H-beta Zeolite Research Articles

Oligomerization of 1-Pentene on Zeolite Catalysts

The oligomerization of 1-pentene is an efficient process for producing environmentally friendly high-quality fuel components. The catalytic properties of FAU, OFF, MOR, BEA, MTW, and MFI zeolites in the H form are studied in the synthesis of pentene oligomers in an autoclave at 110–200°C. It is established that the high activity of H-Y and H-Beta(18) zeolites in the reaction of oligomerization, where the yield of oligomers reaches 97–100%, is determined by their wide-pore structure and high concentration of acid sites. The oligomers prepared on these catalysts are 30–73% dimers, 25–50% trimers, and 2–14% oligomers, with number n > 3 of monomer units. Narrow-pore zeolites (H-ZSM-5) or zeolites with one- and two-dimensional channel systems (H-OFF, H-MOR, and H-ZSM-12) are less active in the oligomerization of 1-pentene, with decenes as the main products of the reaction.

Effect of surface silicon modification of H-beta zeolites for alkylation of benzene with 1-dodecene.

H-beta zeolites of 100–200 nm (named BEA-L) and 20–30 nm (named BEA-S) were treated by chemical liquid deposition (CLD) of tetraethyl orthosilicate (TEOS) to improve the selectivity of 2-phenyl linear alkylbenzene (2-LAB) from benzene alkylation with 1-dodecene. The results indicate that H-beta zeolite with a smaller crystal size has a longer lifetime due to shorter channels and less diffusion limitation. The deposited SiO2 layers passivated the external surface acid sites of the zeolite and made the pores narrower. BEA-L lost more external Brønsted acid sites than BEA-S with the same added amount of TEOS, which was due to the severe aggregation of BEA-S grains. This increased passivation gave BEA-L increased 2-LAB selectivity. And when the added amount of SiO2 was 7.20 wt% of the parent zeolite, the selectivity of 2-LAB over BEA-L significantly increased from 41.9% to 54.7% while that of BEA-S only increased by 2%.

Selective defunctionalization of citric acid to tricarballylic acid as a precursor for the production of high-value plasticizers

In presence of a solid acid H-Beta zeolite and Pd/C catalyst, citric acid was converted to tricarballylic acid via a one-pot sequential dehydration-hydrogenation process with a yield up to 85% and a selectivity exceeding 90%.

Mesoporous HBeta zeolite obtained via zeolitic dissolution–recrystallization successive treatment for vapor-phase Doebner–Von Miller reaction to quinolines

Mesoporous HBeta zeolite was obtained via zeolitic dissolution–recrystallization successive treatment, and exhibited enhanced selectivity to Q, anti-alkylation ability and stability in the vapor-phase Doebner–Von Miller reaction.

Synthesis of the hierarchical Fe-substituted porous HBeta zeolite and the exploration of its catalytic performance

A series of hierarchical isomorphically Fe-substituted porous beta zeolites (BEAs) was synthesised in a one-step process via soft-template approach (nFe-HBeta, n = Fe/Al) and a series of Ni-based catalysts (10Ni/nFe-HBeta) was prepared by equal volume impregnation. The results showed that the nFe-HBeta zeolites possessed a sheet-like structure with a high crystallinity and numerous porous channels. The introduction of the heterogeneous iron atoms can reduce the degree of order of the mesoporous phase and decrease the size of the zeolite particles and the number of moderate and strong acidic sites. For the 10Ni/nFe-HBeta catalyst, a synergistic effect existed between the framework iron and NiO species, which can enhance the interaction between the active Ni and HBeta support, increase the dispersion of the active metal Ni, and reduce the NiO particle size. In the ethanol steam reforming (ESR) reaction, Fe introduction can inhibit the ethanol dehydration reaction through the shielding of acidic sites and could promote the steam reforming reaction of CO and CH4, effectively improving the H2 selectivity. Among the Fe-containing catalysts, 10Ni/0.15Fe-HBeta showed a H2 selectivity of up to 72.15% and an ethanol conversion rate of 99.6% at 500°C, while the amount of coke deposition was only 4.3% after a 12 h reaction.

