Selective hydrogenation of furfural on Ir/TiO2 catalysts

Abstract

Recebido em 23/1/09; aceito em 4/12/09; publicado na web em 8/4/10 Titania-supported Ir catalysts were used in the hydrogenation of furfural. Reactions were carried out in a stirred batch type reactor at 0.62MPa and 363K using a 0.10M solution of furfural in a 1:1 mixture n-heptane -ethanol as solvent. Catalysts containing 2 wt% of Ir were reduced in H 2 flow at different temperatures in the range 473-773K. The catalysts were characterized by H 2 chemisorption, TEM, TPR, TPD of NH 3 and XPS. Conversion of furfural is higher at lower reduction temperatures, but leads to byproducts whereas reduction at higher temperatures shows selectivity to furfuryl alcohol close to 100%.

Batch versus Continuous Flow Performance of Supported Mono‐ and Bimetallic Nickel Catalysts for Catalytic Transfer Hydrogenation of Furfural in Isopropanol

“…[5] The catalytic route to furfural through dehydration and isomerization today is still challenging route. [3] High selectivity to furfuryl alcohol (FA) has been demonstrated for numerous catalysts, [8][9][10][11][12][13][14][15][16][17] as the product of the first step in the hydrogenation pathway (Scheme 1b). [3] The hydrogenation route is a highly reported research area, as it can provide a wide range of bulk chemicals.…”

“…[3] High selectivity to furfuryl alcohol (FA) has been demonstrated for numerous catalysts, [8][9][10][11][12][13][14][15][16][17] as the product of the first step in the hydrogenation pathway (Scheme 1b). Supports often include Lewis acids, such as g-Al 2 O 3 , [14,21,22] TiO 2 , [12,16,23] ZrO 2 , [8] CeO 2 , [14] SiO 2 [9,10] and Al-SBA-15, [24] basic metal oxides (MgO and ZnO) [11,14] and base metal carbonates (CaCO 3 ), [10] which assist in polarizing the furfural carbonyl bond and which can actively take part in one of the reaction pathways. [12,18] The production of MF is attractive, as it has a very low boiling point which enables efficient separation.…”

KINETIC STUDY OF THE HYDROGENATION OF CITRAL ON Ir PROMOTED Au/TiO2 CATALYST

“…In the profile obtained for Au-Ir/TiO 2 , it can be observed four peaks at about 375 K (a), 466 (b) and 570 K (g). Both α and b peaks could be assigned to the reduction of gold species 21 whereas, the g peak could be attributed to the reduction of IrO 2 species 21,[24][25][26] . The shift at higher temperatures of this peaks could be associated to a higher formation of surface oxychlorometal complex (MeO x Cl y where Me: Au or Ir) that inhibits the reduction of metal species 27 .…”

“…This catalytic behavior, in which the main products are the unsaturated alcohols revealed that the catalyst surface possesses active sites with two types of metallic sites (Me° and Me δ+ ). It has been widely reported that if the active phase is present essentially as zero valent state, the favored reaction is the hydrogenation of the C=C bond in the α, β unsaturated aldehyde leading to saturated aldehyde, meanwhile, as the proportion of Me δ+ increases, the pathway shift to the reduction of the carbonyl bond due to this later species contributes to polarize the C=O bond making easier its hydrogenation [25][26][27] . Figure 3.…”

Chemical Dissolution of Iridium Powder Using Alkali Fusion Followed by High-Temperature Leaching

“…In these studies, several thermal treatments were adopted as pre-processing steps before the hydro-chemical Ir dissolution to enhance its solubility. These steps are summarized here: [3][4][5][6][7][8][9][10][11][12][13][14] (1) alloying with base metals (Cu, Al, Ni, Pb), (2) fusion with alkali materials (Na 2 O 2 , NaOH), and (3) oxidation to IrO 2 by heating to 1100 C in oxygen. Even with these thermal treatment, the recovery rate is very slow.…”