Methods and apparatus for synthesizing compounds by a low temperature plasma dual-electric field aided gas phase reaction

Abstract

Method and apparatus for synthesizing compounds by a low temperature plasma dual-electric field aided gas phase reaction are provided. The method utilizes two different electrode corona discharge fields in a plasma aided reactor to form a plasma dual-electric field, using electric energy to convert gas into gas molecules, atoms, ions and/or free radicals, and then reforming and reducing to obtain organic compounds such as aliphatic hydrocarbons, higher carbon ethers, higher carbon alcohols, higher carbon esters, lower carbon alcohols, and the like; also inorganic compounds such as N.sub.2, O.sub.2, H.sub.2SO.sub.4, NH.sub.3, and the like. The apparatus includes a reactor having a plasma region of two different corona discharge fields, wherein an alternating current corona discharge field or a positive corona discharge field is set in the first electric field, and a negative corona discharge field is set in the second electric field.

Claims

1. A method for the plasma dual-electric field aided gas phase reactions, comprising: generating a first electric field that is an alternating current corona discharge field or a positive corona discharge field; generating a second electric field that is a negative corona discharge field; passing a reaction gas stream successively through the first electric field and the second electric field to form a product gas stream, wherein the first electric field and the second electric field are disposed in a reactor, and wherein the reaction gas stream comprises one or more compounds chosen from CH.sub.4, CO, H.sub.2, H.sub.2S, or NO, and one or more compounds chosen from CO.sub.2, O.sub.2, H.sub.2O, SO.sub.2, or NO.sub.2, and the product gas stream comprises one or more compounds chosen from aliphatic hydrocarbons, ethers, alcohols, H.sub.2SO.sub.4, or N.sub.2.

2. The method according to claim 1, wherein the positive corona discharge field is a high voltage positive direct current corona discharge field, and the negative corona discharge field is a high voltage negative direct current corona discharge field.

3. The method according to claim 1, further comprising adjusting an intensity of the first electric field, an intensity of the second electric field, or both to cause a change in a composition of the product gas stream.

4. The method according to claim 3, wherein adjusting the intensity of the first electric field is by adjusting a voltage of the first electric field, and adjust the intensity of the second electric field is by adjusting a voltage of the second electric field.

5. A dual-electric field apparatus, comprising: a housing having an inlet and an outlet, at least a first reaction chamber and a second reaction chamber disposed in the housing, wherein during operation, a reaction gas stream successively passes through the first reaction chamber and the second reaction chamber to form a product gas stream, wherein the first reaction chamber comprises a first electrode disposed inside the first reaction chamber and away from a wall of the first reaction chamber, a first insulating medium layer disposed between the first electrode and the wall of the first reaction chamber, wherein the first electrode is connected to an alternating current or a positive voltage source and the wall of the first reaction chamber is grounded, wherein the second reaction chamber comprises a second electrode disposed inside the second reaction chamber and away from a wall of the second reaction chamber, a second insulating medium layer disposed between the first electrode and the wall of the second reaction chamber, wherein the second electrode is connected to a negative voltage source and the wall of the second reaction chamber is grounded.

6. The apparatus according to claim 5, wherein, when energized, the first reaction chamber contains a first electric field between the first electrode and the wall of the first reaction chamber, and the second reaction chamber contains a second electric field.

7. The apparatus according to claim 5, wherein the first electric field is an alternating current corona discharge field or a positive corona discharge field, and the second electric filed is a negative corona discharge field.

8. The apparatus according to claim 7, wherein the first reaction chamber or the second reaction chamber has a tubular wall, and wherein the first electrode or the second electrode is a metal rod.

9. The apparatus according to claim 8, wherein the first insulating medium layer or the second insulating medium layer has a tubular shape, and is made of a material chosen from glass, ceramic, silica gel, wood, or bamboo.

10. The apparatus according to claim 8, comprising more than two reaction chambers.

11. The apparatus according to claim 5, further comprising a sensor installed in an intake line connected to the inlet for measuring a concentration of methane gas and oxygen in a fluid flowing into the inlet.

