Conversion Of Cyclohexanol Research Articles

Catalysis of chitosan-supported iron tetraphenylporphyrin for aerobic oxidation of cyclohexane in absence of reductants and solvents

The chitosan-supported iron(III) tetraphenylporphyrin was prepared and characterized structurally, and its ability to catalyse oxidation of cyclohexane into cyclohexanone and cyclohexanol with air in absence of any reductants and solvents was studied. The research results showed that the amino groups of the chitosan coordinated axially with the iron atoms of chloro[tetraphenylporphinatoiron(III)] to form chitosan-supported ironporphyrin, which has better catalytic power for cyclohexane oxidation with air than the corresponding unsupported ironporphyrin. Under reaction conditions of 418 K and 0.8 MPa, the cyclohexane oxidation catalyzed by chitosan-supported iron(III) tetraphenylporphyrin had 1.40×10 5 catalyst mole turnover (based on the iron atom), 10.48% cyclohexane conversion and the 79.20% cyclohexanone and cyclohexanol selectivity, respectively. The turnover in cyclohexane oxidation catalyzed by the supported ironporphyrin is about 22 times bigger than that by unsupported ironporphyrin and the conversion is about double. The values are also higher than 3.9% conversion and 78% selectivity catalyzed by soluble cobalt catalyst used in industry at present. This paper has also investigated the influences of reaction time, temperature and pressure on the catalyst turnover, cyclohexane conversion and ratio of cyclohexanol to cyclohexanone in the cyclohexane oxidation catalyzed by the chitosan-supported iron(III) tetraphenylporphyrin.

Acid-Base properties of MgCuAl mixed oxides

MgCuAl layered double hydroxides (LDHs) with a hydrotalcite like structure containing different proportions of Mg2+ and Cu2+ cations have been prepared. Thermogravimetry and X-ray diffraction data indicated that the transformation of LDH into mixed oxides is effective after calcination at 723 K, irrespective of the composition. The acid-base properties of these mixed oxides have been investigated using adsorption microcalorimetry and X-ray photoelectron spectroscopy with NH3 (for acidity) and SO2 (for basicity) as probe molecules. Their catalytic behaviour for the conversion of cyclohexanol has been tested. The acid-base properties and the selectivity of catalysts has been related to their composition.

Promoting effect of CeO2 on cyclohexanol conversion over CeO2-ZnO mixed oxide materials prepared by amorphous citrate process

CeO2-ZnO materials were prepared by amorphous citrate process and characterized by TGA, XRD, UV-DRS and surface area measurements. TGA showed that the citrate precursors decompose in the range 350–550°C producing CeO2-containing catalytic materials. XRD and DRS results indicated the formation of well-dispersed interstitialZn xCe4+ 1−2x Ce3+ 2x O2 solid solution on ZnO matrix. Addition of CeO2 to ZnO produced high surface area mixed oxide materials in citrate method. Cyclohexanol conversion reaction was carried out on these catalytic materials to investigate the effect of rare earth oxide on the activity and selectivity. It was found that CeO2 promotes the activity of ZnO without affecting the selectivity to cyclohexanone significantly. The factors such as reaction temperature and WHSV have turned out to be important for cyclohexanol conversion over CeO2-containing ZnO catalyst materials.

Gas-Phase Oxidative Dehydrogenation of Cyclohexanol over ETS-10 and Related Materials

The gas-phase oxidative dehydrogenation of cyclohexanol with air using ETS-10 and related materials is studied. At reaction temperatures below 200°C, ETS-10 was 100% selective to cyclohexanone and 75% cyclohexanol conversion was achieved. Catalyst deactivation was attributed to pore blockage. The catalyst is completely regenerated by calcination at 400°C. Cyclohexanol conversion increases with temperature and oxygen/cyclohexanol feed ratios. The introduction of Cr, Fe, K, or Cs in ETS-10 affects stability and decreases conversion and selectivity towards cyclohexanone. For comparison, some results on TS-1, zeolites NaX, and mordenite are also presented.

