Abstract
Extracted alkali lignin (AL) and organosolv lignin (OL) from sugarcane bagasse were acid-catalyzed liquefied in methanol with the aim of producing oligomeric aromatic oxides. Acids were screened for their effects on the output of oligomeric aromatic oxides from alkali lignin liquefaction. Based on the highest amount of lignin conversion, the order of catalytic efficiency was: p-toluenesulfonic acid (TsOH) > CCl3COOH (TCA) > KHSO4 > AlCl3 > H3O40PW12 > H2SO4. The most alkali lignin conversion was 86.2 wt% when catalyzed by p-toluenesulfonic acid. Optimized liquefaction temperatures indicated that AL liquefaction optimum temperature was 250°C and OL was 175°C. GPC characterized AL, OL and resultant products implied that TsOH could degrade both lignins to about 780 g/mol of molecular weight. HSQC-NMR and GC-MS observations suggested that simultaneous vinyl ether cleavage and intermediate stabilization of phenolic hydroxyl group etherification at high temperatures achieved AL liquefaction. Acidolysis of β-ether linkages at mild temperatures was the mechanism of OL liquefaction.
Highlights
Lignin is the most abundant natural aromatic polymer
alkali lignin (AL) liquefaction was conducted with the aim of catalyst screening in methanol solvent
Sugarcane bagasse lignin was liquefied for the production of oligomeric aromatic oxides (OAO), which will be used as a methanol gasoline additive
Summary
Lignin is the most abundant natural aromatic polymer It consists of methoxylated phenylpropane units, cross-linked by carbon-carbon and ether bonds (Vanholme et al, 2010). This renewable resource is of interest for producing aromatic chemicals (Zakzeski et al, 2013; Ragauskas et al, 2014). The lignin degradation process inevitably generated oligomers (Joffres et al, 2014) Researchers have recognized this problem and conquered further cracking by developing efficiency catalysts or harsh conditions (Tang et al, 2010; Jongerius et al, 2013; Yoshikawa et al, 2014; Kloekhorst et al, 2015). Confronting the current petroleum market, monomeric chemicals produced from
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