High Epoxide Selectivity Research Articles

Molecular Structure Effect on the Epoxidation of 1-Butene and Isobutene on the Titanium Silicate Catalyst under Transient Conditions in a Trickle Bed Reactor.

Epoxidation of two butane isomers (1-butene and isobutene) on the commercial titanium silicate (TS-1) catalyst was studied in a laboratory-scale trickle bed reactor. The transient step response technique was used as the main tool in the investigation. The transient responses revealed different dynamics of product formation in continuous operation. The study of isomers showed the impact of the molecular structure on the transient and stationary states of the system. The four-carbon chain present in 1-butene displayed a dynamic behavior with a prominent maximum of the conversion as a function of time-on-stream. On the contrary, the behavior of isobutene was displayed to be closer to ethene and propene under similar conditions reaching a steady state after ca. 2 h. The structure of the epoxide was an important factor in order to achieve a high epoxide selectivity. In isobutene epoxidation, the primary product 1,2-epoxy-2-methylpropane was highly reactive, giving a spectrum of parallelly formed byproducts. Therefore, the selectivity of the epoxide from isobutene was limited to ca. 70%. In the epoxidation of 1-butene, 1,2-epoxybutane was displayed to be a highly stable product with a selectivity close to 99%. Based on the transient and stationary data, a reaction mechanism was proposed for the epoxidation and ring-opening reactions present in the system.

Boosting the catalysis of cesium phosphomolybdate encapsulated in hierarchical porous UiO-66 by microenvironment modulation for epoxidation of alkenes.

The chemical microenvironment of polyoxometalates (POMs) encapsulated in metal-organic frameworks (MOFs) presents a significant influence on their catalytic performance, which can be easily regulated by the linker functional group alteration or metal substitution in MOFs. Herein, a series of cesium phosphomolybdate (CsPM) encapsulated in hierarchical porous UiO-66-X composites (CsPM@HP-UiO-66-X, X = H, 2CH3, or 2OH, where X represents the alterable group grafted onto the linker benzene ring) were successfully synthesized through a one pot modulated solvothermal method. The catalytic performances of the obtained materials were explored in alkene epoxidation reaction with tert-butyl hydroperoxide (t-BuOOH). CsPM@HP-UiO-66-2CH3 showed relatively high catalytic activity, stability, and epoxidation selectivity in cyclooctene epoxidation among the CsPM@HP-UiO-66-X composites. Moreover, CsPM@HP-UiO-66-2CH3 was effective in the epoxidation of numerous alkenes, especially cyclic alkenes. The superior catalytic activity of CsPM@HP-UiO-66-2CH3 is mainly attributed to the modulation of the microenvironment surrounding CsPM active sites by introducing a hydrophobic methyl group. Meanwhile, the size-matched effect, the introduction of cesium cations, and the strong metal-support interactions (SMSIs) between CsPM and HP-UiO-66-2CH3 play a crucial role in the stability of CsPM@HP-UiO-66-2CH3.

Soybean Oil Epoxidation Catalyzed by a Functionalized Metal–Organic Framework with Active Dioxo-Molybdenum (VI) Centers

In this work, a functionalized gallium metal–organic framework with active dioxo-molybdenum (VI) centers was evaluated as a catalyst in the epoxidation of soybean oil using tert-butyl-hydroperoxide as an oxidizing agent. The influence of the reaction time, temperature, and concentration of the oxidizing agent was studied, and it was demonstrated that the highest epoxide selectivity was obtained at 110 °C after 4 h of reaction (29% conversion and 91% selectivity) using a soybean oil/oxidizing agent ratio of 1/2. The stability of the metal–organic framework was confirmed by infrared spectroscopy, X-ray powder diffraction, thermogravimetric analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy EDS. The stability tests demonstrated that the catalyst could be reused in the catalytic process for the recovery of vegetable oils.Graphical

Lipase catalyzed green epoxidation of oleic acid using ultrasound as a process intensification method

