Conventional Zeolite Research Articles

PERFORMANCE EVALUATION OF ADSORPTIVE REFRIGERATORS BASED ON COMPOSITE ADSORBENTS "SILICA GEL – SODIUM SULPHATE" AND "SILICA GEL – SODIUM ACETATE"

Abstract. Performance of adsorptive refrigerators based on composite adsorbents ‘silica gel – sodium sulphate’ and ‘silica gel – sodium acetate’ was evaluated. The main characteristics of adsorbents which affect the structural parameters of the adsorptive chilling device are revealed. The method of determining operational characteristics of adsorptive refrigerator has been developed. The main factors affecting the mass of adsorbent are confirmed to be maximal adsorption and the amount of heat required to be taken from the cold box during the day. The advantages of ‘salt in the porous silica gel matrix’ composites are exhibited as compared with conventional silica gels and zeolites. Operational parameters of adsorptive refrigerators based on the composites ‘silica gel – sodium sulphate’ and 'silica gel – sodium acetate' are compared. The calculation procedure to determine the design and operational characteristics is suggested. Proposed procedure includes the calculation of the amount of heat required to be taken from the cold box during the day, water mass, mass of the adsorbent, heat required for regeneration of the adsorbent, computing the surface area of the solar collector, heat supplied by solar collector and net coefficient of performance. The efficiency of operating processes of adsorptive refrigerators based on composites 'silica gel - sodium sulphate' and 'silica gel-sodium acetate' was compared. The correlation between adsorbent composition and design and operational parameters was stated. The surface area of solar collector is stated to be of 9.46 – 9.93. The highest net coefficients of performance of 0.358 and 0.368 are revealed for devices based on composites containing, wt. %: silica gel – 20 and salt (sodium sulphate or sodium acetate) – 80. The influence of meteorological conditions on the net coefficient of performance of the adsorptive refrigerator has been confirmed. The higher efficiency of adsorptive chilling devices based on composites 'silica gel - sodium acetate' is explained by lower values of regeneration temperature, which leads to the decreasing the heat of regeneration. The results of the research can be used for the development of adsorptive chilling devices for domestic needs and warehouse premises.

Synthesis of n-Butyl Levulinate Using Mesoporous Zeolite H-BEA Catalysts with Different Catalytic Characteristics

The present work focuses on the utilization of waste biomass for the improvement of key catalytic properties of conventional zeolite H-BEA. In the present endeavor, zeolite H-BEA has been modified using cetyltrimethyl ammonium bromide (CTAB) and rice husk (a waste biomass resource), via desilication post synthetic route, which is not reported so far. The synthesized mesoporous zeolite H-BEA catalysts have been characterized by various characterization techniques such as, SEM, 27Al and 29Si MAS-NMR, wide and low angle XRD, ICP-OES, FT-IR, TGA, NH3-TPD and BET surface area. The resultant mesoporous zeolite materials (MCCK and MCRK) exhibited bimodal porosity as well as improved physicochemical properties, and the utility of these modified zeolites as heterogeneous catalysts has been demonstrated in the production of n-butyl levulinate via levulinic acid (LA) esterification. The catalytic material, which has been modified using CTAB and rice husk, is found to exhibit better catalytic activity towards the synthesis of n-butyl levulinate (95.6%) as compared to other zeolite counterparts under the optimised reaction conditions, which is attributed to its enhanced surface area and lower Si/Al ratio as compared to other catalysts under study.

Strong nano size effect of titanium silicalite (TS-1) zeolites for electrorheological fluid

