Online catalysis evaluation device and method for methane catalytic cracking hydrogen production small reactor

Abstract

The invention provides an on-line catalysis evaluation device and method for a small reactor for producing hydrogen through catalytic cracking of methane. The on-line catalysis evaluation device comprises a feeding unit, a reaction unit, a condensation drying unit and a metering analysis unit which are connected in sequence, the reaction unit comprises a small reactor, the condensation drying unit comprises a condenser and a dryer which are communicated with each other, and the metering analysis unit comprises a wet flow meter; an inlet of the small reactor is connected with an outlet of the feeding unit, an outlet of the small reactor is connected with an inlet of the condenser, an outlet of the condenser is connected with an inlet of the dryer, and an outlet of the dryer is connected with an inlet of the wet flow meter; wherein the small reactor comprises a tubular reactor and an electric heating furnace arranged on the periphery of the tubular reactor, a gas distributor is arranged at the inlet end of the tubular reactor, and according to the on-line catalysis evaluation device and method for the small reactor for hydrogen production through methane catalytic cracking, the catalysis evaluation of the methane catalytic cracking reaction is accurate, rapid and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts for methane catalytic cracking and hydrogen production, and in particular to an online catalytic evaluation device and method for a small reactor for methane catalytic cracking and hydrogen production. Background Art

[0002] As a clean energy, hydrogen is expected to become one of the main energy sources in the 21st century. Currently, about 96% of the world's hydrogen energy is produced through methods such as coal gasification of fossil fuels (coal, oil, natural gas, etc.), methane steam reforming, partial oxidation of methane, biomass hydrogen production and water electrolysis.

[0003] Natural gas (CH4) is considered to be the best raw material for hydrogen production. Methane catalytic cracking (MCD) to produce hydrogen is a mild endothermic reaction with low energy consumption. The reaction process does not require water-gas replacement and CO2 removal, and high-purity hydrogen without carbon oxides can be obtained. The process is simple, consumes less energy, and is environmentally friendly. In addition, the carbon materials (carbon nanotubes, carbon black, etc.) generated during the MCD reaction are widely used in many fields due to their excellent physical and chemical properties and have high economic value.

[0004] The methane catalytic cracking process is to crack methane into hydrogen and carbon materials under the action of a certain temperature, pressure and metal catalyst or carbon-based catalyst; in the process of catalyst research and development, using a small laboratory reactor as a catalytic evaluation device to evaluate the performance of the catalyst is an indispensable experimental method, and the accuracy and reliability of the catalytic evaluation method is an important prerequisite for successful research and development. For example, Chinese patent CN110683511A discloses a chemical chain circulation method for methane cracking hydrogen production coupled with CO2 reduction, which introduces that the catalyst evaluation uses offline gas chromatography to collect reaction tail gas for component analysis. This offline analysis method inevitably has certain errors when sampling, and the operation also consumes manpower and time; Chinese patent CN105013506A discloses a bifunctional catalyst for methane catalytic cracking and its preparation method and hydrogen production method, and proposes that the catalyst can be used to catalyze methane to produce hydrogen at a lower temperature, and selectively oxidize carbon deposits to CO. The method uses a circulating fluidized bed reactor and a regenerator to catalytically crack the feed gas including methane to produce hydrogen and regenerate and recycle the catalyst. It introduces that the catalyst evaluation is not online analysis, which will cause certain errors in the analysis of the product.

[0005] In summary, traditional catalytic evaluation methods are not only labor-intensive, inefficient, and experimentally cumbersome, but the experimental data obtained are also inaccurate. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the present invention provides an online catalytic evaluation device and method for a small reactor for producing hydrogen using catalytic cracking of methane, so that the catalytic evaluation of the catalytic cracking reaction of methane can be accurate, rapid and efficient.

