Formation Of Phthalic Anhydride Research Articles

Aerobic-peroxide oxidation of naphthalene in the presence of transition metal on a nanocarbon carrier

The paper describes the results of aerobic-peroxide catalytic oxidation of naphthalene in the presence of iron-containing multi-walled carbon nanotubes Fe@MWCNT. The active nanocarbon substrate containing α-iron atoms and carbides realizes by the Fenton reaction active formation of active particles and intensive oxidation of the hydrocarbon under rather mild conditions. It was found that at the temperature range 333 - 353K, in the presence of hydrogen peroxide (30% aqueous solution) and Fe@MWCNT (Fe ≈3.7 wt. %), under intense air current, the reaction proceeds without destroying the cyclic structure of the molecule with predominant formation of phthalic anhydride and naphthol. Identification of the functional groups of the main target products was performed by the infrared (IR) spectroscopy. The results obtained can be proposed for further development of such studies and bringing them into compliance with the standards of the industrial process. Keywords: aerobic oxidation of hydrocarbons; oxidation of naphthalene; hydrogen peroxide; multi-walled carbon nanotubes; nanocarbon catalysis; Fenton system, oxygencontaining aromatic compounds.

The pathways of the phthalic anhydride selectivity and yield increase at C4-C5-hydrocarbons oxidation

The investigation of n-butane and n-pentane oxidation in system with two consecutive reactors confirmed the mechanism of phthalic anhydride formation by Diels-Alder reaction between maleic anhydride and C4 unsaturated hydrocarbons. The process is limited by low stationary concentration of C4 unsaturated hydrocarbons in reaction mixture which is connected with high rate of their oxidation to maleic anhydride. It was shown that n-butane oxidation leads to formation of maleic anhydride only but the introduction of unsaturated C4-hydrocarbons on inlet of the second catalytic reactor accompanied by phthalic anhydride appearance on outlet of these two consecutive reactors system. It was established that in case of 1,3-butene introduction in the second reactor the quantity of phthalic anhydride formed is more than in case of 2-butene addition. It was predicted that a decrease of the temperature in the second reactor can leads to an increase the phthalic anhydride selectivity and its yield as result of Diels-Alder reaction effectiveness. This assumption was confirmed by experimental results. In results the method of phthalic anhydride production by the use of two consecutive reactors was proposed. The summary yield of this product on this new process can reach up to 35 mol. %. In the case of n-pentane oxidation the formation of maleic and phthalic anhydrides was observed with excess of first product but the introduction of unsaturated C4-hydrocarbons in the inlet of second reactor leads to an increase of the phthalic anhydride concentration and its selectivity and yield. In result the yield of phthalic anhydride equal to 35 mol. % can be obtained. So, the proposed by us mechanism of phthalic anhydride was confirmed by new experimental results and other pathways for the selectivity and yield of this product can be predicted.

Electrochemical detector based on a modified graphite electrode with phthalocyanine for the elemental analysis of actinides

The quantification of actinides in aqueous solutions involves complex and expensive separation processes. Electrochemical methods have been widely used for the quick and accurate identification and quantification of organic and inorganic compounds directly or indirectly. Therefore, this work proposes the use of modified graphite with phthalocyanine for electrochemical detection and quantification of Th, U, Pu, Am, and Cm, in aqueous media by cyclic voltammetry. The electrodes were characterized by Raman and infrared spectroscopy, and the cyclic voltammetry data were modeled with Aoki’s model. The detection limits (DL) and the quantification limits (QL) reached by the electrochemical detection of these actinides were of the order of ppt. Aoki’s model fitted perfectly with the experimental data. The functionalization of graphite electrodes promotes the formation of phthalic anhydride, and the phthalocyanine is anchored on the epoxy groups of the graphite. The electrochemical detection process of these actinides is indirect. This electrochemical detector is cheap and disposable and can be an alternative for an initial characterization of actinides in liquid waste.

