Conversion Of Acetic Anhydride Research Articles

Binder‐free Zeolite Beta Beads with Hierarchical Porosity: Synthesis and Application as Heterogeneous Catalysts for Anisole Acylation

AbstractThree zeolites (H‐Beta, H‐ZSM‐5 and H‐Y) were synthesized in the form of binder‐free macroscopic beads (d=215–840 μm) using a hydrothermal method employing anion‐exchange resin beads as hard template. The beads obtained after removal of the hard template by calcination consisted of crystalline zeolite domains connected with each other to form a hierarchical porous network in which the zeolitic micropores are accessible through meso‐ and macropores, as proven by characterization with XRD, N2 physisorption, SEM, and TEM. The composition, the nature and amount of acid sites and the degree of hydrophobicity of these beads were investigated by means of XRF, solid‐state NMR, pyridine‐FTIR and TGA. The zeolite beads were tested as heterogeneous catalysts in the Friedel‐Crafts acylation of anisole with acetic anhydride to produce para‐methoxyacetophenone. H‐Beta‐Beads displayed the best catalytic performance with 95 % conversion of acetic anhydride and 76 % yield of para‐methoxyacetophenone in a batch reactor test (90 °C, 6 h). Next, the catalytic performance of H‐Beta‐Beads was compared in both batch and continuous‐flow mode to extrudates prepared by mixing zeolite Beta powder with either kaolin or bentonite binders. H‐Beta‐Beads outperformed the extrudates in batch‐mode reactions and could be reused in multiple runs without discernible loss of activity. In the continuous‐flow test, H‐Beta‐Beads demonstrated higher average activity but deactivated more rapidly than the extrudates.

Cerium Incorporated Nanocrystalline ZSM-5: An Efficient Catalyst for Friedel Crafts Acylation of Toluene.

In this paper, the application of cerium modified nanocrystalline zeolite ZSM-5 as catalyst for Friedel Crafts acylation of toluene was investigated and compared with nanocrystalline ZSM-5. The acylating agent used was acetic anhydride. The zeolite samples were characterized by means of Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Thermal analysis, ammonia temperature-programmed desorption (NH₃-TPD) and Nitrogen sorption analysis. The results show an enhanced Lewis acidity, pore volume and surface area for cerium modified ZSM-5 providing a superior accessibility for acetic anhydride and toluene to the active sites compared to the unmodified one, thereby leading to 93% conversion of acetic anhydride, which was higher than that of unmodified ZSM-5 sample.

Hydrolysis of acetic anhydride: In situ, real-time monitoring using NIR and UV–Vis spectroscopy

Hydrolysis of acetic anhydride is a fast and very exothermic reaction that has been studied with different analytical techniques to account for the reaction progress. This work presents the real-time monitoring of the hydrolysis of acetic anhydride using in situ NIR and UV–Vis spectroscopy, under non-isothermal and non-adiabatic conditions. The experimental apparatus consists of a reaction vessel equipped with a magnetic stirrer, NIR and UV–Vis immersion probes and a thermocouple. Two multivariate models are proposed to account for the conversion of acetic anhydride as a function of time, one for NIR and other for UV–Vis. The calibration data were generated by calorimetry. The external validation permits the assessment of the adherence of the model to data not used for calibration. The results show that both models can be useful to monitor this hydrolysis, employing a simple and intuitive apparatus.

Hydrolysis of Acetic Anhydride in a CSTR

To find the optimal reactor volume and temperature for the hydrolysis of acetic anhydride at the lowest possible cost with a 90% conversion of acetic anhydride, a formula for the total cost of the reaction was created. Then, the first derivative was taken to find a value for the temperature. This value was then inputted into the second derivative of the equation to find the sign of the value which would indicate whether that point was a minima or maxima value. The minima value would then be the lowest total cost for the optimum reaction to take place.

Continuous liquid phase acylation of toluene over HBEA zeolite: Solvent effects and origin of the deactivation

The continuous liquid phase Friedel–Crafts acylation of toluene (T) by acetic anhydride (AA) over HBEA zeolite was carried out in a fixed bed reactor, with acetic acid (AC) as a solvent. 4-Methylacetophenone (4-MAP) was selectively formed in the initial reaction stage. However, a rapid catalyst deactivation occurred with a sharp decrease of the conversion of acetic anhydride, and this was mainly caused by 4-MAP and heavy compounds (‘coke’) existing in the zeolite pore, which poisoned the active sites of the catalyst. The use of excess toluene and moderate acetic acid enhanced catalyst activity and stability to some extent as it limited both the retention of 4-MAP and the formation of ‘coke’. Moreover, a considerable reduction of Broensted acid sites after deactivation revealed that the toluene acylation is primarily a Broensted acid catalyzed reaction.