Epoxidized fatty acids are important green intermediates for chemical industry. This work was focused on the direct epoxidation of oleic acid (OA) using immobilized lipase Novozym® 435 as the catalyst and hydrogen peroxide (HP) as the epoxidation agent. The impacts of reactant molar ratio (HP:OA = 1…2), reaction temperature (30–60 °C), catalyst loading (7 wt-%) and stirring rate (500–1000 rpm) on the fatty acid conversion and epoxide selectivity were evaluated Acoustic irradiation and an advanced stirring system were implemented for reaction intensification and different ultrasound amplitudes (0–90%) were screened. Novozym® 435 revealed to be an efficient and durable catalyst for fatty acid epoxidation. The reaction was promoted by an excess of HP. The highest epoxide selectivity was about 80% at full conversion of oleic acid reached within 200 min. Ultrasound irradiation (90% amplitude) enhanced the initial reaction rate by a factor two compared to silent conditions and higher oleic acid conversions were reached compared to silent experiments. The catalyst preserved its activity and selectivity rather well, which was confirmed by catalyst recovery experiments conducted in the absence and presence acoustic irradiation. The main ring-opening agent is the fatty acid itself, which resulted in the formation of esters.

Catalytic performance of a wide range of rare-earth titanate pyrochlore (RE2Ti2O7, RE = Sm, Gd, Dy, and Yb) microstructures in the epoxidation of cyclooctene: An electro-structural investigation

A series of rare-earth titanate oxides RE2Ti2O7 (RE =Sm, Gd, Dy and Yb) were synthesized using a solid state method. The pyrochlore structures of these compounds were confirmed by the Rietveld method from X-ray diffraction data (XRD). XRD results showed that RE2Ti2O7 structures had cubic crystal system with the Fd3m space group. Morphology and mean particle sizes of the samples were obtained by the scanning electron microscope (SEM). Chemical characterizations of the samples were confirmed by energy dispersive x-ray spectroscopy (EDX). The specific surface areas were calculated using BET analyses. Fourier transform infrared spectra of the obtained compounds in (400–4000 cm−1) range were also studied. The obtained RE2Ti2O7 pyrochlore materials were used as catalysts for epoxidation of cyclooctene as a model alkene with tert-butyl hydroperoxide. Various parameters including catalyst type and amount, solvent type and amount, oxidant/substrate ratio, and time have been optimized and high catalytic activity and epoxide selectivity have been found. Gd2Ti2O7 showed the best activity and epoxide selectivity.

Direct hydrothermal synthesis of Mo-containing MFI zeolites using Mo-EDTA complex and their catalytic application in cyclohexene epoxidation

A series of Mo-containing MFI zeolites with different Mo loadings (Mo-MFI-n, n represent the initial Si/Mo molar ratio) was hydrothermally synthesized by using tetrapropylammonium hydroxide as the template and Mo-EDTA complex as the Mo source. Various characterization results demonstrated that the use of the Mo-EDTA complex is beneficial for the incorporation of more Mo species into the MFI-type zeolites. The special complexing capability of EDTA2– plays a critical role in adjusting the release rate of the Mo species to combine with the Si tetrahedron species during the zeolite growth process, thus leading to a uniform distribution of Mo in the MFI framework. In addition, a small portion of extra-framework Mo clusters may be distributed inside the channels or near the pore window of the zeolites. The catalytic properties of these Mo-containing MFI zeolites were evaluated for the epoxidation of cyclohexene with H2O2 as the oxidant. The composition-optimized catalyst, Mo-MFI-50, efficiently converted cyclohexene to the corresponding epoxide with a relatively high conversion (93%) and epoxide selectivity (82%) at 75 °C after 9 h of reaction. Moreover, the resultant Mo-containing MFI catalyst exhibited excellent structural stability and recoverability and was easily recycled by simple filtration without the need for calcination treatment.

