Whatever the case, you may be interested in the following items.
Sprinkled throughout the post are TIPS on how to continue the search in a productive manner. As always, your comments are welcome.
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Mesoporous molecular sieve catalysts
Karen Thrane Højholt
PhD Thesis
Department of Chemistry
Technical University of Denmark
August 2011
Abstract
This thesis deals with a very specific class of molecular sieves known as zeolites. Zeolites are a class of crystalline aluminosilicates characterised by pores or cavities of molecular dimensions as part of their crystal structure. In this work zeolites were modified for the use and understanding of different catalytic applications. Primarily the zeolites were modified regarding the porosity and the introduction of metals to the framework. The obtained materials were used as solid acid catalysts, as an inert matrix for stabilising metal nanoparticles and as an anchoring material for molecular metal oxide species.
Nanosized and mesoporous zeolites were prepared to investigate the effect of inter- or intracrystalline mesopores on the catalytic lifetime in the conversion of methanol to hydrocarbons (MTH). It was found that the mesoporous zeolite with intracrystalline mesopores displayed the significantly longest catalytic lifetime compared to the nanosized zeolites and the conventional counterpart.
Even though the introduction of mesopores improved the catalytic lifetime in the MTH reaction it was concluded that the normal benefits from desilication, e.g. mesoporosity and repairing of defects, became masked by the generation of extra-framework aluminum and that the catalytic lifetime was severely dependent on the amount of extra-framework aluminum.
Conventional and mesoporous ZSM-5 zeolites were prepared together with the Ga-MFI zeotype analogues to investigate the differences in activity, selectivity and mode of deactivation. The differences in selectivity were primarily ascribed to the difference in the lower acidity of the individual active sites of the Ga-MFI zeotypes compared to the zeolites. In general, the Ga-MFI zeotypes deactivated faster than the ZSM-5 zeolites. Further investigations of the mode of deactivation revealed that the zeolites deactivated due to coke formation and that the Ga-MFI zeotypes deactivated due to loss of the catalytically active Brønsted acid sites caused by hydrolysis of Ga-O bonds leading to formation of inactive extra-framework gallium.
Zeolites can not only be used as solid acid catalysts but can also be used as a size-selective matrix. It was shown that it is possible to encapsulate 1-2 nm sized gold nanoparticles by silicalite-1 or ZSM-5 zeolite crystals thereby forming a sintering-stable and substrate size-selective oxidation catalyst. After carrying out calcination experiments, both in situ and ex situ indicated that the gold nanoparticles embedded in the crystals were highly stable towards sintering. The catalytic tests proved that the embedded gold nanoparticles were active in selective aldehyde oxidation and were only accessible through the micropores.
Furthermore, preliminary work was done using mesoporous ZSM-5 zeolites as support material for anchoring molecular CoMo6 species for the application as potential bi-functional catalyst in simultaneous hydrodesulfurisation (HDS) and hydrocracking. HDS activity tests revealed that the anchoring improved the activity compared to an impregnated counterpart.
Free full text source: https://backend.orbit.dtu.dk/ws/files/6503563/Karen%20T%20H%c3%b8jholt.pdf
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TIP: Google® Karen Thrane Højholt to see what else she has written.
A couple of results …
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Tight bifunctional hierarchical catalyst.
Karen Thrane Højholt, Peter N R Vennestrøm, +1 author Pablo Beato
Published in Chemical communications 2011
Medicine, Chemistry
A new concept to prepare tight bifunctional catalysts has been developed, by anchoring CoMo(6) clusters on hierarchical ZSM-5 zeolites for simultaneous use in HDS and hydrocracking catalysis. The prepared material displays a significant improved activity in HDS catalysis compared to the impregnated counterpart.
