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Two types of deactivation functions are usually employed when modelling catalytic cracking: the time-based models and the coke-on-catalyst models. In this paper, a comparison is made between these two types of deactivation functions in the simulation of an industrial UOP fluid catalytic cracking (FCC) unit with high-efficiency regenerator. For this purpose, a FCC mathematical dynamic model, previously presented and validated, is used. The dynamic responses to perturbations of +10% increase in the combustor air mass flowrate and +5% in the feedstock flow, were studied. The results for these perturbations show that the slight differences observed were due to the fact that the coke-on-catalyst approach takes into account the coke content present at the riser inlet.

This paper focuses on the fluid catalytic cracking (FCC) process and reviews recent developments in its modeling, monitoring, control, and optimization. This challenging process exhibits complex behavior, requiring detailed models to express the nonlinear effects and extensive interactions between input and control variables that are observed in industrial practice. The FCC models currently available differ enormously in terms of their scope, level of detail, modeling hypothesis, and solution approaches used. Nevertheless, significant benefits from their effective use in various routine tasks are starting to be widely recognized by the industry. To help improve the existing modeling approaches, this review describes and compares the different mathematical frameworks that have been applied in the modeling, simulation, control, and optimization of this key downstream unit. Given the effects that perturbations in the feedstock quality and other unit disturbances might have, especially when associated with fr...

The present work concerns a new synthesis approach to prepare niobium based SAPO materials with AEL structure and the characterization of Nb species incorporated within the inorganic matrixes. The SAPO-11 materials were synthesized with or without the help of a small amine, methylamine (MA) as co-template, while Nb was added directly during the preparation of the initial gel. Structural, textural and acidic properties of the different supports were evaluated by XRD, TPR, UV–Vis spectroscopy, pyridine adsorption followed by IR spectroscopy and thermal analyses. Pure and well crystalline Nb based SAPO-11 materials were obtained, either with or without MA, using in the initial gel a low Si content of about 0.6. Increasing the Si content of the gel up to 0.9 led to an important decrease of the samples crystallinity. Niobium was found to incorporate the AEL pores support as small Nb 2 O 5 oxide particles and also as extra framework cationic species (Nb 5+ ), compensating the negative charges from the matrix and generating new Lewis acid sites.

The transformation of mixtures of methylcyclohexane and small amounts of phenol, added in growing quantities (0.01, 0.06, 0.6, and 1.2 wt %), was carried out over an H-ZSM-5 zeolite at 350 and 450 °C, in order to simulate the biomass-derived oils and fluid catalytic cracking feedstocks cofeeding. At 350 °C, with only 0.6 wt % of phenol fed with methylcyclohexane, a very fast and quasicomplete deactivation of the zeolite occurs. The main cause of deactivation is the strong adsorption of phenol molecules on the acid sites of the zeolite causing at the same time active-site and pore blockage. This could be due to the small size of the ZSM-5 pores that slows down the diffusion of phenol molecules and facilitates their adsorption and retention. This negative effect of phenol addition can be observed whatever the contact time, the reaction temperature, and even after only 2 min of reaction (first experimental value). All this suggests that, depending on the amount of bio-oil incorporated in the classical FCC fe...

The deactivation of acid zeolite catalysts is essentially due to the formation and trapping of heavy secondary products (coke) within the pores (channels and cages). As in these nanosized pores the growth of these products is sterically limited, the coke composition, i.e., the quantitative distribution in nature and size of the components, can be determined and the scheme and mechanisms of coke formation established. Moreover, coupling activity, acidity and adsorption data with coke composition leads to information on the location and deactivating effect of coke molecules. Based on the influence on coking and deactivation rates of the features of reactions and zeolite catalysts, general rules are proposed for limiting the rate of formation of coke molecules and minimising their deactivating effect.

