Isomerization Of Oxide Research Articles

Effect of mesoporosity by desilication on acidity and performance of HZSM-5 in the isomerization of styrene oxide to phenylacetaldehyde

Isomerization of styrene oxide to phenylacetaldehyde was investigated over a series of HZSM-5 zeolites with ordered mesoporosity created by desilication in alkaline solution. NH3-TPD and FT-IR spectra of adsorbed pyridine provided evidences that the alkaline treatment caused slight variation of the acid strengths and concentrations, but the mesopores made some acid sites originally in the micropores exposing to the external surface of zeolites according to FT-IR spectra of adsorbed 2,4,6-trimethylpyridine. The mesopores reduced diffusion path length and enhanced transport of phenylacetaldehyde molecules out of the zeolite crystals, thus markedly preventing the coke formation and catalyst deactivation. However, the resulting external acid sites by alkaline treatment could catalyze trimerization of phenylacetaldehyde, leading to an apparent decline of the phenylacetaldehyde selectivity.

Heterogeneous catalysis for transformation of biomass derived compounds beyond fuels: Synthesis of monoterpenoid dioxinols with analgesic activity

Catalytic synthesis of a dioxinol compound, (2S,4aR,8R,8aR)-4,4,7-trimethyl-2-phenyl-4a,5,8,8a-tetrahydro-4H-benzo[d][1,3]dioxin-8-ol, exhibiting analgesic activity was demonstrated over Fe-modified beta zeolite. During interactions between cis-verbenol oxide and benzaldehyde, two main reactions occurred. In the first reaction, namely isomerization of verbenol oxide both cyclopentenic hydroxyketone, oxetane as well as a cyclohexyl compound, (1R,2R,6S)-3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol were formed. In the second parallel reaction the target compound was generated. The highest yield of the target compound was achieved in the reaction between verbenol oxide and benzaldehyde at their molar ratio of 1:133 with the bifunctional iron modified Fe-H-Beta-150 catalyst at 70°C giving a much higher yield than reported earlier in the literature, being 46mol-% at complete conversion of verbenol oxide.

Isomerisation of α-Pinene Oxide to Campholenic Aldehyde Over Supported Ionic Liquid Catalysts (SILCAs)

The isomerisation of α-pinene oxide to campholenic aldehyde, an expensive ingredient utilized by e.g. flavor industry, was studied over Supported Ionic Liquid Catalysts (SILCAs) consisting of catalytically active species residing in ionic liquid. The ionic liquid, in turn, was immobilized on a solid support material. SILCAs were demonstrated as efficient catalysts for the transformation of α-pinene oxide into campholenic aldehyde, with the product distribution and activity being dependent on the nature of the ionic liquid.

Styrene oxide isomerase of Sphingopyxis sp. Kp5.2.

Styrene oxide isomerase (SOI) catalyses the isomerization of styrene oxide to phenylacetaldehyde. The enzyme is involved in the aerobic styrene catabolism via side-chain oxidation and allows the biotechnological production of flavours. Here, we reported the isolation of new styrene-degrading bacteria that allowed us to identify novel SOIs. Out of an initial pool of 87 strains potentially utilizing styrene as the sole carbon source, just 14 were found to possess SOI activity. Selected strains were classified phylogenetically based on 16S rRNA genes, screened for SOI genes and styrene-catabolic gene clusters, as well as assayed for SOI production and activity. Genome sequencing allowed bioinformatic analysis of several SOI gene clusters. The isolate Sphingopyxis sp. Kp5.2 was most interesting in that regard because to our knowledge this is the first time it was shown that a member of the family Sphingomonadaceae utilized styrene as the sole carbon source by side-chain oxidation. The corresponding SOI showed a considerable activity of 3.1 U (mg protein)(-1). Most importantly, a higher resistance toward product inhibition in comparison with other SOIs was determined. A phylogenetic analysis of SOIs allowed classification of these biocatalysts from various bacteria and showed the exceptional position of SOI from strain Kp5.2.

Suitable acidity of ZSM-5 for the isomerization of styrene oxide to phenylacetaldehyde

The effect of acidity of HZSM-5 (SiO2/Al2O3=25–360) on isomerization of styrene oxide to phenylacetaldehyde was investigated under gas–phase free of solvents. The reaction was mainly catalyzed by the strong acid sites of HZSM-5 and catalyst lifetimes were affected by both acid strength and concentration. Trimerization of phenylacetaldehyde occurred at external acid sites, leading to a sharp decline in product selectivity. High Si/Al HZSM-5 (e.g., SiO2/Al2O3=360), which contains weaker acid sites inside pores and trace amount of external acid sites, was found to be more effective with a higher stability and phenylacetaldehyde yield up to 95%.