A rapid seeded growth was observed on nanosized (50–100 nm) titanium silicalite-1 (TS-1) zeolites (denoted as nano-TS-1) with a recovered mother liquid. Only 3–8 h were required to synthesize the zeolites with a yield above 80% at 393–423 K in a hydrothermal condition. Such a high efficiency is superior to the conventional synthesis, which produces the sub-micron (100–200 nm) TS-1 within 8–36 h without any seeding effect by the mother liquid. The synthesis of the nano-TS-1 was relatively insensitive to the synthesis condition, though dependent on the seeding effect, water content, and titanium precursors. A possible explanation is proposed for the formation of the MFI type TS-1 zeolites based on the ESI-MS spectra analysis on the synthesis gel. The basic building units (BBU), composed of the active SiO2 species, especially the monomer silicic acid, were firstly induced to the polymerization and formed the special secondary building units (SBU), including certain critical SimOn species for constructing. These SBUs were assembled to mfi cages (as a compositing building unit) and pentasil-type chains, fabricated as a MFI-type crystal. The recovered mother liquid not only provided certain amount of SBU-type SixOy species that accelerated the nucleation and formation of the zeolites, but also intensified the super-saturation of the active SiO2 species that would favor the nanosized zeolites. Such nanoscale size endows the TS-1 zeolites with large external surface area (148 m2/g) and zeta potential value (−47 mV), accounting for the novel dispersion of the nanoparticles. The composition of TiO2/SiO2 in the nano-particles created superior electro rheological properties to those of the conventional sub-micron TS-1 zeolites.

Performance of mesoporous HZSM-5 and Silicalite-1 coated mesoporous HZSM-5 catalysts for deoxygenation of straw fast pyrolysis vapors

•Catalytic treating of biomass fast pyrolysis vapors offers a promising route to convert many different types of lignocellulosic biomass into biofuels. Considerable research efforts have focused on using zeolite catalysts, especially the microporous HZSM-5 zeolite. Unfortunately, the zeolite’s initial high activity in forming coke and light gases reduces the overall oil yield. In this contribution, we synthesized conventional HZSM-5 zeolite, mesoporous HZSM-5 zeolite, and a core-shell catalyst consisting of mesoporous HZSM-5 zeolite coated with a thin layer (<20 nm) of silicalite-1 zeolite. The catalysts were characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 and Ar physisorption, temperature programmed desorption of ammonia (NH3-TPD), diffuse reflectance infrared fourier transform spectroscopy (DRIFT) spectra, and 27Al nuclear magnetic resonance (NMR). The catalysts were tested in a tandem micro-pyrolyzer system for deoxygenation of wheat straw derived fast pyrolysis vapors in a downstream catalytic fixed bed reactor and the quantitative product analysis was performed with GC-MS/FID/TCD and TGA-MS. The change in yields of different product groups was monitored during catalyst deactivation for an increasing number of pyrolysis vapor pulses and the cumulative carbon recoveries of all product streams (char, vapors, gas, and coke) were compared at different biomass-to-catalyst ratios (∼4 and ∼1) for catalyst loadings of 2 and 8 mg, respectively. In addition, the yields were compared for the same number of zeolitic acid sites. Even though the coking propensity was highest for the mesoporous HZSM-5 (5.1% carbon recovery of fed biomass at B:C = 1), it showed improved conversion of oxygenates (wt% O of vapors = 15) and a higher tolerance towards deactivation by coking compared to the conventional HZSM-5 (wt% O of vapors = 20). Coating of mesoporous HZSM-5 with silicalite-1 reduced the number of acid sites per mass of catalyst by ∼20%, which is attributed to the addition of the inert silicalite-1 layer and passivation of the external acid sites of the mesoporous HZSM-5. Compared to mesoporous HZSM-5, the added silicalite-1 shell reduced the coke yield by 43% (from 5.1–2.9 wt% of fed biomass carbon) for the same catalyst mass and by 8% (4.7 wt% of fed biomass carbon) for the same total number of acid sites. Furthermore, the tolerance towards deactivation observed for the mesoporous HZSM-5 core was largely preserved—especially for conversion of small oxygenates like acids, alcohols and aldehydes, resulting in vapors with 14 wt% O.

