Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
PROCESS FOR ACIDIC HYDROLYSIS OF A PARTICULATE SOLID MATERIAL CONTAINING HEMICELLULOSE, CELLULOSE AND LIGNIN, AND BASIC PROCESS CONTROL FOR SUCH
Document Type and Number:
WIPO Patent Application WO/2020/157055
Kind Code:
A1
Abstract:
A process for the conversion of a particulate solid material comprising hemicellulose, cellulose and lignin, said process being conducted in at least one reactor comprising said particulate solid material and interstitial space. The process comprises two hydrolysis steps using hydrochloric acid, separated by a displacement step wherein a water-immiscible displacement liquid displaces part of the hydrochloric acid containing hydrolysate products from the interstitial space in the reactor, and wherein the reactor has at least one exit connected to a flow-through section, and wherein said flow-through section comprises non-invasive measurement means. The non-invasive measurement can detect the change in effluent from the reactor: from acid aqueous hydrolysis solution to displacement fluid and/or from displacement fluid to acid aqueous hydrolysis solution.

Inventors:
KERSBULCK MARTIJN (NL)
MCKAY BENJAMIN (NL)
GRUTER GERARDUS JOHANNES MARIA (NL)
Application Number:
PCT/EP2020/052024
Publication Date:
August 06, 2020
Filing Date:
January 28, 2020
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
AVANTIUM KNOWLEDGE CENTRE BV (NL)
International Classes:
D21C1/04; D21C7/08
Domestic Patent References:
WO2016099273A12016-06-23
WO2019149833A12019-08-08
Foreign References:
GB827921A1960-02-10
US2945777A1960-07-19
GB827921A1960-02-10
NL2020356A2018-01-31
Other References:
F. BERGIUS, CURRENT SCIENCE, vol. 5, no. 12, June 1937 (1937-06-01), pages 632 - 637
Attorney, Agent or Firm:
WURFBAIN, Gilles (NL)
Download PDF:
Claims:
CLAIMS

1. Process for hydrolyzing at least part of the hemicellulose and at least part of the cellulose of a particulate solid material comprising hemicellulose, cellulose and lignin, said process being conducted in at least one reactor comprising said particulate solid material and interstitial space, which processes comprises the subsequent steps of:

a. contacting said particulate solid material with an aqueous hydrochloric acid solution by adding to the reactor a first hydrochloric acid solution having a hydrochloric acid concentration of at least 30% and not more than 42%, based on the weight amount of water and hydrochloric acid in the first hydrochloric acid solution, yielding a remaining particulate solid material and a first aqueous hydrolysate product solution;

b. displacing at least part of said first aqueous hydrolysate product solution from the

interstitial space with a water-immiscible displacement liquid that having a solubility in water of less than 3 g liquid per litre of water, at 20°C and atmospheric pressure; c. contacting the particulate solid material resulting from step b. with an aqueous hydrochloric acid solution by adding to the reactor a second hydrochloric acid solution thereby displacing the water-immiscible displacement fluid from the interstitial space, wherein the second hydrochloric acid solution has a hydrochloric concentration of at least 40% and less than 51%, based on the weight amount of water and hydrochloric acid in the second hydrochloric acid solution whilst said second hydrochloric acid solution has a hydrochloric acid concentration which is the same or higher than the first hydrochloric acid solution added in step a., yielding a remaining particulate solid material and a second aqueous hydrolysate product solution;

wherein the reactor has at least one exit, and wherein such exit is connected to a flow-through section through which one or more of:

first aqueous hydrolysate product solution,

water-immiscible displacement liquid,

second aqueous hydrolysate product solution

is flowing during at least part of conducting the process, wherein said flow-through section comprises non-invasive measurement means which non-invasive measurement means provides a signal when the liquid flowing through said flow-through section changes: from first aqueous hydrolysate product solution to water-immiscible displacement liquid, and/or

from water-immiscible displacement liquid to second aqueous hydrolysate product solution, and/or

from second aqueous hydrolysate product solution to water-immiscible displacement liquid,

wherein said flow-through section is of a non-metal material, and wherein the non-invasive measurement means comprises an optical sensor, magnetic field sensor, electric field sensor, capacitative sensor, electric conductivity sensor, or ultrasonic sensor.

2. Process according to claim 1, wherein said non-metal material flow-through section is made of one of glass, quartz or a polymeric material, preferably polyvinyl chloride (PVC) (preferably being PVC-C), polyether ether ketone (PEEK), polyethylene (PE), polypropylene (PP), or a fluorocarbon polymer.

3. Process according to claim 1 or claim 2, wherein said flow-through section is transparent or translucent.

4. Process according to claim 3, wherein the optical sensor is an optrode measuring a change in reflection, absorption, evanescent wave, luminescence (fluorescence and phosphorescences), chemiluminescence, surface plasmon resonance, or a combination thereof.

5. Process according to claim 3 or 5, wherein the optical sensor operates at a wavelength of between 10 nm and 10000 nm, preferably at a wavelength of between 100 and 1000 nm, more preferably at a wavelength of between 400 and 700 nm.

6. Process according to any of the preceding claims, wherein said signal produced by the non- invasive measurement means triggers switching a valve and/or a pump, optionally via a programmable logic controller or a computer.

7. Process according to claim 6, wherein said valve and/or pump being switched changes the direction of flow through the reactor and/or the direction of the effluent and/or stops a flow going in or out of the reactor.

8. Process according to any of the preceding claims, wherein the reactor is a tubular reactor, having a ratio length to diameter of between 2 and 20.

9. Process according to any of the preceding claims, wherein the particulate solid material is a solid material of which the particles prior to hydrolyzing step a. have a particle size of at least P16A and at most P100, preferably P45A or P45B, conforming European standard EN 14961-1 on solid biofuels.

10. Process according to any of the preceding claims, wherein the particulate solid material is one or more of wood chips, pelletized wood matter, briquettes of wood matter, pelletized or briquetted matter of ground matter from one or more of straw, grass, bagasse, corn stover.

