From Fluid Catalytic Cracking Research Articles

Fe-ZSM-5 outperforms Al-ZSM-5 in paraffin cracking by increasing the olefinicity of C3-C4 products

Iron-modified Al-ZSM-5 increases selectivity to propene, a key petrochemical resulting from fluid catalytic cracking (FCC). However, the type and role of active iron species remain unclear, hindering efforts to streamline the design of selective FCC additives. Here, we investigated Al-free Fe-ZSM-5 catalysts containing iron species in the form of framework Fe3+, extra-framework Fe3+, oxidic clusters, and oxide micro aggregates in n-octane cracking (FCC model) to assess their effect on catalytic cracking. DR-UV–Vis spectroscopy, 57Fe Mössbauer Spectroscopy, FTIR studies of pyridine adsorption, and n-octane cracking tests at 500 °C revealed that framework-associated coordinatively unsaturated Fe3+ species, which induce strong Lewis acidity, are responsible for paraffin cracking initiation, whereas bulk iron oxides on the zeolite surface are inactive. In comparison with Al-ZSM-5, Fe-ZSM-5 increases the olefinicity of the valuable C3-C4 fractions (selectivity to propene and butenes) and promotes aromatization reactions due to the lower relative strength of Fe-induced Brønsted acid sites and dehydrogenation properties. As shown by our 57Fe Mössbauer study (performed at −269 °C) of the catalyst in calcined, spent, and regenerated states, Fe-ZSM-5 deactivation is associated with the loss of tetrahedrally coordinated Fe3+ species. Therefore, tuning Fe-ZSM-5 C3-C4 selective FCC additives requires stabilizing framework Brønsted and framework-associated Lewis acid sites while decreasing the concentration of iron oxide species. Ultimately, these findings may enable us to meet the demand for propene derived from FCC cracking, which is expected to grow in the foreseeable future.

Flower-like CoSe2/N, P-doped carbon microspheres accommodated on carbon nanosheets for high-performance potassium-ion batteries

Transition metal selenides (TMSs) have emerged as promising electrode materials for potassium-ion batteries (PIBs), whereas the large volume expansion and sluggish reaction kinetics have seriously hindered the cycle life and rate performance. Herein, a hierarchical composite of flower-like CoSe2/N, P-doped carbon microspheres accommodated on carbon nanosheets (CoSe2-NPC@CNS) was rationally fabricated as the anode for PIBs through a one-pot hydrothermal and subsequent selenization method. The intimate hybridization of CoSe2/N, P-doped carbon microspheres can effectively alleviate the volume expansion of CoSe2 during charge-discharge cycles, and the ultrathin carbon nanosheets derived from fluid catalytic cracking (FCC) slurry serves as a highly conductive and buffered substrate. By robustly merging them together, the interconnected hierarchical nanoarchitecture with exposed active sites achieves promoted potassium storage capacity, electrochemical reaction kinetics, and structural stability. As a result, the PIBs with CoSe2-NPC@CNS anode deliver high reversible capacities of 320.8 mAh g−1 after 100 cycles at 0.1 A g−1 and 213.9 mAh g−1 after 850 cycles at 1.0 A g−1, excellent rate capability (188.8 mAh g−1 at 5 A g−1), and enhanced pseudo-capacitive contribution rate of 88.7 %. This work offers valuable insight into the rational design and development of hierarchical anode materials with high performance for PIBs and beyond.

Highly dispersed carbon-encapsulated FeS/Fe3C nanoparticles distributed in Fe-N-C for enhanced oxygen electrocatalysis and Zn-air batteries