Optimizing the Aromatic Product Distribution from Catalytic Fast Pyrolysis of Biomass Using Hydrothermally Synthesized Ga-MFI Zeolites

A series of gallium-containing MFI (Ga-MFI) zeolites with varying Ga2O3/Al2O3 ratios were synthesized using hydrothermal synthesis and tested as catalyst in catalytic fast pyrolysis (CFP) of beech wood for aromatic production. The results show that the incorporation of Ga slightly reduced the effective pore size of Ga-MFI zeolites compared to conventional HZSM-5 zeolites. Therefore, the Ga-MFI zeolites increased the aromatic selectivity for smaller aromatics such as benzene, toluene, and p-xylene and decreased the aromatic selectivity for bulkier ones such as m-xylene, o-xylene, and polyaromatics in CFP of beech wood relative to HSZM-5. In particular, the yield and selectivity of p-xylene, the most desired product from CFP of biomass, increased considerably from 1.64 C% and 33.3% for conventional HZSM-5 to 2.98–3.34 C% and 72.1–79.6% for the synthesized Ga-MFI zeolites. These results suggest that slightly reducing the pore size of MFI zeolite by Ga incorporation has a beneficial effect on optimizing the aromatic selectivity toward more valuable monoaromatic products, especially p-xylene, during CFP of biomass.

Synthesis and gas permeation properties of chabazite-type titanosilicate membranes synthesized using nano-sized seed crystals

Abstract Chabazite (CHA)-type zeolite membranes have received considerable attention regarding their high permeance and separation performance. A recent report detailing a unique preparation procedure for a CHA-type titanosilicate (Ti-CHA) zeolite—in which titanium heteroatoms were incorporated into the zeolite framework by substitution of aluminum—demonstrates excellent physico-chemical properties when compared with conventional aluminosilicate CHA-type zeolites. In this study, the synthesis of Ti-CHA zeolite membranes (Ti-CHA membrane) was investigated. The Ti-CHA membrane was synthesized on an alumina support via a secondary growth method using Ti-CHA zeolite seed crystals. The Ti-CHA membrane properties were studied as a function of seed crystal size. The average particle diameter was observed to reduce from 2.3 μm to 450 nm by increasing the loading of Ti-CHA into the synthesis gel. Regardless of the seed crystal particle size, the presence of CHA-type zeolites on the alumina support was confirmed by x-ray diffraction. UV–Vis demonstrated the incorporation of titanium heteroatoms into the zeolite framework. The results indicated the successful synthesis of the Ti-CHA membrane regardless of the seed crystal particle size. Additionally, the membrane thickness decreased by using the seed crystal. Single gas permeation tests showed that the thinnest Ti-CHA membrane prepared in this study exhibited a relatively high CO2 permeance of 1.5 × 10−6 mol m−2 s−1 Pa−1, compared with that of previously reported CHA-type zeolite membranes. The influence of moisture on the separation performance of the Ti-CHA membrane was evaluated in the presence of gas mixtures composed of CO2, methane and H2O ranging from 0.1 to 5 vol%. In the presence of 1 vol% H2O, the CO2 permeance and selectivity were only marginally reduced as a result of the highly hydrophobic pore structure.

Bio-based Micro-/Meso-/Macroporous Hybrid Foams with Ultrahigh Zeolite Loadings for Selective Capture of Carbon Dioxide.

Microporous (<2 nm) crystalline aluminosilicates in the form of zeolites offer a great potential as efficient adsorbents for atmospheric CO2 in the eminent battle against global warming and climate change. The processability of conventional zeolite powders is, however, poor, which limits their implementation in many applications, such as in gas filtration industrial systems. In this work, we overcome this issue through the preparation of hybrid foams using mesoporous/macroporous supporting materials based on the strong network properties of gelatin/nanocellulose, which can support ultrahigh loadings of silicalite-1, used as a model sorbent nanomaterial. We achieved up to 90 wt % of zeolite content and a microporous/mesoporous/macroporous hybrid material. The application of hybrid foams for selective CO2 sorption exhibits a linear relationship between the zeolite content and CO2 adsorption capacity and high selectivity over N2, where the gelatin/nanocellulose foam efficiently supports the zeolite crystals without apparently blocking their pores.