11. Process according to any of the preceding claims, wherein the water-immiscible displacement liquid has a solubility in water of less than 2 g liquid per litre of water, at 20°C and atmospheric pressure, preferably having a solubility of less than 1 g/L.

12. Process according to claim 11, wherein the water-immiscible liquid is a hydrocarbon liquid, preferably having a boiling temperature of at least 80°C at a pressure of 0.1 mPa, and preferably has a viscosity at 20° of 5 cP or less.

13. Process according to any of the preceding claims, wherein the water-immiscible displacement liquid comprises or consists of one or more alkanes chosen from the group consisting of cyclic hexane, normal hexane, iso-hexane and other hexanes, normal heptane, iso-heptane and other heptanes, normal octane, iso-octane and other octanes, normal nonane, iso-nonane and other nonanes, normal decane, iso-decane and other decanes, normal undecane, iso-undecane and other undecanes, normal dodecane, iso-dodecane and other dodecanes, normal tridecane, iso- tridecane and other tridecanes, normal tetradecane, iso-tetradecane and other tetradecanes, normal pentadecane, iso-pentadecane and other pentadecanes, normal hexadecane, iso- hexadecane and other hexadecanes.

14. Process according to any of the preceding claims, wherein the reactor comprising said particulate solid material and interstitial space has a porosity calculated as of between 0.1 and 0.5, preferably between 0.2 and 0.4, wherein

preferably the particulate solid material being wood particles.

Description:
PROCESS FOR ACIDIC HYDROLYSIS OF A PARTICULATE SOLID MATERIAL CONTAINING HEMICELLULOSE, CELLULOSE AND LIGNIN, AND BASIC PROCESS CONTROL FOR SUCH

Introduction

The invention relates to a process the conversion of a particulate solid material comprising

hemicellulose, cellulose and lignin, said process being conducted in at least one reactor comprising said particulate solid material and interstitial space. More specifically, said conversion is a two-step acid hydrolysis, for the first step using aqueous hydrochloric acid in a concentration of at least 30% and less than 42%, and for the second step using aqueous hydrochloric acid in a concentration of at least 40% and less than 51% (but at the same or higher concentration than for the first step), with in between these two steps the use of a water-immiscible displacement fluid that can displace at least part of the aqueous hydrochloric acid (further containing hydrolysis products) from the interstitial space. Even more specifically, the process is conducted such that at least one reactor in which the reaction takes place has an exit connected to a flow-through section (e.g. a passage or tube) which flow-through section is equipped with a non-invasive measurement means. The non-invasive measurement means is such that it can detect the difference between aqueous hydrolysate and the water-immiscible displacement fluid flowing past the detection means. Upon such detection the non-invasive

measurement means can send a signal to a process control device which controls a valve or pump or other device for controlling flow of one or more fluids.

Background of the invention

Several processes are known for the production of saccharides out of ligno-cellulosic material. The saccharides so produced can be used as renewable sources or intermediates of chemical building blocks or for use in generating carriers of energy, such as ethanol. One of these processes relate to a hydrolysis of the cellulose using a strong aqueous acid. In such process, the saccharides are typically obtained as a mixture of mono-, di- and oligo-saccharides dissolved in the aqueous acid. Various sources can be used for as ligno-cellulosic material. It is advantageous if sources can be used that do not directly compete with material used in food production. An example of a ligno-cellulosic material that does not compete with the food chain is wood and materials that are made of wood (e.g. wood chips or pellets of saw dust) and waste material like straw, corn stover and bagasse. Such ligno-cellulosic material thus contains next to lignin also cellulose and hemicellulose (and some minor components). A process for the hydrolysis of wood using strong hydrochloric acid is known as the Bergius-Rheinau process (F. Bergius, Current Science Vol. 5, No. 12 (June 1937), pp. 632-637).

The disadvantage, however, of wood as source of cellulose to be hydrolysed is that it further contains considerable amounts of hemi-cellulose. In processes for obtaining saccharides by hydrolysis of cellulose using a strong acid, part of hemi-cellulose being present will also hydrolysed under the influence of strong aqueous acid solutions. Hydrolysis of hemi-cellulose generally yields mixture comprising xylose, arabinose, mannose, glucose and their oligomers as saccharides, i.e. a mixture of pentoses and hexoses (or C5- and C6-saccharides) and their oligomers. Hydrolysis of cellulose on the other hand will yield (mainly) hexoses (C6-sacchharides). It may be an advantage to have a process for producing hexoses out of a ligno-cellulosic source such as wood in which the cellulose is hydrolysed selectively. The process as disclosed in US 2945777, which is the Bergius-Rheinau process as modified by T Riehm (or simply: modified Bergius-Rheinau process), aims to achieve this objective. In this process, the acid hydrolysis occurs in two stages: a first hydrolysis or pre-hydrolysis using hydrochloric acid at a concentration of 34- 37%, followed by a second hydrolysis using hydrochloric acid at a concentration of 40-42%. In the pre hydrolysis (mainly) the hemi-cellulose is hydrolysed, yielding a pre-hydrolysate containing a mixture of pentoses and hexoses and their oligomers. The hydrolysis carried out thereafter will hydrolyse (mainly) the cellulose, yielding a hydrolysate rich in a mixture of hexoses and their oligomers. This facilitates obtaining a stream rich in hexoses.

GB 827921 describes (page 2 lines 76-86) saccharification of cellulosic materials in a two-stage process, in which hydrochloric acid of 29-36% is passed upwards through a column of cellulosic material, and subsequently displacing this hydrochloric acid with a more concentrated hydrochloric acid by passing the more concentrated hydrochloric acid for the main hydrolysis upwardly through the column. Such method has two disadvantages: one is that the two acid fractions are in contact with eachother (as the stronger is to push out the less strong solution) and one is bound to upward flow. The two solutions being in contact with eachother means that some back-mixing will occur or the two fractions, resulting in a less clear separation of pre- and main hydrolysate, which is even more so as these two fractions are not easy to distinguish and it is not clear how the can be collected separately. The limitation to upward flow means the process is less than optimal, as the hydrochloric acid solutions becomes heavier when they move upward (due to saccharides dissolving). The increasing density when moving upward means an increased amount of backmixing, which means that no plug flow character can be obtained, and thus a limited amount of process control being possible.

