For Fluid Catalytic Cracking Research Articles

Selective staining of zeolite acidity: Recent progress and future perspectives on fluorescence microscopy

This perspective article highlights recent methodical approaches for probing acid sites in zeolites using selective chemical staining methods. Research and method development on model systems (large zeolite crystals) is presented in close relation to the investigation of industrially relevant catalyst particles for Fluid Catalytic Cracking (FCC) and zeolite-based extrudates. The article begins with an (1) introduction on characteristics of zeolites and industrial catalyst particles, followed by a methodical overview on (2) probing acidity in zeolites, including temperature programmed desorption (TPD), solid state nuclear magnetic resonance (NMR) spectroscopy, and infrared (IR) spectroscopy. Instrumental details on (3) fluorescence microscopy are provided to prepare for the focus on (4) selective staining by probe molecules and oligomerisation reactions to highlight or distinguish materials (i.e. zeolite vs. binder or matrix components) and visualise acid sites within zeolites. Confocal fluorescence yields, in contrast to the other discussed techniques, a high spatiotemporal resolution giving way to exciting prospects such as probing single (fluorescent) reaction products. (5) Concluding remarks and future perspectives envision how Brønsted and Lewis acid sites can be investigated selectively.Sections: (1) Introduction (2) Probing acidity – methodical overview (3) Confocal fluorescence microscopy – instrumentation (4) Selective staining (5) Concluding Remarks and Future Perspectives.

The fate of bio-carbon in FCC co-processing products

A promising alternative to the first generation of bio-fuels is to produce mixed bio- and fossil fuels by co-processing mixtures of biomass pyrolysis oil with crude oil fractions obtained from distillation in a conventional oil refinery. This was demonstrated to be technically feasible for fluid catalytic cracking (FCC), which is the main refinery process for producing gasoline. However, co-processing leads to more coke formation and to a more aromatic gasoline fraction. A detailed understanding is necessary on how the oxygenated moieties effect the reaction mechanism to further improve the process/catalysts. Moreover, for technical and marketing reasons, it is absolutely required to accurately determine the proportion of renewable molecules in the commercialized products. The carbon-14 method (also called radiocarbon or 14C) has been used as the most accurate and powerful method to discriminate fossil carbon from bio-carbon, since fossil fuel is virtually 14C-free, while biofuel contains the present-day “natural” amount of 14C. This technique has shown that not all FCC products share bio-carbon statistically. The coke formed during a FCC cycle and to a lesser extent the gases are found richer in 14C than gasoline. This result gives valuable information on the co-processing mechanism, supporting that the bio-oil oxygenated molecules are processed more easily at the expenses of the crude oil hydrocarbons, favouring the bio-coke and the bio-light gases production.

Solventless Deasphalting: Selective Sulfonation Chemistry of Petroleum Asphaltenes and Resids

Asphaltenes are the lowest value component of petroleum. They are found in a variety of crude oils and in higher concentrations in resids and bitumens. Petroleum resid is the non-volatile fraction of crude oil or bitumen after distillation. Current disposition of the asphaltenes is high-temperature thermal chemistry to form higher value liquids and coke or as feedstock for asphalt. Asphaltenes are separated from a resid by a commercial process called solvent deasphalting. Deasphalting is accomplished by treating a resid with a hydrocarbon solvent (propane or butane commercially and pentane−heptane in the lab), and the asphaltenes precipitate out of solution. The rest of the resid is soluble, and this is called the deasphalted oil (DAO). The DAO is recovered by evaporation of the solvent. The DAO is higher value than the original resid, and it is used as residual sulfur fuel oil (RSFO) and, in some cases, as a feedstock for fluid catalytic cracking (FCC) to form higher value liquids. Asphaltenes are compos...

Co2e emissions abatement costs of reducing natural gas flaring in Brazil by investing in offshore GTL plants producing premium diesel

Abstract This study evaluates the possibility of installing an offshore gas-to-liquids (GTL) plant in Brazil to reduce Natural Gas (NG) flaring, curb carbon dioxide equivalent (CO 2 e) emissions and produce premium diesel. CO 2 e emissions abatement costs were estimated by comparing two alternatives. The first alternative (baseline) considers that the volume of NG flared will not be reduced. Low-sulfur fuels (diesel and naphtha) will be obtained by investing in treatment units in Brazilian refineries. These are hydrotreating units for unstable compounds and hydrodesulfurizer units for fluid catalytic cracking (FCC) naphtha. Currently in Brazilian refineries, without any investment, the lower-quality streams that should be removed from diesel and gasoline pools to comply with higher specifications are light-cycle oil and FCC naphtha, respectively. The second alternative considers an offshore microchannel GTL plant producing synthetic crude oil, or syncrude. The upgrading of this syncrude is done by a mild-hydrocracking unit. This alternative allows the production of low-sulfur diesel, reducing gas flaring and co-producing high-quality naphtha. The results show that CO 2 e emissions abatement costs of offshore GTL in Brazil should range between negative US$ 2.00 and positive 80.00/tCO 2 e. Nevertheless, the typical scenario shows an average figure of US$ 37.00/tCO 2 e abated.

