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