The oxidation of TiN in an oxygen flow at temperatures in the range 300-500·C has been studied by means of soft x-ray absorption spectroscopy. The analysis of the experimental results indicates that 0 progressively displaces N to form Ti0 2 . The process appears to be controlled by the temperature dependence of the oxygen diffusion. Some oxidation is observed to take place even at room temperature. No evidence of oxynitride formation was found in thermally oxidized TiN, instead complete phase separation is observed. The interface between Ti0 2 and TiN seems to be very abrupt. The appearance of a sharp absorption peak in the N Is spectrum of TiN is believed to be due to nitrogen atoms which are displaced during the oxidation process and remain unbounded within the Ti0 2 matrix. For temperatures above 400 ·C, this peak disappears as the interstitial N atoms migrate to the surface and desorb.

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Biopharmaceutical production processes often use mammalian cells in bioreactors larger than 10,000 L, where gradients of shear stress, substrate, dissolved oxygen and carbon dioxide, and pH are likely to occur. As former tissue cells, producer cell lines such as Chinese hamster ovary (CHO) cells sensitively respond to these mixing heterogeneities, resulting in related scenarios being mimicked in scale-down reactors. However, commonly applied multicompartment approaches comprising multiple reactors impose a biasing shear stress caused by pumping. The latter can be prevented using the single multicompartment bioreactor (SMCB) presented here. The exchange area provided by a disc mounted between the upper and lower compartments in a stirred bioreactor was found to be an essential design parameter. Mimicking the mixing power input at a large scale on a small scale allowed the installation of similar mixing times in the SMCB. The particularities of the disc geometry may also be considered, finally leading to a converged decision tree. The work flow identifies a sharply contoured operational field comprising disc designs and power input to install the same mixing times on a large scale in the SMCB without the additional shear stress caused by pumping. The design principle holds true for both nongassed and gassed systems.

Dedicated to Professor Rüdiger Lange on the occasion of his 65th birthdayThe oxidation of n-butane to maleic anhydride over an industrial vanadyl pyrophosphate oxide catalyst was investigated experimentally in millistructured reactors with varying slit widths to investigate the process intensification potential of this reaction. Although the smaller reactor behaved isothermally, even in the presence of high n-butane concentrations, moderate hot spots never exceeding more than 15 K above the salt bath temperature occurred in the larger catalyst channel. After exposure to high n-butane concentrations, a certain amount of catalyst deactivation was observed, which could be partly restored through reoxidation with pure oxygen. The reactor-specific maleic anhydride productivities obtained are much larger than those in conventional multitubular reactors.

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