Model Fluid Catalytic Cracking Research Articles

CO2 capture from fluid catalytic crackers via chemical looping combustion: Regeneration of coked catalysts with oxygen carriers

Oil refineries are responsible for ∼5% of total global CO2 emissions and approximately 25–35% of these emissions are released from a single unit called Fluid Catalytic Cracking (FCC). Chemical Looping Combustion (CLC) has been recently proposed as a novel CO2 capture method from the regenerator of FCC units as an integrated process of CLC-FCC. In this study, for the first time, the combustion behaviour of three types of cokes, a model FCC coke (which is a low volatile semi-anthracite coal), and cokes deposited on commercial FCC catalysts by n-hexadecane cracking and Vacuum Gas Oil, were comprehensively investigated with oxygen carriers (Co3O4, CuO, and Mn2O3) in a fixed-bed reactor at 700–850 °C. The results demonstrate that a high coke combustion efficiency was achieved with CuO (98 vol %), Co3O4 (91 vol %), and Mn2O3 (91 vol %) at 800 °C for 30 min. CuO was the most effective oxygen carrier, at temperatures greater than 750 °C for 45 min of residence time. These are the regeneration conditions used in the conventional FCC regenerators.

Matrix Effects in a Fluid Catalytic Cracking Catalyst Particle: Influence on Structure, Acidity, and Accessibility.

Matrix effects in a fluid catalytic cracking (FCC) catalyst have been studied in terms of structure, accessibility, and acidity. An extensive characterization study into the structural and acidic properties of a FCC catalyst, its individual components (i.e., zeolite H‐Y, binder (boehmite/silica) and kaolin clay), and two model FCC catalyst samples containing only two components (i.e., zeolite‐binder and binder‐clay) was performed at relevant conditions. This allowed the drawing of conclusions about the role of each individual component, describing their mutual physicochemical interactions, establishing structure‐acidity relationships, and determining matrix effects in FCC catalyst materials. This has been made possible by using a wide variety of characterization techniques, including temperature‐programmed desorption of ammonia, infrared spectroscopy in combination with CO as probe molecule, transmission electron microscopy, X‐ray diffraction, Ar physisorption, and advanced nuclear magnetic resonance. By doing so it was, for example, revealed that a freshly prepared spray‐dried FCC catalyst appears as a physical mixture of its individual components, but under typical riser reactor conditions, the interaction between zeolite H‐Y and binder material is significant and mobile aluminum migrates and inserts from the binder into the defects of the zeolite framework, thereby creating additional Brønsted acid sites and restoring the framework structure.

Synergistic Catalysis of Thermoregulated Ionic Liquid/p-Toluenesulfonic Acid for Alkylation Desulfurization of Fluid Catalytic Cracking Gasoline

The olefin alkylation of thiophenic sulfur (OATS) in model fluid catalytic cracking (FCC) gasoline was carried out using temperature-responsive catalyst which was prepared by mixing the temperature...

The effect of carrier in KCoMoS-supported catalysts for hydro-upgrading of model FCC gasoline

K-CoMo/Sup (where Sup = Al2O3, SiO2, TiO2 and ZrO2) catalysts were synthesized using H3PMo12O40, CoCO3, KOH and citric acid. The catalysts were characterized by temperature-programmed reduction (TPR), temperature-programmed desorption of NH3, X-ray photoelectron spectroscopy, transmission electron microscopy. Samples were tested in hydrotreating of model fluid catalytic cracking gasoline and in selective hydrogenation of 1,5-hexadiene and n-heptene-1. The type of used carrier significantly affected the morphology of active phase and catalytic properties. Active sites productivity of K-CoMo/Sup catalysts in hydrodesulfurization (HDS) and olefin hydrogenation (HYDO) reactions as well as HDS/HYDO selectivity correlated with active phase morphology excepting TiO2-supported sample. Productivity of active sites in reactions of selective hydrogenation of diolefin depended on maximum peak reduction obtained from TPR, which in turn was a function of acidity of using supports. The highest HDS/HYDO selectivity was obtained at catalyst which possessed the lowest selectivity towards partial hydrogenation of diolefine compared to complete hydrogenation.

