Fluidized-bed Catalytic Cracking Research Articles

Catalytic cracking of a model bio-petroleum compound (sugar di-ketals) using beta zeolite as catalyst

Conversion of biomass (BM) to fuel is a promising solution to reduce the carbon footprint. By modifying BM by ketalization, a stable, neutral liquid we call bio-petroleum (BP) is obtained. In this study, a representative compound of BP, DX (1,2:3,5-di-O-isopropylidene-α-D-xylofuranose) was co-processed with n-hexane(nC6) into biofuel. In the search for a process to deoxygenate the DX and avoid over-cracking, to optimize gas and coke yields using a beta catalyst in a fluidized bed catalytic cracking (FCC) unit at a process temperature of 540 °C, we explored mixing 10–70 wt% DX in nC6, with catalyst/feed ratios from 3 to 6 and feed injection time of 30 versus 60 s. DX was fully converting under all conditions tested, while nC6 conversion decreased, reaching zero conversion when DX > 50 wt%. Coke yield varied from 3 to 9 wt%. The mixture containing a low amount of DX provided hydrocarbons without oxygenates. The mixture of 50% DX in nC6 only gave 2.7 wt% of oxygenates such as furans and ketones. Hence, the results confirmed the strong potential of beta catalysts to produce biofuel, superior to ZSM-5 and Y zeolites. Furthermore, the results of the variations of processing parameters added insights about the bio-petroleum conversion steps, contributing to further catalyst and process development.

Исследование каталитического крекинга продуктов деасфальтизации гудрона

Within the frames of research on expanding of the Fluid Catalytic Cracking Process (FCC) feedstock base, a product of vacuum residue de-asphalting using n-pentane has been obtained. The properties of deasphalted oil have been analyzed: fractionaland hydrocarbon content, density, Conradson coking capacity, sulfur, nitrogen, vanadium and nickel content. For comparison, the estimation of the industrial product of propane de-asphalting has been performed according to the specified parameters. Both products as potential components of the FCC feedstock have been processed in a fluidized bed catalytic cracking unit.Indicators of the degree of conversion and yields of gaseous and liquid transformation products have been established. It is proved that propane deasphalted oil by its characteristics is a promising feedstock for the fluid catalytic cracking process. The productof vacuum residue de-asphalting with n-pentane can also be used as a feedstock component of the FCC process, but it is advisable to use it in a mixture with traditional types of feedstock such as vacuum gas oil.

Synthesis and hydration of ye’elimite-containing cement (YCC) produced with spent fluid catalytic cracking catalyst

The consumption of petroleum products from fluidized bed catalytic cracking (FCC) units has increased worldwide. One of the primary materials used in this process is the zeolitic catalyst which loses its catalytic capacity over time, generating the spent FCC catalyst – SFCC. This work evaluated the feasibility of using SFCC as raw material for ye'elimite-containing cements (YCC) production. Specifically, six types of clinkers were synthesized in the laboratory, varying the ye’elimite content, with and without SFCC. Powder and in-situ X-ray diffraction (XRD), isothermal calorimetry, and thermogravimetric analysis (TGA) were conducted in anhydrous and hydrated samples. Clinkers with SFCC stabilized more C4AF than those without SFCC; so there was less Fe3+ available in these systems than in the reference systems to stable the pseudo cubic ye'emelite. As a result, the SFCC-containing cements (with more orthorhombic ye’elimite) had higher reaction rates within the first 12–20 h of hydration. In turn, the higher ye’elimite contents in the high- and medium-ye’elimite reference clinkers led to the further formation of hydrated phases at 28 days of hydration on these samples. The equivalent ye’elimite content in low-ye’elimite clinkers led to equivalent cumulative heat and phase assemblage from 48 h to 28 days. Overall, the use of SFCC allowed to incorporate of up to 20.81 wt% of the residue in raw material replacement, resulting in cements with increased early-age reactivity.