[0007] In order to achieve the above-mentioned object, the present invention provides an online catalytic evaluation device for a small-scale reactor for producing hydrogen by catalytic cracking of methane, comprising a feeding unit, a reaction unit, a condensation and drying unit and a metering and analysis unit connected in sequence;

[0008] The reaction unit includes a small reactor, the condensation and drying unit includes a connected condenser and a dryer, and the metering and analysis unit includes a wet flow meter;

[0009] The inlet of the small reactor is connected to the outlet of the feeding unit, the outlet of the small reactor is connected to the inlet of the condenser, the outlet of the condenser is connected to the inlet of the dryer, and the outlet of the dryer is connected to the inlet of the wet flow meter;

[0010] The small reactor comprises a tubular reactor and an electric heating furnace arranged around the tubular reactor, and a gas distributor is arranged at the inlet end of the tubular reactor.

[0011] In some of the embodiments, the gas distributor is located in the tubular reactor, one end of the gas distributor is connected to the feed port of the small reactor, and the other end of the gas distributor is connected to the distribution pipe.

[0012] In some of the embodiments, the gas distributor is an inverted T-shaped structure; the distribution pipe is opened along the axis of the reactor, and the opening angle direction is parallel to the axis of the reactor.

[0013] In some of the embodiments, the openings on the distribution pipe are evenly and symmetrically distributed around the center of a circle on the distribution pipe, and the total area of ​​the openings is 20-30% of the cross-sectional area of ​​the bed of the small reactor.

[0014] In some of the embodiments, a quartz boat for holding the catalyst and a thermocouple for measuring the reaction temperature of the system are further provided in the tubular reactor.

[0015] In some embodiments, the condensation and drying unit further includes a liquid collecting bottle, which is connected to the outlet of the condenser and the inlet of the dryer.

[0016] In some embodiments, the condenser is a shell and tube structure, a cooling water inlet is provided at the lower end of the condenser, and a cooling water outlet is provided at the upper end of the condenser; the condensing tube in the condenser is a spiral coil; two drying tubes are provided, and desiccant is filled in the drying tubes.

[0017] In some of the embodiments, the feeding unit includes a methane cylinder, a hydrogen cylinder and a nitrogen cylinder, and the methane cylinder, the hydrogen cylinder and the nitrogen cylinder are respectively connected to a pressure reducing valve, each pressure reducing valve is respectively connected to a rotor flowmeter, and each rotor flowmeter is connected to a premixer.

[0018] In some embodiments, the metering and analysis unit further includes a gas chromatograph, and the outlet of the wet flow meter is connected to an inlet of the gas chromatograph or a vent line.

[0019] The present invention also provides an online catalytic evaluation method for a small-scale reactor for producing hydrogen through catalytic cracking of methane, the method using the online catalytic evaluation device as described above, the evaluation method comprising the following steps:

[0020] The weighed and screened methane catalytic cracking hydrogen production catalyst is placed in a quartz boat, which is then placed in the middle of a tubular reactor;

[0021] Inert nitrogen is introduced to exhaust the air in the tube, and the quartz reaction tube is heated at the same time, with the reduction temperature at 200-500°C and the reduction pressure at normal pressure;

[0022] After the temperature reaches the pre-reduction temperature of the catalyst, the nitrogen is cut off, and the reducing gas hydrogen is introduced, and then the temperature is kept constant for a certain period of time to reduce the catalyst;

[0023] After the reduction is completed, the hydrogen valve is closed, and the temperature is rapidly raised under nitrogen purge until the gas chromatograph no longer detects hydrogen, and then methane is introduced to start the reaction;

[0024] During the reaction, the gaseous product first enters the condenser to condense the heavy components in the product, and then enters the drying tube to absorb the water in the product;

[0025] The volume flow of the dried gas product is measured by a wet flow meter, a portion of the tail gas is introduced into an online gas chromatograph, and the rest of the tail gas is discharged;

