Elisabeth Tangstad

Carbon dioxide reforming of methane over lanthanum-modified catalysts in a fluidized-bed reactor

Abstract Nickel on lanthanum-modified aluminas were prepared and tested as catalysts for the CO 2 + CH 4 ⇔ 2CO + 2H 2 reaction in a fluidized-bed reactor. Attrition tests show that lanthanum increases the strength of the carrier significantly. TPR and XRD results indicate that nickel enters into positions in the Al-O spinel blocks of the subsurface LaAl 12 O 19 phase. This results in lower reducibility and thus lower activity for the reforming reaction as compared to nickel on unmodified alumina. While the unmodified catalyst deactivated rapidly under the chosen test conditions, the modified catalysts seem to be stable over several hours. However, the stability is sensitive to the pretreatment conditions of the catalysts.

Partial oxidation of methane to synthesis gas in a fluidized bed reactor

Abstract The partial oxidation of methane to synthesis gas (POX) over N1/AI 2 O 3 catalysts has been studied in a fluidized bed reactor. Flow characterization studies showed that the reaction zone was isothermal, and that the back mixing of gas was negligible. The reaction was rapid, and full O 2 conversion was achieved after 8 ms contact time over 1.5%Ni/Al 2 O 3 at 700°C, with CH 4 /O 2 /N 2 /H 2 O =2/1/2/0.5. The CO selectivity went through a minimum and then increased and approached equilibrium after 48 ms contact time. Simulations of the reaction scheme indicated that the catalyst is active for oxidation of CH 4 , CO and H 2 , as well as for reforming. The simulations further suggested that the reaction rates were diffusion limited.

Quantitative determination of Ni and V in FCC catalysts monitored by ESR spectroscopy

Calibration mixtures containing Ni0 and V4+ in the range from 500 to 4000 ppm have been prepared using various supports (silica, alumina, titania and ultrastable Y zeolite (USY)) with different particle sizes. ESR measurements revealed a linear relation between the impregnated metal amounts and the registered ESR signal integrals and/or intensities, suitable for the determination of the NiO (reduced to Ni0) and V4+ contents in FCC catalysts, respectively. The amount of NiO in a FCC equilibrium catalyst was determined to about 1300 ppm of a total of 2500 ppm Ni compound present in this sample, whereas the amount of V4+ was estimated to about 1800 ppm of a total of 2800 ppm vanadium species. Hence, this catalyst contains about 1000 ppm V5+.

In situ infrared emission spectroscopy for quantitative gas-phase measurement under high temperature reaction conditions: an analytical method for methane by means of an innovative small-volume flowing cell.

We have used infrared emission spectroscopy (IRES) in order to perform in situ studies under flowing gas-phase conditions. When the small-volume cell developed herein is used, we can (1) observe emission spectra from a hot gas-phase sample having an effective volume much less than one milliliter, (2) observe spectra of typical molecular species present, and (3) observe spectra of the more important molecular species down to below 10% and in some cases even as low as 1%. In addition, an analytical method has been derived in order to conduct quantitative studies under typical reaction conditions. We show that simplifications can be made in the data acquisition and handling for a direct linear correlation between band intensity and concentration with only simple background correction. The practical lower limit for methane in the present setup is approximately 0.5–1% v/v depending on the selected temperature. Our data were collected at 500, 600, and 700 °C, respectively. The major features of the present cell design are fairly simple and basically formed by a quartz tube (outer diameter=6 mm, inner diameter=4 mm) inside a metal pipe and two tubular ceramic heaters. This simple setup has advantages and attractive features that have extended the application of IRES to new fields and, in particular, for in situ studies of hydrocarbon reactions at different residence times at high temperature.