Search

The separation of layered MFI into unilamellar nanosheets in solution confirms the general validity of soft-chemical exfoliation for zeolites and allows top-down production of films with potential applications in separation and catalysis.

Furfural is a renewable lignocellulose-derived platform molecule, which can be transformed into biofuels and value-added chemicals (e.g., furfuryl alcohol and 2-methylfuran over metal-supported catalysts). Despite a number of approaches proposed for designing hydrogenation catalysts, highly selective furfural hydrogenation towards furfuryl alcohol (FA) or 2-methylfuran (2-MF) is still challenging. Here, we report on selective transformation of furfural either to FA or 2-MF achieved over zeolite BEA-supported Rh catalysts by optimizing Si/Al ratio and charge-balancing cations of the support. Among studied H- and Na-exchanged aluminosilicate BEA zeolite supports (Si/Al = 12.5; 25; 68; 150), Rh@Na-BEA catalysts lacking Bronsted and strong Lewis acidity showed enhanced selectivity towards FA (75 – 94% depending on the Si/Al ratio) at 74 – 84% conversion of furfural. In turn, selective formation of 2-MF (98% selectivity at 87% conversion) was observed over Al-rich Rh@H-BEA catalyst (Si/Al=12.5) with the highest concentration of Bronsted acid sites. Weaker adsorption of FA on Na- vs. H-form of Rh@BEA-12.5 catalyst was verified by FTIR spectroscopy and is assumed a key factor governing selective hydrogenation of furfural to FA over Rh@Na-BEA catalysts.

Nanoporous crystalline aluminosilicates, zeolites, are synthesised by solvothermal method producing three-dimensional (3D) crystals. An alternative, more controllable approach of zeolite synthesis - ADOR – can be used for preparation of isoreticular zeolites with tuneable porosity. Zeolites porosity allows their wide use as isomerisation catalysts due to their shape selectivity effects. Selective isomerisation of m-xylene towards p-xylene is an industrially important reaction due to a high demand for the latter as a substrate for terephthalic acid production. In this work, we investigated the influence of pore size (shape selectivity effect) on the isomerization of m-xylene using a system of isoreticular Al-containing zeolites. These materials, prepared by ADOR approach (UTL, IPC-7, IPC-2, IPC-6, and IPC-4) had different layers connectivity, and therefore various channel systems. We tracked the influence of the pore systems of ADOR zeolites (8- up to 14-ring channels) on the catalytic performance in gas-phase m-xylene isomerisation. We investigated the crystallinity and interlayer distances, phase purity, textural properties of prepared materials, their crystals morphology, and aluminium content. M-xylene isomerisation was carried out in a fixed-bed reactor at 350 °C. ADOR catalysts were compared with standard ZSM-5 zeolite. We show the dependence of zeolite porosity on the performance in isomerisation of m- to p-xylene. Smaller pore zeolites: IPC-4 (8- and 10-ring channels) and IPC-6 (8-, 10- and 12-ring channels) exhibited the lowest conversions, while the highest conversion and p-xylene yields were observed for IPC-2 (10- and 12-ring channels). Presence of extra-large, 14-ring channels (IPC-7 and UTL) resulted in the drop of selectivity due to the xylene disproportionation.

Titanosilicate zeolites are a prominent class of catalysts applied in various oxidation reactions, including epoxidation of alkenes. Numerous studies have been performed to understand the influence of Ti sites structure (‘open’ vs. ‘closed’) and their distribution between internal and external surface of zeolite on the catalyst performance, although the effect of Ti location in micropores of different sizes remained unrevealed. Here, we report the application of ADOR synthesis strategy for the preparation of model ‘isoreticular’ titanosilicate zeolites with the same topology but continuously tunable porosity for addressing the influence of micropore confinement on the activity and selectivity of the catalysts in alkene epoxidation reaction. A set of ‘isoreticular’ Ti-IPC-n (n = 2, 4, 6, 7) zeolites were synthesized by post-synthesis of Ti-substituted UTL germanosilicate. Structural, textural and acidic properties of the prepared catalysts were characterized by XRD, nitrogen physisorption, FTIR spectroscopy of adsorbed d3-acetonitrile, while their activity and selectivity were compared in the epoxidation of 1-hexene and cyclohexene as model linear and cyclic alkenes with hydrogen peroxide as oxidant. The obtained results confirmed the successful preparation of Ti-substituted IPC-n zeolites with similar total concentration of Ti sites (0.15–0.17 mmol/g). For both 1-hexene and cyclohexene epoxidation, the specific activity of a Ti active center (TOF) gradually decreased with the micropore size in a sequence Ti-UTL (TOF1-hexene = 126 h−1; TOFcyclohexene = 227 h−1) > Ti-IPC-7 (124; 143) > Ti-IPC-2 (124; 130) > Ti-IPC-6 (90; 67) > Ti-IPC-4 (64; 37). In line with reducing diffusion limitations of substrates and products, the site time yield of both targeted epoxides increases with increasing the size of the pores in ‘isoreticular’ zeolites reaching the maximal value for Ti-UTL (586 and 491 h−1 for 1,2-epoxyhexane and cyclohexeneoxide, respectively).

