CN114917950B - Methanol to synthesis gas catalyst and its preparation method and application - Google Patents

Abstract

The present invention belongs to the technical field of new catalytic materials, and specifically relates to a methanol-to-syngas catalyst and its preparation method and application. With a 13X microporous molecular sieve as a carrier, the carrier, an active component precursor, a solvent and an auxiliary agent are placed in a closed kettle, the temperature is raised and kept warm, and the active component is coated on the carrier surface and the inner surface of its micropores under the dual effects of the gas-liquid critical state of the solvent and the auxiliary agent, and then dried and calcined to obtain a methanol-to-syngas catalyst; the present invention also provides its preparation method and application. The active components of the catalyst of the present invention are highly dispersed in the micropores of the molecular sieve, and it has high catalytic activity, high CO selectivity and low _CO2 selectivity when used in the process of methanol-to-syngas, and can stably control the _H2 /CO molar ratio to be close to 2:1, and the synthesis gas product can be directly applied to the Fischer-Tropsch synthesis industry.

Description

Methanol to synthesis gas catalyst and its preparation method and application

Technical Field

The present invention belongs to the technical field of new catalytic materials, and in particular relates to a methanol-to-syngas catalyst and a preparation method and application thereof.

Background technique

Academician Li Can and others have successfully synthesized liquid fuel methanol from green hydrogen produced by solar energy and captured _CO2 , which has once again promoted the widespread application of methanol in the fields of energy and chemical industry. Synthesis gas is an important chemical raw material, which is often produced from fossil fuels such as coal, coke, and natural gas, which has put great pressure on the energy structure. The comprehensive utilization of methanol to prepare synthesis gas is conducive to the sustainable development of energy and chemical industry.

Methanol decomposition to produce synthesis gas technology is the main method for using methanol in the synthesis gas industry.

Chinese patent CN107824190A discloses an efficient copper-based catalyst for hydrogen production by methanol decomposition, wherein the catalyst is a mixture of CuO, _ZnO , _Al2O3 , _{and MxOy} , wherein the weight percentage of each component is as follows: CuO is 10-60%, ZnO is 10-60%, _Al2O3 is 5-50%, _{and MxOy} is 1-10%, wherein _the alkaline earth metal M is selected from one of Mg, Ca, Ce, and Sr, and the following preparation method is adopted: (1) an Al-M modified carrier is prepared by modifying an alumina carrier by adding an alkaline earth metal; (2) a low molecular alcohol is added to the mother liquor of the modified carrier, and then an active metal salt solution and an alkaline precipitant are added to carry out a precipitation reaction, and after the reaction is completed _, the catalyst is obtained by solid-liquid separation, washing, drying, and _{roasting. The catalyst in the patent is a mixture of CuO, ZnO, Al2O3, and MxOy , which} efficiently produces hydrogen and carbon dioxide in the methanol decomposition reaction, but very little carbon monoxide, which does not meet the requirements of producing synthesis gas.

Chinese patent CN108686671A discloses the preparation of a low-temperature methanol decomposition catalyst, wherein the catalyst used is an iron-based catalyst modified with tin oxide, cerium oxide, lanthanum oxide and gallium oxide, and the molar ratio of each metal is Fe:Sn:Ce:La:Ga=100:0.5~10:0.1~1:0.1~1:0.1~1. The iron-based catalyst modified with tin oxide, cerium oxide, lanthanum oxide and gallium oxide in the patent has a CO selectivity of nearly 100% in the production of synthesis gas by methanol decomposition, but the conversion rate of methanol is low, and the best methanol conversion rate is 73.2%.

The Pd/CeO ₂ catalyst designed by Francesco Carraro et al. (Acs Applied Nano Materials 2018(1)41492-1501) achieved a methanol conversion rate of nearly 100% and a CO selectivity of 99.6%, but the high cost of precious metals limits its widespread application. The Cu _0.5 Co _0.5 Fe ₂ O ₄ catalyst designed by Nikolay Velinov et al. (Catalysis Communications 32(2013)41–46) reduced the cost of methanol decomposition catalysts, but its CO selectivity was only about 80%.

Therefore, it is urgent to develop a methanol-to-syngas catalyst that has low cost, high methanol conversion rate, high CO selectivity and a stable H ₂ /CO molar ratio, which has important research significance and economic value.

Summary of the invention

The purpose of the present invention is to provide a methanol to synthesis gas catalyst having high methanol to synthesis gas catalytic activity, high CO selectivity and low CO ₂ selectivity, and a stable H ₂ /CO molar ratio. The product can be directly applied to the Fischer-Tropsch synthesis industry. The present invention also provides a preparation method and application thereof.

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

The methanol-to-syngas catalyst of the present invention uses 13X microporous molecular sieve as a carrier, and the carrier, active component precursor, solvent and auxiliary agent are placed in a closed kettle, and the temperature is increased and kept warm. Under the dual effects of the gas-liquid critical state of the solvent and the auxiliary agent, the active component is coated on the surface of the carrier and the inner surface of its micropores, and then dried and calcined to obtain the methanol-to-syngas catalyst.

