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Bu çalışmada, H-Beta (HB) zeolit destekli tungstofosforik asit (TPA) üzerinde benzenin benzil alkol ile reaksiyonundan difenilmetan (DPM) sentezi araştırılmıştır. Destek zeoliti üzerinde ağırlıkça %5 ila %20 arasında değişen TPA yüklemeleri ıslak emdirme yöntemi kullanılarak elde edilmiş ve desteklenen katalizörler kalsinasyon işlemine tabi tutulmuştur. Hazırlanan katalizörler ICP-OES, XRD, azot adsorpsiyon-desorpsiyon izotermleri, amonyağın sıcaklık programlı desorpsiyonu (NH3-TPD) ve FT-IR ile karakterize edilmiştir. Sonuçlar, %98,9 benzil alkol dönüşümü ve %87,3 difenilmetan seçiciliği ile %5TPA-HB'nin hazırlanan diğer katalizörlerden daha yüksek bir katalitik performansa sahip olduğunu göstermiştir. Çalışma, %5TPA-HB'nin uygun gözenek büyüklüğü ve yüksek erişilebilir güçlü asit bölgelerinin iyi bir kombinasyonu sayesinde DPM sentezinde potansiyel uygulamalara sahip olduğunu göstermiştir.

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H-Beta zeolite is a solid acid catalyst commonly utilized in the catalytic conversion of biomass resources. In this study, H-Beta zeolite was calcined at different temperatures (350, 550, 750, and 1000 °C) to explore the effects of high temperature-induced dealumination on its physicochemical properties and its catalytic ability to convert glucose into 5-hydroxymethylfurfural (HMF). It was shown that as the calcination temperature increased, the Si-O-Al bond of H-Beta zeolite was broken and its dealumination effect was enhanced. Dealumination led to the collapse of the framework of H-Beta zeolite and a reduction in the number of acid sites, which in turn reduced its catalytic performance and the efficiency of HMF formation from glucose. Furthermore, H-Beta zeolite exhibited an extraordinary catalytic ability for the production of HMF from carbohydrates. Using glucose and cellulose as substrates, superior HMF yields of 91% and 46%, respectively, were achieved under optimal reaction conditions. Further, calcination removes carbon deposits in the recovered H-Beta zeolite, but it affects the cycling stability of the catalyst. Meanwhile, the by-products formed during the synthesis of HMF from glucose catalyzed by H-Beta zeolite catalyst were also clearly detected. [ABSTRACT FROM AUTHOR]

The valorization of the underutilized agricultural residues through microwave catalytic pyrolysis (MCP) has attracted much attention in recent years. This article focuses on the MCP technology of agricultural residues, the optimization of MCP conditions of coconut clothing by response surface method, and the application of pyrolysis products, so as to make the process more compatible, acceptable, and sustainable, as well as the future development direction to gain more economic benefits even in small-scale applications. According to the box Behnken experimental design, the MCP conditions of coconut cloths were analyzed and optimized by response surface method, and the optimal pyrolysis process conditions were as follows: nitrogen flow rate 89.79 ml/min, pyrolysis temperature 557.42 °C, pyrolysis time 19.91 min, and heating rate 18.75 °C/min. The results show that under the conditions predicted by the model theory, the relative content of hydrocarbons (aromatics) in the product of coconut microwave pyrolysis catalyzed by H-Beta catalyst with unique pore structure and an appropriate amount of acid sites is as high as 44.71%, while the relative content of hydrocarbons in non-catalytic pyrolysis is 0%. The increase of hydrocarbon content improves the quality of bio-oil, which has great significance for upgrading liquid products to biofuels and becoming important basic chemical raw materials. [ABSTRACT FROM AUTHOR]

BACKGROUND: Fast pyrolysis of lignocellulosics has provided an abundant sugar source for production of value‐added chemicals, and levoglucosan is the most representative sugar in pyrolysis liquid (bio oil). This paper explored the potential for producing methyl lactate from levoglucosan by employing the mixed catalysts of zeolite tin beta (Sn‐Beta) and zeolite hydrogen beta (H‐Beta). RESULTS: Under the optimal conditions (at 200 °C and mixed catalysts with H‐Beta:Sn‐Beta ratio of 1:5), the yield of methyl lactate obtained from levoglucosan conversion was as high as 35%. And the yield was comparable to that of methyl lactate obtained from glucose conversion under the similar conditions (at 200 °C and pure Sn‐Beta). In order to investigate the reason, a contrasting experiment with glucose as substrate also was carried out with the mixed catalysts. The results indicated that during the levoglucosan conversion process, 'the methanolysis of levoglucosan' was likely to compete with 'the dehydration of glucose' for the Brønsted acid sites of H‐Beta. In addition, the catalytic functions of H‐Beta and Sn‐Beta, and the reaction pathway were deeply investigated through tracking and comparing the conversion of levoglucosan over mixed H‐Beta/Sn‐Beta and over pure Sn‐Beta catalysts, respectively. CONCLUSION: The appropriately lower ratio of H‐Beta:Sn‐Beta and relatively higher temperature were favorable for the reaction. H‐Beta containing Brønsted acid could remarkably accelerate the conversion of levoglucosan and methyl‐glucosides to glucose. Sn‐Beta containing Lewis acid mainly promoted the retro‐aldol condensation of glucose and formation of methyl lactate. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

