Search

10 figures y 4 tables.-- Supplementary information available., The growing demand of energy needs the search for alternative energy sources different to fossil fuels. The use of biomass as energy source is one of the most studied, because there are high value products that can be produced from biomass. One of these products is γ-valerolactone, that can be obtained from furfural, which is a biomass derived product. To transform furfural into γ-valerolactone is necessary a bifunctional catalyst and a hydrogen source. In this work, γ-valerolactone was obtained from furfural using 2-propanol as solvent and as hydrogen donor on Zr supported on sepiolite catalysts. It was demonstrated that sepiolite, which is a cheap material, can be used to develop efficient catalysts to produce high yields to γ-valerolactone from furfural in one-pot. The catalysts that presented the highest yield to γ-valerolactone were the ones with intermediate Zr-content (9–17 wt% ZrO2). The highest TOFs have been obtained by those catalysts with Zr-loading up to 9 wt% ZrO2, in which the ZrO2 nanoparticles are well dispersed on the support and no formation of large clusters of ZrO2 has been observed. Lewis and Brønsted acid sites are essential in the catalysts to produce the reactions to transform furfural into γ-valerolactone in one-pot, although in the present work, low concentration of Brønsted acid sites were observed in the catalysts. A possible positive role of basic sites to promote some intermediate steps has been also proposed. The catalytic results obtained are in the order of catalysts with Zr supported on zeolitic supports., A.G. thanks MINECO for the pre-doctoral grant (PRE2018-085211). This work was funded by the MAT2017-84118-C2-1-R, MAT2017-84118-C2-2-R, MCIN/AEI/10.13039/501100011033/projects and FEDER Una manera de hacer Europa. Authors thank the electron microscopy CAI center of UCM. Authors also thank the Generalitat Valenciana for CIAICO/2021/094.

1 scheme, 2 tables, 7 figures.-- Supplementary material available., In the present article, gamma-valerolactone has been obtained from levulinic acid with a yield exceeding 25% using very mild conditions without feeding hydrogen (30 degrees C, atmospheric pressure, water as the hydrogen source). The overall reaction conducted is a two-step process: first, a redox reaction involving the oxidation of metallic Zn to ZnO for in situ hydrogen production through the water splitting reaction and, second, a catalytic reaction involving Ni-supported catalysts for the production of gamma-valerolactone from levulinic acid. Ni active sites have been supported on sepiolite, an abundant and cheap material. The nickel particle size has been demonstrated to be a parameter of paramount importance determining the catalytic activity, since the best catalytic performance is obtained with the smallest Ni nanoparticles. This combination of Zn and Ni supported on sepiolite shows a good catalytic stability after three catalytic runs., Authors from UCM thank MINECO (MAT2017-84118-C2-2-R project) and UCM CAI center of EM. Authors from UV thank MINECO (MAT2017-84118-C2-1-R project) and FEDER for funding. A. G. thanks MINECO for the pre-doctoral grant.

The study for the production of gamma-valerolactone from furfural in one-pot has been carried out using ZrO2 supported on silica spheres. The catalysts synthesized were characterized by XRD, UV-vis, HR-TEM, N-2 adsorption, IR, pyridine adsorption-IR and NH3-TPD in order to determine their physicochemical characteristics. Both, Lewis and Bronsted acid sites are necessary to produce gamma-valerolactone from furfural, because they are involved in different steps of the reaction. Accordingly, a reaction mechanism has been proposed. Lewis acid sites of ZrO2 interacting with the -OH surface groups of the siliceous spheres can generate Bronsted acid sites in the supported Zr catalysts, which are absent in both pure ZrO2 and the silica spheres. Then, by controlling the amount of Zr in the supported catalysts, the relative amount of Lewis and Bronsted acid sites can be optimized to obtain the highest yields to gamma-valerolactone. The Zr-loading of the optimal supported catalyst was ca. 7 wt% Zr, which reached a gamma-valerolactone yield of 72.4 % after 8 h at 180 C using 2-propanol as a solvent and hydrogen donor.

