Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
  • B01J31/18—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms
  • B01J31/1805—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms the ligands containing nitrogen
  • B01J31/181—Cyclic ligands, including e.g. non-condensed polycyclic ligands, comprising at least one complexing nitrogen atom as ring member, e.g. pyridine
  • B01J31/1815—Cyclic ligands, including e.g. non-condensed polycyclic ligands, comprising at least one complexing nitrogen atom as ring member, e.g. pyridine with more than one complexing nitrogen atom, e.g. bipyridyl, 2-aminopyridine
  • B01J31/182—Cyclic ligands, including e.g. non-condensed polycyclic ligands, comprising at least one complexing nitrogen atom as ring member, e.g. pyridine with more than one complexing nitrogen atom, e.g. bipyridyl, 2-aminopyridine comprising aliphatic or saturated rings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
  • B01J31/22—Organic complexes
  • B01J31/2204—Organic complexes the ligands containing oxygen or sulfur as complexing atoms
  • B01J31/2208—Oxygen, e.g. acetylacetonates
  • B01J31/2226—Anionic ligands, i.e. the overall ligand carries at least one formal negative charge
  • B01J31/223—At least two oxygen atoms present in one at least bidentate or bridging ligand
  • B01J31/2239—Bridging ligands, e.g. OAc in Cr2(OAc)4, Pt4(OAc)8 or dicarboxylate ligands
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1026—Other features in bleaching processes
  • D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/16—Bleaching ; Apparatus therefor with per compounds
  • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
  • B01J2531/02—Compositional aspects of complexes used, e.g. polynuclearity
  • B01J2531/0213—Complexes without C-metal linkages
  • B01J2531/0216—Bi- or polynuclear complexes, i.e. comprising two or more metal coordination centres, without metal-metal bonds, e.g. Cp(Lx)Zr-imidazole-Zr(Lx)Cp
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
  • B01J2531/02—Compositional aspects of complexes used, e.g. polynuclearity
  • B01J2531/0238—Complexes comprising multidentate ligands, i.e. more than 2 ionic or coordinative bonds from the central metal to the ligand, the latter having at least two donor atoms, e.g. N, O, S, P
  • B01J2531/0258—Flexible ligands, e.g. mainly sp3-carbon framework as exemplified by the "tedicyp" ligand, i.e. cis-cis-cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
  • B01J2531/70—Complexes comprising metals of Group VII (VIIB) as the central metal
  • B01J2531/72—Manganese
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
  • B01J2531/80—Complexes comprising metals of Group VIII as the central metal
  • B01J2531/84—Metals of the iron group
  • B01J2531/842—Iron

Definitions

• This invention relates to a method for the delignification of fibrous material and the use of a catalyst for application of this method.
• fibrous materials comprises fibers, containing lignin, which have either been pre-treated mechanically or chemically e.g. by the method of ground wood production or pulp production, or which, as chemically or mechanically untreated natural fibers, shall be used in this method.
• the fibers also could have already been processed in several chemical and/or mechanical process steps, for example in a pulping step and then in an initial delignification step after pulping.
• Fibers containing lignin from wood or annual plants should be, for most purposes, free of lignin.
• the fibers should possess a high degree of brightness, preferably 90% ISO. It is only possible to attain these high degrees of brightness after having removed almost all of the lignin from the fiber or its surface. By using elemental chlorine and other chlorine bleaching chemicals, the fibers containing lignin could be efficiently and selectively delignified.
• bleaching chemicals in pulp production are used to brighten the fibers to the highest possible degree.
• residual chromophore groups, or chromophore groups formed during previous process steps should be removed by oxidation.
• the decomposition of fibrous material should be avoided, e.g. to reduce the load of organic material in the waste water of the bleaching steps.
• Hydrogen peroxide is one of the bleaching agents used in the pulping industry for this purpose. Hydrogen peroxide is used for reasons of environmental protection. It is more expensive than chlorine-based bleaching agents and is much less selective.
• Peroxide is used, therefore, only under mild reaction conditions for brightening of fibers but not for delignification steps. Under more severe reaction conditions, such as higher temperature above 100° C.), greater amounts of chemicals, and/or extended reaction times, residual lignin is still removed to a certain extent but at the cost of fiber damage and yield loss. The most unwanted side effect to be avoided is cellulose degradation, caused by the non-selective reaction of hydrogen peroxide, which results in poorer fiber strengths.
