Skeletal isomerization of n-butane under supercritical conditions

轻异烷烃具有较高的辛烷值，被广泛用作绿色汽油的混合原料。硫酸氧化锆是一种强固体酸催化剂，对正构烷烃异构化反应非常有效。为了提高氧化锆-氧化铝的催化活性，我采用共沉淀法在氧化锆-氧化铝表面加入电负性极强的铝原子，制备了硫酸酸化氧化锆-氧化铝。我还研究了Al对其活性和酸度的影响，并测试了反应物分子超临界条件下烷烃的异构化反应。然而，包括硫酸氧化锆在内的大多数固体催化剂都存在由于焦炭形成而快速失活的问题。在本研究中，我使用了反应物分子的超临界条件，因为这种条件会导致较低的粘度和较高的扩散性。在硫酸氧化锆中加入铝抑制了氧化锆的结晶和向单斜晶的相变。在氧化锆结构中加入铝引起结构应变，从而延缓了相变，提高了热稳定性。IR和XPS结果表明，由于Al的高电子负性，Zr原子上正电荷的增强增强了酸性位点。在超临界条件下，失活被很好地抑制，保持了较高的活性。特别是当铝添加量低于5 mol%时，硫酸氧化锆对正构烷烃异构化的催化活性更高。

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.