13 figures, 7 tables.-- © 2021. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0, Ni-based catalysts supported on sepiolite were synthesized by different preparation procedures for the production of γ-valerolactone from levulinic acid and its esters (methyl levulinate and ethyl levulinate). The optimal performance was related to the formation of tiny nickel particles. Interestingly, the reaction conditions significantly influence the reactivity of the substrates. The catalytic performance of the optimal Ni/sepiolite catalyst was compared with two catalysts of ruthenium (supported on γ-alumina or sepiolite). In all cases, the production of γ-valerolactone depends on both the substrate employed and the reaction media. Overall, the preferred reaction media using the Ni-catalyst is 2-propanol whereas pressurized hydrogen in water is the best alternative for Ru-catalysts. In both cases, a reasonable stability has been observed after 3 cycles. Finally, the use of metallic Zn in an aqueous medium to provide hydrogen could not be considered as an appropriate option due to the lack of a stable behaviour., Authors from UCM thank MINECO(MAT2017-84118-C2-2-R project) and UCM CAI center of EM. Authors from UV thank MINECO (MAT2017-84118-C2-1-R project) and FEDER for funding. A.G. thanks MINECO for the pre-doctoral grant.

Isobaric vapor–liquid equilibria for the 1-propanol + 1-ethyl-3-methylimidazolium dicyanamide ([emim [DCA] binary system and for the 1-propanol + water + [emim] [DCA] ternary system have been obtained at 100 kPa using a recirculating still. The electrolyte nonrandom two-liquid (e-NRTL) model was used for fitting successfully the experimental data. The effect of [emim][DCA] on the 1-propanol + water system has been compared with that produced by other ionic liquids reported in the literature. From the results, [emim][DCA] appears as a potential entrainer for the extractive distillation of this solvent mixture, causing the azeotrope to disappear at 100 kPa when the ionic liquid mole fraction is greater than 0.33.

Isobaric vapor–liquid equilibria for the binary systems 2-propanol + water, 2-propanol + 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]), and water + [emim][DCA] as well as the vapor–liquid equilibria for the 2-propanol + water + [emim][DCA] ternary system have been obtained at 100 kPa using a recirculating still. The electrolyte nonrandom two-liquid (e-NRTL) model was used for fitting successfully the experimental data. The effect of [emim][DCA] on the 2-propanol + water system has been compared with that produced by other ionic liquids reported in the literature. From the results, [emim][DCA] appears as a good entrainer for the extractive distillation of this solvent mixture, causing the azeotrope to disappear at 100 kPa when the ionic liquid mole fraction is greater than 0.085.

[EN] There is a need for on-purpose propene production technologies beyond energy-intensive steam cracking. Hexene is a compound with limited value that can be found in several streams in the refinery and can readily crack on zeolites at lower temperatures and shorter contact times than those used for cracking alkanes. Cracking over ZSM-5 zeolite yields high selectivity to light olefins. These results are improved by Theta-1 zeolite, which can yield a remarkable propene molar selectivity of 180% (90 wt%) at 90% conversion, close to the maximum thermodynamic yield. Moreover, crystal engineering allowed its TOF to increase by more than 50%. Based on these results we also identified some prospective applications of Theta-1 zeolite as a catalyst for an integrated process directed to maximize propene., Financial support by the Ministerio de Economia y Competitividad of Spain (MINECO) through the project CTQ2015-70126-R is gratefully acknowledged. V. Blay thanks the support from the Valencian Ministry of Education. The authors thank Costa Lau for creating the graphical abstract.

Densities, speeds of sound, viscosities and refractive indices of two binary systems 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] + methanol and 1-ethyl-3-methylimidazolium tetrafluoroborate [emim][BF4] + methanol, as well as of all pure components, have been measured covering the whole range of compositions at T = (278.15 to 318.15) K and p = 101 kPa. From this data, excess molar volumes, excess isentropic compressibilities, viscosity deviations and refractive index deviations were calculated and fitted to extended versions of the Redlich–Kister equation. Estimated coefficients of these equations taking into account the dependence on composition and temperature simultaneously were also presented.

