Acetone

About: Acetone is a research topic. Over the lifetime, 9458 publications have been published within this topic receiving 120867 citations. The topic is also known as: propanone & dimethylketone.

Continuous acetone-butanol production with free and immobilized Clostridium acetobutylicum

Abstract: Acetone-butanol production was carried out with Clostridium acetobutylicum DSM 792 (ATCC 824) in a two-stage stirred tank cascade with 1.25 l and 2.5 l medium volume using free and immobilized cells. The cells were immobilized by alginate, κ-carrageenan and/or chitosan. The cell-containing pellets were dried or chemically treated to improve their long-term stability. Dried Ca-alginate yielded the best matrix system. It remained stable after a fermentation time of 727 h in stirred tank reactors. The solvent (sum of acetone, butanol and ethanol) productivity of 1.93 g l-1 h-1 at a solvent concentration of 15.4 g l-1 with free cells was increased to 4.02 g l-1 h-1 at a solvent concentration of 4.0 g l-1 h-1 with Ca-alginate immobilized cells (25% cell loading, 12 g l-1 pellet concentration, 3 g l-1 wet cell mass concentration). With 0.5 mm pellet diameter, the biocatalyst efficiency was lower than 50%.

Non-heme iron complexes for stereoselective oxidation: Tuning of the selectivity in dihydroxylation using different solvents

Abstract: A new class of functional models for non-heme iron-based dioxygenases, including [(N3Py-Me)Fe(CH3CN)(2)](ClO4)(2) and [(N3Py-Bn)Fe(CH3CN)(2)](ClO4)(2) {N3Py-Me = [di(2-pyridyl)methyl]methyl(2-pyridyl)methylamine; N3Py-Bn = [di(2-pyridyl)methyl]benzyl(2-pyridyl)methylamine}, is presented here. NMR, UV and X-ray analyses revealed that six-coordinate low-spin Fe-II complexes with the pyridine N-atoms and the tertiary amine functionality of the ligand bound to Fe are formed. The two remaining coordination sites located cis to each other are occupied by labile CH3CN groups that are easily exchanged by other ligands. We demonstrate that the reactivity and stereoselectivity of the complexes investigated depend on the choice of the solvent. The complexes have been examined as catalysts for the oxidation of both alkanes and olefins in CH3CN. In this solvent alkanes are oxidized to alcohols and ketones and olefins to the corresponding cis-epoxides and cis-diols. In acetone as solvent a different reactivity pattern was found, with, as the most striking example, the trans-dihydroxylation of cis-olefins. O-18-labeling studies in CH3CN establish incorporation of O-18 from (H2O2)-O-18 and (H2O)-O-18 in both the epoxide and the diol implicating an HO-Fe-V=O-18 active intermediate originating from an (H2O)-O-18-(FeOOH)-O-III species. These results are in full agreement with mechanistic schemes derived for other dioxygenase model systems. Based on labeling studies in acetone an additional oxidation mechanism is proposed for this solvent, in which the solvent acetone is involved. This is the first example of a catalyst that can give cis- or trans-dihydroxylation products, just by changing the solvent. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Performance of Solvent-Pretreated Polyimide Nanofiltration Membranes for Separation of Dissolved Dyes from Toluene

Abstract: The major problem reported for commercially available membranes is their limited chemical stability in organic solvents. This article reports the influence of organic solvents with different polarity (methanol, acetone, acetic acid, toluene, and n-hexane) on the filtration performance of STARMEM membranes. These membranes are specified to be compatible with the solvents used. The pure toluene flux of these membranes and the rejection of azo dyes (Sudan Black and Rhodanile Blue) were measured before and after a week of exposure to one of the above-mentioned solvents. The results show that the structure of the membrane changed after pretreatment with polar solvents (methanol, acetone, acetic acid) and that the membrane performance shifts toward lower rejections with higher solvent flux. Nonpolar solvents do not change the polyimide membrane performances significantly. Contact angle measurements on new and solvent-treated membranes show that organic solvents change the hydrophobicity of polymeric membrane su...