The racemization of 1-phenylethanol, a chiral alcohol of industrial value, was catalyzed by zeolite H-ZSM-5 in organic medium. In its fully active form, this zeolite was capable of racemizing the substrate at high rates and with limited formation of secondary products. The only significant by-product detected, corresponding to the dehydration of the alcohol, was styrene. To further limit this side reaction, the zeolite acid strength was reduced by ammonia poisoning. After saturation of the acid sites with ammonia, the poison was desorbed at increasingly higher temperatures to produce a series of progressively more acid catalysts. The poisoned zeolites were characterized by temperature-programmed desorption of ammonia, which was also used to determine the acid site strength distributions. The poisoned zeolite series was tested in the racemization reaction and the selectivity, defined as the ratio of the kinetic rate constants of the racemization and dehydration, could be enhanced when compared to the original catalyst, while keeping a high racemization activity.

The main features of methylcyclohexane (mch) and n-heptane (n-C7) transformation at 350°C were compared for fresh samples of HMWW, HMFI and HFAU zeolites. With both reactions, the behavior of HMWW was between those of the medium HMFI and large pore HFAU zeolites. Thus, the values of turnover frequency (TOF) and of the TOFmch/n-C7 ratio were similar with HMWW and HMFI and much higher with HFAU. In contrast, small differences were found between product distributions over HMWW and HFAU but large differences between HMWW and HMFI. These observations can be explained by alkane transformation in the large supercages with 10-MR apertures of HMWW: the narrow apertures limit diffusion of the mch within the supercages, but not the diffusion of the products which are therefore typical of the transformation within large cages hence without any steric limitation.

The structure and morphological aspects of highly porous (higher than 90%) cordierite (Mg2Al4Si5O18) foams, prepared by a direct foaming method, have been evaluated by Scanning Electron Microscopy analysis. The resulting ceramic foams consisted of a three-dimensional array of struts forming a well-defined open-cell structure. This type of structure seems very attractive for catalyst support purposes. Attempts have been made in order to control the pore structure since it directly affects the physical properties, namely the mechanical strength. In this respect, the use of a dip coating method to improve the strength of the resulting foams was found to be effective in reducing defects (e.g. pores, flaws) in the struts. Based on image analysis, estimated mean cell sizes were about 550 µm whereas strut thicknesses varied in the range of 60-70 µm. The compressive strength of the developed foams increased by one order of magnitude (0.1 to 1 MPa) by increasing the relative density from 0.06 to 0.18.

The reactors used for Selective Catalytic Reduction (SCR) of NOx require low pressure drop structured catalyst packing. Structured packings, such as ceramic foams, are gaining increasing interest for application in low pressure drop reactors, membrane reactors and catalytic distillation units. In this work, cobalt ion exchanged mordenite (Co-HMOR)-coated cordierite-based foams produced by the replication method were evaluated for catalytic reduction of NOx with methane. The addition of 0.3 wt.% Pd to 2 wt.% Co-HMOR leads to a material that can convert 50 % NOx to N2 at 450 °C in a reaction mixture containing 2000 ppm CH4, 1000 ppm NOx, 5 % O2 and balance helium, at GHSV=17000 h-1. Although in an early stage of development, an efficient coating procedure was explored and different ways of exchange of Co and Pd cations into mordenite (Si/Al=10) were studied. Additions of 2 wt.% fumed silica enhanced adhesion of the zeolite onto the ceramic foam. Pd-exchanged Co-HMOR showed to be very sensitive to steam. A 50 % decrease in NOx conversion to N2 was observed after Pd/Co-HMOR samples were exposed at 450 °C to a reaction mixture containing 2 vol% H2O. Although further research is needed to ascertain the mechanism of this deactivation behaviour, agglomeration of Pd forming PdO particles is envisaged.

A new copper vanadate precursor with the formula NH(4)[Cu(2.5)V(2)O(7)(OH)(2)] . H(2)O was synthesized and deposited on two different supports, ZSM-5 and amorphous SiO(2), by a hydrothermal method or by mechanical mixture. The catalytic behaviour was evaluated in the total oxidation of toluene and the characterization was performed by H(2)-temperature-programmed reduction (H(2)-TPR), thermogravimetric analysis, elemental analysis, UV-vis diffuse reflectance spectroscopy and X-ray diffraction. It was found that the copper vanadate phase comprises two mixed oxides, one of them crystalline, the Ziesite phase, and the other one amorphous. The supported catalysts presented a content of copper vanadate phase of about 9-11 wt.%. The copper vanadate deposited on ZSM-5 by the hydrothermal method evidences the best performance in the oxidation of toluene. This behaviour can be associated with the smaller size and higher dispersion of the particles on the support, which was confirmed by their better reducibility and higher band gap energy value compared with the other series of studied catalysts.

