AU2018446335B2

AU2018446335B2 - Catalyst for treatment of tail gas and preparation thereof

Info

Publication number: AU2018446335B2
Application number: AU2018446335A
Authority: AU
Inventors: Lei Wang
Original assignee: Pujing Chemical Industry Co Ltd
Current assignee: Pujing Chemical Industry Co Ltd
Priority date: 2018-10-22
Filing date: 2018-10-22
Publication date: 2022-12-08
Anticipated expiration: 2038-10-22
Also published as: WO2020082198A1; AU2018446335A1; RU2703712C1

Abstract

A carrier of a catalyst for treating a CO-coupled oxalate synthesis tail gas is provided. The carrier consists of Al

Description

CATALYST FOR TREATMENT OF TAIL GAS AND PREPARATION THEREOF

FIELD OF THE INVENTION

The invention relates to a catalyst for treating a tail gas.

BACKGROUND OF THE INVENTION

Oxalate is an important organic chemical raw material that can be used in fine chemicals to produce various dyes, medicines, solvents, extraction agents and various intermediates. Among them, hydrogenation of oxalate can be used to prepare a very important chemical raw material ethylene glycol. The synthesis of oxalate is an important step in the coal to ethylene glycol process. In the process of CO coupling synthesis of oxalate, the system pressure can be high due to the generation of an exhaust gas or tail gas, and thus it is necessary to periodically discharge the gas to release the pressure in the system. In this process, nitrogen oxides and alkyl nitrite in the system are released into the atmosphere, causing environmental pollution.

Among current technologies for treatment of a tail gas generated during oxalate synthesis by CO coupling, new processes or equipment are disclosed in most patents to reduce nitrogen oxides in the tail gas. As reported in Chinese Patent No. CN100493674C, the tail gas is first absorbed by an alkyl alcohol and then enters a catalyst bed for treatment. The treatment method not only requires high-energy consumption, but also has a low nitrogen oxide removal rate. The treated tail gas does not meet the emission standard. Chinese Patent No. CN102218259B reports the use of two rotating packed beds to treat a tail gas. Although the purpose of reducing nitrogen oxides is achieved, the energy consumption is high in the rotating bed and alkyl alcohol recycling.

There remains a new for an effective and efficient catalyst for reducing nitrogen oxides and alkyl nitrite in a tail gas.

SUMMARY OF THE INVENTION

The present invention provides a catalyst and its preparation and uses.

A carrier of a catalyst for treating a CO-coupled oxalate synthesis tail gas is provided. The carrier consists of Al ₂O ₃ and having a bimodal pore size distribution. The bimodal pore size distribution may have a first peak at 2-10 nm and a second peak at 10-50 nm. The carrier may have a pore size of 0.05-2.0 cm ³/g. The carrier may have a specific surface area of 5-120 m ²/g. The carrier may have a pore volume of about 0.05-2 cm ³/g. The carrier may consist of α-Al ₂O ₃ and γ-Al ₂O ₃, and the α-Al ₂O ₃ may account for 50-99 wt%of the carrier.

The catalyst may comprise an active component, which may comprise a precious metal. The precious metal may be platinum or palladium.

A catalyst is provided. The catalyst comprises an active component and the carrier of the present invention. The active component is selected from the group consisting of platinum, palladium and a combination thereof. The active component may have a particle size of 2-35 nm. The active component may have a dispersion of 10-50%.

For each carrier of the present invention, a process for preparing the carrier is provided. The carrier preparation process comprises dissolving a carrier precursor and two surfactants of different molecular weights in water to make an aluminum solution; adjusting pH of the aluminum solution to 2-5; aging the acidic aluminum solution to make an aluminum sol; drying the aluminum sol to form a dry sample; grounding the dry sample to make a grounded dry sample; calcining the grounded dry sample to make Al ₂O ₃ powder; and making Al ₂O ₃ particles from the Al ₂O ₃ powder. As a result, a carrier consisting of Al ₂O ₃ particles is prepared. Each of the surfactant may be selected from the group consisting of PEG300, PEG3000, PEG10000 and a combination thereof.

For each catalyst of the present invention, a process for preparing the catalyst is provided. The catalyst preparation process comprises adding the carrier of the present invention into a solution comprising an active component precursor and a solvent; removing the solvent to make a sample; and calcining the sample. As a result, the catalyst is prepared.

