NOVEL SUPPORTED ANTHRAQUINONIC CATALYSTS AND USES OF SAME FOR KRAFT COOKING

Abstract

The present invention relates to a supported anthraquinonic catalyst which may be obtained by radical polymerization of a reaction mixture comprising styrene; at least one initiator generating free radicals; at least one cross-linking agent which is at least difunctional, at least one pore-forming agent; and at least one anthraquinonic styrenic monomer of formula (I)

##STR00001## wherein n is an integer varying from 1 to 5.

Claims

1. A supported anthraquinonic catalyst as a monolith, comprising a polymeric support containing at the surface at least one anthraquinone unit, said supported anthraquinonic catalyst being able to be obtained by radical polymerization of a reaction mixture comprising: styrene; at least one initiator generating free radicals; at least one cross-linking agent which is at least difunctional, selected from the group consisting of: divinylbenzene, ethylene glycol dimethacrylate, di(ethylene glycol) dimethacrylate, compounds comprising an alkyl chain, interrupted by one or several groups ((CH.sub.2).sub.kO).sub.m with 2k5, 1m3, substituted in an or position with at least one acrylate, methacrylate, vinyl or styrenic function, and mixtures thereof; at least one pore-forming agent; and at least one anthraquinonic styrenic monomer of formula (I) ##STR00009## wherein n is an integer varying from 1 to 5.

2. The supported anthraquinonic catalyst according to claim 1, wherein the pore-forming agent is selected from the group consisting of toluene, long chain alcohols comprising at least 10 carbon atoms, long chain alkanes comprising at least 10 carbon atoms, ethylene glycol oligomers and mixtures thereof.

3. The supported anthraquinonic catalyst according to claim 1, wherein the pore-forming agent is a mixture of at least two compounds selected from the group consisting of toluene, long chain alcohols comprising at least 10 carbon atoms and long chain alkanes comprising at least 10 carbon atoms.

4. The supported anthraquinonic catalyst according to claim 1, wherein the pore-forming agent is a mixture of dodecanol and toluene.

5. The supported anthraquinonic catalyst according to claim 1, comprising from 5% to 20% by weight of anthraquinone based on the total weight of the supported anthraquinone catalyst.

6. The supported anthraquinonic catalyst according to claim 1, wherein the reaction mixture comprises: from 10% to 30% by weight of styrene based on the total weight of reaction mixture; from 0.1% to 5% by weight of initiator based on the total weight of reaction mixture; from 10% to 30% by weight of a cross-linking agent based on the total weight of reaction mixture; from 10% to 60% by weight of a pore-forming agent based on the total weight of reaction mixture; and less than 10% by weight of an anthraquinonic styrenic monomer of formula (I).

7. The supported anthraquinonic catalyst according to claim 1, for which the specific surface area determined by the BET method is greater than or equal to 20 m.sup.2/g.

8. The supported anthraquinonic catalyst according to claim 1, for which Young's modulus is comprised between 100 MPa and 400 MPa.

9. A method for catalyzing the kraft or alkaline cooking of the wood, comprising contacting wood with the supported anthraquinonic catalyst according to claim 1.

10. A method for preparing a supported anthraquinonic catalyst, as a monolith, according to claim 1, by radical polymerization of a reaction mixture comprising: styrene; at least one initiator generating free radicals; at least one cross-linking agent which is at least difunctional, selected from the group consisting of: divinylbenzene, ethylene glycol dimethacrylate, di(ethylene glycol) dimethacrylate, compounds comprising an alkyl chain, interrupted with one or several groups ((CH.sub.2).sub.kO).sub.m with 2k5, 1m3, substituted in the or position with at least one acrylate, methacrylate, vinyl or styrenic function, and mixtures thereof; at least one pore-forming agent; and at least one anthraquinonic styrenic monomer of formula (I) ##STR00010## wherein n is an integer varying from 1 to 5.

11. A method for preparing a cellulosic pulp, comprising a kraft or alkaline cooking step of wood shavings or of lignocellulosic biomass at a temperature comprised between 130 C. and 180 C. for a period from 30 minutes to 120 minutes, in the presence of water, of supported anthraquinonic catalyst according to claim 1, and of an aqueous solution of soda and/or sodium sulfide.

Description

EXAMPLES

[0116] The reagents used are available commercially at Sigma-Aldrich.

