Esterification Of Benzyl Alcohol Research Articles

Finding the Compromise between Brønsted Acidity and Mesoporosity in Hierarchical ZSM‐5 Zeolites

AbstractMesoporous ZSM‐5 catalysts were prepared from a commercial ZSM‐5 (Si/Al=15), using a 2‐step micelle‐templating procedure. By varying the NaOH/Si synthesis ratio in the range of 0.3‐0.7, ZSM‐5 catalysts with different textural and acidic properties were obtained. Increasing the NaOH/Si ratio in the synthesis gel leads to zeolites that feature reduced number of Brønsted acid sites, but higher mesopore volume, which allows for reducing the diffusion path length. In order to assess the best compromise between Brønsted acidity and mesopore volume two test reactions were run. The alkylation of phenol with tert‐butyl alcohol allowed to evidence the accessibility of bulky molecules to active sites. The esterification of benzyl alcohol with hexanoic acid allowed to probe the specificity of Brønsted acid sites in ZSM‐5. The best compromise was found for micro‐/mesoporous ZSM‐5 catalysts prepared with the ratio 0.38<NaOH/Si<0.5.

Synthesis of 2D MFI zeolites in the form of self-interlocked nanosheet stacks with tuneable structural and chemical properties for catalysis

This study explores a facile synthesis method by simply changing the type of precursor cations or anions to regulate the nanosheet stack size of mesoporous 2D MFI zeolites while preserving the ‘self-interlocked ordered nanosheet stack’ (SI-ONS) microstructural characteristics. The important roles of precursor cations and anions in controlling the structure and hence chemical properties of the 2D MFI zeolites are demonstrated and the corresponding mechanisms are explained. The ability to facilitate microporous MFI framework development followed the order Na+<K+<Rb+<Cs+ for cations and SO42−≈NO3−≈Cl− for anions. Conversely, the capability to generate inter-crystalline mesopores followed the order Na+>K+>Rb+>Cs+ and SO42−>NO3−>Cl−. The cations and anions showed little effect on the number and strength of strong acid sites, but clearly influenced their hydrothermal stability. The hydrothermal stability of strong acid sites in the resulting 2D MFI zeolites followed the order Na+<K+<Rb+ for cations and SO42−<Cl−<NO3− for anions. A general micelle-aggregation mechanism governing the microstructure formation of SI-ONS in precursors containing different types of cations and anions was proposed established. It was found, for the first time, that a linear relationship exists between nanosheet stack size and mesopore volume of 2D MFI zeolites, which provides a valuable indicator for predicting mesopore volume from nanosheet stack size for a 2D MFI zeolite product. Catalytic performance of the synthesized 2D MFI zeolites was examined using three selected liquid phase reactions including the O-methylation of cyclohexanone, the esterification of benzyl alcohol with hexanoic acid and the protection of benzaldehyde with pentaerythritol. It was shown that the catalytic activity of the 2D MFI zeolites was primarily dictated by the amount of mesopores present, for example, the reaction conversion increased by as much as 300% when the mesopore volume increased from 0.05 to 0.55cm3g−1.

Esterification of Benzyl Alcohol with Acetic Acid over Mesoporous H-ZSM-5

In this study, the performance of mesoporous ZSM-5 has been studied on the esterification of acetic acid (AA) with benzyl alcohol (BA). The mesoporous ZSM-5 catalyst has been synthesized with the variation of aging time i.e. 6, 12, and 24 hours at the same temperature, 70 °C. The cation exchange of Na-ZSM-5 to H-ZSM-5 was performed before the catalytic activity test. The acidity type and amount of solids were determined by FT-IR spectroscopy using pyridine as a probe molecule. The characterization by pyridine adsorption showed that at a higher mesoporous surface area, the number of Lewis acid was increased. The highest mesoporous surface area, Lewis, and Brönsted acid sites were obtained by sample which has the lowest crystallinity, i.e. 255.78 m2/g, 0.2732 mmol/g, and 0.20612 mmol/g, respectively. Influence of mesoporous volume was studied on the catalytic activity of the mesoporous ZSM-5 in the esterification reaction. Conversion of acetic acid in the esterification reaction for samples of HZ-6, HZ-12, and HZ-24 were obtained by titration methods, i.e. 39.59, 36.39, and 32.90 %, respectively. Hence, the reaction temperature of 393 K, molar ratio 1:4 (AA:BA) and catalyst loading 5 % were selected as an optimum reaction parameters.

