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Abstract

A process for making furfural using papermaking black liquor from the kraft pulping process as a feed material. First, the lignin is removed from the black liquor by carbonizing the black liquor to a pH below pH 10 to insolubilize the lignin, neutralize NaOH and other inorganic components of the black liquor. The next step is to treat the carbonated black liquor that contains the hemicellulose to remove the high molecular weight components. In a preferred embodiment the treatment uses multiple sequential steps. The first step of the treatment is to use ultrafiltration, centrifugation or dissolved-air floatation to separate the high molecular weight components. The second filtration is to pass the hemicellulose containing black liquor stream through a nanofilter to remove low molecular weight components. The conversion of xylans in the hemicellulose-containing mixture to furfural is accomplished using a catalytic process. The xylans are converted to pentose sugars and then converted to furfural. The furfural is formed at a low concentration and then further concentrated.

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First Claim