This work was financially supported by the University of Groningen (startup package in the area of green chemistry and technology for Jun Yue). Such enhanced reaction rate is due to the significant mass transfer increase in the microreactor. 15 CuHC reported … DFT and TD−DFT calculations revealed that the oxidation reactions were performed through high‐valent iron center and a probable reaction mechanism was proposed. The relative Gibbs free energies are given in kcal mol−1, FIGURE S35 Spin density plot for FeIII‐OOH and FeIV=O intermediates from complex 2 (isosurface cutoff value) 0.002), FIGURE S36 Frontier molecular orbitals of complex 1 and complex 2 showing significant contribution of iron and ligand (L) in molecular orbitals, FIGURE S37 Electronic configuration for [FeIV(O)(L1)2](ClO4)2 (4) intermediate (isosurface cutoff value = 0.02), FIGURE S38 Profile of the calculated relative ΔG for the reaction of hydrogen peroxide and complex with Lph ligand, the formation of hydroperoxo species and by removal of •OH radical stabilization of FeIV=O intermediate.
Further increasing the catalyst concentration to 45 mM did not improve the benzaldehyde yield. MW 158.04 g/mol + 4 MnO 2 + KOH + 2H2O Potassium Benzoate HCl The dewetted slug flow (also referred to as a [dry] plug flow) is typically characterized by a (partial) absence of liquid film surrounding the bubble.30-32 Under such flow profile, a typically lower specific surface area is obtained in the microreactor, which decreases the multiphase mass transfer rate therein.33, 34 Despite this, there are some advantages over the wetted slug flow for certain applications.
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Microreactors of different inner diameters (dC = 0.5, 0.8, or 1.0 mm) and effective lengths (LC = 0.4–10 m; i.e., of the section immersed in the oil bath) were used. We show that the oxidation of benzyl alcohol can be carried out at 50 °C and below by generating hydrogen peroxide in situ. Figure 4).
The carbocatalysis-assisted PMS activation may provide a cheap process for the selective oxidation of alcohols into aldehydes or ketones. The transition between flow profile when changing the velocity is almost instantaneous. The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acscatal.9b05273. not otherwise permitted to reproduce, republish, redistribute, or sell any Supporting Information The dotted line represents the hydrogen bonding. The nucleophilic carbonyl groups can also induce a redox cycle to generate •OH and SO4•– radicals, but phenolic hydroxyl groups impede the radical process with antioxidative functionality. Furthermore, by using a microreactor material with a better solvent wettability (i.e., a low contact angle), the critical wetting velocity decreases (Equation (7)) so that dewetting could be prevented even at lower flow rates. 49°, cf.
Figure S1b). A Oxidation of benzoin into benzil (n°39) 1. Depending on the bubble velocity and length, a wetted or dewetted slug flow was observed, characterized typically by a complete or partially wetting liquid film surrounding the bubble body.
90°C). For experiments at elevated pressures (5 bar; T = 90–150°C), a compact spring‐loaded, diaphragm‐operated back pressure regulator (BPR) from Porter (Model 9000) was used to control the pressure at the gas outlet (Figure 1). the Altmetric Attention Score and how the score is calculated. 3. The gas and liquid flow rates, or more specifically the superficial gas and liquid velocities (jG and jL) and the resulted bubble velocity (UB), have a significant influence on the liquid‐side mass transfer coefficient (kL) in slug flow microreactors.22, 37, 38 Figure 2a reveals that at 90°C and 1 bar, the measured benzaldehyde yield was not affected by the total mixture flow rate (with QG,0/QL,0 being fixed) and only influenced by the residence time. Thus, the reaction is considered first order in benzyl alcohol, which is consistent with the reported kinetic studies on the oxidation of p‐xylene to terephthalic acid using metal bromide catalysts in acetic acid.52.
However, the latter results are expected to be largely valid as a first approximation. Equation (4)), the rear end cap of bubbles resembles more like a hemispherical or hemi‐ellipsoidal shape (Figure 3b–d), whereas the flattening of the rear end cap was observed at relatively low mixture velocities (Figure 3a,) implying the partial dewetting of the liquid film between the bubble and the microreactor wall. Selective and solventless oxidation of organic sulfides and alcohols using new supported molybdenum (VI) complex in microwave and conventional methods. INTRODUCTION 1.1) Purpose The objective of this experiment is to oxidize benzoin into benzil in an acidic environment. Appendix S1.
