CN110433811B - MgO modified Ni/CaO bifunctional catalyst, preparation method and application - Google Patents
MgO modified Ni/CaO bifunctional catalyst, preparation method and application Download PDFInfo
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Abstract
The invention belongs to the technical field of alkaline earth metal oxide auxiliary agent modified catalysts, and discloses a MgO modified Ni/CaO catalyst, a preparation method and application thereof, wherein Ni is used as a steam reforming catalyst, CaO is used as a carbon dioxide absorbent, and MgO is used as an auxiliary agent; adding an ammonium bicarbonate solution and ammonia water into a salt solution containing three metal ions of Ni, Ca and Mg in two steps to respectively precipitate Ca, Mg, Ni and Mg ions, then filtering, drying, roasting and reducing the precipitate to obtain a target catalyst, wherein Ni particles and MgO particles of the catalyst are uniformly loaded on the surfaces of CaO particles, and the Ni particles and the MgO particles are uniformly distributed and mutually contacted. The catalyst has high activity, high stability and low price; the method is suitable for absorption-enhanced ethanol steam reforming reaction, ethanol-water mixed solution with water-carbon ratio of 4 is used as raw material at 600 ℃, and hydrogen with purity over 96% can be obtained in ten cycles.
Description
Technical Field
The invention belongs to the technical field of alkaline earth metal oxide auxiliary agent modified catalysts, and particularly relates to a MgO modified Ni/CaO bifunctional catalyst, a preparation method and application thereof, which can effectively regulate and control the microstructure of the catalyst so as to improve the activity and stability of the catalyst.
Background
The exploration and establishment of a sustainable energy system are a key problem in the current society, and the development of renewable hydrogen energy can effectively solve the problem, so that the renewable hydrogen energy system plays an important role in long-term energy structure adjustment in various countries. The hydrogen can be used for fuel cells or gas turbines to carry out high-efficiency power generation, only water is generated as a byproduct, and the emission of greenhouse gases is relieved; the hydrogen can also be used as a chemical raw material, is widely applied to the petrochemical industry, and improves the quality and value of products. At present, hydrogen is mainly produced by reforming or partially oxidizing fossil fuels, wherein the fuels comprise natural gas, fuel oil, coal and the like, the equipment investment is high, the water consumption is high, the problems of pollutants and greenhouse gas emission are serious, and the fossil fuels are not renewable. The development of the environment-friendly high-efficiency novel hydrogen production technology based on the renewable fuel ensures the economic feasibility of the renewable hydrogen energy, is an important link for replacing the traditional fossil fuel by the hydrogen energy, and draws wide attention of all countries in the world.
Bioethanol is an important renewable fuel derived from biomass, has been produced on a large scale by fermentation of starch or sugars, and is expected to be prepared from low-cost raw materials (such as straws of grains) and is mainly used for blending with motor gasoline at present. Although the alcohol-based fuel starts late, the development of the alcohol-based fuel is rapid, the yield of the bio-ethanol reaches 260 ten thousand tons in 2017, the third world fuel ethanol production country is second only to the United states and Brazil, and meanwhile, the annual use amount of the bio-fuel ethanol reaches 1000 ten thousand tons in 2020 in China, which is proposed by renewable energy medium and long term development program. In the process of using the bioethanol, the net emission of carbon dioxide is almost zero, and the emission of nitrogen and sulfur pollutants is reduced. In addition, bioethanol is the most widely distributed biofuel, and has the advantages of large reserves, wide sources, high energy density, low toxicity, and easy storage and transportation. In recent years, the problems of steam reforming, partial oxidation and autothermal reforming of ethanol for hydrogen production are reported in the literature, and bioethanol hydrogen production has become an important development direction of renewable hydrogen energy and has attracted much attention.
Although the production of hydrogen by the ethanol steam reforming reaction can achieve high hydrogen yield and concentration, the components such as carbon dioxide, carbon monoxide and methane contained in the tail gas of the ethanol steam reforming reaction still need to be separated by a subsequent complicated separation process. In the conventional methane steam reforming system, the reaction tail gas needs to be subjected to complicated separation operations to remove the byproducts, firstly two water gas shift reactors, a high temperature shift at 350-. A typical (dry basis) gas composition exiting the shift reactor is about 76% hydrogen, 17% carbon dioxide, 2.4% unreacted methane and 3% carbon monoxide. Further operations may then be performed depending on product requirements, which may include removing carbon dioxide from the product using monoethanolamine MEA, further removing carbon monoxide by methanation or partial oxidation, such that the hydrogen purity in the product may be up to 95%, or purifying the hydrogen by pressure swing adsorption. Therefore, the set of separation and purification process is complicated and costly.
