Recovering a co-catalyst from a liquid composition of glycols and co-catalyst

Abstract

A method for recovering a co-catalyst that has been used in a process wherein a carbohydrate fraction is subjected to a catalytical conversion process to form a liquid composition of glycols is disclosed. The method comprises: - subjecting the carbohydrate fraction to the catalytical conversion process in the presence of the co-catalyst to form the liquid composition of glycols, - recovering a mixture feed, - combining the mixture feed with water such as to provide an aqueous mixture feed, - feeding the provided aqueous mixture feed into a combustion chamber, wherein the aqueous mixture feed is subjected to a burning treatment, and - recovering the co-catalyst from the combustion chamber.

Description

[0001] RECOVERING A CO-CATALYST

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a method for recovering a co-catalyst that has been used in a process wherein a carbohydrate fraction is subj ected to a catalytical conversion process to form a liquid composition of glycols .

[0004] BACKGROUND

[0005] Diols such as mono-propylene glycol and monoethylene glycol may be produced from sugars , i . e . carbohydrates , in a method including a catalytical conversion process , where a co-catalyst is used . In such a process also other diols , alcohols , and other substances are produced as side-products . After the catalytical conversion process , the formed glycols may be recovered through distillation of the formed liquid composition . An e f ficient method for recovering and reusing the co- catalyst used in the catalytical conversion process is needed .

[0006] SUMMARY

[0007] Disclosed is a method for recovering a co-cat- alyst that has been used in a proces s wherein a carbohydrate fraction is subj ected to a catalytical conversion process to form a liquid composition of glycols . The method comprises :

[0008] - subj ecting the carbohydrate fraction to the catalytical conversion process in the presence of the co-catalyst to form the liquid composition of glycols ,

[0009] - recovering an outcome stream from the catalytical conversion process , wherein the outcome stream comprises the liquid composition of glycols and co-cat- alyst ,

[0010] - subj ecting the outcome stream to at least one distillation process ,

[0011] - recovering a mixture feed, wherein the mixture feed includes co-catalyst and at least one fraction of heavy compounds received from the at least one di stillation process , wherein the heavy compounds are compounds having a normal boiling point above 200 °C,

[0012] - combining the mixture feed with water such as to provide an aqueous mixture feed having a viscosity value of at most 50 cP while keeping the temperature of the aqueous mixture feed at 65 - 95 °C, wherein the total amount of water used is 1 - 15 weight-% based on the total flow rate of the aqueous mixture feed,

[0013] - feeding the provided aqueous mixture feed into a combustion chamber, wherein the aqueous mixture feed is subj ected to a burning treatment , and

[0014] - recovering the co-catalyst from the combustion chamber .

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings , which are included to provide a further understanding of the embodiments and constitute a part of this speci fication, illustrate some embodiments . In the drawings :

[0017] Fig . 1 presents one embodiment of the method for recovering a co-catalyst ; and

[0018] Fig . 2 and Fig . 3 presents results from example 1 .

[0019] DETAILED DESCRIPTION

[0020] The present disclosure relates to a method for recovering a co-catalyst , that has been used in a process wherein a carbohydrate fraction is subj ected to a catalytical conversion process to form a liquid composition of glycols . The method comprises :

[0021] - subj ecting the carbohydrate fraction to the catalytical conversion process in the presence of the co-catalyst to form the liquid composition of glycols ,

[0022] - recovering an outcome stream from the catalytical conversion process , wherein the outcome stream comprises the liquid composition of glycols and co-cat- alyst ,

[0023] - subj ecting the outcome stream to at least one distillation process ,

[0024] - recovering a mixture feed, wherein the mixture feed includes co-catalyst and at least one fraction of heavy compounds received from the at least one di stillation process , wherein the heavy compounds are compounds having a normal boiling point above 200 °C,

[0025] - combining the mixture feed with water such as to provide an aqueous mixture feed having a viscosity value of at most 50 cP while keeping the temperature of the aqueous mixture feed at 65 - 95 °C, wherein the total amount of water used is 1 - 15 weight-% based on the total flow rate of the aqueous mixture feed,

[0026] - feeding the provided aqueous mixture feed into a combustion chamber, wherein the aqueous mixture feed is subj ected to a burning treatment , and

[0027] - recovering the co-catalyst from the combustion chamber .

