Commercial Cracking Catalysts Research Articles

Catalytic Cracking of n-Hexadecane Using Carbon Nanostructures/Nano-Zeolite-Y Composite Catalyst

Zeolite-based catalysts are usually utilized in the form of a composite with binders, such as alumina, silica, clay, and others. However, these binders are usually known to block the accessibility of the active sites in zeolites, leading to a decreased effective surface area and agglomeration of zeolite particles. The aim of this work is to utilize carbon nanostructures (CNS) as a binding material for nano-zeolite-Y particles. The unique properties of CNS, such as its high surface area, thermal stability, and flexibility of its fibrous structure, makes it a promising material to hold and bind the nano-zeolite particles, yet with a contemporaneous accessibility of the reactants to the porous zeolite structure. In the current study, a nano-zeolite-Y/CNS composite catalyst was fabricated through a ball milling approach. The catalyst possesses a high surface area of 834 m2/g, which is significantly higher than the conventional commercial cracking catalysts. Using CNS as a binding material provided homogeneous distribution of the zeolite nanoparticles with high accessibility to the active sites and good mechanical stability. In addition, CNS was found to be an effective binding material for nano-zeolite particles, solving their major drawback of agglomeration. The nano-zeolite-Y/CNS composite showed 80% conversion for hexadecane catalytic cracking into valuable olefins and hydrogen gas, which was 14% higher compared to that of pure nano-zeolite-Y particles.

Sulfur-reduction additives based on ordered hexagonal mesoporous silica in the catalytic cracking of vacuum gas oil

Materials of the composition of La/hexagonal mesoporous silica/γ–Al2O3 with different contents of components in the carrier have been synthesized and tested as sulfur-reduction additives to the commercial zeolite-containing cracking catalyst. It has been shown that the sulfur content in liquid products decreases by 5–32% when vacuum gas oil is cracked at a temperature of 500°C in the presence of additives in the amount of 10 wt % relative to the weight of the catalyst.

Catalytic cracking additives based on mesoporous MCM-41 for sulfur removal

Materials based on mesoporous MCM-41/γ-Al2O3 silicon oxide with the supported compounds of La, W, and Ni and with W, Co, Mo, Zn, Ni, and La supported on γ-Al2O3 were synthesized and studied as additives to FCC catalysts. The samples were characterized by BET, TEM, and NH3-TPD methods, IR spectroscopy, and XRD analysis. The catalytic tests of the above additives in mixtures with a commercial cracking catalyst were performed in a MAT laboratory system. It was established that the addition of 10wt% La/MCM-41/γ-Al2O3 to the catalyst made it possible to decrease the sulfur content of the liquid products of the cracking of vacuum gas oil to 40%.

Catalytic Cracking of Petroleum Feedstock in the Presence of Additives Derived from Cross–Linked Mesoporous Oxides for Reduction of the Sulfur Content in Liquid Products

Sulfurreducing La/MCM–41/γ–Al2O3 additives to a commercial zeolitecontaining cracking catalyst derived from MCM–41/γ–Al2O3 support with different ratios of the MCM–41 and γ–Al2O3 components were evaluated. Vacuum gas oil cracking at 500°C in the presence of these additives (10 wt. % additive in the catalyst) reduces sulfur in the liquid products by 20–31%.

The effects of magnesium of Zn–Mg–Al additives on catalytic cracking of VGO and in situ reduction of sulfur in gasoline

The scope of the present study is to describe the cracking behavior of hydrocarbons and the reduction of sulfur in gasoline in fluid catalytic cracking (FCC) process using Zn–Mg–Al additives with varying the Mg/Al molar ratios. Experiments have been carried out on a micro-activity-test (MAT) reactor using high-sulfur vacuum gas oil (VGO) feed and zinc impregnated Mg–Al spinels as additive and the commercial cracking catalyst. It was found that Zn–Mg–Al additives exhibited enhanced Lewis acidity compared with the corresponding Zn-free Mg–Al spinels. The MAT results indicated that the addition of additives reduced the yields of liquid petroleum gas and coke at low Mg contents but increased the coke yield at high Mg contents. Overall, the additives improved the yields of gasoline and diesel. It has also been shown that the rich Lewis acidity had a positive effect on the conversion of aromatic sulfur species of gasoline and the maximum reduction of gasoline sulfur was achieved with Zn/Mg4.0Al2O3 due to the synergistic effect of basicity and Lewis acidity.