Mechanistic Pathways for Olefin Hydroisomerization and Aromatization in Fluid Catalytic Cracking Gasoline Hydro-upgrading

The reactivities of model hydrocarbons (n-paraffins, i-paraffins, olefins, naphthenes, and aromatics) typical for fluid catalytic cracking (FCC) gasoline were investigated over a Ni−Mo/modified HZSM-5 + Al2O3 catalyst. Olefins had the highest reactivity and were unidirectionally converted into molecules of the other groups, especially i-paraffins and aromatics. On the basis of the results, a reaction mechanism was proposed for olefin hydroisomerization and aromatization in the presence of excess hydrogen. During the olefin hydroisomerization and aromatization, the initial adsorption sites of the olefins are the acid sites rather than the metal sites of the bifunctional catalyst. The olefin hydroisomerization reaction is in accordance with the hydrogen spillover concept. The function of the metal sites is to dissociate hydrogen molecules into active H ions, and the acid sites are the reaction sites. The olefin aromatization in the presence of hydrogen occurs through diene and cyclo-olefin intermediates by ...

Studies on polyethylene glycol/polyethersulfone composite membranes for FCC gasoline desulphurization by pervaporation

A polyethylene glycol (PEG)/polyethersulfone (PES) composite membrane that can be applied on a commercial (or scale up) plant for fluid catalytic cracking (FCC) gasoline desulphurization was prepared through pre-wetting combined with double-layer coating methodology. Preparation methodology, morphologies characterization and performance test for the composite membranes were conducted. The results indicated that the pre-wetting method effectively confined the intrusion of PEG solution to porous PES support layer in coating process. The composite membrane had a clear-cut boundary surface between the dense active layer and the porous support layer, which was examined by scanning electron microscope (SEM). Pervaporation (PV) experiments indicated that the membrane, with the crosslinking agent amount of 17% and solids content in active layer solution of 16%, had a stable performance for FCC desulphurization. The sulphur enrichment factor came to 3.63, and the total permeation flux was 3.37 kg/m 2 h. It was found that the PV performance of the composite membrane changed slightly when the thickness of active layer varied from 4.25 μm to 33.26 μm.

Coking and Deactivation Behavior of HZSM-5 Zeolite-Based FCC Gasoline Hydro-Upgrading Catalyst

In order to further understand the deactivation behavior of a NiMo/HZSM-5 catalyst system used for fluid catalytic cracking (FCC) gasoline hydro-upgrading, fresh and coked catalysts after operation for different times-on-stream (TOS) with FCC gasoline as a feedstock were characterized by X-ray diffraction, Fourier transformed infrared (FTIR) spectroscopy, nitrogen adsorption, and temperature-programmed desorption of ammonia, as well as FTIR analysis of adsorbed pyridine. The results showed that the amount, nature, and location of coke formed in the catalysts depended upon TOS. Coke was preferentially formed on the strong acid sites, especially on the strong Lewis acid sites in the pore channels and/or on the external surface of the catalysts, resting with the size of the reactant molecules in FCC gasoline. Coke formation led to increases in the selectivities to C8, C9, and C9+ aromatics and decreases in the selectivities to benzene and toluene in the aromatics products. Using real FCC gasoline as a feedst...

Post-riser regeneration technology in FCC unit

In our present work, a post-riser regeneration technology (PRRT) for fluid catalytic cracking (FCC) units was developed to deal with increasingly heavier feedstock and hereby the larger amount of coke deposited on the catalyst particles during reaction. This technology can make full use of the advantages of riser regenerator, such as high cokeburning efficiency and low residual carbon, and at the same time overcome its disadvantages, such as difficulty in starting combustion. The average particles concentration on the cross section of the system was studied on a large scale cold model experimental set-up. Also a necessary software was developed by combining the hydrodynamics research results in our work with the coke-burning kinetics model and the heat and mass transfer model developed by previous researchers. The simulation results showed that the PRRT could increase regeneration capability by 16.28%–26.24% over the conventional turbulent fluidized bed regenerator under the similar operation conditions, and that the residual carbon could be kept below 0.1 wt %.

