Check out our New Publishers' Select for Free Articles

Applied Catalysis A, General (v.378, #1)

Editorial Board (pp. co2).

Contents (pp. iii-vii).

Ethene production by oxidative dehydrogenation of ethane at short contact times over Pt-Sn coated monoliths by S.F. Håkonsen; J.C. Walmsley; A. Holmen (pp. 1-10).

The oxidative dehydrogenation of ethane has been studied in a monolithic reactor. PtSn/Al₂O₃ and LaMnO₃ produce high yields of ethene when operated at short contact times. Pt-Sn was found to give superior performance when H₂ was added to the feed. PtSn was clearly more active towards the oxidation of hydrogen compared to LaMnO₃.Catalysts: 1wt% Pt-2wt% Sn. Feed: C₂H₆/O₂/H₂=4/1/2, total flow rate 2000 is Nml/min. and the flow rate for ethane is 308Nml/min. Blue line: PtSn/Al₂O₃, pink line: PtSn/LaMnO₃, red line: LaMnO, and green line: Al₂O₃.The oxidative dehydrogenation of ethane to ethene was studied in a monolithic reactor at short contact times using a Pt-Sn/Al₂O₃ catalyst. The catalyst was characterised by Temperature Programmed Reduction (TPR), Scanning Transmission Electron Microscopy as well as H₂ and CO chemisorption. Three different preparation methods were used for the Pt-Sn catalyst; two-step impregnation where Pt was impregnated first, two-step impregnation where Sn was impregnated first and co-impregnation. The results from the oxidative dehydrogenation of ethane show that the two-step impregnated catalyst with Sn first gave lower ethene selectivity compared to the other impregnation procedures. TPR results indicate that this could be due to a weaker interaction between Pt and Sn in the catalyst. The Pt-Sn catalyst was also compared to LaMnO₃, another catalyst which has been reported to be active for oxidative dehydrogenation of ethane. In these experiments Pt-Sn was found to give superior performance when H₂ was added to the feed. Pt-Sn was clearly more active towards the oxidation of hydrogen compared to LaMnO₃ which was active towards total combustion of hydrocarbons, even when relatively large amounts of hydrogen were present. It seems that ethene is produced mainly in the gas-phase and that the catalyst is important for the oxidation of hydrogen on the surface thus providing heat to the dehydrogenation reactions. However, the results also indicate that there is some ethene production on the Pt-Sn catalyst, either directly or indirectly.

Keywords: Ethane; Ethene; Monolith; Pt; Sn

Gas-phase dehydration of glycerol to acrolein catalysed by caesium heteropoly salt by Abdullah Alhanash; Elena F. Kozhevnikova; Ivan V. Kozhevnikov (pp. 11-18).

Cs_2.5H_0.5PW₁₂O₄₀ is an active catalyst for the gas-phase dehydration of glycerol to acrolein. Doping Cs_2.5H_0.5PW₁₂O₄₀ with palladium together with co-feeding hydrogen improve catalyst stability to deactivation, while maintaining high selectivity to acrolein.Caesium 12-tungstophosphate, Cs_2.5H_0.5PW₁₂O₄₀ (CsPW), possessing strong Brønsted acid sites is an active catalyst for the dehydration of glycerol to acrolein in the gas-phase process at 275°C and 1bar pressure. The initial glycerol conversion amounts to 100% at 98% acrolein selectivity, however, decreases significantly with the time on stream (∼40% after 6h) due to catalyst coking, without impairing acrolein selectivity. Doping CsPW with platinum group metals (PGM) (0.3–0.5%) together with co-feeding hydrogen improve catalyst stability to deactivation, while maintaining high selectivity to acrolein. The enhancing effect of PGM was found to increase in the order: Ru∼Pt−1g_cat⁻¹ at 275°C and 5h time on stream, exceeding that reported previously for supported heteropoly acids (5–11mmolh⁻¹g_cat⁻¹ per total catalyst mass). Evidence is presented regarding the nature of acid sites required for the dehydration of glycerol to acrolein, supporting the importance of strong Brønsted sites for this reaction.

Keywords: Glycerol; Acrolein; Dehydration; Acid catalysis; Heteropoly acid

Metal organic frameworks as heterogeneous catalysts for the selective N-methylation of aromatic primary amines with dimethyl carbonate by Amarajothi Dhakshinamoorthy; Mercedes Alvaro; Hermenegildo Garcia (pp. 19-25).

