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•83 zeolites with 25 different frameworks have been tested as NH3-SCR catalyst.•Critical parameters that affect catalytic performance were identified.•Si/Al ratio, d6r content, ...framework density and pore dimensionality are important.•MOZ, SZR and GME zeolites were predicted to have good NH3-SCR performance.•Predictions towards new zeolites’ NH3-SCR performance can be made.
Low temperature performance is key for catalysts used in selective catalytic reduction of NOx with ammonia (NH3-SCR). The best performing NH3-SCR catalysts are based on small pore copper loaded zeolites. A key question remains which structural and compositional parameters make a copper zeolite catalytically active in this application. In this work a collection of 83 different zeolite samples having 25 different frameworks and compositional variations was evaluated to uncover the critical structural and compositional parameters governing catalytic activity at 150 °C. The Si/Al ratio, the content of double six-ring building units, the framework density and pore dimensionality were identified as having a strong impact on the catalytic activity of zeolites. A critical value for each of these parameters was determined. This knowledge was used to predict MOZ, SZR and GME as active NH3-SCR catalysts. They were synthesized respecting the compositional prerequisites and their catalytic evaluation confirmed the predicted high catalytic activity.
This paper describes the development of a data‐driven advance warning system for the onset of loss of separation in an industrial distillation column. The system would enable preventive actions to ...avoid several hours of bad operation and subsequent recovery of the process. Data of more than 2 years of process operation were used to identify and validate various monitoring systems based on both static principal component analysis (PCA) and dynamic PCA. Despite the presence of autocorrelation in the data, only minor differences in advance warning were observed between PCA and dynamic PCA.
The developed system provides warnings for 35% to 45% of the observed periods of bad column operation, with respective advance warning times of 16 and 6 minutes. It proves a valuable additional tool to monitor the operation of the distillation column and avoid losses of product, with the potential of reducing bad operation (and the associated costs) by up to 45% and substantially improving overall process reliability.
LEV type zeolites were synthesized with four different structure-directing agents and converted to copper loaded NH
3
-SCR catalysts. The synthesis recipe was found to impact the respective Al ...population in the two topologically different framework sites in double and single 6-rings, resolvable by
27
Al MAS NMR spectroscopy. Hydrothermal stability was found to be related to the silanol concentration, Si/Al ratio, particle size, crystal morphology, crystal defects, external surface area, and microporosity. Catalytic activity in NH
3
-SCR was dependent on preferential Al siting in the double 6-rings. Levinite synthesized using adamantylamine showed the strongest preference for Al atoms sitting in double 6-ring sites, and showed the highest catalytic turnover frequency. Unfortunately, because of the large crystal size, copper loading of this sample was limited to 0.6 wt% while other samples could be loaded with copper up to 3.3 wt%. An optimum combination of hydrothermal stability and catalytic activity was obtained with
N
,
N
′-bis-dimethylpentanediyldiammonium dibromide as structure-directing agent.
The catalytic activity of LEV type zeolites in NH
3
-SCR was dependent on preferential Al siting in the double 6-rings, which in turn was influenced by the choice of structure-directing agent used in the zeolite synthesis.
LEV type zeolites were synthesized with four different structure-directing agents and converted to copper loaded NH
-SCR catalysts. The synthesis recipe was found to impact the respective Al ...population in the two topologically different framework sites in double and single 6-rings, resolvable by
Al MAS NMR spectroscopy. Hydrothermal stability was found to be related to the silanol concentration, Si/Al ratio, particle size, crystal morphology, crystal defects, external surface area, and microporosity. Catalytic activity in NH
-SCR was dependent on preferential Al siting in the double 6-rings. Levinite synthesized using adamantylamine showed the strongest preference for Al atoms sitting in double 6-ring sites, and showed the highest catalytic turnover frequency. Unfortunately, because of the large crystal size, copper loading of this sample was limited to 0.6 wt% while other samples could be loaded with copper up to 3.3 wt%. An optimum combination of hydrothermal stability and catalytic activity was obtained with
,
'-bis-dimethylpentanediyldiammonium dibromide as structure-directing agent.
LEV type zeolites were synthesized with four different structure-directing agents and converted to copper loaded NH3-SCR catalysts. The synthesis recipe was found to impact the respective Al ...population in the two topologically different framework sites in double and single 6-rings, resolvable by 27Al MAS NMR spectroscopy. Hydrothermal stability was found to be related to the silanol concentration, Si/Al ratio, particle size, crystal morphology, crystal defects, external surface area, and microporosity. Catalytic activity in NH3-SCR was dependent on preferential Al siting in the double 6-rings. Levinite synthesized using adamantylamine showed the strongest preference for Al atoms sitting in double 6-ring sites, and showed the highest catalytic turnover frequency. Unfortunately, because of the large crystal size, copper loading of this sample was limited to 0.6 wt% while other samples could be loaded with copper up to 3.3 wt%. An optimum combination of hydrothermal stability and catalytic activity was obtained with N,N′-bis-dimethylpentanediyldiammonium dibromide as structure-directing agent.
