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You searched for subject:(Selective poisoning). Showing records 1 – 3 of 3 total matches.

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Georgia Tech

1. Richardson, John Michael. Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons.

Degree: PhD, Chemical and Biomolecular Engineering, 2008, Georgia Tech

This work focuses on understanding the heterogeneous/homogeneous nature of the catalytic species for a variety of immobilized metal precatalysts used for C-C coupling reactions. These precatalysts include: (i) tethered organometallic palladium pincer complexes, (ii) an encapsulated small molecule palladium complex in a polymer matrix, (iii) mercapto-modified mesoporous silica metalated with palladium acetate, and (iv) amino-functionalized mesoporous silicas metalated with Ni(II). As part of this investigation, the use of metal scavengers as selective poisons of homogeneous catalysis is introduced and investigated as a test for distinguishing heterogeneous from homogeneous catalysis. The premise of this test is that insoluble materials functionalized with metal binding sites can be used to selectively remove soluble metal, but will not interfere with catalysis from immobilized metal. In this way the test can definitely distinguish between surface and solution catalysis of immobilized metal precatalysts. This work investigates three different C-C coupling reactions catalyzed by the immobilized metal precatalysts mentioned above. These reactions include the Heck, Suzuki, and Kumada reactions. In all cases it is found that catalysis is solely from leached metal. Three different metal scavenging materials are presented as selective poisons that can be used to determine solution vs. surface catalysis. These selective poisons include poly(vinylpyridine), QuadrapureTM TU, and thiol-functionalized mesoporous silica. The results are contrasted against the current understanding of this field of research and subtleties of tests for distinguishing homogeneous from heterogeneous catalysis are presented and discussed. Advisors/Committee Members: Dr. Christopher W. Jones (Committee Chair), Dr. E. Kent Barefield (Committee Member), Dr. Marcus Weck (Committee Member), Dr. Pradeep Agrawal (Committee Member), Dr. Rachel Chen (Committee Member).

Subjects/Keywords: Palladium catalysis; Cross coupling reaction; Heterogeneous vs. homogeneous; Selective poisoning; Palladium catalysts; Heterogeneous catalysis; Catalysis; Catalyst poisoning

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Richardson, J. M. (2008). Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/22704

Chicago Manual of Style (16th Edition):

Richardson, John Michael. “Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons.” 2008. Doctoral Dissertation, Georgia Tech. Accessed March 04, 2021. http://hdl.handle.net/1853/22704.

MLA Handbook (7th Edition):

Richardson, John Michael. “Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons.” 2008. Web. 04 Mar 2021.

Vancouver:

Richardson JM. Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/1853/22704.

Council of Science Editors:

Richardson JM. Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/22704


University of Oulu

2. Väliheikki, A. (Ari). Resistance of catalytic materials towards chemical impurities:the effect of sulphur and biomaterial-based compounds on the performance of DOC and SCR catalysts.

Degree: 2016, University of Oulu

Abstract Exhaust gas emissions, e.g. nitrogen oxides (NOx), hydrocarbons (HCs) and carbon monoxide (CO), are harmful to human health and the environment. Catalysis is an efficient method to decrease these emissions. Unfortunately, the fuels and lubricant oils may contain chemical impurities that are also present in exhaust gases. Thus, catalytic materials with high activity and chemical resistance towards impurities are needed in the abatement of exhaust gas emission. In this thesis, the aim was to gain new knowledge about the effects of chemical impurities on the behaviour and activity of the catalysts. To find out these effects, the impurities existing in the exhaust gas particulate matter after combustion of biofuels and fossil fuels were analysed. The studied zeolite (ZSM-5), cerium-zirconium mixed oxides (CeZr and ZrCe) and silicon-zirconium oxide (SiZr) based catalysts were also treated with impurities to simulate the poisoning of the catalysts by, e.g. potassium, sodium, phosphorus and sulphur, using gas or liquid phase treatments. Several characterization techniques were applied to find out the effects of impurities on catalysts’ properties. The activity of catalysts was tested in laboratory-scale measurements in CO and HC oxidation and NOx reduction using ammonia (NH3) and hydrogen (H2) as reductants. The results revealed that the CeZr based catalysts had a high activity in NOx reduction by NH3 and moderate activity by H2. Sulphur was proven to enhance the activity of CeZr catalysts in NOx reduction. This is due to an increase in chemisorbed oxygen after the sulphur treatment on the catalyst surface. Instead, in HC and CO oxidation reactions, sulphur had a negligible impact on the activity of the SiZr based diesel oxidation catalyst. Thus, both CeZr and SiZr based catalysts can be utilized in exhaust gas purification when sulphur is present. ZSM-5 based catalysts were proven to be resistant to potassium and sodium. Alternatively, the activity of SiZr based catalysts decreased due to phosphorus. Thus, the removal of biomaterial-based impurities from the exhaust gases is needed to retain high catalyst activity in the exhaust gas after-treatment system.

