Anti-sulfide poisoning MEMS catalytic methane sensor and preparation method thereof

Abstract

The invention relates to the technical field of MEMS sensors, and discloses an MEMS catalytic methane sensor capable of resisting sulfide poisoning and a preparation method of the MEMS catalytic methane sensor. The preparation method comprises the following steps: S1, carrying out a synthetic reaction on a main body material and a modified material to obtain a carrier material primary product; washing and drying the primary product of the carrier material, and carrying out heat treatment to finally obtain the carrier material; s2, dissolving a catalyst A and a catalyst B in pure water, performing stirring treatment, then adding the carrier material prepared in the step S1, performing ultrasonic oscillation dispersion under a room temperature condition, firstly transferring obtained powder into a muffle furnace, performing heat treatment, and then transferring the powder into a tubular furnace to prepare modified carrier powder; s3, preparing black element slurry, white element slurry and catalyst slurry; and S4, preparing the MEMS catalytic methane element. The sulfide poisoning resistant MEMS catalytic methane sensor prepared by the invention is suitable for a plurality of fields of coal mines, industry, civil use and the like, has wide applicability, and can better improve the low-temperature combustion and sulfide poisoning resistance of methane.

Description

Technical Field

[0001] The invention relates to the technical field of MEMS sensors, in particular to a MEMS catalytic methane sensor resistant to sulfide poisoning and a preparation method thereof. Background Art

[0002] In the process of coal mining, in order to ensure the safety of the operation, it is often necessary to detect the concentration of various alkane gases, and catalytic combustion sensors are often used at this time. Traditional catalytic combustion sensors include detection elements and compensation elements. The detection elements and compensation elements constitute a measuring bridge. The combustible gas catalytically burns under the action of the detection element carrier and the catalyst, releasing heat, and the resistance value of the sensitive element inside increases, the bridge is unbalanced, and the output is an electrical signal proportional to the concentration of the combustible gas.

[0003] However, traditional catalytic combustion sensors mostly use the traditional manual winding method, which has the disadvantages of large size, high operating temperature, high power consumption, poor process consistency, etc. The catalyst usually uses a Pd-based precious metal catalyst. When the concentration of alkane gases such as methane is detected in the underground environment of coal mines, it is easy to cause catalytic combustion sensors to be poisoned. The specific reasons for sensor poisoning are: sulfur is a common toxic substance underground, containing sulfides in different forms, among which hydrogen sulfide is the most abundant. If hydrogen sulfide is adsorbed on the catalyst surface of the catalytic combustion sensor before the gas to be tested, the catalyst will not be able to adsorb and catalyze various alkane gas molecules; and sulfur-containing gases are easy to form sulfates on the surface of the PdO active phase, attached to the catalyst surface, and limit the contact between various alkane gas molecules and the catalyst, causing sensor poisoning.

[0004] MEMS catalytic combustion sensors mainly use silicon-based micro-heating plates, which have the advantages of small size, low power consumption, and fast response, but there is still the problem of catalyst poisoning. Comparative invention patent 1: A MEMS catalytic combustion sensor and its processing method (CN201910257639.0), using a porous magnetic layer to have an obvious adsorption effect on sulfur-containing gases, to prevent sensor poisoning caused by sulfur-containing gases. This method of physical adsorption of sulfides has a saturation phenomenon and cannot fundamentally solve the anti-poisoning problem. Comparative invention patent 2: A gas-interference-resistant MEMS gas sensor and preparation method (CN202010931457.X), the same as comparative invention patent 1, uses a separation membrane with a channel pore size smaller than the diameter of the interfering gas molecule to avoid the influence of interfering gases on sensitive materials in the sensor. The process control of this porous structure size is difficult, which is not conducive to mass production.