Amino acid-assisted synthesis of TS-1 zeolites containing highly catalytically active TiO6 species

Tailoring the Ti coordination states in titanosilicate zeolites to simultaneously improve feedstock conversion and maximize the target product selectivity remains a challenge in the pursuit of high-performance catalysts for selective oxidation reactions. Herein, we provide a facile strategy to synthesize hierarchical anatase-free TS-1 (MFI-type) zeolites with tetrahedrally coordinated (TiO4) and octahedrally coordinated Ti species (TiO6). The TiO4 species provide high epoxide selectivity, while the TiO6 species afford improved alkene conversion. This strategy is achieved by synergistically using an L-lysine-assisted approach and a two-step crystallization; the two-step crystallization approach prevents the formation of anatase TiO2, while L-lysine stabilizes the TiO6 species and ensures efficient incorporation of TiO6 into the anatase-free TS-1 zeolites. Compared with their conventional counterparts, which only contain TiO4 species, the as-prepared TS-1 zeolites (Si/Ti = 36.9) result in a higher 1-hexene conversion (33%), higher TON value (153), and comparable epoxide selectivity (95%). This synthetic strategy provides avenues to tailor the amount and distribution of Ti species in titanosilicate zeolites to achieve high catalytic performances in various processes.

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.

Selective Oxidation of Citronellol over Titanosilicate Catalysts

Citronellol is one of the most widely used fragrances for bouquetting purposes and it is a starting material for synthesis of several other terpenoids. Nevertheless, few data have been reported on citronellol selective oxidation. Accordingly, we report our findings on the selective oxidation of citronellol with hydrogen peroxide using a set of titanosilicate catalysts with different morphologies and textural properties—conventional titanium silicalite 1 (TS-1), mesoporous TS-1, layered TS-1 and silica-titania pillared TS-1 and also studying the effect of the solvent used. Epoxidation of C6=C7 double bond was the main primary reaction in this system and trace signals of C5 allylic oxidation products were observed without formation of citronellal. Due to the presence of post-synthesis introduced additional Ti sites, the silica-titania pillared TS-1 (TS-1-PITi) provided the highest conversion among the tested catalysts; nevertheless, citronellol was oxidized over all the studied catalysts including conventional TS-1; therefore, showing that it penetrates even into MFI micropores (0.55 nm in diameter). When using acetonitrile as a solvent, the conversion was proportional to the titanium content of the catalyst. When studying the effect of the solvent, acetonitrile provided the highest epoxide selectivity (55%) while in methanol, 2-propanol and 1,4-dioxane, ring opening reactions caused epoxide decomposition.

Synthesis and Catalytic Application of Robust Grafted Tripodal (Phenoxy) Ti-POSS Complexes in Crosslinked Hyperbranched Poly(siloxysilane) Matrix

We have studied synthesis, activity, epoxide selectivity, H2O2 efficiency, and recyclability of new robust heterogeneous alkene epoxidation catalysts of grafted tripodal (phenoxy) Ti-polyhedral oligomeric silsesquioxane (Ti-POSS) complexes in hyperbranched poly(siloxysilane) matrix. Crosslinked hyperbranched (CHB) poly(siloxysilane)-grafted [Ti(OC6H4CN-p){(HSiMe2(CH2)3)-(i-C4H9)6Si7O12}] (5) and CHB-poly(siloxysilane)-grafted [Ti(OC6H5){(HSiMe2(CH2)3)(i-C4H9)6Si7O12}] (6) have demonstrated high activity, epoxide selectivity (≥99%) and H2O2 efficiency (≥98%) in cyclohexene and 1-octene epoxidation with aqueous H2O2 higher than titanosilicate catalysts such as TS-1 and Ti-β, due to high Lewis acidity of the Ti-center and to the use of CHB-poly(siloxysilane) matrix. The catalysts are readily recyclable with retained activity.

Homo and Hetero Trinuclear Metal Clusters of Co, Mn and Co/Mn Hybrid Materials as Catalysts for Epoxidation of Cyclohexene

Trinuclear metal clusters of Co, Mn, and Co/Mn hybrid of [Mn3(O)(CH3COO)6-(py)3ClO4], [Co3(O)(CH3COO)6-(py)3ClO4], [Co2Mn(O)(CH3COO)6-(py)3ClO4], and [CoMn2(O)(CH3COO)6-(py)3ClO4] were prepared and characterized by FT-IR and UV–Vis spectroscopic techniques. These homogeneous catalysts were investigated in the epoxidation of cyclohexene in the presence of H2O2/O2 under mechanical stirring conditions. The effect of the oxidant, reaction temperature, kind of promoter, and solvent system were investigated on conversion and epoxide selectivity. In these systems, NaBr was selected as a promoter of oxidation based on standard potential (X = Cl−, Br−) toward Co3+, and Mn3+. These homogeneous catalytic systems can be the perfect choice for epoxidation of cyclohexene with good conversion and high epoxide selectivity over short periods.