High activity of Ga-containing nanosponge MTW zeolites in acylation of p-xylene

Abstract Aluminosilicate and gallosilicate MTW zeolites were prepared in the bulk and nanosponge form by direct hydrothermal synthesis. Designed materials were tested in acylation of p-xylene with benzoyl chloride and compared with large pore zeolite *BEA and medium pore zeolite MFI. Nanosponge MTW exhibited generally better performance than bulk MTW zeolites due to higher accessibility of the catalyst´s active sites in nanosponge zeolite. Selective transformation of benzoyl chloride towards target 2,5-dimethylbenzophenone was achievable over nanosponge MTW zeolites. The gallosilicate nanosponge MTW exhibited significantly higher conversion (61%) of benzoyl chloride than its aluminosilicate counterpart (27%) with the same concentration of Bronsted acid sites (0.04 mmol/g). This result is clearly caused by the suitable strength of acid centres in Ga-MTW, which enables the sufficient activation of BzCl molecules as well as efficient desorption of formed polar products. Additionally, the gallosilicate MTW outperformed both conventional zeolites *BEA and MFI used as reference materials.

Organosilane surfactant-assisted synthesis of mesoporous SSZ-39 zeolite with enhanced catalytic performance in the methanol-to-olefins reaction

SSZ-39 zeolite with AEI framework structure is a good catalyst candidate for the methanol-to-olefins (MTO) reaction. However, the diffusion limitation and coke formation often results in fast deactivation of the SSZ-39 zeolite catalyst. One solution for this challenge is to introduce mesoporosity in the SSZ-39 zeolite. Herein, we report the synthesis of mesoporous SSZ-39 zeolite using an organosilane surfactant, N,N-dimethyl-N-(3-(trimethoxysilyl)propyl)octan-1-aminium chloride, as a mesopore template and N,N-dimethyl-cis-2,6-dimethylpiperidinium as a micropore template. The obtained zeolites were characterized by X-ray diffraction, N2 sorption, scanning electron microscopy, temperature programmed desorption of ammonia, and magic angle spinning nuclear magnetic resonance of 27Al. The results show that the mesoporous SSZ-39 zeolite has high crystallinity, meso/microporosity, high surface area, cuboid morphology, and abundant acidic sites. More importantly, this mesoporous SSZ-39 zeolite exhibits enhanced catalyst lifetime in the MTO reaction due to the presence of mesoporosity for fast mass transfer, compared with a conventional SSZ-39 zeolite without mesoporosity.

Selective ammonia oxidation over ZSM-5 zeolite: Impact of catalyst’s support porosity and type of deposited iron species

In the presented studies an influence of different parameters, such as zeolite sample porosity, form of used iron source ([Fe3(OAc)6O(H2O)3]+oligocations or FeSO4 solutions) and method of iron species deposition (ion-exchange, impregnation), on the catalytic activity in the process of the selective catalytic oxidation of ammonia (NH3-SCO) was studied. Conventional and mesoporous ZSM-5 zeolites, obtained by desilication and modified with iron species, were analysed with respect to their textural, surface and crystalline properties (N2-sorption, HRTEM, SEM, XRD) as well as the form of introduced Fe species (UV–vis-DRS). Ion-exchange with [Fe3(OAc)6O(H2O)3]+ oligocations and impregnation with these oligocations and FeSO4 solutions were found as the most effective methods of the zeolite samples activation for NH3-SCO.

Catalytic conversion of biomass-derived polyols into para-xylene over SiO2-modified zeolites

This work proved that biomass-based polyols (sorbitol, xylitol, erythritol, glycerol and ethanediol) were able to be converted into high-value chemical (p-xylene) by catalytic cracking of polyols, alkylation of aromatics, and the isomerization of xylenes over the SiO2-modified zeolites. Compared to the conventional HZSM-5 zeolite, the SiO2-containing zeolites considerably increased the selectivity and yield of p-xylene due to the reduction of external surface acidity and the narrowing of pore entrance. The influences of the methanol additive, reaction temperature, and types of polyols on the selectivity and yield of p-xylene were investigated in detail. Catalytic cracking of polyols with methanol significantly enhanced the production of p-xylene by the alkylation of toluene with methanol. The highest p-xylene yield of 10.9 C-mol% with a p-xylene/xylenes ratio of 91.1% was obtained over the 15wt%SiO2/HZSM-5 catalyst. The reaction pathway for the formation of p-xylene was addressed according to the study of the key reactions and the characterization of catalysts.

