Pd-based egg-shell nano-catalysts were prepared using porous hollow silica nanoparticles （PHSNs） as support, and the as-prepared catalysts were modified with TiO2 to promote their selectivity for hydro-genation of acetylene. Pd nanoparticles were loaded evenly on PHSNs and TiO2 was loaded on the active Pd particles. The effects of reduction time and temperature and the amount of TiO2 added on catalytic per-formances were investigated by using a fixed-bed micro-reactor. It was found that the catalysts showed better performance when reduced at 300 ℃ than at 500℃, and if reduced for 1 h than 3 h. When the amount of Ti added was 6 times that of Pd, the catalyst showed the highest ethylene selectivity.
Irbesartan （IBS）, an angiotensin II receptor antagonist, is a poorly water-soluble drug. To enhance the dis- solution rate, IBS nanocomposite particles were produced via an anti-solvent precipitation combined with a spray drying process. Four pharmaceutically acceptable excipients, including three different polymers and one charged surfactant, were evaluated as stabilizers to control the particle size and to prevent the agglomeration of particles. The experiment results indicated that polyvinylpyrrolidone （PVP） combined with sodium dodecyl sulfate （SDS） significantly decreased the particle size and enhanced the stability of drug nanoparticles. As a result, we finally obtained stable IBS nanoparticles with an average size of approx- imately 55 nm. In the dissolution test, the IBS nanocomposite particles showed a significantly enhanced dissolution rate and 100% of the drug dissolved within 20 rain. In contrast, the physical mixture with the same recipe as the IBS nanocomposite particles and the raw 1BS reached only 8% and 40% of drug dissolved in 20 rain, respectively, and both of them did not dissolve completely, even after 120 rain.
Precipitation of BaSO4 nanoparticles was studied for the first time in a specially designed rotating packed bed （RPB）, which allowed sampling at different radial positions to provide better insight of the mechanism of precipitation in RPB. Particle size and morphology were characterized by TEM, while the quality of synthesized BaSO4 powders was analyzed by XRD and BET, and compared with those prepared in a stirred-tank reactor. The important role of the inlet region of the RPB in the whole precipitation process was experimentally confirmed, as a significant essence for the design of industrial RPB for the precipitation of sparingly soluble materials. The effects of different operating conditions on particle size were also investigated, showing that particle size decreases with increasing rotational speed and liquid flow rate, due to the enhancement of micromixing in the RPB.
Yang Xiang Guangwen Chu Lixiong Wen Kuang Yang Guangting Xiao Jianfeng Chen
Mesoporous silica microspheres with multi-hollow cores （MSMMCs） were prepared by an O1/W/O2 double emulsion technique. When tetraethyl orthosilicate （TEOS） was hydrolyzed in the O1/W/O2 double emulsion with P123 （a triblock copolymer with a formula of HO（CH2CH20）20（CH2CH（CH3）O）70（CH2CH2O）20H） dissolved in the aqueous phase, the internal oil droplets would serve as templates for the empty hollow cores, P123 function as templates for the mesopores in the shell, and the aqueous phase act as space-limiting micro-reactors for the hydrolysis process, thus forming MSMMCs with controllable size and hollow cores. After further modification by a high-temperature aging process, the prepared MSMMCs had a diameter of 2-10 μm, with macromulti-hollow cores with a size of 100-1000 nm, mesopores in the shell with a size of 3.8-4.4 nm, and a surface area of 383-735 m2/g. In addition, MSMMCs were used as carriers to load avermectin through an immersing and evaporating process, and the loaded avermectin showed a well sustained release behavior from the MSMMCs matrix. This study demonstrated a promising and simple method for preparing silica micro-particles with porous multi-hollow core structure for sustained release applications.
