TY - JOUR
T1 - Coke deactivation of Pd/H-mordenite catalysts used for C5/C6 hydroisomerization
AU - Li, C. L.
AU - Novaro, O.
AU - Muñoz, E.
AU - Boldú, J. L.
AU - Bokhimi, X.
AU - Wang, J. A.
AU - López, T.
AU - Gómez, R.
PY - 2000/6/12
Y1 - 2000/6/12
N2 - Coke formation in C5/C6 alkane isomerization on a Pd/H-Mordenite catalyst discharged from a pilot reactor was studied. Experimental techniques like XRD, EPR, MAS-NMR, FTIR, TGA and TPO, were applied for the characterization of coke and coked catalysts. It was shown that coke content, chemical composition, its structure and nature depended upon time-on-stream and section of the catalyst bed. The coke content increased from 3.0 in the top section, to 4.1 wt.% in the central section and 6.2 wt.% in the bottom of the catalyst bed and C/H ratio of the corresponding coke increased from 1:1.12, 1:0.55 to 1:0.35, which significantly affected the catalytic behavior and regeneration of the catalysts. The selectivity to 2,2-dimethyl butane during n-hexane isomerization, respectively, decreased from 19% for the fresh catalysts, to 10% and 8.3% for the coked catalysts in the central and outlet sections. As time-on-stream increased, coke initially formed on palladium metals and then moved to acidic sites in the support where polyaromatic or pseudographite-like structures were formed through further acid catalyzed reactions. Two kinds of coke with different nature could be combusted below 300 and 600°C, respectively. These results are very useful for choosing operation parameters to restore initial activity of the coked catalysts in the regeneration units in our pilot plant.
AB - Coke formation in C5/C6 alkane isomerization on a Pd/H-Mordenite catalyst discharged from a pilot reactor was studied. Experimental techniques like XRD, EPR, MAS-NMR, FTIR, TGA and TPO, were applied for the characterization of coke and coked catalysts. It was shown that coke content, chemical composition, its structure and nature depended upon time-on-stream and section of the catalyst bed. The coke content increased from 3.0 in the top section, to 4.1 wt.% in the central section and 6.2 wt.% in the bottom of the catalyst bed and C/H ratio of the corresponding coke increased from 1:1.12, 1:0.55 to 1:0.35, which significantly affected the catalytic behavior and regeneration of the catalysts. The selectivity to 2,2-dimethyl butane during n-hexane isomerization, respectively, decreased from 19% for the fresh catalysts, to 10% and 8.3% for the coked catalysts in the central and outlet sections. As time-on-stream increased, coke initially formed on palladium metals and then moved to acidic sites in the support where polyaromatic or pseudographite-like structures were formed through further acid catalyzed reactions. Two kinds of coke with different nature could be combusted below 300 and 600°C, respectively. These results are very useful for choosing operation parameters to restore initial activity of the coked catalysts in the regeneration units in our pilot plant.
KW - Catalyst
KW - Coke composition
KW - Deactivation by coke
KW - Hydroisomerization
KW - Pd/H-mordenite
KW - Pilot plant
UR - http://www.scopus.com/inward/record.url?scp=0001434159&partnerID=8YFLogxK
U2 - 10.1016/S0926-860X(99)00559-1
DO - 10.1016/S0926-860X(99)00559-1
M3 - Artículo
SN - 0926-860X
VL - 199
SP - 211
EP - 220
JO - Applied Catalysis A: General
JF - Applied Catalysis A: General
IS - 2
ER -