[0005] Therefore, there is an urgent need to develop a MEMS catalytic combustion sensor that is resistant to sulfide poisoning and has a fast response. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a MEMS catalytic methane sensor resistant to sulfide poisoning and a preparation method thereof.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] A method for preparing a MEMS catalytic methane sensor resistant to sulfide poisoning comprises the following steps:

[0009] The specific steps include:

[0010] Step S1, preparation of carrier material:

[0011] The main material and the modified material are dissolved in water, and a synthetic reaction is performed to obtain a primary carrier material; the primary carrier material is washed and dried, and then subjected to heat treatment to finally obtain the carrier material;

[0012] Step S2, impregnation coating of carrier material:

[0013] Catalyst A and catalyst B are dissolved in pure water and stirred, and then the carrier material prepared in step S1 is added, dispersed by ultrasonic oscillation at room temperature, and then placed in an oven at 120° C. for 12 hours; the obtained powder is first transferred to a muffle furnace for heat treatment, and then transferred to a tube furnace with an atmosphere of 10% H2 / Ar (the volume percentage of H2 in the mixed gas is 10%) to obtain a modified carrier powder;

[0014] Step S3, preparation of catalyst slurry, comprising:

[0015] Step S31, mixing the modified carrier powder obtained in step S2 with a thickener, adding a mixed solution of ethylene glycol and ethanol, and simultaneously transferring N-methylpyrrolidone to a container, and grinding to obtain a black component slurry;

[0016] Step S32, mixing the carrier material obtained in step S1 with a thickener, adding a mixed solution of ethylene glycol and ethanol, and simultaneously transferring N-methylpyrrolidone to a container, and grinding to obtain a white component slurry;

[0017] Step S4: Preparation of MEMS catalytic methane sensor:

[0018] The black component slurry prepared in step S31 is coated on the black MEMS micro-thermal substrate, and the white component slurry prepared in step S32 is coated on the white MEMS micro-thermal substrate, and then the two substrates are heat-treated at 450°C for 1 hour to obtain black MEMS components and white MEMS components; finally, the black and white MEMS components are packaged through SMD, wire bonding, capping and other packaging processes to obtain a finished MEMS catalytic methane sensor;

[0019] Wherein, in step S1, the main material is Al salt, and the modified material is Ti salt, ZrO2, CeO2 or ZnO;

[0020] The mass ratio of catalyst A to catalyst B in step S2 is (0.5:4.5) to (1:4).

[0021] Furthermore, the synthesis reaction in step S1 is a hydrothermal method, a precipitation method or a sol-gel method; the Al salt is Al(NO3)3 or Al(Cl)3; and the Ti salt is Ti(SO4)2 or Ti(Cl)4.

[0022] Furthermore, the synthesis reaction in step S1 is a hydrothermal method, the hydrothermal temperature is 160-200° C., and the hydrothermal time is 8-24 hours.

[0023] Furthermore, in the heat treatment in step S1, the heat treatment temperature is 400-700° C., and the heat treatment time is 1-3 hours.

[0024] Furthermore, in step S2, the catalyst A is H2IrCl 6· 6H2O or Rh(Cl)3·3H2O, catalyst B uses H2PtCl 6· 2H2O;

[0025] The muffle furnace heat treatment temperature is 400-600° C.; the tube furnace heat treatment temperature is 350-450° C., and the heat treatment time is 40-120 minutes.

[0026] Furthermore, in the step S31, the modified carrier powder obtained in step S2 is mixed with a thickener, wherein the mass percentage of the modified carrier powder is 0.05-2% and the thickener is the balance;

[0027] In the step S32, the carrier material prepared in step S1 is mixed with a thickener, wherein the mass percentage of the carrier material is 0.05-2% and the thickener is the balance;

[0028] In the step S31 and step S32, the thickener is selected from ethyl cellulose or polyvinyl alcohol fiber;

[0029] In step S31 and step S32, the volume ratio of ethylene glycol to ethanol in the mixed solution of ethylene glycol and ethanol is (1:5) to (5:1).

[0030] Furthermore, the grinding in step S31 and step S32 is room temperature ball milling or frozen low temperature ball milling.

[0031] Furthermore, the grinding is cryogenic ball milling, the temperature of the cryogenic ball milling is 0 to 10° C., and the ball milling time is 1 to 12 hours.

[0032] Furthermore, in the step S4, the black component slurry and the white component slurry are respectively coated on the MEMS micro-thermal substrate, and the coating method adopts contact dispensing, silk screen printing or manual coating.

[0033] A MEMS catalytic methane sensor resistant to sulfide poisoning is prepared by adopting the preparation method.

