Vapour Phase Alkylation Of Phenol Research Articles

Separation of Anisole and Valuable Byproducts from Liquid Reaction Mixtures by Solvent Extraction and Multicomponent Distillation

Anisole (methoxybenzene) is a widely used organic intermediate that can be synthesized via vapor-phase alkylation of phenol by methanol in the presence of a commercial NaX zeolite as a catalyst (SiO2:Al2O3 ratio of 2.6:3). The indigenously synthesized anisole is then separated from the multicomponent liquid reaction mixture, consisting of o-cresol, p-cresol and p-xylen, along with unreacted methanol and phenol. The separated anisole has substantial demand for applications in the chemical, pharmaceutical, plastics and pesticides industries. Separation of individual components from the reaction mixture requires identification of techniques that could be scaled up. Distillation is one of the most dependable techniques for the separation of multicomponent liquid mixtures. The novelty of the present study is the synthesis and separation of anisole along with individual components of methanol, phenol and o-cresol from its reaction mixture using a single distillation column under atmospheric and vacuum conditions, respectively. Through this process, the purity of the resulting methanol, anisole and phenol were found to be 99.99, 99.80 and 98.29% by simple distillation, whereas 91.0% pure o-cresol was separated by vacuum distillation due to its high boiling point. The experimental results were used to calculate the material, individual component and energy balances, whereas the PRO/II™ process simulation was performed to scale-up the process. On the other hand, anisole recovery from a synthetic multicomponent liquid mixture was also successfully conducted using solvent extraction. The overall observations found the integration of solvent extraction with distillation to be an effective, economical and dependable solution for the isolation of anisole and other important by-products.

Synthesis of Ethyl Phenol over Modified HZSM-5 Catalyst in a Fixed Bed Reactor

Abstract The selective synthesis of p-ethyl phenol in vapor phase alkylation of phenol with ethanol was investigated in a fixed bed flow reactor on cerium modified zeolite CeZSM5 at temperature 693 K. A series of cerium modified zeolite such as Ce4ZSM54, Ce6ZSM56, Ce8ZSM58, Ce10ZSM5 were prepared by modifying with 4 %, 6 %, 8 % and 10 % ceric ammonium nitrate solution respectively. HZSM-5 zeolite exchanged with 10 % cerium nitrate solution was proved to be the best of all the catalyst used. The modified catalyst was further characterized by SEM, XRD and EDS. Phenol reacted with ethanol to form ethylphenyl ether by O-alkylation, and p-ethylphenol- and o-ethylphenol isomers by C-alkylation; secondary products were m-ethylphenol and dialkylated compounds. Reactions were carried out in the temperature 623 K–693 K, reactant mole ratio 0.2–0.5 over modified HZSM-5 zeolite. The optimum operating condition for maximum selectivity of p-ethyl phenol were EtOH to phenol mole ratio, 4:1; temperature, 623 K; space-time, 10.2 kg h/kmol and 1 atm pressure. A detailed kinetic study was carried out for the ethyl phenol synthesis reaction. From the product distribution pattern, a kinetic model for the reactions was proposed following the Langmuir–Hinshelwood approach. The kinetic and adsorption parameters of the rate equation were determined by non-linear regression analysis. From the kinetic analysis of the experimental data, the apparent activation energy for the reaction was determined as 43.27 kJ/mol.

Shaping of mesoporous AISBA-15 as cylindrical nano reactor for tertiary butylation of phenol.