Characterization of La 2O 3-TiO 2 and V 2O 5/La 2O 3-TiO 2 catalysts and their activity for synthesis of 2,6-dimethylphenol

The La 2O 3-TiO 2 (1:5 molar ratio) mixed oxide was prepared by a co-precipitation method with in situ generated ammonia and was impregnated with various amounts of vanadia (4–12 wt.%). The La 2O 3-TiO 2 and the V 2O 5/La 2O 3-TiO 2 catalysts were subjected to thermal treatments from 773 to 1073 K and were investigated by X-ray diffraction, FT-infrared, BET surface area, and O 2 chemisorption methods to establish the effects of vanadia loading and thermal treatments on the surface structure of the dispersed vanadium oxide species and the temperature stability of these catalysts. Conversion of cyclohexanol to cyclohexanone/cyclohexene was investigated as a model reaction to assess the acid–base properties of these materials. The catalytic property was evaluated for a single step synthesis of 2,6-dimethylphenol from cyclohexanone and methanol in the vapor phase at normal atmospheric pressure. Characterization results suggest that the co-precipitated La 2O 3-TiO 2 when calcined at 773 K is in X-ray amorphous state and exhibits reasonably high specific surface area. The amorphous La 2O 3-TiO 2 is converted into crystalline compounds La 2Ti 2O 7 and La 4Ti 9O 24 at 873 and 1073 K, respectively. The La 2O 3-TiO 2 also accommodates a monolayer equivalent of V 2O 5 (12 wt.%) in a highly dispersed state on its surface. The V 2O 5/La 2O 3-TiO 2 catalyst is thermally quite stable up to 873 K calcination temperature. When subjected to thermal treatments beyond 873 K, the dispersed vanadium oxide selectively interacts with La 2O 3 portion of the mixed oxide and forms a LaVO 4 compound. The remaining TiO 2 appears in the form of anatase phase. The La 2O 3-TiO 2 and the V 2O 5/La 2O 3-TiO 2 differ in terms of acid–base properties and the 12% V 2O 5/La 2O 3-TiO 2 catalyst provided a maximum yield of 2,6-dimethylphenol among various catalysts investigated.

The ionic size of metal atoms in correlation with acidity by the conversion of cyclohexanol over MeAPO-5

The conversion of cyclohexanol was investigated over MeAPO-5 [Me = Mg, Co, Mn and Zn]. The acidity of the catalysts was correlated with the ionic radii of Me atoms incorporated into the structure of the catalysts. Based on this correlation, it is suggested that the distortion of structure by the larger Me atoms was associated with the T–O–P angle and hence the acid strength.

Surface characterization of alumina-supported catalysts prepared by sol–gel method. Part I. Acid–base properties

Surface characterization of Al2O3, In2O3–Al2O3 and Ga2O3–Al2O3 prepared by sol–gel method was made focusing on the acid–base properties. Cyclohexanol conversion as a model reaction revealed that acid sites rather than basic sites are present predominantly on the surface. The presence of Lewis acid sites was confirmed by pyridine adsorption followed by Fourier transform infrared (FT-IR) spectroscopy. In addition, a certain amount of Bronsted acid sites were also revealed by the adsorption of 2,6-dimethylpyridine (DMP). From the adsorption of CO, it was found that the addition of Ga2O3 into alumina leads to a decrease of Lewis acid strength but to an increase of the number of sites, while In2O3 addition caused a global decrease of Lewis acidic properties of alumina. Using CO2 as a probe to study the basicity, the number of surface basic sites on alumina was found to be decreased by the In2O3 and Ga2O3 additives. A good correlation between the catalytic activity for 3,3-dimethylbut-1-ene isomerisation and the surface acidity estimated by CO and DMP adsorption was supposed. The combination of model reactions and adsorption of specific probe molecules gives us detailed information concerning the surface acid–base properties.

