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Citronellal was converted to menthol in a one-pot approach using H-Beta zeolite-based Ni catalyst in a batch reactor at 80 °C, under 20 bar of total pressure. The effects of H-Beta acidity (H-Beta-25 with the molar ratio SiO2/Al2O3 = 25 and H-Beta-300 with SiO2/Al2O3 = 300) and Ni loading (5, 10 and 15 wt %) on the catalytic performance were investigated. Ni was impregnated on H-Beta support using the evaporation-impregnation method. The physico-chemical properties of the catalysts were characterized by XRD, SEM, TEM, ICP-OES, N2 physisorption, TPR, and pyridine adsorption–desorption FTIR techniques. Activity and selectivity of catalysts were strongly affected by the Brønsted and Lewis acid sites concentration and strength, Ni loading, its particle size and dispersion. A synergetic effect of appropriate acidity and suitable Ni loading in 15 wt.% Ni/H-Beta-25 catalyst led to the best performance giving 36% yield of menthols and 77% stereoselectivity to (±)-menthol isomer at 93% citronellal conversion. Moreover, the catalyst was successfully regenerated and reused giving similar activity, selectivity and stereoselectivity to the desired (±)-menthol isomer as the fresh one. [ABSTRACT FROM AUTHOR]

For the development of small-scale desulfurization processes such as fuel cell systems, catalytic decomposition of dimethyl sulfide (DMS) to H 2 S without H 2 addition was investigated using a Co/H-Beta zeolitic catalyst, with its acidity controlled via post-synthesis modification. The protonated zeolite (H-Beta) exhibited little catalytic activity at 400 °C, but Co modification significantly promoted DMS decomposition, with a high H 2 S yield of 50% observed. The optimum Co amount was equivalent to half of the ion-exchange capacity of the original H-Beta zeolite. While the Co/SiO 2 did not display catalytic activity, and thus, the coexistence of acid and Co ion sites is necessary in DMS decomposition. The Co species were introduced at the cation sites of the zeolite, suppressing Co sulfurization, which contributed to the high catalytic activity. [Display omitted] • Co/H-Beta showed high activity for catalytic decomposition of dimethyl sulfide. • Cobalt modification onto protonated Beta zeolite promoted the decomposition. • The coexistence of acid and Co cation sites is necessary for high activity. • The introduction of Co species into the zeolite suppressed its sulfurization. [ABSTRACT FROM AUTHOR]

Coke formation inside heterogeneous reactors is an important industrial problem that leads to reduced catalyst efficiency. However, this study aims to prove the benefits of coke build-up in improving catalyst performance. The formation and decomposition of coke on six different zeolite structures was studied. The dissociation kinetic model of the spent catalysts during the toluene alkylation with 1-heptene inside a stainless-steel autoclave reactor at different temperatures was carried out. Various techniques (XRD, XRF, TPO, CHNS and TGA-DTG) were used. It was found that the conversion and selectivity of the desired product were higher on the parent H-mordenite and the dealuminated H-beta catalysts with conversions of 85.3% and 84.67%, respectively, at a 360 min reaction time. This was attributed to the reduction of the ratio of hard:soft coke. It is confirmed that the decomposition activation energies of hard coke, 140.1–202.6 kJ/mol, are much higher energies than those of soft coke, 89.9–118.7 kJ/mol. It is also noted that the hypothesis of pore mouth catalysis is dominated by non-polyaromatic coke on the surface of the H-beta catalysts, while the hypothesis is dominated by polyaromatic coke on the surface of the H-mordenite catalysts.