Example 1: Preparation of an Anthraquinonic Styrenic Monomer of Formula (I)

[0117] This example relates to the preparation of the monomer of the following formula:

##STR00003##

[0118] The synthesis of this monomer, designated hereafter by AQwittig, is carried out in four steps, according to the scheme below:

##STR00004##

[0119] The first step is a Diels-Alder reaction between myrcene and naphthoquinone which leads to the formation of 2-(4-methyl-pent-3-enyl)-anthraquinone, 1A. This product was synthesized by the company Drivs Rsiniques et Terpniques.

[0120] Myrcene and naphthoquinone are solubilized in toluene or a mixture of toluene and butanol. The solution is heated to 90 C. until consumption of the reagents. The aromatization is achieved subsequently by adding a solution of sodium or potassium hydroxide at 50% while maintaining the mixture at 70 C. while bubbling oxygen. After evaporation of the solvents, the derivative 1A is obtained with a yield of more than 90%.

[0121] The synthesis procedure was described by Cazeils (<<Synthse de nouveaux catalyseurs de cuisson papetire. Etude de leurs mcanismes d'action>>. Thesis No. 3477, University of Bordeaux 1, 2007). The second step of the synthesis of the monomer is epoxidation of the double bond of the side chain of anthraquinone followed by oxidizing cleavage of the epoxide formed into an aldehyde (electrophilic opening of the epoxide). The last step is the Wittig reaction of the aldehyde with the 4-vinylbenzyltriphenylphosphonium chloride in the presence of a phase transfer agent.

[0122] The second step consists of synthesizing 2-[2-3,3-dimethyl-oxiranyl)-ethyl]-anthraquinone (1B).

##STR00005##

TABLE-US-00001 m (g) or Reagents M (g mol.sup.1) V (mL) n (mmol) 1A 290 14 g 48.24 m-CPBA 76% 172 12.04 g 70 NaHCO.sub.3 84 4.46 g 53.1 CH.sub.2Cl.sub.2 500 mL

[0123] In a three-neck flask of one litre provided with a coolant, with a dinitrogen inlet and a magnetized bar, the compound 1A in solution in CH.sub.2Cl.sub.2, meta-chloroperbenzoic acid (m-CPBA) and sodium hydrogen carbonate are introduced and intensively stirred at room temperature (RT) for one hour under a dinitrogen atmosphere. The organic phase is extracted with CH.sub.2Cl.sub.2, washed with an aqueous solution of Na.sub.2S.sub.2O.sub.3 until neutrality, and then dried on sodium sulfate, filtered and evaporated. The compound 1B is obtained as a yellow solid (13.2 g, 43 mmol) with a yield of 94%. It is used without any purification in the next step.

[0124] The third step consists of synthesizing 3-(9,10-Dioxo-9,10-dihydro-anthracen-2yl)-propion-aldehyde (1C).

##STR00006##

TABLE-US-00002 m (g) or Reagents M (g mol.sup.1) V (mL) n (mmol) 1B 306 6.9 g 22.55 NaIO.sub.4 214 14.5 g 67.76 t-Bu-OH 300 mL HCOOH 25 mL H.sub.2O 150 mL

[0125] In a three-neck flask of one litre provided with a coolant and with a magnetized bar, the compound 1B, sodium periodate, tertio-butanol, formic acid and distilled water are introduced and intensively stirred at room temperature for 24 hours under a dinitrogen atmosphere. The organic phase is extracted with ethyl acetate, washed with an aqueous solution of sodium carbonate until neutrality, and then dried on sodium sulfate, filtered and evaporated. The compound 1C is obtained as a pale yellow solid (5.55 g, 21.02 mmol) with a yield of 93%. It is used without any purification in the next step.

[0126] The method further comprises an intermediate step consisting of synthesizing 4-vinyl-benzyl-triphenyl-phosphonium chloride (1E).

##STR00007##

TABLE-US-00003 m (g) or Reagents M (g mol.sup.1) V (mL) n (mmol) p-chloromethylstyrene 152 5 g 32.89 Ph.sub.3P 262 8.62 g 32.89 Toluene 50 mL

[0127] In a three-neck flask of 100 mL provided with a coolant, a dinitrogen inlet and a magnetized bar, p-chloromethylstyrene in solution in toluene and triphenylphosphine are introduced and intensively stirred with reflux of the solvent for 20 hours. The formed white precipitate is filtered and dried in vacuo in the presence of P.sub.2O.sub.5. The compound 1E is obtained as a white solid (12.39 g, 29.93 mmol) with a yield of 91%. It is used without any purification in the next step.

