Catalytic Cracking Activity Research Articles

Insights into Si/Al ratios for enhanced performance of β-zeolites in thermocatalytic cracking of crude oil to light olefins

The escalating demand for key petrochemicals, particularly ethylene and propylene, underscores the critical need for proficient catalysts in crude oil conversion processes. Attaining high propylene selectivity necessitates catalysts with superior adsorption capacity, thermal stability, moderate surface acidity, and pores large enough to facilitate the diffusion of larger crude oil molecules. In the present study, three different BEA Zeolites (β-zeolite) catalysts were successfully synthesized by hydrothermal method and used for catalytic cracking of Arabian Light crude oil to produce valuable petrochemical products, such as propylene, ethylene, and naphtha. The catalysts were characterized using 27Al and 29Si NMR, NH3-TPD, BET, XRD, TGA, FTIR, XRF, and FE-SEM. The thermocatalytic cracking of Arabian Light crude oil was evaluated in a fixed-bed microactivity test (MAT) unit between 550 and 600 °C. The as-prepared β-zeolite with a Si/Al ratio of 50 exhibited better catalytic activity in the catalytic cracking of Arabian Light crude oil compared to counterparts with Si/Al ratios of 35 and 65, This superiority can be attributed to its optimal combination of surface acid site distribution, textural properties, surface morphology, and high adsorption capacity. The highest feed conversion (83.4 %) and selectivity to propylene (16.11 %) were attained using β-zeolite with a Si/Al ratio of 50 at 600 °C. Importantly, our findings suggest that these catalysts hold significant potential, rivalling primary MFI catalysts like ZSM-5 commonly employed in similar reactions. This underscores their promise as catalysts of choice in the realm of catalytic cracking processes, paving the way for advancements in petrochemical production.

Organosilane-assisted synthesis of EU-1 nanozeolite aggregates with improved activity in catalytic cracking of n-hexane

One-dimensional microporous zeolite, EU-1, exhibits more favorable selectivity of propylene in cracking of petroleum components. However, it faced the problem of low catalytic activity for the poor utilization of active sites. In this work, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPOAC) was used to functionalize protozeolitic units and inhibit the excessive growth of crystals by the long hydrophobic alkyl chain. The introduction of TPOAC decreased the crystal sizes into nanoscale, enhanced the mesoporous volume of EU-1 zeolite, and exposed more external acid sites. Moreover, TPOAC could interact with Al species, and in this case, fewer Al atoms were incorporated into the zeolite framework, reducing the acid strength and amount. Intelligent gravitation analyzer test indicated that the zeolite prepared with the presence of 0.30 g TPOAC exhibited the largest accessible volumes in n-hexane adsorption, and the highest accessibility of acid sites, which synergistically promoted cracking of n-hexane for the production of light olefins.

Catalytic dehydrogenation cracking characteristics of vacuum residue over solid basic catalyst

The basic calcium aluminate with appropriate catalytic cracking activity, excellent anti-coking performance, and hydrothermal stability is of great potential for the utilization of heavy oil. However, there is a lack of systematic research on the catalytic dehydrogenation cracking characteristics of vacuum residue (VR) over solid basic catalyst. Thus, by combining the TG and Py-GC/MS methods, the dehydrogenation cracking behavior of S-VR was investigated. The results indicated that S-VR cracking on calcium aluminate leads to less coking and higher olefin content in liquid products compared with FCC catalyst and quartz sand. Then, the activation energy Ea is computed from the catalytic dehydrogenation cracking of S-VR on calcium aluminate. The results show that the Ea values from Friedman and OFW methods range from 68 to 143 kJ∙mol−1 and 114 to 192 kJ∙mol−1, respectively. After that, the molecular-level carbon number distributions of the products obtained from cracking S-VR on different reaction conditions are investigated, and the optimal reaction temperature and the heating rate are 650 °C and 1000 °C/s, respectively. Finally, the free radical regulation theory was constructed to explain the catalytic dehydrogenation cracking mechanism of basic calcium aluminate catalyst.

