Benzylation Of Anisole Research Articles

Catalytic activity of niobium phosphate in the benzylation of anisole with styrene, benzyl alcohol and benzyl chloride

The catalytic activity of niobium phosphate was evaluated in the benzylation of anisole with three alkylating agents. Niobium phosphate was characterized by N2 adsorption, X-ray diffraction (XRD), solid state 31P NMR, NH3-TPD, structural FTIR and FTIR after adsorption of pyridine in order to determine its physico-chemical properties. The influence of catalyst calcination in the benzylation conversion was studied. A comparison between the benzylation with benzyl alcohol, benzyl chloride and styrene was done. The results indicated that the conversion of the benzyl alcohol and styrene on niobium phosphate was extremely dependent on the pre-treatment temperature. The catalyst calcined at 773 K showed high activity and selectivity to benzylated products in the benzylation with all alkylating agents and the conversion order was benzyl chloride > styrene > benzyl alcohol. Competitive reactions were also performed with two alkylating agents simultaneously. In the reaction of anisole with both benzyl alcohol and benzyl chloride, the alcohol was consumed faster than the chloride. The behavior indicates a phenomenon related to preferential adsorption, in which the alkylating agents compete for the sites, mainly Lewis sites, on the niobium phosphate. In the reaction of anisole with both styrene and benzyl alcohol, there was also an inversion of the relative reactivity, the alcohol was consumed faster, and in the reaction of anisole with styrene and benzyl chloride, both of them have presented similar conversions probably because HCl formed in the reaction with benzyl chloride catalysis the reaction of styrene.

Nanocrystals of Zeolite ZSM-5 as Catalysts for the Liquid Phase Benzylation of Anisole with Benzyl Alcohol.

The current paper reports the application of nanocrystalline form of zeolite ZSM-5 in lieu of Friedel Crafts catalysts in the benzylation of anisole using benzyl alcohol. There are many problems associated with the use and disposal of conventional catalysts due to their toxicity, corrosiveness and non-recyclability. Nanocrystalline zeolites can be a less polluting alternative to the conventional Friedel Crafts catalysts. Nanocrystalline ZSM-5 was synthesized by a facile method and was characterized using SEM, XRD and FTIR. The prepared nanocrystalline zeolite was then evaluated for its efficiency and selectivity in liquid phase benzylation of anisole. Optimum conditions of reaction time, temperature, quantity of catalyst and mole ratio of reactants were obtained. Kinetic studies were done to propose a mechanistic model for the catalyzed reaction. Results of this study suggest that the synthesized nanocrystals of zeolites are efficient, selective, stable, consistent and reusable catalysts. This catalyst thus holds the possibility of being a better alternative to homogeneous catalysts, from environmental and economic perspectives.

Comparison of Micro- and Nanoscale Support for Friedel-Crafts Benzylation of Anisole

Comparison of Micro- and Nanoscale Support for Friedel-Crafts Benzylation of Anisole

Acid property of Nb2O5/Al2O3 prepared by impregnation method by using niobium oxalate solution: Effect of pH on the structure and acid property

5 and 16wt% Nb2O5/Al2O3 catalysts were prepared by impregnation method by using niobium oxalate solution with various pH values. The acid property of Nb2O5/Al2O3 was examined by benzylation of anisole and pyridine adsorbed Fourier transform infrared (FT-IR) spectra. The structure of domains of niobium oxide monolayer on 5 and 16wt% Nb2O5/Al2O3 were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, and pyridine adsorbed FT-IR spectra. The acid property of 16wt% Nb2O5/Al2O3 strongly depended on the pH values of niobium oxalate solution. As increase of pH value of niobium oxalate solution, the size of domains of niobium oxide monolayer increased. Brønsted acidity on Nb2O5/Al2O3 increased with increasing in the domain size of niobium oxide monolayer. The structural analysis strongly suggests that the stress triggered by generation of the boundaries between domains is higher, as the domain size of niobium oxide monolayer increases. We proposed that the strong distortion of Nb(OH)Nb bond at the boundaries between domains of niobium oxide monolayer is necessary to generate Brønsted acid sites on Nb2O5/Al2O3 catalysts.

