FTIR Spectroscopy Of Adsorbed Pyridine Research Articles

Acetalization of glycerol with acetone over various metal-modified SBA-15 catalysts

Several catalysts containing metals such as Al, Zr, Ti and Nb were incorporated in SBA-15 with Si/M ratio = 20 using the hydrothermal process. These catalysts were evaluated for their reactivity during acid-catalyzed condensation of glycerol with acetone to yield a mixture of branched compounds, namely (2,2-dimethyl- [1,3] dioxane-4-yl)-methanol (solketal) and 2,2-dimethyl- [1,3] dioxane-5-ol, which are being used as fuel additives. The synthesised catalyst samples were characterized by ICP-AES analysis, N2 adsorption–desorption measurements, X-ray diffraction, FT-IR, SEM–EDX, UV–visible diffuse reflectance spectroscopy, TPD of ammonia and ex situ pyridine-adsorbed FT-IR spectroscopy. The various characterization results confirm that metal oxides were incorporated in the pore wall of the SBA-15 matrices. The results of NH3-TPD and ex situ adsorbed pyridine FT-IR analyses showed that the acidity of the samples increased after incorporation of metal into the pure SBA-15 samples. Among various metals incorporated into the SBA-15, the Nb–SBA-15 (Si/Nb = 20) showed higher catalytic activity toward the acetalization of glycerol in liquid phase compared to that of other samples investigated. Under the optimal reaction conditions, the Nb–SBA-15 (Si/Nb = 20) exhibited 95% glycerol conversion with 100% solketal selectivity. The catalyst reusability studies indicated that the Nb–SBA-15 sample is regenerable and highly stable in the acetalization of glycerol.

Synergistic role of Brønsted and Lewis acidity in alkali metal-exchanged heteropolyacid catalysts for esterification of acetic acid at room temperature

A series of Cs exchanged phosphotungstic acid (PTA) catalysts were synthesized by the ion exchanged method and were characterized by X-ray diffraction, FT-IR spectroscopy, pyridine adsorbed FT-IR spectroscopy, SEM, BF-TEM, ICP-OES and BET surface area analysis. For comparison purposes, K exchanged PTA, Cs and K exchanged phosphomolybdic acid (PMA) catalysts were also prepared. XRD diffractograms showed that the crystallites of the Keggin ion are maintained, while FT-IR spectra also revealed the characteristic bands of the Keggin ion at all metal loadings of all the catalysts. From pyridine adsorbed FT-IR spectroscopy, it was observed that the Bronsted and Lewis acidity were significantly maintained at lower metal loadings, whereas STEM analysis showed a uniform distribution of the elements which correlated well with the theoretical atomic values of the loaded metals for all the catalysts, which were verified by ICP results. The efficiency of various metal-exchanged heteropolyacid catalysts was assessed for the esterification reaction using various substrates, and the Cs exchanged phosphotungstic acid catalysts showed superior activity compared to the other catalysts. In particular, the Cs exchanged phosphotungstic acid with a 1 wt% loading showed the highest activity and was most tolerant to the presence of water that was produced in the reaction. The catalytic activity correlates well with the Bronsted and Lewis acidity, as well as Keggin ion density of the catalysts.

KCC-1/Pr-SO3H as an efficient heterogeneous catalyst for production of n-butyl levulinate from furfuryl alcohol

In this study, production of n-butyl levulinate from furfuryl alcohol was investigated using KCC-1/Pr-SO3H as an efficient heterogeneous catalyst. The catalyst was prepared and characterized using FT-IR, N2 adsorption/desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), pyridine-adsorbed FT-IR spectroscopy and TGA techniques. The effects of different parameters on the reaction conditions including temperature, reaction time, catalyst amount, and furfuryl alcohol volume were evaluated. The highest yield of n-butyl levulinate was 81.9% at 120°C after 3h. The catalyst was recovered and reused at least four times with insignificant change in yield of n-butyl levulinate.

