Naphtha yield

When the catalysts were evaluated in the pilot unit it was found that the product yields were influenced by the selected impregnation method. The maximum naphtha yield (50.7 wt%) occurred at 76.5 wt% conversion for the standard impregnated catalyst. For the direct impregnated catalyst the maximum naphtha yield (50.9 wt%) occurred at a somewhat lower conversion (75.8 wt%). The comparison of product yields from the two impregnation methods shown in Table 3.6 is made at constant conversion (76.5 wt%). The hydrogen yield as well as the dry gas yield is slightly... 

The second group was characterized by well-performing catalysts with high naphtha yields combined with low yields of coke and gas. At that time this was rather unexpected, since it was commonly accepted in those days that a residue catalyst should have a medium zeolite content and a high matrix surface area [15]. Obviously more studies were necessary within this held. 

The catalyst activity increased when the RE level increased as expected [16]. Product yields compared at the same conversion (76.2 wt%) are shown in Table 3.9. When the RE level increased, the decreased LPG yield was as expected, as well as the increased naphtha yield and the decreased ECO yield. The decreased coke yield was also expected becanse of the behavior of the catalysts with low RE content in the pilot unit. 

The naphtha yield was lower for Catalyst B than for the reference and this illustrates the necessity to have enough zeolite surface area in the catalyst to be able to crack all the components in the feed, both those that can be cracked directly and those that must be precracked on the matrix before they can be cracked by the zeolite. Catalyst C had a slightly higher naphtha maximum than the reference catalyst, despite its high matrix surface area. The high matrix surface area of Catalyst C,... 

However, the naphtha yield for the somewhat heavier feed C was lower than the naphtha yield of feed B, especially at the naphtha maximum around 75 wt% conversion, see Figure 3.23. 

FIGURE 3.23 Comparison of Feed-B and Feed-C. Naphtha yield as a function of conversion ( = Feed-B, = Feed-C). 

All feeds require an optimized catalyst for the optimal conversion to lighter and more valuable products. This insight has always concerned FCC professionals. Even with vacuum gas oil as feed the optimization problem was evident. Wear and Mott used a MAT reactor to optimize the zeolite to matrix surface area ratio (ZSA/MSA) for a vacuum gas oil catalyst [4]. The naphtha yield increased with increasing ZSA/ MSA ratio, while the coke and dry gas yields decreased. This investigation showed that the optimization of the catalyst indeed was necessary and was very profitable even when vacuum gas oil was used as feed to the catalytic cracker. 

Pilot unit tests have indicated that there is an upper limit for the zeolite to matrix surface area ratio (ZSA/MSA) for a residue catalyst. This observation was in contrast to the optimization study, which indicated that the ZSA/MSA should be as high as possible for maximum naphtha yield. An increase in the zeolite surface area is, according to the optimization study, expected to increase both the activity of the catalyst and its naphtha yield. But for catalysts with a high ZSA/MSA ratio, close to four or even higher, the observed naphtha yields have been lower than expected in the pilot unit tests, which indicate that there might be an upper limit for the ZSA/ MSA ratio in a residue application. 

When the naphtha yields were studied (see Figure 4.9) it was obvious that the results were not as expected. The maximum naphtha yield increased when the zeolite content of the zeolite limited catalyst C-1 was increased, such that the ZSA/MSA ratio became almost optimal in catalyst C-2. This increase was expected, and fully in... 

Installation of more conversion equipment both in new refinery construction and as additions to existing hydroskimming facilities is already a trend. The production of more naphtha by providing new conversion units would, of course, make the additional naphtha more costly. In this connection a number of studies both our own and others (4) have attempted to determine the cost of incremental naphtha production. These indicate that in typically sized European hydroskimming refinery (operating on either Libyan or Arabian crudes) gasoline plus petrochemical naphtha yields can be increased by about 50% by installation of catalytic cracking. Based on today s prices for the other refinery products, the cost... 

In Table II, the boiling ranges of petroleum and the two major syncrudes are shown. The very high naphtha yield and the absence of residue in coal derived syncrudes are significant. 

Table 23 gives the main physicochemical properties of a number of naphtha cuts derived from Kirkuk and Hassi-Messaoud crudes. The steam cracking of these naphthas yields a wide variety of products, ranging from hydrogen to highly aromatic heavy liquid fractions. 

An example of the need for sharpness control might be the benefit of removing dicyclic hydrocarbons boiling at 400° F or above from the catalytic reforming feed, while maintaining naphtha yield. These dicyclics are known to foul platinum reforming catalysts with carbon. 

Thermal cracking of naphtha yields the following gas, which is to be separated by a distillation train into the products indicated. If reasonably sharp separations are to be achieved, determine by heuristics two good sequences. 

Figure 11.31 shows that this is indeed true. The responses with temperature control are represented by solid lines. The responses with 95% boiling point control are represented by dashed lines. The disturbance is a swing in crude oils to less OlL-1 and more OIL-2. The process steadies out in about 90 min with temperature control. The naphtha boiling point is not held exactly at 191 °C, but ends up at about 189.3 °C. The naphtha yield is somewhat smaller, with more bottoms. 

Figure 3.33 Naphtha yield from catalytic cracking of various hydrocarbon mixtures...

The experience accumulated over eight years in four refineries and one petrochemical complex has shown that light olefin yields are greatly dependent on the feedstock properties as detailed in Table 8. Daqing paraffinic feedstock gives the highest propylene and isobutylene 5delds, with 23.0 wt% and 6.9 wt% respectively. For intermediate base feeds, propylene yield is more than 18 wt% for DCC-I and 14.4 wt% for DCC-II operation with an FCC naphtha yield near 40 wt%. 

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