25087-26-7Relevant academic research and scientific papers
Selective oxidation of methacrolein to methacrylic acid on carbon catalysts
Zhou, Lilong,Sun, Ye,Li, Bin,Li, Zhengjie,Zhang, Zhikun,Yun, Jimmy,Liu, Runjing
, p. 44 - 49 (2019)
Different carbon structures (activated carbon, carbon nanotubes, graphene and graphite)were investigated for the replacement of heteropoly catalysts for the oxidation of methacrolein to methacrylic acid. Activated carbon showed the best catalytic performance with higher catalytic activity than molybdovanaphosphoric acid at lower temperatures. The catalytic performance of activated carbon was further improved by the addition of heteroatoms, such as P, B, N and S. The latter occupy the electrophilic oxygen functional groups thus preventing further oxidation of methacrylic acid and improving reaction selectivity. The best catalytic performance results were obtained on activated carbon with 10 wt% P, where methacrolein conversion, methacrylic acid selectivity and yield at 270 °C were 40.1, 70.8 and 30.3%, respectively. The results of the present work show a novel way to design non-metal catalysts for the selective oxidation of methacrolein to methacrylic acid.
Structure-activity relationships in the hydrolysis of acrylate and methacrylate esters by carboxylesterase in vitro
McCarthy, Timothy J.,Witz, Gisela
, p. 153 - 158 (1997)
Acrylate esters are important chemicals in the plastics industry, whose toxicity is theorized to involve alkylation of critical cellular nucleophiles via the Michael addition. Carboxylesterase-mediated hydrolysis of acrylates may be a detoxification mechanism as the unsaturated acid produced is not electrophilic under physiological conditions. Using purified porcine liver carboxylesterase, the enzymatic hydrolysis of several acrylate eaters was characterized to determine K(m) and V(max) values for each ester. The K(m) (μM) and V(max) (nmol/min) values observed for ethyl acrylate were 134 ± 16 (S.D.) and 8.9 ± 2.0, respectively. While the K(m) for ethyl methacrylate was not significantly different, the V(max), 5.5 ± 2.5, was significantly lower compared with the corresponding value for ethyl acrylate. The K(m) and V(max) for butyl acrylate were 33.3 ± 8.5 μM and 1.49 ± 0.83 nmol/min, respectively, and the corresponding values for its α-methyl analog were not significantly different. The K(m) and V(max) for tetraethyleneglycol dimethacrylate were 39 ± 15 μM and 2.9 ± 1.0 nmol/min, respectively. The V(max) for ethyleneglycol dimethacrylate, 6.9 ± 2.4 nmol/min, was significantly higher than that of the larger bifunctional ester tetraethyleneglycol dimethacrylate, but the K(m) was not significantly different. These results indicate that α-methyl substitution appears to have a minor effect in the enzymatic hydrolysis of acrylates, and suggest that the relative toxicity of acrylates is not due to differences in carboxylesterase-mediated hydrolysis.
Catalysis by Heteropoly Compounds. XVIII. Oxidation of Methacrylaldehyde over 12-Molybdophosphoric Acid and Its Alkali Salts
Mizuno, Noritaka,Watanabe, Tetsuji,Misono, Makoto
, p. 243 - 247 (1991)
The reaction scheme for the methacrylaldehyde oxidation over heteropoly compounds proposed previously (M.Misono et al., Proc. 7th Intl.Congr.Catal., 1980) was confirmed by 18O tracer experiments using the Pulse-MS method (combination of pulse reactor/mass spectrometer).The occurrence of direct and rapid oxygen exchange between methacrylaldehyde and the polyanion of MxH3-xPMo12O40 (M=Na, Cs, x=0-3.15) was verified under the reaction conditions.The results also suggested that this reaction is catalyzed by Broensted acid sites of the catalysts via such intermediates as (I) and/or (II) in scheme 1.It was shown that the methacrylaldehyde oxidation is a surface-type reaction and the catalytic activity is controlled by the oxidizing ability of the catalyst surface.
