Catalytic Cracking Products Research Articles

Aromatic Steroids in Crude Oils and Petroleum Products and Their Applications in Forensic Oil Spill Identification

Aromatic steroids including monoaromatic (MAS) and triaromatic steroids (TAS) are a series of naphthenoaromatic hydrocarbons, which consist of mixed structures of aromatic and saturated 6-carbon or 5-carbon rings. Although these aromatic steroids are in relatively low concentration in oils, their specific fingerprints and high weathering resistance make them desirable biomarkers for the characterization, correlation, differentiation, and source identification in environmental forensic investigations of oil spills. This study presents a quantitative GC/MS analysis of these aromatic hydrocarbons in a number of crude oils and refined petroleum products including light and mid-range distillate fuels, heavy fuels, and lubricating oils collected from various sources. TAS-cholestanes (C26), TAS-ergostanes (C27), and TAS-stigmastanes (C28) are the most distinguishable triaromatic steroids in most oil samples. C26 TAS-cholestane (20R) and C27 TAS-ergostane (20S) are coeluted and often present as the highest peak in m/z 231 chromatograms. A cluster of aromatic steroids were determined in nearly all the studied crude oils at various concentrations. These compounds are generally not detected in light fuel oil like gasoline and light diesel, but at variable abundance in heavy fuels and lubricating oils. In order to better understand the occurrence of aromatic steroids in refined petroleum products, a crude oil was compared with its products of laboratory fluid catalytic cracking (FCC) and hydrotreating processes. The effects of evaporative weathering and biodegradation on these compounds were evaluated with suites of weathered oil samples.

Effect of process conditions on the composition of products in the conventional and deep catalytic cracking of oil fractions

With the purpose of increasing the yield of light C2-C4 olefins in comparison with that in conventional catalytic cracking, we experimentally study the effect of temperature and catalyst-to-oil ratio on the distribution of the basic products of oil catalytic cracking on the bizeolite and industrial LUX catalysts. The bizeolite catalyst contains ZSM-5 and ultrastable Y zeolites in equivalent amounts, while the LUX catalyst contains 18 wt % of Y zeolite in the HRE form. As shown by the results of our tests, the yield of C2-C4 olefins and gasoline in the deep catalytic cracking of hydrotreated vacuum gasoil on the bizeolite catalyst within a range of catalyst-to-oil ratios of 5–7 and temperatures of 540–560°C reaches 32–36 and nearly 30 wt %, respectively. In cracking on the LUX catalyst under similar conditions, the yield of light olefins and gasoline is 12–16 and 37–45 wt %, respectively. The distribution of target products in the deep catalytic cracking of different hydrocarbon fractions (vacuum gasoil, gas condensate, its fraction distilled from the cut boiling below 216°C, and the hydrocracking heavy residue) on the bizeolite catalyst is studied. It is shown that the fractions of gas condensate and hydroc-racking residue can serve as an additional source of hydrocarbon raw materials in the production of olefins.

Hydrothermal Stability of Meso-microporous Composites and Their Catalytic Cracking Performance

Meso-microporous composites show great promise for catalysis because of their variously-sized porous structures. A series of composites containing uniform mesopores and MFI zeolitic channels were prepared by a template-free sol-gel method. The composite containing silicalite-1 structures was found to be much more hydrothermally stable than MCM-41. The composites with ZSM-5 structures showed higher catalytic activity and resistance to deactivation than commercial HZSM-5 in the catalytic cracking reaction of 1,3,5-triisopropylbenzene. The conversion and catalytic cracking product distribution of 1,3,5-triisopropylbenzene depended highly on the mesopore size of the composites. Higher conversions and small molecule cracking products were obtained using composites with smaller mesopores. ：采用无模板剂的溶胶凝胶法 制备了一系列具有均一介孔和 MFI 沸石微孔的复合材料. 与 MCM-41 相比, 包含 silicalite-1 沸石结构的复合材料的水热稳定性得到显著改善. 1,3,5-三异丙苯的催化裂化反应结果表明, 与商品 HZSM-5 沸石相比, 包含 ZSM-5 沸石结构的复合材料具有更高的催化活性和抗积炭性能. 三异丙苯的转化率和裂化产物的分布主要取决于介孔-微孔复合材料的介孔孔径, 较小的介孔孔径有利于提高转化率和生成更多小分子裂化产物. Meso-microporous composites prepared from a ZSM-5 precursor xerogel generally gave higher catalytic activity and had better resistance against deactivation than commercial HZSM-5 in the catalytic cracking reaction of 1,3,5-triisopropylbenzene.