[0026] The gases after a certain reaction time are sampled and analyzed.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The online catalytic evaluation device provided by the present invention adopts a gas distributor, which can eliminate the problem of uneven gas distribution, thereby eliminating the short-circuit phenomenon in the reactor and ensuring the full play of the catalyst; at the same time, through the effects of the condenser and the dryer, the product condensation phase separation and water are avoided, thereby avoiding the experimental errors caused; the online catalytic evaluation device provided by the present invention adopts online analysis, thereby avoiding the cumbersome operation caused by offline analysis and the experimental errors caused by sampling, thereby improving the experimental efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is a structural schematic diagram of an online catalytic evaluation device for a small-scale reactor for producing hydrogen by catalytic cracking of methane shown in an embodiment of the present invention;

[0031] in:

[0032] 11- condenser;

[0033] 12-dryer;

[0034] 13-liquid collection bottle;

[0035] 14-Cooling water inlet;

[0036] 15-Cooling water outlet;

[0037] 16- condenser;

[0038] 21- Wet flow meter;

[0039] 22- Gas chromatograph;

[0040] 31- tubular reactor;

[0041] 32-electric heating furnace;

[0042] 33-gas distributor;

[0043] 34-distribution pipe;

[0044] 35-quartz boat;

[0045] 36-thermocouple;

[0046] 41-Methane cylinder;

[0047] 42-Hydrogen cylinder;

[0048] 43-Nitrogen cylinder;

[0049] 44-pressure reducing valve;

[0050] 45-Rotameter;

[0051] 46-Premixer. DETAILED DESCRIPTION

[0052] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments to further understand the purpose, solution and effect of the present invention, but it is not intended to limit the scope of protection of the claims attached to the present invention.

[0053] Certain words are used in the specification and subsequent claims to refer to specific components or parts. It should be understood by those of ordinary skill in the art that technical users or manufacturers may refer to the same component or part by different nouns or terms. This specification and subsequent claims do not use differences in names as a way to distinguish components or parts, but use differences in the functions of components or parts as the criteria for distinction. "Including" and "comprising" mentioned throughout the specification and subsequent claims are open-ended terms and should be interpreted as "including but not limited to". In addition, the word "connect" here includes any direct and indirect electrical connection means. Indirect electrical connection means include connection through other devices.

[0054] It should be noted that, in the description of the present invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and "about", or "approximately", "substantially", "left and right" and the like indicating directions or positional relationships or parameters are all based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description content, and do not indicate or imply that the referred device or element must have a specific direction, specific size, or be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0055] See also Figure 1An embodiment of the present invention provides an online catalytic evaluation device for a small reactor for producing hydrogen from methane by catalytic cracking, comprising a feed unit, a reaction unit, a condensation and drying unit and a metering and analysis unit connected in sequence; the reaction unit comprises a small reactor, the condensation and drying unit comprises a connected condenser 11 and a dryer 12, and the metering and analysis unit comprises a wet flow meter 21; the inlet of the small reactor is connected to the outlet of the feed unit, the outlet of the small reactor is connected to the inlet of the condenser 11, the outlet of the condenser 11 is connected to the inlet of the dryer 12, the outlet of the dryer 12 is connected to the inlet of the wet flow meter 21, the condenser 11 is used to condense the heavy hydrocarbons in the gas phase product, and the dryer 12 is used to absorb the moisture in the gas phase product; wherein the small reactor comprises a tubular reactor 31 and an electric heating furnace 32 arranged around it, and a gas distributor 33 is provided at the inlet end of the tubular reactor 31. The small reactor is a tubular reactor with a heating furnace, the inner diameter of the small reactor is 25 mm, the length is 600 mm, and the catalyst loading is 0.1-10 g. The tubular reactor is a quartz tube with an inner diameter of 10 mm and a length of 300 mm, which is heated by an electric heating furnace, and the reaction product flows from the quartz reaction tube to the condensation drying unit.

[0056] The gas distributor 33 in this embodiment is located in the tubular reactor 31, one end of which is connected to the feed port of the small reactor, and the other end of which is connected to the distribution pipe 34. The gas distributor 33 is an inverted T-shaped structure; the diameter of the distribution pipe 34 is 20 mm, and the hole is opened along the axial direction of the reactor. The angle of the hole is parallel to the axial direction of the reactor, that is, the angle of the hole is 0° with the axial direction of the reactor; the "T" type gas distributor is convenient for the gas entering the reactor to form a plug flow for reaction, avoiding gas flow back mixing. Among them, the openings on the distribution pipe 34 are symmetrically and evenly distributed on the distribution pipe with the center of the circle as the center point, and the total area of ​​the openings is 20-30% of the cross-sectional area of ​​the bed of the small reactor. The tubular reactor 31 is also provided with a quartz boat 35 for holding the catalyst and a thermocouple 36 for measuring the reaction temperature of the system.