Hierarchically structured MFI zeolite monolith prepared using agricultural waste as solid template

Hierarchically structured MFI zeolite monoliths were prepared using corn and sorghum stem piths as sacrificial solid templates. The monoliths were characterized using XRD, SEM, TEM, N2 adsorption, mercury porosimetry, 27Al MAS NMR and NH3-TPD. The textural porosity characterization results indicated presence of micropores, mesopores and macropores in the monoliths. H-ZSM-5 monolith prepared by this method exhibited superior catalytic performance than conventional H-ZSM-5, mesoporous H-ZSM-5 and mesoporous Al-SBA-15 in esterification of benzyl alcohol with hexanoic acid. The superior catalytic performance of the zeolite monolith is due to hierarchical nature of the pores present in it.

Evaluation of Catalytic Activity of Acid Activated Multiwalled Carbon Nanotubes in an Esterification Reaction

Multiwalled carbon nanotubes (MWCNTs) synthesized earlier by catalytic chemical vapor deposition of acetylene, were used to develop heterogeneous supported acid catalysts by sonicating with 50% aqueous solutions of H2SO4, H3BO3 and H3PO4. The effect of acid treatment of MWCNTs, on their textural properties such as crystallinity, surface area, nature of the surface functional groups and elemental composition was investigated by appropriate instrumental methods of analysis such as BET surface area, Powder XRD, FT-IR, SEM-EDS, TEM and XPS. Acidity of the materials was estimated by n-butyl amine back titration method and the catalytic activity was evaluated in an acid catalyzed esterification reaction between benzyl alcohol and acetic acid. Further, the effect of duration and temperature of the reaction on the conversion of benzyl alcohol to benzyl acetate was studied. The product analysis was made by GC, LC-MS and 1HNMR techniques. The characterization techniques indicated that, the textural properties of the acid activated MWCNTs were distinctly different from those of the pristine MWCNTs inferring a possible incorporation of oxoacids into the mesoporous structure of MWCNTs. All the materials showed catalytic activity in the esterification of benzyl alcohol with acetic acid resulting benzyl acetate with 100% selectivity and 10-88% yield depending on the experimental conditions. Sulphuric acid activated MWCNTs exhibited highest surface acidity and catalytic activity. These catalysts were also found to be recyclable up to 5 times without any significant loss in its catalytic activity. Keywords: Acid activation, benzyl acetate, carbon nanotubes, catalytic activity, esterification, surface acidity.

Undecatungstophosphate anchored to MCM-41: An ecofriendly and efficient bifunctional solid catalyst for non-solvent liquid-phase oxidation as well as esterification of benzyl alcohol

Undecatungstophosphate anchored to MCM-41 was synthesized and characterized by various physicochemical techniques. The bifunctional catalytic activity was evaluated for esterification as well oxidation reactions of benzyl alcohol. The influence of different parameters such as molar ratio, amount of catalyst, reaction time and reaction temperature on oxidation as well as esterification of benzyl alcohol was investigated for maximum conversion. Detailed kinetic studies reveal that the reactions follow first order kinetics and the low values of activation energy for esterification and oxidation indicates that the reaction rate is truly governed by the chemical step. The present bifunctional catalyst can be recycled without any significant difference in % conversion for both reactions. Further, oxidation and esterification of various alcohols were also carried out under optimized conditions to see the effect of chain length and type of alcohols.

Ruthenium/NHC-catalyzed tandem benzylic oxidation/oxidative esterification of benzylic alcohols with phenols

Abstract An efficient methodology to access benzoate derivatives via tandem benzylic oxidation/oxidative esterification of benzylic alcohols with phenols catalyzed by ruthenium/NHC was developed. This operationally simple one-pot process uses O 2 as the clean oxidant, producing esters in good to excellent yields.

ChemInform Abstract: Palladium/NHC‐Catalyzed Tandem Benzylic Oxidation/Oxidative Esterification of Benzylic Alcohols with Phenols.

AbstractTitle tandem benzylic oxidation—oxidative esterification represents a novel efficient access towards aryl benzoates (III) and (V) directly from benzylic alcohols (I), (IV) and phenols (II).

