SiCl4 Research Articles

Adjusting the Number of Functional Groups in Vicinal Bis(trichlorosilylated) Benzenes.

Organo(chloro)silanes are essential chemicals, but the synthesis of compounds of the formula RnSiCl4‒n with defined values of n is usually laborious. Herein, we first disclose that a [4+2]-cycloaddition between readily available Cl3SiC≡CSiCl3 and selected dienes provides facile access to vicinal bis(trichlorosilylated) benzenes and bicyclo[2.2.2]octa-2,5-dienes. Second, we show how the number of six Si‒Cl bonds in 1,2-(Cl3Si)2C6H2Me2 (1) can be selectively reduced to four or two by reaction with pinacol (H2pin) or catechol (H2cat), which act as Si···Si'-bridging and/or Si-chelating ligands. Third, we demonstrate that the thermolysis of compound 6, which contains a benzannulated eight-membered C2(SiCl2)2(μ-pin) ring with Si···Si'-bridging pin moiety, furnishes 13 with a benzannulated five-membered C2(SiCl2)2O ring via the release of pinacolone. Such cyclic disiloxanes are valuable building blocks for specialty silicones; an alternative assembly of the Si‒O‒Si unit by controlled hydrolysis of 1 is not feasible if the four valuable Si‒Cl functionalities are to be retained for further derivatization. Substitution of one Cl atom per Si site of 13 gives the rac-1,3-disila-2-oxaindane rac-15 with high selectivity.

Transformation of by-product silicon tetrachloride to an efficient and stable heterogeneous base catalyst: Valorization of glycerol into valuable glycerol carbonate

The by-product silicon tetrachloride (SiCl4) from the polysilicon industry was recycled to fabricate a highly efficient and stable lithium silicate (LS) catalyst for upgrading of oversupplied biodiesel by-product glycerol to valuable glycerol carbonate (GC). The characteristics of the LS catalyst were systematically investigated by various experimental characterization techniques and density functional theory (DFT) calculations. The experimental results showed that the hydrolysis of SiCl4 in the lithium nitrate solution helping to the solid phase synthesis of the LS catalyst as lithium could be uniformly dispersed in the silica gel. The as-synthesized LS catalyst mainly consists of lithium orthosilicate with strong basic sties, favoring the catalytic conversion of glycerol. The LS catalyst exhibited an appreciably high catalytic efficiency (turnover frequency of 2.72 min−1) and glycerol conversion (99.8±1.8 %) compared to other reported solid base catalysts. The apparent activation energy (Ea) of this reaction was calculated to be 39.51 kJ/mol. Further, benefiting from the stable silicate structure, the LS catalyst showed an enhanced catalytic stability as the glycerol conversion declined less than 5 % after five times reuse without regeneration. The LS catalyst also revealed marked resistance to the solid base catalyst poisons like water and methanol compare to that of commercial calcium-based catalyst. The temperature-programmed desorption of CO2 (CO2-TPD) and DFT results affirmed that the low-coordination lattice oxygen of the isolated SiO4 tetrahedron on the surface of the LS catalyst acting as a strong basic electron donor promoted the transesterification reaction between DMC and glycerol. As a result, the SiCl4-derived LS catalyst possessed remarkable catalytic efficiency and reusability, which could be an ideal candidate to meet the requirements for industrial application and highlight the potential application of the by-product SiCl4.

Investigation of the Thermodynamic Characteristics of Low-Temperature Hydrogenation of silicon Tetrachloride

Investigation of the Thermodynamic Characteristics of Low-Temperature Hydrogenation of silicon Tetrachloride

Exploring the Potential of Silicon Tetrachloride as an Additive in CO2-Based Binary Mixtures in Transcritical Organic Rankine Cycle—A Comparative Study with Traditional Hydrocarbons

Exploring the Potential of Silicon Tetrachloride as an Additive in CO2-Based Binary Mixtures in Transcritical Organic Rankine Cycle—A Comparative Study with Traditional Hydrocarbons

