Silane Oxidation Research Articles

Preparation of short carbon fiber reinforced photosensitive resin and composite material properties study

AbstractLight‐curing rapid prototyping (SLA) has become an emerging technology in the manufacturing industry because of its high precision, rapid prototyping, and the ability to mold complex parts. To enhance the mechanical properties and thermal stability of its raw material photosensitive resin (PR), carbon fiber (CF) was surface modified by chemical oxidation and grafting of amino silane (KH550) to obtain KH550‐modified carbon fiber (ACF). Then, ACF was composited with photosensitive resin to obtain modified carbon fiber/photosensitive resin (ACF/PR) composites. The viscosities of ACF/PR composites, including the viscosity, curing shrinkage, mechanical properties, and thermal stability of the ACF/PR composites, were characterized. The results showed that KH550 was successfully grafted onto CF. When the addition of ACF in the composites was 0.6%, the tensile strength, elongation at break, and impact strength of ACF/PR reached 39.48 MPa, 20.32%, and 13.62 kJ/m2, which were 120%, 27.15%, and 154% higher than that of the pure resin; the thermal decomposition temperatures and the maximum thermal decomposition temperatures at 50% mass loss of ACF/PR increased to 457.66°C and 442.44°C at 50% mass loss, which is 3.95% and 3.63% higher than that of the pure resin. Currently, the composites have excellent strength, toughness, and thermal stability. This paper gives a cost‐efficient method for improving the functioning of PR.Highlights Mixed acid oxidation and amino silane modification of CFs. Preparation of modified CF/photosensitive resin composites. Composites with excellent mechanical properties and thermal stability.

Bromide-Mediated Silane Oxidation: A Practical Counter-Electrode Process for Nonaqueous Deep Reductive Electrosynthesis

Bromide-Mediated Silane Oxidation: A Practical Counter-Electrode Process for Nonaqueous Deep Reductive Electrosynthesis

Electrochemical Benzylic C(sp3)-H Imidation Enabled by Benzoic Acid Derived Radicals.

We developed an electrochemical approach for benzylic C(sp3)-H imidation by virtue of the in situ generated oxygen-centered radicals (OCRs). The electrochemical imidation provides a complementary approach to giving distinct imide products compared with previous acyloxylation products. This protocol exhibits good site selectivity and broad substrate generality. Moreover, the utility of the OCR-mediated protocol was extended to the electrochemical oxidation of silane, and its robustness was also highlighted by the imidation of complex substrates, which would otherwise be inaccessible for previous approaches. A plausible reaction mechanism was proposed to rationalize the experimental observations.

Pd single-atom decorated OMS-2 nanorod for efficient silane oxidation

Single Pd atom-anchored OMS-2 material was synthesized and exhibited excellent catalytic performance for silane oxidation with H2O. Note that Pd species was trapped into frameworks of OMS-2 by substituting Mn ions and formed strong Pd–O bonds.

Single‐Atom Manganese‐Catalyzed Oxygen Evolution Drives the Electrochemical Oxidation of Silane to Silanol

AbstractThe oxygen evolution reaction (OER), characterized by a four‐electron transfer kinetic process, represents a significant bottleneck in improving the efficiency of hydrogen production from water electrolysis. Consequently, extensive research efforts have been directed towards identifying single‐atom electrocatalysts with exceptional OER performance. Despite the comprehensive understanding of the OER mechanism, its application to other valuable synthetic reactions has been limited. Herein, we leverage the MOOH intermediate, a key species in the Mn−N−C single‐atom catalyst (Mn‐SA@NC), which can be cyclically delivered in the OER. We exploit this intermediate’ s capability to facilitate electrophilic transfer with silane, enabling efficient silane oxidation under electrochemical conditions. The SAC electrocatalytic system exhibits remarkable performance with catalyst loadings as low as 600 ppm and an exceptional turnover number of 9132. Furthermore, the catalytic method demonstrates stability under a 10 mmol flow chemistry setup. By serving as an OER electrocatalyst, the Mn‐SA@NC drives the entire reaction, establishing a practical Mn SAC‐catalyzed organic electrosynthesis system. This synthesis approach not only presents a promising avenue for the utilization of electrocatalytic OER but also highlights the potential of SACs as an attractive platform for organic electrosynthesis investigations.