Therefore, the absorption enhanced steam reforming process developed based on the le chatelier principle has received a great deal of attention from researchers. The carbon dioxide absorbent is used in the reaction process to capture the carbon dioxide generated in the reforming process in situ, and meanwhile, the forward movement of the reforming reaction and the water-gas shift reaction is promoted, the concentration of other byproducts is reduced, and the aim of producing high-purity hydrogen in one step is fulfilled. Compared with the traditional steam reforming process, the absorption enhanced steam reforming has the following advantages: (1) obtaining high-purity hydrogen by a one-step method; (2) the conversion rate of reaction raw materials is improved; (3) simplifies the hydrogen production reactor and reduces the cost.
Typically, absorption enhanced steam reforming systems comprise a reforming catalyst and a carbon dioxide absorbent. Reforming catalysts can be classified into noble metal-based catalysts (e.g., Rh, Ru, Pt, and Pd) and non-noble metal-based catalysts (Ni and Co) according to the active metal. Noble metals are more active for reforming reactions and have better resistance to carbon deposition than non-noble metals, but their commercial use is limited by the high cost. Therefore, non-noble metal-based catalysts, particularly Ni-based catalysts, have been widely studied because of their reforming activity close to that of noble metals. For the carbon dioxide absorbent, in order to match the temperature of the ethanol steam reforming reaction, a medium-high temperature (400-. There are a number of carbon dioxide absorbents in this temperature range including hydrotalcites, magnesium oxide, silicates, zirconates and calcium oxide. Among them, CaO has been widely studied and applied due to its high stoichiometric carbon dioxide uptake, rapid carbonation kinetics, low cost, ready availability, and wide distribution.
In summary, despite the current higher price of ethanol than natural gas, with the continuous consumption of fossil energy and the continuous improvement of bioethanol production technology, ethanol steam reforming technology has great potential as a planned middle-stage hydrogen production technology. The ethanol steam reforming reaction is combined with the absorption enhanced steam reforming strengthening process, so that the cost for preparing high-purity hydrogen is reduced, and the method is a feasible way. However, the conventional Ni-based catalyst is easily deactivated by sintering and carbon deposition, and the CaO-based absorbent has poor cycle stability, so that the industrialization of the technology still faces a great challenge. Therefore, the development of highly efficient and stable multifunctional catalysts has been the focus of research in this field.
Disclosure of Invention
The invention provides an MgO modified Ni/CaO catalyst with strong sintering resistance and carbon deposition resistance, high activity and high stability and a preparation method thereof, aiming at solving the technical problem of poor activity and stability of an absorption enhanced steam reforming catalyst based on a Ni-based catalyst and a CaO-based absorbent, and applying the MgO modified Ni/CaO catalyst to an absorption enhanced ethanol steam reforming reaction.
In order to solve the technical problems, the invention is realized by the following technical scheme:
an MgO modified Ni/CaO dual-function catalyst, wherein Ni particles and MgO particles are uniformly loaded on the surfaces of CaO particles, and the Ni particles and the MgO particles are uniformly distributed and mutually contacted; based on the total mass of the catalyst, the mass percent of Ni in the catalyst is 5%, the mass percent of MgO is 10-30%, and the mass percent of CaO is 65-85%.
Further, the particle size of the Ni particles is 9.5-22.9nm, and the particle size of the MgO particles is 26.6-51.7 nm.
Furthermore, Ni in the catalyst is a steam reforming catalytic active component, CaO is a carbon dioxide absorption active component, and MgO is a catalyst auxiliary agent.
Furthermore, the catalyst is prepared by high-temperature roasting and hydrogen reduction treatment of a precursor which comprises a calcium magnesium carbonate and nickel magnesium solid solution.
