IT202000025960A1 - PROCESS FOR THE ISOMERIZATION OF GLUCIDS IN HYDROXYMETHYLFURFURAL - Google Patents

Description

Description of Patent for Industrial Invention having the title:

?PROCESS FOR THE ISOMERIZATION OF GLUCIDS INTO HYDROXYMETHYLFURFURAL?.

DESCRIPTION

The present invention relates to a process for the isomerization of carbohydrates in hydroxymethylfurfural.

In the last few years ? particularly felt the need? to develop a sustainable chemical industry.

There? ? due to several factors including? the exhaustion of fossil fuel reserves, the high cost of oil, the need? to decrease CO2 emissions, the increase in energy demand and environmental laws more and more? restrictive.

In this context, biomass and waste raw materials deriving from industrial processes have aroused particular interest in the possibility to be converted into chemical compounds, i.e. the so-called ?platform molecules?, useful for the production of numerous products applicable in various industrial and technological fields.

The development of sustainable catalytic processes and therefore the creation of industrial plants suitable for the conversion of the aforementioned biomass and/or waste raw materials, ? currently a particularly felt need in order to provide an alternative to petrochemicals.

With particular reference to the synthesis of ?platform molecules?, the synthesis processes of hydroxymethylfurfural are of considerable interest in the light of the numerous applications of the aforementioned molecule.

The numerous applications of hydroxymethylfurfural include the use of hydroxymethylfurfural for the synthesis of furandicarboxylic acid, a molecule of fundamental importance for the production of polyethylenefuranoate, an environmentally friendly alternative to polyethylene terephthalate. Furthermore, hydroxymethylfurfural ? widely used, through conversion, to obtain dimethylfuran, a molecule that can be used as a biofuel.

To there? it is added that the? hydroxymethylfurfural? can also be used in the food, pharmaceutical and nutraceutical industries.

Currently, hydroxymethylfurfural is synthesized from waste of vegetable origin through a process that requires extreme process conditions, i.e. presenting extremely high temperature and pressure conditions.

These process conditions significantly influence the energy management of the synthesis process which has extremely high management costs, as well as the cost of the final product itself, which is also high.

The main task of the present invention ? that of devising a process for the isomerization of glucids in hydroxymethylfurfural which has mild process conditions, compared to known processes, considerably reducing the energy management costs of the process itself.

A purpose of the present invention ? that of devising a process for the isomerization of glucids in hydroxymethylfurfural which allows to significantly reduce the sale cost of the aforesaid molecule.

Another object of the present invention ? that of devising a process for the isomerization of glucides in hydroxymethylfurfural which allows the aforementioned drawbacks of the prior art to be overcome within the scope of a simple, rational, easy and effective to use and low-cost solution.

The above objects are achieved by the present process for the isomerization of carbohydrates in hydroxymethylfurfural having the characteristics of claim 1.

Furthermore, the above objects are achieved by the catalyst for the isomerization of carbohydrates in hydroxymethylfurfural having the characteristics of claim 13.

Again, the above objects are achieved by the use of a metal phosphate for the isomerization of carbohydrates in hydroxymethylfurfural having the characteristics of claim 14.

In a first aspect, the present invention relates to a process for the isomerization of carbohydrates in hydroxymethylfurfural (HMF), comprising the following steps.

The process includes a supply phase of:

- at least one carbohydrate selected from the list comprising: lactose, glucose, galactose, fructose and sucrose; And

- at least one catalyst comprising at least one metal phosphate in which the metal is chosen from the list including: niobium, zirconium, hafnium, titanium, aluminium.

It is specified that in the context of the present discussion the term "mixture", used in the claims and in the description, means both homogeneous mixtures, for example liquid or solid solutions, and heterogeneous mixtures such as suspensions of a solid particulate in a liquid or mixtures solid-liquid in which the solid is wholly or partially sedimented. Furthermore, with the term ?mole? and ?molar ratio? reference is made both to compounds consisting of molecules and with reference to atoms and ions, leaving out for the latter the terms gram-atom or atomic ratio, even if more? scientifically correct.

Moreover, ? necessary to underline that the process in accordance with the present invention ? conducted in an inert atmosphere.

There? does it mean that the process ? conducted, for example, in a nitrogen atmosphere. The process in accordance with the present invention ? conducted in a reactor which, once sealed, is purged in order to ensure the creation of an inert environment.

However, it is not excluded from the scope of this discussion that the process is conducted in a non-inert atmosphere, ie? in the presence of other gases such as oxygen, air, carbon dioxide.

In this case, the carbohydrate and the catalyst are present in a molar ratio between 1:0.01 and 1:1.

In accordance with a preferred embodiment, the metal phosphate comprises Niobium (Nb/P/O).

Alternatively, the metal phosphate comprises Zirconium (Zr/P/O).

