Pulping of lignocellulosic material with oxygen in two stages at increasing pH
First Claim
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1. A process for preparing cellulose pulp which comprises pulping lignocellulosic material with oxygen under superatmospheric pressure in the presence of an alkaline compound in at least two oxygen pulping stages, in a first stage at a pH within the range from about 6 to about 9 and at a temperature within the range from about 110°
- to about 160°
C; and
in a second stage at a pH of at least about 10 and at a temperature within the range from about 80°
to about 160°
C; and
continuing the pulping with oxygen under superatmospheric pressure at a temperature within the range from about 80°
to about 160°
C until cellulose pulp is obtained.
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Abstract
A process is provided for producing cellulose pulp of high brightness, which comprises pulping lignocellulosic material such as wood with oxygen under superatmospheric pressure in two stages, in the first at a pH within the range from about 6 to about 9, and in the second at a more alkaline pH of at least about 10.
26 Citations
28 Claims
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1. A process for preparing cellulose pulp which comprises pulping lignocellulosic material with oxygen under superatmospheric pressure in the presence of an alkaline compound in at least two oxygen pulping stages, in a first stage at a pH within the range from about 6 to about 9 and at a temperature within the range from about 110°
- to about 160°
C; and
in a second stage at a pH of at least about 10 and at a temperature within the range from about 80°
to about 160°
C; and
continuing the pulping with oxygen under superatmospheric pressure at a temperature within the range from about 80°
to about 160°
C until cellulose pulp is obtained. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
- to about 160°
Specification