Facile and seed-direct synthesis of pure EUO zeolite with enhanced catalytic performance

The preparation of pure EUO zeolite under conventional conditions usually takes more than three days, limiting the application of the EUO zeolite. It is widely acquainted that the seed-assisted synthesis of zeolites without organotemplates is inexpensive, environmentally-friendly and lead to Al-rich products. However, synthesis with EUO seeds in the absence of organic-templates always leads to the formation of impurity phases. In this work, EUO zeolite (s-EUO) is successfully obtained by seed-directed synthesis without organotemplates. This is the first seed- directed synthesis of pure EUO zeolite with special Al source. Physicochemical characterization results show that the synthesized s-EUO zeolite exhibits high crystallinity and high specific surface area, and contains uniform crystals and plenty acidic sites. The s-EUO crystallization (by this method) occurs in a considerably shorter time (18 h) and in a more mild condition (160 °C, static state), compared to that of the conventional EUO zeolites (c-EUO, 72 h at 180 °C, at rotation) in the presence of organotemplate. Moreover, the catalytic performance of the H-form of the s-EUO zeolite is enhanced to that of the c-EUO zeolite for m-xylene isomerization, confirming the NH3-TPD results.

Facile synthesis of mesoporous zeolite Y using seed gel and amphiphilic organosilane

Abstract Zeolite Y is widely used as an industrial catalyst for catalytic cracking of heavy feedstocks to lighter olefins. However, incorporation of uniform mesoporosity in zeolite Y without compromising the microporous characteristics is required to improve the catalyst efficiency and minimize catalyst deactivation. Here, we report a facile synthesis method for mesoporous zeolite Y (MPY sg ) using seed gel and amphiphilic organosilane, that results in mesoporous zeolite showing a narrow mesopore size distribution (3–4 nm) with high external surface area (110 m 2 g -1 ) and high micropore surface area (654 m 2 g -1 ). During the crystallization of MPY sg , the organosilane acted as a mesopore-generating agent, and the seed gel provided secondary nuclei that created a uniform mesoporous structure in the zeolite Y nanocrystals. Analysis of aluminosilicate precursors collected during the crystallization revealed that the crystallization process starts with a long nucleation period, followed by rapid crystal growth. Due to the highly accessible strong acid sites present on its external surface, MPY sg shows catalytic activity in the decalin cracking reaction higher than that of conventional microporous zeolite Y.

Catalytic fast pyrolysis of maize straw with a core–shell ZSM-5@SBA-15 catalyst for producing phenols and hydrocarbons

Zeolites have been widely used as catalysts in the catalytic pyrolysis of biomass to produce biofuels and/or bio-based chemicals, which could lead to the replacement of fossil sources by renewable ones. However, conventional zeolites often suffer from diffusion resistance for large intermediate oxygenates. To solve this problem, a micro/mesoporous core–shell composite zeolite ZSM-5@SBA-15 was prepared and employed as a catalyst in the catalytic pyrolysis of maize straw. ZSM-5@SBA-15 was synthesized by crystallizing mesoporous silica on the external surface of ZSM-5 using the triblock copolymer Plunoric P123 as the template. The core–shell and hierarchical structures were verified using PXRD, TEM, and N2 sorption experiments. In the catalytic pyrolysis of maize straw, ZSM-5@SBA-15 significantly enhanced the yield of valuable phenols and hydrocarbons in bio-oil, compared to ZSM-5 and SBA-15. The results demonstrated the potential application of micro@mesoporous core–shell composite zeolites in the catalytic pyrolysis of biomass.

Characterization of hierarchical zeolites: Combining adsorption/intrusion, electron microscopy, diffraction and spectroscopic techniques

Abstract Conventional and hierarchical faujasite zeolites, which are relevant to xylene separation by adsorption processes, are characterized using a broad set of complementary experimental techniques. In addition to a conventional faujasite zeolite, hierarchical faujasite zeolites consisting either of nanoparticle aggregates or of a layer-like zeolite are considered. For all samples, both the sodium and barium forms of these X zeolites are investigated. With the goal to predict and rationalize the efficiency of these materials for a given application, the fine characterization reported here aims at identifying key parameters such as their multiscale pore size distribution, pore connectivity/morphology, and external surface physical chemistry. X-ray diffraction is first used to probe the different crystalline phases and domain sizes coexisting in each sample. Electron microscopy at different scales (scanning and transmission microscopies) is also used to determine the morphology of the different porosity domains as well as to investigate the core-shell structure of the samples. N2 adsorption and mercury intrusion are then combined to provide a consolidated multiscale pore size distribution of each sample. Furthermore, adsorption scanning curves are determined to analyze the topology/connectivity of the porosity domains. Finally, infrared spectroscopy and nuclear magnetic resonance are used to assess the chemistry of the samples with special focus on their external surface. The combination of these different techniques is found to provide a rich and detailed picture of these heterogeneous and multiscale solids that goes beyond standard routine characterization.

