Valorization of native birch wood lignin into monomeric phenols over nickel-based catalysts has been studied. High chemoselectivity to aromatic products was achieved by using Ni-based catalysts and common alcohols as solvents. The results show that lignin can be selectively cleaved into propylguaiacol and propylsyringol with total selectivity >90% at a lignin conversion of about 50%. Alcohols, such as methanol, ethanol and ethylene glycol, are suitable solvents for lignin conversion. Analyses with MALDI-TOF and NMR show that birch lignin is first fragmented into smaller lignin species consisting of several benzene rings with a molecular weight of m/z ca. 1100 to ca. 1600 via alcoholysis reaction. The second step involves the hydrogenolysis of the fragments into phenols. The presence of gaseous H 2 has no effect on lignin conversion, indicating that alcohols provide active hydrogen species, which is further confirmed by isotopic tracing experiments. Catalysts are recycled by magnetic separation and can be reused four times without losing activity. The mechanistic insights from this work could be helpful in understanding native lignin conversion and the formation of monomeric phenolics via reductive depolymerization. Broader contextNature efficiently synthesizes aromatic structures and deposits them as lignin in plants. Incorporation of catalytic technologies into lignin conversion is a possible option for valorizing the feedstock as a renewable raw material for aromatic chemical production. Use of heterogeneous catalysts facilitates separation and recycling, and has attracted great attention. However, the detailed chemistry between solid catalysts and solid feedstocks still remains unknown because of mass transfer limitations. Herein we report the valorization of native birch wood lignin into monomeric phenols over nickel-based catalysts. High chemoselectivity to aromatic products was achieved by using Ni-based catalysts and common alcohols as solvents. The results show that lignin can be selectively cleaved into propylguaiacol and propylsyringol with total selectivity >90% at a lignin conversion of about 50%. Analysis results show that birch lignin is rst fragmented into smaller lignin species consisting of several benzene rings with a molecular weight of m/z ca. 1100 to ca. 1600 via alcoholysis reaction. The second step involves the hydrogenolysis of the fragments into phenols. This study will greatly contribute to the understanding of the lignin depolymerization reaction and will be interesting for other biomass conversion.

The use of a heterogeneous Lewis acid catalyst, which is insoluble and easily separable during the reaction, is a promising option for hydrolysis reactions from both environmental and practical viewpoints. In this study, ceria showed excellent catalytic activity in the hydrolysis of 4-methyl-1,3-dioxane to 1,3-butanediol in 95% yield and in the one-pot synthesis of 1,3-butanediol from propylene and formaldehyde via Prins condensation and hydrolysis reactions in an overall yield of 60%. In-depth investigations revealed that ceria is a water-tolerant Lewis acid catalyst, which has seldom been reported previously. The ceria catalysts showed rather unusual high activity in hydrolysis, with a turnover number (TON) of 260, which is rather high for bulk oxide catalysts, whose TONs are usually less than 100. Our conclusion that ceria functions as a Lewis acid catalyst in hydrolysis reactions is firmly supported by thorough characterizations with IR and Raman spectroscopy, acidity measurements with IR and (31)P magic-angle-spinning NMR spectroscopy, Na(+)/H(+) exchange tests, analyses using the in situ active-site capping method, and isotope-labeling studies. A relationship between surface vacancy sites and catalytic activity has been established. CeO(2)(111) has been confirmed to be the catalytically active crystalline facet for hydrolysis. Water has been found to be associatively adsorbed on oxygen vacancy sites with medium strength, which does not lead to water dissociation to form stable hydroxides. This explains why the ceria catalyst is water-tolerant.

This work demonstrates the synthesis of an efficient photocatalyst, Au25(PPh3)10Cl2(SC3H6SiO3)5/TiO2, for selective oxidation of amines to imines. The photocatalyst is prepared via hydrolysis of Au25(PPh3)10Cl2[(SC3H6Si­(OC2H5)3]5 nanoclusters in the presence of TiO2 support. The gold nanoclusters exhibit good photocatalytic activity using visible light and under mild thermal conditions for the selective oxidation with molecular oxygen (O2). The turnover frequency (TOF) of 4-methylbenzylamine oxidation is found to be 1522 h–1, which is considerably higher than that conventional gold catalysts. The gold nanoclusters present good recyclability and stability for the oxidation of a wide range of amines. The superior activity of the photocatalyst is associated with its unique electronic structure and framework. The catalytically active sites are deemed to be the exposed gold atoms upon detaching protecting ligands: i.e., PPh3. The Hammett parameter suggests that the photocatalytic process involves the formation of carbocation intermediate species. Further, Au–H species were confirmed by TEMPO (2,2,6,6-tetramethylpiperidinyloxy) as a trapping agent.