H-ZSM-5 and H-Beta zeolites ion-exchanged with alkali (Na+ and K+) and alkaline-earth (Mg2+) metals have been explored for the catalytic fast pyrolysis of lignin. Incorporating these metals led to a significant change in the acidic properties of the parent zeolites turning into mostly Lewis-type acidity. Catalytic fast pyrolysis experiments of lignin were performed in a fixed bed reactor with ex-situ configuration operating at 550 °C (thermal zone) and 450 °C (catalytic zone), atmospheric pressure and under a nitrogen flow. Moreover, two catalysts to lignin mass ratios (C/L = 0.2 and 0.4) were studied. Compared with non-catalytic tests, the use of parent zeolites caused a decrease in the bio-oil* (water-free basis) yield due to enhanced production of gases, water, and the coke deposition on the catalyst. In addition, the quality of bio-oil* was improved since it presents a lower oxygen content regarding the thermal test. H-Beta zeolite showed a higher deoxygenation degree than H-ZSM-5, but the latter exhibited a higher share of light components in the bio-oil* that can be detected by GC-MS analyses. Both catalysts promoted the production of light oxygenates, aromatics, and oxygenated aromatics. Regarding the effect of the incorporation of metals, oxygenated aromatic compounds were the predominant family in the bio-oil* obtained with all ion-exchanged zeolites. Likewise, significant differences were observed among the catalysts regarding the main components of this family (alkylphenols, guaiacols, syringols, catechols, and methoxybenzenes), achieving guaiacols concentrations in bio-oil* near to 24 wt.% for NaH-ZSM-5 and KH-ZSM-5 catalysts, and alkylphenols concentrations close to 16 wt.% for MgH-Beta and KH-Beta zeolites. [Display omitted] • Compared to thermal test, bio-oil* quality is improved by using H-Beta and H-ZSM-5. • CFP increases the concentration of GC-MS detected bio-oil* compounds. • The main family in bio-oil* is oxygenated aromatics for all the ion-exchanged zeolites. • NaH-ZSM-5 and KH-ZSM-5 catalysts favoured the formation of guaiacols. • MgH-Beta and KH-Beta zeolites promote guaiacols and alkylphenols production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-step conversion of carbohydrates to DFF in high yield (>91%) in O 2 (1 atm). • Fructose, glucose, sucrose, and starch were converted to DFF. • Two simple heterogenous catalysts, H-Beta and MnO 2 molecular sieve were used. • Catalysts were easily separated and recycled. • HMF and DFF were isolated from the reaction mixture just by solvent extraction. This study deals with an economical, efficient, and sustainable catalytic process with excellent EcoScore and E-factor values for the selective, two-step synthesis of 2,5-diformylfuran (with a yield higher than 90%) from carbohydrates, especially disaccharide and polysaccharide. This catalytic process involves the abundant and low cost carbohydrate as reactant and economical and sustainable catalysts, H-Beta and octahedral MnO 2 molecular sieve. In this two step approach, H-Beta is used in the first step for the conversion of carbohydrate to 5-hydroxymethylfurfural (HMF). Brönsted acidity of H-Beta catalyzes the hydrolysis and dehydration reactions whereas Lewis acidity catalyzes the isomerization to produce HMF. Thus, H-Beta is suitable for the conversion of various carbohydrate molecules (starch, sucrose, glucose and fructose) to HMF. After the first step, H-Beta is withdrawn and then the reaction mixture is subjected to oxidation catalyst, octahedral MnO 2 molecular sieve, in the presence of O 2 atmosphere to achieve the high 2,5-diformylfuran (DFF) yield. Molecular oxygen (1 atmosphere, O 2 filled balloon) is used as an eco-friendly and economical oxidant. Furthermore, no over oxidation product of DFF is observed. HMF and DFF are recovered from the reaction mixture by the extraction with methyl isobutyl ketone (MIBK) using water and brine solutions. DFF yields of 97.1%, 95.3%, 93.4% and 91.5% are obtained when the reactions are carried out using fructose, sucrose, glucose, and starch, respectively. Stepwise addition of catalysts improves DFF yield (>90%) from fructose, glucose, sucrose, and especially starch. Moreover, the H-Beta and octahedral MnO 2 molecular sieve are easily separable and recyclable. [ABSTRACT FROM AUTHOR]

Catalytic hydroconversion of C 10 + heavy aromatics (C 10 + Aro) from an aromatic complex was studied to produce benzene, toluene, and xylenes (BTX), rich in xylenes. Two catalytic schemes, direct hydrocracking (HDC) and hydrotreating (HDT) followed by HDC, were explored. The Mo 2 C/γ-Al 2 O 3 catalyst exhibits excellent selectivity for mono -aromatics and catalytic stability in the HDT of C 10 + Aro. HDC catalysts containing BZ (H-Beta/H-ZSM-5 = 9/1 weight ratio) exhibited a significantly enhanced yield of BTX but significantly reduced the formation of alkylbenzenes (other than BTX) and heavy aromatic residues compared to the HDC catalyst without H-ZSM-5. H-ZSM-5 with smaller pore size and higher Brönsted acidity than H-Beta promoted dealkylation of alkylbenzenes into BTX while limiting heavy residue formation. HDC of HDT-C 10 + Aro over NiMo/BZ catalyst resulted in BTX and BTX + C 9 Aro yields as high as 47.7 and 61.1 wt%, respectively, which were significantly higher than those obtained from direct HDC of C 10 + Aro (44.4 and 53.8 wt%). Unlike model tetralin HDC, the BTX distribution was in the order X > T > B from the HDC of HDT C 10 + Aro. Transalkylation reactions between benzene/toluene and tetramethylbenzenes (in C 10 + Aro) have been suggested as possible mechanisms for the formation of xylene-rich BTX. [Display omitted] • Hydroconversion of a plant C 10 + heavy-aromatics into BTX is studied. • Hydrotreating followed by hydrocracking (HDC) gives higher BTX yield than direct HDC. • Xylene-rich BTX is formed from C 10 + aromatics, while B > T > X is obtained from tetralin HDC. • HDC catalyst with H-Beta and H-ZSM-5 gives high BTX yield by synergistic shape selectivity. • Transalkylation between benzene/toluene and tetramethylbenzene promotes xylene formation. [ABSTRACT FROM AUTHOR]