In this work, densities and sound velocities of three ionic liquids, 3-butyl-1-ethylimidazolium trifluoromethanesulfonate, 3-butyl-1-methylimidazolium trifluoromethanesulfonate, and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, and their binary mixtures with water have been obtained at p = (101 ± 2) kPa and T = (278.15 to 338.15) K, covering the whole range of concentration. The isentropic compressibility and molar isentropic compression of pure components and mixtures have been calculated using the Newton–Laplace equation. Moreover, the excess molar volume and excess molar isentropic compression of mixtures have been then determined, and they have been fitted to temperature and composition by an extended Redlich–Kister equation. Optimal fitting parameters have been reported.

Isobaric vapor–liquid equilibria (VLE) for the ternary system acetone + methanol +1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) as well as the two solvent + IL binary systems have been obtained at 100 kPa using a recirculating still. The addition of [emim][DCA] to the solvent mixture produced a salting-out effect greater than that produced by other ionic liquids, showing that this ionic liquid is, until now, the best IL tested as an entrainer for the extractive distillation of the acetone + methanol mixtures, causing the azeotrope to disappear for an ionic liquid mole fraction as low as 0.031, at 100 kPa. This behavior can be explained on the basis of the influence of the IL concentration on the activity coefficient of each solvent in the binary mixtures. The electrolyte nonrandom two-liquid (NRTL) model was used for fitting successfully the experimental data.

Isobaric vapor–liquid equilibria (VLE) for the binary systems ethanol + 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) and water + [emim][DCA] as well as the VLE for the ternary system ethanol + water + [emim][DCA] have been obtained at 100 kPa using a recirculating still. The effect of [emim][DCA] on the ethanol + water system has been compared with that produced by another ionic liquid reported in the literature on the basis of the variation of solvent activity coefficients in ionic liquid (IL) + molecular solvent binary systems. From the results, [emim][DCA] appears as one of the best entrainers for the extractive distillation of the ethanol + water mixtures, causing the azeotrope to disappear at 100 kPa for ionic liquid mole fractions as low as 0.019. The experimental data were fitted with the Mock's electrolyte nonrandom two-liquid (NRTL) model, with a good agreement.

Isobaric vapor–liquid equilibria (VLE) for the 1-propanol + 1-butyl-3-ethylimidazolium trifluoromethanesulfonate ([beim][triflate]), water + [beim][triflate], 1-propanol + 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([bmpyr][triflate]), and water + [bmpyr][triflate] binary systems, as well as the VLE for the 1-propanol + water + [beim][triflate] and 1-propanol + water + [bmpyr][triflate] ternary systems have been obtained at 100 kPa using a recirculating still. The salting-out effect on the 1-propanol produced by the [bmpyr][triflate] was stronger than that produced by the [beim][triflate], although for the IL concentrations used in this study the effect was not enough to break the azeotrope, unlike of that produced by the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]). The electrolyte nonrandom two-liquid (NRTL) model was used for fitting successfully the experimental data.

Refractive indices were determined for four different ionic liquid + water binary systems, from (288.15 to 338.15) K, and covering the entire composition range. The four ionic liquids used were 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 3-butyl-1-ethylimidazolium trifluoromethanesulfonate, 3-butyl-1-methylimidazolium trifluoromethanesulfonate, and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, all of them being completely miscible in water. From the experimental data, deviations in refractive indices, defined on a volume fraction basis, have been calculated and fitted to an extended version of the Redlich–Kister equation. The behavior of the deviations in refractive indices with composition, temperature, and size of the anion of ionic liquid has been analyzed and compared with that presented by the excess molar volume of the same systems.