Investigation and Control of Fluidized Bed Catalytic Cracking Unit

The fluidized catalytic cracking (FCC) unit is one of the main units of the oil refinery, its objective is to upgrade heavy low-value petroleum streams into higher-value products, mainly gasoline and olefin. In this process the catalyst is circulated into the regenerator, the coke is burned, and the catalyst is regenerated. Many parameters are used to control FCC, the most important is temperature, which should be kept at (505C ) and the catalyst temperature (655 C). Other parameters are the level and flow rate of the catalyst. In this work, a control strategy was built and the transfer functions were detected, so, the characteristic equations were calculated as well as the open-loop transfer functions. Tuning, stability analysis and simulation response of the system were achieved by using Routh, direct substitution, RootLocus and bode methods

Sr-Nd-Hf isotopic analysis of reference materials and natural and anthropogenic particulate matter sources: Implications for accurately tracing North African dust in complex urban atmospheres.

We present novel chemical separation protocols for isotopic analysis of low mass aliquots (0.3mg and 25mg) of several reference materials and real-world samples of relevance to urban airborne particulate matter (PM) investigations. A high-yielding gravity flow column chromatography scheme was developed for facile and quantitative separation of Sr, Nd, and Hf prior to multi collector - inductively coupled plasma - mass spectrometry (MC-ICP-MS). Because we are interested in isolating and accurately quantitating individual anthropogenic and natural aerosol sources in complex industrial/metropolitan atmospheric environments, laboratory protocols were optimized using National Institute of Standards and Technology Standard Reference Material (SRM) 1648a (urban atmospheric PM), SRM 1633b (coal fly ash), and European Commission standards BCR-723 (vehicular road dust), and BCR-2 (basalt rock standard). Sr, Nd, and Hf procedural blanks from column chromatography were low (averaging only 37pg, 17pg, 11pg, respectively) and recoveries were high (averaging 95%, 82%, and 92%, respectively). A volume-adjustment protocol was established using isotope reference solutions SRM 987 (SrCO3), JNdi (Nd2O3), and in-house Hf standards to dilute the dried samples prior to MC-ICP-MS based on projected uncertainties for low sample masses. 87Sr/86Sr, 143Nd/144Nd, and 176Hf/177Hf isotopic ratios in SRM 1648a, BCR-723, and SRM 1633b are reported for the first time that can serve as provisional reference values. The novel method was used to characterize isotopic ratios and elemental abundances in two anthropogenic urban aerosol sources, namely motor vehicles and petroleum refining using airborne fine PM collected in a vehicular tunnel and fluidized-bed catalytic cracking catalysts, respectively. Two other important mineral-rich urban PM sources, namely soil (i.e., resuspended crustal material) and concrete/cement dust (i.e., construction activity) were also characterized. These are the first isotopic measurements in these environmental compartments and were compared with literature data for long-range transported North African dust, which is a prominent summertime PM source in urban regions in southeastern United States. We demonstrate the capability of coupled Sr-Nd-Hf isotopes to uniquely trace different mineral dust sources with overlapping elemental composition (Sahara-Sahel region, local soil, and concrete/cement) and accurately isolate various urban PM sources demonstrating the superiority of isotopic markers over elemental tracers.

Sources and fluxes of rare earth elements in wet deposition at a Chinese coastal city downstream of the Asian continental outflow