A further improvement of the above process of US2945777 is one in which the aqueous pre-hydrolysate (of the hemi-cellulose fraction of the starting material) and the aqueous hydrolysate (of the cellulose fraction of the starting material) can be kept separate largely. A process in which in between the hydrolysis and pre-hydrolysis the material to be hydrolysed is treated with a non-aqueous, preferably hydrophobic, displacement fluid achieves this. This has been set out in non-pre-published patent application NL2020356 (published as WO2019/149833). The process in this reference uses a system of at least one reactor in which wood chips are present as a stationary phase, which stationary phase is flooded with hydrochloric acid of e.g. 37% for a pre-hydrolysis step. After carrying out the pre-hydrolysis to a sufficient degree, a non-aqueous displacement fluid is fed to the reactor, which pushes out at least part of the aqueous hydrochloric acid and hydrolysis products. Thereafter, the non-aqueous displacement fluid is pushed out in turn by feeding to the reactor the hydrochloric acid solution of higher concentration, e.g. 42%, to effect the hydrolysis.

In the process of the non-prepublished patent application referred to above (published as

WO2019/149833), after the pre-hydrolysis is sufficiently complete, non-aqueous displacement fluid is fed to the reactor. When feeding the reactor with non-aqueous displacement fluid to displace the aqueous pre-hydrolysate from the reactor initially pre-hydrolysate comes out (followed by the non- aqueous displacement fluid if continued long enough). This pre-hydrolysate will be pushed out by the displacement fluid as long as inlet of displacement fluid and exit of pre-hydrolysate are carefully chosen, taking into account the density of both aqueous pre-hydrolysate and non-aqueous displacement fluid. More specifically, if the non-aqueous displacement fluid has a density lower than that of the aqueous pre-hydrolysate and is pumped into the reactor at the top, and the aqueous pre-hydrolysate can be collected at the bottom, the displacement fluid pushes (like a plug) the aqueous pre-hydrolysate out at the bottom. Hence, a downward flow in this process is possible, which can better retain a plug-like character.

The aim of the above referred process is to be able to collect most of the pre-hydrolysate (aimed at hydrolyzing hemi-cellulose) separate from the hydrolysate (aimed at hydrolyzing cellulose), as this is an important step towards obtaining a hydrolysate of ligno-cellulosic matter (which also includes hemi- cellulose) which is relatively rich in glucose and its oligomers and which contains relatively little hydrolysates from hemi-cellulose, such as xylose and its oligomers. It is preferred that both pre hydrolysate of hemi-cellulose and hydrolysate stream of cellulose can be obtained as much as possible separated from eachother, as such will result in better defined product streams. To facilitate such, there is a desire for good process control in the modified Bergius-Rheinau process to separate as much hydrolysis of hemi-cellulose from hydrolysis of cellulose. More specifically, the desire is to have good process control in the sense that most of the pre-hydrolysis products can be obtained as much as possible separated from the hydrolysis products. More specifically it is preferred to achieve such in an improved version of the modified Bergius-Rheinau process which uses a water-immiscible displacement fluid in between the two hydrolysis steps. Even more preferred is an improvement in which one can obtain a pre-hydrolysate which contains no or only a small amount of water-immiscible displacement fluid, and likewise that when a water-immiscible displacement fluid is used it can be obtained with only low amounts of pre-hydrolysate or hydrolysate product. There is also a desire for operational simplicity.

Thus, for the system as described in non-pre-published patent application NL2020356 (published as WO2019/149833) means for controlling the various flows is desired.

Summary of the invention

It has now been found that the objectives as above could be achieved, at least in part, by a process for hydrolyzing at least part of the hemicellulose and at least part of the cellulose of a particulate solid material comprising hemicellulose, cellulose and lignin, said process being conducted in at least one reactor comprising said particulate solid material and interstitial space, which processes comprises the subsequent steps of:

a. contacting said particulate solid material with an aqueous hydrochloric acid solution by adding to the reactor a first hydrochloric acid solution having a hydrochloric acid concentration of at least 30% and not more than 42%, based on the weight amount of water and hydrochloric acid in the first hydrochloric acid solution, yielding a remaining particulate solid material and a first aqueous hydrolysate product solution;

b. displacing at least part of said first aqueous hydrolysate product solution from the interstitial space with a water-immiscible displacement fluid; c. contacting the particulate solid material resulting from step b. with an aqueous hydrochloric acid solution by adding to the reactor a second hydrochloric acid solution thereby displacing the water-immiscible displacement fluid from the interstitial space, wherein the second hydrochloric acid solution has a hydrochloric concentration of at least 40% and less than 51%, based on the weight amount of water and hydrochloric acid in the second hydrochloric acid solution whilst said second hydrochloric acid solution has a hydrochloric acid concentration which is the same or higher than the first hydrochloric acid solution added in step a., yielding a remaining particulate solid material and a second aqueous hydrolysate product solution;

wherein the reactor has at least one exit, and wherein such exit is connected to a flow-through section through which one or more of:

first aqueous hydrolysate product solution,

water-immiscible displacement fluid,

second aqueous hydrolysate product solution

is flowing during at least part of conducting the process, wherein said flow-through section comprises non-invasive measurement means which non-invasive measurement means provides a signal when the liquid flowing through said flow-through section changes:

from first aqueous hydrolysate product solution to water-immiscible displacement fluid, and/or from water-immiscible displacement fluid to second aqueous hydrolysate product solution, and/or

from second aqueous hydrolysate product solution to water-immiscible displacement fluid.

