3077-71-2Relevant articles and documents
The role of N-hydroxyphthalimide in the reaction mechanism of liquid-phase oxidation of p-cymene
Sapunov,Koshel',Rumyantseva,Kurganova,Kukushkina
, p. 171 - 176 (2013)
The reaction of the liquid-phase oxidation of p-cymene to hydroperoxide with a selectivity of up to 95% at a hydrocarbon conversion of 25-30% has been studied at a reaction temperature of 80-120 C in the presence of N-hydroxyphthalimide as the catalyst. The catalytic role of N-hydroxyphthalimide has been substantiated. A kinetic model of the liquid-phase oxidation reaction in the presence of the catalyst N-hydroxyphthalimide has been developed and adequately described.
Efficient and selective oxidation of tertiary benzylic C[sbnd]H bonds with O2 catalyzed by metalloporphyrins under mild and solvent-free conditions
Hu, Meng-Yun,Liu, Lei,Qi, Bei,She, Yuan-Bin,Shen, Hai-Min,Ye, Hong-Liang
, (2020/05/19)
The direct and efficient oxidation of tertiary benzylic C[sbnd]H bonds to alcohols with O2 was accomplished in the presence of metalloporphyrins as catalysts under solvent-free and additive-free conditions. Based on effective inhibition on the unselective autoxidation and deep oxidation, systematical investigation on the effects of porphyrin ligands and metal centers, and apparent kinetics study, the oxidation system employing porphyrin manganese(II) (T(2,3,6-triCl)PPMn) with bulkier substituents as catalyst, was regarded as the most promising and efficient one. For the typical substrate, the conversion of cumene could reach up to 57.6% with the selectivity of 70.5% toward alcohol, both of them being higher than the current documents under similar conditions. The superiority of T(2,3,6-triCl)PPMn was mainly attributed to its bulkier substituent groups preventing metalloporphyrins from oxidative degradation, its planar structure favoring the interaction between central metal with reactants, and the high efficiency of Mn(II) in the catalytic transformation of hydroperoxides to alcohols.
Synthesis of Terephthalic Acid by p-Cymene Oxidation using Oxygen: Toward a More Sustainable Production of Bio-Polyethylene Terephthalate
Nea?u, Florentina,Culic?, Geanina,Florea, Mihaela,Parvulescu, Vasile I.,Cavani, Fabrizio
, p. 3102 - 3112 (2016/11/17)
The synthesis of terephthalic acid from biomass remains an unsolved challenge. In this study, we conducted the selective oxidation of p-cymene (synthesized from biodegradable terpenes, limonene, or eucalyptol) into terephthalic acid over a Mn–Fe mixed-oxide heterogeneous catalyst. The impact of various process parameters (oxidant, temperature, reaction time, catalyst amount, oxygen pressure) on the selectivity to terephthalic acid was evaluated, and some mechanistic aspects were elucidated. An unprecedented synthesis of biobased terephthalic acid (51 % yield) in the presence of O2 is reported.
Nanosized ruthenium particles decorated carbon nanofibers as active catalysts for the oxidation of p-cymene by molecular oxygen
Makgwane, Peter R.,Ray, Suprakas Sinha
, p. 1 - 11 (2013/06/26)
Highly dispersed, nanosized ruthenium (Ru) particles anchored on carbon nanofibers (CNFs) with varying Ru loadings (1-7 wt.%) showed effective catalytic activity in the aerobic oxidation of p-cymene using molecular oxygen. The activity of the Ru catalysts was influenced by the structural properties that resulted from the different metal loadings and by various reaction variables, such as the temperature, the amount of catalyst and the type of radical-initiator substrate. Under optimized reaction conditions, the 3%Ru/CNF catalyst exhibited excellent performance with a selectivity of 42% toward primary cymene hydroperoxide (PCHP) and 33% toward tertiary cymene hydroperoxide (TCHP) at 55% p-cymene conversion achieved within 5 h at 90 °C. The results demonstrated that the direct participation of the catalyst in p-cymene CH bond activation occurred via catalytic decomposition of tertiary-butyl hydroperoxide (TBHP), which was added as an initiator, into a free-radical chain initiator rather than the direct H-atom abstraction by the catalyst itself. The catalytic efficacy displayed by the Ru/CNF catalysts provides encouraging results for the activation of CH bonds of liquid-phase alkyl aromatic hydrocarbons, such as p-cymene, toward the introduction of an oxygen atom. The catalyst was reusable for five consecutive reaction cycles without appreciable loss of activity. Moreover, Ru/CNF catalyst was active for extended substrate scope application in the oxidation of other alkyl-substituted aromatics.