Single-Atom Manganese-Catalyzed Oxygen Evolution Drives the Electrochemical Oxidation of Silane to Silanol.

The oxygen evolution reaction (OER), characterized by a four-electron transfer kinetic process, represents a significant bottleneck in improving the efficiency of hydrogen production from water electrolysis. Consequently, extensive research efforts have been directed towards identifying single-atom electrocatalysts with exceptional OER performance. Despite the comprehensive understanding of the OER mechanism, its application to other valuable synthetic reactions has been limited. Herein, we leverage the MOOH intermediate, a key species in the Mn-N-C single-atom catalyst (Mn-SA@NC), which can be cyclically delivered in the OER. We exploit this intermediate' s capability to facilitate electrophilic transfer with silane, enabling efficient silane oxidation under electrochemical conditions. The SAC electrocatalytic system exhibits remarkable performance with catalyst loadings as low as 600 ppm and an exceptional turnover number of 9132. Furthermore, the catalytic method demonstrates stability under a 10 mmol flow chemistry setup. By serving as an OER electrocatalyst, the Mn-SA@NC drives the entire reaction, establishing a practical Mn SAC-catalyzed organic electrosynthesis system. This synthesis approach not only presents a promising avenue for the utilization of electrocatalytic OER but also highlights the potential of SACs as an attractive platform for organic electrosynthesis investigations.

Water Activation Triggered by Cu-Co Double-Atom Catalyst for Silane Oxidation.

High-performance catalysts sufficient to significantly reduce the energy barrier of water activation are crucial in facilitating reactions that are restricted by water dissociation. Herein we present a Cu-Co double-atom catalyst (CuCo-DAC), which possesses a uniform and well-defined CuCoN6 (OH) structure, and works together to promote water activation in silane oxidation. The catalyst achieves superior catalytic performance far exceeding that of single-atom catalysts (SACs). Various functional silanes are converted into silanols with up to 98 % yield and 99 % selectivity. Kinetic studies show that the activation energy of silane oxidation by CuCo-DAC is significantly lower than that of Cu single-atom catalyst (Cu-SAC) and Co single-atom catalyst (Co-SAC). Theoretical calculations demonstrate two different reaction pathways where water splitting is the rate-determining step and it is accelerated by CuCo-DAC, whereas H2 formation is key for its single-atom counterpart.

Water Activation Triggered by Cu−Co Double‐Atom Catalyst for Silane Oxidation

AbstractHigh‐performance catalysts sufficient to significantly reduce the energy barrier of water activation are crucial in facilitating reactions that are restricted by water dissociation. Herein we present a Cu−Co double‐atom catalyst (CuCo‐DAC), which possesses a uniform and well‐defined CuCoN6(OH) structure, and works together to promote water activation in silane oxidation. The catalyst achieves superior catalytic performance far exceeding that of single‐atom catalysts (SACs). Various functional silanes are converted into silanols with up to 98 % yield and 99 % selectivity. Kinetic studies show that the activation energy of silane oxidation by CuCo‐DAC is significantly lower than that of Cu single‐atom catalyst (Cu‐SAC) and Co single‐atom catalyst (Co‐SAC). Theoretical calculations demonstrate two different reaction pathways where water splitting is the rate‐determining step and it is accelerated by CuCo‐DAC, whereas H2 formation is key for its single‐atom counterpart.

Visible Light-Mediated Organoboron-Catalyzed Metal-Free Synthesis of Silanols from Silanes.

Herein, a four-coordinated organoboron compound, aminoquinoline diarylboron (AQDAB), is utilized as the photocatalyst in the oxidation of silane to silanol. This strategy effectively oxidizes Si-H bonds, affording Si-O bonds. Generally, the corresponding silanols can be obtained in moderate to good yields at room temperature under oxygen atmospheres, representing a green protocol to complement the existing preparation methods for silanols.

