US2009090478A1PendingUtilityA1

Selectivity improvement in oxygen delignification and bleaching of lignocellulose pulp using singlet oxygen

46
Individually held — no corporate assignee on recordPriority: Oct 5, 2007Filed: Oct 5, 2007Published: Apr 9, 2009
Est. expiryOct 5, 2027(~1.2 yrs left)· nominal 20-yr term from priority
Inventors:Martha HollomonHuai N. Cheng
D21C 9/1015D21C 9/147
46
PatentIndex Score
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Claims

Abstract

A process to enhance delignification or bleaching in chemical or mechanical pulps comprising generation of singlet oxygen as a separate step and subsequent transport of singlet oxygen to pulp to effect bleaching or brightening of the pulp.

Claims

exact text as granted — not AI-modified
1 . A process for the delignification or bleaching of lignocellulosic pulp comprising the steps of a) providing an aqueous or non-aqueous mixture of pulp, b) providing a stream of molecular oxygen, reacting the molecular oxygen in the presence of visible light and at least one chemical agent photochemically converting a portion of the molecular oxygen to singlet oxygen and c) subsequently contacting pulp or pulp mixture with the singlet oxygen stream. 
     
     
         2 . The process of  claim 1  wherein the chemical agent comprises at least one photosensitizer dye. 
     
     
         3 . The process of  claim 2  wherein at least one photosensitizer dye is selected from the group consisting of methylene blue and rose bengal or combination thereof. 
     
     
         4 . The process of  claim 1  wherein at least 10% of the molecular oxygen is converted to singlet oxygen. 
     
     
         5 . The process of  claim 1  wherein the mixture of pulp is at a consistency of 14% or less. 
     
     
         6 . The process of  claim 1  wherein the mixture of pulp is at a temperature of from about 20° C. to 160° C. 
     
     
         7 . The process of  claim 1  wherein the selectivity improvement is at least 9% based on molecular weight. 
     
     
         8 . A process for the delignification or bleaching of lignocellulosic pulp comprising the steps of: a) providing an aqueous or non-aqueous mixture of pulp under typical oxygen delignification conditions, b) separately providing a stream of molecular oxygen, reacting the molecular oxygen light in the presence of visible light and a chemical agent, photochemically converting a portion of the molecular oxygen to singlet oxygen, and c) subsequently contacting pulp or pulp mixture with the singlet oxygen stream. 
     
     
         9 . The process of  claim 8  wherein the chemical agent comprises at least one photosensitizer dye. 
     
     
         10 . The process of  claim 8  wherein at least 10% of the molecular oxygen is converted to singlet oxygen. 
     
     
         11 . The process of  claim 8  wherein the mixture of pulp is at a consistency of 14% or less. 
     
     
         12 . The process of  claim 8  wherein the mixture of pulp is at a temperature of from about 80° C. to 150° C. 
     
     
         13 . The process of  claim 8  wherein the mixture of pulp is at a pressure of at least 0.1 MPa. 
     
     
         14 . The process of  claim 8  wherein the mixture of pulp is at a pH of at least about 8.5 or higher. 
     
     
         15 . The process of  8  wherein the singlet oxygen is added to one of more stages of an oxygen delignification process. 
     
     
         16 . A process for the delignification or bleaching of lignocellulosic pulp comprising the steps of: a) providing an aqueous or non-aqueous mixture of mechanical pulp under typical mechanical pulping conditions, b) separately providing a stream of molecular oxygen, reacting the molecular oxygen in the presence of visible light and a chemical agent, photochemically converting a portion of the molecular oxygen to singlet oxygen and c) subsequently contacting pulp or pulp mixture with the singlet oxygen stream. 
     
     
         17 . The process of  claim 16  wherein the chemical agent comprises at least one photosensitizer dye. 
     
     
         18 . The process of  claim 16  wherein at least 10% of the molecular oxygen is converted to singlet oxygen. 
     
     
         19 . The process of  claim 16  wherein the mixture of pulp is at a consistency of 14% or less. 
     
     
         20 . The process of  claim 16  wherein the singlet oxygen is applies to the mechanical pulp during the pulping process at the eye of a mechanical pulp refiner or through the dilution water for stone groundwood. 
     
     
         21 . A method to generate singlet oxygen that comprises the steps of providing a molecular oxygen source, a visible light source, a chemical agent wherein the molecular oxygen source provides a stream of molecular oxygen into a chamber or a series of chambers containing the chemical agent, contacting the molecular oxygen with the chemical agent in the presence of visible light from the light source. 
     
     
         22 . The process of  claim 21  wherein the chemical agent comprises at least one photosensitizer dye. 
     
     
         23 . The process of  claim 21  wherein the chamber contains the chemical agent wherein the chemical agent is affixed to gas filters, glass beads, wire mesh, or a catalytic bed. 
     
     
         24 . A pulp or paper product produced by the process of  claim 1 .

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