Skeletal isomerization of 1-butene on WOx/Y-AI2O3

BENITEZ, VIVIANA M; QUERINI, CARLOS A; FIGOLI, NORA; COMELLI, RAÚL A

APPLIED CATALYSIS A-GENERAL

ELSEVIER SCIENCE BV

Año: 1999 vol. 178 p. 205 - 218

0926-860X

The catalytic behavior of WOx/g-Al2O3 (having different tungsten loading) during the 1-butene skeletal isomerization at 3808C, atmospheric pressure, and 0.15 atm 1-butene partial pressure was measured. Catalysts were prepared by impregnation using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 3808C, atmospheric pressure, and 0.15 atm 1-butene partial pressure was measured. Catalysts were prepared by impregnation using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 3808C, atmospheric pressure, and 0.15 atm 1-butene partial pressure was measured. Catalysts were prepared by impregnation using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 3808C, atmospheric pressure, and 0.15 atm 1-butene partial pressure was measured. Catalysts were prepared by impregnation using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis indicated that the coke deposited during the reaction burns at high temperature independently of both tungsten loading and calcination conditions, mainly differing in the total amount. Product distribution shows the absence of C1 and C2 using an equilibrium±adsorption technique, being characterized by speci®c surface area and cumulative pore volume measurements, temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), and microcalorimetric measurements. After a standard calcination procedure the isobutene production (which was practically constant with time-on-stream) reached a maximum when increasing the tungsten loading. After 240 min of reaction the catalytic bed showed two layers: the upper part of the bed is completely black and the bottom is light brown. By modifying the calcination conditions, the isobutene production is decreased with time and the catalyst ®nished completely black all along the bed. Temperature-programmed oxidation (TPO) analysis i