Yield of products from catalytic cracking of vacuum gasoils

In catalytic cracking of vacuum gasoils, the yields of products are correlated with their hydrogen content. A correlation that allows predicting the yields of products of this process was elaborated based on the results of cracking of 11 gasoils of different origin and data on their density, refractive index, and 50% distillation temperature. However, it is not possible to predict the octane number of the naphtha obtained in cracking with the group hydrocarbon composition of the feedstock. __________ Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 31–34, July–August, 2007.     

Dependence of Fluid Catalytic Cracking Unit Performance on H-Oil Severity,Catalyst Activity,and Coke Selectivity

The effect of the quality of ebullated bed vacuum residue H-Oil hydrocracking gas oils cracked in a commercial fluid catalytic cracking unit (FCCU) on its performance was studied. Six different catalysts were employed in this study. Four catalysts were tested in a commercial FCCU, and two in a laboratory FCCU. An increase of the H-Oil hydrocracker reaction temperature was associated with a decrease in the K_W factor of the H-Oil gas oils. The diminished K_W factor of H-Oil gas oils resulted in lower FCCU conversion and higher regenerator temperatures. The FCC conversion at maximum gasoline yield is best predicted by the feed K_W factor. The higher-activity, higher-Δcoke catalyst is unfavorable for FCCU performance because the excessive regenerator temperature excursions require reduction of the throughput.     

Effect of nitrogen-containing compounds in catalytic feedstock on the composition of gasoline

Hydrotreated vacuum gasoil from straight-run distillation of a Russian export mixture (GRES) and the same gasoil after treatment with sulfuric acid (OGRES) so that nitrogen-containing compounds were totally removed and the hydrocarbon composition was almost unchanged were investigated as catalytic feedstock. Cracking was conducted on a MAT laboratory setup with different catalyst and feedstock ratios, constant reactor temperature of 527°C, and feedstock contact time with catalyst of 30 sec. Elimination of nitrogen-containing compounds from GRES increased the yield of cyclic hydrocarbons in the naphtha cut with lower aromatization and decreased the yield of macromolecular aliphatic hydrocarbons with lower olefination. In the absence of basic nitrogen, the activity and selectivity of the catalyst for the naphtha and light cyclic petroleum products increased. The naphtha obtained from OGRES, in comparison to the naphtha obtained from GRES, contains more cycloalkanes and less alkanes and alkenes and has lower research and motor octane numbers.     

Investigation of the fluid catalytic cracking of different H-Oil vacuum gas oils and their blends with hydrotreated vacuum gas oil

H-Oil vacuum gas oils obtained during hydrocracking of vacuum residual oils originated from the crudes Russian Export Blend, Basrah light, and Heavy Kazakh were cracked in a mixture with a hydrotreated vacuum gas oil in the LUKOIL Neftohim Burgas commercial fluid catalytic cracking (FCC) unit. Some of the H-Oil vacuum gas oils were also cracked in a laboratory FCC (ACE) unit. The results from the commercial and the laboratory tests showed that the laboratory FCC experiments in an ACE unit can be used to evaluate the effect of feed quality on the commercial FCC unit performance. The assumption that the conversion of a vacuum gas oil (VGO) blend in the fluid catalytic cracking could be considered as a linear combination of the conversion of the individual components made by other researchers was also confirmed in this study. The higher the hydrogen content in the vacuum residual oil of a crude is the higher the FCC conversion of the H-Oil VGO, obtained during hydrocracking of that high saturate vacuum residual oil, will be expected.     

Investigation of relationships between bulk properties and fraction properties of crude oils by application of the intercriteria analysis

Data from assays of 244 crude oils (condensates, extra light, light, intermediate, and heavy crudes) were processed by the InterCriteria Analysis with the aim to investigate the relationships between bulk properties and fraction properties of the crude oils and the degree of similarity between them. It was found that except the crude bulk properties sulfur, Conradson carbon, and metals content all other studied crude bulk properties exhibited lack of statistically meaningful relations or presence of weak statistically meaningful relations with the crude fraction properties. The use of the InterCriteria Analysis showed that crudes with very similar properties could be identified when a large crude database is available. In this way based on a previous experience in oil refining a selection of potentially beneficial new crudes for processing in a refinery could be made.     

Effect of commercially available antioxidants over biodiesel/diesel blends stability

The main obstacle in biodiesel/conventional diesel blends acceptance worldwide seems to be its poor oxidative stability. Low resistance towards oxygenation is due to the fatty constituent in the blend. Even low concentrations of biodiesel (5%, 10% and 20%) can contribute to sticky, viscous and polymeric deposits formation after several months of storage. Two correlations were derived concerning insolubles formed in both stabilized and not stabilized blends, stressed under conditions of ASTM D2274.For treated with antioxidant additive:

Total insol.=0.6561+80.1213∗ΔTAN-114.27∗ΔPC-2.6073∗ΔIV     

Relationship of the aromatic structural types in vacuum gas oil to empirical correlations based on bulk properties

Five empirical methods toestimate the content of aromatic, naphthenic, and paraffinic carbon and hydrogen content and the bulk properties were tested for prediction of aromatic structures content of 95 vacuum gas oils. The density demonstrated the highest correlation with the aromatic structures content among all other studied bulk properties and empirical parameters. The aromatic structures content could be predicted by a second order power law dependence on density with accuracy commensurable with the reproducibility of SARA analysis. The poly-nuclear aromatic structures content was also found to depend on the density and can be expressed by a linear function.     

Impact of feed properties on gasoline olefin content in the fluid catalytic cracking

Eight vacuum gas oils (VGOs) having different hydrocarbon composition and different distillation characteristics were cracked in a laboratory fluid catalytic cracking (FCC) advanced cracking equipment (ACE) unit. The experimental results showed that FCC VGO feedstock reactivity correlates with the content of saturates plus light aromatics, and with the content of nitrogen. The FCC gasoline olefin content was found to depend on T_50% and saturate content of the FCC VGO feedstock. The results from a commercial FCC unit that processes a hydrotreated straight-run VGO and a VGO from ebullated bed residue H-Oil hydrocracker confirmed the results from the laboratory FCC ACE unit showing that reducing T_50% and increasing saturate content of the FCC feedstock leads to a reduction of the FCC gasoline content.     

Fluid catalytic cracking feed hydrotreatment and its severity impact on product yields and quality

This paper investigates the effect of fluid catalytic cracking (FCC) feed hydrotreatment and its severity increase on product yields and quality obtained in a commercial and a laboratory MAT FCC units. The hydrotreatment of Ural heavy vacuum gas oil reduces not only sulfur, nitrogen, Conradson carbon and metals content in the FCC feed but also increases the mononuclear aromatic hydrocarbons content by 8% absolute at almost no change in the total aromatics content. Regardless of this 8% increase of the mononuclear aromatics in the hydrotreated FCC feed the conversion increase in both commercial and laboratory MAT units was only 2%. The severity increase in the FCC feed hydrotreater leads to a higher conversion in the FCC, higher hydrogen transfer rate that results in higher isobutane/butylenes ratio, lower gasoline olefins content, and higher gasoline motor octane number. The hydrotreatment of the Ural heavy vacuum gas oil exhibited the same changes in FCC catalyst selectivities: lower coke and LCO selectivities and higher gasoline selectivity in both commercial riser FCC unit that has between 2 and 3 s time on stream, and the fixed bed reactor MAT unit, that has 30 s time on stream.