Solvent-promoted photochemical carbonylation of benzylic C-H bonds under iron catalysis.

This paper describes the iron-catalyzed photochemical carbonylation of benzylic C-H bonds resulting in the synthesis of various aryl ketones. Using 5 W blue LED irradiation, the reactions proceed smoothly in the presence of 2 mol% of FeBr3 in MeOH at 35 °C. The catalytic system could be extended for the oxidation of silane, thioether, and phosphine into silenol, sulphoxide, and phosphoxide, respectively. A mechanistic study suggests that a hydrogen bond-stabilized iron-hydroperoxo species is the reactive intermediate. It is shown that the reaction proceeds via a four-electron-transfer pathway, and a benzylic cation seems to be the crucial reactive species. The method is applied for the synthesis of pomalyst, haloperidol, melperone, and lenperone.

Identifying silica types using viscosity data and principal component analysis

As the most important glass former, silica has a plethora of relevant industrial and commercial applications. Silica glass can be classified into several types depending on the starting materials, production method, content and impurities. Briefly, type I is obtained by melting natural or synthetic quartz in electrical furnaces, presenting alkali and metal impurities (in ppm). Type II is obtained from melting natural or synthetic quartz in hydrogen–oxygen or natural gas flames with few impurities (in ppm) but high concentration of structural water. Type III is obtained from high-temperature hydrolysis of volatile compounds of silicon with low metal impurities and considerable concentrations of structural water and chlorine. Type IV is obtained from high-temperature oxidation of silane with small amounts of metal impurities, almost no structural water but high chlorine content. We analyzed literature data on viscosity, η, for 44 batches over a wide temperature range, from glass transition, Tg, to far beyond the melting point, Tm, for four of five silica types. The viscosity behavior in silica follows the Arrhenius expression: log10η(T)=A+BT, with η in Pa⋅s, T in K, where A and B are constants. However, the Vogel-Fulcher-Tammann-Hesse (VFTH) equation: log10η(T)=A+BT−T0,can also be applied to this system, with T0 → 0 as another constant (in K). For a fixed temperature, a variance of η, covering two orders of magnitude, was observed for types I and II, and about one order for the other two types, mainly due to impurity content and the manufacturing process. Another important observation was that the highest viscosities were found in the purest silicas. Not all samples presented T0 = 0, as expected for Arrhenius viscosity behavior. An analysis considering the Mauro-Yue-Ellison-Gupta-Allan (MYEGA) viscosity equation was also performed. Previous studies of principal component analysis (PCA) considering A, B and T0 allowed the mapping of binary and ternary silicate and borate systems. In brief, PCA is a mathematical technique which rearranges information from datasets and can classify silica types according to their viscosity parameters. The results show that it is possible to map the four silica glass types according to viscosity VFTH and MYEGA parameters taken from experimental data.

Current status of the high-temperature kinetic models of silane: Part II. Oxidation

Abstract The present study is the second part of our work on the current status of high-temperature kinetic models of silane. Except Slakman’s model, all the models tested in the first part of the study, restricted to the pyrolysis dataset, are now compared against a large validation dataset (230 conditions) for silane oxidation. This large validation dataset is composed of both new and literature data, mainly representative of the highly-diluted and high-temperature oxidation of silane with different oxidizers ( O 2 , N 2 O , and NO) and diluents (Ar and N 2 ) over an extensive range of temperature ( T = [801– 2955 K]) and pressure ( P = [50 – 629 kPa]) conditions. The new experimental data are limited to SiH 4 - O 2 -Ar mixtures, obtained in a double-diaphragm shock tube equipped with an Atomic Resonance Absorption Spectroscopy (ARAS) detection technique. Experimental results present the temporal evolution of the total absorption signal, considering the absorption of O, Si, N 2 O , and SiH 4 . The performance of the models is assessed based on the same five validation criteria and objective function calculation, as presented in the first part of the study. The model of Chatelain and of Mevel present good performances with a global error of 2.4, i.e. meaning an average error of 2.4 fold above the experimental uncertainty, and high fraction (70 %) of criteria predicted within two times the experimental uncertainty. Although the reference reaction models performed better on the oxidation dataset compared to the pyrolysis dataset (part I), their global error is still 50 to 125 % higher than the two most accurate reaction models. Rate of production and sensitivity analyses revealed that the origin of the discrepancy of the least performing models can be attributed to the reaction pathways consuming/producing Si and O atoms and to some kinetic rates that must be updated.