Further, alternatively, the metal phosphate comprises Hafnium (Hf/P/O).

In addition, as an alternative to the above catalyst embodiments, the metal phosphate comprises Titanium (Ti/P/O). Again, alternatively, the metal phosphate comprises Aluminum (Al/P/O). Subsequently, the process comprises a step of adding at least one reaction solvent to obtain a reaction mixture.

In detail, the reaction solvent comprises at least one of water and an organic solvent.

There? means that the reaction mixture includes:

- water; or

- water and an organic solvent; or

- an organic solvent.

Preferably, the organic solvent ? selected from the list including: methyl tetrahydrofuran, tetrahydrofuran, n-butanol and gamma-valerolactone. The presence of water in the reaction mixture assumes particular importance due to its easy separation from the organic solvent.

The water, therefore, being highly polar, ? insoluble in most organic solvents.

Preferably, the organic solvent and water are present in the reaction mixture with a molar ratio between 1:1 and 4:1.

At this point, the process according to the present invention provides for the heating of the reaction mixture to a temperature higher than 80°C.

Preferably, the reaction mixture is heated to a temperature between 80?C and 200?C.

Furthermore, the process ? conducted at pressure values between 5 bar and 25 bar.

Subsequently, after the heating step, the process comprises a cooling step of the reaction mixture.

In detail, the cooling phase? adapted to allow the cooling of the reaction mixture until the ambient temperature is reached.

It is specified that in the context of this discussion with the expression ?ambient temperature? reference is made to a temperature substantially equal to 20°C.

At this point, the process includes a regeneration phase of the catalyst in which the latter is thermally dried at a temperature above 200?C.

Preferably, the catalyst ? dried at a temperature higher than 400?C, pi? preferably between 400?C and 600?C.

Usefully, the regeneration phase? conducted for an operating time substantially equal to 5 hours.

The process according to the present invention has a yield of hydroxymethylfurfural (HMF) higher than 20%.

? It must be emphasized that the process according to the present invention comprises a preparation step, in turn comprising the precipitation of the catalyst in an acid environment starting from at least one metal precursor or by hydrolysis and condensation of the metal precursor.

Preferably, the hydrolysis and condensation of the metal precursor occurs with the sol-gel method.

By way of example, the steps for preparing the catalyst are listed below.

PREPARATION EXAMPLE 1:

Catalyst Nb/P/O - PRECIPITATION IN ACID ENVIRONMENT WITH HYDROTHERMAL METHOD

In a Teflon beaker, 25 ml of 0.4 M alcoholic solution of H3PO4 are slowly added to 25 ml of 0.2 M alcoholic solution of NbCl5.

What is the mixture? obtained ? kept under stirring for 30 minutes.

Subsequently, under conditions of continuous stirring, NH3 concentrated at 25% is added to the above mixture until a pH equal to 2.6 is reached, obtaining the formation of a white precipitate.

The resulting precipitate is filtered and washed several times with ethanol. The white precipitate is added to a beaker containing an alcoholic solution of hexadecylamine 0.6M.

H3PO4 is then added to the above mixture in a concentration by weight, evaluated with respect to the total weight of the mixture itself, substantially equal to 85% until a pH substantially equal to 3.9 is reached.

The resulting gel is heated in a Teflon autoclave at 65°C for two days under autogenous pressure.

At this point, the product obtained? filtered, washed with ethanol, dried at 120°C and calcined in a muffle under static conditions at a temperature between 400°C and 600°C.

The speed? of heating ? substantially equal to 10?C/min for a duration substantially between 3 and 6 hours.

PREPARATION EXAMPLE 2:

Catalyst Nb/P/O - PRECIPITATION IN ACID ENVIRONMENT WITH HYDROTHERMAL METHOD and ADDITION OF TEMPLANT

In a Teflon beaker, 25 ml of 0.4 M alcoholic solution of H3PO4 are slowly added to 25 ml of 0.2 M alcoholic solution of NbCl5.

What is the mixture? obtained ? kept under stirring for 30 minutes.

Subsequently, under conditions of continuous stirring, NH3 concentrated at 25% is added to the above mixture until a pH equal to 2.6 is reached, obtaining the formation of a white precipitate.

The resulting precipitate is filtered and washed several times with ethanol. The white precipitate is added to a beaker containing an alcoholic solution of hexadecylamine 0.6M.

H3PO4 is then added to the above mixture in a concentration by weight, evaluated with respect to the total weight of the mixture itself, substantially equal to 85% until a pH substantially equal to 3.9 is reached.

The resulting gel is heated in a Teflon autoclave at 65°C for two days under autogenous pressure.

At this point, the product obtained? filtered, washed with ethanol, dried at 120°C and calcined in a muffle under static conditions at a temperature between 400°C and 600°C.

The speed? of heating ? substantially equal to 10?C/min for a duration substantially between 3 and 6 hours.