• Hydrogen peroxide has hardly been used as a delignifying agent because due to its reacting mechanisms it is not able to remove the highly condensed phenol components of the residual lignin under sufficiently mild reaction conditions.
• Some known methods use a catalyst to accelerate the reactions of the oxidizing agent. These methods recommend the joint or separate addition of metal and ligand and the treatment of the pulp fibers at reaction temperatures between 60° C.-98° C. and at a pH level of 3.7. This acid treatment method results however in considerable cellulose degradation.
• catalysts which contain transition metals improve the bleaching and brightening effects of peroxides in washing agents, also enable a greatly improved delignification of fibers by a very selective removal of lignin.
• catalysts are applied that have been described in the European patent applications EP 0 458 397 A2, EP 0 458 398 A2, EP 0 544 490 A1, as well as in WO 95/30681 and its priority document DE OS 44 16 438, and that are herewith expressly incorporated into the description of this invention at least as far as the detailed description of metal complexes is concerned.
• These catalysts are single or multiple nuclea metal complexes with the following general formula:
• Mt stands for manganese or iron, which can be present in the oxidation state II, III, IV or V or in mixtures of these state; n and m are an integer of 1-4, X is a coordinating ligand; p is an integer of 0 to 12; Y is a counter ion or—molecule which depends on the charge of z of the complex and can be positive, neutral or negative; q is equal to z divided by the charge of Y; and L is a ligand and is represented by a macrocyclic organic molecule with the following general formula:
• R 1 , R 2 , R 3 and R 4 can be either zero, H, alkyl, aryl or otherwise optionally substituted; D and D are either N, NR, PR O, or S, wherein R can be substituted by H or alkyl or aryl or otherwise optionally substituted; t and t′ are whole integers from 2 to 3, s is an integer between 2 and 4, u is an integer of 1 to 20, and v is 0 or 1.
• Bis-azamacrocycles in which two molecules of the general formula I to V are connected between both nitrogen atoms by one of the residuals R 1 to R 4 or R 5 through a connecting part of the -T- or -A-(O-A) h structure, wherein h stands for a whole integer between 1 and 19 and the residual R 5 herein can also be R 1 to R 4 ;
• T is a C 2 to C 8 -alkylene group
• A is a C 2 to C 4 alkylene group
• R 1 and R 4 stand for hydrogen, C 1 to C 60 -alkyl, which can be interrupted by up to 19 disconnected oxygen atoms and can contain up to 5 additional hydroxyl groups, C 1 - C 30 - alkyl-, phenyl-or benzyl-groups, wherein the aromatic ring can be substituted by up to 3 C 1 to C 4 alkyl groups, C 1 to C 4 alkoxy groups, halogen atoms, hydroxyl groups, sulfo groups or carboxyl groups, or groups of the formula —(CH 2 ) I —COOH, —(CH 2 ) I —SO 3 H, —(CH 2 ) I —PO 3 H 2 or —(CH 2 ) I —OH, wherein I means a whole integer from 1 to 4, respectively and the named acid groups can also be present in the form of salt;
• R 5 stands for the groups of the formula —(CH 2 ) I —COOH, —(CH 2 ) I —SO 3 H, —(CH 2 ) I —PO 3 H 2 or —(CH 2 ), —OH, or for a C 2 -C 60 alkyl, which is either interrupted by 1 to 19 disconnected oxygen atoms and/or contains 1 to 5 hydroxyl groups, wherein I is a whole integer from 1-4, respectively and the named acid groups can also be present in the form of salt;
• R 6 stands for hydrogen, C 1 to C 60 alkyl, which can be interrupted by up to 19 disconnected oxygen atoms and can contain up to 5 additional hydroxyl-, phenyl-or benzyl-groups, wherein the aromatic ring can be substituted by up to 3 C 1 to C 4 alkyl groups, C 1 to C 4 alkoxy groups, halogen atoms, hydroxyl groups, sulfo groups or carboxyl groups, or groups of the formula —(CH 2 ) r —COOH, —(CH 2 ) r —SO 3 H, —(CH 2 ) r —PO 3 H 2 or —(CH 2 ) r —OH, wherein r is a whole integer from 0 to 4, respectively and the named acid groups can also be present in the form of salt;
• Q is a group comprising 1 to 3 C -atoms with 1 or 2 carbonyl groups and methylene groups as residual elements.