Selective vapor‐phase oxidation of o‐xylene to phthalic anhydride over Co‐Mn/H3PW12O40@TiO2 using molecular oxygen as a green oxidant

The oxidation of o‐xylene to phthalic anhydride over Co‐Mn/H3PW12O40@TiO2 was investigated. The experimental results demonstrated that the prepared catalyst effectively catalyzed the oxidation of o‐xylene to phthalic anhydride. Also, the synergistic effect between three metals plays vital roles in this reaction. From a green chemistry point of view, this method is environmentally friendly due to carrying out the oxidation in a fixed‐bed reactor under solvent‐free condition and using molecular oxygen as a green and cheap oxidizing agent. The resulting solid catalysts were characterized by FT‐IR, XRD, XPS, ICP‐OES, FESEM, TEM, EDX, DR‐UV spectroscopy, BET and thermogravimetric analysis. The oxidation of o‐xylene yields four products: o‐tolualdehyde, phthaldialdehyde, phthalide and finally phthalic anhydride as the main product. The reaction conditions for oxidation of o‐xylene were optimized by varying the temperature, weight hourly space velocity and oxygen flow rate (contact time). The optimum weight percentage of phosphotungstic acid (HPW) and Co/Mn for phthalic anhydride production were 15 wt % and 2 wt%, respectively. The best Co/Mn ratio was found to be 10/1. Oxygen flow rate was very important on the phthalic anhydride formation. The optimum conditions for oxidation of o‐xylene were T = 370 °C, WHSV = 0.5 h−1 and oxygen flow rate = 10 mL min−1. Under optimized conditions, a maximum of 88.2% conversion and 75.5% selectivity to phthalic anhydride was achieved with the fresh catalyst. Moreover, reusability of the catalyst was studied and catalytic activity remained unchanged after at least five cycles.

Formation of Phthalic Anhydride by Diels–Alder Reaction During n-Pentane Oxidation on VPO Catalysts and Control of the Process Selectivity

The oxidation of n-pentane at VPO catalyst was studied in two-step catalytic reactor, and it was shown that phthalic anhydride is formed by Diels–Alder reaction between maleic anhydride and 1,3-butadiene. The selectivity in phthalic anhydride was increased by the introduction of additives that increase the Lewis acidity of the catalyst surface to the basic VPO composition, by reducing the temperature in the lower part of catalytic reactor, and layer-by-layer loading various VPO catalysts with different acidic properties into the reactor.

V-Mn-MCM-41 catalyst for the vapor phase oxidation of o-xylene

The role of V and Mn incorporated mesoporous molecular sieves was investigated for the vapor phase oxidation of o-xylene. Mesoporous monometallic V-MCM-41 (Si/V = 25, 50, 75 and 100), Mn-MCM-41 (Si/Mn = 50) and bimetallic V-Mn-MCM-41 (Si/(V + Mn) = 100) molecular sieves were synthesized by a direct hydrothermal (DHT) process and characterized by various techniques such as X-ray diffraction, DRUV-Vis spectroscopy, EPR, and transmission electron microscopy (TEM). From the DRUV-Vis and EPR spectral study, it was found that most of the V species are present as vanadyl ions (VO2+) in the as-synthesized catalysts and as highly dispersed V5+ ions in tetrahedral coordination in the calcined catalysts. The activity of the catalysts was measured and compared with each other for the gas phase oxidation of o-xylene in the presence of atmospheric air as an oxidant at 573 K. Among the various catalysts, V-MCM-41 with Si/V = 50 exhibited high activity towards production of phthalic anhydride under the experimental condition. The correlation between the phthalic anhydride selectivity and the physico-chemical characteristics of the catalyst was found. It is concluded that V5+ species present in the MCM-41 silica matrix are the active sites responsible for the selective formation of phthalic anhydride during the vapor phase oxidation of o-xylene.

