In heterogeneous catalysis, supports play a crucial role in modulating the geometric and electronic structure of the active metal phase for optimizing the catalytic performance. A γ‐Al2O3 nanosheet ...that contains 27 % pentacoordinate Al3+ sites can nicely disperse and stabilize raft‐like Pt‐Sn clusters as a result of strong interactions between metal and support. Consequently, there are strong electronic interactions between the Pt and Sn atoms, resulting in an increase in the electron density of the Pt sites. When used in the propane dehydrogenation reaction, this catalyst displayed an excellent specific activity for propylene formation with >99 % selectivity, and superior anti‐coking and anti‐sintering properties. Its exceptional ability to maintain the high activity and stability at ultrahigh space velocities further showed that the sheet construction of the catalyst facilitated the kinetic transfer process.
Stable and selective: γ‐Al2O3 nanosheets rich in pentacoordinate Al3+ ions can well disperse and stabilize raft‐like Pt‐Sn clusters, which results in an increase of the electron density of the Pt sites. This material catalyzes the conversion of propane into propylene with >99 % selectivity, and minimizes coke formation and sintering processes.
The dehydrogenation of ethanol to acetaldehyde is of great importance in synthetic chemistry and the fine chemical industry. In this study, we report that a mesoporous‐carbon‐supported Cu catalyst ...exhibited a high reaction rate and excellent product selectivity in ethanol dehydrogenation to acetaldehyde. Under the severe conditions of an ethanol concentration of 15 vol % and a gaseous hourly space velocity of 8 600 h−1, the Cu‐based carbon catalyst maintains a conversion of ≈73 % and an acetaldehyde selectivity of ≈94 % at 553 K. Meanwhile, a prominent space time yield (225 h−1) of acetaldehyde is obtained, which is far higher than that (112 h−1) on the mesoporous‐SBA‐15‐supported Cu catalyst. Ethanol adsorption studies prove that the enrichment of the carbon support for reactants makes a contribution to the high reaction rate. Importantly, kinetic measurements indicate that the scarce surface groups of the mesoporous carbon support minimize the secondary reactions of acetaldehyde, which are generally catalyzed by OH and/or COOH on the surface of the support as exemplified by the mesoporous‐SBA‐15‐supported Cu catalyst. This accounts for the excellent selectivity toward acetaldehyde on the mesoporous‐carbon‐supported Cu catalyst. Therefore, these surface characteristics of the carbon support show great advantages in this dehydrogenation reaction.
Blessing in disguise: The relatively inert nature and strong enrichment towards ethanol of the carbon support increase the product selectivity and reaction rate in ethanol dehydrogenation to acetaldehyde over a Cu‐based mesoporous carbon catalyst.
In heterogeneous catalysis, supports play a crucial role in modulating the geometric and electronic structure of the active metal phase for optimizing the catalytic performance. A γ-Al2O3 nanosheet ...that contains 27% pentacoordinate Al(3+) sites can nicely disperse and stabilize raft-like Pt-Sn clusters as a result of strong interactions between metal and support. Consequently, there are strong electronic interactions between the Pt and Sn atoms, resulting in an increase in the electron density of the Pt sites. When used in the propane dehydrogenation reaction, this catalyst displayed an excellent specific activity for propylene formation with >99% selectivity, and superior anti-coking and anti-sintering properties. Its exceptional ability to maintain the high activity and stability at ultrahigh space velocities further showed that the sheet construction of the catalyst facilitated the kinetic transfer process.
Lewis‐acid properties of the coordinatively unsaturated metal ions are highly relevant to the coordination environment; however, it remains a challenge to establish the coordination ...structure‐activity relationship, especially in heterogeneous catalysis. Here, a typical metal‐organic framework, ZIF‐8, is selected as the precursor to prepare Lewis‐acid based Zn−N/P−C mononuclear catalysts, with well‐designed external structures but difference in the local coordination. The obtained mononuclear Zn(II) catalysts can not only inherit the advantages of MOF in coordination, but also simulate the homogeneous environment during the catalysis owing to the monodispersed metal sites in ZIF‐8. Eventually, relation between coordination and Lewis‐acid property toward epoxide hydroxylation has been illustrated. Results show the substituted coordination atom of P and the decrease of coordination number strongly enhance the Lewis‐acidity of Zn2+, causing the TOF values changes from 8.7 to 80.1 h−1 based on Zn content. The work affords an understanding and inspiration of coordination environment matters toward Lewis‐acid catalysis in organic transformations.
Metal‐organic frameworks: Zn‐centered mononuclear catalysts with tuned N/Zn and P/Zn molar ratios have been obtained through calcination in the presence of defect modulators. The samples possess local structure of ZnNxPy. The decrease of coordination numbers in Nx, and the substitution by coordination atom of P, synergistically promote the Lewis acidity of Zn2+, leading to the enhancement of catalytic performance from 8.7 h−1 for ZIF‐8‐700 to 80.1 h−1 for ZIF‐8‐P‐900.