Biomass to value added chemicals: Isomerisation of β-pinene oxide over supported ionic liquid catalysts (SILCAs) containing Lewis acids

The isomerisation of β-pinene oxide was studied over supported ionic liquid catalysts (SILCAs) consisting of Lewis acids in immobilized ionic liquid. SILCAs were demonstrated as efficient catalysts for the transformation of β-pinene oxide to myrtanal with the product distribution and activity being dependent on the nature of the ionic liquid and Lewis acid strength of catalytic species. With the catalyst ZnCl2/[N(3-OH-Pr)Py][NTf2]/ACC, the highest myrtanal molar yield obtained was 68%.

A chiral two-dimensional coordination polymer based on CuII and (S)-4,4′-bis(4-carboxyphenyl)-2,2′-bis(diphenylphosphinoyl)-1,1′-binaphthyl: Synthesis, structure, and magnetic and optical properties

The functionalized binaphthyl derivative (S)-4,4′-bis(4-carboxyphenyl)-2,2′-bis(diphenylphosphinoyl)-1,1′-binaphthyl (H2L) was employed as linker in the synthesis of the chiral CuII-based two-dimensional network {[Cu2(L)2(dmf)2]·H2O·9dmf}n (1). Single-crystal X-ray analysis showed a two-dimensional structure with a copper paddle wheel as secondary building unit. One dmf molecule is additionally axially coordinated to each Cu cation. A lamellar structure results consisting of alternating [Cu2(L)2(dmf)2]n and solvent (dmf, H2O) layers. According to DTA/TG measurements the coordinated dmf molecules are released at about 320°C, followed by decomposition around 460°C. Magnetic susceptibility measurements on 1 indicate strong antiferromagnetic coupling between the two metal centers in Cu2(L)2(dmf)2. Compound 1 exhibits ligand-based luminescence, assigned to the S1→S0 transition of the aromatic units. Moreover, the emission spectrum of 1 is blueshifted in comparison to H2L, due to different dihedral angles within the respective structures. Activated 1 (heating to 300°C under vacuum for 3h) showed low activity in the catalytic cyanosilylation of benzaldehyde (up to 27.1% conversion) and the isomerization of α-pinene oxide to campholenic aldehyde (up to 15.5% conversion).

Effect of phosphorus on acidity and performance of HZSM-5 for the isomerization of styrene oxide to phenylacetaldehyde

A series of phosphorus modified HZSM-5 (SiO2/Al2O3=25, P/Al=0.5, 1.0, 1.5, 2.0) samples were prepared and tested in the isomerization of styrene oxide to phenylacetaldehyde under a gas-phase atmosphere free of solvents. The strength and concentration of Brønsted acid sites decreased with increased phosphorus content, while all samples exhibited initial conversions of styrene oxide greater than 99%. External acid sites were gradually deactivated with phosphorus addition, improving the phenylacetaldehyde selectivity by suppressing its trimerization which occurred at external acid sites. When the P/Al ratio≤1, catalyst lifetimes extended because of the decrease in strong acid strength. Hard coke, which preferentially formed on strong acid sites, was considerably inhibited in the presence of phosphorus.

Catalytic performance of boron and aluminium incorporated ZSM-5 zeolites for isomerization of styrene oxide to phenylacetaldehyde

A series of boron and aluminium incorporated ZSM-5 catalysts were synthesized to study the performance of styrene oxide isomerized to phenylacetaldehyde. The physicochemical properties were characterized by a combination of nitrogen adsorption, in situ IR, XRD, SEM, NMR (27Al, 29Si, 11B), NH3-TPD and TG-DTA. The weak acidity of B containing ZSM-5 zeolites is sufficient to facilitate the reaction at high initial conversion and selectivity, but the stability of the catalysts relies heavily on the concentration of weak acid sites and the properties of strong acid sites. It is implied that the incorporation of B into Al-ZSM-5 influences the distribution of Al in the framework and has promoting effect on the stability of the catalysts. 1,3,5-Triphenylbenzene was not detected with increased concentration of weak acids, indicating that the weak acid sites will not lead to its formation. BAlZ-2 shows the best performance at 300°C without deactivation after 120h on stream.

Application of an indenyl molybdenum dicarbonyl complex in the isomerisation of α-pinene oxide to campholenic aldehyde

The complex [{(η5-Ind)Mo(CO)2(μ-Cl)}2] (1) has been tested for the industrially relevant catalytic isomerisation of α-pinene oxide (PinOx) to campholenic aldehyde (CPA) in the liquid phase. PinOx conversion and CPA selectivity are strongly influenced by the solvent employed. Complete conversion of PinOx was achieved within 1 min at 55 °C or 30 min at 35 °C using 1,2-dichloroethane as solvent, giving CPA in 68% yield. Other products included trans-carveol, iso-pinocamphone and trans-pinocarveol. The stability of 1 under the reaction conditions used was investigated by using FT-IR spectroscopy and electrospray ionisation mass spectrometry (ESI-MS) to characterise recovered solids. In the presence of air/moisture 1 undergoes oxidative decarbonylation upon dissolution to give oxomolybdenum species that are proposed to include a tetranuclear oxomolybdenum(V) complex. Conversely, ESI-MS studies of 1 dissolved in dry acetonitrile show mononuclear species of the type [IndMo(CO)2(CH3CN)n]+. The crystal structure of the ring-slipped dicarbonyl complex [(η3-Ind)Mo(CO)2Cl(CH3CN)2] (2) (obtained after dissolution of 1 in acetonitrile) is reported.