[0028] A co-catalyst is used in a process wherein a carbohydrate fraction is subj ected to a catalytical conversion process to form a liquid composition of glycols . The carbohydrate fraction to be used in the catalytical conversion proces s may be formed for example through a process , wherein a wood-based feedstock, such as wood chips , are firstly pretreated to form a liquid fraction and a fraction comprising solid cellulose particles . The fraction comprising solid cellulose particles may then be subj ected to enzymatic hydrolysis to form a lignin fraction and a carbohydrate fraction, which carbohydrate fraction may then be subjected to the catalytical conversion process to form the liquid composition of glycols.

[0029] The wood-based feedstock may be pretreated by at least one of the following: pre-steaming of the woodbased feedstock, subjecting the wood-based feedstock to an impregnation treatment, and subjecting the wood-based feedstock to steam explosion. The pre-steaming of the wood-based feedstock may be carried out with steam having a temperature of 95 - 130 °C at atmospheric pressure. The impregnation treatment may be carried out with an impregnation liquid selected from water, at least one acid, at least one alkali, at least one alcohol, or any combination or mixture thereof. The pretreatment may comprise subjecting the wood-based feedstock to steam explosion. In this specification, the term "steam explosion" may refer to a process of hemihydrolysis in which the wood-based feedstock is treated in a reactor with steam having a temperature of 130 - 240 °C under a pressure of 0.17 - 3.25 MPaG followed by a sudden, explosive decompression of the steam-treated wood-based feedstock that results in the rupture of the fiber structure. The output from the steam explosion may be mixed with a suitable liquid, e.g. water, to form a slurry comprising solid cellulose particles. The fraction comprising solid cellulose particles may be separated from the liquid fraction by a suitable separation method, e.g. by a solid-liquid separation .

[0030] The enzymatic hydrolysis of the fraction comprising solid cellulose particles may be carried out at a temperature of 30 - 70 °C, or 35 - 65 °C, or 40 - 60 °C, or 45 - 55 °C, or 48 - 53 °C while keeping the pH of the fraction comprising solid cellulose particles at a pH value of 3.5 - 6.5, or 4.0 - 6.0, or 4.5 - 5.5, and wherein the enzymatic hydrolysis is allowed to continue for 20 - 120 h, or 30 - 90 h, or 40 - 80 h . Enzymatic hydrolysis may result in the formation of a lignin fraction and a carbohydrate fraction . At least one enzyme may be used for carrying out the enzymatic hydrolysis and may be selected from a group consisting of cellulases , hemicellulases , laccases , and lignolytic peroxidases . Cellulases are multi-protein complexes consisting of synergistic enzymes with di f ferent speci fic activities that can be divided into exo- and endo-cellu- lases ( glucanase ) and p-glucosidase ( cellobiose ) . The enzymes may be either commercially available cellulase mixes or on-site manufactured .

[0031] Also other processes may be used to provide the carbohydrate fraction . Thus , the method as described in the current speci fication should not be understood to be bound to the above-described process for producing the carbohydrate fraction .

[0032] The catalytical conversion process of the carbohydrate fraction may be carried out at a temperature of 120 - 300 °C, or 180 - 270 °C , or 230 - 270 °C . The initial pressure in room temperature may be 1 - 15 MPa, or 9 - 12 MPa . The catalytical conversion may be carried out in a continuous manner . The time that the carbohydrate fraction is subj ected to catalytical conversion may be 5 minutes - 3 hours , or 30 minutes - 2 . 8 hours .

[0033] The catalytical conversion may take place in a conversion reactor, such as a fixed bed or a slurry reactor . The catalytical conversion of the carbohydrate fraction may take place as a slurry reaction .

