期刊
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
卷 8, 期 5, 页码 2158-2166出版社
AMER CHEMICAL SOC
DOI: 10.1021/acssuschemeng.9b05574
关键词
hierarchical Ni catalyst; hydrogenation; fast stabilization; C-O bond hydrogenolysis; alkanes; in situ FTIR
资金
- National Key Research and Development Program of China [2016YFB0701100]
- Recruitment Program of Global Young Experts in China
- Natural Science Foundation of China [21573075]
- Australian Research Council [DP150103842]
The depolymerization of lignin into liquid products in high yields is particularly challenging because of the poor solid solid contact during heterogeneous catalysis and the formation of benzylic carbocations (Ph-C alpha H-OH) and unstable intermediates bearing aldehyde groups, leading to repolymerization. Herein, we report a hierarchical Ni/ASA microreactor catalyst for the hydrodeoxygenation of lignin comprising ca. 17 aromatic monomers into light cyclic hydrocarbons in a nearly theoretical yield at a high reactant/catalyst ratio. The matched sizes in the macropores of Ni/ASA (3-6 mu m) and the particle size of polymeric lignin (4.4 mu m) resulted in fast lignin particle entrapment and an increased adsorption rate for larger amounts of lignin into the Ni/ASA, with better solid-solid contact compared to nonhierarchical Ni/ASA, as evidenced by UV-vis spectra. The lignin aromatics trapped in the macropores are quickly and fully hydrogenated to poly-cyclitols (stable intermediates), which are then transferred to the mesopores for further depolymerization and hydrodeoxygenation to the final cyclic hydrocarbons, as monitored and tracked by two-dimensional heteronuclear single quantum correlation NMR, in situ Fourier transform infrared, gel permeation chromatography, and time-of-flight mass spectrometry. The designed microreactor with suitable hierarchical pores facilitated the entrapment, adsorption, and catalyst-lignin macromolecule contact. The fast elimination of unstable intermediates of aromatics and aldehydes by efficient hydrogenation suppresses repolymerization and increases yields. We suggest that this can be a useful strategy for the efficient direct liquefaction of a diverse set of lignin or lignite polymeric materials and for the hydrogenation of polyaromatics in coal tar.
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