Optimizing both the CoMo/Al2O3 catalyst and the technology for selectivity enhancement in the hydrodesulfurization of FCC gasoline

Herein, a series of alumina supports were prepared by rehydration-dehydration of the traditional γ-Al2O3 under different hydrothermal temperatures. After loading CoMo species, it was found the selectivity factor of corresponding CoMo/Al2O3 catalysts was improved greatly from 1.21 to 2.51 with the increased hydrothermal temperature of alumina supports in the hydrodesulfurization (HDS) of a model fluid catalytic cracking (FCC) naphtha. The improved HDS selectivity is attributed to the weakened metal-support interaction and lowered dispersion of MoS2 particles, resulting in catalysts with larger edge-to-corner ratios of CoMoS slabs ((fe/fc)CoMo). Besides, the recombination mercaptans formed by reaction of produced H2S and olefins were found as a big challenge to reach a high HDS conversion (S < 10 ppm) when only using the selective HDS catalyst (one-unit process). Therefore, a two-unit process has been developed by using a selective HDS catalyst to remove the most of the refractory sulfur compounds firstly, after which using another mercaptan-removing catalyst to deal with the recombination mercaptans specially. The catalytic results show that the two-unit process has a smaller olefin loss (4.38 v%) than that of one-unit process (7.08 v%) when reducing the sulfur concentration of a heavy FCC fraction to less than 10 ppm, thus resulting in a 0.7 unit less of the research octane number loss. The present work shows that high HDS conversion and low olefin hydrogenation conversion in selective HDS of FCC gasoline can be achieved through optimization design of both the selective HDS catalyst and the whole technology.

8-Lump kinetic model for fluid catalytic cracking with olefin detailed distribution study

Modeling fluid catalytic cracking (FCC) riser reactors is of significant importance in FCC unit control, optimization and failure detection, as well as development and design of new riser reactors. In this study, kinetic behavior of vacuum gas oil (VGO) catalytic cracking is studied by developing an 8-lump kinetic model to describe the product distribution. The feedstock and products are divided into eight lumps by reasonably simplifying reaction network, including VGO feed, diesel oil and gasoline, LPG, butylenes, propylene, ethylene, light gases, and coke. A time-on-stream non-selective catalytic activity equation is also assumed to model deactivation mechanism. Twenty-seven pairs of model kinetic parameters are estimated using two different optimization methods, namely: non-dominated sorting genetic algorithm II (NSGA-II), and chaotic particle swarm optimization (C-PSO) algorithm. Performances of both optimization methods are compared and C-PSO algorithm is selected as the superior method in terms of computation time and finding the global optimum. In the current research, based on validated estimated parameters of the preferred C-PSO method, the effects of some operating parameters on product yields distribution are investigated and discussed. This model can be used to predict the riser key products and their compositions with high degree of accuracy which may be especially useful for the conventional FCC processes with olefins production streams.

Desulfurization of model FCC gasoline by extraction with ionic liquid and conventional extraction solvents

ABSTRACTTo compare the desulfurization performance of conventional extraction solvents and novel ionic liquid, desulfurization experiments by extraction were conducted on sulfolane, acetonitrile, N-formyl morpholine, and [BPy]BF4 using model Fluid Catalytic Cracking gasoline (thiophene and n-octane) as feedstock. Results showed that the desulfurization rate of ionic liquid was worse than conventional extraction solvents, but its yield of sweet gasoline was higher, which could reach to 90.36%. Among the four solvents, N-formyl morpholine had the best desulfurization performance, while sulfolane was the most stable extraction agent.

Amorphous silica-alumina – perspective supports for selective hydrotreating of FCC gasoline: Influence of Mg

CoMo/Al2O3-ASA catalysts with Mg were synthesized. Catalysts differed in the way of Mg addition: 1. Mg was added to ASA, 2. Mg was added to the kneading paste during the support preparation, 3. Mg was added before or after Co and Mo by the impregnation. Catalysts were characterized by the following techniques: low-temperature N2 adsorption, IR of CO and CO2 adsorption, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy. Synthesized catalysts were tested in hydrotreating of the model fluid catalytic cracking gasoline containing 250 ppm of sulfur from thiophene, 40 wt.% of toluene, 40 wt.% of heptane and 20 wt.% of n-hexene-1. It was found that the addition of Mg resulted in changes of physico-chemical properties of catalysts and their HDS and HYD activities. The way of Mg addition influenced the content of Lewis and Brønsted acid sites and morphology of sulfide active component. Mg increased HDS activity and decreased octane number loss. The catalysts with Mg in the kneading paste of the support and with Mg added after active metals showed the best combination of HDS activity and selectivity.