A preparation method of the MgO modified Ni/CaO bifunctional catalyst comprises the following steps:
(1) completely dissolving 0.1 part by mass of nickel nitrate hexahydrate, 0.52-1.55 parts by mass of magnesium nitrate hexahydrate and 1.11-1.45 parts by mass of calcium nitrate tetrahydrate in deionized water to form a precursor solution; preparing ammonium bicarbonate into aqueous solution;
(2) under the condition of violent stirring, dropwise adding the ammonium bicarbonate aqueous solution prepared in the step (1) into the precursor solution at a constant speed, wherein the total dropwise adding amount is in accordance with the following formula
After the dropwise addition is finished, continuously dropwise adding 25-28% of concentrated ammonia water into the mixed solution until the pH is controlled to be 7.5-9;
(3) standing and aging the suspension obtained in the step (2) for 2-12H, filtering, drying the obtained precipitate, roasting at the temperature of 700-900 ℃ for 2-4H after completely drying, and then roasting at the temperature of 600-750 ℃ and 10-20 vol% H2/N2Reducing for 1-2h under the atmosphere to obtain the target catalyst.
Preferably, the drying temperature in the step (3) is 100-120 ℃, and the drying time is 12-24 h.
The MgO modified Ni/CaO bifunctional catalyst is applied to the absorption-enhanced ethanol steam reforming reaction.
The invention has the beneficial effects that:
the invention regulates and controls the distribution of Ni, MgO and CaO by a simple step-by-step coprecipitation method, and makes Ni and MgO contact with each other and have interaction on the basis that Ni and MgO can be uniformly loaded on the surface of CaO particles, and the structure has the following advantages:
ni and MgO are mutually contacted and interacted, so that the sintering resistance of Ni is improved; meanwhile, MgO is used as an inert component and is uniformly loaded on the surface of CaO particles, so that the CaO is inhibited from absorbing CO2After-formation of CaCO3Contact in the reaction-regeneration cycle, thereby improving the absorption cycle stability of CaO; that is, MgO helps stabilize the Ni, CaO particles, thereby improving the stability of the catalyst；
In the invention, under the reaction condition, the MgO surface can dissociate water molecules to form active hydroxyl, which helps promote the conversion of reaction intermediates, improves the reaction activity, avoids the generation of carbon deposition and further improves the stability of the catalyst;
the invention provides new knowledge for the structure of the absorption enhanced steam reforming catalyst designed based on Ni and CaO, and confirms that the CaO absorbent absorbs CO2CaCO formed later3Negative effect on the conversion of reaction intermediate, and MgO auxiliary agent is introduced to participate in the reaction process, so that the negative effect is eliminated;
the catalyst of the invention can be applied to an absorption enhanced steam reforming reaction system, and has excellent catalytic performance and thermal stability and long service life.
Drawings
FIG. 1 is a TEM and EDS scan of a 20 wt% MgO-modified Ni/CaO catalyst prepared in example 2,
wherein (a) TEM image of the catalyst prepared in example 2, (b), (c), (d), (e) are distribution diagrams of the four elements of Ni, Mg, Ca and O in the catalyst prepared in example 2, respectively, and (f) is a combination diagram of the distribution of the four elements in the catalyst prepared in example 2;
FIG. 2 is a stability test result of the Ni/CaO catalyst prepared in comparative example and the 20 wt% MgO-modified Ni/CaO catalyst prepared in example 2,
wherein (a) is a stability test result of the Ni/CaO catalyst prepared in comparative example, and (b) is a stability test result of the 20 wt% MgO-modified Ni/CaO catalyst prepared in example 2;
FIG. 3 is a thermogravimetric analysis curve of the catalysts of example 2 and comparative example after stability testing;
FIG. 4 is an in situ diffuse reflectance infrared spectrum of the Ni/CaO catalyst prepared in comparative example and the 20 wt% MgO-modified Ni/CaO catalyst prepared in example 2,
wherein (a) is an in situ diffuse reflectance infrared spectrum of the Ni/CaO catalyst prepared in comparative example, and (b) is an in situ diffuse reflectance infrared spectrum of the 20 wt% MgO-modified Ni/CaO catalyst prepared in example 2;
FIG. 5 is a graph showing temperature programmed desorption of ethanol for the Ni/CaO catalyst prepared in comparative example and the 20 wt% MgO-modified Ni/CaO catalyst prepared in example 2,
wherein (a) is a temperature programmed ethanol desorption profile of the Ni/CaO catalyst prepared in the comparative example, and (b) is a temperature programmed ethanol desorption profile of the 20 wt% MgO-modified Ni/CaO catalyst prepared in example 2.