Catalytic oxidation of toluene in low concentration (800 ppm) in air was carried out over catalysts prepared from a new copper vanadate phase calcined at different temperatures. The catalysts were composed of different crystalline phases, namely ziesite, fingerite, blossite and other copper vanadium oxides. The best catalytic performance was obtained with the material calcined at 320 °C (composed of ziesite phase and an amorphous copper vanadium oxide) that showed a light off temperature of 265 °C. H 2 -TPR measurements indicated that the most active catalysts (calcined at 320 and 400 °C) are also the most easily reducible.

The catalytic hydrogenation of nitrobenzene using a commercial nickel catalyst supported on silica was studied in a three-phase batch laboratory scale stirred tank reactor. Reaction mixture samples were analyzed by gas chromatography. The aim of the work consists in obtaining a fully functional and practical mathematical model of the reaction kinetics that is easy to implement and able to describe the reaction progression in a wide range of conditions. The effects of temperature, pressure and nitrobenzene concentration for a given catalyst concentration were studied. The model that was obtained is able to describe all the experiments with just one set of parameters and helped to describe and explain phenomena that were observed in an industrial system; the results obtained indicated the possibility of the catalyst surface changing with time by contact with the reaction mixture.

The possibility of existence of multiple steady states in fluid catalytic cracking (FCC) units has a major impact in the supervision of these systems. The origins of these behaviours are usually due to the exothermicity of the catalyst regeneration reactions and to the strong interactions between the reactor and the regenerator system. Prior work has focused on modelling and control problems of different operating FCC units. However, none of these studies have considered a high-efficiency regenerator. This paper presents an analysis of the existence of output and input multiple steady states in an UOP FCC unit with a high-efficiency regenerator. The influence of unit disturbances and model uncertainties, such as coke composition and cracking enthalpy, in the output multiplicity, was studied and the results show that the high-efficiency regenerator exhibits at least three multiple output steady states and a maximum of five output steady states, in the operating range considered. Moreover, the state multiplicity analysis revealed that input multiplicity can be present in this FCC unit, depending on the choice of the control structure, and that operating the unit in full combustion mode can prevent instabilities due to input and output multiplicities. Therefore, these results can be used to guide the design of the most appropriate control structures in industrial applications. For the FCC unit with high-efficiency regenerator the most appropriate control structure corresponds to the control of the riser reactor temperature and the oxygen level in the flue gas, with the catalyst circulation rate and the combustion air flow rate, respectively.

We report herein the first regioselective synthesis of β-galactofuranosides by Fischer glycosidation of GalNAc with methanol catalyzed by HY, HZSM-5 and HBEA acid zeolites. The zeolite HY (Si/Al ratio 3.1) was the most efficient catalyst, leading to the highest yield of methyl β-galactofuranoside, isolated as its acetylated or isopropylidene derivatives, indicating that with large pore zeolites, the reaction efficiency depends upon the concentration of the zeolite acid sites and its hydrophilicity. However, the best regioselectivity for β-galactofuranoside versus β-galactopyranoside was obtained with the medium pore zeolite HZSM-5, which also led to the lowest starting material conversion, suggesting that both the zeolite pore size and topology are determinant for the obtained results. Furthermore, these acid zeolites proved to be efficient catalysts to transform 1,5-anhydro-3,4,6-tri-O-benzyl-2-deoxy- d -arabino-hex-1-enitol (6) (3,4,6-tri-O-benzyl- d -glucal) exclusively in the 2,3-unsaturated-O- and -S-α- d -glycosides by Ferrier rearrangement, in moderate yield. For this reaction, the number of acid sites was the key factor for the reaction yield, being HY (Si/Al ratio 3.1) also the most effective zeolite.

