Method for the delignification of fibrous material and use of catalyst

Abstract

The invention refers to a method to delignify fibrous material comprising an aqueous suspension of fibers which has a consistency between 5%-40%, with a peroxy compound that is used in amounts between 0.5%-10% based on bone dry fibrous material, and with a metal complex of this general formula [L n Mn m X p ] z y q wherein Mn stands for manganese or iron, which can be present in the oxidation state II, III, IV or V or in mixtures of these states; n and m are the integers 1-4, X is a coordinating ligand; p is an integer from 0 to 12; z is the charge of the complex and can be positive, neutral or negative; Y is a counter-ion or -molecule which depends on the charge of the complex; 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: wherein 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 from 1 to 20, and v is 0 or 1; this metal complex is used at an amount of 0.0001%-0.1% based on bone dry fibrous material, wherein the fibers are delignified at an initial pH-level between 7.5 and 13.5, at a reaction temperature between 20° C. and 130° C., and with a reaction time between 15 and 360 minutes. Further, the invention relates to the use of a metal complex.

What is claimed is:  
     
         1 . Method to delignify fibrous material comprising 
 an aqueous suspension of fibers which has a consistency between 5%-40%, with    a peroxy compound that is used in amounts between 0.50%-10% based on bone dry fibrous material, and with    a metal complex of this general formula    [L n Mt m X p]   z     y    q   wherein Mt stands for manganese or iron, which can be present in the oxidation state II, III, IV or V or in mixtures of these states; n and m are the integers 1-4, X is a coordinating ligand; p is an integer from 0 to 12; z is the charge of the complex and can be positive, neutral or negative; Y is a counter-ion or -molecule which depends on the charge of the complex; 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: 
                 
   wherein 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 from 1 to 20, and v is 0 or 1; this metal complex is used at an amount of 0.0001%-0.1% based on bone dry fibrous material, wherein the fibers are delignified at an initial pH-level between 7.5 and 13.5, at a reaction temperature between 20° C. and 130° C., and with a reaction time between 15 and 360 minutes thereby reducing the residual lignin content of the fibrous material by at least 20% compared to the residual lignin content of the fibrous material prior to catalyst treatment.    
     
     
         2 . Method according to    claim 1   , characterized in that the fiborus materials are pulp or natural fibers.  
     
     
         3 . Method according to    claim 1   , characterized in that hydrogen peroxide or compounds which release hydrogen peroxide are used as peroxy compound.  
     
     
         4 . Method according to    claim 1   , characterized in that anorganic or organic peroxy acids or their salts are used as peroxy compounds.  
     
     
         5 . Method according to one of the claims described above, characterized in that a mixture of different peroxy compounds is used.  
     
     
         6 . Method according to    claim 1   , characterized in that the delignification is conducted at a consistency between 3% and 40%.  
     
     
         7 . Method according to    claim 6   , characterized in that the delignification is conducted at a consistency between 10% and 15%.  
     
     
         8 . Method according to    claim 1   , characterized in that 0.5% to 10% of a peroxy compound is used for delignification.  
     
     
         9 . Method according to    claim 8   , characterized in that 1% to 6% of a peroxy compound is used for delignification.  
     
     
         10 . Method according to    claim 1   , characterized in that 0.001% to 0.06% of the metal complex based on bone dry fiber is used for delignification.  
     
     
         11 . Method according to    claim 1   , characterized in that the pH-level at the beginning of the delignification is above 10.  
     
     
         12 . Method according to    claim 1   , characterized in that the pH-level at the beginning of the delignification is above 11.  
     
     
         13 . Method according to    claim 1   , characterized in that the reaction temperature is 40° C. to 110° C.  
     
     
         14 . Method according to    claim 13   , characterized in that the reaction temperature is 50° C. to 98° C.  
     
     
         15 . Method according to    claim 1   , characterized in that the ID reaction time is between 30 minutes to 240 minutes.  
     
     
         16 . Method according to    claim 15   , characterized in that the reaction time is between 45 minutes to 150 minutes.  
     
     
         17 . Method according to    claim 1   , characterized in that the delignification is conducted at a pressure between 0.15 and 1.5 MPa.  
     
     
         18 . Method according to    claim 18   , characterized in that the delignification is conducted at a pressure between 0.2 and 0.9 MPa.  
     
     
         19 . Method according to claims  1 ,  17  or  18 , characterized in that the delignification is conducted in the presence of oxygen.  
     
     
         20 . Method according to one of the claims described above, characterized in that chelating agents, sodium silicate and/or magnesium sulfate are added before delignification.  
     
     
         21 . Method according to    claim 20   , characterized in that DTPA and/or DTPMPA are added as chelating agent before delignification.  
     
     
         22 . Use of a manganese complex with the general formula  
       [L n Mt m X p]   z     y    q 
       wherein Mt stands for manganese or iron, which can be present in the oxidation state II, III, IV or V or in mixtures of these states; n and m are an integer of 1-4, respectively; X is a coordinating ligand; p is an integer of 0 to 12; z is the charge of the complex and can be positive, neutral or negative; Y is a counter-ion or -molecule which depends on the charge of the complex; 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: 
                 
 
       wherein 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,respectively; s is an integer between 2 and 4, u is an integer of 1 to 20, and v is 0 or 1; 
 wherein this metal complex is used with 0.00010%-0.1% based on bone dry fiber material, for application of a method according to one or more of the patent claims  1 - 21  for the delignification of fibrous material thereby reducing the residual lignin content of the fibrous material by at least 20% compared to the residual lignin content of the fibrous material prior to catalyst treatment.