Hydrotreating of shale oil

Benson, D. B., Berg, L., Catalytic Hydrotreating of Shale Oil, Chem. 

From an extensive investigation of the potential of hydrotreating of shale oil using a solvent under supercritical conditions, the following conclusions are made ... 

Figure 3. Hydrotreating of shale oil with ICR 106 0.6 LHSV 8000 scf/bbl recycle gas rate.

H-Coal, and EDS middle distillates, and hydrotreated Paraho shale oil residual were tested in a subscale 5-inch diameter, staged rich-lean combustor at conditions representative of baseload and part power settings of 30-MW utility combustion turbine. A minimum NO emission level corrected to 15% oxygen of approximately 35 ppmv was attained for all the fuels despite fuel bound nitrogen levels of up to 0.8 percent by weight. 

The feasibility of hydrotreating whole shale oil is demonstrated by means of several long pilot plant tests using proprietary commercial catalysts developed by Chevron. One such test was on stream for over 3500 hr. The rate of catalyst deactivation was very low at processing conditions of 0.6 LHSV and 2000 psia hydrogen pressure. The run was shut down when the feed supply was exhausted although the catalyst was still active. 

One of the aims of this research study is to assess the economic feasibility of shale oil hydrotreating. These cost studies are reported elsewhere (1,3). 

Using the assumptions outlined above, an estimate of hydrogen requirements for heteroatom removal can be made. This estimate is shown in Table IV. This particular shale oil is, in fact, the Paraho shale oil (direct heated mode) which was hydrotreated for the U.S. Navy by The Standard Oil Company (Ohio). Results from hydrotreating tests on this oil were reported by Robinson (3). The hydrotreater was said to add about 1,600 SCF per barrel of shale oil feed (12.05 kmol/m3). However, complete heteroatom removal was not achieved during hydrotreating. The composition of the hydrotreated whole shale oil was reported as ... 

The diesel fuel fraction from the raw shale oil is too high in sulfur and olefins and too low in cetane number and storage stability to meet specifications. Product which meets all specifications can be made, however, by hydrotreating crude shale oil followed by distillation, refer to Table VII. An increasing number of petroleum crudes also require hydrotreating of the diesel fraction to reduce sulfur content. 

Because some of the pressures on world petroleum supplies have been relieved, it is now expected that, at most, synthetic fuels will have only a minor impact in the 1980 s. However, at least some synthetic crudes from oil shale are expected to be available in the latter part of the decade. Hydrocracking remains the logical choice for conversion of shale oil to jet fuel (44). Similarly, when coal liquids become available, they too will be likely candidates for hydrocracking (45). We are continuing our research on the upgrading of synthetic crudes by hydrotreating and hydrocracking. 

We will consider three processes in more detail to show how the sulfur in the original feedstock material (coal or oil shale) is recovered as elemental by-product sulfur. In this way yields of sulfur per barrel of product can be computed. The three processes will illustrate examples of coal gasification for production of SNG, methanol or indirect liquids, direct liquefaction for production of naphtha and synthetic crude oil and finally, oil shale retorting for production of hydrotreated shale oil. 

The process considered is the Colony hydrotreated shale oil plant using the TOSCO II pyrolysis retort (4). In this process raw shale, crushed to 1/2" or smaller, is contacted with hot ceramic balls in a rotating drum. Downstream of the retort the balls and spent shale are separated by screening. The balls are then transported by an elevator to a vessel in which they are reheated by direct contact with hot combustion gases. The heated balls are then recycled to the rotating retort. 

The plant will produce 198 TPSD of elemental sulfur. This represents a sulfur output of 0.0045 tons of sulfur/barrel of hydrotreated shale oil. 

The first feedstock studied under this contract was Paraho shale oil. In a series of recent papers (1-4) and a DOE report (5 ), three basic shale oil processing routes for the production of transportation fuels were studied hydrotreating followed by hydrocracking, hydrotreating followed by fluid catalytic cracking (FCC), and severe coking followed by hydrotreating. 

Supercritical Hydrotreatment of SCE Shale Oil. SCE shale oil was hydrotreated at high severity because of its high nitrogen content (Table i) and extremely high viscosity. The experimental results are shown in Table III. Based on the shale oil fed, the product distribution is the following 12 gases, 52 boiling less than 300°F (calculated by difference) and 36 in the heavy... 

Reaction Parameter Studies. Experiments were carried out with conventional shale oil [direct retorted Paraho shale oil) for the purpose of studying the effects of reaction parameters in hydrotreating under supercritical conditions. In one group of experiments, the space velocity was varied (1.6, 3.2, and 5)... 

The use of a non-aromatic solvent as the supercritical hydrotreating solvent was studied first with Arabian topped crude and then with Paraho shale oil in hope of reducing hydrogen consumption. The results are tabulated in Tables IV and VI. 

Although obviously not a coal liquefaction product, shale oil represents another synthetic fuel option. During the last quarter of 1979, the Department of Defense arranged with Standard Oil of Ohio through the Paraho Development Corporation to refine 100,000 barrels of raw shale oil. EPRI arranged for delivery of 4,500 barrels of the hydrotreated 700°F residue. 

The shale oil residual had been hydrotreated to a substantial degree, providing it with a hydrogen content very similar to the No. 2 petroleum distillate fuel. The shale oil residual fuel had viscosity characteristics similar to a viscous No. 4 petroleum distillate fuel. The nitrogen content of the hydrotreated shale oil residual was 0.49 weight percent. 

The character and hydrocarbon-type composition of several syncrudes have been investigated by adaptation of methods developed for heavier fractions of petroleum crude oils. The methods are reviewed briefly, and results are summarized for five coal liquids and a hydrotreated shale oil Refining requirements for removal of heteroatoms, especially nitrogen, and conversion of polynuclear aromatics are discussed in relation to the composition of the syncrudes and the character of refined products to be expected. A preliminary report is given on the preparation of liquid samples from coals of widely different rank to permit more systematic correlation of hydrocarbon character with coal source in relation to refining. 

---