The Steric Effect in Green Benzylation of Arenes with Benzyl Alcohol Catalyzed by Hierarchical H-beta Zeolite

For decades the steric effect was still ambiguously understood in catalytic benzylation reactions of arenes with benzyl alcohol, which limited the green synthesis of phenylmethane derivates in industrial scale. This research applies a series of silica–alumina beta zeolites to systematically evaluate factors like catalyst porosity, reactants molecule size, and reaction temperature on catalytic benzylation. First, a suitable hierarchical beta zeolite catalyst was screened out by X-ray powder diffraction, N2 adsorption−desorption, and probe benzylation with p-xylene. In the following substrates expanding study, for a typical benzylation of benzene, it showed extraordinary performance among literature reported ones that the conversion was 98% while selectivity was 90% at 353 K only after 10 min. The steric effect of aromatics with different molecular sizes on benzylation was observed. The reaction activities of four different aromatics followed the order: benzene > toluene > p-xylene > mesitylene. Combined with macroscopic kinetic analysis, this comprehensive study points out for the first time that the nature of this steric effect was dominated by the relative adsorption efficiency of different guest aromatic molecules on the host zeolite surface.

Catalytic arene alkylation over H-Beta zeolite: Influence of zeolite shape selectivity and reactant nucleophilicity

Renewable arenes and aromatic alcohols can be derived from lignocellulose by biorefineries, which has been considered as a sustainable alternative to replace petrochemical feedstocks in the synthesis of monobenzylation products, key industrial intermediates, via benzylation reactions. Zeolites with micropores are the most widely used catalysts in the benzylation of arenes, however, their performance suffers from diffusion limitations in converting large arenes. In this work, mesoporous and microporous H–Beta zeolites were prepared and applied in the systematic study of benzylation of arenes (benzene, toluene, p-xylene and mesitylene) with benzyl alcohol (BA). The porous structure of these zeolites has been confirmed by XRD, BET and TEM techniques. The catalytically active Brønsted acid sites (BAS) were determined by quantitative 1H magic-angle spinning (MAS) nuclear magnetic resonance (NMR) experiments. The benzylation studies have shown that introducing mesopores into H–Beta zeolites can significantly increase the diffusion/access of arenes to surface sites, particularly for bulky arenes (e.g. mesitylene), while micropores are mainly selective for the conversion of small arenes (e.g. benzene). Increasing the nucleophilicity of arenes with more alkyl groups can enhance their catalytic performance in mesopores, however, the increase hinders their conversion in micropores because of the shape selectivity due to their increasing molecular size. Compared to mesopores, micropores promote the conversion of small arenes (e.g. benzene), which can be additionally enhanced by a high Brønsted acidity. Therefore, introducing a suitable porosity balanced with acidity are keys in the tailoring of the catalytic performance of H-Beta zeolites for target benzylation reactions.

Catalytic performance of modified beta zeolite on the synthesis of styrene and xylene: a kinetic study

ABSTRACT The catalytic performance of K-modified zeolite beta (Kβ) was investigated for the synthesis of industrially important products styrene and xylene by alkylation of toluene with methanol. A series of beta zeolites Kβ0.25, Kβ0.5, Kβ1.0 and Kβ1.5 were prepared by modification with different concentration of potassium chloride solution (0.25%, 5%, 1.0% and 1.5%). The modified zeolites were characterised by XRD, SEM, EDS and FTIR. Toluene and methanol in a molar ratio of 0.5:1–7:1 were subjected to vapour phase alkylation reaction in the temperature range of 733–793 K, space-time 0.009–0.025 kgh/kmol at 1 atm pressure. However, maximum toluene conversion was achieved at temperature 773 K, reactant ratio 2.5:1 and space-time 0.010 kgh/kmol over catalyst Kβ0.25. After modification with K, the acidic Hbeta zeolite become partly basic in nature. A kinetic model was evaluated to find the reaction constants. The activation energy of ring alkylation was found to be 76 kJ/mol.

