Metal containing layered double hydroxides as efficient catalyst precursors for the selective conversion of acetone

Koot²,

Dillen³

et al. 2005

Journal of Catalysis

Mechanically strong carbon nanofiber spheres of millimeter size were grown from methane over a preshaped Ni/SiO 2 catalyst. Mg-Al hydrotalcites (HTs) were precipitated in the porous carbon bodies by consecutive impregnation of the reactants and an aging step. In a single sequence, HT loadings as high as 16 wt% were obtained. HTs turned out to be present as platelets with a lateral size of ∼20 nm supported on the carbon nanofibers. After activation by heat treatment and subsequent rehydration, a high number of accessible Brønsted base sites were found (0.7-0.9 mmol g −1 HT ), as determined by CO 2 adsorption measurements. High specific activity of the supported HTs was found in the self-condensation of acetone, more than four times higher than that of unsupported catalysts. The greatly improved efficiency of the supported HTs was ascribed to the high number of active edge sites. Results show no loss of HTs from the carbon bodies after catalysis and demonstrate that the used catalyst can be easily reactivated by the thermal activation procedure. An efficient and mechanically strong catalyst for the single-stage liquid-phase synthesis of methyl isobutyl ketone from acetone and H 2 at 331 K was obtained with the deposition of Pd and HTs on the same support.

Section: Introductionmentioning

confidence: 99%

Hydrotalcites supported on carbon nanofibers as solid base catalysts for the synthesis of MIBK

Koot²,

Dillen³

et al. 2005

Journal of Catalysis

“…To deal with the thermodynamic constraints and the more stringent environmental legislation, several catalytic systems have been investigated for the single-stage process wherein n-butyraldehyde and H 2 into 2-ethylhexanal or acetone and H 2 into MIBK are directly converted. Examples of these catalytic systems are Pd on ion-exchange resin [5], Pd or Pt on ZSM-5 [6][7][8], Pd on zeolite X [9,10], Pd on Na/SiO 2 [11], Pd/Nb 2 O 5 / SiO 2 [12,13], Ni/g-Al 2 O 3 [14] and Ni or Pd on Mg(Al)O [15][16][17][18][19][20][21]. Although these single-stage processes seem promising, still high reaction temperatures and pressures are required and side-reactions occur that lower the selectivity of the process and cause catalyst deactivation [17,22,23].…”

Section: Introductionmentioning

confidence: 99%

A hydrotalcite-based catalyst system for the single-stage liquid-phase synthesis of MIBK

Applied Catalysis A: General

Wolters

Dillen

et al. 2006

A comparative study was performed between Pd supported on activated hydrotalcites bi-functional catalysts and physical mixtures of activated hydrotalcites with Pd supported on carbon nanofibers for the single-stage liquid-phase synthesis of methyl isobutyl ketone from acetone and H 2 . Since it was found earlier that the dehydration reaction of diacetone alcohol over activated hydrotalcites is the rate-determining step in this process, Mg-Al hydrotalcites were investigated in the condensation of acetone to diacetone alcohol and its dehydration to mesityl oxide to enhance the activity. A correlation between the number of active base sites, as determined by volumetric CO 2 adsorption measurements at low pressures, and the activity in the dehydration reaction could be derived. A dependency on the Pd-loading (0-1 wt%) of Pd supported on activated hydrotalcites catalysts was found in the single-stage synthesis of methyl isobutyl ketone, whereas no such an effect was found when using physical mixtures of activated hydrotalcites with Pd on carbon nanofibers. Results from TEM, CO 2 chemisorption and N 2 physisorption as well as catalytic experiments in the hydrogenation of mesityl oxide and of cyclohexene indicate that this dependency is largely accounted for by entrapment of Pd particles in the agglomerates of the irregular stacks of hydrotalcite platelets, making these sites inaccessible for the reactants. #

“…Several studies have been reported on the use of hydrotalcite-based catalyst systems for the single-stage production of MIBK [15,16,[18][19][20], in which the process is mainly performed at high temperatures and/or hydrogen pressures. In these studies, the actual condensation catalyst is a mixed oxide obtained by calcination of the hydrotalcite.…”

Section: Introductionmentioning

confidence: 99%

Single-stage liquid-phase synthesis of methyl isobutyl ketone under mild conditions

Journal of Molecular Catalysis A: Chemical

Dillen

Jong

2004

In this study, a catalyst mixture of activated Mg/Al hydrotalcite as solid base and Pd on carbon nanofibers was investigated for the single-stage liquid-phase synthesis of methyl isobutyl ketone (MIBK) from acetone and H 2 at 313 K and H 2 pressures of 1-20 bar. With this catalyst system acetone and H 2 are selectively converted into MIBK in a single reactor, even at 1.2 bar H 2 . Although the hydrogenation of one of the intermediates, mesityl oxide (MO), at 1.2 bar suffers from severe mass transfer limitations in H 2 , the catalytic activity in the single-stage synthesis is stable over several hours if the steady-state concentration of MO is kept low. Under the presented conditions the dehydration reaction of diacetone alcohol to MO is rate limiting in the production of MIBK.