Atmospheric deposition is an important source of dissolved rare earth elements (REEs) to the oceans, but the flux estimating from various sources of REEs in atmospheric wet deposition (AWD) have received little attention to date. To quantify the contributions of the fluxes of REEs in AWD, 38 wet deposition samples were collected for a year in Qingdao, China, a coastal city on the transport path of the continental aerosols heading toward the Pacific Ocean as they are carried on the westerlies. According to the results from Post-Archean Australian Sedimentary rock (PAAS) normalization, REEs in wet deposition showed four types of patterns during observation. Types A (47% of a total of 38 AWD samples) and B (34%) were the main REE patterns, showing a convex-up pattern and Heavy REE enrichment, respectively. Both Types C and D were characterized by higher Light REE with significant La anomalies, while Type C tended to be relatively flat and Type D transitioned downward from Tb to Lu. Meanwhile, the optimum multiparameter method was used to quantify the contribution from each source. Consequently, loess-dust (46% ± 19%) and coal fly ash (38% ± 17%) were the main contributors in Type A, while loess-dust (45% ± 15%) and sea salt (44% ± 14%) account for high proportions in Type B. Fluidized-bed catalytic cracking contributes extra La in types C and D. Annual total REE flux was 55.3 μg m−2 y−1, of which loess-dust contributed 63%, coal fly ash 20%, sea salt 13%, and the catalyst of fluidized-bed catalytic cracking 5% of annual La deposition flux. Furthermore, since aerosols can be transported over long distances, human activities could significantly increase the input fluxes of REEs to the ocean's surface, especially for Middle REE and La.

Source apportionment of volatile organic compounds, CO, SO2 and trace metals in a complex urban atmosphere

A commixture of gasphase compounds including carbon monoxide (CO), sulphur dioxide (SO2), volatile organic compounds (VOCs) and trace metals were collected at a site located at the urban/industrial interface in Houston, Texas. Positive Matrix Factorization (PMF) analysis yielded nine factors: gas/crude oil (21.3±5.5%), isoprene emission (17.0±7.1%), Si-rich (14.6±1.3%), liquefied petroleum gas (LPG) (11.2±4.0%), traffic (10.6±0.4%), Fluidized-bed Catalytic Cracking (FCC)/high temperature operations (7.2±4.3%), oil refinery (6.8±0.9%), soil and road dust (6.2±0.6%), and petrochemical industries (5.0±5.0%). Daytime and nighttime PMF runs were carried out to see potential differences among and within emission sources. Notable findings include: (1) Nocturnal isoprene emission was identified from traffic exhaust and industrial sources. (2) LPG emissions were higher during the day most likely due to temperature dependent evaporative processes. (3) V/Ni and SO2/V ratios reveal greater contribution from crude oil in the merged natural gas/crude oil emission factor. Corrosion might be responsible for emitting metals (i.e., Cr, Cu, Mo, Ni) from oil refineries during nighttime. (4) In the soil and road dust factor, metals relevant to plant physiological processes are mostly retained by the plants while the lanthanoids and other metals (i.e. Y, Pb, Mn, Ga, Ba) are more prone to physical removal during the day. (5) FCC/high temperature operations are dominated by metals at night. (6) The traffic factor increases during the day possibly due to the higher number of vehicles. Bivariate polar plots suggest the Houston Ship Channel area as the primary emission source for LPG, natural gas/crude oil, FCC/high temperature operations, and petrochemical industries.

Composite Binder Containing Industrial By-Products (FCCCw and PSw) and Nano SiO2.

This article analyzes the integrated effect of industrial by-products (spent fluidized bed catalytic cracking catalyst waste (FCCCw) and paper sludge waste (PSw) generated in paper manufacturing) combined with nano-SiO2 (NS) on the properties of cement binder, when a certain part of the binder is replaced with the said by-products in the cement mix. Standard testing methods were used to analyze the physical and mechanical properties of cement-based materials. For structure analysis, we used X-ray diffraction (XRD), derivative thermogravimetry (DTG), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). It was found that the replacement of cement by a combined additive of FCCCw, PSw and NS is important not only for ecological reasons (abatement of CO2 emissions and recovery of waste through secondary raw materials), but also in order to enhance the properties of cement-based binders. Presumably, higher amounts of calcium silicate hydrate (CSH) and calcium alumina silicate hydrate (CASH) in the compound binder are the result of the low content of portlandite and alite in the test specimens. The specimens modified with all three additives had the highest density (~2100 kg/m3), ultrasonic pulse velocity (UPV) (~4160 m/s) and compressive strength (~105 MPa), which was ~40% higher than in the control specimens. The average pore diameter of the complex binder decreased by 21%, whereas the median pore diameter decreased by 47%.