A method for treating a CO-coupled oxalate synthesis tail gas is provided. The treatment comprises exposing the tail gas to an effective amount of the catalyst of the present invention that has been reduced. The treatment lowers the level of the nitrogen oxides in the tail gas from higher than 80 ppm to below 50 ppm.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a catalyst for treating a tail gas and its preparation and uses. The catalyst comprises an active component and a carrier. The inventors have surprisingly discovered that the structure of a catalyst can be modified by adjusting the pore size distribution, specific surface area and pore volume of its carrier Al ₂O ₃ such that the active component in the catalyst can be highly dispersed. Such a catalyst can effectively reduce nitrogen in a tail gas generated in oxalate synthesis by CO coupling. For example, the resulting treated tail gas contains nitrogen oxides at a level below 50 ppm and meets the emission standard.

The term “tail gas” used herein refers to a gas discharged into the atmosphere from a chemical process that generates the gas. A CO-coupled oxalate synthesis tail gas is a tail gas that is generated in oxalate synthesis by CO-coupling and is discharged into the atmosphere. The CO-coupled oxalate synthesis tail gas may comprise nitrogen oxides (NO _x) and methyl nitrite (MN) .

The term “feed gas” used herein refers to a gas that is introduced into a chemical process. The feed gas may react with other substances in the chemical process. The feed gas used in oxalate synthesis by CO-coupling may comprise nitrogen monoxide (NO) , carbon monoxide (CO) , methanol (CH ₃OH or CH ₄O) , methyl nitrite (MN) and nitrogen (N ₂) .

The term “catalyst” used herein refers to a substance in a chemical reaction that promotes the chemical reaction. A catalyst for treating a CO-coupled oxalate synthesis tail gas promotes chemical reactions to reduce nitrogen oxides (NO _x) and/or methyl nitrite (MN) in the tail gas. The catalyst comprises an active component and a carrier.

The term “active component” used herein refers to a substance in the catalyst that is responsible for promoting chemical reactions to reduce nitrogen oxides (NO _x) and/or methyl nitrite (MN) in a CO-coupled oxalate synthesis tail gas.

The term “carrier” used herein refers to a substance in the catalyst that provides support for an active component. Depending on its structure, the carrier may change the distribution of the active component on the carrier such that the catalytic activity of the active component may be modified.

The term “pore size” used herein refers to the diameter of a pore. Where the pore is not spherical, the pore size may be an average diameter of the pore. The term “bimodal pore size distribution” used herein refers to the biomodal shape of a pore size distribution (PSD) for pores having different pore sizes in a carrier or a catalyst, i.e., a PSD having two distinct peaks (or local maxima) .

The term “specific surface area” used herein refers to a property of a solid defined as the total surface area of a material per unit of mass, or solid or bulk volume. The term “pore volume” used herein refers to the total volume of small openings in a substance. A substance having a large pore volume may have a large specific surface area.

The term “particle size” used herein refers to the diameter of a particle, which may be solid, liquid or gas. Where the particle is not spherical, the particle size may be the average diameter of the particle. The term “nanoparticle size distribution” used herein refers to a number percentage of particles in a size range over the total number of particles. The term “dispersion” used herein refers to a number percentage of atoms of an active component exposed on the surface of a catalyst.

The term “active component loading” refers to the mass ratio of an active component to a carrier in a catalyst.

A carrier of a catalyst for treating a CO-coupled oxalate synthesis tail gas is provided. The carrier is aluminum oxide (Al ₂O ₃) . The carrier may consist of one or more crystalline polymorphic phases. For example, the carrier may consist of α-Al ₂O ₃ and γ-Al ₂O ₃. α-Al2O ₃ may account for about 50-95 wt%or 87-99 wt%of the carrier.

The carrier may have a bimodal pore size distribution. The bimodal pore size distribution may have a first peak at about 2-8 nm and a second peak at about 20-50 nm, or a first peak at about 15-35 nm and a second peak at about 65-100 nm. The carrier may have a pore size of about 1-200 nm, 2-120 nm, 2-35 nm or 55-120 nm

The carrier may have a specific surface area of about 5-35 m ²/g or 55-120 m ²/g. The carrier may have a pore volume of about 0.05-1.05 cm ³/g or 1.2-2 m ²/g.