12. The apparatus according to claim 5, further comprising a condensing separator connected to the outlet for separating a fluid from the outlet into a gas stream and a liquid stream.

13. A method for preparing organic compounds, comprising: energizing the dual electric field apparatus of claim 5 to generate the first electric field in the first reaction chamber and to generate the second electric filed in the second reaction chamber; feeding a reaction gas stream into the inlet of the dual electric field apparatus; and obtaining a product gas stream from the outlet of the dual electric field apparatus, wherein the reaction gas stream comprises one or more compounds chosen from chosen from CH.sub.4, CO.sub.2, CO, O.sub.2, H.sub.2O or H.sub.2, and the product gas stream comprises one or more compounds chosen from aliphatic hydrocarbons, ethers, or alcohols.

14. A method for purifying a gas stream, comprising: energizing the dual electric field apparatus of claim 5 to generate the first electric field in the first reaction chamber and to generate the second electric filed in the second reaction chamber; feeding the gas stream into the inlet of the dual electric field apparatus; and obtaining a purified gas stream from the outlet of the dual electric field apparatus, wherein the reaction gas stream comprises one or more compounds chosen from SO.sub.2, H.sub.2S, NO, NO.sub.2, or CO, and the product gas stream comprises one or more compounds chosen from H.sub.2SO.sub.4, N.sub.2, or CO.sub.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view showing a specific configuration of an apparatus for plasma aided gas phase reaction according to the present disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(2) The disclosure will now be further described with reference to specific embodiments. It should be understood that these examples are merely illustrative of the disclosure and are not intended to limit the scope of the disclosure. In addition, it should be understood that various changes and modifications may be made to the present disclosure after reading the teachings of the present disclosure, which also fall within the scope of the disclosure.

(3) The term “gas” as used in the present specification and claims refers to gases in which atoms or molecules are capable of capturing additional electrons to form electronegative ions. Other technical and scientific terms in this specification have the general meaning known in the art.

(4) An example of the present disclosure which provides alternating current corona discharge field or positive corona discharge field by using an electrode is described below. It should be understood that the present disclosure is not limited thereto and if the electrode is capable of generating a plasma discharge in a sufficiently high energy state to generate electrons, it can also be used in the present disclosure.

(5) FIG. 1 is a schematic view showing a specific configuration of an apparatus for plasma aided gas phase reaction according to the present disclosure. In the corona discharge dual-electric field, the reaction gas preferentially passes through a high frequency alternating current corona discharge field or a high frequency high voltage positive direct current corona discharge field, and is converted into positive ions and free radicals in the electric field, and then passes through a high frequency high voltage negative direct current corona discharge field, and is reduced and converted into a product in the electric field.

(6) In one embodiment of the apparatus of the present disclosure, the reactor has a corona discharge dual-electric field, i.e., a high frequency alternating current corona discharge field or a high frequency high voltage positive direct current corona discharge field and a high frequency high voltage negative direct current corona discharge field. The voltage is a high voltage, for example, 15,000 volts. The high frequency is a high frequency voltage, for example, 25 kHz. In the reactor, there is an electrode or an anode in the region of the high frequency alternating current corona discharge field or the high frequency high voltage positive direct current corona discharge field, and an electrode or cathode in the region of the high frequency high voltage negative direct current corona discharge field. The two corona discharge fields can provide a sufficiently high energy, for example 5 eV, to convert the gas molecules. Apparatus 117 has an outer housing that can be made of carbon steel, stainless steel or other suitable materials.

(7) Two cylinder or tubular reaction chambers 111 and 118 are disposed within the apparatus 117 formed by the outer housing, wherein the material of the cylindrical or tubular reaction chamber may be made of stainless steel, carbon steel or copper and other metals. The center of each cylindrical or tubular reaction chamber is provided with center electrodes 112 and 116, which are needle-like or saw tooth rod electrodes with tips. The center electrode 116 in the first electric field applies a high frequency positive direct current voltage (or alternating current) to generate a high frequency high voltage positive direct current corona discharge field (or high frequency alternating current corona discharge field). A high frequency negative direct current voltage is applied to the center electrode 112 in the second electric field to generate a high frequency high voltage negative direct current corona discharge field. The voltage (strength) is selected to satisfy the condition that the gas delivered to the apparatus can be highly ionized in the metal cylindrical or metal tubular reaction chambers 111 and 118.

