CN106881133B

CN106881133B - Catalyst for synthesizing ammonia

Info

Publication number: CN106881133B
Application number: CN201510933395.5A
Authority: CN
Inventors: 陈萍; 常菲; 郭建平; 王培坤; 高文波
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2015-12-15
Filing date: 2015-12-15
Publication date: 2019-12-06
Anticipated expiration: 2035-12-15
Also published as: CN106881133A

Abstract

The invention relates to a catalyst for ammonia synthesis, comprising nitrides of manganese and related supports and additives. The invention is used as a novel catalytic material, and shows good catalytic activity in the synthesis ammonia reaction.

Description

Catalyst for synthesizing ammonia

Technical Field

The invention relates to a catalyst technology, and particularly provides a catalyst for ammonia synthesis and application thereof in ammonia synthesis reaction.

Background

Ammonia is a basic raw material for producing important chemical products such as chemical fertilizers, nitric acid, plastics and the like, Haber-Bosch realizes high-pressure synthesis of ammonia for the first time, and the synthesis of ammonia has very important significance in industrial production. The catalysts currently widely used in industry for ammonia synthesis are iron-based and ruthenium-based catalysts. Mittasch found a K promoted Fe-based catalyst; M.Muhler loads metal ruthenium on MgO carrier, and adds alkali (earth) metal auxiliary agents Ba and Cs for synthetic ammonia reaction, so as to obtain better synthetic ammonia activity [ H.Bielawa, O.Hinrichsen, A.Birkner, M.Mullerangew.chem.int.Ed, 2001,40,6 ]. Although iron-based and ruthenium-based catalysts have been industrialized for ammonia synthesis reaction, the high energy consumption of the process and how to improve the harsh conditions of high temperature and high pressure required by the reaction are major problems faced by the development of the ammonia synthesis industry. According to the thermodynamic equilibrium of the reaction, the synthetic ammonia reaction can be carried out at normal temperature and normal pressure, the limitation of iron-based and ruthenium-based catalysts is overcome, other metal-based catalysts are explored, and the method is an effective way for developing a new generation of synthetic ammonia catalysts.

Disclosure of Invention

MnN and LiH are fully ball-milled, and then are heated to more than 250 ℃ in a mixed gas of N2/H2 with the ratio of 1:3, and the excellent synthetic ammonia performance is shown as shown in figure 1. In the reaction of synthesizing ammonia, the catalyst provided by the invention can obtain ideal effect, and the reaction performance is superior to that of a 5% Ru/MgO catalyst under the same condition. XRD results after reaction show that the sample is Mn nitride and LiH, and further confirm the catalytic action of the Mn-based catalyst and the auxiliary agent thereof on the synthesis of ammonia.

Further studies have shown that catalysts formed by combining manganese nitrides (MnN, Mn3N2, Mn2N, Mn4N, Li7MnN4, etc.) with supports or additives all have similar catalytic activity for ammonia synthesis.

The catalyst carrier for synthesizing ammonia consists of main body and additive, the main body is nitrogen-containing compound of manganese, and the additive includes one or more of alkali/alkaline earth metal hydride, carrier or metal alloy;

The mass ratio of the catalyst body to the additive is in the range of 1000: 1 to 1: 500.

the nitrogen-containing compound of manganese is one or a mixture of more than two of MnN, Mn3N2, Mn4N, Mn2N and Li7MnN 4.

The carrier is one or the combination of more than two of Li2O, MgO, CaO, SrO, BaO, Al2O3, BN, Si3N4, Mg3N2, Ca3N2, AlN, molecular sieves, carbon materials and metal organic framework Materials (MOFs).

The alkali/alkaline earth metal hydride is one or a mixture of more than two of LiH, NaH, KH, CsH, MgH2, CaH2 and BaH 2.

the metal alloy is as follows: one or more than two elements in IVB, VB, VIB, VIIB or VIIIB groups and Mn to form binary or ternary alloy; the above IVB, VB, VIB, VIIB or VIIIB group elements are one or more of Ti, Zr, Cr, Mo, W, Fe, Ru, Co, Rh, Ir, Ni, Pd and Pt.

