Liquid phase hydrogenation of citral: suppression of side reactions

Mäki‐Arvela, Päivi; Tiainen, Lasse-Pekka; Neyestanaki, Ahmad Kalantar; Sjöholm, Rainer; Rantakylä, Tiina-Kaisa; Laine, E.; Salmi, Tapio; Murzin, Dmitry Yu.

doi:10.1016/s0926-860x(02)00333-2

Cited by 82 publications

(79 citation statements)

References 29 publications

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“…Citronellol (see Fig. 1) which, due to its pleasant odour of roses, is of interest in the flavor industry, is the third interesting product of citral hydrogenation and can be produced by hydrogenation over Ni catalysts: with Ni/Al 2 O 3 , selectivity is 95 % at complete conversion (T = 343 K), if ethanol is used as solvent [35]. However, with alcohols as solvents, acetals may be formed, reducing selectivity.…”

Section: Selective Hydrogenation Of Citral To Citronellalmentioning

confidence: 99%

Selective Hydrogenation of Citral in an Organic Solvent, in a Ionic Liquid, and in Substance

et al. 2007

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It is investigated whether the catalyst system Ag-In/SiO 2 can be applied in the selective hydrogenation of citral, with the aim of synthesizing the acyclic, allylic terpene alcohols geraniol/nerol with high selectivity and space-time yield. In addition, as liquid-phase hydrogenations are often also influenced by the choice of solvent, it is of interest to know how the solvent, in particular in terms of its polarity and hydrogen solubility, affects the activity and the selectivity of catalysts during hydrogenation of the a,b-unsaturated aldehyde citral. ProblemTerpenes are a low-cost class of compounds for the production of fragrances, flavors and pharmaceuticals, with terpenoid hydrocarbons (e.g., myrcene) being used less than terpene alcohols (e.g., geraniol, nerol, citronellol) and aldehydes (e.g., citral, citronellal). The compounds are often extracted from essential oils (e.g., lemon grass oil, citrus oil) by fractional distillation. Geraniol is the most frequently used terpenoid fragrance compound and, like its isomer nerol, applied in perfumes of roses and in citrus fragrances [1,2]. As an a,b-unsaturated aldehyde citral itself is an important educt for the synthesis of terpene alcohols and aldehydes because of its three functionalities (carbonyl group, conjugated C=C bond, isolated C=C bond) and thus, with the right choice of catalyst and reaction conditions, enables the synthesis of geraniol/ nerol, citronellal and/or citronellol by selective hydrogenation. Fig. 1 shows the reaction network of citral hydrogenation up to the completely hydrogenated reaction product 3,7-dimethyloctan-1-ol.In academia, citral hydrogenation is often used as a model reaction to study the influence of metal specificities, support materials and solvents on the intramolecular selectivitiy and product yield [3][4][5][6]. From a vulcano plot of the specific activity (turnover frequency) vs. the %-d character [7] of the metal used at 300 K and 0.1 MPa hydrogen pressure it follows, as expected, that Pd is the most active metal, whereas Ni, Co and Rh catalysts exhibit an activity which is about one to two orders of magnitude lower [6] (1) = 3,7-dimethyl-2-octenal, (2) = dihydrocitronellal, (3) = 3,7-dimethyl-2-octenol, (4) = 3,7-dimethyloctan-1-ol.

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Section: Selective Hydrogenation Of Citral To Citronellalmentioning

confidence: 99%

Selective Hydrogenation of Citral in an Organic Solvent, in a Ionic Liquid, and in Substance

et al. 2007

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“…Hydrogenation of citral gives valuable products, including citronellal, geraniol, nerol, and citronellol. Hydrogenation of citral has been studied using Ru [4][5][6][7][8][9], Pt [7,[10][11][12][13][14][15], Pd [7,16,17], Rh [6,7,11], Au [18], Ni [6,7,19,20], Ir [7,[21][22][23], Co [7], Os [7], Ag [24] and bimetallic [12,21,[25][26][27][28][29] catalysts. Citral contains three double bonds of which two are conjugated (C=O and C=C) and the third is isolated.…”

Section: Introductionmentioning

confidence: 99%

Hydrogenation of Citral Over Carbon Supported Iridium Catalysts

et al. 2012

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Hydrogenation of citral (3,7-dimethyl-2,6-octadienal) was carried out in a batch reactor at atmospheric hydrogen pressure and 70°C over Sibunit (mesoporous carbon) supported iridium catalysts with different metal loadings. The major products were isopropyl ethers of geraniol and nerol (2-propanol was used as solvent), but also geraniol, nerol, citronellal di-isopropyl acetal and citronellal were formed. The metal particle size was determined by CO-chemisorption and varied from 2 to 6 nm. The turnover frequency for hydrogenation reactions increased with the metal particle size.

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“…Vast literature survey is available on the selective hydrogenation of α, β-unsaturated aldehydes catalyzed by different noble metals supported catalysts [15][16][17] . In addition catalytic hydrogenation of α, β-unsaturated aldehydes are mostly based on supported metals platinum based bimetallic catalysts [18][19][20][21][22][23][24][25][26][27][28][29][30] . The selectivity towards unsaturated alcohols (geraniol and nerol) could also be increased by metal has deposited on reducible support as TiO 2 , the hydrogenation of the C=O bond can be promoted due to the presence of partially reduced species generated upon reduction at high temperature, that is strong metal-support interaction (SMSI effect) [31][32][33][34] and also addition of second metals at the same phenomena.…”

Section: S112mentioning

confidence: 99%

TiO2 Supported Pt Based Bimetallic Nanocatalysts for Selective Hydrogenation of Citral

2013

Chem Sci Trans

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TiO 2 supported Pt based bimetallic nanocatalysts were prepared by impregnation method and reduced at two different temperatures, 375 °C and 575 °C for the selective hydrogenation of citral to the corresponding unsaturated alcohols namely; geraniol (GOL) and nerol (NOL). The catalysts were characterized by BET surface area measurement, FT-IR, SEM, EDAX, TEM, XRD and XPS. The prepared nanocatalysts are uniformly dispersed with an average particles size 50-100 nm and zero valence metallic state. The SMSI (Strong Meal-Support Interaction) effect shows that the catalysts reduced at higher temperature leads to an increase in selectivity toward unsaturated alcohols (GOL & NOL) for Pt-Ru/TiO 2 compared to Pt-Pd/TiO 2 and Pt-Au/TiO 2 nanocatalysts. In addition a second metal (Ru) also leads to an increase of the GOL & NOL selectivity during the citral hydrogenation. The generated partially oxidized second metal species due to the difference in electronegativity, strongly binds the C=O group and also paves the way for the selective activation of the C=O bond. Metal support interaction and promoter active metal interaction increased the unsaturated alcohol formation.

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Liquid phase hydrogenation of citral: suppression of side reactions

Cited by 82 publications

References 29 publications

Selective Hydrogenation of Citral in an Organic Solvent, in a Ionic Liquid, and in Substance

Selective Hydrogenation of Citral in an Organic Solvent, in a Ionic Liquid, and in Substance

Hydrogenation of Citral Over Carbon Supported Iridium Catalysts

TiO2 Supported Pt Based Bimetallic Nanocatalysts for Selective Hydrogenation of Citral

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