Elizabeth R. Lachter

Liquid phase benzylation of aromatic compounds with benzyl alcohol catalyzed by niobium phosphate

The catalytic activity of commercial niobium phosphate was evaluated in the benzylation of aromatic compounds with benzyl alcohol, in liquid phase. The conversion of benzyl alcohol was 100% in the reactions with toluene, ethylbenzene, propylbenzene and p-xylene while the highest selectivity in monobenzyl derived compounds (91%) was achieved with p-xylene. The formation of dibenzyl ether was also observed, indicating the presence of Bronsted acids sites in this type of catalyst.

Etherification of glycerol with benzyl alcohol catalyzed by solid acids

In this work we present the results of glycerol etherification with benzyl alcohol, catalyzed by different solid acids. The mono-benzyl-glycerol ether was the main product in the reactions catalyzed by β zeolite and Amberlyst-35 acid resin, whereas di-benzyl-ether was formed in higher yield with the use of p-toluene-sulfonic acid and K-10 montmorillonite as catalyst. Niobic acid was inactive in this reaction. The porous structure of the zeolite impaired the formation of di and tri-benzyl-glycerol ethers.

Aerobic hydroxylation of hydrocarbons catalysed by vanadate ion

Vanadate anion catalyses aerobic hydroxylation of hydrocarbons in acetonitrile in the presence of solid ascorbic acid or zinc and with obligatory participation of pyridine, pyrazine-2-carboxylic acid and acetic acid as mediators of proton and electron transfer. If sufficient amount of water is present in the reaction mixture, ascorbic acid is dissolved in aqueous acetonitrile and no hydroxylation occurs in this case. The dependencies of the product yields on the concentrations of the reactants have been studied and a mechanism of the formation of hydroxyl radicals has been proposed. These systems mimic generation of hydroxyl radicals in certain vanadium-dependent biological processes.

Oxidations by the reagent “O2–H2O2–vanadium derivative–pyrazine-2-carboxylic acid”. Part 13.For parts 1–12 see refs. 4(a)–(l), respectively. Kinetics and mechanism of the benzene hydroxylation

It has been concluded on the basis of the kinetic study of benzene hydroxylation by the “O2–H2O2–nBu4NVO3–PCA” reagent in acetonitrile at various temperatures that the oxidation is induced by the attack of hydroxyl radical on the benzene molecule. The rate-limiting step of the reaction is the monomolecular decomposition of the complex containing one coordinated PCA molecule as well as one hydrogen peroxide molecule: VV(PCA)(H2O2) → VIV(PCA) + HOO˙ + H+. The V(IV) species thus formed reacts further in a non-limiting stage with the second H2O2 molecule to generate the hydroxyl radical: VIV(PCA) + H2O2 → VV(PCA) + HO˙ + HO−. The effective activation energy is 19 ± 3 kcal mol−1.

Iron-Exchanged Zeolite as Effective Catalysts for Friedel–Crafts Alkylation with Alkyl Halides

Friedel–Crafts alkylation of benzene and ethylbenzene with butyl halides has been investigated in the presence of iron-exchanged zeolites. The catalysts showed high conversions and selectivity for monoalkylated products with tertiary and secondary halides under mild reaction conditions (45–60°C). Alkylation of ethylbenzene with 2-chlorobutane can be achieved in 99% yield and 100% selectivity to the monoalkylated product.

Benzylation of toluene and anisole by benzyl alcohol catalysed by niobic acid

Abstract The catalytic activities of commercial niobic acid, niobium pentoxide prepared in laboratory and niobic acid treated with phosphoric acid, were evaluated in the benzylation of toluene and anisole with benzyl alcohol, in liquid phase. The best results were achieved with niobic acid treated with phosphoric acid (pretreatment at 423 K), the conversion of benzyl alcohol was 99.2% with anisole and the main product was the benzylation product. The acidity of these solids has been determined by infrared spectrometry using pyridine as a probe molecule. The ratio of Lewis acidity/Bronsted acidity was higher for niobic acid treated with phosphoric acid.

Alkylation of toluene with aliphatic alcohols and 1-octene catalyzed by cation-exchange resins

The catalytic activity of macroreticular cation-exchange resin (Amberlyst-15) was evaluated for the reaction of toluene with isopropanol, 1-octanol, 2-octanol and 1-octene at 80°C, in the liquid phase. The best results were achieved with octene. The reaction yielded only monoalkylation products. The conversion of octene was 75% after 4 h of reaction. In the reaction with isopropanol the main product was propene. In the reaction with 1-octanol and 2-octanol the conversion was very low and the main products were the octyl ethers.

Benzylation of toluene and anisole by benzyl alcohol catalyzed by niobic acid: influence of pretreatment temperature in the catalytic activity of niobic acid

Abstract We have studied the influence of the pretreatment temperature (423 K and 573 K) on the catalytic activity of commercial niobic acid for the benzylation of toluene and anisole with benzyl alcohol. The reactions were carried out in liquid phase at reflux temperature of the mixture. Best results were achieved with niobic acid pretreated at 573 K, The conversion of benzyl alcohol was 78.9 to anisole and the main product was the monobenzylation product.

Benzylation of benzene, toluene and anisole with benzyl alcohol catalyzed by cation-exchange resins

The catalytic activity of gel and macroreticular ion-exchange resins (Lewatit and Amberlyst-15) was evaluated for the reaction of benzene with benzyl alcohol and benzyl chloride at 80°C in the liquid phase. With benzyl chloride, the monobenzylation product, diphenylmethane, was obtained in low yield, both with the gel and the macroreticular resins. Better results were obtained with benzyl alcohol as benzylation agent and the most active resin was Amberlyst-15. The benzylation of toluene and anisole with benzyl alcohol, catalyzed by Amberlyst-15, was also evaluated, the conversion of benzyl alcohol being proportional to the concentration of acid sites in the resin. Monobenzylation to benzyl toluene or benzyl anisole is the main reaction and the selectivity was usually found to be higher than 80%, when a toluene/alcohol or anisole/alcohol molar ratio of 10 is used. Secondary reactions to dibenzyl toluenes, dibenzyl anisole and benzyl ether occur to a varying extent, depending on the substrate ratios. In all cases, predominance of ortho/para isomers was observed.

Biodiesel production by in situ transesterification of sunflower seeds by homogeneous and heterogeneous catalysis

The objective of this work is to show the results of the in situ transesterification of sunflower seed oil with methanol on basic homogeneous and heterogeneous catalysis for the production of biodiesel. In homogeneous catalysis, the activity of KOH and K2CO3 were evaluated using the same oil:methanol ratio of 1:90. KOH showed to be more active than K2CO3, leading to total conversion in biodiesel after 1h reaction time. In the heterogeneous catalysis the activity of K2CO3/Al2O3 was comparable to the activity of K2CO3 bulk: 53.0 and 66.6% resp. The properties of samples of biodiesel produced by homogeneous and heterogeneous catalysis were evaluated and are in accordance with the recommended fuel properties.