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•Wet ball milling of -COK-14 zeolite in presence of a dissolved Al source.•Particle size reduction and framework aluminum introduction result from milling.•Milled and aluminated ...COK-14 contains Brønsted acid sites.•Milled and aluminated COK-14 loaded with platina is an ideal bifunctional catalyst.
The precursor of all-silica COK-14 zeolite (OKO topology) with interrupted framework was subjected to wet ball milling in the presence of aluminum isopropoxide. Alumination and particle size reduction of the zeolite crystals was combined in this way. Wet ball milling resulted in fragmentation of the platelet-shape COK-14 crystals while preserving crystallinity. 27Al NMR spectroscopy of the fully condensed COK-14 zeolite, obtained by calcination of milled -COK-14 precursor, confirmed the incorporation of tetrahedrally coordinated Al atoms in the framework. The creation of Brønsted acid sites was confirmed by pyridine adsorption. Loaded with platinum, the sample showed ideal bifunctional catalytic behavior in hydroisomerization and hydrocracking of n-decane model alkane compound. Aluminum incorporation by milling is an alternative to the atomic layer deposition (ALD) process using trimethylaluminum and to thermal alumination. Wet ball milling in presence of aluminum isopropoxide shows great potential for making siliceous zeolites catalytically active.
EU-7 zeolite with Si/Al ratio of 15 is identified as a BIK type zeolite. The framework charge is compensated with Cs
+
cations located in 8-ring channels at regular distances. Even partially ...exchanged, Cu-loaded EU-7 is active in NH
3
-SCR and withstands hydrothermal aging at 900 °C needed for application in diesel particulate filters.
EU-7 is identified as BIK topology and proves stable to withstand steaming at 900 °C relevant to DeNOx catalysis.
EU-7 zeolite with Si/Al ratio of 15 is identified as a BIK type zeolite. The framework charge is compensated with Cs+ cations located in 8-ring channels at regular distances. Even partially ...exchanged, Cu-loaded EU-7 is active in NH3-SCR and withstands hydrothermal aging at 900 °C needed for application in diesel particulate filters.
-COK-14 zeolite, the variant of COK-14 (OKO topology) with a systematically interrupted framework, exhibits unusual behaviour in high pressure intrusion-extrusion cycles of 20 M LiCl solution. After ...the first cycle with deviating behaviour and partially irreversible intrusion, subsequent cycles show stable reversible behaviour. The system behaves like a spring with unique progressive intrusion in the range of 10-120 MPa followed by enhanced uptake before saturation. While the intrusion-extrusion cycling leads to fragmented crystals, powder diffraction reveals high crystallinity of the fragments. Based on the detailed characterisation of the zeolite samples with XRD, Rietveld refinement, N
2
adsorption, TGA and
29
Si MAS NMR before and after intrusion-extrusion experiments, a model of the structure of the intruded -COK-14 samples is proposed. Intrusion-extrusion of LiCl solution systematically breaks the most strained bonds in the structure which results in a new framework connectivity with enhanced stability, which persists during the harsh intrusion-extrusion conditions.
Unusual energetic behaviour of -COK-14 zeolite in high pressure intrusion-extrusion cycles of 20 M LiCl solution.
-COK-14 zeolite, the variant of COK-14 (OKO topology) with a systematically interrupted framework, exhibits unusual behaviour in high pressure intrusion-extrusion cycles of 20 M LiCl solution. After ...the first cycle with deviating behaviour and partially irreversible intrusion, subsequent cycles show stable reversible behaviour. The system behaves like a spring with unique progressive intrusion in the range of 10-120 MPa followed by enhanced uptake before saturation. While the intrusion-extrusion cycling leads to fragmented crystals, powder diffraction reveals high crystallinity of the fragments. Based on the detailed characterisation of the zeolite samples with XRD, Rietveld refinement, N2 adsorption, TGA and (29)Si MAS NMR before and after intrusion-extrusion experiments, a model of the structure of the intruded -COK-14 samples is proposed. Intrusion-extrusion of LiCl solution systematically breaks the most strained bonds in the structure which results in a new framework connectivity with enhanced stability, which persists during the harsh intrusion-extrusion conditions.
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