KR20040053678A - A Method for preparing methylchlorosilane by direct-synthetic process - Google Patents

Abstract

PURPOSE: A method for preparing methylchlorosilane by means of direct-synthetic process is provided, thereby improving productivity of dimethyldichlorosilane and trimethylchlorosilane which are useful components in industry, and removing a preparation process of contact mass of silica powder and copper. CONSTITUTION: The method for preparing methylchlorosilane comprises directly reacting silica powder with methane chloride using 1 to 5 parts by weight of copper per 100 parts by weight of silica powder as catalyst and 0.004 to 0.03 parts by weight of tartar, 0.014 to 0.042 parts by weight of phosphorous, and 0.05 to 0.3 parts by weight of zinc as co-catalyst, wherein the copper is a mixture of two compounds selected from CuCl, Cu2O, CuO, oxidized copper and copper metal; the tartar is copper-tartar alloy(bronze) or tartar powder; the phosphorous is copper-phosphorous alloy or Cu3P; and the zinc is selected from zinc powder, zinc chloride and zinc oxide.

Description

A method for preparing methylchlorosilane by direct-synthetic process

The present invention relates to a methylchlorosilane production method by a direct synthesis method, more specifically, powdered silicon (Si) and methane chloride (CH ₃ Cl) as a raw material, copper (Cu) as a catalyst, zinc By using (Zn), tin (Sn) and phosphorus (P) as cocatalysts, by restricting the composition ratio of the composition, the amount of dimethyldichlorosilane and trimethylchlorosilane, which are useful in industrial use, is increased, A method capable of reducing the amount of methyldichlorosilanes produced by the decomposition of methane. In addition, the present invention relates to a method for producing methylchlorosilane by a direct synthesis method with excellent reproducibility that can shorten the manufacturing process of the contact mass production of powder silicon and copper.

Known as an industrially used method for synthesizing methylchlorosilanes (hereinafter referred to as "MCS"), a typical method is a direct synthesis of Rochow, the direct synthesis method using copper as a catalyst as shown below And direct reaction of solid silicon and methane chloride [US Pat. No. 2,380,995].

The MCS is a generic expression for various monomers of silane, methyltrichlorosilane (hereinafter referred to as "M1"), dimethyldichlorosilane (hereinafter referred to as "M2"), trimethylchlorosilane (trimethylchlorosilane, (Hereinafter referred to as "M3"), methyldichlorosilane (hereinafter referred to as "MH"), silicon tetrachloride (hereinafter referred to as "STC"), and other residues (high boiling fraction, residue), etc. have.

Among the MCSs classified as above, M2 is the most commercially available material because M2 is a basic material capable of preparing a polymer of a polymer through hydrolysis, and various methods for increasing its production amount have been studied. Has the following:

First, Rochow [Rochow et., J. Am. Chem. Soc., 63, 798 (1941)], presented for the first time the use of zinc and tin as substances capable of improving the selectivity of M2, and later T. Margaria [T. Margaria et., WO / 95/01303, (1994) published the results of increasing the selectivity of M2 by using phosphorus. The main catalyst used in the direct method by Rochow is copper, and zinc, tin, and phosphorus are used as cocatalysts, and many results have been reported due to the reactivity and selectivity of MCS. U.S. Pat.No. 5,059,343 investigated the effect of phosphorus in direct reactions with copper, zinc, tin and phosphorus, and in addition, the selectivity of M2 using these catalysts and promoters in U.S. Patent 6,258,970 and U.S. Patent 6,423,860. The results of improving the are described.

However, there has been pointed out a problem of reproducibility in which the selectivity of MCS varies greatly depending on the impurity contained in the metal silicon used in the above technique, the amount of catalyst and promoter and the type of the reactor.

Therefore, the inventors of the present invention have made efforts to solve the above problems, using powdered silicon and methane chloride, using copper as a catalyst, by using zinc, tin and phosphorus as a promoter, by limiting the component ratio In particular, the selectivity of MCS can improve the selectivity of M2 and M3, and can eliminate the manufacturing process that can form an intermediate of powder silicon and copper. In addition, the component ratio of the catalyst and the cocatalyst according to the present invention is applied, and in particular, in the case of using a stirred fluidized bed reactor, even if the reaction conditions are changed by the continuous reaction and the batch reaction, the process is more reproducible in the selectivity of the MCS. Confirming the results appear to complete the present invention.

