Influence of the Template Removal Method on the Mechanical Stability of SBA-15.

Removing the template from the pores after the polycondensation of the silica precursor is a necessary step in the synthesis of mesoporous silica materials. In our previous work, we developed a method for the efficient and spatially controlled functionalization of SBA-15. First, the silanol groups on the particle surface and in the pore entrances were passivated. After extraction of the template, a pretreatment step in N2 converted the silanol groups to the single and geminal state. Afterwards, an azide functionality was introduced exclusively into the mesopores. This ensured that the catalyst could afterwards be immobilized unambiguously in the mesopores. The mechanical stability of a material functionalized in such a spatially controlled manner is studied and compared to other template removal methods. Even though several studies investigated the influence of the calcination temperature, the presence or the absence of oxygen during the template removal, the specific conditions used during the herein reported selective functionalization procedure have not been covered yet.

Mechanisms and Intermediates in the True Liquid Crystal Templating Synthesis of Mesoporous Silica Materials.

Mesoporous silica materials (MSMs) produced by true liquid crystal templating (TLCT) are often considered as direct inverted replicas of the initial lyotropic liquid crystal (LLC) phase. However, the predictive design of tailor-made MSMs requires the full knowledge of the TLCT process, which is still incomplete. Here, we tackle this issue by monitoring the structural evolution during the templating process by small-angle X-ray scattering, showing that after the addition of the silica source the reaction mixture is first isotropic and then an intermediary liquid crystal phase appears, which is the key to the success of the templating process, namely the formation of ordered MSMs. We analyze the structure and the formation dynamics of this intermediary phase and present a simple theoretical model, which allows us to connect the structural parameters of the initial LLC and the MSM. These results provide an enhanced understanding of the TLCT process and are an important step toward the predictable synthesis of new MSMs in the future.

Synthesis of Acrylonitrile from Renewable Lactic Acid.

Acrylonitrile (ACN) is widely used as monomer in the synthesis of polymers and carbon fibers. Nowadays, its production is based on fossil resources. Herein, an alternative process based on renewable resources is presented. Lactic acid (LA), which can be obtained by fermentation of biomass, was converted to ACN in two steps with an overall selectivity of 57 %. In the first step, a direct amidation of LA in the presence of water was conducted at 230 °C. Zeolites can catalyze the formation of lactamide, and a selectivity of 92 % was reached at 33 % conversion with NH4 -ZSM-5. In the second step, the dehydration of lactamide to ACN was performed with acetic anhydride, and an ACN selectivity of 62 % was achieved at full conversion.

Dehydroalkylation of toluene with ethane in a packed-bed membrane reactor with a bifunctional catalyst and a hydrogen-selective membrane.

The dehydroalkylation of toluene with ethane to form isomeric ethyltoluenes has been carried out in a packed-bed membrane reactor under mild conditions of 350 degrees C, where it is shown that ethyltoluene yields significantly increase with increasing sweep gas flow rate and pressure.

Internal concentration gradients of guest molecules in nanoporous host materials: measurement and microscopic analysis.

Evolution of internal concentration profiles of methanol in 2-D pore structure of ferrierite crystal was measured in the pressure range of 0 to 80 mbar with the help of the recently developed interference microscopy technique. The measured profiles showed that both a surface barrier and internal diffusion controlled the kinetics of adsorption/desorption. Furthermore, they indicated that in the main part of the crystal, the z-directional 10-ring channels were not accessible to methanol and that the transport of methanol mainly occurred via 8-ring y-directional channels. The roof-like part of the crystal was almost instantaneously filled/emptied during adsorption/desorption, indicating accessible 10-ring channels in this section. The measured profiles were analyzed microscopically with the direct application of Fick's second law, and the transport diffusivity of methanol in ferrierite was determined as a function of adsorbed phase concentration. The transport diffusivity varied by more than 2 orders of magnitude over the investigated pressure range. Transport diffusivities, calculated from measured profiles from small and large pressure step changes, were all found to be consistent. Simulated concentration profiles obtained from the solution of Fick's second law with the calculated functional dependence of diffusivities on concentration compared very well with the measured concentration profiles, indicating validity and consistency of the measured data and the calculated diffusivities. The results indicate the importance of measuring the evolution of concentration profiles as this information is vital in determining (1) the direction of internal transport, (2) the presence of internal structural defects, and (3) surface/internal transport barriers. Such detailed information is available neither from common macroscopic methods since, they measure changes in macroscopic properties and use model assumptions to predict the concentration profiles inside, nor from microscopic methods, since they only provide information on average displacement of diffusing molecules.

Is a renaissance of coal imminent?--challenges for catalysis.

In the introduction, the reserves and resources of coal and other fossil fuels are discussed, also with regard to the regional distribution and consumption. Then, coalification and the classification of coal are described. The main part of the article is devoted to the most important processes using coal where challenges for catalysis still exist, with a focus on recent literature. First, technologies based on the production of synthesis gas, i.e., Fischer-Tropsch synthesis as well as MTO/MTP (Methanol To Olefins/Methanol To Propylene), are discussed. Secondly, direct coal liquefaction is treated. The last part of the article is devoted to "clean" coal and gives an outlook on the future of coal.