Various metallic components (Ni, NiSn, NiW-S, CoMo-S and NiMo-S) with different hydrogenation (HYD) activities were supported on H-Beta or hybrid zeolites (BZ( x ), where x denotes the weight percentage of H-ZSM-5 in the physical mixture of H-Beta and H-ZSM-5). These bifunctional catalysts were applied to the hydrocracking (HYC) of tetralin in a fixed-bed down-flow reactor at 4 MPa as a model reaction for polycyclic aromatic hydrocarbon (PAH) conversion to high-value benzene, toluene, and xylenes (BTX). From the HYC of tetralin over the series of metals/H-Beta catalysts, it was found that CoMo-S/H-Beta and NiMo-S/H-Beta, whose metallic components show moderate activities in the HYD of tetralin, exhibit higher BTX yields than the other catalysts whose metals have excessively high or low HYD activities. However, these catalysts show limited BTX yield (∼47.3 wt% at 425 °C) owing to the large coproduction of alkylbenzenes other than BTX. When metals with moderate HYD activities are supported on the hybrid zeolites, the BTX yield is significantly enhanced by the effect of H-ZSM-5 in the dealkylation of alkylbenzenes into BTX. NiMo-S/BZ(10) provides a BTX yield of 54.3 wt% and a total 1-ring aromatic yield as high as 63.8 wt% (corresponding to 94.4% of the theoretical maximum of 67.6 wt%) at 425 °C. Therefore, the NiMo-S/BZ(10) catalyst, where the metallic and acidic functions and structural properties of the zeolite are well balanced, show promise as an HYC catalyst for the hydroconversion of PAHs into high-value BTX mixtures. [ABSTRACT FROM AUTHOR]

NH-SCR performance of the combined catalyst (CombiCats) prepared by mechanical mixing of CeO-ZrO and H-Beta is studied in details. It was shown, that individual standard SCR activities of CeO-ZrO and H-Beta are negligible, while their mixing results in the significant improvement of NO conversion. The absence of standard SCR activity of individual components enabled us to estimate the contribution of fast SCR, NO and NH oxidation reactions to the overall process on CombiCat. Comparison of catalytic data obtained for layered configurations and CombiCats with various CeO-ZrO/H-Beta ratios also allowed us to determine the rate-limiting step and role of each component in the process. [ABSTRACT FROM AUTHOR]

In this paper, we report on the reaction of phenol benzoylation with benzoic acid, which was carried out in the absence of solvent. The aim of this reaction is the synthesis of hydroxybenzophenones, which are important intermediates for the chemical industry. H-beta zeolites offered superior performance compared to H-Y, with a remarkably high conversion of phenol and high yields to the desired compounds, when using a stoichiometric amount of benzoic acid. It was found that the reaction mechanism did not include the intramolecular Fries rearrangement of the primary product phenyl benzoate, but indeed, the bimolecular reaction between phenyl benzoate and phenol mainly contributed to the formation of hydroxybenzophenones. The product distribution was greatly affected by the presence of Lewis-type acid sites in H-beta; it was suggested that the interaction between the aromatic ring and the electrophilic Al3+ species led to the preferred formation of o-hydroxybenzophenone, because of the decreased charge density on the C atom at the para position of the phenolic ring. H-Y zeolites were efficient than H-beta in phenyl benzoate transformation into hydroxybenzophenones. [ABSTRACT FROM AUTHOR]

The catalytic copyrolysis of waste particle board (WPB) and polypropylene (PP) was investigated for the first time over HY (5.1), HY (30), H-Beta and Ga/H-Beta catalysts. The catalysts were characterized by BET and NH3-TPD analyses. The catalytic pyrolysis of the WPB increased the production of gas products (CO, CO2, C1-C4) compared to non-catalytic pyrolysis. Acids and levoglucosan, which are the main components of bio-oil produced from non-catalytic pyrolysis, were converted to more valuable aromatics, phenolics, and furans through dehydration, deoxygenation and aromatization. The most abundant products from the copyrolysis of WPB and PP were large-molecular-mass hydrocarbons (=C10). However, catalytic copyrolysis increased the yields of small-molecular-mass hydrocarbons in the gasoline range, aromatics and phenolics. The water content in bio-oil was reduced significantly by copyrolysis with PP, contributing to the improvement in oil quality. HY (5.1) with the largest number of acid sites showed higher catalytic activity than HY (30) and H-Beta because the decomposition and reforming reactions during catalytic copyrolysis occurred on the acid sites of the catalysts. Ga/H-Beta showed even higher selectivity toward the aromatics than H-Beta despite the smaller quantity of acid sites, suggesting that Ga promoted the dehydrocyclization of the reaction intermediates. [ABSTRACT FROM AUTHOR]