Open cell cordierite foams were prepared by a direct foaming two-component polyurethane (PUR)/ceramic system. Through optimization of several experimental parameters, such as contents of catalyst, and ceramic cordierite precursor, as well plasticizer presence, foams with porosities 85-95 % and densities ranging from 130-410 kg/m 3 were obtained. These foams characteristics make them attractive to be used as catalyst supports. The new two-component PUR/ceramic system developed allows the high solid's loading (higher than 40 wt. %). Finer ceramic particles in this system provide better particles' package and cohesion upon sintering, favouring the cordierite foam stability.

The aim of this study is to obtain a model that can simulate the performance of an industrial fluid catalytic cracking (FCC) unit in steady and dynamic state, and which will subsequently be used in studies of control and real time optimisation. In this paper, a dynamic model for a R2R type FCC unit is presented. The model includes the riser, the stripper/disengager, the regeneration system and the catalyst transport lines. Mass, energy and pressure balances are performed for each of these sections. Simulation results for steady state are presented and compared qualitatively to those obtained from previous FCC models. The dynamic behaviour of the system is explored through two perturbations in open loop, one on the fresh feed flow rate and one on the air flow rate to the first regenerator. The results illustrate the consistency of the model and are in agreement with what has been observed in studies available in the open literature.

Bimetallic catalysts Pt–Ni/HBEA prepared by different methods, were studied in the reaction of n-hexane hydroisomerization and compared with Pt and Ni/HBEA. The results showed that the highest conversion and selectivity were obtained for the bimetallic catalysts, prepared by ion exchange with simultaneous addition of Pt and Ni, which reveals a synergistic effect between the two metals.

Direct C–N bond formation has been accomplished by reaction of 1,5-anhydro-3,4,6-tri-O-benzyl-2-deoxy-D-arabino-hex-1-enitol (3,4,6-tri-O-benzyl-D-glucal) with N-nucleophiles, using triphenylphosphane hydrobromide as catalyst in dichloromethane or THF. 2-Deoxy-S- and -O-glycosides have also been prepared with thiols, sterols, flavonoids, alcohols and sugars as nucleophiles, with α-stereoselectivity. Sterically demanding reagents such as sterols, flavonoids, sugars and an indole give only the α-anomer in dichloromethane, while the purine nucleosides in THF were obtained as anomeric mixtures whilst maintaining the α-stereoselectivity. This procedure has led to an easy and straightforward synthesis of a variety of biomolecules, in moderate to high yield, with the first use of triphenylphosphane hydrobromide for N- and S-glycosylation. An alternative method for C–O and C–S bond formation uses HY zeolite to promote theFerrier rearrangement of 3,4,6-tri-O-benzyl-D-glucal to give exclusively the corresponding 2,3-unsaturated α-O- and α-S-glycosides in moderate yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The presence of alkali cations in zeolite framework provides peculiar basic properties that influence the characteristics and reactivity of supported metal particles. Particularly, the addition of increasing amounts of cesium in Pt/Na-BEA and Pt/Cs-BEA catalysts, by CsOH impregnation, leads to changes of the oxidation state and reducibility of Pt species present in the zeolite microporosity. For similar contents of impregnated Cs, the metal dispersion is higher in Pt/Cs-BEA than in Pt/Na-BEA series, showing that both the amount of Cs excess and the nature of the compensating cation affect the characteristics of the Pt species. In the case of Cs-overloaded Pt/Cs-BEA, the size of Pt nanoclusters is below 10 A. The very small Pt nanoparticles in reduced Cs-overloaded Pt/Cs-BEA are particularly active in aromatization of n-hexane.