[0034] The beneficial effects of the present invention are: the present invention has reasonable design and simple preparation method, and specifically includes the following advantages:

[0035] (1) The Al2O3 in the carrier material is a γ-Al2O3 phase, which has a very high specific surface area and high temperature stability, and the addition of transition metal oxides (TiO2, CeO2 and ZrO2) can better promote the electronic interaction between the carrier and the catalyst; in addition, catalyst A (Ir and Rh) and catalyst A oxidation state (IrO2 and RhO2) have more oxygen vacancy defects, which can significantly improve the adsorption and activation of oxygen on the catalyst surface, thereby improving the low-temperature methane redox ability, and the metal modification of catalyst B (Pt) can increase the electron cloud density of catalyst A (Ir and Rh), making it more difficult for the catalyst A (Ir and Rh) surface to adsorb and activate sulfides, thereby greatly improving the resistance to sulfide poisoning; the above catalyst carrier is coated on the surface of the MEMS chip, which can better improve the low-temperature combustion of methane and the resistance to sulfide poisoning;

[0036] (2) The MEMS catalytic methane sensor resistant to sulfide poisoning prepared by the present invention is suitable for coal mining, industry, civil use and other fields, and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 1 is a SEM image of Example 1, wherein a is a SEM image of a black MEMS element, and b is a local enlarged image of a;

[0039] Figure 2 It is a graph of H2S ventilation test of modified element (Example 1) and unmodified element (Comparative Example 1). DETAILED DESCRIPTION

[0040] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0042] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] A method for preparing a MEMS catalytic methane sensor resistant to sulfide poisoning comprises the following steps:

[0044] Step S1, preparation of carrier material:

[0045] The main material and the modified material are dissolved in water, and a synthetic reaction is performed to obtain a primary carrier material; the primary carrier material is washed and dried, and then subjected to heat treatment to finally obtain the carrier material;

[0046] Step S2, impregnation coating of carrier material:

[0047] Catalyst A and catalyst B are dissolved in pure water and stirred, and then the carrier material prepared in step S1 is added, dispersed by ultrasonic oscillation at room temperature, and then placed in an oven at 120° C. for 12 hours; the obtained powder is first transferred to a muffle furnace for heat treatment, and then transferred to a tube furnace with an atmosphere of 10% H2 / Ar (the volume percentage of H2 in the mixed gas is 10%) to obtain a modified carrier powder;

[0048] Step S3, preparation of catalyst slurry, comprising:

[0049] Step S31, mixing the modified carrier powder obtained in step S2 with a thickener, adding a mixed solution of ethylene glycol and ethanol, and simultaneously transferring N-methylpyrrolidone to a container, and grinding to obtain a black component slurry;

[0050] Step S32, mixing the carrier material obtained in step S1 with a thickener, adding a mixed solution of ethylene glycol and ethanol, and simultaneously transferring N-methylpyrrolidone to a container, and grinding to obtain a white component slurry;

[0051] Step S4: Preparation of MEMS catalytic methane sensor:

[0052] The black component slurry prepared in step S31 is coated on the black MEMS micro-thermal substrate, and the white component slurry prepared in step S32 is coated on the white MEMS micro-thermal substrate, and then the two substrates are heat-treated at 450°C for 1 hour to obtain black MEMS components and white MEMS components; finally, the black and white MEMS components are packaged through SMD, wire bonding, capping and other packaging processes to obtain a finished MEMS catalytic methane sensor;

[0053] Among them, in step S1, the main material is Al salt, and the modified material is Ti salt, ZrO2, CeO2 or ZnO; in step S2, the mass ratio of catalyst A to catalyst B is (0.5:4.5) to (1:4).

[0054] The synthesis reaction in step S1 is a hydrothermal method, a precipitation method or a sol-gel method; the Al salt is Al(NO3)3 or Al(Cl)3; the Ti salt is Ti(SO4)2 or Ti(Cl)4. The synthesis reaction in step S1 is a hydrothermal method, the hydrothermal temperature is 160-200°C, and the hydrothermal time is 8-24h; in the heat treatment in step S1, the heat treatment temperature is 400-700°C, and the heat treatment time is 1-3h.