Fuel production from plastics is a promising way to reduce landfilling rates while obtaining valuable products. The usage of Ni-supported hierarchical Beta zeolite (h-Beta) for the hydroreforming of the oils coming from LDPE thermal cracking has proved to produce high selectivities to gasoline and diesel fuels (>80%). In the present work, the effect of the Ni loading on Ni/h-Beta is investigated in the hydroreforming of the oils form LDPE thermal cracking. h-Beta samples were impregnated with Ni nitrate, calcined and reduced in H 2 up to 550 °C to achieve different Ni contents: 1.5%, 4%, 7% and 10%. Larger and more easily reducible metal particles were obtained on Ni 7%/h-Beta and Ni 10%/h-Beta. Hydroreforming tests were carried out in autoclave reactor at 310 °C, under 20 bar H 2 , for 45 min. Ni content progressively increased the amount of gases at the expenses of diesel fractions, while gasoline remained approximately constant about 52–54%. Maximum selectivity to automotive fuels (∼81%) was obtained with Ni 7%/h-Beta. Ni loading also enhanced olefins saturation up to Ni 7%/h-Beta. High cetane indices (71–86) and octane numbers (89–91) were obtained over all the catalysts. Regarding the different studied Ni contents, Ni 7%/h-Beta constitutes a rather promising catalyst for obtaining high quality fuels from LDPE thermal cracking oils. [ABSTRACT FROM AUTHOR]

Abstract: Catalytic dehydration of methanol to dimethyl ether was carried out over nano-zeolites and their modified samples via ultrasonic technique. Parent H-Beta and Parent H-Mordenite zeolites are used as synthesized and after sonication. H-Mordenite sonicated for 20 and 120min whereas H-Beta sonicated for 20min only. The reaction temperature was varied between 100 and 225°C at three different contact times. The different catalyst samples were characterized using: XRD, FTIR, TEM, SEM and NH3-TPD techniques. The results revealed that sonication of parent zeolite samples affects on the unit cell dimensions and their crystal size. FTIR-spectroscopic analysis indicated that sonication may decrease the pore opening and cause framework structure defects. TEM and SEM micrographs showed that sonication broke-up and re-ordered zeolite crystals with longer time resulted in a different morphology relative to parents and also change the particle size. Sonicated samples have a good performance in methanol dehydration with complete conversion and complete selectivity to dimethyl ether at lower temperature relative to the corresponding parent zeolites. TPD results indicated that the concentration of strong acid sites decreased in sonicated H-Mordenite samples leading to an increase of their catalytic activity and the selectivity to DME. On the other hand, ultrasonic treatment of H-Beta sample decreased its catalytic activity. [Copyright &y& Elsevier]

Abstract: The development of novel catalytic processes for the upgrading of F–T waxes towards the production of clean transportation fuels as well as other valuable gaseous alkenes in the overall Biomass-to-Liquid (BTL) process would increase the sustainability of this growing technology significantly. Recent studies have shown that an alternative to the classical hydrocracking process for the upgrading of heavy waxy hydrocarbons could be the Fluid Catalytic Cracking (FCC) process, which aims mainly to the production of gasoline and gaseous (C3, C4) alkenes. In the present work, we have used “model” zeolitic and mesoporous aluminosilicate catalytic materials that exhibit different acidic and porosity characteristics, in order to elucidate the reaction mechanism of F–T wax cracking and to identify the effects of these catalyst properties on conversion and product yields. In addition, the effect of moderating the acidity of zeolites via steaming (in analogy to commercial FCC equilibrated catalysts) or by using alkaline metals that block the acid sites and the effect of using specific metals with dehydrogenation activity, have also been studied. It was shown that the Brönsted zeolitic acid sites, mainly the ones of higher strength, are responsible for the high cracking activity of the heavy paraffinic feed, while the Lewis acid sites contributed to a lesser extent. Furthermore, the different micropore structure/size of zeolites Y, ZSM-5 and Beta had a significant effect on conversion and product yields (C2–C4 gases, gasoline, LCO, coke), as well as on gasoline composition (PIONA) and octane number (RON/MON). The mildly acidic amorphous mesoporous aluminosilicates exhibited moderate conversion and different product yields and gasoline composition, compared to zeolites. The catalytic results of the present study were rationalized on the basis of well-established reaction mechanisms for n-paraffins cracking on zeolites, and can be utilized for the design of new cracking catalysts with tailored catalytic properties in F–T wax upgrading. [Copyright &y& Elsevier]

Abstract: Benzene methylation by methanol is studied on acidic zeolites H-ZSM-5 (MFI) and H-beta (BEA) to investigate the influence of the catalyst topology on the reaction rate. Experimental kinetic measurements at 350°C using extremely high feed rates to suppress side reactions show that methylation occurs considerably faster on H-ZSM-5 than on H-beta. Theoretical rate constants, obtained from first-principles simulations on extended zeolite clusters, reproduce a higher methylation rate on H-ZSM-5 and provide additional insight into the various molecular effects that contribute to the overall differences between the two catalysts. The calculations indicate this higher methylation rate is primarily due to an optimal confinement of the reacting species in the medium pore material. Co-adsorption of methanol and benzene is energetically favored in H-ZSM-5 compared with H-beta, to the extent that the stabilizing host–guest interactions outweigh the greater entropy loss upon benzene adsorption in H-ZSM-5 vs. in H-beta. [Copyright &y& Elsevier]