Synthesis of 1,3-Diols from Isobutene and HCHO via Prins Condensation-Hydrolysis Using CeO2 Catalysts: Effects of Crystal Plane and Oxygen Vacancy

We herein report the synthesis of 3-methyl-1,3-butanediol from isobutene and HCHO in water via a Prins condensation-hydrolysis reaction over CeO2, which is a water-tolerant Lewis acid catalyst. The CeO2 exhibits significant catalytic activity for the reaction, giving 95% HCHO conversion and 84% 3-methyl-1,3-butanediol selectivity at 150 °C for 4 h. The crystal planes of CeO2 have a significant effect on the catalytic activity for the Prins reaction. The (110) plane shows the highest catalytic activity among the crystal planes investigated (the (100), (110), and (111) planes), due to its higher concentration of Lewis acid sites, which is in line with the concentration of oxygen vacancies. Detailed characterizations, including NH3-TPD, pyridine-adsorbed FT-IR spectroscopy, and Raman spectroscopy, revealed that the concentration of Lewis acid sites is proportional to the concentration of oxygen vacancies. This study indicates that the Lewis acidity induced by oxygen vacancy can be modulated by selective synthesis of CeO2 with different morphologies, and that the Lewis acidity and oxygen vacancy play an important role in Prins condensation and hydrolysis reaction.

Transesterification of croton megalocarpus oil to biodiesel over WO3 supported on silica mesoporous-macroparticles catalyst

The transesterification of croton megalocarpus oil with methanol to fatty acid methyl ester (FAME) was carried out using WO3 supported on silica mesoporous-macroparticles (WO3/SMP) as a heterogeneous acid catalyst. The silica mesoporous-macroparticles (SMP) and WO3/SMP were synthesized by sol-gel and impregnation method, respectively. The catalysts were characterized with XRD, FTIR, N2 adsorption-desorption, SEM and TEM. The presence of WO3 gave a negative effect on the crystallinity and surface area of the SMP as evidenced by XRD and N2 adsorption-desorption studies, respectively. Pyridine adsorbed FTIR spectroscopy showed that the concentration of Brønsted and Lewis acid sites was dependent on the WO3 loading on SMP. 2wt% of WO3 loading on SMP (2WO3/SMP) exhibited the highest intensity of Lewis acid sites which is vital in transesterification reaction. Under the optimum reaction condition determined through response surface methodology (RSM), 2wt% WO3 loading, 4.5wt% catalyst amount, 9:1 methanol to oil molar ratio, 45min reaction time and 343K reaction temperature yielded a 96% of biodiesel product. The highest catalytic activity of 2WO3/SMP may be attributed to the high Lewis acid sites content and the presence of both intra- and interparticle pores of the catalyst that facilitated and enhanced the transport of reactants and products during the reaction.

Tuning surface composition of Cs exchanged phosphomolybdic acid catalysts in C[sbnd]H bond activation of toluene to benzaldehyde at room temperature

A series of Cs exchanged phosphomolybdic (PMA) catalysts were synthesised by the ion exchange method. The prepared materials were characterized by various physico-chemical techniques such as X-ray diffraction, FT-IR, Raman spectroscopy, pyridine adsorbed FT-IR spectroscopy, 31P NMR, BET surface area, nitrogen isotherms, TEM and STEM analysis. XRD results show crystallites of the Keggin ion of heteropolyacid catalysts. FT-IR and Raman spectra data reveal that the Keggin structure of PMA catalyst is maintained even after the exchange of the protons with Cs ions. Pyridine adsorbed FT-IR spectra show that available Brønsted acidic sites increases after Cs is incorporated in PMA. TEM analysis shows that the spherical shape remains intact after Cs exchange and STEM analysis shows a uniform distribution of elements in the Cs exchanged PMA catalyst. Nitrogen isotherms studies reveal a type IV isotherms for the Cs exchanged catalyst. The Cs exchanged phosphomolybdic acid (CsPMA) showed better catalytic performance than the phosphomolybdic acid (PMA) catalyst when evaluated for the CH bond activation of toluene to benzaldehyde. The catalyst was easily recovered and reused for five cycles with stable activity.

The Role of Copper Exchanged Phosphomolybdic Acid Catalyst for Knoevenagel Condensation

Cu exchanged heteropolyacid catalysts were synthesized by ion exchange method and characterized using various physico-chemical techniques such as X-ray diffraction (XRD), FT-IR, Raman, BET surface area, temperature programmed desorption (TPD) of ammonia, 31P NMR, pyridine adsorbed FT-IR spectroscopy, ICP-AES and STEM analysis. XRD diffractograms shows crystallites of heteropolyacid, while FT-IR and Raman spectra indicate that the Keggin ion is retained in the catalysts. 31P NMR, ammonia TPD and pyridine adsorbed FT-IR spectra results suggest that acidity decreases once Cu was incorporated in the heteropolyacid catalyst. For the Knoevenagel condensation reaction, the Cu exchanged phosphomolybdic acid (Cu–PMA) exhibits better catalytic performance than the phosphomolybdic acid (PMA) catalyst and this is related closely with the structural and acidic properties of the catalyst.

