Fluid Cracking Catalyst Research Articles

Traveling column for comparison of invasive and non-invasive fluidization voidage measurement techniques

This paper compares invasive and non-invasive voidage measurement techniques from five different Canadian laboratories for the determination of local voidage profiles in gas-fluidized beds of 104 μm Fluid Cracking Catalyst (FCC) and 332 μm silica sand in a column of 133 mm i.d. A novel modular system and auxiliary components were designed and constructed to facilitate transportation to, and deployment at, different research centers. Profiles of time-averaged voidage were determined by optical fiber probes, dynamic pressure measurements, electrical capacitance tomography, X-ray computed tomography and radioactive particle tracking by researchers from different research groups. These results are compared with average measurements from pressure gradients and overall bed expansion. Results were kept separate from each other in a double-blind method. There is general, but imperfect, agreement among the different methods for average voidage for both the FCC and silica sand. Invasive probes gave similar results and scatter to non-invasive techniques.

Study on Void Behavior in a Turbulent Fluidized Bed with Catalyst Powders

Turbulent fluidized beds have been recognized as very effective gas−solids contacting devices because of their outstanding performance in gas−solids contact, heat transfer, and mass transfer. To characterize the void behavior, which governs the hydrodynamics and the efficiency of operation of turbulent fluidized beds, an optical fiber probe with a separation distance of 5 mm between the two measuring tips has been used to measure the axial and radial profiles of the bubble/void parameters in a turbulent fluidized bed over a gas velocity range of 0.4−1.0 m/s. Experiments were carried out in a Plexiglas column with an inner diameter of 0.19 m and a height of 5.5 m. Fluid cracking catalyst (FCC) powders with a mean size of 78 μm were used as bed particles, and air was used as the fluidizing gas. Signals from the optical fiber probe were used to obtain the rise velocity and the chord length of voids at various spatial positions and superficial gas velocities. The results show that, in the turbulent fluidization regime, the void size and the void rise velocity have a relatively uniform distribution along the radial direction in the bed. Based on the assumption that bubble splitting is dominant over bubble coalescence at high superficial gas velocities, a modified bubble coalescence−splitting balance model was found to give reasonable agreement with the measured void size profiles.

Evaluation of Separation Efficiency of Fuel Oil Treatment Systems for Fluid Catalyst Cracking Particles Onboard Actual Vessels

Contamination of marine fuel oil with fluid catalyst cracking (FCC) particles, which are used as catalysts in refining crude oil, is a major source of engine problems. FCC particles have high hardness and can enter the space between the plunger and barrel of the fuel oil pump as well as that between the cylinder liner and piston ring, resulting in abrasive wear of these parts. Therefore, the particles are removed by a fuel oil treatment system onboard the vessel in an effort to prevent engine problems. However, FCC particles in marine fuel oil remain a major problem.Methods of testing the separator performance for a specific test oil were established in JIS F6601-1996 and in the European Committee for Standardization (CEN)’s Agreement CWA15375. Moreover, separator manufacturers report separation efficiencies of 80-90% for FCC particles using these test methods. However, the results do not reflect the separation efficiency of the fuel oil treatment system onboard an actual vessel. Therefore, we evaluated the separation efficiency of fuel oil treatment systems for FCC particles onboard actual vessels with an inductively coupled plasma metal analyzer and particle counter.

Increase Flexibility to Upgrade Residuum Using Recent Advances in RDS/VRDS-RFCC Process and Catalyst Technology

An overview of several refinery process options that convert high boiling point fractions of crude oil into more valuable distillates is presented. The combination of Residuum Desulfurization (RDS) with Residuum Fluid Catalyst Cracking (RFCC) produces high yields of transportation fuels and chemicals feedstock with minimal fuel oil by-product. This process scheme can present formidable technical challenges for the catalysts of each process to handle the increased levels of contaminants such as Microcarbon Residue (MCR), nickel and vanadium present in heavy oil. This paper presents the results of hydrotreating heavier Atmospheric Residuums (AR) in RDS pilot plants with Ni-Mo supported catalysts. RDS pilot plant life tests are conducted and middle of run products are collected and distilled for analysis and further RFCC testing. Process condition variation and new catalyst development has been applied to improve RDS capability to handle heavier, more contaminated residuum. The RDS products are tested for RFCC reactivity using Advanced Cracking Evaluation (ACE) tests. The development of improved RFCC catalyst is applied to boost cracking catalyst tolerance of residuum metal contaminants. Judicious selection of newly developed RDS and RFCC catalysts enable production of higher yields of gasoline from heavier AR's. The coordinated application of new RDS and RFCC catalysts enables the conversion of dirtier residuum feedstock to produce greater yields of distillates.