(8) An insulating medium tube 122 is disposed between the center electrode and the cylinder to form a dielectric barrier discharge (DBD) in the electric field, and provide a narrow collision reaction zone to enhance the decomposition of all molecules into free radicals or ions, thereby forming product molecules, enhancing the electric field strength of the plasma-aided reaction process. The material of the insulating medium tube 122 is, for example, glass, ceramic, silicone, polytetrafluoroethylene sheet or the like.

(9) The electrode material of the center electrodes 112 and 116 may be nickel, iron, steel, tungsten, copper, silver, carbon or platinum, or any other material that can be used for the electrodes and generates corona around the electrodes to generate electrons. The electrode can also be coated with a metal catalyst. Available precious metal catalysts are: gold, nickel, ruthenium, cobalt, ruthenium and platinum. Any precious metal catalyst capable of generating electrons can be used.

(10) During operation, when the center electrode 116 is energized by an alternating current corona discharge field or a positive corona discharge field source, a positive corona is generated at the tip end of the center electrode 116 to generate a positive corona field discharge, and high energy electrons hit the gas molecules. If an insulating medium tube 122 is added, a DBD can be formed to enhance the electric field strength to enhance the oxidation reaction. When the center electrode 112 is energized by the negative corona discharge field source, a negative corona is generated at the tip end of the center electrode 112 to generate a negative corona field discharge, mainly for the reduction and reforming reaction.

(11) The high voltage electricity is supplied to the center electrodes 112 and 116 through the cable electrode distribution plates 115 and 123 for discharge. The two cylindrical or tubular reaction chambers 111 and 118 are connected to the counter electrodes 120 and 121, respectively. The outer housing of the apparatus 117 is connected to the ground.

(12) Gas filters 127, 128 and 129 are provided at the opening 113 at the bottom of the apparatus, the opening 110 at the top of the apparatus, and the junction of the two electric fields, respectively, which can be used for a gas filter having the function of adsorbing harmful chemicals and particles.

(13) The gas mixture is fed into the corona discharge dual-electric field in the apparatus through the opening 113 at the bottom of the apparatus. Some gas molecules can receive the discharged electrons for oxidation and reforming in a high frequency alternating current corona discharge field or a high frequency high voltage positive direct current corona discharge field. In the high frequency high voltage negative direct current corona discharge field, the gas oxide or ions can be reduced and converted again. The product is removed through the opening 110 at the top of the apparatus and is vapor-liquid separated by a condenser 133 where liquid can be discharged through port 125 and gas can be discharged through port 124.

(14) In a preferred embodiment of the present application, the center electrode 116 is connected to the positive electrode of the positive corona discharge field source, and the counter electrode 120 opposite to the center electrode 116 is disposed on the outer wall of the reaction chamber and connected to the negative electrode of the positive corona discharge field source, generating a strong positive electric field within the positive corona discharge field. The center electrode 112 is connected to the negative electrode of the negative corona discharge field source, and the counter electrode 121 opposite to the center electrode 112 is disposed on the outer wall of the reaction chamber and connected to the positive electrode of the negative corona discharge field source, generating a strong negative electric field within the negative corona discharge field.

(15) In a preferred embodiment of the present application, the center electrode 116 is connected to the positive electrode of the positive corona discharge field source, and the counter electrode 120 is grounded, generating a weak positive electric field within the positive corona discharge field. The center electrode 112 is connected to the negative electrode of the negative corona discharge field source, and the counter electrode 121 is grounded, generating a weak negative electric field within the negative corona discharge field.

(16) With the above apparatus, the gas of different sources can be reformed, and according to the strength of the electric field, for example, organic compounds such as aliphatic hydrocarbons, higher carbon ethers, higher carbon alcohols, higher carbon esters, and the like, and inorganic compounds such as N.sub.2, O.sub.2, H.sub.2SO.sub.4, NH.sub.3, and the like are produced in a strong electric field, for example, lower carbon alcohols are produced in a weak electric field.

