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It is important to develop new promoters of fluid catalytic cracking (FCC) catalyst to increase iso-paraffin yield and avoid the decrease of research octane number (RON) caused by olefin saturation in gasoline hydrofining. SAPO-11 and LaAPO-11 molecular sieves were used as promoters to FCC catalyst to increase gasoline RON and were tested in the cracking reaction of n-dodecane on FCC conditions. LaAPO-11 molecular sieve has less and weaker acidity than SAPO-11 molecular sieve. LaAPO-11’s metallic sites polarize the C H bonds to form carbenium ions for isomerization reaction and weak acid sites make less contributions to the cracking of iso-paraffin. LaAPO-11 promoter increases the yield of iso-paraffin (C 5-9 ) from 6.4% to 10.2%. Besides that, a high yield of arene (2.0%) is caused by the dehydrogenation activity of LaAPO-11 promoter. The new contributions of this paper are the synthesis of a hydrothermal stable LaAPO-11 molecular sieve with isomerization activity and proposing the reaction routes of iso-paraffin. These new contributions are important for developing more effective RON promoters of FCC catalyst. [ABSTRACT FROM AUTHOR]

-Highlights: [•] The concentration of BrÃnsted and Lewis sites increases upon desilication. [•] Desilication with NaOH&TBAOH preserves the crystallinity of mesoporous Beta zeolite. [•] Cracking of gasoil over mesoporous Beta results in high propylene selectivity. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this paper is to present a damage assessment technique for the non-destructive detection and sizing of multiple open cracks in beams. The constitutive relation error updating method is used for the identification of the location and the size of multi-cracks in a simply supported beam. The present identification method is illustrated through numerical examples including double and triple cracks. Moreover, the efficiency and robustness of the proposed method is demonstrated through various numerical simulations in regard to the non-dimensional crack depth and the crack location. It is demonstrated that the constitutive relation error updating method can detect the number of cracks on the beam and can estimate both the crack positions and sizes with satisfactory precision, even if 10% or 20% noise levels has been added to the simulations, and only few degrees of freedom are used for the identification procedure. [Copyright &y& Elsevier]

Abstract: The catalytic transformation of methylcyclohexane (mcha), as representative of the reactions taking place during catalytic cracking, was carried out on a H-EU-1 zeolite under the following conditions: 623 K, atmospheric pressure, ratio equal to 9, contact time (taken as the reciprocal of the weight hourly space velocity) between 0.016 and 0.3 h. Whatever the contact time and time-on-stream, cracking was the main reaction, like on other 10-MR zeolites, but significant amounts of isomers and aromatics were produced. Moreover, cracking led predominantly to branched products, in contradiction with the shape selectivity expected from the narrow pore openings of this 10-MR zeolite. All this could be explained by a very important catalytic contribution of the protonic sites located at the pore mouths. Additional experiments using bulky basic compounds (γ-collidine) confirmed this hypothesis and allowed estimation of the selectivity of these acid sites. [Copyright &y& Elsevier]

Abstract: The structural collapse and the reconstruction of Brønsted acid sites in zeolite Y were investigated by combining propane monomolecular cracking with various structural characterization techniques. Destruction of Brønsted acid sites, together with a loss of catalytic activity, was found after calcination and exposure to moisture at room temperature. A loss in long-range structure was observed by XRD. Adsorption of NH3 before exposure to air prevents the structural collapse of Brønsted acid sites and the loss of catalytic activity. The collapsed Brønsted acid sites and long-range order recover fully after thermal treatment with NH3 at moderate temperature, as does the catalytic activity. Reheating of HY causes further structural collapse. Water molecules are involved in structural destruction, and also play a role in structural recovery with ammonia. The structure of zeolites is very sensitive to temperature and presence of moisture. Because various characterization methods are preceded by various pretreatment methods, the zeolite structure probed by these methods is not necessarily the same. [Copyright &y& Elsevier]

Abstract: The catalytic activities of a series of porous oxides prepared from silsesquioxanes for the cracking of hydrocarbons have been examined. In addition to known group 13 element-containing silsesquioxanes, new aluminum-bridged silsesquioxanes bearing various countercations, [Y]+[{(c-C5H9)7Si7O12(SiMe3)}2Al]− ([Y]+ = [H2NMe2]+ (2b), [HNMe2(C8H17)]+ (2c), [HNMe2(C18H37)]+ (2e), [HNC5H5]+[{(c-C5H9)8Si8O13}2Al]− (3d), and [HNC5H5]+[{(i-C4H9)8Si8O13}2Al]− (4d), have been synthesized. The controlled calcination of these silsesquioxanes at around 823 K produced amorphous porous acidic oxides with high BET surface areas of 360–520 m2 g−1 and uniformly controlled micropores of 5–6 Å diameter. Among the oxides examined, those prepared from aluminum-bridged silsesquioxanes show excellent catalytic activities for the cracking of cumene even at low reaction temperatures of around 523 K. Under identical conditions commercially available silica–alumina catalysts do not show significant activities, indicating exceptionally high activities of the silsesquioxane-based oxides despite their amorphous nature. [Copyright &y& Elsevier]

Nanostructured SiO2–CeO2 composite materials were prepared by embedding monodispersed, inorganic colloids in ultrafine structured layers of mineral binder using a self-assembly process. Cohesive, highly concentrated CeO2 nanoparticle arrays, characterized by a spacing in the range of a nanoparticle diameter, were synthesized. These materials possess high surface areas and are stable to temperatures up to 800 °C by virtue of surface roughness on the nanometer scale and relatively large inorganic layer thickness. Gaseous access to the CeO2 nanoparticle surfaces was obtained through a matching of nanoparticle sizes to the thickness of the structured layers. These SiO2–CeO2 nanostructured materials showed very good catalytic properties as additives for reducing sulfur concentration in gasoline through fluid catalytic cracking. We demonstrate that these thermally stable, high-surface-area arrays of CeO2 nanoparticles are best suited for the cracking of long-chain, those which commonly present the greatest difficulty, alkylthiophenes and alkylbenzothiophenes. [Copyright &y& Elsevier]

