Heavy Oil Molecules Research Articles

イオンモビリティー・質量分析を用いた重質油分子のサイズ解析（２）

イオンモビリティー・質量分析を用いた重質油分子のサイズ解析（２）

Temperature and Solvent Effect on the Molecular Size and Shape of Heavy Oil Fractions

Two kinds of heavy oil were fractionated into eight fractions by liquid–solid adsorption chromatography. The viscosity curves of relative viscosity versus concentration for dilute solutions of heavy oil fractions were determined, using the isovolume viscosity determination method. The intrinsic viscosity was obtained according to the Einstein law, and subsequently, the equivalent sphere hydrodynamic diameter was calculated. The results show that the equivalent sphere hydrodynamic diameters of heavy oil fractions are 1.1–4.0 nm under the experimental condition, while the molecular size of asphaltene is much larger than that of other fractions. The molecular size is not only related to the molecular weight but also affected by the spatial configuration of the heavy oil molecule. Different temperature and solvent conditions lead to various spatial configurations of heavy oil molecules, which results in different molecular sizes.

Restricted diffusion of residual molecules in catalyst pores under reactive conditions

The restricted diffusion of residual molecules under catalytic conversion conditions was investigated using commercial catalysts. The effectiveness factor, η, and the effective diffusion coefficient, D e , for residual molecules were evaluated and explicitly compared based on a pseudo-first-order reaction kinetic model and the Thiele modulus. The experimental results showed that the restrictive diffusion of heavy oil molecules is affected by the joint functions of several factors, such as the operating conditions, the size and configuration of the reactant molecules, and the average pore diameter of the catalyst. The reaction temperature has a greater influence on restrictive diffusion than the other operating factors, and the ratio of reactant molecular size to catalyst pore size is the most critical factor that determines the degree of restrictive diffusion. Moreover, a mathematical expression was derived for the restrictive factors in order to describe the relationship between the effective diffusivity and ratio of molecule-to-pore size.

Production of Lighter Fuels by Cracking Petroleum Residual Oils with Steam over Zirconia-Supporting Iron Oxide Catalysts

Zirconia-supporting iron oxide catalysts were developed for recovery of lighter fuels in a steam atmosphere from residual oils in petroleum refinery processes. In these processes, steam is first decomposed on zirconia, yielding active hydrogen and oxygen species. These oxygen species spill over to the surface of iron oxide and react with heavy oil molecules, producing lighter molecules and carbon dioxide. The remaining active hydrogen species are then added to the lighter molecules. This reaction therefore proceeds by oxidative degradation. It was found in the present study that the catalysts exhibited catalytic activity to decompose the residual oil without any carbonaceous residue. The catalysts were, however, deactivated when the sequence of reaction and regeneration was repeated, which is attributed to a change in the iron oxide, namely, between hematite and magnetite, and subsequent peeling of zirconia from the catalyst. To avoid this phase change, Al2O3 was added to the iron oxide lattice. The secon...