In this work, the formation of levulinic acid (LA) as one of the top-twelve chemical building blocks from glucose was studied. In particular, the formulations of heterogeneous acid catalysts based on SBA-15, MCM-41 mesoporous silica was carried out and their performance in catalytic conversion of glucose to LA were assessed and compared with commercial H-Beta-25 (SiO2/Al2O3 = 25) microporous zeolite. The high surface area, suitable porosity, balanced acid sites were considered as the main factors of a proper catalytic performance. Thus, essential modification of mesoporous SBA-15 and MCM-41 materials was carried out by introducing Al in their structures for Lewis acid sites improvement. Alumina was introduced to SBA-15 by post synthesis evaporation impregnation method while it was embedded inside the MCM-41 mesoporous material during the synthesis. In addition, Brønsted acidity was introduced via post-synthesis grafting of sulfonic acid groups. The textural and morphological features and acidity of the materials were investigated using N2 physisorption, SEM, EDX, TEM, XRD and pyridine-FTIR. All catalysts were tested for aqueous glucose conversion in an autoclave at 180 °C. Al-MCM-SO3H has shown the best performance with 54% of LA yield after 4 h reaction. According to Py-FTIR introduction of alumina and sulfonic acid groups improved weak and medium Lewis and Brønsted acid sites. However, the Brønsted to Lewis acid site ratio (B/L) was higher for Al-MCM-SO3H compared to SBA-Al-SO3H leading the reaction pathway to LA. H-Beta-25 zeolite displayed a poor performance because of harsh medium and strong acid sites catalyzing humins formation. [ABSTRACT FROM AUTHOR]

The 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. [ABSTRACT FROM AUTHOR]

Coumarin is an important chemical in agricultural and pharmaceutical industries. This work studied the synthesis of 7‐hydroxy‐4‐methylcoumarin via the Pechmann condensation reaction catalyzed by H‐Beta zeolite catalyst using a combination of experimental and theoretical means. Adsorptions and reactions taking place inside the 34T cluster (T=Si or Al atoms) of H‐Beta zeolite were examined by using density functional theory with the M06‐2X functional. The coumarin synthesis reaction was proposed to be a three‐step mechanism: the transesterification, the intramolecular hydroxyalkylation and the dehydration. The total activation energies for each step were calculated to be 17.8, 3.5 and 13.5 kcal⋅mol−1, respectively. The zeolite framework stabilized the adsorption complexes and decreased the activation barriers for the Pechmann condensation reaction. The synthesis of 7‐hydroxy‐4‐methylcoumarin from resorcinol and ethyl acetoacetate on H‐Beta zeolite was experimentally examined without solvent at various conditions. The adsorption of 7‐hydroxy‐4‐methylcoumarin on H‐Beta zeolite was detected by the FT‐IR spectroscopy technique. The experimental activation energy of 6.7 kcal⋅mol−1 agreed very well with the calculated apparent value of 10.6 kcal⋅mol−1. The H‐Beta zeolite can be reused at least four times with persistently high percent yield. [ABSTRACT FROM AUTHOR]

A convenient and facile synthesis of tertiary butyl carbazate based Schiff base compounds is accomplished using an efficient high yielding and reusable H-BETA catalyst in ethanol. The catalyst was prepared and characterised by FT-IR, XRD, DSC-TGA, BET and SEM analysis. The heterogenous catalyst is selective, easily recovered, can be used for up to five times without obvious loss in catalytic activity and is well applicable to gram scale synthesis of these compounds. Resulting Schiff bases were characterised by spectral data analysis. Simple workup procedure, no column chromatography, short reaction time, high yield and reusability of the catalyst are the characteristic features of the developed protocol. [ABSTRACT FROM AUTHOR]

Limited by low surface area and insufficient photoelectric conversion efficiency, bulk g-C 3 N 4 showed unsatisfactory photocatalytic pollutant degradation and H 2 evolution performance. Herein, hydrophilic and porous H-Beta zeolite was employed to prepare g-C 3 N 4 /H-Beta composite via facile in-situ polymerization method. The role of H-Beta zeolite manifested in increased surface area, improved hydrophilicity and facilitated separation and transportation of photoexcited charge carriers. Hence, the obtained g-C 3 N 4 /H-Beta photocatalyst with an optimal content of H-Beta zeolite showed highest photocatalytic pollutant degradation efficiency and H 2 generation rate, which were 7.31- and 6.32-fold greater than that of bulk g-C 3 N 4. [Display omitted] • The hydrophilic and porous H-beta zeolite was employed to prepare g-C 3 N 4 /H-beta composite. • The introduction of H-beta zeolite contributed to increased surface area and improved hydrophilicity. • The employment of H-beta zeolite facilitated separation and migration of photoexcited charge carriers. • The obtained g-C 3 N 4 /H-beta photocatalyst exhibited enhanced pollutant degradation efficiency and H 2 production rate. [ABSTRACT FROM AUTHOR]