PREPARATION EXAMPLE 3:

Catalyst Nb/P/O - PRECIPITATION IN ACID ENVIRONMENT WITH HYDROTHERMAL METHOD and ADDITION OF TEMPLANT

In a Teflon beaker, 25 ml of 0.4 M alcoholic solution of H3PO4 are slowly added to 25 ml of 0.2 M alcoholic solution of NbCl5.

What is the mixture? obtained ? kept under stirring for 30 minutes.

Subsequently, under conditions of continuous stirring, NH3 concentrated at 25% is added to the above mixture until a pH equal to 2.6 is reached, obtaining the formation of a white precipitate.

The resulting precipitate is filtered and washed several times with ethanol. The white precipitate is added to a beaker containing an alcoholic solution of cetyltrimethylammonium (CTAB) 0.6M.

H3PO4 is then added to the above mixture in a concentration by weight, evaluated with respect to the total weight of the mixture itself, substantially equal to 85% until a pH substantially equal to 3.9 is reached.

The resulting gel is heated in a Teflon autoclave at 65°C for two days under autogenous pressure.

At this point, the product obtained? filtered, washed with ethanol, dried at 120°C and calcined in a muffle under static conditions at a temperature between 400°C and 600°C.

The speed? of heating ? substantially equal to 10?C/min for a duration substantially between 3 and 6 hours.

PREPARATION EXAMPLE 4:

Catalyst Ti/P/O - SYNTHESIS BY HYDROLYSIS AND CONDENSATION WITH THE SOL-GEL METHOD OF THE METALLIC PRECURSOR ? Titanium (IV) butoxide

The metal precursor used? titanium butoxide (IV).

Titanium alkoxide? was added dropwise to an aqueous solution of dihydrogen ammonium phosphate (NH4)H2PO4 containing nbutanol.

In detail, the molar ratio between butanol/alkoxide/(NH4)H2PO4/water ? of 1/0.125/0.0124/2.

At the end of the addition, the pH of the solution is brought to a value of 7 by adding a 25% concentrated ammonia aqueous solution. At this point, the system ? kept under stirring for 24 hours at room temperature.

After 24 hours, the solvent is removed and the nanoparticles are dried at 120°C overnight.

Subsequently, the nanoparticles are calcined at temperatures between 400°C and 600°C.

The speed? of heating ? substantially equal to 10?C/min for a duration substantially between 3 and 6 hours.

PREPARATION EXAMPLE 5:

Ti/P/O catalyst ? SYNTHESIS OF THE METALLIC PRECURSOR BY HYDROLYSIS AND CONDENSATION WITH THE SOL-GEL METHOD ? Titanium isopropoxide (IV).

The metal precursor used? titanium isopropoxide (IV).

Titanium alkoxide? was added dropwise to an aqueous solution of dihydrogen ammonium phosphate (NH4)H2PO4 containing a 90:10 mixture of ethanol and isopropanol.

In detail, the molar ratio between ethanol|isopropanol/alkoxide/(NH4)H2PO4/water ? of 1/0.125/0.0124/2.

At the end of the addition, the pH of the solution is brought to a value of 7 by adding a 25% concentrated ammonia aqueous solution. At this point, the system ? kept under stirring for 24 hours at room temperature.

After 24 hours, the solvent is removed and the nanoparticles are dried at 120°C overnight.

Subsequently, the nanoparticles are calcined at temperatures between 400°C and 600°C.

The speed? of heating ? substantially equal to 10?C/min for a duration substantially between 3 and 6 hours.

CATALYTIC EFFICIENCY TEST

A test set up in order to evaluate the catalytic efficiency of metal phosphates in the isomerization reaction of carbohydrates, preferably in the isomerization reaction of lactose, is reported below.

The reaction conditions are given below:

- V= 20ml

- Lactose: 0.005 g/l in water;

- mcat/mlat=1:1;

- T= 200?C;

- t=3 hours;

- P autogenous

TEST CORRELATION OF REACTION TEMPERATURE AND CATALYTIC EFFICIENCY

? an experimental test was set up in order to evaluate the catalytic efficiency as the temperature varies. In detail, the aforementioned test ? was prepared using the Nb/P/O catalyst on a lactose substrate. The reaction conditions are given below:

- V= 20ml

- Lactose: 0.005 g/l in water;

- mcat/mlat=1:1;

- T= 200?C;

- t=3 hours;

- P autogenous;

From the above table it can be seen that as the temperature increases, the reactivity also increases. and then the yield in hydroxymethylfurfural.

However, ? it is necessary to emphasize that below 150°C the splitting of lactose into its two components, glucose and galactose, does not occur.

TEST CORRELATION OF REACTION TIME AND EFFICIENCY

CATALYTIC

? an experimental test was set up in order to evaluate the catalytic efficiency as the reaction time varied. In detail, the aforementioned test ? was prepared using the Nb/P/O catalyst on a lactose substrate.