Isobaric vapor–liquid equilibria (VLE) for the binary systems acetone + 1-butyl-3-ethylimidazolium trifluoromethanesulfonate ([beim][triflate]), methanol + [beim][triflate], acetone + 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([bmpyr][triflate]), and methanol + [bmpyr][triflate] as well as the VLE for the acetone + methanol + [beim][triflate] and acetone + methanol + [bmpyr][triflate] ternary systems have been obtained at 100 kPa using a recirculating still. The addition of both ionic liquids to the solvent mixtures produced an important salting-out effect, and the azeotrope tended to disappear for small amounts of ionic liquid. The experimental binary data sets were independently fitted with the electrolyte nonrandom two-liquid (NRTL) model, and the parameters of the Mock's model were estimated for each binary system. These parameters were used to predict the ternary VLE, which agreed very well with the experimental ones.

Isobaric vapor−liquid equilibria (VLE) for the ethanol + water + [emim][triflate] ternary system have been obtained at 100 kPa using a recirculating still. The ethanol + water binary system was also obtained. Furthermore, data were simulated with the Mock’s electrolyte nonrandom two-liquid (NRTL) model, using the solvent−solvent interaction parameters obtained from VLE data of the ethanol + water system and taking the solvent−ionic liquid (IL) interaction parameters for the other binary systems from previous works. The agreement between experimental and calculated data is very good, showing the predictive capacity of the model. The addition of [emim][triflate] produces the disappearance of the ethanol + water azeotrope when the mole fraction of ionic liquid in the liquid phase is greater than 0.023 at 100 kPa. The effect of [emim][triflate] on the ethanol + water system has been compared with that produced by other ionic liquids reported in the literature.

Isobaric vapor−liquid equilibria for the binary system chloroform + methanol as well as the vapor−liquid equilibria for the chloroform + methanol + [emim][triflate] ternary system have been obtained at 100 kPa using a recirculating still. The ternary ionic liquid (IL) system presents an immiscibility zone at high chloroform composition, which increases with the temperature. Liquid−liquid equilibria for this system have also been determined. The measured ternary vapor−liquid equilibrium data were correlated using the Mock’s electrolyte nonrandom two-liquid (NRTL) model which reproduces reasonably well the experimental values and predicts the total disappearance of the azeotrope when the mole fraction of ionic liquid in the liquid phase is 0.25. The immiscibility does not affect the use of [emim][triflate] as the entrainer for the complete chloroform + methanol separation.

Isobaric vapor−liquid equilibria for the binary systems 1-propanol + water, 1-propanol + 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]), and water + [emim][triflate] as well as the vapor−liquid equilibria for the 1-propanol + water + [emim][triflate] ternary system have been obtained at 100 kPa using a recirculating still. Electrolyte NRTL fitting parameters for the 1-propanol + water and water + [emim][triflate] systems were calculated. The measured ternary data were correlated using Mock’s electrolyte NRTL model which reproduces reasonably well the experimental values. The results show that the addition of [emim][triflate] to 1-propanol + water produced an important salting-out effect, and the model predicts that at 100 kPa the azeotrope disappears when the mole fraction of ionic liquid in the liquid phase is greater than 0.34.

Isobaric vapor−liquid equilibria for the binary systems ethyl acetate + ethanol, ethyl acetate + 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]), and ethanol + [emim][triflate] as well as the vapor−liquid equilibria for the ethyl acetate + ethanol + [emim][triflate] ternary system have been obtained at 100 kPa using a recirculating still. NRTL fitting parameters for the ethyl acetate + ethanol and ethanol + [emim][triflate] systems were calculated. The measured ternary data were correlated using the Mock electrolyte NRTL model, which reproduces reasonably well the experimental values. The results suggest that the addition of [emim][triflate] to the ethyl acetate + ethanol mixture produced an important salting-out effect, and the azeotrope disappears when the mole fraction of ionic liquid in the liquid phase is greater than 0.20.

The speed of sound and density of mixtures of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]) with methanol, ethanol, 1-propanol, and water, as well as of the pure components have been experimentally measured over the whole range of compositions at T = (278.15 to 338.15) K and atmospheric pressure. From these experimental data, the excess molar volume, excess isentropic compressibility, and excess speed of sound have been calculated and fitted to an extended version of the Redlich−Kister equation, which takes into account the dependence on composition and temperature simultaneously. The Prigogine−Flory−Patterson theory has also been used to explain the behavior of these systems.

