Abstract
Citronellal cyclization was carried out in a continuous mode over H-beta-25 zeolite-based extrudates in a trickle-bed reactor at 35 °C and 10 bar of Ar. The physicochemical properties of zeolitic c...
Highlights
Isopulegol is commonly employed in the production of fragrances with blossom compositions and as an important intermediate in menthol synthesis.[1−3] (−)-Menthol is one of the major volume chiral chemicals applied in pharmaceuticals, being an essential component of mouthwash, toothpaste, tobacco, chewing gum, candy, and various cosmetics.[2,4] Direct isolation from natural sources, semi-synthetic protocols, or direct asymmetric synthesis are used for (−)-menthol production.[5]
Alumina, aluminosilicate clay or colloidal silica were used as a binder for shaping the H-beta-25 zeolite catalyst
The trickle-bed reactor was used to elucidate the effect of the binder and the extrudate diameter in cyclization of citronellal
Summary
Isopulegol is commonly employed in the production of fragrances with blossom compositions and as an important intermediate in menthol synthesis.[1−3] (−)-Menthol is one of the major volume chiral chemicals applied in pharmaceuticals, being an essential component of mouthwash, toothpaste, tobacco, chewing gum, candy, and various cosmetics.[2,4] Direct isolation from natural sources, semi-synthetic protocols, or direct asymmetric synthesis are used for (−)-menthol production.[5]. Various heterogeneous catalysts have been examined in the cyclization of citronellal, including mixed cogels,[9] Zn(II)-based catalysts (ZnBr2/SiO2 and ZnBr2/γ-Al2O3),[10,11] Zr(II)-based TcmaietOaslo2y)ps,ot1s2ro−(u1Z4srOsm2il,aicStea−r,1iZa0l,r1sO3,8−21, a5ZnrdaOlu2z−meoPinlOiate,41,s4.Z2,1,8r5,O13c2,1−l6a−SyO18m4,TaathneedriaZllisrq,O1u3i2,d1−6phase reaction has been mainly studied with powder catalysts in batch reactors under high catalyst/reactant ratios and high temperatures. Continuous flow mode of industrial operations allowing much more efficient operation and ensuring constant product quality, requires scaling-up catalysts into shaped bodies to decrease high-pressure drop in large trickle-bed reactors. This can lead to mass transfer limitations accompanied by catalyst deactivation as well as alternation of product distribution. This work is focused on the influence of the binder type and size of extrudates on their catalytic behavior in continuous citronellal cyclization to isopulegol in a trickle-bed reactor
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