A new generic reaction for modeling fluid catalytic cracking risers

Abstract A new generic reaction in the form of PC i → PC m + [ i , m ] → PC m + λ i , m coke + surplusage has been proposed for describing the catalytic cracking behavior of petroleum narrow cuts or pseudo-components (PCs), where the rate constant formula is derived from the transition state theory and the coking amount is correlated to the properties of the intermediate substance [ i , m ]. In composing the cracking reaction network for feedstock and product oils, only the product PC m of the proposed generic reaction is used, which together with a criterion for excluding exothermic reactions, distinctly reduces the number of reactions in the network. With the proposed cracking reaction scheme coupled with special pseudo-components, a predictive one-dimensional steady state model for fluid catalytic cracking risers is formulated in the sense that for a given riser and given catalyst, the model parameters are independent of stock oils, product schemes and other operational conditions. The great correlating and predicting capability of the resulted model is tested with production data in different scenarios of four commercial risers.

Comparable investigation of spillover and cobalt promoter effects in CoMoS/CoSx/SiO2 catalysts for selective hydrotreating of model FCC gasoline

Cox-Co2Mo10/SiO2 and Co2Mo10/Cox/SiO2 catalysts with various Co/Mo ratios and active species compositions are prepared using H6[Co2Mo10O38H4] heteropolyacid, CoCO3 and citric acid. Catalysts are characterized using the following techniques: low-temperature N2 adsorption, temperature-programmed reduction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalytic activities of the synthesized catalysts are examined in hydrotreating of model fluid catalytic cracking (FCC) gasoline that contains 1000ppm of sulphur from thiophene and 36wt.% of n-hexene-1. As the Co/Mo ratio increases, hydrodesulphurization (HDS) and hydrogenation (HYD) activities of the prepared catalysts significantly builds up. The changes of catalytic properties and specifically of the HDS/HYDO selectivity factor of the synthesized CoMo catalysts arise from two effects: an alteration of the promotion degree of CoMoS active phase particles and a hydrogen spillover from CoSx species to active sites. The developed silica-supported CoMo catalysts may be a prospect for selective HDS and hydro-upgrading of FCC gasoline.

Alkylation desulfurization of FCC gasoline over organic-inorganic heteropoly acid catalyst

The alkylation reaction of thiophenic sulfides with olefin in model fluid catalytic cracking (FCC) gasoline has been carried out over many kinds of organic-inorganic heteropoly acids, H3PW12O40, and AlPW12O40. The results have showed that organic-inorganic heteropoly acid [Bmim]H2PW12O40 exhibits the best catalytic activity for the alkylation of thiophene (T), 2-methyl thiophene (2-MT) and 3-methyl thiophene (3-MT). Many effect factors for the alkylation of thiophenic sulfides catalyzed by [Bmim]H2PW12O40 have been fully investigated. Under the optimal reaction conditions (the catalyst dosage 1wt%, reaction temperature 120°C, reaction time 40min and the stirring rate 500rpm), the conversions of T, 2-MT and 3-MT all can nearly reach up to 100%. [Bmim]H2PW12O40 has also exhibited good stability and recyclability. The conversions of thiophenic sulfides nearly remain unchanged during 11 recycles of [Bmim]H2PW12O40. Apparent reaction kinetics for the alkylation of thiophenic sulfides is studied. The alkylations of T, 2-MT and 3-MT all show the pseudo-first-order kinetic characteristics. The order of the reaction rate constants of three thiophenic sulfides is 2-MT>3-MT>T. However, the calculated apparent activation energies of T, 2-MT and 3-MT are 62, 45.54 and 71.33kJ/mol, respectively. So, the order of apparent activation energies is 3-MT>T>2-MT.

Selective hydrodesulfurization of model fluid catalytic cracking gasoline over sulfided Al2O3-supported Anderson heteropolyoxomolybdate-based catalysts

XMo6/Al2O3 catalysts were synthesized using XMo6-heteropolycompounds with Anderson’s structure (where X = Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Al). The sulfided catalysts were characterized by N2 adsorption, temperature-programmed reduction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The catalysts were tested in hydrotreating of model FCC gasoline contained thiophene (1000 ppm of sulfur) and 1-hexene (36 wt%). The correlations between HDS/HYDO selectivity and characteristics of XMoS species depending on the nature of the heteroatom X in XMo6-heteropolycompound indicated the predominance of the electronic effect under the geometrical impact in the catalytic properties. It was found that to create a catalyst with high HDS/HYDO selectivity, reaching the mixed CoMoS active phase is the key requirement.