Non-noble metal single-atom catalysts with phosphotungstic acid (PTA) support: A theoretical study of ethylene epoxidation

Geometric and electronic structures of phosphotungstic acid (PTA) supported single transition metal atom (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt) catalysts have been systematically investigated by using the first-principles theoretical methods. Possible reaction mechanism for ethylene epoxidation was explored. The most possible anchoring site for the single transition metal atom is the fourfold hollow site on PTA. As the non-noble metal Fe1-PTA system possesses considerable adsorption energies towards both O2 and C2H4, the strong bonding interaction between Fe1 and PTA cluster was analyzed. It is found that the electron transfers from Fe atom to PTA cluster and strong covalent metal-support interactions (CMSI) between the Fe 3d orbitals and O 2p orbitals of PTA lay the foundation of high stability. The proposed catalytic reaction mechanism for ethylene epoxidation on Fe1- PTA single-atom catalyst (SAC) includes three steps: the O2 adsorbs on Fe1-PTA via electron transfer; the first ethylene attacks the adsorbed O2 molecule on Fe1-PTA followed by the formation of C2H4O; finally, the O atom remained on Fe1-PTA reacts with a second ethylene to form the product and accomplish the catalytic cycle. The Fe1-PTA has high selectivity and catalytic activity for ethylene epoxidation via an Eley–Rideal mechanism with low energy barriers. A potentially competitive pathway for the formation of acetaldehyde is not kinetically favorable. These results provide insights for the development of highly efficient heterogeneous SACs for ethylene epoxidation with non-noble metals.

A Stable Zn-Based Metal–Organic Framework as an Efficient Catalyst for Carbon Dioxide Cycloaddition and Alcoholysis at Mild Conditions

Developing highly efficient heterogeneous catalysts for cycloaddition of CO2 and epoxides to produce cyclic carbonates is promising but challenging. In this work, a novel three-dimensional metal organic framework (MOF) with cylinder pore systems and unsaturated Zn sites has been demonstrated as potent candidate in CO2 fixation at mild and solvent-free conditions. The Zn(atz)(bdc)0.5, where atz = aminotriazole and H2bdc = terephthalic, exhibits microporous nature that can regulate the catalytic interaction of active centers and substrates. The structure stability has been systematically investigated and proven to be sufficient for practical application. Furthermore, the cooperative effects of porosity, CO2 binding affinity, activation centers, and synergism with co-catalyst have been deeply investigated. Moreover, high propylene epoxide conversion (97%) and selectivity (> 99%) have been achieved at mild conditions (60 °C and 1 MPa) with excellent cycle stability. Owing to the well-defined pore system, an obvious substrates selectivity has been clearly observed. A possible catalytic mechanism has been proposed and verified by DFT calculations. Furthermore, the prepared Zn-MOF can also be used as an efficient heterogeneous catalyst for the reaction of epoxides with alcohols to produce β-alkoxy alcohol.

Structure and reactivity of single site Ti catalysts for propylene epoxidation

Propylene epoxidation using molecular oxygen and hydrogen mixture on Au-based catalysts has attracted attention because of high propylene oxide selectivity and the use of an inexpensive and environmental friendly oxidant. Single-site titanium on metal oxide supports plays an important role in achieving high reactivity and selectivity in propylene epoxidation. Here we used TiO2 atomic layer deposition (ALD) to synthesize single-site titanium imbedded in the SiO2 framework for propylene epoxidation. High temperature calcination was used as post-treatment to control the titania structure and TiO coordination number. Using UV–vis spectroscopy and X-ray absorption spectroscopy, we successfully established that under similar propylene conversion the selectivity to propylene oxide (PO) is strongly correlated to the TiO coordination number and bond length. Using a cluster model, density functional theory (DFT) calculations indicate that the partial charges of single TiSiO2 sites scale linearly as a function of the coordination number. Also, the predicted TiO bond lengths follow the same trend as found in the experiments, providing additional support for the observed experimental activity relationships.

