Isolation of lignin by organosolv process from different varieties of rice husk: Understanding their physical and chemical properties

Selective Primary Alcohol Oxidation of Lignin Streams from Butanol‐Pretreated Agricultural Waste Biomass

“…In contrast to other rice husk product streams, the lignin has been little studied with the exception of its structural characterization . It was therefore decided to assess whether RHBL could be converted into a precursor for novel materials.…”

“…In the case of butanosolv lignins, only the β‐ O ‐4 α‐hydroxy group is substituted, providing an opportunity to carry out site‐selective oxidation of the γ‐hydroxy to the corresponding γ‐carboxylic acid (to give lignin γ‐oxCA ). It should be noted that some of the β‐ O ‐4 units in RHBL are natively γ‐acylated with sidechain esters, such as p ‐coumarates (Figures and S10), and that these γ‐Ac‐β‐ O ‐4 units would be inert to the planned oxidation reactions …”

“…In contrast to other rice huskp roduct streams, [35][36][37] the lignin has been little studied with the exception of its structuralc haracterization. [26,38,39] It was therefore decided to assess whether www.chemsuschem.org RHBL could be converted into ap recursor forn ovel materials. Strategies for lignin modification often focus on the use of phenolic end groups and/ort he unselective conversion of b-O-4u nits by reaction at both the a-a nd g-hydroxy groups.I n the case of butanosolv lignins,o nly the b-O-4 a-hydroxy group is substituted, [8] providing an opportunity to carry out site-selective oxidation of the g-hydroxyt ot he corresponding g-carboxylic acid (to give lignin g-oxCA ).…”

“…It should be noted that some of the b-O-4 units in RHBL are natively g-acylated with sidechain esters, such as p-coumarates (Figures 3a nd S10), and that these g-Ac-b-O-4 units would be inert to the planned oxidation reactions. [26,38,39] Previousr eports on b-O-4 g-oxidation have focusedo nt he generation of aldehydes( lignin g-oxALD )i nm odel systemsa nd en route to lignin depolymerization. [40,41] To our knowledge, only three reports have described the preparation of model b-O-4 g-carboxylic acids and organosolv lignin g-oxCA .A ll of these have used TEMPO as the catalytic oxidant under electrochemical catalystr egeneration conditions.…”

Effect of Acidity of Ionic Liquids on Hydrogen Bonding Interaction between Ionic Liquids and Lignin Monomers

“…Lignin composed of mainly three aromatic moieties i. e. coumaryl, coniferyl and sinapyl alcohols, and these moieties are linked with ≡C−O−C≡ and ≡C−C≡ bonds, with assorted functional groups such as –CHO, ‐CH 2 OH, ‐COC, C(O)OC‐, ‐OCH 3 , ‐OH, etc ,. In this text, without a forehead mentioned functional groups (e. g. cumene), and with functional groups (e. g. vanillin and 4‐hydroxy‐3‐methoxyacetophenone) were studied with neutral [BMIM][Cl] and Brønsted acidic ionic liquids [C 3 SO 3 HMIM][PTS] in details, to find out the role of acidity on interaction.…”