TW201326043A - Utilization of low-boiling compounds in chlorosilane processes - Google Patents

Abstract

The invention provides a process for preparing trichlorosilane by reaction of metallurgical silicon and hydrogen chloride in a reactor at a temperature of 200 to 400 DEG C, which is characterized in that low-boiling by-products of the product gas are fed back into the reactor.

Description

Use of low boiling point compounds in chlorodecane process

This invention relates to a process for the use of unwanted secondary streams comprising low boiling by-products in a chlorodecane process.

First of all, the decane market has grown substantially, and furthermore, it is necessary to reduce waste as much as possible to improve competitiveness. Therefore, improving the process is the goal of industrial efforts.

In the present invention, the following abbreviations are used:

One of the industrially accepted methods for producing pure decane products (e.g., trichloromethane) after chlorodecane synthesis is distillation. Undesirable decane compounds having carbon or DCS result in lower product quality and, in the prior art, must be disposed of in many cases. In the present invention, this distillation stream having an undesired decane compound is also referred to as a "secondary stream".

The industrial distillation design usually consists of at least 3 columns connected in series, wherein the distillate secondary stream of ruthenium tetrachloride (57 ° C at a boiling point of 1013 mbar) is distilled with high boiling components (for example, A Trichloromethane (66 ° C boiling point at 1013 mbar), and oligononane, and additional trichloro Hydrane (32 ° C at 1013 mbar) and low boiling components (eg, methyl dichloromethane (42 ° C at 1013 mbar), and trichloromethane and dichloromethane (at 1013 mil) The boiling point of Ba is 8 ° C)) is removed together. The use of secondary flow has high potential.

WO 2007/101789 discloses the use of high boiling compounds, in particular dioxane and dioxane, in the production of chlorodecane by hydrochlorination in a fluidized bed reactor, in the deposition of polycrystalline germanium, in distillation and in chlorodecane. Formed by semi-hydrolysis purification.

Understanding high boiling compounds refers to molecules composed of ruthenium, chlorine, and any hydrogen, oxygen, and carbon having a boiling point higher than tetrachloromethane (57 ° C at 1013 mbar).

WO 2009/029794 discloses an improved process utilizing synthetic dichloromethane by-products by means of catalytic disproportionation by means of an ion exchanger. However, the improved results of the process have not been revealed. However, those skilled in the art believe that the process is complicated by the complex disproportionation balance of the system.

Accordingly, it is an object of the present invention to provide an improved and simple process which uses a secondary stream comprising a low boiling point compound and slightly alters the fluidized bed, moving bed or fixed bed in which trichloromethane is produced according to the prior art. Ultra-pure method for hydrochlorination.

In the present invention, it is understood that a low boiling point means a substance or a mixture of substances containing a compound of ruthenium and chlorine having a boiling point lower than that of tetrachloromethane (57 ° C at 1013 mbar). These substances or mixtures also contain hydrazine and chlorine, hydrogen, oxygen and/or A compound of carbon.

Surprisingly, it has been found that when a secondary stream comprising a low boiling point compound and a metallurgical crucible are returned to the hydrochlorination reactor at 200 to 400 ° C, a secondary stream comprising low boiling by-products can be utilized. This decomposes the low boiling by-products into more desirable or desirable compounds in the process technology. Surprisingly, the trichloromethane present in the secondary stream is also almost unconverted, if any, to a negligible or as small as TCS conversion. This hydrochlorination reaction is hardly affected.

Accordingly, the present invention provides a process for producing trichloromethane by reacting metallurgical hydrazine with hydrogen chloride in a reactor at a temperature of from 200 to 400 ° C, characterized in that the low-boiling by-product of the product gas is returned to the reactor.

An advantage of the process according to the invention is that, due to the decomposition of the low-boiling by-products, there is no secondary flow, or a smaller amount, which occurs in the process and thus achieves a higher yield of the product of the chloroform.

The invention is described in detail below.

The low boiling by-products of the product stream can be returned to the reactor in part or in whole.

The secondary stream obtained by distillation of the reactor product gas comprises TCS and DCS or a mixture of TCS and MHDCS. Other low boiling compounds may also be present.

