Lignin removal method using ozone and acetic acid
First Claim
1. A method of bleaching a cellulosic pulp material containing a substantial amount of lignin for removal of said lignin from said cellulosic pulp material consisting essentially of the steps of:
- contacting said cellulose pulp material with a gaseous medium containing ozone in the presence of a liquid processing agent comprising an aqueous acetic acid solution having an acid content of at least 50% by weight, and causing an oxidative conversion of said lignin so as to increase the solubility of said lignin in said liquid processing agent and to improve said removal of said lignin from said cellulosic pulp material.
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Accused Products
Abstract
Lignin contained in a cellulosic or lignocellulosic pulp product is removed by contacting the product with a gaseous medium containing ozone in the presence of a liquid agent which is a lower fatty acid, such a formic, acetic or propionic acid, having only a low solvent capacity for lignin; as a consequence of this treatment, lignin which is present in the product will be converted into a lignin derivative that has an increased solubility in the fatty acid and can be removed quantitatively by extraction from the lignocellulosic material. Purified pulp can thus be obtained with increased processing efficiency and without most pollution problems of prior art processing methods because the fatty acid used as the main constituent of the processing liquid in all stages of pulp production can be circulated counter-currently through the stages of the process with purification of the acid for recirculation only after its use in the digestion step where the normal starting materials of pulp production, i.e. wood or annual plants, are treated according to the acetosolve process at ambient pressure and temperatures of below 120° to form a raw pulp product.
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Citations
34 Claims
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1. A method of bleaching a cellulosic pulp material containing a substantial amount of lignin for removal of said lignin from said cellulosic pulp material consisting essentially of the steps of:
- contacting said cellulose pulp material with a gaseous medium containing ozone in the presence of a liquid processing agent comprising an aqueous acetic acid solution having an acid content of at least 50% by weight, and causing an oxidative conversion of said lignin so as to increase the solubility of said lignin in said liquid processing agent and to improve said removal of said lignin from said cellulosic pulp material.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of producing a high grade pulp from a cellulosic material containing a substantial amount of lignin consisting essentially of the steps:
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digesting said cellulosic material with an aqueous liquid comprising a major amount of acetic acid and obtaining a raw pulp which includes a residual amount of lignin; solubilizing the residual lignin in said pulp in 50% or more acetic acid aqueous liquid mixture and from about 1% to about 3% gaseous ozone; and recovering said pulp as a substantially lignin-free pulp. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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Specification