Tiivistelmä Pakokaasupäästöissä olevat typen oksidit (NOx), hiilivedyt (HCs) ja hiilimonoksidi (CO) ovat haitallisia ihmisten terveydelle ja ympäristölle. Katalyysi on tehokas menetelmä vähentää näitä päästökomponentteja. Polttoaineet ja voiteluöljyt sisältävät epäpuhtauksia, jotka siirtyvät myös pakokaasuihin. Tästä johtuen pakokaasupäästöjen hallinnassa tarvitaan katalyyttimateriaaleja, joilla on hyvä vastustuskyky myrkyttymistä vastaan. Tavoitteena oli saada uutta tietoa kemiallisten epäpuhtauksien vaikutuksesta katalyyttien toimintaan. Biopolttoaineiden sisältämät mahdolliset epäpuhtaudet selvitettiin analysoimalla fossiilisen ja biopolttoaineen palamisessa muodostuvia partikkeleita ja vertaamalla niitä polttoaineiden hivenaineanalyysiin. Tutkimuksessa käytetyt zeoliitti (ZSM-5), cerium-zirkonium-sekaoksidi (CeZr) ja pii-zirkonium-oksidipohjaiset (SiZr)…

Advisors/Committee Members: Keiski, R. (Riitta), Kolli, T. (Tanja), Huuhtanen, M. (Mika).

Subjects/Keywords: catalyst; cerium-zirconium mixed oxides; diesel oxidation catalyst; phosphorus; poisoning; potassium; selective catalytic reduction; silicon-zirconium oxide; sodium; sulphur; tungsten; zeolite; cerium-zirkonium-sekaoksidi; dieselhapetuskatalyytti; fosfori; kalium; katalyytti; myrkyttyminen; natrium; pii-zirkoniumoksidi; rikki; selektiivinen katalyyttinen pelkistys; volframi; zeoliitti

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APA (6th Edition):

Väliheikki, A. (. (2016). Resistance of catalytic materials towards chemical impurities:the effect of sulphur and biomaterial-based compounds on the performance of DOC and SCR catalysts. (Doctoral Dissertation). University of Oulu. Retrieved from http://urn.fi/urn:isbn:9789526212845

Chicago Manual of Style (16th Edition):

Väliheikki, A (Ari). “Resistance of catalytic materials towards chemical impurities:the effect of sulphur and biomaterial-based compounds on the performance of DOC and SCR catalysts.” 2016. Doctoral Dissertation, University of Oulu. Accessed March 04, 2021. http://urn.fi/urn:isbn:9789526212845.

MLA Handbook (7th Edition):

Väliheikki, A (Ari). “Resistance of catalytic materials towards chemical impurities:the effect of sulphur and biomaterial-based compounds on the performance of DOC and SCR catalysts.” 2016. Web. 04 Mar 2021.

Vancouver:

Väliheikki A(. Resistance of catalytic materials towards chemical impurities:the effect of sulphur and biomaterial-based compounds on the performance of DOC and SCR catalysts. [Internet] [Doctoral dissertation]. University of Oulu; 2016. [cited 2021 Mar 04]. Available from: http://urn.fi/urn:isbn:9789526212845.

