FR2727967A1 - PROCESS FOR THE MANUFACTURE OF HYDROXYMETHYLFURFURAL FROM ALDOHEXOSE - Google Patents

Abstract

A method for making hydroxymethylfurfural from a liquid medium containing at least one aldohexose or a saccharide capable of releasing at least one aldohexose, wherein the liquid is heated to a temperature higher than 100 DEG C in the presence of two separate acidic catalysts at once. The first catalyst consists of an aluminosilicate in proton form having an Si/Al ratio lower than 4, while the second is an aluminosilicate in proton form having an Si/Al ratio higher than 5.

Description

PROCESS FOR PRODUCING HYDROXYMETHYLFURFURAL
FROM ALDOHEXOSE.

 The invention relates to a process for the manufacture of 5-hydroxymethyl furan-2-carboxaldehyde, more often designated hydroxymethylfurfural (HMF), from a liquid medium comprising at least one aldohexose and / or at least one oside capable of releasing at least an aldohexose.

 HMF can be manufactured in an organic medium (FR 2 669 635) or in an aqueous medium (WO 92/10486) from fructose or polyfructans. In particular, the synthesis of HMF can be obtained by heating the medium in the presence of a heterogeneous acid catalyst.

 However, if the synthesis is relatively satisfactory from ketohexoses, the transformation of aldohexoses, in particular glucose, under the conditions described by the prior art is, in practice, almost zero. However, the sugar solutions available on the market at low cost often include either osides (sucrose, inulin, starch, etc.) releasing at least one aldohexose by hydrolysis, or invert sugars obtained by hydrolysis of these osides, in the form of a mixture of simple sugars comprising a high proportion of aldohexose (s). The known methods therefore require carrying out a prior or subsequent separation of the unprocessed sugars, and in particular of aldohexoses such as glucose.

 The invention aims to overcome these drawbacks by proposing a process for manufacturing HMF from a sweet liquid medium which can comprise any proportion of at least one aldohexose and in particular which consists of a solution or a syrup d 'aldohexose (s).

 Thus, the invention aims to propose a process for the manufacture of HMF from a sugar solution or from a syrup which can comprise a high proportion of aldohexose (s) (such as glucose, galactose, mannose or l 'idose) and / or polysaccharide (s) (such as cellulose, starch, ...) and / or oligoholoside (s) (such as sucrose, lactose, maltose, cellobiose .. .), with sufficiently high sugar transformation and HMF production yields to envisage profitable industrial production. The invention aims in particular to propose a process for manufacturing HMF from a sugar solution or a syrup, the sugars of which only consist of aldohexose (s) and / or polysaccharide (s) and / or oligoholoside (s).

 The invention also aims to reduce the cost of preparing HMF by lowering the price of the raw material without increasing that of the process.

 The object of the invention is in particular to authorize the direct use of a greater variety of sugar solutions as a raw material for the manufacture of HMF, including sugar solutions extracted from natural products (Jerusalem artichokes, beets, canes sugar ...) or sugar solutions from the hydrolysis of naturally occurring sugars (which include as many aldohexoses as ketohexoses and residual osides). The object of the invention is also to reduce or even eliminate the cost of the separation steps, and to increase the rate of conversion of the sugars into HMF.

 The invention aims in particular to propose such a manufacturing process in a single step, which can be carried out continuously, and producing a high purity HMF solution.

 The invention also aims to propose such a process for manufacturing HMF by heterogeneous acid catalysis and heating in a single step, rapid, low polluting, profitable whatever the size and capacity of the installation, in particular with large installations. and low or medium capacity.

 To do this, the invention relates to a process for the manufacture of hydroxymethylfurfural (HMF) from a liquid medium comprising at least one aldohexose and / or at least one oside capable of releasing at least one aldohexose, in which the liquid medium at a temperature above 1000 C in the presence of a heterogeneous acid catalysis, characterized in that the liquid medium is simultaneously brought into contact with at least two distinct acid catalysts, the first of which is a tectosilicate or a non-functionalized clay by acid groups, in protonic form, and of Si / Al ratio less than 4, in particular between 2 and 4, and the second of which is a tectosilicate not functionalized by acid groups, in protonic form, and of Si / Al ratio greater than 5.

 It has in fact been found that the combination of two heterogeneous acid catalysts, the first of which is more weakly acid in the sense of BRONSTED while the second is more strongly acid makes it possible to obtain a high conversion rate of aldohexoses without otherwise producing drawbacks. . In a process according to the invention, two acid catalysts are therefore used (in protonic form) having different BRONSTED acidities.