For air‐water flow in glass/silica square microchannels (dC = 0.5 mm), a UCW of 7 mm/s (Ca = 9.61 × 10−5) was found for gas to liquid flow ratios between 0.4 and 4.43 Despite that the film thickness is higher for acetic acid at a given bubble velocity (due to the higher Ca given the lower surface tension of air with acetic acid than that with water46), UCW for the air‐acetic acid system is probably higher due to the higher contact angle of acetic acid on PTFE (41°) compared with water on glass/silica (8–18°),43 as inferred qualitatively in Equation (7).
Given that under the same flow conditions the mass transfer rate was not limiting at 90°C and this is not considerably affected by temperature (in contrary to the kinetic rate), it is reasonable to assume that these experiments were also in the kinetic regime. The value for Ea is some what higher than those reported for the benzyl alcohol oxidation using a cobalt oxide catalyst in toluene (46.2 kJ/mol), or tetrabutylphosphonium and tetrabutylammonium bromide as phase transfer catalysts in benzene (29–30 kJ/mol).55, 56 The estimated k value at 75°C (2.26 × 10−4 s−1) is about half of that for the same reaction with a Co/Mn/Br/Zr catalyst in acetic acid (4.04 × 10−4 s−1), probably due to the enhanced catalytic activity by zirconium present in the latter case.8. At 130°C and the same residence time, a benzaldehyde yield of 59.9% was obtained. Any queries (other than missing content) should be directed to the corresponding author for the article. For experiments under elevated pressure conditions, the setup was prepressurized with air up to 5 bar before the liquid flow was introduced.
Lab 2 orgo - Oxidation of Benzyl Alcohol to Benzoic Acid REPORT SHEET Dept of Chemistry NAME DATE Christina Salama LAB DAY TIME Wednesday 8:00 11:20 am, 6 out of 6 people found this document helpful. Please check your email for instructions on resetting your password. At 90°C and 5 bar, the benzaldehyde yield was 4.2% at a residence time of ca.
Learn more. You have to login with your ACS ID befor you can login with your Mendeley account. Jun Yue, Department of Chemical Engineering, Engineering and Technology Institute Groningen, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands. FIGURE S34 Profile of the calculated relative ΔG for the reaction of hydrogen peroxide and complex 2, the formation of hydroperoxo species and by removal of ‐•OH radical stabilization of FeIV=O intermediate. Learn more. Potassium benzoate can be classified as the potassium salt of the benzoic acid. Therefore, only at low benzyl alcohol concentrations, the further oxidation of benzaldehyde toward benzoic acid occurs significantly. The prediction according to Equation, Influence of the residence time on the measured benzyl alcohol conversion and product yield for (a) the wetted slug flow (, Bubble and slug dimensions for a wetted gas–liquid slug flow (, For the dewetted slug flow, the film rupture around the bubble body did not induce a complete disappearance of the film area.
The insight achieved from this fundamental study may be further applied to other organic syntheses via selective oxidation. Working off-campus?
For all the experiments, the molar catalyst composition is Co/Mn/Br = 1/1/3.3. The subscripts 0 and 1 refer to the microreactor inlet and outlet, respectively. Peixian Li, Hui Zhao, Xuyan Yan, Xue Yang, Jingjun Li, Shuiying Gao, Rong Cao.
Note that QG,0, QL,0, and Qtot,0 as shown in Figure S1 and hereafter refer to the respective gas, liquid and total mixture flow rates evaluated at the microreactor inlet temperature (i.e., ca. Helium was used as the carrier gas with a split ratio of 50 and a split flow of 48.2 mL/min. PRODUCT Benzyl In this respect, cheaper homogeneous catalysts (e.g., metal bromides) are more favored in the industry. This justifies the use of Equation (18) for reaction performance prediction under the dewetted slug flow, and the use of Lfilm,eff for the estimation of aeff (and vice versa) under such flow conditions (Equation (12)). O
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