PARTIAL OXIDATION OF ISOBUTENE TO METHACRYLIC ACID ON V2O5 -P2O5 CATALYSTS.
Ai
, p. 2949 - 2953 (1988)
The vapor-phase air oxidation of isobutene was studied with V//2O//5, V//2O//5-TiO//2, V//2O//5-MoO//3, V//2O//5-P//2O//5, V//2O//5-P//2O//5-TeO//2, and heteropoly compound catalysts, such as H//3PMo//1//2O//4//0, Cs//2HPMo//1//2O//4//0, H//5PMo//1//0V//2O//4//0, and Cs//2//. //5H//2//. //5PMo//1//0V//2O//4//0, in the presence of water vapor. On pure V//2O//5, the oxidation products were acetic acid and carbon oxides, plus small amounts of acetone and methacrylaldehyde. With the addition of TiO//2 to V//2O//5, the selectivity to acetic acid increased a little, but the formation of methacrylaldehyde disappeared. The addition of MoO//3 to V//2O//5 enhanced the formations of acetone and methacrylaldehyde, to a certain extent, but methacrylic acid was not obtained.
Direct Oxidation of Isobutane in to Methacrylic Acid and Methacrolein over Cs2.5Ni0.08-substituted H3PMo12O40
Mizuno, Noritaka,Tateishi, Masaki,Iwamoto, Masakazu
, p. 1411 - 1412 (1994)
Cs+, and Ni2+, Mn2+ or Fe3+ substitution for H+ in H3PMo12O40 greatly enhanced the catalytic activity for the title reaction and among the catalysts tested Cs2.5Ni0.08H0.34PMo12O40 gave the highest yield of methacrylic acid and methacrolein.
Spectroscopy of hydrothermal solutions 18: PH-dependent kinetics of itaconic acid reactions in real time
Li, Jun,Brill, Thomas B.
, p. 10839 - 10845 (2001)
The kinetics of decarboxylation of the α-substituted acrylic acid itaconic acid were analyzed at 280-330 °C, 275 bar, and solution pH25 = 0.8-5.75 using an FTIR spectroscopy flow reactor. As the pH was increased, the observed rate constant initially decreased to a minimum at pH25 = 1.82, then increased and reached its maximum at pH25 = 3.75, and then decreased again up to the limit of study at pH25 = 5.75. The decarboxylation rate depends on the molecular form of itaconic acid in the order of itaconate monoanion > protonated itaconic acid > neutral itaconic acid ≈ itaconate dianion. Insight into possible reasons for this trend was obtained from geometry-optimized structures using density functional theory with the B3LYP method at the 6-31 +G* level.
Kinetics of oxidation of α,β-unsaturated aldehydes by quinolinium dichromate
Chaubey, Girija S.,Das, Simi,Mahanti, Mahendra K.
, p. 204 - 208 (2003)
A series of α,β-unsaturated aldehydes (crotonaldehyde, cinnamaldehyde, acrylaldehyde, and methacrylaldehyde) were oxidized by quinolinium dichromate in sulfuric acid to the corresponding acids in 50% (v/v) acetic acid water medium. The kinetic data have been discussed with reference to the aldehyde hydration equilibria. The kinetic results support a mechanistic pathway proceeding via a rate-determining oxidative decomposition of the chromate ester of the aldehyde hydrate.