Detailed Description
The present invention is further described in detail below by way of specific examples, which will enable one skilled in the art to more fully understand the present invention, but which are not intended to limit the invention in any way.
Example 1
5.2g of Mg (NO)3)2·6H2O,14.5g Ca(NO3)2·4H2O and 1g Ni (NO)3)2·6H2Dissolving O in 34ml of deionized water by ultrasonic to obtain solution A with the total metal ion concentration of 2.5 mol/L; 6.9g of NH are weighed4HCO3Dissolved in 27ml of deionized water to prepare a solution B with the concentration of 3 mol/L. The solution B was slowly added dropwise to the solution A (wherein the total molar amount of bicarbonate was equal to the sum of the total molar amounts of calcium and magnesium) at a uniform rate using a constant pressure dropping funnel while monitoring the solution pH using a pH meter, under vigorous stirring. After the dropwise addition, ammonia water with the concentration of 25-28 wt% is continuously and dropwise added into the mixed solution, and the pH value is adjusted to 7.5. Standing and aging the obtained light green suspension for 2 hours at normal temperature, performing suction filtration and separation, and drying the obtained filter cake in an oven at 100 ℃ for 24 hours. Subsequently, the completely dried solid was transferred to a muffle furnace and calcined at 700 ℃ for 4 hours in an air atmosphere at a temperature rise rate of 5 ℃/min. After the muffle furnace temperature was reduced to room temperature, the sample was removed, ground to a powder, and then treated at 600 ℃ with 10 vol% H2/N2Reducing for 2h under the atmosphere to obtain the MgO modified Ni/CaO catalyst with the weight percentage of 10 percent and the weight percentage of 85 percent, wherein the weight percentage of Ni in the catalyst is 5 percent, the weight percentage of MgO is 10 percent, and the weight percentage of CaO is 5 percent.
Example 2
10.3g of Mg (NO)3)2·6H2O,12.7g Ca(NO3)2·4H2O and 1g Ni (NO)3)2·6H2Dissolving O in 39ml of deionized water by ultrasonic to obtain solution A with the total metal ion concentration of 2.5 mol/L; 7.9g of NH were weighed4HCO3Dissolved in 31ml of deionized water to prepare a B solution with the concentration of 3 mol/L. The solution B was slowly added dropwise to the solution A (wherein the total molar amount of bicarbonate was equal to the sum of the total molar amounts of calcium and magnesium) at a uniform rate using a constant pressure dropping funnel while monitoring the solution pH using a pH meter, under vigorous stirring. After the dropwise addition, ammonia water with the concentration of 25-28 wt% is continuously and dropwise added into the mixed solution, and the pH value is adjusted to 8.5. Standing and aging the obtained light green suspension for 8 hours at normal temperature, performing suction filtration and separation, and drying the obtained filter cake in an oven at 110 ℃ for 18 hours. Subsequently, the completely dried solid was transferred to a muffle furnace and calcined at 800 ℃ for 3 hours in an air atmosphere at a temperature rise rate of 5 ℃/min. After the muffle furnace temperature was reduced to room temperature, the sample was removed, ground to a powder, and then ground to 15 vol% H at 700 deg.C2/N2Reducing for 1.5h under the atmosphere to obtain the MgO modified Ni/CaO catalyst with the weight percent of 20 percent, wherein the weight percent of Ni in the catalyst is 5 percent, the weight percent of MgO is 20 percent, and the weight percent of CaO is 75 percent.
Example 3
15.5g Mg (NO)3)2·6H2O,11.1g Ca(NO3)2·4H2O and 1g Ni (NO)3)2·6H2Dissolving O in 44ml of deionized water by ultrasonic to obtain solution A with the total metal ion concentration of 2.5 mol/L; 9.0g of NH were weighed4HCO3Dissolved in 36ml of deionized water to prepare a solution B with the concentration of 3 mol/L. The solution B was slowly added dropwise to the solution A (wherein the total molar amount of bicarbonate was equal to the sum of the total molar amounts of calcium and magnesium) at a uniform rate using a constant pressure dropping funnel while monitoring the solution pH using a pH meter, under vigorous stirring. After the dripping is finished, continuously dripping 25-28 wt% of concentration into the mixed solutionAdjusting the pH to 9. Standing and aging the obtained light green suspension for 12 hours at normal temperature, performing suction filtration and separation, and drying the obtained filter cake in an oven at 120 ℃ for 12 hours. Subsequently, the completely dried solid was transferred to a muffle furnace and calcined at 900 ℃ for 2 hours in an air atmosphere at a temperature rise rate of 5 ℃/min. After the muffle furnace temperature was reduced to room temperature, the sample was removed, ground to a powder, and then dried at 750 ℃ and 20 vol% H2/N2Reducing for 1h under the atmosphere to obtain the 30 wt% MgO modified Ni/CaO catalyst, wherein the mass percent of Ni in the catalyst is 5%, the mass percent of MgO is 30%, and the mass percent of CaO is 65%.