An extended dual kinetic model allows to fit the n-heptane cracking results working in a wide range of reaction conditions. The duality of the model is provided by the contribution of monomolecular and bimolecular cracking mechanisms. It takes into account the role played by the olefins formed on the global cracking or added within the feed. Furthermore by means of this model and the kinetic parameters obtained when cracking n-heptane on ZSM-5, it has been observed that, while some characterization techniques show a homogeneous zeolite surface from the point of view of the active sites, rigorous kinetic experiments point to the possibility that the reactant sees a heterogeneous surface with, at least, two groups of cracking active sites. Those differentiated active sites give different cracking rates and different activation energies for the process and, in the case of ZSM-5, could be assimilated to sites pointing to the 10R channels and sites pointing into the crossing of the 10R channels, mainly due to differences in kid site location and confinement effects. (C) 2015 Elsevier Inc. All rights reserved., Financial support by the Ministerio de Economia y Competitividad of Spain (MINECO) [Programa Estatal (Project MAT2012-31657) and Programa Consolider-Ingenio 2010 (Project MULTICAT)] is gratefully acknowledged.

Isobaric vapor–liquid equilibria for the ternary system acetone + methanol + lithium nitrate have been measured at 100 kPa using a recirculating still. The addition of lithium nitrate to the solvent mixture produced an important salting-out effect and the azeotrope tended to disappear for small contents of salt. The experimental data sets were fitted with the electrolyte NRTL model and the parameters of the Mock's model were estimated. These parameters were used to predict the ternary vapor–liquid equilibrium which agreed well with the experimental one.

Densities of 1-butyl-3-methylimidazolium octylsulfate ([bmim][OcOSO3]) solutions in water and 1-propanol have been measured with an oscillating-tube densimeter at temperatures from 278.15 K to 328.15 K. From these densities, apparent molar volumes Vϕ of [bmim][OcOSO3] in both solvents have been calculated, and its dependence on the molality has been treated with the Redlich and Meyer equation. Debye–Huckel limiting slopes for 1-propanol at working temperatures have been calculated, and apparent molar volumes of [bmim][OcOSO3] at infinite dilution V ϕ ∘ in both solvents have been evaluated. The partial molar volume at infinite dilution of [bmim][OcOSO3] in water is higher than in 1-propanol and augments when the temperature augments. On the other hand, the partial molar volume at infinite dilution of [bmim][OcOSO3] in 1-propanol decreases when the temperature augments.

Isobaric vapor−liquid equilibria have been obtained for the systems tetrachloroethylene + 1-pentanol, tetrachloroethylene + 3-methyl-1-butanol, and tetrachloroethylene + 2-methyl-1-butanol, using a...

Isobaric vapor–liquid equilibria (VLE) have been obtained for the systems trichloroethylene+1-pentanol, trichloroethylene+2-methyl-1-butanol and trichloroethylene+3-methyl-1-butanol at 100 kPa using a dynamic still. The experimental error in temperature is ±0.1 K, in pressure ±0.1 kPa, and in the liquid and vapor mole fraction ±0.001. The three systems satisfy the point-to-point thermodynamic consistency test. All the systems show positive deviations from ideality. The data have been correlated with the Margules, van Laar, Wilson, NRTL and UNIQUAC equations.

Isobaric vapor–liquid equilibria have been obtained for the systems 3-methyl-1-butanol+chlorobenzene, 3-methyl-2-butanol+chlorobenzene and 2-methyl-2-butanol+chlorobenzene at 100 kPa, using a dynamic still. The experimental error in temperature is ±0.1 K, in pressure ±0.1 kPa, and in the liquid and vapor mole fraction ±0.001. The three systems satisfy the point-to-point thermodynamic consistency test. All the systems show positive deviations from ideality. The data have been correlated with the Margules, Van Laar, Wilson, NRTL and UNIQUAC equations.

n-heptane cracking has been carried out for very short time periods on an established reaction mechanism which includes the following group of stream reactions on different zeolites: Initiation reactions (protolytic cracking), charge isomerization, chain isomerization, hydride transfer, β-scission–alkylation, desorption–adsorption, and hydrogen transfer–cyclization. It has been observed that a given experimental distribution of products can be explained by more than just one reaction scheme. This does not allow one to clearly distinguish the fraction of reactant which disappears via monomolecular initiation reactions with respect to bimolecular hydride transfer reactions.