The secondary stream can be added to the gas-solid chlorination in vapor form or in liquid form. The device. TCS/DCS can, like TCS/MHDCS, be discharged from the column in vapor form. The by-product of the liquid starting form can also be supplied in the form of a vapor by evaporation in the HCl stream or by means of a thermal evaporator. However, due to the strong exothermic nature of the hydrochlorination reaction, a liquid that is sufficiently vapor-distributed can be added directly to the hot solid or thermal reactor location.

In the process according to the invention, the reactor used may be a fluidized bed reactor or a vibrating fluidized reactor. These reactors achieve high heat transfer in the solid bed to control the intense exothermic reaction. Also preferred are fixed bed reactors having a low reactor diameter wherein the fixed bed reactor is efficiently temperature controlled.

During the passage through the reactor, a portion of the desired low boiling point compound is converted to the product of the target of trichloromethane and the high boiling point compound (e.g., methyltrichloromethane).

In the distillation of the chlorodecane after the reaction, the low boiling MHDCS and/or DCS compound is removed from the product mixture. These low boiling by-products are then returned to the reactor. These may preferably be DCS, further preferably MHDCS, or a mixture of MHDCS and DCS. The low boilers that have been converted to high boiling compounds are finally discharged in a secondary stream with high boiling by-products.

Instance

In the following examples of the invention, a low boiling secondary stream added to a hydrochlorinated fluidized bed was examined in a glass reactor equipped with a 4 cm diameter glass frit.

In all of the examples, 200 grams of 98% pure metallurgical crucible having a particle size of 150 to 250 microns was applied over the glass frit. Provided by Bronkhorst The mass flow regulator was injected with each gas at a volume flow rate of 60 standard liters/hour, whereby the hydrogen chloride reactant gas was diluted with argon.

The intense exothermic reaction was adjusted by heating and cooling zones to a typical selected temperature of 320 °C.

The discharged product gas is filtered and analyzed by a gas chromatograph connected by a wire. The reaction conditions in the examples of the present invention are the same.

The results of the examples and comparative examples of the present invention are summarized in Table 1. The conversion rate is described by the following chemical index.

The abbreviations represent:

Comparative example: Hydrochlorination without recycle of by-products

To compare with the pure hydrochlorination reaction, the hydrochlorination reaction was first determined without adding by-products (refer to Table 1). When the HCl conversion is 99%, hydrogen chloride reacts with metallurgical oxime at a high selectivity of about 90% to form trichloromethane, abbreviated as TCS. Otherwise, ruthenium tetrachloride is formed substantially.

Example 1: Hydrochlorination with MHDCS at 10% by volume

As in the comparative example, a secondary stream of low boiling point was added to the reactant gas, i.e., an additional 10% by volume of reactant gas, a TCS:MHDCS mixture having a molar ratio of 99:1. The low boilers are added in the form of a vapor.

In the experiment, about 25% of the unwanted low boilers MHDCS were converted to high boiling MTCS. Based on negligible TCS conversion and maintaining a high selectivity of HCl for TCS, it was found that the value of the TCS species was completely retained and that the hydrochlorination reaction did not adversely affect the process according to the invention.

Example 2: Hydrochlorination with DCS at 10% by volume

As in the comparative example, a 10% by volume low boiling TCS:DCS secondary stream was added to the reactant gas at a molar ratio of 99:1. The low boilers are added in the form of a vapor.

84% of the unwanted DCS components were converted to TCS or STC. Based on negligible TCS conversion and maintaining a high selectivity of HCl for TCS, it was also found that retention of the desired TCS product and hydrochlorination did not adversely affect the process according to the invention.

Claims (3)

A process for producing trichloromethane by reacting metallurgical ruthenium with hydrogen chloride in a reactor at a temperature of from 200 to 400 ° C, characterized in that the low-boiling by-product of the product gas is returned to the reactor. The method of claim 1, wherein the reactor used is a fluidized bed reactor or a vibrating fluidized reactor. The method of claim 1, wherein the low-boiling by-products DCS and/or MHDCS are present.