Abstract
Ordered mesoporous nickel (mesoNi) was successfully synthesized with a hard templating method by using KIT-6 ordered mesoporous silica as a template. With small-angle X-ray diffraction (SAXRD), transmission electron microscopy (TEM) and N2 sorption technique, the mesoporous structures of synthesized catalysts were characterized with desired high surface area (84.2 m2·g−1) and narrow pore size distribution. MesoNi exhibited outstanding catalytic cleavage activity for lignin model compounds (benzyl phenyl ether, BPE) with high selectivity of arenes in the flow reactor system. MesoNi also showed higher regeneration rates than non-porous ones, which were confirmed from deactivation and regeneration mechanism studies in the flow reaction system with varied high temperature and pressure. The adsorbed poisoning species on the mesoporous Ni surface were analyzed and phenol could be the main poisoning species. The excellent catalytic cleavage performance of mesoNi originates from their unique mesoporous structure, which offers high surface area and Ni active sites. The outstanding catalytic performance shows that this process provides a promising candidate for improved lignin valorization with general applicability.
Highlights
Increased demand for energy and value-added chemicals has motivated the development of lignocellulose, which consists of cellulose, hemicellulose, and lignin [1]
A non-porous Raney Ni catalyst with similar particle size was synthesized with a hydrothermal method to compare with mesoporous Ni (mesoNi)
Combined with the small-angle X-ray diffraction (SAXRD) results in Figure S2, the intense peak around 1.15◦ corresponds to the (211) diffraction of Ia3d symmetry, which indicated the whole mesoNi nanoparticle remained in the long-range mesostructured regularity of the KIT-6 template [25,26]
Summary
Increased demand for energy and value-added chemicals has motivated the development of lignocellulose, which consists of cellulose, hemicellulose, and lignin [1]. 40% of its total energy content, its potential as a renewable source of aromatic compounds has recently received great attention [2,3]. A number of homogeneous catalysts (e.g., complexes of Ru [6], V [7], and Ni [8]) and heterogeneous catalysts (e.g., Ni/SiO2 [9], Ru/Nb2 O5 [10], and Pd/Zn [11]) have shown high hydrogenolytic performance in cleaving the C–O bonds of lignin and related dimeric lignin model compounds under mild conditions. Catalysts 2019, 9, 904 in insoluble lignin due to their high mobility, which increases the hydrogenolytic activity of these catalysts [12]. Heterogeneous catalysts are better adapted to continuous processing [13]
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