Enantioselective epoxidation of β-methylstyrene catalyzed by immobilized Mn(salen) catalysts in different mesoporous silica supports

The Encapsulation of Illite Powders with Al2(SO4)3·18H2O and Hydrophilic Copolymers: Accelerating and Toughening Cement Hydration Through the Proliferation of 54CaO·MgO·Al2O3·16SiO2 Clinker

Two hydrophilic copolymers containing functional groups such as carboxyl, amido, and sulfonic acid are synthesized using ammonium persulfate-catalyzed free radical polymerization in water. Aluminum sulfate is then introduced, resulting in two polymer complexes that exhibit reduced cement setting times (initial, 1.16-2.44 min; final, 2.02-3.14 min) and improved compressive (24 h, 5.81-7.25 MPa) and flexural (24 h, 2.80-2.99 MPa) strengths compared to pure aluminum sulfate-facilitated cementing (initial, 19.11 min; final, 37.05 min; compressive, 24 h, 5.51 MPa; flexural, 24 h, 2.56 MPa). Following this, ball-milled illite powder is added, and the resulting admixtures further display slightly prolonged setting times (initial, 2.35-2.99 vs. 1.16-2.44 min; final, 3.98-4.35 vs. 2.02-3.14 min), along with comparable compressive strengths (5.85-7.11 vs. 5.81-7.25 MPa) and enhanced flexural strengths (3.92-5.83 vs. 2.80-2.99 MPa). Notably, a unique adhesive pozzolanic clinker, Ca54MgAl2Si16O90 (54CaO·MgO·Al2O3·16SiO2), emerges in the presence of illite-based admixtures, contributing to the mechanical strength development of the hydrated mortars. Although illite itself is hydrophobic, the coating of ball-milled illite powder with aluminum sulfate and copolymers facilitates its dispersion into the gaps and pores of the cement matrix during setting, thereby increasing the flexural strength. This work presents an interesting approach to utilizing illite materials in cement applications, which is significant for reducing CO2 emissions during cement production and use.

The Efficient and Environmentally Friendly Chlorination of Arene, Alcohol, Halobenzene, and Peroxide Catalyzed by Fe-Ba Binary Oxides Using Hydrochloric Acid as Chlorine Source and Aqueous H2O2 as Oxidant

A series of Fe-Ba mixed oxides, including a pure Fe-containing sample as a reference, have been synthesized via a sol-gel process using Fe3+ or Fe2+ salts and BaSO4 as raw materials, with Pluronic P123 serving as a template. These oxides have been thoroughly characterized and subsequently utilized as catalysts for the chlorination of various organic molecules. Commercial hydrochloric acid, known for its relative safety, and environmentally friendly aqueous hydrogen peroxide were employed as the chlorine source and oxidant, respectively. The pure Fe-containing catalyst displays excellent thermal stability between 600 and 800 °C and exhibited moderate to high conversions in the chlorination of toluene, benzene, and tert-butyl hydroperoxide, with remarkable ortho-selectivity in chlorination of toluene. The combination of Fe3+ salt with BaSO4 in the sol-gel process results in a Fe-Ba mixed oxide catalyst composed of BaO2, BaFe4O7, and Fe2O3, significantly enhancing the chlorination activity compared to that displayed by the pure Fe catalyst. Notably, the chlorination of tert-butyl hydroperoxide (TBHP) does not require additional oxidants such as H2O2, and involves both electrophilic substitution and nucleophilic addition. Notably, the chlorination of bromobenzene yields chlorobenzene as the sole product, a transformation that has not been previously reported. Overall, this catalytic chlorination system holds promise for advancing the chlorination industry and enhancing pharmaceutical production.