Council of Science Editors:

Väliheikki A(. Resistance of catalytic materials towards chemical impurities:the effect of sulphur and biomaterial-based compounds on the performance of DOC and SCR catalysts. [Doctoral Dissertation]. University of Oulu; 2016. Available from: http://urn.fi/urn:isbn:9789526212845

3. Okolie, Chukwuemeka. Catalytic conversion of methane into alkanes and oxygenates and deactivation of hydrodeoxygenation catalysts.

Degree: PhD, Chemical and Biomolecular Engineering, 2017, Georgia Tech

In this thesis, a catalyst comprising of NiO/Ce0.83Zr0.17O2 (NiO/CZ) that is capable of activating methane to form surface methyl groups was developed. Some of these species couple to higher alkyl chains. These alkyl groups can be removed as ethane and ethylene at temperatures below 500 °C in a non-oxidative environment. Bi-functional activity on the catalyst also leads to the production of aromatics. However, due to thermodynamic constraints, only very low yields of higher hydrocarbons is achievable in this reaction. To facilitate the production of oxygenates, steam was used to hydrolyze the surface groups from methane activation into methanol and ethanol. Oxygen is co-fed to convert surface hydrogen to water providing a thermodynamic driving force. In addition to alcohols, carbon dioxide and hydrogen and small amounts of aromatics are formed as by-products. Importantly, the formation of alcohols occurs at 450 °C in steady state with a turnover frequency of at least 50 h-1. This is a significant improvement from previous studies, in which a high-temperature calcination step was required for every turnover. The performance of NiO/CZ towards alcohol production was optimized by using several synthesis techniques. Strong electrostatic adsorption (SEA) of Ni on ceria zirconia was found to be the best catalysts showing improved dispersion of Ni and subsequently, improved reactivity towards alcohol production. In this thesis, the effect of strongly adsorbed “roadblocks” on zeolitic catalysts during hydrodeoxygenation of bio-oils was illustrated. This was done by deliberately introducing “roadblocks” from catechol. Physicochemical characterization and reactivity studies were performed on certain HDO catalysts (Pt/HBEA, Ni/ZSM-5 and Ga/ZSM-5). These provided insight on the effect of “roadblocks” on the catalysts as a pathway for deactivation during hydrodeoxygenation. Advisors/Committee Members: Sievers, Carsten (advisor), Agrawal, Pradeep (committee member), Meredith, Carson (committee member), Lively, Ryan P. (committee member), Orlando, Thomas (committee member).

Subjects/Keywords: NOCM; Selective oxidation; Heterogenous catalysts; Coking; Carbon nanotubes; Lewis acid; Dispersion; Nickel oxide; Ceria; Ceria-zirconia; Biomass; Coke; Poisoning; Bio-oil

…very non-selective and formed large amounts of hydrocarbons.22 The catalysts were later… …oxidecontaining catalysts promoted by heavy alkali were more active and selective than the copper4… …intrinsically difficult problem in catalysis, requiring both highly active and highly selective… …catalytic systems. Methane monooxygenase in methanotrophic bacteria catalyzes the selective… …occur through poisoning by nitrogen species or water, sintering of the catalyst, deposition of… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Okolie, C. (2017). Catalytic conversion of methane into alkanes and oxygenates and deactivation of hydrodeoxygenation catalysts. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60691

Chicago Manual of Style (16th Edition):

Okolie, Chukwuemeka. “Catalytic conversion of methane into alkanes and oxygenates and deactivation of hydrodeoxygenation catalysts.” 2017. Doctoral Dissertation, Georgia Tech. Accessed March 04, 2021. http://hdl.handle.net/1853/60691.

MLA Handbook (7th Edition):

Okolie, Chukwuemeka. “Catalytic conversion of methane into alkanes and oxygenates and deactivation of hydrodeoxygenation catalysts.” 2017. Web. 04 Mar 2021.

Vancouver:

Okolie C. Catalytic conversion of methane into alkanes and oxygenates and deactivation of hydrodeoxygenation catalysts. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/1853/60691.

Council of Science Editors:

Okolie C. Catalytic conversion of methane into alkanes and oxygenates and deactivation of hydrodeoxygenation catalysts. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/60691

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