The influence of rare earth (RE) elements on the acidic properties of H-MCM-22 and H-Beta was studied by pyridine adsorption followed by infrared spectroscopy (FTIR) and n-heptane cracking, as a model reaction. The zeolites were submitted to ion exchange with rare earth nitrate solutions of La, Nd and Yb. The FTIR spectra of REH-MCM-22 indicate the presence of RE elements inside supercages and in the sinusoidal channels of the zeolite. After pyridine adsorption two additional bands are detected in REH-MCM-22 and REH-Beta, related to pyridine bonded to RE3+ cations. The n-heptane cracking reaction shows that the effect of rare earth elements is related not only to the acidity but also with the porous structure of both zeolites. In H-Beta zeolite, the presence of RE elements enhances the acidity of the catalysts. In H-MCM-22 zeolite, the most relevant effect of rare earth elements is on the shape selectivity that becomes more pronounced with the ionic radius of the RE elements. The nature of the coke deposited on the two materials shows distinct profiles that are also related to its porous structure.

Ion-exchanged Co and PdCo-BEA zeolite-based catalysts were studied for the selective catalytic reduction (SCR) of NO with methane under oxygen excess. Bimetallic samples were submitted to several hydrothermal treatments (steaming) and tested under dry and wet conditions (2% H2O). These hydrothermal treatments resulted in significant modifications in the amount and distribution of metal species, namely an increase of Co oxides and Co-oxo species, simultaneously with the preservation of Co2+ isolated exchanged cations. H2-TPR measurements detected, on these catalysts, a fraction of Co species more easily reducible, eventually interacting with Pd species and possibly related to dispersed nanosized oxide species, placed in more accessible positions. All the steamed catalysts exhibit a higher NO conversion into N2 and an increased water resistance. The Co and/or Co-Pd species formed during steaming treatment, the balance between them and the framework dealumination are important issues for the high and stable catalyst activity under the presence of water vapor.

A series of HBEA samples were prepared by dealumination through steaming or treatment by hydrochloric acid of a parent commercial zeolite. Treatments with acid solutions were shown to cause a rapid dissolution of the extraframework Al (EFAL) species, especially the monomeric ones and a slow dissolution of the framework Al (FAL) atoms of bridging OH groups and structure defects. Steaming at high temperatures (500–700 °C) causes both an extraction of FAL atoms and a significant increase in the degree of polymerization of the EFAL species. A quantitative distribution of the various Al species of the parent HBEA zeolite was established. The nature of the hydroxylated Al species responsible for the IR bands in the OH region was specified: the band at 3607 cm–1 was ascribed to bridging OH groups responsible for the Bronsted acidity, that at 3660 cm–1 to monomeric and polymeric EFAL species, that at 3680 cm–1 to hydroxylated EFAL clusters resulting from acid extraction of Lewis framework defects; that at 3780 cm–1 to both monomeric EFAL species and framework defects with Lewis acidity. To cite this article: F.R. Ribeiro and al., C. R. Chimie 8 (2005).

A series of four chiral pentacoordinated aluminium salen complexes differing in the apical ligand have been prepared. The complexes exhibit an intense emission (ϕ from 0.271 to 0.35) arising from the LMCT band excitation. The complexes were submitted to laser flash photolysis. The same transient was observed in the four cases (τ under N2 between 1.1 and 3.5 μs) and the corresponding UV–visible transient spectrum exhibits two absorption bands at 320 and 500 nm. This transient is quenched by oxygen, hydrogen donors (1,4-cyclohexadiene and 1-octanethiol) and alkenes and it was assigned to the neutral Al(II) salen complex generated by homolytic bond cleavage of the apical ligand. This transient exhibits different degrees of asymmetric recognition for its quenching with enantiomerically pure pinene kq(R)/kq(S) varying between 1.68 up to 12.26 depending on the nature of the apical ligand.

The macroscopic distribution of platinum in extrudates of bifunctional PtHFAU/Al2O3 catalysts is shown to have a significant effect on their activity, stability and selectivity in n-hexane transformation under hydrogen pressure. The best catalysts are those for which platinum is homogeneously dispersed. n-Hexane transformation is proposed as a model reaction for estimating the macroscopic distribution of platinum in industrial catalyst pellets.