[0055] In step S2, catalyst A is H2IrCl 6· 6H2O or Rh(Cl)3·3H2O, catalyst B uses H2PtCl 6· 2H2O; the heat treatment temperature of the muffle furnace is 400-600℃; the heat treatment temperature of the tube furnace is 350-450℃, and the heat treatment time is 40-120min.

[0056] In step S31, the modified carrier powder obtained in step S2 is mixed with a thickener, wherein the mass percentage of the modified carrier powder is 0.05-2%, and the thickener is the balance; in step S32, the carrier material obtained in step S1 is mixed with a thickener, wherein the mass percentage of the carrier material is 0.05-2%, and the thickener is the balance; the thickener is selected from ethyl cellulose or polyvinyl alcohol fiber; the volume ratio of ethylene glycol to ethanol in the mixed solution of ethylene glycol and ethanol is (1:5) to (5:1).

[0057] The grinding in step S31 and step S32 is room temperature ball milling or refrigerated low temperature ball milling. The grinding is preferably refrigerated low temperature ball milling, the temperature of the refrigerated low temperature ball milling is 0-10°C, and the ball milling time is 1-12h.

[0058] In step S4, the black component slurry and the white component slurry are respectively coated on the MEMS micro-thermal substrate, and the coating method adopts contact dispensing, silk screen printing or manual coating.

[0059] A MEMS catalytic methane sensor resistant to sulfide poisoning is prepared by adopting the preparation method.

[0060] Example 1

[0061] A method for preparing a MEMS catalytic methane sensor resistant to sulfide poisoning comprises the following steps:

[0062] Step S1, preparation of Al2O3-TiO2 carrier material:

[0063] Dissolve 1.5g Al(NO3)3·9H2O and Ti(SO4)2 in 40ml water, add 5g urea, stir for 3h, transfer the solution to a 100ml hydrothermal reactor, and perform a hydrothermal reaction. The reaction conditions are heating at 160℃ for 12h. After the hydrothermal reaction, centrifuge the precipitate to remove impurity ions, dry it at 80℃ for 12h, and then put it into a muffle furnace for heat treatment at 550℃ for 2h to finally obtain an Al2O3-TiO2 carrier material, in which Al2O3 is γ-Al2O3 phase.

[0064] Step S2, Ir-Pt impregnation coating Al2O3-TiO2:

[0065] 0.02 g H2IrCl 6· 6H2O and 0.08g H2PtCl 6· 2H2O was dissolved in 2ml pure water and stirred, and then 0.5g Al2O3-TiO2 carrier material (prepared in step S1) was added, and ultrasonic oscillation was performed at room temperature for 30min, and then placed in a 120°C oven for 12h; the obtained powder was transferred to a 500°C muffle furnace for heat treatment for 2h, and then transferred to a 400°C tubular furnace with an atmosphere of 10% H2 / Ar and a heating time of 1h to obtain Ir-Pt modified Al2O3-TiO2 powder;

[0066] Step S3, catalyst slurry preparation:

[0067] Step S31, preparation of black component slurry:

[0068] 0.2 g of Ir-Pt modified Al2O3-TiO2 powder (obtained in step S2) was mixed with 2 mg of ethyl cellulose, and then 5 ml of a mixed solution of ethylene glycol and ethanol and 2 ml of N-methylpyrrolidone were added and simultaneously transferred to a frozen ball mill jar. The ball milling time was 1 h, and the temperature of the frozen ball mill was controlled at 5°C to obtain a black component slurry.

[0069] Step S32: Preparation of white component slurry:

[0070] 0.2 g of Al2O3-TiO2 carrier material (prepared in step S1) was mixed with 2 mg of ethyl cellulose, and then 5 ml of a mixed solution of ethylene glycol and ethanol and 2 ml of N-methylpyrrolidone were added and simultaneously transferred to a frozen ball mill jar. The ball milling time was 1 h, and the temperature of the frozen ball mill was controlled at 5°C to obtain a white component slurry.

[0071] Step S4: Preparation of MEMS catalytic methane sensor:

[0072] The black component slurry (prepared in step S31) and the white component slurry (prepared in step S32) are transferred to two MEMS micro-thermal substrates respectively by contact dispensing method, and then the two substrates are heat treated at 450°C for 1 hour to obtain black MEMS components and white MEMS components; finally, the black and white MEMS components are packaged through packaging processes such as patching, wire bonding, and capping to obtain a finished MEMS catalytic methane sensor.

