A preliminary study of the influence of alkali-metal promoters on the selectivity and activity of vanadium catalysts in the oxidation of naphthalene

1981 ◽  
Vol 34 (6) ◽  
pp. 1325 ◽  
Author(s):  
NR Foster ◽  
MS Wainwright ◽  
DWB Westerman
Keyword(s):  
Alkali Metal ◽  
Partial Oxidation ◽  
Alkali Metals ◽  
Catalyst Activity ◽  
Fixed Bed ◽  
Oxidation Products ◽  
Metal Sulfate ◽  
Sodium Potassium ◽  
Fixed Bed Reactors ◽  
Preliminary Study

The oxidation of naphthalene over vanadia catalysts promoted by alkali- metal sulfates was studied in the temperature range 400-440°C. The effects of SO3 levels and alkali-metal sulfate promoter type on catalyst activity and selectivity were investigated in laboratory fixed-bed reactors employing integral conversions. ��� The relative promoting abilities of the alkali metals sodium, potassium, rubidium and caesium were investigated with laboratory catalyst preparations. Alkali metals of higher atomic number favoured selectivity to partial oxidation products with an associated loss in overall activity.

Support Effects for Pt and Rh-Based Catalysts for Partial Oxidation of n-Tetradecane

2006 ◽  
Author(s):  
David A. Berry ◽  
Dushyant Shekhawat ◽  
Todd H. Gardner ◽  
Maria Salazar ◽  
Daniel J. Haynes ◽  
...  
Keyword(s):  
Partial Oxidation ◽  
Catalyst Activity ◽  
Fixed Bed ◽  
Sulfur Poisoning ◽  
Liquid Fuels ◽  
Superior Performance ◽  
Pt Catalysts ◽  
Reforming Catalysts ◽  
High Sulfur Content ◽  
Attractive Option

Catalytic partial oxidation (CPOX) of liquid fuels is an attractive option for producing a hydrogen-rich gas stream for fuel cell applications. However, the high sulfur content along with aromatic compounds present in liquid fuels may deactivate reforming catalysts. Deactivation of these catalysts by carbon deposition and sulfur poisoning is a key technical challenge. The relationship between catalyst supports and deactivation have been studied here for three catalysts (Rh/Ce0.5Zr0.5O2, Pt/Ce0.5Zr0.5O2, and Pt/Al2O3) in a fixed bed catalytic reactor using a mixture of n-tetradecane, 1-methylnaphthalene, and dibenzothiophene to simulate logistic fuels. Carbon production during CPOX reforming was directly related to olefin formation. Olefins, which are known coke precursors, were observed on the Pt catalysts during CPOX of n-tetradecane with no sulfur (particularly from Pt/Al2O3), but not on Rh/Ce0.5Zr0.5O2. For the Rh/Ce0.5Zr0.5O2, yields of H2 and CO dropped to a stationary level after the introduction of sulfur-containing feed (1000 ppm sulfur) or aromatic-containing feed (5 wt%), however, the catalyst activity was restored after removing the sulfur or aromatics from the feed. For the Pt catalysts, H2 and CO yields dropped continuously over time in the presence of sulfur or aromatics in feed. The superior performance of Rh/Ce0.5Zr0.5O2 can be attributed to the higher oxygen-ion conductivity of the Ce0.5Zr0.5O2 support as well as the activity of the Rh sites.

scholarly journals Alkali Metal Re-Distribution after Oxidation of 4H-SiC

2016 ◽  
Vol 858 ◽  
pp. 677-680
Author(s):  
Margareta K. Linnarsson ◽  
Sethu Saveda Suvanam ◽  
Lasse Vines ◽  
Anders Hallén
Keyword(s):  
Alkali Metal ◽  
Alkali Metals ◽  
Main Part ◽  
Secondary Ion Mass Spectrometry ◽  
Minor Amount ◽  
Sodium Potassium ◽  
Alkali Atoms ◽  
A Minor ◽  
P Type ◽  
Secondary Ion

Relocation of alkali metals sodium, potassium and cesium during oxidation of 4H-SiC has been studied by secondary ion mass spectrometry. The alkali metal source has been introduced by ion implantation before oxidation into n-and p-type 4H-SiC samples. Dry oxidation of SiC has been performed at 1150 oC during 4, 8 and 16 h. In the formed oxide, the main part of the alkali metals diffuses out via the SiO2 surface. Close to the moving SiO2/SiC interface, a minor amount of alkali metals is retained. In the SiC material, the main amount of implanted alkali atoms is not redistributed during the oxidation, although a minor amount diffuses deeper into the samples. For p-type 4H-SiC, the diffusion deeper into the samples of the studied alkali metals decreases as the mass increases, Na+<K+<Cs+, but the sodium mobility is substantial already at 1150 °C.

