Details

Autor(en) / Beteiligte

• Xu, Bo-Qing
• Sun, Ke-Qiang
• Zhu, Qi-Ming
• Sachtler, Wolfgang M.H

Titel

Unusual selectivity of oxygenate synthesis: Formation of acetic acid from syngas over unpromoted Rh in NaY zeolite

Ist Teil von

• Catalysis today, 2000-12, Vol.63 (2), p.453-460

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2000

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Syngas conversion over Rh/zeolite-NaY catalysts at high-pressure lead to high yields of acetic acid. This unusual selectivity toward one oxygenate in the absence of any catalyst promoter is most pronounced at lower temperature; the apparent activation energy for overall CO-hydrogenation is 23.7 kcal/mol, but for the formation of acetic acid it is 11.9 kcal/mol. The selectivity is little affected by the protons formed during the reduction of Rh. In stiu FT-IR measurement reveals that changes in activity and selectivity during the start-up period are caused by thorough catalyst reconstruction, converting the original Rh 0 clusters to multinuclear Rh 6(CO) 16 and CH 3Rh y (CO) x and/or mononuclear CH 3Rh(CO) x carbonyl complexes, and smaller Rh 0 clusters. Stable acetate groups, but not the surface bound acetyls, are formed and detected by FT-IR. Most of the cooperating Rh species survive when the pressure is lowered from 1.0 to 0.1 MPa, maintaining a high acetic acid selectivity that is vastly superior to that of the fresh catalyst.