Abstract: The stability of H-ZSM-11 (H-Z) and H-BETA (H-B) zeolites during the catalytic degradation of low-density polyethylene (LDPE) was studied using the same sample of catalyst in eleven consecutive cycles. The gaseous hydrocarbons, liquid hydrocarbons and waxes generated in each cycle were analyzed as well as the used catalyst. The zeolites were characterized by XRD, FTIR of adsorbed pyridine and N2 adsorption, while the physical mixtures of LDPE/zeolites were subjected to TG-DTG analysis.The H-Z zeolite exhibited an important stability during the successive cycles of LDPE conversion. On the contrary, the behavior H-B zeolite was completely different; from the sixth cycle the yields of products changed progressively, approaching to that obtained in a purely thermal process. The yields of accumulated coke increased steadily throughout the cycles up to maximum values in the eleventh cycle of ∼6 and ∼15wt% for H-Z and H-B, respectively. These results were confirmed by TG under air flow. [Copyright &y& Elsevier]

n examination of the kinetics of the alkylation of anisole with 1-hexene and 1-hexanol to produce alkylates over zeolite H-beta is presented. Anisole alkylation is found to occur by a set of parallel reactions when hexene is used as the alkylating agent. When hexyl alcohol is the alkylating agent, the reaction follows a multi-step parallel-series mechanism to form monoalkylates and dihexylether. With 1-hexene, a group of isomeric alkylates, viz., ortho-2-hexyl anisole (2-OHA), ortho-3-hexyl anisole (3-OHA), para-2-hexyl anisole (2-PHA), and para-3-hexyl anisole (3-PHA) was obtained. With hexanol, the olefin (hexene) and dihexyl ether were obtained additionally. The influence of process parameters like temperature, catalyst quantity, and alkylating agent on reaction behavior is reported. [ABSTRACT FROM AUTHOR]

Abstract: The reaction mechanism for the conversion of methanol to hydrocarbons over three large cavity zeolites, H-beta, H-MCM-22, and H-mordenite, has been investigated. 13C methanol was co-reacted with 12C benzene to study the buildup and further reactions of the intermediates formed. Co-reaction was required, as these aromatic intermediates will not be formed from pure methanol at temperatures low enough to actually monitor these events. The reactions were followed by dissolving quenched catalysts in HF followed by extraction of the organic compounds and analysis by GC–MS. The same hydrocarbon compounds are formed inside the pores of three zeolites, and it is the most substituted methylbenzenes that function as reaction intermediates in the hydrocarbon pool mechanism for the conversion of methanol. The heptamethylbenzenium cation was for the first time detected and shown to serve as a key reaction intermediate in zeolite catalysts other than H-beta. The formation of bicyclic coke precursors was also investigated, and progress has been made toward a more complete description of the reactions leading to catalyst deactivation. Quantum chemical calculations have shed light on the processes leading to coke precursors. The profound similarities between H-beta, H-mordenite, and H-MCM-22 shown herein constitute a significant step toward a unified understanding of the MTH reaction over acidic zeolites. [ABSTRACT FROM AUTHOR]

Abstract: Selectivity control is a key issue in the zeolite facilitated conversion of methanol to hydrocarbons. This work addresses: (a) How the zeolite topology (MFI versus BEA) determines the type of intermediate participating in the catalytic cycle thereby controlling the ethene/propene product selectivity in the methanol to alkenes reaction, and (b) to what extent light alkene formation occurs via aromatic and alkene reaction intermediates for H-ZSM-5. Three catalyst samples have been studied in experiments relying on isotopic labeling. For H-beta, penta- and hexamethylbenzene are involved in an aromatics based hydrocarbon pool type mechanism leading predominantly to propene and the higher alkenes (a very low yield of ethene is observed), whereas for H-ZSM-5, the lower methylbenzenes are the aromatic intermediates and represent the major route for ethene formation. For H-ZSM-5, an alkene based and an aromatics based catalytic cycle for product formation are distinguishable. By conducting co-reaction experiments (MeOH+propene or MeOH+ p-xylene) over H-ZSM-5 we were able to evaluate the relative rates of ethene and propene formation from both the alkene and the aromatics based catalytic cycles. [Copyright &y& Elsevier]

Abstract: The present paper deals with the liquid-phase synthesis of di-n-pentyl ether (DNPE) by dehydration of 1-pentanol over H-Beta, H-ZSM-5, H-mordenite and H-Y zeolites. Their SiO2/Al2O3 ratios were about 25 for H-Beta, 28 for H-ZSM-5, 35 for H-mordenite and 6 for H-Y. Experiments were performed in a batch reactor in the temperature range 140–180°C at 1.6MPa. Comparison of the catalysts behaviour shows that H-Beta is the most active and selective to DNPE, although it is less active than microporous ion-exchange resins. Kinetics of DNPE synthesis was studied. The best kinetic model for all the catalysts stems from a reaction mechanism whose rate-limiting step is the surface reaction between two 1-pentanol molecules adsorbed on adjacent sites, to yield DNPE and water both adsorbed on single site. Activation energy, on each single catalyst, was estimated to be in the range 94–118kJmol−1. [Copyright &y& Elsevier]