Detailed description of the invention

"Water-immiscible" herein means, in connection to the displacement fluid and displacement liquid, that such displacement fluid or displacement liquid has a solubility in water of less than 3 g displacement fluid (or displacement liquid) per litre of water, at 20°C and atmospheric pressure. Preferably, such solubility is less than 2 g/L, even more preferably less than 1 g/L, under such conditions.

"Interstitial space" herein means the voids in a reactor filled with particulate solid material, or in other words the space inside the reactor but outside the particulate solid material. "Non-invasive measurement means" herein means any measurement means which is capable of indicating the difference between a flow of aqueous hydrolysate or pre-hydrolysate on the one hand and water-immiscible displacement fluid on the other hand flowing past such, and more specifically the changeover of one the aqueous liquids herein for the water-immiscible displacement fluid and vice versa, wherein the measurement means does not penetrate the flow-through section. Thus, the measurement means is not in direct physical contact with either the aqueous (pre-) hydrolysate product or the water-immiscible displacement fluid.

In the present invention the fluids like the aqueous pre-hydrolysate, water-immiscible displacement fluid and aqueous hydrolysate can flow through the non-invasive measurement means or past such, depending on the type of measurement means. In many cases, the measurement means will comprise a sending and a receiving unit: the sending unit sends a signal (e.g. light, ultrasound, electrical or magnetic field, or other) and the receiving unit can receive (part of) such emitted signal, which may have been modified in one or more properties by the fluid which flows through the flow-through section. The aqueous (pre-) hydrolysate and the water-immiscible displacement fluid have different properties in several aspects, and the non-invasive measurement means may rely on one or more of such difference in properties to sense the difference between the aqueous (pre-)hydrolysate or water-immiscible displacement fluid flowing through or past the non-invasive measurement means.

In the process according to the present invention the flow-through section connected to the exits of the reactor can be a pipe or tube. It is preferred, given the oxidative nature of the strong hydrochloric acid involved that the flow-through section of the present invention is of a non-metal material. Preferred non-metal materials in this connection are preferably glass, quartz or a polymeric material, and of the polymeric materials polyvinyl chloride (PVC), polyether ether ketone (PEEK), polyethylene (PE), polypropylene (PP) or a fluorocarbon polymer are preferred. If PVC is used a PVC-C is the preferred PVC. It is furthermore preferred that the flow-through section in the present invention is transparent or translucent, as this allows also visible control of the flows, as the pre-hydrolysate and the hydrolysate are dark-colour liquids, and for the water-immiscible displacement fluids easily colourless or light- coloured liquids can be selected. The non-invasive measurement means in the presently claimed process should be able to sense the difference between on the one hand aqueous pre-hydrolysate or hydrolysate flowing past or through the means, and water-immiscible displacement fluid (and preferably also air) on the other hand. These fluids have several differences, such as colour, electrical (field) properties, magnetic (field) properties, how they respond to or influence (ultra) sound waves, etcetera. Hence, in the present invention is preferred that the non-invasive measurement means comprises an optical sensor, magnetic field sensor, electric field sensor, capacitative sensor, electric conductivity sensor, or ultrasonic sensor.

In case the non-invasive measurement means comprises an optical sensor, it is preferred that the optical sensor is an optrode measuring a change in reflection, absorption, evanescent wave, luminescence (fluorescence and phosphorescences), chemiluminescence, surface plasmon resonance, or a combination thereof, depending on the fluid flowing past or through the measurement means. For economic reasons if an optical sensor is used in the present invention, it is preferred that the optical sensor operates at a wavelength of between 10 nm and 10000 nm, more preferably at a wavelength of between 100 and 1000 nm, and even more preferably at a wavelength of between 400 and 700 nm.

The non-invasive measurement means which senses the difference between aqueous (pre-)hydrolysate and water-immiscible displacement fluid can be used in a simple way that a visible or audible signal is given upon a change in the fluid flowing through or past the measurement means, and an operator may act upon such signal. However, it is more convenient that the signal produced by the non-invasive measurement means (upon a difference in the fluid flowing past or through) triggers switching a valve and/or a pump, optionally via a programmable logic controller or a computer. Such valve and/or pump being switched may then change the direction of flow through the reactor and/or the direction of the effluent (e.g. to a different storage tank) and/or stops a flow going in or out of the reactor.

In the present invention the process is preferably carried out in a tubular reactor, as such may facilitate the establishment of a plug flow (and a plug flow may lead to better separation of the pre-hydrolysate and hydrolysate by the displacement fluid). Such a tubular reactor preferably has a ratio length to diameter of between 2 and 20, more preferably between 2.5 and 15, even more preferably between 3 and 10. Feeding the reactor with the aqueous hydrochloric acid solutions can be at the top or at the bottom of the reactor. At the start of step (c) the feeding of the second hydrochloric acid solution to the reactor is preferably at the bottom of the reactor, especially when the water-immiscible displacement fluid is a liquid having a density equal to or less than 1100 kilograms per cubic meter (kg/m 3 ), more preferably less than 1000 kilograms per cubic meter (kg/m 3 ), even more preferably less than 950 kilograms per cubic meter (kg/m 3 ). Feeding of the water-immiscible displacement fluid can be at the top or at the bottom of the reactor, and is preferably at the at the top of the reactor, in particular when the water-immiscible displacement fluid is a liquid having a density equal to or less than 1100 kilograms per cubic meter (kg/m 3 ), more preferably less than 1000 kilograms per cubic meter (kg/m 3 ), even more preferably less than 950 kilograms per cubic meter (kg/m 3 ).