Friedel–Crafts acylation of pyrrole over ultrasonic-assisted phosphoric acid-modified Hβ zeolite

Friedel–Crafts acylation of pyrrole with acetic anhydride was studied over different zeolites and an ultrasonic-assisted phosphoric acid-modified Hβ (P-Hβ-US) zeolite was found to have the best catalytic performance among all the zeolites examined. The conversion of acetic anhydride reached 98.8% and the selectivity to acetylpyrroles was 97.0% under the optimized conditions. The high activity of the P-Hβ-US zeolite is attributed to the increase of weak acid sites, caused by the synergistic effect between the phosphoric acid modification and ultrasound. Moreover, the carbonaceous deposits, mainly due to the adsorption of reactants and products, on the surface acid sites and the blockage of the pores is believed to be the reason for the deactivation of the reused P-Hβ-US zeolite, confirmed from the Brunauer–Emmett–Teller (BET) method, scanning electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, the catalyst activity can be recovered effectively by a subsequent calcination.

Modeling of Toluene Acetylation with Acetic Anhydride on H-USY Zeolite

The liquid-phase acetylation of toluene with acetic anhydride was carried out in a continuous-flow reactor over H-USY zeolites with different Si/Al ratios at 180 °C, at different contact times and feed compositions. H-USY is an active catalyst for this reaction because the main reaction products at all times on stream are the desired methylacetophenone (MAP) and its reaction byproduct acetic acid. Within the different MAP isomers, the selectivity toward 4-MAP equals 85%. Although the initial acetic anhydride conversion is 100%, the zeolite is subject to deactivation. Small amounts of side products such as methylbenzoic acid and isopropenyltoluene were also identified and their formation explained. The data and insights obtained during these experiments were used to obtain models describing the formation of MAP and the other components present in the reactor effluent. The most plausible model, obtained via model discrimination, was validated at different reaction conditions and takes into account adsorption of the chemical compounds, the catalytic reactions, and deactivation of the catalyst. It also includes hydrolysis of acetic anhydride and the formation of side products originating from MAP. According to this model, catalyst deactivation starts from MAP and acetic anhydride, whereby acetic acid is liberated. Fitting of the model to the experimental data shows that the kinetic constant for the formation of 4-MAP is comparable to that of the deactivation reaction.

Friedel–Crafts acylation of anisole over Cr-doped Hβ zeolite

Cr-doped Hβ zeolite is found to have better catalytic performance than Hβ zeolite in the Friedel–Crafts acylation of anisole, with acetic anhydride conversion of over 99% and nearly 100% selectivity to furnish para-methoxyacetophenone under the optimized reaction conditions. This is attributed to the increase of weak and moderately strong acid sites, caused by the Cr addition. The formation of carbonaceous materials and their coating of the acid sites are believed to be the reasons for the deactivation of the reused Cr-doped Hβ zeolite, as indicated by the Brunauer−Emmett−Teller (BET) method, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and NH3 temperature-programmed desorption (NH3-TPD) measurement results. The catalyst activity can be recovered by a subsequent calcination.

Characterization and the catalytic applications of mesoporous AlSBA-1

Three-dimensional mesoporous cage type aluminosilicates (AlSBA-1) with different n Si/ n Al ratios have been prepared by using cetyltriethylammonium bromide as a structure directing agent under highly acidic medium at hydrothermal conditions. The materials were characterized by various analytical techniques. XRD results reveal that the AlSBA-1 samples exhibit well-ordered three dimensional cage type porous structure, which is almost similar to its parent silica SBA-1. The nitrogen adsorption results show that the textural parameters of AlSBA-1 materials are much superior to those of the pure SBA-1 silica. The Al atoms in the AlSBA-1 samples are incorporated in the silica framework and mostly occupy tetrahedral position, which was confirmed by 27Al magic angle spinning nuclear magnetic resonance. The AlSBA-1 catalysts were tested in the acylation of veratrole using acetic anhydride as the acylation agent under liquid phase conditions. The reaction conditions were optimized in order to get more conversion of acetic anhydride and the catalytic results of AlSBA-1 with different Al contents were compared with BEA, MOR, MFI, and AlMCM-41. Of the AlSBA-1 catalysts studied, AlSBA-1(39) where the number in the parenthesis indicates the n Si/ n Al ratio in the final product was found to be the best catalyst, showing a high acetic anhydride conversion with almost 100% selectivity to 3,4-dimethoxyacetophenone. On the other hand, the catalytic activity of AlSBA-1(39) is almost similar to that of BEA but higher than MOR and MFI. In addition, the kinetics of the acylation of veratrole by acetic anhydride in excess of veratrole over AlSBA-1(39) was also thoroughly investigated and the results were discussed.