The term “carrier precursor” used herein refers to a substance that provides the carrier in the catalyst. The carrier precursor may be a substance containing aluminum. For example, the carrier precursor may be aluminum isopropoxide, aluminum nitrate or aluminum chloride.

A catalyst comprising an active component and the carrier of this invention is provided. The active component may be about 0.01-2.00 wt%, 0.01-0.5 wt%or 0.5-2.0 wt%of the weight of the carrier. The catalyst may have a specific surface area of 1-200 m ²/g, 3-100 m ²/g, 3-20 m ²/g or 25-100 m ²/g. The catalyst may have a pore volume of about 0.01-2.00 m ²/g, 0.02-1.00 m ²/g, 0.02-0.50 cm ³/g or 0.5-1.0 m ²/g.

The active component may comprise platinum (Pt) , palladium (Pd) or a combination thereof, preferably Pt. The active component may be in the form of particles, for example, nanoparticles. The active component may have a particle size of about 1-30 nm, 2-25 nm, 2-15 nm or 15-25 nm. The active component may have a dispersion of about 5-60%, 10-50%, 10-30%or 30-50 %.

The term “active component precursor” used herein refers to a substance that provides the active component in the catalyst. For example, the active component precursor may be platinum nitrate, platinum sulfate, or platinum chloride. The active component precursor may be dissolved in a solvent to form an active component precursor solution.

For each carrier of the present invention, a process for preparing the carrier is provided. The process may comprise dissolving a carrier precursor and two surfactants of different molecular weights in water to make an aluminum solution; adjusting pH of the aluminum solution to be acidic; aging the acidic aluminum solution to make an aluminum sol; drying the aluminum sol to form a dry sample; grounding the dry sample; calcining the grounded dry sample to make Al ₂O ₃ powder; and making Al ₂O ₃ particles from the Al ₂O ₃ powder. As a result, a carrier consisting of Al ₂O ₃ particles is prepared.

In the dissolving step, each surfactant may be PEG300, PEG3000, PEG10000 or a combination thereof. The solution may be heated for hydration. The hydration temperature may be about 40-100 ℃.

In the pH adjustment step, an acid may be added to the aluminum solution to adjust its pH. The acid may be malic acid, tartaric acid, acetic acid or a combination thereof. The acidic aluminum solution may have a pH of 2-5.

In the aging step, the acidic aluminum solution may be aged for 4-24 h.

In the drying step, the aluminum sol may be dried by evaporation. The evaporation temperature may be 60-100 ℃.

In the calcining step, the grounded dry sample may be heated at a heating rate of 1 ℃/min to a calcining temperature and calcined in an air atmosphere to obtain the Al ₂O ₃ powder. The calcining temperature may be 1000-1300 ℃. The calcining time may be 5-8 h. Al ₂O ₃ powders may be shaped into Al ₂O ₃ particles.

For each catalyst of the present invention, a process for preparing the catalyst is provided. The catalyst preparation process comprises adding the carrier of the present invention, consisting of Al ₂O ₃ particles, into a solution comprising an active component precursor in a solvent; removing the solvent to obtain a sample; and calcining the sample. As a result, the catalyst is prepared. The solvent may be removed by rotary evaporation. The sample may be heated at a heating rate of 1 ℃/min to a calcining temperature. The calcining temperature may be 450 ℃. The calcining time may be 3-8 h.

A method for treating a CO-coupled oxalate synthesis tail gas having a high level of nitrogen oxides is provided. The treatment method comprises exposing the tail gas to an effective amount of the catalyst of the present invention that has been reduced. Before the treatment, the tail gas may have the nitrogen oxides at a level greater than about 50, 60, 70, 80, 90 or 100 ppm. After the treatment, the tail gas may have the nitrogen oxides at a level below about 80, 70, 60, 50, 40, 30, 20 or 10 ppm, preferably below about 50 ppm.

The catalyst may be reduced under reducing conditions before or during the treatment of the CO-coupled oxalate synthesis tail gas. For example, the catalyst may be exposed to a reducing gas. The reducing gas may comprise hydrogen (H ₂) , nitrogen (N ₂) or a combination thereof. The catalyst may be reduced at a temperature of 300-500 ℃, for example 400 ℃, for at least, for example, about 3, 6, 9, 12, 15, 18, 21 or 24 h.

