Performance of ferrierite promoted with tungsten or boron species during the linear butene skeletal isomerization

ALEJANDRO ASTUDILLO, DARÍO FAUDA, CARLOS QUERINI AND RAÚL COMELLI

current topics in catalysis

Research Trends

Año: 2006 vol. 5 p. 89 - 102

0972-4508

Ammonium and potassium ferrierite were modified with tungsten or boron species using incipient wetness and wet impregnation or ion exchange. Catalytic behavior  during the linear butene skeletal isomerization was measured at 300 and 450ºC, at atmospheric pressure and 0.15 atm 1-butene partial pressure. Catalysts having strong acid sites reach at 300ºC and a short time practically the same high butene conversion with a low isobutene selectivity. Those acid sites favor undesirable side reactions. Conversion decreases at a long time. At a short time, tungsten exchanged on potassium-ferrierite produces two times the ferrierite?s isobutene yield. At a long time, boron impregnated on ferrierite reaches the largest isobutene production. At 450ºC, the high conversion is maintained even at a long time. At this temperature, tungsten impregnated on potassium-ferrierite, sample without strong acid sites, practically produces the same isobutene yield of ferrierite, even though  its conversion is only a half of the ferrierite one. By considering by-product distributions, dimerization and oligomerization reactions take place. Carbonaceous deposits were characterized by temperature-programmed oxidation and FTIR. The acid strength of active sites influences the coke amount. Independent of temperature, carbonaceous deposit formed on samples with strong acid sites is between 6.0 and 7.4%. The smallest amount (1.0%) is formed on tungsten impregnated potassium-ferrierite, which only displays the low-temperature combustion peak after reaction at 300ºC. Reaction temperature and type of acid sites affect the nature of carbonaceous deposit. Both olefinic species and aromatic rings appear in the deposit formed at 300ºC; at 450ºC, aromatic coke increases. Isobutene dimeric species play a role in coke formation.