Recovery and Enrichment of Organic Acids from Kraft Black Liquor by Simulated Moving Bed Adsorption

Abstract

The C 1 −C 6 organic acid fraction of kraft black liquor has potential as a valuable and high-volume biomass-derived molecular feedstock for the production of chemicals and materials. However, large-scale recovery and purification of the multicomponent acid fraction are challenging. This paper presents the design and demonstration of a continuous simulated moving bed (SMB) adsorption process for the recovery and production of organic acids from kraft black liquor (BL). A combination of experimental multicomponent adsorption measurements, SMB operation, and model-guided process design was applied, using a granulated activated carbon adsorbent. The SMB modeling parameters, including adsorption isotherms and mass transfer parameters, were obtained experimentally through batch-mode and column breakthrough measurements using synthetic multicomponent acid streams. The preliminary SMB operating conditions were then determined by detailed SMB process modeling and optimization and fine-tuned experimentally with the aid of internal concentration profile measurements and heuristic principles of SMB operation. The adjusted operation condition was then validated by continuous production of acids with an actual pretreated BL stream. A high-quality organic acid mixture with 98% purity and 95% water rejection was obtained, with >85% acid recovery from the pretreated BL feed and a 4-fold increase in acid productivity per unit mass of adsorbent relative to a cyclic fixedbed process. Approaches for managing the effects of residual lignin content in the pretreated feed are discussed.

Catalytic Upgrading of a Mixed Hydroxy Acid Feedstock Derived from Kraft Black Liquor

“…Recently, separation processes based on graphene oxide membranes and granulated activated carbon adsorbents have been developed for the scalable and continuous fractionation of BL into lignin-rich and HA-rich streams. In particular, HA streams with >90% acid purity are produced. ,, This advance enables the use of the HA stream as a feedstock for producing value-added chemicals via a heterogeneous catalysis pathway.…”

“…In particular, HA streams with >90% acid purity are produced. 40 , 41 , 45 This advance enables the use of the HA stream as a feedstock for producing value-added chemicals via a heterogeneous catalysis pathway.…”