Abstract: The effect of the addition of a nanocrystalline H-beta zeolite in the pyrolysis of a commercial LDPE has been studied using dynamic conditions in a thermobalance and in a batch reactor, the results have been compared with those obtained using a HZSM-5 zeolite. The H-beta catalyst has an important influence on the decomposition of the polymer even at very low zeolite concentration. Although this mixture has a saturating effect at a certain concentration of catalyst (around 7%), a remarkable effect in the first steps of LDPE decomposition as increasing the catalyst loading has been observed. This important catalytic effect has been attributed to the external acid sites present in the H-beta zeolite. The study of the gaseous products evolved in the catalytic pyrolysis shows the influence of the structure and the temperature on the composition of the gas, and a possible effect of the deactivation of the catalyst. The isobutane/n-butane ratio obtained showed an important variation with temperature and was higher in the gas produced using H-beta than with HZSM-5. This different behaviour can be explained by the different pore structure. A preliminary study of the coke formed with the H-beta zeolite has been carried out and the results show that the zeolite causes an important delay in the oxidation process. [Copyright &y& Elsevier]

Abstract: Cyclohexyl hydroperoxide, a key intermediate in the cyclohexane autoxidation for the manufacture of cyclohexanone and cyclohexanol, was decomposed over transition metal-free zeolite H-beta. The CHHP decomposition efficiency reached 191mmolg−1 h−1, which is almost equal to that over 5% Ru/Al2O3 under the same conditions. The highest combined yield of cyclohexanol and cyclohexanone reached 84.6mol% at 125°C. Elevation of reaction temperature can increase the activity and selectivity to cyclohexanone. Correlating study between the catalytic activity and the acidity reveals that the medium strength Brönsted acid sites of H-beta are the main active centers for the decomposition reaction. [Copyright &y& Elsevier]

Abstract: The effect of the addition of H-Beta and HZSM-5 zeolites on the pyrolysis of commercial LDPE has been studied using dynamic experiments in a thermobalance. The H-Beta zeolite shows an important influence on the decomposition of the polymer even at a very low zeolite concentration. A remarkable effect in the first steps of LDPE decomposition on increasing the catalyst loading has been observed and a two-step process occurs in the presence of H-Beta zeolite. A pseudo-kinetic model has been proposed in order to adequately reproduce this behaviour. The model developed has been applied to simultaneously correlate the TG and DTG curves obtained under dynamic conditions at heating rates of 5, 10 and 35°C/min and at several catalyst concentrations. The model is capable of simultaneously correlating all the experiments, thus demonstrating the validity of the hypothesis suggested and revealing a notable ability as a predictive model. [Copyright &y& Elsevier]

Abstract: Conversion, selectivity, yield, and kinetics of the liquid-phase dehydration of 1-pentanol to di-n-pentyl ether (DNPE) were determined at 403–463 K on a recently developed sulfonated resin, Amberlyst 70, which is thermally stable up to 473 K. The behavior of Amberlyst 70 was compared with that of Nafion resin NR50, an H-Beta zeolite, and styrene-divinylbenzene resins stable up to 423 K (i.e., Amberlyst 36 and CT-224). Amberlyst 70 was found to be the most suitable catalyst for this application, showing the highest conversion and yield, with a selectivity to DNPE⩾93%, despite the fact that NR50 showed the highest selectivity to ether at 423–463 K. The kinetic study reveals that a model stemming from an ER mechanism in which 1-pentanol from the liquid phase reacts with 1-pentanol adsorbed on a single center to give ether adsorbed on a single site represents data on each catalyst. The activation energy was computed to be in the range 110–120 kJ/mol on all the catalysts. [Copyright &y& Elsevier]

The dehydration of 2-(4′-ethylbenzoyl) benzoic acid (BE acid) for the synthesis of 2-ethylanthraquinone (2-EAQ) has been studied over solid acid catalysts. Among the catalysts tested, a H-Beta zeolite, which was modified by dilute HNO3 solution, exhibited high catalytic performances. A 96.7% yield of 2-EAQ was achieved in our study in a batch reactor. The influences of various parameters, such as reaction temperature and time, the weight ratio of BE acid to H-Beta zeolite were investigated in detail. [ABSTRACT FROM AUTHOR]

Abstract: The influence of rare earth (RE) elements on the acidic properties of H-MCM-22 and H-Beta was studied by pyridine adsorption followed by infrared spectroscopy (FTIR) and n-heptane cracking, as a model reaction. The zeolites were submitted to ion exchange with rare earth nitrate solutions of La, Nd and Yb. The FTIR spectra of REH-MCM-22 indicate the presence of RE elements inside supercages and in the sinusoidal channels of the zeolite. After pyridine adsorption two additional bands are detected in REH-MCM-22 and REH-Beta, related to pyridine bonded to RE3+ cations. The n-heptane cracking reaction shows that the effect of rare earth elements is related not only to the acidity but also with the porous structure of both zeolites. In H-Beta zeolite, the presence of RE elements enhances the acidity of the catalysts. In H-MCM-22 zeolite, the most relevant effect of rare earth elements is on the shape selectivity that becomes more pronounced with the ionic radius of the RE elements. The nature of the coke deposited on the two materials shows distinct profiles that are also related to its porous structure. [Copyright &y& Elsevier]

Abstract: The bisphenol F synthesis from the liquid-phase phenol and formaldehyde condensation reaction in the presence of water over microporous H-beta zeolites, with different Si/Al ratios, has been investigated. The catalysts have been characterized for their phase purity and acidity. With an increase in the aluminum content in beta zeolite, the acidity is increased gradually; however, the catalytic activity is increased and passes through a maximum. Among the different Al-containing beta zeolites (having Si/Al ratios from 11.5 to 124.5molmol−1), the catalyst with Si/Al ratio of 75.0molmol−1 shows the best catalytic performance in the bisphenol F synthesis process. The influences of catalyst amount, phenol/formaldehyde ratio and reaction temperature on the phenol and formaldehyde condensation over the catalyst showing the highest bisphenol F activity have been thoroughly studied. [Copyright &y& Elsevier]