Brønsted acid generation of alumina-supported molybdenum oxide calcined at high temperatures: Characterization by acid-catalyzed reactions and spectroscopic methods

The acidic properties of alumina-supported molybdenum oxide (MoO3/Al2O3) calcined at high temperatures, with MoO3 loadings of 5–30wt%, were investigated using acid-catalyzed reactions (benzylation of anisole and isomerization of α-pinene), and Fourier-transformed infrared spectroscopy (FT-IR). The structure of MoO3 on Al2O3 was characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectra (XPS), and X-ray absorption fine structure (XAFS) analysis. The correlation between acidic property and structure is discussed. Brønsted acid sites, where acid-catalyzed reactions take place, are generated on MoO3/Al2O3 by calcination at high temperatures. 11wt% MoO3/Al2O3 calcined at 1073K exhibited the highest activity, and the largest numbers of Brønsted acid sites were generated. XPS and Mo K-edge XAFS revealed that molybdenum oxide monolayer domains with distorted MoO6 units and small MoO3 clusters were formed and molybdenum oxide monolayer domains were stabilized on alumina below 11wt% of MoO3 loading. Brønsted acid sites are probably generated at boundaries between molybdenum oxide monolayer domains and/or small MoO3 clusters. When the MoO3 loading was sufficient to form two-dimensional molybdenum oxide overlayers (>11wt%), some of the Brønsted acid sites on MoO3/Al2O3 was covered with Al2Mo3O12 having no Brønsted acid site, resulting in a lowering of the catalytic activity.

Samarium‐exchanged Heteropoly Tungstate: An Efficient Solid Acid Catalyst for the Synthesis of Glycerol Carbonate from Glycerol and Benzylation of Anisole

AbstractSamarium‐exchanged heteropoly tungstate (SmxTPA) is an efficient catalyst for the synthesis of glycerol carbonate from glycerol and urea. The catalysts with varying Sm content were prepared and characterized by FT‐IR spectroscopy, XRD, laser Raman spectroscopy, temperature‐programmed desorption of ammonia, and X‐ray photo electron spectroscopy. The activity of the catalysts is related to the Lewis and Brønsted acidity, which depends on the Sm content in the catalysts. Partially exchanged SmxTPA catalyst showed high activity, owing to a higher number of Lewis acidic sites. The catalyst exhibited consistent activity and selectivity during recycling. A plausible reaction mechanism is presented. The catalyst also exhibited high activity in the acid‐catalyzed benzylation of anisole.

Direct synthesis of well-ordered mesoporous Al-SBA-15 and its correlation with the catalytic activity

The synthesis of Al-SBA-15 under milder acidic conditions were made through an adjusting the molar H 2O/HCl ratio which indicate the formation of Si–O–Al linkages that lead to isomorphous substitution of Si 4+ by some Al 3+ ions. By adjusting the H 2O/HCl molar ratio, Al gets incorporated into the lattice of SBA-15, which is evidenced by XRD, N 2 adsorption, TEM, 29Si and 27Al MAS NMR spectroscopic data. Aluminium incorporated SBA-15 samples retained both structural and textural properties of SBA-15. The 27Al MAS NMR confirms that a large proportion of the Al is inserted into tetrahedral positions within the framework. The Al 3+ ions could assume a tetrahedral coordination and be part of the hexagonal structure of silica in Al-SBA-15. In the present study, we have examined the effectiveness of Al-SBA-15, as an acid catalyst for the esterification of acetic acid and in benzylation of anisole. The high activity of Al-20 sample in esterification reaction has been attributed to isolated, generally tetrahedrally coordinated, framework Al species. While in benzylation of anisole, the best result was achieved with Al-5 catalyst. The selectivity for benzylanisole increases and that for dibenzylether decreases with increase in the Si/Al ratio of Al-SBA-15.