Comparative example
16.1g Ca (NO)3)2·4H2O (1.61 parts by mass) and 1g of Ni (NO)3)2·6H2Dissolving O (0.1 part by mass) in 29ml of deionized water by ultrasonic wave to obtain solution A with the total metal ion concentration of 2.5 mol/L; 5.7g of NH are weighed4HCO3Dissolved in 23ml of deionized water to prepare a solution B with the concentration of 3 mol/L. Under vigorous stirring, solution B was slowly added dropwise at a uniform rate to solution A (where the total molar amount of bicarbonate was equal to the total molar amount of calcium ions) using an isopiestic dropping funnel while monitoring the solution pH using a pH meter. After the dropwise addition, ammonia water with the concentration of 25-28 wt% is continuously and dropwise added into the mixed solution, and the pH value is adjusted to 7.5. Standing and aging the obtained light green suspension for 8 hours at normal temperature, performing suction filtration and separation, and drying the obtained filter cake in an oven at 120 ℃ for 12 hours. Subsequently, the completely dried solid was transferred to a muffle furnace and calcined at 800 ℃ for 2 hours in an air atmosphere at a temperature rise rate of 5 ℃/min. After the muffle furnace temperature was reduced to room temperature, the sample was removed, ground to a powder, and then treated at 600 ℃ with 10 vol% H2/N2Reducing for 2h under the atmosphere to obtain the Ni/CaO catalyst.
Discussion of results and data with respect to the above examples:
the present invention was made in detail by examining the effects of the MgO-modified Ni/CaO catalyst prepared in examples 1 to 3 on the catalyst structure, reactivity and reactive intermediates.
Referring to fig. 1, the TEM and EDS scans of example 2 show that Ni and MgO are uniformly supported on CaO particles. At the same time, the elements Ni and Mg exhibit a very uniform distribution, indicating that close contact between the metal Ni and MgO is maintained. The particle size of the Ni particles is 9.5-22.9nm, and the particle size of the MgO particles is 26.6-51.7 nm. The same TEM and EDS surface scan characterization was performed on the MgO modified Ni/CaO catalysts prepared in the remaining examples and the results showed that all catalysts exhibited similar structure and particle size ranges.
Reactivity of (di) MgO-modified Ni/CaO catalysts
Tabletting the catalyst sample powder to 20-40 meshes, loading the prepared catalyst sample into a fixed bed reactor, controlling the bed temperature of the reactor at 400-600 ℃ and the reaction space velocity of 4,400 mL-h-1·gcat -1Reaction gas is introduced for reaction, wherein the molar ratio of ethanol to water is 1:8, the ethanol gas accounts for 4.4% of the total volume of the gas, and the balance gas is nitrogen. After reacting for 1h, stopping introducing the ethanol-water mixed solution, heating the catalyst bed layer to 700 ℃, and reacting at N2And (3) regenerating the catalyst by keeping the atmosphere for 2h, then cooling to 600 ℃, and repeating the cycle for 10 times to test the cycle stability of the catalyst, wherein the product concentration distribution in the reaction stage is taken as the evaluation standard of the reaction performance and stability of the catalyst.
The catalyst activity is expressed by ethanol conversion and product concentration, which are calculated by the following formula:
the cycle stability results for example 2 and the comparative example are shown in figure 2. On both catalysts, the ethanol conversion was maintained at 100% over 10 cycles. However, the hydrogen purity of example 2 was higher than that of the comparative example,it is shown that the addition of 20 mass percent of MgO improves the reaction activity of the catalyst. Further, comparative example H2The purity decreases with increasing number of cycles, CH4The concentration rises significantly indicating a decrease in the methane steam reforming performance of the catalyst. For example 2, H in the reaction off-gas2The purity can be kept stable over 10 cycles with only a slight decrease from 97.2% to 96.0%. The addition of 20 mass percent of MgO obviously improves the cycle stability of the catalyst. The same reaction performance test was performed on the MgO modified Ni/CaO catalysts prepared in the remaining examples, and the results showed that the MgO modified catalysts all showed higher activity and stability than the comparative examples.