Catalysis by heteropoly compounds Part 39. The structure and redox behaviour of vanadium species in molybdovanadophosphoric acid catalysts during partial oxidation of isobutane
Inumaru, Kei,Ono, Akiko,Kubo, Hiroshi,Misono, Makoto
, p. 1765 - 1770 (1998)
The states and roles of vanadium of 11-molybdo-1-vanadophosphoric acid (H4PMo11VO40, PMo11V) catalyst in the partial oxidation of isobutane (2-methylpropane) were analysed by EPR, 51V and 31P NMR, IR spectroscopy, and redox titration, and compared with dodecamolybdophosphoric acid (H3PMo12O40, PMo12) catalyst. Thermal treatment of PMo11V at 623 K in O2 caused the elimination of V from the Keggin anion and formed undefined polymeric and a monomeric V species. It was shown based on the redox titration and EPR spectra that the average valency of V in used catalysts significantly changed with the oxygen partial pressure, while that of Mo remained almost unchanged for both PMo11V and PMo12. The selectivities to methacrylic acid (MAA) and methacrolein (MAL) extrapolated to zero conversion were similar for both catalysts, but PMo11V showed a significantly higher selectivity as the conversion increased. This is because the secondary reaction, that is, oxidative decomposition of MAL and MAA, was slower over PMo11V than over PMo12. This was consistent with the marked difference in the reaction order in oxygen pressure, and corresponded to the differences in the above redox properties.
Partial oxidation of 2-methyl-1,3-propanediol to methacrylic acid: experimental and neural network modeling
Darabi Mahboub, Mohammad Jaber,Rostamizadeh, Mohammad,Dubois, Jean-luc,Patience, Gregory S.
, p. 114123 - 114134 (2016)
Methacrylic acid (MAA) is a specialty intermediate to produce methyl methacrylate (MMA), which is a monomer for poly methyl methacrylate. Current processes to MMA and MAA rely on expensive feedstocks and multi-step processes. Here we investigate the gas-phase oxidation of 2-methyl-1,3-propanediol (2MPDO) to MAA over heteropolycompounds as effective catalysts, finding that the maximum selectivity to MAA was 41% with 63% conversion of reactant at 250 °C over Cs(NH4)2PMo12O40(VO)Cu0.5. Cesium (Cs) stabilized the catalyst structure at 250 °C, and vanadium(v) and copper (Cu) played a positive role as an oxidant and promoter, respectively. A 0.3 mm nozzle atomized the liquid reactant over the catalyst surface into a μ-fluidized bed reactor. The proposed Artificial Neural Network (ANN) model predicts MAA selectivity based on 2MPDO and oxygen compositions and catalyst components (Cs, V, Cu) as independent factors. The model accounts for 97% of the variance in the data (R2 = 0.97). Vanadium as a catalyst component and oxygen concentration are the two most significant factors. Genetic algorithms (GA) coupled with ANN modeling optimized the input parameters to improve the selectivity. The selectivity to MAA over the optimized catalyst (Cs(NH4)2PMo12O40(VO)Cu0.15) and optimum feed compositions (2MPDO/O2/Ar = 13%/10%/77%) was 43% at 250 °C.
The role of steam in selective oxidation of methacrolein over H3PMo12O40
Yasuda, Shuhei,Hirata, Jun,Kanno, Mitsuru,Ninomiya, Wataru,Otomo, Ryoichi,Kamiya, Yuichi
, p. 164 - 172 (2019)
Role of steam in selective oxidation of methacrolein with molecular oxygen over H3PMo12O40 catalyst was investigated. Addition of steam to feed gas significantly enhanced both catalytic activity and selectivity to methacrylic acid, which were fivefold and twice increases, respectively, under the optimal steam pressure (PH2O = 0.13 atm). Kinetic analysis demonstrated that the addition of steam caused 200-fold increase in the pre-exponential factor for the formation of methacrylic acid, leading to the significant increase in the activity. The steam in the feed gas varied hydrous state of H3PMo12O40 under the reaction conditions, while did not alter redox property, molecular and crystalline structures, and surface area of the catalyst. In the presence of steam at 573 K, three H2O per one H3PMo12O40 were absorbed and hydrated protons like [H3O]+ were formed in the bulk of H3PMo12O40. Methacrolein was adsorbed on the surface of the hydrous catalyst, but not on anhydrous one at all. Based on the results, it was concluded that activation of methacrolein readily occurred on the catalyst in the presence of steam, leading to the significant increase in the pre–exponential factor. Quantum chemical calculation supported the smooth activation of methacrolein by the reaction with [H3O]+ without any transition state.
