阅读说明：本技术 一种多价态异质结铁基催化剂及其应用 (Multi-valence heterojunction iron-based catalyst and application thereof ) 是由 陈海鹏 马宁宁 王晨玮 王幽娇 刘晨磊 申嘉淼 于 2021-09-26 设计创作，主要内容包括：本发明提供一种多价态异质结铁基催化剂及其应用,属于催化剂制备技术领域。所述多价态异质结铁基催化剂由以下质量份数的各组份组成：60～75份磁铁矿石粉作催化剂、15～20份纳米镁粉作还原剂、5～10份草木灰作加氢助剂、5～10份石英粉作助磨剂。该催化剂的原料成本低、制备方法简单、使用条件温和。使用时,经过一定浓度的氢气进行预活化,可以显著提高低碳烯烃的选择性和二氧化碳的转化率。(The invention provides a multivalent heterojunction iron-based catalyst and application thereof, belonging to the technical field of catalyst preparation. The multi-valence heterojunction iron-based catalyst comprises the following components in parts by mass: 60-75 parts of magnetite powder as a catalyst, 15-20 parts of nano magnesium powder as a reducing agent, 5-10 parts of plant ash as a hydrogenation aid and 5-10 parts of quartz powder as a grinding aid. The catalyst has the advantages of low raw material cost, simple preparation method and mild use conditions. When the catalyst is used, the selectivity of low-carbon olefin and the conversion rate of carbon dioxide can be obviously improved by pre-activating with hydrogen with a certain concentration.)

1. A multi-valence heterojunction iron-based catalyst, characterized in that: the paint comprises the following components in parts by mass: 60-75 parts of magnetite powder, 15-20 parts of nano magnesium powder, 5-10 parts of plant ash and 5-10 parts of quartz powder;

the multivalent heterojunction iron-based catalyst is prepared by the following steps:

1) sequentially adding the following materials in parts by weight into a ball milling tank: 60-75 parts of magnetite powder, 15-20 parts of nano magnesium powder, 5-10 parts of plant ash and 5-10 parts of quartz powder, wherein the mass ratio of grinding balls to materials in a ball milling tank is 55: 1-30: 1; replacing air in the ball milling tank with hydrogen, and placing the ball milling tank on a ball mill for ball milling for 3-5 hours after the air in the ball milling tank is completely replaced by the hydrogen to obtain powder;

2) placing the powder obtained in the step 1) in a tablet press for cold press molding, wherein the cold press pressure is 250-300 MPa, and crushing and granulating to obtain the multi-valence heterojunction iron-based catalyst.

2. The multivalent heterojunction iron-based catalyst of claim 1, wherein: the granularity of the magnetite powder is below 200 meshes.

3. The multivalent heterojunction iron-based catalyst of claim 1, wherein: the particle size of the magnesium powder is less than 100 nm.

4. The multivalent heterojunction iron-based catalyst of claim 1, wherein: the ball milling atmosphere in the step 1) is hydrogen, and the rotating speed of a main shaft of the ball mill is 500-600 rpm.

5. The multivalent heterojunction iron-based catalyst of claim 1, wherein: the particle size of the multivalent heterojunction iron-based catalyst prepared in the step 2) is 0.5-1 mm.

6. The use of the multi-valence heterojunction iron-based catalyst of any one of claims 1 to 5 in the preparation of low-carbon olefins by carbon dioxide hydrogenation.

Technical Field

The invention belongs to the technical field of catalyst preparation, relates to an iron-based catalyst, and particularly relates to a multi-valence heterojunction iron-based catalyst and application thereof.

Background

With the increasing content of carbon dioxide, the global greenhouse effect is more and more remarkable. The carbon dioxide is hydrofined to produce high-quality chemical products such as low-carbon olefin and the like, so that the emission of the carbon dioxide can be reduced, and a scheme is provided for sustainable development of the chemical industry. The energy barrier for preparing the low-carbon olefin by directly hydrogenating the carbon dioxide is high, the selectivity of the low-carbon olefin is poor, the additional values of byproducts such as methane, carbon monoxide and the like are low, the economic benefit is poor, and a high-efficiency catalyst is required. The existing carbon dioxide hydrogenation for preparing low-carbon olefin generally adopts two schemes of reverse water gas conversion combined with a Fischer-Tropsch synthesis route (RWGS + FTS) and a methanol route, and the corresponding catalysts are an iron-based catalyst and a metal oxide/zeolite composite catalyst respectively. However, when iron-based catalysts are used, the selectivity to lower olefins in the product is poor (< 58%). Although the selectivity of the low-carbon olefin of the metal oxide/zeolite composite catalyst (such as ZnO-ZrO 2/SAPO-34) is high (80%), the conversion rate of carbon dioxide is low (less than 20%). At present, the carbon dioxide hydrogenation catalyst has short service life, high requirements on operation and equipment, high energy consumption and high cost.