2D-to-3D transformation of layered zeolite precursors (e.g., MCM-22P, IPC-1P, pre-FER) into three-dimensional frameworks in combination with metal encapsulation has been recently shown as efficient synthetic strategy to stabilize metal clusters in a zeolite matrix. Even though, tailoring the number of acid sites in a zeolite support and its effect on the properties of thus prepared metal@zeolite materials (e.g., metal dispersion and catalytic activity) remained unrevealed. Herein, we report on the synthesis of Pd@MCM-22 catalysts via modified 2D-to-3D transformation method, which allows to achieve close to nominal loading of noble metal (e.g., 0.1, 0.3, 0.8 wt.%) by time-separation of swelling of MCM-22P layered zeolite precursor and subsequent incorporation with metal. In turn, alternating Si/Al ratio of MCM-22P (e.g., Si/Al = 15, 20, 30) enabled the preparation of Pd@MCM-22 catalysts with variable concentration of acid sites (0.28 – 0.55 mmol/g), while not affecting the Pd dispersion. Decrease in Pd dispersion with increasing metal loading was accompanied with declining catalytic activity in a model reaction of selective hydrogenation of nitro-group in 3-nitrotoluene: 0.1 wt. % Pd (dispersion = 52.6%, reaction rate = 21.2 mol·g-1Pd·h-1) > 0.3 wt. % Pd (9.6 mol·g-1Pd·h-1) > 0.8 wt. % Pd (23.2%, 3.7 mol·g-1Pd·h-1). The results of this study reveal that the reported synthesis strategy can be successfully used to confine small metal nanoparticles in a zeolite matrix while tuning its acidic characteristics for designing bifunctional metal-acidic catalysts.

Hydrogenation of nitroarenes is a catalytic reaction of high interest owing to the importance of the resulting aromatic amines in the chemical industry. Up to date, various metal@zeolite catalysts have been reported for this transformation. Herein, Pd@Beta and Pd@MWW catalysts were synthesized by ion exchange with Pd(NH3)4(NO3)2 and characterized by XRD, nitrogen sorption, ICP-OES, electron microscopy and FTIR(CO). Structural and textural analysis proved no significant changes of the zeolites after the Pd precursor was introduced. STEM images proved the uniform distribution of metal species in zeolite crystals. Average size of Pd NPs is 2.6 nm and 1.7 nm for Beta and MWW zeolites, respectively. The resulting Pd@Beta catalyst exhibited higher catalytic activity compared to Pd@MWW in the hydrogenation of nitroarenes. The electronic/steric effects of substrates and products were also investigated for both catalysts. Nitroarenes with electron-donating groups exhibit higher initial reaction rates than nitroarenes containing electron-withdrawing groups. The nitroarenes bearing functionalized groups in the ortho-position are harder to hydrogenate than corresponding meta- and para- isomers because of the steric hindrance effect.

This article demonstrates preparation of metal functionalized zeolite catalysts via a new homogeneous solution pathway enabled by the recently reported exfoliation of zeolite MWW into solution of unilamellar nanosheets. The preparation is carried out by mixing solutions of exfoliated MWW monolayers and Pt nanoparticles with initial size of ca 3 nm and isolation of such hybrid catalysts by freeze-drying. Optionally, the MWW layer solutions were purified by dialysis prior to mixing with the metal solution, which turned out to be beneficial for quality and textural characteristics. However, catalytic performance in the model reaction – 3-nitrotoluene hydrogenation, was mostly determined by the Pt level, i.e. at least 0.3%, and less affected by the apparent quality of the final zeolite support. The catalysts revealed agglomeration of the Pt nanoparticles from roughly 3 nm to between 5 and 10 nm.

Layered zeolites, especially MWW, have been used to synthesize pillared micro/mesoporous hybrids with the goal to enhance catalytic activity towards larger molecules. The critical preparation step is expansion of the interlayer space by swelling with cationic surfactants at high pH. Recently reported solutions of MWW monolayers, obtained by exfoliation of the zeolite MCM-56, can be used to prepare analogous materials by flocculation (precipitation) with surfactant solutions. This previously unavailable approach is studied in this work with both high pH (0.2 M, pH > 13.3) and lower pH (0.01 M, pH~12) solutions, and resulted in finding conditions for preparation of catalysts that can be more active than pure microporous layers (zeolite) despite large content of unreactive silica pillars. Both the high and low pH conditions afforded similar expanded surfactant-MWW composites, but their behavior differed during pillaring with TEOS. Well-defined expanded interlayer distances indicated by a low angle reflection in XRD above 3 nm d-spacing was observed only with the high alkalinity preparations. An additional benefit was observed with TEOS treatment in the presence of isopropyl alcohol leading to a product showing high catalytic activity in model alkylation reaction (mesitylene with benzyl alcohol) proceeding faster than with the pure zeolite. The products obtained under different conditions were characterized by textural methods, nitrogen adsorption and QE-TPDA, and FT-IR to investigate acid site parameters. Notably, the MCM-56 used in this work was prepared with addition of aniline as the structure-promoting agent and is the second formulation affording exfoliable MWW materials.