Reactor wall effects in Si–Cl2–Ar atomic layer etching

This work complements our previous manuscript [J. Vac. Sci. Technol. A41, 062602 (2023)] where predictions from molecular dynamics (MD) simulations of silicon–chlorine–argon (Si–Cl2–Ar) atomic layer etching (ALE) are compared to experiments. When etch product distributions for atomic chlorine (Cl) and silicon chlorides were initially compared to optical emission spectroscopy (OES) signals, it appeared that there was a discrepancy between the MD predictions and experimental results at higher ion fluences. Experiments showed a relatively long period of nearly constant Cl-containing etch products released from the ion-bombarded surface (referred to as the “plateau”) but this effect was not observed in MD simulations. In this report, we demonstrate that the “plateau” observed in the OES signals is most likely due to the desorption of Cl-containing etch products from the walls of the reactor and subsequent adsorption on the Si substrate. Experiments varying the gas residence time in the chamber while keeping incoming gas concentrations and pressure constant support this interpretation. We also conducted experiments with an additional Ar-only flow in the chamber to reduce the concentration of Cl-containing species on the chamber walls. For both sets of flow modification experiments, we observe results consistent with the hypothesis that Cl-containing species desorbing from chamber walls are a significant cause of the observed discrepancy between MD predictions and experimental observations. If the measured OES signals are corrected for this “additional” source of Cl-containing species at the surface, the MD predictions and measured OES signals are in excellent agreement. This further supports the predictive capability of MD simulations to accurately capture the relevant physical and chemical processes in plasma-assisted ALE processes. We provide an order of magnitude estimate of the required density of Cl-containing species that would account for the additional etch products observed. Finally, we discuss the implications of this effect on ALE in plasma nanofabrication.

Fabrication of superhydrophobic all-biomass aerogels with ultralight, elasticity and degradability for efficient oily wastewater treatment

Oily wastewater has seriously threatened the water ecology and human health. Superhydrophobic biomass-based aerogels are ideal candidates to remedy the oily wastewater, but facing challenges for the usage of toxic small molecules crosslinker and the rational construction of elasticity. Herein, we employed the natural non-toxic citral as crosslinker, and then constructed a superhydrophobic chitosan/bamboo cellular fibers aerogel (S-CS/BCF-A) with ultra-light, high elasticity and degradation performances. Wherein the hydrolysis of methyltrichlorosilane produced silicon hydride and hydrogen chloride, enhanced the hydrophobicity of the aerogel surface and partially reduced rigidity of the pore walls, respectively. The S-CS/BCF-A displayed outstanding fatigue durability, which benefited for its lamellar-fiber interweaved structure. In addition, this aerogel could undergo tape-peeling, UV radiation, and organic solvents immersion without superhydrophobic variation, even in seriously abrasing that the surface still maintained high hydrophobicity. The as-made aerogel possessed high oil adsorption capacity (17.95–44.57 g/g), combined with pump-supported device for effectively recovering large-area oil spills (66,348 L·m−2·h−1). Furthermore, the resultant aerogel could efficiently separate the immiscible oil-water mixture and emulsifying wastewater (types of Oil-in-Water and Water-in-Oil emulsions). This work provides a rational design method for constructing the elastic, durable and biodegradable aerogels, used for speedy and economical separation of oil-water mixtures.

Silicon Tetrachloride as innovative working fluid for high temperature Rankine cycles: Thermal Stability, material compatibility, and energy analysis