The process of the present invention is preferably carried out with an aqueous hydrochloric acid flowing through a bed of particulate solid material comprising hemicellulose, cellulose and lignin. For such flow, it is preferred that the particles are neither too small (as then flow can be difficult and the flow may be blocked) nor too big (as then it is difficult to hydrolyse the (hemi-)cellulose as the hydrochloric acid may have trouble reaching the inner part of the particulates. Particulates the size of sawdust will be too small, and logs the size as used in domestic open fireplaces will be too big. Flence, the particulate solid material in the present process is a solid material of which the particles prior to hydrolyzing step a. preferably have a particle size of at least P16A and at most P100, preferably P45A or P45B, conforming European standard EN 14961-1 on solid biofuels. Alternatively, the particulate solid material in the present process is a solid material of which the particles prior to hydrolyzing step a. preferably have a minimum size of 3 mm and maximum size of 100 mm, and more preferably have a size of between 8 mm and 45 mm, as measured following European standard EN 15149 on solid biofuels. Such particulates may also be pelletised material, such as pelletised wood matter, briquettes of wood matter, pelletized or briquetted matter of ground matter from one or more of straw, grass, bagasse, corn stover, as pelletised material may e.g. be made from sawdust or ground bagasse or ground corn stover which would otherwise be too small to be used in the present process.

Following the above on the bed of particulate solid material, it is preferred that in the process according to the present invention, the reactor comprising said particulate solid material and interstitial space preferably has a porosity calculated of between 0.1 and 0.5, preferably between 0.2 and 0.4. In such formula, Flerein, is the volume of the particles of particulate solid matter in the reactor, Vi nterstitiai space means the volume of the space in the reactor between the particulate solid matter (i.e. the voids), and V buik means the volume of the packed bed of particulates in the reactor. Preferably, the particulate solid material in the present invention are wood particles, such as wood chips.

A wide variety of materials is suitable as the water-immiscible displacement fluid for use in the process of this invention, as long as it does not blend well with the aqueous hydrolysate. Hence, the water- immiscible displacement fluid preferably is a gas or a water-insoluble liquid. More preferably, the water- immiscible displacement fluid is liquid that has a solubility in water of less than 3 g liquid per litre of water, at 20°C and atmospheric pressure, preferably having a solubility of less than 2 g/L, even more preferably less than 1 g/L, at said conditions. The water-immiscible displacement fluid preferably is a hydrocarbon liquid, more preferably having a boiling temperature of at least 80°C at a pressure of 0.1 mPa, and preferably also has a viscosity at 20° of 5 cP or less. Suitable water-immiscible displacement fluids comprise or consist of one or more alkanes chosen from the group consisting of cyclic hexane, normal hexane, iso-hexane and other hexanes, normal heptane, iso-heptane and other heptanes, normal octane, iso-octane and other octanes, normal nonane, iso-nonane and other nonanes, normal decane, iso-decane and other decanes, normal undecane, iso-undecane and other undecanes, normal dodecane, iso-dodecane and other dodecanes, normal tridecane, iso-tridecane and other tridecanes, normal tetradecane, iso-tetradecane and other tetradecanes, normal pentadecane, iso-pentadecane and other pentadecanes, normal hexadecane, iso-hexadecane and other hexadecanes. Preferably, the water-immiscible displacement fluid is a liquid having a density equal to or less than 1100 kilograms per cubic meter (kg/m 3 ), more preferably less than 1000 kilograms per cubic meter (kg/m 3 ), even more preferably less than 950 kilograms per cubic meter (kg/m 3 ), and is preferably one of the alkanes chosen from the group above.

In the process according to the present invention there are two hydrolysis steps (a) and (c), separated by a step in which a water-immiscible displacement fluid is used displacing at least part of the first aqueous hydrolysate product solution from the interstitial space in the reactor, as it was found that a water- immiscible displacement fluid can be effective for such. Likewise, a water-immiscible displacement fluid can be used to displace at least part of the second hydrolysate solution from the interstitial space in the reactor (i.e. an additional step (d)). This can be with the same or a different water-immiscible displacement fluid. After such the water-immiscible displacement fluid used in such step (d) may then be drained from the reactor, leaving a residue of mainly lignin particulates. The process can be carried out in one reactor, but preferably the process is carried out using a plurality of reactors. More preferably, the process according to the invention is carried out in a plurality of reactors connected in series, from 2 to 16 reactors, more preferably from 3 to 12 reactors, even more preferably from 4 to 9 reactors.

The process according to the present invention is preferably carried out with the particulate solid material is residing as a stationary phase within a reactor (or a plurality of reactors) and

wherein the particulate solid material is contacted with a mobile phase that moves through such reactor(s), which mobile phase includes:

- a zone comprising one or more portions of first aqueous hydrochloric acid solution;

- a zone comprising one or more portions of a liquid water-immiscible displacement fluid; and

- a zone comprising one or more portions of second aqueous hydrochloric acid solution.

More preferably, in the process according to the present invention:

the particulate solid material containing hemicellulose, cellulose and lignin is residing in a stationary phase within a reactor, and is contacted in step (a) with a zone of a mobile phase that moves through the interstitial space in such reactor, said mobile phase being formed by the first hydrochloric acid solution added to the reactor, to yield an aqueous first hydrolysate product solution and pre hydrolyzed solid material; and

the aqueous solution is subsequently displaced from the interstitial space around the remaining solid material with a water-immiscible displacement fluid, by contacting such remaining particulate solid material in step (b) with a subsequent zone of the mobile phase that moves through the interstitial space in such reactor, which subsequent zone comprises a water-immiscible displacement fluid; and the water-immiscible displacement fluid is subsequently displaced from the interstitial space around the remaining solid material with a second aqueous hydrochloric acid solution, by contacting the remaining solid material in step (c) with a zone of a mobile phase that moves through the interstitial space in such reactor, said mobile phase being formed by the second hydrochloric acid solution added to the reactor, to yield an aqueous second hydrolysate product solution and a residue; and

optionally said aqueous second hydrolysate product solution is subsequently displaced from the interstitial space around the residue in such reactor with a water-immiscible displacement fluid, by contacting such residue in an optional step (d) with a subsequent zone of the mobile phase that moves through the interstitial space in such reactor, which subsequent zone comprises a water-immiscible displacement fluid.