Monomolecular cracking of alkanes was investigated over zeolites of different structure types and after different treatments. Large deviations in apparent rates of reaction and apparent kinetic parameters were detected for zeolites of different structure types; smaller changes were observed within a structure type. The Si/Al ratio and different crystal sizes had no effect on turnover frequency; however, steaming of mordenite and ZSM-5 enhances the rate of reaction by a factor of 2–5 due to the formation of Lewis acid sites with enhanced heat of adsorption, although the number of Brønsted sites decreased. The apparent activation energies and preexponential factors showed a linear compensation relation in a Constable plot. Using the Langmuir–Hinshelwood kinetics formalism, the apparent kinetic parameters include enthalpy and entropy of adsorption and surface reaction terms. If the enthalpy and entropy of adsorption are linearly related, which is experimentally observed for unsteamed and steamed mordenite, then the apparent compensation effect implies that the observed differences in rate are dominated by differences in adsorption of the reactant in the pores of the zeolites, rather than by differences in acid strength. Zeolites with smaller pores show enhanced adsorption, and consequently the rate of reaction increases in the order H-Y

This study intends to illustrate the application of transient kinetics in combinatorial research. Thus, it is shown through various case studies how high-throughput transient kinetics may both accelerate the search for new catalytic materials and bring fundamental insights in reaction mechanisms. As a first case study, the cracking reactions of the C6 isomers (n-hexane, 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, and 2,3-dimethylbutane) over a fluidised catalytic cracking (FCC) catalyst at temperatures between 300 and 650 °C have been studied in a temporal-analysis-of-product (TAP) reactor. A mathematical model taking into account the extra- and intracrystalline transport phenomena was used to determine the diffusion, sorption, and kinetic parameters for the hydrocarbons studied. Sorption and diffusion decrease with increasing branching in agreement with literature data. Except product distribution, the activation energies for the overall cracking of the C6 isomers are similar for all isomers. As a second case study, a “paralleled” TAP reactor with a multisample holder is shown to be an efficient tool for acquiring adsorption/desorption parameters for a series of zeolites, tested to evaluate their potential as catalyst supports in the oxidative dehydrogenation of ethane. Finally, the applied combinatorial study was found also suitable for discovering new materials precursors of dense oxygen-conducting membranes. From high-throughput transient TAP and TPD experiments, it was possible to derive a strategy directing the rapid combinatorial evolution within the available parameter space. It was shown that high-quality information is accessible from these data, providing all parameters necessary for a well fitting description with a kinetic model. [Copyright &y& Elsevier]

The nanostructured CeMCM-41 material was synthesized by the hydrothermal method, using cethyltrimethylammonium bromide as template. The sample was characterized by X-ray diffraction, energy-disperse X-ray, thermogravimetry, nitrogen adsorption isotherm and pore size distribution. The specific surface area of CeMCM-41 was equivalent to 850 m2 g−1, with the pore width and mesopore volume of 3.8 nm and 0.8 cm3 g−1, respectively. To evaluate the catalytic performance of the CeMCM-41, a mass of ca. 0.1 g was heated from room temperature up to 723 K at heating hate of 10°C min−1 using oxygen flowing at 50 ml min−1. The CeMCM-41 was tested as catalyst for n-heptane oxidation, in a fixed-bed continuous-flow reactor, at 723 K and F/W ratio (molar flow of reactant per mass of catalyst) of 0.4–0.6 g h mol−1. The obtained products were analyzed in a gas chromatograph coupled to a mass spectrometer. The GC-MS analysis revealed that the main oxidation products obtained were typically CO and CO2, with 12% of hydrocarbon conversion. [Copyright &y& Elsevier]

Ring opening as practiced in hydrocracking of naphthenic molecules results from multiple cleavages of both endo- and exocyclic C–C bonds. Selective ring opening requires that only one endocyclic C–C bond per naphthene ring be severed, preserving thereby reactant molecular weight. The products of selective ring opening are alkanes and alkylnaphthenes. Over hydrocracking catalysts the yield of alkanes with the same number of carbon atoms as the reactant naphthenes is unacceptably low as a result of extensive dealkylation of alkylnaphthenes and secondary cracking of alkanes. Alkylcyclopentanes, in contrast, selectively ring open by hydrogenolysis over a number of noble metal catalysts. Under similar reaction conditions the selective ring-opening rates of alkylcyclohexanes are, however, one to two orders slower than those of alkylcyclopentanes. Addition of a ring-contraction acidity function converts alkylcyclohexanes into more easily ring-opened alkylcyclopentanes, greatly facilitating selective ring opening. Selective ring-opening rates and selectivities are optimum when ring isomerization occurs by a nonbranching ring contraction. Branching ring contraction, creating increased numbers of ring substituents, is detrimental to both ring-opening rates and selectivities. When an effective acidity function is coupled with a high-activity hydrogenolysis metal, such as iridium, the resulting bifunctional catalyst system greatly outperforms conventional hydrocracking catalysts for the selective conversion of naphthenes to alkanes. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

Two series of sublibraries consisting of data for an overall 10 mixtures (five supported metal catalysts each) were constructed and tested for the selection of catalysts in terms of activity and/or selectivity in the cracking/isomerization of n-heptane. [Copyright &y& Elsevier]