Recycling waste polyethylene into fuels over Fe/USY catalyst: Evaluation on the catalytic activities of varied iron states

Iron-modified zeolite catalyst has a good application prospect on recycling the waste plastics into value-added fuels via catalytic pyrolysis. Distinguishing the catalytic activities of varied iron states on catalyst is crucial to catalyst designation and plastic-to-fuel process. In this work, we prepared three Fe/USY catalysts, termed Fe(O-550)/USY, Fe(R-300)/USY and Fe(R-450)/USY, that contain different iron states – Fe2O3, Fe3O4 + Fe (dominantly) and Fe respectively, and investigated their catalytic activities in polyethylene pyrolysis for fuel oils. The results show that loading of the iron species on USY zeolite decreases the catalyst acidity. H2 reduction treatment in catalyst preparation has no significant influence on the total acidity but slightly changes the concentration of Brønsted and Lewis acid sites. The oil yield after catalysis with different catalysts follows the order: Fe(O-550)/USY (72.5 %) > Fe(R-300)/USY (69.9 %) > Fe(R-450)/USY (66.7 %) > USY (56.5 %). The oil includes a mixture of C6-C34 compounds especially abundant in C6-C10. It is mainly in gasoline and diesel range and consists of alkanes as majority. Generally, loading of the iron species on USY zeolite increases the oil yield and produces lighter oil and more aromatics and alkenes, while the Fe(R-450)/USY shows higher catalytic cracking activity than Fe(O-550)/USY, Fe(R-300)/USY and USY catalysts. Among the varied iron states, the metallic iron is more active than the other iron oxides to promote the catalytic cracking of PE to produce fuel oil, especially the light oil and aromatic fractions.

Preparation of hierarchical EU-1 zeolite via NH4F etching and the catalytic activity in cracking of n-hexane

One-dimensional microporous zeolite, EU-1, has tighter restriction for bulky intermediates, exhibiting more favorable selectivity of propylene than ZSM-5 in catalytic cracking. However, the diffusion limitation accelerates coke generation, passivates acid sites and deactivates the zeolite. In this study, a strategy was proposed to etch amorphous species between EU-1 nanocrystals using NH4F solution to improve the diffusion property. It was found that the etching process occurred on the crystal surface and mesopores were introduced. Catalytic performance evaluation in n-hexane cracking demonstrated that the maximum propylene selectivity over parent EU-1 was 33.6 wt% (vs. 5.7 wt% for ZSM-5). The n-hexane conversion was increased by 24 wt% over EU-1 etched in 20 wt% NH4F solution. Moreover, the introduction of mesopores provides accommodation space for coke. This study developed hierarchical EU-1 zeolite with favorable diffusion ability and reported a feasible strategy to improve the catalytic performance of EU-1 for propylene production.

Catalytic cracking of heavy atmospheric gas oil to light olefins over ZSM-5 zeolite: Effect of crystal size in the absence/presence of steam

The catalytic cracking of heavy atmospheric gas oil (AGO) has been investigated to study the effect of ZSM-5 zeolite crystal size on the selectivity to light olefin in the absence and presence of steam. Dodecane (used as model compound) and heavy AGO feed streams were utilized to study the influence of changing pore shape selectivity when comparing cracking performance by nano and micro ZSM-5 zeolites. The zeolites were characterized using BET, XRD NMR, NH3-TPD and Py-FTIR. In the presence of steam, the short pores length nano ZSM-5 crystals showed enhanced catalytic cracking activity and selectivity to light olefins. The nano ZSM-5 catalyst promoted higher selectivity to light olefins through β-scission while reducing the extent of hydrogenation reactions towards the formation of liquefied petroleum gas components (LPG). In contrast, the long pores length of micro ZSM-5 tended to favor the production of more naphtha, kerosene and LPG through hydrogen transfer routes, resulting in lower selectivity to light olefins. The resulting propylene/ethylene (P/E) ratios were altered by the type of feed used, cracking reaction temperature, influence of steam and catalyst crystal size. Specifically, higher P/E ratio was achieved over nano ZSM-5 zeolite, especially with the cracking of heavy AGO feed in the presence of steam, due to an increase of monomolecular reactions through β-scission cracking mechanism.