Natural and Activated Allophane Catalytic Activity Based on the Microactivity Test in Astm Norm 3907/D3907M-2019

The optimal conditions of the catalytic activation of allophane were evaluated for possible use as a catalyst within a fluidized bed catalytic cracking unit (FCC). The physicochemical properties of natural allophane and activated allophane were studied by using an alkaline activating agent, followed by a hydrothermal treatment. For the characterization, analytical techniques were used: Fourier transform infrared spectroscopy, particle size, (BET) surface area, thermogravimetry (TGA), X-ray diffraction (XRD), chemisorption, X-ray fluorescence (XRF), atomic force microscopy (AFM), and chromatography. The catalytic evaluation was determined by the (MAT) micro activity test equipment constructed according to ASTM D-3907/D3907M-2019. In addition, the Navier–Stokes 3D equations (nonlinear partial derivatives) were studied, which allow studying molecular dynamics contributing substantively to chemical kinetics describing the process of decomposition of crude oil in thermal cracking, determining the maximum temperature at which it retains its properties through the action of heat.

Metallic elements emitted from industrial sources in Taiwan: Implications for source identification using airborne PM

Filterable stack total suspended particle (TSP) samples emitted from electric arc furnace (EAF) steel manufacturing plants, coal-fired power plants (CPP), cement mills (CM), and petroleum refineries (PR), were isokinetically collected using an in-stack PM device and analyzed for thirty-one targeted elements. The results showed that metallic elements constituted a majority (43–61%) of stack TSP mass in EAF steel plants and CM whereas contributed to a less fraction (11–27%) in CPP and PR. The coefficient of divergence (COD) values varied from 0.58 to 0.81, indicating that the elemental profiles between each industrial source were very distinct. Geological elements such as Al, Fe, Ca, Na, Mg, and K were the dominant elements in all industrial sources (50–96% of elemental mass). Besides, Zn was another dominant metal (22–40% of element mass) in addition to Fe in EAF steel plants and Ni (~3.6%) was the most predominant metal in oil-refinery. Tracers in different industrial sectors were also identified by source marker calculations. Moreover, the ratios of La/Ce (1.8) and La/Nd (6.0) in fluidized bed catalytic cracking (FCC) were 20–30 times higher than those of other industrial sectors. Utilizing both La/Ce and La/Nd ratios, the contribution of FCC PR to ambient primary TSP surrounding by the petroleum refinery was estimated to be 0.6%, which was comparable to the Taiwan Emission Data (0.7%). This highlighted that La/Ce and La/Nd ratios can be able to track the influence of petroleum refining sources on airborne particles in an industrial urban area in Taiwan.

A twin-fluid injector for FCC feed injection

In Fluidized Bed Catalytic Cracking (FCC) process, hydrocarbon feed undergoes vapour phase cracking in presence of hot regenerated catalyst to produce valuable products like LPG, Gasoline and Diesel. FCC feed injection system is most critical hardware component of FCC unit in order to get desired product yield by minimizing the undesirable dry gas and coke yield. Typically, twin-fluid nozzles (hydrocarbon and stream) are used to atomize the feed. In the present study, a twin-fluid injector, with an internal impactor to minimize the droplet size and velocity, is designed, developed and characterized. The performance of the feeding injector was evaluated using water and air as operating fluids and the droplet size and velocity were measured 150 mm downstream of the injector tip using a PDPA system for different water and air flow rates. The average droplet size (D32) showed an increase while the droplet velocity remained almost constant with the increase in the liquid flow rate for a given flow rate of air, consistent with the increase in droplet size with decreasing air-liquid ratio for twin–fluid atomizers. But, for a given liquid flow rate, the droplet SMD decreased and the droplet velocity increased with increasing airflow rate, which can be attributed to the increase in overall kinetic energy due to the increase in air flow rate. The flow rate of liquid was seen to be independent of air flow rate unlike conventional twin-fluid atomizers. The droplet size was found to be a function of ALR and the local volume flux of the droplets was found to be a function of the liquid flow rate.

