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In oxidative esterification of methacrolein to methyl methacrylate, mass transfer of O2 and N2 in methanol is of vital importance for the determination of reaction kinetics and design of industrial units. The mass transfer coefficients kL of O2 and N2 in methanol were determined by the decreasing‐pressure method in a gas‐liquid stirred reactor at temperatures ranging from 298.15 to 333.15 K, pressures ranging from 0.5 to 1.2 MPa, and agitation speeds ranging from 100 to 200 rpm. It could be shown that kL‐O2 and kL‐N2 increased with increasing temperature and agitation speed, but did not change significantly with partial pressure. On the basis of the experimental results, theoretical and empirical equations were proposed. This work provides an example of a study on the mass transfer of gases in a liquid. [ABSTRACT FROM AUTHOR]

It is challenging to produce methyl methacrylate with high yield using direct oxidative esterification of methacrolein with methanol under oxygen atmosphere, and the key factor is the development of high-efficient and long-life supported Pd catalyst. In order to get the excellent catalyst, the effect of main influencing factors, such as promoters, supports, Pd precursors and reduction agents, on the catalyst structure and the catalytic performance were systematically studied. The results of the analysis indicated that the addition of promoters Pb to Pd crystallites catalyst, made the formation of new active bimetallic Pd 3 Pb crystallites, which could improve the catalytic activity; supports with different components and physico-chemical properties had great influence on the size of bimetallic Pd 3 Pb crystallites; different Pd precursors had different adsorption mechanisms on the support which affected the dispersion of Pd; reductant and reduction temperature affected the size of Pd 3 Pb crystallites. These studies are important clues for developing the new and cheap catalyst for this kind of direct oxidative esterification reactions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Deactivation of Pd–Pb catalyst in the repeated batch reactions was investigated. [•] Deactivation is associated with deposition of organic substances on catalyst. [•] Washing the deactivated catalyst with MeOH could completely recover the activity. [•] There was no distinct deactivation of the activity in continuous-flow reaction. [ABSTRACT FROM AUTHOR]

MDH-7 (2,3,9-tri- O -acetyl-5,6-dideoxy-1,10-di-[N4′-pentoxycarbonyl-5′-fluoro cytosine]-4-ulose 1,4: 7,10-difuranose-4,8-pyranose) is a novel anti-tumor drug candidate. To study the pharmacokinetic interaction between MDH-7 and 5-fluorouracil (5-FU), a sensitive and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to simultaneously determine the concentrations of MDH-7 and 5-fluorouracil (5-FU) in rat plasma. Plasma samples were prepared by simple liquid-liquid extraction with ethyl acetate. Chromatographic separation was performed on a Waters XBridge™ C18 column (5 μm, 2.1 mm × 150 mm) with the mobile phase of methanol and H 2 O (80:20, v/v). The ESI positive and negative ion switch was operated in the multiple reactions monitoring (MRM) mode. The calibration curves showed good linearity (r 2  > 0.99) over the ranges of 50–8000 ng/mL for MDH-7 and 10–2000 ng/mL for 5-FU, respectively. The lower limit of quantitations (LLOQs) was 50 ng/mL (MDH-7) and 10 ng/mL (5-FU) with relative standard deviation (RSD) < 13.0%. The proposed method was successfully applied to simultaneous assessment of pharmacokinetic drug-drug interaction between MDH-7 and 5-FU in rats. [ABSTRACT FROM AUTHOR]