Activity for gas-oil cracking

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. 

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... 

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. 

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. 

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]. 

Thus, the rates of activity decline are substantially constant for these two cases, and the gasoline production is similar with both operations. This is true even though the initial activity of the catalyst employed for cracking the heavy gas oil falls toward the terminal activity of the catalyst applied to the light gas oil cracking operation. 

Cruz et al. (36) also found that AFS preferentially dealumi-nates the surface of zeolite Y crystals to a depth of about 100 A and produces an extra-framework-Al-free zeolite. They found that the activity for n-heptane cracking is the same as for a steamed dealuminated sample, while the gas oil cracking was lower, being controlled by the outer shell. 

The distribution of A1 spedes of varying coordination (tetrahedral, pentacoordinated and octahedral) can be influenced by changing the conditions of hydrothermal pretreatment of amorphous silica-alumina catalysts. However, for a given composition, activity per unit surface area and selectivity were independent of pretreatment conditions. Thus, gas oil cracking activity and selectivity in amorphous silica-alumina cannot be... 

A new class of hi alumina silica-aluminas has been prepared with hi pore volume and with controllable pore size. For 20 wt % Si02 content materials steam treatment at 760°C serves to substantially increase the gas oil cracking activity. Steam stability at 870°C has also been demonstrated for these unique materials. These samples are prepared by recrystallization of co-gels of aluminum and silicon alkoj compounds losing a two-step procedure. AmorjAious alumina shows similar physical properties to those of the silica-alumina co-gels vhen re-crystallized in an analogous manner. 

If water was added to the 15% Si02 co-gel to fill the pore voids a partially recrystallized boehmite was formed with a surface area of 464 m /g and with a pore volume of 1.8 oc/g. If water was added to the 15% Si02 co-gel to form a slurry and then dried and calcined at 500 a partially recrystallized bodunite was formed with a surface area of 334 m /g. steam treatment at 760 of this second, small pore, bodunite-like silica-alumina resulted in no change in the surface area. The gas oil cracking activity of the steamed sample was definitely hi er than that for the amorphoias co-gel, i.e., a Micro Activity Test (MAT) Activity Number of 38 (see Table 1.). 

As it is both inexpensive and easy to handle, steam is a potential candidate carrier gas for waste plastic recycling in chemical plants. Furthermore, as mentioned in Section 2.1, the degradation temperatures for polyester resins are remarkably shifted to low-temperature regions, and the amount of carbonaceous residue produced in the degradation process is reduced in a steam atmosphere, as compared with that in a nitrogen atmosphere. Accordingly, the preparation of a catalyst that could demonstrate both stable activity for the catalytic cracking of PE-derived heavy oil, but that would also remain stable in a steam atmosphere, was examined [16],... 

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... 

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