阅读说明：本技术 一种三段式催化剂装填法脱除co原料气中氢气杂质的方法 (Method for removing hydrogen impurities in CO raw material gas by three-stage catalyst filling method ) 是由 姚元根 乔路阳 周张锋 宗珊珊 崔国静 吴娟 许东杰 于 2020-07-22 设计创作，主要内容包括：本发明提供了一种三段式催化剂装填法脱除CO原料气中H<Sub>2</Sub>杂质的方法。本发明根据整个催化剂床层中反应物和产物浓度的变化趋势以及反应热效应的差异,设计选用了三种具有特定化学结构和性能的催化剂,将三种催化剂按特定的顺序和比例装填在反应床层的不同浓度区间,利用它们各自的化学性质,对反应热效应以及副反应的速率进行协同控制。本发明提供的三段式催化剂装填法脱除CO原料气中H<Sub>2</Sub>杂质的工艺方法,在不增加催化剂制备成本和工艺设备成本的基础上,使催化剂的反应温度由现有技术的145-150℃降低至125-130℃,可大幅度降低能源消耗,同时降低了催化剂的热烧结风险,且有助于延长工业用催化剂的使用寿命和更换周期,具备大规模工业化应用的前景。(The invention provides a three-stage catalyst filling method for removing H in CO raw material gas 2 A method for producing impurities. The invention designs and selects three catalysts with specific chemical structures and performances according to the change trend of the concentrations of reactants and products in the whole catalyst bed layer and the difference of reaction heat effects, fills the three catalysts in different concentration intervals of the reaction bed layer according to a specific sequence and proportion, and utilizes the respective chemical properties of the three catalysts to carry out cooperative control on the reaction heat effects and the rates of side reactions. The invention provides a three-stage catalyst filling method for removing H in CO raw material gas 2 The impurity process method reduces the reaction temperature of the catalyst from 145-130 ℃ to 125-130 ℃ in the prior art on the basis of not increasing the preparation cost of the catalyst and the cost of process equipmentThe energy consumption is reduced, the thermal sintering risk of the catalyst is reduced, the service life and the replacement period of the industrial catalyst are prolonged, and the method has a prospect of large-scale industrial application.)

1. A method for removing hydrogen impurities in CO raw material gas by a three-stage catalyst filling method comprises the following specific steps:

A. three different catalysts are adopted in a tubular fixed bed reaction device to be filled according to a specified sequence and proportion; the three catalysts are respectively expressed by GL-1, GL-2 and GL-3, and the mass percent of Pd of the three catalysts used each time is required to be the same; firstly, determining the total loading amount of the catalyst, and expressing the total loading amount by GL-Z; filling GL-1, GL-2 and GL-3 catalysts in three sections from top to bottom; the loading of each catalyst is determined by the mole number of Pd of the catalyst in the catalyst section in percentage of the total mole number of Pd of the whole catalyst, and is respectively as follows: 10-30% of GL-1, 40-70% of GL-2 and 15-50% of GL-3;

B. continuously introducing H into the tubular fixed bed reactor filled with the catalyst₂CO raw material gas with impurities of 5000-15000 ppm and high-purity O₂(ii) a Added O₂With H in the feed gas₂The volume ratio of (A) to (B) is 3-1: 1; the reaction space velocity is 500-3000 h^-1(ii) a The pressure of the bed layer is 0.2-0.5 MPa; the heating temperature of the reactor is 125-130 ℃; h in CO raw material gas at outlet of reactor₂The impurity is reduced to 0-20 ppm, the dehydrogenation selectivity of the catalyst is 78.9-87.1%, and the loss rate of CO is less than 0.1%;

the chemical expression of the catalyst GL-1 is PdCl_x/Al₂O₃The active center is PdCl_xThe mass percent of Pd in the catalyst is 0.5-2 wt%, and the catalyst is characterized by Al₂O₃The catalyst has stronger surface acidity;

the catalyst GL-2 has a chemical expression formula of Pd/CeO₂-Al₂O₃The active center is Pd, and the mass percent of Pd in the catalyst is 0.5-2 wt%; the catalyst is formed of CeO₂Has certain hydrophobicity;

the catalyst GL-3, its productionThe chemical expression is Pd-PdO/CeO_xThe active centers are Pd and PdO, and the mass percent of Pd in the catalyst is 0.5-2 wt%; the catalyst is characterized in that the carrier CeO_xThe surface of the composite material is weak in acidity and strong in hydrophobicity, and simultaneously has rich defects such as surface oxygen vacancy and the like.

Technical Field

The invention belongs to the technical field of coal-to-ethylene glycol, and is suitable for the dehydrogenation and purification process of CO raw gas obtained by taking fossil resources or organic matters as raw materials, such as coal gasification, methanol cracking, methane reforming and the like, and is particularly suitable for the dehydrogenation and purification process of the CO raw gas in the coal-to-ethylene glycol technology.