Mixed stochastic-deterministic tube MPC for offset-free tracking in the presence of plant-model mismatch

This paper presents a stochastic-tube model predictive control (MPC) strategy that systematically handles plant-model mismatch, guarantees stability in the presence of changing operating conditions, and ensures offset-free tracking for all reachable operating conditions. The key notion of this work is to separate the system uncertainty into two distinct sources of additive bounded state error. The first source is a non-random uncertainty that represents mismatch between the linear model of the controller and the true plant (as well as other types of persistent disturbances). The second source represents random fluctuations due to either the intrinsic stochastic variability of the system, or exogenous disturbances. Recursive feasibility and stability of the stochastic-tube MPC strategy is guaranteed by defining the terminal invariant set to include the effect of changes in the steady-state operating conditions. Offset-free tracking is achieved with a disturbance estimator that can be tuned independently of the controller. To reduce the conservatism inherent to robust control performance, a new filter model for deterministic disturbances is proposed that predicts uncertainty in the future evolution of the disturbances based on a bound on how quickly the plant-model mismatch can vary. The stochastic-tube MPC strategy is demonstrated on two simulation case studies—a benchmark DC-DC converter and an industrially-motivated fluidized-bed catalytic cracking unit.

Mathematical Modeling of Catalytic Cracking Fluidized Bed Process for the Production of Hydrocarbons

The purpose of the catalytic cracking process fluid bed is conversion of heavy oil to light hydrocarbon at a lower cost and more reliable method. Some of the products include with the distillates, gasoline and light olefins. Efficient performance of catalytic cracking fluidized bed for the refinery economy is essential and important process in oil refineries. The efficiency of the FCC unit depends to a large number of parameters such as feed composition, residence time, temperature, the ratio of catalyst to feedstock oil, catalytic properties, the partial pressure of hydrocarbons and hydrodynamic riser.In this study fluidized bed catalytic cracking process modeling was performed and operating conditions as input to the program and the results obtained. The modeling of kinetic model was used four lumps, first order and changes in radius is ignored. The balance of energy, mass and momentum are written that yield can be calculated via the mass balance, velocity can be achieved through the momentum equation and temperature profiles during reactor can be obtained via energy balance. Products yield, profiles of temperature and velocity of the gas phase were obtained by using the proposed model. The results showed that feed efficiency is increased and products yields are reduced during reactor length. It was observed that during the process catalyst performance is decreased and also compare the results with experimental results indicate good agreement between the proposed model and industrial results that these results can be used to achieve high-precision products. The mean error is 3.3% for gasoline yield, 5.5% for coke yields and 2% for reactor temperature.

Recent research progress on bio‐oil conversion into bio‐fuels and raw chemicals: a review

AbstractRecent advances in lignocellulosic biomass valorization for producing fuels and commodities (olefins and BTX aromatics) are gathered in this paper, with a focus on the conversion of bio‐oil (produced by fast pyrolysis of biomass). The main valorization routes are: (i) conditioning of bio‐oil (by esterification, aldol condensation, ketonization, in situ cracking, and mild hydrodeoxygenation) for its use as a fuel or stable raw material for further catalytic processing; (ii) production of fuels by deep hydrodeoxygenation; (iii) ex situ catalytic cracking (in line) of the volatiles produced in biomass pyrolysis, aimed at the selective production of olefins and aromatics; (iv) cracking of raw bio‐oil in units designed with specific objectives concerning selectivity; and (v) processing in fluidized bed catalytic cracking (FCC) units. This review deals with the technological evolution of these routes, in terms of catalysts, reaction conditions, reactors, and product yields. A study has been carried out on the current state‐of‐knowledge of the technological capacity, advantages and disadvantages of the different routes, as well as on the prospects for the implementation of each route within the scope of the Sustainable Refinery. © 2018 Society of Chemical Industry