ChemInform Abstract: Degenerate Non-Primary Products in Catalytic Cracking of Isoalkanes.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Prospects for hydrotreating of catalytic feedstock

Experimental data on hydrotreating and cracking of vacuum gasoil on industrial catalysts are reported. Conclusions are drawn concerning the advantages of preliminary hydrotreating of the feedstock over posthydrotreating products of catalytic cracking.

Development of a catalytic cracking process with a high yield of light olefins: study of the structure of the yield of products

The structure of the yield of products of catalytic cracking of vacuum gasoil and repeated cracking of light naphtha in the high-temperature region was investigated. The results of the studies served as the basis for developing catalytic cracking technology with a high yield of light olefins.

The density of petroleum products in a wide range of parameters of state

The density of liquid products of catalytic cracking (CC) and viscosity breaking (VB) is measured in the temperature range from 293 K to 473 K at atmospheric pressure and at pressures elevated to 60 MPa. The resultant data are generalized along with experimental data on the density of directly distilled liquid petroleum fractions and commercial petroleum products. Dependences are obtained, which are suitable for determining the density of a wide range of petroleum products in view of the special features of their hydrocarbon composition.

Reduction of light cycle oil in catalytic cracking of bitumen-derived crude HGOs through catalyst selection

In an attempt to reduce the production of light cycle oil (LCO), a non-premium fluid catalytic cracking (FCC) product in North America, a large-pore catalyst containing rare-earth-exchanged Y (REY) zeolite, was used to crack two Canadian bitumen-derived crude heavy gas oils (HGOs) hydrotreated to different extents. For comparison, a regular equilibrium FCC catalyst with ultra-stable Y (USY) zeolite and a conventional western Canadian crude HGO were also included in the study. Cracking experiments were conducted in a fixed-bed microactivity test (MAT) reactor at 510 °C, 30 s oil injection time, and varying catalyst-to-oil ratios for different conversions. The results show that pre-cracking of heavy molecules with wide-pore matrix, followed by zeolite cracking, enhanced conversion at the expense of light and heavy cycle oils at a constant catalyst-to-oil ratio, giving improved product selectivities (e.g., higher gasoline and lower dry gas, LCO, and coke yields, in general, at a given conversion). To systematically assess the benefits of employing the specialty catalyst over the regular catalyst in cracking Canadian HGOs, individual product yields were compared at common bases, including constant catalyst-to-oil ratios, conversions, and coke yields for three feeds, and at maximum gasoline yield for one feed. In most cases, the preferred choice of large-pore zeolite-rich catalyst over its counterpart was evident. The observed cracking phenomena were explained based on properties of catalysts and characterization data of feedstocks, including their hydrocarbon type analyses by gas chromatograph with a mass-selective detector (GC-MSD).

Effects of metal modifications of Y zeolites on sulfur reduction performance in fluid catalytic cracking process

The acidity of catalytically active component, e.g., ultra stable Y zeolite (USY), plays an important role in determining their cracking activity and selectivity. To develop advanced sulfur reduction catalytic cracking catalysts, different type of elements were used to modify USY and the resulting catalysts were evaluated in a confined fluidized bed reactor and a micro-activity testing unit. The relation between the acidity of the zeolite and the conversion of sulfur compounds as well as the distributions of fluid catalytic cracking (FCC) products were discussed. The results showed that the rare earth (RE) metal can stabilize the catalyst and increase the conversion, but cannot increase the selectivity to thiophene compounds; V can reduce the sulfur content by 36.3 m%, but decreases the overall conversion compared with the base catalyst. An optimum catalyst was obtained by the combined RE and V modification, over which the sulfur content in FCC gasoline can be decreased and the selectivity for the target products can be improved, with the sulfur content reduced by 30 m% and the selectivity to coke even decreased by 0.20 m% at a comparable conversion level of the base catalyst.

In situ thermogravimetric study of coke formation during catalytic cracking of normal hexane and 1-hexene over ultrastable Y zeolite

The in situ behaviour of n-hexane and 1-hexene over ultrastable Y zeolite was studied quantitatively using thermogravimetric equipment at low (323–423 K), middle (523–623 K), and high (623–773 K) temperatures. At low temperatures, adsorption is the absolute dominant cause of catalyst weight change when either n-hexane or 1-hexene come in contact with US-Y, whose amount decreases with temperature. At middle temperatures, adsorption is also the dominant cause of catalyst weight change in the case of n-hexane, with the adsorbed amount, however, about one order of magnitude lower than at low temperatures, while for 1-hexene, oligomerisation from the olefinic reactant becomes the dominant cause of catalyst weight change. At high temperatures, oligomerisation from the olefinic products of catalytic cracking becomes the dominant cause of catalyst weight change for both cases, n-hexane as well as 1-hexene, while the extent of coke formation increases with temperature.