Catalytic deep oxidation of toluene at low concentration in air, has been studied over CuNaHY zeolites with different copper contents. The reaction has been investigated in the course of time-on-stream, at temperatures between 150 and 500°C. The effect of copper content on the conversion of toluene into CO 2 and on the formation of carbonaceous deposits (coke) retained inside the zeolite pores has been analyzed as a function of the reaction temperature. The analysis of the coke extracted from the catalysts showed that it is mainly composed of aromatic hydrocarbons and oxygenated aromatic compounds, the latter being predominant at low temperature and preferentially formed on the catalysts containing more copper. A bifunctional mechanism was proposed to explain the formation of coke over CuNaHY catalysts. Based on the differences of the nature of coke formed on NaHY and CuNaHY catalysts, and on a discussion about the coke formation and location, it was possible to conclude that copper sites are involved in both toluene and coke oxidation reactions. The increase of copper content from 1 to 8 wt.% promotes the oxidation of toluene and facilitates the removal of coke formed in the course of reaction.

In this paper the relation between activity and acidity in a variety of ZSM-5 zeolite catalysts, with different Si/Al ratios and different protonic content, is analysed and a quantitative correlation is obtained. The acid site strength distribution was estimated using temperature-programmed desorption (TPD) of ammonia by applying a digital deconvolution method to the curves. These data were then correlated with experimental catalytic activity data for the same catalysts towards n-heptane cracking reaction, by means of a Bronsted-type equation similar to the ones used for homogeneous acid catalysis and already used for other zeolites. It can be noticed that the same types of equation that are used for homogeneous acid catalysis also hold for heterogeneous acid catalysis and that the activation energy for ammonia desorption can be used as acid-strength scale for the purpose of correlation with catalytic activity.

A recombinant cutinase from Fusarium solani pisi was immobilized by adsorption on titanosilicates, titanoaluminosilicates, and vanadosilicate, and its activity in the alcoholysis of butyl acetate with hexanol, in organic media (isooctane), was measured as a function of the water content and water activity.

A simplified three-parameter model for the interpretation of the kinetic data of coke formation during transformation of light olefins is presented. This model has been applied to the transformation of ethene, propene and 1-butene over fresh and regenerated zeolite USHY at 623 K. The proposed model covers both the coverage of the acid sites and the autocatalytic growth of coke.

International audience; Copper-exchanged zeolites with different structures (CuMFI, CuMOR and CuY) used as catalysts on the selective catalytic reduction (SCR) of NO by propene have been studied. Different types of Cu species were identified (Cu2+, Cu+, and CuO) by H2-TPR and NO TPD. The structure of each zeolite determines the nature and concentration of those species and the catalytic behavior for SCR of NO by propene in the presence of oxygen. A correlation was observed between the catalytic activity, and the presence of isolated Cu2+ species, which is enhanced by MFI structure.

Two series of supports and catalysts were prepared exchanging β zeolite with alkali or alkali-earth cations. The influence of the exchanged cation (M=Na, K, Rb, Cs, Mg, Ba) on the catalytic behaviour of Pt/Mβ catalyst in n -heptane reactions was studied. Platinum was introduced into the supports by ionic exchange. The supports and Pt catalysts were chemical and structurally characterized by different techniques (AA, ICP, XRD, ammonia TPD, cyclohexane adsorption, H 2 -TPR, etc.). The acidity and adsorption capacity decrease as the cation size increases. In the case of alkali cations, the catalytic activity of the support is negligible. However, greater acidity and stronger acid sites present on alkali-earth supports provide a high catalytic activity. The deactivation rate and the amount of coke determined by TG are related. The nature of the coke was discussed on the basis of DSC results obtained during the coke burning. Coke deposited on alkali and alkali-earth Mβ zeolite during the n -heptane transformation becomes progressively more stable as the support acidity and the time on stream increase. The localization of Pt particles and their proximity to the acid sites influence the coke composition and its removal. The regeneration of Pt/Kβ was performed and the results showed that the catalyst fully recovers its catalytic behaviour.