Abstract: The paper deals with the liquid-phase synthesis of isopropyl tert-butyl ether (IPTBE) from 2-propanol and isobutene over H-Beta, H-ZSM-5, and H-Y zeolites. The SiO2/Al2O3 ratio of tested zeolites was about 25 for H-Beta, 28 for H-ZSM-5, and 6 for H-Y. Experiments were performed in a batch reactor in the temperature range of 70–90 °C at 1.6 MPa. A comparative study of the behaviour of these catalysts was made at 80 °C by with an initial alcohol-to-isobutene molar ratio () of 1. We optimised the activation process of the three zeolites by varying the temperature and time of calcination, thus selecting the experimental conditions of activation leading to the highest activity and selectivity. H-Beta was the most active and selective catalyst. Therefore, the kinetics of IPTBE synthesis was studied on H-Beta in the temperature range of 70–90 °C, with a varying from 0.7 to 2. The best kinetic model stems from a mechanism in which isobutene reacts with 2-propanol, with both adsorbed on one site, to give the ether adsorbed on one site. The apparent activation energy was estimated to be . [Copyright &y& Elsevier]

Intermolecular hydroamination of phenyl acetylene (PhAc) by aniline to give phenyl-(1-phenylethylidene) amine has been investigated using Zn2+ exchanged K-10 montmorillonite clay (hereafter Zn/K-10) catalysts. Under optimized reaction conditions, aniline to PhAc mole ratio 2, toluene solvent, catalyst Zn/K-10 (0.5g) and at 130°C gave 77wt.% conversion of PhAC after 20h. The activities of Zn/K-10, Zn/H-beta and Zn/silica having same amount of Zn2+ were compared. Zn/H-beta and Zn/K-10 showed nearly the same activity at the end of 10h and others followed in the order Zn/silica, H-beta, K-10 and silica. The role played by Lewis and Brönsted acidities of the catalysts in influencing the catalytic activity for hydroamination reaction has been discussed. It is suggested that Brönsted acidity acts as a co-catalyst for Lewis acidic metal center. Zn/K-10 is the inexpensive but efficient catalyst for intermolecular hydroamination of alkynes, which can be utilized as an alternative to Zn/H-beta catalyst. [Copyright &y& Elsevier]

The liquid-phase alkylation of α-methylnaphthalene with long-chain olefins (C11–12) has been investigated firstly in the presence of H-Y and H-Beta zeolites with different pore architectures. The H-Y zeolites exhibited outstanding catalytic performances. The influences of various reaction parameters like temperature, pressure, mole ratio of α-methylnaphthalene to olefins (nrea), solvent concentration, volume hour space velocity (VHSV) and time on stream on the reaction were studied in detail. Under the optimal reaction parameters, more than 90% conversion of olefins and 100% selectivity for the desired mono-alkyl methylnaphthalene were achieved. [ABSTRACT FROM AUTHOR]

Acetylation of thioanisole (TA) with acetic anhydride (AA) to give p-(methylthio) acetophenone (4-MTAP) has been investigated using different solid acid catalysts such as H-Y, H-ZSM-5, H-mordenite and H-beta in liquid phase conditions. The reaction is studied in the temperature range 80–180 °C in a pressure reactor under nitrogen atmosphere. Among the catalysts tested, H-beta is found to be more active and shape selective than other zeolite catalysts. The conversion of TA (32 mol%) with a turnover frequency, TOF, 30.6 (10−4 s−1 mol−1 Al) gave exclusively 4-MTAP (99.9%) and the other o-(methylthio) acetophenone (2-MTAP) over H-beta at 150 °C after 2 h. Acidity and structural features of zeolites play an important role in the conversion and product distribution in acetylation of TA. The effect of AA/TA molar ratio, catalyst concentration and reaction temperature have been optimized to get higher conversion of TA and product selectivity. Efficient utility of AA has been established in the reaction. H-beta catalyst has been reused in few cycles after regeneration by washing with ethyl acetate followed by calcination at 500 °C for 4 h without loss in its activity. [Copyright &y& Elsevier]

The regioselective nitration of o-xylene to 4-nitro-o-xylene (4-NOX) has been studied in the liquid and vapor phase over zeolites H-beta, H-ZSM-5 and silica supported molybdenum oxide (MoO3/SiO2) catalysts. Zeolite H-beta showed the maximum conversion of 28% and 63% selectivity for 4-NOX in liquid phase nitration at 70 °C with 70% HNO3. The conversion increased to 65% when the reaction was carried out in vapor phase at 150 °C using dilute 30% HNO3. The formation of α-methylphenyl nitromethane by alkyl nitration in liquid phase was decreased in vapor phase reaction. The formation of oxidation products was also decreased in vapor phase reaction with minor amounts of dinitro and ipso-products. The influence of experimental parameters such as temperature, nitric acid concentration and WHSV on conversion and selectivity has been investigated. The use of dilute nitric acid and the selective formation of 4-NOX using dilute HNO3 makes this process environmental friendly with a potential for commercialization. [Copyright &y& Elsevier]