Mechanism of phthalic anhydride formation in the oxidation of n-pentane on a vanadium-phosphorus oxide catalyst

The reaction paths of product formation in the partial oxidation of n-pentane on vanadium-phosphorus oxide (VPO) and VPO-Bi catalysts are considered. The condensed products of n-pentane oxidation were analyzed by chromatography-mass spectrometry, and the presence of C4 rather than C5 unsaturated hydrocarbons was detected. It was found that the concentration of phthalic anhydride in the products increased upon the addition of C4 olefins and butadiene to the n-pentane-air reaction mixture. With the use of a system with two in-series reactors, it was found that the addition of butadiene to a flow of n-butane oxidation products (maleic anhydride, CO, and CO2) resulted in the formation of phthalic anhydride. The oxidation of 1-butanol was studied, and butene and butadiene were found to be the primary products of reaction; at a higher temperature, maleic anhydride and then phthalic anhydride were formed. The experimental results supported the reaction scheme according to which the activation of n-pentane occurred with the elimination of a methyl group and the formation of C4 unsaturated hydrocarbons. The oxidation of these latter led to the formation of maleic anhydride. The Diels-Alder reaction between maleic anhydride and C4 unsaturated hydrocarbons is the main path of phthalic anhydride formation.

Use of Fourier Transform Infrared Spectroscopy to Follow the Heterocumulene Aided Thermal Dehydration of Phthalic and Naphthalic Acids

Fourier transform infrared (FT-IR) spectroscopy has been successfully employed to follow the formation of phthalic anhydride and 1,8-naphthalic anhydride on heating their corresponding acids. The effects of three heterocumulenes, cyanamide, dicyandiamide, and sodium cyanate, on the temperature of formation of the anhydrides were also investigated using this method. It was found that the carbodiimides cyanamide and dicyandiamide dramatically lowered the temperature at which thermal dehydration of the acid led to anhydride formation. It was noted that cyanamide had a stronger catalytic effect than dicyandiamide, presumably due to the electron-withdrawing effect of the amidine group. Sodium cyanate was also found to promote the thermal dehydration of the acids to form the corresponding anhydrides. Under more severe conditions, phthalic acid anhydride formed is seen to react further, leading to the formation of phthalimide. The discrepancy between the products obtained with cyanamide and sodium cyanate leads to the conclusion that, unlike earlier claims, imide formation is not due to the reaction of the anhydride with the urea formed but with sodium cyanate itself. However, only the phthalic anhydride five-membered ring system is sufficiently reactive towards the CNO- nucleophile to form the imide; the six-membered 1,8-naphthalic anhydride system does not react in this way.

Intramolecular carboxylic group‐assisted cleavage of N‐(2‐hydroxyphenyl)phthalamic acid (7) and N‐(2‐methoxyphenyl)phthalamic acid (8): Absence of intramolecular general acid catalysis due to 2‐OH in 7

AbstractThe values of pseudo first‐order rate constants (kobs) for the cleavage of N‐(2‐hydroxyphenyl)phthalamic acid (7), obtained at 4.9 × 10−2 M HCl, 35°C, and within CH3CN content range 2–80% (v/v) in mixed aqueous solvent are smaller than kobs for the cleavage of N‐(2‐methoxyphenyl)phthalamic acid (8), obtained under almost similar experimental conditions, by nearly 1.5‐ to 2‐fold. These observations show the absence of expected intramolecular general acid catalysis due to 2‐OH group in 7. The values of kobs for the cleavage of 7 and 8 decrease by more than 20‐fold with the increase in the content of CH3CN from 2 to 80–82% (v/v) in mixed aqueous solvent. The kinetic data reveal that in acidic aqueous cleavage of 7, N‐cyclization (leading to the formation of imide) and O‐cyclization (leading to the formation of phthalic anhydride) vary from ∼10 to 15% and ∼90 to 85%, respectively, with the increase in CH3CN content from 2 to 80% (v/v). Similar increase in CH3CN content causes increase in N‐cyclization from ∼0 to 5% and decrease in O‐cyclization from ∼100 to 95% in the acidic aqueous cleavage of 8. Some speculative, yet conceivable, reasons for nearly 10 and 0% N‐cyclization in the cleavage of respective 7 and 8 at low content of CH3CN have been described. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 746–758, 2006