Numerical Simulation of Hydrodynamics and Coke Combustions in FCC Regenerator

A gas-particle, two-phase flow-reaction model of fluid catalyst cracking (FCC) regenerators was established in this article according to the characteristics of FCC catalyst particle clusters and coke combustion reaction. Numerical simulations of the gas-particle flow behavior, heat transfer, and coke combustion process in the commercial regenerator were carried out to obtain detailed distributions of velocity, temperature, and species concentration. The fluidized processing can be well predicted, although there are still some differences between computational results and commercial data for the assumption of a mean diameter of an FCC catalyst. Obtained distributions of temperature and component concentration was also agreeable with commercial data.

Study of transition velocities from bubbling to turbulent fluidization by statistic and wavelet multi-resolution analysis on absolute pressure fluctuations

Experiments were conducted in three circulating fluidized beds of 70 mm - i . d . × 2.2 in high, 108 mm - i . d . × 7 m high and 108 mm - i . d . × 5.75 m high (with an expanded top section of 1.5 m high) at ambient condition. The spent fluid cracking catalyst (FCC), glass beads and sand particles were taken as bed materials. The transition velocities U c and U k were analyzed by means of traditional statistic analysis and multi-resolution analysis (MRA) of wavelet analysis on the absolute pressure fluctuation (APF) signals acquired at different axial positions in the beds. According to the standard deviation of APF, the effects of axial positions and static bed heights on U c and U k were systematically investigated. An appropriate measuring interval of relative axial position was recommended to identify U k and two correlations calculated by regression of data in literatures and this work were proposed to predict U c and U k for absolute pressure measurement. By means of MRA of wavelet analysis, a redefined variable, homogeneous index HI, deduced from the energy of SF and LF subsignals, was successfully applied to determine the U c and U k and demarcated the dynamic behaviors of Geldart group A (spent FCC) and group B (sand particles and glass beads) particles in the circulating fluidized beds.

Options for Nitriles Removal from C4–C5 Cuts: 1. Via Adsorption

Light cuts from fluid catalyst cracking (FCC) units are commonly used as feedstocks for etherification units in oil refineries. These feedstocks contain nitriles and diolefins that poison the etherification catalyst. PDVSA Intevep has developed several methods for removing these nitriles. An adsorption-based option is discussed in this paper; two other options reported recently were based on catalytic conversions (Ramirez-Corredores et al. 2002, 2003). The oligomerization tendencies of the diolefins dictated the use of a rather inert adsorbent. Some of the critical features of this adsorbent and the adsorption process are discussed. The adsorbent design was based on a geometrical premise and on active non-acid sites to achieve a highly selective adsorbent with a high adsorption capacity for nitriles. Chemical shift was selected for the desorption stage of the removal process to preserve the active lifetime of the adsorbent in the treatment of reactive feedstocks. This was demonstrated to be both effective...

Sulphur reduction additive prepared from caustic-modified kaolin

AbstractThe performance of a fluidized cracking catalyst additive prepared from caustic-modified kaolin microspheres for gasoline S reduction was investigated using N2 adsorption, infrared acid-site characterization, X-ray diffraction and small-scale fluid bed reactor tests. The additive exhibited improved coke selectivity and yield distribution, and the S content of cracked gasoline was reduced significantly. The results indicated that a reactive mesoporous structure was formed in the modified kaolin.

Degradação de poliolefinas utilizando catalisadores zeolíticos

Neste trabalho foi estudada a degradação de alguns dos principais constituintes dos rejeitos plásticos (polietileno de alta densidade (HDPE), polietileno de baixa densidade (LDPE) e polipropileno (PP)), empregando-se um catalisador exausto de unidades de craqueamento de fluidos (FCC) e um catalisador zeolítico (ADZ3) sintetizado em laboratório. Utilizando técnicas de termogravimetria (TG-DTG) e cromatografia gasosa (CG), foi possível avaliar os produtos gerados no craqueamento destas poliolefinas. Na degradação catalítica de poliolefinas com catalisadores zeolíticos, verificou-se a obtenção preferencial de gasolina, GLP e diesel, produtos importantes na matriz energética brasileira. O catalisador de FCC exausto foi mais seletivo para a produção de gasolina e GLP, enquanto que a produção de diesel foi mais favorecida com o catalisador ADZ3.