Some Surface and Catalytic Properties of V2O5–Cr2O3/SiO2, MoO3–Cr2O3/SiO2 and NiO–Cr2O3/SiO2 Ternary Solid Catalysts

Ternary vanadia–chromia/silica, molybdena–chromia/silica and nickel oxide–chromia/silica solid catalysts were prepared by the impregnation method. Their structural characteristics were examined using differential thermal analysis (DTA) and X-ray diffraction techniques. The catalytic activities of the prepared samples towards the conversion of isopropanol and cyclohexanol and the kinetics of these catalytic conversions were studied with the aid of a microcatalytic pulse technique. In addition, the surface acidities of selected samples were measured from the percentage of propene produced by the poisoned catalysts. X-Ray diffraction and differential thermal analysis revealed that the only detectable phase was α-Cr2O3 with the presence of all other phases or spinel not being confirmed. The order of the surface acidities was found to lie in the sample sequence: 3 wt% V2O5–20 wt% Cr2O3/SiO2 > 3 wt% MoO3–20 wt% Cr2O3/SiO2 > 20 wt% Cr2O3/SiO2 > 3 wt% NiO-20 wt% Cr2O3/SiO2, all samples having been precalcined at 500°C. Catalytic conversion of isopropanol gave propene and acetone, whereas cyclohexene, cyclohexanone and methylcyclopentene (as an isomerization product) were produced from the catalytic conversion of cyclohexanol. The catalytic activity was found to be influenced considerably by the type of impregnating ion employed and by the precalcination temperature, and hence by the surface acidity of the examined catalysts. On the other hand, the Bassett–Habgood and Kiperman equations could be applied in a satisfactory manner to the generation of the various reaction products. The calculated activation energies for the catalytic conversion of isopropanol and cyclohexanol were compared.

Genetic analysis of a gene cluster for cyclohexanol oxidation in Acinetobacter sp. Strain SE19 by in vitro transposition.

Biological oxidation of cyclic alcohols normally results in formation of the corresponding dicarboxylic acids, which are further metabolized and enter the central carbon metabolism in the cell. We isolated an Acinetobacter sp. from an industrial wastewater bioreactor that utilized cyclohexanol as a sole carbon source. A cosmid library was constructed from Acinetobacter sp. strain SE19, and oxidation of cyclohexanol to adipic acid was demonstrated in recombinant Escherichia coli carrying a SE19 DNA segment. A region that was essential for cyclohexanol oxidation was localized to a 14-kb fragment on the cosmid DNA. Several putative open reading frames (ORFs) that were expected to encode enzymes catalyzing the conversion of cyclohexanol to adipic acid were identified. Whereas one ORF showed high homology to cyclohexanone monooxygenase from Acinetobacter sp. strain NCIB 9871, most of the ORFs showed only moderate homology to proteins in GenBank. In order to assign functions of the various ORFs, in vitro transposon mutagenesis was performed using the cosmid DNA as a target. A set of transposon mutants with a single insertion in each of the ORFs was screened for cyclohexanol oxidation in E. coli. Several of the transposon mutants accumulated a variety of cyclohexanol oxidation intermediates. The in vitro transposon mutagenesis technique was shown to be a powerful tool for rapidly assigning gene functions to all ORFs in the pathway.

Dehydration and dehydrogenation of cyclohexanol over AlPO4-5 based molecular sieves

The role of incorporated divalent metal (Mn, Mg, Co and Zn) incorporated into the framework of AlPO4-5 in conversion of cyclohexanol has been examined. The influence of these metals to cyclohexene and cyclohexanone selectivities was correlated to the acidity and basicity properties of these molecular sieves. Possible mechanism for the dehydration and dehydrogenation for cyclohexanol was proposed.