Zeolites with encapsulated metal nanoparticles (NPs) attract much attention due to the catalytic activity, stability and shape-selective properties of such materials in heterogeneous catalysis. One of the methods for introduction of metal NPs into the zeolite system is based on use of two dimensional (2D) layered precursors that are loaded with Pt source and consecutively transformed to three dimensional (3D) zeolites. This method can be combined with recently developed approach for zeolite synthesis; the ADOR (Assembly, Disassembly, Organization, and Reassembly) approach that is based on the 3D-2D-3D transformation of zeolites. Here, we report a synthesis of two ADOR zeolites: IPC-2 (OKO topology) and IPC-4 (PCR topology) functionalized with Pt NPs, Pt@IPC-2 and Pt@IPC-4, respectively. Pt@IPC-2 was prepared by intercalation of platinum(0)-2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetra siloxane into IPC-1P layered precursor and subsequent calcination. Pt@IPC-4 zeolite was prepared by the swelling of IPC-1P with the mixture of surfactant and Pt source. Final materials were investigated by XRD, nitrogen sorption, ICP-OES, and electron microscopy (SEM and STEM). Structural and textural analysis confirmed the successful syntheses of two ADOR zeolites. The size and distribution of Pt NPs were investigated by STEM. The platinum content was 0.34 wt% and 0.32 wt% and the average size of Pt NPs of 0.98 nm and 0.96 nm for Pt@IPC-2 and Pt@IPC-4, respectively. Pt@IPC-2 exhibited a broader range of Pt sizes due to larger pores.

Acid site strength in MWW and MFI zeolites was investigated by isotopic exchange reaction between deuterated hydroxyl groups of zeolites and ethane molecules. The course of the reaction was monitored by FT-IR spectroscopy through time changes of integral intensities of the Si(OD)Al Bronsted acid sites represented by absorption bands at 2644, 2655, and 2657 cm−1 for MFI, MWW and MCM-36 zeolite, respectively. The rate of the reaction was described by pseudo first order kinetics and acid site strength was compared using rate constants characteristic of individual zeolites at constant temperature. The exchange reaction is significantly faster over MFI zeolite compared with MWW zeolites, suggesting a higher acid strength of Bronsted sites in MFI zeolite than in MWW. In our previous study (Arean et al. Phys. Chem. Chem. Phys. 16 (2014) 10,129), we found notable discrepancy in the relation between OH group frequency shift induced by adsorption of weak base molecules like CO and N2 and the change of adsorption enthalpy of these probe molecules for MWW zeolites, which calls into question the use of frequency shifts as a measure of acidity. Our reported results based on isotopic exchange reaction rate measurement correlate with the change of the probe molecules adsorption enthalpy involved in hydrogen bonding. Therefore, we believe that enthalpy change or H/D exchange activity measurement is more reliable method for assessment of acid strength than O H frequency shift probed by a weak base adsorbed at a low temperature.

Zeolites doped with metal nanoparticles have shown the outstanding activity in many processes involving heterogeneous catalysis. The size of metal nanoparticles plays a decisive role in the performance of zeolite catalysts. However, the precise control of the size of nanoparticles is still limited. Herein, we present the synthesis of Pt-MWW zeolites with controllable nanoparticle size using a series of surfactants with different alkyl chain lengths for swelling of layered MCM-22 P. The interlayer distances of swollen materials increases with the length of the surfactant from 1.06 nm (C12OH) to 2.89 nm (C18OH). During swelling, the Pt nanoparticles were intercalated to the interlayer space of MCM-22 P. Further calcination resulted in Pt-MWW materials showing similar morphologies, textural properties and Pt content despite the differences in the initial interlayer distances. The factor that differentiated the synthesized materials was the average diameter of metal nanoparticles. As a result, the average size of Pt nanoparticles increased from 0.85 nm (MCM-22-C12OH-Pt) to 2.04 nm (MCM-22-C18OH-Pt) which is related to the length of the hydrocarbon chain of the surfactant used for the swelling process.

Since the discovery of synthetic zeolites in the early 1950 s, a significant progress has been made in the area of zeolite science. Zeolites have found widespread applications in industrial processes because of their unique porous structures and properties. In the last decades, a number of new zeolites were discovered - some of them with interesting structural features for further research. This review discusses recent advances in the synthesis, characterization, and catalytic applications of well-known 10-ring zeolites: MEL, MFI, MWW, EUO, *MRE, MTT, STF, TON and novel TUN, IMF, -SVR, MVY, JRY, JST and SFG which are among the most crystallographically complex zeolites known to date. Strategies to tailor the properties of zeolites by post-synthesis techniques to enhance the catalyst effectiveness are described and the relation among the structures, activities and selectivities is discussed.

New zeolitic frameworks can be prepared through the Assembly-Disassembly-Organisation-Reassembly (ADOR) process by exploiting the lability of Ge-O bonds in germanosilicate zeolites to control their hydrolysis. In the disassembly step, two key factors are water and germanium content, but their exact roles remain unknown. Nevertheless, we combined experimental water-vapor adsorption with first principles simulations to identify the mechanism of germanosilicate zeolite disassembly. The results showed that water vapor adsorption on UTL germanosilicate proceeds in reversible (at low partial pressures) and irreversible (at higher partial pressures) modes. Based on our ab initio molecular dynamics simulations, we related these two modes to weak physisorption at low water loading and to reactive transformations at high water loading, via collective mechanisms requiring high local water concentrations. This bimodal behavior also depends on the germanium content as high Ge-content further decreases UTL hydrolytic stability by opening up yet another low-energy disassembly pathway at high water loading. Overall, we discovered, verified and explained the mechanisms of UTL disassembly and its factors. These findings will likely be generalized to other ADORable germanosilicate zeolites and help to find the optimal protocol for the synthesis of new zeolites.

