Quartz Crystal Microbalances for Evaluating Gas Motion Differences between Dichlorosilane and Trichlorosilane in Ambient Hydrogen in a Slim Vertical Cold Wall Chemical Vapor Deposition Reactor

A dichlorosilane gas and a trichlorosilane gas in ambient hydrogen were evaluated to show their different gas flow motions in a slim vertical cold wall chemical vapor deposition reactor for the Minimal Fab system. This evaluation was performed for improving and controlling the film qualities and the productivities, using two quartz crystal microbalances (QCM) installed at the inlet and exhaust of the chamber by taking into account that the QCM frequency corresponds to the real time changes in the gas properties. Typically, the time period approaching from the inlet to the exhaust was shorter for the trichlorosilane gas than that for the dichlorosilane gas. The trichlorosilane gas was shown to move like plug flow, while the dichlorosilane gas seemed to be well mixed in the entire chamber.

Simulation of Reactive Distillation Process for Monosilane Production via Redistribution of Trichlorosilane

The reactive distillation process for producing high purity monosilane via trichlorosilane redistribution reaction was simulated. Rigorous RadFrac block was employed in Aspen Plus simulation package. Accurate results could be given when the chemical kinetics was taken into account in the equilibrium stage model. A single column process was used for the verification of previous studies. The results showed that 99.9% purity monosilane could be achieved in the reactive distillation. A pumparound block was employed to reduce the condenser duty with inexpen-sive coolant. The effects of operating pressure, feed stage location, liquid holdup per stage and pumparound location were also investigated. The energy consumption was limited, but the refrigerant temperature was too low, which is the fatal disadvantage. Therefore, a double columns process was developed to increase the condenser tem-perature. The simulation results demonstrated that a reasonable temperature could be achieved by varying the recycle stream location.

Application of Energy Saving Technology in Trichlorosilane Distillation Purification Process

The trichlorosilane(TCS)purification process consumes a significant amount of energy to achieve the high purity requirement for TCS quality(99.9999%).This work proposed a series of energy saving technology to enhance the TCS purification process,including the conventional process,the conventional process coupled with heat-pump(HP),the multi-effect distillation process,and the dividing-wall columns process.All proposed schemes have been conceptually constructed by Aspen Plus.The design and optimization of the processes have been performed by the sensitivity analysis and the response surface methodology.Moreover,the energy consumption and total annual cost(TAC)for these schemes were discussed.The simulation results show that the TAC of the conventional process coupled with the integrated heat pump can reduce 50.5%of energy consumption as compared with the conventional process;the double-effect and three-effect processes can save 15.6%and 33.8%of energy consumption,respectively;the dividing wall column process and that coupled with the heat pump process can reduce by 22.3%and 48.1%of energy consumption,respectively.It can be found that the operating cost can be saved by using the heat pump technology,while the capital cost increases due to the investment in the compressor,when the processes coupled with the heat pump are used.These results demonstrate that the conventional process coupled with the HP technology has advantages over other distillation schemes for TCS purification in terms of the energy saving and economic effects.

A general bottom-up synthesis of CuO-based trimetallic oxide mesocrystal superstructures for efficient catalytic production of trichlorosilane

Mesocrystals, the non-classical crystals with highly ordered nanoparticle superstructures, have shown great potential in many applications because of their newly collective properties. However, there is still a lack of a facile and general synthesis strategy to organize and integrate distinct components into complex mesocrystals, and of reported application for them in industrial catalytic reactions. Herein we report a general bottom-up synthesis of CuO-based trimetallic oxide mesocrystals (denoted as CuO-M1Ox-M2Oy, where M1 and M2 = Zn, In, Fe, Ni, Mn, and Co) using a simple precipitation method followed by a hydrothermal treatment and a topotactic transformation via calcination. When these mesocrystals were used as the catalyst to produce trichlorosilane (TCS) via Si hydrochlorination reaction, they exhibited excellent catalytic performance with much increased Si conversion and TCS selectivity. In particular, the TCS yield was increased 19-fold than that of the catalyst-free process. The latter is the current industrial process. The efficiently catalytic property of these mesocrystals is attributed to the formation of well-defined nanoscale heterointerfaces that can effectively facilitate the charge transfer, and the generation of the compressive and tensile strain on CuO near the interfaces among different metal oxides. The synthetic approach developed here could be applicable to fabricate versatile complicated metal oxide mesocrystals as novel catalysts for various industrial chemical reactions.

Variation of Surface Adhesion Force During the Formation of OTS Self-assembled Monolayer Investigated by AFM

Variation of the surface adhesion force during the formation of octadecyl trichlorosilane (OTS) self-assembled monolayer on a glass substrate surface was investigated by atomic force microscope (AFM). The research shows that the hydrophobicity and the adhesion force of the sample surface increases gradually while the substrate surface is covered by OTS molecules as the reaction proceeds. After 15min reaction, a close-packed and smooth OTS self-assembled monolayer could form on the glass substrate surface with an advancing contact angle of 105° and an interfacial energy of 55.79mJ·m-2.

Experimental Study on Hydrogenation of SiCl_4 to SiHCl_3 in a Stirred Bed Reactor

The hydrogenation of SiCl_4 to SiHCl_3 was studied in a stirred bed reactor with CuCl catalyst.The properties of the CuCl catalysts and silicon particles before and after the reaction were characterized by SEM,XRD and XPS.The XRD showed that the active component of Cu3Si was formed during the reaction,and the EDX proved the molar ratio of Cu and Si on the region of apertures.The valent of Cu was discussed by XPS before and after the hydrogen reaction.Then the effects of the reaction temperature,pressure,molar ratio of H2 to SiC l4,weight hourly space velocity(WHSV),and catalyst loading were studied.The results showed that the conversion rate of Si Cl4 was about 38%at WHSV of 190 Nm3/(t·h),temperature of 540℃,pressure of 1.8 MPa,catalyst loading of 0.9%(ω),and molar ratio of H2 to Si Cl4 1.7:1.Based on the experemental results,a reaction mechanism was proposed,which involved the continuous consumption of silicon(many apertures was showed on SEM image)and formation of new Cu3Si active component during the hydrogenation reaction.

Ab initio Calculation and Kinetic Study for the Abstraction Reaction of H with SiHCl_3

The mechanism of the reaction of H with SiHCl_3 has been investigated at highlevel of ab initio molecular orbital theory. Theoretical analysis provides a conclusive evidencethat the main process occurring in this reaction is the hydrogen abstraction from the Si―H bond,the abstraction of Cl has higher barrier and is difficult to react. The kinetics has been studiedusing canonical variational transition-state theory (CVT) with small curvature tunneling effect(SCT) correction. The rate constants have been calculated over a wide temperature range of 200―3000K. The CVT/SCT rate constants exhibit typical non-Arrhenius behavior, a three-parameterrate-temperature formula is fitted as follows; k( T) = (3.24 x 10^(-19)) T^(2.30) exp( - 250/T) [inunit of mL/(molecule·s). The calculated CVT/SCT rate constants match well with the experimentalvalues.