In the present invention, it may be preferred that the process is carried out in a reactor sequence of at least two reactors, wherein during steps (a), (b), and (c) the particulate solid material is residing stationary within each reactor, whilst the aqueous hydrochloric acid solutions and the water-immiscible displacement fluid are passed, preferably in a continuous or semi-continuous fashion, from one reactor into another reactor. Preferably, the reactor in the present invention is completely kept filled with fluid (hydrochloric acid, (pre-)hydrolysate, displacement fluid, wash water) throughout the process.

In the process according to the present invention it is preferred that the process is carried out in a reactor which comprises or is a cylindrical vessel with its axis arranged in an essentially vertical manner, and wherein the water-immiscible displacement fluid is a water-immiscible liquid having a density equal to or less than 1000 kilograms per cubic meter (kg/m 3 ), and wherein the water-immiscible displacement fluid is supplied to such reactor in a downward fashion.

In the presently claimed process it is preferred that the water-immiscible displacement fluid after step (b) is removed from the top of the reactor by pumping the second aqueous hydrochloric acid solution into the reactor from the bottom. In particular, this is the case when the water-immiscible displacement fluid is a water-immiscible liquid having a density equal to or less than 1100 kilograms per cubic meter (kg/m 3 ) (or more preferably less than 1000 kg/m 3 ). Similarly, it is preferred that after the water- immiscible displacement fluid being supplied from the top of the reactor in step (b) has reached the bottom of the reactor, supplying displacement fluid in step (b) is stopped and the pumping in of the second aqueous hydrochloric acid solution is started. The second aqueous hydrochloric acid solution is the preferably pumped into the reactor from the bottom.

The above leads to a preferred process for hydrolyzing at least part of the hemicellulose and at least part of the cellulose of a particulate solid material comprising hemicellulose, cellulose and lignin, said process being conducted in at least one reactor comprising said particulate solid material and interstitial space, which processes comprises the subsequent steps of:

a. contacting said particulate solid material with an aqueous hydrochloric acid solution by adding to the reactor a first hydrochloric acid solution having a hydrochloric acid concentration of at least 30% and not more than 42%, based on the weight amount of water and hydrochloric acid in the first hydrochloric acid solution, yielding a remaining particulate solid material and a first aqueous hydrolysate product solution;

b. displacing at least part of said first aqueous hydrolysate product solution from the

interstitial space with a water-immiscible displacement fluid;

c. contacting the particulate solid material resulting from step b. with an aqueous hydrochloric acid solution by adding to the reactor a second hydrochloric acid solution thereby displacing the water-immiscible displacement fluid from the interstitial space, wherein the second hydrochloric acid solution has a hydrochloric concentration of at least 40% and less than 51%, based on the weight amount of water and hydrochloric acid in the second hydrochloric acid solution whilst said second hydrochloric acid solution has a hydrochloric acid concentration which is the same or higher than the first hydrochloric acid solution added in step a., yielding a remaining particulate solid material and a second aqueous hydrolysate product solution;

wherein the reactor has at least one exit, and wherein such exit is connected to a flow-through section through which one or more of:

first aqueous hydrolysate product solution,

water-immiscible displacement fluid,

second aqueous hydrolysate product solution

is flowing during at least part of conducting the process, wherein said flow-through section comprises non-invasive measurement means which non-invasive measurement means provides a signal when the liquid flowing through said flow-through section changes:

from first aqueous hydrolysate product solution to water-immiscible displacement fluid, and/or

from water-immiscible displacement fluid to second aqueous hydrolysate product solution, and/or

from second aqueous hydrolysate product solution to water-immiscible displacement fluid

wherein process step (a) is carried out in at least one reactor of cylindrical shape with its axis arranged in an essentially vertical manner, and

wherein said water-immiscible displacement fluid is a water-immiscible liquid having a density equal to or less than 1100 kilograms per cubic meter (kg/m 3 ), preferably having a density of less than 1000 kilograms per cubic meter (kg/m 3 ), even more preferably less than 950 kilograms per cubic meter (kg/m 3 ) and wherein the water-immiscible displacement fluid is supplied to such reactor at the top of said reactor, pushing out said aqueous first hydrolysate product solution at the bottom from said reactor.

In the process as set out above, it is preferred that said water-immiscible displacement fluid is supplied at the top of said reactor until said water-immiscible displacement fluid exits the bottom of the reactor, at or after which moment the supply of water-immiscible displacement fluid at the top of said reactor is stopped and subsequently or simultaneously the second aqueous hydrochloric acid solution is supplied at the bottom of said reactor thereby reversing the flow of water-immiscible displacement fluid in an upward fashion and pushing out the water-immiscible displacement fluid at the top of the reactor. The moment "until" can in the present process be determined by the non-invasive measurement means.

In the process according to the present invention the reactor in which step (a) takes place is preferably flooded with intermediate pre-hydrolysate solution prior to step (a). "Flooded" herein is to be understood as filling the reactor (which is loaded with the particulate solid material) in fairly short time (when compared to the reaction cycle times of e.g. 8 hours), preferably in less than one hour, more preferably in less than 45 minutes, with at least a layer of the intermediate pre-hydrolysate. Preferably the layer ("plug") is such that it completely fills the interstitial space of the reactor (which is otherwise filled with the particulate solid material). In other words, the amount used for the flooding is such that all of the interstitial space of the reactor is filled with intermediate pre-hydrolysate solution.

The intermediate pre-hydrolysate used for the above-described flood filling is an aqueous hydrochloric acid solution having about the same concentration hydrochloric acid as will be used as first hydrochloric acid solution (i.e. at least 30% and not more than 42%) but it will also contain some hydrolysed hemi- cellulose material (i.e. it comprises a mixture of C5-saccharides and C6-saccharides), e.g. in a concentration of about 1 to 6% by weight. It can suitably be obtained from an earlier hydrolysis process which may not have progressed fully or which is diluted by hydrochloric acid. Without wishing to be bound by theory, it is believed that flood filling in this process in the way as described above can reduce the tendency of swelling of the particulate solid material comprising hemicellulose, cellulose and lignin that may happen if the reactor is slowly filled with intermediate pre-hydrolysate (e.g. using 8 hours). Such swelling may result in difficulties in offloading the lignin material particles after step (c) or (d). EXAMPLES

Example 1: simple set-up testing suitability optrode measurement means.

