14 research outputs found
Impact of the Local Environment of Amines on the Activity for CO Hydrogenation over Bifunctional Basic â Metallic Catalysts
Bifunctional basic-metallic catalysts proved to be efficient for the selective hydrogenation of CO to methanol. The activity of these catalysts depends on the cooperative interaction between the amine groups and metallic sites, which is a function of amine group density, Pd particle perimeter length and the geometric properties of support pores. The pore width has the highest effect on the activity, increasing the methanol yield by about half an order of magnitude. Confining the space leads to a three-dimensional utilization of the available metal surface sites compared to a two-dimensional distribution of the bifunctional sites in larger pores, where the metal particle diameter is the decisive factor for the catalytic properties
Thermally stable mesoporous tetragonal zirconia through surfactant-controlled synthesis and Si-stabilization
Thermally stable, highly mesoporous Si-stabilized ZrOâ was prepared by solâgel-synthesis. By utilizing the surfactant dodecylamine (DDA), large mesopores with a pore width of âŒ9.4 nm are formed. Combined with an NHâ-treatment on the hydrogel, a high specific surface area of up to 225 mÂČ gâ»Âč and pore volume up to 0.46 cmÂł gâ»Âč are obtained after calcination at 973 K. The individual contributions of Si-addition, DDA surfactant and the NHâ-treatment on the resulting pore system were studied by inductively coupled plasma with optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), Nâ sorption, and transmission electron microscopy (TEM). Electron tomography was applied to visualize and investigate the mesopore network in 3D space. While Si prevents the growth of ZrOâ crystallites and stabilizes the t-ZrOâ phase, DDA generates a homogeneous mesopore network within the zirconia. The NHâ-treatment unblocks inaccessible pores, thereby increasing specific surface area and pore volume while retaining the pore width distribution
Porosity and Structure of Hierarchically Porous Ni/AlâOâ Catalysts for COâ Methanation
CO methanation is often performed on Ni/AlO catalysts, which can suffer from mass transport limitations and, therefore, decreased efficiency. Here we show the application of a hierarchically porous Ni/AlO catalyst for methanation of CO. The material has a well-defined and connected meso- and macropore structure with a total porosity of 78%. The pore structure was thoroughly studied with conventional methods, i.e., N sorption, Hg porosimetry, and He pycnometry, and advanced imaging techniques, i.e., electron tomography and ptychographic X-ray computed tomography. Tomography can quantify the pore system in a manner that is not possible using conventional porosimetry. Macrokinetic simulations were performed based on the measures obtained by porosity analysis. These show the potential benefit of enhanced mass-transfer properties of the hierarchical pore system compared to a pure mesoporous catalyst at industrially relevant conditions. Besides the investigation of the pore system, the catalyst was studied by Rietveld refinement, diffuse reflectance ultraviolet-visible (DRUV/vis) spectroscopy, and H-temperature programmed reduction (TPR), showing a high reduction temperature required for activation due to structural incorporation of Ni into the transition alumina. The reduced hierarchically porous Ni/AlO catalyst is highly active in CO methanation, showing comparable conversion and selectivity for CH to an industrial reference catalyst
Porosity and Structure of Hierarchically Porous Ni/AlâOâ Catalysts for COâ Methanation
COâ methanation is often performed on Ni/AlâOâ catalysts, which can suffer from mass transport limitations and, therefore, decreased efficiency. Here we show the application of a hierarchically porous Ni/AlâOâ catalyst for methanation of COâ. The material has a well-defined and connected meso- and macropore structure with a total porosity of 78%. The pore structure was thoroughly studied with conventional methods, i.e., Nâ sorption, Hg porosimetry, and He
pycnometry, and advanced imaging techniques, i.e., electron tomography and ptychographic X-ray computed tomography. Tomography can quantify the pore system in a manner that is not possible using conventional porosimetry. Macrokinetic simulations were performed based on the measures obtained by porosity analysis. These show the potential benefit of enhanced mass-transfer properties of the hierarchical pore system compared to a pure mesoporous catalyst at industrially relevant
conditions. Besides the investigation of the pore system, the catalyst was studied by Rietveld refinement, diffuse reflectance ultraviolet-visible (DRUV/vis) spectroscopy, and Hâ-temperature programmed reduction (TPR), showing a high reduction temperature required for activation due to structural incorporation of Ni into the transition alumina. The reduced hierarchically porous Ni/AlâOâ catalyst is highly active in COâ methanation, showing comparable conversion and selectivity for CHâ
to an industrial reference catalyst
One Planet: One Health. A Call to Support the Initiative on a Global Science-Policy Body on Chemicals and Waste
