CN111762783A

CN111762783A - Method for removing hydrogen impurities in CO raw material gas by three-stage catalyst filling method

Info

Publication number: CN111762783A
Application number: CN202010711873.9A
Authority: CN
Inventors: 姚元根; 乔路阳; 周张锋; 宗珊珊; 崔国静; 吴娟; 许东杰
Original assignee: Fujian Institute of Research on the Structure of Matter of CAS
Current assignee: Fujian Institute of Research on the Structure of Matter of CAS
Priority date: 2020-07-22
Filing date: 2020-07-22
Publication date: 2020-10-13
Anticipated expiration: 2040-07-22
Also published as: CN111762783B

Abstract

The invention provides a three-stage catalyst filling method for removing H in CO raw material gas₂A 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 gas₂The 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.

Description

Method for removing hydrogen impurities in CO raw material gas by three-stage catalyst filling method

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.

Example 1:

preparation of three catalysts:

weighing Al₂O₃Putting the powder into a palladium active component solution with the concentration of 0.02mol/L for 6 hours; after filtering, putting the product in a drying oven for drying at 100 ℃ for 10h, and then putting the product in a muffle furnace for roasting at 250 ℃ for 8 h; mixing the roasted product and ammonium chloride in a molar ratio of 1: 0.2 mixing and then placing in H₂Processing for 3 hours at 350 ℃ in atmosphere to obtain PdCl_x/Al₂O₃Labeled GL-1, wherein PdThe mass percentage of (B) is 1 wt%.

CeO is weighed₂CeO in an amount of 20 wt%₂-Al₂O₃Putting the powder into a palladium active component solution with the concentration of 0.02mol/L for 20 hours; after filtering, putting the product in an oven for drying at 100 ℃ for 10h, and then putting the product in a muffle furnace for roasting at 450 ℃ for 8 h; soaking the roasted product in NaOH-NaHCO3 solution with the concentration of 0.1mol/L, stirring for 6H, filtering, drying, and placing in H₂Treating at 180 ℃ for 3h in atmosphere to obtain Pd/CeO₂-Al₂O₃Marked as GL-2, wherein the mass percentage of Pd is 1 wt%.

CeO is weighed₂Putting the powder into a palladium active component solution with the concentration of 0.02mol/L for 20h, drying for 3h in vacuum until the solvent disappears, and then putting the solution into a muffle furnace to be roasted at 900 ℃ for 20h to obtain Pd-PdO/CeO_xMarked as GL-3, wherein the mass percentage of Pd is 1 wt%.

Three-stage removal of H in CO raw material gas₂Impurities:

the inner diameter of the tubular fixed bed reactor is 25mm, the bed height is 250mm, three catalysts of GL-1, GL-2 and GL-3 are loaded into the reactor from top to bottom, and the proportion of the mole number of Pd of each section of catalyst to the mole number of the total Pd is as follows: and (3) filling 15g of GL-3, 20g of GL-2 and 15g of GL-1 into the bed layer in sequence, wherein the GL-1 is 30%, the GL-2 is 40% and the GL-3 is 30%. The reactor was charged with H mixed with 10000ppm of H₂CO raw material gas of impurities and high-purity O₂；O₂And H₂Is 3: 1; the reaction space velocity is 2000h^-1(ii) a The pressure of the bed layer is 0.2 MPa; the reactor heating temperature was 125 ℃.

The results of the analysis and calculation of the gas sampling at the outlet of the reactor by gas chromatography were: h in CO raw material gas after reaction₂The impurity is reduced from 10000ppm to 7ppm, H₂The conversion rate reaches 99.9 percent, the dehydrogenation selectivity reaches 81.4 percent, and the loss rate of CO is less than 0.1 percent. The results are shown in Table 1 for ease of comparison.

Example 2:

the catalyst was prepared in the same manner as in example 1.

Three-stage removal of H in CO raw material gas₂Impurities: catalyst and process for preparing sameThe filling ratio of Pd mole number is as follows: the procedure of example 1 was repeated except that GL-1 (25%), GL-2 (50%) and GL-3 (25%) were used, and the bed was charged with 12.5g of GL-3, 25g of GL-2 and 12.5g of GL-1 in that order. The catalyst dehydrogenation results are shown in table 1.