The use of solid state nuclear magnetic resonance (NMR) to study the effect of composition on the properties of equilibrium fluid cracking catalysts (FCCs)

Solid state nuclear magnetic resonance (NMR) spectroscopy together with microactivity testing have been used to characterize the changes that occur in a fluid cracking catalyst (FCC) during gas oil cracking in a refinery fluid catalytic cracking unit (FCCU). The 29 Si NMR spectra of fresh FCCs show the well known five peaks pattern attributed to the presence of HY-type crystals. However, after aging, equilibrium FCCs are generated in which the 29 Si NMR spectrum of the zeolitic component is reduced to one main dominant resonance near −107 ppm representative of T[4Si,0Al] sites. Thus, irrespective of composition, extensive dealumination of the cracking component in FCCs occurs during recirculation in a FCCU yielding 29 Si NMR spectra in which the presence of framework Al is no longer visible. Similar conclusions have been obtained from the corresponding 27 Al MAS NMR spectra showing that the dealuminated faujasite structure in equilibrium FCCs contains only extra-framework Al(IV), Al(V), and Al(VI) species. In the presence of tin, vanadium effects on the coordination of Al and Si in equilibrium FCCs, could not be observed by 29 Si or 27 Al NMR spectroscopy.

Determination of Pore Size Distribution, Surface Area, and Acidity in Fluid Cracking Catalysts (FCCs) from Nonlocal Density Functional Theoretical Models of Adsorption and from Microcalorimetry Methods

A method based on nonlocal density functional theory (NLDFT) has been used to interpret the data for the adsorption of nitrogen at 77 K within the pores of three different commercial fluid cracking catalysts (FCCs) before and after their use in a refinery catalytic cracking unit. The integral equation of adsorption was inverted by a regularization method to yield the micropore and mesopore size distribution over a wide range of pore widths. The results obtained are compared with the results of more traditional data treatments and indicate that the NLDFT model can provide a realistic pore volume and surface area estimation in commercial FCCs irrespective of their chemical composition and pore width distribution. Both BET and Langmuir methods grossly underestimate the FCCs surface area, and only the NLDFT method yields reliable surface area and pore volume measurements over the entire micro−meso porosity range present in the cataysts under study. Adsorption microcalorimetry results using ammonia as a probe ...

Reactivity of Sorbents with Hot Hydrogen Sulfide in the Presence of Moisture and Hydrogen

Hot-gas desulfurization for the integrated gasification combined cycle (IGCC) process has been investigated by many researchers to remove effectively hydrogen sulfide (H2S) with various metal oxide sorbents at elevated temperatures. Various metal oxide sorbents are formulated with metal oxides such as Fe, Co, Zn, and Ti. In this article, reactivity of AHI-1 sorbent, obtained from the Research Triangle Institute (RTI), was investigated. Initial reactivity of AHI-1 sorbent with hydrogen sulfide was studied in the presence of various amounts of moisture and hydrogen at various reaction temperatures. AHI-1 sorbent consists of 20-w% Fe2O3, 10-w% ZnO, and 70-w% spent fluid cracking catalyst (FCC). The objectives of this research were to study initial reaction kinetics for the AHI-1 sorbent–hydrogen sulfide heterogeneous reaction system, to investigate effects of concentrations of hydrogen sulfide, hydrogen, and moisture on dynamic absorption of H2S into the sorbent, to understand effects of space time of reaction gas mixtures on initial reaction kinetics of the sorbent–hydrogen sulfide system, and to evaluate effects of temperature and sorbent amounts on dynamic absorption of H2S into the sorbent. Experimental data on initial reaction kinetics of hydrogen sulfide with the metal oxide sorbent were obtained with a 0.83-cm3 differential reactor. The sorbent in the form of 130-μm particles was reacted with 1000 to 4000 ppm hydrogen sulfide at 450 to 600°C. The range of space time of reaction gas mixtures is 0.03 to 0.09 s. The range of reaction duration is 4 to 14,400 s.

The Location and Effects of Coke Deposition in Fluid Cracking Catalysts during Gas Oil Cracking at Microactivity Test Conditions

Nitrogen porosimetry, atomic force microscopy (AFM), and microcalorimetry together with microactivity testing have been used to characterize some of the effects of coke deposition on a fluid cracking catalyst (FCC) during gas oil cracking. Contact mode AFM images have revealed that coke forms raised surface features consisting of molecules and chain of molecules; evidence of pore blockage by coke deposits could not be obtained in the images generated. Nitrogen porosimetry results indicate that during gas oil cracking, coke is deposited inside (68%) as well as outside (32%) the catalyst porous structure. About 60% of the total coke in the porous structure is uniformly deposited within its microspace, decreasing the micropore volume and causing a shift of its pore size distribution profile toward smaller pore width values. The rest of the coke (40%) is located in mesopores without closing any part of the internal porosity to nitrogen sorption and therefore to catalysis. There is a moderate decrease in acid site strength and acid site density in the coked FCC. Both BET and Langmuir methods grossly underestimate the FCC surface area and only the density functional theory method yields reliable surface area and pore volume measurements over the entire micro–meso porosity range.