Mesoporous AISBA-15 with different n(Si)/n(Al) ratios (45, 136 and 215) in the powder (P) form were synthesized by hydrothermal technique. The powder materials were shaped into cylindrical extrudates (Ex) by compounding with additives such as bentonite (binder) and methylcellulose (plasticizer). The AISBA-15 materials were characterized by XRD, N2 adsorption, AAS, 27Al MAS-NMR and thermogravimetric analysis. The orderly growth of AISBA-15 is evidenced by its XRD patterns. The surface area and pore volume of AISBA-15 catalysts were around 950 m2/g and 1.3 cm3/g respectively. A decrease in surface area and pore volume were observed for AISBA-15 (Ex) materials in comparison to AISBA-15 (P) materials. This may be due to partial blocking of pore entry and surface area coverage of additives during the shaping of extrudates. Vapor phase alkylation of phenol with tert-butanol was carried out over AISBA-15 (P) and AISBA-15 (Ex) catalysts and the results revealed that both powder and extrudate samples showed similar activity for phenol conversion. The activity of AISBA-15 catalysts follows the order: AISBA-15 (45) > AISBA-15 (136) > AISBA-15 (215) for both powder and extrudate forms. The major products were 2-tert-butylphenol (2-TBP), 4-tert-butylphenol (4-TBP) and 2,4-di-tert-butylphenol (2,4-DTBP). The selectivity to para product is much higher than other products. The catalyst exhibited steady conversion, and deactivation by coke formation of the catalyst is much reduced in AISBA-15 materials.

Phenol alkylation over lanthana modified zinc manganese ferrospinels

Various compositions of zinc manganese ferrospinels and their lanthana modifications were tested as catalysts for the vapor phase alkylation of phenol with methanol. The zinc manganese ferrospinels were prepared by the controlled low temperature hydroxide co-precipitation method and their lanthana modification by the wet impregnation method. The prepared systems were characterized by various physico-chemical methods. All the ferrite samples proved to be active for the alkylation of phenol using methanol and lanthana modified systems exhibited cent percent for o-cresol. Being an acid–base catalyzed reaction, the enhancement in the phenol conversion for the phenol alkylation reaction using methanol in the prepared systems is mainly due to their increased acidity, especially in the strong regions. Under the optimized reaction conditions, all the systems showed constant activity for a long time.

Vapor-Phase Alkylation of Phenol with Tert-butyl Alcohol Catalyzed by H3PO4/MCM-41

The catalytic performance of Al-MCM-41 containing 5-35 wt% H3PO4 was studied for the vapor phase alkylation of phenol with tert-butyl alcohol (TBA) from 383 to 493 K. 4-Tert-butyl phenol was produced as the main product with moderate selectivity. The product distribution depends on the reaction temperature, number of acid sites, and the Bronsted to Lewis sites ratios. A lower molar ratio of reactants (TBA/phenol=2) and a higher space velocity facilitated the production of 4-tert-butyl phenol. The influence of various parameters such as temperature, reactant feed molar ratio, feed rate, and time on stream were investigated for conversion yield and product selectivity.

Extrusion of AlSBA-15 molecular sieves: An industrial point of view

AlSBA-15 in the powder form with different nSi/nAl ratios (45, 136 and 215) were synthesized by hydrothermal technique. The powdered materials were made into cylindrical extrudates with the addition of bentonite as a binder. The AlSBA-15 materials were characterized by XRD, N2 adsorption, AAS and thermogravimetric analysis. The orderly growth of AlSBA-15 is evidenced by its XRD. The surface area of the powder catalyst is around 950m2/g and that of extrudate is close to 600m2/g. Vapor phase alkylation of phenol with tert-butanol was carried out over the extrudates of AlSBA-15 as a model reaction. The activity of AlSBA-15 extrudates follows the order: AlSBA-15 Si/Al=45>AlSBA-15 Si/Al=136>AlSBA-15 Si/Al=215. The reaction products were found to be 2-TBP, 4-TBP and 2,4-DTBP. The selectivity to para tertiary butylation is higher than other reactions.