The suitability of a photometric (optical) sensor operating at various wavelengths for detecting the difference in tridecane and an aqueous pine hydrolysate obtained by acidic hydrolysis of pine wood chips was tested in a simple set-up.

Materials

The photometric sensor was of the type Optrode as marketed by Metrohm, which can be operated at different set wavelengths: 470, 502, 520, 574, 590, 610, 640, 660 nm.

Measurements were carried out at all these different wavelength, and it works for the given liquids at all wavelengths, but for brevity we give the result for only two wavelengths (470 nm and the one at 660 nm).

Method

A jar (volume 100 ml) was filled with a layer of tridecane (about 2.5 cm height) and a layer of pine hydrolysate obtained by acid hydrolysis similar to the process described in example 2 herein (about 4 cm height). The tridecane was a clear, almost colourless liquid, the pine hydrolysate was dark brown/black coloured liquid.

The sensor was immersed in the liquid in the jar, with the sensing point in the upper layer (tridecane) and switched on. The read-out (continuous signal) of the sensor was registered. After about 10 seconds after switching on the sensor was lowered such that after about 1-2 seconds the sensing point was immersed in the lower layer of pine hydrolysate, whilst continuing to register the sensor signal. After about a further 8 seconds the measurement was terminated, and the procedure was repeated for a different wavelength.

Results

The sensor signal read-out for 470 nm and for 660 nm are given in figures 1 and 2. As can be seen, the sensor is suitable for measuring the difference between (clear) tridecane and (dark) pine hydrolysate (albeit by immersion, no test results are available of this sensor used in a non-invasive manner). At 470nm the signal drops from 170mV for tridecane to -1 mV for the hydrolysate, and at 660nm the signal drops from 420mV for tridecane to -0.9 mV for the hydrolysate.

Although this sensor was tested by immersion, it is clear from the example that the principle can also be used in a non-invasive set-up, when light source and sensor are sufficiently far apart from eachother so that fluid can flow between the light source and sensor, separated from them by e.g. a tube of non- metallic material.

Example 2: usage of an optical sensor in the hydrolysis process

Experimental set-up

In this lab-scale example on a vertical board 7 tubular reactors made of transparent PVC were mounted in a row, the reactors having a height of 0.53m and a diameter of 0.053m. Each reactor was equipped with a glass filter plate pore size 0 at the bottom and top (removable at both ends, to allow filling with woodchips and emptying lignin particles). Both bottom and top of each reactor had a liquid tight closure screwed at both ends, said closure having one (central) opening for allowing liquids to be fed to the reactor or liquids to be drained or pumped out of the reactor, with a diameter of 1/16 inch. All reactors were identical.

Storage tanks were present for: fresh 37% hydrochloric acid solution, tridecane displacement fluid, fresh 41-42% HCI solution (cooled to 0 °C). Also present was a tank for receiving a mixture of both used displacement fluid as well as pre-hydrolysate as well as a tank for receiving a mixture of both used displacement fluid as well as hydrolysate. All tanks had an open vent so there was not pressure build up. Linked to each reactor were two 10-port selector valves operated by an electric drive: one with the inlet of selector valve connected to the outlet at the bottom of the reactor, one with the inlet of the selector valve connected to the outlet at the top of the reactor. Between inlet of selector valve and outlet of reactor was a section of transparent tube (material PTFE, diameter about 1/16 inch, length varying for different reactors, at about 10 cm). Mounted onto each tube between reactor outlet (top and bottom) and selector valve was an optical sensor. The sensor was a combination of a yellow LED on one side of a l/16 th inch quartz tube (connected to the PTFE tube) and a light detector on the other side. The electronic output of the sensor was linked via a computer to one of five pumps. Outlets of the selector valve were connected to the inlets (top and bottom) of the neighboring reactors (two), and with the storage tanks (4). The connecting tube of the outlets was of the same material and diameter as at the inlets.

Five pumps were present: one for pumping in fresh 37% acid at the start (flood filling), one for pumping 37% hydrochloric acid during the process from a storage tank, one for pumping 42% hydrochloric acid from a storage tank, one for displacement fluid to be used in between pre- and main hydrolysis, one for displacement fluid after the main hydrolysis. The pumps were connected to manifolds, both at the top and bottom inlet.

Materials

Chips of rubberwood. Size of woodchips: about 50% had a size of 8-16 mm, about 50% had a size of 16-45 mm. The chips had a moisture content of about 5%. The content of the reactors filled with the woodchips had a bulk density of about 260 kg/m 3 .

Hydrochloric acid of a concentration of about 37%

Hydrochloric acid of a concentration of 41-42%, as made in-situ by a conventional method. Tridecane as non-aqueous displacement fluid.

Procedure

At the start of the experiment all reactors were empty, clean, and the hydrochloric acid solutions and displacement fluid were present in sufficient quantities in the storage tanks. Then all reactors were filled with approximately 300 g of wood chips, sieve places and closures put in place and tubing connected.

The system was operated along the scheme as set out in table 1, which states what goes in each reactor and when. Herein, the abbreviations have the following meaning:

Rl, R2, .... R6, R7 as headers of the columns: reactor 1, reactor 2, .... reactor 6, reactor 7.

In the table:

N no operation

FF flood filling

S stationary

FP1 fresh plug of 37% hydrochloric acid

DF1 displacement fluid to displace 37% hydrochloric acid pre-hydrolysate

FP2 fresh plug of 42% hydrochloric acid DF2 displacement fluid to displace 42% hydrochloric acid hydrolysate

R1 flow coming from reactor 1 into reactor 2

R2 flow coming from reactor 2 into reactor 3

R3 flow coming from reactor 3 into reactor 4; and so forth

FIN reaction finalized, removing reactor for offloading of lignin.

Each row in this table was planned to last for about 6 hours.