Biofabrication of nanomaterials is currently constrained by a low production efficiency and poor controllability on product quality compared to chemical synthetic routes. In this work, we show an ...attractive new biosynthesis system to break these limitations. A directed production of selenium-containing nanoparticles in Shewanella oneidensis MR-1 cells, with fine-tuned composition and subcellular synthetic location, was achieved by modifying the extracellular electron transfer chain. By taking advantage of its untapped intracellular detoxification and synthetic power, we obtained high-purity, uniform-sized cadmium selenide nanoparticles in the cytoplasm, with the production rates and fluorescent intensities far exceeding the state-of-the-art biosystems. These findings may fundamentally change our perception of nanomaterial biosynthesis process and lead to the development of fine-controllable nanoparticles biosynthesis technologies.
Aromatic alcohols are essential components of many solvents, coatings, plasticizers, fine chemicals, and pharmaceuticals. Traditional manufacturing processes involving the oxidation of ...petroleum-derived aromatic hydrocarbons suffer from low selectivity due to facile overoxidation reactions which produce aromatic aldehydes, acids, and esters. Here we report a Co-containing hydroxyapatite (HAP) catalyst that converts ethanol directly to methylbenzyl alcohols (MB–OH, predominantly 2-MB–OH) at 325 °C. The dehydrogenation of ethanol to acetaldehyde, which is catalyzed by Co2+, has the highest reaction barrier. Acetaldehyde undergoes rapid, HAP-catalyzed condensation and forms the key intermediate, 2-butenal, which yields aromatic aldehydes through self-condensation and then MB–OH via hydrogenation. In the presence of Co2+, 2-butenal is selectively hydrogenated to 2-butenol. This reaction does not hinder aromatization because cross-coupling between 2-butenal and 2-butenol leads directly to MB–OH without passing through MBO. Using these insights a dual-bed catalyst configuration was designed for use in a single reactor to improve the aromatic alcohol selectivity. Its successful use supports the proposed reaction mechanism.
Cisplatin-based concurrent chemoradiotherapy is currently considered to be the standard treatment regimen for patients with advanced nasopharyngeal carcinoma, but has well known side-effects such as ...gastrointestinal reactions, nephrotoxicity, and ototoxicity. Nedaplatin was developed to decrease the toxic effects induced by cisplatin, and in this trial we assessed whether a nedaplatin-based concurrent chemoradiotherapy regimen was non-inferior to a cisplatin-based regimen in patients with locoregional, stage II–IVB nasopharyngeal carcinoma.
We did an open-label, non-inferiority, phase 3, randomised, controlled trial at two centres in China. Patients aged 18–65 years with non-keratinising stage II–IVB (T1–4N1–3 or T3–4N0) nasopharyngeal carcinoma, a Karnofsky score of at least 70, and adequate haematological, renal, and hepatic function were randomly assigned (1:1) to receive intravenously either nedaplatin 100 mg/m2 or cisplatin 100 mg/m2 on days 1, 22, and 43 for three cycles concurrently with intensity-modulated radiotherapy. Randomisation was done manually using a computer-generated random number code and patients were stratified by treatment centre and clinical stage. Patients and clinicians were not masked to treatment allocation. The primary endpoint was progression-free survival at 2 years; non-inferiority was shown if the upper limit of the 95% CI for the difference in 2-year progression-free survival between the two groups did not exceed 10%. Analyses were by both intention to treat and per protocol, including all patients who received at least one complete cycle of chemotherapy. This trial is registered with ClinicalTrials.gov, number NCT01540136, and is currently in follow-up.
Between Jan 16, 2012, and July 16, 2014, we randomly assigned 402 patients to nedaplatin-based (n=201) or cisplatin-based (n=201) concurrent chemoradiotherapy. In the intention-to-treat population, 2-year progression-free survival was 89·9% (95% CI 85·8–94·0) in the cisplatin group and 88·0% (83·5–94·5) in the nedaplatin group, with a difference of 1·9% (95% CI −4·2 to 8·0; pnon-inferiority=0·0048). In the per-protocol analysis (cisplatin group, n=197; nedaplatin group, n=196), 2-year progression-free survival was 89·7% (95% CI 85·4–94·0) in the cisplatin group and 88·7% (84·2–94·5) in the nedaplatin group, with a difference of 1·0% (95% CI −5·2 to 7·0; pnon-inferiority=0·0020). A significantly higher frequency of grade 3 or 4 vomiting (35 18% of 198 in the cisplatin group vs 12 6% of 200 in the nedaplatin group, p<0·0001), nausea (18 9% vs four 2%, p=0·0021), and anorexia (53 27% vs 26 13%, p=0·00070) was observed in the cisplatin group compared with the nedaplatin group. 11 (6%) patients in the nedaplatin group had grade 3 or 4 thrombocytopenia compared with four (2%) in the cisplatin group (p=0·065). Patients in the cisplatin group had a higher frequency of any grade or grade 3 or 4 late auditory or hearing toxicities than did patients in the nedaplatin group (grade 3 or 4: three 2% in the nedaplatin group vs 11 6% in the cisplatin group, p=0·030). No patients died from treatment-related causes.