[0128] The last step of the method is the synthesis of 2-[4-(4-vinyl-phenyl)-but-3-enyl]-anthraquinone (1D).

##STR00008##

TABLE-US-00004 m (g) or Reagents M (g mol.sup.1) V (mL) n (mmol) 1C 264 0.2 g 0.757 1E 414 0.314 g 0.757 K.sub.2CO.sub.3 138 0.157 g 1.14 Bu.sub.4N.sup.+HSO.sub.4.sup. Cat. H.sub.2O 10 mL CH.sub.2Cl.sub.2 10 mL

[0129] In a three-neck flask provided with a coolant and a magnetized bar, the salt 1E and an aqueous solution of potassium carbonate are introduced and intensively stirred at room temperature for 3 h. And then the compound 1C solubilized in dichloromethane and the phase transfer catalyst, Bu.sub.4N.sup.+HSO.sub.4.sup., are added; the reaction mixture is intensively stirred at room temperature for 24 hours. The organic phase is extracted with CH.sub.2Cl.sub.2, washed with an aqueous solution of 3% hydrochloric acid until neutrality, and then dried on sodium sulfate, filtered and evaporated. After purification by chromatography on a silica column (eluant CH.sub.2Cl.sub.2), the compound 1D is obtained pure (TLC) as a yellow solid (225 mg, 0.621 mmol) with a yield of 82%.

Example 2: Preparation of a Supported Anthraquinonic Catalyst

[0130] The general scheme of the polymerization reaction for the synthesis of anthraquinonic catalysts according to the invention (monoliths) is illustrated hereafter. The monolithic supports are prepared in glass tubes of variable dimensions (diameterheight=640 mm or 1050 mm).

[0131] The table hereafter indicates the amounts of the reagents used for the synthesis of the monoliths St-DVB-AQ of diameter 10 mm according to this example (monolith with divinylbenzene as a cross-linking agent).

TABLE-US-00005 m (g) or Reagents M (g mol.sup.1) V (mL) n (mmol) (g/cm.sup.3) AIBN 164 0.026 g 0.16 AQwittig 364 0.262 g 0.72 Styrene 172 0.96 mL 5.12 0.914 DVB (cross- 104 0.64 mL 5.58 0.909 linking agent) Dodecanol 186 2 mL 8.98 0.833 Toluene 92 0.4 mL 3.8 0.867

[0132] The reaction mixture consisting of styrene, cross-linking agent (DVB, EGDMA or DEGMDA), of toluene, of dodecanol, of AQwittig and AIBN (purified in ethanol at 50 C. and recrystallized at 0 C.) is introduced into a tube and hermetically closed by a septum. As the free space in the tube is too small relatively to the gas volume released by the initiator decomposition, it is necessary to add more volume by means of a thin rubber balloon and of a needle which pierces the septum. The reaction medium is homogenized with ultrasonic waves at 50 C. (10 minutes) and degassed by bubbling of nitrogen (10 minutes) in order to remove the dioxygen which inhibits polymerization. The medium is drawn in vacuo and then immersed in an oil bath brought to 70 C. for 24 hours. After polymerization, the monolith is extracted with precaution from the tube contacted with liquid nitrogen and then washed with 700 mL of THF on the soxhlet for about 8 hours in order to remove the pore-forming agents and the monomers which are unreacted. After purification, it is dried in vacuo at 200 C. for 12 hours. The synthesis yield is determined by an indirect method by UV-Visible light spectrometry. The extraction solvent is concentrated for assaying therein, by UV spectrometry, the AQwittig monomer being unreacted in order to determine the AQ functionality of the monolith. The monolith is analyzed in UV, GC, SEM, TEM and PIM.

[0133] AIBN is purified by crystallization from ethanol. After dissolution of 5 g of AIBN in 50 mL of ethanol at 50 C., the solution is immediately filtered and the filtrate is cooled to 0 C. The AIBN rapidly crystallizes and the crystals obtained by filtration are dried in vacuo at room temperature and kept in a bottle away from light.

[0134] The detailed example above relates to the preparation of monoliths from divinylbenzene as a cross-linking agent but was also applied identically with the cross-linking agents EGDMA or DEGDMA, and this by using the same amounts of reagents as a number of moles.