(17) In a preferred embodiment of the present application, the flue gas (which is composed of nitrogen, carbon oxides (such as carbon dioxide, carbon monoxide), oxygen, water vapor, nitrogen oxides (such as nitrogen monoxide, nitrogen dioxide) and sulfides (such as hydrogen sulfide, sulfur dioxide), inorganic pollutants, and the like, accounted for more than 99%, and the contents of dust, powder and sulfur dioxide being less than 1%) and water vapor are introduced into the above apparatus. In the apparatus, the center electrode 116 is connected to the positive electrode of the alternating current corona discharge field or the positive corona discharge field source, and the counter electrode 120 is grounded, generating a weak positive electric field in the alternating current corona discharge field or the positive corona discharge field. The center electrode 112 is connected to the negative electrode of the negative corona discharge field source, and the counter electrode 121 is grounded, generating a weak negative electric field in the negative corona discharge field.

(18) Specifically, high energy electrons are provided by passing through an alternating current corona discharge field or a positive corona discharge field first, then a negative corona discharge field to carry out gas reactions. In the region of the alternating current corona discharge field or positive corona discharge field, high energy electrons or high energy positive charges are provided to decompose gas molecules, which can be activated to undergo decomposition and oxidation reactions to generate various components. Specifically, mainly in the alternating current electric discharge field or positive electric discharge field, electrons are collided with H.sub.2O steam to generate OH and H atoms or H.sub.2, CO.sub.2 reacts with electrons to generate CO and O.sub.2.sup.−, sulfide SO.sub.2 with electrons reacts with H.sub.2O and oxygen O.sub.2 to produce H.sub.2SO.sub.4 sulfuric acid liquid, nitrogen oxides NO.sub.x are decomposed with electrons, and may form N and O radicals; in the second subsequent negative corona discharge field, the electric cathode with high negative potential conducts corona discharge to release electrons, and CO and H.sub.2 gas molecules capture these high energy electrons to form high energy electronegative gas ions, for example to form negative ions such as H.sup.−, CO.sup.− or H.sup.− etc., and these negative ions will be reformed and reduced to form ethanol and methanol, so as to achieve the minimum system energy. Moreover, N and O radicals generate N.sub.2 and O.sub.2.sup.−. The specific reactions are as follows: carbon oxides, nitrogen oxides and sulfides in the flue gas may undergo but are not limited thereto the following main reactions with the added water vapor, as well as the oxygen contained in the flue gas in the alternating current or positive corona discharge field:
CO+H.sub.2O+e.sup.−====>CO.sub.2+H.sub.2.sup.−
2CO.sub.2+e.sup.−====>2CO+O.sub.2.sup.−
2SO.sub.2+2H.sub.2O+3O.sub.2+2e.sup.−2e.sup.−====>2H.sub.2SO.sub.4+2O.sub.2.sup.−
NO.sub.x+e.sup.−====>+N.+xO.+e.sup.−
2H.sub.2S+3O.sub.2+e.sup.−====>2SO.sub.2H.sub.2O+e.sup.−

(19) In the subsequent negative corona discharge field, the main chemical reaction process is that carbon monoxide and charged hydrogen negative ion will spontaneously synthesize ethanol and methanol, and release negative oxygen ions:
H.sub.2+2e.sup.−====>2H.sup.−<===>H.sub.2.sup.−
4CO+6H.sub.2.sup.−==2C.sub.2H.sub.5(OH)+O.sub.2.sup.−+5e.sup.−
CO+2H.sub.2.sup.−==>CH.sub.3(OH)+2e.sup.−
2N.+2O.+e.sup.−====>N.sub.2+O.sub.2.sup.−

(20) According to the above principle, the apparatus of the present disclosure can purify and recycle industrial exhaust gas including the above flue gas, for example refinery waste gas, automobile or internal combustion engine exhaust gas, and coke oven gas, water gas and syngas do not need any other additional reaction gas because of the hydrogen source contained therein, the dual-electric field apparatus of the disclosure utilizes a hydrogen source to convert CO and CO.sub.2 into organic or inorganic compound, to convert nitrogen oxides into an inert gas, and to convert sulfide into easily separated or easily removed sulfuric acid droplets, which can clean and purify the environment, as well as turn waste into treasure.