Laboratory deactivation testing for the stability of FCC CO combustion promoters

Realistic lab deactivation facilitates the development of low NOx, CO combustion promoters for fluid catalytic cracking (FCC) applications. Cyclic deactivation, which provides a close simulation of the FCC operation, can address many possibilities for the deactivation of CO combustion promoters. Here we present our results using a combination of cyclic deactivation and a coke combustion test to predict additive performance after deactivation. By using this newly developed method, CO combustion promoters with exceptional performance were identified. These novel materials feature CO reduction performance similar to that of Pt-based promoters while still offering significant NOx reduction relative to Pt. Examples are also given using a more traditional hydrothermal deactivation approach.

Selection and crosslinking modification of membrane material for FCC gasoline desulfurization

Selection and modification of membrane material is important fundamental research for fluid catalytic cracking (FCC) gasoline desulfurization by membrane process. Solubility parameters of FCC gasoline components and typical polymeric membrane materials were calculated and given out. For thiophene species, which are the primary ones in FCC gasoline, solubility parameters were about 19–21 (J/cm 3) 1/2, while about 14–15 (J/cm 3) 1/2 for most hydrocarbon species in FCC gasoline. The distinct difference in solubility parameter between the two typical species was just the key to fulfill the separation. By the study and analysis of solubility parameter theory, pervaporation (PV) performance and membrane preparation, polyethylene glycol (PEG) was determined as the promising membrane material for gasoline desulfurization. In spite of its desulfurization capacity, PEG needs modification for its easier swelling and unstable PV performance. According to the comparison on PV performance of PEG before and after modification as well as the swelling experiments, crosslinking was an effective modification way for PEG membrane applied in gasoline desulfurization. After crosslinking, not only the sulfur enrichment factor increased distinctly, but also the membrane performance was stable which was the most important point for practical application. Sulfur enrichment factor increased with the increase of amount of crosslinking agent and crosslinking time, while total permeation flux decreased. Unfavorable results occurred with exorbitant crosslinking resulted form excessive crosslinking agent and overlong crosslinking time. Since sulfur enrichment factor was for key consideration, 16% of crosslinking agent amount and 60 min of crosslinking time were more practical.

Pervaporation performance of crosslinked polyethylene glycol membranes for deep desulfurization of FCC gasoline

An crosslinked polyethylene glycol (PEG) membrane was prepared for fluid catalytic cracking (FCC) gasoline desulfurization. Sulfur enrichment factor come to 4.75 and 3.51 for typical FCC gasoline feed with sulfur content of 238.28 and 1227.24 μg/g, respectively. Pervaporation performance of membranes kept stable within the long time run of 500 h, which indicated that crosslinked PEG membranes had the property of resisting pollution. Judging from chromatographic analysis, the membranes were more efficient for thiophene species. Effects of operation conditions including permeate pressure, feed temperature, feed flow rate and feed sulfur content level on the pervaporation performance were investigated. Permeation flux decreased with increasing permeate pressure while increased with the operating temperature increase. Sulfur enrichment factor increased firstly and decreased then when permeate pressure and temperature rose. The peak value occurred at 10.5 mm Hg and 358 K for model compounds feed (378 K for FCC gasoline feed). Arrhenius relationship existed between flux and operating temperature. Both sulfur enrichment factor and flux were shown to increase with increasing feed flow rate. Permeation flux increased while sulfur enrichment factor decreased as the feed sulfur content increased, but the influence of increasing sulfur content on pervaporation performance weakened when sulfur content come to 600 μg/g.

Production of clean transportation fuels and lower olefins from Fischer-Tropsch Synthesis waxes under fluid catalytic cracking conditions: The potential of highly paraffinic feedstocks for FCC

The potential of Fischer-Tropsch Synthesis (FTS) waxes as a feedstock for fluid catalytic cracking (FCC) has been evaluated with a once-through microriser reactor operating under realistic conditions. The highly paraffinic feedstock has a high reactivity and can be converted under industrial conditions to a high extent (>90wt%). The product distribution can be optimised by the process parameters and catalyst formulation. A high gasoline fraction (70wt%) with a very low aromatics concentration can be obtained. As a result of the formation of i-paraffins, n-olefins and i-olefins the gasoline is expected to possess an acceptable octane number. The reaction scheme derived predicts that the degree of branching in the paraffinic diesel-range product is lower than that of the gasoline-range product and that a relatively good diesel is expected. Due to the absence of sulfur and nitrogen in the feed extremely clean transportation fuels are obtained. The addition of ZSM-5 to an equilibrium catalyst allows the production of significant amounts of light olefins, in particular propene (16wt%) and butenes (15wt%).

Are Fischer–Tropsch waxes good feedstocks for fluid catalytic cracking units?