The active component precursor is one or more of nitrate, hydrochloride, acetate or zirconium oxychloride of nickel, copper, iron, cerium or zirconium.

The solvent is one or two of water, methanol, ethanol, acetone or ether.

The auxiliary agent is ammonium lauryl sulfate, sodium lauryl sulfate, EDTA, citric acid or sodium gluconate.

Based on the mass of the carrier, the loading amount of the active component in the methanol to synthesis gas catalyst is 0.5-40wt.%.

The preparation method of the methanol-to-syngas catalyst of the present invention comprises the following steps: using a 13X microporous molecular sieve as a carrier, mixing the carrier and an active component precursor and placing the mixture in a closed kettle, adding a solvent and an auxiliary agent into the closed kettle and sealing the kettle body; heating and keeping the closed kettle warm, coating the active component onto the carrier surface and the inner surface of its micropores under the dual effects of the gas-liquid critical state of the solvent and the auxiliary agent, then cooling and releasing the pressure, taking out the catalyst precursor, drying and calcining, and obtaining the methanol-to-syngas catalyst.

in:

The sealed kettle is heated to 40-260°C and kept warm for 2-36 hours.

The drying temperature is -50 to 80°C, and the drying time is 2 to 36 hours; the roasting temperature is 300 to 1000°C, and the roasting time is 2 to 24 hours.

The calcination atmosphere during the calcination process is air, nitrogen or H ₂ /N ₂ mixed gas.

The amount of the solvent used is 5% to 200% of the mass of the carrier; the amount of the auxiliary agent used is 1% to 15% of the mass of the solvent.

Application of the methanol-to-syngas catalyst of the present invention: After being loaded into a fixed bed reactor, the methanol-to-syngas catalyst is first pretreated and then used in the methanol-to-syngas reaction; the pretreatment atmosphere is _H2 / _N2 mixed gas, water vapor/ _H2 / _N2 mixed gas, methanol/ _H2 / _N2 mixed gas or water vapor/methanol/ _H2 / _N2 mixed gas; the pretreatment temperature is 300-600°C, and the pretreatment time is 0.5-8h.

The beneficial effects of the present invention are as follows:

The present invention provides a novel catalyst with 13X microporous molecular sieve as carrier and one or more of nickel, copper, iron, cerium, zirconium metal or its metal oxide as active component, and its preparation method has the following advantages: the closed kettle is heated to above the boiling point temperature of the solvent and the pressure in the closed kettle is increased by adjusting the temperature, so that the solvent is in a critical state where the gas phase and the liquid phase coexist, the liquid phase continues to gasify while the gas phase continues to liquefy, and the solvent is uniformly diffused inside the carrier. Nickel, copper, iron, cerium or zirconium metal ions migrate into the micropores of the 13X molecular sieve in the solvent in a critical state until they are uniformly coated on the surface of the molecular sieve and the inner surface of its micropores. However, only by transferring metal ions through the solvent, in the process of cooling and drying the raw materials, the re-migration of the solvent easily brings the metal ions out of the micropores of the molecular sieve and enriches them on the macroscopic surface of the carrier, which easily causes the agglomeration of the metal to reduce the activity of the catalyst. Therefore, the present invention introduces ammonium dodecyl sulfate, sodium dodecyl sulfate, EDTA, citric acid or sodium gluconate as an auxiliary agent during the preparation process, so that it is combined with the metal ions, thereby limiting the precipitation of the metal ions after entering the molecular sieve micropores, improving the dispersion of the metal in the molecular sieve micropores, and enhancing the catalytic activity of the catalyst. At the same time, the addition of the auxiliary agent can also optimize the surface tension of the solvent and promote the rate at which the solvent enters the molecular sieve micropores.

The active components of the catalyst of the present invention are highly dispersed in the micropores of the molecular sieve. When used in the process of preparing synthesis gas from methanol, the catalyst has high catalytic activity, high CO selectivity and low CO ₂ selectivity, and can stably control the H ₂ /CO molar ratio to be close to 2:1. The synthesis gas product can be directly applied to the Fischer-Tropsch synthesis industry.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is an XRD pattern of the catalyst in Example 1 of the present invention;

FIG. 2 is a SEM photograph of the catalyst in Example 1 of the present invention.

Detailed ways

The present invention is further described below with reference to the embodiments.

Example 1

Weigh 10g of 13X microporous molecular sieve and nickel nitrate, mix them evenly and place them in a sealed kettle, add water and citric acid to the sealed kettle and seal the kettle; heat the sealed kettle to 180°C and keep it for 12 hours, then cool it to room temperature, release the pressure and take out the catalyst precursor, dry it at 60°C for 12 hours, and calcine it at 600°C for 6 hours in an air atmosphere to obtain catalyst 1. The loading amount of nickel, the active component of the catalyst, is 5%; the amount of solvent is 10% of the mass of the carrier; and the amount of additive is 10% of the mass of the solvent. Specific parameters are shown in Table 1.

