阅读说明：本技术 一种用于草酸酯合成的催化剂及其制备方法和应用 (Catalyst for synthesizing oxalate and preparation method and application thereof ) 是由 肖招金 单文波 汪俊 唐大川 倪菁华 于 2019-02-22 设计创作，主要内容包括：本发明提供一种用于CO与亚硝酸甲酯合成草酸酯的催化剂及其制备方法。该催化剂的活性组分是Pd,载体为经铝溶液改性处理后的<I>α</I>-Al<Sub>2</Sub>O<Sub>3</Sub>,所述催化剂的组分和含量包括：0.01～1wt%的活性组分Pd,0.01～0.5wt%的助剂Fe,采用浸渍沉淀法制备。该催化剂用于一氧化碳与亚硝酸甲酯合成草酸二甲酯的反应中,具有高活性及高选择性,且稳定性很好,在空速3000h-1,以CO计草酸二甲酯的选择性达到98.5%,以MN计草酸二甲酯的选择性达到95%,草酸二甲酯的时空收率最高达到1200g/L.Cat/h。(The invention provides a catalyst for synthesizing oxalate from CO and methyl nitrite and a preparation method thereof. The active component of the catalyst is Pd, and the carrier is modified by aluminum solution α ‑Al 2 O 3 The components and contents of the catalyst comprise: 0.01-1 wt% of active component Pd and 0.01-0.5 wt% of auxiliary agent Fe, and adopting an immersion precipitation method for preparation. The catalyst is used for the reaction of synthesizing dimethyl oxalate from carbon monoxide and methyl nitrite, has high activity, high selectivity and good stability, and has the selectivity of the dimethyl oxalate calculated by CO reaching 98.5 percent, the selectivity of the dimethyl oxalate calculated by MN reaching 95 percent and the space-time yield of the dimethyl oxalate reaching 1200g/L.Cat/h at the airspeed of 3000 h-1.)

1. A catalyst for synthesizing oxalate, which is modified by aluminum solutionα-Al₂O₃The catalyst comprises the following components in percentage by weight: 0.01-1 wt% of active component Pd and 0.01-0.5 wt% of auxiliary agent Fe.

2. The catalyst for oxalate synthesis according to claim 1, wherein said carrierα-Al₂O₃Soaking the mixture in 0.01-1 wt% aluminum solution for 2-6 hr, and drying at 100-300 deg.c for 1-5 hr.

3. The catalyst for oxalate synthesis according to claim 1, wherein said aluminum solution is an aqueous solution of a salt such as aluminum chloride, aluminum nitrate, aluminum acetate, or aluminum oxalate.

4. The catalyst for synthesizing oxalate according to claim 1, wherein the content of Pd is 0.05-0.5 wt%, and the content of Fe is 0.1-0.3 wt%.

5. The catalyst for oxalate synthesis according to claim 1, wherein said catalyst is characterized in thatα-Al₂O₃The specific surface area of the carrier before being modified by the aluminum solution is 3-30 m²A pore volume of 0.01 to 0.5 cm/g³(ii)/g, the average pore diameter is 50 to 200 nm.

6. The method for preparing the catalyst for synthesizing oxalate according to claim 1, comprising the following steps in sequence:

a vectorα-Al₂O₃Soaking the mixture in 0.01-1 wt% aluminum solution for 2-6 hr, filtering, and stoving at 100-300 deg.c for 1-5 hr;

b, preparing an impregnating solution by using Fe salt according to a certain amount, and adjusting the pH value of the impregnating solution to 0.1-5;

c, putting the carrier obtained in the step a into the impregnation liquid obtained in the step b for soaking for 1-12 hours;

d, drying the solid obtained in the step c at 50-200 ℃, and then treating for 1-24 hours by using an alkali solution;

e, drying the solid obtained in the step d at 50-200 ℃, fully washing with deionized water, and exchanging to remove residual anions; then drying at 50-200 ℃, and roasting at 600-1200 ℃;

f, preparing a palladium solution with a certain concentration according to the proportion requirement of the content of the active components, wherein the PH value of the palladium solution is 1-6;

g, putting the solid obtained in the step e into the palladium solution prepared in the step f to be soaked for 1-24 hours;

h, drying the solid obtained in the step g at 50-200 ℃, and roasting at 200-600 ℃;

and i, obtaining a solid in the step h, and reducing to obtain a finished product catalyst.