Isobaric vapor−liquid equilibria were obtained for 1-butanol + chlorobenzene and for 2-butanol + chlorobenzene systems at 20 and 100 kPa using a dynamic still. The experimental error in temperature was ±0.1 K, in pressure ±0.01 kPa and ±0.1 kPa for the experiments carried out at 20 and 100 kPa, respectively, and in liquid and vapor composition ±0.001. The two systems satisfy the point-to-point thermodynamic consistency test. Both systems show a positive deviation from ideality. The data were correlated with the Wilson equation.

Steam catalytic cracking of naphtha in smaller FCC units can be considered an option to produce more ethene and propene. These units will operate at high reaction temperatures and in the presence of steam. The profitability of these units could be improved with the use of new catalysts with higher activity and hydrothermal stability, without compromising the selectivity to light olefins. We have explored the possibilities of IM-5 zeolite for high temperature steam catalytic cracking (SCC) of a naphtha, as an alternative to commonly used ZSM-5 zeolite. So, we compare the catalytic activity, the effect of operating variables of the process and the yields of interest products between the two zeolites, the IM-5 zeolite and the best of ZSM-5 zeolites studied previously for SCC reaction. Furthermore, we study post-synthesis treatment of zeolite with phosphorous containing precursors to enhance the hydrothermal stability, and the effect of it on the catalytic activity and the yield of products. It can be seen as the use of the zeolite proposal improve the catalytic activity with respect to the best of ZSM-5 zeolite in SCC process, without compromising the yield to products of interest. Furthermore, the incorporation of phosphorous has a large effect on hydrothermal stability of zeolite, showing this zeolite as an important competitor to the ZSM-5 zeolite for steam catalytic cracking of naphtha., Financial support by the Ministerio de Ciencia e Innovacion of Spain (MICINN) [Programa Nacional (Project MAT2006-14274-C02-01) and Programa Consolider-Ingenio 2010 (Project MULTICAT)] is gratefully acknowledged.

Cracking of C 7 , C 10 , C 12 and C 14 n-alkanes, over USY, Beta and ZSM-5 zeolites was carried out in a reaction system which allows to obtain instantaneous conversions at very short times on stream. With this system the influence of operation variables, chain length of the paraffin fed, and catalyst structure on product selectivity was established. Positive and negative effects of catalyst decay on product selectivity were obtained, and this behaviour could be simulated by using a deactivation model in which the rate of deactivation depends on the product concentration. It was observed that olefin/paraffin, branched/normal paraffin, branched/normal olefin ratios and aromatic selectivities are affected by chain length, conversion level, and time on stream. Their evolution was explained by taking into account bimolecular reactions of hydrogen and hydride transfer, and the effect of deactivation at very short times on stream, similar to those in FCC units, could be determined. Furthermore, the catalyst structure showed an significant effect on space demanding reactions, such as bimolecular ones. The importance of that effect follows the order USY > Beta > ZSM-5 .

Isobaric vapor−liquid equilibria were obtained for tetrachloroethylene + 1-propanol and +2-propanol systems at 20 and 100 kPa using a dynamic still. The experimental error in temperature was ±0.1 K, in pressure ±0.01 kPa and ±0.1 kPa for the experiments carried out at 20 and 100 kPa, respectively, and in liquid and vapor composition 0.001. The two systems satisfy the point-to-point thermodynamic consistency test. Both systems show a positive deviation from ideality. The data were well correlated with the Wilson equation.