[0073] The SEM image of the black MEMS element in this embodiment is as follows: Figure 1 As shown. Figure 1 It can be seen that the black MEMS element diaphragm is dense, the particle size is small and uniform, and the particle consistency is good, which makes the particles more sensitive to contact with gas.

[0074] In view of the limitations of traditional Pd-based catalysts such as poor low-temperature activity and easy sulfide poisoning, this embodiment uses Al2O3-TiO2 nanocomposite oxide as a carrier material, and then impregnates two precious metal catalysts, Ir and Pt, to form a coating slurry through slurry proportioning, and finally coats it on a MEMS micro-thermal substrate to prepare a MEMS catalytic combustion sensor with resistance to sulfide poisoning.

[0075] Among them, the γ-Al2O3 phase has a very high specific surface area and high temperature stability, and the addition of nano-TiO2 can better promote the electronic interaction between the carrier and the catalyst; in addition, Ir and IrO2 have strong low-temperature methane oxidation performance. Due to their limited surface electron-donating capacity, their oxidation capacity is often limited. Pt metal modification improves oxidation capacity and further improves resistance to sulfide poisoning. The above catalyst carriers are mixed with a certain proportion of slurry and coated on the surface of the MEMS chip, which can better improve methane low-temperature combustion and resistance to sulfide poisoning.

[0076] A MEMS catalytic methane sensor resistant to sulfide poisoning is prepared by adopting the preparation method.

[0077] Example 2

[0078] A method for preparing a MEMS catalytic methane sensor resistant to sulfide poisoning comprises the following steps:

[0079] Step S1, preparation of Al2O3-ZrO2 carrier material:

[0080] Dissolve 2g Al(NO3)3·9H2O and Zr(NO3)4·5H2O in 50ml water, add 5g urea, stir for 3h, transfer the solution to a 150ml hydrothermal reactor, and perform a hydrothermal reaction at 160℃ for 24h. After the hydrothermal reaction, centrifuge the precipitate to remove impurity ions, dry it at 80℃ for 12h, and then heat it at 400℃ for 3h in a muffle furnace to obtain an Al2O3-ZrO2 carrier material.

[0081] Step S2, Rh-Pt impregnation coating Al2O3-ZrO2:

[0082] 0.01g Rh(Cl)3·3H2O and 0.09g H2PtCl 6· 2H2O was dissolved in 2ml pure water and stirred, and then 0.5g Al2O3-ZrO2 carrier material (prepared in step S1) was added, and ultrasonic oscillation was performed at room temperature for 30min, and then placed in a 120℃ oven for 12h. The obtained powder was then transferred to a 400℃ muffle furnace for heat treatment for 2h to obtain Rh-Pt modified Al2O3-ZrO2 powder;

[0083] Step S3, catalyst slurry preparation:

[0084] Step S31, preparation of black component slurry:

[0085] 0.2 g of Rh-Pt modified Al2O3-ZrO2 powder (obtained in step S2) was mixed with 1 mg of ethyl cellulose, and then 6 ml of a mixed solution of ethylene glycol and ethanol and 1.5 ml of N-methylpyrrolidone were added and simultaneously transferred to a frozen ball mill jar for 2 h. The temperature of the frozen ball mill was controlled at 10°C to obtain a black component slurry.

[0086] Step S32: Preparation of white component slurry:

[0087] 0.2 g of Al2O3-ZrO2 carrier material (prepared in step S1) was mixed with 1 mg of ethyl cellulose, and then 6 ml of ethylene glycol and ethanol mixed solution and 1.5 ml of N-methylpyrrolidone were added and simultaneously transferred to a frozen ball mill jar. The ball milling time was 2 h, and the temperature of the frozen ball mill was controlled at 10°C to obtain a white component slurry;

[0088] Step S4: Preparation of MEMS catalytic methane sensor:

[0089] The black component slurry (prepared in step S31) and the white component slurry (prepared in step S32) are respectively transferred to two MEMS micro-thermal substrates by contact dispensing method, and then the two substrates are heat-treated at 500°C for 1 hour to obtain black MEMS components and white MEMS components; finally, the black and white MEMS components are packaged through packaging processes such as patching, wire bonding, and capping to obtain a finished MEMS catalytic methane sensor.

