Oxidative dehydration of glycerol to acrylic acid over vanadium-impregnated zeolite beta

Abstract

A desidratação oxidativa do glicerol a ácido acrílico foi estudada com o uso de zeólita Beta impregnada com vanádio. Os catalisadores foram preparados por impregnação úmida do metavanadato de amônio sobre a zeólita Beta na forma amoniacal, seguida de calcinação em ar a 823 K. A impregnação reduziu a área superficial específica, mas não afetou significativamente a acidez (Brønsted e Lewis) da zeólita. A avaliação dos catalisadores foi realizada num reator de leito fixo usando ar como gás de arraste e injetando o glicerol por meio de uma bomba seringa. Acroleína foi o principal produto formado, tendo também sido observados acetaldeído e hidróxi-acetona (acetol). O ácido acrílico foi formado em aproximadamente 25% de seletividade a 548 K sobre as zeólitas impregnadas. O resultado pode ser explicado por análises de XPS (espectroscopia fotoeletrônica de raios X), que mostraram uma boa dispersão de vanádio nos poros da zeólita.The oxidative dehydration of glycerol to acrylic acid was studied over vanadium-impregnated zeolite Beta. Catalysts were prepared by wet impregnation of ammonium metavanadate over ammonium-exchanged zeolite Beta, followed by air calcination at 823 K. Impregnation reduced the specific surface area, but did not significantly affected the acidity (Brønsted and Lewis) of the zeolites. The catalytic evaluation was carried out in a fixed bed flow reactor using air as the carrier and injecting glycerol by means of a syringe pump. Acrolein was the main product, with acetaldehyde and hydroxy-acetone (acetol) being also formed. Acrylic acid was formed with approximately 25% selectivity at 548 K over the impregnated zeolites. The result can be explained by XPS (X-ray photoelectron spectroscopy) measurements, which indicated a good dispersion of the vanadium inside the pores.Keywords: glycerol, acrylic acid, zeolite, dehydration, oxidation IntroductionGlycerol is usually found in combination with fatty acids of natural occurrence forming the triglycerides. Today, the major source of glycerol is the transesterification of oils and fats to produce biodiesel. 1 In this reaction, a molecule of triglyceride reacts with three molecules of methanol, under base catalysis conditions, to afford three molecules of fatty acid methyl esters (the biodiesel) and a molecule of glycerol (Scheme 1). In recent years, the growing concern about global warming has motivated the use of biofuels. Biodiesel, together with bioethanol, is one of the most important biofuels used nowadays.For each 90 m 3 of biodiesel produced by transesterification, about 10 m 3 of glycerol are obtained. The worldwide glycerol production will reached 2 approximately 1.2 million tons in 2012 and most of this production will come from the biodiesel industry. In Brazil, for instance, there is a mandatory blend of 5% of biodiesel in the petrodiesel, which represents an annual glycerol production of approximately 300,000 tons. The traditional markets for glycerol are cosmetics, soaps, pharmaceuticals and personal care products. However, with the increasing ...

One-step glycerol oxidehydration to acrylic acid on multifunctional zeolite catalysts

“…In a publication of 2013, the production of acrylic acid from glycerol oxidehydration using vanadium impregnated on an acid zeolite with BEA structure was mentioned for the first time [30].…”

Glycerol oxidehydration to acrylic acid on complex mixed-metal oxides

“…Taking into consideration the products distribution obtained on V/V-CoAlPO, the extra-framework vanadium species seem to (i) block the active in-framework-V-sites, (ii) enhance total oxidation to carbon oxides and (iii) be completely inactive towards the selective oxidation of acrolein to acrylic acid. It is of interest to compare our results to the ones obtained by Pestana et al using vanadium-impregnated zeolitebeta [61]. Indeed, although extra-framework vanadium species were also present in the latter materials, acrylic acid selectivity up to 25% were obtained, although at glycerol conversion lower than 80%.…”

“…vanadium, was present. This was the case of vanadium-substituted HTBs, vanadiumcontaining zeolites [61] and Vanadium-Phosphorus-Oxides (VPOs) [78]. Indeed, looking at these results, catalysts related to the Perovskites family seems to be the only mixed-oxides capable of efficiently carrying out the whole glycerol oxidehydration to acrylic acid, with selectivities greater than 50% at total glycerol conversion.…”

Atmospheric Pressure Continuous Production of Solketal from the Acid-Catalyzed Reaction of Glycerol with Acetone

“…[4][5][6][7] Hydrogenolysis over metal catalysts affords 1,2-and 1,3-propanediols, which can be used in the production of polymers. 8,9 Dehydration over acidic catalysts produces acrolein, [10][11][12][13] an important intermediate in the synthesis of acrylic acid and other chemicals. Synthesis gas, a mixture of CO and H 2 , can be produced from glycerol aqueous phase reforming.…”