Accordingly, an object of the present invention is to provide a method for preparing methylchlorosilane by direct synthesis, which improves the selectivity and reproducibility of MCS by limiting the component ratio of catalyst and promoter.

The present invention is a method for producing methylchlorosilane by direct synthesis using powdered silicon and methane chloride (CH ₃ Cl), 1 to 5 parts by weight of copper as a catalyst and 100 parts by weight of copper as a catalyst, tin as a promoter A method for producing methylchlorosilane using a catalyst and a promoter comprising 0.004 to 0.03 parts by weight, phosphorus 0.014 to 0.042 parts by weight, and 0.05 to 0.3 parts by weight of zinc.

The present invention will be described in detail as follows.

The present invention improves the selectivity of M2 and M3 by using powdered silicon and methane as a raw material, using copper as a catalyst, and using zinc, tin, and phosphorus as cocatalysts, and limiting the compositional ratio thereof. The present invention relates to a method for producing methylchlorosilane having excellent reproducibility even when the reaction conditions are different, and a catalyst and a cocatalyst used therein, which can reduce the manufacturing process of the intermediate of powdered silicon and copper. .

Powdered silicon, which is a metal, was used as the main raw material, and an average powder size of 500 μm or less was used. It is preferable to use an average size of 10 to 300 μm, and a more preferable effect of using 100 to 200 μm. Can be obtained. As impurities contained in the powder silicon, the content of iron (Fe) is 0.1 to 0.5% by weight, the content of aluminum (Al) is 0.1 to 0.5% by weight, the content of calcium (Ca) is about 0.01 to 0.2% by weight, Purity is 98% or more, and the specific surface area of 1-10 m <2> / g can be used.

Copper used as the catalyst is a mixture of two selected from copper chloride (I) (CuCl), cuprous oxide (Cu ₂ O), cuprous oxide (CuO), paulownia (oxidized copper) and copper metal (copper metal) When the copper chloride (I) and copper oxide are mixed in a weight ratio of 1: 0.5 to 0.8, and copper chloride (I) and paulownia are mixed in a weight ratio of 4 to 10: 1, a more preferable effect can be obtained. The copper may be used in an amount of 1 to 5 parts by weight based on 100 parts by weight of powdered silicon, and when 2.5 to 3.5 parts by weight is used, a more preferable effect may be obtained. When the amount of use is less than 1 part by weight, the reactivity decreases and more than 5 parts by weight. When the yield of M2 is lowered, while the yield of M1 is increased.

The amount of zinc known as a methylating agent in the cocatalyst is 0.05 to 0.3 parts by weight based on 100 parts by weight of the powder silicon, and specifically zinc powder (Zn Powder) and zinc chloride which satisfy the above conditions. (Zn chloride) and zinc oxide (Zn oxide) can be used.

Tin may be bronze, tin powder, or the like having a copper-tin ratio of 80 to 90: 10 to 20, and 0.004 to 0.03 parts by weight based on 100 parts by weight of the silicon powder. When the weight part is used, more preferable effect can be obtained. If the tin is less than 0.004 parts by weight, the reactivity and the yield of M2 is drastically lowered, and if it is used in excess of 0.03 parts by weight, the residue is increased.

Phosphorus may be an alloy having a copper-phosphorus ratio of 86 to 93: 7 to 14, Cu ₃ P, or the like, and 0.014 to 0.042 parts by weight based on 100 parts by weight of the powder silicon, but 0.014 to 0.035 parts by weight. Desirable effects can be obtained. If the phosphorus is used less than 0.014 parts by weight, the yield of M2 is sharply lowered, and if it is used in excess of 0.042 parts by weight, MH is generated more than M3.

In the present invention, a stirred fluidized-bed reactor (hereinafter referred to as "FBR") was used as a reactor, and the reproducibility of the reaction results was observed while proceeding with a batch reaction and a continuous reaction, respectively. As the bed (Bed), only methane chloride was used by fluidizing.