Deactivating Species Deposited on Pt–Pd Catalysts in the Hydrocracking of Light-Cycle Oil

The nature and composition of the coke deposited on Pt–Pd catalysts supported on acid carriers during the hydroprocessing (hydrocracking and hydrotreating) of light-cycle oil (LCO) has been studied. Five types of supports have been used: a commercial cracking catalyst, alumina, Hβ zeolite, and two HY zeolites (with different acidities). The hydrocracking runs have been performed at 350 °C and 50 bar for up to 24 h. The characterization of the deactivating species on the catalyst used has been performed using temperature-programmed oxidation (TPO) coupled with mass spectrometry (MS) and Fourier transformed infrared (FTIR) spectroscopy, ultraviolet–visible (UV–vis) spectroscopy, and comprehensive two-dimensional gas chromatography/mass spectrometry (GC × GC/MS) analysis of the soluble coke extracted from the deactivated catalyst. The complex composition of the coke has been simplified in three families, each related to a different composition and location. The composition of the coke (and the amount of each...

Toluene Decomposition in the Presence of Hydrogen on Tungsten-Based Catalysts

Removal of NH3, tars, and H2S from biomass gasification gas represents a significant step in the commercial use of biomass gasification as a source of hydrogen, syngas, and electricity. This paper reports the results of an investigation into the use of W-based catalysts [tungsten carbide (WC), tungstated zirconia (WZ), and platinum supported on tungstated zirconia (PtWZ)] for catalytic tar removal. In this study, toluene was used as a model compound for tars. In the case of WZ, the effect of calcination temperature on the activity of toluene decomposition was also investigated. The toluene decomposition reaction was conducted at 1 atm, in the temperature range of 300−800 °C, and in the presence of 10% H2. CH4 and benzene were the only detectable products of toluene decomposition on all the catalysts. Incorporation of 5 wt % Pt with WZ was found to give the most effective catalyst considering initial rates of product formation. WC, WZ, and PtWZ each showed an initial partial deactivation for both CH4 and benzene formation due to coke deposition on active sites. Pt incorporation had a significant effect on the steady-state activity of WZ for toluene decomposition at temperatures below 600 °C; however, at temperatures above 700 °C, the effect was nullified. All W-based catalysts showed comparable performance to that of a commercial cracking catalyst (ultra-stable Y zeolite) above 700 °C.

Chemical catalysed recycling of polypropylene over a spent FCC catalyst and various commercial cracking catalysts using TGA

Thermogravimetric analysis (TGA) has been used as a tool to characterise the activity, regenerability and deactivation behaviour of spent FCC commercial catalyst (FCC-s1) in the degradation of polypropylene. The FCC-s1 catalysts and amorphous silica–alumina (SAHA) significantly reduced the activation energy as compared with thermal process, and zeolites (ZSM-5 and HUSY) further reduced the activation energy. However, silicalite catalysts gave very minimal effect on PP degradation at a temperature similar to that of thermal cracking. Analysis of the TGA results allowed a relationship between catalyst activity and coke content to be derived. The activity of FCC-s1 catalysts was found to fall exponentially with coke content, and it could be recover most its initial value. The results represent an interesting alternative to have significant impact on the economics of a catalytic polymer degradation process employing post-use FCC commercial catalysts of zero market value.

A study on sulfur reduction in FCC gasoline using Zn–Mg–Al spinels

It has been previously demonstrated that zinc aluminates are useful additive materials for gasoline sulfur reduction. To enquire about the nature of the catalyst active site in Zn aluminates, in the present work, [Zn ( x) 2+Mg (1− x) 2+]Al 2O 4, ternary spinels with 0 ≤ x ≤ 1 were synthesized to obtain samples with different Lewis acidity. The Zn–Mg–Al spinels were tested as FCC sulfur reduction additives, using the elimination of sulfur from thiophene at 793 K as model test. The thiophene conversion with the Zn–Al spinel was higher than with ternary Zn–Mg–Al spinels or the commercial cracking catalyst. It was found that although to a small extent, the Zn-free Mg–Al spinel converted thiophene. The IR study on the adsorption of CO 2 over Zn–Mg–Al spinels with different amounts of Zn and over ZnO suggested that: (i) no strong Lewis sites are located on Zn and (ii) the Lewis acidity of the ternary spinels is due to aluminum sites and increases with the Zn content. So, it appears that the Lewis acid sites located on aluminum are responsible for the adsorption of thiophene and that one of the benefits of Zn incorporation is the increase of this acidity, which would lead to increased adsorption and reactivity.