Catalytic activity of iron-substituted polyoxotungstates in the oxidation of aromatic compounds with hydrogen peroxide
Estrada, Ana C.,Simoes, Mario M. Q.,Santos, Isabel C. M. S.,Neves, M. Graca P. M. S.,Cavaleiro, Jose A. S.,Cavaleiro, Ana M. V.
experimental part, p. 1223 - 1235 (2011/09/12)
The tetrabutylammonium (TBA) salts of Keggin-type polyoxotungstates of the general formula [XW11FeIII(H2O)O39] n-, where X = P, B or Si, were evaluated as catalysts in the oxidation, under mild conditions, of ethylbenzene, cumene, p-cymene and sec-butylbenzene with aqueous H2O2 in CH3CN at 80 °C. The influence of various factors, such as the substrate/catalyst molar ratio, the amount of oxidant added or the reaction time, was investigated in a systematic way. Generally, the system exhibited moderate conversion, with good selectivity towards the corresponding acetophenone and hydroperoxide. In order to understand the reaction pathways, the oxidation of several products and presumed intermediates was also carried out in the presence of TBA 4[PW11Fe(H2O)O39]?2H 2O. Under the conditions used, the oxidation of styrene and styrene derivatives gave rise mainly to carbon-carbon double-bond cleavage, affording the corresponding products in very high yields (81-87%). Possible reaction pathways are presented.
Liquid Phase Oxidation of p-cymene by (VO)2P2O 7 and VO(PO3)2 Catalysts
Makgwane, Peter R.,Ferg, Ernst E.,Billing, David G.,Zeelie, Ben
experimental part, p. 105 - 113 (2010/08/06)
Vanadium phosphate oxide (VPO) catalysts derived from VOHPO 4?0.5H2O and VO(H2PO4) 2 precursors showed improved rates in the catalysed liquid phase oxidation of p-cymene. Both catalysts showed high performance with conversions of up to 30% achieved within 3 h with a selectivity towards the tertiary cymene hydroperoxide (TCHP) of 75-80% when compared to lower conversions and poorer TCHP selectivity in the non-catalysed industrial oxidation processes that takes about 8-12 h reaction time. The temperature dependent structural changes during activation within the catalysts were studied by in situ XRD and TGA-MS. The in situ XRD showed that the VO(H2PO4)2 form mainly an amorphous phase at temperature up to 600 °C while above 650-750 °C a stable VO(PO3)2 phase was obtained. The in situ XRD studies of the (VO)2P2O7 phase derived from VOHPO4?0.5H2O showed to became more crystalline with increasing temperature from 400 to 750 °C. No formation of VOPO4 phases were observed in the activated (VO)2P2O7 catalyst even at high temperature under the in situ XRD conditions. Graphical Abstract: VPO catalysts derived from VOHPO4?0.5H2O and VO(H2PO4)2 precursors improve oxidation rates and improved tert-cymene hydroperoxide selectivity during the liquid-phase oxidation of p-cymene compared to non-catalyzed oxidations. [Figure not available: see fulltext.]
Formation mechanism of p-methylacetophenone from citral via a tert-alkoxy radical intermediate
Ueno, Toshio,Masuda, Hideki,Ho, Chi-Tang
, p. 5677 - 5684 (2007/10/03)
The aim of this study was to clarify the formation mechanism of a potent off-odorant, p-methylacetophenone, from citral under acidic aqueous conditions. An acidic aqueous solution (pH 3.0) containing 10 mg/L of citral was stored at 40 °C for 2 weeks. Among the compounds detected in the stored citral solution, 4-(2-hydroxy-2-propyl)benzaldehyde was identified for the first time as a degradation product from citral. The formation of p-methylacetophenone and 4-(2-hydroxy-2-propyl)-benzaldehyde behaved the same when antioxidants were added to the citral solution. In addition, both compounds were formed by the Fe2+-induced decomposition of 8-hydroperoxy-p-cymene, another compound identified in the stored citral solution. These results suggested that both p-methylacetophenone and 4-(2-hydroxy-2-propyl)benzaldehyde can be formed via the same radical intermediate [p-CH3C6H 4C(CH3)2O.] that can be derived from the O-O bond homolysis of 8-hydroperoxy-p-cymene. On the other hand, the degradation of 8-hydroperoxy-p-cymene without Fe2+ under acidic aqueous conditions did not yield p-methylacetophenone and 4-(2-hydroxy-2-propyl) benzaldehyde, but the degradation of citral without Fe2+ did. Therefore, other than the decomposition of 8-hydroperoxy-p-cymene, a mechanism to generate the tert-alkoxy radical intermediate was proposed for the formation of p-methylacetophenone and 4-(2-hydroxy-2-propyl)benzaldehyde in the citral solution.
A Facile Synthesis of 5-Methylene-1,3-cyclohexadienes (o-Isotoluenes) and 1,2,4,6-Heptatetraenes
Andemichael, Yemane W.,Wang, Kung K.
, p. 796 - 798 (2007/10/02)
Condensation between 4-methyl-2,3-pentadienal and γ-(trimethylsilyl)allylboranes 3,4, and 16 followed by Peterson olefination reaction afforded the corresponding o-isotoluenes and diene-allenes.
CERIUM (IV) AMMONIUM NITRATE CATALYSED PHOTOCHEMICAL AUTOXIDATION OF ALKYLBENZENES
Baciocchi, E.,Giacco, T. Del,Sebastiani, G. V.,Rol, C.
, p. 3353 - 3356 (2007/10/02)
The autoxidation of alkylbenzenes can be promoted photochemically in the presence of catalytic amounts of cerium (IV) ammonium nitrate (CAN) under very mild conditions, the efficiency of the process being significantly increased by added acids.It is suggested that the reaction is promoted by NO3 radicals formed in the light induced decomposition of CAN and that Ce(III) may be reoxidized to Ce(IV) by benzylperoxy radicals.
