Environmental Impact Evaluation for Heterogeneously Catalysed Starch Oxidation.

Oxidised starch is currently produced from native starch using sodium hypochlorite as an oxidising agent. The use of hypochlorite has undesired side reactions and produces stoichiometric amounts of waste (salt), thus alternative oxidation methods are desired. In this study, the potential of two catalysed starch oxidation methods to reduce the environmental impact (EI) of oxidised starch production are assessed. We compared the EI of oxidation with molecular oxygen (heterogeneously catalysed) and hydrogen peroxide (homogeneously catalysed) to hypochlorite oxidation through life cycle assessment (LCA). The results confirm that hypochlorite oxidation is the main environmental hotspot in the current process of oxidised starch production, and that both hydroperoxide oxidation and molecular oxygen oxidation can significantly lower the EI of the process. The impact reduction is most significant in the categories of freshwater eutrophication (∼67 %), ozone depletion (∼66 %), climate change (35-60 %) and resource use (40 %-78 %) for peroxide and molecular oxygen oxidation, respectively.

Coatings of active and heat-resistant cobalt-aluminium xerogel catalysts.

The application of catalytically coated metallic foams in catalytic processes has a high potential for exothermic catalytic reactions such as CO2 methanation or Fischer-Tropsch synthesis due to good heat conductivity, improved turbulent flow properties and high catalyst efficiencies. But the preparation of homogenous catalyst coats without pore blocking is challenging with conventional wash coating techniques. Here, we report on a stable and additive free colloidal CoAlOOH suspension (sol) for the preparation of catalytically active Co/Al2O3 xerogel catalysts and coatings. Powders with 18wt% Co3O4 prepared from this additive free synthesis route show a catalytic activity in Fischer-Tropsch synthesis and CO2 methanation which is similar to a catalyst prepared by incipient wetness impregnation (IWI) after activating the material under flowing hydrogen at 430°C. Yet, the xerogel catalyst exhibits a much higher thermal stability as compared to the IWI catalyst, as demonstrated in catalytic tests after different heat agings between 430°C and 580°C. It was also found that the addition of polyethylene glycol (PEG) to the sol influences the catalytic properties of the formed xerogels negatively. Only non-reducible cobalt spinels were formed from a CoAlOOH sol with 20wt% PEG. Metallic foams with pores sizes between 450 and 1200µm were coated with the additive free CoAlOOH sol, which resulted in homogenous xerogel layers. First catalytic tests of the coated metal foams (1200µm) showed good performance in CO2 methanation.

Electrodeless dielectrophoresis: Impact of geometry and material on obstacle polarization.

Insulator-based (electrodeless) dielectrophoresis (iDEP) is a promising particle manipulation technique, based on movement of matter in inhomogeneous fields. The inhomogeneity of the field arises because the excitatory field distorts at obstacles (posts). This effect is caused by accumulation of polarization charges at material interfaces. In this study, we utilize a multipole expansion method to investigate the influence of geometry and material on field distortion of posts with arbitrary cross-sections in homogeneous electric fields applied perpendicular to the longitudinal axis of the post. The post then develops a multipole parallel or anti parallel to the excitatory field. The multipoles intensity is defined by the post's structure and material properties and directly influences the DEP particle trapping potential. We analyzed posts with circular and rhombus-shaped cross-sections with different cross-sectional width-to-height ratios and permittivities for their polarization intensity, multipole position, and their particle trapping behavior. A trade-off between high maximum field gradient and high coverage range of the gradient is presented, which is determined by the sharpness of the post's edges. We contribute to the overall understanding of the post polarization mechanism and expect that the results presented will help optimizing the structure of microchannels with arrays of posts for electrodeless DEP application.

Numerical simulation of Electron Energy Loss Spectroscopy using a Generalized Multipole Technique.

We numerically simulate low-loss Electron Energy Loss Spectroscopy (EELS) of isolated spheroidal nanoparticles, using an electromagnetic model based on a Generalized Multipole Technique (GMT). The GMT is fast and accurate, and, in principle, flexible regarding nanoparticle shape and the incident electron beam. The implemented method is validated against reference analytical and numerical methods for plane-wave scattering by spherical and spheroidal nanoparticles. Also, simulated electron energy loss (EEL) spectra of spherical and spheroidal nanoparticles are compared to available analytical and numerical solutions. An EEL spectrum is predicted numerically for a prolate spheroidal aluminum nanoparticle. The presented method is the basis for a powerful tool for the computation, analysis and interpretation of EEL spectra of general geometric configurations.