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US 7,867,360 B2Granted
Generation of active polysulphide with manganese and bismuth catalysts
AssigneeFPInnovations
InventorsYujun Sun, Richard McKinnon Berry
Life of this patent
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AssigneeFPInnovations
InventorsYujun Sun, Richard McKinnon Berry
Estimating the term…
Polysulphide produced by oxidizing white liquor includes both active and inactive components. “Active” polysulphide is the only component that increases pulp yield. The amount of active polysulphide formed when manganese oxides are used as catalysts in the generating process is increased by adding a co-catalyst. Adding bismuth compounds and, in particular, bismuth oxide as a co-catalyst increases the total amount of polysulphide formed with all the manganese oxides and increases the amount of active polysulphide produced particularly when using the lower manganese oxides. The co-catalyst also increases the number of cycles in which the most active catalyst, manganese dioxide, can participate before losing efficiency. Other elements in the same group and adjacent groups in the periodic table are active but these other elements are more soluble than bismuth and are toxic.
In a method of generating polysulphide by oxidation of a sulphide-containing liquor with an oxygen-containing gas in the presence of a manganese compound as catalyst, the improvement wherein the oxidation is carried out in the further presence of a co-catalyst for the catalyst effective to enhance the content of active polysulphide formed in the oxidation as a component of the total polysulphide comprising active polysulphide and inactive polysulphide, said co-catalyst being a bismuth compound.
A method of increasing the yield of pulp in kraft pulping with a white liquor containing polysulphide comprising:
A method of producing an oxidized white liquor containing active polysulphide comprising:
Dependencies are inferred from the claim text.