The influence of phosphotungstic acid acidity on Al-MCM-41 in t-butylation of phenol with t-butyl alcohol

Al-MCM-41 (Si/Al = 20) molecular sieve was synthesized hydrothermally and phosphotungstic acid (PW) of 10, 20 and 40 wt% was supported on it. Their catalytic performance was examined in the vapour phase alkylation of phenol with tert-butyl alcohol (TBA) in the temperature range 190–275 °C. The major products were 2- tert-butyl phenol (2-TBP), 4- tert-butyl phenol (4-TBP), 2,4-di- tert-butyl phenol (2,4-DTBP) and small amounts of undesired products. 4-TBP was obtained as the major product with high selectivity. The results revealed that 20 wt% PW supported on Al-MCM-41 is found to be more active than other catalysts. The effects of molar feed ratio, space velocity and reaction temperature on conversion and products selectivity were studied and the results are discussed. The reaction parameters were optimized to obtain high selectivity of 4-TBP at high phenol conversion.

Alkylation of phenol with methanol over molybdenum oxide supported on NaY zeolite

A series of MoO 3/NaY catalysts were prepared with Mo loadings ranging from 2 to 16 wt% and characterized by X-ray diffraction (XRD), BET specific surface area and temperature-programmed desorption (TPD) of ammonia. XRD results revealed that the crystallinity of NaY zeolite was found to decrease with increase in Mo loading in the catalysts. The total acidity measured by ammonia TPD of the catalysts was found to decrease with increase in Mo loading. The catalytic properties were evaluated for the vapor phase alkylation of phenol with methanol and the results were correlated with results obtained from different characterization techniques. The conversion of phenol decreases as Mo loading increases in the catalyst. With increase in Mo loading on NaY zeolite the selectivity for the formation of C-alkylated compounds was decreased. However, the selectivity towards the formation of O-alkylated products was increased.

Vapour phase alkylation of phenol with methanol over vanadium oxide supported on zirconia

Abstract A series of vanadium oxide supported on zirconia catalysts with varying vanadium oxide content (2.5–12.5 wt.%) were prepared by wet impregnation method. The catalysts were characterised by X-ray diffraction (XRD), temperature-programmed reduction (TPR) of hydrogen, temperature-programmed desorption (TPD) of NH 3 and specific surface area measurements. X-ray diffraction patterns indicate the presence of crystalline V 2 O 5 phase from 7.5 wt.% of V 2 O 5 on zirconia. TPR patterns reveal the presence of V 3+ species on zirconia. Ammonia TPD results suggest that acidity of the catalysts increased with increase in V 2 O 5 loading up to 7.5 wt.% and decreased with further increase in V 2 O 5 loading. The catalytic properties were evaluated for the vapour-phase alkylation of phenol with methanol. During alkylation of phenol with methanol exclusively C-alkylated (alkylation proceeds through ring) products were formed. The selectivity towards 2,6-xylenol was high when compared to o -cresol. The activity of the catalysts was found to increase with V 2 O 5 loading up to 7.5 wt.% of V 2 O 5 and decreased with increase in further vanadia content.

Para-Selective t-butylation of phenol over mesoporous H-AlMCM-41

Vapour phase alkylation of phenol with t-butyl alcohol (2-methyl-2-propanol) was carried out over mesoporous H-AlMCM-41 in the temperature range 448−498 K. In this reaction, p- t-butyl phenol was obtained as a major product with high selectivity. While the phenol conversion increases with a decrease in phenol-to- t-butyl alcohol ratio, the catalytic activity decreases with time-on-stream due to deactivation of the catalyst. At higher temperatures, both the ortho- and para-isomers, viz., o- t-butyl phenol and p- t-butyl phenol, undergoes isomerization leading to m- t-butyl phenol.

Selective Ortho alkylation of phenol with alcohols over catalysts derived from hydrotalcite-like anionic clays

The vapour phase alkylation of phenol with a series of alcohols containing different number of carbons ranging from C1 to C8 were investigated over catalysts derived from magnesium-aluminium hydrotalcite with Mg/Al atomic ratio 3 (MgAl 3.0-HT). The results indicated that at 623 K the catalytic activity for phenol conversion increased with increasing chain length of linear long chain alcohols to give 2-alkylated linear alkyl phenols, without any isomerisation of the alkyl moiety. Isomorphous substitution of Mg2+ by Cu2+ or Ni2+ in the MgAl 3.0-HT resulted in an increase in selectivity of 2-alkyl and 2,6-dialkylphenols (≈60%) in the alkylation of phenol with 1-hexanol or 1-octanol.