[Display omitted] • The formation of cumene over H-beta zeolite is more preferred through associative mechanism. • The charge reservoir property of the zeolite framework is proven based on the charge transfer analysis. • The H proton connected to benzene ring transferred back to zeolite framework after the formation of cumene. The reaction mechanism of alkylation of benzene with propylene to produce cumene over H-beta zeolite was investigated by density functional theory (DFT) using a 5T cluster model at the B3LYP/6-31G* level. The Mulliken population analysis was conducted to investigate the charge transfer analysis. Two possible reaction pathways, i.e., consecutive (stepwise) and associative (one-step) mechanism, were proposed. DFT simulation results revealed that the activation energy of associative mechanism (106 kJ/mol) is much lower than that of consecutive reaction pathway (294 kJ/mol). That is, the formation of cumene over H-beta zeolite is more preferred through associative mechanism, wherein the protonation and alkylation occur simultaneously without isopropoxide formation. Then, Mulliken charge transfer (CT) analysis for the two reaction mechanisms was conducted. Both reaction mechanism and CT analysis results proved that it is the H proton connected to benzene ring transferred back to zeolite framework during the formation of cumene from transition state in the alkylation step, not the original active center H atom of H-beta zeolite. Finally, it was found that the electric properties of zeolite framework play an important role in the alkylation of benzene with propylene. [ABSTRACT FROM AUTHOR]

Coke formation inside heterogeneous reactors is an important industrial problem that leads to reduced catalyst efficiency. However, this study aims to prove the benefits of coke build-up in improving catalyst performance. The formation and decomposition of coke on six different zeolite structures was studied. The dissociation kinetic model of the spent catalysts during the toluene alkylation with 1-heptene inside a stainless-steel autoclave reactor at different temperatures was carried out. Various techniques (XRD, XRF, TPO, CHNS and TGA-DTG) were used. It was found that the conversion and selectivity of the desired product were higher on the parent H-mordenite and the dealuminated H-beta catalysts with conversions of 85.3% and 84.67%, respectively, at a 360 min reaction time. This was attributed to the reduction of the ratio of hard:soft coke. It is confirmed that the decomposition activation energies of hard coke, 140.1–202.6 kJ/mol, are much higher energies than those of soft coke, 89.9–118.7 kJ/mol. It is also noted that the hypothesis of pore mouth catalysis is dominated by non-polyaromatic coke on the surface of the H-beta catalysts, while the hypothesis is dominated by polyaromatic coke on the surface of the H-mordenite catalysts. [Display omitted] • At different temperatures, the toluene alkylation reactions with 1-heptene were conducted. • Parents H-beta and H-mordenite Zeolites along with their modified samples were used as catalysts. • Influence of zeolite structural pores on type of accumulated coke, activity and selectivity. • Study of the decomposition of coke using multiple reaction kinetic models. [ABSTRACT FROM AUTHOR]