Mild modification of lignin pyrolysis vapors by metal oxide catalysts: A comparative study with molecular sieve catalysts

ABSTRACT Compared with strongly acidic molecular sieve catalysts, metal oxide catalysts are less prone to deactivation by coking due to their mild acid-base properties. Several metal oxides (Al2O3, MgO, CaO, CuO, Fe2O3, NiO, ZnO, ZrO2, TiO2 and CeO2) were selected for mild catalytic pyrolysis of lignin and compared with molecular sieve catalysts (MCM-41, HZSM-5, ZSM-5). Among the metal oxide catalysts studied, CuO, Fe2O3 and TiO2 inhibited the formation of acids/alcohols (1–2%) and promoted the production of hydrocarbons (15.31%, 20.17% and 28.83%, respectively). Especially when TiO2 catalyst was added, the proportion of hydrocarbons reached the highest (28.83%), but it inhibited the production of phenols (3.3%). The presence of CuO promoted the production of phenols (9.70%), showing a good deoxidation performance. Compared with the oxide catalysts, the addition of molecular sieve catalysts only resulted in 2 ~ 3% phenols. Compared with strongly acidic molecular sieve catalysts, metal oxide catalysts showed certain catalytic activity in deoxidation and cracking, and showed some advantages in the formation of phenols.

Carbon catalyst from palm kernel shell (PKS) for methane cracking: Effect of preparation

The effect of preparation on the performance of carbon catalyst derived from palm kernel shell (PKS) in methane cracking was evaluated. The PKS-carbon catalysts were prepared via pyrolysis at different temperatures (550, 650, 750 °C) and for different pyrolysis times (30, 60, 100 min) and their catalytic performance in methane cracking was analysed in a fixed bed reactor. The BET surface area of the PKS-carbon catalyst increased from 40.7 to 43.0 m2/g as the pyrolysis temperature increased from 550 to 650 °C, but decreased to 24.1 m2/g at 750 °C. During methane cracking, the PKS-carbon catalyst prepared at 650 °C demonstrated 30 % initial CH4 conversion and gave the highest initial H2 yield of up to 88 %. This indicates that pyrolysis temperature influences the carbon catalyst’s surface area, and a higher surface area promotes better initial catalytic activity in methane cracking. In addition, the PKS-carbon catalyst prepared for longer pyrolysis time (100 min) contained more desirable surface oxygen-containing functional groups (–OH, C=O, –COOH) than the ones prepared for 30 and 60 min. Therefore, the PKS-carbon catalyst pyrolyzed for 100 min exhibited 35 % initial CH4 conversion and the highest initial H2 yield of 95 %. This suggests that a longer pyrolysis time produces more desirable surface oxygen-containing functional groups, which enhance reactant activation in methane cracking. In conclusion, the preparation of PKS-carbon catalyst influences the surface area and surface oxygen- containing functional groups, which affect the catalyst’s performance in methane cracking.

Production of Biodiesel from Jatropha Curcas by using Heterogenous Dopped Zinc Oxide

Heterogenous copper based nano catalyst was synthesized by Co-precipitation method. The effect of nano catalyst particle size from 0.5 to 52 nm was investigated. The Cupper dopped zinc oxide the nano particle size was used from 0.5 to 52 nm, and Transesterification method was used to produce the biodiesel. The optimum yield of bio-biodiesel was obtained 92% from Jatropha Curcas seed oil. SEM shows the surface morphology, topography, composition, crystallographic and structural shape of synthesized Cu-ZnO nano catalyst. XRD and EDX results depicted good morphology of prepared catalyst. XRD and EDX also displays the pattern of a model Cu-ZnO. FTIR results showed the major functional groups identified were alkanes , aromatics and carboxylic acid . Among these functional groups, alkanes were qualitatively noted to be the main constituents which indicate the good catalytic cracking activity of the catalyst.The UV, absorbance peak indicated the presence of ZnO nanoparticles, which is in accordance of UV absorbance result shown by previous studies. The effect of temperature on biodiesel yield showed from higher yield with 45 o C from 64.33 to 80 ml of ethanol concentration at 45 o C. On further rise in temperature resulted 92% product yield. Furthermore, effect of methanol on bio- diesel yield showed that, as the methanol ratio subsequently increased from 1: 05 to 1: 12increased the product yield. Besides this, the heterogeneous nano catalyst showed good catalytic activity in transforming Jatropha seed oil up to 92% of biodiesel yield.