Background

In the implementation process of the technology for preparing the ethylene glycol from the coal, the coal is firstly gasified and reformed to obtain CO/H₂And (4) carrying out pressure swing adsorption separation on the mixed gas to obtain the CO raw material gas. However, due to the restriction of separation efficiency and other factors, the obtained CO raw material gas still has a certain concentration of H₂Impurities. In order to avoid the problems of catalyst deactivation, byproduct increase and the like in the CO oxidative coupling process, the residual H needs to be further oxidized by a selective oxidation method₂The impurities are removed.

In industrial trials or scale-up, tubular fixed bed reactors are generally chosen for the selective oxidative dehydrogenation. Because the tube side of the reaction tube is longer (the length of the catalyst filling layer exceeds 50cm), the residence time of the reaction raw materials and the products in the catalyst bed layer is longer, and the concentration of each component in the gas flow has larger difference at different positions of the bed layer. In addition, the system has side reactions such as CO oxidation and CO water vapor shift, and the side reactions and H₂The main oxidation reactions belong to strong exothermic reactions, the raw material gas reacts violently and releases heat greatly when just contacting the catalyst bed, and the raw material gas leaves the catalyst bed, so that the reaction is mild and the heat release is small, and the temperature distribution of the whole catalyst bed is uneven. Therefore, the above factors inevitably result in large differences in conversion, selectivity and stability of catalysts having the same chemical structure but loaded at different positions, so that the catalysts cannot exert the maximum efficiency in the reaction.

According to the tubular fixed bed dehydrogenation process, the catalyst is generally diluted with inert filler in a gradient manner and then the bed height is reduced toFilling at a high speed; or filling the catalyst with higher active metal content in the lower part of the bed layer, and filling the catalyst with lower active metal content in the upper part of the bed layer, so that the active metal concentration in the bed layer is in gradient distribution. For example, Chinese patent CN102219214A proposes a method for removing H by stages₂The method of impurity, i.e. the upper layer of the reactor is filled with a catalyst with lower palladium content, and the lower layer is filled with a catalyst with higher palladium content, aims to balance H of the upper and lower layers of the reactor by adjusting the palladium loading₂The oxidation reaction rate increases the dehydrogenation efficiency of the overall catalyst. The method can balance the heat effect of the reaction to a certain extent, but cannot effectively control the degree of side reaction; the reactor is generally heated integrally, the temperature of each catalyst filling layer of the reactor cannot be controlled independently, the palladium content of the catalyst on the upper layer of the reactor is low, and H is high₂The concentration is high, the dehydrogenation efficiency cannot be guaranteed at low temperature, and in order to meet the temperature requirement of a low-load catalyst, the catalytic system needs to operate at a high temperature of 180-260 ℃; while raising the reaction temperature will inevitably result in low H in the lower layer of the reactor₂The catalyst in the concentration zone is operated in an overheating mode, the palladium loading capacity of the catalyst is high, CO is excessively consumed in the reaction at the high temperature of 180-260 ℃, palladium metal is easy to sinter, and the selectivity and the service life of the catalyst are not good. Generally, the above problems can be solved by using two or more series reactors with independent temperature control. However, in industrial scale-up production, the reactor of this type has the problems of high manufacturing cost, complex process, high operation energy consumption, many potential safety hazards of equipment and the like, and is difficult to be applied to actual production.

In order to solve the problems of difficult control of reaction heat effect and side reaction and the like in the selective oxidative dehydrogenation purification process of CO raw material gas, the invention aims to develop a process method with higher conformity degree with the reaction process. The method can drive the catalyst to complete the reaction at a lower temperature, and is beneficial to reducing the risk of high-temperature sintering of the catalyst while exerting the maximum effectiveness of the catalyst.

Disclosure of Invention

The invention provides a three-stage catalyst filling method for removing H in CO raw material gas₂A process method of impurities.

The invention is based on the fact that the reactant (H) is present in the entire catalyst bed₂、O₂CO) and product (H)₂O、CO₂) Three catalysts with different structures and performances are filled in different concentration intervals of a reaction bed layer according to a specific sequence and proportion, and the reaction thermal effect and the rate of side reaction are cooperatively controlled by utilizing respective chemical properties of the catalysts.

The invention provides a three-stage catalyst filling method for removing H in CO raw material gas₂The method for removing impurities comprises the following specific steps:

A. three different catalysts are adopted in a tubular fixed bed reaction device to be filled according to a specified sequence and proportion; the three catalysts are respectively expressed by GL-1, GL-2 and GL-3, and the mass percent of Pd of the three catalysts used each time is required to be the same; firstly, determining the total loading amount of the catalyst, and expressing the total loading amount by GL-Z; filling GL-1, GL-2 and GL-3 catalysts in three sections from top to bottom; the loading of each catalyst is determined by the mole number of Pd of the catalyst in the catalyst section in percentage of the total mole number of Pd of the whole catalyst, and is respectively as follows: 10-30% of GL-1, 40-70% of GL-2 and 15-50% of GL-3.

