Catalytic depolymerization of the hydrolyzed lignin over mesoporous catalysts

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.

Section: Characterizations Of the Catalystsmentioning

confidence: 92%

Enhanced Selective Production of Arenes and Regenerating Rate in Aryl Ether Hydrogenolysis over Mesoporous Nickel in Plug-Flow Reactors

Zheng

Wang

et al. 2019

“…In these studies, the catalysts play a major role in the conversion and the selectivity of the final products. The most widely used catalysts are Pd/C [81,[92][93][94][95][96], Ni/C [93][94][95][96][97], Pt/C [93][94][95]98], Pt/Al 2 O 3 [99], Cu-based porous oxides [100,101], supported NiW and NiMo [102], Ru-based materials [93][94][95][96]103], bimetallic NiM (M = Ru, Rh, Pd) [66], Ni-Au [65,104], WP [105], Ru x Ni 1-x /SBA-15 [106], modified SBA-15 and Al-SBA-15 [107], MoO x /CNT [108], S 2 O 8 2− -KNO 3 /TiO 2 [109]. Another significant parameter in the reductive depolymerization using molecular H 2 is the reaction medium.…”

Section: Depolymerization With External Hydrogen Sourcementioning

confidence: 99%

Catalytic Transfer Hydrogenolysis Reactions for Lignin Valorization to Fuels and Chemicals

Margellou

Triantafyllidis

2019

Lignocellulosic biomass is an abundant renewable source of chemicals and fuels. Lignin, one of biomass main structural components being widely available as by-product in the pulp and paper industry and in the process of second generation bioethanol, can provide phenolic and aromatic compounds that can be utilized for the manufacture of a wide variety of polymers, fuels, and other high added value products. The effective depolymerisation of lignin into its primary building blocks remains a challenge with regard to conversion degree and monomers selectivity and stability. This review article focuses on the state of the art in the liquid phase reductive depolymerisation of lignin under relatively mild conditions via catalytic hydrogenolysis/hydrogenation reactions, discussing the effect of lignin type/origin, hydrogen donor solvents, and related transfer hydrogenation or reforming pathways, catalysts, and reaction conditions.

“…Ni supported on acidic supports such as zeolites and silicates with both Brønsted and Lewis acidity are active catalysts for lignin hydrogenolysis by promoting dealkylations and deacylations and minimizing repolymerizations [100,101]. With suitable pore size and well-ordered pore structure, SBA-15 can effectively suppress repolymerization, with 81.4% liquefaction yield and 21.9 wt % monomer yields.…”

Section: Monometallic Ni-based Catalysts For Hydrogenolysis Of Ligninmentioning

confidence: 99%

Lignin Valorizations with Ni Catalysts for Renewable Chemicals and Fuels Productions

Chen

Guan

Tsang³

et al. 2019

Energy and fuels derived from biomass pose lesser impact on the environmental carbon footprint than those derived from fossil fuels. In order for the biomass-to-energy and biomass-to-chemicals processes to play their important role in the loop of the circular economy, highly active, selective, and stable catalysts and the related efficient chemical processes are urgently needed. Lignin is the most thermal stable fraction of biomass and a particularly important resource for the production of chemicals and fuels. This mini review mainly focuses on lignin valorizations for renewable chemicals and fuels production and summarizes the recent interest in the lignin valorization over Ni and relevant bimetallic metal catalysts on various supports. Particular attention will be paid to those strategies to convert lignin to chemicals and fuels components, such as pyrolysis, hydrodeoxygenation, and hydrogenolysis. The review is written in a simple and elaborated way in order to draw chemists and engineers' attention to Ni-based catalysts in lignin valorizations and guide them in designing innovative catalytic materials based on the lignin conversion reaction.Catalysts 2019, 9, 488 2 of 39 processes to play their important role in the loop of the circular economy, first, the process must be energy efficient itself [2]. Second, according to Anastas's second principle [3], atom economy should be maximized and excess starting materials which will not be contained in the final product should be avoided. Thus, developing highly active and selective catalysts and enzymes is an urgent need. Current technology for lignocellulosic valorization includes biochemical fermentation, chemical and thermochemical methods using enzymes and metal catalysts, respectively. Thermochemical methods, including combustion, pyrolysis, and gasification, and chemical methods, such as hydrodeoxygenation (HDO), hydrogenolysis, and oxidative cleavage, have the advantages of higher throughputs due to the short reaction time, and thus are more suitable for commercialized and industrialized scale-up.Woody and herbaceous biomasses are large polymeric networks consisting of ca. 35-50% cellulose, 25-30% hemicellulose (glucomannan and glucuronoxylan), and 15-30% of lignin (macromolecular polymer networks with interconnected phenylpropane and phenol units with various formula, e.g., (C 31 H 34 O 11 ) n ) by weight. Lignin is one of the most thermal stable fractions and a particularly important resource for the production of chemicals and fuels. With careful design of the metal catalysts, either aromatic platform molecules, or fuels components such as naphthenes, can be preferentially produced in high yields and with high selectivity.Over the past decade, numerous monometallic and bimetallic metal catalysts using both precious and base metal precursors on various supports have been reported to successfully convert lignin into valuable products. Transition metals such as Ni (price = US$ 12.628/kg as of April 2019) are much more economically viable than precious metals...