[0090] Example 3

[0091] A method for preparing a MEMS catalytic methane sensor resistant to sulfide poisoning comprises the following steps:

[0092] Step S1, preparation of Al2O3-CeO2 carrier material:

[0093] 3g Al(NO3)3·9H2O and Ce(NO3)3·6H2O were dissolved in 40ml water, and 5g urea was added. After stirring for 3h, the solution was transferred to a 150ml hydrothermal kettle for hydrothermal reaction. The reaction conditions were heating at 180℃ for 12h. After the hydrothermal reaction, the precipitate was centrifuged and washed to remove impurity ions, and then dried at 80℃ for 12h, and then placed in a muffle furnace for heat treatment at 500℃ for 1h to finally obtain Al2O3-CeO2 carrier material;

[0094] Step S2, Rh-Pt impregnation coating Al2O3-CeO2:

[0095] 0.01g Rh(Cl)3·3H2O and 0.09g H2PtCl 6· 2H2O was dissolved in 2ml pure water and stirred, and then 0.5g Al2O3-CeO2 carrier material (prepared in step S1) was added, and ultrasonic oscillation was performed at room temperature for 30min, and then placed in a 120°C oven for 12h; the obtained powder was then transferred to a muffle furnace at 400°C for heat treatment for 2h to obtain Rh-Pt modified Al2O3-CeO2 powder;

[0096] Step S3, catalyst slurry preparation:

[0097] Step S31, preparation of black component slurry:

[0098] 0.15 g of Rh-Pt modified Al2O3-CeO2 powder (obtained in step S2) was mixed with 7.5 mg of ethyl cellulose, and then 3 ml of a mixed solution of ethylene glycol and ethanol and 1 ml of N-methylpyrrolidone were added and simultaneously transferred to a frozen ball mill jar. The ball milling time was 2 h, and the temperature of the frozen ball mill was controlled at 10°C to obtain a black component slurry.

[0099] Step S32: Preparation of white component slurry:

[0100] 0.15 g of Al2O3-CeO2 carrier material (prepared in step S1) was mixed with 7.5 mg of ethyl cellulose, and then 3 ml of ethylene glycol and ethanol mixed solution and 1 ml of N-methylpyrrolidone were added and simultaneously transferred to a frozen ball mill jar. The ball milling time was 2 h, and the temperature of the frozen ball mill was controlled at 10°C to obtain a white component slurry;

[0101] Step S4: Preparation of MEMS catalytic methane sensor:

[0102] The black component slurry (prepared in step S31) and the white component slurry (prepared in step S32) are respectively transferred to two MEMS micro-thermal substrates by contact dispensing method, and then the two substrates are heat-treated at 500°C for 1 hour to obtain black MEMS components and white MEMS components; finally, the black and white MEMS components are packaged through packaging processes such as patching, wire bonding, and capping to obtain a finished MEMS catalytic methane sensor.

[0103] Comparative Example 1

[0104] A method for preparing a MEMS catalytic methane sensor specifically comprises the following steps:

[0105] Step S1, preparation of γ-Al2O3 carrier material:

[0106] 1.5 g Al(NO3)3·9H2O was dissolved in 40 ml water, and then 5 g sodium hydroxide was added. After stirring for 3 h, the precipitate was centrifuged and washed to remove impurity ions, and then dried at 120°C for 12 h, and then placed in a muffle furnace for heat treatment at 700°C for 3 h to finally obtain a γ-Al2O3 carrier material;

[0107] Step S2, Pd impregnation coating γ-Al2O3:

[0108] 0.1 g of Pd(NO3)2·2H2O was dissolved in 2 ml of pure water and stirred, and then 0.5 g of γ-Al2O3 carrier material (prepared in step S1) was added, and ultrasonic oscillation was performed at room temperature for 30 min, and then placed in a 120° C. oven for 12 h; the obtained powder was then transferred to a 600° C. muffle furnace for heat treatment for 2 h to obtain Pd-modified Al2O3 powder;

[0109] Step S3, catalyst slurry preparation:

[0110] Step S31, preparation of black component slurry:

[0111] 0.2 g of Pd-modified Al2O3 powder (obtained in step S2) was mixed with 4 mg of ethyl cellulose, and then 5 ml of a mixed solution of ethylene glycol and ethanol and 1.5 ml of N-methylpyrrolidone were added and simultaneously transferred to a frozen ball mill jar for 2 h. The temperature of the frozen ball mill was controlled at 0°C to obtain a black component slurry.