• w designates the integer 3 or 4
• a further, well-suited ligand is 1,2-bis-(4,7-dimethyl-1,4,7-triaza-1,-cyclononyl)ethane.
• Me stands for methyl group and TACN stands for triazacyclononane.
• Hydrogen peroxide compounds which release hydrogen peroxide, organic or inorganic peroxy acids or their salts, i.e. per-acetic acid, per-monosulfuric-acid, or per-carbonic acid and their salts can all be used as a peroxy compound. Mixtures of different peroxy compounds can also be used in a delignification step. This allows an exact adjustment to any special process requirements.
• Consistency refers to the quantity of bone dry fiber mass based on the total weight. Consistency may range from 3 to 40%, but a consistency between 10% and 15% is preferred.
• the method according to the invention yields excellent delignification results when a metal complex to bone dry fiber mass ratio of 0.0001% to 0.06% based on bone dry fiber mass is used.
• the reaction temperature may be varied greatly, depending on the type of fibrous raw material. Most fibers will be delignified between 20° C. to 130° C. or more preferably between 40° C. to 1100° C. A temperature range between 50° C. to 98° C. is especially preferred, because a very selective delignification is induced under mild conditions and with relatively short reaction times.
• the reaction time in coordination with the reaction temperature, can also be varied within the range of 15 to 360 minutes.
• a reaction time of 30 to 240 minutes is, however, preferred. Chosing a reaction time of 45 to 150 minutes will show a favourable result.
• a very extensive delignification is attained during a reaction time of 60 to 120 minutes. Often, the reaction time is shorter than in conventional P-stages.
• the metal complexes used for delignification improve not only the effectiveness of a simple peroxide stage but also increase the delignification rate of an oxygen stage conducted with the addition of peroxide.
• very good results can be attained by using pressures between 0.15 to 1.5 MPa.
• a reaction pressure of 0.2 to 0.9 MPa is especially preferred.
• Chelating of the heavy metal ions has a positive effect.
• DPTA, DTPMPA or poly-a-hydroxyacrylic acid which is also stable at higher pH-levels, are preferably used as chelating agents. Additionally or alternatively sodium silicate and/or magnesium sulfate may be used.
• the method according to the invention was conducted in a water bath adjusted to reaction temperature with charges of 10 g bone dry pulp in polyethylene bags. Pulp, water and chemicals were mixed as described in the following procedure. The chemicals were added in three steps, first by mixing an aqueous solution of the additives and catalyst into the pulp. NaOH was then added to adjust the pH-level of the reaction. Finally, the amount of hydrogen peroxide required for delignification was added. After measuring the pH-level of each sample, the samples were sealed into the plastic bags and placed into the water bath which was adjusted to temperature.
• the Kappa number was determined according to the Zellcheming regulation number IV/37/80, and the micro kappa number according to TAPPI regulation number UM 246.
• the pulp viscosity was determined in a copper-ethylene-diamine solution according to Zellcheming regulation number IV/36/61. Brightness was measured with an Elrepho 2000 (Datacolor) according to the SCAN-C regulation 11:75.
• Every example includes a table of the same number which lists the corresponding reaction conditions, especially the catalyst used in each case, and the corresponding results.
• GURNAGUL et al. “The effect of cellulose degradation on the strength of wood pulp fibres”(Nordic Pulp and Paper Research Journal 7, (3), 1992, p. 152-154).
• Table 3 shows the influence of increasing amounts of catalysts on delignification. Kraft pulp is again being used here after acid washing. An increase of the delignification rate can be determined at amounts of the catalyst of up to 0.006% of bone dry pulp. No further increase in delignification was observed with amounts of the catalyst greater than 0.006%. The catalyst that was used is noted in Table 3.
• the amount of residual peroxide decreases but does not cause any improvements in delignification or any increases in brightness.
• the amount of the catalyst for the following experiments will be 0.006%.
• Table 5 shows that the same pulp was used as in the previous Example. Two different catalysts, K 1 and K 2 , were tested. The catalysts and the corresponding ligands are described in Table 5. The use of DTPA (Diethylene-triamine-pentaacetic acid) and DTPMPA, each applied together with 0.5% magnesium sulfate on bone dry pulp, is also tested.