Cracking behavior of organic sulfur compounds under realistic FCC conditions in a microriser reactor

A laboratory-scale once-through microriser reactor was used in a qualitative study on the distribution of aromatic sulfur in the catalytic cracking products of an extra heavy gas oil (EHGO) under a broad range of conditions overlapping with realistic fluid catalytic cracking (FCC) conditions. Fifteen to twenty percent of the feed was uncrackable, corresponding to the amount of polycyclic aromatics in the feed. Gasoline was not overcracked to gas. The selectivity to gasoline was found to be independent of process parameters, in contrast to the selectivity to light cycle oil (LCO) and gas. Higher temperature and catalyst-to-oil (CTO) ratio led to an increased overall cracking rate. Initially, the amount of gasoline sulfur increased with residence time due to the formation of aliphatic sulfur compounds. Subsequently, these aliphatic species were cracked to hydrocarbons and H 2S. The gasoline sulfur concentration decreased as function of conversion due to the dilution of sulfur compounds by the additional formed sulfur-free gasoline hydrocarbons. Stable LCO sulfur species were predominantly formed by dealkylation of alkylated benzothiophenes from the heavy cycle oil (HCO) fraction. The LCO sulfur concentration was found to be temperature dependent. Aromatics without side chains, such as thiophene, benzothiophene and dibenzothiophene, were found to be uncrackable under the applied conditions. It is discussed if optimization of the conditions can contribute to significant lower sulfur levels in gasoline.

The influence of process parameters on catalytic cracking LPG fraction yield and composition

The influence of catalyst type, temperature, and feedstock, on the distribution of catalytic cracking products has been determined. The experiments have been performed according to the microactivity procedure MAT ASTM D-3907, with two commercial fluid catalitic cracking (FCC) catalysts and two gas oils as feedstock, at C/O ratio from 2.25 to 3.75, and in the range of 482–520°C. The effects of catalyst and feedstock properties on gasoline and liquefied petroleum gas (LPG) yields were established from the selectivity curves. Also, the influence of these parameters on the LPG composition and its applicability to alkylation and oxygenate production was determined in relation to the P/O ratios, as well as the corresponding isomerization/hydrogen transfer ratios. The temperature effects were in accordance with the thermodynamics of main catalytic cracking reactions.

Acid-catalyzed cracking of polystyrene

The effects of catalyst acidity and the restricted reaction volume afforded by HZSM-5 on the volatile cracking products derived from poly(styrene) are investigated. Three catalysts: silica/alumina, HZSM-5, and sulfated zirconia, were employed as cracking catalysts. Styrene, which is the principal radical depolymerization product from poly(styrene), is a minor catalytic cracking product. The most abundant volatile product generated by catalytic cracking is benzene. Alkyl benzenes and indanes are also detected in significant yields. Various thermal analysis techniques are employed to obtain volatilization activation energies for polymer-catalyst samples and to elucidate probable reaction pathways. Detected products are explained by reaction mechanisms that begin with protonation of poly(styrene) aromatic rings. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1287–1298, 1997

P-Xylene yield in fluid catalytic cracking products

Both direct dealkylation of feed aromatics and hydrogen transfer chemistry contribute to the production of para-xylene in fluid catalytic cracking gasoline products. Based on laboratory scale FCC riser testing, it was found that catalysts containing high rare earth and low matrix activity are the preferred catalysts for high p-xylene yields in fluid catalytic cracking products. Aromatic feedstocks yield higher p-xylene than paraffinic feeds. Catalyst or feed change did not alter the distribution among the three xylene isomers. p-Xylene yield increases with conversion, but the o,m,p distribution does not change much with conversion.