Solvent-free synthesis of crystalline ZSM-5 zeolite: Investigation of mechanochemical pre-reaction impact on growth of thermally stable zeolite structures

In this study, we investigate the synthetic tunability of a solvent-free synthesis of crystalline ZSM-5 zeolite. Conventional zeolite syntheses use hydrothermal reactions to facilitate reagent dissolution and atomic level mixing that lead to zeolite crystallization at moderate temperatures near 200 °C. In solvent-free reactions, a reagent mixing step is very important to a successful synthesis of homogeneous and structurally stable zeolites. Key to synthetic success in our ZSM-5 zeolite syntheses is utilization of extended grinding that facilitates identifiable chemical exchange reactions prior to thermal processing. This mechanochemical pre-reaction step allows several key energy intensive or costly synthetic variables to be reduced and still yield thermally stable ZSM-5 products. A grinding induced exchange reaction yields a strongly basic ammonia environment as paste formed by reagents and released waters of hydration. This locally basic environment likely contributes to formation and assembly of tetrahedral structure building components (MO4 where M = Si, Al) that assemble into extended zeolite pore structures around the amine template. Specific synthetic conditions examined here for their influence on stable crystalline ZSM-5 growth include variation in reaction temperature (120–180 °C), reaction time (4–22 h) and amount of organic template (0–15 wt%). With the appropriate mechanochemical pre-reaction chemistry and reagent intimate mixing, crystalline and thermally robust ZSM-5 is formed at temperatures as low as 160 °C in 10 h with as little as 5 wt% organic template. The as-formed zeolite shows high relative crystallinity and is structurally stable during higher temperature 550 °C air calcination to remove the organic template from the internal pores and yields zeolites with surface areas near 300 m2/g. The decrease in organoamine template content is noteworthy as it is an expensive non-recyclable molecular template and lower template use appears to increase zeolite crystallite size. The synthesized ZSM-5 materials shows expected catalytic activity in biomass conversion of cellulose and glucose into hydroxymethylfurfural (HMF). Glucose showed higher catalytic degradation (biomass conversion 72–79% with 33–42% yield of HMF) than the cellulose (biomass conversion 55–58% with 33–38% yield of HMF).

Synthesis, characterization and modification of monolithic ZSM-5 from geopolymer for CO2 capture: Experiments and DFT calculations

Zeolites exhibit the highest performance metrics among the second generation of post-combustion CO2 capture materials; however, conventional synthetic zeolite powders are relatively expensive and need to be shaped by binding agents for end use. In this study, cost-effective monolithic Na/ZSM-5 was successfully prepared for the first time using metakaolin and industrial silica fume waste as starting materials via polycondensation and seed-induced hydrothermal crystallization. The synthesised Na/ZSM-5 exhibited an adsorption capacity of 1.79 mmol/g CO2. To further enhance the CO2 adsorption capacity, the Ni/ZSM-5 was modified by ion-exchange of Na+ with Ni2+, revealing an improved adsorption capacity of 2.38 mmol/g CO2. Density functional theory (DFT) calculations were employed to explain the adsorption mechanism and the superior CO2 adsorption performance of Ni/ZSM-5 compared to Na/ZSM-5. The results show that the sorption of CO2 in both Na/ZSM-5 and Ni/ZSM-5 is physisorption by ion–dipole interaction, and the energy emission using Ni/ZSM-5 is higher than that using Na/ZSM-5 for the same CO2 capture efficiency. This research demonstrates a new method of preparing cost-effective shape-controllable zeolites with excellent CO2 capture capacity. Furthermore, it enables the high value-added utilization of the industrial waste of silica fume.