Example 3: Assay

[0135] As indicated in Example 2, the extraction solvent is concentrated for assaying therein, by UV spectrometry, the AQwittig monomer being unreacted in order to determine the anthraquinone functionality (AQ) of the monolith.

[0136] The assay of grafted AQ is carried out by indirect dosage by evaluating the amount of AQ which is unreacted. AQwittig has a characteristic band at 327 nm which gives the possibility of inferring after calibration the concentration of non-grafted AQ. The grafted AQwittig amount is the difference between the initial amount and the assayed amount.

[0137] UV-Vis Spectrometry: Dosage of the AQwittig Monomer

[0138] The UV-Visible dosages are carried out with a Perkin Elmer Lambda 18 apparatus.

[0139] The grafted anthraquinone is dosed by UV-Visible absorption in the following washing mixture: the THF solvent used for purifying the monoliths, diluted in dichloromethane. After having determined absorbance at 327 nm of the solution, the amount of AQ is determined on the basis of a calibration carried out beforehand with AQwittig solutions of known concentrations. The linearity of the calibration gives the possibility of applying Beer-Lambert's law:

A.sub.327=.sub.327.Math.l.Math.C

[0140] wherein l is the length of the optical path (the thickness of the quartz tank is 1 cm), .sub.327 is the molar extinction coefficient at 327 nm and at 20 C. determined by linear regression from the calibration straight line (.sub.327 of 57,000 L.Math.mol.sup.1.Math.cm.sup.1) and C is the AQwittig concentration (in mM) (y=0.57+0.02).

[0141] Beer-Lambert's law gives the possibility of determining the concentration of AQwittig equivalent in the washing mixture.

[0142] The gravimetric yield (Y) of AQwittig is determined by making the ratio between the grafted mass and the initial introduced mass. The grafted AQ level (T.sub.AQ) is determined after having calculated the remaining mass (m.sub.r) of AQwittig according to the following equations:

[00001]$T_{\mathrm{AQ}}=\frac{m_{\mathrm{initiale}}-m_r}{m_{\mathrm{monolithes}}}.Math.\frac{M_{\mathrm{AQ}}}{M_{\mathrm{AQwittig}}}.Math.100.Math.\left(\%\right)$$Y=\frac{m_{\mathrm{initiale}}-m_r}{m_{\mathrm{initiale}}}.Math.100.Math.\left(\%\right)$$m_r=C.Math.M_{\mathrm{AQwittig}}.Math.V_{\mathrm{mlange}}\left(g\right)$

[0143] The obtained results are indicated in the table below:

Grafted AQ level and gravimetric yield of AQwittig incorporated into the monoliths

TABLE-US-00006 St-DVB-AQ St-EGDMA-AQ St-DEGDMA-AQ A 0.521 0.819 0.689 T.sub.AQ exp 10.58% 8.77% 9.22% T.sub.AQ th 10.66% 8.81% 9.31% Y 99.3% 100% .sup.99%

[0144] The grafted AQ level (T.sub.AQ) on the monoliths is comprised between 8 and 11% of AQ per gram of monolith. The gravimetric yield (Y) of grafted AQwittig, determined by UV, is greater than 99% in the case of the three types of monoliths.

Example 4: Properties of the Catalysts

[0145] 1. Thermal Stability of the Catalysts

[0146] The thermal stability of the catalysts was tested by thermogravimetric analysis (TGA).

[0147] TGA was carried out by means of a Shimadzu apparatus, version TGA-50TA. An amount of about 10 mg of product is laid on a platinum boat and then heated to 500 C., with a gradient of 10 C./min, under a nitrogen atmosphere or an oxidizing atmosphere (air).

[0148] This analysis gave the possibility of demonstrating that the monolithic catalysts according to the invention are stable up to 300 C. and that they may therefore be used during cooking.

[0149] 2. Mechanical Stability of the Catalysts

[0150] The mechanical stability of the catalysts according to the invention was tested according to the test described hereafter.

[0151] Three-Point Flexure: Mechanical Stability of the Monoliths

[0152] The apparatus used is a tensile machine of the MTS QTest25 Elite type with a maximum force of 25 kN. It gives the possibility of calculating the Young modulus by means of a piece of software TestWorks 4. The measurements were carried out on cylindrical samples (radius 10 mm, height 40 mm) with an initial imposed compression rate of 1 mm/min. The length between the supports is equal to 35 mm.