source: https://www.semanticscholar.org/paper/Tight-bifunctional-hierarchical-catalyst.-H%C3%B8jholt-Vennestr%C3%B8m/563610ddb71074a1243bca0479574ad2b331f701
Free full text source: https://pdfs.semanticscholar.org/fbd2/0b5e0e98e384793261f26418ce7851d13177.pdf?_ga=2.198196393.789065448.1589380351-310489785.1589380351
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Patent
Process For The Preparation Of Hybrid Zeolite Or Zeolite-Like Materials
Application WO-2010097224-A2
Abstract
A process for the preparation of hybrid zeolite or zeolite-like materials comprising the steps of : - providing a solution or suspension or solid material containing nanoparticles comprising at least one metal, - providing a synthesis gel or a synthesis gel precursor of a zeolite or zeolite-like material, - mixing the synthesis gel or the synthesis gel precursor of the zeolite or zeolite-like material with the solution or suspension or solid material containing nanoparticles comprising at least one metal, to form a mixture, - converting the mixture under zeolite or zeolite-like synthesis conditions to hybrid zeolite or zeolite-material encapsulating nanoparticles comprising at least one metal.
Inventors
HØJHOLT, Karen, Thrane
EGEBLAD, KRESTEN
CHRISTENSEN, CLAUS, HVIID
HELVEG, STIG
LAURSEN, BO, ANDERS
BRORSON, MICHAEL
Original Assignee
Haldor Topsoe (Denmark)
HOEJHOLT KAREN THRANE [ different spelling ]
EGEBLAD KRESTEN
CHRISTENSEN CLAUS HVIID
HELVEG STIG
LAURSEN BO ANDERS
BRORSON MICHAEL
Publication date 2010/09/02
source: https://app.dimensions.ai/details/patent/WO-2010097224-A2
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TIP#1: Google Karen Thrane Højholt with various additional keywords, like Haldor Topsoe (listed as Assignee on the patent above), Denmark, etc.
TIP #2: If your focus is dibenzothiophene, one of the more recalcitrant components contained in heavy crude, follow these steps …
- Download the PDF (thesis). I have found it is easier to search a PDF once it has downloaded, than to search it in a browser.
- Open the PDF
- Ctrl+F to search: dibenzothiophene
Here are the paragraphs in Højholt’s thesis containing the word dibenzothiophene.
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In particular HDS of petroleum feedstocks has become more and more important to protect the environments by producing sulfur-free fuels. Environmental regulations have been introduced in many countries around the world to reduce the sulfur content of e.g. diesel fuel to ultra low levels (10 ppm) with the aim of lowering the diesel engine’s harmful exhaust emission and improving air quality. Sulfur can be present in crude oil in many forms e.g. thiols (mercaptans), sulfides, disulfides, thiophenes and thiophenic compounds containing both benzo- and dibenzothiophene structures. The sulfur content of crude oil varies significant with their origin and may be as low as 0.1 wt% but may increase up to 2-5 wt%.
[page 142]
Catalysts consisting of molybdenum supported on high surface area support and promoted with cobalt or nickel are traditionally used in hydrotreating processes. Typical support materials in industry are alumina and silica-alumina, while silica, zeolites, kieselguhr and magnesia have been and is explored in research. Usually the surface areas are in the range of 100 to 300 m2/g. The metals are added to the support by impregnation yielding a final composition of metals with 8-16 wt% molybdenum and 1-4 wt% cobalt or nickel. The choice of catalyst type and the type of feed varies according to the application, desired activity and the process conditions for a given reaction. Often CoMo catalysts are chosen as HDS catalysts rather than the NiMo counterpart. Dibenzothiophene is an important structure in HDS of diesel fuel and Figure 6.1 shows that there exist two different products depending on whether the sulfur atom is directly abstracted from dibenzothiophene or takes place due to prehydrogenation of the polyaromatic compound. CoMo catalysts are better than NiMo catalysts, to directly remove sulfur from dibenzothiophene. The use of CoMo catalysts therefore entails lower direct hydrogen consumption and is often the preferred choice as industrial catalyst.
[page 142]
The prepared catalysts were tested for HDS activity. Due to the complexity of natural oil in terms of hydrocarbon matrix and the various sulfur compounds present, the use of real oil in these screening experiments has been avoided. As a model activity test reaction the conversion of 131 dibenzothiophene (DBT) is chosen, as it is a representative sulfur compound in real oil and is here used in its pure form dissolved in a matrix of a pure hydrocarbon, in casu n-heptane. Besides containing 3 % DBT, the model oil also contains 0.5 % indole, 1 % naphthalene and 2.5 % dimethyldisulfide in n-heptan to mimic real oil. Using this feed it is also possible to investigate HDN and HYD but in this work the focus is on the performance of the catalysts in HDS. Dimethyldisulfide is present in the model feed to keep the catalyst in a fully sulfided state. Thus DMDS decomposes in the presence of H2 much below reaction temperature to create a partial pressure of H2S inside the reactor.