Disclosure of Invention

In order to solve the defects in the prior art, the first purpose of the present invention is to provide a multivalent heterojunction iron-based catalyst, and the second purpose is to provide an application of the multivalent heterojunction iron-based catalyst in the preparation of low carbon olefins by carbon dioxide hydrogenation. The multi-valence heterojunction iron-based catalyst disclosed by the invention is low in raw material cost, simple in preparation method and capable of remarkably improving the selectivity of low-carbon olefin and the conversion rate of carbon dioxide.

In order to achieve the purpose, the invention adopts the following specific scheme:

a multi-valence state heterojunction iron-based catalyst comprises the following components in parts by mass: 60-75 parts of magnetite powder, 15-20 parts of nano magnesium powder, 5-10 parts of plant ash and 5-10 parts of quartz powder;

the multivalent heterojunction iron-based catalyst is prepared by the following steps:

1) sequentially adding the following materials in parts by weight into a ball milling tank: 60-75 parts of magnetite powder, 15-20 parts of nano magnesium powder, 5-10 parts of plant ash and 5-10 parts of quartz powder, wherein the mass ratio of grinding balls to materials in a ball milling tank is 55: 1-30: 1; replacing air in the ball milling tank with hydrogen, and placing the ball milling tank on a ball mill for ball milling for 3-5 hours after the air in the ball milling tank is completely replaced by the hydrogen to obtain powder;

2) placing the powder obtained in the step 1) in a tablet press for cold press molding, wherein the cold press pressure is 250-300 MPa, and crushing and granulating to obtain the multi-valence heterojunction iron-based catalyst.

As a further optimization of the above scheme, the particle size of the magnetite powder is 200 mesh or less.

As a further optimization of the scheme, the particle size of the magnesium powder is less than or equal to 100 nm.

As a further optimization of the scheme, the ball milling atmosphere in the step 1) is hydrogen, and the rotation speed of a main shaft of the ball mill is 500-600 rpm.

As a further optimization of the scheme, the particle size of the multivalent heterojunction iron-based catalyst prepared in the step 2) is 0.5-1 mm.

The invention also provides application of the multivalent heterojunction iron-based catalyst in preparation of low-carbon olefin by carbon dioxide hydrogenation.

The beneficial effects of the invention are mainly expressed as follows:

in the raw material composition of the multivalent heterojunction iron-based catalyst, magnetite ore powder is used as the catalyst, nano magnesium powder is used as a reducing agent, plant ash is used as a hydrogenation aid, and quartz powder is used as a grinding aid, the magnetite ore powder is partially chemically reduced under the action of high-energy mechanical force through the nano magnesium powder, the reduction degree is controlled through the grinding aid, powder containing multivalent iron is formed, and the granular multivalent heterojunction iron-based catalyst is prepared through cold press molding, crushing and granulation. The present invention utilizes the principle of mechanochemical reduction action and uses nano magnesium powder as reducing agent to partially reduce magnetite powder in the course of ball milling. The high-energy mechanical force can not only reduce the particle size and the grain size, but also can locally reduce the grain sizePartially reducing the iron oxide to a multivalent state: such as Fe³⁺、Fe²⁺、Fe⁰Etc., and oxygen vacancy defects are generated. The oxygen vacancy defect can be used as a trap site to efficiently trap magnesium atoms and K₂CO₃(plant ash) to form a local heterostructure. When the catalyst is used for the hydrogenation reaction of carbon dioxide, the local heterostructure on the surface of the catalyst provides an active site for carbon dioxide molecules, so that the adsorption structure of the carbon dioxide molecules is changed, and the conversion rate of the carbon dioxide and the selectivity of low-carbon olefin are improved.

Detailed Description

The technical scheme of the invention will be clearly and completely described in the following by combining the embodiment of the invention.

Example 1

A multivalent state heterojunction iron-based catalyst for preparing low-carbon olefin by carbon dioxide hydrogenation comprises the following components in parts by weight: 60 parts of magnet ore powder, 20 parts of nano magnesium powder, 10 parts of plant ash and 10 parts of quartz powder.