H- and Fe-modified zeolite beta catalysts for preparation of trans-carveol from α-pinene oxide

The isomerisation of α-pinene oxide has been intensively investigated for selective preparation of campholenic aldehyde, a compound used in the synthesis of fragrances. Selective preparation of another product of α-pinene oxide rearrangement, trans-carveol, still remains a challenging task. Trans-carveol is a highly valuable compound used in perfume bases, food flavour compositions and as an active pharmaceutical substance in chemoprevention of mammary carcinogenesis.In the present work zeolite beta with different SiO2/Al2O3 molar ratios was modified by iron, characterised and tested per se and in the modified form for trans-carveol preparation from α-pinene oxide. The isomerisation reaction was carried out in a polar basic solvent N,N-dimethylacetamide at 140°C. The activities and selectivities of the catalysts were correlated with their acid properties and with the iron content.

Isomerization of α-pinene oxide using Fe-supported catalysts: Selective synthesis of campholenic aldehyde

α-Pinene oxide, an oxygenated derivative of α-pinene, can be converted into various valuable substances useful as flavour, fragrance and pharmaceutical compounds. Campholenic aldehyde is one of the most desired products of α-pinene oxide isomerization being a valuable intermediate for the production of sandalwood-like fragrances. Iron modified zeolites Beta-75 and ZSM-5, mesoporous material MCM-41, silica and alumina were prepared by two methods (impregnation and solid-state ion exchange) and tested for selective preparation of campholenic aldehyde by isomerization of α-pinene oxide. The characterization of tested catalyst was carried out using scanning electron microscope analysis, nitrogen adsorption measurements, pyridine adsorption–desorption with FTIR, X-ray absorption spectroscopy measurements, XPS-analysis, 29Si MAS NMR and 27Al MAS NMR and X-ray diffraction. The isomerization of α-pinene oxide was carried out in toluene as a solvent at 70°C. The main properties influencing the activity and the selectivity are the acidic and structural properties of the tested catalysts. The highest selectivity of 66% was achieved at complete conversion of α-pinene oxide with Fe-MCM-41.

Effect of iron content on selectivity in isomerization of α-pinene oxide to campholenic aldehyde over Fe-MMM-2 and Fe-VSB-5

Isomerization of α-pinene oxide to campholenic aldehyde (CA) was investigated over Fe-containing mesoporous mesophase materials (Fe-MMM-2) and microporous nickel phosphate molecular sieves (Fe-VSB-5). Activity and selectivity of reaction towards CA over Fe-containing materials was found to depend on iron content in materials that affects oligomeric state of Fe and amount of Lewis acid sites. In the presence of Fe-VSB-5 selectivity towards CA increased with increase in iron content in structure, while that decreased in the presence of Fe-MMM-2. This phenomenon is related to change in agglomeration of iron species in Fe-MMM-2 structure. The high selectivity towards CA in the presence of Fe-VSB-5 was suggested to arise from unique structure of these materials, which favours shape selectivity.

Opening of monoterpene epoxide to a potent anti-Parkinson compound of para-menthane structure over heterogeneous catalysts

High selectivity (82 %) to 3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol, a potent anti-Parkinson drug, was achieved in the isomerization of verbenol oxide at the conversion level of 96 % in N,N-dimethylacetamide at 140 °C over a metal modified zeolite, Fe-Beta-300 with SiO2 to Al2O3 ratio of 300. This catalyst exhibits both weak and medium strong Bronsted and Lewis acid sites.

Selective Preparation of trans-Carveol over Ceria Supported Mesoporous Materials MCM-41 and SBA-15

Ce-modified mesoporous silica materials MCM-41 and SBA-15, namely 32 wt % Ce–Si–MCM-41, 16 wt % Ce–H–MCM-41 and 20 wt % Ce–Si–SBA-15, were prepared, characterized and studied in the selective preparation of trans-carveol by α-pinene oxide isomerization. The characterizations of these catalysts were performed using scanning electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption and FTIR pyridine adsorption. Selective preparation of trans-carveol was carried out in the liquid phase in a batch reactor. The activity and the selectivity of catalyst were observed to be influenced by their acidity, basicity and morphology of the mesoporous materials. The formation of trans-carveol is moreover strongly influenced by the basicity of the used solvent and in order to achieve high yields of this desired alcohol it is necessary to use polar basic solvent.