[0112] Step S32: Preparation of white component slurry:

[0113] 0.2 g of Al2O3 carrier material (prepared in step S1) was mixed with 4 mg of ethyl cellulose, and then 5 ml of ethylene glycol and ethanol mixed solution and 1.5 ml of N-methylpyrrolidone were added and simultaneously transferred to a frozen ball mill jar for 2 h. The temperature of the frozen ball mill was controlled at 0°C to obtain a white component slurry.

[0114] Step S4: Preparation of MEMS catalytic methane sensor:

[0115] The black component slurry (prepared in step S31) and the white component slurry (prepared in step S32) are respectively transferred to two MEMS micro-thermal substrates by contact dispensing method, and then the two substrates are heat treated at 600°C for 1 hour to obtain black MEMS components and white MEMS components; finally, the black and white MEMS components are packaged through packaging processes such as patching, wire bonding, and capping to obtain a finished MEMS catalytic methane sensor.

[0116] The MEMS catalytic methane sensors prepared in Examples 1 to 3 and Comparative Example 1 were placed in a test box, and then H2S gas with a concentration of 100 ppm was introduced for 15 to 20 minutes, and then 1.2% CH4 gas was introduced for testing, and the sensitivity changes were compared. The test results are shown in Tables 1 and Figure 2 shown.

[0117] Table 1 Test results of Examples 1 to 3 and Comparative Example 1

[0118]

[0119] From Table 1 and Figure 2 It can be seen that the MEMS catalytic methane element prepared in Example 1 does not have the sensitivity attenuation problem caused by the corresponding catalyst poisoning in the hydrogen sulfide gas environment, and the sensitivity is greater than 12mV / 1% CH4, meeting the coal mine standard requirements of "AQ6202-2006 Carrier Catalytic Element for Coal Mine Methane Detection"; in comparison, the traditional element (Comparative Example 1) showed significant poisoning phenomenon and was unable to oxidize methane gas.

[0120] In summary, the present invention has reasonable design and simple preparation method, and specifically includes the following advantages:

[0121] (1) The Al2O3 in the carrier material is a γ-Al2O3 phase, which has a very high specific surface area and high temperature stability, and the addition of transition metal oxides (TiO2, CeO2 and ZrO2) can better promote the electronic interaction between the carrier and the catalyst; in addition, catalyst A (Ir and Rh) and catalyst A oxidation state (IrO2 and RhO2) have more oxygen vacancy defects, which can significantly improve the adsorption and activation of oxygen on the catalyst surface, thereby improving the low-temperature methane redox ability, and the metal modification of catalyst B (Pt) can increase the electron cloud density of catalyst A (Ir and Rh), making it more difficult for the catalyst A (Ir and Rh) surface to adsorb and activate sulfides, thereby greatly improving the resistance to sulfide poisoning; the above catalyst carrier is coated on the surface of the MEMS chip, which can better improve the low-temperature combustion of methane and the resistance to sulfide poisoning;

