A Study of Propane and Propene Ammoxidation over Antimony-Vanadium-Oxide Catalysts at Steady-State and Transient Conditions
(1997)- Abstract
- Propane ammoxidation catalysts of differing Sb/V ratio and consisting of differing amounts of the V2O5, alpha-Sb2O4, and Sb0.92V0.92O4 phases were prepared.
In the first paper, the structure of Sb0.92V0.92O4 was determined by thermogravimetry, X-ray microanalysis, X-ray powder diffraction, and neutron powder diffraction. Sb0.92V0.92O4 was found to have a defective rutile structure involving cation vacancies.
In the second, third, and fourth papers, the initial rates and selectivities of these catalysts were determined when used in the ammoxidation of propane and propene, respectively. The main products obtained in propane ammoxidation were acrylonitrile, acetonitrile, carbon oxides and propene. Two... (More) - Propane ammoxidation catalysts of differing Sb/V ratio and consisting of differing amounts of the V2O5, alpha-Sb2O4, and Sb0.92V0.92O4 phases were prepared.
In the first paper, the structure of Sb0.92V0.92O4 was determined by thermogravimetry, X-ray microanalysis, X-ray powder diffraction, and neutron powder diffraction. Sb0.92V0.92O4 was found to have a defective rutile structure involving cation vacancies.
In the second, third, and fourth papers, the initial rates and selectivities of these catalysts were determined when used in the ammoxidation of propane and propene, respectively. The main products obtained in propane ammoxidation were acrylonitrile, acetonitrile, carbon oxides and propene. Two synergy effects were revealed; catalysts rich in vanadium showed a maximum in total reaction rate and catalysts rich in antimony a maximum in selectivity to acrylonitrile formation. The main products obtained in propene ammoxidation were acrylonitrile, acetonitrile, carbon oxides and acrolein. The catalysts were characterised by XRD, XPS, FTIR, and FT-Raman measurements before and after their use in propane and propene ammoxidation, respectively. In the course of ammoxidation, catalysts with an excess of alpha-Sb2O4 were found to be enriched at the surface with antimony, creating a surface that was selective for nitrile formation. This enrichment appeared to be caused by the migration of antimony from alpha-Sb2O4 to the surface of Sb0.92V0.92O4. No evidence that antimony migrates from the bulk of Sb0.92V0.92O4 up to the surface of it was obtained.
The fifth and sixth papers concerned the transient response method. Differential equations describing the consumption of reactants and the formation of products were solved numerically for a step change from inert to reactant feed. Different types of propene/propane oxidation/ammoxidation mechanisms were considered. In comparing the experimental and the simulated responses, it was found that the adsorption of propane was rate limiting for its consumption in the ammoxidation of it. However, the propene/acrylonitrile product ratio was governed by the step in which water desorbs. These results were not contradicted by the results reported in paper four, in which dependencies of the rate on the partial pressure of the reactants was investigated under steady-state conditions. (Less) - Abstract (Swedish)
- Popular Abstract in Swedish
Akrylfibrer, SAN-plast (Styren-AkrylNitril) och ABS-plast (Akrylnitril-Butadien-Styren) är tre viktiga polymerer som tex används för textilier (akrylfibrer) och optiska instrument (SAN). ABS-plast har hög motståndskraft mot kemikalier samt är slagtålig och används tex i bilar. Gemensamt för dessa tre polymerer är att akrylnitril används som monomer. Akrylnitril tillverkas idag genom ammoxidation av propen:
C3H6 + 1.5 O2 + NH3 ======> CH2CHCN + 3 H2O
För att denna reaktion ska gå att genomföra måste man använda en katalysator. En katalysator är ett ämne som påskyndar en kemisk reaktion utan att själv förbrukas. En katalysator kan också förändra... (More) - Popular Abstract in Swedish
Akrylfibrer, SAN-plast (Styren-AkrylNitril) och ABS-plast (Akrylnitril-Butadien-Styren) är tre viktiga polymerer som tex används för textilier (akrylfibrer) och optiska instrument (SAN). ABS-plast har hög motståndskraft mot kemikalier samt är slagtålig och används tex i bilar. Gemensamt för dessa tre polymerer är att akrylnitril används som monomer. Akrylnitril tillverkas idag genom ammoxidation av propen:
C3H6 + 1.5 O2 + NH3 ======> CH2CHCN + 3 H2O
För att denna reaktion ska gå att genomföra måste man använda en katalysator. En katalysator är ett ämne som påskyndar en kemisk reaktion utan att själv förbrukas. En katalysator kan också förändra produktbilden, dvs en bra katalysator kan påskynda önskvärda reaktioner mer än den påskyndar icke önskvärda bireaktioner.