Crude oil conversion to chemicals over green synthesized ZSM-5 zeolite

The study reports the conversion of crude oil to basic chemicals over a template-free green synthesis of ZSM-5(40) zeolite using halloysite (HAL) and bolus alpha (BA) as silica and alumina precursors. The Z(40)HAL and Z(40)BA exhibited hierarchical pores with high surface area of 248 m2/g and 257 m2/g, respectively. The addition of soft template during the synthesis of Z(40)BA forms a Z(40)BAT zeolite with lower surface area. The synthesized zeolites were impregnated with 2wt%Mn and tested for the steam catalytic cracking of crude oil to light olefins and aromatics catalysts at 675 °C in a fixed-bed reactor. Maximum light olefins (C2=-C4=) yield (47 wt%) and total aromatics (14.7 wt%) were attained over 2Mn/Z(40)HAL catalyst. The conversion of crude oil (68.4%) is attributed to hierarchical pores and the presence of large weak and strong acid sites in the 2Mn/Z(40)HAL zeolite. Moreover, due to the high reaction temperature, some effects of thermal cracking such as protolytic cracking reactions with high ethylene yield (22%) were introduced. The addition of 1% phosphorus and 1%Mn to Z(40)HAL resulted in lower catalytic cracking activity. Similarly, the 2Mn/Z(40)BAT performed slightly lower than the template-free 2Mn/Z(40)BA additive. The experimental results demonstrate the technical feasibility of template-free green synthesis of ZSM-5 zeolite in the conversion of crude oil to basic chemicals.

Synthesis of Hierarchical ZSM‐5 Submicron Spheres for Catalytic Cracking

AbstractA kind of hierarchical ZSM‐5 submicron sphere composed of zeolite nanocrystals was one‐pot synthesized with polydiene dimethyl ammonium chloride as template. X‐ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images show that the hierarchical ZSM‐5 submicron spheres have good crystallinity. N2 adsorption‐desorption isotherm and transmission electron microscopy (TEM) images indicate that the hierarchical ZSM‐5 submicron spheres have both micropores and mesopores. The results show that the hierarchical ZSM‐5 submicron spheres are formed by stacking nanocrystals, exhibits high crystallinity, microporous, mesoporous structures and higher catalytic activity in the catalytic cracking of 1, 3, 5‐triisopropylbenzene.

Increased Light Olefin Production by Sequential Dehydrogenation and Cracking Reactions

In this study, a sequential reaction using selected metal oxides, followed by ZSM-5-based catalysts, was employed to demonstrate a promising route for enhancing light olefin production in the catalytic cracking of naphtha. The rationale for the reaction is based on the induction of alkenes into hydrocarbon feeds prior to cracking. The optimum olefin induction was achieved by carefully optimizing the dehydrogenation active sites Mo/Al2O3 catalyst. The formed alkenes have a lower activation energy for C-H/C-C bond breaking compared to alkanes. This could accelerate the formation of carbenium ions, thus promoting the conversion of n-octane to produce light olefins. Detailed product distribution and DFT calculation indicated a remarkable increase in ethylene and propylene production in the final product through a modified reaction pathway. Compared with the common metal-promoted zeolite catalysts, the new route could avoid the block of zeolite channels and corresponding decreased catalytic cracking activity. The feasibility of the proposed route was confirmed with different ratios of dehydrogenation catalyst to the reactant. The highest yields of ethylene and propylene reached 13.22% and 33.12% with ratios of Mo/Al2O3 and ZSM-5-based catalyst to n-octane both 10:1 at 600 °C. Stability tests showed that the catalytic activity of the double-bed system was stable over 10 cycles.