Metal organic frameworks (MOFs) with aluminium, copper and iron as central metal atoms with 1,4-benzenedicarboxylic acid (aluminium) and 1,3,5-benzenetricarboxylic acid (copper and iron) as ligands are selective and active catalysts in promoting the methylation of aromatic amines with dimethyl carbonate (DMC).Metal organic frameworks (MOFs) with aluminium, copper and iron as central metal atoms with 1,4-benzenedicarboxylic acid (aluminium) and 1,3,5-benzenetricarboxylic acid (copper and iron) as ligands are selective and active catalysts in promoting the polymethylation of aromatic amines with dimethyl carbonate (DMC). N-methylation prevails over carbamoylation even though they are competing parallel processes. The present N-methylation protocol using DMC enjoys advantages such as convenient reaction conditions, benign, reusable, cost-effective catalyst, avoids the use of additional solvent and uses a safe, green methylating agent that only produces CO₂ and methanol as by-products.

Keywords: Green chemistry; Heterogeneous catalysis; Dimethyl carbonate as methylating agent; Methylation of amines; Metal organic frameworks as solid catalysts

The effect of ultrasound on the N-alkylation of imidazole over alkaline carbons: Kinetic aspects by S. Ferrera-Escudero; E. Perozo-Rondón; V. Calvino-Casilda; B. Casal; R.M. Martín-Aranda; A.J. López-Peinado; C.J. Durán-Valle (pp. 26-32).

N-Alkylimidazoles have been synthesized by sonochemical irradiation of imidazole and 1-bromobutane using alkaline-promoted carbons. Under the experimental conditions, N-alkylimidazoles can be prepared with a high activity and selectivity. It is observed that imidazole conversion increases in parallel with increasing the basicity of the catalyst.N-Alkylimidazoles have been synthesized by sonochemical irradiation of imidazole and 1-bromobutane using alkaline-promoted carbons. The catalysts were characterized by X-ray photoelectron spectroscopy, thermal analysis and nitrogen adsorption isotherms. Under the experimental conditions, N-alkylimidazoles can be prepared with a high activity and selectivity. It is observed that imidazole conversion increases in parallel with increasing the basicity of the catalyst. For comparison, the alkylation of imidazole has also been performed in a batch reactor system under thermal activation.

Keywords: Reaction kinetic; Sonocatalysis; Basicity; Activated carbons; Imidazole; Alkylation

Oxidation of amines over alumina based catalysts by Karol Rakottyay; Alexander Kaszonyi; Stanislav Vajíček (pp. 33-41).

Amines were oxidized by molecular oxygen in the vapor phase at atmospheric pressure over silicotungstic acid/alumina catalysts. Cycloalkylamines were oxidized mainly to oximes and cycloalkanones, primary alkylamines to nitriles and aldehydes, and 1,6-hexanediamine to caprolactam and dinitrile. Carbonyl compounds and amines formed Schiff bases. The adsorption of amines on weak acidic sites is essential for their oxidation to mentioned reaction products.Amines were oxidized by molecular oxygen in the vapor phase at atmospheric pressure over alumina and silicotungstic acid/alumina catalysts. The study is focused on the influence of structure of amine and catalyst properties on the composition of the main reaction products and byproducts. Coating of γ-Al₂O₃ with silicotungstic acid or its semisalt can significantly enhance its catalytic activity in amine oxidation. The adsorption of amine on weak acidic sites of catalyst is essential for its oxidation to main reaction products. Cycloalkylamines are oxidized mainly to cyclic oximes (selectivity up to 64%) and Schiff bases of appropriate cycloalkanone and cycloalkylamine (selectivity up to 38%). Mainly nitriles (selectivity up to 55%) and appropriate Schiff bases (selectivity up to 54%) were observed in the oxidation products of primary alkylamines. Their molar ratio depends on the catalyst acidity and reaction conditions. 1,6-Hexanediamine is oxidized mainly to caprolactam (yield 48%) and other cyclic lactames and Schiff bases as well as to dinitrile (yield 13%).

Keywords: Alumina; Cycloalkylamine; Primary aliphatic amine; Isoalkylamine; Oxidation; Acidic sites determination; NH; ₃; -TPD; FT-IR; Catalyst titration; Caprolactam; Oximes; Nitriles; Schiff bases; Carbonyl compounds; Condensation reactions; Reaction pathway

Nickel nanoparticles in hydrogen-transfer reductions: Characterisation and nature of the catalyst by Francisco Alonso; Paola Riente; Juan Alberto Sirvent; Miguel Yus (pp. 42-51).