Cardanol (a mixture of phenols with C 15 aliphatic unsaturated chain in meta position, manufactured from cashew nut shell liquids) is an abundant and till now practically waste natural material. An important way leading to its utilization as a renewable source of valuable phenolic compounds is represented by olefin metathesis. Quaternary ammonium tagged Ru complex of Hoveyda-Grubbs type immobilized on SBA-15 mesoporous molecular sieve by non-covalent interactions was proved as a very efficient catalyst for cardanol metathesis under mild conditions (35 °C, toluene, 0.1 mol% of catalyst). The catalyst was used also in cross-metathesis of cardanol with alkenes (1-hexene, 1-heptene, 3-hexene, 4-octene) and unsaturated esters (methyl acrylate, 1,4-diacetoxybutene-2) under high yields of cross-metathesis products. The catalysts exhibited low leaching (from 0.2 ppm to 2.9 ppm Ru in products) and can be used in a continuous flow reactor (cumulative TON = 2500).

Homopolymerizations of 2,5-diethynylthiophene into conjugated microporous polymers by (i) chain-growth polymerization and (ii) polycyclotrimerization are described. Both methods provide nearly quantitative yields of thiophene-rich (7.6 mmol thiophene rings/g) networks with specific surface area up to 839 m2/g. The thiophene units enhance the affinity of the networks to CO2 and red-shift the UV/vis and fluorescence absorption and emission bands of the networks, respectively.

SSZ-70 is one of several layered forms of zeolite MMW obtained by direct synthesis with consecutive layers shifted by approximately ±1/3 of a unit cell in the horizontal direction (⟨110⟩), according to the recent structure solution report. Zeolite MWW is a valuable industrial alkylation catalyst and SSZ-70 itself was called by the inventors 'a successful catalytic material'. SSZ-70 shows characteristic powder X-ray diffraction pattern (XRD), containing a unique broad band with a roughly triangular shape and maximum at 8.5–9.0° 2θ (Cu Kα radiation), which can be used to distinguish SSZ-70 from the other MWW materials with different layer arrangements. This work concerns post-synthesis treatments of SSZ-70 to investigate its ability to produce more expanded structures by silylation, swelling and pillaring. Both boron- and aluminum-containing SSZ-70 were investigated. They showed the ability for interlayer expansion by swelling with cationic surfactants and were pillared with silica to produce micro/mesoporous hybrids with increased BET area. Not too surprisingly, the original unique layer stacking of SSZ-70 seems to have become more random and not distinguishable from the swollen forms of the other swellable MWW materials MCM-22 P and the monolayer MCM-56. Calcined SSZ-70 zeolites showed an unusual peak, assigned to (002) reflection, with d-spacing shorter than c-unit cell of the 3D MWW framework, which suggests collapse with formation of the so-called sub-zeolite form. Silylation resulted in different outcomes for B and Al SSZ-70 samples. The former produced interlayer expanded (IEZ) forms of B-SSZ-70 but did not show significant increase in pore volume and BET surface area. Silylation of Al-SSZ-70 did not yield the stabilized (IEZ) form but had a positive effect as it prevented the collapse to sub-zeolite upon calcination. Catalytic testing was carried out for the Al-containing SSZ-70 obtained by direct synthesis and for B-SSZ-70 activated by Al insertion. The former showed much higher concentration of Bronsted acid sites and 5 times faster conversion in a model alkylation reaction between benzyl alcohol and mesitylene. Pillared Al-SSZ-70 showed highest activity despite lower Al concentration due to silica pillars. Both silylation and pillaring had a positive effect on the activity in alkylation reaction with bulky molecules.

Zeolites loaded with metal nanoparticles (NPs) stand out for their distinct activity and selectivity as heterogeneous catalysts. However, the poor stability of metal species limits their applications. Herein, we report a novel synthetic strategy for stabilizing metal nanoparticles inside the MFI zeolite. For the first time, alkoxysilane functional imidazolium-type ionic liquids (ImILs) were used as assistant agents to protect metal precursors (Pt and Pd) against precipitation during the hydrothermal synthesis of the MFI zeolite. The positively charged imidazolium groups in ImILs interact with the negatively charged metal precursors (PtCl42−, PdCl42− etc.), while the alkoxysilane groups participate in zeolite crystallization. Scanning transmission electron microscopy images indicate that most of the Pt and Pd nanoparticles (average diameters of approximately 1.0 nm and 1.7 nm, respectively) are confined in channels or intersections of the MFI zeolite. The shape-selectivity effect on nitroarene hydrogenation over Pt@MFI_ImILs confirmed the successful encapsulation of metal NPs into the MFI matrix. The conversion of the small molecule 4-nitrotoluene is >99%, whereas the bulky 1,3-dimethyl-5-nitrobenzene shows 5.8% conversion. Simultaneously, the Pd@MFI_ImILs catalyst affords a higher reaction rate (25 mmol/s/gMe) than the impregnated Pd@MFI_Imp catalyst (9 mmol/s/gMe) in propene hydrogenation, which is ascribed to the uniform distribution of Pd nanoparticles. The ImIL-assisted synthesis strategy can be therefore successfully used to confine small metal nanoparticles in the MFI zeolite while maintaining its high catalytic activity and shape-selectivity.