The chemical pollution crisis severely threatens human and environmental health globally. To tackle this challenge the establishment of an overarching international scienceâpolicy body has recently been suggested. We strongly support this initiative based on the awareness that humanity has already likely left the safe operating space within planetary boundaries for novel entities including chemical pollution. Immediate action is essential and needs to be informed by sound scientific knowledge and data compiled and critically evaluated by an overarching scienceâpolicy interface body. Major challenges for such a body are (i) to foster global knowledge production on exposure, impacts and governance going beyond data-rich regions (e.g., Europe and North America), (ii) to cover the entirety of hazardous chemicals, mixtures and wastes, (iii) to follow a one-health perspective considering the risks posed by chemicals and waste on ecosystem and human health, and (iv) to strive for solution-oriented assessments based on systems thinking. Based on multiple evidence on urgent action on a global scale, we call scientists and practitioners to mobilize their scientific networks and to intensify scienceâpolicy interaction with national governments to support the negotiations on the establishment of an intergovernmental body based on scientific knowledge explaining the anticipated benefit for human and environmental health
German Catalysis Society Meeting: Exploring the Various Facets of Catalysis
Tradition is tradition: Already for the 52nd time the Annual Meeting of the German Catalysis Society (GeCatS) took place from March 13th to 15th, 2019. Following its longâstanding tradition, the meeting was organized in the Neue Weimarhalle in the beautiful city of Weimar, Thuringia
German Catalysis Society Meeting: Exploring the Various Facets of Catalysis
Tradition is tradition: Already for the 52nd time the Annual Meeting of the German Catalysis Society (GeCatS) took place from March 13th to 15th, 2019. Following its longâstanding tradition, the meeting was organized in the Neue Weimarhalle in the beautiful city of Weimar, Thuringia
Impact of the local environment of amines on the activity for CO hydrogenation over bifunctional basic â metallic catalysts
Bifunctional basic-metallic catalysts proved to be efficient for the selective hydrogenation of CO to methanol. The activity of these catalysts depends on the cooperative interaction between the amine groups and metallic sites, which is a function of amine group density, Pd particle perimeter length and the geometric properties of support pores. The pore width has the highest effect on the activity, increasing the methanol yield by about half an order of magnitude. Confining the space leads to a three â dimensional utilization of the available metal surface sites compared to a two â dimensional distribution of the bifunctional sites in larger pores, where the metal particle diameter is the decisive factor for the catalytic propertie
Weimar 2015: Catalysing Tomorrowâs Solutions
The YounGeCatS put the cat in catalysis: The 48th annual meeting of the German Catalysis Society (GeCatS), hosted by DECHEMA, was recently held in Weimar. There were numerous presentations, from keynotes to posters, put together to form a very attractive program depicting the catalysis research in all its breadth
Hierarchically Structured Porous Spinels via an Epoxide-Mediated SolâGel Process Accompanied by Polymerization-Induced Phase Separation
Enhancing the activity
and stability of catalysts is a major challenge
in scientific research nowadays. Previous studies showed that the
generation of an additional pore system can influence the catalytic
performance of porous catalysts regarding activity, selectivity, and
stability. This study focuses on the epoxide-mediated solâgel
synthesis of mixed metal oxides, NiAl<sub>2</sub>O<sub>4</sub> and
CoAl<sub>2</sub>O<sub>4</sub>, with a spinel phase structure, a hierarchical
pore structure, and Ni and Co contents of 3 to 33 mol % with respect
to the total metal content. The solâgel process is accompanied
by a polymerization-induced phase separation to introduce an additional
pore system. The obtained mixed metal oxides were characterized with
regard to pore morphology, surface area, and formation of the spinel
phase. The BrunauerâEmmettâTeller surface area ranges
from 74 to 138 m<sup>2</sup>·g<sup>â1</sup> and 25 to
94 m<sup>2</sup>·g<sup>â1</sup> for Ni and Co, respectively.
Diameters of the phase separation-based macropores were between 500
and 2000 nm, and the mesopore diameters were 10 nm for the Ni-based
system and between 20 and 25 nm for the cobalt spinels. Furthermore,
NiâAl spinels with 4, 5, and 6 mol % Ni were investigated in
the dry reforming of CH<sub>4</sub> (DRM) with CO<sub>2</sub> to produce
H<sub>2</sub> and CO. CH<sub>4</sub> conversions near the thermodynamic
equilibrium were observed depending on the Ni content and reaction
temperature. The Ni catalysts were further compared to a noble metal-containing
catalyst based on a spinel system showing comparable CH<sub>4</sub> conversion and carbon selectivity in the DRM