For this experiment, for an average amount of biomass of 300 g a theoretical amount of fresh 37% hydrochloric acid and fresh 42% hydrochloric acid required was calculated. The acid was pumped in at a fixed pump speed, for the time required to pump in (about) the calculated amount of acid. When it was determined that the right amount of acid was pumped in, the pump was stopped. Thereafter, displacement fluid (DF1 after FP1, and DF2 after FP2) was pumped into the reactor from the top.

The time allowed for DF1 and DF2 being pumped in was 6 hours. As will follow, the sensors at the bottom of each reactor were triggered earlier than that: after about 2-3 hours, by the change from dark coloured (pre)-hydrolysate to clear DF liquid. The sensor tripping caused the pump pumping in DF liquid to stop. The next step was only started after the end of the 6 hour time frame.

The 16 hours pre-hydrolysis was made up of 1 hour flood fill, 2 hours fresh plug into reactor R+l, 6 hours displacement fluid into reactor R+l, 1 hour wait (as R-l flood fills), 2 hours fresh plug into this reactor, 6 hours displacement in to this reactor. The flow of acids were controlled by timers. Ideally, the pump would be running for the full phase time, as this keeps the flow in the reactors stable and therefore the reaction stable, but that was not achieved yet. The flow of displacement fluid was controlled by optical sensors.

In practice:

Cycle 1 at t = 0 hours: for the first reaction cycle reactor 1 was flood-filled from the bottom in about 30 minutes with fresh 37% acid. The system then was idle for 8 hours, as the hydrolysate needed to build up enough color on start up for the required optical sensor colour difference. At the end of this period (t=8 hours) the reactor 2 was flood filled from the bottom with fresh 37% acid.

Thereafter (t=8.5 hours, start cycle 2) fresh hydrochloric acid solution at 37% was fed to the top of reactor 1, pushing out the obtained pre-hydrolysate at the bottom of reactor 1, which was fed to the top of reactor 2. At the bottom outlet of reactor 2 pre hydrolysate was collected. By doing it this way, the reactor stays completely filled with biomass to be hydrolysed and liquid solution, without any headspace or vacuum. The pre-hydrolysate was collected in a storage tank.

Subsequently (t = 16 hours) displacement fluid (DF1) was pumped in at the top of reactor 1, which DF1 pushed out pre-hydrolysate of the bottom of reactor 1. This step was programmed to last 8 hours but the pump was stopped when the sensor at the bottom of R1 sensed the step change from pre hydrolysate (dark) to displacement fluid (clear due to its immiscibility with FICI/pre-hydrolysate).

Reactor 3 was now flood filled while reactor 2 stayed stationary for 30 mins, after which fresh 37% hydrochloric acid was at the top of reactor 2, followed by displacement fluid DF1.

Reactor 1 was now finished with pre-hydrolysis and DF1, and entered the stage of main hydrolysis. For this, 42% hydrochloric acid (FP2) was added to the bottom of reactor 1 for about 16 hours which drove out the displacement fluid at the top of reactor 1.

The main hydrolysate was in this experiment collected jointly with the displacement fluid that pushed it out (DF2) and collected in one tank initially (after which separation by hand by separation funnel of the two immiscible phases was conducted).

Table 1: sequence of activities in reactors 1 to 7.

Moment A in Table 1 (time = T + 3 hours)

At the outlet at the bottom of reactor Rl, the sensor "sensed" a colour change of the flow changing from FP2 (very dark coloured to almost black) to DF2 (clear) and sent a signal to the computer which triggered the pump for DF2 to stop pumping in DF2. After this, reactor Rl was emptied.

Moment B in Table 1 (time = T + 2 hours) At the outlet at the bottom of reactor R4, the sensor "sensed" a colour change of the flow changing from FP1 (very dark coloured to almost black) to DF1 (clear) and sent a signal to stop the pump that pumps in DF1. After this, liquid R3 was pumped in from the bottom and DF1 was released at the top.

Summary mass flows in

Table 2 gives the mass flows into the system in this experiment. In reactor 7, during fresh 42% acid flowing in a pump failed.

Table 2: mass flows in experiment.

*: pump failed. Sensor activity

Results

Part of the results, e.g. on the lignin and efficiency of hydrolysis are given in table 2.

Further results on the hydrolysates are in table 3. Although for lignin the amount per reactor was measured, the liquid hydrolysates of the various reactors were jointly collected (hydrolysate and pre hydrolysate separate). Hydrolysates were, prior to analysis on monomers, subjected to a second hydrolysis, which hydrolysed oligomers obtained in each of the pre- and main hydrolysate. Table 3: analysis of hydrolysates obtained

As to the amount referred to as "lost" in table 3: this relates to hydrolysed sugars which are still present in the liquid which is retained in the lignin particles that are obtained from the reactors (the lignin chips are still wet) we well as any potential (hemi-)cellulose which was not hydrolysed.

Conclusion

When ligno-cellulosic biomass (in the form of wood chips) was subjected to the process of the current invention in this experiment, it yielded two products: an aqueous pre-hydrolysate rich in xylose and mannose (and their oligomers) and an aqueous hydrolysate rich in glucose (and oligomers), next to lignin.

Additionally it was shown that this process can be operated in a continuous way, in the sense that one reactor was emptied of lignin (and could be filled with fresh wood chips) whilst the other reactors continued to operate, whilst also a minimum of pumps and storage tanks is needed.

The use of a non-aqueous displacement liquid secured separation of hydrolysate of hemicellulose and hydrolysate of cellulose to a large extent and contributed to steady state as well as providing a driving force for sequential reactions. Simultaneously, it also facilitated control of the various reactions without the danger of diluting the acids needed for the hydrolysis steps. Still further, the sensors at the bottom of each reactor being triggered earlier than the allowed 6 hours (after about 2-3 hours) by the change from dark coloured (pre)-hydrolysate to clear DF liquids passing the sensor showed process control in the claimed process was possible with non-invasive sensors.