95/00226 Gasoline range ether synthesis from light naphtha products of fluid catalytic cracking of Fischer-Tropsch wax

95/00226 Gasoline range ether synthesis from light naphtha products of fluid catalytic cracking of Fischer-Tropsch wax

Degenerate Non-primary Products in Catalytic Cracking of Isoalkanes

Product distributions in catalytic cracking of a series of C10-C17 isoalkanes over two acidic catalysts, a Y-zeolite-based commercial catalyst and SiO2-Al2O3, were studied at 250 and 350°C. The cracked products from a Cn alkane belong to two distinct groups, primary products (isomerized Cn alkanes), and degenerate non-primary products, isoalkanes ranging from C3 to Cn−1. Degeneration of the non-primary products is expressed in two ways: 1. In each carbon number range, the non-primary products from alkanes are the mixtures of isoalkanes containing mostly monomethyl- and dimethyl-branched alkanes. The compositions of the mixtures are practically independent of the structures of feed alkanes, and the relative yields of isoalkanes with different skeletons are mostly determined by the thermodynamic stabilities of respective isomers. 2. The distributions of the non-primary products with respect to their carbon numbers have the inverted-U shapes with the maxima at C4-C5. These distributions also do not depend on the skeleton structure of the feeds. The main reason for the cracked product degeneration is high reactivity of a part of the reaction products, light olefins, in reactions over acidic catalysts. This conclusion is based on the experimental cracking study of a series of C3-C14 olefins with the same catalysts under mild conditions (100-250°C).

ChemInform Abstract: Primary Products in Catalytic Cracking of Alkanes: Quantitative Analysis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Primary products in catalytic cracking of alkanes: Quantitative analysis

Catalytic cracking of several C 8 and C 10 isoalkanes over a zeolite-based catalyst at 250 and 350°C was studied and the distributions of primary cracked products (isomerized saturated hydrocarbons with the same carbon atom numbers as in the feed alkane) were analyzed. Comparison of relative yields of the primary products showed that not only the same products were formed in cracking of different isoalkanes but that their distributions did not depend on the structure of the feed molecules. The relative yields of different primary products were found to be generally proportional to the thermodynamic stabilities of corresponding isoalkanes. All isoalkane products with a methyl group in the second positions of alkyl chains represent an exception: their relative yields are uniformly 2–2.5 times higher than those expected from thermodynamics due to the additional stabilizing effect of the second methyl group on the concentration of respective carbocations.

Effect of feedstock variability on catalytic cracking yields

Nine compositionally distinct vacuum gas oil feedstocks have been studied to develop a rational basis for understanding the distribution of major products in fluid catalytic cracking (FCC) reactions. Key hydrocarbon and carbon types have been quantitated from mass spectrometric data. Product yields were determined, under standardized conditions, using an FCC microactivity test (MAT) system. Severity conditions were varied to obtain yield profiles encompassing that MAT conversion where the yield of C 5F + gasoline was at maximum. These optimum yield profiles were correlated with the feedstock properties which characterized and quantitated those precursors capable of producing gasoline molecules. The correlations were tested against two further vacuum gas oils. The conclusions are that realistic comparisons between feeds may be made at conversions where the yield of gasoline is at maximum.

Rules for the distribution of sulfur among the products of Stag-Countercurrent Catalytic Cracking (SCCC)

1. Increasing the temperature increases the degree of decomposition of the sulfurous compounds in the crude stock, in which case the sulfur concentration in the liquid cracking products increases. 2. Decreasing the specific, gravimetric flow rate not only increases the degree of decomposition of the sulfurous compounds of the crude stock but also results in a decrease in the sulfur concentration in the liquid cracking products because of the occurrence of secondary desulfurization reactions. 3. Increasing the number of sections both for identical conditions and for the same degree of decomposition of the crude stock also increases the extent of decomposition of the sulfurous compounds and results in a desulfurization of the liquid cracking products. Upon increasing the number of sections, the amount of sulfur which is removed with the coke and gas also increases. 4. For the same conditions the greater the activity of the catalyst, the greater the extent of decomposition of the sulfurous compounds. Mainly, this takes place because of the more extensive decomposition of the crude stock itself. 5. For the same degree of decomposition of the crude stock and the same number of sections a different rule is observed. On the low-active, natural catalyst the decomposition of the sulfurous compounds of the crude stock takes place to a greater degree than on the synthetic catalyst but in this case a significant part of the decomposed sulfurous compounds is converted into the naphtha and light gas oil whereas on the synthetic catalyst the sulfur is removed more with the gas and coke than in the case for the natural catalyst. This indicates a smaller amount of secondary reactions for the cracking on the natural catalyst. 6. In cracking crude stock with a larger concentration of aromatic hydrocarbons (mainly heavy aromatic hydrocarbons) the sulfur which passes into the naphtha and light gas oil is greater than for the cracking of the less aromatic crude stock with predominantly light and medium aromatic hydrocarbons.