Al(SO4)(OH)·5H2O Stemming from Complexation of Aluminum Sulfate with Water-Soluble Ternary Copolymer and further Stabilized by Silica Gel as Effective Admixtures for Enhanced Mortar Cementing

A water-soluble ternary copolymer bearing carboxyl, sulfonic, and amide functional groups was synthesized using ammonium persulfate-catalyzed free radical polymerization in water, resulting in high monomer conversion. This copolymer was then complexed with aluminum sulfate, forming an admixture containing Al(SO4)(OH)·5H2O, which was subsequently combined with silica gel. Characterization revealed that the synthesized copolymer formed a large, thin membrane that covered both the aluminum compounds and the silica gel blocks. The introduction of this complex admixture, combining the copolymer and aluminum sulfate, not only reduced the setting times of the cement paste but also enhanced the mechanical strengths of the mortar compared to using aluminum sulfate alone. The complex admixture led to the formation of katoite, metajennite, and C3A (tricalcium aluminate) in the mortar, demonstrating significant linking effects, whereas pure aluminum sulfate could not completely transform C3S within 24 h. Further addition of silica gel to the complex admixture further shortened the setting times of the paste, slightly reduced compressive strength, but improved flexural strength compared to the initial complex admixture. The silicon components appeared to fill the micropores and mesopores of the mortar, accelerating cement setting and enhancing flexural strength, while slightly decreasing compressive strength. This study contributed to the development of new cementing accelerators with improved hardening properties.

The Coordination of Aluminum Sulfate with a Water-Soluble Block Copolymer Containing Carboxyl, Amide, Sulfonic and Anhydride Groups Providing Both Accelerating and Hardening Effects in Cement Setting

Two water-soluble block copolymers composed of acrylic acid (AA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and optionally maleic anhydride (MAH) were synthesized through ammonium persulfate-catalyzed free radical polymerization in water. The introduction of aluminum sulfate (AS) into the resulting mixtures significantly reduced the setting times of the paste and enhanced the mechanical strength of the mortar compared to both the additive-free control and experiments facilitated solely by pure AS. This improvement was primarily attributed to the inhibition of rapid Al3+ hydrolysis, which was achieved through coordination of the synthesized block copolymers, along with the formation of newly identified hydrolytic intermediates. Notably, the ternary copolymer (AA-AMPS-MAH) exhibited superior performance compared to that of the binary copolymer (AA-AMPS). In the early stages of cement setting, clusters of ettringite (AFt) were found to be immobilized over newly detected linkage phases, including unusual calcium silicate hydrate and epistilbite. In contrast to the well-documented role of polymers in retarding cement hydration, this study presents a novel approach by providing both accelerating and hardening agents for cement setting, which has significant implications for the future design of cement additives.

Aqueous Room Temperature Mono-Dehydration of Sugar Alcohols Using Functionalized Yttrium Oxide Nanocatalysts

The aqueous room temperature mono-dehydration of sugar alcohols (D-sorbitol and D-mannitol) was conducted using functionalized yttrium oxide nanocatalysts prepared via sol-gel methods. Materials exhibited high selectivity to mono-dehydration products. Solvent and catalyst effects were also investigated and discussed. The introduction of titanium into the yttrium oxide framework would decrease both substrate conversion and mono-dehydration efficiency. In addition, studies of the catalytic mechanism indicate high mono-dehydration efficiency may come from the stability of the formed intermediate during catalysis. This work provides a highly efficient and benign system for catalytic mono-dehydration of sugar alcohols.

Novel Schiff base Mn(iii) and Co(ii) complexes supported on Co nanoparticles: efficient and recyclable magnetic nanocatalysts for alcohol oxidation

In this study, efficient and highly selective heterogeneous catalysts were developed by immobilization of manganese and cobalt Schiff base complexes on Co magnetite nanoparticles (MNPs).

Novel Mesoporous Silica Materials with Hierarchically Ordered Nanochannel: Synthesis with the Assistance of Straight-Chain Alkanes and Application

The straight-chain alkane-assisted synthesis of hierarchical mesoporous silica materials (MSM) results in variable mesostructures and morphologies due to remarkably different self-assembly routes of template agent from those without the assistance of straight-chain alkanes. The textural properties, particularly pore size, channel structure, morphology, and hierarchical structure of those MSM make them demonstrate peculiar effects in the immobilization of homogeneous catalysts.