Symmetric ethers can be synthesized through the acid-catalyzed self-etherification of biomass-derived alcohols. However, synthesis of asymmetric ethers via catalytic cross-etherification of alcohols is limited by poor selectivity. Herein, we developed an efficient zeolite-catalyzed one-step synthesis of valuable asymmetric cyclopentyl methyl ether (CPME) using gas-phase reaction of bio-based cyclopentanol and methanol. Among different medium- (FER, MCM-22, ZSM-5) and large-pore (BEA, MOR, USY) aluminosilicate zeolites, commercial ZSM-5 catalysts with 2D system of intersecting channels are markedly more selective to CPME. The targeted CPME was produced with a selectivity of 83 % and a yield higher than 80 % over the ZSM-5 catalysts with Si/Al ratios ranging from 15 to 40. Decrease in Si/Al ratio in ZSM-5 enhanced the conversion value, while not affecting the selectivity. FTIR study of the step-by-step adsorption of both reactants in ZSM-5 evidenced the Rideal-Eley mechanism with cyclopentanol adsorbed on acid sites. Therefore, heterogeneously catalyzed gas-phase cross-etherification of renewable cyclopentanol and methanol is a promising process for large-scale applications thanks to its mild operating conditions, high yields and selectivity when using commercial ZSM-5 zeolites as catalysts.

Ethyltoluenes (ET) synthesis via different alkylation routes; toluene with ethanol and ethylbenzene (EB) with methanol, was investigated over zeolites with three-dimensional (3D) pore system i.e. SSZ-33, TNU-9, ZSM-5, IM-5, and one-dimensional zeolite MOR in a fluidized-bed reactor in the temperature range 250–350 °C for reaction times of 5–20 s. Alkylation of toluene with ethanol provided higher yields and selectivities to ethyltoluenes over all zeolites. The maximum ET yield achieved for toluene ethylation was 13.7 wt.% using IM-5 and ZSM-5 whereas 12.5 wt.% was obtained in EB methylation over SSZ-33. SSZ-33 provided the highest ET-selectivity of ∼50% due to the combine effect of its 3D topology and 12-ring channels. In contrast to ET selectivity, p-ethyltoluene selectivity was almost the same, ∼26%, irrespective of the zeolite topology. Kinetic studies of toluene ethylation over the zeolites were conducted using power law coupled with time-on-stream deactivation model. A satisfactory correlation between experimental data and the model result was achieved. The activation energy of the various zeolites used for the alkylation of toluene to ET decreased in the order: IM-5 (58.2 kJ/mol) > SSZ-33 (39.7 kJ/mol) > TNU-9 (27.3 kJ/mol) > MOR (20.2 kJ/mol) > ZSM-5 (17.0 kJ/mol) which was explained by different acid strength and nature of the zeolites.

Highly active olefin metathesis catalysts were prepared by thermal spreading MoO3 and/or MoO2(acac)2 on MWW zeolites (MCM-22, delaminated MCM-56) and on two-dimensional MFI (all in NH4 + form). The catalysts‘ activities were tested in the metathesis of neat 1-octene (as an example of a longer chain olefin) at 40 °C. Catalysts with 6 wt % or 5 wt % of Mo were used. The acidic character of the supports had an important effect on both the catalyst activity and selectivity. The catalyst activity increases in the order 6MoO3/HZSM-5(25) (Si/Al = 25) << 6MoO2(acac)2/MCM-22(70) < 6MoO3/2D-MFI(26) < 6MoO3/MCM-56(13) < 6MoO3/MCM-22(28) reflecting both the enhancing effect of the supports‘ acidity and accessibility of the catalytic species on the surface. On the other hand the supports‘ acidity decreases the selectivity to the main metathesis product C14 due to an acid-catalyzed double bond isomerization (followed by cross metathesis) and oligomerization. 6MoO3/2D-MFI(26) with a lower concentration of the acidic centres resulting in catalysts of moderate activity but with the highest selectivity.

TS-1-based catalysts with different textural features, namely layered TS-1, pillared TS-1, and Ti-pillared TS-1 as well as mesoporous TS-1, were investigated in the liquid-phase epoxidation of methyl oleate as a model compound for plant oil-derived substrates with hydrogen peroxide at 50 °C. While over the TS-1-based catalysts, except Ti-pillared TS-1, an epoxide selectivity of up to 93% is achieved, layered and pillared TS-1 are the most active (the amounts of methyl oleate converted after 5 h per number of Ti-sites are 4.64 mol mol−1 and 4.68 mol mol−1) with an efficiency for H2O2 conversion to the epoxide of 27%. Mesoporous TS-1 and conventional microporous TS-1 exhibit a similar activity (3.64 mol mol−1vs. 3.37 mol mol−1), whereas the mesoporous catalyst most efficiently utilizes H2O2 (39% efficiency). The lowest catalytic activity (0.82 mol mol−1), epoxide selectivity as well as H2O2 efficiency are observed over Ti-MCM-36, possessing mainly octahedrally coordinated Ti-sites. The results demonstrate the importance of accessibility of Ti-sites at external crystal surfaces within layered and pillared TS-1, significantly increasing the epoxidation activity with respect to the number of Ti-atoms present in the catalysts.

Three-dimensional 10-ring zeolites TUN, IMF, –SVR, MFI and MEL were investigated as for their acid properties, adsorption of 2,2-dimethylbutane and in toluene disproportionation and its alkylation with isopropyl alcohol. The results were compared against zeolite *SFV, the structure of which consists mainly of MEL zeolite with some additional 12-ring channel system. With exception of –SVR synthesized with high Si/Al ratio, all other zeolites provided Si/Al ratios in a narrow region. Novel zeolites TUN, IMF, and –SVR exhibited higher conversions than MFI and MEL in toluene alkylation. TUN and IMF were substantially more active in toluene disproportionation indicating less diffusion restrictions of channel structure on the disproportionation reaction. *SFV showed a similar catalytic behavior to MEL with much lower selectivity to p-xylene and p-cymene. This could indicate that both toluene disproportionation and alkylation proceed in reaction space of *SFV being similar to those of MFI and MEL. *SFV and TUN exhibited much faster adsorption of 2,2-dimethylbutane than MFI, MEL, IMF, and –SVR. It was concluded that the presence of some larger transport pores in *SFV than in other zeolites is responsible for fast adsorption of 2,2-dimethylbutane and transport of products resulting in a low selectivity to p-xylene and p-cymene.