(21) In a preferred embodiment of the present application, the water gas and/or syngas (which is composed of CO.sub.2 of 5%, H.sub.2 of 50%, CO of 40%, N.sub.2 of 5%) specifically react(s) in the dual-electric field (the center electrode 116 is connected to the positive electrode of the alternating current corona discharge field or the positive corona discharge field source, and the counter electrode 120 is grounded, generating a weak positive electric field in the alternating current corona discharge field or the positive corona discharge field. The center electrode 112 is connected to the negative electrode of the negative corona discharge field source, and the counter electrode 121 is grounded, generating a weak negative electric field in the negative corona discharge field) of the present disclosure as follows: CO.sub.2 therein will undergo the following main reaction in the alternating current or positive corona field:
2CO.sub.2+e.sup.−====>2CO+O.sub.2.sup.−

(22) In the negative corona discharge field, carbon monoxide and charged hydrogen negative ion will spontaneously synthesize ethanol and methanol, and release negative oxygen ions:
H.sub.2+2e.sup.−====>2H.sup.−<===>H.sub.2.sup.−
4CO+6H.sub.2.sup.−====>2C.sub.2H.sub.5OH+O.sub.2.sup.−+5e.sup.−
CO+2H.sub.2.sup.−====>CH.sub.3(OH)+2e.sup.−

(23) In a preferred embodiment of the present application, the apparatus of the present disclosure not only can reform an exhaust gas such as flue gas, but also can reform a main source of carbonaceous energy containing CH.sub.4, such as coal-bed gas. Methane in the coal-bed gas may undergo but not limited thereto the following main reactions with the added water vapor, as well as the oxygen contained in the coal-bed gas in the alternating current or positive corona discharge field:
CH.sub.4+H.sub.2O+3e.sup.−====>CO+3H.sub.2.sup.−
CH.sub.4+½O.sub.2+2e.sup.−====>CO+2H.sub.2.sup.−
CO+H.sub.2O+e.sup.−====>CO.sub.2+H.sub.2.sup.−
2CO.sub.2+e.sup.−====>2CO+O.sub.2.sup.−

(24) In the subsequent negative corona discharge field, the main chemical reaction process is the same as those of the above flue gas, i.e., carbon monoxide and charged hydrogen negative ion will spontaneously synthesize ethanol and methanol, and release negative oxygen ions.
H.sub.2+2e.sup.−====>2H.sup.−<===>H.sub.2.sup.−
4CO+6H.sub.2.sup.−==>2C.sub.2H.sub.5(OH)+O.sub.2.sup.−+5e.sup.−
CO+2H.sub.2.sup.−==>CH.sub.3(OH)+2e.sup.−

(25) According to the above principle, the apparatus of the present disclosure can reform and purify any gas source containing a carbon source. The main component CH.sub.4 in the gases, such as coalbed gas, refining gas, shale gas, biogas, etc. is reformed, biogas does not require the addition of other gas reactants, since as the main components, methane and CO.sub.2 can be reformed in the dual-electric field.

(26) In a preferred embodiment of the present application, the shale gas mainly reacts with O.sub.2 or CO.sub.2 in the alternating current or positive corona field as follows:
CH.sub.4+½O.sub.2+2e.sup.−====>CO+2H.sub.2.sup.−
CH.sub.4+CO.sub.2+2e.sup.−====>2CO+2H.sub.2.sup.−

(27) In the negative corona discharge field, the main chemical reaction process is that carbon monoxide and charged hydrogen negative ion will spontaneously synthesize ethanol and methanol, and release negative oxygen ions:
H.sub.2+2e.sup.−====>2H.sup.−<===>H.sub.2.sup.−
4CO+6H.sub.2.sup.−==>2C.sub.2H.sub.5(OH)+O.sub.2.sup.−+5e.sup.−
CO+2H.sub.2.sup.−==>CH.sub.3(OH)+2e.sup.−