Ionic liquid-functionalized graphene oxide as an efficient support for the chiral salen Mn(iii) complex in asymmetric epoxidation of unfunctionalized olefins

Chiral salen Mn(iii) complex covalently grafted on IL-functionalized GO sheet, was a highly efficient, universal and reusable catalyst for asymmetric epoxidation of unfunctionalized olefins using aqueous NaOCl as an oxidant.

A magnetically recyclable Fe3O4@SiO2/Mn(iii) chiral salen complex as a highly selective and versatile heterogeneous nanocatalyst for the oxidation of olefins and sulfides

An efficient system for the selective oxidation of alkenes using TBHP and sulfides using aqueous 30% H₂O₂ catalyzed by a new magnetically recoverable Mn(iii) salen complex with high selectivity and excellent yields was developed.

Chiral Schiff base Ligated Dioxomolybdenum (VI) Complexes and their Asymmetric Catalytic Properties in the Epoxidation of Styrene

Two series of Schiff base dioxomolybdenum (VI) complexes of the general formula [MoO2(L)(MeOH)] (L = D-glucosamine-derived Schiff base) have been synthesised, characterised and their asymmetric catalytic activities evaluated through the epoxidation of styrene. The molybdenum complexes with acetyl-protected D-glucosamine Schiff base ligands exhibited higher enanatioselectivity than those with unprotected sugar ligands. Protecting D-glucosamine by acetyl groups is an effective way to improve asymmetric catalytic epoxidation activities.

Epoxidation of alkenes catalyzed by phenyl group-modified, periodic mesoporous organosilica-entrapped, dimeric manganese-salen complexes

A series of reusable, recoverable, diamine-bridged dimeric manganese-salen complexes were prepared by the encapsulation of homogeneous dimeric Mn(salen) complexes into nanocages of a 3D periodic mesoporous organosilica (PMO) support followed by silylation of the support with organosilane. The composition, structure, morphology, and textural properties of the prepared PMO-entrapped dimeric Mn(salen) complexes were characterized, and their catalytic performances were tested in the epoxidation of alkenes (styrene, cyclohexene, and 1-phenylcyclohexene), with NaClO as an oxygen source and 4-phenylpyridine-N-oxide as an axial ligand. Furthermore, the influences of the textural and morphological properties of the entrapped dimeric Mn(salen) complexes and the key reaction parameters on the catalytic activity and selectivity are discussed. Finally, the reusability of the supported dimeric Mn(salen) complexes was evaluated over three catalytic runs.

Mesoporous silica SBA-15 sheet with perpendicular nanochannels

Free-standing thin sheet form of mesoporous silica materials with perpendicular orientation is a much desired materials for its possible applications in catalysis, mask, and separation. A three component amphiphile system of sodium dodecyl sulfate/hexadecyltrimethylammonium bromide/pluronic-123(C(16)TMAB/SDS/P123) was employed to template the condensation of sodium silicates for the formation of SBA(⊥), a thin sheet of SBA-15 with perpendicular nanochannels. SBA(⊥) can be synthesized at SDS/C(16)TMAB=1.5 and T≥40°C and shows pH-dependent morphology. It has uniform pore size ∼9 nm, homogeneous sheet thickness in the range of 60-300 nm and dimension of several microns. We studied in details the structure and morphology of the SBA(⊥) with variation of three experimental parameters: the SDS/C(16)TMAB ratio, the temperature, and the pH condition in the synthetic gel. It is proposed that the mixed surfactants of SDS and C(16)TMAB form catanionic vesicle in which the P123 and silicates are condensed. The balanced interaction of P123/silicate with the narrow confinement under surfactant bi-layers of C(16)TMAB/SDS promoted the formation of perpendicular nanochannels. Low temperature and pH conditions favor stronger segregation of the PPO and PEO-oligosilicate segments in the SBA(⊥) structure which gives the basis of thickness control of the sheet. The control of structure and morphology are discussed with modern theory of microphase separation in block copolymers under confinement.