[page 147]
1.5 Model activity test
Catalytic testing was performed in a fixed bed reactor charged with 300 mg catalyst in the fraction 600-850 μm. To achieve a steady flow the catalyst was mixed with Ballotini glass balls (150-250 μm) until a final volume of 1 ml was obtained. Prior to catalytic test the catalyst was sulfidized in a flow of 2.5 % dimethyldisulfide (DMDS) dissolved in n-heptane at 350 ºC and 50 bar for 4 hours. Helium was used as a carrier gas with a flow of 250 Nml/min. After 4 hours of sulfidation the feed was changed to a model oil feed containing 3 % dibenzothiophene (DBT), 0.5 % indole, 1 % naphtalene, 2.5 % dimethyldisulfide (DMDS), 0.5 % nnonane, the rest being n-heptan solvent.. The catalytic reaction was also performed at 350 ºC, 50 bar using helium as a carrier gas with a flow of 250 Nml/min. The employed feed rate of oil was 0.3 ml/min and the total WHSV was 68 h-1. The products from the reaction were analysed by an on-line GC equipped with a FID using n-nonane as an internal standard. The reaction was allowed to stabilize over 4 hours in order to obtain steady state conditions after changing to the oil feed prior to catalytic measurements. Afterwards eight GC analyses of the product stream were made with 1 hour intervals.
[page 219]
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TIP: Google® HOEJHOLT KAREN THRANE. Hoejholt is a variant of the Danish spelling … Højholt
Result From Searching HOEJHOLT KAREN THRANE
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FISCHER-TROPSCH SYNTHESIS CATALYST STRUCTURE ...
app.dimensions.ai › details › patent › WO-2018221700-A1
TOPSOE HALDOR AS, HOEJHOLT KAREN THRANE, EGEBLAD KRESTEN, CHRISTENSEN CLAUS HVIID, HELVEG STIG, LAURSEN ANDERS BO, ...
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TIP: Add keywords to Højholt to Google® search phrases. For example: Karen Thrane Højholt denmark
Some results …
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DOI:10.1002/anie.200906977Corpus ID: 21056811
Substrate size-selective catalysis with zeolite-encapsulated gold nanoparticles.
Anders B. Laursen, Karen Thrane Højholt, +8 authors Kresten Egeblad
Published in Angewandte Chemie 2010
Chemistry, Medicine
Over the years, many strategies have been developed to address the problem of sintering of nanoparticle catalysts, including encapsulating metal nanoparticles in protective shells, and trapping nanoparticles in the cavities of certain zeolites in post-synthesis steps. In general, materials that contain metal nanoparticles that are only accessible via zeolite micropores are intriguing, specifically, but not exclusively, for catalytic applications. The encapsulation of carbon nanoparticles during…
source: https://www.semanticscholar.org/paper/Substrate-size-selective-catalysis-with-gold-Laursen-H%C3%B8jholt/8777b270f8cc92c8f211737f81d697fb95bbf07f
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DOI:10.1007/s11244-011-9722-xCorpus ID: 96241826
Size-Selective Oxidation of Aldehydes with Zeolite Encapsulated Gold Nanoparticles
Karen Thrane Højholt, Anders B. Laursen, +1 author Claus Christensen
Published 2011
Chemistry
Topics in Catalysis
Here, we report a synthesis and catalytic study of hybrid materials comprised of 1–3 nm sinter-stable Au nanoparticles in MFI-type zeolites. An optional post-treatment in aqua regia effectively remove Au from the external surfaces. The size-selective aerobic aldehyde oxidation verifies that the active Au is accessible only through the zeolite micropores.
source: https://www.semanticscholar.org/paper/Size-Selective-Oxidation-of-Aldehydes-with-Zeolite-H%C3%B8jholt-Laursen/85712f0585ab0db2de6b855c6024bc1ebd42e576
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