FCC Feed Characterization

Refiners process many different types of crude oil. As market conditions and crude quality fluctuate, so does cat cracking feedstock. Often the only constant in FCC operations is the continual change in feedstock quality. 

Feed characterization is the process of determining the physical and chemical properties of the feed. Two feeds with similar boiling point ranges may exhibit dramatic differences in cracking performance and product yields. 

FCC feed characterization is one of the most important activities in monitoring cat cracking operation. Understanding feed properties and knowing their impact on unit performance are essential. Troubleshooting, catalyst selection, unit optimization, and subsequent process evaluation all depend on the feedstock. 

Feed characterization relates product yields and qualities to feed quality. Knowing the effects of a feedstock on unit yields, a refiner can purchase the feedstock that maximizes profitability. It is not uncommon for refiners to purchase raw crude oils or FCC feedstocks without knowing their impact on unit operations. This lack of knowledge can be expensive. 

Sophisticated analytical techniques, such as mass spectrometry, are not practical for determining complete composition of FCC feedstocks on a routine basis. Simpler empirical correlations are more often used. They require only routine tests commonly performed by the refinery laboratory. They are excellent alternatives, but they have their limitations  

---

Dhulesia, H. January 1986. New correlations predict FCC feed characterizing parameters. Oil Gas J. 13 51-54. 

Aniline point is used in some correlations to estimate the aromaticity of gas oil and light stocks. TOTAL S [1] correlation uses aniline point and refractive index. Others, such as n-d-M [2], employ refractive index to characterize FCC feed. 

Characterizing FCC feed provides quantitative and qualitative csti mates of the FCC unit s performance. Process modeling uses the feed properties to predict FCC yields and product qualities. The process model should be used in daily unit monitoring, catalyst evaluations, optimization, and process studies. 

It is important to characterize FCC feeds as to their molecular structure. Once the molecular configuration is known, kinetic models can be developed to predict product yields. The simplified correlations above do a reasonable job of defining hydrocarbon type and distribution in FCC feeds. Each correlation provides satisfactory results within the range for which it was developed. Whichever correlation is used, the results should be trended and compared with unit operation. 

In the previous examples, the feed characterizing correlations in Chapter 2 are used to determine composition of the feedstock. The results show that the feedstock is predominantly paraffinic (i.e., 61.6% paraffins. 19.9% naphthenes, and 18.5% aromatics). Paraffinic feedstocks normally yield the most gasoline with the least octane. This confirms the relatively high FCC gasoline yield and low octane observed in the test run. This is the kind of information that should be included in the report. Of course, the effects of other factors, such as catalyst and operating parameters, will also affect the yield structure and will be discussed. 

Discussion. Characterization of biomass oil with bonded phase chromatography could only be done after deoxygenation. This resulted in an FCC-feed stock with a high content of aromatics. Similar results have been obtained by Elliot and Baker (20). 

Saraf, A. V., Silerman, M. A., and Ross, J. L. FCC Modeling Based on Advanced Feed Characterization Techniques, in Circulating Fluidized Bed Technology IV (Amos A. Avidan, ed.), pp. 559-564. Somerset, Pennsylvania (1993). 

Characterizing an FCC feedstock involves determining both its chemical and physical properties. Because sophisticated analytical techniques, such as mass spectrometry, are not practical on a daily basis, physical properties are used. They provide qualitative measurement of the feed s composition. The refinery laboratory is usually equipped to carry out these physical property tests on a routine basis. The most widely used properties are ... 

We may thus conclude after this short overview on DeNO technologies that NH3-SCR using catalysts based on V-W-oxides supported on titania is a well-established technique for stationary sources of power plants and incinerators, while for other relevant sources of NO, such as nitric acid tail gases, where emissions are characterized from a lower temperature and the presence of large amounts of NOz, alternative catalysts based on transition metal containing microporous materials are possible. Also, for the combined DeNO -deSO, alternative catalysts would be necessary, because they should operate in the presence of large amounts of SO,.. Similarly, there is a need to develop new/improved catalysts for the elimination of NO in FCC emissions, again due to the different characteristics of the feed with respect to emissions from power plants. 

Characterization and selection of heavy feeds for upgrading through FCC. 12th WPC, Houston 1987, John Wiley Sons Ltd. 

In this work Micro Activity Tests with an aluminosilicate MCM-41 and a silica-containing VPI-5 were carried out using n-hexadecane as the model feed. Special emphasis was given to the catalytic activity, thermal stability and selectivity of the different materials studied in comparison with a commercial equilibrium FCC catalyst. Additionally, the possible structural and textural changes during the above-mentioned catalytic process were characterized. 

J.L. Mauleon and J.B. Sigaud, Characterization and Selection of Heavy Feeds for Upgrading through FCC. 23rd WPC Houston, John Wiley Sons Ltd,1987. 

In order to apply the proposed sequential method for kinetic parameter estimation in the FCC process three feeds were used for MAT experiments GO-1, a typical FCC feedstock, GO-2, Heavy Vacuum Gas Oil and, GO-3, the typical FCC feedstock plus 5 vol% atmospheric residuum. Characterization of theses feeds were presented in a previous work [5]. 

---