Relation between composition and morphology of K(Co)MoS active phase species and their performances in hydrotreating of model FCC gasoline

K-Mo/Al2O3 and K-CoMo/Al2O3 catalysts with various amount of potassium (up to 15wt. %) were synthesized using H3PMo12O40, CoCO3 and KOH. The catalysts were characterised by the following techniques: low-temperature N2 adsorption, Raman spectroscopy, temperature-programmed reduction, temperature-programmed desorption of NH3, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy. Synthesized catalysts were tested in hydrotreating of model fluid catalytic cracking gasoline containing 1000ppm of sulphur from thiophene and 36wt. % of n-hexene-1. It was found that potassium incorporation led to the strong changes in both physical-chemical characteristics and catalytic behaviour of sulphide catalysts. Using potassium favoured the growth of average slab length and sulphidation degree of metals with selective formation of CoMoS active phase. Addition of potassium also led to the partial poisoning of the active sites what resulted in decrease of catalyst activities compared with the reference Mo/Al2O3 and CoMo/Al2O3 samples. Olefin hydrogenation was more sensitive to potassium than thiophene hydrodesulphurization what resulted in the growth of the dependence of selectivity factor on potassium content in the catalysts. Obtained results allowed us to suppose that potassium partially inserts in sulphide slabs with changing the nature of active sites and probably with formation of new type of active “KCoMoS” sites.

Ten-lump kinetic model for the two-stage riser catalytic cracking for maximizing propylene yield (TMP) process

Modeling Fluid Catalytic Cracking (FCC) riser reactors is of significance to FCC unit control, optimization and failure detection, as well as the development and design of new riser reactors. Under the guidance of catalytic reaction mechanisms and the demands for commercial production, a ten-lump kinetic model was developed for the TMP process in this study. The feedstock and products were divided into ten lumps by reasonably simplifying the reaction network, including heavy oil, diesel oil, gasoline olefins, gasoline aromatics, gasoline saturates, (butane + propane), butylene, propylene, dry gas and coke. Thirty-five sets of model parameters were estimated with the combined simulated annealing method and the damped least square method. The findings indicated that the model could predict the riser key products and their compositions quite well; thereby it could be useful to the production practice for the TMP process.

An integrated methodology for the modeling of Fluid Catalytic Cracking (FCC) riser reactor

Modeling description of the riser reactor is a highly interesting issue in the development of FCC process. However, one of the challenging problems in the modeling of FCC riser reactors is that sophisticated flow-reaction models with high accuracy need long computational time, while simple flow-reaction models give rise to results with fast computation but low accuracy. This dilemma requires new type of coupled flow-reaction models. The goal of this study was to propose a novel integrated model with time-efficient computation and acceptable accuracy. The integrated model, named equivalent reactor network (ERN) model, was established based on Aspen Plus simulator with considering gas–solid hydrodynamics via built-in modules and catalytic reactions via external FORTRAN subroutines, as well as lump mixtures characterized by real components. Through comparing with pilot-scale experimental data and industrial plant data in two case studies, the developed ERN model was justified to be capable of precisely and quickly modeling FCC riser reactors. Furthermore, the proposed methodology is expected to be readily applied to studies on the dynamic simulation, optimization, and control of FCC units in future studies.

Effects of composition and morphology of active phase of CoMo/Al2O3 catalysts prepared using Co2Mo10–heteropolyacid and chelating agents on their catalytic properties in HDS and HYD reactions

CoMo/Al2O3 catalysts were synthesised from the ammonium and Co salts of [CoMo6O24H6]3− and [Co2Mo10O38H4]6− anions as well as Co–chelate complexes with nitrilotriacetic, ethylenediaminetetraacetic, citric and tartaric acids. The catalysts were characterised using X-ray powder diffraction, Raman spectroscopy, N2 physisorption, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalysts were tested in the hydrotreating (HDT) of a mixture containing thiophene and n-hexene-1, the hydrodesulphurisation (HDS) of dibenzothiophene and 4,6-dimethyldibenzothiophene and the HDT of diesel. The type of chelating agent significantly affects the structure of the active phase and catalytic properties. The catalytic activity, selectivity and turnover frequency during the HDS and hydrogenation reactions depend on the number and location of CoMoS sites, as well as the shape of the active phase crystallites. New “structure–activity” relationships were established. These approaches yielded catalysts that demonstrated high efficiency towards the deep diesel HDT and selective HDS of a model fluid catalytic cracking gasoline.

