Catalytic Epoxidation Of Styrene Research Articles

Facile synthesis of nanoscale CuO and NiO via the PVA-assisted sol-gel method and their exploration in the catalytic epoxidation of styrene

The full-text of the article will be published in the English version of the journal "Catalysis in Industry" No. 4, 2024.Both nanoscale copper oxide and nickel oxides, with diameter 17 and 25 nm respectively, have been synthesized via an easy sol-gel method using polyvinyl alcohol. The method involves the simple dispersion of metal ions (M2+ = Cu or Ni) into the PVA gel and subsequent calcination of the dried gel at 400 °C for 3 h. The synthesized oxide materials are characterized by different physical tools like TGA, powder XRD, SEM, TEM and DRS UV-visible spectroscopic technique. The oxides are found to be very efficient catalysts in the epoxidation of styrene. CuO gives 87 % styrene conversion and 88 % SO selectivity while, NiO gives 69 % styrene conversion and 80 % with TBHP as an oxidant at the end of 6 h. Both the catalysts can suitably be reused for several successive runs without appreciable loss in activity and selectivity. The cost-effective synthesis, excellent catalytic performance and reusability make these oxides promising catalysts for the industrial use.

Synthesis of nanoscale CuO via precursor method and its application in the catalytic epoxidation of styrene.

Nanoscale CuO with diameters in the range of 7–8 nm has been synthesized via a two-step precipitation–calcination method using copper(ii) isonicotinate tetrahydrate as the precursor. The first step involves the room temperature stirring of an alkaline ethanolic solution of the precursor which gives a non-crystalline CuO species, while the second step involves the calcination of the product of the first step at 180 °C to form nanocrystalline CuO which has been characterized by PXRD, TEM, SEM, H2-TPR and Raman spectroscopy, etc. The CuO material has shown excellent catalytic activity in the oxidation of styrene using TBHP as the oxidizing agent leading to complete styrene conversion with more than 95% styrene oxide selectivity at the end of 6 h. The oxide catalyst can be reused for at least 6 successive runs without significant loss in activity.

Aerobic epoxidation of styrene over Zr-based metal-organic framework encapsulated transition metal substituted phosphomolybdic acid

• Hybrid composites TM-HPA@UiO-66 (TM = Fe, Co, Ni, or Cu) and HPA@UiO-66 were solvothermal synthesized. • Heteropoly acid compounds are uniformly dispersed in the cage of metal organic framework. • Co-HPA@UiO-66 exhibits high catalytic activity, selectivity and stability for styrene epoxidation. • Aerobic epoxidation of styrene over Co-HPA@UiO-66 involves an acylperoxy radical route. • The UiO-66 framework provides an ideal environment for stabilizing the heteropoly acid compounds. Catalytic epoxidation of styrene with molecular oxygen is regarded as an eco-friendly alternative to producing industrially important chemical of styrene oxide (STO). Recent efforts have been focused on developing highly active and stable heterogeneous catalysts with high STO selectivity for the aerobic epoxidation of styrene. Herein, a series of transition metal monosubstituted heteropolyacid compounds (TM-HPAs), such as Fe, Co, Ni or Cu-monosubstituted HPA, were encapsulated in UiO-66 frameworks (denoted as TM-HPA@UiO-66) by direct solvothermal method, and their catalytic properties were investigated for the aerobic epoxidation of styrene with aldehydes as co-reductants. Among them, Co-HPA@UiO-66 showed relatively high catalytic activity, stability and epoxidation selectivity at very mild conditions (313 K, ambient pressure), that can achieve 82 % selectivity to STO under a styrene conversion of 96 % with air as oxidant and pivalaldehyde (PIA) as co-reductant. In addition, the hybrid composite catalyst can also efficiently catalyze the aerobic epoxidation of a variety of styrene derivatives. The monosubstituted Co atoms in Co-HPA@UiO-66 are the main active sites for the aerobic epoxidation of styrene with O 2 /PIA, which can efficiently converting styrene to the corresponding epoxide through the activation of the in-situ generated acylperoxy radical intermediate.