[0034] The catalytical conversion process of the carbohydrate fraction may comprise subj ecting the carbohydrate fraction to catalytical hydrogenolysis . I . e . the carbohydrate fraction may be subj ected to catalysts in the presence of hydrogen . The hydrogen and the carbohydrate fraction may be added to the reactor separately or simultaneously using respective pumps and compressors . The co-catalyst may be added to the reactor separately or simultaneously with the carbohydrate fraction. The catalyst may be provided to the reactor separately from the carbohydrate fraction, preferably before the carbohydrate fraction is fed to the reactor. Also a solvent, such as water, may be present. Adding the different components into the reactor may comprise separate addition timewise or e.g. through separate feeding nozzles.

[0035] The catalytical conversion process may thus be carried out in the presence of a catalyst system comprising e.g. a main catalyst and the co-catalyst. The main catalyst may comprise an active metal component selected from Group 8, Group 9, or Group 10 of the TUPAC periodic table of elements such as iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, and platinum, or a mixture of at least two of these. As an example may be mentioned that the main catalyst may comprise or consist of a heterogeneous Ni-alloy, such as Raney Nickel. The active metal component of the main catalyst may be supported by a carrier comprising activated carbon, alumina, silica, silicon carbide, zirconia, zinc oxide, titanium dioxide, or a mixture thereof. The active metal component of the main catalyst may account for 0.05 - 70 weight-% of the total weight of the catalyst.

[0036] In one embodiment, the co-catalyst is in the form of a salt such as sodium salt or potassium salt. In one embodiment, the co-catalyst is in the form of a salt solution. In one embodiment, the co-catalyst is used in the catalytical conversion process as an aqueous solution of the salt form thereof. Being in the form of a salt, the co-catalyst does not evaporate during processes like distillation or separation. This allows it to remain in the mixture feed throughout processing, enabling its recovery and reuse. The co-catalyst, being a solid, may dissolve in a solvent and may thus be soluble in the aqueous mixture feed. Therefore, it may not precipitate but stays dissolved in the aqueous mixture. Interestingly, the inventors discovered that the co-catalyst is soluble in the mixture feed as well as water, unlike in e.g. monohydric alcohols.

[0037] In one embodiment, the co-catalyst is a cocatalyst based on tungsten oxide, tungsten sulfide, tungsten hydroxide, tungsten bronze oxide, tungstic acid, tungstate, metatungstic acid, metatungstate, paratungstate acid, para-tungstate, peroxotungstic acid, pertungstate, or hetero-poly acid containing tungsten .

[0038] In one embodiment, the co-catalyst is in the form of a salt solution based on tungsten bronze oxide, tungstate, metatungstate, para-tungstate, or pertungstate, or a hetero-poly salt containing tungsten.

[0039] In one embodiment, the co-catalyst is sodium tungstate. In one embodiment, the co-catalyst is based on sodium tungstate.

[0040] Thus, subjecting the carbohydrate fraction to catalytical conversion results in a liquid composition of glycols. The method comprises recovering an outcome stream from the catalytical conversion process, wherein the outcome stream comprises the liquid composition of glycols and co-catalyst. The outcome stream is then subjected to at least one distillation process.

[0041] A distillation process may generally be considered a process of separating components or substances from a mixture by using selective boiling and condensation. Distillation may result in essentially complete separation into nearly pure components, or it may be a partial separation that increases the concentration of selected components in the mixture. The distillation process exploits differences in the relative volatility of the different components in the mixture.

[0042] In one embodiment, the at least one distillation process comprises fractional distillation of the liquid composition of glycols formed in the catalytical conversion process, i.e. of the outcome stream. I.e. the at least one distillation process conducted after the catalytical conversion process may result in di f ferent products and side-products , which are further processed into valuable products , recycled in the process , or thrown away as waste . In such distillation processes are formed one or more fractions of heavy compounds . The term "heavy compounds" is , in this speci fication, to refer to compounds having a normal boiling point above 200 °C . The term "normal boiling point" is to be taken as the boiling point in atmospheric pressure . Such compounds may also be referred to as "heavies" or "heavies fraction" . Such heavy compounds are usually formed as side-products that may not be o f further use in industrial products . Sorbitol and glycerol may be mentioned as examples of such compounds .

[0043] In one embodiment , the method comprises :

[0044] - recovering an outcome stream from the catalytical conversion process , wherein the outcome stream comprises the liquid composition of glycols and co-cat- alyst ,

[0045] - subj ecting the outcome stream to at least one distillation process to remove water and monohydric alcohols from the outcome stream to form a dewatered stream, and subj ecting the dewatered stream a to a separation treatment to separate the co-catalyst and the fraction of heavy compounds from the dewatered stream, to recover a mixture feed .