Isomerization of α-Pinene Oxide Over Iron-Modified Zeolites

Fe-modified mordenite, ferrierite, Y, ZSM-5, ZSM-12 and beta zeolite catalysts were prepared by solid state ion-exchange and conventional liquid phase ion-exchange methods from aqueous solutions. Sn- modified H-beta-300 zeolite catalyst was prepared by the later method. The characterization of proton form, Fe and Sn modified zeolites was carried out using X-ray powder diffraction, scanning electron microscopy, Mossbauer spectroscopy with magnetic measurements, transmission electron microscopy, nitrogen adsorption, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma spectroscopy, thermo-gravimetric analysis and FTIR spectroscopy using pyridine as a probe molecule. Isomerization of α-pinene oxide over the Fe and Sn modified zeolite catalysts was carried out in the liquid phase using a batch-wise glass reactor. Formation of campholenic aldehyde and fencholenic aldehyde were observed to be influenced by the structure, acidity of zeolite and contents of Fe and Sn, reaction temperature and the catalysts pretreatment.

Isomerization of α-pinene oxide in the presence of methyltrioxorhenium(VII)

Abstract The catalytic performance of methyltrioxorhenium(VII) (MTO) has been investigated for the first time in the isomerization of α-pinene oxide (PinOx) into campholenic aldehyde (CPA). The high isomerization activity of MTO is coupled with high selectivity to CPA: CPA yield of up to 87% (100% conversion) was obtained by using α,α,α-trifluorotoluene as solvent at 15 °C. Catalyst recycling is possible in a relatively simple fashion by using MTO coupled to an appropriate ionic liquid. The catalytic application of MTO in the isomerization of PinOx versus the integrated epoxidation–isomerization process of the conversion of α-pinene into CPA is discussed.

Heteropoly acid catalysts for the synthesis of fragrance compounds from biorenewables: isomerization of limonene oxide

The liquid-phase isomerization of limonene oxide was studied in the presence of heteropoly acid catalysts in aprotic solvents in homogeneous and heterogeneous systems. Among the catalysts were bulk and silica-supported tungstophosphoric acid H3PW12O40 and its acidic Cs salt Cs0.5H0.5PW12O40 (CsPW). The reaction gave dihydrocarvone, a valuable fragrance intermediate, as the main product with turnover numbers of up to 8000. The nature of the solvent had a strong effect on reaction rate and selectivity. CsPW (0.1 mol%) was found to be a highly efficient and truly heterogeneous catalyst for this reaction, providing 82% yield of dihydrocarvone in 1,4-dioxane as a solvent under ambient conditions. This simple catalytic method represents economically attractive route to industrially important compounds starting from bio-renewable substrates easily available from essential oils.

Isomerization of β-pinene oxide over Sn-modified zeolites

Four different Sn modified zeolites, namely three Beta zeolites with varying SiO2/Al2O3 ratio along with Sn-Y were synthesized, and characterized by XRD, TEM, SEM, pyridine adsorption desorption, nitrogen adsorption, XPS and EXAFS. Kinetics in β-pinene oxide isomerization into myrtanal was studied at 70°C in toluene as a solvent with different catalysts. The initial isomerization rate increases with increasing acidity. Complete conversion of β-pinene oxide was achieved with the three most acidic catalysts within 30min, whereas only 72% conversion in 1440min was obtained with the catalyst exhibiting the lowest acidity, Sn-Beta-300. The catalyst most selective to the formation of myrtanal was Sn-Beta-300 giving 64% selectivity at 72% conversion, which is related to low amounts of acid sites.

Isomerization of α-pinene oxide catalyzed by iron-modified mesoporous silicates

Iron-modified mesoporous silicates (Fe-MCM) were prepared through a direct hydrothermal method and characterized by N2 adsorption–desorption, XRD, Mössbauer spectroscopy and SEM-EDS techniques. The nature of the iron precursor (Fe2+ or Fe3+) strongly affected the textural and morphological properties of the materials. Fe2+-MCM presented the morphology similar to sheets with nanometer dimensions, while Fe3+-MCM was more similar to the non-modified MCM. Characterizations suggest that most of the introduced iron species present on the material surface rather than in the silicate framework. Besides the framework included Fe3+ ions (0.2–0.3wt.%), both materials contain only the trivalent iron (as hematite). Hematite nanoparticles are highly dispersed on the Fe3+-MCM surface, whereas in Fe2+-MCM, hematite forms particles of both low and high dispersion. The materials were shown to be efficient heterogeneous catalysts for the transformation of α-pinene oxide in various value-added fragrance compounds, with the product distribution being remarkably dependent on the solvent nature.