Temperature hydrotreatment

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical Hquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of Hquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quaHty transportation fuels, and to study Hquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

Naphtha hydrotreatment takes place at temperatures from 290°C to 370°C, pressures from 350 to 450psig and space velocity between 2 and 6h 1. Preferred catalysts are usually CoMo, but if coker naphthas and in some instances FCC or HCK naphthas are incorporated to the feed, then NiMo can represent a better option. 

For Runs 2, 3, 1, and 5 the feed entered the hydrotreater directly from the supercritical extraction unit. The extract contained about k% shale oil in toluene. Runs 2 and 3 were carried out at 81+2F, and Runs k and 5, at T50F. At the lower reaction temperature (750F), the yield of gases dropped to less than 2, and the yield of heavy oil fraction increased by about 10. The extent of nitrogen removal was reduced significantly at the lower temperature. However, the sulfur removal seemed to be unaffected by the lowering of reaction temperature from 8 2F... 

Figure U. Effect of temperature on supercritical hydrotreatment of shale oil.

Hydrotreat To contact a hydrocarbon with hydrogen at moderate to high temperatures and pressures in order to perform hydrogenation reactions. 

Hydrotreatment was carried out over a commercial UOP black oil conversion catalyst in bench-scale units of 200-800 mL catalyst capacity. Temperature range was 375°-450°C and the pressure range was 2000-3000 psig. Weight hourly space velocity (WHSV) varied from 0.1 to 1.0 depending on the heptane-insoluble content of the feed. A flow diagram of a typical plant is shown in Figure 1. The stripper bottoms usually... 

A direct application is the study and optimization of catalyst pretreatment. In industrial practice, catalysts are frequently pretreated using a temperature-programmed technique. Examples are reduction in the fat hardening catalysis and sulphiding in the hydrotreatment of oil fractions in the refinery. 

We have collected operating data over a period of 15 years from four separate trickle-bed hydrotreater reactors. These four have operated with a number of different catalyst loadings, have processed a variety of feedstocks, and have operated over a wide range of average temperatures and pressures. Physical descriptions of the four reactors are given in Table I. 

Figure 1 shows the atomic H/C vs. O/C ratios for a series of fossil fuels. It is evident from the figure that coal-derived asphaltenes stand alone, with H/C atomic ratio about 60% of those derived from other fossil fuels. The asphaltenes from coal liquefaction products have experienced hydrotreatment at high pressures (2000-4000 psi) and temperatures near 450° C, yet they are much more aromatic than petroleum asphaltenes. Asphaltenes from coal have an aromaticity, /a, determined from 13C nuclear magnetic resonance, of 0.60-0.70, while petroleum values are listed as 0.40-0.55. 

The hydrotreatments are carried out at pressures in the range 250 to 2500 psig and temperatures from 230° to 510°C. The exact conditions used depend on the feedstock and extent of dewaxing required. The products from the hydrocracking of the wax in heavy distillate feedstocks boil below 177°C with C3, C4, and C5 hydrocarbons predominating. 

Hydrotreatment (HT) of coal-derived liquids (CDL) is required to remove heteroatom constituents. These are reacted at high hydrogen pressures and high temperatures to hydrocarbons, H2S, NH and water. A typical catalyst is NiMo/alumina. 

An example where changes in pretreatment steps are very drastic is in hydrotreatment. The most applied catalysts are based on a combination of molybdenum and cobalt sulphides. They are manufactured in the oxidic state, and under reaction conditions these oxides are not stable and are transformed into the sulphidic state. In practice, the oxidic catalyst is presulphided, either in the reactor (by adding H2S or a compound that is easily converted into H2S), or ex situ by the manufacturer. These presulphiding procedures often involve temperature-programmed reactions. 

Fig. la shows the adsorption isotherms of >29Xe for the different dealuminated samples of H-mordenites. As observed in the graph, the adsorption capacity of the sample decreases as the dealumination degree increases. These results are in agreement with those obtained by Springuet-Huet and Fraissard (6) who compared two solids dealuminated by acid treatment and hydrotreatment, respectively, and the parent sample. Fig. lb. compares the adsorption isotherms of the H-mordenite catalyst with a Si/Al ratio = 5.9, for fresh samples and deactivated samples on stream at 650°C. The lesser adsorption capacity of the catalyst which has been imder reaction conditions indicates a structural change of the latter probably due to the combination of temperature with small amounts of water (approx. 500 ppm) formed as product. The behavior of the other catalysts under study is qualitatively similar. 

This research was carried out in a system of two trickle-bed reactor for hydrotreatment of deasphalted vacuum bottoms with a capacity of 22.000 b/d at 1.500 psi and a maximum temperature of425 °C. The quality of the inflow and outflow streams are given in Table 1. 

---