Synthesis, Crystal Structures and Catalytic Property of Oxidovanadium(V) Complexes with N’-(4-Oxopentan-2-ylidene)nicotinohydrazide and 4-Bromo-N’-(4-oxopentan

A pair of structurally similar oxidovanadium(V) complexes with the general formula [VOLL’], with the hydrazone compounds N' -(4-oxopentan-2-ylidene)nicotinohydrazide (H 2 L 1 ) and 4-bromo- N' -(4-oxopentan-2-ylidene)benzohydrazide (H 2 L 2 ), and the acetohydroxamic acid (HL’) as ligands, have been synthesized and structurally characterized by physico-chemical methods and single crystal X-ray determination. Single crystal X-ray analysis indicates that the V atoms in the complexes are in octahedral coordination, with the ONO donor atoms of the hydrazone ligands, and the OO donor atoms of the acetohydroxamate ligands, as well as an oxido O atom. The complexes showed good property for the catalytic epoxidation of styrene.

One-pot synthesis of silanol-free nanosized MFIzeolite.

The synthesis of nanostructured zeolites enables modification of catalytically relevant properties such as effective surface area and diffusion path length. Nanostructured zeolites may be synthesized either in alkaline media, and so contain significant numbers of hydrophilic silanol groups, or in expensive and harmful fluoride-containing media. Here, we report and characterize, using a combination of experimental and theoretical techniques, the one-pot synthesis of silanol-free nanosized MFI-type zeolites by introducing atomically dispersed tungsten; this prevents silanol group occurrence by forming flexible W-O-Si bridges. These W-O-Si bonds are more stable than Si-O-Si in the all-silica MFI zeolite. Tungsten incorporation in nanosized MFI crystals also modifies other properties such as structural features, hydrophobicity and Lewis acidity. The effect of these is illustrated on the catalytic epoxidation of styrene and separation of CO2 and NO2. Silanol-free nanosized W-MFI zeolites open new perspectives for catalytic and separation applications.

Synthesis of CoFe Prussian blue analogue/carbon nanotube composite material and its application in the catalytic epoxidation of styrene

Synthesis and characterization of CoFePBA alone and CoFePBA/CNTs and their catalytic properties and kinetic studies of styrene epoxidation are presented.

Comparison of different prepared Mn-MCM-41 catalysts in the catalytic epoxidation of alkenes with 30% H2O2

Manganese containing mesoporous materials Mn-MCM-41 were prepared by template-ion exchange (TIE), in situ reduction (ISR), direct hydrothermal (DHT) and wetness impregnation (WI) methods. The samples were characterized by XRD, N2 adsorption–desorption, HR-TEM, TG, UV–Vis, H2-TPR and ESR techniques, which illustrated that the definite structure of the MCM-41 was retained after introducing Mn into MCM-41 by different method. The catalytic activity and selectivity of the Mn-MCM-41 in the epoxidation of styrene with 30% H2O2 as an oxidant agent were explored. The TIE catalysts showed the highest activity but Mn2+ was leached during the reaction. The ISR catalysts exhibited high activity for epoxidation of styrene. Furthermore, recycling studies proved the ISR catalysts as heterogeneous catalysts, which did not lose the catalytic activity after four recycles appreciably. However, the DHT and WI catalysts showed poor performance in the catalytic epoxidation of styrene. Various parameters such as different reaction molar ratio of H2O2/styrene, catalyst amount, and kinds of solvents were studied to optimize the reaction conditions.

Catalytic Performance of Cobalt-Schiff Base-Chitosan/attapulgite for Epoxidation of Styrene

With the Schiff base of L-aspartic acid and salicylaldehyde as the ligands,the composite resin of chitosan/attapulgite(CS/ATP) produced by NaOH curing method as the carrier,the Schiff base metal complexes and the load-type Schiff base metal complexes of Co,Mn,Cu,Fe,Ni were synthesized.Their structural characterizations were determined by FT-IR.The catalytic performance of each catalyst for epoxidation of styrene was studied.Experiments show that the catalytic performance of Co-Schiff base is better in small molecule ligand Schiff base metal complexes.Therefore,Co-Schiff base was loaded in CS/ATP composite resin and the effects of the amount of Co-Schiff base-CS/ATP catalyst,reaction temperature and reaction time on the catalytic epoxidation of styrene were investigated.Finally the results show that the best reaction conditions are as follows:the temperature is 80 ℃ and the reaction time is 8 h,which results in a conversion rate of 93.1% for epoxidation of styrene.