Titanium-dioxide-mediated photocatalysed reaction of selected organic systems

The photocatalysed reaction of four selected organic systems, namely dichlone (1), 2-amino-5-chloropyridine (2), benzoyl peroxide (3) and 3-chloro perbenzoic acid (4), has been investigated in an acetonitrile/water mixture in the presence of titanium dioxide and oxygen. An attempt has been made to identify the products formed during the photo-oxidation process using the GC/MS analysis technique. The photolysis of dichlone (1) leads to the formation of phthalic anhydride (11) and 1H-indene-1,2,3-trione (10), whereas 2-amino-5-chloropyridine (2) gave rise to 2,2′-diamino bipyridyl (14), 2-pyridinamine (16), 2-hydroxy-5-chloropyridine (18), bipyridyl (19) and 2-amino bipyridyl (21). The photolysis of benzoyl peroxide (3) yielded a mixture of products such as benzoic acid (24), biphenyl (27), biphenyl-4-carboxylic acid (29) and benzoic acid phenyl ester (30). Two intermediate products, as 3-chlorobenzaldehyde (35) and hydroxyl added 3-chlorobenzaldehyde (33), have been identified in the case of 3-chloro perbenzoic acid (4). The products have been identified by comparing the molecular ion and mass fragmentation peaks of the products with those reported in the GC-MS library. A probable mechanism for the formation of the products has been proposed.

Unexpected Rate Retardation in the Formation of Phthalic Anhydride from N-Methylphthalamic Acid in Acidic H2O-CH3CN Medium

Kinetic study on the cleavage of N-methylphthalamic acid (NMPA) in mixed acidic aqueous-acetonitrile solvent reveals the formation of both phthalic anhydride (PAn) (through O-cyclization) and N-methylphthalimide (NMPT) (through N-cyclization). The formation of NMPT varies from similar to 20% to similar to 3% with the increase in the content of acetonitrile from 2 to 70% v/v. Pseudo first-order rate constants for the formation of PAn are more than 4-fold larger than those for the formation of NMPT at 2% v/v CH3CN in mixed aqueous solvents. Pseudo first-order rate constants for alkaline hydrolysis of NMPT reveal a nonlinear decrease with increase in the content of CH3CN in mixed aqueous solvents.

Effects of mixed aqueous‐organic solvents on the rate of intramolecular carboxylic group‐catalyzed cleavage of N‐(4′‐methoxyphenyl)phthalamic acid

AbstractKinetic study on the cleavage of N‐(4′‐methoxyphenyl)phthalamic acid (NMPPAH) in mixed H2O‐CH3CN and H2O‐1,4‐dioxan solvents containing 0.05 M HCl reveals the formation of phthalic anhydride (PAn)/phthalic acid (PA) as the sole or major product. Pseudo first‐order rate constants (k1) for the conversion of NMPPAH to PAn decrease nonlinearly from 60.4 × 10−5 to 2.64 × 10−5 s−1 with the increase in the contents of 1,4‐dioxan from 10 to 80% v/v in mixed aqueous solvents. The rate of cleavage of NMPPAH in mixed H2O‐CH3CN solvents at ≥50% v/v CH3CN follows an irreversible consecutive reaction path: NMPPAH PA. The values of k1 are larger in H2O‐CH3CN than in H2O‐1,4‐dioxan solvents. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 316–325, 2004

Kinetics and mechanism of intramolecular carboxylic acid participation in the hydrolysis of N-methoxyphthalamic acid.

The rate of formation and disappearance of phthalic anhydride (PAn) intermediate in the aqueous cleavage of N-methoxyphthalamic acid (NMPA) under acidic pH was studied spectrophotometrically in mixed CH3CN-H2O solvents. The rate of formation of PAn from NMPA is almost independent of the change in acetonitrile content from 20 to 70% v/v in mixed aqueous solvents. The rate constants for the formation of PAn from NMPA are approximately 10-fold smaller than the corresponding rate constants for the formation of PAn from o-carboxybenzohydroxamic acid (OCBA). These observations are ascribed to the consequence of the occurrence of slightly different mechanisms in these reactions.