Catalytic transformation of cyclohexanol over aluminophosphate-based molecular sieves

Catalytic transformation of cyclohexanol over AlPO 4-5, AlPO 4-11, SAPO-5, SAPO-11, VAPO-5, VAPO-11, CoAPO-5, CoAPO-11, NAPO-5, NAPO-11, ZAPO-5 and ZAPO-11 has been studied. The main product formed from this transformation is cyclohexene. The product distribution is influenced by acidity, inverse weight hourly space velocity (WHSV) −1 and temperature. Increase of (WHSV) −1 and temperature increase the formation of dehydrogenated product with simultaneous decrease of dehydrated product. The effect of various parameters like acidity, (WHSV) −1 and temperature on the conversion of cyclohexanol and the product distribution has been fully discussed.

Evaluation of the acid-base surface properties of several oxides and supported metal catalysts by means of model reactions

Acid-base properties of oxides (Al 2O 3, SiO 2, ZrO 2, CeO 2, MgO, SiO 2Al 2O 3 and CeO 2Al 2O 3) were investigated by means of model reactions: 3,3-dimethylbut-1-ene isomerization (33DMB1), methylene cyclohexane isomerization (MECH), cyclohexanol conversion (CHOL) and CO 2 chemisorption at room temperature. The effect of acid (Cl −, SO 2− 4) and basic (K +) promoters on certain oxides (Al 2O 3, ZrO 2) was also studied. Surface acidity was evaluated by means of 33DMB1 or MECH isomerization and of CHOL dehydration into cyclohexene. CO 2 chemisorption as well as the cyclohexanone to cyclohexene ratio in CHOL conversion were used to measure the surface basicity of the solids. Except for very few cases, all the tests gave coherent results which led to well-defined scales of acidity and of basicity. Contrary to what could be observed with the conventional isopropanol test, the CHOL test proves to be little sensitive to the redox sites of the oxides. The presence of metals can create significant perturbations in these acid-base tests, except in the case of 33DMB1 isomerization. The latter reaction is not catalyzed by Pt and Rh surfaces, which allows to measure (in the presence of these metals) the acid properties of the support and to investigate the changes in surface acidity, resulting from the metal impregnations (metal → support electronic effect, presence of anions,…).

Application of KBigraphite intercalation compounds as stereoselective catalysts of cyclohexanol conversion

The second stage of KBigraphite intercalation compounds with interplanar distance of 1320 pm was used as a catalyst for cyclohexanol conversion. Intercalation of a KBi alloy into graphite caused a two-fold increase in activity for cyclohexanol dehydrogenation to cyclohexanone and dehydration to cyclohexene in the temperature range 200–400 °C. The KBiGICs catalyst was also stereoselective; complete inactivity in the dehydrogenation to benzene was found. A correlation was found between the catalytic activity and thermally stimulated electron emission from the KBiGICs in the temperature range of 300–350 °C

Synthesis and catalytic activity of sodium-magnesium orthophosphates of different stoichiometry

This paper reports on the synthesis and characterization of various mixed orthophosphates [NaMgPO4, Na4Mg(PO4)2 and NaMg4(PO4)3] obtained from freshly prepared Mg3(PO4)2 gel by using various treatments. The solids exhibit excellent selectivity in the gas-phase conversion of cyclohexanol (CHOL) to cyclohexanone (CHONE).

Titanium incorporated ATS and AFI type aluminophosphate molecular sieves

Titanium aluminophosphate molecular sieves of ATS and AFI (with two different titanium levels in the framework) have been synthesized. These materials were characterized using XRD, SEM, BET, 27Al and 31P MAS NMR, XPS and EXAFS techniques. The results of XRD, SEM, BET and 27Al and 31P MAS NMR indicated the highly crystalline nature and phase purity of the samples. All these materials show a significant pre-edge peak at 4968 eV for Ti, characteristic of tetrahedral Ti. The average Ti—O coordination number for the ATS and AFI titanium aluminophosphates is 4.4 ± 0.3. XAFS obtained at the Ti K edge indicated the Ti incorporation in the ATS and AFI AlPO frameworks. In the ATS aluminophosphate, Mg and Ti are present in the framework. The catalytic performance of the ATS and AFI titanium aluminophosphate catalysts were investigated in the conversion of cyclohexanol to cyclohexanone with hydrogen peroxide in the presence of acetone at 353 K. The catalytic activity of these molecular sieves are compared with that of the titanium silicalite-1 zeolite.