Catalytic degradation of plastic waste to liquid fuel over commercial cracking catalysts: Effect of polymer to catalyst ratio/acidity content

The catalytic degradation of polyethylene over two commercial cracking catalysts, containing 20% and 40% ultrastable Y zeolite, respectively, was studied in a semi-batch reactor. More specifically, the effect of the polymer to catalyst ratio – expressed as the acidity content of the polymer/catalyst system – was studied on the formation of liquid hydrocarbons. After a sharp increase at small values, the liquid yield seemed to have a negative correlation to the acidity content, showing a maximum at acidity values around 7% of pure US-Y. Regarding the boiling point distribution of the liquid fraction in systems with higher content of active catalyst, a shift was generally observed towards lighter products. Comparing liquid samples during the same experiment, later samples contained heavier components with the exception of the system with the smallest US-Y content of this study.

Conversion of naphthenes to a high value steamcracker feedstock using H-ZSM-5 based catalysts in the second step of the ARINO ®-process

Future regulations for the limitation of sulfur and aromatics in fuels driven by the European Auto Oil Program (AOP II) stimulate the need for an alternative utilization of the resulting surplus of pyrolysis gasoline (pygas). The conversion of heavy pyrolysis gasoline into valuable steam cracker feedstock with a maximum yield of C 2–C 4 n-alkanes is achieved via the ARINO ® two-step process, jointly developed by Linde, VEBA Oil and Süd-Chemie. The first step involves a hydrogenation of aromatics to naphthenes followed by the subsequent ring opening and cracking in the second step. Süd-Chemie developed a new commercial cracking catalyst for the second step of the ARINO ® process with the aim to maximize the yield of C 2–C 4 n-alkanes at low formation of methane and aromatics. The ring opening and cracking reaction of naphthenes was studied in a bench scale tubular reactor over extruded H-ZSM-5 based zeolite catalysts. In a series of screening tests using a commercial, hydrogenated and desulphurized heavy pyrolysis gasoline, the influence of the preparation parameters such as zeolite acidity, palladium content as well as the type of binder were investigated. Furthermore, the influence of the process conditions space velocity and temperature was studied. High yields of C 2–C 4 n-alkanes at low formation of undesired methane and aromatics were achieved over an alumina bound zeolite with medium Brønsted acidity loaded with palladium. The reduction of the space velocity resulted in an increase in the C 2–C 4 n-alkane yield and lower formation of aromatics, but a simultaneous increase in the methane make. Raising the temperature from 280 to 370 °C significantly increased the catalyst activity.

Thermogravimetric study of polymer catalytic degradation over microporous materials

The apparent activation energy of the overall process of polymer catalytic cracking over zeolites, commercial cracking catalysts, clays and pillared clays was estimated using thermogravimetric analysis. The activation energy of polymer cracking over ultrastable Y zeolite showed the lowest value due to the strongest acidity of this zeolite. Commercial cracking catalysts showed considerably higher activation energy than their parent ultrastable Y zeolite as they contained only 20% and 40% of the active zeolite. Over clays and pillared clays, polymer degradation showed even higher apparent activation energy values due to their weak acidity.

Polymer degradation to fuels over microporous catalysts as a novel tertiary plastic recycling method

The catalytic degradation of polyethylene over various microporous materials—zeolites, zeolite-based commercial cracking catalysts as well as clays and their pillared analogues—was studied in a semi-batch reactor. Over all catalysts the liquid products formed had a boiling point distribution in the range of motor engine fuels, which increases considerably the viability of the method as a commercial recycling process. From the zeolites, ZSM-5 resulted mostly in gaseous products and almost no coking due to its shape selectivity properties. Commercial cracking catalysts fully degraded the polymer resulting in higher liquid yield and lower coke content than their parent ultrastable Y zeolite. This confirmed the suitability of such catalysts for a polymer recycling process and its commercialisation potential, as it confirmed the potential of plastic waste being co-fed into a refinery cracking unit. Clays, saponite and Zenith-N, a montmorillonite, and their pillared analogues were less active than zeolites, but could fully degrade the polymer. They showed enhanced liquid formation, due to their mild acidity, and lower coke formation. Regenerated pillared clays offered practically the same performance as fresh samples, but their original clays' performance deteriorated after removal of the formed coke. Although performance of the regenerated saponite was satisfactory, with the regenerated Zenith the structural damage was so extensive that plastic was only partly degraded.

Aluminosilicate nanoparticles for catalytic hydrocarbon cracking.

