodium hydroxide) and gas feed were fed into the reactor separately.

[0071] The effective liquid volume of the reactor was set to 148 ml. The liquid feed was fed into the reactor by an HPLC pump, and nitrogen (for flushing before the reaction) and hydrogen were fed by mass flow controllers. The reactor was stirred using a radial blade, hollow shaft stirrer. The output line to the effluent capture vessel was equipped with a 20 μm stainless steel filter (to retain the ruthenium catalyst particles in the reactor).

[0072] The reactor is pressurized by a back pressure regulator on the output line (liquid / gas is only allowed to pass when a threshold pressure is exceeded, e.g. if the BPR is set at 60 bar, material will only be allowed to pass when the reactor exceeds 60 bar).

[0073] Nominal parameter settings for the experiment:

[0074] Liquid flow rate: 5-7 ml / min

[0075] Gas flow rate: 2L / min

[0076] Reactor pressure: 65-80 bar

[0077] Heterogeneous catalyst loading: 5-9 g ruthenium (5%) on activated carbon support (water content 50 wt%)

[0078] Stirring speed: 900RPM

[0079] The tests performed were codes P101 (invention) and P039 (control), and the feed and catalyst are shown in Table 6.

[0080] Table 6: Hydrogenolysis test

[0081]

[0082] EG: Ethylene glycol

[0083] *Since the tungstic acid content in the ash cannot be directly determined: ICP gives the pure tungsten content

[0084] The above process resulted in the initial concentrations in the reactor as shown in Table 7.

[0085] Table 7: Hydrogenolysis test - concentrations

[0086] P101 (the present invention) P039 (control) Sucrose (wt%) 20 20 Water (wt%) 60.7 60.6 <![CDATA[H 2 WO 4 (weight%)]]> 0.34 0.30 EG (wt%) 19.0 19.1 NaOH solution (g / L) 0.41 0.35 <![CDATA[NaOH / H 2 WO 4 Weight Ratio]]> 0.12 0.12 <![CDATA[NaOH / H 2 WO 4 Molar Ratio]]> 0.73 0.73

[0087] EG: Ethylene glycol

[0088] The experiments were performed for 300 min (P101) and 360 min (P039).

[0089] The reaction effluent was analyzed for ethylene glycol, propylene glycol, butanediol, and sorbitol levels. The results are expressed as mass excess and compound selectivity (the latter for ethylene glycol, propylene glycol, 1,4-butanediol, and sorbitol). Mass excess and compound selectivity are defined herein as:

[0090] Mass margin (%) = 100x (sum of all compounds - cosolvent input) / sugar input Compound selectivity (%) = 100x (cosolvent output - cosolvent input) / sugar input

[0091] The results are presented in graphical form in Figure 1-6 (The line with the closed circle refers to P101, the line with the closed triangle refers to P039).

Claims

1. A method for recovering and regenerating a tungsten compound from ash containing one or more tungsten oxide components, the tungsten compound being suitable for use as a catalyst for converting carbohydrates with hydrogen into alkylene glycols and polyols, the method comprising the steps of: a. contacting the ash with an inorganic acid having a pH below 2; b. separating the mixture obtained from step a into a solid fraction and a liquid fraction; c. washing the solid fraction obtained by step b with an aqueous liquid; d. solubilizing at least a portion of the washed solid obtained in step d in an alkylene glycol composition and dissolving an alkali metal hydroxide in the alkylene glycol composition, wherein, The amount of alkali metal hydroxide is selected so that the molar ratio of alkali metal hydroxide:tungstic acid in the resulting composition is between 0.2 and 2.

2. The method of claim 1, wherein: The pH of the inorganic acid in step a is below 1.

3. The method according to claim 1 or 2, wherein: The inorganic acid in step a includes hydrochloric acid.

4. The method of claim 3, wherein: The inorganic acid in step a includes hydrochloric acid having a concentration of 1 to 6M.

5. The method of claim 3, wherein: The inorganic acid in step a includes hydrochloric acid having a concentration of 1.2 to 4M.