Aerobic epoxidation of limonene using cobalt substituted mesoporous SBA-16 Part 1: Optimization via Response Surface Methodology (RSM)

Cobalt substituted mesoporous SBA-16 catalysts, made by post grafting technique using directly cobalt acetylacetonate as the precursor was prepared. High loading of cobalt finely dispersed on SBA-16 silica was obtained. The Co/SBA-16 catalysts exhibited high conversion and selectivity in epoxidation of limonene towards limonene epoxides with molecular oxygen as the most desirable oxidant and isobutyraldehyde as co-reagent under very mild conditions in the presence of the green solvent ethylacetate. A variety of characterization techniques such as nitrogen physisorption, XRD, DR-UV–vis, XPS, TEM indicates that the proposed impregnation procedure is a highly tunable and reproducible strategy to disperse transition metals in mesoporous silica materials. The unique pore structure of Co/SBA-16 catalysts could be beneficial for the epoxidation of bulky alkene molecules. The reaction conditions were systematically investigated using a statistical experimental design. Repeated catalytic tests showed no remarkable difference in the activity of fresh and recycled catalysts over three process cycles.

Microkinetic Modeling of Homogeneous and Gold Nanoparticle-Catalyzed Oxidation of Cyclooctene

Small gold nanoparticles (AuNPs) have recently shown potential to act as a catalyst for oxidation reactions mediated by free radicals, with their role postulated to be facilitating hydrogen abstraction by gold superoxo species and/or activation of hydroperoxides. Cyclooctene oxidation using molecular oxygen as the oxidant at 373 K showed high selectivity to the epoxide product, cyclooctene oxide, with either tert-butyl hydroperoxide as an initiator or in the presence of small AuNPs (5–8 atoms). While previous studies have investigated the mechanism leading to high epoxide selectivity using density functional theory, a full microkinetic model was developed in this work using automated network generation to determine the relative contributions of elementary reactions and the role of AuNPs. A cycle of radical addition of peroxy and alkoxy radicals with subsequent epoxidation reactions can justify the observed activity and selectivity to epoxide at multiple temperatures and initiator concentrations. The alcoh...

Effects of TiO2 in Low Temperature Propylene Epoxidation Using Gold Catalysts

Propylene epoxidation with molecular oxygen has been proposed as a green and alternative process to produce propylene oxide (PO). In order to develop catalysts with high selectivity, high conversion, and long stability for the direct propylene epoxidation with molecular oxygen, understanding of catalyst structure and reactivity relationships is needed. Here, we combined atomic layer deposition and deposition precipitation to synthesize series of well-defined Au-based catalysts to study the catalyst structure and reactivity relationships for propylene epoxidation at 373 K. We showed that by decorating TiO2 on gold surface the inverse TiO2/Au/SiO2 catalysts maintained ∼90% selectivity to PO regardless of the weight loading of the TiO2. The inverse TiO2/Au/SiO2 catalysts exhibited improved regeneration compared to Au/TiO2/SiO2. The inverse TiO2/Au/SiO2 catalysts can be regenerated in 10% oxygen at 373 K, while the Au/TiO2/SiO2 catalysts failed to regenerate at as high as 473 K. Combined characterizations of ...