The Use of Nuclear Magnetic Resonance, Microcalorimetry, and Atomic Force Microscopy to Study the Aging and Regeneration of Fluid Cracking Catalysts

The accelerated steam-aging procedure (with 100% steam at 760°C for 5 h) used in this study reduces the surface area (SA) of a fresh fluid cracking catalyst (FCC) to a value close to that measured in the corresponding equilibrium sample. In addition, 29Si nuclear magnetic resonance (NMR) spectra of steam-aged and equilibrium FCC samples are practically indistinguishable. However, the steam-aged and equilibrium FCCs have different pore structures, initial heats of ammonia and pyridine chemisorption as well as different distributions of Al(IV), Al(V), and Al(VI) species. The 29Si NMR spectrum of the fresh or steam-aged FCC can be considered a superposition of the spectra of its components (the HY zeolite, kaolin, and aluminosilicate matrix). After aging, the 29Si NMR spectrum of zeolitic component is reduced to one main dominant resonance near the −107 ppm representative of T(4Si, 0Al) sites. Thus extensive dealumination of the cracking component in FCCs occurs during recirculation in a fluid cracking catalyst unit (FCCU). Similar conclusions have been obtained from 27Al magic angle spinning (MAS) NMR spectra. Microcalorimetry experiments with ammonia and pyridine have shown that after aging either under microactivity test (MAT) conditions or in a FCCU, the fresh FCC undergoes severe losses in acid site density while retaining most of the strength of its strongest Lewis acid sites. These sites, and the retention of an open micro- and mesoporosity, are believed to be responsible for the aged FCCs' cracking activity. Atomic force microscopy images have shown that the equilibrium FCC contains on its surface debris attributed to nickel and vanadium oxides and that most of this debris disappears from the surface of the regenerated catalyst. 27Al and 29Si MAS NMR spectroscopy results have revealed that the demetallation (DEMET) process, in addition to removing most of the metal contaminants, leaves a completely dealuminated zeolitic component. These results indicate that cracking activity in these FCCs does not depend on the presence of framework Al in the faujasite crystals present. The increase in acidity and microporosity is consistent with the observed enhanced cracking activity, under MAT conditions, of the regenerated FCC.

Gallioaluminosilicate Molecular Sieves with the Faujasite Structure

Gallioaluminosilicate hydrogels with composition 0.1 Ga2O3:0.9 Al2O3:10 SiO2:4.0 Na2O:150 H2O were prepared using sodium aluminate, colloidal silica, and a soluble galliosilicate with composition Ga2O3:15 SiO2:10 Na2O:400 H2O as a source of gallia. The hydrothermal transformation of these gels at 95°C yields crystals with the faujasite structure when the crystallization reaction is performed in the absence of stirring and with the gmelinite structure (with minor amount of Pt) when crystallization is completed with stirring of the hydrogel. The crystallization time for Na(Ga,Al)Y can be decreased to 15 h from 48 h by raising the crystallization temperature to 110°C from 95°C. The calcined Na(Ga,Al)Y crystals have surface area in the 600 to 660 m2/g range and, unless La-stabilized, suffer partial lattice degradation when, following an exchange with an NH4NO3 solution, the NH4(Ga,Al)Y crystals are calcined at 500°C in air. This finding is clearly indicated by 27Al, 71Ga, and 29Si MAS NMR spectroscopic results. The 29Si NMR spectra of samples exchanged and calcined in the absence of La are poorly resolved and their quantitative analysis indicates substantial loss of Al and Ga from the faujasite framework. Consistent with this interpretation, 27Al MAS NMR spectra reveal large amounts of octahedrally coordinated species in H(Ga,Al)Y. Moreover, the 71Ga spectra show no evidence of tetrahedrally coordinated framework Ga. In contrast, the multinuclear NMR data of the H(Ga,Al,La)Y crystals indicate only minor Al and Ga losses from the framework, thus revealing the stabilizing influence of La. Thermodesorption of pyridine and microcalorimetry results with NH3 have indicated that the La-stabilized H(Ga,Al,La)Y crystals have a more moderate acidity than the reference HY sample. Model fluid cracking catalyst (FCC)-containing H(Ga,Al,La)Y crystals are more active when cracking gas oil under microactivity testing conditions than similarly prepared FCC-containing HY-type zeolites and a reference equilibrium catalyst containing a rare-earth-stabilized HY, indicating that these crystals should be considered as acidic components in commercial FCC preparations.