(28) In a preferred embodiment of the present application, methane and CO.sub.2, as the main components of the biogas, mainly react in the alternating current or positive corona discharge field as follows:
CH.sub.4+CO.sub.2+2e.sup.−====>2CO+2H.sub.2.sup.−

(29) In the negative corona discharge field, the main chemical reaction process is that carbon monoxide and charged hydrogen negative ion will spontaneously synthesize ethanol and methanol, and release negative oxygen ions:
H.sub.2+2e.sup.−====>2H.sup.−<===>H.sub.2.sup.−
4CO+6H.sub.2.sup.−==>2C.sub.2H.sub.5(OH)+O.sub.2.sup.−+5e.sup.−
CO+2H.sub.2.sup.−==>CH.sub.3(OH)+2e.sup.−

(30) Accordingly, when the dual-electric field in the plasma gas conversion apparatus provided by the present disclosure is a weak electric field, it can be used to prepare ethanol and/or methanol. Specifically, the apparatus converts a carbon source-containing gas, for example, CH.sub.4 and/or CO, CO.sub.2, and the like, into ethanol and methanol. The positive-negative corona dual-electric field or the alternating current-negative corona dual-electric field apparatuses of the present disclosure can be arranged in series, and the unreacted CH.sub.4 or CO, CO.sub.2 in the product mixture can be passed to the next dual-electric field apparatus, optionally with the addition of additional water vapor or hydrogen to further convert the reaction gas to the final product. Such a cyclic conversion can achieve a very high gas conversion rate. For example, methane is reformed with the above-described dual-electric field apparatus of the present disclosure. In the alternating current corona discharge field or positive corona discharge field, the conversion ratio of methane to syngas i.e., CO and H.sub.2 can reach 45%, and in the subsequent second electric field of the negative corona discharge field, syngas can be converted to ethanol in a conversion ratio of up to 90% or more. If four reactors are used in series, the conversion of methane can reach 95% or more.

(31) When the dual-electric field in the plasma gas conversion apparatus provided by the present disclosure is a strong electric field, it can be used for preparing organic compounds such as aliphatic hydrocarbons, higher carbon ethers, higher carbon alcohols, higher carbon esters, and inorganic compounds such as N.sub.2, O.sub.2, H.sub.2SO.sub.4, NH.sub.3, and the like.

(32) In a preferred embodiment of the present application, CO and water vapor are introduced into the aforesaid apparatus, wherein in the reaction chamber 118, the center electrode 116 is connected to the positive electrode of the positive corona discharge field source, and the counter electrode 120 is connected to the negative electrode of the positive corona discharge field source, generating a strong positive electric field in the positive corona discharge field. In the reaction chamber 111, the center electrode 112 is connected to the negative electrode of the negative corona discharge field source, and the counter electrode 121 is connected to the positive electrode of the negative corona discharge field source, generating a strong negative electric field in the negative corona discharge field. At this time, the main components into which CO and water vapor are reformed in the reactor are C.sub.7-C.sub.20 organic compounds, and the main components include heptane, diethyl phthalate, diisooctyl phthalate and the like.

(33) In a preferred embodiment of the present application, the aforesaid center electrode 112 is a stainless steel electrode, and the counter electrode 121 of the outer wall of the reaction chamber 111 is connected to the positive electrode of the power supply. Inside the steel pipe between the positive electrode and the negative electrode, a silicone tube abutting against the inner wall of the reaction chamber 111 and a thin glass tube covering the stainless steel negative electrode (center electrode 112) are inserted as an insulating medium tube. Between the two medium tubes, titanium dioxide particles are filled as a third layer of insulating medium to form a dielectric barrier structure of the slit sandwich. In such a reactor, reactions are carried out to produce C.sub.3-C.sub.20 organic compounds, and the main components include propane, methyl benzyl alcohol, hexadecane, octadecane, and the like.

(34) The embodiments of the present disclosure have been described above. However, the present disclosure is not limited to the above-described embodiments. Any modifications, equivalent substitutions, improvements, and the like within the spirit and principles of the disclosure are intended to be included within the scope of the present disclosure.