Transition metal complexes with polydentate ligands for enhancing the bleaching and delignifying effect of peroxo compounds

Inactive Publication Date: 2002-06-06
DEGUSSA AG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

0010] It has now been surprisingly found that the above and other objects of the present invention can be achieved by using certain transition metal complex compounds with polydentate ligands which considerably surpass the delignifying and bleaching performance of hitherto known catalytic systems. In this c

Problems solved by technology

In order to obtain approximately the same effect as with chlorine-containing bleaching agents, it is necessary to select more drastic conditions, such as for example higher reaction temperatures and longer reaction times. A disadvantage with oxygen-containing bleaching agents is that the reaction mechanisms of these chemicals are far less selective than is the case with chlorine or chlorine-containing chemicals, so that the delignification or bleaching entails greater damage to the cellulose.
It is more expensive than chlorine-containing bleaching agents, and significantly less selective.
Under more intense reaction conditions, for example higher temperature, greater use of chemicals and/or longer reaction time, although the residual lignin still present does become broken down to some extent, this is accompanied by increased damage to the fiber and yield losses.
A particularly undesirable feature is that the unselective reaction of hydrogen peroxide attacks the cellulose, so that the strength of the fiber is significantl

Method used

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  • Transition metal complexes with polydentate ligands for enhancing the bleaching and delignifying effect of peroxo compounds
  • Transition metal complexes with polydentate ligands for enhancing the bleaching and delignifying effect of peroxo compounds
  • Transition metal complexes with polydentate ligands for enhancing the bleaching and delignifying effect of peroxo compounds

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0097] Synthesis of {[Co(N4Py)].sub.2O.sub.2}Cl.sub.2(ClO.sub.4).sub.2, referred to below as (Co--N4Py).sub.2(.mu.-O.sub.2)

[0098] A solution of 1.43 g (3.89 mmol) of the ligand N4Py in a small amount of methanol (approx. 5 ml) was added at room temperature to a solution of 925 milligrams (mg) (3.89 mmol) of CoCl.sub.2.times.6H.sub.2O and 1.09 grams (g) (7.78 mmol) of sodium perchlorate monohydrate in 10 milliliters (ml) of water. Air in moderation was then introduced into the reaction solution over 2 h. A red-brown solid immediately precipitated. The product was filtered off and dried in air. 2.07 g (92%) of (Co--N4Py).sub.2(.mu.-O.sub.2) was obtained as a red-brown powder.

[0099] C.sub.46H.sub.42N.sub.10Cl.sub.4Co.sub.2O.sub.10 (1154.6 g / mol)

1 Calculated C 47.85 H 3.67 N 12.13 Co 10.2 Found C 47.74 H 3.72 N 11.73 Co 9.9

example 2

[0100] Synthesis of (Co--N4Py).sub.2(.mu.-O.sub.2) by the "one-pot method"

[0101] 2.5 M aqueous NaOH solution was added to a solution of 476 mg (2.00 mmol) of CoCl.sub.2.times.H.sub.2O and 1.54 g (2.00 mmol) of N4Py-4HClO4 in 100 ml of methanol / water (1:1) until pH>7. Air in moderation was then passed through the reaction solution over 2 h. The solution was then vacuum-evaporated to half volume, the red-crystalline solid was filtered off and the latter was dried in air (820 mg, 71%).

examples 3-16

[0102] The chemicals were added to 30 g of b.d. pulp so that an aqueous solution of the additives and the catalyst was first mixed in. The pH needed for the reaction was then adjusted using NaOH. The corresponding amount of hydrogen peroxide was subsequently kneaded in and the pH was measured. The sample was then held at temperature in a polyethylene bag (PE bag) in a water bath. The results without (Comparative Example A) and with bleaching catalyst ((Co--N4Py).sub.2(.mu.-O.sub.2), (Co-MeN4Py).sub.2(.mu.-O.sub.2); Co--N4Py(CH.sub.3CN) and Fe-MeN4Py(CH.sub.3CN)) can be found in Table 1.

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Abstract

Transition metal complex compounds of polydentate ligands with improved delignifying and bleaching performance. These polydentate ligands are organic ligands which, in aqueous solution and in the presence of atmospheric oxygen, or hydrogen peroxide, form a complex with a transition metal, in particular cobalt. The complexes are mono- or polynuclear and they have, when peroxo compounds are used, better delignifying and bleaching performances than conventional transition metal complex compounds. A delignifying and bleaching method, in which these transition metal complex compounds with polydentate ligands having improved delignifying and bleaching performance are used as catalysts, is also described.

Description

INTRODUCTION AND BACKGROUND[0001] The present invention relates to transition metal complexes with polydentate ligands for enhancing the bleaching and delignifying effect of peroxo compounds. In a further aspect, the present invention relates to the use of such complexes and to a method for the delignification of fibrous materials.[0002] The term "fibrous materials" will be used below to denote all lignin-containing fibers, which have either been mechanically and / or chemically pretreated by the process of lignin production or pulp production or are subjected to this method as chemically or mechanically untreated natural fibers. These fibers may also have undergone several stages of chemical and / or mechanical processing, for example chemical pulping and a first delignifying treatment after pulping.[0003] Lignin-containing fibers from wood or from annual plants should, as far as possible, be freed from lignin for most applications. The fibers should furthermore have high brightnesses,...

Claims

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Application Information

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IPC IPC(8): D21C9/16D21C9/10
CPCD21C9/163D21C9/1042D21C9/16
Inventor JAKOB, HARALDKUNZ, ULRIKE
Owner DEGUSSA AG
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