Our findings show that nedaplatin-based concurrent chemoradiotherapy represents an alternative doublet treatment strategy to cisplatin-based concurrent chemoradiotherapy for patients with locoregional, advanced nasopharyngeal carcinoma. Further investigations are needed to explore the potential use of this treatment as induction or adjuvant chemotherapy or in combination with other agents.
National Key R&D Program of China, National Natural Science Foundation of China, Sun Yat-sen University Clinical Research 5010 Program, Sci-Tech Project Foundation of Guangzhou City, National Key Basic Research Program of China, Special Support Plan of Guangdong Province, Sci-Tech Project Foundation of Guangdong Province, Health & Medical Collaborative Innovation Project of Guangzhou City, National Science & Technology Pillar Program during the Twelfth Five-year Plan Period, PhD Start-up Fund of Natural Science Foundation of Guangdong Province, Cultivation Foundation for the Junior Teachers in Sun Yat-sen University, and Fundamental Research Funds for the Central Universities.
Understanding the synergy of Cu0 and Cu+ in hydrogenation reactions is indispensable for reasonably modulating the product distributions and improving the catalyst design. Herein, we investigated the ...hydrogenation of dimethyl oxalate on CeZrO x -supported Cu with varying molar ratios of n Cu +/n Cu 0. A volcano-type correlation of structure and activity indicates that the selectivity of ethylene glycol is strongly dependent on the n Cu +/n Cu 0 ratio, arising from the matching of rates for the activation of carbonyl group-included reactants and H2 on Cu+ and Cu0, respectively. The maximal selectivity toward ethylene glycol is achieved at a ratio of 0.15; deviating from this value leads to the favorable formation of methyl glycolate, a primary product. Results obtained from temperature-programmed surface reactions indicate that the presence of Cu+ and oxygen vacancies (OV) reduces the reaction temperature for the hydrogenation of carbonyl groups. Theoretical data show that the OV located at the copper–ceria interface induces a downward-directed adsorption configuration of the reaction intermediate adsorbed at the Cu+ site, compared to the presence of an upward-directed counterpart at the Cu0–Cu+ center. This change leads to a reduction in the kinetic barrier for the subsequent hydrogenation step, which consumes active *H species transferred from adjacent Cu0 via a hydrogen spillover process. Manipulating the Cu valence state and oxygen vacancies via interfacial engineering offers a viable strategy for governing product distributions, serving as an inspiration for the design of selective hydrogenation catalysts.
The crystal facets of semiconductors often have critical effects on photocatalytic reactions. The spatial charge separation between different facets in TiO2 reveals a preferential accumulation of ...photogenerated holes on the {001} facet; thereby, the activation of the C–H bond predominantly occurs on the {001} facet. However, the dissociative adsorption of initially generated p-methylbenzyl alcohol (p-MBY) forms alcoholate species, which impedes the interaction between p-xylene and the {001} facet, and thus blocks the photocatalytic reaction of p-xylene oxidation on {001}-72%. On the other hand, H3PO4 predominantly adsorbs on the {001} facet, with an adsorption energy higher than p-MBY (−5.15 vs −3.90 eV). Therefore, adding H3PO4 can prevent the dissociative adsorption of p-MBY on the {001} facet. The addition of H3PO4 also significantly improves the injection efficiency of photogenerated holes into p-xylene and suppresses the generation of ·O2 2–, thereby enhancing the conversion and selectivity. Consequently, the addition of H3PO4 obtains a selectivity as high as 94.8% to the primary products at 15.2% conversion on {001}-72%. The results demonstrate that facet engineering for a semiconductor-based photocatalyst can regulate the charge separation, charge injection, and adsorption behavior of intermediates, which is an effective strategy to accomplish high performance of photocatalytic reactions.
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•p-Methyl benzaldehyde and p-methylbenzyl alcohol are both initial products.•The COx is mainly generated by the combustion of p-methylbenzyl alcohol.•WOx terminates the COx generation ...by weakening adsorption of p-methylbenzyl alcohol.•WOx suppresses the formation of O2–, which is the main cause of overoxidation.
Photocatalytic selective oxidation of p-xylene with O2 offers a mild pathway to synthesize p-methyl benzaldehyde (p-MBA), which is one of the primary precursors in the manufacture of fine chemicals. Here, we report that Au/WOx/TiO2 photocatalyst selectively catalyzes the oxidation of p-xylene to p-MBA with 88.6% selectivity at 1.0% conversion, the formation of COx is suppressed to 0.8%. Kinetic experiments indicate that p-methylbenzyl alcohol and p-MBA are initial products. p-Methylbenzyl alcohol is further oxidized to form p-MBA, p-methylbenzyl acid and COx; p-MBA is further oxidized to p-methylbenzyl acid and COx. On TiO2 surface, p-methylbenzyl alcohol is more prone to directly combust to COx by O2–. Loading of WOx can weaken the adsorption ability of p-methylbenzyl alcohol on the catalyst surface to avoid the combustion. Meanwhile, WOx and Au can facilitate the separation of photo-generated carriers to attain high activity and suppress the O2– formation to obtain high selectivity.