B. Continuously introducing H into the tubular fixed bed reactor filled with the catalyst₂CO raw material gas with impurities of 5000-15000 ppm and high-purity O₂(ii) a Added O₂With H in the feed gas₂The volume ratio of (A) to (B) is 3-1: 1; the reaction space velocity is 500-3000 h^-1(ii) a The pressure of the bed layer is 0.2-0.5 MPa; the heating temperature of the reactor is 125-130 ℃.

The raw material gas passes through the GL-1, GL-2 and GL-3 three-section catalysts in sequence, and H in the gas flow is generated when the raw material gas contacts GL-1₂And O₂Highest concentration, most exothermic reaction, PdCl in GL-1_xThe components can avoid excessive adsorption and dissociation of the catalyst to reactants, thereby controlling the heat effect of the reaction; h in the gas flow when the raw material gas contacts GL-2₂Has a reduced concentration of CO and a substantially constant concentration of H₂The concentration of O is remarkably increased, GLThe Pd component in-2 can enhance the catalyst pair H₂Adsorption and activation capacity of, with respect to, CeO surrounding Pd₂-Al₂O₃Component (A) can inhibit H₂The dissociation of O on the surface of the catalyst effectively reduces the CO water-vapor transformation side reaction (CO + H)₂O＝CO₂+H₂) The rate of (d); when the raw material gas contacts GL-3, O in the gas flow₂Is significantly reduced and the concentration of CO is slightly increased, in which case O is present₂The activation of the catalyst is a main factor influencing the reaction process, and the Pd component in GL-3 is beneficial to activating H₂And PdO/CeO_xThe component has abundant surface defects, and can inhibit H₂The dissociation of O is simultaneously helpful for improving the catalyst to O₂Adsorption and activation capacity of.

The gas at the outlet of the reactor is sampled and analyzed, and the result shows that the invention reacts H in the CO feed gas₂The impurity is reduced to 0-20 ppm, the dehydrogenation selectivity of the catalyst is 78.9-87.1%, and the loss rate of CO is less than 0.1%.

The chemical expression of the catalyst GL-1 is PdCl_x/Al₂O₃The active center is PdCl_xThe mass percent of Pd in the catalyst is 0.5-2 wt%, and the catalyst is characterized by Al₂O₃The catalyst has stronger surface acidity. The catalyst is prepared by mixing Al₂O₃The powder is immersed in a palladium salt solution for loading, and is obtained by aging, drying, roasting, uniformly mixing with ammonium chloride and reducing at 350 ℃.

The catalyst GL-2 has a chemical expression formula of Pd/CeO₂-Al₂O₃The active center is Pd, and the mass percent of Pd in the catalyst is 0.5-2 wt%; the catalyst is formed of CeO₂Has certain hydrophobicity. The catalyst is prepared by mixing CeO₂-Al₂O₃The composite oxide powder is immersed in a palladium salt solution for loading, and is obtained by treating with an alkaline solution and reducing at 180 ℃ after aging, drying and roasting.

The catalyst GL-3 has a chemical expression of Pd-PdO/CeO_xThe active centers are Pd and PdO, and the Pd content in the catalystThe weight percentage is 0.5-2 wt%; the catalyst is characterized in that the carrier CeO is used_xThe surface of the composite material is weak in acidity and strong in hydrophobicity, and simultaneously has rich defects such as surface oxygen vacancy and the like. The catalyst is prepared by reacting CeO₂The powder is immersed in a palladium salt solution for loading, and is obtained after aging, drying and roasting.

The invention has the beneficial effects that:

(1) compared with the existing process method of gradient filling of the catalyst with the decreased or increased active metal content or the process method of gradient dilution and recharging of the catalyst with the same structure by the inert filler, the catalyst process method provided by the invention improves the low-temperature dehydrogenation efficiency of the catalyst, reduces the high-temperature sintering risk of the catalyst, is beneficial to optimizing the dehydrogenation process and prolonging the service life of the catalyst, does not need to increase the active metal dosage or increase the reaction temperature, and has obvious advantages in the aspects of catalyst manufacturing cost and energy consumption cost control.

(2) Compared with the technical scheme of two-section or multi-section series reactors which are independently heated, the catalyst design method provided by the invention has obvious advantages in the aspects of reactor manufacturing cost and potential safety hazard control.

Detailed Description

In order to make the technical solution of the present invention better understood by those skilled in the art, the following examples and comparative examples are now listed. However, these examples should not be construed as limiting the scope of the invention, and all such insubstantial changes and modifications which are made in accordance with the scope of the claims should be considered as being covered by the claims.