[0153] 3. Morphology of the Monoliths

[0154] The morphology of the monolithic catalysts may be analyzed according to different techniques described hereafter.

[0155] Scanning Electron Microscopy (SEM)

[0156] The internal structure of the monoliths was viewed with a scanning electron microscope of the JOEL JMS-6700 Field Emission type between 2-5 kV. The dry monoliths were first metallized with a gold layer deposited for 20 seconds with a JOEL-JFC-1200 Fine Coater, in order to facilitate discharge of the electrons at the surface.

[0157] Transmission Electron Microscopy (TEM)

[0158] Observations with the transmission electron microscope were carried out on an apparatus of the MET CM 10 (FEI) type at 80 kV for observing the internal structure of the monoliths.

[0159] Sections of a sample with a thickness of 50 and 75 nm were made on an ultramicrotome, ultracut E (Leica) by means of a diamond knife at the rate of 1 mm/s floating on water. These sections were deposited on copper grids of 600 mesh, with fine hexagonal bars and are observed with the microscope.

[0160] In particular, the SEM photographs gave the possibility of ascertaining that the monoliths are porous and homogeneous and that the presence of anthraquinone modifies the size of the grains and of the intergranular empty spaces.

Example 5: Porosity and Specific Surface Area of the Catalysts

[0161] The methods used for measuring these two parameters are described hereafter.

[0162] 1. Porosimetry by Nitrogen Adsorption: Porosity of the Monoliths (BET)

[0163] The specific surface area of the monoliths was measured by nitrogen adsorption at 77K with a Micrometrics ASAP2100 apparatus, by assuming that the surface of a single nitrogen molecule is 16.2 . The samples are degassed and dried in vacuo at 120 C. for 24 hours before each measurement.

[0164] By tracking the pressure, the number of adsorbed molecules is determined and an adsorption isotherm is obtained which allows calculation of the specific surface area by means of the BET (Brunauer, Emmett, Teller) model based on the analytical calculation of the adsorption isotherms determined experimentally. This method measures the adsorption (multimolecular) and the desorption of nitrogen at the surface of the monolith during its cooling with liquid nitrogen and gives the possibility of inferring the porosity from the isotherms.

[0165] For a given temperature, the relationship between the amount of adsorbed gas (by mass or volume) and its pressure is called an adsorption equilibrium isotherm. It expresses thermodynamic equilibrium between the gas phase and the solid phase.

[0166] The aspect of the adsorption isotherms gives indications on the characteristics of the material. In the literature, six adsorption isotherm curves are described (Rouquerol, F.; Llewellyn, P.; Rouquerol, J.; Luciani, L.; Denoyel, R. Techniques de l'ingnieur 2003, P1050). [0167] The isotherm of type I is obtained for materials exclusively having micropores which are filled at pressures which are all the lower since their diameter is smaller. [0168] The adsorption isotherm of type II is characteristic of multimolecular adsorption and it is obtained with non-porous or macroporous adsorbents at the surface of which the adsorbed layer gradually thickens. [0169] The adsorption isotherm of type IV is obtained with mesoporous adsorbents wherein a capillary condensation occurs. The desorption of nitrogen condensed by capillarity in the mesopores is not reversible: hysteresis of the desorption is generally observed relatively to the adsorption. [0170] The adsorption isotherms of type III and V are observed in the case of adsorption of steam by a hydrophobic surface. They are much rarer for materials having low adsorbent/adsorbable interactions. [0171] The adsorption isotherm with steps, of the type VI, was observed more recently in the case of adsorption by energetically homogeneous surfaces on which the adsorbed layers form one after the other.

[0172] The BET method gives the possibility of determining in the dry condition the total porosity of a monolith: micropores, mesopores and macropores.

[0173] 2. Porosimetry by Intrusion of Mercury: Porosity of the Monoliths (PIM)

[0174] Porosimetry by intrusion of mercury is used for characterizing the distribution of the size of pores and the porosity of macroporous materials. These measurements are conducted on a Micrometrics AutoPore IV 9500 apparatus on samples for which the mass is comprised between 0.4 and 1 g. The volume of non-wetting mercury (the contact angle of the mercury, .sub.Hg, is generally comprised between 110 and 160 according to the relevant surfaces) penetrates into the pores of the sample (in vacuo) depending on the pressure applied to the mercury.