Capture of Alkali Metals by Kaolin

2003 ◽  
Author(s):  
Khanh-Quang Tran ◽  
M. Kristiina Iisa ◽  
Britt-Marie Steenari ◽  
Oliver Lindqvist ◽  
Magnus Hagstro¨m ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Fluidized Bed ◽  
Alkali Metals ◽  
Fixed Bed ◽  
Capture Efficiency ◽  
Fixed Bed Reactor ◽  
Fluidized Bed Combustion ◽  
Biomass Fuels ◽  
Metal Source ◽  
On Line

Alkali metals present in biomass fuels may cause increased bed agglomeration during fluidized bed combustion. In worst case this may lead to complete defluidization of the bed. Other problems caused by alkali metals include increased fouling and slagging. One possibility to reduce the impact of alkali metals is to add sorbents, e.g. aluminosilicates, to the bed for the capture of alkali metals. In the current investigation, the capture of vapor phase potassium compounds by kaolin was investigated in a fixed bed reactor. The reactor consisted of an alkali metal source placed at a variable temperature from which gaseous potassium compounds were generated, a fixed bed holding the kaolin, and an on-line detector for the alkali metal concentration. The on-line alkali metal detector was based on ionization of alkali metals on hot surfaces and is capable of detecting alkali metals down to ppb levels. This makes it possible to perform experiments at alkali metal concentrations relevant to fluidized bed combustion of biomass fuels. In the experiments, KCl was used as the alkali metal source with inlet concentrations of 0.5–3.5 ppm. The experiments were performed at reactor temperatures of 800–900°C and a contact time of 0.26 s. The capture efficiencies of KCl were always above 97%. The capture efficiency was somewhat higher in oxidizing than in reducing gas atmospheres. In the oxidizing gas atmosphere, the conversion was slightly higher with H2O addition than without. The capture efficiency decreased slightly as temperature or KCl concentration was increased.

Estimation of catalyst activity profiles in fixed bed reactors

1972 ◽  
Vol 27 (2) ◽  
pp. 329-338 ◽  
Author(s):  
G.R. Gavalas ◽  
G.C. Hsu ◽  
J.H. Seinfeld
Keyword(s):  
Catalyst Activity ◽  
Fixed Bed ◽  
Fixed Bed Reactors

A Study of Chemical Reactions in Molton Sodium-Potassium Hydrogen Sulfate Eutectic. IV. The Reaction of Eight Oxalates

1985 ◽  
Vol 38 (7) ◽  
pp. 1123
Author(s):  
JO Sabato ◽  
SA Tariq
Keyword(s):  
Alkali Metals ◽  
Alkaline Earth ◽  
Hydrogen Sulfate ◽  
X Ray Diffraction ◽  
Metal Sulfate ◽  
Chemical Methods ◽  
Sodium Potassium ◽  
X Ray ◽  
Potassium Hydrogen ◽  
Wet Chemical

The reactions of oxalates of ammonium, alkali metals (Li, Na and K) and alkaline earth metals (Mg, Ca, Sr and Ba ) with sodium-potassium hydrogen sulfate eutectic were investigated. Oxalic acid was found to be an intermediate product in all these reactions. Final products of the reactions as determined by thermogravimetry , differential thermal analysis, X-ray diffraction, infrared and 'wet' chemical methods consisted of a mixture of H2O, CO, CO2 and the corresponding metal sulfate. The stoichiometries of the reactions were elucidated.

Estimation of catalyst activity profiles in fixed-bed reactors with decaying catalysts

1993 ◽  
Vol 106 (2) ◽  
pp. 193-199 ◽  
Author(s):  
Ying-Sheng Cheng ◽  
Felipe López-Isunza ◽  
Tharathon Mongkhonsi ◽  
Lester Kershenbaum
Keyword(s):  
Catalyst Activity ◽  
Fixed Bed ◽  
Fixed Bed Reactors
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