Heike Ehrich

Application of microstructured reactor technology for the photochemical chlorination of alkylaromatics

The advantageous application of a falling-film microreactor for a photochemical gas/liquid reaction was demonstrated by the selective photochlorination of toluene-2,4-diisocyanate (TDI) In the microstructured reactor the selectivity to the side-chain chlorinated product 1 -chloromethyl-2,4-diisocyanatobenzene (1CI-TDI) achieved a value of 80% at 55% TDI conversion, whereas the side product toluene-5-chloro-2,4-diisocyanate (5CI-TDI) was formed with only 5% selectivity. The yield of 1CI-TDI was enhanced by increasing the residence time from 24% after 5 s to 54% after 14 s. At the same time the formation of consecutive products increased and the selectivity to 1CI-TDI decreased to 67% after 14 s residence time. The influence of the reactor material was shown. In presence of a Lewis acid such as FeCl 3 , formed by chlorination using a reaction plate made of iron, consecutive products were formed and the selectivity to 1CI-TDI was lowered. The microstructured reactor led to remarkably higher selectivities than the conventional batch reactor, where the selectivity to 1CI-TDI was only 45% at 65% TDI conversion and the side product 5CI-TDI was formed with 50% selectivity. The space-time yield of 1CI-TDI achieved in the microstructured reactor (400 mol I - 1 h - 1 ) clearly exceeded the performance of the batch reactor (space-time yield 1.3 mol I - 1 h - 1 ). Based on the microreactor data, a kinetic model for the TDI chlorination including by-product formation was suggested and used to predict product selectivity at full TDI conversion.

Effect of Al2O3/ZnO Ratio on Ni(Co)–AlZnOx Catalysts for Syngas Production by Steam Reforming of Acetic Acid

Co- and Ni-based catalysts supported on AlZnOx were prepared using two different Al2O3/ZnO molar ratios in order to study the effect on syngas production by steam reforming of acetic acid. The catalytic properties analyzed by in-situ XRD, TEM, and TPR demonstrated that their composition affects the catalytic performance.Graphical Abstract

AlZn based Co and Ni catalysts for the partial oxidation of bioethanol — influence of different synthesis procedures

The catalytic performance of Co and Ni catalysts on AlZn mixed oxide supports depends on the synthesis procedure used for their preparation. For this study CoAlZn and NiAlZn catalysts were prepared by conventional sol-gel synthesis of the mixed oxide and subsequent impregnation of the support with the transition metal (SG = sol gel method) as well as by a single-step method were a gel is formed based on salts of all components using citric acid as chelating agent (CM = citrate method). The structure and morphology of the catalysts were characterized by nitrogen sorption, XRD and TPR measurements. They showed high activity in the partial oxidation of ethanol at 600–750 °C, but their properties depend on the preparation method. The higher performance of the catalysts prepared by the citrate method, where the transition metal is incorporated into the crystal structure of the support during preparation, is based on a change in morphology and structure, resulting in more active sites exposed on the surface. Compared to the Co catalysts, Ni catalysts showed a higher performance. This might be due to the higher reducibility and the smaller Ni particles size, which allows a better interaction with the support in NiAlZn catalysts.

Syngas production by catalytic reforming of renewables for power generation in solid oxide fuel cells

Ni and Co as active metals, supported on Al2O3, ZnO and AlZnOx were tested in partial oxidation and the steam reforming processes. The effect of catalysts for syngas production by catalytic reforming of bioethanol and acetic acid for power generation of SOFC was studied. Single supported Ni or Co catalysts, showed high activity but different product distribution. The Al2O3 supported catalysts were quickly deactivated by carbon deposition because of ethylene and acetone formation over the strong acidic sites of alumina. The ZnO supported catalysts showed a remarkable higher syngas productivity compared to the Al2O3 supported samples. The catalysts supported over mixed oxide, showed higher activity in partial oxidation and the steam reforming in comparison to single oxide samples. In partial oxidation of ethanol NiAlZnOx sample was more active, however in steam reforming of acetic acid CoAlZnOx sample showed better performance. In situ XRD study of ZnO and AlZnOx supported samples showed that both series have similar phase composition, which is determined by the properties of ZnO, especially its oxygen mobility at high temperature. Alloy structure formation and the reduction of active metals under the reaction conditions provided high performance of these catalysts in partial oxidation and steam reforming with high production to syngas.