Silicon Tetrachloride (SiCl4) is proposed as a new potential working fluid for high-temperature Rankine Cycles. The capability to overcome the actual thermal stability limit of fluids commercially employed in the state-of-the-art Organic Rankine Cycles (ORC) is demonstrated by static thermal stability and material compatibility tests. Experimental static test proves its thermo-chemical stability with a conventional stainless-steel alloy (AISI 316L) up to 650 °C. A preliminary material compatibility analysis performed with optical microscope on the AISI 316L cylinder, after exposure of 300 h to SiCl4 at temperature higher than 550 °C, confirms the potentiality of this fluid when coupled with high-grade heat sources. A thermodynamic analysis has been carried out accounting for the effect of operating conditions on the axial turbine efficiency. A comparison with fluids adopted in medium–high temperature ORCs is performed, evidencing that the proposed fluid could achieve more than + 10 % points as thermal efficiency gain compared to any commercial solutions when coupled with high-temperature sources such as solar, biomass, waste heat from industrial processes and prime movers. A 2 MW SiCl4 cycle operating full-electric at 550 °C reaches a thermal efficiency of 38 %, exceeding values attainable by any other working fluid under similar conditions and power size.

Study of the impurity composition of silicon tetrachloride by gas chromatography-mass-spectrometry

Silicon tetrachloride is a sought-after substance in the semiconductor and optoelectronics industries. High demands placed on its purity entail the need for detail information about the impurities present. The impurity composition of silicon tetrachloride obtained by different technologies (chlorination of diatomite and charcoal, disproportionation of trichlorosilane and chlorination of isotopically enriched silicon) was studied using the method of chromatography-mass spectrometry. Study of the possibility of using a DB-5MS 30 m × 0.32 mm × 0.25 μm capillary column with methylsiloxane as a stationary liquid phase to separate impurities revealed that most of the identified substances are eluted in the form of separate chromatographic peaks, which simplifies their determination. The exceptions are impurities N2, O2, Ar, as well as CO2, SiF4, and CHClF2, HCl, H2S. They were registered using the characteristic peaks of the mass spectra. To identify impurities, experimental mass spectra were compared to data from the NIST library and those known from the literature. Information on the impurity composition of SiCl4 has been expanded. It contains permanent gases, aliphatic and chlorine-containing hydrocarbons, chlorides of elements, sulfur-containing substances, and organosilicon compounds. A total of 30 compounds are identified, 19 being discovered for the first time. The mass spectrum of C2H6Cl4OSi2, which is absent in the literature, was obtained and described. For the first time, data on the impurity composition of isotopically enriched silicon tetrachloride have been obtained. A comparative analysis of the impurity composition of the samples under study was carried out and the impurities characteristic of each of them were determined. The data obtained in the study can be used in developing the technology for deep purification of silicon tetrachloride and in characterization of SiCl4 by manufacturing enterprises.

Functionalization of porous silica with graphene oxide and polyethyleneimine, containing zinc copper ferrite nanoparticles for water treatment and antibacterial application

The article discusses the removal of methylene blue (MB) dye, a common cationic dye used in the textile industry, from aqueous solutions through an adsorption process. The use of porous components as adsorbents are shown to facilitate complete separation after the process is completed. The substrate was synthesized by connecting zinc copper ferrite (ZnCuFe2O4), polyethyleneimine (PEI), and Graphene Oxide (GO) sheets to MCM-48, which is a mesoporous material. The surface of MCM-48 was modified using CPTMS, which created an O–Si–Cl bridge, thereby improving the adsorption rate. The substrate was shown to have suitable sites for electrostatic interactions and creating hydrogen bonds with MB. The adsorption process from the Freundlich isotherm (R2 = 0.9224) and the pseudo-second-order diagram (R2 = 0.9927) demonstrates the adsorption of several layers of dye on the heterogeneous surface of the substrate. The synthesized substrate was also shown to have good bactericidal activity against E. coli and S. aureus bacterial strain. Furthermore, the substrate maintained its initial ability to adsorb MB dye for four consecutive cycles. The research resulted that ZnCuFe2O4@MCM-48/PEI-GO substrate has the potential for efficient and economical removal of MB dye from aqueous solutions (R = 88.82%) (qmax = 294.1176 mg. g−1), making it a promising solution for the disposal of harmful industrial waste.

