Process for the manufacture of furfural

{
  "publication_number": "US6743928B1",
  "country": "US",
  "kind": "B1",
  "title": "Process for the manufacture of furfural",
  "abstract": "Process for the manufacture of furfural wherein a pentosan-containing raw material acidified or not, is heated to a temperature T 1 by admitting steam through valve 2 while the valves 3 and 4 are closed. During the very short heating process, the steam condenses, thus increasing the moisture content of the charge. Then, valve 2 is closed and a leak valve 3 is opened so as to produce a steady small flow of product vapor by gradual depressurization. This causes a slow drop in temperature. When a suitably chosen temperature T 2 is reached, the leak valve 3 is closed to terminate the first “gradual depressurization”. If at the end of this period no more furfural was obtained, the digestion is completed by opening valve 4 to discharge the residue. If, however, furfural was still obtained, the reactor is reheated and submitted to another “gradual depressurization” period.",
  "claims": [
    "1. A process for manufacturing furfural which comprises the steps of: charging a reactor with pentosan containing material; heating the charge to a first predetermined temperature by introducing pressurized steam via a steam inlet valve; closing the steam inlet valve; and subjecting the charge to a gradual depressurization by reducing the pressure in the reactor until a second predetermined temperature is attained; the depressurization being at a rate sufficient to maintain the liquid phase within the reactor in a constantly ebullient state.",
    "2. The process according to claim 1, further comprising the step of acidifying the charge prior to heating.",
    "3. The process according to claim 1, wherein the rate of depressurization is sufficient to complete conversion to furfural before the second predetermined temperature is reached.",
    "4. The process according to claim 1, wherein the complete conversion to furfural is obtained in more than one depressurization from the first predetermined temperature to the second predetermined temperature by the addition of steam.",
    "5. The process according to claim 1, wherein steam is added during the depressurization, for a predetermined period.",
    "6. The process according to claim 1, wherein the gradual depressurization comprises a controlled leaking of a stream of vapor from the reactor until the second predetermined temperature is attained.",
    "7. The process according to claim 1, wherein the gradual depressurization takes place at a temperature range between 280° C. and 150° C.",
    "8. The process according to claim 7, wherein the temperature range is between 230° C., and 170° C.",
    "9. The process according to claim 1, further comprising the step of using phosphoric acid as a catalyst.",
    "10. The process according to claim 1, further comprising the step of adding acetic acid as a catalyst."
  ],
  "description_excerpt": "This application is a 371 of PCT/2A00/00024 filed on Feb. 11, 2000.\n\nThis invention relates to a process for the manufacture of furfural.\n\nChemical reactors must be designed to suit the characteristics of the process intended. In making furfural, this has not been the case. For the first industrial production of furfural, QUAKER OATS used reactors from an abandoned cereal process as they happened to be available, and such reactors leave been used ever since. Later, ROSENLEW and ESCHER WYSS built furfural plants based on reactors designed for making wood pulp. None of the industrial furfural reactors employed today were conceived to meet the special requirements of furfural production, and it is, therefore, not surprising that the yields obtained with these reactors do not even exceed 60%.\n\nThe principal yield losses are caused by a reaction between furfural and xylose, so that striving for a high yield forbids having furfural and xylose in the same place. All existing furfural reactors violate this requirement. By pointedly eliminating this deficiency, the process here described permits attaining yields in the order of 100%.\n\nIn analytical chemistry, the conversion of pentosan or pentose to furfural is used for a quantitative determination of these substances. This is possible as it was shown that in this procedure the furfural yield is a proven 100%. The procedure consists in an atmospheric digestion of pentosan or pentose in 12% aqueous HCl saturated with NaCl. By contrast, in the present industrial furfural processes mentioned above, a pressure reactor is used to submit the raw material to a steam treatment.",
  "cpc": [
    "C07D 307/50"
  ],
  "ipc": [
    "C07D 307/50"
  ],
  "assignees": [
    "International Furan Technology Pty Ltd"
  ],
  "inventors": [
    "Karl J. Zeitsch"
  ],
  "filing_date": "2000-02-11",
  "publication_date": "2004-06-01",
  "grant_date": "2004-06-01",
  "priority_date": "1999-02-11",
  "application_number": "US-91328002-A",
  "family_id": "7897146",
  "cited_by_count": 71,
  "citations": [
    "US4029515A",
    "WO1981000407A1",
    "DE3139188C1",
    "US4533743A",
    "DE3842825A1",
    "US4912237A",
    "EP0346836A2",
    "WO1996025553A1"
  ]
}