Effects of non‐ionic and mixed cationic–non‐ionic micelles on the rate of alkaline hydrolysis of phthalimide

AbstractPseudo‐first‐order rate constants (kobs) for the alkaline hydrolysis of phthalimide (PTH) show a monotonic decrease with the increase in [C16E20]T (total concentration of Brij 58) at constant [CH3CN] and [NaOH]. This micellar effect is explained in terms of the pseudophase model of micelles. The rate of hydrolysis of PTH in C16E20 micellar pseudophase appears to be negligible compared with that in the aqueous pseudophase. The values of kobs for C12E23 (Brij 35) show a sharp decrease at very low values of [C12E23]T followed by a very slow decrease with increase in [C12E23]T at relatively higher values of the latter. The rate of hydrolysis becomes too slow to monitor at [C12E23]T ≥0.04 M in the absence of cetyltrimethylammonium bromide (CTABr) and at [C12E23]T ≥0.05 M in the presence of 0.006–0.02 M CTABr at 0.02 M NaOH whereas such characteristic behavior is kinetically absent with C16E20. The values of kobs, obtained at different [NIS]T (where NIS represents C16E20 and C12E23) in the presence of a constant amount of CTABr, follow the empirical relationship kobs = (k0 + kK[NIS]T)/(1 + K[NIS]T) where k and K are empirical parameters. The values of k are only slightly affected whereas the values of K decrease with increase in [CTABr]T for the mixed C16E20–CTABr micellar system. The rate of hydrolysis of PTH at ≥0.01 M C12E23 and ≥0.01 M CTABr reveals the formation of phthalic anhydride whereas this was not observed in the mixed C16E20–CTABr micellar system under similar experimental conditions. Copyright © 2002 John Wiley & Sons, Ltd.

Effect of cyclodextrin on the intramolecular catalysis of aryl hydrogen phthalate ester hydrolysis

The kinetics of the hydrolysis of Z-phenyl hydrogen phthalate (Z = H, p-Me, m-Me, m-Cl and p-Cl) was studied in the presence of hydroxypropyl-β-cyclodextrin (HPCD) at pH 2.00, 3.00 and 12.00. In acid solutions these reactions involve two kinetic processes, which correspond to the formation and decomposition of phthalic anhydride. At pH 12 only the formation of phthalic anhydride could be measured because it decomposes very fast under these conditions. The rate constant for the formation of phthalic anhydride decreases as the HPCD concentration increases whereas the decomposition of phthalic anhydride is almost constant. The kinetic results are interpreted in terms of the formation of an inclusion complex of the neutral, KCDAH, or ionized substrate, KCDA, with HPCD. In all cases KCDAH > KCDA, so part of the observed inhibition is due to an increase in the amount of substrate in its unreactive neutral form. Comparison of the rate constants for the reaction of the complexed substrates with those in the bulk solution indicates that the transition state for the cyclodextrin-mediated reaction is less stabilised than the ionised substrate with values of ΔΔG ranging from 0.28 to 1.59 kcal mol−1 depending on the substituent on the aryl ring.

Kinetic study of the hydrolysis of phthalic anhydride and aryl hydrogen phthalates.

The kinetics of the hydrolysis of phthalic anhydride and X-phenyl hydrogen phthalate (X = H, p-Me, m-Cl, and p-Cl) were studied. Several bases accelerate the reaction of phthalic anhydride: acetate, phosphate, N-methyl imidazole, 1,4-diazabicyclo[2,2,2]octane (DABCO), and carbonate. Phosphate, DABCO, and N-methyl imidazole react as nucleophiles, whereas the data do not allow the determination of whether the other bases react in the same way or as general bases catalyzing the water reaction. The rate constants for all of them including water and HO- define a Brönsted plot with beta = 0.46. The kinetics of the hydrolysis of the esters were studied below pH 6.20, and the mechanism involves the formation of phthalic anhydride, which then is hydrolyzed to the phthalic acid. Phenoxide ion has a very high rate constant for the reaction with phthalic anhydride, so above pH 6.20 it competes significantly with the hydrolysis of the anhydride. The reactions of the esters as a function of pH allow the determination of the kinetic pK(a) which are 3.06, 3.02, 2.95, and 2.93 for X = H, p-Me, m-Cl, and p-Cl, respectively. The data also show that the catalysis by the neighboring carboxy group takes place only when it is ionized (i.e., as carboxylate).