Catalytic process toward green recycling of polyvinyl chloride: A study on thermodynamic, kinetic and pyrolysis characteristics

Municipal solid wastes (MSW) include a considerable amount of polyvinyl chloride (PVC). How to quickly and harmlessly dispose of the PVC-containing MSW and convert them into a valuable resource is an urgent issue at present. The application of catalysts has yet been proven to be effective in mitigating organic pollutant production. In the present study, a thermogravimetric analyzer (TGA) and pyrolysis-gas chromatography-mass spectrometer (Py-GC/MS) were utilized to investigate the thermodynamic properties, kinetic parameters and pyrolysis characteristics of PVC with different zeolites including HZSM-5 with the Si/Al of 80 and 280, ferrierite, HY and MCM-41 zeolite. It turned out that the introduction of different catalysts with different pore structures and acid site concentrations made different catalytic effects on the cracking mechanism of PVC. Among the five zeolites, MCM-41 decreased temperature at the 50 % conversion to 296 °C, increased weight loss mate at a maximum of 25 %/min and generated fewer PAHs (whose changing amplitude decreased by 94 % in ex-situ catalytic mode in comparison to non-catalytic mode), indicative of its higher catalytic activity in PVC polymer degradation. Under the consideration of maximizing catalytic cracking activity and minimizing secondary pollutants production, non-catalytic dechlorination at approximately 300 °C followed by catalytic degradation in ex-situ mode over mesoporous MCM-41 at higher temperatures was the best recommendation.

Efficient processing of crude oil using direct cracking at high temperatures over modified FCC catalysts

The direct cracking of Bach Ho crude oil, having API gravity of 41°, over equilibrium FCC catalyst (Ecat), modified FCC catalyst (HT-FCC) and ZSM-5 additive were studied at 620–650 °C using short-contact-time micro activity testing unit. HT-FCC catalyst was prepared by the treatment of Ecat with oxalic acid in reflux condition. This treatment largely improves the porosity while keeping the particle size of Ecat. Hence, it leads to an important enhancement in catalytic cracking activity. Due to high activity of HT-FCC catalyst, the direct cracking of crude oil can be performed at a low catalyst-to-oil ratio (C/O) which helps to decrease the yield of dry gas. At 620–650 °C, C/O of 1.5–2.5, 18–23 wt.% of light olefins, 3–6 wt.% of dry gas together with 51–59 wt.% of gasoline yields can be obtained with HT-FCC catalyst. ZSM-5 addition favors the conversion of gasoline to light olefins. Compared to the results reported in literature, the use of HT-FCC and ZSM-5 catalysts at 650 °C, low C/O of 1.5 shows promising performances: (i) much lower dry gas yield (8%), (ii) high light-olefins yield (32%) while maintaining high gasoline yield (43%), and (iii) high BTXs content in gasoline (45%).

Synthesis of amorphous silica-alumina with enhanced specific surface area and acidity by pH-swing method and its catalytic activity in cumene cracking

High-performance amorphous silica-alumina (ASA) is an important acid material in the chemical industry. In this work, we successfully synthesized mesoporous ASA with enhanced specific surface area, Lewis acidity and total acidity by pH-swing method. The morphology and structure of ASA were systematically investigated. With the increase of SiO2 content from 20.1% to 67.0%, the morphology of ASA varied considerably from fibrous to granular, and the specific surface area decreased from 436 to 306 m2 g−1. Meanwhile, the gradual increase of surface silanol groups facilitated the formation of pseudo-bridged silanol groups and promoted the formation of Brønsted acid sites (BAS). Furthermore, the concentration of BAS was found to increase with increasing tetra- and penta-coordinated aluminum and decrease with increasing octa-coordinated aluminum. In addition, the acidity-activity relationship was also explored by applying the as-synthesized ASA samples directly to the cracking reaction of cumene. The results showed that the activity of ASA was proportional to the concentration of BAS. The pH-swing method can controllably synthesize ASA materials with different structures and acidity for petrochemical industry.