CuMOR catalysts with different Si/Al ratios and copper contents, prepared from the acid and sodium forms, were studied in NO reduction with propene in the presence of excess oxygen. It was observed that the influence of zeolite Si/Al ratio on CuMOR catalytic activity for NO SCR by propene depends on the catalyst copper content, the reverse being also true. For mordenites prepared from the acid form, it was shown that the most active catalyst must have ∼60% of copper exchange, whereas for those prepared from the sodium form, the maximum catalytic activity is obtained for catalysts with 20% of copper exchange. Moreover, it was observed that at low copper-exchange levels, the catalyst prepared from the sodium form exhibits much higher activity than those prepared from the acid form. Although, when the copper-exchange level increases, the effect of zeolite form is less pronounced. Thus, it was indicated that Bronsted acidity does not promote the NO selective reduction by propene.

An integrated view is presented of several possible mechanisms applicable to the interpretation of homogeneous Ziegler-Natta polymerisation. In this paper, the transient aspects related to the kinetics of Ziegler-Natta polymerisation are investigated. Extensive data are used to construct kinetic profiles (r M vs. t) from a theoretical approach. Special attention is given to the duration of the transient period as a function of the different kinetic parameters. The kinetic models developed are fitted to experimental data, either directly obtained by the authors or published in the literature. These general models have a broad range of application.

Selective catalytic reduction of nitrogen oxide by propene in an oxidising atmosphere was studied on several CuMFI catalysts with different Si/Al ratios (11 ⩽ Si/Al ⩽ 100) and different copper loadings (between 0 and 5.5 wt.-%). From the results it was observed that the influence of zeolite Si/Al ratio on CuMFI catalytic activity for NO SCR by propene is dependent on the catalyst copper loading. Furthermore, the effect of catalyst copper loading on catalytic performance depended on the catalyst Si/Al ratio. The results also demonstrated that CuMFI catalysts with different Si/Al ratios and copper loadings, but with the same Cu/Al ratio and, therefore, the same copper exchange level have similar catalytic activity profiles for NO SCR. It was further observed that not all Cu cations exchanged into MFI catalysts have equivalent catalytic activity for NO SCR, which made the existence of different copper environments on CuMFI catalysts evident, isolated Cu 2+ ions being the most active species for NO SCR by propene. Moreover, the results showed an improvement of the CuMFI catalytic activity at low temperatures by increasing the catalyst copper exchange level and, consequently, decreasing the number of Bronsted acid sites, which can be performed either by increasing the zeolite Si/Al ratio or copper loading.

Deactivation of CuMFI catalysts under NO selective catalytic reduction (SCR) by propene in both the absence and the presence of water was investigated as a function of zeolite form, Si/Al ratio and copper content. It was verified that the CuMFI deactivation extent is higher on H-form zeolite compared to Na-form and decreases when the copper exchange level increases, which can be achieved either by increasing the zeolite Si/Al ratio or the copper content. Furthermore, the results indicated that the catalyst deactivation is mainly due to a change in copper species rather than in MFI structure.

Catalytic activity of CuMOR catalysts for NO selective catalytic reduction by propene was investigated as a function of the cocation (H, Na, Cs, Mg and Ba) present in the zeolite. It was verified that the cocation plays an important role in the CuMOR activity, its effect being more pronounced at low temperatures. Moreover, the results suggest that we can prevent the catalyst deactivation by choosing the appropriate cocation.

The performances of platinum β zeolite exchanged with alkali (Na, K, Cs) and alkali-earth (Mg, Ba) cations have been examined for n-hexane reactions. The nature of coke deposited on the catalysts is slightly influenced by alkali cations because coke is deposited on metallic sites. In Pt/alkali-earth catalysts the coke depends on the support acidity.

The transformation ofn-decane was studied at 473 K, 101 kPa andpH2/pn-decane = 9 on a series of PtHY catalysts containing from 0.02 to 1.5 wt% platinum and with Si/Al atomic ratios of 3, 9, or 35. The ratio between the number of accessible Pt atoms and the number of acid sites on which the heat of ammonia adsorption is greater than 100 kJ mol−1(nPt/nA) was chosen for characterizing the balance between the hydrogenating and the acid functions. The activities, stabilities, and selectivities of the catalysts are definitely governed by this balance. For low values ofnPt/nA( Methyl shift > Branching > B cracking >> C cracking.