Transition metal single-atom catalysts (SACs) have been widely used in oxygen reduction reactions (ORR) and oxygen evolution reaction (OER) due to its greatest atomic utilization and low costs, which catalytic performance can be further enhanced by electron distribution adjustment. Herein, we synthesized a carbon-encapsulated FeS/Fe3C nanoparticles doped carbon-based Fe single atom catalyst from fluid catalytic cracking (FCC) slurry though a one-pot pyrolysis. The synergistic effect between FeS/Fe3C nanoparticles and Fe single atom structure (FeNx) promotes the ORR/OER processes, which may due to the reduction of the adsorption free energy of intermediates. Meanwhile, the polyaromatic hydrocarbon in FCC slurry enhances the graphitization of catalyst to facilitate charge transfer in electrocatalysis process, and the carbon-encapsulated nanoparticles sites possess higher stability and dispersion. As a result, the optimized catalyst (FeS/Fe3C@Fe-N-C) presents a high nanoparticles dispersion and graphitization level, which has a higher ORR catalytic ability (E1/2 = 0.91 V vs RHE) compared with commercial Pt/C (20 wt%, E1/2 = 0.879 V vs RHE) and a similar OER catalytic ability (E10 = 0.1.506 V vs RHE) compared with RuO2 (E10 = 1.518 V vs RHE). A liquid Zn-air battery assembled with FeS/Fe3C@Fe-N-C show a peak power density of 113 mW cm−2 and an open potential of 1.432 V. This work sheds light on a new method to design transition metal active sites carbon based single-atom catalyst for enhanced ORR and OER processes.

An Industrial Data-Based Model to Reduce Octane Number Loss of Refined Gasoline for S Zorb Process

S Zorb process is one of the main technologies for deep desulfurization of gasoline from fluid catalytic cracking (FCC) process, which by the process will also cause some research octane number (RON) loss of gasoline. Establishing a data-driven model with data mining technologies to optimize production is one of the development directions in petrochemical field. Based on the industrial data from a 1.20 Mt/a S Zorb unit in China in recent three years, 422 modeling samples and 22 modeling variables were screened out and then three data-driven models were established by back propagation neural network (BPNN), radial basis function neural network (RBFNN) and generalized regression neural network (GRNN) to predict RON of refined gasoline (r-RON). The results show that the BPNN model has the best prediction effect and generalization ability. Genetic algorithm (GA), particle swarm optimization algorithm (PSO) and simulated annealing algorithm (SA) in combination with the BPNN model respectively were used to optimize the operation variables to reduce the r-RON loss. The results indicate that the optimized performance of PSO-BPNN model is best because of its largest reduction in r-RON loss at 48.55%. The validity of the PSO-BPNN model was verified in the S Zorb unit and the research methods to establish a data-driven model for reducing r-RON loss are also worthy of reference for other S Zorb units.

Extraction of polycyclic aromatic hydrocarbons from fluid catalytic cracking diesel with ionic liquids

AbstractIonic liquids (ILs) as promising green solvents were first proposed to extract polycyclic aromatic hydrocarbons (PAHs) from fluid catalytic cracking (FCC) diesel. The COSMO‐RS model was used for preliminary screening of IL extractants. The liquid–liquid equilibrium (LLE) experiments were performed to show that the IL [BMIM][BF4] has a high selectivity for the model oil system. Further, the LLE experimental results show that the solubility of 1‐methylnaphthalene in [BMIM][BF4] is relatively low, while the IL exhibits a high selectivity of n‐hexadecane to 1‐methylnaphthalene. This means that the use of [BMIM][BF4] can obtain the high‐purity products when considering the almost nonvolatility of IL. Compared to the benchmark process, the multistage countercurrent–reflux extraction process can improve the PAHs purity by about 2% at the expense of 5.06% total annual cost and 6.42% energy consumption, rendering the use of IL to extract PAHs from FCC diesel more feasible in industry.

Purification of fluid catalytic cracking slurry oil at room temperature using ceramic membrane

The catalyst particles were removed from fluid catalytic cracking (FCC) slurry oil by two-step separation processing. FCC slurry oil was mixed with water and surfactant to make the lower viscosity emulsion. The catalyst particles were removed from the emulsion using the modified hydrophobic ceramic membrane (0.1 μm) and then the water was filtered out from oil/water emulsion using an unmodified hydrophilic ceramic membrane (0.05 μm) at room temperature. The separation efficiency of catalyst particles and emulsion reached 99.9% and the oil/water separation efficiency also reached 99.9%. FCC slurry oil was effectively purified at room temperature by a two-step treatment.