 According to the invention, said second catalyst is a zeolite chosen to transform ketohexoses - in particular fructose - into HMF with a selectivity of transformation greater than 90% when it is used alone, under the operating conditions of the reaction (temperature, pressure , initial concentrations, flow rates, etc.), and said first catalyst is a zeolite whose acidity (in the sense of BRONSTED) is lower than that of said second catalyst. Preferably and according to the invention, the second catalyst is chosen to transform the ketohexoses - in particular fructose - into HMF with a yield of HMF greater than 50% when it is used alone under the operating conditions of the reaction.

 According to the invention, the liquid medium is a concentrated aqueous solution, in particular a syrup, comprising more than 150 g / l of aldohexose (s) and / or of oside (s).

 Advantageously and according to the invention, said first catalyst is a zeolite, in particular a faujasite Y in protonic form. Advantageously and according to the invention, the Si / Al ratio of this first catalyst is of the order of 2.5 to 3.

 According to the invention, said first catalyst advantageously has a three-dimensional structure having pores of around 7.5 A in diameter connected to cages of around 13 A in diameter arranged in cubic symmetry.

According to the invention, said second catalyst is a zeolite, in particular a H mordenite, and its ratio
If / Al is of the order of 5 to 20, in particular of the order of 10.

 According to the invention, the liquid medium is heated to a temperature above 1500 C and below 2000 C, in particular of the order of 1650 C.

 Advantageously and according to the invention, the method can be implemented continuously. To do this, the liquid medium is circulated continuously in at least one multi-stage reactor - in particular a pulsed column in the presence of catalysts in cocurrent suspension of the liquid medium and the HMF is extracted continuously in an immiscible solvent with the liquid medium circulating against the current. The solvent is preferably an organic solvent, in particular MIBC (methyl isobutyl ketone).

 The invention further relates to a method comprising in combination all or part of the features mentioned above or below.

 Other characteristics and advantages of the invention will appear on reading the following description which refers to the single appended figure which is a diagram of a pulsed column stage of an installation for implementing a method according to the invention.

 This installation comprises a supply 1 of sugar solution, and supplies 2, 3 of acid catalysts. The feed 2 provides the first catalyst which is for example a faujasite Y in protonic form in powder with an SiO2 / Al203 ratio of 6.5 (ie an Si / Al ratio of 3.25). This zeolite defines pores of 0.75 nanometer in diameter connected to cages of 1.3 nanometer in diameter in a symmetrical cubic structure.

 The feed 3 provides the second catalyst, which is for example formed of a mordenite in protonic form with an Si / Al ratio of the order of 10. This catalyst is also present in pulverulent form.

 The two catalysts are mixed in suspension with the sugar solution in a mixer 4. The mixture obtained is introduced into the upper part 5 of a pulsed column 6. The pulsed column 6 is temperature controlled. According to the invention, the temperature is above 1500 C, in particular of the order of 1650 C.

Simultaneously, there is continuously introduced into the lower part 7 of the pulsed column 6, an extraction solvent for the HMF produced. The sugar solution advantageously being an aqueous solution, the extraction solvent used is advantageously MIBC. In the upper part 5 of the pulsed column 6, the extraction solvent which has circulated against the current and which is loaded with HMF is recovered. This solvent loaded with HMF is passed through an evaporator 8 which provides at outlet 9 a concentrated solution of HMF free of sugars and by-products, and in particular free of aldohexoses.

 At the lower part 7 of the pulsed column 6, the residue of sugar solution not transformed into HMF is recovered with the catalysts in suspension. This mixture is passed through a filter 10 which makes it possible to separate the liquid and solid phases. The solid phase consisting of the catalysts is recycled directly or through a regeneration furnace 11 into the mixer 4. The liquid phase is discharged directly or to a purifier.

With such an installation, it is possible to continuously produce a concentrated solution of pure HMF from a sugar solution introduced continuously by food 1, and which can comprise any proportion, large or not, of aldhehexoses or osides capable of releasing aldohexoses. For example, this solution can be composed of sucrose or a solution of invert sugars (50% glucose and 50% fructose) or a solution of fructose and glucose comprising a higher proportion of glucose, or even d 'a pure glucose solution. It should be noted that in the case where the starting solution comprises osides, there is carried out in a single step in the pulsed column 1 continuously, the hydrolysis of the osides into simple sugars (aldohexoses or ketohexoses) and the transformation of these sugars simple in
HMF.

 It should also be noted that the invention allowing the transformation of aldohexoses into HMF, the operating conditions of the reaction are chosen to minimize the production of degradation products or byproducts of the reaction other than sugars and HMF.

Consequently, the selectivity and the yield of the overall reaction in HMF do not constitute priority criteria.