[0046] In one embodiment , the outcome stream is subj ected to at least one distillation process to remove water and monohydric alcohols from the outcome stream to form a dewatered stream as a bottom stream from said distillation process . Also other components may be recovered from said distillation process for removing water and used in further distillation processes to recover desired end products . Monohydric alcohols are alcohols contain only one hydroxyl group in their molecules . Examples of monohydric alcohols are methanol , ethanol , and iso-propa- nol .

[0047] In one embodiment , the separation treatment is selected from adsorption, evaporation, fractional distillation, extractive distillation, azeotrope distillation, vacuum distillation, atmospheric distillation, membrane separation, filtration, reactive puri fication or a combination of at least two of these . In one embodiment , the separation treatment is evaporation .

[0048] The method comprises recovering a mixture feed, wherein the mixture feed includes co-catalyst and at least one fraction of heavy compounds received from the at least one distillation process . The mixture feed thus contains the co-catalyst and distillation components , which are obtained from at least one distillation process conducted after the catalytical conversation process . The mixture feed may thus be formed of or be comprised of streams from di f ferent distillation processes taking place after the catalytical conversion proces s . The mixture feed may be formed or comprise at least two streams from at least two dif ferent distillation processes .

[0049] In one embodiment , the mixture feed comprises heavy compounds in a total amount o f 55 - 85 weight-% , or 57 - 80 weight-% , or 60 - 70 weight-% , based on the total weight of the mixture feed .

[0050] In addition to the at least one fraction of heavy compounds , the mixture feed comprises the co-cat- alyst . In one embodiment , the mixture feed comprises co- catalyst in a total amount of 5 - 25 weight-% , or 7 - 20 weight-% , or 9 - 15 weight-% , based on the total weight of the mixture feed .

[0051] The mixture feed may in addition to the at least one fraction of heavy compounds and the co-cata- lyst also contain mono-ethylene glycol (MEG) . The mixture feed may comprise some amount of mono-ethylene glycol originating from a distillation process taking place after the catalytical conversation process . In one embodiment , the mixture feed comprises mono-ethylene glycol in a total amount of 0 - 30 weight-% , or 5 - 25 weight-% , or 10 - 20 weight-% , or 14 - 15 weight-% , based on the total weight of the mixture feed .

[0052] The mixture feed may in addition to the at least one fraction of heavy compounds and the co-cata- lyst also contain organic acids . Organic acids may have a lower normal boiling point than the heavy compounds but during the distillation processes they may still end up in the same fraction together with the heavy compounds . This may be the result of the organic acids being in a dissociated state and thus they do not evaporate during the distillation process .

[0053] The mixture feed formed of the fraction o f heavy compounds and the co-catalyst may have a high viscosity, which has the adverse ef fect of making its feeding, e . g . by atomi zation, into the combustion chamber challenging . The high viscosity of the mixture feed may be a result of it containing heavy compounds li ke glycerol and the co-catalyst , which af fect the viscosity thereo f by increas ing it to a level which may be challenging to further process . Further, safe handling of the heavy compounds present in the mixture feed may require cooling of the mixture feed, which thus may further increase the viscosity thereof . The allowable level for the viscosity is at most 50 cP . Above said viscosity, the feeding into the combustion chamber becomes challenging from industrial point of view . In order to keep the viscosity on an allowable level , one may allow valuable diols , such as mono-ethylene glycol , from the distillation process to follow with the mixture feed into the combustion chamber to be burnt . However, in this manner valuable products are lost to burning resulting in an expensive process . The inventors surprisingly found out that in order to keep the viscosity of the mixture feed on a usable level, i.e. of at most 50 cP, water can be combined with the mixture feed. Using water has the added utility of being cost-effective to prevent valuable products from being burned in a combustion chamber. Taking into consideration that the mixture feed is to be fed into a combustion chamber for burning the same, one would not expect that water could be used as a working component as the expectation would be to try to avoid adding water into a combustion chamber.