6. The method of claim 3, wherein: The inorganic acid in step a includes hydrochloric acid having a concentration of 1.5 to 3M.

7. The method according to claim 1 or 2, wherein: The amount of inorganic acid in step a is such that the weight ratio of inorganic acid:ash is 50:1 to 1:

1.

8. The method of claim 7, wherein: The amount of inorganic acid in step a is such that the weight ratio of inorganic acid:ash is 30:1 to 2:

1.

9. The method according to claim 1 or 2, wherein: The one or more tungsten oxide components of the ash include: alkali metal tungstates and / or tungstic acid.

10. The method according to claim 1 or 2, wherein: The alkali metal hydroxide added in step d includes sodium hydroxide, potassium hydroxide or a mixture thereof.

11. The method according to claim 1 or 2, wherein: The amount of alkali metal hydroxide in step d is such that the molar ratio of alkali metal oxide:tungstic acid in the resulting composition is from 0.3 to 1.

5.

12. The method of claim 11, wherein: The molar ratio of alkali metal oxide:tungstic acid in the obtained composition is 0.4 to 1.

2.

13. The method of claim 11, wherein: The molar ratio of alkali metal oxide:tungstic acid in the obtained composition is 0.5 to 1.

14. The method according to claim 1 or 2, wherein: The alkylene glycol composition in step d comprises at least 50 wt% of ethylene glycol or propylene glycol.

15. The method of claim 14, wherein: The alkylene glycol composition in step d comprises at least 70 wt% ethylene glycol.

16. The method according to claim 1 or 2, wherein: The ash may be obtained from the combustion of a liquid mixture comprising an alkylene glycol and / or a polyol and sodium tungstate and / or tungstic acid.

17. The method of claim 1 or 2, wherein: The polyol includes one or more of glycerol, sorbitol and erythritol.

18. The method of claim 1 or 2, wherein: Tungsten compounds produced by regeneration that are suitable for use as co-catalysts for converting carbohydrates and hydrogen to alkylene glycols and polyols include tungstic acid.

19. A method for producing ethylene glycol and / or propylene glycol and / or glycerol in a continuous manner from a feed comprising a carbohydrate source and hydrogen in a diluent to a reactor system comprising a catalyst system comprising a tungsten compound and a hydrogenolysis metal selected from Groups 8, 9 or 10 of the Periodic Table of Elements, wherein: The effluent of the reactor system includes a diluent, a tungsten compound, one or more of ethylene glycol, propylene glycol, glycerol, and one or more polyols having a boiling point higher than ethylene glycol, wherein the effluent of the reactor system undergoes the following process steps: a. separating the reactor effluent by one or more distillation stages into ethylene glycol and / or propylene glycol and / or glycerol and a bottom stream comprising one or more polyols having a boiling point higher than that of ethylene glycol and one or more tungsten compounds; b. subjecting the bottom stream of the distillation stage comprising a polyol having a boiling point higher than that of ethylene glycol and one or more tungsten compounds to a burner in which at least a portion of the polyol is combusted and at least a portion of the ash is recovered; c. contacting the recovered ash with an inorganic acid having a pH below 2; d. separating the mixture obtained from step c into a solid fraction and a liquid fraction; e. washing the solid fraction obtained by step d with an aqueous liquid; f. solubilizing the washed solid obtained in step e in an alkylene glycol composition and dissolving an alkali metal hydroxide in the alkylene glycol composition, wherein the amount of the alkali metal hydroxide is selected so that the resulting composition has a molar ratio of alkali metal hydroxide: tungstic acid of 0.2 to 2; g. feeding at least a portion of the mixture obtained in step f back into the reactor system.

20. The method of claim 19, wherein: The ash from method step b contains alkali metal tungstate and / or tungstic acid.

21. The method of claim 20, wherein: The alkali metal tungstate includes sodium tungstate and / or potassium tungstate.

22. The method of claim 19, wherein: The inorganic acid in step c includes hydrochloric acid.

23. The method of claim 22, wherein: The concentration of the hydrochloric acid is 1 to 6M.

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