Conversion of cyclohexanol to dicyclohexyl ether catalyzed by cation-exchanged bentonite clays

Bentonite clays modified by exchanging Al 3+, Co 2+ and its Na + form were used in etherification of cyclohexanol to dicyclohexyl ether. Product yields obtained for metal cation exchanged clays followed the order Al 3+ > Co 2+ > Na +. Brønsted acidity of the solid catalysts is suggested to play the key role in the studied reaction.

Modification of the Activity of Mg 3(PO4) 2 in the Gas-Phase Conversion of Cyclohexanol by Addition of Sodium-Carbonate

This paper reports the synthesis and characterization of solid NaMgPO 4, obtained by adding Na 2CO 3 to freshly formed Mg 3(PO 4)(2) · 22H 2O. The magnesium orthophosphate was prepared by gelling an aqueous solution of MgCl 2 and Na 2HPO 4 with 3 N NaOH. The solid products thus obtained were characterized by using various structural (XRD), surface (XPS, DRIFT, BET), and morphological (SEM) elucidation techniques. The results show that the NaMgPO 4 surface also contains Na 2CO 3, NaCl, and MgO, which endow it with increased activity and selectivity. Thus, Mg 3(PO 4) 2 yields cyclohexene (CHE) preferentially, and some cyclohexanone (CHONE), in the gas-phase conversion of cyclohexanol. On the other hand, NaMgPO 4 produces CHONE selectively under the same reaction conditions.

Catalytic conversion of oxygen containing cyclic compounds. Part I. Cyclohexanol conversion over H[Al]ZSM-5 and H[B]ZSM-5

Cyclohexanol (CHL) conversion was measured under low-pressure on-stream conditions on HZSM-5 zeolites and on H-boralite using small amounts of catalysts. Catalytic runs were followed by TPD of the surface species, which also were studied using FTIR spectroscopy. It was found that the individual reaction steps, low-temperature dehydration (yielding cyclohexene), skeletal isomerization (ring contraction to methylcyclopentene) and reactions involving H-transfer (formation of methylcyclopentane, substituted aromatics and simple olefins) were conditioned by the presence of strong acid sites whose number needed for these reactions increased from the dehydration to the H-transfer reactions. The CHL reaction was compared with the reactions of cyclohexene, and the effect of Lewis acid sites present in some cases together with the Brønsted sites was discussed. Ammonia was found to block the active centers, reduce the isomerization and especially the reactions involving H-transfer. Contrary to ammonia, methanol reacted with the CHL surface complexes yielding more substituted aromatics and more olefins than CHL or methanol alone (and/or simple sum of CHL and methanol products).

In situ fiber‐optic Raman spectroscopy of organic chemistry in a supercritical water reactor

AbstractIn situ measurements were made of several organic chemical reactions in supercritical water using fiber‐optic probes, near‐infrared excitation and CCD array detection. The reactions studied include the conversion of cyclohexene to cyclohexane and benzene in the presence of a platinum catalyst, conversion of cyclohexanol to cyclohexene in the presence of a cobalt catalyst and the homopolymerization of styrene. Transition to the supercritical state was marked by a sudden decrease in the background and the appearance of intense Raman bands for dissolved organic compounds. The results indicate that this method of study is both sensitive and rapid enough to permit kinetic measurements, even when reactions are completed in less than 2 min.

Cyclohexanol conversion of Pt-and Co-promoted molybdena-alumina; Effect of S-uptake

The uptake of sulfur reduces the overall activity of PtMo/Al2O3 and enhances that of CoMo/Al2O3 in conversion of cyclohexanol. Significant changes in selectivity indicate the existence of different active sites of the initial catalyst for hydro-dehydrogenation and dehydration. The differences in catalytic activity expressed in terms of overall TOF decrease with increasing sulfur treatment like for Ru and Ir promoted catalysts.