Catalytic cracking of polystyrene pyrolysis oil: Effect of Nb2O5 and NiO/Nb2O5 catalyst on the liquid product composition

The catalytic cracking of polystyrene pyrolysis oil was investigated over a Nb2O5 and a NiO/Nb2O5 catalyst in a fixed bed reactor. First, the pyrolysis of two different polystyrene feedstock (polystyrene foam and polystyrene pellet) was carried out in a semi-batch reactor, and the resulting polystyrene pellets pyrolysis oil was selected for catalytic cracking reaction because of its high liquid yield (85%). Catalytic cracking experiments were then performed at different temperatures (350–500 °C) using Nb2O5 or NiO/Nb2O5 catalyst. Gas chromatography–mass spectrometry analysis of liquid product obtained from the catalytic cracking process showed that the dimers in the pyrolysis oil were converted to monomers during the catalytic cracking process. The catalytic cracking results also showed that the NiO/Nb2O5 catalyst (having slightly higher acidic sites) had slightly higher activity for monomer conversion than the Nb2O5 catalyst (having less acidic sites). X-ray diffraction, transmission electron microscopy, pyridine Fourier transform infrared spectroscopy, NH3 Temperature Programmed Desorption and X-ray photoelectron spectroscopy were used to characterize the catalyst. The highest catalytic cracking activity was observed at 400 °C with the Nb2O5 catalyst with 4% toluene, 6% ethylbenzene, approximately 50% styrene, 13% α-methyl styrene, and only 6% of dimers in the liquid oil. The increase in temperature positively affected the yield of gases during catalytic cracking process.

Zr-doped SAPO-34 with enhanced Lewis acidity

Zr-doped SAPO-34 has enhanced Lewis acidity, leading to high catalytic activity for LDPE cracking.

An environment-friendly and acid-degradable polymer templated synthesis of single-crystal hierarchical zeolites

A green and novel strategy to construct single-crystal hierarchical zeolites has been developed by using a degradable polymer as a multiple-functional template. The obtained MFI zeolite shows excellent catalytic activity in bulky molecules cracking.

Noble metal (Pd, Pt and Rh) incorporated LaFeO3 perovskite oxides for catalytic oxidative cracking of n-propane

Noble metals (Pd, Pt and Rh) incorporated LaFeO3 (LaFe) perovskite oxide nanostructures were synthesized by adapting hydrothermal synthesis method. The synthesized materials were used as catalysts for production of olefins via oxidative cracking of n-propane. The bare LaFe sample exhibited n-propane conversion of 18% with 42% olefins selectivity at reaction temperature of 600 °C. Substantial increase in n-propane conversion and olefins selectivity was perceived after incorporation of Pd, Pt and Rh in LaFe framework. The LaFe sample incorporated with Rh exhibited superior oxidative cracking performance (85% conversion of n-propane and 79% olefins selectivity) at optimized reaction conditions. A thorough characterization of synthesized catalysts was performed using various characterization techniques to obtain a correlation between the structural properties of Pd, Pt and Rh incorporated LaFe perovskite nanostructures and their catalytic activity in olefin production. The characterization results indicated that Rh and Pt species were expelled from the bulk LaFe framework and dispersed over the surface, while Pd species were strongly interacted with LaFe and occluded inside the LaFe framework. It appears that presence of expelled Rh and Pt species on the LaFe surface are responsible for better redox properties of LaFeRh and LaFePt samples. The highest oxidative catalytic cracking activity of LaFeRh sample is due to presence of high surface area, easily reducible and great number of adsorbed oxygen moieties. Catalyst durability test results indicated that Rh incorporated LaFe sample possessed stable oxidative cracking activity for 72 h without considerable loss in performance

Effects of Pressured Steaming on the Migration of La3+ Ions and the Performance of As-Prepared LaY Zeolite

As a novel method, LaY zeolites were prepared by liquid rare earth ion exchange and further subjected to steaming under different pressures. The obtained LaY zeolites were investigated by detailed physic-chemical characterizations and catalytic cracking performance. It has been indicated that La3+ ions migrated into sodalite cages much more easily due to the steaming calcination with increased pressure at 500 °C. The pressured steaming improved the hydrothermal stability and the acidic stability of the LaY zeolite, resulting in a much higher catalytic cracking activity. After hydrothermal aging with 100% steaming at 800 °C for 17 h, the obtained LaY zeolite exhibits a much higher conversion and yield of gasoline and a lower coke yield than those of conventional LaY.