Vapor Phase Dehydration of Glycerol to Acrolein Over SBA-15 Supported Vanadium Substituted Phosphomolybdic Acid Catalyst.

Vapor phase dehydration of glycerol to acrolein was investigated over heteropolyacid (HPA) catalysts containing vanadium substituted phosphomolybdic acid (H4PMo11VO40) supported on mesoporous SBA-15. A series of HPA catalysts with HPA loadings varying from 10-50 wt% were prepared by impregnation method on SBA-15 support. The catalysts were characterized by X-ray diffraction, Raman spectroscopy, Fourier Transform infrared spectroscopy, temperature-programmed desorption of NH3, pyridine adsorbed FT-IR spectroscopy, scanning electron microscopy, pore size distribution and specific surface area measurements. The nature of acidic sites was examined by pyridine adsorbed FT-IR spectroscopy. XRD results suggest that the active phase containing HPA was highly dispersed at lower loadings on the support. FT-IR and Raman spectra results confirm that the presence of primary Keggin ion structure of HPA on the support and it was not affected during the preparation of catalysts. Pore size distribution results reveal that all the samples show unimodel pore size distribution with well depicted mesoporous structure. NH3-TPD results suggest that the acidity of catalysts increased with increase of HPA loading. The findings of acidity measurements by FT-IR spectra of pyridine adsorption reveals that the catalysts consist both the Brønsted and Lewis acidic sites and the amount of Brønsted acidic sites are increasing with HPA loading. SBA-15 supported vanadium substituted phosphomolybdic acid catalysts are found to be highly active during the dehydration reaction and exhibited 100% conversion of glycerol (10 wt% of glycerol) and the acrolein selectivity was appreciably changed with HPA active phase loading. The catalytic functionalities during glycerol dehydration are well correlated with surface acidity of the catalysts.

The role of niobia location on the acidic and catalytic functionalities of heteropoly tungstate

12-Tungstophosphoric acid (TPA) was modified systematically by incorporating niobium into its primary and secondary structure. TPA supported on niobia catalyst was also prepared by impregnation method. These catalysts were characterized by FT-infra red, X-ray diffraction, Laser Raman, X-ray photo electron spectroscopy, X-ray absorption spectroscopy, UV–vis diffuse reflectance spectroscopy, solid state 31P nuclear magnetic resonance spectroscopy, temperature programmed desorption of ammonia and pyridine adsorbed FT-IR spectroscopy. Characterization results suggest the presence of intact Keggin structure after modification of parent TPA. Incorporation of Nb into the secondary structure results in generation of Lewis acidic sites. Nb containing TPA catalysts exhibited high acidity compared to the TPA supported on niobia catalyst. The activity of the catalysts was evaluated for benzylation of anisole with benzyl alcohol. Catalyst activity depended on the location of niobium ion in the heteropoly tungstate.

Vapour-Phase Hydrogenolysis of Glycerol to 1,3-Propanediol Over Supported Pt Catalysts: The Effect of Supports on the Catalytic Functionalities

Platinum catalysts with 2 % (w/w) Pt supported on ZrO2, Sulfated ZrO2, γ-Al2O3, AlPO4, activated carbon and Y-Zeolite have been investigated for the selective vapour phase hydrogenolysis of biomass derived glycerol to 1,3-propanediol at moderate reaction temperature and atmospheric pressure. All the catalysts were synthesized by the wet impregnation method using chloroplatinic acid precursor. The physico-chemical properties of the catalysts were investigated by XRD, FTIR, SEM, CO-chemisorption, TPR, TEM, NH3-TPD and Pyridine adsorbed FTIR spectroscopy. The catalytic experimental results combined with the characterization studies showed that the glycerol conversion and the yield of 1,3-propanediol greatly depend on the nature of the support. The results also suggest that a correlation exists between catalytic activity and acidity. A key parameter to assess the best catalyst performance is the dispersion of Pt on the support and the metal-support interaction. Among various supported Pt catalysts screened for vapour phase glycerol hydrogenolysis, the Pt/AlPO4 catalyst exhibited the best activity towards glycerol conversion (100 %) and 1,3-propanediol selectivity (35.4 %). .