Om man kunde använda propan istället för propen skulle man kunna få ned kostnaderna för framställning av akrylnitril eftersom propan är billigare än propen. Man måste isåfall använda en annan typ av katalysator. I patent från USA finns beskrivet att antimon-vanadin-oxider ingår som en beståndsdel i de katalysatorer som verkar mest lovande.
Syftet med arbetet som mynnade ut i denna avhandling var att försöka förstå hur dessa antimon-vanadin-oxider fungerar när de används som katalysatorer för ammoxidation av propan. Frågor som därvid ställts och till viss del besvarats är:
Vad är det som gör att en katalysator med en viss sammansättning är bra medan en annan katalysator med en annan sammansättning är dålig?
Fungerar en katalysator bra under vissa förhållanden (tex högt partialtryck av ammoniak) men dåligt under andra förhållanden?
Vilka delsteg ingår i reaktionen och vilket eller vilka av dessa är långsamma ("den svaga länken i kedjan") ? (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/29254
- author
- Nilsson, Roland LU
- supervisor
- opponent
-
- Prof Holmen, Anders, Norwegian University of Science and Technology, Norway
- organization
- publishing date
- 1997
- type
- Thesis
- publication status
- published
- subject
- keywords
- Kemiteknik och kemisk teknologi, Chemical technology and engineering, oxidation, Ammoxidation, propane, propene, propylene, catalysis, transient response, antimony vanadium oxides
- pages
- 147 pages
- defense location
- Lecture hall C, Center for Chemistry and Chemical Engineering
- defense date
- 1997-05-22 13:15:00
- external identifiers
-
- other:ISRN: LUTKDH/TKKT--97/1044--SE
- language
- English
- LU publication?
- yes
- id
- 7177c2e7-f52d-4407-afac-53e644fb3083 (old id 29254)
- date added to LUP
- 2016-04-04 13:49:02
- date last changed
- 2018-11-21 21:16:28
@phdthesis{7177c2e7-f52d-4407-afac-53e644fb3083,
abstract = {{Propane ammoxidation catalysts of differing Sb/V ratio and consisting of differing amounts of the V2O5, alpha-Sb2O4, and Sb0.92V0.92O4 phases were prepared.<br/><br>
<br/><br>
In the first paper, the structure of Sb0.92V0.92O4 was determined by thermogravimetry, X-ray microanalysis, X-ray powder diffraction, and neutron powder diffraction. Sb0.92V0.92O4 was found to have a defective rutile structure involving cation vacancies.<br/><br>
<br/><br>
In the second, third, and fourth papers, the initial rates and selectivities of these catalysts were determined when used in the ammoxidation of propane and propene, respectively. The main products obtained in propane ammoxidation were acrylonitrile, acetonitrile, carbon oxides and propene. Two synergy effects were revealed; catalysts rich in vanadium showed a maximum in total reaction rate and catalysts rich in antimony a maximum in selectivity to acrylonitrile formation. The main products obtained in propene ammoxidation were acrylonitrile, acetonitrile, carbon oxides and acrolein. The catalysts were characterised by XRD, XPS, FTIR, and FT-Raman measurements before and after their use in propane and propene ammoxidation, respectively. In the course of ammoxidation, catalysts with an excess of alpha-Sb2O4 were found to be enriched at the surface with antimony, creating a surface that was selective for nitrile formation. This enrichment appeared to be caused by the migration of antimony from alpha-Sb2O4 to the surface of Sb0.92V0.92O4. No evidence that antimony migrates from the bulk of Sb0.92V0.92O4 up to the surface of it was obtained.<br/><br>
<br/><br>
The fifth and sixth papers concerned the transient response method. Differential equations describing the consumption of reactants and the formation of products were solved numerically for a step change from inert to reactant feed. Different types of propene/propane oxidation/ammoxidation mechanisms were considered. In comparing the experimental and the simulated responses, it was found that the adsorption of propane was rate limiting for its consumption in the ammoxidation of it. However, the propene/acrylonitrile product ratio was governed by the step in which water desorbs. These results were not contradicted by the results reported in paper four, in which dependencies of the rate on the partial pressure of the reactants was investigated under steady-state conditions.}},
author = {{Nilsson, Roland}},
keywords = {{Kemiteknik och kemisk teknologi; Chemical technology and engineering; oxidation; Ammoxidation; propane; propene; propylene; catalysis; transient response; antimony vanadium oxides}},
language = {{eng}},
school = {{Lund University}},
title = {{A Study of Propane and Propene Ammoxidation over Antimony-Vanadium-Oxide Catalysts at Steady-State and Transient Conditions}},
year = {{1997}},
}