[0057] The small reactor described in this embodiment is a horizontal structure, and the front and rear ends of the reactor are connected to the pipeline through flanges. Before the experiment, a certain amount of catalyst is weighed in advance and placed in a quartz boat 35, which is then placed in the middle of the tubular reactor 31. A thermocouple 36 is set in the reactor to measure the reaction temperature of the system.

[0058] The condensation and drying unit in this embodiment further includes a liquid collecting bottle 13, which is connected to the outlet of the condenser 11 and the inlet of the dryer 12. The liquid collecting bottle 13 is a wide-mouth flask with a rubber stopper, and its volume is 500 mL. Two holes are punched in the rubber stopper, which are the gas outlet of the condenser 11 and the gas inlet of the drying tube 12.

[0059] Among them, the condenser 11 is a shell and tube structure, the reaction product goes through the tube side, and the cooling water medium goes through the shell side. The lower end of the condenser 11 is provided with a cooling water inlet 14, and the upper end of the condenser 11 is provided with a cooling water outlet 15; the condenser tube 16 in the condenser 11 is a spiral coil, and the gas-phase reaction product enters from the top of the condenser tube 16 and flows out from the bottom, and exchanges heat with the cooling water in a countercurrent partition wall type. The liquid condensate in the condenser tube flows into the liquid collecting bottle 13, and the gas-phase product continues to enter the dryer 12. Through the partition wall heat exchange, the heavy component hydrocarbons in the gas-phase product are condensed and discharged into the liquid collecting bottle 13; the drying tube is provided with two, one is open and the other is standby during normal operation, and the drying tube is filled with a desiccant, which adsorbs the moisture that may exist in the gas-phase product before entering the metering and analysis unit.

[0060] The feeding unit in this embodiment includes a methane cylinder 41, a hydrogen cylinder 42 and a nitrogen cylinder 43, which are used to store methane, hydrogen and nitrogen respectively; the methane cylinder 41, the hydrogen cylinder 42 and the nitrogen cylinder 43 are respectively connected to a pressure reducing valve 44, each pressure reducing valve 44 is respectively connected to a rotor flowmeter 45, and each rotor flowmeter 45 is connected to a premixer 46. After the methane, hydrogen and nitrogen gases are reduced in pressure by the pressure reducing valve, their volume flow is controlled by the rotor flowmeter 45 and then enters the premixer 46. Among them, methane is the reactant, hydrogen is the catalyst reduction gas, and the nitrogen inert gas is used for device purging and preheating.

[0061] The metering and analysis unit in this embodiment also includes a gas chromatograph 22, and the outlet of the wet flowmeter 21 is connected to the inlet or a venting line of the gas chromatograph 22. The gas chromatograph in this embodiment is a 7890GC from Agilent, USA, with a TCD detector, a chromatographic column of 5A molecular sieve, and Ar gas as a carrier gas.

[0062] Another embodiment of the present invention provides an online catalytic evaluation method for a small-scale reactor for producing hydrogen from catalytic cracking of methane. The method uses the online catalytic evaluation device as described above. The evaluation method comprises the following steps:

[0063] The weighed methane catalytic cracking hydrogen production catalyst that has been sieved to 60 to 80 mesh is placed in a quartz boat 35, and then placed in the middle of the tubular reactor 31;

[0064] Inert nitrogen gas is introduced to exhaust the air in the tube, and the quartz reaction tube is heated at the same time, and the reduction temperature is set to 200-500° C., specifically 300° C. in this embodiment, and the reduction pressure is normal pressure;