Embodiments 2 to 10

The specific steps are the same as those in Example 1, except for the following: active component precursor, solvent, additive, closed kettle temperature and holding time, low temperature drying temperature and time, calcination atmosphere, calcination temperature and calcination time. The specific parameters are shown in Table 1 and Table 2.

Table 1 Reaction conditions and reaction data of Examples 1 to 5

Table 2 Reaction conditions and reaction data of Examples 6 to 10

Comparative Example 1

No auxiliary agent citric acid was added, and the remaining steps and data were the same as in Example 1.

Comparative Example 2

No auxiliary agent EDTA was added, and the remaining steps and data were the same as in Example 2.

The catalysts obtained in Examples 1 to 10 and Comparative Examples 1 to 2 were used in the methanol-to-syngas reaction: the methanol-to-syngas catalyst was first loaded into a fixed bed reactor, and then used in the methanol-to-syngas reaction after pretreatment. The pretreatment atmosphere, pretreatment temperature and pretreatment time during the pretreatment process are specifically shown in Table 3. The pretreatment of the catalyst in Comparative Examples 1 and 2 was the same as that in Examples 1 and 2, respectively.

The catalytic performances of the catalysts in Examples 1 to 10 and Comparative Examples 1 to 2 are shown in Table 4. The test conditions are: 1 g catalyst, water-to-alcohol ratio 2:1, liquid flow rate 7.4 ml/h, and reaction temperature 350°C.

Table 3 Pretreatment atmosphere, pretreatment temperature and pretreatment time data in the pretreatment process of Examples 1 to 10

Example Pretreatment atmosphere Pretreatment temperature/℃ Pretreatment time/h Example 1 _H2 / _N2 mixed gas 500 1.5 Example 2 Water vapor/methanol/H ₂ /N ₂ mixed gas 450 2 Example 3 _H2 / _N2 mixed gas 500 1 Example 4 Water vapor/H ₂ /N ₂ mixed gas 600 0.5 Example 5 Water vapor/methanol/H ₂ /N ₂ mixed gas 300 8 Example 6 _H2 / _N2 mixed gas 400 1.5 Example 7 Water vapor/H ₂ /N ₂ mixed gas 550 4 Example 8 Water vapor/methanol/H ₂ /N ₂ mixed gas 350 4 Example 9 Methanol/ _H2 / _N2 mixed gas 450 1 Example 10 Water vapor/H ₂ /N ₂ mixed gas 500 1

Table 4 Performance data of the catalysts obtained in Examples 1 to 10 and Comparative Examples 1 to 2 for use in methanol to synthesis gas

Claims (6)

1. An application of a methanol-to-syngas catalyst, characterized in that: after being loaded into a fixed bed reactor, the methanol-to-syngas catalyst is first pretreated and then used in the methanol-to-syngas reaction; the preparation process of the methanol-to-syngas catalyst is as follows: using 13X microporous molecular sieve as a carrier, placing the carrier, active component precursor, solvent and auxiliary agent in a closed kettle, heating to 40-260° C. and keeping the temperature, so that the solvent is in a critical state where gas and liquid phases coexist, the liquid phase continues to gasify while the gas phase continues to liquefy, under the dual effects of the gas-liquid critical state of the solvent and the auxiliary agent, the active component is coated on the carrier surface and the inner surface of its micropores, and then dried and calcined to obtain the methanol-to-syngas catalyst; the auxiliary agent is ammonium dodecyl sulfate, sodium dodecyl sulfate, EDTA, citric acid or sodium gluconate; The active component precursor is one or more of nitrate, hydrochloride, acetate or zirconium oxychloride of nickel, copper, iron, cerium or zirconium; the solvent is one or two of water, methanol, ethanol, acetone or ether. 2. The use of the methanol to synthesis gas catalyst according to claim 1, characterized in that: based on the mass of the carrier, the loading amount of the active component in the methanol to synthesis gas catalyst is 0.5~40wt.%. 3. The use of the methanol to synthesis gas catalyst according to claim 1 is characterized in that: the closed kettle is heated to 40~260°C and kept warm for 2~36 hours; the drying temperature is -50~80°C and the drying time is 2~36 hours; the roasting temperature is 300~1000°C and the roasting time is 2~24 hours. 4. The use of the methanol to synthesis gas catalyst according to claim 1, characterized in that the calcination atmosphere during the calcination process is air, nitrogen or a _H2 / _N2 mixed gas. 5. The use of the methanol to synthesis gas catalyst according to claim 1, characterized in that the amount of the solvent is 5% to 200% of the mass of the carrier; the amount of the auxiliary agent is 1% to 15% of the mass of the solvent. 6. The use of the methanol to synthesis gas catalyst according to claim 1, characterized in that: the pretreatment atmosphere is _H2 / _N2 mixed gas, water vapor/ _H2 / _N2 mixed gas, methanol/ _H2 / _N2 mixed gas or water vapor/methanol/ _H2 / _N2 mixed gas; the pretreatment temperature is 300-600°C, and the pretreatment time is 0.5-8h.