7. The method for preparing a catalyst for oxalate synthesis according to claim 6, wherein said palladium salt and iron salt are selected from one or more of nitrate, halide, oxalate and acetate.

8. The method according to claim 6, wherein the base is one or more selected from the group consisting of carbonate, bicarbonate and hydroxide.

9. The catalyst obtained in claim 6 is used in the reaction for synthesizing oxalate, the selectivity of the by-products of Methyl Formate (MF) and dimethyl carbonate (DMC) is low; the content of laughing gas (N2O) which is a byproduct is low, so that the unit consumption of nitric acid in an industrial device and the content of nitrogen oxides in waste gas are reduced.

10. A method for synthesizing dimethyl oxalate comprises the following steps of carrying out contact reaction on raw material gas carbon monoxide and nitrous acid ester, and adopting nitrogen or carbon dioxide as a diluent; the raw material gas contacts with the catalyst of claim 1, the contact time is 0.1-5 seconds, the reaction temperature is 100-160 ℃, the reaction pressure is normal pressure-1.0 MPaG, and the gas hourly space velocity is 2000-5000 h < -1 >.

Technical Field

The invention belongs to the technical field of catalysts, and particularly relates to a catalyst Pd-Fe/a-Al for synthesizing dimethyl oxalate through CO gas phase coupling₂O₃And a method for preparing the same.

Background

Oxalic ester is an important chemical raw material, and can be used for synthesisOxalic acid, glycol and phthalide amine, and has important application in medicine and dye intermediate industry. The gas-phase synthesis of dimethyl oxalate by CO and the further hydrogenation synthesis of ethylene glycol are the current popular research subjects of C1 chemical industry at home and abroad, and the industrial production is primarily realized in China. The industrial production must comprehensively consider the recycling of materials, heat transfer and unit process, the conversion per pass is not necessarily high, but the higher the selectivity of the product, the better. The synthesis of dimethyl oxalate by carbon monoxide gas-phase catalytic coupling is an environment-friendly and atom-economical green chemical production process, and is very in line with the current resource situations of oil shortage, gas shortage and coal enrichment in China. The key to the success of this process is the development of catalysts. As for the oxalate synthesis catalyst, the catalyst Pd-Fe/Al2O3 catalyst adopted on the existing industrial device has the noble metal Pd content of 1.2-1.5 percent and the performance index of DMO yield of 750 g/L.h. The traditional impregnation method has the defects of high precious metal consumption, uneven dispersion, agglomeration of active components and catalyst inactivation caused by temperature runaway in the reaction, and the like, and further improvement of the preparation technology is needed to improve the efficiency and reduce the cost. As the process for synthesizing dimethyl oxalate by CO catalysis is a new technology for realizing industrial production in recent years, the research on related catalysts is mostly stopped at the laboratory stage, and related Pd/Al₂O₃The preparation method of series catalysts is characterized in that the problems of airspeed, heat release, diffusion and the like related to catalytic reaction in the process are fully considered as a catalyst product, so that the method requires deep research on the dispersion degree and distribution form of active components in the catalyst, the size of catalyst particles, the carrier property, the impregnation sequence of the active components and auxiliaries, different selected auxiliaries, roasting temperature, the pH value of an impregnation liquid and the like.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a catalyst for synthesizing oxalate from CO and methyl nitrite and a preparation method thereof, wherein the catalyst has high space-time yield and selectivity for generating dimethyl oxalate, low selectivity of byproducts and especially lower selectivity of N2O.