Four organic–inorganic compounds based on polyoxometalates: crystal structures and catalytic epoxidation of styrene

Four compounds based on polyoxometalates, [Cu(4-bpo)(H2O)][Cu2(μ2-Cl)(4-bpo)2(H2O)][SiW12O40][N(CH3)4]2·H2O (1), [Cu(4-bpo)]4[P2W18O62][N(CH3)4]2·6H2O (2), [Cu2(μ2-OH)(4-bpo)2(Hina)(H2O)2]2[P2W18O62]·4H2O (3), and [Cu2(Hina)4(H2O)2][H2P2W18O62](Hina)·11H2O (4) (4-bpo=2,5-bis(4-pyridyl)-1,3,4-oxadiazole, ina=isonicotinic acid), have been hydrothermally synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. The 3-D framework of 1 is composed by Keggin-type polyoxoanions {SiW12} and two types of infinite chains, {Cu(4-bpo)(H2O)}n and {Cu2(μ2-Cl)(4-bpo)2(H2O)}n, through hydrogen bonds. Compound 2 has a 3-D rigid framework which is fabricated by Wells–Dawson type polyoxoanions {P2W18} and Cu-(4-bpo) chains through covalent bonds. Compound 3 contains an infinite {Cu2(μ2-OH)(4-bpo)2(Hina)(H2O)2}n double-chain and {P2W18} polyoxoanions immobilized in the voids between the chains. Compound 4 exhibits a 3-D supramolecular network directed by hydrogen bonds between {P2W18} polyoxoanions and the double paddle-wheel {Cu2(Hina)4(H2O)2}. Compounds 1–4 were tested as heterogeneous catalysts for the epoxidation of styrene using tert-butyl hydroperoxide (TBHP) as oxidant. The compounds show catalytic activity with 2 giving the highest yield of styrene oxide.

N‐Tetradentate SPANamine Derivatives and Their MnII‐Complexes as Catalysts for Epoxidation of Alkenes

AbstractFive new tetradentate N‐donor ligands with the spirobi(chroman) skeleton (either chiral or racemic) have been synthesized and fully characterized by NMR, ESI‐MS, and optical polarimetry. These ligands have been coordinated to a series of manganese salts, affording a family of new chiral and racemic MnII complexes, which have also been characterized through analytical and spectroscopic techniques. The crystallographic structures of five of them have been obtained by X‐ray diffraction; all show a distorted octahedral geometry with the ligand adopting a cis‐α conformation over the Mn ion. All the complexes have been tested in the catalytic epoxidation of styrene, showing that both conversion and selectivity values increase in the presence of additives in the catalytic media. Experimental results and computational calculations explain the stereospecificity for the cis epoxide in the epoxidation of cis‐β‐methylstyrene mediated by one of the complexes synthesized.

Catalytic epoxidation of styrene and methyl oleate over peroxophosphotungstate entrapped in mesoporous SBA-15

A new route for the heterogenization of peroxophosphotungstate species was developed for the epoxidation of olefins such as styrene and methyl oleate with hydrogen peroxide. The polyoxometalate based catalyst was entrapped inside the pores of a mesoporous SBA-15 support thanks to the grafting of octyl groups at the pores entrance allowing their convenient recycling.

Synthesis and catalytic performance of mono-Schiff base manganese(III) complexes with aza-crown or morpholino pendants

Mono-Schiff base Mn(III) complexes of general formula MnL2Cl, with pendant aza-crown or morpholino substituents, have been synthesized and investigated as catalysts for the epoxidation of styrene at ambient temperature and pressure. The highest conversion yield of styrene and selectivity for epoxide were 40 and 96%, respectively. These complexes have been also studied as catalysts for the aerobic oxidation of p-xylene to p-toluic acid. The effects of the crown ether group on the catalytic properties of the complexes are discussed. The oxidation of p-xylene to p-toluic acid with air at 120 °C under normal pressure proceeded efficiently in the presence of the aza-crown ether substituted complexes. Significant selectivity for p-toluic acid (up to ~87%) and conversion of p-xylene (up to ~30%) were obtained. Six mono-Schiff base Mn(III) complexes, MnL 2 1 Cl–MnL 2 6 Cl, with pendant aza-crown or morpholino substituents have been synthesized and employed as models of mimic mono-oxygenase to catalyze epoxidation of styrene at ambient temperature and pressures. Meanwhile, the corresponding Mn(III) complexes have been also studied as catalysts in aerobic oxidation of p-xylene to p-toluic acid. The effects of crown ether on the catalytic epoxidation of styrene and oxidation of p-xylene are discussed.

Heterotrinuclear manganese(II) and vanadium(IV) Schiff base complexes as epoxidation catalysts

The catalytic epoxidation of styrene using urea-hydrogen peroxide and heterotrinuclear Cu(II) complexes with general formula (ML n )2Cu(acac)2, where n = 1–3 and M = VO2+ or Mn2+ is reported. Schiff base complexes ML n involving a 3,4-diaminopyridine bridge with free coordination site were used as the ligand, where (Ln)2− is [(5-x-Sal)2Py]2 and x = H, Br or NO2. The complexes were characterized by physico-chemical and spectroscopic methods. The electrochemical properties of M were modified upon trinuclear complex formation. The trinuclear complexes show high catalytic activity, with up to 86% conversion and 93% selectivity, while no catalytic properties were observed for the monomeric complexes. The catalyst could be reused with some loss of activity.