Aluminosilicate nanoparticles containing 9.0-20 nm mesopores were prepared through the use of protozeolitic nanoclusters as the inorganic precursor and starch as a porogen. The calcined, porogen-free composition containing 2 mol % aluminum exhibited the porosity, hydrothermal stability, and acidity needed for the cracking of very large hydrocarbons. In fact, the hydrothermal stability of the nanoparticles to pure steam at 800 degrees C, along with the cumene cracking activity, surpassed the analogous performance properties of ultrastable Y zeolite, the main catalyst component of commercial cracking catalysts. The remarkable hydrothermal stability and catalytic reactivity of the new nanoparticles are attributable to a unique combination of two factors, the presence of protozeolitic nanoclusters in the pore walls and the unprecedented pore wall thickness (7-15 nm). In addition, the excellent catalytic longevity of the nanoparticles is most likely facilitated by the small domain size of the nanoparticles that greatly improves access to the acid sites on the pore walls and minimizes the diffusion length of coke precursors out of the pores.

Predict Yields from a Kinetic Model of Catalytic Cracking Process at Any Temperature

It has been observed that yields of gasoline and other petroleum fraction in a catalytic cracking process depends significantly upon the reaction temperature besides on other operating conditions. In this work, first the model was developed with the help of literature data with out considering the temperature effect. The important optimum parameters like relative rate constant (K 1), rate of coke deactivation or decay constants (Kd ), order of reaction (m) etc. over suitable catalysts of cracking process were obtained using suitable numerical analysis techniques. On comparing the error based on the least square criteria, it has been noticed that the results from the first model show about 4% improvement in predicted error against literature results on cracking of normal Heptane [Corma, A., Wojciechowsky, B. W. ([1983]). Recent work on the fundamentals of catalytic cracking. American Chemical Society Reprints, Div. Chem. 28(3):861–874.] for fifteen data points. In the second step the software was modified to simulate the effect of reaction temperature by using two sets of laboratory data for the reaction of normal Hexadecane over ReY-Zeolite, a commercial cracking catalysts at two different reaction temperatures of 400 and 450°C respectively. Validation of modified software has been checked with the above system at 500°C and found that the predictions are quite close to experimental values. Such analytical model will be useful for finding optimum operating conditions to achieve maximum yields of potential products on cracking of a given feed without resource to conducting large number of experiments.

Comparison of particle size of cracking catalyst determined by laser light scattering and dry sieve methods

A method of interconversion of dry sieve and laser light scattering particle size values has been developed for cracking catalysts. Values obtained by light scattering techniques were consistently larger than those obtained by dry sieve analysis. The differences were primarily due to lack of sphericity of the particles. The particle size distribution determined by light scattering techniques was based on an average particle diameter. Conversely, the sieve measured the smallest diameter of the particle which can pass through the opening. Microscopic examination of commercial cracking catalysts confirmed their nonuniformity. The sphericity of the catalyst particles decreased as particle size increased. Therefore, the divergence between the laser light scattering and dry sieving value became greater as the catalyst particle size increased.

Fluid catalytic cracker catalyst design for nitrogen tolerance

Pulse reaction experiments in which mixtures of 1-4 wt % quinoline or pyridine in hexadecane were reacted over a commercial cracking catalyst (Davison's Super DX) demonstrated the reversible equilibrium process of poison adsorption. The use of a low-activity (for cracking hexadecane) silica-alumina amorphous matrix component, mixed with the Super DX, resulted in a higher conversion of a hexadecane-quinoline mixture compared to Super DX alone. Gas oil cracking studies with various levels of preblended quinoline were performed using catalysts in which both zeolite and active matrix content were varied. The activity and selectivity results can be used to develop design criteria for cracking catalysts that are to be used in the processing of feedstocks containing unusually high organic nitrogen levels. The general applicability of the quinoline studies was verified by similar studies using a naturally occurring high nitrogen content gas oil and blends of it with a shale oil.

Modification of zeolite-containing cracking catalyst by WO 3/SiO 2

The combination of a commercial cracking catalyst with a Group VIb oxide, supported on silica, results in an increase in the gasoline yield in the process of gas oil cracking in a laboratory reactor. Experiments on the cracking of blended hydrocarbon fractions over ”sandwich“ catalyst combinations demonstrate the possibility of non-stoichiometric hydrogen transfer reactions (H spill-over).

Contact time distribution in fluidized-bed reactors part I: Measurements at room and higher temperatures

The contact time distribution (CTD) is required in order to predict the performance of gas/solid fluidized-bed reactors. By using certain plausible assumptions, the CTD can be determined from two total residence time decay functions for an adsorbable tracer corresponding to different extents of adsorption. The gas-phase residence time distribution (RTD) can also be determined. The total residence time decay functions were measured using a 6 inch diameter fluidized bed of commercial cracking catalyst with air as the fluidizing gas and nitrous oxide as the tracer. The determinations of the CTD and RTD were carried out at various flow rates and temperatures. The fraction bypassing can be obtained from the CTD curves.