Utilizing carbon dioxide from refinery flue gas for methanol production: System design and assessment

As a main growing greenhouse gas emitter, petroleum refining is responsible for 4%–10% of the global carbon dioxide (CO2) emissions, of which approximately 25% is derived from fluid catalytic cracking (FCC) units. The flue gas released by FCC units has a high CO2 content (11–17 vol%), creating potential for methanol production when the methane and hydrogen in the dry gas as a byproduct of FCC are considered. To unlock this low-carbon opportunity for refineries, we employed Aspen Plus to develop a methanol synthesis system by recovering the CO2 in the flue gas and the methane and hydrogen in the dry gas of an FCC unit. Based on pinch theory, a process heat integration technique was designed and optimized to reduce the energy penalty of the system. The developed system enables an annual CO2 mitigation of 2.80 million tons and boosts the energy efficiency of the FCC units by 2.8%. The system developed by this study is more economically favorable than traditional coal-to-methanol production. The developed system provides technological routes for refineries to achieve large-scale CO2 mitigation, thus advancing the green transition of the petrochemical industry.

Quantitative determination of nickel speciation for the presence of free oxide in commercial fluid catalytic cracking catalysts

Motivated by the potential over-catalysis and hazardousness of free nickel oxide (NiO) in the equilibrated catalysts (Ecats) collected from fluid catalytic cracking (FCC) refineries, this study aims to establish a simple bulk method, namely chemical leaching method to rapidly quantify the NiO content within thirteen commercial Ecats collected from different units. The synchrotron-–based, X–ray absorption near–edge structure (XANES) was performed to assess the validity of this method, as well as to examine the coordination structure of Ni by the extended X–ray absorption fine structure (EXAFS) analysis. Additionally, thermodynamics calculation was attempted to validate the affiliation of Ni with other metal oxides. The optimum leaching condition was validated as 60 °C in 60 min using 1 M sulfuric acid. Accordingly, the NiO was determined to reach 70–439 ppm in all Ecats, which warrants a non–hazardousness of these samples. Additionally, for the Ecats with a remarkably higher Ni content, the XANES results are biased by the enrichment of NiO on the catalyst surface. The majority of Ni was found to affiliate with Al in the form of aluminate, with the remaining 11%–15% Ni passivated effectively by lanthanum (La). The oxygen–rich regeneration condition could be beneficial for promoting the affiliation of Ni by La.

Membranes and adsorbents in separation of C4 hydrocarbons: A review and the definition of the current upper bounds

• A critical review on membrane and adsorption technologies for separation of C4 hydrocarbons. • Current upper bounds of membrane selectivity and permeance are defined. • Comparative selectivity and uptake performance for reported adsorbents is presented. • C4 membrane permeance and selectivity values reach up to ~4 × 10 −6 mol/m 2 s Pa and 1000, respectively. • C4 adsorption uptake and selectivity values extend to ~13 mmol/g and 300, respectively. C4 hydrocarbons are valuable fractions of the oil and gas processing industry due to their market size and importance as raw materials in the manufacture of several products. C4s are derived from fluid catalytic cracking (FCC) and from natural gas fractionation, and are often produced as mixture of associated hydrocarbons that are typically recovered by cryogenic distillation. Yet, the latter is rather challenging, energy-consuming, and economically inefficient due to the similarity in vapor pressures of the constituents. To this end, technologies to separate these hydrocarbons using membranes and adsorption are being intensively explored as efficient, economical, and energy-saving alternatives. This review presents a critical summary of these technologies and the involved materials along with their comparative performance in C4 hydrocarbon separations. In addition, the current upper bounds of membrane selectivity (~1000) and permeance (~4 × 10 −6 mol/m 2 s Pa), and adsorbent selectivity (~300) and uptake (~13 mmol/g) are presented for the separation of various C4 pairs of industrial interest.

Practical Approaches towards NOx Emission Mitigation from Fluid Catalytic Cracking (FCC) Units

There appears to be consensus among the general public that curtailing harmful emissions resulting from industrial, petrochemical and transportation sectors is a common good. However, there is also a need for balancing operating expenditures for applying the required technical solutions and implementing advanced emission mitigation technologies to meet desired sustainability goals. The emission of NOx from Fluid Catalytic Cracking (FCC) units in refineries for petroleum processing is a major concern, especially for those units located in densely populated urban settings. In this work we strive to review options towards cost-efficient and pragmatic emissions mitigation using optimal amounts of precious metal while evaluating the potential benefits of typical promoter dopant packages. We demonstrate that at present catalyst development level the refinery is no longer forced to make a promoter selection based on preconceived notions regarding precious metal activity but can rather make decisions based on the best “total cost” financial impact to the operation without measurable loss of the CO/NOx emission selectivity.

