Technology
Process upgrades shale oil to usable crude Making whole shale oil usable by conventional refineries, Chevron Research process catalytically hydrofines shale oil to yield crude feedstock Conversion of kerogen to whole shale oil is now a fairly well-defined technology; retorting, in such as the Paraho process, is the preferred method. It now appears, however, that unless the whole shale oil can be used directly by a conventional refinery, the use of shale oil will remain stalled. A new impetus to remove some of the technical bottlenecks comes from Chevron Research Co., under contract to the Department of Energy. The potential crude oil equivalent volume of shale oil in the western U.S. exceeds 2 trillion bbl. But converting any of that volume to conventional fuels and feedstocks has been held up by the vagaries of national energy policy, world oil prices, and a still dimly perceived necessity for alternate sources of hydrocarbons. One effect of these impediments has been a piecemeal approach to utilizing shale oil. Without pretreatment shale oil is not
suitable for conventional crude processing. Although lower in sulfur (typically 0.6% by weight) than many crude oils, whole shale oil still must be desulfurized. Whole shale oil also contains considerable oxygen and trace metal contaminants such as iron, zinc, selenium, and arsenic, all of which act as catalyst poisons. The principal contaminant, however, is nitrogen. Whole shale oils typically contain more than 2% by weight of nitrogen and this concentration must be reduced drastically before the oil can be further processed to fuels and feedstocks for petrochemical plants. Nitrogen quickly poisons the catalysts commonly utilized in fluid-bed crackers and hydrotreaters. Most of the past attempts to further refine whole shale oil have assumed that a primary distillation would yield appropriate fractions, which then would be individually treated before being sent on to the appropriate points in a refinery. This means considerable duplication of facilities and consequently undesirable processing economics. The Chevron approach calls for upgrading the whole shale oil such that the product will be suitable for use as a bulk refinery feed when added to or as a supplement to conventional crude. According to Chevron's R. F. Sullivan, the basic idea in the new approach is to
hydrofine catalytically whole shale oil to yield an upgraded crude. Work already done has shown that whole shale oil can be hydrodenitrified catalytically to reduce nitrogen concentration as low as 1 ppm in a single pass. Simultaneously oxygen is reduced and sulfur is all but eliminated. However, such a drastic nitrogen reduction calls for low flow rates. For economic reasons, nitrogen concentrations of 500 ppm appear to be optimum. One of the advantages of upgraded shale oil is that unlike conventional crudes it has essentially no residuum that need be contended with in further processing. The whole shale oil used in the Chevron investigations was obtained from the Paraho retort, a privately sponsored mining, retorting, and shale disposal project that operated for several years near Rifle, Colo. As received, the shale oil contained 6% water and 0.5% fine particles suspended in the emulsion. The emulsion was broken by mild heating, but some of thefinesremained. After removing trace metal contaminants in a fixed bed (guard bed) of alumina, the whole shale oil then was hydrofined over a proprietary Chevron catalyst. Downstream processing studies were conducted with the upgraded oil. Fractionation of the upgraded oil suggests that it is eminently suitable for use in conventional refineries. The heavy naphtha cut (180° to 350° F) is compa-
Hydrofining is heart of shale oil refinery design C4's
