The effect of crystal size of HMOR from micro size to 50 nm, with the apparent similar acid site density, on catalytic performance for the dimethyl ether (DME) carbonylation was investigated. The crystal size of HMOR is sensitive to the deactivation rate of DME carbonylation reaction, and the higher stability around 200 nm can be achieved. The characterization studies reveal that the diffusions of MA product play a key role during the induction and deactivation period in DME carbonylation. These will be helpful for guiding the large-scale synthesis of mordenite zeolites catalysts with high efficiencies for DME carbonylation.
Dorsal hand defects accompanied by exposure of bones and tendons remain a huge challenge for plastic surgeons. The pedicled perforator flaps have unique advantages in resurfacing the defects. This study aimed to investigate the clinical efficacy of the sequential posterior interosseous artery perforator flap for repairing dorsal hand defects. This study was composed of an anatomical study and clinical application. Anatomically, 30 adult upper limb specimens injected with red latex were dissected, the perforators from the branches of the posterior interosseous artery were observed in the dorsal forearm, and the sequential flap based on them was designed based on the anatomical characteristics. Clinically, nine cases of soft tissue defects on the dorsum of the hand were treated by this flap. Anatomically, the posterior interosseous artery divided into an ascending branch and a descending branch, and the descending branch traveled 1.0 ± 0.3 cm down to divide into the ulnar and radial terminal branches. The ulnar terminal branch presented constantly, and the radial terminal branch had an occurrence rate of 93.33%. Clinically, all flaps survived completely and possessed a soft texture and satisfactory appearance, as well as a nonbloated pedicle, and the donor region had a natural color and appearance with only a linear scar left behind. The sequential posterior interosseous artery perforator flap could become a useful option for repairing dorsal hand defects, as it has the advantages of being easy to perform without sacrificing the main vessels and avoiding donor area skin grafting.
To improve the flavor of Ostrea rivularis Gould, enzymatic hydrolysis was conducted and xylose-OEH Maillard reaction products were prepared. Then, their physicochemical properties and metabolites were determined by UHPLC-MS-MS, and volatile compounds were determined by GC-MS to investigate the changes. The results showed that His, Gln, Lys, Asp, and Cys were the major amino acids consumed. After being heated at 120 °C for up to 150 min, the DPPH (2,2-Diphenyl-1-picrylhydrazyl) was 85.32 ± 1.35% and the reducing capacity was 1.28 ± 0.12. Both were the highest in the groups. Additionally, 45 volatile compounds, including 2-ethyl-5-methyl-pyrazine and 2-ethyl-3,5-dimethyl-pyrazine, and 678 compounds were identified. We also found that 18 metabolites with significant differences (VIP ≥2) were differential metabolites, which involved lipid oxides and amino acid derivatives. The content of lipids favored the regulation of Maillard products and affected the lower threshold of the flavor of aldehydes, which contributed to the flavor and antioxidant activity. These results suggested the potential of xylose-OEH MRPs as a natural antioxidant for further processing oysters.
The selective conversion of methane to high value-added chemicals under mild conditions is of great significance for the commercially viable and sustainable utilization of methane but remains a formidable challenge. Herein, we report a strategy for efficiently converting methane to acetic acid via CH3 Cl as an intermediate. Up to 99.3 % acetic acid and methyl acetate (AA+MA) selectivity was achieved over pyridine-pretreated MOR (MOR-8) under moderate conditions of 523 K and 2.0 MPa. Water, conventionally detrimental to carbonylation reaction over zeolite catalysts, was conducive to the production of AA in the current reaction system. In the 100 h continuous test with the MOR-8 catalyst, the average AA+MA selectivity remained over 98 %. AA was formed by carbonylation of methoxy groups within 8-membered rings of MOR followed by hydrolysis. This strategy provided an approach for highly efficient utilization of methane to oxygenates under mild reaction conditions.
The conversion of methanol into aromatics over unmodified H-ZSM-5 zeolite is generally not high because the hydrogen transfer reaction results in alkane formation. Now circa 80 % aromatics selectivity for the coupling reaction of methanol and carbon monoxide over H-ZSM-5 is reported. Carbonyl compounds and methyl-2-cyclopenten-1-ones (MCPOs), which were detected in the products and catalysts, respectively, are considered as intermediates. The latter species can be synthesized from the former species and olefins. 13 C isotope tracing and 13 C liquid-state NMR results confirmed that the carbon atoms of CO molecules were incorporated into MCPOs and aromatic rings. A new aromatization mechanism that involves the formation of the above intermediates and co-occurs with a dramatically decreased hydrogen transfer reaction is proposed. A portion of the carbons in CO molecules are incorporated into aromatic, which is of great significance for industrial applications.
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