Acetone, simulation studies

The liquid phase kinetics of the selective hydrogenation of mesityl oxide in acetone were studied for the purpose of developing a robust kinetic model to be integrated into an existing non-equilibrium rate-based model for the simulation of the CD process for MIBK production. A typical concentration versus time profde is illustrated in Figure 2. MIBK was produced with veiy high selectivity with essentially all of the MO converted to MIBK. Products from the... 

Acetone / Carbon Dioxide. A molecular simulation study for this binary system has appeared in (4). In that study, good qualitative, but not quantitative, agreement was obtained between simulation and experimental results. The differences were ascribed to the inadequacy of the U potential to represent the properties of carbon dioxide and acetone. However, in that work, the pure component potential parameters for acetone were not optimized. The simulations in this... 

Lin, Y. L., Gao, J. L. (2007). Solvatochromic Shifts of the N ->Pi Transition of Acetone from Steam Vapor to Ambient Aqueous Solution A Combined Configuration Interaction QM/MM Simulation Study Incorporating Solvent Polarization, / Chem. Theory Comp., 3, 1484-1493. 

Br up to 10" M and are F + OA similar to that observed in the corresponding fructose oscillator without acetone. On the other hand, oscillations that occur after time pause (second type oscillations) are stopped when [Br ]10 M. This gives an indication that the first type is non-bromide ion-controlled while the second is Br -controlled. Computer simulation studies confirm that both control mechanisms are operative in the system [46]. 

This theoretical study is focused on the process combination of a distillation column and a pervaporation unit located in the side stream of the column. This hybrid membrane process can be applied for the separation of azeotropic mixtures such as acetone, isopropanol and water. Water is removed from the side stream of the column by pervaporation, while pure acetone and isopropanol are obtained at the top and bottom of the column. Detailed simulation studies show the influence of decisive structural parameters like side stream rate and recycle position as well as operational parameters like reflux ratio and mass flow on concentration profiles, membrane area and product compositions. 

Lin YL, Gao J (2007) Solvatochromic shifts of the n tc transition of acetone from steam vapor to ambient aqueous solution a combined configuration interaction QM/MM simulation study incorporating solvent polarization. J Chem Theory Comput 3 1484—1493... 

The present economic and environmental incentives for the development of a viable one-step process for MIBK production provide an excellent opportunity for the application of catalytic distillation (CD) technology. Here, the use of CD technology for the synthesis of MIBK from acetone is described and recent progress on this process development is reported. Specifically, the results of a study on the liquid phase kinetics of the liquid phase hydrogenation of mesityl oxide (MO) in acetone are presented. Our preliminary spectroscopic results suggest that MO exists as a diadsorbed species with both the carbonyl and olefin groups coordinated to the catalyst. An empirical kinetic model was developed which will be incorporated into our three-phase non-equilibrium rate-based model for the simulation of yield and selectivity for the one step synthesis of MIBK via CD. 

If the neurotoxicity of /7-hexane was potentiated in this study by co-exposure to acetone, the level of n-hexane alone required to produce these effects would be higher than 58 ppm and the MRL level would be higher. Results from simulations with a PBPK model that accurately predicted /7-hexane blood and 2,5-hexanedione urine levels (Perbellini et al. 1986, 1990a) indicate that at concentrations of 50 ppm, the rate-limiting factor in /7-hexane metabolism is delivery to the liver, not metabolic activity. This suggests that at this concentration (and at the MRL concentration of 0.6 ppm), induction of P-450 enzymes in the liver by acetone or other chemicals would not affect the rate at which 2,5-hexanedione was produced. 

Time Resolved Spectra. We have studied the time evolution of the fluorescence of BA in acetone as shown in Figure 29. The results are in qualitative agreement with the simulated time-dependent spectra using the simulated p(z,t) and Eq. (38) (see Figure 30). This strongly supports the validity of the adiabatic GLE model for the charge transfer of S, BA. 