[0054] Adding water to the mixture feed has the added utility that it improves the solubility of the co-cat- alyst in the mixture feed, thus reducing the risk of fouling by precipitation.

[0055] The mixture feed is thus combined with water. The mixture feed may be mixed with water by using e.g. a static mixer or an injection mixer. The mixture feed may be provided or fed e.g. into a feed tank where also the water is provided. The aqueous mixture feed may then be fed from the feed tank into the combustion chamber. The water may alternatively or in addition be combined with the mixture feed, when feeding the mixture feed from the feed tank to the combustion chamber.

[0056] In one embodiment, the total amount of water used is 1 - 15 weight-%, or 2 - 14 weight-%, or 3 - 13 weight-%, or 4 - 12 weight-%, or 5 - 11 weight-%, or 6 - 10 weight-%, or 7 - 9 weight-%, based on the total flow rate of the aqueous mixture feed. In one embodiment, total amount of water in the aqueous mixture feed is 1 - 15 weight-%, or 2 - 14 weight-%, or 3 - 13 weight- % , or 4 - 12 weight-%, or 5 - 11 weight-%, or 6 - 10 weight-%, or 7 - 9 weight-%, based on the total flow rate of the aqueous mixture feed.

[0057] In one embodiment, the total amount of water used is 1 - 5 weight-% or 5 - 10 weight-% based on the total flow rate of the aqueous mixture feed. In one embodiment , the total amount of water in the aqueous mixture feed is 1 - 5 weight-% or 5 - 10 weight-% based on the total flow rate of the aqueous mixture feed .

[0058] The total amount of water to be used in the aqueous mixture feed may depend on the temperature of the aqueous mixture feed . The temperature of the aqueous mixture feed is to be kept at 65 - 95 °C . The higher the temperature of the aqueous mixture feed, the lesser total amount of water may be needed to ensure a viscosity level o f at most 50 cP . In a s imilar manner, the lower the temperature of the aqueous mixture feed is , the higher amount of water may be needed to ensure a viscosity level of at most 50 cP . In one embodiment , the total amount of water used in the aqueous mixture feed depends on the temperature of the aqueous mixture feed .

[0059] The total amount of water combined with the mixture feed may be determined by measuring the viscosity of the aqueous mixture feed and then adj usting the amount o f water added when needed . The amount o f water added may be proportional to the flow of the mixture feed before adding the water .

[0060] The inventors surprisingly found out that water can be used to ensure that the viscosity of the feed subj ected into the combustion chamber is on a suitable level without causing adverse ef fects in the combustion chamber during the burning treatment . Further, surprisingly already a small amount of water is suf ficient to be added .

[0061] The water thus has the added utility of one being able to add only a small amount of water with the mixture feed to provide the aqueous mixture feed with a viscosity value suitable for the aqueous mixture feed to be fed into the combustion chamber . Us ing water has the added utility that it does not harmfully af fect the burning treatment of the co-catalyst nor does any harmful precipitation of the co-catalyst in the aqueous mixture feed take place prior to being fed into the combustion chamber .

[0062] In one embodiment, provided is an aqueous mixture feed having a viscosity value of at most 50 cP, or at most 40 cP, or at most 30 cP, or at most 25 cp, or at most 20 cp .

[0063] In one embodiment, provided is an aqueous mixture feed having a viscosity value of at most 50 cP, or at most 40 cP, or at most 30 cP, or at most 25 cp, or at most 20 cp, while keeping the temperature of the aqueous mixture feed at 65 - 95 °C , or 70 - 90 °C , or 75 - 85 °C .

[0064] In one embodiment, provided is an aqueous mixture feed having a viscosity value of 5 - 50 cP, or 8 - 40 cP, or 11 - 30 cP, or 14 - 25 cp, or 17 - 20 cp, while keeping the temperature o f the aqueous mixture feed at 65 - 95 °C, or 70 - 90 °C, or 75 - 85 °C . The viscosity may be determined by using a Rotational Viscometer ( e . g . from Anton Paare ) or a Fork Viscosity Meter . The viscosity may be determined at the temperature of the aqueous mixture feed . A temperature-controlled viscometer may be used . Alternatively, the viscosity may be determined at room temperature and then the viscosity at the desired temperature , i . e . at the actual temperature of the aqueous mixture feed, may be calculated using known formulas for the temperature dependence of viscosity .