The mass ratio of the catalyst body to the additive ranges from 200:1 to 1: 100.

The operating conditions of the catalyst for synthesizing ammonia are as follows: the sample is heated to a certain reaction temperature in the reaction atmosphere, and the composition of the product is analyzed on line by a conductivity meter; the reaction atmosphere is mixed gas of N2 and H2.

Drawings

FIG. 1 Synthesis of Ammonia with MnN/LiH (molar ratio 1:5) prepared in example 1 under atmospheric pressure conditions.

FIG. 2 reaction activity of Li7MnN4 prepared in example 2 for synthesizing ammonia under normal pressure.

FIG. 3 Synthesis Ammonia reactivity under atmospheric pressure conditions for MnCl2/LiH prepared in example 3.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

The following specific examples are presented to further illustrate the invention and are not intended to limit the scope of the invention as defined by the appended claims.

Example 1:

in an argon glove box, 1.0000g of manganese nitride (MnN) and 0.5797g of LiH are accurately weighed and placed in a self-made stainless steel ball milling tank. After the jar was closed, the mixture was charged into a planetary ball mill (Fischt PM400) under ball milling conditions of 150rpm for 3 hours. Thus obtaining the MnN/LiH sample (the molar ratio is 1: 5).

0.0690g of MnN/LiH (molar ratio 1:5) is accurately weighed in an argon glove box and placed in a fixed bed quartz tube reactor. The sample was heated to the desired temperature in the reaction atmosphere (1:3N2/H2 gas mixture), the reaction gas flow rate was controlled at 20mL/min, and after 30 minutes, the sample was sampled and analyzed. The test results are shown in fig. 1. The ammonia gas generation rate reached a maximum at 275 c, after which the ammonia gas generation rate decreased as the temperature increased.

Example 2:

Accurately weighing Li3N 0.1598g and Mn powder 0.1082g in a stainless steel reactor in an argon glove box, pressurizing to 10MPa with N2, heating to 750 ℃, and reacting in a closed system for 24 hours. The reaction product was collected to give Li7MnN 4.

Li7MnN40.0200g is accurately weighed in an argon glove box and placed in a fixed bed quartz tube reactor. The sample was heated to the desired temperature in the reaction atmosphere (1:3N2/H2 gas mixture), the reaction gas flow rate was controlled at 33mL/min, and after 30 minutes, the sample was sampled for analysis. The test results are shown in fig. 2. Starting at 300 ℃, the ammonia gas generation rate increases with increasing temperature, 375 ℃ reaching a maximum generation rate.

Example 3:

In an argon glove box, accurately weighing MnCl20.504g and LiH 0.192g, and placing the weighed materials in a self-made stainless steel ball milling tank. After the jar was closed, the mixture was charged into a planetary ball mill (Fischt PM400) under ball milling conditions of 200rpm for 3 hours. Thus obtaining a sample MnCl 2/LiH. Accurately weighing 0.0400g of MnCl2/LiH in an argon glove box, and placing the MnCl2/LiH in a fixed bed quartz tube reactor. The sample was heated to the desired temperature in the reaction atmosphere (1:3N2/H2 gas mixture), the reaction gas flow rate was controlled at 30mL/min, and after 30 minutes, the sample was sampled for analysis. The test results are shown in fig. 3. The catalyst has good activity for synthesizing ammonia in a low-temperature area, and the reaction activity is increased along with the rise of temperature.

Claims

1. A manganese catalyst for use in ammonia synthesis, characterized by: the catalyst consists of a main body and an additive, wherein the main body is a nitrogen-containing compound of manganese, and the additive is LiH;

the mass ratio of the catalyst body to the additive is in the range of 200:1 to 1:100, respectively;

The nitrogen-containing compound of manganese is one or a mixture of MnN or Li7MnN 4.

2. Use of a catalyst according to claim 1, wherein: the operating conditions of the catalyst for synthesizing ammonia are as follows: the sample is heated to a certain reaction temperature in the reaction atmosphere, and the composition of the product is analyzed on line by a conductivity meter; the reaction atmosphere is mixed gas of N2 and H2.