Process for producing cellulose pulp by digestion with a diol or triol solvent and an aniline or phenol salt

Claim 2

A PROCESS FOR PRODUCING CELLULOSE PULP COMPRISING CONTACTING WOOD CHIPS CONTAINING LIGNIN WITH A SOLUTION OF A SOLVENT SELECTED FROM THE GROUP CONSISTING OF AT LEAST ONE SATURATED ALIPHATIC DIOL OR TRIOL AND A SUFFICIENT AMOUNT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF AN ALKALI METAL SALT OF ANILINE, AN ALKALINE EARTH METAL SALT OF ANILINE AND SODIUM PHENATE TO DISSOLVE THE LIGNIN IN SAID WOOD CHIPS; DIGESTING THE SOLUTION CONTACTED WOOD CHIPS AT A TEMPERATURE HIGHER THAN 100*C FOR ABOUT 30 MINUTES TO 3 HOURS WHEREBY SAID LIGNIN IS DISSOLVED IN THE FORM OF A SOLUTION DERIVATIVE; SEPARATING THE RESULTANT CELLULOSE PULP FROM SAID SOLUTION; CONVERTING SAID LIGNIN SOLUBLE DERIVATIVE TO AN INSOLUBLE PRODUCT; SEPARATING SAID INSOLUBLE PRODUCT FROM THE SOLVENT SOLUTION; AND RECOVERING SAID SOLVENT WHICH IS SUITABLE FOR REUSE.

Claim 3

A process for producing cellulose pulp comprising contacting wood chips containing lignin with a solution of a solvent selected from the group consisting of at least one saturated aliphatic diol or triol and a sufficient amount of a compound selected from the group consisting of an alkali metal salt of aniline, an alkaline earth metal salt of aniline and sodium phenate to dissolve the lignin in said wood chips; digesting the solution contacted wood chips at a temperature higher than 100*C for about 30 minutes to 3 hours whereby said lignin is dissolved in the form of a soluble derivative; separating the resultant cellulose pulp from said solution; converting said lignin soluble derivative to an insoluble product; separating said insoluble product from the solvent solution; and recovering said solvent which is suitable for reuse.

Claim 4

A process for producing cellulose pulp comprising contacting wood chips containing lignin with a solution of a solvent selected from the group consisting of at least one saturated aliphatic diol or triol and a sufficient amount of a compound selected from the group consisting of an alkali metal salt of aniline, an alkaline earth metal salt of aniline and sodium phenate to dissolve the lignin in said wood chips; digesting the solution contacted wood chips at a temperature higher than 100*C for about 30 minutes to 3 hours whereby said lignin is dissolved in the form of a soluble derivative; separating the resultant cellulose pulp from said solution; converting said lignin soluble derivative to an insoluble product; separating said insoluble product from the solvent solution; and recovering said solvent which is suitable for reuse.

Claim 5

Process as claimed in claim 1, characterized in that the digestion is conducted under atmospheric pressure.

Claim 6

Process as claimed in claim 2, characterized in that the solvent used is ethylene glycol.

Claim 7

Process as claimed in claim 1, characterized in that the salt is sodium phenate.

Claim 8

Process as claimed in claim 1, characterized in that the salt is sodium anilide.

Claim 9

Process as claimed in claim 1, characterized in that the solution is maintained substantially anhydrous during the digestion.

Claim 10

Process as claimed in claIm 1, characterized in that the wood chips are digested while suspended in said solution.

Claim 11

Process as claimed in claim 1, characterized in that the wood chips are digested while being impregnated with a quantity of said solution such that practically all the solution is absorbed by the wood.

Claim 12

Process as claimed in claim 1, characterized in that the dissolved lignin is precipitated by adding a strong acid to the solution.

Claim 13

Process as claimed in claim 9, characterized in that the strong acid is hydrochloric acid.

Claim 14

Process as claimed in claim 7, characterized in that the following operations are conducted in the form of a continuous manufacturing process: wood chips are charged, with the above solution, into a digester, the mixture is digested at a temperature which is maintained above 100*C, the digested mixture, consisting of a suspension of cellulose pulp in a solution containing lignin, is removed from the digester and filtered, the yield of cellulose pulp is washed on the filter with water, the effluent wash waters from the filter are distilled, to the distilled water there is added at least a part of the water obtained by condensing the vapors leaving the digester, the combined waters are recycled as the water used for washing the yield of cellulose pulp, the tail fraction from the distillation is combined with the filtrate from the filter, to the combined liquids there is added calcium hydroxide, which precipitates the lignin in the form of a suspension of calcium lignate, the resulting mixture is filtered, the yield of calcium lignate is washed with water on the filter; the effluent wash waters from the filter are distilled, the resulting distilled water is the water used for washing the calcium lignate, the tail fraction from the distillation is combined with the filtrate, the combined liquid is recycled and used as the solvent in the digester.