The conversing fructose into furfural could be manipulated by the location of framework Al. [Display omitted] • Converting fructose into furfural and 5-hydroxymethylfurfural could be manipulated by location of framework aluminum. • These Al species occupied at T1, T5 and T6 paly crucial roles for furfural formation, while Al populated at T1 sites is probably responsible for CxC bond cleavage of fructose. • Disappearance of Al atoms at T2 and T7 is no influence on the selectivity of furfural. Selectively converting fructose into furfural by H-beta catalyst is a very interesting catalytic process. However, it is a challenging task to clearly elucidate the roles of framework Al for selective scission of C C and C O bond. Herein, selective elimination of framework Al atoms is realized. Several detailed investigations showed that the framework Al species located in different sites play important role in furfural formation. The framework Al atoms of pristine H-beta mainly occupied at T1, T2, T5, T6 and T7 sites. These Al species at pore mouth can be removed by citric acid, while the treatment of nitric acid mainly eliminated the framework Al atoms from T2 and T7 sites. As for oxalic acid, the Al atoms occupied at T2, T5, T6 and T7 was primarily leached. Upon citric acid and nitric acid treatment afforded the similar yield of furfural, indicating that the formation of furfural could not be governed by these Al species at pore mouth, T2 and T7 sites. However, in the case of oxalic acid treatment, complete removal of the Al species on T2, T5, T6 and T7 sites decreased the yield of furfural. Thus, it is reasonably inferred that these Al atoms populated at T1 sites and intersecting channels is more encouraging for the splitting of C C bond, while the Al species occupied at T5, T6 sites and the larger straight channels is probably more favorable to scission of C O bond. [ABSTRACT FROM AUTHOR]

Room temperature synthesis of solketal from acetalization of glycerol with acetone was carried out over various types of Brønsted solid acid catalysts in the liquid phase. Among the catalysts screened, H-Beta zeolite showed the best performance in less time period with 86% glycerol conversion and 98.5% selectivity to solketal. The chemical and structural properties of modified and unmodified beta catalysts were studied by X-ray diffraction, AAS, SEM, NH 3 -TPD and FTIR-pyridine adsorption. The H-Beta catalyst with lower crystallite size gave better conversion and solketal selectivity compared to H-Beta with higher crystallite size. The effect of acidity of the catalyst on acetalization of glycerol was studied by modified beta catalysts of varying acidities. Glycerol conversion decreased with decrease in total acidity of beta catalysts. Strong to weak acidity ratio of the catalysts was found to have a direct correlation with catalyst performance. [ABSTRACT FROM AUTHOR]

Two-layer ONIOM calculations have been carried out to study methanol to propene (MTP) conversion reactions catalyzed by H-beta zeolite. On the basis of the so-called side-chain hydrocarbon pool (HCP) mechanism, this work proposes the complete catalytic cycle pathway for the MTP reaction. The cycle starts from the methylation of pentamethylbenzene (PMB), which leads to the formation of hexamethylbenzenium ion (hexaMB +). Subsequent steps involving deprotonation, methylation, an internal H-shift, and a unimolecular CH 3-shift are required to produce propene and ethene. The calculated activation barriers and reaction energy data indicate that propene is the more favored product, rather than ethene, from both kinetic and thermodynamic perspectives, which is consistent with experimental observations. In addition, the calculations suggest that the activation barriers of the reaction steps decrease in the order: internal H-shift > methylation > unimolecular CH 3-shift ≥ deprotonation. In the methylation step, methylation of the exocyclic double bond is easier than methylation of the ring carbons on the aromatic benzene derivative. [ABSTRACT FROM AUTHOR]

Abstract: One-pot three-component Kabachnik–Fields synthesis of α-aminophosphonates with high yields from the reaction between carbonyl compound, primary amine, and substituted phosphite can be carried out in a short period, using H-beta zeolite as a reusable catalyst. [ABSTRACT FROM AUTHOR]

Nanosized H-ZSM-5 (NZ) was synthesized and characterized for BET surface area, pore volume, pore size distribution, and acidity. The catalyst was tested toward esterification of cyclohexanol with acetic acid under autogenous pressure condition and the activity was compared with that of commercial H-ZSM-5 (HZ) and H-beta zeolite (BZ). Nanosized H-ZSM-5 was found to be more active than commercial H-ZSM-5, whereas beta zeolite showed remarkably higher activity than H-ZSM-5 and nanosized H-ZSM-5. The catalysts exhibited the increasing activity in the order of HZ < NZ < BZ. The superior activity of BZ was found to be due to higher Brønsted acidity and higher surface area. The maximum conversion was found to be 72% for H-beta zeolite, whereas nanosized H-ZSM-5 gave 69% conversion in esterification reaction. [ABSTRACT FROM AUTHOR]