We report the synthesis of conjugated highly cross-linked polyacetylene-type networks with a high content of functional groups (–CH2OH, –NO2, –Ph2N, content up to 3.9 mmol/g) via a chain-growth copolymerization of either 1,4-diethynylbenzene or 4,4′-diethynylbiphenyl with functionalized mono- and diethynylbenzenes. The backbone of the networks consists of substituted polyene main chains that are cross-linked by arylene links. The optimized combinations of comonomers in the feed provide functionalized networks with a Brunauer–Emmett–Teller specific surface area up to 667 m2/g and enhanced affinity for CO2 adsorption (compared to the non-functionalized hydrocarbon networks of the same type). The dependence of the specific surface area of the networks on the size and architecture of the comonomers used for the synthesis is discussed in the paper. The reported networks can be classified into the group of conjugated microporous polymers (CMPs). Contrary to the CMPs synthesized by step-growth couplings, significantly lower average comonomer functionality in the feed (f = 1.5–2.0) is sufficient for the high specific surface area to be achieved in the reported polyacetylene-type CMPs.

Desilication conditions (concentration of NaOH, duration of the treatment) of SSZ-33 zeolite (CON topology) were investigated in respect to the textural and acidic properties of the obtained materials. As-synthesized borosilicate SSZ-33 was transformed by isomorphous substitution to Al-form. The alkaline treatment of Al-SSZ-33 zeolite resulted in the formation of mesopores and enhanced accessibility of Bronsted acid sites. The increase in the mesopore volume and also changes in the concentration of acid sites depends mainly on the concentration (pH) of the treatment. Simultaneously, the increase in the pH of the alkaline solution led to the slight increase in Bronsted acid sites and substantial decrease in the micropore volume more than 50%, in comparison with the parent material while the volume of mesopores increased significantly. All desilicated SSZ-33 zeolites are characterized by a broad mesopore-size distribution in the range of 5–20 nm with the maximum depending both on the harshness and duration of the treatment. The average size of mesopores increases with increasing pH of NaOH solution.

The unique features of the germanosilicate zeolite possessing the UTL framework topology offer various post-synthetic modifications such as ‘top-down’, ‘inverse sigma’ or solid-state transformations. The presented work describes several different synthetic routes generating the IPC-2 type zeolite (OKO topology) utilizing UTL as the parent material. In total, five approaches were investigated which exhibit this topological transformation from germanosilicate UTL to OKO type material: (1) alkoxysilylation of the layered precursor (IPC-1P) formed by hydrolysis of UTL; (2) direct conversion of UTL by treatment in 7–12 M hydrochloric acid; (3) direct transformation under mild conditions of water and ammonium nitrate solution on Al- and B-UTL; (4) repeated calcinations of boron-containing UTL; (5) using organic solutions as self-stabilization agents. Resulting materials were examined by powder XRD, nitrogen sorption, SEM and EDX. Briefly, all the materials possessed the same OKO topology but had differing BET surface areas and micropore volumes in the ranges of 201–493 m 2 /g and 0.095–0.189 cm 3 /g, respectively. The morphologies of crystals were very similar, while the size of them varied between 10 and 50 μm. The main goal of the study was to emphasize the complexity of post-synthetic UTL zeolite chemistry and the diverse range of solid-state transformations possible.

A new equation describing isotherms of C5 hydrocarbons on metal–organic framework Cu3(BTC)2 in the temperature range from 273 to 333 K was developed. The isotherms of n-pentane, isopentane and cyclopentane on Cu3(BTC)2 belonging to the Type 5 according to the IUPAC classification are characterized by a long vertical part in the low pressure region. An analysis of isosteric adsorption heats has revealed that lateral interactions among pentane molecules adsorbed on Cu3(BTC)2 dominate over gas–solid interactions. Because there is no equation in the literature, which can be used for the description of isotherms under investigation, equation based on the Dubinin theory of S-shaped adsorption isotherms was developed. According to this theory each adsorbed molecule is a secondary center, which is capable to adsorb other molecules. The equation was suggested with respect to the leveling-off of the isotherms as at the end of the adsorption process the whole adsorption volume becomes filled with adsorbed molecules. Despite only three constants included in the equation, its accuracy in experimental data description is satisfactory.

Hydrolysis of germanosilicate zeolites with the IWW structure shows two different outcomes depending on the composition of the starting materials. Ge-rich IWW (Si/Ge=3.1) is disassembled into a layered material (IPC-5P), which can be reassembled into an almost pure silica IWW on treatment with diethoxydimethylsilane. Ge-poor IWW (Si/Ge=6.4) is not completely disassembled on hydrolysis, but retains some 3D connectivity. This structure can be reassembled into IWW by incorporation of Al to fill the defects left when the Ge is removed., Angewandte Chemie, 53 (27), ISSN:1521-3757, ISSN:0044-8249

Zeolites of different structural types were used as catalysts for aldol condensation of furfural and acetone in batch reaction conditions at T = 20–100 °C and time 0–24 h. To establish a relation between physico-chemical and catalytic properties of microporous materials, the samples were characterized by SEM, N 2 adsorption, FTIR and TGA. It was found that the acidic solids possessed appreciable activity in the reaction and resulted in a formation of products of aldehyde–ketone interaction. Nevertheless, furfural conversion decreased rapidly due to coke formation inside zeolite pores. Simultaneously with a general route of the reaction observed for basic catalysts, dimerization of the condensation product on acidic sites occurred. It was supposed that catalytic behavior of zeolites considerably affected by their both structural and textural properties. Experiments with re-used samples showed that zeolites totally restored their activity and selectivity after calcination at 530 °C.