[0065] After the temperature reaches the pre-reduction temperature of the catalyst, the nitrogen is cut off and the reducing gas hydrogen is introduced at a volume flow rate of 100 to 500 ml / min, and then the temperature is kept constant for 2 hours to reduce the catalyst;

[0066] After the reduction is completed, the hydrogen valve is closed, and the temperature is rapidly raised under nitrogen purge until the gas chromatograph no longer detects hydrogen, and then 99% pure methane is introduced to start the reaction. The experimental operating conditions are: volume flow rate 100-500 ml / min, reaction temperature 700°C, reaction pressure normal pressure;

[0067] During the reaction, the gaseous product first enters the condenser 11 to condense the heavy components in the product, and then enters the drying tube 12 to absorb the water in the product.

[0068] The volume flow of the dried gas product is measured by a wet flow meter 21, a portion of the tail gas is introduced into an online gas chromatograph 22, and the rest of the tail gas is discharged;

[0069] The calculation formula of the methane conversion rate of the gas reactant is as follows:

[0070] Methane conversion rate

[0071] in, and represent the inlet flow rate and outlet flow rate of methane gas respectively.

[0072] The gases at reaction times of 0.5h, 1.0h, 1.5h and 2.0h were sampled and analyzed respectively.

[0073] Specific:

[0074] Example 1

[0075] This embodiment provides an online catalytic evaluation method for a methane catalytic cracking hydrogen production catalyst A. The catalyst "A" is composed of 20% Ni and 80% magnesium aluminum spinel. The preparation method is as follows:

[0076] (1) Solution preparation

[0077] 4.7 g of nickel nitrate, 2.6 g of magnesium nitrate, and 7.5 g of aluminum nitrate were dissolved in 450 ml of aqueous solution to form solution I, and 11 g of ammonium bicarbonate was prepared into 550 ml of aqueous solution to obtain solution II.

[0078] (2) Preparation of precipitate

[0079] Solution II was dripped into the strongly stirred solution I at a rate of about 120 ml / h to obtain precipitate III.

[0080] (3) Preparation of Catalyst

[0081] The obtained precipitate III was washed with deionized water and filtered, the filter cake was dried at 110°C for 6 hours, and calcined at 800°C for 8 hours in an air atmosphere to obtain a catalyst.

[0082] The small reactor of the present invention is used to carry out online reaction catalytic evaluation on the prepared catalyst.

[0083] Example 2

[0084] Catalyst "B" is composed of 30% Ni and 70% magnesium aluminum spinel, and the precipitant is ammonium bicarbonate. The preparation process of the catalyst is the same as that of "A".

[0085] Example 3

[0086] Catalyst "C" is composed of 20% Co and 80% magnesium aluminum spinel, the precipitant is ammonium bicarbonate, and the Co salt is cobalt nitrate. The preparation process of the catalyst is the same as that of "A".

[0087] Example 4

[0088] Catalyst "D" is composed of 30% Co and 70% magnesium aluminum spinel, the precipitant is ammonium bicarbonate, and the Co salt is cobalt nitrate. The preparation process of the catalyst is the same as that of "A".

[0089] Comparative Example 1

[0090] Catalyst "E" consists of 10% Ni and 90% MgO, and the precipitant is ammonium bicarbonate. The preparation process of the catalyst is the same as that of "A".

[0091] Table 1 Catalyst activity (methane conversion rate) of methane catalytic cracking hydrogen production measured in Examples and Comparative Examples

[0092]

[0093] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. An online catalytic evaluation device for a small reactor for producing hydrogen from methane by catalytic cracking, characterized in that: It includes a feeding unit, a reaction unit, a condensation and drying unit and a metering and analysis unit connected in sequence; The reaction unit includes a small reactor, the condensation and drying unit includes a connected condenser and a dryer, and the metering and analysis unit includes a wet flow meter; The inlet of the small reactor is connected to the outlet of the feeding unit, the outlet of the small reactor is connected to the inlet of the condenser, the outlet of the condenser is connected to the inlet of the dryer, and the outlet of the dryer is connected to the inlet of the wet flow meter; The small reactor comprises a tubular reactor and an electric heating furnace arranged around the tubular reactor, and a gas distributor is arranged at the inlet end of the tubular reactor.