Influence of Fine Structural Characteristics of VPO Catalysts on the Formation of Maleic and Phthalic Anhydrides in the Oxidation of n-Pentane

We report on the influence of the stages of preparation of a vanadium phosphate on the selectivity to phthalic anhydride (PA) and maleic anhydride (MA) in n-pentane oxidation. The attention was mainly focused on the extent of structural defects observed in precursors and catalysts. Vanadium phosphate catalysts were obtained from precursors prepared by a two-step synthesis. In the first step VOPO4-mixed isobutanol–water intercalates, with the amount of isobutanol per VOPO4 molecule varying from 1.6 to 0.05, were prepared by precipitation from a solution containing vanadyl isobutoxide and H3PO4 and a carefully adjusted water content. In the second step the precursors were formed by reflux using two different procedures: (i) in an inert medium (n-octane) or (ii) in a reductive medium (isobutanol). Catalysts were obtained by treating the precursors under the reaction conditions for about 40 h. By such procedures VPO precursors and catalysts with bulk P/V atomic ratio equal to 1.05 and displaying widely different structural defects were obtained. Precursors and catalysts were characterised by elementary chemical analysis, carbon analysis, oxidation state of vanadium, BET, XRD, FTIR, and XPS. Long range and short range orders were considered. Results show that the parallel routes of the n-pentane oxidation into MA and PA require different structural features of the catalyst. The formation of phthalic anhydride demands an ordered structure while maleic anhydride could be formed on a highly defective VPO catalyst. It is suggested that this high structural order for PA formation is necessary to create the complex active structure to provide the concerted process of PA formation.

The partial oxidation of C 5 hydrocarbons over vanadia-based catalysts

The partial oxidation of C 5 hydrocarbons was investigated over unpromoted and alkali-promoted V 2O 5 catalysts. Products of this mild oxidation reaction include both maleic and phthalic anhydride. The apparent effect of alkali promotion is to facilitate the loss of surface oxygen species which are important in the activation of alkanes and the complete oxidation of intermediate species. Studies performed using 1-pentene as feed have indicated that once the first oxidative dehydrogenation step is eliminated, pentene oxidation proceeds readily towards maleic and phthalic anhydride formation. The use of 1-pentene in the feed stream caused a bulk reduction of the catalyst from V 2O 5 to VO 2 in the presence of gas phase oxygen.

The reaction mechanism of alkane selective oxidation on vanadyl pyrophosphate catalysts. Features gleaned from TAP reactor transient response studies

Some aspects of the reaction mechanism of n-butane and n-pentane selective oxidation on vanadyl pyrophosphate obtained in transient response studies using the TAP (Temporal Analysis of Products) reactor system are presented. Key features include the evolution of the surface properties of the catalyst during alkane oxidation, the role of organic adspecies and different types of reactive oxygen in the reaction mechanism and their influence on the surface microkinetics, the relationship between surface lifetime of adsorbed species and selectivity, and the role of organic precursors in phthalic anhydride formation from n-pentane.

Facile and not facile reactions for the production of maleic and phthalic anhydrides with vanadium mixed oxides based catalysts

Vanadium is a key element in the formulation of catalysts for the production of anhydrides by selective vapor oxidation with molecular oxygen. A study of the oxidations ofo-xylene,n-butane and benzene on V-P, V-Mo and V-Ti mixed oxides, the commercial catalysts for the synthesis of anhydrides, was carried out. The oxidation ofo-xylene on the three catalysts was the most facile reaction leading to high yields in phthalic anhydride; on the contrary in the oxidation ofn-butane only V-P mixed oxide was active and selective. V-P mixed oxide is active and selective in the oxidation of all the feedstocks and can be identified as the most polyfunctional catalyst. V-Mo is active and selective in botho-xylene and benzene oxidation and V-Ti only ino-xylene oxidation. Moreover the lesser selectivity in phthalic anhydride observed with V-P and V-Mo mixed oxides has been attributed to parallel oxidation reactions to the formation of phthalic anhydride, evidenced by a higher amount of phthalide.