Lignin conversion to high-octane fuel additives

Continuing previous studies on the conversion of lignin to reformulated gasoline compositions, new lignin upgrading processes were developed that allow preferential production of specific high-octane fuel additives of two distinct types: (1) C-7-C-10 alkylbenzenes; and (2) aryl methyl ethers, where aryl mostly = phenyl, 2-methylphenyl, 4-methylphenyl, and dimethylphenyl. Process (1) comprises base-catalyzed depolymerization (BCD) and simultaneous partial (similar to 50%) deoxygenation of lignin at 270 - 290 degrees C, in the presence of supercritical methanol as reaction medium, followed by exhaustive hydrodeoxygenation and attendant mild hydrocracking of the BCD product with sulfided catalysts to yield C-7-C-10 alkylbenzenes as main products. Process (2) involves mild BCD at 250 - 270 degrees C with preservation of the lignin oxygen, followed by selective C-C hydrocracking with solid superacid catalysts. This method preferentially yields a mixture of alkylated phenols, which upon acid-catalyzed etherification with methanol are converted into corresponding aryl methyl ethers (see above) possessing blending octane numbers in the range of 142 - 166. In a recent extension of this work, a greatly advantageous procedure for performing the BCD stage of processes (1) and (2) in water as reaction medium was developed.