Titanium containing extra-large pore zeolite CIT-5 (IZA code: CFI) was successfully prepared by direct synthesis using Cab-O-Sil M5 and titanium(IV) butoxide in the presence of LiOH. N -Methylsparteinium hydroxide was used as a structure directing agent. The product crystallized into thin plate crystals with an approximate size of 20 × 5 × 0.2 μm. The lowest achieved Si/Ti ratio was 23. The necessary duration of hydrothermal synthesis increased with increasing concentration of Ti in the reaction mixture from 11 days (Si/Ti = 63 in product) to 17 days (Si/Ti = 36) at 155 °C. Prepared Ti-CFI samples exhibit BET surface areas in the range of 308–346 m 2 /g and micropore volumes of 0.094–0.097 cm 3 /g. CFI possesses extra-large pores (14-ring, 7.2 × 7.5 A) accessible for bulky molecules, therefore, Ti-CFI is a useful catalyst for epoxidation of double bonds in bulky molecules used in perfumery and pharmacy. The Ti-CFI samples proved to be catalytically active in epoxidation of 1-octene, cyclooctene, α-pinene, and norbornene with hydrogen peroxide as oxidation agent.

Desilication conditions (concentration of NaOH and TPAOH solution, duration of the treatment) of -SVR zeolite were varied and related to the textural and acidic properties of the obtained materials. The treatment of -SVR zeolite with NaOH solution led to the formation of mesopores and also the increasing of the concentration of surface acid sites, accessible for bulky molecules (e.g. 2,6-ditertbutyl-pyridine). The volume of mesopores as well as the concentration of accessible acid centres in desilicated materials depends mainly on the concentration of the alkaline solution. The increase in the pH of the treatment resulted in moderate decrease of both micropore volume and Bronsted acid sites concentration, while the volume of mesopores increased significantly. Independently of the duration and pH of the treatment with NaOH solution, all desilicated -SVR zeolites are characterized by broad pore-size distribution in the range of 5–20 nm with the maximum around 14 nm. At fixed pH of the treatment with TPAOH, the volume of mesopores and their average size decreased, while the Si/Al ratio and the concentration of Bronsted acid sites in desilicated materials increased which indicates the inhibiting effect of TPA+ cations on the extraction of Si from -SVR zeolite.

The crystallization of zeolite TUN with 1,4-bis(N-methylpyrrolidinium)butane as template proceeds through an intermediate, designated IPC-3P, following the Ostwald rule of successive transformations. This apparently layered transient product has been thoroughly investigated and found to consist of MWW monolayers stacked without alignment in register, that is, disordered compared with MCM-22P. The structure was confirmed based on X-ray diffraction and high-resolution (HR)TEM analysis. The layered zeolite precursor IPC-3P can be swollen and pillared affording a combined micro- and mesoporous material with enhanced Brunauer-Emmett-Teller (BET) surface area (685m(2)g(-1)) and greater accessibility of BrOnsted acid sites for bulky molecules. This mesoporous material was probed with 2,6-di-tert-butylpyridine (DTBP). IPC-3P and its modification create a new layered zeolite sub-family belonging to the MWW family. FTIR data indicate that (Al)MWW materials MCM-22 and IPC-3 with Si/Al ratios greater than 20 exhibit a lower relative ratio of BrOnsted to Lewis acid sites than MCM-22 (with Si/Al ratios of around 13), that is, less than 2 versus more than 3, respectively. This is maintained even upon pillaring and warrants further exploration of materials like IPC-3P with a higher Al content. The unique XRD features of IPC-3P indicating misaligned stacking of layers and distinct from MCM-22P, are also seen in other MWW materials such as EMM-10P, hexamethonium-templated (HM)-MCM-22, ITQ-30, and UZM-8 suggesting the need for more detailed study of their identity and properties. Postprint

Two different types of layered MWW zeolite, i.e., delaminated MCM-56 and multilayer MCM-22P, have been studied for swelling using a new surfactant/tetraalkylammonium combination as the swelling reagent. The commonly used in the past tetrapropylammonium hydroxide (TPA-OH) was replaced by its tetramethylammonium (TMA-OH) homologue. The latter was previously considered unsuitable for use in swelling of MCM-22P. The extent of swelling with different amounts of TMA-OH accompanying surfactant was determined first by X-ray diffraction. Selected samples were pillared with silica and evaluated quantitatively by nitrogen sorption at 77 K and FTIR. The swelling of MCM-56, which is reported in detail for the first time, has been found to be more facile and extensive compared to the multi-layer MCM-22P, consistent with its delaminated nature. BET surface areas of pillared MCM-56 samples increase with the amount of hydroxide used for swelling and approach 700 m 2 /g. Pillared MCM-22P show similar trend but have somewhat lower BET values than pillared MCM-56. The observed successful swelling of MCM-22P is notable because the presence of small cations was previously found to be unfavorable for this process. FTIR measurements of selected samples confirmed higher Al/acid center content in pillared MCM-56 products in comparison to MCM-22 ones. Compared to unmodified MCM-22, there was an increase in most cases in the concentration of acid sites interacting with di-tert-butyl-pyridine. This confirms increased access of larger molecules to acid sites, which is the main goal of such swelling/pillaring treatments.