EFFECTS OF SECONDARY AIR INJECTION ON GAS-SOLID FLOW BEHAVIOR IN CIRCULATING FLUIDIZED BEDS

Effects of secondary air injection on the hydrodynamics such as solid holdup and gas-solid flow behavior were investigated in a circulating fluidized bed. The gas velocity in the riser, the ratio of secondary air velocity to that of primary air, and the solid circulating rate were chosen as operating variables. Fluid cracking catalyst(FCC) with a density of 1840 kg/m3 and a mean diameter of 74 um was employed as the solid phase. The secondary air was fed to the riser radially or tangentially at the wall of the column. Pressure drop fluctuations in the riser were measured and analyzed by adopting the stochastic method to characterize the effects of secondary air injection on the gas-solid flow behavior in the bed. It has been found that the injection of secondary air into the riser can increase the solid holdup in the riser considerably, and that the tangential injection of secondary air is more effective for the increasing the solid holdup than the radial injection. However, the gas-solid flow behavior has been found to become less persistent with the injection of secondary air; the resultant flow behavior is more complex when the air is injected tangentially than radially. The solid holdups in the primary as well as secondary zones of the riser have been well correlated in terms of not only operating variables but also fractal dimension of the pressure fluctuations.

Hydration of Cement Slurry in The Presence of Spent Cracking Catalyst

The physicochemical properties of spent fluidized bed cracking catalyst and its influence on hydration process of cement slurry were studied. The samples were cement slurries prepared with water/solid=0.5 and additions of used catalyst amounted to 0, 5, 10, 15, 20 and 25%with resp. to the solid. After definite time they were subjected to thermogravimetric analysis (TG, DTG, DTA) and, in order to determine the progress of reaction with water, the heat of hydration was measured by means of isotherm calorimetry. The studies disclosed that the spent cracking catalyst is not merely an inactive filler in cement slurries, but it modifies the course of the hydration process. The spent catalyst is a pozzolana additive and its presence leads to a decrease of calcium hydroxide contents in the system. The spent catalyst affect on the heat of cement hydration. Small amounts additive accelerate the process of binding.

Fluid Cracking Catalysts

Fluid Cracking Catalysts

Fluidization Characteristics of Bagasse in a Gas-Fluidized Bed

Bagasse, a by-product of sugar cane processing and an important potential energy resource, could be used as a fuel in fluidized bed combustors for energy generation. Bagasse can not be fluidized alone because of its nature, which has many fibrous, low density and high moisture content. These properties make it an unsuitable material to fluidize under normal circumstances. Thus, for its thermochemical processing (such as combustion, gasification, pyrolysis, etc.) in fluidized bed it has to be mixed with some other inert fluidizing solid, so that it is effectively suspended in the emulsion phase of the admixed materials. Hence, with a correct choice of the inert fluidizing solid, the successful fluidization of bagasse is possible. This paper reports the fluidization characteristics of bagasse using spent fluid cracking catalyst (FCC) and pumice powder as candidate admix materials. Several problems and characteristics which were exhibited during fluidization are discussed. The limiting bagasse contents in the mixture in order to distinguish between fluidizable and non-fluidizable mixture is presented. This study explore the conditions giving stable and satisfactory fluidization of bagasse, which may be selected as an operating condition to promote and improve its thermochemical processing in fluidized bed.

Fluidization Characteristics of Bagasse in a Gas-Fluidized Bed

Bagasse, a by-product of sugar cane processing and an important potential energy resource, could be used as a fuel in fluidized bed combustors for energy generation. Bagasse can not be fluidized alone because of its nature, which has many fibrous, low density and high moisture content. These properties make it an unsuitable material to fluidize under normal circumstances. Thus, for its thermochemical processing (such as combustion, gasification, pyrolysis, etc.) in fluidized bed it has to be mixed with some other inert fluidizing solid, so that it is effectively suspended in the emulsion phase of the admixed materials. Hence, with a correct choice of the inert fluidizing solid, the successful fluidization of bagasse is possible. This paper reports the fluidization characteristics of bagasse using spent fluid cracking catalyst (FCC) and pumice powder as candidate admix materials. Several problems and characteristics which were exhibited during fluidization are discussed. The limiting bagasse contents in the mixture in order to distinguish between fluidizable and non-fluidizable mixture is presented. This study explore the conditions giving stable and satisfactory fluidization of bagasse, which may be selected as an operating condition to promote and improve its thermochemical processing in fluidized bed.