Thermal and hydrothermal stability of SAPO-40 were studied by X-ray powder diffraction (XRD) and magic-angle spinning nuclear magnetic resonance (MAS-NMR). For the X-ray study, the hydrothermal treatments were carried out, in situ, in a high-temperature chamber. The SAPO-40 structure shows a remarkable stability to high temperatures under both dry and humid air. At high temperatures a reorganisation of silicon occurs, but the long-range order is only lost above ca. 1000°C. Changes in the XRD pattern induced by water at room temperature are completely reversible upon re-heating at 200°C, as well as the changes in the coordination and local environments of aluminium and phosphorus observed by NMR. For silicon however, some changes, that are observed upon hydration, remain after dehydration.

Zeolite HY proved to be a suitable catalyst for the acetonation of sugars. The method consists of a very simple and economic experimental procedure, in which the catalyst is recovered and can be regenerated. Reaction with D-galactose, L-arabinose, D-glucose, D-xylose, L-sorbose, D-glucofuranurono-6,3-lactone, D-ribose and its methyl glycoside led to the formation of di-O- and/or mono-O-isopropylidene derivatives in yields from 37–75%. Reaction with D-galactose and L-arabinose afforded the synthesis of the corresponding furanose derivatives as major products, together with minor quantities of the thermodynamically more stable pyranose derivatives. Acetonation of D-glucose, D-galactose, L-arabinose, D-xylose, L-sorbose, D-ribose, methyl β-D-ribofuranoside and D-glucofuranurono-6,3-lactone was performed by reaction with acetone using the zeolite HY as catalyst. Synthesis of O-isopropylidene derivatives was accomplished in moderate to good yields (37 – 75%). The method consists of a very simple and economic experimental procedure, in which the catalyst is recovered and can be regenerated. Reaction with D-galactose and L-arabinose afforded the synthesis of the corresponding di-O-isopropylidene and mono-O-isopropylidene furanose derivatives as major products, together with minor quantities of the thermodynamically more stable pyranose derivatives.

International audience; n-Hexadecane hydroisomerization at 220 C and 30 bar was used as a model reaction for comparing the catalytic performances of a Pt/HBEA sample whose zeolite crystals were germinated on an a alumina surface with those of 1Pt/ HZM-22 catalyst well-known for its high isodewaxing selectivity. Similar values of selectivity to isomers were obtained with both catalysts even at high conversions. Moreover, despite its low zeolite content (13 wt%), the Pt/HBEA Al2O3 catalyst had the important advantage to be 4.6 times more active.

This work considers the catalyst deactivation phenomena in ethyl tert-butyl ether (ETBE) reactors, and the estimation of the corresponding kinetic parameters from industrial plant data. For this purpose a simulation model of these units is developed, and used to build a parameter estimation problem constrained by partial differential equations. Good agreement between the model predictions and the available industrial data is achieved, enabling the use of the resulting model in several process related tasks.

The scheme of the gas phase phenol acylation with acetic acid on a HZSM5 zeolite was established from the effect of contact time (hence of conversion) on the product distribution. Phenyl acetate and o -hydroxyacetophenone are primary products, O-acylation being much faster than C-acylation. At high conversion, part of the o -hydroxyacetophenone results from the acylation of phenol with phenyl acetate. The formation of p -hydroxyacetophenone which does not occur through phenol acylation involves the hydrolysis of p -acetoxyacetophenone selectively formed through the autoacylation of phenyl acetate. The ortho -selectivity of phenol acylation can be related to a pronounced stabilization of the transition state while the para -selectivity of phenyl acetate autoacylation could be due to a steric hindrance to the approach of the acetyl group in the ortho -position of phenyl acetate.

Methods of Characterization of Deactivating Species and Aged Catalysts Deactivation Mechanisms: Poisoning, Fouling and Coking, Structural and Physical Degradations Prevention of Deactivation and Optimal Regeneration Industrial Examples: Catalytic Cracking (FCC), Methanol to Olefins (MTO), Aromatic Alkylation, Isomerization and Transalkylation, Organic Commodity and Fine Chemicals Synthesis.