The granularity of the magnetite powder is below 200 meshes.

The granularity of the magnesium powder is less than 100 nm.

A multivalent state heterojunction iron-based catalyst for preparing low-carbon olefin by carbon dioxide hydrogenation comprises the following preparation steps:

1) sequentially adding the following materials in parts by weight into a ball milling tank: 60 parts of magnetite powder, 20 parts of magnesium powder, 10 parts of plant ash and 10 parts of quartz powder, wherein the mass ratio of grinding balls to materials in a ball milling tank is 55:1, then replacing air in the ball milling tank with hydrogen, placing the ball milling tank on a ball mill for ball milling for 5 hours after the air in the ball milling tank is completely replaced by the hydrogen, and obtaining powder when the rotating speed of a main shaft of the ball mill is 500 rpm;

2) putting the powder obtained in the step 1) into a tablet press for cold press molding, wherein the cold press pressure is 300 MPa, and crushing and granulating to obtain the multi-valence heterojunction iron-based catalyst.

The ball milling atmosphere in the step 1) is hydrogen.

The particle size of the multivalent heterojunction iron-based catalyst prepared in the step 2) is 0.5-1 mm.

The following tests were performed on a multivalent heterojunction iron-based catalyst product:

and (2) loading the multivalent state heterojunction iron-based catalyst into a continuously operated fixed bed reactor, heating to 400 ℃, continuously introducing hydrogen for 4 hours at a gas flow rate of 50 ml/min, and activating the catalyst. Then, the temperature is adjusted to 320 ℃, the pressure is 1.0 MPa, carbon dioxide and hydrogen are introduced at the hydrogen-carbon ratio of 3:1, the gas flow rate is carbon dioxide: 17.5 ml/min, hydrogen 52.5 ml/min, argon: 10 ml/min. The selectivity of the hydrogenated low-carbon olefin was 49.5% and the conversion of carbon dioxide was 21.3% as determined by gas chromatography.

Example 2

A multivalent state heterojunction iron-based catalyst for preparing low-carbon olefin by carbon dioxide hydrogenation comprises the following components in parts by weight: 75 parts of magnet ore powder, 15 parts of nano magnesium powder, 5 parts of plant ash and 5 parts of quartz powder.

The granularity of the magnetite powder is below 200 meshes.

The granularity of the magnesium powder is less than 100 nm.

A multivalent state heterojunction iron-based catalyst for preparing low-carbon olefin by carbon dioxide hydrogenation comprises the following preparation steps:

1) sequentially adding the following materials in parts by weight into a ball milling tank: 75 parts of magnetite powder, 15 parts of magnesium powder, 5 parts of plant ash and 5 parts of quartz powder, wherein the mass ratio of grinding balls to materials in a ball milling tank is 55:1, then replacing air in the ball milling tank with hydrogen, placing the ball milling tank on a ball mill for ball milling for 5 hours after the air in the ball milling tank is completely replaced by the hydrogen, and obtaining powder when the rotating speed of a main shaft of the ball mill is 500 rpm;

2) putting the powder obtained in the step 1) into a tablet press for cold press molding, wherein the cold press pressure is 300 MPa, and crushing and granulating to obtain the multi-valence heterojunction iron-based catalyst.

The ball milling atmosphere in the step 1) is hydrogen.

The particle size of the multivalent heterojunction iron-based catalyst prepared in the step 2) is 0.5-1 mm.

The following tests were performed on a multivalent heterojunction iron-based catalyst product:

and (2) loading the multivalent state heterojunction iron-based catalyst into a continuously operated fixed bed reactor, heating to 400 ℃, continuously introducing hydrogen for 4 hours at a gas flow rate of 50 ml/min, and activating the catalyst. Then, the temperature is adjusted to 320 ℃, the pressure is 1.0 MPa, carbon dioxide and hydrogen are introduced at the hydrogen-carbon ratio of 3:1, the gas flow rate is carbon dioxide: 17.5 ml/min, hydrogen 52.5 ml/min, argon: 10 ml/min. The selectivity of the hydrogenated low-carbon olefin was 50.6% and the conversion of carbon dioxide was 20.7% as determined by gas chromatography.

It should be noted that the above-mentioned embodiments illustrate rather than limit the scope of the invention, which is defined by the appended claims. It will be apparent to those skilled in the art that certain insubstantial modifications and adaptations of the present invention can be made without departing from the spirit and scope of the invention.