Hydrotreatment process

FIGURE 11.1 Acid treating process schematic for white oil production. 

Source J. Weeks, The White Oil Industry in North America, Paper LW-98-131, presented at the Lubricants and Waxes meeting, National Petroleum Refiners Association, Houston, Texas, November 13-14, 1998. With permission. 

FIGURE 11.2 BASF process schematic for two-stage hydroprocessing route to food grade white oil manufacturing. 

Source W. Himmel, T. Anstock, R. Spahl, and K. Kussner, White Oils and Fully Refined Paraffins, Erdol und Kohle 39 408 -14 (1986). With permission. 

In these cases, white oil is an additional product to the base stocks. Of course, there is much more to white oil than the ability to produce it. Maintaining quality through product storage and delivery is not a simple undertaking. 

---

Fig. 1. Distillation—hydrotreat process, where CW = cooling water.

Most sulfur compounds can be removed from petroleum streams through hydrotreatment processes, where hydrogen sulfide is produced and the corresponding hydrocarbon released. Hydrogen sulfide is then absorbed in a suitable absorbent and recovered as sulfur (Chapter 4). 

Manufacturing high quality fuels would require not only more hydroprocessing but also other chemical processing. In the immediate future, most of the refinery investments are made to cope with these requirements and particularly involve hydrotreatment processes. However, commercially available technology does not have all the answers to the market needs. Some niches are open for new technology development. 

Run 15 was carried out with a higher LHSV of 1.6, and the results are not too much different from Runs 13 and lit. The heteroatom removals are about the same. The heavy oil fraction, however, was increased to 13 from 30 and 36% (Runs 13 and lit). Thus, the conclusion is that the lignite extract, a solid, can also be upgraded to yield a syncrude by the supercritical hydrotreatment process. 

Mixtures of transition metal (Mo or W) sulphides dispersed on y-alumina supports are used in hydrotreatment processes to remove sulphur, nitrogen, oxygen and metals from oil fractions. The addition of phosphorus to these catalysts enhances the solubility and stability of molybdate and improves the thermal stability of the alumina support. Solid state P double-resonance NMR experiments ( P- AI REDOR and TRAPDOR) have been used to investigate the interaction between the impregnating phosphorus and the support surface (van Eck etal. 1995). The results showed that most of the phosphorus is in close contact with the aluminium, and that the layer of AIPO4 formed on the surface is not completely amorphous, but is slightly more ordered. 

The dilution of the impregnating solution RhMoe with AlMoe (which is poorly active for hydrotreatment processes) shows that the catalyst behaviour is function of Rh content. 

With the exception of these newer hydrotreatment processes, all other processes used in modern base oil plants are physical separation techniques, i.e. all the essential constituents of the finished base oil were present in the original crude oil and processing methods are used to concentrate the desirable components by removing the less desirable components as by-products. 

Another variant of the severe hydrotreatment process is the substitution of wax for lubricant distillate as feedstock. The wax recovered from conventional solvent dewaxing units is essentially a pure alkane feedstock containing a high proportion of linear alkanes. With this type of feedstock and under appropriate operating conditions, the isomerisation reaction can be made to predominate over cracking reactions. Unconverted wax can be removed by conventional methods to yield a base oil that is exclusively composed of isoalkanes and that resembles synthetic polyal-phaolefin base fluids more closely than the hydrocracked base oils described in Section 1.5.2. A comparison of some of these base fluid properties is shown in Table 1.4. 

Base oils produced by the distillation/hydrotreatment processes are of superior quality compared to the older, previously described, used lubricant recycling technologies. They can certainly be of Gp. I quality, in some cases Gp. I+, with some re-refining processors now claiming Gp. II quality standard with improved process technologies. 

The distillation/hydrotreatment process is comparatively sophisticated, capital intensive and requires skilled operation, although operating costs are not exceptionally high. It appears to be the preferred process for the re-refining of used lubricants to produce high-quality base oils which can compete with virgin base oils at the Gp. I/II level. 

The dewaxed distillate feed contains a range of thiophenes, from ben-zothiophene and up, but no alkyl thiophenes themselves. The extrac-tion/hydrotreatment process is most effective in removing the two-ring and four-ring or greater thiophenes, and evidently the dibenzothiophenes are the most resistant. The decrease in average Z number is consistent with this. The authors see the decrease in the number of side chain carbons in sample B versus... 

Sulfur in catalysis is an object of outstanding interest both as atom(s) in compounds being transformed catal3d,icaUy, and as a part of catalysts applied in chemical transformations, especially in hydrotreatment processes. Catalytic methods — both homogenous and heterogeneous — of sulfuric acid production were known before the concept of catalysis was formulated the heterogeneous SO2-SO3 oxidation was one of the phenomena leading Berzelius to introduce the concept and the name of catalysis. 

Hydrotreatment processes, including hydrodesulfurization, are carried out in practice on supported catalysts, mostly on alumina or silica supports, on... 

In this chapter, the effect of capillary condensation upon catalytic reactions in porous media has been reviewed. It was shown that capillary condensation could have a strong influence upon catalytic reactions on its kinetics, transient dynamics, and catalyst pellet effectiveness factor. The reaction rate in the liquid phase is usually slower than in the gas phase due to the difference in adsorption equilibrium, and due to low solubility of hydrogen in the liquid (in hydrotreatment processes). 

Moreover, these sites present Lewis acid type properties and interact with molecules involved in the hydrotreatment process through a n-electrodonation for imsaturated compounds or via the lone pair of electrons for... 

Froment GF. Modeling in the development of hydrotreatment processes. Catal. Today 2004 98 43-54. 

Today, in addition to naphtha, hydrotreaters process kerosene, gas oil, vacuum gas oil, and residue. Hydrocrackers process vacuum gas oil, coker gas oil, visbreaker gas oil, FCC heavy cycle oil, and/or other feeds that boil between 650°F and 1050°F (343°C and 566°C). Most residue hydrocrackers use fluidized bed or ebullated bed technology. 

---