[0175] The diameter of the pore into which the mercury may penetrate is inversely proportional to the applied pressure: the smaller the pores, the more a high pressure is needed (Krajnc, P.; Leber, N.; Stefanec, D.; Kontrec, S.; Podgornik, A. Journal of Chromatography A 2005, 1065, (1), 69-73). The cylindrical pore model and the variation of the intrusion volume according to the pressure give the possibility of calculating the average diameter of the pores.

[0176] This technique gives the possibility of only measuring the macropores which cannot be compared with the BET method which also measures small pores (Svec, F.; Frechet, J. M. J. Chemistry of Materials 1995, 7, (4), 707-715).

[0177] 3. Results

[0178] Influence of the presence of AQ with different cross-linking agents on the porosity

TABLE-US-00007 Cross- d.sub.pores d.sub.pores linking S.sub.sp, PIM.sup.1), BET.sup.2), agent % AQ m.sup.2/g nm nm DVB 0 21 265 DVB 10.5 134 118 5 EGDMA 0 113 ND 10 EGDMA 8.8 153 46 6 DEGDMA 0 130 46 5 DEGDMA 9.2 97 ND 4 Conditions: M/P = 2/3 (volumetric ratio between the monomers and the pore-forming solvents); 1.5% of AIBN; 24% of St; 16% of Cross-linking agent; 50% Dod; 10% Tol; d.sub.monolith = 10 mm, .sup.1)average diameter of the pores by PIM, .sup.2)average diameter of the pores by BET.

[0179] The obtained results show that the presence of the AQwittig monomer in the hydrophobic monoliths St-DVB-AQ, increases the specific surface area and reduces the diameter of the pores.

[0180] In the case of more hydrophilic monoliths, based on EGDMA, the presence of anthraquinone causes an increase in the specific surface area but remains without any consequence on the porosity.

[0181] The porosity of the monolith based on DEGDMA is not measurable by the PIM technique due to the absence of penetration of the mercury. This monolith does not have any macroporosity. According to the results obtained by PIM measurement for monoliths based on EGDMA or on DVB, both of these types of monoliths have macropores with additionally mesopores in the case of the monolith based on EGDMA.

Example 6: Kraft Cooking in the Presence of the Catalysts of the Invention

[0182] The cookings are carried out by means of the rotary digester of Smurfit Kappa Cellulose du Pin. The maritime pine unrolling wood, as shavings, is sorted out by means of sieves of different dimensions for using the fractions with a diameter of 7 mm and a thickness of 4 mm. The digester is an autoclave consisting of six shells, which are immersed in an oil bath. In order to determine the amount of required humid wood, the dryness is measured in the oven at 105 C. for 24 hours on 200 g of humid wood. In each shell, are introduced 450 g of wood shavings (expressed in seconds) including 180 g (40%) of a thickness of 4 mm and 270 g (60%) with a diameter of 7 mm. For each cooking, we have three control shells, without any catalyst and three shells in the presence of a catalyst.

[0183] The cooking conditions are different according to the value of the targeted kappa number. The example was carried out for a targeted kappa number of 25. The white liquor is sampled in the plant (industrial leaching). The active alkali (total amount of soda and of sodium sulfide expressed in equivalent grams of NaOH and of Na.sub.2O) and the sulfidity (corresponding to the existing sulfur level defined as the ratio between sodium sulfide and the active alkali) are determined by an assay method of the white liquor on two tests. The active alkali level used in cooking varies between 9-22% and the sulfidity between 25-30%. For all the cookings, we kept a same water content. The dilution factor equal to 3.5 represents the ratio between the total amount of water contained in a shell (the sum between the water of the wood, the volume of white liquor and the supply water) and the amount of dry wood.

[0184] The digester set into rotation without the shell is preheated to 80 C. At this temperature, are introduced the shells filled with wood, liquor, water and in certain cases with the catalyst. For example, for an alkali of 20%, in a control shell, about 360 g of humid wood with a thickness of 4 mm, 520 g of humid wood of diameter of 7 mm, 770 ml of white liquor of active alkali of 116 g/l of Na.sub.2O and 380 ml of water are introduced.