An efficient and closed-loop approach to convert silicon tetrachloride to silicon nanospheres anode materials via hydrogen thermal plasma

Solar energy is growing due to global “carbon peak and neutrality” targets. Silicon tetrachloride (SiCl4) is mass-produced from polycrystalline silicon (p-Si), an important solar material. Therefore, an efficient and cost-effective process is needed to transform this byproduct into a higher-value product. In this work, we present a new approach utilizing hydrogen thermal plasma (H-plasma) to directly convert SiCl4 into silicon nanospheres (Si NSs) and analyzed the reaction process by optical emission spectroscopy diagnostic. The Si NSs produced possess a spherical shape, with a smooth surface and a compact interior. With a diameter of ∼90 nm, Si NSs exhibits exceptional electrochemical performance when used as anode materials. Significantly, H-plasma is expected to be combined with the current tail gas recovery system of the p-Si industry to form a closed circuit, increasing yield and lowering costs. Our work demonstrates economically viable and widespread nano-silicon fabrication for sustainable energy solutions.

Inside Back Cover

The main idea described in this paper is Iron catalyzed reductive cross‐coupling of diaryl ethers and chlorosilanes via strong electrophilic C(aryl)—O and Si—Cl bonds cleavage. More details are discussed in the article by Liu et al. on page 578—584.image

The reactor for catalytic hydrogenating of silicon tetrachloride

The reactor for catalytic hydrogenating of silicon tetrachloride

From 'halogen' to 'tetrel' bonds: matrix isolation IR spectroscopic and quantum mechanical studies of the effect of central atom substitution in donor tetrahalogens on binary complex formation with formic acid.

Binary complex formation between silicon tetrachloride (SiCl4) and formic acid (FA) has been observed in an argon matrix environment. Such complex formation manifests as spectral shifts in signature vibrations of the latter, namely the νCO, νC-O and νO-H vibrations. Quantum chemical calculations reveal that the most stable conformers of the complex involve predominantly the tetrel bond, which has been defined in existing literature as a variant of the "σ-hole" interactions. Here, regions of positive electrostatic potential on the tetrahedral face of SiCl4 act as electrophilic centers (σ-hole) to which the nucleophilic carbonyl group of FA is able to bind. Atoms-in-molecules analysis predicts a bond critical point along the non-covalent contact between the tetrel atom Si and the carbonyl oxygen on FA, corroborating the presence of the tetrel bond. The hyperconjugative interaction parameters at the binding interface obtained from Natural Bond Orbital (NBO) analysis are also consistent with such observations. Although apparently similar to SiCl4, there are noticeable differences in the binding preferences of the lower homologue carbon tetrachloride (CCl4). The binary complexes of the latter with the same FA acceptor molecule have been previously shown to involve halogen bonded, rather than tetrel bonded interactions (Banerjee and Bhattacharya, Spectrochim. Acta Mol. and Biomol. Spectrosc., 2021, 250, 119355). Such variations in the nature of non-covalent interactions of these tetrahalogens are attributed to differences in the distribution of electronic charge density surrounding the central tetrel atom, as obtained from mappings of their electrostatic potential surfaces. Our combined experimental and theoretical findings therefore provide direct evidence of the growing propensity of tetrel atoms to engage in tetrel bonding as we move lower down Group 14, and re-assert the reluctance of the smaller and more electronegative carbon atom to serve as a tetrel bond participant.

Chemisorption of silicon tetrachloride on silicon nitride: a density functional theory study.

We studied the chemisorption of silicon tetrachloride (SiCl4) on the NH2/NH-terminated silicon nitride slab model using density functional theory (DFT) for atomic layer deposition (ALD) of silicon nitride. Initially, two reaction pathways were compared, forming HCl or NH3+Cl- as a byproduct. The NH3+Cl- complex formation was more exothermic than the HCl formation, with an activation energy of 0.26 eV. The -NH2* reaction sites are restored by desorption of HCl from the NH3+Cl- complexes at elevated temperatures of 205 °C or higher. Next, three sequential ligand exchange reactions forming Si-N bonds were modeled and simulated. The reaction energies became progressively less exothermic as the reaction progressed, from -1.31 eV to -0.30 eV to 0.98 eV, due to the stretching of Si-N bonds and the distortion of the N-Si-N bond angles. Also, the activation energies for the second and third reactions were 2.17 eV and 1.55 eV, respectively, significantly higher than the 0.26 eV of the first reaction, mainly due to the additional dissociation of the N-H bond. The third Si-N bond formation is unfavorable due to the endothermic reaction and higher activation energy. Therefore, the chemisorbed species would be -SiCl2* when the surface is exposed to SiCl4.