Nickel nanoparticles used in the transfer hydrogenation of carbonyl compounds have been characterised by different means and their catalytic activity, deactivation and nature studied. Surface oxidation seems to be the main reason for catalyst deactivation after reuse. The nickel nanoparticles are the true catalyst instead of a reservoir for metal atoms that leach into solution.Nickel nanoparticles, readily prepared by reduction of nickel(II) chloride with lithium and a catalytic amount of DTBB, have been used in the transfer hydrogenation of carbonyl compounds and have been fully characterised by different means. The reaction rate of the transfer hydrogenation was found to be dependent on the acetophenone and isopropanol concentration but independent on the amount of lithium chloride. The deactivation of the catalyst after reuse has been mainly attributed to surface oxidation but not to coke formation. All the experiments performed are in agreement with the process being of heterogeneous nature. The nickel nanoparticles unveiled a superior behaviour in comparison with commercially available nickel catalysts.

Keywords: Hydrogen transfer; Heterogeneous catalysis; Nickel nanoparticles

Hydrodenitrogenation property–reactivity correlation by Teh C. Ho (pp. 52-58).

This work seeks a correlation between the property of a middle distillate feedstock and its reactivity toward hydrodenitrogenation (HDN). Experiments were conducted over 25 widely different feedstocks over sulfided CoMo/Al₂O₃ and NiMo/Al₂O₃ catalysts. It is found that the HDN reactivity is primarily governed by feedstock's nitrogen content.This article is about the relationship between the properties of a refinery middle distillate feedstock and its reactivity toward hydrodenitrogenation (HDN). The HDN experiments were conducted with 12 raw middle distillates over a sulfided CoMo/Al₂O₃ catalyst and with 13 prehydrotreated middle distillates over a sulfided NiMo/Al₂O₃ catalyst. Of the multitude of physicochemical properties, the feed nitrogen content, which usually reflects the heaviness of the feedstock, is a rough indicator of the HDN reactivity. This suggests a self-inhibition effect whose implications are discussed.

Keywords: Hydrodenitrogenation; Hydrodesulfurization; Hydrocracking; Property–reactivity correlation; Middle distillate; Feedstock heaviness

A study of K-promoted MoP–SiO₂ catalysts for synthesis gas conversion by Sharif F. Zaman; Kevin J. Smith (pp. 59-68).

The conversion of synthesis gas over K-promoted MoP–SiO₂ catalysts is reported as a function of K and MoP loading. The major products were acetaldehyde, acetone and ethanol. Selectivities to methanol (<5Catom%) and methane (<10% for the 5% K–10% MoP–SiO₂ catalyst) were low. The product distribution obtained over the K–MoP–SiO₂ catalyst was distinct from that reported in the literature over other Mo-based catalysts.The conversion of synthesis gas to oxygenated hydrocarbons over a series of K-promoted MoP–SiO₂ catalysts, is reported. Catalysts with 5, 10, and 15wt% MoP on SiO₂ and promoted with 1 and 5wt% K, were prepared, characterized and tested at 548K, 8.27MPa and a H₂:CO=1. An increase in CO conversion was observed with increased MoP and K loading and the highest oxygenate space time yield of 147.2mggcat⁻¹h⁻¹ was obtained over the 5wt% K–15wt% MoP–SiO₂ catalyst. CH₄ was produced with high selectivity (29–40Catom%) over the un-promoted MoP catalysts, but with the addition of K, the CH₄ selectivity was suppressed and the C₂₊ oxygenated product selectivity increased as the surface K/Mo atom ratio increased, up to a maximum at a K/Mo ratio of 3.2. The highest selectivity towards C₂₊ oxygenates (76.6Catom%) and lowest selectivity towards CH₄ (9.7Catom%) occurred on the 5wt% K–10wt% MoP–SiO₂ catalyst. The major oxygenates in the product were acetaldehyde, acetone and ethanol. In all cases, catalyst selectivity to methanol was low (<5Catom%). The product distribution obtained over the K–MoP–SiO₂ catalysts was distinct from that reported on other Mo-based catalysts.

Keywords: Synthesis gas; Gas-to-liquids; MoP; Catalyst; Ethanol; Acetaldehyde; Acetone; C; ₂₊; oxygenates; Alcohols

CO₂ reforming of methane over La₂NiO₄/α-Al₂O₃ prepared by microwave assisted self-combustion method by B.S. Barros; D.M.A. Melo; S. Libs; A. Kiennemann (pp. 69-75).