Pyrolysis of waste rubber tires with palladium doped zeolite

This paper investigates the pyrolysis of waste rubber tires using zeolite-based heterogeneous catalysts. The catalytic activity of Hbeta and Pd/Hbeta was studied by examining the pyrolysis product yields. The gas yield from non-catalytic pyrolysis was at 20% while the use of Hbeta increased the gas yield to 28%. Doping Hbeta with Pd noble metal made a significant enhancement in hydrocarbon cracking producing a gas yield of 37%. The enhanced catalytic activity of Pd/Hbeta was due to dehydrogenation-hydrogenation reactions induced by the Pd metal sites. The incorporation of Pd into zeolite Hbeta led to appreciable improvements in the morphology of the catalyst. Pd-doping increased the surface area from 434 m2/g to 450 m2/g. The pore size also increased from 2.96 nm to 3.69 nm with a smaller crystallite size of 1.59 nm. The MO4 tetrahedra structure was preserved in Pd/Hbeta with the acidity characterized by hydroxyl groups (OH) at FTIR absorption bands of 631 cm−1.

Hexadecane hydrocracking for production of jet fuels from renewable diesel over proton and metal modified H-Beta zeolites

Hydrocracking of hexadecane to produce jet fuel components was investigated over proton and metal modified Beta zeolites with different acidity. They were characterized by a range of physico-chemical methods. The initial catalyst screening was performed at 210 °C under 40 bar hydrogen showing that the most promising catalysts were 2.5 wt% Pt-H-Beta-25 and 2.5 wt% Ru-H-Beta-300, which were also tested at 240 °C under 45 bar hydrogen. The results revealed that the yield of jet fuel components was maximally 27% over 2.5 wt% Pt-H-Beta-25. This catalyst gave, however, only 55% mass balance closure to the liquid phase products, while a mildly acidic 2.5 wt% Ru-H-Beta-300 afforded 24% yield of the jet fuel components and 89% liquid mass balance closure.

Ru/H-beta as an efficient catalyst for the conversion of furfural into 3-acetyl-1-propanol (3-AP) toward one-pot transformation of xylan to 3-AP

A highly active and robust catalyst composed of Ru nanoparticles highly dispersed on zeolite H-beta was developed for transforming furfural into 3-acetyl-1-propanol (3-AP) in good yield (81%)under mild conditions (80 °C, 1 MPa H2). Both the support nature and the preparation methods had significant impacts on the dispersion of Ru, eventually on the yield of 3-AP. Ion-exchange method proved best for obtaining the highly active and selective catalyst for this reaction. Moreover, the catalyst can be regenerated easily by calcination and reduction. This catalyst was further explored for the one-pot conversion of xylose and xylan to 3-AP with a yield of 46% and 31%, respectively, thus opening a new feasible pathway from biomass to valuable fine chemicals.

Screening of solid acid catalysts for etherification of glycerol with isobutene under identical conditions

We compared the performance of more than 70 solid acid catalysts with Brønsted acid function for the etherification of glycerol with isobutene under identical reaction conditions of 75 °C, 10 bar, 6 h and with an isobutene/glycerol molar ratio of 3/1. The catalysts were selected from a wide range of solid acid catalysts including ion exchange resins, zeolites, silica, and heteropolyacids, and their counterparts modified by simple treatments, with more than half of them being investigated for the first time for this reaction. For the modified commercial acid catalysts, the desired glycerol tertiary butyl ether (DTBGE and TTBGE) selectivity improved from 75 to 87 wt% upon partial cation exchange of the sulfonic acid protons in Amberlyst™ type ion exchange resins with Na+ cations; from 66 to 85 wt% by hydrothermal steam treatment of zeolite H-Y (SiO2/Al2O3 = 80); and from 75 to 80 wt% with partial La+-exchange of zeolite H-Beta (SiO2/Al2O3 = 300), all at high (90–100%) glycerol conversion. Impregnation of the heteropolyacids, tungstosilicic acid (TSA) and tungstophosphoric acid (TPA), on silica at a loading of 50 wt% provided a glycerol conversion of higher than 65 wt% and with a desired ether selectivity in the range of 62 to 76 wt%. In general, total ether selectivity increased with decreasing acid capacity for ion exchange resins, while the desired ether selectivity was enhanced with increasing acid strength for zeolites and supported heteropolyacids on mesoporous silica. Data present a detailed guideline for the selection of solid acid catalysts for the etherification of glycerol with isobutene.