Tertiary butylation of phenol over mesoporous H–FeMCM-41

Trivalent-iron-substituted mesoporous molecular sieve catalysts (FeMCM-41) were synthesized hydrothermally and characterized systematically by various analytical and spectroscopic techniques. Temperature-programmed desorption studies of ammonia of the protonated catalyst (H–FeMCM-41) indicate a broad distribution of the acid sites. Vapour-phase alkylation of phenol with t-butyl alcohol (2-methyl-2-propanol) was carried out over this solid acid catalyst and p-t-butyl phenol was obtained as the major product with high selectivity.

Ortho-Selective Alkylation of Phenol with 1-Propanol Catalyzed by CeO2–MgO

Vapor-phase alkylation of phenol with 1-propanol was investigated over CeO2–MgO catalysts prepared utilizing a molten mixture of the corresponding nitrates and citric acid. The CeO2–MgO had a stable catalytic activity at 475°C, and had an excellent selectivity to 2-propylphenol, higher than 82% based on phenol. Although a portion of the 2-propylphenol produced was decomposed intoo-cresol and 2-ethylphenol, a sum of selectivities to the monoalkylated phenols exceeded 97%. During the alkylation, propanal and 3-pentanone was observed. In the results of 1-propanol conversion without phenol, it was found that 1-propanol was dehydrogenated to propanal and that the propanal produced was dimerized to 3-hydroxy-2-methylpentanal via aldol addition, followed by the deformylation into 3-pentanone. Namely, in the reaction of phenol and 1-propanol, the propylation of phenol and the dehydrogenation of 1-propanol occurred concurrently over the CeO2–MgO. The pure CeO2, having both the redox property with Ce4+–Ce3+and weak basic sites, catalyzed both the propylation of phenol and the 1-propanol transformation into 3-pentanone, while the pure MgO with strong basicity was less active for the 1-propanol transformation and had a low reaction rate in the alkylation. The reaction mechanism of theortho-propylation over the CeO2–MgO catalyst is speculated as follows. Theorthoposition of phenol adsorbed perpendicularly on weak basic sites of the catalyst is selectively alkylated by 1-propanol, which is possibly activated in the form of 1-hydroxypropyl radical on CeO2species rather than as a form ofn-propyl cation. The redox property of CeO2is probably attributed to the homolitic activation of 1-propanol to produce 1-hydroxypropyl radical.

Ortho-Selective Methylation of Phenol Catalyzed by CeO2-MgO Prepared by Citrate Process

Vapor-phase alkylation of phenol with methanol was investigated over CeO2-MgO catalysts prepared utilizing a molten mixture of the corresponding nitrates and citric acid. The CeO2-MgO had attractive catalytic performance without decay of activities at the temperature range between 450 and 550°C, and it had excellent selectivities to the sum ofo-cresol and 2,6-xylenol higher than 98%. The CeO2-MgO catalysts were found to be mixtures of MgO and an interstitial solid solution of MgxCe1−x/2O2as a result of XRD measurement. It is confirmed that citric acid used in the preparation heightens the dispersion of the solid solution in the MgO matrix. The pure CeO2, which also exhibited efficient ortho-selectivity, had only weak basic sites in the TPD experiment of adsorbed CO2, while the pure MgO with strong basicity showed very low reaction rate in the methylation. The solid solution of MgxCe1−x/2O2in the CeO2-MgO catalyst probably provides active centers for the methylation of phenol. In the results of methanol decomposition, methanol was converted into CO, CO2, and CH4over the CeO2-MgO catalysts, without producing dimethyl ether. The reaction mechanism of the ortho-methylation over the CeO2-MgO catalyst is speculated: the ortho position of phenol adsorbed perpendicularly on weak basic sites on the MgxCe1−x/2O2solid solution is selectively alkylated by methanol which is possibly activated in the form of formyl or hydroxy methyl group rather than methyl cation.

