Skeletal isomerization of n-butane under supercritical conditions

轻异构烷烃具有较高的辛烷值，被广泛用作绿色汽油的调和剂。硫酸化氧化锆是一种强固体酸催化剂，对正构烷烃异构化反应具有很好的催化效果。为了提高其催化活性，我用共沉淀法在其表面添加了高电负性的铝原子，从而制备了硫酸化的氧化锆-氧化铝。考察了铝对催化剂活性和酸性的影响，考察了烷烃在反应物分子超临界条件下的异构化反应。然而，大多数固体催化剂，包括硫化氧化锆，由于结焦而存在快速失活的问题。在这项研究中，我应用了反应物分子的超临界条件，因为这些条件导致了较低的粘度和较高的扩散性。Al的加入抑制了产物的晶化和向单斜晶系的转变。Al的加入引起了结构应变，延缓了相变，提高了热稳定性。IR和XPS结果表明，由于Al具有较高的电子负电性，因此，由于Al具有较高的电子负电性，增加了Zr原子上的正电荷，从而加强了这些酸性中心。在超临界条件下，失活得到了很好的抑制，并保持了较高的活性。特别是在氧化铝加入量小于5%的情况下，硫酸化氧化锆对正构烷烃异构化反应表现出较高的催化活性。

Light isoalkanes have high octane numbers and are widely used as the blendstock for the green gasoline. Sulfated zirconia is a strong solid acid catalyst and is efficient for isomerization of n-alkane. To promote its catalytic activity, I prepared sulfated zirconia-alumina by addition of aluminum, which is a highly electronegative atom, to its surface with a co-precipitation technique. I also investigated the effect of Al on its activity and acidity, and tested the isomerization reaction of the alkanes under supercritical conditions of reactant molecules. However, most of the solid catalysts including sulfated zirconia have a problem of rapid deactivation due to the coke formation. In this research, I applied super critical conditions of reactant molecules because the conditions result in lower viscosity and higher diffusibility. Addition of Al into sulfated zirconia suppressed the crystallization and the phase transition to monoclinic. Al addition to zirconia structure caused the structural strain leading to retarding the phase transitions and improving the thermal stability. IR and XPS results suggested that the enhancement of positive charges on Zr atoms strengthens those acidic sites because of the high electron negativity of Al. Under the supercritical condition, the deactivation was well suppressed, and the higher activity was maintained. Especially for below 5 mol% alumina-added, sulfated zirconia showed the higher catalytic activity for isomerization of n-alkane.