COMPARATIVE EXAMPLE 1
2.5 liters of MIBC having an organic phase level on the aqueous phase of 6.5, and 350 ml of concentrated aqueous glucose solution at 200 g / l, as well as mordenite, are introduced into a 4 liter autoclave. in protonic form at a rate of 10 g per 65 g of glucose, or 10.8 g. The autoclave is heated to 1650 C and placed under a pressure of 10 bars. After stirring for 30 minutes, the contents of HMF, fructose, glucose, mannose in solution are determined, in particular by HPLC high pressure liquid chromatography. This gives the molar conversion rates of the initial glucose into products in solution, that is to say not including the products adsorbed on the solids.

 A molar conversion rate of glucose into HMF is obtained (number of moles of HMF in solution obtained / number of moles of initial glucose) of 8%.

The molar rate of transformation of glucose into HMF and fructose is 15%. The molar rate of total transformation into HMF, fructose and mannose, is 17%.

EXAMPLE 2
Under the same operating conditions as those mentioned in Example 1, faujasite is added simultaneously in protonic form with an Si / Al ratio equal to 3.25. In this example, the weight of faujasite used was half the weight of mordenite, or 5.4 g. A molar conversion rate of glucose into HMF of 10% is obtained. The molar rate of conversion of glucose into
HMF and fructose is 28%. The total molar rate of transformation into HMF, fructose and mannose is 33%.

EXAMPLE 3
This example is identical to Example 2, but a weight of faujasite identical to the weight of mordenite is used, ie 10.8 g. The molar rate of transformation into HMF is 13%. The molar rate of transformation into
HMF and fructose is 34%. The total molar rate of transformation into HMF, fructose and mannose is 41%.

EXAMPLE 4
This example is identical to Example 2, but a weight of faujasite is used which is twice the weight of mordenite, ie 21.6 g.

The molar rate of transformation into
HMF is 12%. The molar rate of transformation into HMF and fructose is 35.5%. The total molar rate of transformation into HMF, fructose and mannose is 43.5%.

It is thus noted between comparative example 1 and example 2 that the total transformation of glucose into
HMF and direct precursors of HMF (fructose and mannose) is doubled by the simple addition of a small amount of faujasite. The transformation is further improved in Examples 3 and 4. However, between Examples 3 and 4, the transformation is not significantly improved. On the other hand, in example 4, a significant increase in the production of undesirable by-products is noted.

 The continuous extraction of HMF in the solvent against the current in an installation such as that of the figure will make it possible to shift the equilibrium of the transformation of fructose, and even of mannose into HMF, and to obtain a good conversion and good selectivity of the process.

 HMF can thus be prepared directly and in a single operation from glucose, or from a mixture of oses consisting of aldohexoses or comprising aldohexoses such as glucose, by optimizing the relative amounts of the two catalysts.

Claims (11)

 1 / - Process for the manufacture of hydroxymethylfurfural (HMF) from a liquid medium comprising at least one aldohexose and / or at least one oside capable of releasing at least one aldohexose, in which the liquid medium is heated to a higher temperature at 1000 C in the presence of a heterogeneous acid catalysis, characterized in that the liquid medium is simultaneously brought into contact with at least two distinct acid catalysts, the first of which is a tectosilicate or a clay not functionalized by acid groups, under protonic form, and of Si / Al ratio generally less than 4, and the second of which is a tectosilicate not functionalized by acid groups, in protonic form, and of Si / Al ratio greater than 5.  2 / - Process according to claim 1, characterized in that said second catalyst is a zeolite chosen to provide a selectivity for the transformation of ketohexoses into HMF greater than 90% under the operating conditions of the reaction, and in that said first catalyst is a zeolite whose acidity is lower than that of said second catalyst.  3 / - Method according to one of claims 1 and 2, characterized in that said second catalyst is chosen to transform the ketohexoses into HMF with an HMF yield greater than 50% when used alone under the operating conditions of the reaction .  4 / - Method according to one of claims 1 to 3, characterized in that said first catalyst is a faujasite Y in protonic form.  5 / - Method according to one of claims 1 to 4, characterized in that said first catalyst has an Si / Al ratio of the order of 2.5 to 3.  6 / - Method according to one of claims 1 to 5, characterized in that said second catalyst is a mordenite in protonic form.  7 / - Method according to one of claims 1 to 6, characterized in that said second catalyst has an Si / Al ratio of the order of 5 to 20.  8 / - Method according to one of claims 1 to 7, characterized in that the liquid medium is a concentrated aqueous solution.  9 / - Method according to one of claims 1 to 8, characterized in that the aqueous solution is a syrup comprising more than 150 g / l of aldohexose or oside.  10 / - Method according to one of claims 1 to 9, characterized in that the liquid medium is heated to a temperature above 1500 C and below 2000 C, in particular of the order of 1650 C.  11 / - Method according to one of claims 1 to 10, characterized in that the liquid medium is circulated continuously in at least one multi-stage reactor -notably a pulsed column in the presence of the co-current catalysts of the medium liquid and in that the HMF is continuously extracted in a solvent immiscible with the liquid medium circulating against the current.