Biomass-derived oxygenates are promising future feedstocks for the chemical industry. Fluid catalytic cracking of these feedstocks has the advantage of enabling their deoxygenation without external hydrogen consumption. Six model feedstocks have been tested using the microactivity test with the aim to describe the impact of the feedstock structure on its conversion and product distribution. It has been shown that saturated alcohols are the feedstocks yielding the most valuable iso-alkanes. Fatty acids and triglycerides yielded more aromatics and with increasing molecular weight the formation of di- and polyaromatics was preferred. When unsaturated feedstocks were used instead of the saturated ones, the formation of aromatics was further augmented.

FTIR study of iron and aluminium forms of zeolite MCM-58 showed that location of heteroatoms in this IFR structure depends on the type of heteroatom. The combination of the pyridine and CO adsorption allowed determination of the concentration of hydroxyls in the 12- and 5/6-rings. Both Fe and Al are generating hydroxyls pointing towards either 12-ring or 5/6-rings but the former are located in positions giving Si–OH–Fe hydroxyls pointing mainly to the 12-rings while the latter gives rise to the Si–OH–Al groups pointing primarily to the narrower 5- and 6-rings. (Al)MCM-58 undergoes only minor dehydroxylation associated with the acid sites even at temperatures as high as 700 °C, which indicates unique stabilization of Al atoms in the IFR structure. In the case of (Fe)MCM-58, dehydroxylation is more extensive. Furthermore the OH located in the 5/6-rings dehydroxylate at lower temperatures than those in the 12-rings. The study also demonstrates that the concentration of the framework and extraframework iron atoms can be determined by a simple method based on pyridine adsorption followed by IR spectroscopy.

Lamellar zeolite forms like layered MCM-22 precursor, MCM-22P, offer unprecedented opportunities for creating diversity of more open zeolite structures prepared post-synthesis by expanding and modifying the interlamellar space. This is a relatively unexplored area with regard to procedures ensuring easy, least destructive and most efficient expansion of layered zeolites. Herein we explore concentrated surfactant solutions with high pH for their ability to provide swollen MCM-22 that can be converted to the pillared MCM-36. High pH of the swelling solutions was obtained by addition of tetrapropylammonium hydroxide and by partial conversion of the surfactant chloride into hydroxide by ion exchange. The products were evaluated based on their X-ray diffraction characteristics, sorption properties, scanning electron microscopy and IR spectra as indicators of catalytic potential. The swelling/pillaring efficiency was judged based on BET surface area and depended on swelling conditions, especially the apparent basicity. There was an overall decrease in acid site concentration due to incorporation of inert silica pillars. The MCM-36 zeolite with the highest BET showed increased uptake of 2,6-di-tert-butyl-pyridine by 75% compared to the parent MCM-22 suggesting enhanced accessibility of acid sites for bulky probe molecules. We conclude that concentrated surfactant solutions can be effective in swelling MCM-22P even at room temperature but an optimal approach must balance many factors including yield and activity of the final product.

Dealumination, desilication and silylation of TUN zeolite was investigated and related to the catalytic behavior in toluene disproportionation and its alkylation with isopropyl alcohol. Only negligible concentration of acid sites was identified on the “external” surface of parent TUN zeolite and this concentration increased with increasing desilication. Silylation resulted in channel narrowing and probably some plugging. As a result, significant increase in the para -selectivity in toluene disproportionation and its alkylation with isopropyl alcohol was achieved. No changes in toluene conversion were observed for all parent and modified samples in toluene alkylation confirming diffusion and transport of products as the rate determining step in 10-ring zeolites. Selectivity to cymenes and p -cymene decreased with dealumination as well as desilication. In contrast, silylation increased both cymene (80%) and p -cymene (90%) selectivity in toluene alkylation.

Catalytic transformation of three methyl benzenes (toluene, m -xylene, and 1,2,4-trimethyl benzene) has been investigated over ZSM-5, TNU-9, mordenite and SSZ-33 catalysts in a novel riser simulator at different operating conditions. Catalytic experiments were carried out in the temperature range of 300–400 °C to understand the transformation of these alkyl benzenes over large pore (mordenite and SSZ-33) in contrast to medium-pore (ZSM-5 and TNU-9) zeolite-based catalysts. The effect of reaction conditions on the isomerization to disproportionation product ratio, distribution of trimethylbenzene (TMB) isomers, and p -xylene/ o -xylene ratios are reported. The sequence of reactivity of the three alkyl benzenes depends upon the pore structure of zeolites. The zeolite structure controls primarily the diffusion of reactants and products while the acidity of these zeolites is of a secondary importance. In the case of medium pore zeolites, the order of conversion was m -xylene > 1,2,4-TMB > toluene. Over large pore zeolites the order of reactivity was 1,2,4-TMB > m -xylene > toluene for SSZ-33 catalyst, and m -xylene ∼ 1,2,4-TMB > toluene over mordenite. Significant effect of pore size between ZSM-5 and TNU-9 was observed; although TNU-9 is also 3D 10-ring channel system, its slightly larger pores compared with ZSM-5 provide sufficient reaction space to behave like large-pore zeolites in transformation of aromatic hydrocarbons. We have also carried out kinetic studies for these reactions and activation energies for all three reactants over all zeolite catalysts under study have been calculated.