2. The on-line catalytic evaluation device for a small-scale reactor for producing hydrogen from methane by catalytic cracking according to claim 1, characterized in that: The gas distributor is located in the tubular reactor, one end of which is connected to the feed port of the small reactor, and the other end of which is connected to the distribution pipe.

3. The on-line catalytic evaluation device for a small-scale reactor for producing hydrogen from methane by catalytic cracking according to claim 2, characterized in that: The gas distributor is an inverted T-shaped structure; the distribution pipe is opened along the axial direction of the reactor, and the opening angle direction is parallel to the axial direction of the reactor.

4. The on-line catalytic evaluation device for a small-scale reactor for producing hydrogen from methane by catalytic cracking according to claim 3 is characterized by: The openings on the distribution pipe are evenly and symmetrically distributed with the center of the circle as the center point, and the total area of ​​the openings is 20-30% of the cross-sectional area of ​​the bed layer of the small reactor.

5. The on-line catalytic evaluation device for a small-scale reactor for producing hydrogen from methane by catalytic cracking according to claim 1, characterized in that: The tubular reactor is also provided with a quartz boat for holding the catalyst and a thermocouple for measuring the reaction temperature of the system.

6. The on-line catalytic evaluation device for a small-scale reactor for producing hydrogen from methane by catalytic cracking according to claim 1, characterized in that: The condensation and drying unit further comprises a liquid collecting bottle, and the liquid collecting bottle is connected to the outlet of the condenser and the inlet of the dryer.

7. The on-line catalytic evaluation device for a small-scale reactor for producing hydrogen from methane by catalytic cracking according to claim 1, characterized in that: The condenser is a shell and tube structure, a cooling water inlet is provided at the lower end of the condenser, and a cooling water outlet is provided at the upper end of the condenser; the condensing tube in the condenser is a spiral coil; two drying tubes are provided, and desiccant is filled in the drying tubes.

8. The on-line catalytic evaluation device for a small-scale reactor for producing hydrogen from methane by catalytic cracking according to claim 1, characterized in that: The feeding unit comprises a methane cylinder, a hydrogen cylinder and a nitrogen cylinder, each of which is connected to a pressure reducing valve, each of which is connected to a rotor flowmeter, and each of which is connected to a premixer.

9. The on-line catalytic evaluation device for a small-scale reactor for producing hydrogen by cracking methane catalyst according to claim 1, characterized in that: The metering and analyzing unit also includes a gas chromatograph, and the outlet of the wet flow meter is connected to the inlet of the gas chromatograph or a venting pipeline.

10. An online catalytic evaluation method for a small reactor for producing hydrogen by catalytic cracking of methane, characterized in that: The method adopts the online catalytic evaluation device according to any one of claims 1 to 9, and the evaluation method comprises the following steps: The weighed and screened methane catalytic cracking hydrogen production catalyst is placed in a quartz boat, which is then placed in the middle of a tubular reactor; Inert nitrogen is introduced to exhaust the air in the tube, and the quartz reaction tube is heated at the same time, and the reduction temperature is set to 200-500°C and the reduction pressure is normal pressure; After the temperature reaches the pre-reduction temperature of the catalyst, the nitrogen is cut off, and the reducing gas hydrogen is introduced, and then the temperature is kept constant for a certain period of time to reduce the catalyst; After the reduction is completed, the hydrogen valve is closed, and the temperature is rapidly raised under nitrogen purge until the gas chromatograph no longer detects hydrogen, and then methane is introduced to start the reaction; During the reaction, the gaseous product first enters the condenser to condense the heavy components in the product, and then enters the drying tube to absorb the water in the product; The volume flow of the dried gas product is measured by a wet flow meter, a portion of the tail gas is introduced into an online gas chromatograph, and the rest of the tail gas is discharged; The gases after a certain reaction time are sampled and analyzed.

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