Acylation of anisole over 12-heteropolyacid of tungsten and molybdenum promoted zirconia

The liquid-phase acylation of anisole using acetic anhydride was performed over 12 heteropoly acid of tungsten and molybdenum (PWM) modified zirconia (ZPWM). Catalysts with different PWM loadings (3–20 wt.%) were prepared by the incipient wetness impregnation method using mesoporous zirconia and 12-heteropolyacid of W and Mo. The samples calcined at 500 °C were characterized by chemical analysis, nitrogen adsorption–desorption, surface acid sites, powder X-ray diffraction patterns, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, 31P nuclear magnetic resonance spectroscopy and electron probe microanalysis The sample promoted by 15 wt.% PWM was found to be the most active in the acylation reaction giving 89% conversion with 97% para-selectivity. The effect of temperature, molar ratio and catalyst amount on the conversion of acetic anhydride and anisole were studied in detail to optimize the process parameters. Reusability of the catalyst was also appraised.

Hexagonally ordered mesoporous highly acidic AlSBA-15 with different morphology: An efficient catalyst for acetylation of aromatics

Hexagonally ordered mesoporous AlSBA-15 with different n Si/ n Al ratios and morphology have been hydrothermally synthesized using the non-ionic copolymer Pluronic P123 surfactant as the structure directing agent and characterized by XRD, N 2 adsorption–desorption, SEM–EDX, elemental mapping, 27Al MAS NMR, and NH 3-TPD. It has been found that the shape and size of the particles can be controlled by the simple adjustment of the amount of Al content in the silica framework. Polygonal shaped particles with small (ca. 600 nm) and uniform size are observed for the AlSBA-15 materials with higher amount of Al in the framework. Acetylation of the aromatic compounds veratrole, anisole, and 2-methoxynaphthalene with acetic anhydride has been investigated over AlSBA-15 with different n Si/ n Al ratios under liquid phase conditions and the results are discussed. The activity of the AlSBA-15 catalysts in the acetylation of veratrole was found to increase with decreasing the n Si/ n Al ratio up to 45, and decreased with the further loading of Al in the framework. The effect of various reaction parameters such as reactant mole ratio, temperature, and catalyst concentration on the acetic anhydride conversion has been investigated in detail. The activity of the AlSBA-15 catalysts with different Al contents in the acetylation of veratrole was compared with various zeolite catalysts such as BEA, FAU, MOR, MFI, and AlMCM-41(22) where the number in parentheses denotes the n Si/ n Al ratio. It has been found that AlSBA-15 with the n Si/ n Al ratio of 45 showed the best performance in the acetylation of veratrole, with high acetic anhydride conversion and 100% selectivity to 3,4-dimethoxyacetophenone under the optimized reaction conditions. Moreover, the kinetics of the acetylation of veratrole over AlSBA-15 catalysts is discussed in detail.

Highly active three-dimensional cage type mesoporous aluminosilicates and their catalytic performances in the acetylation of aromatics

Three-dimensional cage type mesoporous aluminosilicates (AlKIT-5) with different n Si /n Al ratios have been successfully synthesized hydrothermally using pluronic F127 as a template under highly acidic medium [P. Srinivasu, S. Alam, V.V. Balasubramanian, S. Velmathi, D.P. Sawant, W. Böhlmann, S.P. Mirajkar, K. Ariga, S.B. Halligudi, A. Vinu, Adv. Funct. Mater., in press]. The catalysts have been unambiguously characterized by XRD, N 2 adsorption, and TPD of NH 3, and utilized for the acetylation of veratrole, and other aromatic substrates such as anisole, isobutylbenzene, and 2-methoxynaphthalene, using acetic anhydride (AA) as an acylating agent under liquid phase conditions. The effect of various parameters such as the reaction temperature, reaction time, reactant mole ratios, and amount of aluminium, on the AA conversion in the acetylation of veratrole has been investigated in detail to discover the optimized reaction condition. The reaction conditions were optimized to get more conversion of acetic anhydride and the activity of these catalysts has been compared with zeolite catalysts namely HY, Hβ, H-mordenite, and HZSM-5 zeolites, and the results are discussed in detail. It has been found that the AlKIT-5 catalysts showed excellent performance in the acetylation of veratrole over zeolites and other mesoporous catalysts studied under the optimized reaction conditions. Among the catalysts studied, AlKIT-5(10) was found to be the best catalyst, showing high conversion of AA and very high selectivity to the desired products. The conversion of AA decreases in the following order: AlKIT-5(10) > AlKIT-5(28) > HY(13.5) > Hβ(30) > AlKIT-5(44) > AlMCM-41(22) > H-mordenite(20) > ZSM-5(60). Moreover, the kinetics of the AlKIT-5(10) catalyst in the acetylation of veratrole has been investigated in detail and the results are clearly discussed.

