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Progressing batch hydrolysis process

  • US 4,615,742 A
  • Filed: 01/10/1985
  • Issued: 10/07/1986
  • Est. Priority Date: 01/10/1985
  • Status: Expired due to Term
First Claim
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1. A progressive batch prehydrolysis and hydrolysis process for producing sugar from a lignocellulosic feedstock, comprising:

  • (a) providing at least one percolation reactor, said reactor being initially charged with lignocellulosic feedstock including hemicellulose components and cellulose components, which feedstock has not been prehydrolyzed;

    (b) prehydrolyzing said feedstock by passing a liquid stream of dilute acid into and then serially through said reactors in (a) which are charged with said lignocellulosic feedstock, said dilute acid being at a temperature, pressure, and flow rate sufficient to convert, by hydrolysis, substantially all of the hemicellulose components of said feedstock to sugar comprising xylose, glucose and other sugars carried by said liquid acid stream without completely hydrolyzing said cellulose components of said feedstock, said liquid stream of dilute acid being at a temperature and maintained at a temperature such that said sugars produced within said reactors from said hemicellulose component and carried by said dilute acid stream are not subjected to any significant heat degradation;

    (c) cooling and recovering said dilute sugar containing acid stream after it exits the last reactor in (a);

    (d) providing at least one additional percolation reactor initially charged with said lignocellulosic feedstock including hemicellulose components and cellulose components, which feedstock has not been prehydrolyzed;

    (e) serially connecting said reactors in (a) to and upstream of said additional reactors in (d);

    (f) passing a liquid stream of dilute acid serially through said reactors in (a) which are now charged with prehydrolyzed lignocellulosic feedstock which is now substantially free of unreacted hemicellulose, said liquid stream of dilute acid being at a temperature, said temperature being higher than the temperature of said liquid acid stream in (b), pressure and flow rate sufficient to convert substantially all of said remaining cellulose components of said feedstock to sugars comprising glucose and other sugars carried by said dilute acid stream;

    (g) cooling said dilute acid stream containing sugar after exiting the last reactor in (f), and then prehydrolyzing the feedstock in the additional reactors in (d) by feeding said dilute acid stream containing sugar serially through said additional reactors in (d) charged with said lignocellulosic feedstock including hemicellulose components and cellulose components, said dilute acid being at a temperature, pressure and flow rate sufficient to convert by hydrolysis substantially all of the hemicellulose components of said feedstock to sugars comprising xylose, glucose and other sugars carried by said liquid acid stream without completely hydrolyzing said cellulose components of said feedstock, said cooled liquid stream being at a temperature and maintained at a temperature such that said sugars produced from said hemicellulose components of said feedstock are not subjected to any significant heat degradation; and

    then(h) cooling and recovering said dilute sugar containing acid stream after it exits the last reactor in (g).

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