Correction of reaction models using collision limit violation analyses: Application to a silane reaction model

This study presents a detailed methodology to verify and correct the chemical consistency of any reaction model based on collision limit violations (CLV) analyses, thermochemical data calculations, and reaction rates reffiting. As a study case, an a priori well validated reaction model representative of silane chemistry is selected to highlight the benefit of this methodology. In the final mechanism, 30 new thermochemical data obtained using a high theory composite method (G4//B3LYP/6-311++G(3df,2p)) are corrected, as well as 13 reaction rates initially above the collision limits. In addition to the suppression of unphysically high reaction rates, the collision limit violation analyses allow to identify and correct important inconsistencies of the initial reaction model such as species mislabeling or discontinuities in some thermodynamic data, which are not easily detectable without an extensive review of each submodels. The novelties of the present work include (i) the discussion of the CLV uncertainty, (ii) the use of this uncertainty to identify CLVs, and (iii) the establishment of the relationship between high CLV values and species mislabeling. As a results of this study case on a specific mechanism, this work also provides a more consistent reaction model for silane chemistry, relevant for both high temperature combustion and flame relevant conditions, as well as a large number of ab initio calculation results, relevant to the SixHyOz chemical system. Based on the present analyses, the predictions of the final reaction model are mainly improved for silane pyrolysis, while the benefits are more limited for silane oxidation.

Selective Enzymatic Oxidation of Silanes to Silanols

AbstractCompared to the biological world's rich chemistry for functionalizing carbon, enzymatic transformations of the heavier homologue silicon are rare. We report that a wild‐type cytochrome P450 monooxygenase (P450BM3 from Bacillus megaterium, CYP102A1) has promiscuous activity for oxidation of hydrosilanes to give silanols. Directed evolution was applied to enhance this non‐native activity and create a highly efficient catalyst for selective silane oxidation under mild conditions with oxygen as the terminal oxidant. The evolved enzyme leaves C−H bonds present in the silane substrates untouched, and this biotransformation does not lead to disiloxane formation, a common problem in silanol syntheses. Computational studies reveal that catalysis proceeds through hydrogen atom abstraction followed by radical rebound, as observed in the native C−H hydroxylation mechanism of the P450 enzyme. This enzymatic silane oxidation extends nature's impressive catalytic repertoire.

Selective Enzymatic Oxidation of Silanes to Silanols.

Compared to the biological world's rich chemistry for functionalizing carbon, enzymatic transformations of the heavier homologue silicon are rare. We report that a wild-type cytochrome P450 monooxygenase (P450BM3 from Bacillus megaterium, CYP102A1) has promiscuous activity for oxidation of hydrosilanes to give silanols. Directed evolution was applied to enhance this non-native activity and create a highly efficient catalyst for selective silane oxidation under mild conditions with oxygen as the terminal oxidant. The evolved enzyme leaves C-H bonds present in the silane substrates untouched, and this biotransformation does not lead to disiloxane formation, a common problem in silanol syntheses. Computational studies reveal that catalysis proceeds through hydrogen atom abstraction followed by radical rebound, as observed in the native C-H hydroxylation mechanism of the P450 enzyme. This enzymatic silane oxidation extends nature's impressive catalytic repertoire.

Highly Selective Hydroxylation and Alkoxylation of Silanes: One-Pot Silane Oxidation and Reduction of Aldehydes/Ketones

An efficient chemoselective iridium-catalyzed method for the hydroxylation and alkoxylation of organosilanes to generate hydrogen gas and silanols or silyl ethers was developed. A variety of steric...