Promotive effect of hydrogen in n-hexane isomerization over Ni/PtHY catalyst

Bifunctional catalyst containing 0.1 wt% Ni and 0.1 wt% Pt supported on HY were prepared by incipient wetness impregnation method. The properties of the catalyst were determined by XRD analysis and pyridine adsorbed FTIR spectroscopy. The catalytic activities were tested on n-hexane isomerization by pulse method in a microcatalytic reactor under atmospheric pressure in the presence of hydrogen or nitrogen carrier gas. XRD result showed the decrease of the crystallinity of PtHY after introduction of 0.1 wt% of Ni. While, the ratio of Lewis to Brønsted acid sites increased after the introduction of Ni on PtHY as evidenced by pyridine adsorbed FTIR spectroscopy. In the presence of hydrogen gas, 0.1 wt% Ni increased the yield of isohexane by about 24 % and decreased the activation energy from 124.1 to 111.2 kJ/mol at the temperature range of 403-423 K. In addition, the activation energy decreased to 48.3 kJ/mol for Ni/PtHY at high temperature range of 478-498 K. The presence of hydrogen as a carrier gas gave a promotive effect on the reaction which led to increase the formation of isohexane and suppress the cracking process. While, the presence of nitrogen as a carrier gas promoted dimerization of nhexane which formed the cracking products.

Vapor Phase Dehydration of Glycerol to Acrolein Over Phosphotungstic Acid Catalyst Supported on Niobia

The vapor phase dehydration of glycerol was carried out on niobia-supported phosphotungstic acid (PTA) catalysts. The catalysts were prepared by varying the active component PTA loadings ranging from 10 to 40 wt% on the support. The catalysts were characterized by powder X-ray diffraction, laser Raman spectroscopy, temperature programmed desorption of ammonia, ex-situ FT-IR spectra of adsorbed pyridine, BET surface area and pore size distribution. The XRD results suggest that the active phase of phosphotungstic acid was found to be highly dispersed at lower PTA loadings on the support. The findings of Raman spectra reveals that the catalyst with 30 PTA/Nb-400 clearly exhibit the primary structure of Keggin ion of hetropolyacid on the niobia support. NH3-TPD experiments confirm that the acidity of the catalyst increases with increase of PTA loading and decreases at higher loadings. The nature of acidic sites on the catalyst surface was investigated by the ex-situ pyridine adsorbed FT-IR spectroscopy and the results suggest that the catalyst with 30 PTA/Nb has shown stronger Bronsted acidic sites. Pore size distribution reveals that 30 PTA/Nb-400 exhibited lager average pore diameter than the other loadings. The Nb2O5-supported PTA catalysts have shown remarkable catalytic performance during the dehydration of glycerol to acrolein. The catalytic properties during glycerol dehydration are related to the surface acidic functionality of the catalyst.

Activation of ethyl acetate over metal substituted MCM-41: application to alkylation and acylation

Al-MCM-41, Fe,Al-MCM-41 and Zn,Al-MCM-41 materials with different silicon to metal ratios were synthesized hydrothermally and characterized by XRD, BET, FT-IR, Acidity measurement by pyridine adsorbed FT-IR spectroscopy, 29Si and 27Al MAS NMR and ESR techniques. The orderly arrangement of mesoporous materials was clearly revealed from the XRD patterns. 29Si and 27Al MAS NMR established the co-ordination environment of silicon and aluminium. Electron paramagnetic resonance (EPR) study confirmed the co-ordination environment of Fe in Fe,Al-MCM-41 framework. The catalytic activity of these materials was evaluated in the vapour phase alkylation and acylation of ethylbenzene with ethyl acetate in the temperature range between 250 and 400 °C. The products were found to be 1,3-diethylbenzene (1,3-DEB), 1,4-diethylbenzene (1,4-DEB), 1,2-diethylbenzene (1,2-DEB), 4-ethylacetophenone (4-EAP) and acetophenone (AP). The reaction products revealed that activation of ethyl acetate is a convenient route for both alkylation and acylation reactions. The order of the catalysts activity for the reaction is found to be Fe,Al-MCM-41 (50) > Fe,Al-MCM-41 (100) > Zn,Al-MCM-41 (50) > Zn,Al-MCM-41 (100) > Al-MCM-41 (50) > Al-MCM-41 (100). In addition to the density of acid sites, the strength of acid sites is also important for this reaction. The effects of temperature, feed ratio, WHSV and time on stream were also examined and the results are discussed.