Exploring the Scope of Nitrogen Acyclic Carbenes (NACs) in Gold-Catalyzed Reactions

The catalytic activity of the recently reported nitrogen acyclic carbene (NAC) complexes of gold(I) has been investigated and compared with the reported activity of other gold(I) and gold(III) complexes. The complexes studied, [AuCl{C(NEt2)(NHTol-p)}], [AuCl{C(NEt2)(NHXylyl)}], and [Au(NTf2){C(NEt2)(NHXylyl)}], are very active in processes such as the rearrangement of homopropargylsulfoxides, the intramolecular hydroamination of N-allenyl carbamates, the intramolecular hydroalkoxylation of allenes, the hydroarylation of acetylenecarboxylic acid ester, and the benzylation of anisole. Although the NAC ligands have not been optimized for the reactions tested, the yields obtained are usually similar and sometimes better than those reported with other catalysts, showing that the presence of N−H bonds and the wider N−C−N angle in the NAC (as compared to the NHC) complexes are not detrimental for the catalysis. For the hydroarylation reaction (where two competing products can be formed), the NAC complexes allow ...

Enhancement of the Catalytic Activity of a Dawson-type Heteropoly Acid Induced by the Loading on a Silica Support

The Friedel–Crafts alkylation, benzylation of anisole with benzyl alcohol, was carried out over heteropoly acids (HPAs) supported on SiO2. A Dawson-type HPA, in which Nb atoms were partially substituted with W atoms, exhibited the highest activity among various kinds of HPAs. The catalyst was reusable in the reaction after the filtration and it kept high activity even after the washing with hot water when the catalyst was calcined at 743 K. In contrast, the unsupported catalyst was almost inactive after the thermal treatment. The change in the activity was in good agreement with the degree in the acid amount measured by NH3-TPD. Unlike the Dawson-type heteropoly acid, the activity of the Keggin-H3PW12O40/SiO2 remarkably dropped through the repeated use for the reaction. Based on the structural analysis of Dawson-type HPAs, the partially decomposed HPA on the support of SiO2 was ascribed to the active species.

Sulfated and Phosphated Mesoporous Nb Oxide in the Benzylation of Anisole and Toluene by Benzyl Alcohol

Materials possessing the high acidities of sulfated zirconia and the diffusion properties of mesoporous oxides are predicted to have numerous applications in the petrochemical industry. Because of surface deactivation and loss of structure under highly acidic conditions, there are few examples of materials which meet these specifications. In this work, mesoporous Nb oxide was treated with 1 M sulfuric acid or phosphoric acid and evaluated for their catalytic activities in the benzylation of toluene or anisole with benzyl alcohol. Characterization by XRD, nitrogen adsorption/desorption, and TEM demonstrated that the mesostructure was surprisingly stable to acid treatment. Pyridine adsorption and infrared spectroscopy (IR) showed a mixture of Lewis and Bronsted sites before and after acid treatment. Titration with a series of indicators demonstrated that sulfated mesoporous Nb oxide possesses a pKa of -8.2 and 31.784 mmol/g acid sites, roughly 100 times stronger than either bulk phosphated or sulfated niobia, which both possess pKa values in the range of -3.0. The best catalytic results in this study were achieved when using mesoporous Nb oxide treated with sulfuric acid; the conversion of benzyl alcohol with anisole to the benzylation product was 100% in 30 min, which is 200 times faster than the bulk catalyst. The extremely high activity was rationalized by the high number of strong Brønsted sites on the surface coupled with the superior diffusion properties of the mesoporous system.

Active and Reusable Catalyst in the Friedel—Crafts Alkylation Derived from a Heteropoly Acid.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Active and Reusable Catalyst in the Friedel–Crafts Alkylation Derived from a Heteropoly Acid

Abstract The H3PO4–WO3–Nb2O5 derived catalyst exhibited excellent activity and reusability in the benzylation of anisole at low temperature. On the basis of the XRD and IR data, the oxide derived from heteropoly acid was ascribed to the active and insoluble species in the reaction. It was found that the calcination temperature was the key factor in the generation of active species.

Explanation of an unusual substituent effect in the benzylation of anisole and identification of the origin of the active site in Clayzic.

The surprisingly low reaction rate of anisole (compared to benzene) towards “Clayzic” catalysed Friedel-Crafts benzylation at ambient temperature, has been explained and used to show the presence and identify the origin of, both Brønsted and Lewis acid sites in “Clayzic”.