Catalytic cracking of bitumen with steam was examined. The heavy oil fraction of bitumen reacted with active oxygen species generated from steam with the iron oxide catalyst, producing significant amounts of light oil. However, some coke formed in the reaction of bitumen using toluene solvent because the oxygen species might be insufficient to react with heavy oil fraction. To enhance the reaction of heavy oil with the oxygen species, 1-methylnaphthalene was used as solvent at higher time factor. As a result, coke formation was successfully suppressed.
Eight polyaromatic hydrocarbons that are model compounds of coal extract were added to coal blends to clarify the mechanism of the effects of coal extract (HyperCoal) on coke strength. Addition of large aromatic-ring compounds (coronene, perylene, naphtho[2,3-a]pyrene) greatly enhanced coke strength, whereas three-ring aromatics (anthracene, phenanthrene) had no significant effect on coke strength. Because large polyaromatic compounds have greater affinity for coal molecules, they co-fused with the coal particles. As a result, formation of large pores during coking was suppressed, leading to increased coke strength.
This paper describes catalytic cracking, with zirconia-supporting iron oxide catalysts in a steam atmosphere, of heavy oil, such as petroleum residual oil, to recover as much lighter fuel as possible. In this process, the heavy oil reacts with active oxygen species generated from steam over the iron oxide catalyst and significant amounts of lighter fractions and carbon dioxide are produced with almost no coke. Active hydrogen species generated from steam are added to the heavy and middle fractions, producing gasoline, kerosene, and gas oil (boiling points less than 350 °C). Large amounts of these lighter fuels (48 mol % C) were produced by the catalytic cracking of residual oil, which contained 93 mol % C of heavy oil fraction (boiling points above 350 °C), with a zirconia−alumina−iron oxide catalyst at 500 °C, with lesser amounts (20 mol % C) at 450 °C. More alumina was mixed to the catalyst to promote the cracking of heavy oil at lower temperatures. This modified catalyst was found to be better for cracking heavy oil, even at 450 °C, and the total amount of lighter fuels was as large as that obtained at 500 °C.
The energy-minimum conformation calculated by molecular mechanics−molecular dynamics simulation for the asphaltene obtained from the vacuum residue of Khafji crude oils showed that structures aggregated through several noncovalent interactions are the most stable. Changes induced in aggregated structures by heating were investigated using molecular dynamics calculations. The simulation showed that the hydrogen bond between asphaltene molecules dissociated at 523 K, while aromatic−aromatic stacking interactions appeared to be stable. At 673 K, however, some stacking interactions could be disrupted, but some stable aggregates remained even at this high temperature where some decomposition reactions would be expected to occur. Simulations on two model compounds were carried out to investigate the effects of aliphatic chains and polar functional groups on the stability of asphaltene aggregates during heating. Aliphatic chains and polar functional groups contributed to the stability of aggregates; in simulations of "imaginary" structures in which the original structure was modified by removing the aliphatic side chains and then replacing heteroatoms with carbon, dissociation occurred at lower temperatures at to greater extents than for the original structure; van der Waals interactions between aliphatic chains acted cooperatively to stabilize the asphaltene aggregates.