The potential of a highly paraffinic Fischer–Tropsch synthesis (FTS) wax as a feedstock for Fluid Catalytic Cracking (FCC) has been evaluated. A once-through microriser reactor was used to mimic realistic FCC conditions. FTS waxes are indeed attractive feedstocks for FCC. As a result of its high paraffinicity an interesting spectrum of products can be obtained by tuning process conditions and catalyst formulations. A high gasoline fraction (70 wt%) with an apparent high-quality motor octane number can be obtained. Also a relatively good diesel is expected. Due to the absence of sulfur and nitrogen in the feed extremely clean transportation fuels can be obtained that are additionally low on aromatics. The combination of an equilibrium catalyst with a steam-deactivated ZSM-5 additive yields high amounts of propene (16 wt%), isobutene (7 wt%) and n-C 4-olefins (8 wt%).

A New Approach to Determining Product Selectivity in Gas Oil Cracking Using a Four-Lump Kinetic Model

A simplified four-lump model for fluid catalytic cracking (FCC) as reported in the literature has been examined. The model, which relates the coke yield to other yields, is important to FCC operation but requires intensive data analyses. In this article, a new methodology that can validate the model and substantially simplify the data treatments is proposed. The method is applicable to both steady-state FCC riser cracking and unsteady-state microactivity tests (MAT). An explicit expression, derived for the coke yield as a function of conversion, is shown to describe the reported data well. The method is independent of the catalyst decay function and the reaction order of gas oil cracking. This enables the model to be applicable to many systems, even noncatalytic pyrolysis. A case study of the model, which uses the proposed method, suggests that for a given feed-catalyst system the relative rates of coke formation from either gasoline or gas oil may be the same for different reactors.

00/01731 Production of lubricant base oils

The potential of Fischer-Tropsch Synthesis (FTS) waxes as a feedstock for fluid catalytic cracking (FCC) has been evaluated with a once-through microriser reactor operating under realistic conditions. The highly paraffinic feedstock has a high reactivity and can be converted under industrial conditions to a high extent (>90 wt%). The product distribution can be optimised by the process parameters and catalyst formulation. A high gasoline fraction (70 wt%) with a very low aromatics concentration can be obtained. As a result of the formation of i-paraffins, n-olefins and i-olefins the gasoline is expected to possess an acceptable octane number. The reaction scheme derived predicts that the degree of branching in the paraffinic diesel-range product is lower than that of the gasoline-range product and that a relatively good diesel is expected. Due to the absence of sulfur and nitrogen in the feed extremely clean transportation fuels are obtained. The addition of ZSM-5 to an equilibrium catalyst allows the production of significant amounts of light olefins, in particular propene (16 wt%) and butenes (15 wt%).

98/03587 Athabasca oil sands produce quality FCC feeds

Syncrude Canada Limited and Mitsubishi Oil Company's (MOC) Petroleum Research Laboratory jointly evaluated the quality of various Athabasca bitumen-derived vacuum gas oils (VGOs) and solvent-deasphalted oil (DAOs) as feedstocks for fluid catalytic cracking (FCC) units. They determined that FCC feeds comparable to the VGO from a typical Alberta light crude oil can be produced from oil sands bitumen by selecting appropriate upgrading processes. Of the nine Athabasca bitumen feeds tested, three can be processed in the FCC unit. Another four can be processed in the residual FCC unit.

Upgrading of directly liquefied biomass to transportation fuels: catalytic cracking

Hydroprocessed oil derived from biomass via direct liquefication using the PERC process was catalytically cracked in a fixed-bed reactor. The fraction of the hydroprocessed oil used as feed for fluid catalytic cracking (FCC) had a boiling point range over 350°C. The FCC feed had an oxygen content of 0·8 wt% and a hydrogen to carbon ratio of 1·3:1. Compared with cracking at normal reactor temperatures of 500°C, cracking at 562°C resulted in the production of excessive amounts of coke and gas. Cracking at catalyst to oil ratios lower than the ASTM standard of 4:1·33 reduced the yields of coke and gas and improved the yields of liquid products.

A lumping and reaction scheme for catalytic cracking

AbstractA predictive kinetic model has been developed for fluid catalytic cracking (FCC). The kinetic scheme involves lumped species consisting of paraffins, naphthenes, aromatic rings, and aromatic substituent groups in light and heavy fuel oil fractions. The kinetic model also incorporates the effect of nitrogen poisoning, aromatic ring adsorption, and time dependent catalyst decay. The rate constants for these lumped species are invariant with respect to charge stock composition. The predictive capabilities of the model have been verified for wide ranges of charge stocks and process conditions.