Hydroisomerization of ethylbenzene over bimetallic bifunctional zeolite catalysts

Zeolite-β and mordenite were impregnated with 0.1 wt.% Pt and varying (0, 0.1, 0.3, 0.5 wt.%) amount of Ni. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. The TEM analysis indicates that the average metal particle size increases with increasing Ni addition. The states of Ni and Pt were analyzed by ESCA. The acidity measurements by both TPD of ammonia and pyridine adsorbed FT-IR spectroscopy show the occupation of some of the acid sites by the added Ni species. Ni addition up to 0.3 wt.% over 0.1 wt.% Pt/H-β and 0.1 wt.% over 0.1 wt.% Pt/H-MOR enhances the ethylbenzene conversion, isomerization selectivity and sustainability of the catalysts. Further Ni addition above the threshold value leads to a drastic drop in activity and isomerization selectivity. Zeolite-β-based Ni–Pt catalysts always show higher activity and selectivity than mordenite-based catalysts.

Tertiary butylation of phenol over hexagonal p6 mm mesoporous aluminosilicates with enhanced acidity

Through a two-step crystallization procedure and using cetyltrimethylammonium bromide (CTAB) as template, hexagonal p6 mm mesoporous aluminosilicates (denoted as MB41) with n Si/ n Al ratios from 15 to 50 have been assembled from the preformed zeolite Beta precursors under alkaline conditions. MB41 materials were characterized by powder XRD, N 2 adsorption–desorption, 27Al-MAS NMR and pyridine adsorbed FT-IR spectroscopy techniques. Results obtained show that they are highly ordered hexagonal symmetry, and Al atoms are in tetrahedral coordination. Compared with classic Al-MCM-41, MB41 materials have stronger acidity, and also show significantly higher activities in the alkylation reaction of phenol with tert-butanol. At the reaction temperature of 145 °C, phenol conversion of 85.7% and 2,4-DTBP selectivity of 43.1% over MB41(25) are observed, but these over Al-MCM-41(25) are only 61.3% and 13.2%, respectively.

The vapour phase reaction of tert-butylbenzene and tert-butyl acetate over Al-MCM-41 molecular sieves

Hydrothermal synthesized Al-MCM-41 with different Si/Al ratios (30, 54, 78 and 107) were characterized by XRD, ICP-AES, BET, acidity measurement by pyridine adsorbed FT-IR spectroscopy, 29Si and 27Al MAS NMR techniques. The catalytic activity of these materials was tested in the vapour phase alkylation of tert-butylbenzene (TBB) with tert-butyl acetate (TBA) in the temperature range 200–400 °C. The products were found to be 1,4-di- tert-butylbenzene (1,4-DTBB), 1,3-di- tert-butylbenzene (1,3-DTBB), 4-acetyl- tert-butylbenzene (4A-TBB), 3-acetyl- tert-butylbenzene (3A-TBB), 2-acetyl- tert-butylbenzene (2A-TBB) and 2-acetyl-1,4-di- tert-butylbenzene (2A-1,4-DTBB). The selectivity towards 1,3-DTBB increased with increase in temperature, conversely the selectivity of 1,4-DTBB decreased. The selectivity to 4A-TBB, which is higher than that of other compounds, also increased with increase in temperature. The effect of temperature, flow rate and feed ratio was also studied over all the catalysts to arrive optimum conditions for higher conversion with product selectivity. The effect of time-on-stream was studied over all the catalysts and the results are discussed.

Hydroisomerization of ethylbenzene over bimetallic bifunctional zeolite catalysts: Maximization of xylene production

Zeolite-β and mordenite were impregnated with 0.1 wt.% Pt and varying (0, 0.1, 0.3, 0.5 wt.%) amount of Ni and reduced at 475 °C. The line broadening in the XRD patterns reveals that the increasing Ni addition decreases the crystallinity of zeolites. The catalysts were also characterized by TEM, ESCA and TPD of ammonia and pyridine. The TEM results show that the average metal particle size increases with increasing Ni addition. ESCA studies clearly points to the maximum percentage of Ni reduction in the Pt loaded zeolite-β and mordenite catalysts. The acidity measurements by both TPD of ammonia and pyridine adsorbed FT-IR spectroscopy show that the number of the acid sites of the catalysts decreases upon the addition of the Ni species. Hydroisomerization of ethylbenzene over the Pt–Ni loaded zeolite and mordenite was carried out in the temperature range 250–400 °C. It has been found that the addition of Ni up to 0.3 wt.% over 0.1 wt.% Pt loaded zeolite-β and 0.1 wt.% over 0.1 wt.% Pt loaded mordenite greatly enhances the ethylbenzene conversion, isomerization selectivity and sustainability of the catalysts. Further addition of Ni above the threshold value leads to a drastic reduction in the activity and isomerization selectivity. Zeolite-β-based Ni–Pt catalysts show higher activity and selectivity than mordenite-based catalysts under the optimized reaction conditions.