• DTPA Diethylene-triamine-pentaacetic acid
• Both catalysts cause distinctly higher delignification rates as compared to the conventional P-stage (experiments P21 and P24). Because catalyst K 1 effects 100% greater delignification rates than the conventional P-stage, it is particularly suitable. In addition, K 1 exhibits higher and therefore better viscosities of the pulp fibers than K 2 . Finally, K 1 also caused higher brightness increase than K 2 . Principally, both catalysts are, however suitable for the projected purpose.
• Table 7 shows the influence of the use of alkali and the initial pH-level on the delignification rate, the brightness development, and the viscosity.
• the removal of the residual lignin increases with increasing amounts of NaOH. This increase is, however, extremely low in the conventional P-stages (Experiments P37 to P40), whereas the delignification rate increases in the presence of the catalyst from 42,6% to 64.4%.
• a distinct improvement of the delignification rate can be determined already at an initial pH-level of 10.4 (Experiment P33) as compared to the standard experiment without the catalyst.
• An initial pH-level above 11 is especially efficient.
• the removal of residual lignin at extremely low temperatures is increased by 217% compared to standard experiment (P40).
• a kappa number of 12 was attained without a catalyst in the OP-stage.
• a kappa number of approx. 7 and a brightness above 85% ISO was attained by adding the catalyst and 0.% DTPMPA on bone dry pulp.
• the use of DTPA or sodium silicate resulted in similar delignification rates, but also in a lower increase in brightness.
• the pulp delignified with the use of the catalyst possesses higher viscosities between 1033 and 1074.
• An oxygen bleached softwood kraft pulp from industrial production was first subjected to an acid chelating treatment (Q-stage). Then an oxygen-peroxide-delignification stage was conducted with the addition of a catalyst. For final bleaching, a peroxide bleaching stage followed.
• table 10 comprises data of a reference pulp sample after a bleaching sequence which is identical to O Q (OP) cat P, only that no “cat” i.e. catalyst was applied.
• Residual lignin content was reduced from 11.9 to 3.8 in the catalysed bleaching sequence.
• the reference shows a residual lignin content of 4.7.
• Viscosity of the finally bleached pulp is almost identical for both sequences, 833/839 vs. 983 of the unbleached pulp. Due to the difference in residual lignin content, the final brightness after bleaching has risen from 32.2 to 81.7 for the reference sample whereas catalysed bleaching has yielded a final brightness of 87.8.
• viscosity of the pulp is an indicator of fiber strength.
• strength testing reveals that the strength properties of the fibers after final bleaching are not in the least impaired.
• Catalysed bleaching does not affect the fiber structure as might be expected because of the enhanced delignification. Instead, burst index and tensile index are even higher than for the reference sample and the development of the tear index is as high as after reference bleaching.
• the catalyst improves delignification of lignocellulosic material with peroxy compounds without affecting strength properties of the fibers.
• This highly selective reaction allows extensive delignification of fibers with chlorine free bleaching compounds and as a consequence of extensive delignifaction, high final brightness of the pulp.
• Example 9 shows further that the catalyst proves to be beneficial in delignification stages.
• the final P-stage in both, the catalysed and the reference bleaching sequence was conducted without catalyst.
• the catalyst application was limited to the (OP) delignification stage.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Inorganic Chemistry (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
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• 1996
  • 1996-05-20 DE DE19620241A patent/DE19620241A1/de not_active Withdrawn
• 1997
  • 1997-05-20 US US09/194,385 patent/US20010025695A1/en not_active Abandoned
  • 1997-05-20 CN CN97196582.XA patent/CN1225698A/zh active Pending
  • 1997-05-20 JP JP09541528A patent/JP2000510914A/ja active Pending
  • 1997-05-20 WO PCT/EP1997/002557 patent/WO1997044520A1/en not_active Ceased
  • 1997-05-20 CA CA002255588A patent/CA2255588A1/en not_active Abandoned
  • 1997-05-20 BR BR9709108A patent/BR9709108A/pt not_active Application Discontinuation
  • 1997-05-20 EP EP97923942A patent/EP0900300A1/en not_active Withdrawn

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