Utilization of sewage sludge-biomass gasification residue in cement-based materials: effect of pozzolant type

ABSTRACTIn this study, the viability to utilize the residue, obtained from a sewage sludge (SS) and biomass combustion/gasification plant (GR), in cement-based materials was analysed. Two pozzolanic materials were selected to make GR more recyclable: metakaolin (MK) and spent catalyst waste (Z), received from fluidized-bed catalytic cracking process. Functional and environmental properties of standard cement pastes and mortars as well as binary and ternary combinations of GR with MK and Z were assessed. Results showed that enhanced mechanical strength, reduced water absorption and heavy metals release were obtained for compositions when GR was combined with one of the pozzolanic material MK or Z. Microstructural analysis revealed that due to addition of pozzolan the surface of GR particles was covered by a layer of hydration products. In particular, the use of MK led to the formation of more porous layer whereas application of Z tends to the formation of a dense-layered structure on the surface of GR. N2 sorption results showed that contrary to MK the incorporation of Z into cement composition with GR reduced volume of small capillary pores, and therefore, resulted in lower water absorption and heavy metals release. The obtained results suggest that the application of Z appears to be advantageous pozzolan for the stabilization of SS-biomass gasification residue in cement-based materials.

Process simulation of a fluidized-bed catalytic cracking process for the conversion of algae oil to biokerosene

The ambitious targets of the aviation industry to reduce greenhouse gas emissions require the use of biofuels in this transport sector in the short and medium term. While five biogenic aviation turbine fuels have already been certified by the American Society for Testing and Materials (ASTM D7566), the search for suitable alternatives continues, seeking higher possible blending ratios or better fuel qualities. Fluidized-bed catalytic cracking (FCC) of algae oil, followed by hydrotreatment of intermediates, could be such a potential option. This conversion concept has several potential advantages, such as aromatic compounds in the biokerosene and the use of a non-food biogenic oil as feedstock. Material and energy balances are obtained from flowsheet simulation using ASPEN Plus®, with the aim to assess the efficiency of the process. The simulation model contains all relevant conversion and separation steps, and auxiliary components such as a steam reformer and a furnace. Simulation parameters for all unit operations were based on current literature to represent the state-of-the-art of the involved technologies. Additionally, the process was optimized by heat integration and waste heat utilization. The established simulation model is proposed to serve as a concept study and basis for the implementation of future experimental results and perceptions. With an energy efficiency of 95% and a biokerosene yield of 41%, the results emphasize the potential of this conversion process.

Indoor/Outdoor Relationships and Anthropogenic Elemental Signatures in Airborne PM2.5 at a High School: Impacts of Petroleum Refining Emissions on Lanthanoid Enrichment.

Outdoor emissions of primary fine particles and their contributions to indoor air quality deterioration were examined by collecting PM2.5 inside and outside a mechanically ventilated high school in the ultraindustrialized ship channel region of Houston, TX over a 2-month period. By characterizing 47 elements including lanthanoids (rare earth elements), using inductively coupled plasma-mass spectrometry, we captured indoor signatures of outdoor episodic emissions arising from nonroutine operations of petroleum refinery fluidized-bed catalytic cracking units. Average indoor-to-outdoor (I/O) abundance ratios for the majority of elements were close to unity providing evidence that indoor metal-bearing PM2.5 had predominantly outdoor origins. Only Co had an I/O abundance ratio >1 but its indoor sources could not be explicitly identified. La and 17 other elements (Na, K, V, Ni, Co, Cu, Zn, Ga, As, Se, Mo, Cd, Sn, Sb, Ba, W, and Pb), including air toxics were enriched relative to the local soil both in indoor and outdoor PM2.5 demonstrating their noncrustal origins. Several lines of evidence including receptor modeling, lanthanoid ratios, and La-Ce-Sm ternary diagrams pointed to petroleum refineries as being largely responsible for enhanced La and total lanthanoid concentrations in the majority of paired indoor and outdoor PM2.5.