The batch reaction is a method in which silicon, a catalyst, and a promoter are added to a reactor at the beginning of the reaction, and then reacted for at least 8 hours without additional input of raw materials, and a continuous reaction is performed after the silicon, a catalyst, and a promoter are added to the reactor at the beginning of the reaction. As the reaction proceeds, the silicon, the catalyst and the cocatalyst are added and reacted as much as the amount consumed in the same formulation as the initial blending. The reaction temperature is generally known to proceed at 250-350 ° C., and the reaction pressure is generally known to proceed at 1.1-3.5 atm. In the present invention, the results according to the reaction temperature and reaction pressure are excluded, and the catalyst and Attention was paid to the results according to the composition ratio of the cocatalyst composition.

In general, the contact mass of metal silicon and copper is prepared by mixing copper and metal silicon and reacting with methane chloride as a material which is made as a preliminary step in manufacturing MCS, but the present invention excludes the process of preparing the intermediate. It is possible to shorten the process, and unlike the conventional catalyst and the copper and cocatalyst was added separately, the reaction is characterized by mixing the copper and the cocatalyst as a catalyst and reacting with methane chloride. In addition, the powder silicon, catalyst and cocatalyst which are additionally added into the spent reactor during the MCS production reaction are prepared first, and then used without mixing. That is, according to the method of manufacturing MCS according to the present invention, it is possible to omit the intermediate manufacturing process, thereby producing an MCS by a simpler method.

MCS generated by the reaction is analyzed by using gas chromatograph (Gas Chromatograph, hereinafter referred to as "GC"). The generated MCS and methane chloride are analyzed immediately to calculate the reactivity, and then additionally added at an hourly interval. It was. Reactivity as well as selectivity of MCS were also measured using GC. The GC detector used was a thermal conductivity detector, and each MCS component was accurately measured by mass quantification using a standard reagent from Sigma or Aldrich. In the case of manufacturing MCS, since the STC is included in the material generated within the initial reaction time of about 30 minutes, it can be directly confirmed that the intermediate is formed in the initial reaction, and about 1 hour 30 after the reaction proceeds, The MCS is normally produced as the STC disappears.

Both batch and continuous reactions were based on values where the ratio of M1 to M2 (hereinafter T / D) was the lowest. The ratio of M1 to M2 (T / D) is used as a measure of the selectivity and is used as a basis for finding a compounding ratio for producing a small amount of M1. MH is known to be produced when methane chloride is cracked and carbon builds up on the surface of silicon, which increases with time and is produced during long-term operation. It is advantageous that the results are interpreted using the ratio of MH / M3.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

Example 1 MCS Selectivity by Changing Zinc Content and Continuous Reaction

The glass material has an inner diameter of 3 cm and a length of 30 cm, and the FBR with a glass distributor was used to support the inner bed at the bottom of the reactor. MCS was prepared by a continuous reaction.

100 parts by weight of powdered silicon was added to the bed, and the catalyst copper was mixed with copper chloride (CuCl) and paulownia in a weight ratio of 5: 1 by 2.5 parts by weight and 3.5 parts by weight, respectively. Was 200 μm, the specific surface area was 5 m 2 / g, and main impurities were 0.28 wt% iron, 0.18 wt% aluminum, and 0.13 wt% calcium. Zinc was used in an amount of 0.05 to 0.3 parts by weight, tin was used as a raw material of bronze having a copper-tin weight ratio of 90:10, and 0.008 parts by weight of tin and phosphorus was an alloy having a weight ratio of copper: phosphorus 86:14. 0.014 parts by weight of phosphorus was used as a raw material. The reaction rate of methane chloride was maintained at 282 g / h, the reaction temperature was 330 ℃, the reaction pressure was 1.2 atm, the reaction time was more than 8 hours.

Part of the unreacted methane chloride and the reaction product was passed through a reactor and passed through a freezer maintained at -18.5 ° C. The resulting MCS was collected in a separate container, and part of the MCS was passed through the GC every hour. The selectivity and reactivity of were measured, and the value when T / D was minimum was used as a reference for the analysis value. The results of the continuous reaction according to the zinc content are shown in Table 1 below.