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-clusters/ceria) in the ethylene methoxycarbonylation (EMC) reaction in the absence of acid promoter. The catalyst offers 92% yield of MP with TOF of 8666 h, which is about 2.5 times of homogeneous Pd catalyst (∼3500 h). The interfacial Lewis acid-base pair [Ru-O-Ce-Vö], which consists of acidic Ce-Vö (oxygen vacancy) site and basic interfacial oxygen of Ru-O-Ce linkage, acts as active site for the dissociation of methanol and the subsequent transfer of hydrogen to the activated ethylene, which is the key step in acid-promoter-free EMC reaction. The combination of H MAS NMR, pyridine-IR and DFT calculations reveals the hydrogen species derived from methanol contains Brönsted acidity. The EMC reaction mechanism under acid-promoter-free condition over Ru-clusters/ceria catalyst is discussed.

Gold nanoparticles supported on ceria{110} crystal planes were more reactive than on ceria{111} and {100} in the oxidative dehydrogenation of alcohols. Kinetic analysis and a Hammett plot suggest that hydride transfer is involved, and the cationic gold is catalytically active.

Elevated serum levels of both total and allergen-specific immunoglobulin E (IgE) correlate with atopic diseases such as allergic rhinitis and allergic asthma. Neutralization of IgE by anti-IgE antibodies can effectively treat allergic asthma. Preclinical studies indicate that targeting membrane IgE-positive cells with antibodies against M1 prime can inhibit the production of new IgE and significantly reduce the levels of serum IgE. We report results from two trials that investigated the safety, pharmacokinetics, and activity of quilizumab, a humanized monoclonal antibody targeting specifically the M1 prime epitope of membrane IgE, in subjects with allergic rhinitis (NCT01160861) or mild allergic asthma (NCT01196039). In both studies, quilizumab treatment was well tolerated and led to reductions in total and allergen-specific serum IgE that lasted for at least 6 months after the cessation of dosing. In subjects with allergic asthma who were subjected to an allergen challenge, quilizumab treatment blocked the generation of new IgE, reduced allergen-induced early and late asthmatic airway responses by 26 and 36%, respectively, and reduced allergen-induced increases in sputum eosinophils by ~50% compared with placebo. These studies indicate that targeting of membrane IgE-expressing cells with anti-M1 prime antibodies can prevent IgE production in humans.

Selective cleavage of C-C bond is pursued as a useful chemical transformation method in biomass utilization. Herein, we report a hybrid CuO x /ceria/anatase nanotubes catalyst in the selective oxidation of C-C bond under visible light irradiation. Using lignin β-1 model as substrate offers 96% yields of benzaldehydes.Characterized results by high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectroscopy-element

Defect chemistries of metal-doped CeO 2 catalysts have attracted extensive scientific interests in heterogeneous catalysis. Here, we report the structure−activity relationship of CeO 2 catalysts doped by Pr. The Pr-doped CeO 2 solid solution catalysts were prepared by a coprecipitation method and evaluated in Prins condensation−hydrolysis of isobutene with formalin to 3-methyl-1,3-butanediol. Raman and infrared (IR) spectroscopies were used to characterize the defect sites of the catalysts. Pr creates two kinds of defects in Pr-doped CeO 2 : oxygen vacancy and lattice distortion (Pr 3+ O 8 -type complex, which was confirmed by the Raman and XPS spectra), whose concentrations depend on the Pr doping amount. The relationship between defect properties (type and concentration) and their catalytic consequence is established. The catalytic performance significantly depends on the oxygen vacancy concentration in Pr-doped CeO 2 catalysts. This study also shows that a Pr 3+ O 8 -type complex has little effect on the catalytic performance, indicating that the Pr 3+ O 8 -type complex is a spectator during the reaction. DFT calculations have indicated that the oxygen vacancy induced by the Pr dopant on a CeO 2 surface promotes the adsorption of HCHO and inhibits the adsorption of isobutene, suggesting the condensation of HCHO and isobutene occurs via an Eley−Rideal (ER) mechanism.