Mathematical Modeling of Catalytic Cracking Fluidized Bed Process for the Production of Hydrocarbons

The purpose of the catalytic cracking process fluid bed is conversion of heavy oil to light hydrocarbon at a lower cost and more reliable method. Some of the products include with the distillates, gasoline and light olefins. Efficient performance of catalytic cracking fluidized bed for the refinery economy is essential and important process in oil refineries. The efficiency of the FCC unit depends to a large number of parameters such as feed composition, residence time, temperature, the ratio of catalyst to feedstock oil, catalytic properties, the partial pressure of hydrocarbons and hydrodynamic riser. In this study fluidized bed catalytic cracking process modeling was performed and operating conditions as input to the program and the results obtained. The modeling of kinetic model was used four lumps, first order and changes in radius is ignored. The balance of energy, mass and momentum are written that yield can be calculated via the mass balance, velocity can be achieved through the momentum equation and temperature profiles during reactor can be obtained via energy balance. Products yield, profiles of temperature and velocity of the gas phase were obtained by using the proposed model. The results showed that feed efficiency is increased and products yields are reduced during reactor length. It was observed that during the process catalyst performance is decreased and also compare the results with experimental results indicate good agreement between the proposed model and industrial results that these results can be used to achieve high-precision products. The mean error is 3.3% for gasoline yield, 5.5% for coke yields and 2% for reactor temperature.

Structural and morphological evolutions of spent FCC catalyst pellets toward NaA zeolite

Spherically shaped pellets, usually discarded after use in fluidized-bed catalytic cracking units (FCCs), were converted to zeolite A-surface-enriched pellets. The final pellets were obtained through a two-step treatment consisting of: (1) alkaline thermal activation followed by (2) a hydrothermal crystallization in selected reaction conditions. The alkaline thermal activation provided pellets mainly constituted by silico-aluminate compounds. When the pellets are heated at 800 °C in contact with sodium carbonate, a structural rearrangement occurs which includes nepheline, crystalline aluminosilicate, and an amorphous fraction expected to be silicon-enriched, preserving the pellet original geometry. Afterward, reaction mixtures were prepared by adding sodium hydroxide solution to the heat-treated product. Then, commercial sodium aluminate was added. During the hydrothermal synthesis at 85 ± 3 °C, zeolite A was formed from the calcined product and NaAlSiO4 turned out to be an intermediary crystalline compound. The LTA crystals were already observed for a reaction time of 0.5 h, but the highest conversion to pure zeolite A was reached after 6 h. Those final round solid pellets showed an external surface fully covered by well anchored zeolite A cubic crystals about 1–2 μm in size. Such materials may be very useful in ion exchange, molecular sieving, and adsorption processes. The crystalline ordering was followed by XRD, SEM, NMR, and water adsorption.

Removal and cementitious immobilization of heavy metals: chromium capture by zeolite-hybridized materials obtained from spent fluid cracking catalysts

An alternative for the reutilization of spent catalyst industrial residue for removal and immobilization of heavy metals is presented. A solid containing about 80% (w/w) of NaA zeolite was hydrothermally synthesized by reconversion of a spent catalyst discarded from a fluidized-bed catalytic cracking unit (FCC). The obtained material (ZFCC) was afterwards used for Cr(III) removal from aqueous solutions. Chromium cation was incorporated in the zeolitized structure by ionic exchange in liquid media, and the exchange level was determined by atomic absorption spectrometry. To analyze the viability of final disposal for the chromium sludge obtained using this methodology (Cr-ZFCC), cement mortars containing Cr-ZFCC in variable percentages were prepared and their mechanical and metal retention properties were evaluated. Mechanical strengths and drying shrinkage shown by mortars containing not more than Cr-ZFCC 5% (w/w) were similar to those corresponding to control mortars without zeolitic additions. Leaching tests indicated that mortars with Cr-ZFCC 5% (w/w) produce an effective immobilization of Cr(III) and should be considered as a viable alternative for safe chromium disposal.