Nitrogen oxides (NO _x) may include various substances such as nitrous oxide (N ₂O) , nitrogen monoxide (NO) , nitrogen dioxide (NO ₂) , dinitrogen tetroxide (N ₂O ₃) , dinitrogen tetroxide (N ₂O ₄) and nitrous oxide (N ₂O ₅) and the like.

The term “about” as used herein when referring to a measurable value such as an amount, a percentage, and the like, is meant to encompass variations of ±20%or ±10%, more preferably ±5%, even more preferably ±1%, and still more preferably ±0.1%from the specified value, as such variations are appropriate.

Example 1. Carrier Al ₂O ₃-1

Carrier Al ₂O ₃-1 was prepared. 40.848 g aluminum isopropoxide was dissolved in 150 ml deionized water to make a solution in a 250 ml beaker. 10 g PEG 300 was added to the solution, stirred, and heated to 80 ℃. After the solution became transparent and uniform, 0.4 g glacial acetic acid was added and refluxed for 6h to obtain aluminum sol. The aluminum sol was dried in a vacuum oven at 60 ℃ to obtain a dry sample. The dry sample was grounded, heated to 1200 ℃ at a rate of 5 ℃/min, and calcined for 3 h to obtain Al ₂O ₃-1 powder. The Al ₂O ₃-1 powder was molded to obtain Al ₂O ₃-1 granules.

Example 2. Carrier Al ₂O ₃-2

Carrier Al ₂O ₃-2 was prepared according to the process as described in Example 1 except that PEG 3000 was used instead of PEG 300.

Example 3. Carrier Al ₂O ₃-3

Carrier Al ₂O ₃-3 was prepared according to the process as described in Example 1 except that PEG 10000 was used instead of PEG 300.

Example 4. Carrier Al ₂O ₃-4

Carrier Al ₂O ₃-4 was prepared according to the process as described in Example 3 except that malic acid was used instead of acetic acid.

Example 5. Carrier Al ₂O ₃-5

Carrier Al ₂O ₃-5 was prepared according to the process as described in Example 3 except that tartaric acid was used instead of acetic acid.

Example 6. Carrier Al ₂O ₃-6

Carrier Al ₂O ₃-6 was prepared according to the process as described in Example 5 except that 5 g PEG 3000 and 5 g PEG 10000 was used instead of 10 g PEG 10000.

Example 7. Carrier Al ₂O ₃-7

Carrier Al ₂O ₃-7 was prepared according to the process as described in Example 6 except that 0.2 g tartaric acid was used instead of 0.4 g tartaric acid.

Example 8. Carrier Al ₂O ₃-8

Carrier Al ₂O ₃-8 was prepared according to the process as described in Example 6 except that 0.3 g tartaric acid was used instead of 0.4 g tartaric acid.

Example 9. Carrier Al ₂O ₃-9

Carrier Al ₂O ₃-9 was prepared according to the process as described in Example 6 except that 0.5 g tartaric acid was used instead of 0.4 g tartaric acid.

Example 10. Catalysts Pt-Al ₂O ₃

Catalyst Pt-Al ₂O ₃-1 was prepared with 0.5 wt%Pt loading. Al ₂O ₃-1 particles were added to 16 g of a 0.511 wt%platinum nitrate solution in a 10 ml beaker, and then dried under rotary evaporation at 80 ℃ to obtain a dry sample. The dried sample was grounded and heated to 450 ℃ for 5 h at a heating rate of 1 ℃/min in an air atmosphere to obtain a catalyst Pt-Al ₂O ₃-1.

Catalysts Pt-Al ₂O ₃-2, Pt-Al ₂O ₃-3, Pt-Al ₂O ₃-4, Pt-Al ₂O ₃-5, Pt-Al ₂O ₃-6, Pt-Al ₂O ₃-7, Pt-Al ₂O ₃-8 and Pt-Al ₂O ₃-9 were prepared according to the process used to prepare Pt-Al ₂O ₃-1 except that carriers Al ₂O ₃-2, Al ₂O ₃-3, Al ₂O ₃-4, Al ₂O ₃-5, Al ₂O ₃-6, Al ₂O ₃-7, Al ₂O ₃-8 and Al ₂O ₃-9 were used instead of Al ₂O ₃-1, respectively.