(III) Effect of MgO auxiliary agent on carbon deposition
And (3) characterizing and analyzing the carbon deposition condition on the surface of the catalyst after reaction by using a thermogravimetric analysis technology. The method comprises the following specific steps: for carbon deposition analysis, about 15mg of an accurately weighed sample was placed in a crucible, raised to 1000 ℃ at a rate of 10 ℃/min, and the atmosphere was nitrogen or air. In the thermogravimetric test, the control experiment was carried out by changing the test atmosphere (including air and nitrogen) in order to eliminate the interference of the catalyst with the residual carbon dioxide. CaCO3And Ca (OH)2The decomposition reaction of (a) occurs in both atmospheres, whereas the oxidation of Ni and the elimination of carbon deposit occur only in an air atmosphere. Therefore, the amount of carbon deposition can be obtained by the following formula:
mCoke＝mFinal in N2-mFinal in Air+(mNiO-mNi)
the results are shown in FIG. 3, and the decrease in thermogravimetric curves of the two catalysts between 350 ℃ and 450 ℃ is attributed to Ca (OH)2Decomposition of (3). The test results for nitrogen and air atmospheres in the same temperature range showed different amounts of weight loss due to the oxidation of Ni in air. The open line in FIG. 3 shows a significant mass gain above 450 deg.C, which is caused by CO formed by oxidation of carbon deposits2Is absorbed by CaO. CaCO when the temperature rises to 620 DEG C3Begin to decompose into CaO and CO2. Thus, in excess of 450 DEG CThe mass gain can be used as a criterion for assessing the presence of carbon deposits on the catalyst surface. Clearly, there was no significant mass increase, indicating that the catalyst prepared in example 2 produced little carbon deposition on the catalyst surface over the 10 cycle stability test. The thermogravimetric curve of the comparative example catalyst in the air atmosphere after reaction shows that the weight gain is about 10% between 450 ℃ and 600 ℃, which indicates that the surface of the comparative example catalyst has serious carbon deposition, and finally the calculated carbon deposition amount on the surface of the comparative example catalyst is about 10.2%, while the surface of the catalyst of the example 2 hardly generates carbon deposition. In conclusion, the 20 wt% MgO-modified Ni/CaO catalyst has excellent anti-carbon properties. The MgO modified Ni/CaO catalysts prepared in the other examples are subjected to the same thermogravimetric test, and the results show that the MgO modified catalysts show excellent carbon deposition resistance.
Effect of (tetra) MgO adjuvant on reaction intermediates
The reaction process is characterized by an in-situ diffuse reflection infrared experiment, and the method comprises the following specific steps: all test samples were first tested at 650 ℃ with 10 vol% H2Reducing in situ for 1 hour under the Ar condition, purging for 1 hour by Ar gas, reducing to the target temperature, and collecting a background spectrum. After the collection, the infrared spectrum was obtained by subtracting the previously collected background from 50 ℃ to 400 ℃ in the ethanol steam reforming condition with a step of 50 ℃, and the obtained result is shown in fig. 4.
Appearing in the initial sample at about 1050cm-1And 1100cm-1The peak of (a) was attributed to the vibration of the C-O bond, demonstrating the dissociation of ethanol into ethoxy species. In this connection, it is located at 2901cm-1，2937cm-1And 2974cm-1The peak of (A) is ascribed to the vibration of the C-H bond in the ethoxy group. Furthermore, it is located at 3646cm-1And 3730cm-1(the latter is present only in example 2) the oscillation peaks are attributed to the hydroxyl groups on the CaO and MgO surfaces, respectively. Comparative example 3000 + 3600cm-1The broad hump of (a) is attributed to water molecules adsorbed on the surface of the CaO. The intensity of the peak ascribed to the ethoxy species gradually decreased with increasing temperature, while 1788cm-1And 2501cm-1A new vibration peak (in comparative example) appears at the position of (a). These two peaks are associated with adsorbed aldehyde groups (HCO), the HCO species being C-CThe product of bond breaking, HCO, can be converted to HCOO species with the aid of surface hydroxyl groups.