Copper content (parts by weight) Zinc content (parts by weight) M2 (%) T / D ^*) MH / M3 Residue (%) 2.5 0.3 89.480 0.034 0.726 3.658 2.5 0.2 90.049 0.033 0.786 3.438 2.5 0.05 86.190 0.049 0.669 4.587 3.5 0.2 87.899 0.023 0.805 7.413 3.5 0.1 91.691 0.020 0.793 4.439 3.5 0.07 90.299 0.036 0.434 2.787 *) T / D: Methyltrichlorosilane / Dimethyldichlorosilane

As shown in Table 1, when the amount of copper used is 2.5 parts by weight, the highest selectivity of M2 is shown when the amount of zinc is 0.2 parts by weight, and when the amount of copper is 3.5 parts by weight, the content of zinc is 0.1 parts by weight. It can be seen that the negative indicates the highest selectivity of M2. The value of T / D shows a big difference depending on the selectivity of M1 to be produced. The value of T / D is lowest when the amount of copper used is 3.5 parts by weight and the content of zinc is 0.1 parts by weight.

When the amount of copper used is 3.5 parts by weight and the zinc content is 0.07 parts by weight, the ratio of MH / M3 is 0.43, indicating that the amount of MH produced is minimal.

Example 2 MCS Selectivity by Variation of Zinc Content and Batch Reaction

Using the same reactor as in Example 1, MCS was prepared by applying a batch reaction while changing the content of zinc. That is, 100 parts by weight of powdered silicon was added to the bed, and copper was used 2.5 parts by weight of copper chloride and cupric oxide (CuO) in a weight ratio of 1: 0.75, zinc was used in 0.05 to 0.2 parts by weight, and tin was copper-tin. 0.008 parts by weight of tin as a raw material, and phosphorus is 0.014 parts by weight of phosphorus as a raw material of an alloy having a weight ratio of copper: phosphorus of 86:14. During the reaction, the injection rate of methane chloride was maintained at 93 g / h, the reaction temperature was 330 ° C., the reaction pressure was 1.2 atm, and the reaction time was more than 8 hours. The results of the batch reaction according to the mass ratio of copper / zinc are shown in Table 2 below.

Zinc content (parts by weight) Reactivity (gMC / gSi.h) M2 (%) T / D ^*) MH / M3 Residue (%) 0.2 0.161 94.82 0.019 0.930 0.67 0.1 0.159 94.68 0.017 0.734 1.79 0.07 0.161 92.93 0.028 0.918 1.44 0.05 0.153 91.06 0.037 0.685 1.94 *) Same as Table 1 above

As shown in Table 2, when the zinc content is 0.1 to 0.2 parts by weight, it shows the highest selectivity of M2 and the value of T / D also shows the minimum value in the same range. As shown in Example 1, when the zinc content is 0.05 parts by weight, the ratio of MH / M3 is 0.685, which is the lowest value, indicating that the results are reproducible in the continuous reaction and the batch reaction. Reactivity is low when the zinc content is 0.05 parts by weight, but there is no significant difference when the zinc content is 0.05 parts by weight or more.

Example 3 MCS Selectivity by Changing Tin Content and Continuous Reaction

MCS was prepared by using the same reactor as Example 1 and applying a continuous reaction while varying the amount of tin used. That is, 100 parts by weight of powdered silicon is added to the bed, and copper is 2.5 parts by weight of copper chloride and paulownia having a weight ratio of 10: 1, and tin is an alloy having a weight ratio of copper-tin of 90: 10 by using powder silicon 100 The amount of tin was changed to 0.004, 0.008, 0.012, and 0.016 parts by weight, respectively. In addition, 0.14 parts by weight of zinc and 0.014 parts by weight of phosphorus were used as a raw material using an alloy having a weight ratio of copper to phosphorus of 86:14. The reaction rate of methane chloride was maintained at 282 g / h, the reaction temperature was 330 ℃, the reaction pressure was 1.2 atm, the reaction time was more than 8 hours. The results of the continuous reaction according to the amount of tin used are shown in Table 3 below.

Copper content (parts by weight) Tin content (parts by weight) M2 (%) T / D ^*) MH / M3 Residue (%) 2.5 0.004 88.30 0.045 0.821 2.38 2.5 0.008 90.275 0.029 0.876 3.752 2.5 0.012 92.17 0.023 0.543 3.22 2.5 0.016 92.379 0.021 0.271 3.721 *) Same as Table 1 above

As shown in Table 3, when the amount of tin used is 0.014 to 0.016 parts by weight, it shows a high selectivity for M2 as a whole, and at the same time it can be seen that the value of T / D is also low. Among them, when the amount of tin used is 0.004 parts by weight, the amount of residue is reduced, the selectivity of M2 is somewhat lower, and MH and M1 are increased, but when the amount of tin is 0.008 to 0.016 parts by weight, the ratio of MH / M3 becomes very small. , The value of T / D decreases, indicating that the selectivity of MH and M1 is significantly reduced.