Influence of solvent structure on the extraction of aromatics from FCC diesel and computational thermodynamics study

The separation of aromatics from fluid catalytic cracking (FCC) diesel is of great significance for environmental protection. The extraction ability of 1-methyl-2-pyrrolidinone (NMP), sulfolane (SUL), and 4-formylmorpholine (NFM) were studied by the liquid-liquid equilibrium (LLE) experimental, and the corresponding LLE data of NMP/SUL/NFM + 1-methylnaphthalene + dodecane systems were obtained. The calculated distribution coefficients and separation factors showed that the solubility of 1-methylnaphthalene was the highest in NMP and the selectivity of SUL to 1-methylnaphthalene was the strongest. The effects of solvent structures were investigated by a combination of experiments and quantum chemical calculations. The 1-methylnaphthalene is more soluble in solvents with planar molecular structure because the steric hindrance between the two molecules is smaller, and the group with more electronegative has higher selectivity for 1-methylnaphthalene. Moreover, the reduced density gradient (RDG) and atoms in molecules (AIM) analyzed found that the main extraction mechanism of the three solvents was van der Waals (VDW) and weak hydrogen bond, in which VDW was dominant. Finally, the binary interaction parameters of NRTL and UNIQUAC models were obtained, which make up for the blank in Aspen simulation for the separation of FCC diesel by organic solvents.

Online Optimization of Fluid Catalytic Cracking Process via a Hybrid Model Based on Simplified Structure-Oriented Lumping and Case-Based Reasoning

The mechanism models based on structure-oriented lumping (SOL) deliver a satisfactory prediction on the properties and yield distribution of the products from fluid catalytic cracking (FCC). Howeve...

Liquid-liquid equilibria and mechanism exploration for the extraction of sulfides from FCC naphtha via organic solvent as extractant

Separation of sulfides from fluid catalytic cracking (FCC) naphtha is of great significance for environmental protection. In this work, the organic solvents N-methyl-2-pyrrolidone (NMP), sulfolane (SUL), and their mixtures were selected to extract sulfides (3-methylthiophene) from model FCC naphtha (n-heptane). Correspondingly, the liquid-liquid phase equilibrium (LLE) data of the systems n-heptane +3-methylthiophene + SUL/NMP/(NMP + SUL) were experimentally obtained at 298.15 K and 101.3 kPa. The distribution coefficient and separation factor were calculated to assess the extraction performance of the solvents. The results showed that mixed solvent (NMP + SUL) could be used as a potential solvent to extract 3-methylthiophene due to its suitable selectivity and solubility. Meanwhile, the density functional theory (DFT) method was applied to explore the extraction mechanism of 3-methylthiophene from n-heptane by NMP or SUL. Electrostatic potential (ESP) analysis, interaction energies, and reduced density gradient (RDG) analysis showed that the main interactions between NMP/SUL and 3-methylthiophene were van der Waals and weak hydrogen bond forces. In addition, the LLE data were correlated by the NRTL and UNIQUAC thermodynamic models with the RMSD values were all <0.30%. Also, the binary interaction parameters were regressed which could be applied for the optimization and design of the separation process.

Properties and Composition of Products from Hydrotreating of Straight-Run Gas Oil and Its Mixtures with Light Cycle Oil Over Sulfidic Ni-Mo/Al2O3 Catalyst.