Monometallic and heterobimetallic complexes derived from salen-type ligands

Abstract Mononuclear and heterodinuclear complexes of the salen-type ligand H2LH2 [H2LH2 = 2,2′-[1,2-dihydroxybenzene-4,5-diylbis(nitrilomethylidine)]bis(3,5-di-tert-butylphenol)] were prepared, whereof [{Mn(CH3OH)2}LH2]Cl, [ML( ZrCp 2 ∗ )] (M = Ni, Cu, CrCl(py); py = pyridine, Cp∗ = pentamethylcyclopentadienyl) were characterized by X-ray analysis. Additionally, cyclic voltammetric investigations were performed to ascertain the influence of the second transition metal complex fragment [ ZrCp 2 ∗ ]2+ on the metallo salen ligand. Moreover, the complexes were tested in the catalytic epoxidation of styrene. Although the complexes are quite sensitive towards oxidants, monometallic complex [{Mn(CH3OH)2}LH2]Cl exhibited a conversion of 70.6% with styrene oxide selectivity of 88% over 1 h at room temperature.

Magnetically recyclable Ag-ferrite catalysts: general synthesis and support effects in the epoxidation of styrene

A series of new magnetically recyclable catalysts (MRCs), Ag-M(1-x)Fe(2+x)O(4) (M = Co, Ni, Mn, Zn) nanocomposites, have been synthesized via a generalized one-pot route, and these materials prove to be efficient MRCs in the catalytic epoxidation of styrene. Characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared (IR) and X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and magnetic measurement reveal that the nanocomposites are assembled from well crystallized Ag and corresponding ferrite primary particles with the assistance of polyvinylpyrrolidone (PVP). The nanocomposite samples are comparable in Brunauer-Emmett-Teller (BET) specific surface areas and are superparamagnetic at room temperature. The as-prepared MRCs exhibit high activities in the epoxidation of styrene in toluene with tert-butylhydroperoxide (TBHP) as the oxidant and very high yields of styrene oxide can be achieved within 5 h of reaction. All the MRCs can be easily recovered by using a magnet and no decrease in the yield of styrene oxide has been observed after several consecutive rounds of reaction. It has been demonstrated that the ferrite supports affect the structure of Ag and the efficiency in oxygen supply and thus the catalytic performance.

Synthesis and characterization of a new kind of immobilized Mn(salen) and catalytic epoxidation of styrene on the catalyst

AbstractA linear polystyrene‐isopropenyl phosphonic acid (PS‐IPPA) copolymer was newly synthesized by free radical reaction in solution with isopropenyl phosphonic acid (IPPA) and styrene. Zirconium poly(styrene‐isopropenyl phosphonate)‐phosphate acid (ZPS‐IPPA) was also synthesized. The benzene rings of ZPS‐IPPA were hydroxylated and then further reacted with Mn(salen)Cl. Thus the heterogeneous catalyst, Mn(salen) axially immobilized onto ZPS‐IPPA was synthesized. These substances were characterized by IR spectra, X‐ray diffraction (XRD), SEM, TEM, NMR, thermogravimetric analysis, and AAS. The catalyst showed good activity to epoxidation of styrene, which is close to that of the corresponding homogeneous catalyst. Copyright © 2008 John Wiley & Sons, Ltd.

Host (nanopores of zeolite-Y)/guest (Co(II)-azamacrocyclic complexes) nanocomposite materials: synthesis, characterization and catalytic epoxidation of styrene with molecular oxygen

A series of Co(II) azamacrocyclic complexes, 12aneN4, 14aneN4, Bzo212aneN4 and Bzo214aneN4, have been encapsulated in the nanocavity of zeolite-Y by a one pot template condensation reaction. Co(II) complexes with azamacrocyclic ligands were entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of [bis(diamine)cobalt(II)], [Co(N–N)2]-NaY, in the supercages of the zeolite, and (ii) in situ condensation of the cobalt(II) precursor complex with diethyloxalate. The new host/guest nanocomposite materials (HGNM) have been characterized by FTIR, DRS and UV-Vis spectroscopic techniques, XRD and elemental analysis, as well as nitrogen adsorption. These complexes (neat and HGNM) were used for epoxidation of styrene with O2 as oxidant in different solvents. Electronic spectra of the reaction mixture indicated oxidation proceeds through a free radical mechanism.