One option to produce more ethene and propene can be to crack naphtha type fractions in dedicated smaller FCC units. We present here the results obtained for high temperature steam catalytic cracking (SCC) of a representative naphtha product (n-heptane) with ZSM-5. It has been found that under those conditions the presence of steam produces an irreversible dealumination of the zeolite as well as a reversible deactivation due to the interaction of water with active sites with a negative effect on protolytic cracking. A kinetic decay model that takes into account the two phenomena has been developed. The apparent activation energy is lower in the presence of steam. It appears that whilst the presence of steam is vital when processing heavy feeds to achieve a better feed dispersion and a more effective catalytic cracking in conventional fluid catalytic cracking (FCC) units, in the case of steam catalytic cracking of naphtha (n-heptane) the presence of steam has a negative effect on the final performance of the catalyst. On the other hand, whilst steam does not modify ethene and propene selectivity, significantly decreases H 2 and CH 4 formation, as well as formation of potential coke precursors., Financial support by the Ministerio de Ciencia e Innovacion of Spain (MICINN) (Project MAT2006-14274-C02-01) and Consolider-Ingenio 2010 (Project MULTICAT) is gratefully acknowledged.

In order to increase ethene and propene, naphtha steam catalytic cracking has been considered. The cracking of C 5-C 12 n-alkanes with ZSM-5 has been studied in absence and in presence of steam and the influence of the operation variables was studied. Irreversible catalyst deactivation by dealumination also occurs in the reactor when the cracking is carried out in the presence of steam. To diminish steam deactivation, the influence of zeolite Si/Al framework and a postsynthesis treatment by phosphorous have been studied and optimized. Much more stable catalyst can be achieved that result in an increase in activity without penalty for production of ethene and propene., Financial support by the Ministerio de Ciencia e Innovacion of Spain (MICINN) (Project MAT2006-14274-C02-01) and by Consolider-Ingenio 2010 (Project MULTICAT) is gratefully acknowledged.

Kinetic determinations of the cracking and catalytic decay of n-heptane, n-decane, n-dodecane and n-tetradecane have been carried out on USY, Beta and ZSM-5 zeolites by means of an experimental set which allows to take samples of products coming out from the reactor at very short time on stream. The influence of the zeolite properties on the catalytic activity and catalyst decay has been obtained. By studying the evolution of the rate constants with the number of carbon atoms in the n-alkanes it has been found that the existence of a PCP cracking mechanism would be consistent with the observed evolution.

Long-chain alkyl aromatics are important precursors for FCC gasoline. It is well known that for short-chain alkyl aromatics like cumene the dominant cracking process is simple alkyl aryl cleavage. In contrast we have found that for long-chain alkyl aromatics like 1-phenylheptane, cracking over in situ USY catalysts is much more complex. Cracking in a long alkyl side chain results in a carbenium ion that isomerizes easily and gives self-alkylation of the aromatic ring. Self-alkylation produces coke precursors and heavy gasoline aromatics. Product selectivities vary with zeolite unit cell size in ways that are rationalized on the basis of decreasing acid site density and zeolite adsorption properties.

Long-chain alkyl aromatics are important precursors for FCC gasoline. It is well known that for short-chain alkyl aromatics like cumene the dominant cracking process is simple alkyl aryl cleavage. In contrast we have found that for long-chain alkyl aromatics like 1-phenylheptane, cracking over in situ USY catalysts is much more complex. Cracking in a long alkyl side chain results in a carbenium ion that isomerizes easily and gives self-alkylation of the aromatic ring. Self-alkylation produces coke precursors and heavy gasoline aromatics. Product selectivities vary with zeolite unit cell size in ways that are rationalized on the basis of decreasing acid site density and zeolite adsorption properties.

RESULTS: Of 7758 patients, 2597 (33.4%) were geriatric patients; mortality rate of 7.4% and tracheostomy rate of 1.9%. 15% received PMC with a 16.2% mortality rate. 65.8% of geriatric patients with head injuries received PMC. Patients with PMC: 5.1% underwent tracheostomy; mortality 15%. One with PMC and tracheostomy went to hospice; discharge was LTAC ( 70%), inpatient rehab (IPR; 10%).5161 were non-geriatric patients; mortality rate of 2.3% and tracheostomy rate of 2.9% (p