Analytical Study of Shilajatu

Background Rasashastra is a branch in Ayurveda Pharmaceutics that deals with utilization of varied origin of drugs like metals minerals etc. in articulating different formulations. Among the mineral group of drugs a mineral very commonly used in designing formulations is lsquoShilajatursquo. It is a pale brown to black coloured exudate available in mountainous regions. Based on the region and mountainous area it is collected from its appearance and the composition vary. Research studies revealed it to be a combination of organic elements and inorganic substances. Vast content relating to Shilajatu is available in the treatises of Rasashastra and much research was carried out on it. However it still remains a drug of ambiguity. Therefore this analytical study was conducted to evaluate the varied composition of Shilajatu. Methods Two samples of Shilajatu were collected from two different sources one from Nepal and another from local market in India and the samples were analyzed to determine the organic constituents and also the elemental constituents. Physico chemical analysis Phyto chemical test and Energy Dispersive X-ray Spectroscopy EDAX were carried out. Results Phytochemical evaluation of aqueous extracts of Shilajatu samples demonstrated presence of carbohydrates protein tannin steroid saponin and mucilage. EDAX revealed the presence of different elements and the sample from Nepal showed the presence of more elements. Conclusion Shilajatu is a combination of organic and inorganic elements. Various phyto constituents are present and the elemental analysis showed presence of C O Na Mg S Cl and K in Indian sample and presence of C N O Na Mg Al Si Cl K and Ca in Nepal sample.

Plasma-Chemical Disposal of Silicon and Germanium Tetrachlorides Waste by Hydrogen Reduction

The processes of hydrogen reduction of silicon and germanium chlorides under the conditions of high-frequency (40.68 MHz) counteracted arc discharge stabilized between two rod electrodes are investigated. The main gas-phase and solid products of plasma-chemical transformations are determined. Thermodynamic analysis of SiCl4 + H2 and GeCl4 + H2 systems for optimal process parameters was carried out. Using the example of hydrogen reduction of SiCl4 by the method of numerical modeling, gas-dynamic and thermal processes for this type of discharge are investigated. The impurity composition of gas-phase and solid reaction products is investigated. The possibility of single-stage production of high-purity Si and Ge mainly in the form of compact ingots, as well as high-purity chlorosilanes and trichlorogermane, is shown.

Iron‐Catalyzed Reductive C(aryl)—Si Cross‐Coupling of Diaryl Ethers with Chlorosilanes

Comprehensive SummaryThe reductive cross‐coupling between C(aryl)—O and Si—Cl bonds is of much importance as a valuable strategy for the construction of C(aryl)—Si bonds but has remained a great challenge. Herein, we report a reductive cross‐coupling of diaryl ethers and chlorosilanes via strong electrophilic C(aryl)—O and Si—Cl bonds cleavage by iron catalysis, which constitutes an efficient protocol for the synthesis of a range of functionalized arylsilanes. The combination of low cost FeCl2 as the precatalyst and iPrMgCl as the reductant shows high activity in the successive cleavage of unactivated C(aryl)—O bonds of diaryl ethers and strong electrophilic Si—Cl bonds of chlorosilanes, allowing their cross‐coupling in a reductive fashion. The low‐valent iron species generated in situ by reduction of FeCl2 with iPrMgCl was proposed, which prefers to initially cleavage the C(aryl)—O bond of diaryl ethers with the chelation help of an o‐amide auxiliary.