Unique characteristics of MnOx-incorporated mesoporous silicate, Mn-FDU-5, prepared via evaporation induced self assembly

Mn containing 3D mesostructured FDU-5 (Ia3d) silicates with varying Si/Mn ratios were synthesized for the first time via evaporation induced self assembly (EISA) technique under acidic conditions at room temperature, employing Pl23 triblock copolymer as a structure directing agent. This method facilitates complete incorporation of higher amounts of Mn in the framework and extraframework locations of FDU-5 even under highly acidic synthesis conditions. The Mn-FDU-5 samples possessed surface areas of 300–500 m2/g, pore volumes of 0.42–0.55 cm3/g and narrow pore size distributions of 4.1–4.9 nm. Homogeneous dispersion of Mn species and aggregated Mn oxide clusters were evidenced from FIB-SEM micrographs. Complementary analytical techniques such as diffuse reflectance UV–Vis, FTIR, TPR and EPR analyses provide insights into the nature of the different types of Mn species (Mn2+, Mn3+ and Mn3O4 nanoparticles) that co-exist in FDU-5. The Mn-FDU-5 material is shown to be active for the epoxidation of trans-stilbene (TS, ~60 % conversion) to trans-stilbene epoxide (~64 % selectivity) with TBHP as oxidant. Although the activity of Mn-FDU-5 (~45 % TS conversion) is similar to those observed with MCM-41 and MCM-48 supports containing similar amounts of Mn (1 wt%), higher epoxide selectivity (~64 %) was observed with Mn-FDU-5. The mixed oxidation states of Mn (Mn2+, Mn3+) along with the extraframework Mn3O4 are found to be beneficial in catalyzing TS epoxidation.

Co(II), Fe(III) or VO(II) Schiff base metal complexes immobilized on graphene oxide for styrene epoxidation

Cobalt(II), iron(III) or oxovanadium(II) Schiff base metal complexes have been covalently grafted onto graphene oxide (GO) previously functionalized with 3‐aminopropyltriethoxysilane. Potential catalytic behaviors were tested in the epoxidation of styrene, using air as the oxidant. The catalysts were characterized using infrared (IR) and Raman spectroscopies, thermogravimetric analyses, inductively coupled plasma atomic emission spectrometry (ICP‐AES), X‐ray diffraction, nitrogen adsorption–desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). IR spectroscopy, thermogravimetric analyses and ICP‐AES confirmed the successful incorporation of the metal Schiff base complexes onto GO. X‐ray diffraction, nitrogen adsorption–desorption, Raman spectroscopy, SEM and TEM showed the intact structure of the GO. Co-GO and Fe-GO showed high styrene conversion (90.8 versus 86.7%) and epoxide selectivity (63.7 versus 51.4%). Nevertheless, VO-GO showed poorer catalytic performance compared with Co-GO and Fe-GO. The recycling results of these heterogeneous catalysts showed good recoverability without significant loss of activity and selectivity within four successive runs. Copyright © 2015 John Wiley & Sons, Ltd.

Synthesis and Catalytic Applications of Chemically Grafted SiH-Functionalized Tripodal Ti-POSS Complexes in Crosslinked Hyperbranched Poly(siloxysilane)

This study investigated the synthesis, activity, epoxide selectivity, H2O2 efficiency, and recyclability of new heterogeneous alkene epoxidation catalysts prepared by chemical grafting of new SiH-functionalized tripodal Ti–polyhedral oligomeric silsesquioxane (Ti-POSS) complexes in hyperbranched poly(siloxysilane) via hydrosilation. Crosslinked hyperbranched poly(siloxysilane)-grafted [{(p-HSiMe2(CH2)2C6H4)(c-C6H11)6Si7O12}Ti(NMe2)] (11) and crosslinked hyperbranched poly(siloxysilane)-grafted [{(HSiMe2(CH2)3)(i-C4H9)6Si7O12}- Ti(NMe2)] (12) displayed high activity, epoxide selectivity (≥98 %), and H2O2 efficiency (≥97 %) in cyclohexene and 1-octene epoxidation with aqueous H2O2. Moreover, these catalysts were highly recyclable with retained activity and durability and proved to be truly heterogeneous. Using chemical grafting for the synthesis of 11 and 12 enhanced their recyclability and durability with retained activity. The high H2O2 efficiency can be attributed to the uniformly non-polar environment provided about Ti in 11 and 12 by the polymer; this results in low water concentrations and higher [alkene] : [H2O2] ratios at the Ti active site than in the rest of the solution. These effects enhance the epoxide selectivity and minimize leaching of titanium.