Modeling fluid catalytic cracking risers with special pseudo-components

Special pseudo-components (SPCs) are proposed to be the compositional entities for characterizing the complicated mixtures of stock and product oils involved in fluid catalytic cracking risers. SPCs have invariant and definite physicochemical properties and are defined in pairs of light and heavy oil cuts of narrow boiling range. A narrow cut of true boiling point distillation of a stock or product oil is expressed with a pair of SPCs, which constitutes the basis for the characterization procedure developed in this paper. A steady state model for a prototype riser with a side feed stream is formulated where material and heat balance is strictly observed, the hydraulic behavior is considered, and the kinetic scheme of Gupta et al. (2007) is adopted. Results of tests with production data from three commercial risers show that the kinetic scheme of Gupta et al. (2007) is predictive as coupled with the suggested characterization procedure in the sense that for a given riser and given catalyst, the kinetic parameters are independent of stock oils.

Ionic Liquid‐Coated Nickel Phosphide Catalysts for Selective Hydrodesulfurization

AbstractNi2P/SiO2 catalysts were coated with the ionic liquid (IL) 1‐butyl‐3‐methylimidazolium bis[(trifluoromethyl)sulfonyl]amide with different coating thicknesses and their selective hydrodesulfurization performances were investigated using a model fluid catalytic cracking gasoline. The selective factor on the IL‐coated catalysts (IL‐Ni2P/SiO2) first increased and then decreased as the initial mass ratio of IL to Ni2P/SiO2 catalyst ranged from 0.02 to 0.18. A maximum selectivity factor of 16.7 was found at a mass ratio of 0.10 which corresponds to full monolayer coverage on the original Ni2P/SiO2 catalyst by the IL. In comparison, the selectivity factor was 6.7 for the Ni2P/SiO2 catalyst, indicating a significant selectivity improvement by the IL coating method.

The performance of solid phosphoric acid catalysts and macroporous sulfonic resins on gasoline alkylation desulfurization

Sulfur removal has received increasing attention in recent years primarily for environmental protection purpose. As an attractive technology in the case of gasoline, OATS (olefinic alkylation of thiophenic sulfur) proposed to separate sulfur compounds by distillation after being weighed down by alkylation with olefins in the feed. In this paper, alkylation reactions of thiophenic compounds were studied over solid phosphoric acid catalysts (SPAM and SPAS using MCM-41 and Silicalite-1 zeolite as supporters respectively) and macroporous sulfonic resins (including NKC-9, D005-2 and Amberlyst 35) with model gasoline and FCC (fluid catalytic cracking) gasoline. Results showed that macroporous sulfonic resins showed better performance than solid phosphoric acid catalysts under milder conditions in both feeds. Among the resins, Amberlyst 35 was the most suitable catalyst for the application of catalytic distillation for its good performance at the temperature range of 353–413 K in FCC gasoline. However, the selectivity of isoamylene dimerization over Amberlyst 35 decreased with the temperature, which was harmful to the product yield and catalyst stability. Besides, different activity orders of solid phosphoric acid catalysts in model gasoline and FCC gasoline were explained by combining the acidic properties of the catalysts with the species of olefins in two feeds.

Modeling Fluid Catalytic Cracking in a Novel CREC Riser Simulator: Adsorption Parameters under Reaction Conditions

The complexity of a heavy gas oil feedstock and the multitude of reaction pathways have limited previous attempts to model fluid catalytic cracking (FCC). The demand for more detailed kinetic information motivates the use of pure components to first elucidate the dominant pathways and mechanisms and then determine the associated rate parameters, including adsorption constants and heats of adsorption. The aim of the present work is to evaluate adsorption constants and heats of adsorption, under FCC relevant reaction conditions. The experiments are carried out in a novel CREC Riser Simulator (batch reactor unit) using USY zeolite catalysts with different crystallite sizes (0.4 and 0.9 microns). This study confirms a special feature of the CREC Riser Simulator, as a valuable tool for the study of adsorption phenomena. Adsorption constants and heats of adsorption are evaluated for benzene, toluene, xylene and trimethylbenzene, at initial reaction conditions. Catalytic conversion experiments for 1,2,4-trimethylbenzene help to demonstrate the consistency of the determined adsorption parameters at various temperatures and reaction times. In addition, adsorption constants and heats of adsorption are found to be constant throughout the reaction time and the formation of coke does not hinder the adsorption of 1,2,4-TMB, although it significantly affects the reactivity of this model compound.