Good test cases would be the solvent effects on the UV-vis absorption spectra of formaldehyde and acetone that have been the subject of innumerous theoretical studies. Innovative theoretical methods have been applied to formaldehyde (see also the compilation of results in [20,32,113,114,115,116]). Unfortunately the experimental result for formaldehyde in water is not clear because of chemical problems mostly associated to the aggregation and formation of oligomers. Therefore a better test case is the UV-vis spectra of acetone, because reliable experimental solvent shifts and several theoretical results are available (see the compilation of results in [117]). The Stokes shift of the n-rr transition of acetone has been critically discussed by Ohrn and Karlstrom [118], Grozema and van Duijnen [17] studied the solvatochromic shift of the absorption band of acetone in as much as eight different solvents. Acetone is known to shift the maximum of the n-rr band by 1500-1700 cm 1 when immersed in water [119,120,121], Using the conventional HF/6-31 G(d) point charges, Coutinho and Canuto [54] simulated acetone in water and performed INDO/CIS... 

Effect of Unlike-Pair Interactions on Phase Behavior. No adjustment of the unlike-pair interaction parameter was necessary for this system to obtain agreement between experimental data and simulation results (this is, however, also true of the cubic equation-of-state that reproduces the properties of this system with an interaction parameter interesting question that is ideally suited for study by simulation is the relationship between observed macroscopic phase equilibrium behavior and the intermolecular interactions in a model system. Acetone and carbon dioxide are mutually miscible above a pressure of approximately 80 bar at this temperature. Many systems of interest for supercritical extraction processes are immiscible up to much higher pressures. In order to investigate the transition to an immiscible system as a function of the strength of the intermolecular forces, we performed a series of calculations with lower strengths of the unlike-pair interactions. Values of - 0.90, 0.80, 0.70 were investigated. 

Triose Phosphate Isomerase Diffusional Encounters with D-Glyceraldehyde-3-Phosphate In this section we use a real system, triose phosphate isomerase (TIM) and its substrate D-glyceraldehyde—3-phosphate (GAP) to demonstrate the capabilities of Brownian dynamics simulations with electrostatics. TIM is a glycolytic enzyme that catalyzes the interconversion of GAP and dihydroxy-acetone phosphate (DHAP). It has been described as an almost perfea catalyst because of its remarkable efficiency. Structurally, TIM is a dimeric enzyme consisting of two identical polypeptide chains of 247 amino acid residues. Each subunit consists of eight loop-p/loop-a units and contains one aaive site. Located near each aaive site is a peptide loop, which is mobile in the native enzyme and folds down to cover the active site when the substrate is bound. Kinetically, the reaction appears to be diffusion controlled and proceeds with a measured rate constant of 4.8 x 10 M s L TIM has consequently been the focus of many kinetic and struaural studies. ... 

Interestingly, mostly those aqueous binary mixtures that contain a marked amphiphilic character towards water are found to be particularly important in chemistry and biology. This is clearly manifest in all useful aqueous binary mixtures such as DMSO, methanol, ethanol, TBA, acetone, and dioxane to name a few. Some of these solvents (DMSO, EtOH) are used at high concentration as effective denatur-ants of protein. At low concentration they can exhibit a reversal of role and serve as a promoter of stability. In this low-concentration regime the binary mixtures also promote the catalytic activity of enzymes, as discussed above. Recent experimental, theoretical, and simulation results exhibit the phase-transihon-hke scenarios discussed in this chapter. These systems need to be studied in great detail as much remains to be understood. 

Efforts to assist search-and-rescue teams in locating people buried under collapsed structures by using handheld IMS instruments have been proposed. One study focused on detection of VOCs anitted in expired air of fasting monks in Greece, with the objective to simulate the breath exhaled by people who could be trapped under collapsed buildings in an event such as an earthquake indeed, a 30-fold increase in acetone level was found using a portable GC-IMS. In another study, the objective was to detect vapors emanating from human urine, mainly acetone, to indicate the presence of people under debris. ... 

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