Palladium/NHC-catalyzed tandem benzylic oxidation/oxidative esterification of benzylic alcohols with phenols

A palladium/NHC-catalyzed tandem benzylic oxidation/oxidative esterification of benzylic alcohols with phenols to access aryl benzoate derivatives is described. The procedure tolerates a series of functional groups, such as methoxy, nitro, cyano, chloro, fluoro and bromo groups. Thus, it represents a practically alternative method to access aryl benzoate derivatives.

Dealumination of Zeolite Beta Catalyst Under Controlled Conditions for Enhancing its Activity in Acylation and Esterification

This work deals with the dealumination of zeolite beta under different conditions to optimize its catalytic performance. The dealumination was carried out either using oxalic or tartaric acid solution of different pH values or steaming up to 500 °C. The dealuminated zeolite samples were characterized using X-ray diffraction, N2-physisorption, ICP, 27Al NMR and NH3-TPD. Their catalytic activities were studied for acylation reaction of 2-methoxy naphthalene or naphthalene with acetic anhydride and esterification of benzyl alcohol with hexanoic acid. Among the dealuminated samples examined, those treated with oxalic acid or tartaric acid at pH 2 showed high activity. The high activity can be correlated with the relative increase in the amount of strong acid sites and with the enhanced accessibility of the reactants to the active sites, which are caused by removal of extra-framework Al species on the acid treatments.

Polymer-Supported Carboxylate as a New Polymeric Reagent for Synthesis of Alkyl Esters

Polymer supported reagents especially anion exchange resins have been widely applied in organic synthesis. These polymeric reagents are generally used in single step reactions. Their main advantage over monomeric reagents is their insolubility in the reaction medium and consequently the easier workup by a simple filtration. The reactions can often be driven to completion by using excess of these reagents without the fear of separating the unspent reagent from the desired products. The spent polymeric reagents can usually be removed quantitatively and regenerated. In addition, anions bound to the macroporous resin have the advantage that they often react successfully in non-polar solvents. The ester group is an important functional group that can be synthesized in a number of different ways such as acylation of alcohols, oxidation of aldehydes, addition of carboxylic acids to alkenes, reaction of carboxylic acids with diazomethane, Bayer-Villiger oxidation of ketones, reaction of organoboranes with α-halo esters, rearrangement of α-haloketones (Favorskii reaction) and especially for large scale operation by reaction of carboxylate salts or Amberlite IRA-904 supported carboxylate ion with alkyl halides or tosylates. Sodium carboxylate, however, has been the reagent most widely used. Unfortunately, each of these methods suffer from at least one of the following disadvantages: (1) the yields of the reactions are low, (2) the reaction has to be carried out in the presence of phase transfer catalyst, (3) the reaction mixture has to be acidified or the reaction has to be catalyzed by a base such as pyridine, and (4) tedious work-up procedure. Polymer-supported carboxylate ion overcomes most of the above mentioned disadvantages. In this study we wish to report an important, efficient, and easy method for preparation of alkyl acetate or alkyl formate esters from crosslinked poly(4-vinylpyridinium) acetate (I) or crosslinked poly(4-vinylpyridinium) formate (II) with alkyl halides (Scheme 1). While there are numerous applications of solid-supported reagents and scavengers only a few examples for the formation of esters were described. Solid-supported acids were used as catalysts in the esterification of carboxylic acids with alcohols. Carboxylates, generated with solidsupported organic bases, were alkylated with alkyl halides. Solid-supported organic bases were also used as scavenger resins in the esterification of benzyl alcohol with benzyl chlorides, giving clean benzyl esters in high yields. A modification of the Mitsunobu reaction with resin-bound triphenylphosphine and soluble di-t-butylazodicarboxylate was described, that allowed for the isolation of pure products without chromatography. A very recent report described the alkylation of carboxylic acids with carbenium ions, generated from polymer-supported triazines, for the ester formation. We report here a convenient and general procedure for the synthesis of esters from alkyl halides and polymer-supported carboxylate ion that readily prepared from employing the commercially available poly(4-vinylpyridine) (2% crosslinked with DVB) resin as the solid-supported condensation reagent. Crosslinked poly(N-methyl-4-vinylpyridinium) acetate (I) and crosslinked poly(N-methyl-4-vinylpyridinium) formate (II) were prepared by an exchange reaction between crosslinked poly(N-methyl-4-vinylpyridinium) iodide with a slight excess of sodium acetate or sodium formate solution in water. Using these heterogeneous reagents converted benzyl halides to benzyl acetate or benzyl formate esters in acetone under reflux condition. The advantages of this method are: 1) the reaction can be performed in non-aqueous medium; 2) an excess of the reagent can be used; 3) the product can be obtained by simple filtration and evaporation of the solvent; and 4) the polymeric reagent is easily regenerable with a sodium acetate or sodium formate solution. Crosslinked polymers (I) and (II) can be easily prepared and used as mild and efficient polymeric reagents for conversion of benzyl halides to the corresponding benzyl acetate and benzyl formates. It was proved that acetone is the best solvent for these reactions. In these conversions, the best molar ratio of reagent/substrate proved was 1.5, but