Oligomerization of pent-1-ene over zeolite catalysts

Oligomerization of pent-1-ene is an effective process for synthesis of high-quality environmentally friendly fuel components. Catalytic properties of H-zeolites FAU, OFF, MOR, ВЕА, MTW and MFI were studied for synthesis of pentene oligomers in an autoclave at 110–200 °C. The wide-pore structure of H-Y and H-Beta (18) zeolites and the high concentration of acid sites were established to cause the high oligomerization activity to obtain 97–100 % yields of oligomers. Oligomers obtained over these catalysts comprised, depending on the reaction conditions, 30–73 % dimers, 25–50 % trimers and 2–14 % oligomers with more than three monomer units (n > 3). Fine-pore zeolites (H-ZSM-5) and zeolites with one-dimensional channel systems (H-OFF, H-MOR, H-ZSM-12) were less active to oligomerization of pent-1-ene, decenes being the main reaction products.

Oligomerization of Unsaturated Compounds in the Presence of Amorphous Mesoporous Aluminosilicates

High activity and selectivity of the samples of ASM amorphous mesoporous aluminosilicates in the synthesis of practically important oligomers of various unsaturated compounds (C5–C16 linear α-olefins, cyclooctene, norbornene, and α-methylstyrene) is found. The oligomerization products obtained in the presence of ASM have a broader molecular weight distribution in comparison with the oligomers synthesized over the H-Beta zeolite. The mesoporous structure of the ASM aluminosilicate provides the preparation of dimers of cyclooctene with high selectivity without cycle opening.

Alkylation of Aromatic Hydrocarbons with 2-Methyl-2-Vinyl-gem-Dichlorocyclopropane over Zeolite Catalysts

It has been found as a result of the investigation of the catalytic properties of various microporous zeolites (of FAU, BEA, MOR, and MFI structural types) and a micro–meso–macroporous H-Ymmm zeolite (FAU) in the alkylation reaction of arenes (benzene (II) and toluene (III)) with the unsaturated compound 2-methyl-2-vinyl-gem-dichlorocyclopropane (I) that the reaction proceeds with the formation of chloroalkylarenes [1-(2,2-dichloro-1-methylcyclopropyl)ethyl]benzene (IV) and 1-[1-(2,2-dichloro-1-methylcyclopropyl)ethyl]-4-methylbenzene(V). Compounds IV and V are the most selectively formed over H-Beta (up to 82%) and H-Ymmm (up to 79%) zeolite catalysts with a high conversion of I (from 90% to full). It has been shown that high selectivity for chloroalkylarenes IV and V is achieved at 100°C, an arene : unsaturated compound molar ratio of 8 : 1, a catalyst concentration of 20 wt % of the reaction mass, and a reaction time of 2 h.

Catalytic Copyrolysis of Lignocellulose and Polyethylene Blends over HBeta Zeolite

Coprocessing of Eucalyptus woodchips (EU) and low-density polyethylene (LDPE) has been investigated using two HBeta zeolites as catalyst. The reactions were carried out in a two-step (thermal/catalytic) system, varying the catalyst to feed (C/F) ratio. A maximum in the yield of the liquid organic fraction (oil*) was observed for both HBeta samples at intermediate C/F ratios due to the occurrence of sequential cracking reactions, which were accompanied by a significant reduction of the oil* oxygen content. This finding, together with the results obtained when feeding pure EU and LDPE, denotes that remarkable synergistic effects occur during the coprocesssing of lignocelllulosic biomass and polyolefinic plastics over HBeta zeolite, mainly by Diels–Alder condensation between furans and light olefins. The presence of acid sites with moderate strength in the HBeta samples is an essential factor to obtain high oil* yields since it limits the extension of severe cracking reactions.

PVA/H-β zeolite mixed matrix membranes for pervaporation dehydration of isopropanol-water mixtures

Mixed matrix membranes (MMMs) of poly (vinyl alcohol) (PVA) containing certain amounts of H-beta zeolite for pervaporation were manufactured by using a solution casting protocol. These zeolite-embedded membranes were then characterized with scanning electron microscope (SEM), X-ray diffraction (XRD) and swelling tests. The membrane separation performance has been examined by means of isopropanol (IPA) dewatering from its highly concentrated aqueous solutions via response surface methodology (RSM). The results have demonstrated that the influences of feed IPA composition (85-95 wt.%), feed temperature (50-70 Celcius degree), zeolite loading (15-25 wt.%) and their interactive influences are all statistically significant on both pervaporation flux (398-1228 g/m2.h) and water/isopropanol separation factor (617-2001). The quadratic models based on the RSM analysis have performed excellently to correlate experimental data with very high determination coefficients and very low relative standard deviations. The optimal pervaporation predictions given by using the RSM models demonstrate a total flux of 953 g/m2.h and separation factor of 1458, and are excellently verified by experimental results. As reflected by these results, PVA MMMs embedded with hydrophilic H-beta zeolite entities have performed considerably better than its pure counterpart and indicated great potential for isopropanol dehydration applications.