Ni–Pt/H–Y Zeolite Catalysts for Disproportionation of Toluene and 1,2,4-trimethylbenzene

Ni–Pt/H–Y zeolite catalysts with different Ni contents were prepared and applied to the disproportionation of toluene and 1,2,4-trimethylbenzene in the temperature range 250–400 °C. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. ESCA studies show the complete reduction of Ni species up to 0.3 wt.% Ni addition over 0.1 wt.% Pt/H-Y and further addition leads to the occurrence of unreduced nickel species as NiAl2O4. A TEM study shows the formation of bimetallic (Ni–Pt) particles of nanoscale size and the average particle size is found to increase with increasing Ni loading. Acidity measurements by NH3-TPD and pyridine-adsorbed FT–IR spectroscopy show the increasing occupation of acid sites by increasing nickel loading. The catalytic activity of Ni–Pt/H–Y zeolite and Pt/H–Y catalysts was compared and it was found that addition of Ni up to 0.3 wt.% increases conversion of toluene and 1,2,4-trimethylbenzene, disproportionation selectivity and sustainability of the catalysts. Further addition of Ni leads to a decrease in conversion and disproportionation selectivity and increasing dealkylated products, which may be due to the presence of unreduced Ni species and pore blockage by large-sized bimetallic particles formed.

Selective formation 2,6-diisopropyl naphthalene over mesoporous Al-MCM-48 catalysts

The protonated cubic mesoporous aluminosilicate (Al-MCM-48) molecular sieves have been synthesized hydrothermally and characterized by powder X-ray diffraction (XRD), nitrogen adsorption studies, thermogravimetric analysis (TGA) and solid-state 29Si and 27Al MAS NMR spectroscopy. The XRD patterns and nitrogen adsorption results reveal the cubic structural order and the mesoporous nature of the catalysts. 27Al MAS NMR spectra demonstrate that most of the Al is incorporated in the framework in tetrahedral coordination. Acidity measurement by pyridine-adsorbed FT-IR spectroscopy reveals that the incorporation of Al in the framework imparts substantial Brönsted acidity, which increases with increase in metal content. Lewis acidity is probably generated by extra-framework Al species. Vapour phase isopropylation of naphthalene (NAP) with isopropyl alcohol (IPA) was carried out over H-form of Al-MCM-48 catalysts with different n Si/ n Al ratios. The feed molar ratio of 1:2:10 (NAP:IPA:CYH) and WHSV (5.36 h −1) were found to be the optimized conditions for good NAP conversion with selectivity of 2,6-diisopropylnaphthalene (2,6-DIPN). The effect of 2,6/2,7-DIPN ratio was also studied for catalysts with various n Si/ n Al ratios and at different temperatures. Among the catalysts used in the present study, AlMCM-48 (25) showed a high NAP conversion and selectivity to 2,6-DIPN under the optimized reaction conditions.

Vapour phase alkylation of ortho-, meta- and para-cresols with isopropyl alcohol in the presence of sol–gel prepared alumina catalyst

Nanosized γ-Al 2O 3 catalyst was prepared by the alkoxide sol–gel method and characterized by XRD and TEM. The porous nature of the catalyst was studied by nitrogen adsorption–desorption isotherms. Acidity of the synthesised material was analyzed by pyridine-adsorbed FT-IR spectroscopy. The gas phase alkylation of isomeric methylphenols (cresols) with isopropyl alcohol over sol–gel prepared alumina catalyst was studied. The reactions were carried out in a continuous process at the atmospheric pressure with dependence on temperature, starting at 210 °C up to the point when the amount of alkylated cresols dropped due to decomposition. Both, O- and C-alkylated products were obtained at lower temperatures, while at higher temperatures ortho-isopropylated derivatives of isomeric cresols were the main products. According to the present method isopropylated cresols can be efficiently obtained with selectivity higher than 90%.