Assessment of the mesopore wall catalytic activities of MFI zeolite with mesoporous/microporous hierarchical structures

MFI zeolite with a mesoporous/microporous hierarchical structure (MeMFI zeolite) was hydrothermally synthesized with an organosilane surfactant. The acid catalytic activities of the mesopore walls were evaluated for various reactions involving bulky molecules, such as the protection of benzaldehyde with pentaerythritol, the condensation of benzaldehyde with 2-hydroxyacetophenone, the esterification of benzylalcohol with hexanoic acid, and the cracking of branched polyethylene. The catalytic activities of pristine MeMFI zeolite were very high compared with those of a conventional MFI catalyst. The catalytic activities of MeMFI were lost almost completely after selective dealumination of the surface Al on the mesopore walls using tartaric acid. For small molecular reactions, however, the mesoporous zeolite still exhibited high catalytic activities even after the dealumination process. This indicates that bulky molecular reactions occurred due to Al sites located at the surface of the mesopore walls.

Mesoporous materials with zeolite framework: remarkable effect of the hierarchical structure for retardation of catalyst deactivation

Hierarchical MFI zeolite was synthesized following a synthesis route using organic-inorganic hybrid surfactants; the resultant zeolite with mesoporous/microporous hierarchical structure exhibited remarkably high resistance to deactivation in catalytic activity of various reactions such as isomerization of 1,2,4-trimethylbenzene, cumene cracking, and esterification of benzyl alcohol with hexanoic acid, as compared with conventional MFI and mesoporous aluminosilicate MCM-41.

Polylactones 48. SnOct2-Initiated Polymerizations of Lactide: A Mechanistic Study

Sn(II)2−ethylhexanoate (SnOct2) was reacted with 2 equiv of benzyl alcohol at 20 °C, and a liberation of octanoic acid in a rapid equilibration was found. When the temperature was raised to 180 °C in steps of 40 °C, esterification of benzyl alcohol and octanoic acid was observed up to a conversion of 90%. This esterification was catalyzed by Sn(II) and not by the protons of the free octanoic acid. The esterification liberated Sn(OH)2, which finally precipitated in the form of SnO. This precipitate proved to be a good initiator for the polymerization of lactide above 120 °C. Analogous results were obtained with 1-decanol, triethylene glycol monomethyl ether, and neopentane diol. When SnOct2 was reacted with methyl lactate at 20 °C, a chelate complex of one Sn with two lactate ligands was formed, liberating almost all octanoic acid. At higher temperatures, esterification of octanoic acid with methyl lactate and transesterification of the methyl group (yielding methyl octoate) were observed. The latter ester...

Novel preparation method for surfactant-lipase complexes utilizing water in oil emulsions

A novel preparation method for surfactant-lipase complexes has been developed utilizing water in oil emulsions. In order to optimize the preparation conditions, we have investigated the effects of several operational parameters on the enzymatic activity of the surfactant-lipase complexes in organic media. When a nonionic surfactant was employed under optimal preparation conditions [alkaline pH 8-10, organic/aqueous = 90/10 (v/v), concentration of surfactant, 10 mM[, the surfactant-lipase complex efficiently catalyzed the esterification of benzyl alcohol with lauric acid in organic media. The esterification rate of the surfactant-lipase complex was increased over 16-fold relative to the native powder lipase. Furthermore, the lipase complex showed high storage stability. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 455-460, 1997.