The technical scheme of the invention is to provide a catalyst for synthesizing dimethyl oxalate, which is α -Al modified by aluminum solution₂O₃The catalyst comprises the following components in percentage by weight: 0.01-1 wt% of active component Pd and 0.01-0.5 wt% of auxiliary agent Fe. Pd refers to elemental palladium and Fe refers to elemental iron.

One of the preferable embodiments of the catalyst for synthesizing oxalate is that the content of Pd is 0.05-0.5 wt%.

In another preferred embodiment of the catalyst for synthesizing oxalate, the content of Fe is 0.1-0.3 wt%.

In another preferred embodiment of the catalyst for synthesizing oxalate, α -Al which is not modified by aluminum solution is₂O₃The specific surface area of the carrier is 3-30 m²/g。

The fourth preferable embodiment of the catalyst for synthesizing oxalate is that α -Al is not modified by aluminum solution₂O₃The pore volume of the carrier is 0.01-0.5 cm³(ii)/g, the average pore diameter is 50 to 200 nm.

The technical scheme of the invention is to provide a preparation method of the catalyst for synthesizing oxalate, which sequentially comprises the following steps:

a) preparing an impregnating solution by using Fe salt according to a certain amount, and adjusting the pH value of the impregnating solution to 0.1-5;

b) α -Al after modification treatment of aluminum solution₂O₃Soaking the carrier in the soaking solution obtained in the step a) for 1-12 hr;

c) drying the solid obtained in the step b) at 50-200 ℃, and then treating for 1-24 hours by using an alkali solution;

d) drying the solid obtained in the step c) at 50-200 ℃, fully washing with deionized water, and exchanging to remove residual anions. Then drying at 50-200 ℃, and roasting at 600-1200 ℃;

e) preparing a palladium solution with a certain concentration according to the proportion requirement of the content of the active components, wherein the PH value of the palladium solution is 1-6;

f) putting the solid obtained in the step d) into the palladium solution prepared in the step e) to soak for 1-24 hours;

g) drying the solid obtained in the step f) at 50-200 ℃, and roasting at 200-600 ℃.

h) And g) obtaining a solid, and reducing to obtain a finished product catalyst.

One of the preferable embodiments of the above-mentioned preparation method of the catalyst for oxalate synthesis is that the palladium salt and the iron salt are selected from one or more of nitrate, halide, oxalate and acetate.

The second preferred embodiment of the preparation method of the catalyst for oxalate synthesis is that the pH of the iron salt impregnation solution is adjusted to 0.1-5, and the pH of the palladium solution is 1-6.

In a third preferred embodiment of the above method for preparing the catalyst for oxalate synthesis, the catalyst is reduced by hydrogen or carbon monoxide.

The fourth technical scheme of the invention is to provide a synthetic method of oxalate, namely using nitrogen or carbon dioxide as diluent, and contacting raw material gas carbon monoxide and nitrite with the catalyst for 0.1-5 seconds, wherein the reaction temperature is 100-160 ℃, and the reaction pressure is normal pressure-1.0 MPaG.

The volume content of CO in the feed gas is 10-50%, and the volume content of RONO is 5-30%.

The reaction is reduced by hydrogen or carbon monoxide, the airspeed of the reducing gas is 50-500 ml/min.L.cat, the reducing temperature is 100-250 ℃, and the reducing time is 1-6 hours.

Advantageous effects

The Pd-Fe/a-Al2O3 catalyst prepared by the method runs on an oxalic acid synthesis device of CO and CH3ONO, and has good effects: under the conditions of normal pressure to 0.4MPaG, 100 to 140 ℃ and GHSV of 3000 to 4000 hours^-1Under the reaction condition, after 20000 hours of continuous operation, the catalyst performance has no decline tendency, the average space-time yield of dimethyl oxalate is up to 950 g/L. cat.h, and the DMO selectivity reaches 99%.

Detailed Description

The invention is further illustrated by the following examples, but is not limited thereto.