Depolymerization of lignin meets the difficulty in cleaving the robust aryl ether bond. Herein, through installing an internal nucleophile in the β-O-4′ linkage, the selective cleavage of aryl ether was realized by the intramolecular substitution on aryl rings affording non-phenolic arylamine products. In particular, nitrogen-modified lignin models and lignin samples were employed to generate the iminyl radical under photocatalytic reduction, which acted as the internal nucleophile inducing aryl migration from O to the N atom. The following hydrolysis released primary arylamines and α-hydroxy ketones. Mechanism studies including electron spin resonance (ESR), fluorescence quenching experiments, and density functional theory (DFT) calculations proved the aryl migration pathway. This method enables access to non-phenolic arylamine products from lignin conversion.
We demonstrate the coproduction of H2 and diesel fuel precursors from lignocellulose-derived methylfurans via acceptorless dehydrogenative C−C coupling, using a Ru-doped ZnIn2S4 catalyst and driven by visible light. With this chemistry, up to 1.04 g gcatalyst−1 h−1 of diesel fuel precursors (~41% of which are precursors of branched-chain alkanes) are produced with selectivity higher than 96%, together with 6.0 mmol gcatalyst−1 h−1 of H2. Subsequent hydrodeoxygenation reactions yield the desired diesel fuels comprising straight- and branched-chain alkanes. We suggest that Ru dopants, substituted in the position of indium ions in the ZnIn2S4 matrix, improve charge separation efficiency, thereby accelerating C−H activation for the coproduction of H2 and diesel fuel precursors.
Selective conversion of an aqueous solution of mixed oxygenates produced by biomass fermentation to a value-added single product is pivotal for commercially viable biomass utilization. However, the efficiency and selectivity of the transformation remains a great challenge. Herein, we present a strategy capable of transforming ~70% of carbon in an aqueous fermentation mixture (ABE: acetone–butanol–ethanol–water) to 4-heptanone (4-HPO), catalyzed by tin-doped ceria (Sn-ceria), with a selectivity aas high as 86%. Water (up to 27 wt%), detrimental to the reported catalysts for ABE conversion, was beneficial for producing 4-HPO, highlighting the feasibility of the current reaction system. In a 300 h continuous reaction over 2 wt% Sn-ceria catalyst, the average 4-HPO selectivity is maintained at 85% with 50% conversion and > 90% carbon balance. This strategy offers a route for highly efficient organic-carbon utilization, which can potentially integrate biological and
The increasing emissions of carbon dioxide (CO2) are primarily driven by the rapid expansion of energy-intensive sectors such as the chemical industry. This work selects ethylene, one of the most important chemicals, as a model study to represent the low-carbon roadmap of chemical production. Four strategies improving the efficiency of fossil resource usage, developing the technology for carbon capture and storage (CCS), CO2 chemical conversion, and converting biomass resources into chemicals, are used to reduce CO2 emissions. A comprehensive analysis of the life cycle CO2 emissions of different ethylene production routes has been performed to compare their emission reduction potential. The results indicate that the BMTO (biomass to olefins via methanol-to-olefins) pathway releases the least CO2 (− 1.3 t CO2/t ethylene)
Quinazolinones, an important class of heterocyclic compounds, have been widely used in pharmaceuticals because of their biological activity. However, the efficient and economical synthesis of quinazolinones has remained a challenge. A novel synthetic approach has now been developed to produce quinazolinones from olefins, CO, and amines over heterogeneous Ru‐clusters/ceria catalyst in the absence of acids, bases, and oxidants. Furthermore, H2O is generated as the only by‐product. A series of quinazolinones with aromatic or non‐aromatic substituents can be obtained in yields of up to 99 %. The Ru‐clusters/ceria can be reused at least four times. The analysis of the E‐factor (environmental impact factor) for the synthesis of 2‐ethyl quinazolinone suggests that this system is more environmentally friendly than other processes reported previously.
Lignin is a renewable and abundant aromatic polymer found in plants. We herein propose a "cutting tail" methodology to produce phenol from lignin, which is achieved by combining Ru/CeO2 catalyst and CuCl2 oxidant via an oxidation–hydrogenation route. Phenol was obtained from separated poplar lignin with 13 wt % yield. Even raw biomass, such as poplar, birch, pine, peanut, bamboo willow, and straw, could be converted into phenol in 1–33 mg per gram of biomass.
Photocatalysis is a potentially promising approach to harvest aromatic compounds from lignin. However, the development of an active and selective solid photocatalyst is still challenging for lignin transformation under ambient conditions. We herein report a mild photocatalytic oxidative strategy for C–C bond cleavage of lignin β-O-4 and β-1 linkages using a mesoporous graphitic carbon nitride catalyst. Identifications by solid-state NMR techniques and density functional theory (DFT) calculations indicate that π–π stacking interactions are most likely present between the flexible carbon nitride surface and lignin model molecule. Besides, low charge recombination efficiency and high specific surface area (206.5 m2 g–1) of the catalyst also contribute to its high catalytic activity. Mechanistic investigations reveal that photogenerated holes, as the main active species, trigger the oxidation and C–C bond cleavage of lignin models.
Valuable polyester monomers and plasticizers—1,4‐cyclohexanedimethanol (CHDM), 1,4‐cyclohexanedicarboxylic acid (CHDA), and 1,2‐cyclohexanedicarboxylates—have been prepared by a new strategy. The synthetic processes involve a proline‐catalyzed formal [3+1+2] cycloaddition of formaldehyde, crotonaldehyde, and acrylate (or fumarate). CHDM is produced after a subsequent hydrogenation step over a commercially available Cu/Zn/Al catalyst and a one‐pot hydrogenation/oxidation/hydrolysis process yields CHDA, whereas 1,2‐cyclohexanedicarboxylate is obtained by a Pd/C‐catalyzed tandem decarbonylation/hydrogenation step.
The interface of metal-oxide plays pivotal roles in catalytic reactions, but its catalytic function is still not clear. In this study, we report the high activity of nanostructured Ru/ceria (Ru-cluste...
Defect chemistries of metal-doped CeO2 catalysts have attracted extensive scientific interests in heterogeneous catalysis. Here, we report the structure–activity relationship of CeO2 catalysts doped ...