La₂NiO₄/α-Al₂O₃ catalyst was prepared by a microwaves assisted self-combustion reaction. In order to understand the effect of the preparation method on the catalytic properties, a sample was prepared by an incipient wetness nitrate impregnation method. The catalysts were tested in CO₂ reforming of methane. The samples prepared by self-combustion showed high CH₄ conversion without coke deposition.La₂NiO₄/α-Al₂O₃ catalyst was prepared by a microwaves assisted self-combustion method using glycine or urea as fuel and metal nitrates as oxidizers. In order to understand the effect of the preparation method and the fuel type used on the catalytic properties, a sample was prepared by an incipient wetness nitrate impregnation method (without fuel). All obtained samples were used as catalysts precursors for the CO₂ reforming of methane to syngas between 500 and 800°C. The catalysts were characterized by X-ray diffraction (XRD), specific surface area measurements (BET), temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), before and after reactivity tests. XRD analyses indicate the formation of La₃Ni₂O_6.92, La₂NiO₄ and LaAl_xNi x₋₁O₃ crystalline structures independently of the preparation method. All samples prepared with fuel showed high CH₄ and CO₂ conversions with low carbon deposition. No change was observed in the crystalline structure of the perovskite-related oxides. On the other hand, the sample prepared by nitrate impregnation showed high activity but destruction of the perovskite-related structure with significant carbon formation, mainly multi-walled carbon nanotubes.

Keywords: La; ₂; NiO; ₄; /α-Al; ₂; O; ₃; Self-combustion; Microwaves; CO; ₂; /CH; ₄; reforming

Performance of WO_x-added Mo–V–Te–Nb–O catalysts in the partial oxidation of propane to acrylic acid by Bu Young Jo; Sang Seop Kum; Sang Heup Moon (pp. 76-82).

The activity of Mo_1.0V_0.3Te_0.23Nb_0.23O_x catalysts for propane oxidation was increased by WO_x addition due to the promotion of the propanol dehydration step and oxygen mobility in the catalysts. The selectivity for acrylic acid was also improved due to the increased rates of the dehydration step and the decreased number of acidic sites in the catalysts.The performance of Mo_1.0V_0.3Te_0.23Nb_0.23O_x catalyst in the partial oxidation of propane to acrylic acid was improved when the catalyst was modified with an optimal amount of tungsten oxide (WO_x), which was present largely in an amorphous phase. The added WO_x increased the catalyst activity by promoting the dehydration of the oxygenate intermediates in the oxidation process, which eventually accelerated the production of propylene. An increase in the dehydration rates on the W-added catalysts was verified by separate experiments using 1- and 2-propanol as the reactants. The selectivity for the production of acrylic acid was also improved for the W-added catalysts because the dehydration step was promoted to a greater extent than the dehydrogenation step and the number of acidic sites in the catalysts was decreased. The reaction results obtained using the W-added catalysts can be explained based on the reaction paths involved in the propane-oxidation process and on the surface properties of the catalysts analyzed using X-ray diffraction (XRD), infrared (IR) spectroscopy, and the temperature-programmed desorption of ammonia (NH₃-TPD).

Keywords: Propane; Oxidation; Acrylic acid; Tungsten oxide; Dehydration; Acidity

Palladium(0) nanoparticles formed in situ in the Suzuki–Miyaura reaction: The effect of a palladium(II) precursor by T. Borkowski; A.M. Trzeciak; W. Bukowski; A. Bukowska; W. Tylus; L. Kępiński (pp. 83-89).

Two palladium catalyst precursors were prepared by immobilizing PdCl₂ and Pd(OAc)₂ on cyclohexyldiamine-modified glycidyl methacrylate polymer (GMA-CHDA) and used in the Suzuki–Miyaura reaction. The important influence of the palladium precursor on the structure and catalytic activity of Pd(0) nanoparticles formed in situ was demonstrated.Two palladium catalyst precursors were prepared by immobilizing PdCl₂ and Pd(OAc)₂ on cyclohexyldiamine-modified glycidyl methacrylate polymer (GMA-CHDA) and used in the Suzuki–Miyaura reaction (80°C, 2h) without any pre-treatment. Using the TEM, SEM, EDS, and XPS methods, we were able to characterize the Pd(0) nanoparticles formed in situ during the catalytic process. The catalyst obtained from Pd(OAc)₂ (P₂) contained Pd(0) nanoparticles with a diameter of 3–5nm, whereas much bigger agglomerates were found for P₁, which had been obtained from PdCl₂. The P₂ catalyst exhibited much better catalytic performance than P₁, pointing to an important role of the palladium precursor in the preparation of the catalyst.