Example 4 MCS Selectivity by Changing Tin Content and Batch Reaction

MCS was prepared by using the same reactor as Example 1 and applying a batch reaction while varying the amount of tin used. That is, 100 parts by weight of powdered silicon is added to the bed, copper is 2.5 parts by weight of copper chloride and cuprous oxide (CuO) having a weight ratio of 1: 0.75, and tin is an alloy having a weight ratio of copper: tin of 90:10. It was added while varying the amount of use to 0.004, 0.008, 0.016 and 0.03 parts by weight of tin, based on 100 parts by weight of powder silicon. In addition, 0.14 parts by weight of zinc and 0.014 parts by weight of phosphorus were used as a raw material using an alloy having a weight ratio of copper to phosphorus of 86:14. During the reaction, the injection rate of methane chloride was maintained at 93 g / h, the reaction temperature was 330 ° C., the reaction pressure was 1.2 atm, and the reaction time was more than 8 hours. The results of the batch reaction according to the amount of tin used are shown in Table 4 below.

Tin content (parts by weight) Reactivity (gMC / gSi.h) M2 (%) T / D ^*) MH / M3 Residue (%) 0.004 0.112 93.66 0.027 0.87 0.46 0.008 0.159 94.68 0.017 0.734 1.79 0.016 0.213 93.52 0.017 0.602 3.12 0.03 0.216 93.63 0.023 0.551 2.08 *) Same as Table 1 above

As shown in Table 4, it can be seen that when the amount of tin used is 0.004 to 0.03 parts by weight, it shows a high selectivity for M2, and when the amount of tin is used as in the continuous reaction of Example 3, In this case, since the ratio of MH / M3 becomes very small, it can be seen that the selectivity of M3 increases. T / D represents the smallest value when the amount of tin used is 0.008 to 0.016 parts by weight, and the amount of residue shows the smallest amount of production when the amount of tin is least, which is similar to the case of applying the continuous reaction as in Example 3 above. It can be seen that similar results are shown to produce reproducible results.

Example 5 MCS Selectivity by Changes in Phosphorus Content and Continuous Reaction

Using the same reactor as in Example 1, MCS was prepared by applying a continuous reaction method while varying the amount of phosphorus used. That is, 100 parts by weight of powdered silicon is added to the bed, copper is 2.5 parts by weight of copper chloride and paulownia having a weight ratio of 10: 1, 0.1 parts by weight of zinc, and 90% by weight of tin of copper-tin. An alloy containing 0.008 parts by weight of tin and phosphorus of copper-phosphorus of 86:14 was added with varying amounts of use of 0.014, 0.021, 0.028, and 0.035 parts by weight, respectively, of phosphorus. The reaction rate of methane chloride was maintained at 282 g / h, the reaction temperature was 330 ℃, the reaction pressure was 1.2 atm, the reaction time was more than 8 hours. The results of the continuous reaction according to the amount of phosphorus used are shown in Table 5 below.

Copper content (parts by weight) Phosphorus content (parts by weight) M2 (%) T / D ^*) MH / M3 Residue (%) 2.5 0.014 91.405 0.028 0.915 3.759 2.5 0.021 89.319 0.034 0.778 3.643 2.5 0.028 90.000 0.031 0.920 4.520 2.5 0.035 89.824 0.038 0.796 2.648 *) Same as Table 1 above

As shown in Table 5, when the amount of phosphorus used is 0.014 parts by weight, the T / D value shows the minimum value, indicating that the amount of M1 produced is reduced. In addition, when the amount of phosphorus used is 0.035 parts by weight, it can be seen that the amount of residue produced is small, and the influence of phosphorus on the selectivity of MH and M3 is not large.

