Gino V. Baron

An Amine-Functionalized MIL-53 Metal−Organic Framework with Large Separation Power for CO2 and CH4

Functionalizing the well-known MIL-53(Al) metal-organic framework with amino groups increases its selectivity in CO(2)/CH(4) separations by orders of magnitude while maintaining a very high capacity for CO(2) capture.

Pore-filling-dependent selectivity effects in the vapor-phase separation of xylene isomers on the metal-organic framework MIL-47.

Vapor-phase adsorption and separation of the C8 alkylaromatic components p-xylene, m-xylene, o-xylene, and ethylbenzene on the metal-organic framework MIL-47 have been studied. Low coverage Henry adsorption constants and adsorption enthalpies were determined using the pulse chromatographic technique at temperatures between 230 and 290 degrees C. The four C8 alkylaromatic components have comparable Henry constants and adsorption enthalpies. Adsorption isotherms of the pure components were determined using the gravimetric technique at 70, 110, and 150 degrees C. The adsorption capacity and steepness of the isotherms differs among the components and are strongly temperature dependent. Breakthrough experiments with several binary mixtures were performed at 70-150 degrees C and varying total hydrocarbon pressure from 0.0004 to 0.05 bar. Separation of the different isomers could be achieved. In general, it was found that the adsorption selectivity increases with increasing partial pressure or degree of pore filling. The separation at a high degree of pore filling in the vapor phase is a result of differences in packing modes of the C8 alkylaromatic components in the pores of MIL-47.

Biobutanol Separation with the Metal–Organic Framework ZIF‐8

Bioalcohols, such as bioethanol and biobutanol, are a promising alternative to petroleum-based chemicals. As a fuel, biobutanol has superior properties compared to bioethanol, including a higher energy density and a lower volatility. A major challenge in the economical production of biobutanol as chemical or fuel is its separation from the aqueous medium in which it is produced by the fermentation of biomass. Given the low concentration of the alcohols in the fermentation broth, separation of the butanol fraction via distillation would be energyand cost-intensive. Among alternative separation methods to recover butanol from fermentation broth, adsorption has been identified as the most energy-efficient technique. This requires adsorbents that, besides a high adsorption capacity and stability, have a high affinity towards alcohols (typically, the final butanol concentration is at most 20 g L ) and a low affinity for water. Typical adsorbents (i.e. , most zeolites, silica, and alumina) have a high preference to water and so are not suitable for this particular application. Oudshoorn et al. reported that among the commercially available hydrophobic zeolites, silicalitetype zeolites are the most selective for alcohols, but their adsorption capacity remains low. Although active carbon selectively adsorbs alcohols from water, the recovery of adsorbed alcohols is problematic. Metal–organic frameworks (MOFs) offer new opportunities in adsorption technology, with unprecedented capacities and chemical and structural tunability. Herein, it is demonstrated that the MOF ZIF-8, a member of the zeolitic imidazolate framework (ZIF) family, has promising features for the production of pure biobutanol from its fermentation medium. ZIFs contain tetrahedral Zn atoms linked by imidazolate ligands. A large variety of zeolite-like structures can be obtained by modification of the ligands. ZIFs offer high hydrothermal, chemical, and thermal stabilities. ZIF-8, discovered by Huang et al. , crystallizes into the zeolite sodalite topology, generating a resistant structure with cages of 12.5 connected via hexagonal windows of 3.3 . (Figure S2). Adsorption isotherms on ZIF-8 have been reported for Ar, CO2, CH4, N2, C2H6, C2H4, and H2, and also for longer alkanes, alkenes, and organic compounds. b, 7] Molecular simulations have been used to identify the adsorption sites of H2, N2, and CH4. [8] Selective ZIF-8-membranes have been designed, and their permeability for light gasses has been investigated. 9] ZIF-8 shows an only very low [a] J. Cousin Saint Remi, T. R my, V. Van Hunskerken, S. van de Perre, T. Duerinck, Prof. Dr. G. V. Baron, Prof. Dr. J. F. M. Denayer Department of Chemical Engineering Vrije Universiteit Brussel Pleinlaan 2, 1050 Brussel (Belgium) Fax: (+ 32) 2 629 17 98 E-mail : joeri.denayer@vub.ac.be [b] Dr. M. Maes, Prof. Dr. D. De Vos, Dr. E. Gobechiya, Prof. Dr. C. E. A. Kirschhock Centre for Surface Chemistry and Catalysis Katholieke Universiteit Leuven Kasteelpark Arenberg 23, 3001 Heverlee (Belgium) Supporting Information for this article is available on the WWW under http://dx.doi.org/10.1002/cssc.201100261. Figure 1. Vapor-phase adsorption on ZIF-8. Full symbols: adsorption; open symbols: desorption. a) Adsorption isotherms at 50 8C. b) Adsorption capacity at 50 8C. c) Butanol isotherms at varying temperature. d) Isosteric heat of adsorption as a function of pore filling.

