Niobium to alcohol mol ratio control of the concurring esterification and etherification reactions promoted by NbCl5 and Al2O3 catalysts under microwave irradiation

Barbosa, Sandro L.; Hurtado, Gabriela R.; Klein, Stanlei Ivair; Valdemar, L.; Dabdoub, Miguel J.; Guimarães, Carlos F. R. C.

doi:10.1016/j.apcata.2007.12.013

Cited by 21 publications

(12 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Further experiments indicated that higher yields of ether could be obtained with increased amounts of catalyst; at 20%-w/w, only the ether was formed. The maximum yield of benzoate free from ether is 93.61%, with a catalyst load of 6%; this yield is superior to that obtained by us using NbCl 5 catalyst [12] or by others using ionic liquids [6,7]. Similar yields can be obtained in about 4 h using conventional heating at 80°C.…”

Section: Reactionsmentioning

confidence: 48%

Benzyl benzoate and dibenzyl ether from of benzoic acid and benzyl alcohol under microwave irradiation using a SiO2–SO3H catalyst

Barbosa

Ottone

Santos

et al. 2015

Catalysis Communications

Self Cite

View full text Add to dashboard Cite

A sulfonated silica gel of small surface area with large pore diameters was prepared from the sodium silicate obtained from the reaction of construction sand and sodium carbonate, and sulfated with concentrated sulfuric acid. At 7%-w/w it promotes in 5 min the Fischer-Speier esterification of benzoic acid/benzyl alcohol in 93% yields, and at higher concentrations, dibenzyl ether is produced selectively and quantitatively, in solvent free reactions induced by microwave irradiation.

show abstract

Section: Reactionsmentioning

confidence: 48%

Benzyl benzoate and dibenzyl ether from of benzoic acid and benzyl alcohol under microwave irradiation using a SiO2–SO3H catalyst

Barbosa

Ottone

Santos

et al. 2015

Catalysis Communications

Self Cite

View full text Add to dashboard Cite

show abstract

“…The infrared spectrum of the silica ( Fig. 4 , left) is representative of an amorphous silica gel [2] . The characteristic absorption bands around 3400 and 1630 cm −1 are associated with the stretching and bending modes of molecular water, whereas the shoulder at 3200 and the weak absorption at 960 cm −1 are related to the –OH and Si-OH vibrations of the silica silanol groups.…”

Section: Resultsmentioning

confidence: 99%

“…The bands at 1090 and the associated shoulder at 1190 cm −1 are characteristic of the asymmetric stretching modes of the Si-O-Si bonds. The absorption at 800 cm −1 is characteristic of the ring-structured tetrahedral SiO 4 (Si-O-Si symmetric stretchings), the Si-O-Si bending vibrations at 470 cm −1 , and the overtones typical of the amorphous silicas in the region of 1800–1900 cm −1 complete the spectrum of the gel [2] . The small quantity of niobium in the catalyst prevented the observation of particular Si-O-Nb IR vibrations in the spectrum of the SiO 2 -Nb catalyst ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In the search for an active catalyst for the latter transformations, we found that suspensions of NbCl 5 /Al 2 O 3 in carboxylic acid-alcohol mixtures did afford the corresponding esters from mixtures of benzyl alcohol with acetic acid but, more interestingly, from the also aromatic ring bearing benzoic acid, all the reactions promoted by microwave irradiation. In that study, it was found that the mole ratio of catalyst to alcohol could be tuned to produce exclusively dibenzyl ether, independent of the presence of excesses of the acid; moreover, no organic products were obtained when the catalyst was treated with the benzoic acid alone [2] . Interestingly, a recent report called the attention for the fact that niobium, when grafted on silica, does have a great affinity for carboxylic acids [3] .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The preparation of benzyl esters using stoichiometric niobium (V) chloride versus niobium grafted SiO2 catalyst: A comparison study

Barbosa

Lima

Almeida

et al. 2018

Heliyon

Self Cite

View full text Add to dashboard Cite

Two solvent free methods of a one-to-one alcohol/acid mol ratio synthesis of benzyl esters of the formic, acetic, benzoic, salicylic, nicotinic, and oxalic acids are described. The stoichiometric reactions used 1.5 mol ratio solid NbCl5 as the reagent and required from two to three hours for completion at room temperature; for the catalytic processes, NbCl5 was grafted directly, at room temperature, onto a silica gel of specific area of 507 m2g−1, produced from construction sand and sodium carbonate, forming a 5.4% Nb w/w SiO2-Nb gel with a specific area of 412 m2g−1. At 10% w/w catalyst/alcohol ratio, this SiO2-Nb catalyst gave similarly very good yields but required from 6 to 9 hours at the reflux temperature of the slurry. The catalyst could be re-used three times.

show abstract

“…During our study of developing solid catalysts for esterification reactions mediated by microwave irradiation [44][45], our attention was drawn to the transesterification reactions of triglycerides and biodiesel formation. The several drawbacks of this process start with the fact that the triglycerides are poorly soluble in alcohol, which means that either long reaction times or conditions such as high temperatures, high pressures, or microwave or ultrasound reaction enhancement are necessary for good conversions.…”

Section: Resultsmentioning

confidence: 99%

Biodiesel from waste cooking oil: sodium carbonate modified sand as filter, TLC and the unmodified domestic microwave oven approach

et al. 2016

View full text Add to dashboard Cite

Biodiesel is obtained by transesterification of animal and vegetable triglycerides (fats), and have several advantages over fossil fuel, perhaps the most important being its renewable source and its lack of pollutants such as aromatic and sulfur components. However, biodiesel from vegetable sources such as Soya beans is expensive, and it raises the question of planting for combustibles not for food. The most interesting alternative source for biodiesel is the non expensive waste cooking oil, WCO, which also brings the obvious benefit of transforming a severe pollutant into a green combustible. WCO consists of the triglycerides, but also contains left over food solids, which must be removed by filtration, mono and diglycerides, which are the source of the WCO free fatty acids (FFA), which must be converted to esters before the transesterification of the triglycerides, or, as usually reported, saponification of the final biodiesel mixture will occur. Several methods have been devised to deal with these drawbacks, and generally involve expensive equipment in multistage processes, which include filtration, acid catalysis for the esterification of free fatty acids, removal of the acid catalyst, a base catalyzed transesterification reaction, and, finally, the separation of the glycerol by product and purification of the biodiesel. Herein we propose a new silica gel filtering system, which in one step removes both solids and free fatty acid contents of WCO. In this new approach for biodiesel, an unmodified household microwave oven is used to speed up the base catalyzed transesterification reaction, and a useful piece of advice is given for the easy follow up of the reaction progress by thin layer chromatography.

show abstract

Niobium to alcohol mol ratio control of the concurring esterification and etherification reactions promoted by NbCl5 and Al2O3 catalysts under microwave irradiation

Cited by 21 publications

References 22 publications

Benzyl benzoate and dibenzyl ether from of benzoic acid and benzyl alcohol under microwave irradiation using a SiO2–SO3H catalyst

Benzyl benzoate and dibenzyl ether from of benzoic acid and benzyl alcohol under microwave irradiation using a SiO2–SO3H catalyst

The preparation of benzyl esters using stoichiometric niobium (V) chloride versus niobium grafted SiO2 catalyst: A comparison study

Biodiesel from waste cooking oil: sodium carbonate modified sand as filter, TLC and the unmodified domestic microwave oven approach

Contact Info

Product

Resources

About