Keywords: Palladium; Nanoparticles; Suzuki–Miyaura; Immobilized catalyst; XPS

In situ generated catalysts for NaBH₄ hydrolysis studied by liquid-phase calorimetry: Influence of the nature of the metal by Anthony Garron; Simona Bennici; Aline Auroux (pp. 90-95).

Several metal chloride salts have been evaluated as precursors of in situ generated catalysts for sodium borohydride hydrolysis. The kinetics of hydrogen production and the corresponding heat evolved were studied in a reaction calorimeter coupled with a hydrogen volumetric flow-meter. The metals which can be readily oxidized and form stable boride species are the best catalysts for the borohydride hydrolysis reaction, at a lower cost compared to platinum.Several metal chloride salts have been evaluated as precursors of in situ generated catalysts for borohydride hydrolysis. The apparatus used for this study is a reaction calorimeter coupled with a hydrogen volumetric flow-meter. Successive additions of low and high concentration solutions of NaBH₄ were performed within this system in order to determine the stability of the catalysts and the poisoning effect of residual metaborate. Both the kinetics of hydrogen production and the concomitant calorimetric signal were studied from this perspective. This work highlights the occurrence of two different types of behaviours among the in situ generated catalysts, and demonstrates that those metals which can be readily oxidized and form stable boride species are the best catalysts for the catalytic borohydride hydrolysis reaction, at a lower cost compared to precious metals. The performances of these catalysts are not affected by the concentration of the NaBH₄ solution, and the rate of hydrogen generation remains constant during the reaction.

Keywords: Nanoparticles; Calorimetry; NaBH; ₄; Hydrolysis; Hydrogen storage; Heterogeneous catalysis

Influence of crystallinity on the physico-chemical properties of SAPO-31 and hydroconversion of n-octane over Pt loaded catalysts by O.V. Kikhtyanin; A.V. Toktarev; A.B. Ayupov; G.V. Echevsky (pp. 96-106).

Study of SAPO-31 samples of different crystallinity showed that the adsorptive, acidic properties are in relation with the crystallinity of SAPO-31. The conversion of n-octane and the content of isomerized products decrease for the Pt/SAPO-31 catalysts with low crystallinity, but a prolonged duration of hydrothermal synthesis exerts a beneficial effect on the catalytic properties of the Pt/SAPO-31 catalysts.SAPO-31 samples of different crystallinity were prepared at various stages of hydrothermal synthesis and characterized by XRD, SEM, chemical analysis, TGA/DTA, N₂ adsorption, IR spectra of adsorbed CO, and solid state NMR. The obtained data showed that the adsorptive and acidic properties of SAPO-31 are related to the crystallinity of the material. The concentration of strong acid sites increased simultaneously with the growth of the content of the microporous phase and attained a maximum value at a crystallinity of 80% with no further change. During earlier stages of crystallization, a microporous material deficient in silica is formed, and Si atoms are predominantly introduced into the framework by the substitution of P by Si according to a SM2 mechanism. At later stages, silica domains are formed in SAPO-31 due to the combined SM2+SM3 substitution mechanisms. NMR data showed that the environment of the Si atoms changes after the maximum crystallinity is attained, which points to the continuous modification of the acidic properties of SAPO-31. The hydroconversion of n-octane was performed over Pt-containing silicoaluminophosphates with different crystallinity. Catalytic experiments showed that an increased time of hydrothermal synthesis of the silicoaluminophosphate gives rise to a further increase of both the catalytic activity and isomerization selectivity of Pt loaded catalysts. It was supposed that the acidic sites located in the near-surface layer of the SAPO-31 crystals are responsible for the improved catalytic properties of Pt/SAPO-31.

Keywords: Microporous aluminophosphates; ATO topology; NMR; Crystallinity; n; -Octane hydroisomerization

Evaluation of the efficiency of solvent extraction for template removal in the synthesis of MCM-41 type materials to be used as tobacco additives for smoke toxicity reduction by A. Marcilla; M. Beltran; A. Gómez-Siurana; I. Martínez; D. Berenguer (pp. 107-113).