Cyclization of (phenylthio)acetaldehyde diethylacetal was examined in 1,2-dichloroethane and chlorobenzene solvents in the presence of H-beta zeolite and Zn2+ ion-exchanged beta zeolite under reflux conditions. Zn2+ ion-exchanged beta zeolite showed better activity than its H-form counterpart owing to its higher Lewis acidity. The cyclization proceeds via two different pathways. At lower temperature the reaction proceeds predominantly via a pathway in which deacetalization of the reactant occurs first and then the resulting aldehyde cyclizes to benzo[b]thiophene. [ABSTRACT FROM AUTHOR]

Liquid phase alkylation of phenol with 4-hydroxybutan-2-one was carried out in presence of H-beta zeolite modified by different techniques, such as thermal treatment, acid washing, ion-exchange and surface passivation. Thermal- and acid-treated samples showed decrease in activity due to the removal of aluminium from the framework. The new Lewis acid sites generated by thermal treatment increased the selectivity of the O-alkylated product. Ion-exchange with cesium favoured the O-alkylated product due to the introduction of basic sites. Low temperature favoured the O-alkylated product, whereas high temperatures favoured the para alkylated product. When methyl vinyl ketone was used as the alkylating agent instead of 4-hydroxybutan-2-one, the change led to an increase in the selectivity of oligomers and other polyalkylated products. The increase in the concentration of the alkylating agents increased the selectivity of the O-alkylated product, due to the greater possibility of nucleophilic attack of phenoxide ion over the alkylating agents. The increase in the catalyst weight decreased the yield of O-alkylated product and increased the yield of para alkylated product. This demonstrated the conversion of the O-alkylated product into the para alkylated product. The studies on the rearrangement of the O-alkylated product which was synthesised separately also confirmed this fact. The para to O-alkylated product ratio observed over surface-passivated H-beta zeolite was the same as that observed over H-beta. This identity showed that the rearrangement takes place mainly inside the micropores. [Copyright &y& Elsevier]

The liquid-phase isopropylation of isobutylbenzene (IBB) with 2-propanol to 3-isobutylcumene (3-IBC) and 4-isobutylcumene (4-IBC) using zeolite H-beta as a catalyst is reported. The zeolite H-beta-catalyzed isopropylation of isobutylbenzene is found to be more selective for 4-isobutylcumene (52 wt%) than using the conventional catalyst, AlCl3 (19 wt%). [ABSTRACT FROM AUTHOR]

A comparative study of the reaction kinetics involving the vapour phase isopropylation of benzene with iso-propanol over H-beta and SAPO-5 catalysts is taken up to evaluate the performance of these two potential catalysts for the industrially important cumene synthesis. Their activity is compared in the temperature range 378–513 K. A lab scale fixed bed flow reactor was used at atmospheric pressure for the experiments. Power law equation assuming pseudo first-order kinetics for iso-propanol conversion fit the data reasonably well. Kinetic parameters such as activation energy (Ea) and Arrhenius frequency factor (ln A0) for the disappearance of iso-propanol over a series of SAPO-5 molecular sieves with varying acidity and over zeolite beta have been evaluated at 383 K. The reaction rate on beta is higher than that of the most active SAPO-5 catalyst at the same temperature. The existence of the compensation effect between Ea and ln A0 has been tested over the SAPO-5 catalysts. [Copyright &y& Elsevier]

The self-condensation of acetophenone (ACP) to α,β-unsaturated ketone in the liquid phase has been studied using sulfated zirconia (SZ), sulfated titania (ST) and H-beta zeolite as catalysts in the temperature range of 403–433 K. It is found that SZ and H-beta exhibit similar activity (rate of ACP conversion), which is higher than that of ST. From the TPD of NH3 it is seen that both SZ and H-beta are highly acidic and possess strong acid sites, as seen from NH3 desorption in the temperature range of 513–873 K, which are responsible for the reaction. The conversion of ACP increases with reaction time, the catalyst concentration and reaction temperature. The SZ is recycled two times to show that there is only a marginal decrease in activity on recycled catalyst with no loss in the selectivity for dypnone. [Copyright &y& Elsevier]

Phenol is selectively nitrated in liquid phase to ortho-nitrophenol in high yield using dilute nitric acid over solid acid catalysts. Zeolite H-beta was found to be a very active catalyst for nitration of phenol to ortho-nitrophenol at room temperature in carbon tetrachloride as a solvent. Compared to the conventional process, phenol nitration over solid acid catalyst is a clean and environment friendly process with a simpler workup procedure for quantitative isolation of the products. [Copyright &y& Elsevier]

Selective formation of 4,4′-dichlorobenzophenone (>88%) at 19.8 wt% conversion level of 4-chlorobenzoylchloride (4-ClBC) and at 8.4×10−4 s−1mol−1 turnover frequency (TOF) of 4-chlorobenzoylchloride is reported for the first time in the benzoylation of chlorobenzene using 4-ClBC as benzoylating agent and zeolite H-beta as the catalyst. [ABSTRACT FROM AUTHOR]Al turnover frequency (TOF) of 4-chlorobenzoylchloride is reported for the first time in the benzoylation of chlorobenzene using 4-ClBC as benzoylating agent and zeolite H-beta as the catalyst. [ABSTRACT FROM AUTHOR]

Trace amounts of ethylene impurities in the methane used for benzene methylation over ZSM-5 and H-beta catalysts are found to enhance benzene conversions and selectivity to ethylbenzene. However, methane containing ethane impurities yielded negligible benzene conversion in the absence of oxygen over CoZSM-5 while a much higher conversion is obtained over H-beta due to cracking of benzene as previously reported. [ABSTRACT FROM AUTHOR]