[0065] Keeping the temperature of the aqueous mixture feed at 65 - 95 °C has the added utility of the process being safe to use without having to use any additional equipment to ensure that the components in the aqueous mixture feed remain in a safe state .

[0066] In one embodiment , feeding the provided aqueous mixture feed into a combustion chamber comprises keeping the temperature of the provided aqueous mixture feed at 65 - 95 °C, or 70 - 90 °C , or 75 - 85 °C, when fed into the combustion chamber . In one embodiment , the burning treatment is conducted in a combustion chamber at a temperature of 1000 - 1400 °C .

[0067] The co-catalyst may be recovered from the combustion chamber in the form of ash . In one embodiment , the method comprises recovering the co-catalyst from the combustion chamber to be reused in the catalytical conversion process .

[0068] The method as described in the current specification has the added utility of one being able to provide an aqueous mixture feed having the viscosity and the temperature thereof on a level such that the handling and processing of the aqueous mixture feed become easier . The method as described in the current specification has the added utility of one being able to easily feed the aqueous mixture feed into the combustion chamber without the need of complicated processing equipment .

[0069] The method as described in the current specification has the added utility that us ing water in the method keeps the costs o f the total process on an economical level . The method as described in the current speci fication has the added utility of one being able to avoid letting valuable end products , such as monoethylene glycol (MEG) to go into the fraction of heavy compounds during the distillation processes only for the purpose of having a suitable vi scosity for the feed that is to be fed into the combustion reactor .

[0070] Using water has the further added utility of providing additional atomi zation because water has a low normal boiling point and will thus vapori ze more quickly than the other components present in the aqueous mixture feed and therefore the presence of water may provide an explosion-like ef fect . EXAMPLES

[0071] Reference will now be made in detail to various embodiments .

[0072] The description below discloses some embodiments in such a detail that a person skilled in the art is able to utili ze the embodiments based on the disclosure . Not all steps or features of the embodiments are discussed in detail , as many of the steps or features will be obvious for the person skilled in the art based on this speci fication .

[0073] For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components .

[0074] The enclosed Fig . 1 illustrates one embodiment of the method for recovering a co-catalyst that has been used in a process wherein a carbohydrate fraction is subj ected to a catalytical conversion process to form a liquid composition of glycols .

[0075] Fig . 1 presents a conversion reactor 1 , wherein a carbohydrate fraction is subj ected to the catalytical conversion proces s in the presence of a co-catalyst to form a liquid composition of glycols .

[0076] Fig . 1 further presents a feed tank 3 , whereto a mixture feed is provided . The mixture feed includes the co-catalyst and at least one fraction of heavy compounds received from distillation processes 4 , 5 conducted after the catalytical conversion process 1 . The heavy compounds are compounds having a normal boiling point of above 200 °C .

[0077] In the embodiment of Fig . 1 the fractions of heavy compounds are received from two di fferent distillation proces ses 4 and 5 . The distillation proces s indicated by number 5 i s a di stillation process for removing water from the liquid composition of glycols and the distillation process indicated by number 4 is for recovering especially mono-ethylene glycol and monopropylene glycol , but in addition also e . g . 1 , 2- butanediol, 2 , 3-butanediol , 1 , 2-pentanediol , and 1,2- hexanediol, in a stream indicated by number 4b.

[0078] In the embodiment of Fig. 1, the mixture feed is combined with water 9 in the feed tank 3, whereby an aqueous mixture feed is provided. Water is used in the total amount 1 - 15 weight-% based on the total flow rate of the aqueous mixture feed. Alternatively, or in addition, water may also be added to the mixture feed prior to the feed tank. The viscosity value of the aqueous mixture feed is to be at most 50 cP while keeping the temperature of the aqueous mixture feed at 65 - 95 °C.

[0079] From the feed tank 3 the provided aqueous mixture feed is fed into a combustion chamber 2, wherein the aqueous mixture feed is subjected to a burning treatment. The co-catalyst is recovered 7 from the combustion chamber 2 to be reused in the catalytical conversion process in the conversion reactor 1.