Evidences for pore mouth and key–lock catalysis in hydroisomerization of long n-alkanes over 10-ring tubular pore bifunctional zeolites

Abstract The evidence for the pore mouth catalysis model for n-alkane methylbranching on Pt/H-ZSM-22 hydroisomerization catalyst is reviewed. It is based on adsorption equilibria at catalytic temperatures determined using tracer and perturbation chromatography, reaction product distributions obtained with nC8–nC24 n-alkanes and rival model screening for catalytic conversions. In the Henry regime, methylbranched isomers have lower adsorption entropy and enthalpy compared to n-alkanes explained by the enhanced rotational and translational freedom of methyl and methylene groups positioned outside the pore interacting with the external surface. Adsorption isotherms for isoalkanes are in agreement with dual site adsorption in pore mouths and on external surfaces, respectively. The hydroisomerization can be modeled with a bifunctional reaction scheme and adsorption on the external crystal surfaces and pore mouths. The selectivity for 2-methylbranching reflects the optimum van der Waals interaction of the n-alkane with the zeolite pore and methylbranching in that part of the chain that is located outside the first 10-ring of the zeolite pore to facilitate desorption. Very long n-alkanes (C12+) exhibit key–lock adsorptions and penetrate simultaneously with their two ends into two different pores. Key–lock physisorption leads to branching at more central C atom positions.

GEL ENTRAPMENT AND MICRO-ENCAPSULATION: METHODS, APPLICATIONS AND ENGINEERING PRINCIPLES

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Adsorption and Separation of Light Gases on an Amino-Functionalized Metal–Organic Framework: An Adsorption and In Situ XRD Study

The NH(2)-MIL-53(Al) metal-organic framework was studied for its use in the separation of CO(2) from CH(4), H(2), N(2)C(2)H(6) and C(3)H(8) mixtures. Isotherms of methane, ethane, propane, hydrogen, nitrogen, and CO(2) were measured. The atypical shape of these isotherms is attributed to the breathing properties of the material, in which a transition from a very narrow pore form to a narrow pore form and from a narrow pore form to a large pore form occurs, depending on the total pressure and the nature of the adsorbate, as demonstrated by in situ XRD patterns measured during adsorption. Apart from CO(2), all tested gases interacted weakly with the adsorbent. As a result, they are excluded from adsorption in the narrow pore form of the material at low pressure. CO(2) interacted much more strongly and was adsorbed in significant amounts at low pressure. This gives the material excellent properties to separate CO(2) from other gases. The separation of CO(2) from methane, nitrogen, hydrogen, or a combination of these gases has been demonstrated by breakthrough experiments using pellets of NH(2)-MIL-53(Al). The effect of total pressure (1-30 bar), gas composition, temperature (303-403 K) and contact time has been examined. In all cases, CO(2) was selectively adsorbed, whereas methane, nitrogen, and hydrogen nearly did not adsorb at all. Regeneration of the adsorbent by thermal treatment, inert purge gas stripping, and pressure swing has been demonstrated. The NH(2)-MIL-53(Al) pellets retained their selectivity and capacity for more than two years.