Kinetics of the alkylation of phenol with methanol over catalysts derived from hydrotalcite-like anionic clays

Vapor phase alkylation of phenol with methanol was carried out over catalysts derived from a series of hydrotalcite (HT)-like compounds of the form M(II)Al-HT; where M(II)=Mg, Mn, Co, Ni, Cu and Zn with M(II)/Al atomic ratios of2–5. The kinetic parameters such as rate constant (k), apparent activation energy (Ea) and Arrhenius frequency factor (Ao) for the disappearance of phenol were evaluated employing a power law equation assuming pseudo-first order kinetics. The kinetic parameters were found to be in good agreement with phenol conversion. The existence of the compensation effect between Ea and ln Ao was tested.

Effect of substitution of [formula omitted] on the alkylation of phenol with methanol over magnesium-aluminium calcined hydrotalcite

Hydrotalcite (HT)-like compounds with the general formula, Mg 0.8M(III) 0.2(OH) 2(CO 3) 0.1·yH 2O with M(III)=Al, Fe and Cr ( Mg Al atomic ratio 4) were synthesized by coprecipitation method using a mixture of NaOH Na 2CO 3 as precipitant. The Powder X-ray diffraction (PXRD) of aluminium and iron containing samples (M(III)=Al, Fe) showed single phase corresponding to HT when a mixture of HT and MgCrO 4·7H 2O phase was detected for chromium containing sample (M(III)=Cr). These samples after calcination at 450°C/8 h/air, were used as catalyst for vapour phase alkylation of phenol with methanol. MgAl 4.0-CHT showed nearly 100% phenol conversion around 400°C and the reaction was found to proceed predominantly through the formation of anisole (O-alkylation). Isomorphous substitution of Al 3+ by Fe 3+ or Cr 3+ in the HT framework resulted in a decrease in phenol conversion in the order MgAl 4.0-CHT MgCr.0-CHT MgFe 4.0-CHT and the alkylation reaction was found to proceed exclusively at C-centres (C-alkylation) to give o-cresol as a major product. The catalytic performance for the methylation of phenol has been correlated with acid-base properties of the catalysts as determined by test reactions such as decomposition of 2-methyl-3-butyne-2-ol (MBOH) and cyclohexanol.

Selective C-alkylation of phenol with methanol over catalysts derived from copper-aluminium hydrotalcite-like compounds

Copper aluminium hydrotalcites (CuAl-HT) with a Cu/Al atomic ratio of 2, 3 and 4 (CuAl 2.0-HT, CuAl 3.0-HT, CuAl 4.0-HT) were synthesised by the coprecipitation method using a mixture of NaOH/Na 2CO 3 as precipitant. The pure crystalline hydrotalcite (HT) phase was detected by X-ray diffraction when the copper-aluminium hydrotalcite was prepared without ageing (CuAl 3.0-WAHT). Vapour phase alkylation of phenol with methanol was carried out over CuAl-HT calcined at 450°C/8 h in air (CuAl-CHT). The activity and selectivity of these catalysts were compared with those of magnesium-aluminium calcined hydrotalcites (MgAl 4.0-CHT) from our earlier report. MgAl 4.0-CHT showed higher selectivity for 2,6-xylenol whereas CuAl-CHT was selective for o-cresol. Among the CuAl-CHT studied, CuAl 3.0-CHT showed higher phenol conversion at low temperatures (250–350°C). The catalyst derived from pure copper-aluminium hydrotalcite (CuAl 3.0-WACHT) showed lowest phenol conversion compared to other copper based catalysts obtained from a mixture of HT and malachite phases. The selectivity for o-cresol decreased in the order CuAl 3.0-CHT > CuAl 2.0-CHT > CuAl 3.0-WACHT ≈ CuAl 4.0-CHT > MgAl 4.0-CHT at low phenol conversion levels (15–20%). A suitable reaction pathway for the alkylation of phenol with methanol over these catalysts has been proposed after a careful examination of the reaction sequence. The selective C-alkylation to give o-cresol and 2,6-xylenol over CuAl-CHT could be attributed to the higher acidity of these catalysts as evidenced by the higher cyclohexanol dehydration activity.