[0080] In the embodiment of Fig. 1 is further presented that an outcome stream 8 is recovered from the catalytical conversion process 1 and subjected to a distillation process 5 to remove water. The outcome stream comprises the liquid composition of glycols and co-cat- alyst. The outcome stream is subjected to the distillation process 5 to remove water and monohydric alcohols therefrom to form a dewatered stream 5a. A fraction 5b of light compounds, such as ethanol, methanol, iso-pro- panol, and water, are removed from the distillation process 5. The dewatered stream 5a is subjected from said distillation process 5 to a separation treatment 6, which in the embodiment of Fig. 1 is an evaporator 6. A stream 6a containing the co-catalyst and the fraction of heavy compounds is recovered from the evaporator 6 and provided as part of the mixture feed in the feed tank 3. Further a stream 6b comprising heavy diols is subjected to the distillation process indicated with number 4 to recover a fraction of especially mono- ethylene glycol and mono-propylene glycol, but in addition also e.g. 1 , 2-butanediol , 2 , 3-butanediol , 1,2-pen- tanediol, and 1 , 2-hexanediol , as a stream 4b and a fraction of heavy compounds 4a such glycerol and 14-butane- diol. A minor amount of mono-ethylene glycol may also be present in stream 4a. The fraction of heavy compounds 4a is fed into the feed tank 3.

[0081] Further distillation processes may also be used, from which further fractions of heavy compounds may be recovered and used in the mixture feed.

[0082] Example 1 - Testing how to control the viscosity of the aqueous mixture feed to be fed into a combustion chamber

[0083] In this example, the method as described in Fig. 1 was tested especially for the purpose of ensuring that the burning treatment in the combustion chamber can be carried out efficiently.

[0084] In all the examples, some mono-ethylene glycol (MEG) was allowed to follow from distillation processes, conducted after the catalytical conversion process to the formed liquid composition of glycols to separate different compounds therefrom, into the mixture feed.

[0085] In the comparative examples, instead of water, additional amount of mono-ethylene glycol, having a high normal boiling point, was added into the mixture feed to adjust the viscosity thereof.

[0086] The viscosities of the different feeds were determined in various conditions (different temperatures of the (aqueous) mixture feed to be fed into the combustion chamber) . Aspen Plus software was used to model the viscosity. A property method package was used. Viscosity parameters were fitted with experimental data. In all the examples, the base monoethylene glycol flow (kg / h) was 197 kg / h and the total flow rate was 1341 kg / h. The tests and their results are shown in Table 1 (corresponding Fig. 2) and Table 2 ( corresponding Fig . 3 ) as well as in Table 3 and Table 4 below . In the tables 1 and 3 those values are bolded that would be acceptable from the viscosity point of view but not all of them are acceptable for use due to a too high temperature .

[0087] Table 1 . The addition of water to the mixture feed

[0088] Table 2 . The addition of additional amount of mono- ethylene glycol to the mixture feed

[0089] Table 3 . The addition of water to the mixture feed | 12 | 200 | 12 . 4 % | 6 | 9 | 16 | 29 |

[0090] Table 4 . The addition of additional amount of mono- ethylene glycol to the mixture feed From the above results one may see that high amounts of additional mono-ethylene glycol are needed to control that the viscosity of the feed that is to be fed into the combustion chamber is below 50 cP . Further, one may see that when water is used, a highly less amount of water is needed to control that the viscosity is below 50 cP . Even in the lowest temperatures les s than 15 weight-% of water is needed . Increasing the temperature of the aqueous mixture feed to 100 °C or 120 °C results in an acceptable viscosity level of below 50 cP but such a high temperature i s not acceptable since water starts to boil which cannot be the case when providing the same into the combustion chamber .

[0091] It is obvious to a person skilled in the art that with the advancement of technology, the basic idea may be implemented in various ways . The embodiments are thus not limited to the examples described above ; instead they may vary within the scope of the claims .

