FCC gasoline composition

Also for the ARCO Pilot Riser this is the case, but by drastically adapting the operating conditions (Table 2) it is possible to achieve the correct FCC gasoline composition. 

Impact of Riser Temperature on FCC Gasoline Composition Constant Conversion Comparison... 

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. 

The demonstrated performance of ZSM-5 in over 35 cracking units is reviewed. The main features of ZSM-5 are its high activity and stability, favorable selectivity, metals tolerance and flexibility, particularly when used as an additive catalyst. ZSM-5 cracks and isomerizes low octane components in the naphtha produced by the faujasite cracking catalyst. As a result and olefins are produced and gasoline compositional changes occur which explain its increased research and motor octanes. A model was developed which predicts ZSM-5 performance in an FCC unit. 

Extensive studies describe the development of new materials, such as transition-metal nitrides and oxynitrides, as new potential catalysts for hydroprocessing operations. Studies were performed to acquire information on the effect of high levels of ZSM-5 additive on light olefins and gasoline composition in FCC.289 It was found that ZSM-5 can substantially increase propylene and butenes, and... 

This paper documents compositional analyses obtained for FCC gasolines produced over two commercially produced and available faujasite catalysts with and without the addition of ZSM-5 additive. 

An interesting point to note is that the gasoline compositions obtained from the ASTM and Ketjen-MAT deviate significantly from the commercial FCC results. 

The main aim for FCC gasoline desulfurization is to remove thiophenic sulfur compounds. Membranes made from polar polymers with solubility parameter close to thiophenic sulfur are used for desulfurization of gasolines by PV It is evident that solubility parameter of primary sulfur components of gasolines, that is, thiophenic sulfur components, is 19-21 (J/cm )", while for other hydrocarbons, these values are 14-15 (J/cm )". This difference can be exploited for separation by PV. Solubility parameter values of most of the polymers used as membrane material lie in the range of 21-26 (J/cm )". Thus, membranes made from these polymers afford good selectivity for thiophenic sulfur. Apart from various homopolymers, chemically and physically modified polymers have also been used for per-vaporative desulfurization. Some of these modifications include using different types and amounts of cross-linkers, blending two polymers, and copolymerization. Composite and treated ionic membranes have also been tried for this separation. Polymer membranes tried for this separation include PDMS/PAN, PDMS/PEI, PDMS/PES, PDMS/ ceramic, polyetherimine (PI)/polyester, PEG/PES, and PU/PTEE. ... 

Blending components used in the Auto/Oil Study were obtained from various streams from current refinery configurations. They include FCC gasolines, reformates, straight run naphtha, alkylates and isomerate. Table 3 shows the compositional analysis and physical properties of these blending stocks. 

Impact of FCC Unit Cell Size on Gasoline Composition... 

Pappal, D. A., and Schipper, P. H., (1991), "Increasing Motor Octane by Using ZSM-5 in Catalytic Cracking Riser Pilot Plant Gasoline Compositional Analysis", Ocecelli, M.L., (ed), FCC II, ACS Symposium Series, Vol,. 452, pp45-55. 

The low H/C-ratio of FCC feed derived from liquefied biomass led to low conversion and poor gasoline selectivity. Addition of alumina to the matrix resulted in a catalyst more active for heavy oil cracking but with a poor selectivity. Alumina-montmorillonite catalysts showed activities for heavy oil cracking comparable to that of a conventional, zeolite based, cracking catalyst. Effects of matrix composition and zeolite type on the heavy oil cracking performance are discussed. 

The main objective in FCC catalyst design is to prepare cracking catalyst compositions which are active and selective for the conversion of gas-oil into high octane gasoline fraction. From the point of view of the zeolitic component, most of the present advances in octane enhancement have been achieved by introducing low unit cell size ultrastable zeolites (1) and by inclusion of about 1-2 of ZSM-5 zeolite in the final catalyst formulation (2). With these formulations, it is possible to increase the Research Octane Number (RON) of the gasoline, while only a minor increase in the Motor Octane Number (MON) has been obtained. Other materials such as mixed oxides and PILCS (3,4) have been studied as possible components, but there are selectivity limitations which must be overcome. 

Critical parameters to simulate are the ratio of Catalytic to Thermal cracking and the related chemical composition of the gasoline fraction. Obviously, these parameters are particularly important for the research into FCC product properties and, for instance, for the evaluation of potential octane catalysts. 

The various sulfur compounds present in the FCC feedstock show different behaviour, which is due to different chemical compositions. For example, most mercaptanes decompose under typical FCC conditions into hydrocarbons and hydrogensulfide as shown in Figure 13, while the thiophenic compounds are relatively stable in the FCC unit. The lower molecular weight thiophenic compounds end up in the gasoline and LCO, while the higher molecular weight compound remain in the HCO and coke [7]. The sulfur in the coke is subsequently transferred into the regenerator and oxidised to SOx. 

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