Kinetics of the alkylation of phenol with methanol over magnesium-aluminium calcined hydrotalcites

Vapour phase alkylation of phenol with methanol over magnesium-aluminium calcined hydrotalcites (MgAl-CHT) with an Mg/Al atomic ratio of 3–10 has been investigated in detail and reported previously. This study concerns the evaluation of the kinetic parameters such as the activation energy ( E a) and Arrhenius frequency factor (ln A 0) for the disappearance of phenol employing the Power law equation assuming pseudo first order kinetics. The kinetic parameters were found to be in good agreement with the specific activity of the catalysts. The existence of the compensation effect between E a and ln A 0 has been tested.

Alkylation of phenol with 1-propanol and 2-propanol over catalysts derived from hydrotalcite-like anionic clays

Vapour phase alkylation of phenol with 1-propanol and 2-propanol was carried out in a fixed-bed flow reactor over calcined magnesium aluminium hydrotalcites (MgAl-CHT) with Mg/Al atomic ratios 2, 3 and 4. MgAl 3.0-CHT showed higher phenol conversion (∼80% at 350‡C, in the alkylation of phenol with 1-propanol. Both O- and C-alkylations were found to be taking place without any skeletal isomerization of the propyl moiety, suggesting an SN2 type mechanism. Isomorphous substitution of Mg2+ by Cu2+ or Ni2+ in the hydrotalcite framework resulted in the predominant C-alkylation to give 2-n-propylphenol (60–70%) with nearly 40–50% phenol conversion at 350‡C. When 2-propanol was used as an alkylating agent, the phenol conversion decreased over all these catalysts and the alkylation was noticed exclusively at C-centers. Comparison of the product selectivity at constant phenol conversion revealed that CuAl 3.0-CHT is more selective for 2-n-propylphenol and 2-isopropylphenol in the reaction of phenol with 1-propanol and 2-propanol respectively. The participation of a pair of acid-base sites in the calcined hydrotalcites for the alkylation reaction has been proposed. The acid-base properties of these catalysts have been examined by the decomposition of cyclohexanol as a test reaction. Analysis of the spent catalysts revealed that Cu2+ in CuO gets reduced into Cu1+ and metallic copper during the reaction in the case of CuAl-CHT, while MgO and NiO phases of MgAl-CHT and NiAl-CHT are retained.

Alkylation of phenol with methanol over magnesium-aluminium calcined hydrotalcites

Vapour phase alkylation of phenol with methanol was carried out in a fixed-bed flow reactor over thermally calcined magnesium aluminium hydrotalcites, with Mg/Al atomic ratios from 3 to 10. The main products were anisole, o-cresol, and 2,6-xylenol. The influence of phenol-to-methanol molar ratio, reaction temperature and contact time on the product yields were examined. The activity of these catalysts was compared with MgO, Al 2O 3 and physically mixed MgO-AL 2O 3. Of the catalysts studied, Mg-Al 4.0:1 calcined hydrotalcite (CHT) was the most active. These catalysts are more active than magnesia and γ-alumina. On the basis of the results obtained, a suitable reaction pathway was proposed. The participation of combined acidic and basic sites in the calcined hydrotalcites for the alkylation of phenol with methanol over magnesium-aluminium calcined hydrotalcites has been suggested. Prior to the reaction, the catalyst precursors were characterised by X-ray powder diffraction and surface area measurements.