[0092] The embodiments described hereinbefore may be used in any combination with each other . Several of the embodiments may be combined together to form a further embodiment . A method disclosed herein, may comprise at least one of the embodiments described hereinbefore . It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all o f the stated benefits and advantages . It will further be understood that reference to ' an ' item re fers to one or more of those items . The term "comprising" is used in this speci fication to mean including the feature ( s ) or act ( s ) followed thereafter, without excluding the presence of one or more additional features or acts .

Claims

CLAIMS1 . A method for recovering a co-catalyst that has been used in a process wherein a carbohydrate fraction is subj ected to a catalytical conversion process to form a liquid composition of glycols , wherein the method comprises :- subj ecting the carbohydrate fraction to the catalytical conversion process in the presence of the co-catalyst to form the liquid composition of glycols ,- recovering an outcome stream from the catalytical conversion process , wherein the outcome stream comprises the liquid composition of glycols and co-cat- alyst ,- subj ecting the outcome stream to at least one distillation process ,- recovering a mixture feed, wherein the mixture feed includes co-catalyst and at least one fraction of heavy compounds received from the at least one di stillation process , wherein the heavy compounds are compounds having a normal boiling point above 200 °C,- combining the mixture feed with water such as to provide an aqueous mixture feed having a viscosity value of at most 50 cP while keeping the temperature of the aqueous mixture feed at 65 - 95 °C, wherein the total amount of water used is 1 - 15 weight-% based on the total flow rate of the aqueous mixture feed,- feeding the provided aqueous mixture feed into a combustion chamber, wherein the aqueous mixture feed is subj ected to a burning treatment , and- recovering the co-catalyst from the combustion chamber .2 . The method of any one of the preceding claims , wherein the mixture feed comprises co-catalyst in a total amount of 5 - 25 weight-% , or 7 - 20 weight- % , or 9 - 15 weight-% , based on the total weight of the mixture feed .3 . The method of any one of the preceding claims , wherein the at least one distillation process comprises fractional distillation of the liquid composition of glycols formed in the catalytical conversion process .4 . The method of any one of the preceding claims , wherein total amount of water used is 1 - 15 weight-% , or 2 - 14 weight-% , or 3 - 13 weight-% , or 4- 12 weight-% , or 5 - 11 weight-% , or 6 - 10 weight-% , or 7 - 9 weight-% , based on the total flow rate o f the aqueous mixture feed .5 . The method of any one of the preceding claims , wherein provided is an aqueous mixture feed having a viscosity value of 5 - 50 cP, or 8 - 40 cP, or 11- 30 cP, or 14 - 25 cp, or 17 - 20 cp, while keeping the temperature o f the aqueous mixture feed at 65 - 95 °C, or 70 - 90 °C, or 75 - 85 °C .6 . The method of any one of the preceding claims , wherein the method comprises :- recovering an outcome stream from the catalytical conversion process , wherein the outcome stream comprises the liquid composition of glycols and co-cat- alyst ,- subj ecting the outcome stream to at least one distillation process to remove water and monohydric alcohols from the outcome stream to form a dewatered stream, and subj ecting the dewatered stream a to a separation treatment to separate the co-catalyst and the fraction of heavy compounds from the dewatered stream, to recover a mixture feed .7 . The method of claim 6 , wherein the separation treatment is selected from adsorption, evaporation, fractional distillation, extractive distillation, azeotrope distillation, vacuum distillation, atmospheric distillation, membrane separation, filtration, reactive puri fication or a combination of at least two of these .

8. The method of any one of the preceding claims, wherein the co-catalyst is a co-catalyst based on tungsten oxide, tungsten sulfide, tungsten hydroxide, tungsten bronze oxide, tungsten acid, tungstate, meta- tungstate acid, metatungstate, paratungstate acid, para-tungstate, peroxotungstic acid, pertungstate, or hetero-poly acid containing tungsten.

9. The method of any one of the preceding claims, wherein feeding the provided aqueous mixture feed into a combustion chamber comprises keeping the temperature of the provided aqueous mixture feed at 65 - 95 °C, or 70 - 90 °C, or 75 - 85 °C, when fed into the combustion chamber.

10. The method of any one of the preceding claims, wherein the burning treatment is conducted in a combustion chamber at a temperature of 1000 - 1400 °C.

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