Example 3:

the catalyst was prepared in the same manner as in example 1.

Three-stage removal of H in CO raw material gas₂Impurities: the catalyst is loaded according to the mole ratio of Pd as follows: the procedure of example 1 was repeated except that the bed was charged with 7.5g of GL-3, 35g of GL-2 and 7.5g of GL-1 in this order, 15% of GL-1, 70% of GL-2 and 15% of GL-3. The catalyst dehydrogenation results are shown in table 1.

Example 4:

the preparation method of the catalyst is the same as that of example 1, except that the mass percent of Pd in the prepared GL-1, GL-2 and GL-3 is 2 wt%.

Three-stage removal of H in CO raw material gas₂Impurities: the catalyst loading method was the same as in example 1, H in CO feed gas₂The concentration of impurities is 5000ppm, and the reaction space velocity is 3000h^-1. The catalyst dehydrogenation results are shown in table 1.

Example 5:

the preparation method of the catalyst is the same as that of example 1, except that the mass percent of Pd in the prepared GL-1, GL-2 and GL-3 is 0.5 wt%.

Three-stage removal of H in CO raw material gas₂Impurities: the catalyst loading method was the same as in example 1, H in CO feed gas₂The concentration of impurities is 15000ppm, and the reaction space velocity is 500h^-1. The catalyst dehydrogenation results are shown in table 1.

Example 6:

the catalyst was prepared in the same manner as in example 1 except that CeO was used for preparing GL-2₂-Al₂O₃CeO of powder₂The content was 40 wt.%.

Three-stage removal of H in CO raw material gas₂Impurities: the catalyst is loaded according to the mole ratio of Pd as follows: the procedure of example 1 was repeated except that GL-1 (10%), GL-2 (40%) and GL-3 (50%) were used, and the bed was charged with 5g of GL-3, 20g of GL-2 and 25g of GL-1 in this order. Dehydrogenation result of catalystSee table 1.

Comparative example 1:

this example was designed to compare the process of the present invention with a one-stage dehydrogenation purification process that has been used. The one-stage method is to fill a catalyst in the reaction bed layer.

In order to avoid the influence of factors except the method on the result, the catalyst is prepared, filled and evaluated according to the method disclosed in the Chinese patent CN104162443A, wherein the indexes of the catalyst such as Pd mass percent, filling amount and the like, the reaction space velocity, the temperature, the pressure and the O₂/H₂The conditions such as volume ratio were the same as in example 1. The catalyst dehydrogenation results are shown in table 1.

Comparative example 2:

this example was designed to compare the process of the present invention with the gradient dehydrogenation purification process that has been used. The gradient method is to fill two sections of catalysts with the same structure and different mass percentages of Pd in a reaction bed layer in proportion.

In order to avoid the influence of factors other than the method on the results, the catalyst was prepared, loaded and evaluated according to the method disclosed in chinese patent CN 102219214A. According to the following steps: the Pd mass percentages of the two-stage catalyst sequentially loaded in a volume ratio of 1 are respectively 0.05 wt% and 0.5 wt%, and the total Pd mole number is 36.7% of that of the catalyst in the embodiment 1, so that the reaction space velocity is set to 733h^-1(36.7% of example 1), reaction temperature, pressure, O₂/H₂Other conditions such as volume ratio were the same as in example 1. The catalyst dehydrogenation results are shown in table 1.

Table 1: dehydrogenation result of catalyst

As can be seen from table 1: comparative example 1 only H was reacted at 125 deg.C₂To remove 146ppm, the reaction temperature was raised to 145 ℃ to achieve a dehydrogenation index of 20 ppm. Comparative example 2 only H was reacted at 125 deg.C₂The removal is carried out to 233ppm, the dehydrogenation selectivity is only 65%, and the reaction temperature is required to be raised to 150 ℃ to reach the dehydrogenation index of 20 ppm. Certificate (certificate)Compared with the one-stage and gradient dehydrogenation purification method, the method provided by the invention has the advantage of low dehydrogenation temperature, and can greatly save energy.

Claims

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.