[0185] At the end of the cooking, the shells are suddenly cooled by immersing them in cold water. In the case of shells with monoliths (catalysts), the latter are recovered and kept in the black liquor. For each shell, the shavings are pre-washed for one night, defibrated for 2 minutes, washed and wringed; the paper pulp is obtained at the end of this sequence of operations. The yield is calculated by weighing taking into account the dryness of the pulp over 50 g.

[0186] An amount of 50 g of the recovered pulp is diluted in 2.5 L of water and defibrated for 10 minutes. A sheet is made by means of the Noble Wood form with one litre of the diluted suspension. After drying the sheet on the Noble and Wood dryer at 120 C. until constant weight, the dry weight of the sheet is determined by weighing. This then allows calculation of the volume required for sampling one gram of pulp for measuring the kappa number.

[0187] In order to determine the kappa number of the pulp which measures the degree of delignification of an unbleached pulp, the following procedure was used. The kappa number is obtained by oxidation of the residual lignin in the presence of a specific volume of potassium permanganate put into contact with the pulp for a determined time. In the presence of lignin, there is consumption of permanganate which has to be located between 20% and 60% of the initial amount. The reaction is blocked by adding a solution of potassium iodide. The released iodine is then assayed by a solution of sodium thiosulfate in an acid medium (ISO 302:2004 standard, PulpsDetermination of Kappa number; 2nd edition ed.; French Standardization Association (Association Franaise de Normalisation) (AFNOR), 2004).

[0188] After having reduced the total volume (pulp+water) to 910 mL, it is placed with stirring and at the same time 40 ml of KMnO.sub.4 0.6 N and 50 mL of H.sub.2SO.sub.4 8 N are poured. The stopwatch is triggered after 2 minutes, by means of a thermometer the temperature C is measured. The reaction is left to continue until 5 minutes and it is then stopped by adding 20 ml of KI (160 g/l). The released iodine is titrated by a solution of Na.sub.2S.sub.2O.sub.3 0.6 N, in the presence of the fibers. A few drops of starch paste are added towards the end of the assay.

The volume V of Na.sub.2S.sub.2O.sub.3 required for discolorizing the solution allows calculation of the kappa number according to the relationship:

Kappa number=(VV.sub.white)6{1+[(25C)0.013]}

wherein V.sub.white corresponds to the volume of consumed Na.sub.2S.sub.2O.sub.3 by only using water (without any pulp).

[0189] The table hereafter lists all the results of the control cookings and with the monoliths.

TABLE-US-00008 Water/ Wood = 3.5 Amount of Pinus anthraquinone, Active Maritima = 450 g % (relatively alkali % Sulfidity Kappa Yield t = 140 minutes to dry wood) in Na.sub.2O % number % DVB 0 20 31 27 44.8 0 21 31 25.2 43.5 0 22 31 21.3 40.9 0.2 16 31 37.3 46.9 0.2 18 31 30.8 46.3 0.2 20 31 22.5 43.9 DVB 0 20 30 40.1 50.1 0 21 30 26.7 47.7 0 22 30 23.7 46 0.2 16 30 47.4 51.4 0.2 18 30 34.6 49.9 0.2 20 30 27.4 47.6 DVB 0 20 27 36.6 45.1 0 21 27 30.9 44.3 0 22 27 20.8 43 0.2 16 27 44.2 46 0.2 18 27 34.1 45.1 0.2 20 27 31.2 43.7 DVB 0 20 29 34.7 47 0 21 29 26.5 45.3 0 22 29 22.4 44.2 0.2 16 29 37.4 47.3 0.2 18 29 32.4 46 0.2 20 29 27.8 44.8 DEGDMA 0 20 31 29 44.8 0 21 31 24.7 44 0 22 31 23.6 43.8 0.2 16 31 48.9 48.5 0.2 18 31 32.6 46.6 0.2 20 31 25.4 45.4 DEGDMA 0 18 28 36.6 46.2 0 20 28 30.9 44.7 0 22 28 20.8 45.2 0.2 16 28 44.2 49.8 0.2 18 28 34.1 47.1 0.2 20 28 31.2 47 DEGDMA 0 18 29 40.6 48.6 0 20 29 30.5 46.6 0 22 29 25.2 45.1 0.2 16 29 54.3 50.1 0.2 18 29 37.9 47.1 0.2 20 29 29.5 45.7 DEGDMA 0 18 26 35.6 46.8 0 20 26 31.3 44.7 0 22 26 27 43.9 0.4 16 26 42.4 47.9 0.4 18 26 36.3 46.6 0.4 20 26 27 45

[0190] This table of results gives the possibility of ascertaining the efficiency of the catalysts of the invention in terms of yield.