Chiral Salen Mn(III) complex axial coordination immobilized on diamine modified ZSPP and their catalytic epoxidation of styrene

Abstract Chiral Salen Mn(III) complex axial coordination immobilized on diamine modified zirconium oligo-styrenyl phosphonate hydrogen phosphate (ZSPP) were prepared by a covalent grafting method. All the supported heterogeneous chiral Salen Mn(III) complexes prepared were characterized by FT-IR, diffusion reflection UV–vis, AAS, N 2 volumetric adsorption, SEM, TEM and TG. These supported chiral catalysts showed a little lower chiral induction (ee, 72%) contrast of its homogeneous counterpart 1 (ee, 86%) for asymmetric epoxidation of styrene in presence of NMO as axial ligands with m -CPBA as an oxidant. The catalysts were easily recovered by filtration and could be reused at least five times with little loss of activity and enantioselectivity.

Direct immobilisation versus covalent attachment of a Mn(III) salen complex onto an Al-pillared clay and influence in the catalytic epoxidation of styrene

A Mn(III) salen complex was immobilised onto an aluminium-pillared clay (Al-WYO) by three different methodologies: method A (catalyst A2), direct immobilisation of the complex into the Al-WYO; method B (catalyst A4), covalent anchoring through cyanuric chloride (CC); and method C (catalyst A7), covalent attachment onto a 3-aminopropyltriethoxysilane (APTES) modified Al-WYO mediated by CC. All the materials were characterised by XPS and FTIR; the Mn content of the materials with the immobilised complex was determined by AAS. FTIR and XPS spectra confirmed the organo-functionalisation of Al-WYO and complex immobilisation in the parent and organo-modified Al-PILCs. Direct immobilisation of the complex into the Al-WYO (method A) leads to the highest immobilisation efficiency ( η = 37.5%) compared with the anchoring procedures using the two spacers, methods B and C, which gave η = 7.4% and 8.7%. Nevertheless, the surface Mn contents are always higher than those obtained by bulk analysis, suggesting that in all materials the complexes are located within the most external pores. The Mn(III) salen-based pillared clays were tested in catalytic epoxidation reaction of styrene using iodosylbenzene as the oxygen source and were reused for several cycles. The catalyst A2 was the best heterogeneous catalyst among the catalysts prepared since it showed similar substrate conversion and styrene epoxide selectivity to the homogeneous counterpart; the heterogeneous catalysts A4 and A7 showed considerably lower values for these parameters. The styrene epoxide yields decrease in the order, A2 ≫ A4 > A7, which might be associated with some pernicious catalytic activity of the organo-modified supports (A3 and A6). Moreover, A2 could be reused for four times with a slight decrease in its catalytic activity and with almost no leaching of the active phase.

Synthesis, characterization and catalytic epoxidation of styrene using molecular oxygen over “neat” and host–guest nanocomposite materials

The complexes of Fe(II) were synthesized with the azamacrocyclic ligands; [12]aneN 4: 1,4,7,10-tetraazacyclododecane-2,3,8,9-tetraone; [14]aneN 4: 1,4,8,11-tetraazacyclotetradecane-2,3,9,10-tetraone; Bzo 2[12]aneN 4: dibenzo-1,4,7,10-tetraazacyclododecane-2,3,8,9-tetraone and Bzo 2[14]aneN 4: dibenzo-1,4,8,11-tetraazacyclotetradecane-2,3,9,10-tetraone. Iron(II) complexes with azamacrocyclic ligand were entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of bis(diamine)iron(II); in the supercages of the zeolite, and (ii) in situ condensation of the iron(II) precursor complex with diethyloxalate. The new nanocomposite materials were characterized by several techniques: chemical analysis, spectroscopic methods (DRS, BET, FTIR and UV/vis). Analysis of the data indicated that the Fe(II) complexes were encapsulated in the nanodimensional pores of zeolite-Y and exhibited different from those of the free complexes, which can arise from distortions caused by steric effects due to the presence of sodium cations, or from interactions with the zeolite matrix. The encapsulated nanomaterials are active catalyst for the epoxidation of styrene using molecular oxygen as an oxidant. By comparing the performance of the heterogeneous system with the free complex in the oxidation of styrene using O 2, protection effect of the matrix over the active center was evidenced by a higher conversion and yield of products.