Different methods of elimination of the organic template remaining in an as-synthesized Si-MCM-41 material have been studied: calcination, and two different extraction processes, with ethanol and hydrogen peroxide. The textural properties of the samples resulting, as well as the resulting hydrothermal stability of the materials, have been evaluated. Finally, its ability as tobacco additives has been studied.In this work different methods of elimination of the organic template remaining in a piece of as-synthesized Si-MCM-41 material have been studied: calcination, and two different extraction processes, with ethanol and with hydrogen peroxide. TGA has been applied in order to analyze and to compare the characteristics of the materials obtained by the three different treatments studied. The textural properties of the samples resulting after the extraction of the template, as well as the resulting hydrothermal stability of the materials, have been evaluated. Finally, the ability of the different samples as tobacco additives in order to reduce tobacco toxicity has been studied.The results show that TGA is an excellent tool for the evaluation of the efficiency of the different treatments applied. It can be concluded that the samples treated with a mixture of HCl/EtOH and with hydrogen peroxide, respectively, are able to be used as tobacco additives. Depending of the experimental conditions for the leaching process, the samples can have hydrothermal stability and activity similar to that of the conventional MCM-41, where the template has been removed by calcination.

Keywords: MCM-41; Template elimination; Tensioactive; Extraction; Additive; Tobacco; Smoke

A theoretical–experimental study of Wells-Dawson phospho-tungstic heteropolyacid: An explanation of the pseudoliquid or surface-type behaviour by Jorge E. Sambeth; Gustavo Romanelli; Juan C. Autino; Horacio J. Thomas; Graciela T. Baronetti (pp. 114-118).

Theoretical calculations and experimental results together with our previous works indicate that the catalytic behaviour of WDA is a function of the dipolar moment of organic molecules and the presence of H₅O₂⁺ species. The pseudoliquid or surface-type behaviour depends on the physicochemical properties of the organic structure and its possibility of interaction with H₅O₂⁺.The aim of the present work is to predict theoretically the nature of the mechanism of catalytic behaviour, pseudoliquid or surface-type, of Wells-Dawson solid acid (WDA). For this purpose, we took into account the dipolar moment of the substrates and the presence of H₅O₂⁺ species in their structure, considering both theoretical and experimental results.In the present paper we studied experimentally the deprotection reaction of aldehydes from 1,1-diacetates. These theoretical and experimental results together with our previous works indicate that the catalytic behaviour of WDA is a function of the dipolar moment of organic molecules and the presence of H₅O₂⁺ species. The pseudoliquid or surface-type behaviour depends on the physicochemical properties of the organic structure and its possibility of interaction with H₅O₂⁺.

Keywords: Wells-Dawson acid; Heteropoly compounds; Extended Huckel method; Pseudoliquid phase; Surface-type activity

Modification of acid properties and catalytic properties of AlPO₄ by hydrothermal pretreatment for methanol dehydration to dimethyl ether by Krit Lertjiamratn; Piyasan Praserthdam; Masahiko Arai; Joongjai Panpranot (pp. 119-123).

Hydrothermal treatment with 10mol% water vapor at 200–300°C for 15min resulted in an increase of both acid strength and number of acid sites on the AlPO₄ catalysts. As a consequence, their catalytic activities in dehydration of methanol to dimethyl ether (DME) were enhanced with no change in the product selectivities (>99% DME).An amorphous AlPO₄ catalyst prepared by precipitation method was subjected to pretreatment with 10mol% water vapor at 100–300°C for 15min prior to activity tests in the dehydration of methanol to dimethyl ether (DME). The catalysts pretreated at 200–300°C exhibited higher methanol conversion than the non-treated catalyst while the one treated at a lower temperature of 100°C showed lower activity. As revealed by FT-IR and FT-Raman results, there was an increase of lattice hydroxyls on the hydrothermally treated catalysts in the form of P-OH group (weak Brønsted acid sites). Amine titration using Hammett indicators confirmed the increase of both strength and number of acid sites on these catalysts. However, hydrothermal pretreatment at 100°C may result in catalyst poisoning by weakly bonded water molecules instead so that lower catalyst activity was obtained. More than 99% selectivity to DME was achieved on both non-treated and hydrothermally treated AlPO₄ catalysts in this study.

Keywords: Dimethyl ether; Methanol dehydration; AlPO; ₄; Hydrothermal treatment; Acid properties

Corrigendum to “Kinetics of H₂ recovery from dodecahydro-N-ethylcarbazole over a supported Pd catalyst” [Appl. Catal. A: Gen. 362 (2009) 155–162] by Farnaz Sotoodeh; Liang Zhao; Kevin J. Smith (pp. 124-124).

Sections

Personal tools

Applied Catalysis A, General (v.378, #1)

Sections

Personal tools

Local resources

Applied Catalysis A, General (v.378, #1)