Abstract: Structural properties of H-Beta (BEA) zeolite were optimized by steam dealumination followed by acid leaching. At mild dealumination, the zeolite (BZ-2) exhibited higher values of surface area pore volume and improved acid properties. On BZ-2, 0.3wt% of Pt was loaded by incipient wetness impregnation method (Pt/BZ-2) and used for production of branched paraffins from two industrial feedstocks. The feedstock containing heavier hydrocarbons (feed 1) could yield as high as 26U increase in Research Octane Number (RON), against 11–13U increase in RON observed for lighter feedstock (feed 2). The study indicated that isomerization and cracking followed by dimerization (alkylation) reactions are responsible for the production of branched paraffins. The catalyst exhibited more octane gain when tested in the presence of N2, but the corresponding catalyst exhibited comparatively lower TOS yields and inferior intensity of XRD bands after the reaction. [Copyright &y& Elsevier]

Abstract: Selective synthesis of para–para′-dimethyldiphenylmethane (para–para′-DMDPM) from the condensation between toluene and formaldehyde was investigated over H-X, H-Y, H-ZSM-5, H-mordenite and MCM-41. Characterizations (NH3-TPD-MS and pore structure) disclosed that the catalytic activity of various zeolites depends mainly on its strong acid site and accessibility of the internal pores. H-beta zeolite, with a unique pore sized in 0.66nm and higher proportion of stronger acid site, exhibited the highest activity and stereo-selectivity (86.5%). Small sized H-beta zeolite was more active due to the enhanced accessibility of its acid site, and this kind of zeolite remained a higher stereo-selectivity (>80%) even at higher temperature, longer reaction time and recycle usage. The best yield of para–para′-DMDPM reached 71.1% at 140°C over H-beta zeolite and it could be used in recycle without loss of its structure, activity and stereo-selectivity. [Copyright &y& Elsevier]

Abstract: Liquid phase Friedel–Crafts acylation of 2-methylnaphthalene (2-MN) has been investigated over zeolite catalyst. The influence of zeolite structures, substituents on naphthalene, acylating agents and solvents on the acylation has been discussed. 2-Methyl-6-butyrylnaphthalene (2,6-BMN), a promising precursor of 2,6-naphthalenedicarboxylic acid (2,6-NDCA), has been synthesized by the acylation of 2-MN using butyric anhydride (BA) as an acylating agent and H-beta zeolite as a catalyst. The influence of the preparative methods and dosage of H-beta zeolite, the molar ratio of reactants, the reaction temperature and reaction time on the catalytic butyrylation was also studied. The H-beta zeolite exchanged for four times and calcined at 550°C possessed relatively better catalytic performance. Under the optimized condition, the conversion of BA reached 78.3% and the selectivity for 2,6-BMN was 53.1%. [Copyright &y& Elsevier]

Abstract: Liquid phase di-tert-butylperoxide synthesis from the condensation reaction between tert-butyl alcohol and tert-butylhydroperoxide over microporous H-beta zeolites, having Si/Al molar ratios ranging from 11.5 to 120, has been investigated. With increasing Al content or in other words the acidity of H-beta zeolite, the catalytic activity is increased and passes through maxima; however, the selectivity for di-tert-butylperoxide is decreased initially to a small extent and then maintain almost the same level. Among the different Al-containing beta zeolites, the catalyst with a Si/Al molar ratio of 40 shows the best performance in the above condensation reaction. Additionally, when compared with other commonly used heterogeneous acidic microporous zeolites (H-ZSM-5, H-mordenite, H-Y, H-MCM-22) and mesoporous solids (Al–MCM-41, Al:SBA-15) having similar Si/Al ratios but different pore structures, the catalytic activity of the H-beta zeolite in the di-tert-butylperoxide synthesis process is found to be much higher. [Copyright &y& Elsevier]