Straight-run gas oil (SRGO) and its mixtures with 5, 10, 15, and 20 wt % light cycle oil (LCO) from fluid catalytic cracking (FCC) were hydrotreated on a commercial NiMo/Al2O3 catalyst in a laboratory tubular reactor with the cocurrent flow of the raw material and hydrogen. The hydrotreating of the raw material was undertaken at a temperature of 350 °C, a pressure of 4 MPa, a weight hourly space velocity of ca 1.0 h–1, and a hydrogen-to-raw-material ratio of 240 m3·m–3. The LCO had a high density due to the high content of bicyclic aromatics and the high content of sulfur species, which are difficult to desulfurize. Therefore, increasing the content of the LCO in the raw material resulted in increasing the density and increasing the content of the sulfur and polycyclic aromatics in the hydrotreated products. Only the products prepared from the raw material with LCO content up to 10 wt % fulfilled the density requirement of EN 590. To improve the product density, the products prepared from the raw material containing 15 wt % LCO were blended with refined kerosene. The addition of the kerosene decreased the density of the mixtures prepared, but the cold filter plugging point (CFPP) of the mixtures was only lowered by about 1–2 °C. It was necessary to add a depressant in an amount of 600 mg·kg–1 to achieve a cold filter plugging point of −20 °C. Some refined products were blended with desulfurized heavy naphtha from the FCC. The addition of the heavy naphtha was mainly limited by its high density. Up to 10 wt % heavy naphtha could be added to the product obtained by hydrotreating the raw material containing 10 wt % LCO. More than 15 wt % heavy naphtha could be added to the mixture of the hydrotreated product and 20 wt % kerosene.

Effects of an effective adsorption region on removing catalyst particles from an FCC slurry under a DC electrostatic field

Electrostatic separation can be used to remove micron-sized catalyst particles from fluid catalytic cracking (FCC) slurry. In this study, simulations were performed with experimental parameters. The distributions of the electric field, slurry flow and particle motion were studied. According to the particle movement characteristics, an effective adsorption region was found in which the particles would be adsorbed on the surface of the fillers. The effect of the effective adsorption region on the electrostatic removal of catalyst particles from the FCC slurry was discussed. The size of the effective adsorption region was inversely proportional to the voltage and ionic carrier concentration. Under the same parameters, the size of the effective adsorption area and the motion of the particles were compared between the experiment and the simulation. The results showed that the numerical simulation results were in good agreement with the experimental results.

High efficiency separation of olefin from FCC naphtha: Influence of combined solvents and related extraction conditions

Separation of olefin from fluid catalytic cracking (FCC) naphtha is a high way to protect the research octane number (RON) from a loss during hydrodesulfurization. Solvent extraction is a promising way to separate olefin and extract sulfides simultaneously. In order to realize effective separation of olefin from FCC naphtha, this paper focused on the development of a kind of high efficient solvent and optimization of corresponding operation conditions for olefin separation. The results showed the combined solvents consisted of sulfolane (95 v%) and N-methyl-2-pyrrolidone (5 v%) exhibited high separation capability for olefin, and the best solvent to oil ratio was 3:1. Based on the combined solvent and optimal solvent to oil ratio, the best olefin enrichment coefficient could be up to 97.63 indicating lots of olefin enriched in raffinate. The desulfurization efficiency exceeded 90% after 3-stage extraction by the combined solvents, which was close to and even prior to some kinds of ionic liquids. Moreover, the combined solvents exhibited remarkable stability, and variation of desulfurization efficiency of the combined solvents was only around 1% after recycled 8 times. These studies gave a high efficient way to upgrade clean gasoline by separating olefin and enriching sulfides from FCC naphtha.

Effect of regeneration conditions on the emission of HCN in FCC regeneration process

Stringent environmental regulations have made HCN emission from fluid catalytic cracking (FCC) unit attracted more attention. HCN is always considered as a volatile intermediate, which is transformed into NOx after oxidation. However, the on-site monitoring data from a typical FCC unit in this work showed that HCN emissions were much higher than expected. The spent FCC catalysts were analyzed by different methods to identify HCN precursors, and found that pyridinic nitrogen (N-6), pyrrolic nitrogen (N-5), and quaternary nitrogen (N-Q) are the main precursors of HCN. In the regeneration process, most of pyridinic nitrogen was transformed into NH3 and HCN, while the rest were partially oxidized to N-5, and the degree of oxidization conversion is related to regeneration temperature and oxygen concentration. A series of experiments were conducted on a fixed-bed regenerator to evaluate the effects of different regeneration conditions on the nitrogen-containing gas emission. Experiment results demonstrated that low oxygen concentration is beneficial to the reduction of HCN emission during the partial combustion regeneration stage. Under complete combustion condition, with excess oxygen content, the contents of NO, HCN and NO2 are much higher than these under partial combustion conditions, indicating that the oxygen content affects the emission of nitrogen-containing gas significantly.