Example 11. Carrier structure

The structure of the carriers of Examples 1-9 was analyzed. Table 1 shows the specific surface area, average pore size, content of α-Al ₂O ₃ and pore distribution for these carriers. Carriers Al ₂O ₃-6, Al ₂O ₃-7, Al ₂O ₃-8 and Al ₂O ₃-9 exhibited a bimodal pore size distribution.

Table 1. Carrier structure

Example 12. Catalytic effects

The catalysts of Example 10 were evaluated according to the following method:

(1) The temperature was raised to 400 ℃ at a heating rate of 1 ℃/min under an atmosphere of 20%H ₂ and 80%N ₂, and the temperature was maintained for 12 h.

(2) A feed gas was introduced. The feed gas contained 4 %methyl nitrite (MN) , 10 %NO, 10 %CO, 3 %CH ₄O, and the remaining was N ₂, based on the total volume of the feed gas.

(3) The temperature was maintained at 230 ℃, the pressure was 0.1 MPa, and the space velocity was 3000 h ^-1.

Table 2 shows the specific surface area, average pore size, Pt dispersion and Pt average pore size of the catalysts and the contents of nitrogen oxides (NO _x) and methyl nitrite (MN) in the tail gas treated with the catalysts. For all the catalysts tested, the treated tail gas contained no MN and contained NO _x below 50 ppm. The tail gas treated with catalysts Pt-Al ₂O ₃-6, Pt-Al ₂O ₃-7, Pt-Al ₂O ₃-8 or Pt-Al ₂O ₃-9, whose respective carriers had a bimodal particle size distribution, showed a NO _x level no more than 20 ppm and no MN.

Table 2. Catalytic effects

Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims without departing from the invention.

Claims

A carrier of a catalyst for treating a CO-coupled oxalate synthesis tail gas, consisting of Al ₂O ₃ and having a bimodal pore size distribution.
The carrier of claim 1, wherein the bimodal pore size distribution has a first peak at 2-10 nm and a second peak at 10-50 nm.
The carrier of claim 1, wherein the carrier has a pore size of 0.05-2.0 cm ³/g.
The carrier of claim 1, wherein the carrier has a specific surface area of 5-120 m ²/g.
The carrier of claim 1, wherein the carrier has a pore volume of about 0.05-2 cm ³/g.
The carrier of claim 1, wherein the carrier consists of α-Al ₂O ₃ and γ-Al ₂O ₃, and wherein the α-Al ₂O ₃ accounts for 50-99 wt%of the carrier.
The carrier of claim1, wherein the catalyst comprises an active component, and wherein the active component comprises a precious metal.
The carrier of claim 6, wherein the precious metal is platinum or palladium.
A catalyst comprising an active component and the carrier of claim 1, wherein the active component is selected from the group consisting of platinum, palladium and a combination thereof.
The catalyst of claim 9, wherein the active component has a particle size of 2-35 nm.
The catalyst of claim 9, wherein the active component has a dispersion of 10-50%.
A process for preparing the carrier of claim 1, comprising:

(a) dissolving a carrier precursor and two surfactants of different molecular weights in water to make an aluminum solution;

(b) adjusting pH of the aluminum solution to 2-5;

(c) aging the acidic aluminum solution to make an aluminum sol;

(d) drying the aluminum sol to form a dry sample;

(e) grounding the dry sample to make a grounded dry sample;

(f) calcining the grounded dry sample to make Al ₂O ₃ powder; and

(g) making Al ₂O ₃ particles from the Al ₂O ₃ powder, whereby a carrier consisting of Al ₂O ₃ particles is prepared.
The process of claim 12, wherein each of the surfactants is selected from the group consisting of PEG300, PEG3000, PEG10000 and a combination thereof.
A process for preparing the catalyst of claim 9, comprising:

(a) adding the carrier of claim 1 into a solution comprising an active component precursor and a solvent;

(b) removing the solvent to make a sample; and

(c) calcining the sample, whereby the catalyst is prepared.
A method for treating a CO-coupled oxalate synthesis tail gas having nitrogen oxides at a level higher than 80 ppm, comprising exposing the tail gas to an effective amount of the catalyst of claim 9, wherein the catalyst has been reduced, whereby the level of the nitrogen oxides in the tail gas is lowed to below 50 ppm.