Water-Soluble Manganese Catalyst Salts for Low-Temperature Peroxide Bleaching
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Solution Overview
Problem
Current bleaching processes for cotton and wood pulp require high temperatures and long reaction times, leading to fiber susceptibility and inefficient bleaching, particularly with hydrogen peroxide, which necessitates the development of more active bleaching catalysts to reduce these constraints.
Innovation Solution
The use of preformed transition metal catalyst salts, specifically mononuclear or dinuclear manganese complexes with non-coordinating counter ions like chloride, acetate, or sulfate, which are highly water-soluble, allowing for efficient bleaching of cellulose-containing substrates and starches with hydrogen peroxide at lower temperatures and shorter times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If hydrogen peroxide is used for bleaching cotton and wood pulp, then environmental benefits are achieved by replacing chlorine-based bleaches, but high temperatures and long reaction times are required which lead to fiber susceptibility and inefficient bleaching
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the bleaching system - specifically by adding transition metal catalysts (manganese, cobalt, nickel, copper, or zinc salts) to the hydrogen peroxide solution. This changes the reaction kinetics parameters, enabling effective bleaching at lower temperatures (reducing from 80-95°C to potentially lower ranges) and shorter reaction times, thereby improving productivity while maintaining the environmental advantage of oxygen-based bleaching
2Productivity
If hydrogen peroxide is applied at high temperatures to achieve effective bleaching, then bleaching efficiency is improved, but cotton fibre becomes susceptible and tendering occurs
Solution Approach 1:
The patent changes the temperature parameter by introducing transition metal catalysts that lower the activation energy required for peroxide decomposition. This enables the same bleaching efficiency to be achieved at lower temperatures, thereby preserving fiber strength and reducing susceptibility while maintaining productivity
Solution Approach 2:
The transition metal catalyst acts as an intermediary substance that facilitates the decomposition of hydrogen peroxide into reactive oxygen species. This intermediary enables the bleaching reaction to proceed efficiently at lower temperatures, indirectly protecting the fiber from thermal damage while achieving the desired whitening effect
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables effective bleaching of substrates with improved solubility and stability of the catalyst, reducing costs and side reactions, while maintaining bleaching efficiency and whiteness, as demonstrated by comparable whiteness values across different catalyst-salt complexes.
Implementation Method 1
the use of preformed transition metal catalyst salts, specifically mononuclear or dinuclear manganese complexes with non-coordinating counter ions like chloride, acetate, or sulfate, which are highly water-soluble, allowing for efficient bleaching of cellulose-containing substrates and starches with hydrogen peroxide
Implementation Method 2
efficient bleaching of substrates with improved solubility and stability of the catalyst, reducing costs and side reactions, while maintaining bleaching efficiency and whiteness
Data Source
AI summary
The invention provides a preformed transition metal catalyst salt, which salt is a mononuclear or dinuclear complex of a Mn(III) or Mn(IV) transition metal catalyst having a non-coordinating counter ion selected to provide a preformed transition metal catalyst salt that has a water solubility of at least 30 g/l at 20 °C and wherein the ligand of the transition metal catalyst is of formula (I): wherein: p is 3; R is independently selected from: hydrogen, C1-C6-alkyl, CH2CH2OH, and CH2COOH, or one of R is linked to the N of another Q via an ethylene bridge; and R1, R2, R3, and R4 are independently selected from: H, C1-C4-alkyl, and C1-C4-alkylhydroxy, which salt is in the form of: (i) an aqueous solution present in a buffer system that maintains the solution in a pH range of 2 to 7; (ii) an aqueous solution comprising the salt at a concentration of 0.1 to 10%; (iii) a solid; or (iv) a slurry.