Example 6 MCS Selectivity by Phosphorus Content Change and Batch Reaction

MCS was prepared by using the same reactor as Example 1 and applying a batch reaction method while varying the amount of phosphorus used. That is, 100 parts by weight of powdered silicon is added to the bed, and copper is used in the weight ratio of copper chloride and cupric oxide (CuO) of 1: 0.75, 2.5 parts by weight, zinc is 0.1 parts by weight, tin is the copper-tin weight ratio A 90:10 phosphorus alloy was added in an amount of 0.008 parts by weight as tin, and an alloy in which the weight ratio of copper-phosphorus was 86:14 was added with varying amounts of 0.014, 0.021, 0.028, and 0.042 parts by weight, respectively. During the reaction, the injection rate of methane chloride was maintained at 93 g / h, the reaction temperature was 330 ° C., the reaction pressure was 1.2 atm, and the reaction time was more than 8 hours. The results of the batch reaction according to the amount of phosphorus used are shown in Table 6 below.

Phosphorus content (parts by weight) Reactivity (gMC / gSi.h) M2 (%) T / D ^*) MH / M3 Residue (%) 0.014 0.159 94.68 0.017 0.7339 1.79 0.02 0.154 93.73 0.024 0.932 1.89 0.028 0.154 93.90 0.024 0.958 1.41 0.042 0.108 93.05 0.025 0.973 2.13 *) Same as Table 1 above

As shown in Table 6, it can be seen that when the amount of phosphorus used is 0.014 to 0.042 parts by weight, the selectivity for M2 is high, and thus T / D is also reduced. From the above results, it can be seen that the phosphorus of the amount of use greatly improves the selectivity of M1 while greatly improving the selectivity of M1.

As shown in Examples 1 to 6 above, by using a limited amount of promoters such as zinc, tin, phosphorus, etc., the selectivity to M2 and M3 is improved, and production of MH, M1, residues, etc. is suppressed. Formulations were found and the selectivity for each monomer can be adjusted based on the above results.

As described above, in the method for producing methylchlorosilane by direct synthesis using powdered silicon and methane as the main raw materials and applying copper as a catalyst, the amount of copper, a catalyst used, and zinc, tin and phosphorus as catalysts, and the amount thereof By limiting the ratio, the selectivity of the desired methylchlorosilane can be improved, and in particular, the composition and the amount of the catalyst and the cocatalyst which greatly improved the selectivity of the commercially useful dimethyldichlorosilane (M2) can be found.

In addition, the method of preparing methylchlorosilane by the direct synthesis method increases the content of hydrogen-containing silane, that is, methyldichlorosilane (MH) by decomposition of methane chloride according to the reaction time required. It was found that the composition and the amount of the catalyst and the promoter which can reduce the amount of produced and increase the amount of trimethylchlorosilane (M3).

That is, in the present invention, the composition and the amount of the catalyst and the promoter can be adjusted according to the kind of the desired product. For example, by applying the composition and the amount of the catalyst and the promoter which can maintain the T / D of 0.05 or less, The selectivity of M2 can be increased, and the composition and the amount of the catalyst and the promoter which can maintain the ratio of MH / M3 at 1 or less can be applied to reduce the amount of MH produced and to increase the amount of M3 produced.

Claims (6)

In the method for producing methylchlorosilane by direct synthesis using powdered silicon and methane chloride (CH ₃ Cl), The direct synthesis method is a catalyst and a bath containing 1 to 5 parts by weight of copper, 0.004 to 0.03 parts by weight of tin, 0.014 to 0.042 parts by weight of phosphorus and 0.05 to 0.3 parts by weight of zinc, based on 100 parts by weight of powder silicon as a catalyst. Method for producing methylchlorosilane, characterized in that using a catalyst. The method of claim 1, wherein the copper is selected from copper chloride (I) (CuCl), cuprous oxide (Cu ₂ O), cuprous oxide (CuO), paulownia (oxidized copper) and copper metal (copper metal) Method for producing methylchlorosilane, characterized in that a mixture of two kinds. The copper according to claim 2, wherein the copper is a mixture in which copper chloride (I) and copper oxide are in a weight ratio of 1: 0.5 to 0.8 or a mixture in which copper chloride (I) and paulownia is in a weight ratio of 4 to 10: 1. Methylchlorosilane Preparation Method. The method of claim 1, wherein the tin is a copper-tin alloy (Bronze) or tin powder. The method of claim 1, wherein the phosphorus is a copper-phosphorus alloy or Cu ₃ P. The method of claim 1, wherein the zinc is selected from zinc powder, zinc chloride, and zinc oxide.