Claim 15

Process as claimed in claim 8, characterized in that the following operations are conducted in the form of a continuous manufacturing process: wood chips impregnated with the above solution are charged into a digester, the mixture is digested at a temperature maintained above 100*C, the digested mixture is removed from the digester, the mixture being in the form of a solid mass consisting of cellulose pulp impregnated with a solution containing lignin, the pulp is dispersed in the effluent wash waters from the subsequent pulp filtration, forming a suspension of cellulose pulp in an aqueous solution containing lignin, the resulting mixture is filtered, the yield of cellulose pulp is washed with water on the filter, the effluent wash waters being used for the dispersion mentioned above, to the filtrate there is added calcium hydroxide, which precipitates the lignin in the form of a suspension of calcium lignate, the mixture is filtered, the yield of calcium lignate is washed with water, the effluent wash waters are combined with the filtrate, the mixed liquids are distilled, the resulting distilled water is the water used for washing the calcium lignate on the filter, the tail fraction from the distillation is recycled and used as the solvent for impregnating the wood chips.

Claim 16

Process as claimed in claim 12, characterized in that, using sodium phenate as the reagent, the mixture is digested by live steam introduced into the digester, the water vapor loaded with phenol leaving the digester is condensed, the resulting condensate is separated into two phases, of which the aqueous phase is used for washing the yield of cellulose pulp, the phenolic phase being combined with the recycled solvent, which contains sodium hydroxide, in order to regenerate sodium phenate in the solvent.

Claim 17

Process as claimed in claim 1, characterized in that the process is conducted as a batch-continuous process using several digesters which operate in alternating sequence, each batch being processed by the following sequence of operations, a charge of wood chips is introduced, together with solvent containing reagent, into a digester, the solution is circulated in a closed circuit containing a heater, which heats the solution up to the reaction temperature and maintains this temperature throughout the digestion, the circuit is changed so that the solution flows through a heat exchanger instead of through the heater, after cooling sufficiently, the solution is drained out of the digester, the cellulose pulp is washed in the digester, from which it is then removed, the lignin in the solvent is precipitated as calcium lignate, which is removed from the solvent and washed, the lignin in the wash waters is also precipitated and recovered as calcium lignate, the purified wash waters are distilled, giving distilled water and a tail fraction, which is combined with the recovered solvent, the wash waters before distillation passing through the heat exchanger for cooling the solution in the digester during the digestion.

Claim 18

Process as claimed in claim 1, characterized in that the following operations are performed: (a) a charge of wood chips is digested in a first digester in a solution which is circulated through a closed circuit containing a heater which heats the solution up to the reaction temperature and maintains this temperature throughout the digestion whereupon, after the digestion has been completed, the solution is circulated through a heat exchanger which cools it down; (b) the solution is removed from the digester and the dissolved lignin is precipitated as calcium lignate, which is recovered; (c) the purified solution, after removal of the lignin, is used for digesting a second batch of chips in a second digester, repeating operations (a) and (b) above; (d) during operation (a) in the second digester the cellulose pulp in the first digester is washed with water, the lignin in the wash waters is precipitated as calcium lignate, which is recovered, the purified wash waters are distilled, the solvent being recovered as the tail fraction, the wash waters being used, before distillation, as the coolant in the heat exchanger which cools the solution during the digestion; (e) the washed cellulose pulp is removed from the first digester and a third batch of chips is charged to the first digester, during which time operation (b) is repeated on the solution which has been circulating through the second digester; (f) operations (d) and (e) are repeated in the second digester while operation (a) is being repeated in the first digester, and so on, the digesters being operated in alternation.

Claim 19

Process as claimed in claim 14, characterized in that the salt used is sodium phenate, and in that the phenol vaporized during the digestion is recovered by combining it with the purified wash waters from which the lignin has been removed, the phenol being absorbed into these waters before their distillation.

Claim 20

Process as claimed in claim 15, characterized in that the salt used in sodium phenate, and in that the phenol vaporized during the digestion is recovered by combining it with the purified wash waters from which the lignin has been removed, the phenol being absorbed into these waters before their distillation.

Claim 21

Process as claimed in claim 1, wherein said solvent is selected from the group consisting of ethylene glycol and glycerol.

Claim 22

Process as claimed in claim 17, characterized in that the calcium lignate, which contains some calcium phenate, is reacted with CO2 followed by steam, in order to recover the phenol.

Claim 23

Process as claimed in claim 1, wherein said recovered solvent is recycled for use in another cycle of said process.