Starch Coated Silica Nanospheres Parenting the Growth of Trimodal Porous Zeolites for Catalysis Involving Large Molecules

A simple method for the synthesis of nanocrystalline ZSM-5 and Beta zeolites with trimodal porosity was developed using starch coated silica nanospheres (as silica precursor) for generating interparticle porosity (50–200 nm); propyltriethoxysilane was used as an additive for generating intercrystalline mesopores (2–50 nm) in the presence of microporous zeolite porogen. Loading of starch and propyltriethoxysilane additive played a pivotal role in obtaining trimodal porosity with very small size zeolite nanoparticles having high surface area and pore volume. The possible growth mechanism for the fabrication of trimodal porous zeolite is presented. The resultant zeolite demonstrated excellent acidity and activity in the liquid phase acid catalyzed reactions such as esterification of hexanoic/oleic acid with benzyl alcohol, condensation of benzaldehyde and 2-hydroxyacetophenone, and Friedel–Crafts alkylation followed by ring closure reaction for the synthesis of vitamin E when compared to conventional zeolite with excellent recyclability. Such an economical starch mediated synthesis strategy can be extended to other zeolite frameworks and similar heterogeneous catalytic materials.

Basic Cu/ETS-10-N Catalyst Induced the Chemisorption and Alkyl Radical Formation of the Substrates Enhanced the Cinnamic Acid Decarboxylative Cross-Coupling Reaction Activity

Development of a high-efficiency heterogeneous catalyst for modern organic synthesis is greatly important. Herein, a nanosized ETS-10 zeolite (ETS-10-N) with strong Lewis basicity was synthesized, and used as support for prepared Cu catalyst (Cu/ETS-10-N) showing superior catalytic activity and selectivity in the decarboxylative cross-coupling of cinnamic acid and tetrahydrofuran, as compared to acidic mesoporous Beta and conventional bulk ETS-10 zeolite supported Cu catalysts. The strong Lewis basic site in the Cu/ETS-10-N not only could facilitate the formation of the alkyl radical transformed from tetrahydrofuran, but also could favor the chemisorption of cinnamic acid and activate the carbon–carbon double bond, enhancing the catalyst activity. Additionally, the Cu2+ and Cu+ species in the Cu/ETS-10-N could coordinated with the carboxylate oxygen atoms derived from cinnamic acid, improving the reaction activity of the substrate.

New insight into the alkylation-efficiency of methanol with toluene over ZSM-5: Microporous diffusibility significantly affects reacting-pathways

Abstract Here we show a new insight into the methanol alkylation-efficiency in toluene alkylation. Concretely, nanosheet (SH-), nano-particle (N-), alkali treated (AT-), conventional (C-) HZSM-5 zeolites with similar acidic properties, silica-modified C-HZSM-5 and HSAPO-34 were respectively tested in this catalytic reaction, at an enough high linear velocity of fluid in reactor with eliminating the influence of external diffusion. Combining with the characterizations such as XRD, BET, NH3-TPD, Py-IR, SEM, EDX, probe reactions etc., the effect of ZSM-5 microporous diffusibility on methanol reacting-pathways was studied from the two aspects of (i) the diffusion-constraint at pore-openings and (ii) the effective length of diffusion-reaction path in intracrystal micropore. It was found that the excellent diffusibility (SH-, N- or AT-HZSM-5) can effectively improve the methanol alkylation with aromatics to form desired products. Significantly, up to 96.7% of alkylation-efficiency and 16.4% of toluene conversion were obtained over the ∼10 nm thickness nanosheet HZSM-5 (normal pore-opening diffusion-constraint and shortest diffusion-reaction path) at the 6.0 molar ratio of toluene/methanol. On the contrary, the enhanced pore-opening diffusion-constraint (4Si-C-HZSM-5) or the overlong diffusion-reaction path (C-HZSM-5) resulted in the much lower alkylation-efficiency (38.2% and 67.4% respectively), owing to the enhanced methanol-to-olefins side-reaction with dual-cycle process which converted much more methanol into light aliphatic-hydrocarbons but not the alkyl of aromatics. Our work may provide a theoretical guidance for improving the shape-selective alkylation-efficiency for this reaction process.