Formation of a Pd/MgO Structured Catalyst for the Aqueous Oxidation of Silane to Silanol

The catalytic oxidation of silanes to produce silanols using water as an oxidant at mild temperatures is a major challenge in Si-H activation. Highly efficient and easy-to-recycle catalysts based on Pd nanoparticles are in high demand. In this study, Pd nanoparticles embedded in an MgO porous overlayer on an Mg plate as a structured catalyst was prepared by the plasma electrolyte oxidation (PEO) technique. The Pd/MgO catalyst is strongly anchored to the MgO plate, building a structured catalyst. Fabrication parameters such as the temperature of the electrolyte and applied voltage significantly influenced the structure of the obtained Pd/MgO catalyst and in turn its catalytic activity. The catalytic activities of Pd/MgO were evaluated by activation of a Si-H bond for catalyzing the aqueous oxidation of silanes to silanol at mild temperatures. The catalytic activity of Pd nanoparticles is favored by their electro-deficient state due to influence from the MgO substrate. The Pd/MgO catalyst exhibits good performance stability during recycling. This work paves the way for fabricating structured catalysts with long-term stability and enhanced metal–oxide interaction.

Etching-Assisted Route to Heterophase Au Nanowires with Multiple Types of Active Surface Sites for Silane Oxidation.

The construction of multiple types of active sites on the surface of a metallic catalyst can markedly enhance its catalytic activity toward specific reactions. Here, we show that heterophase gold nanowires (Au NWs) with multiple types of active surface sites can be synthesized using an etching-assisted process, yielding the highest reported turnover frequency (TOF) for Au catalysts toward the silane oxidation reaction by far. We use synchrotron powder X-ray diffraction (PXRD) and aberration-corrected (scanning) transmission electron microscopy (TEM) to show that the Au NWs contain heterophase structures, planar defects, and surface steps. Moreover, the contribution to the catalytic performance from each type of active sites was clarified. Surface steps on the Au NW catalysts, which were identified using aberration-corrected (scanning) TEM, were shown to play the most important role in enhancing the catalytic performance. By using synchrotron PXRD, it was shown that a small ratio of metastable phases within Au NWs can enhance catalytic activity by a factor of 1.35, providing a further route to improve catalytic activity. Of the three types of surface active sites, surface terminations of planar defects such as twin boundaries (TB) and stacking faults (SF) are less active than metastable phases and surface steps for Au catalysts toward the silane oxidation reaction. Such an etching-assisted synthesis of heterophase Au NWs promises to open new possibilities for catalysis, plasmonic, optics, and electrical applications.

Cobalt-Catalyzed Selective Synthesis of Disiloxanes and Hydrodisiloxanes

Selective syntheses of symmetrical siloxanes and cyclotetrasiloxanes are attained from reactions of silanes and dihydrosilanes, respectively, with water, and the reactions are catalyzed by a NNNHtBu cobalt(II) pincer complex. Interestingly, when phenylsilane was subjected to catalysis with water, a siloxane cage consisting 12 silicon and 18 oxygen centers was obtained and remarkably the reaction proceeded with liberation of 3 equiv of molecular hydrogen (36 H2) under mild experimental conditions. Upon reaction of silane with different silanols, highly selective and controlled syntheses of higher order monohydrosiloxanes and disiloxymonohydrosilanes were achieved by cobalt catalysis. The liberated molecular hydrogen is the only byproduct observed in all of these transformations. Mechanistic studies indicated that the reactions occur via a homogeneous pathway. Kinetic and independent experiments confirmed the catalytic oxidation of silane to silanol, and further dehydrocoupling processes are involved in syn...

Mathematical modeling of the detonation wave structure in the silane-air mixture

ABSTRACTThe paper deals with the problem of the structure of detonation waves in the silane-air mixture within the framework of mathematical model of a nonequilibrium gas dynamics. Detailed kinetic scheme of silane oxidation as well as the newly developed reduced kinetic model of detonation combustion of silane are used. On its basis, the detonation wave (DW) structure in stoichiometric silane-air mixture and dependences of Chapman–Jouguet parameters of mixture on stoichiometric ratio between the fuel (silane) and an oxidizer (air) were obtained. It was revealed that in the reaction zone, in the structure of DW, the heat release in the model with detailed kinetics is non-monotonic.