New assignments of Raman spectra of tetrahedra and the effects of electronegativity. I. P4O10 and Si-containing molecules

Our new density functional theory calculations by Gaussian reproduce the bond lengths and Raman spectra of a number of model tetrahedral Si and P compounds [the ten compounds in the SiHxD4−x and SiFxCl4−x (x = 0–4) series, and the tetramer P4O10]. The number of symmetric A1 peaks is determined by group theory, and the center of mass is especially important for the assignment of the three A1 peaks for P4O10 to the two P–O stretches and the O–P–O bend. Additional Gaussian calculations on isolated C3v PO4 tetrahedra, using the P–O bond lengths and O–P–O bond angles from the P4O10 optimization, also reproduce the three peak P4O10 Raman spectra and provide an important guide to the assignment of the two low energy peaks at ∼500 and ∼700 cm−1 to the P–BO (BO = P–O–P) stretch and BO–P–BO bend, respectively, in contrast to all earlier assignments. In the SiFxCl4−x series, there is a regular increase in the Si–F A1 frequency and a decrease in the Si–Cl A1 frequency across the series. Similar trends are seen in the SiClx(CH3)4−x series, and these trends are due to changes in the electron densities in the tetrahedron when an electronegative F or Cl is replaced by a less electronegative Cl or CH3, as measured by previous Si 2p, F 1s, Cl 2p, and C 1s x-ray photoelectron spectroscopy. These considerations serve as a guide for the interpretation of the Raman spectra of silicate glasses in Paper II [Bancroft et al., AIP Adv. 13, 125216 (2023)].

High-performance silicon/graphite anode prepared by CVD using SiCl4 as precursor for Li-ion batteries

Graphite/silicon composite anode shows increased capacity but suffering from the volume expansion of Si during cycling. Herein, we reported a facile chemical vapor deposition (CVD) method using silicon tetrachloride (SiCl4) as precursor to deposit silicon into graphite to prepare composite as anode for Li-ion batteries. Si can be deposit as the nano-sized particles in the open spaces of graphite, and closely attached on the graphite flakes. Such architecture effectively increased the contact between Si and graphite, and provided semi-enveloping confinement for Si volume change. Typically, the composite anode with 10% Si could maintain above 600 mAh/g for 100 cycles.

Numerical Simulation of Fluidization Behavior and Chemical Performance for Hydrochlorination of Silicon Tetrachloride in a Fluidized Bed Reactor

Exploring the fluidization behaviors and chemical performance in silicon tetrachloride (SiCl4) hydrochlorination processes within a fluidized bed reactor (FBR) poses significant challenges. In this study, we developed an Eulerian-granular model (EGM) by integrating the Eulerian–Eulerian two-fluid model with the kinetic theory of granular flow (KTGF). The effect of fluidization velocities on the flow regime, heat transfer, and chemical reaction performance were investigated. The applicability of the simulation method and the validity of the model were confirmed through comprehensive comparisons, including the simulated values of the maximum bed expansion height (Hmax) with theoretical values derived from empirical formulas and the simulated gas temperature profile with Hsu’s experimental data. The results indicate that the present EGM can be feasible to describe the variation of the flow regime within the FBR. An increase in bed voidage over time, coinciding with transitions in the flow regime, can be observed. Particularly noteworthy was the attainment of a more uniform distribution of SiCl4 under the bubbling fluidization state. Furthermore, the FBR possess high heat transfer characteristics, and the reaction gas can reach the set temperature of the bed after entering a small distance (about 10 mm). The presence of circulating bubbles within the FBR enhances the mixing uniformity of the SiCl4 reaction gas and silicon particles, particularly in the central and upper regions of the bed under the bubbling fluidization state. As a result, the predicted highest concentration of SiHCl3 was 13.08% and the conversion rate of SiCl4 was 28.97% under the bubbling fluidization state. Our results can provide a theoretical basis for further understanding of the hydrochlorination process of SiCl4 within the FBR.