For example in the naphtha steam reforming alkali

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: oking of the catalyst. Although the basicity of the studied catalysts can be regarded to increase with increasing Mg content more detailed measurements of the surface basicity were attempted. 3.2.8.1. Temperature programmed desorption of CO2 The catalysts calcined at 900°C were used to investigate the influence of the composition of the catalysts on the basicity by TPD of CO2 after adsorption at 100°C for 1 hour. The TPR spectra of the catalysts after adsorption at 100°C/1h exhibited one broad peak for each catalyst (Fig. 27). Two trends were observed. With decreasing Ni/Mg ratios of the catalysts increases the total amount of desorbed CO2 and the position of the maximum is shifted to slightly higher temperatures in the order Ni0C900 > Ni10C900 > Ni30C900 > Ni50C900 ≈ Ni72C900. However, specific desorption amount expressed as the amount of desorbed CO 2 divided by the BET surface area, showed hardly any dependence on the composition of the catalysts (Fig. 28). Such results indicated that non specific adsorption of CO 2 on the catalyst surface took place. 102 3. Results and discussion - catalyst preparation and characterisation 0.1 a.u. CO2 / (s·g) Ni72C900 desorption rate [a.u.] Ni50C900 Ni30C900 Ni10C900 Ni0C900 0 200 400 temperature [°C] 600 Fig. 27 Profiles of the TPD of CO2 of the catalysts calcined at 900°C after 1h adsorption at 100°C. Values are expressed in arbitrary units (a.u.) because no valid calibration data were available for this series of experiments 103 3. Results and discussion - catalyst preparation and characterisation 4.1 4.3 4.2 4.2 2 CO 2 desorbed [a.u. / m ] 3.4 Ni0C900 Ni10C900 Ni30C900 Ni50C900 Ni72C900 catalyst Fig. 28 specific desorption amount of CO2 of the catalysts calcined at 900°C determined by TPD of CO2 after 1h adsorption at 100°C. Values are expressed in arbitrary units (a.u.) because no valid calibration data were available for this series of experiments In order to improve the TPD conditions detailed studies of the adsorption time and temperature were performed for the catalyst Ni0C900 that was expected to show maximum basicity due to the highest Mg content. Theses studies revealed that the amount of adsorbed CO2 increased with the time of adsorption and...
View Full Document

This document was uploaded on 10/07/2013.

Ask a homework question - tutors are online