Activity for gas-oil

Figure 8. Correlation between catalyst activity for gas-oil cracking and Br nsted acidity of Ca, Mn, and REX zeolites...

Figure 4. Activity for gas-oil cracking as a function of FAL per unit cell, for samples dealuminated by ...

FIGURE 26. Activity for gas-oil cracking on steam (O) and SiCl4 ( ) dealuminated Y zeolites. 

Due to the water requirement of biocatalytic systems, BDS is typically carried out as a two-phase aqueous-oil process. However, increased sulfur removal rates could be accomplished by using an aqueous-alkane solvent catalytic system [46,203,220,255], The BDS catalytic activity depends on both, the biocatalysts and the nature of the feedstock. It can vary from low activity for crude oil to as high as 60% removal for light gas-oil type feedstocks [27,203,256], or 70% for middle distillates, 90% for diesel, 70% for hydrotreated diesel, and 90% for cracked feedstocks [203,256], The viscosity of the crude oil poses mixing issues in the two-phase oil-water systems however, such issues are minimal for distillate feedstocks, such as diesel or gasoline [257]. 

Comparison of the catalytic properties of H-Beta and H-Y zeolites for cracking n-heptane and gasoil shows that zeolite Beta should have more than one type of channel with different dimensions. For gas-oil cracking, zeolite Beta is less active and produces more coke and less gasoline than zeolite HY. 

Figure 7. Comparison between H-Beta zeolites (open circles and dashed lines) and HY zeolites (continuous lines) for gas-oil cracking (a) First-order activity constant by specific surface area vs, Si/Al ratio (b) and (c) Average total conversion vs. gas-oil ratio for a H-Beta with Si/Al=27 and a HY Si/Al=35, and for a H-Beta with Si/Al=10 and a Hy with Si/Al=7.7 respectively. Solid circles correspond to the H-Beta steamed at 750 C and 1 atmosphere of water pressure.

H-Beta are more active for n-heptane cracking than HY-zeolites with the same Si/Al ratio, while for gas-oil cracking the opposite occurs. Nevertheless we have not looked here to mesoporosity of the zeolites which may be critical for explaining the activity in gasoil cracking. Steaming causes a smaller decreases in activity of H-Beta than on HY zeolite. H-Beta gives a lower ratio than... 

In a practical HDS process for gas oil, both aromatic species existing in the feed and various types of sulfur compounds compete for the active sites on the catalyst surface. Moreover, H2S and some other hydrocarbons produced in the early stages of the desulfurization appear to inhibit the HDS of the less reactive sulfur species. The reactivities of refractory sulfur compounds and the effects of inhibitors in gas oils need to be fully understood for the development of an improved economical desulfurization process. 

Activity per Unit Surface Area for Gas Oil Cracking. A second order kinetic conversion parameter (conversion + 100 - conversion) was used (13) to monitor gas oil cracking activity. The activity relationship as a function of surface area and catalyst composition is described in Figure 4. As expected, activity increased linearly with surface area. Activity per unit surface area depended on composition and increased with increasing alumina content. 

There is disagreement about the role (if any) of Mo in hds catalysis. Mo concentration correlated with hds activity for sulphided Mo03 and for various Ni-Mo/Al203 catalysts (diesel oil, thiophen ). The concentration of Mo (e.s.r.) was, however, much less in M0/AI2O3 catalysts promoted by Fe, Co, Ni than in the unpromoted catalysts. Since the promoted catalysts were more active in gas oil hds, Mo was not considered to be a hds site. 

When petroleum or kerosene (as the raw materials for gas oil or lubricants) are purified by using oleum or sulfuric acid, a reaction with the aromatic compounds takes place. While these substances were originally seen as waste products, later their chemical structures and surface-active properties were identified, thus leading to special applications for such products. Nowadays, petroleum fractions with a high content of aromatic hydrocarbons are treated with sulfur trioxide to form alkylaryl sulfonates. These products are then transformed into the sodium, ammonium or alkaline-earth salts. They are soluble in oils and therefore are of some importance as additives in lubricants, oil fuels and corrosion-inhibiting oils. Further more, they are also used as auxiliaries in production of fabrics and as dispersants in enhanced oil recovery processes. 

Pillared rectorites are expanded clay minerals with a surface area in the 150-220 mVg range, and thermal and hydrothermal stability similar to that of zeolites with the faujasite structure (1-4). After steaming at 760°C/5h (100% steam, 1 atm), these materials retain their pillared structure, and at microactivity test conditions (MAT) they are as active as commercial fluid cracking catalysts (FCC) for gas oil conversion... 

The high activation energy for gas oil cracking to dry gas is an indication that this reaction is of a thermal nature. 

From equation (1.8) it is apparent that two parameters, k and n, are required to describe the decay kinetics. TTius, authors such as Nace et al.(1971) and Corella et al.(1985) who used the decay function of the form = Df did not evaluate k but instead included it in their overall kinetic constant, a combined cracking and decay constant. This is certainly sufficient from an empirical stand point but to adequately describe the deactivation kinetics the value of k must be assessed. As well, the activation energy from these studies represents the combination of the energy of activation of gas oil cracking and the activation energy for the loss of active sites. 

After separation from its quartz matrix, the beneficiated rectorite dries into aggregates of flakes resembling mica particles. Similar materials are obtained also after drying the product of the pillaring reaction. Prior to evaluation for gas oil cracking activity, the pillared rectorite samples were crushed and sized into 20x60 mesh (flake-like) particles and calcined. Typical chemical composition of these clay catalysts is given in Table I. 

Cracking, a rupturing of carbon-carbon bonds—for example, of gas oils to gasohne—is favored by sihca-alumina, zeolites, and acid types generally. Zeohtes have pores with small and narrow size distribution. They crack only molecules small enough to enter the pores. To restrain the undesirable formation of carbon and C3-C4 hydrocarbons, zeolite activity is reduced by dilution to 10 to 15 percent in silica-alumina. 

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