[0191] The above catalysts (DVB, EGDMA and DEDGMA) have the following characteristics:

TABLE-US-00009 S.sub.sp d.sub.pores BET PIM AQ/monolith Monoliths/dry wood (m.sup.2/g) (nm) (% by mass) (% by mass) St-DVB-AQ 134 118 10.6 1.9 St-EGDMA-AQ 153 46 8.8 2.3 St-DEGDMA-AQ 97 NM 9.2 2.2

[0192] It was ascertained that the monoliths St-DVB-AQ, St-EGDMA-AQ and St-DEGDMA-AQ are resistant under the cooking conditions and are not degraded.

Example 7: Recycling of the Catalysts

Example 7.1

[0193] The monoliths are entirely recovered and without any losses during a first cooking and are again tested during a second cooking. Between two cookings, the monoliths are kept in the black liquor and are used without any purification step. The black liquor allows them to be kept in the same swelling and hydration condition that at the end of cooking.

[0194] The obtained results are indicated in the table hereafter (same conditions as in Example 6).

TABLE-US-00010 Water/ Wood = 3.5 Amount of Pinus anthraquinone, Active Maritima = 450 g % (relatively alkali % Sulfidity Kappa Yield t = 140 minutes to dry wood) in Na.sub.2O % number % Recycled DVB 0 20 31 25.5 45.6 0 21 31 23.4 43.9 0 22 31 23.4 43.7 0.2 16 31 47.4 47.9 0.2 18 31 33.3 46 0.2 20 31 24.6 44.7 Recycled DVB 0 18 30 33.9 45 0 20 30 31.4 44.5 0 22 30 22.2 44 0.2 16 30 44.9 47.9 0.2 18 30 33.2 46.1 0.2 20 30 27.1 45 Recycled DVB 0 18 30 36.8 47.3 0 20 30 31.7 45.9 0 22 30 26.4 44.4 0.2 16 30 44.4 48.7 0.2 18 30 36.1 47.2 0.2 20 30 30.7 45.3 Recycled 0 18 30 40.9 46.7 DEGDMA 0 20 30 29.8 45 0 22 30 26.7 44.1 0.2 16 30 49.2 47.6 0.2 18 30 38.7 46.6 0.2 20 30 27.1 45.4

[0195] This table of results gives the possibility of ascertaining the efficiency of the catalysts according to the invention, once they are recycled.

Example 7.2.Study of the Time-Dependent Change of the Kappa Number Values Versus the Number of Cookings by Recycling the Same Monoliths

[0196] The Kappa number which takes into account the residual lignin level on the fibers (the lower it is, the more delignification has been performing) was measured on classified pulps. This classification consists of separating the fibers from the uncooked.

[0197] The measurement of the classified Kappa number corresponds to the measurement of the Kappa number at the output of the method, while doing without the uncooked.

TABLE-US-00011 TABLE 1 The Classified Kappa Number ([IK].sub.c) depending on the number of recyclings of the monoliths for an active alkali of 22% relatively to the controlled cookings. Number [IK].sub.c [IK].sub.c delta of uses Control Catalyst [IK] 1 58.9 58.7 0.2 2 72.3 65.6 6.7 3 72.5 67.0 5.5

[0198] At a weight content of active alkali of 22%, the effect on the Kappa number is retained after 3 cookings in spite of the sources of variation related to the method. No physical degradations of the monoliths were observed.

TABLE-US-00012 TABLE 2 The Classified Kappa Number according to the number of recyclings of the monoliths for an active alkali of 26% relatively to the control cookings. Number [IK].sub.c [IK].sub.c delta of uses Control Catalyst [IK] 1 44.6 44.3 0.3 2 49.4 45.8 3.6 3 57.0 54.9 2.1 4 60.2 54.9 5.3 5 60.2 54.9 5.3

[0199] The first two cookings were achieved with a batch of wood different from the three last ones.

[0200] In spite of this, for a weight content of active alkali of 26%, the effect on the Kappa number is retained after 5 cookings, and this in spite of the variation sources related to the method. No physical degradations of the monoliths were observed.

[0201] All these results demonstrate the efficiency of the monolithic catalysts according to the invention, and this even after several uses.