Tungstophosphoric acid supported over zirconia in mesoporous channels of MCM-41 as catalyst in veratrole acetylation

Tungstophosphoric acid (TPA) over zirconia dispersed uniformly in mesoporous silica (MS) channels of MCM-41 and MCM-48 were synthesized and tested for their catalytic activity in veratrole acetylation. Catalysts with different TPA loadings (5–50 wt.%) on 22.4 wt.%ZrO 2/MCM-41 and 15 wt.%TPA on different zirconia loadings (10–70 wt.%)/MCM-41 were prepared and calcined at 1123 K. The physico-chemical characterization of the supported catalysts was done by powder X-ray diffraction (XRD), surface area measurement (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed-infrared (FT-IR) spectroscopy, UV–vis diffuse reflectance spectra, Temperature programmed desorption (TPD) of ammonia, FT-IR pyridine adsorption and 31P cross polarization-magic angle spinning (CP-MAS) NMR spectroscopy. The mesoporous silica supports play an important role in stabilizing catalytically active TPA along with tetragonal phase of zirconia. Among the catalysts, 15 wt.%TPA/22.4 wt.%ZrO 2/MCM-41 calcined at 1123 K was found to have highest acidity and at least four times more active than neat 15 wt.%TPA/ZrO 2 in veratrole acetylation to acetoveratrone by acetic anhydride. Reaction conditions were evaluated with 15 wt.%TPA/22.4 wt.%ZrO 2/MCM-41 calcined at 1123 K to get higher conversion of acetic anhydride to acetoveratrone. The reaction was found to be heterogeneously catalyzed and no contribution from homogeneous (leached) TPA into the medium under the reaction conditions.

Critical Temperatures and Pressures of the Reacting Mixture in the Acylation of Anisole with Acetic Anhydride

To determine the supercritical reaction conditions of anisole acylation with acetic anhydride using certain solvents such as carbon dioxide or propane, the critical temperatures and pressures of the nominal reacting mixture (anisole + acetic anhydride + p-methoxyacetophenone + acetic acid + carbon dioxide or propane) were measured with the composition representing the extent of reaction (conversion of acetic anhydride) by using a high-pressure viewing cell. The effects of the initial composition, the addition of suitable solvent, and the extent of reaction on the critical properties of the reacting mixture were then investigated. Such information may be helpful to those who intend to carry out the acylation of anisole with acetic anhydride under supercritical conditions to improve the efficiency of current processes in the gas or liquid phase.

Liquid-phase veratrole acylation and toluene alkylation over WO x/ZrO 2 solid acid catalysts

The liquid-phase acylation of veratrole with acetic anhydride and alkylation of toluene with 1-dodecene were carried out over WO x /ZrO 2 solid acid catalysts. The catalysts were prepared by wet impregnation method using zirconium oxyhydroxide and ammonium metatungstate. Catalysts with different WO 3 loading (5–30 wt.%) were prepared and calcined at 800 °C and catalyst with 15% WO 3 was calcined from 650 to 850 °C. All the catalysts were characterized by nitrogen adsorption, XRD and NH 3-TPD. The catalyst with 15% WO 3 calcined at 800 °C (15 WZ-800) was found to be the most active in acylation and alkylation reactions. The effect of temperature, molar ratio and catalyst weight on the conversions of acetic anhydride and dodecene were studied in detail. The catalyst 15 WZ-800 gave 67% acetic anhydride conversion in veratrole acylation under the reaction conditions of 70 °C, veratrole/acetic anhydride molar ratio 2, time 4 h and 99% dodecene conversion with >99% monododecyl toluene selectivity at 100 °C, toluene/1-dodecene molar ratio 10 and time 1 h.

Vapor‐phase synthesis of acetophenone in benzene acylation over CeHZSM‐5(30) zeolite

The benzene acylation was carried out with acetic anhydride as an acylating agent in vapor phase over HZSM‐5, Si/Al =30 and 280, HY and Ce‐, V‐modified HZSM‐5(30) zeolite catalysts at atmospheric pressure. The yield of acylated product acetophenone was found to be 82.1 wt% with 95.0% selectivity at 86.4 wt% conversion of acetic anhydride over Ce‐modified HZSM‐5(30) where Bronsted acidic sites are active for this reaction.