[0122] (2) The MEMS catalytic methane sensor resistant to sulfide poisoning prepared by the present invention is suitable for coal mining, industry, civil use and other fields, and has wide applicability.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a MEMS catalytic methane sensor resistant to sulfide poisoning, characterized in that: The specific steps include: Step S1, preparation of carrier material: The main material and the modified material are dissolved in water, and a synthetic reaction is performed to obtain a primary carrier material; the primary carrier material is washed and dried, and then subjected to heat treatment to finally obtain the carrier material; Step S2, impregnation coating of carrier material: Catalyst A and catalyst B are dissolved in pure water and stirred, and then the carrier material prepared in step S1 is added, dispersed by ultrasonic oscillation under room temperature, and then placed in an oven at 120° C. for 12 hours; the obtained powder is first transferred to a muffle furnace for heat treatment, and then transferred to a tube furnace with an atmosphere of 10% H2 / Ar to obtain a modified carrier powder; Step S3, preparation of catalyst slurry, comprising: Step S31, mixing the modified carrier powder obtained in step S2 with a thickener, adding a mixed solution of ethylene glycol and ethanol, and simultaneously transferring N-methylpyrrolidone to a container, and grinding to obtain a black component slurry; Step S32, mixing the carrier material obtained in step S1 with a thickener, adding a mixed solution of ethylene glycol and ethanol, and simultaneously transferring N-methylpyrrolidone to a container, and grinding to obtain a white component slurry; Step S4: Preparation of MEMS catalytic methane sensor: The black component slurry prepared in step S31 is coated on the black MEMS micro-thermal substrate, and the white component slurry prepared in step S32 is coated on the white MEMS micro-thermal substrate, and then the two substrates are heat-treated at 450°C for 1 hour to obtain black MEMS components and white MEMS components; finally, the black and white MEMS components are packaged through SMD, wire bonding, capping and other packaging processes to obtain a finished MEMS catalytic methane sensor; Wherein, in step S1, the main material is Al salt, and the modified material is Ti salt, ZrO2, CeO2 or ZnO; The mass ratio of catalyst A to catalyst B in step S2 is (0.5:4.5) to (1:4).

2. The method for preparing the MEMS catalytic methane sensor resistant to sulfide poisoning according to claim 1, characterized in that: The synthesis reaction in step S1 is a hydrothermal method, a precipitation method or a sol-gel method; the Al salt is Al(NO3)3 or Al(Cl)3; and the Ti salt is Ti(SO4)2 or Ti(Cl)4.

3. The method for preparing the MEMS catalytic methane sensor resistant to sulfide poisoning according to claim 2, characterized in that: The synthesis reaction in step S1 is a hydrothermal method, the hydrothermal temperature is 160-200° C., and the hydrothermal time is 8-24 hours.

4. The method for preparing the MEMS catalytic methane sensor resistant to sulfide poisoning according to claim 1, characterized in that: In the heat treatment in step S1, the heat treatment temperature is 400-700° C. and the heat treatment time is 1-3 hours.

5. The method for preparing the MEMS catalytic methane sensor resistant to sulfide poisoning according to claim 1, characterized in that: In step S2, catalyst A is H2IrCl 6· 6H2O or Rh(Cl)3·3H2O, catalyst B uses H2PtCl 6· 2H2O; The muffle furnace heat treatment temperature is 400-600° C.; the tube furnace heat treatment temperature is 350-450° C., and the heat treatment time is 40-120 minutes.

6. The method for preparing the MEMS catalytic methane sensor resistant to sulfide poisoning according to claim 1, characterized in that: In the step S31, the modified carrier powder obtained in step S2 is mixed with a thickener, wherein the mass percentage of the modified carrier powder is 0.05-2% and the thickener is the balance; In the step S32, the carrier material prepared in step S1 is mixed with a thickener, wherein the mass percentage of the carrier material is 0.05-2% and the thickener is the balance; In the step S31 and step S32, the thickener is selected from ethyl cellulose or polyvinyl alcohol fiber; In step S31 and step S32, the volume ratio of ethylene glycol to ethanol in the mixed solution of ethylene glycol and ethanol is (1:5) to (5:1).

7. The method for preparing the MEMS catalytic methane sensor resistant to sulfide poisoning according to claim 1, characterized in that: The grinding in step S31 and step S32 is room temperature ball milling or frozen low temperature ball milling.

8. The method for preparing the MEMS catalytic methane sensor resistant to sulfide poisoning according to claim 7, characterized in that: The grinding is performed by freezing low-temperature ball milling, the temperature of freezing low-temperature ball milling is 0-10° C., and the ball milling time is 1-12 hours.

9. The method for preparing the MEMS catalytic methane sensor resistant to sulfide poisoning according to claim 1, characterized in that: In the step S4, the black component slurry and the white component slurry are respectively coated on the MEMS micro-thermal substrate, and the coating method adopts contact dispensing, silk screen printing or manual coating.

10. A MEMS catalytic methane sensor resistant to sulfide poisoning, characterized in that: The method is as described in any one of claims 1 to 9.

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