Nanodiamonds with novel properties: A biological study

This paper discusses the prospects for using modified detonation nanodiamonds with novel properties as a new promising material for the development of nanotechnologies intended for biological and medical purposes. The authors report that nanodiamonds synthesized by detonation can be used to further purify commercial protein preparations and that enzymes adsorbed on diamond nanoparticles retain their activity. The paper presents results of in vivo experiments with nanodiamonds administered to animals via different routes.     

Size distribution of the particles entrained from fluidized beds: Gas humidity effects

Experimental results obtained with 65 μm sand and 69 μm cracking catalyst showed that the smallest particles were not the most easily elutriated from fluidized beds of mixed size particles. This is in contradiction with the assumption applied to existing models for the prediction of the flux and size distribution of particles elutriated from a fluidized bed. The smallest particles cannot be removed by elutriation from a mixture of particles of various sizes. The smallest particles may be agglomerated with larger particles. Increasing the gas humidity, which would presumably reduce electrostatic effects, did not greatly affect the size distribution of the elutriated particles.     

Dynamical modelling of a reactive extrusion process: Focus on residence time distribution in a fully intermeshing co-rotating twin-screw extruder and application to an alginate extraction process

The context of this study is the modelling of reactive extrusion process based on an alginate extraction protocol. Residence Time Distribution (RTD) is one important part to predict the kinetics of reactive compounds. A simple model is proposed to predict RTD in fully intermeshing co-rotating twin-screw extruders without reaction. This model, which can be easily extended to reactive case in a future work, is based on the extension of an axial dispersion model, including control parameters (screw speed and flow rate) and geometrical parameters (screw profile and die design). Simulations were performed for various operating and geometrical conditions so as to illustrate possibilities offered by the proposed model. Validation was conducted for two different extrusion applications, seaweed extrusion and polymer extrusion. This highlighted the model ability to predict RTD for various kinds of materials after adjusting only one parameter thanks to a unique experimental RTD curve.     

Performance limits of isothermal packed bed and perforated monolithic bed reactors operated under laminar flow conditions. I. General optimization analysis

A global optimization analysis of a general class of perforated monolithic bed reactors is presented for the case of an isothermal first-order reaction and for laminar flow conditions. The resulting design rules indicate how a given amount of catalyst material should best be perforated or distributed in space as a function of the available inlet pressure. It is shown that the influence of the different process variables (k,ΔP,V_cata,C_in/C_out,D_mol, S_reac) on the reactor productivity and on the optimal bed design can be grouped into a single dimensionless number E. This number also allows to discuss the sensitive relation between the total and the volumetric productivity of single bed reactors in a very general, compact manner. Two different perforated monolithic bed designs, a slit pore bed (SPB) and a cylindrical pore bed (CPB) are considered. It is found that, when there is an excess inlet pressure (i.e., for E?1), the optimal catalyst layer thickness is given by φ=0.3-0.5 and that the optimal pore diameter is in both cases 1.4-1.45 times smaller than the catalyst layer, independently of the internal catalyst diffusivity (D_int) and the other process variables. When the available inlet pressure is limiting (E>10⁻⁴), and when the absolute reactor productivity is more important than the volumetric productivity, it is found that much more open structures, with much wider pores are needed, i.e., perforated beds show the same behavior as packed beds, where the occurrence of a pressure-drop limitation also induces a shift from the use of full particles to the use of hollow extrudates.