A Comparative Study of n-Butane Isomerization over H-Beta and H-ZSM-5 Zeolites at Low Temperatures: Effects of Acid Properties and Pore Structures

The influences of acidic properties and pore structures of H-Beta and H-ZSM-5 zeolites on the reaction properties of n-butane isomerization at low temperatures were investigated. The results showed that bimolecular pathway of n-butane conversion predominates over H-ZSM-5 zeolites, while the monomolecular and bimolecular pathways occur simultaneously over H-Beta zeolites. The conversion rate of n-butane strongly relies on the amount of strong Bronsted acid sites regardless of zeolite topology. However, the topology of zeolites crucially determines the products distribution, and the density of strong Bronsted acid sites plays a secondary role. The cavities of zeolites, formed in the intersections of channels, provide the places for the bimolecular reaction. The formation of trimethyl C8 intermediates is spatially restricted in the narrow channel intersections of H-ZSM-5 zeolites, resulting in higher contribution of n-butane disproportionation reaction. In addition, the narrow pore channels of H-ZSM-5 zeolite limit the monomolecular isomerization of n-butane molecules and affect the diffusion of heavier products (pentane) produced from bimolecular reaction, leading to the severe secondary reaction and high selectivity to propane. In contrast, the pore channels of H-Beta zeolite allow the monomolecular isomerization of n-butane and the deposition of coke. The topology of zeolites crucially determines the products distribution.

Synthesis of 5-hydroxymethylfurfural from glucose using H-Beta catalyst treated with phosphoric acid in one-pot biphasic solvent system

ABSTRACTThe production of 5-hydroxymethylfurfural (5-HMF) from glucose by using phosphoric acid (H3PO4) treated H-Beta zeolite (P-H-Beta) as the catalyst in a one-pot biphasic solvent system is presented. The catalysts with varied contents of H3PO4 over Beta-zeolite were synthesized by wet method and characterized by X-ray diffraction, scanning electron microscopy, fourier transform infrared spectroscopy, and NH3-temperature-programmed desorption. Under the optimized catalytic conditions, the catalyst prepared by the treatment of H-Beta zeolite with 2 M H3PO4 (2P-H-Beta) gave high conversion with almost 54% yield of 5-HMF at 150°C for 90 min reaction time and 0.1:1 mass ratio of catalyst to glucose with the THF/NaCl/H2O solvent system. This resulted from the appropriate acidity of the strong acid sites on the catalyst which promoted the formation of 5-HMF and its effective partition in the biphasic H2O/THF/NaCl solvent system.

Efficient and controllable alcoholysis of Kraft lignin catalyzed by porous zeolite-supported nickel-copper catalyst

The alcoholysis of Kraft lignin was catalyzed by bimetallic Ni-Cu supported on H-Beta, HZSM-5, MAS-7, MCM-41 and SAPO-11 zeolite materials in isopropanol solvent. Results showed that a higher bio-oil yield of 98.80 wt% and monomer yield of 50.83 wt% without obvious char were achieved at 330 °C for 3 h over Ni-Cu/H-Beta catalyst. Isopropanol was found to be more effective in H2 generation and facilitated to the hydrodeoxygenation of lignin-derived phenolic compounds. Moreover, the composition of liquid products was also influenced by the acidity and pore structure of catalyst. The superior cycloalkanes yield was produced over Ni-Cu/H-Beta with larger pore size and more acidity. In contrast, a large number of cyclic ketones/alcohols and alkanes were obtained over other zeolites supported catalysts with smaller pore size and less acid content. Besides, the temperature, time and solvent effect on the lignin depolymerization were also researched.