Regeneration study of ecat-R as adsorbent for denitrogenation and desulfurization of diesel fuels

The purpose of this paper is to present the third stage of regeneration for ecat: deactivated or equilibrium catalysts which are waste from fluidized catalytic cracking (FCC) units. This stage is going to compose a complete circular economy (CE) model and increase the life cycle of the catalyst. The third stage of regeneration, after the adsorption process for sulfur and nitrogen compounds from real diesel, was assessed using as solvents: acetone (propanone), ethanol, benzene and toluene. For sulfur and nitrogen compounds, ethanol achieved the best performance. The variations of physical and chemical properties of regenerated ecats in the cycles of adsorption and desorption were evaluated using x-ray diffraction, x-ray fluorescence, nitrogen adsorptiondesorpion, thermogravimetric and differential thermal analysis, scanning electron microscopy and Fourier-transform infrared spectroscopy. The recovery rate over four cycles is superior for sulfur compounds. After all cycles, ecat-R- -SA exhibited 5.09% reduction in the recovery for sulfur and 24.58% reduction in the recovery for nitrogen. The nitrogen adsorption-desorption analysis suggests the adsorption of compounds by ecat-R may be more correlated with the adsorption sites than with specific area. Overall, the results of this work are promising and allows for ecat to integrate a complete CE model.

Catalyzed pyrolysis of SRC poplar biomass. Alkaline carbonates and zeolites catalysts

Poplar biomass of nine different genotypes, from short rotation coppice, was pyrolyzed in a fixed bed reactor using several solid catalysts. Pine bark was used as reference for uncatalyzed pyrolysis. Pyrolysis tests were performed for temperatures in the range 425–500 °C, selected from the thermal degradation profiles obtained by thermogravimetry under N2 flow. All the analyzed poplar genotypes showed similar pyrolysis behavior, with the highest bio-oil yield (53% average value) being obtained for the highest tested temperature (500 °C). In analogous conditions, the pine bark resulted in higher bio-char yields than poplar biomass, due to its larger lignin content.Catalyzed pyrolysis carried out at 500 °C using 10% of catalyst (Wcat/Wbiomass) for H-ZSM5 and FCC (spent catalyst from Fluid Catalytic Cracking unit) zeolites, and Mg and Na carbonates, showed improved gasification with slightly lower liquid production. The FCC catalyst promoted the lowest depreciation of bio-oil yield with the highest decrease of acid functional groups. All the used catalysts were effective to lessen the acidic components of the produced bio-oils thus having a beneficial effect on the pyrolysis liquid products.

Adsorption of Cu2+, Zn2+, and Ni2+ ions onto the adsorbent prepared from fluid catalytic cracking spent catalyst fines and diatomite

An adsorbent prepared from fluid catalytic cracking (FCC) spent catalyst fines and diatomite, and its adsorption of Cu2+, Zn2+, and Ni2+ ions were investigated. The adsorbent was characterized by XRD, SEM, and N2 adsorption-desorption techniques. The results showed that the specific surface area and pore volume of adsorbent increased with the increase in FCC spent catalyst fines. The influence factors on the adsorption of the adsorbents were studied. The suitable adsorption conditions were: pH value of 5.0, ratio of solid to liquid of 1 : 600 (g:ml), adsorption time of 4 h, room temperature. The adsorption of metal ions varied with the type of metal cations. The adsorption isotherms suggested that the sequence of the adsorption efficiency was Cu2+ &amp;gt; Zn2+ &amp;gt; Ni2+. The amount of Cu2+, Zn2+, and Ni2+ metal ion adsorbed onto the adsorbent was 49.17 mg g–1, 46.83 mg g–1, and 35.72 mg g–1, respectively. The adsorption data of Cu2+, Zn2+, and Ni2+ ions fitted well with the Freundlich adsorption isotherm model.