A novel catalytic filter for tar removal from biomass gasification gas: Improvement of the catalytic activity in presence of H2S

A 1 wt%/0.5 wt% nickel-calcium catalyst was co-precipitated inside porous filter discs using the urea method to develop a gas cleaning technique involving the combined removal of tars and particles from hot biomass gasification gas. Special attention was paid to the improvement of the resistance of the catalyst against sulphur poisoning by the H 2 S present in the gasification gas. Deactivation tests were performed on catalytic filter discs using either benzene, naphthalene or a mixture of benzene and naphthalene as tar model compounds in a simulated gasification gas containing up to 200 ppm H 2 S. At 900°C and at a filtration velocity of 2.5 cm/s, the developed catalyst formulation shows a benzene conversion of 93% (50 ppm H 2 S), 78% (100 ppm H 2 S) and 57% (200 ppm H 2 S). However, benzene is not a problematic compound concerning the utilization of biomass gasification. More important is the removal capacity of this catalytic filter disc for the problematic heavy tars like naphthalene. Subsequent deactivation tests with naphthalene and with a mixture of benzene and naphthalene as tar model compounds showed that for simulated gasification gas containing up to 100 ppm H 2 S and for a filtration velocity of 2.5 cm/s (typical value in real gas) the naphthalene conversion is 98% in both cases. As a result, the target tar conversion (>95%) was achieved in typical hot gas filtration conditions. The significant improvement over a pure nickel based catalyst by adding the appropriate amount of CaO is encouraging towards the further improvement of the sulphur tolerance of this catalyst.

Adsorption competition effects in hydroconversion of alkane mixtures on zeolites

In the present work, molecular competition effects in the hydroconversion of alkane mixtures in vapor and liquid phase were studied. The influence of the pore size was investigated by performing catalytic experiments with equimolar heptane/nonane mixtures on a series of bifunctional zeolite catalysts (Pt/H-Y, Pt/H-USY, Pt/H-Beta, Pt/H-MCM-22). Vapor phase catalytic experiments were performed at a total pressure of 4.5 bar, while a total pressure of 100 bar was applied in the liquid phase experiments. The experimental results were analyzed using a lumped adsorption-reaction model. In vapor phase, the longest chain is preferentially converted on all studied catalysts. In liquid phase, the differences in conversion rate were less pronounced. On Pt/H-MCM-22, with active pockets on the surface, and Pt/H-USY having large mesopores, the competition between short and long alkanes in liquid phase reflect the intrinsic reactivities of the reacting molecules. In zeolites with smaller pores (Pt/H-Y, Pt/H-Beta), an inversion of the reactivity order of alkanes of different chain length was observed when increasing the pressure from 4.5 bar and vapor phase to 100 bar and liquid phase. The inversion of apparent reactivity orders is due to changes in physisorption at high pressure, favoring uptake of the smallest molecules.

Effect of agitation on growth and enzyme production of Trichoderma reesei in batch fermentation

Growth, enzyme-producing activity and respiratory properties of Trichoderma reesei QM 9414 were examined under various agitation intensities. Two substrates were compared: lactose and Avicel. Pellet formation occurred at all agitation intensities for both substrates. Oxygen dependence at the lower agitation rate varied with the substrate type. With lactose as the carbon source, linear growth was observed, despite a regulation of the dissolved oxygen concentration at 30% saturation. The enzyme production was strongly affected by the agitation. At the higher agitation rates the enzyme production dropped. With Avicel as the carbon source, the production of enzymes surged as soon as the growth was limited by the hydrolysis of Avicel.Growth on Avicel, in the conditions we used, was limited by Avicel hydrolysis. Cubic growth was observed when lactose was the carbon source. A new derivation for a model of the observed cubic growth is proposed and is used to correlate growth, CO2 production and oxygen consumption in a consistent way, impossible with exponential growth models.

Adsorption of normal and branched paraffins in faujasite zeolites NaY, HY, Pt/NaY and USY

The effect of chain length and branching of paraffins (from C6 to C12) on adsorption and diffusion in zeolites NaY, Pt/NaY, HY and USY has been investigated using the chromatographic method at 275–400°C. The Henry constants of the paraffins increase exponentially with the chain length (with a factor two per extra carbon group), the heats of adsorption increase with circa 7 kJ/mol per extra carbon group. Multicomponent sorption experiments reveal that longer chains are adsorbed preferentially over shorter chains, even at higher loadings. The multicomponent adsorption can be reasonably well described by an extended Langmuir adsorption isotherm, in which the stronger adsorption of the longer chains is reflected by their higher Henry constants. The molecular shape and zeolite type within this FAU group has only a small influence on the adsorption properties. Mass transfer in the pellets as used in catalytic conditions seems to be limited by macropore diffusion, rather than by micropore diffusion, which cannot be measured with the chromatographic method. Increasing the Si/Al-ratio of the zeolite reduces the adsorption capacity, but does not influence the relative adsorption properties.