The reaction conditions are given below:

- V= 20ml

- Lactose: 0.005 g/l in water;

- mcat/mlat=1:1;

- T= 150?C;

- P autogenous;

From the above table it is observed that the reaction time of observes that the yield in HMF ? directly proportional to the reaction time.

TEST CORRELATION OF REACTION VOLUME AND CATALYTIC EFFICIENCY

? an experimental test was set up in order to evaluate the catalytic efficiency as the reaction volume varies. In detail, the aforementioned test ? was prepared using the Nb/P/O catalyst on a lactose substrate.

The reaction conditions are given below:

- V= 50ml

- Lactose: 0.005 g/l in water;

- mcat/mlat=1:1;

- T= 150?C;

- P autogenous;

From the above table it can be seen that as the reaction volume increases, the yield of HMF decreases.

CORRELATION TEST TYPE OF SUBSTRATE AND CATALYTIC EFFICIENCY

? an experimental test was set up in order to evaluate the catalytic efficiency as the substrate varies. In detail, the aforementioned test ? was prepared using the Nb/P/O catalyst on a substrate alternatively selected from: lactose, glucose, galactose, fructose, sucrose.

The reaction conditions are given below:

- V= 50ml

- Lactose: 0.005 g/l in water;

- mcat/mlat=1:1;

- T= 150?C;

- P autogenous;

In a second aspect, the present invention relates to a catalyst for the isomerization of carbohydrates in hydroxymethylfurfural (HMF) comprising at least one metal phosphate in which the metal is chosen from the list including niobium, zirconium, hafnium, titanium, aluminium.

In a third aspect, the present invention relates to the use of a metal phosphate comprising one of niobium, zirconium, hafnium, titanium, aluminum as a catalyst for the isomerization of a glucide, in the presence of an organic solvent, for the preparation of hydroxymethylfurfural (HMF).

Yup ? in practice it has been observed that the described invention achieves the proposed aim and objects.

In particular, it is emphasized that the particular expedient of providing for the use of a metal phosphate in which the metal is? selected from niobium, zirconium, hafnium, titanium, aluminum in combination with the use of a substrate selected from the list comprising glucose, galactose, fructose and sucrose allows to obtain hydroxymethylfurfural with a considerably higher yield than known processes.

Claims (14)

1) Process for the isomerization of carbohydrates in hydroxymethylfurfural, including the following steps: - provision of: - at least one carbohydrate selected from the list comprising: lactose, glucose, galactose, fructose and sucrose; And - at least one catalyst comprising at least one metal phosphate in which the metal is chosen from the list including: niobium, zirconium, hafnium, titanium, aluminium; - addition of at least one reaction solvent to obtain a reaction mixture; - heating said reaction mixture to a temperature higher than 80°C. 2) Process according to claim 1, wherein said temperature ? between 80?C and 200?C. 3) Process according to one or more? of the preceding claims, wherein said glucide and said catalyst are present in a molar ratio comprised between 1:0.01 and 1:1. 4) Process according to one or more? of the preceding claims, wherein said reaction solvent comprises at least one of water and an organic solvent. 5) Process according to one or more? of the preceding claims, wherein said organic solvent ? selected from the list including: methyl tetrahydrofuran, tetrahydrofuran, n-butanol and gamma-valerolactone. 6) Process according to one or more? of the preceding claims, wherein said organic solvent and said water are present in said reaction mixture with a molar ratio between 1:1 and 4:1. 7) Process according to one or more? of the preceding claims, characterized in that it is carried out in an inert atmosphere. 8) Process according to one or more? of the preceding claims, characterized in that it is conducted at pressure values ranging from 5 bar to 25 bar. 9) Process according to one or more? of the preceding claims, characterized in that it has a yield of hydroxymethylfurfural greater than 20%. 10) Process according to one or more? of the preceding claims, characterized in that it comprises a regeneration step of said catalyst in which the latter is thermally dried at a temperature above 200?C. 11) Process according to one or more? of the preceding claims, characterized in that it comprises at least one preparation step of said catalyst, said preparation step being prior to said supply step. 12) Process according to one or more? of the preceding claims, wherein said preparation step comprises the precipitation of said catalyst in an acid medium starting from at least one metal precursor or by hydrolysis and condensation of said metal precursor. 13) Catalyst for the isomerization of carbohydrates in hydroxymethylfurfural according to one or more? of the preceding claims, comprising at least one metal phosphate in which the metal is chosen from the list including niobium, zirconium, hafnium, titanium, aluminium. 14) Use of a metal phosphate comprising one of niobium, zirconium, hafnium, titanium, aluminum as a catalyst for the isomerization of a glucid, in the presence of an organic solvent, for the preparation of hydroxymethylfurfural.