For example 2, a depth of 1600cm at 200 ℃ was observed-1And 1385cm-1Peak of (2). This indicates the presence of HCOO on the 20 wt% MgO modified Ni/CaO catalyst. When the temperature is gradually increased from 200 ℃ to 400 ℃ and the temperature is 1600cm-1Has peak at 1572cm-1The latter is due to monodentate CO adsorbed on the surface of CaO2。1572cm-1The vibration peak of (A) is along with the progress of the reaction, CO2Is continuously generated and adsorbed to be continuously enhanced. At 2863cm in the high-temperature region-1And 2958cm-1The peak of (a) is attributed to stretching vibration and skeleton vibration of the C-H bond in HCOO. Notably, this peak was also observed in the comparative example.
In summary, the presence of formic acid intermediates on both the catalysts of example 2 and comparative example can be confirmed. In the infrared spectrum of the comparative example, a more pronounced vibrational peak of HCO species was observed. In contrast, in the initial reaction stage, CaO adjacent to Ni is reacted to produce CO2Quickly consumed and converted into CaCO3，H2O and CaCO3The surface has a strong interaction, but H2O is not present in CaCO3(104) And (4) surface dissociation. Thus, under the reaction conditions, CaCO3The surface of (a) was covered with a layer of water molecules, which failed to provide the-OH species required for HCO conversion, resulting in HCO accumulation on the comparative example surface. For example 2, MgO was able to dissociate water and provide — OH, promoting the conversion of HCO to HCOO on adjacent Ni sites.
Further, the interaction between the surface of the catalyst and ethanol molecules is investigated through ethanol temperature programmed desorption, and the specific steps are as follows: before testing, 10 vol% H was used for all samples2and/Ar is subjected to in-situ reduction. After the reduction is completed, the temperature is reduced to 50 ℃ under Ar purging. Gas containing 90 vol% ethanol was carried into the sample tube using pulsed injection and repeated 20 times to ensure saturation of the catalyst surface adsorption. After adsorption was complete, the sample tube was purged with He for 30 minutes. Subsequently, the temperature was raised to 700 ℃ at a rate of 10 ℃/min under He atmosphere. Reaction tail gas is detected and recorded by mass spectrumThe resulting signal is shown in FIG. 5.
At about 230 ℃ CH is present simultaneously4CO and H2It was confirmed that the ethanol underwent decomposition reaction on the Ni surface. Followed by the appearance of a new H at 300-2The peaks and no other gas production are accompanied, indicating that another hydrogen production path is present, and the adsorbed ethanol undergoes dehydrogenation to generate hydrogen and acetaldehyde. In example 2, H2Occurs at a lower temperature, indicating that the catalyst has a greater capacity for the dehydrogenation of ethanol. At the same time, CH3CHO will decompose further on the catalyst. In situ IR spectroscopy showed that the Ni/CaO catalyst prepared in the comparative example was more prone to dissociation into CHxAnd HCO; whereas the 20 wt% MgO-modified Ni/CaO catalyst prepared in example 2 was more easily dissociated and converted to CHxAnd HCOO, which will subsequently be further decomposed to H2And CO2. CO and H were present simultaneously in the temperature programmed ethanol desorption curve of example 2 at 381 deg.C2Shows the CH on the surface of example 2xSpecies reacted with hydroxyl groups. To the comparative ratio, CH4And CO is desorbed at about 440 ℃ without concomitant production of H2. This emphasizes CH4And CO is CH adsorbed from Ni/CaO catalystxOr converted from carbon deposit. The difference in the two desorbed products and temperatures confirms that the surface hydroxyl groups are for CHxImportance of species transformation.
Based on the results of the in-situ infrared spectroscopy and the ethanol temperature programmed desorption. C2H5OH can be dehydrogenated to CH3CHO, followed by C-C bond cleavage to CHxAnd HCO. In example 3, HCO can be combined with-OH on the MgO surface and converted to important reaction intermediate HCOO, which subsequently decomposes to H2And adsorbed CO2. In contrast, CaO existing around Ni rapidly reacts with CO initially formed2Reaction to form CaCO3。CaCO3The lack of-OH on the surface inhibits the conversion of HCO species. CH (CH)3Another part of the product CH of CHO decompositionxWill hydrogenate to CH4Dehydrogenation to carbon deposits or synergies in oxygen-containing speciesConversion to CO is assisted. Example 2 in the presence of-OH on the MgO surface, adsorbed CHxSpecies will rapidly dissociate into CO and H2. In contrast, CH in comparative examplexWill be further hydrogenated and converted into CH4Or dehydrogenated to carbon. Therefore, microscopically, the addition of the MgO auxiliary agent influences the conversion of the reactive intermediate, further influences the carbon deposition condition on the surface of the catalyst, and finally influences the activity and stability of the catalyst.
Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and those skilled in the art can make various changes and modifications within the spirit and scope of the present invention without departing from the spirit and scope of the appended claims.
Claims (5)
1. An MgO modified Ni/CaO bifunctional catalyst is characterized in that the catalyst is used in an absorption enhanced ethanol steam reforming reaction; in the catalyst, Ni particles and MgO particles are uniformly loaded on the surfaces of CaO particles, and the Ni particles and the MgO particles are uniformly distributed and mutually contacted; based on the total mass of the catalyst, the mass percent of Ni, MgO and CaO in the catalyst is 5%, 10-30% and 65-85%;
and the catalyst is prepared by the following steps:
(1) completely dissolving 0.1 part by mass of nickel nitrate hexahydrate, 0.52-1.55 parts by mass of magnesium nitrate hexahydrate and 1.11-1.45 parts by mass of calcium nitrate tetrahydrate in deionized water to form a precursor solution; preparing ammonium bicarbonate into aqueous solution;
(2) under the condition of violent stirring, dropwise adding the ammonium bicarbonate aqueous solution prepared in the step (1) into the precursor solution at a constant speed, wherein the total dropwise adding amount is in accordance with the following formula
After the dropwise addition is finished, continuously dropwise adding 25-28% of concentrated ammonia water into the mixed solution until the pH is controlled to be 7.5-9;
(3) standing and aging the suspension obtained in the step (2) for 2-12H, filtering, drying the obtained precipitate, roasting at the temperature of 700-900 ℃ for 2-4H after completely drying, and then roasting at the temperature of 600-750 ℃ and 10-20 vol% H2/N2Reducing for 1-2h under the atmosphere to obtain the target catalyst.
2. An MgO modified Ni/CaO bi-functional catalyst according to claim 1, wherein the Ni particles have a particle size of 9.5-22.9nm and the MgO particles have a particle size of 26.6-51.7 nm.
3. A method for preparing an MgO-modified Ni/CaO bifunctional catalyst according to any one of claims 1-2, wherein the method is performed according to the following steps:
(1) completely dissolving 0.1 part by mass of nickel nitrate hexahydrate, 0.52-1.55 parts by mass of magnesium nitrate hexahydrate and 1.11-1.45 parts by mass of calcium nitrate tetrahydrate in deionized water to form a precursor solution; preparing ammonium bicarbonate into aqueous solution;
(2) under the condition of violent stirring, dropwise adding the ammonium bicarbonate aqueous solution prepared in the step (1) into the precursor solution at a constant speed, wherein the total dropwise adding amount is in accordance with the following formula
After the dropwise addition is finished, continuously dropwise adding 25-28% of concentrated ammonia water into the mixed solution until the pH is controlled to be 7.5-9;
(3) standing and aging the suspension obtained in the step (2) for 2-12H, filtering, drying the obtained precipitate, roasting at the temperature of 700-900 ℃ for 2-4H after completely drying, and then roasting at the temperature of 600-750 ℃ and 10-20 vol% H2/N2Reducing for 1-2h under the atmosphere,and obtaining the target catalyst.
4. The method for preparing an MgO modified Ni/CaO bifunctional catalyst according to claim 3, wherein the drying temperature in the step (3) is 100-120 ℃, and the drying time is 12-24 h.
5. Use of a MgO modified Ni/CaO bi-functional catalyst according to any one of claims 1-2 in an absorption enhanced steam reforming reaction of ethanol.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB916216A (en) * | 1961-08-16 | 1963-01-23 | Ici Ltd | Steam reforming of hydrocarbons and catalyst therefore |
| GB1064481A (en) * | 1963-01-28 | 1967-04-05 | Ici Ltd | Improvements in or relating to catalysts useful in the steam reforming of hydrocarbons |
| JP2002126529A (en) * | 2000-10-18 | 2002-05-08 | Japan National Oil Corp | Method for preparing reforming catalyst |
| CN101224427A (en) * | 2008-02-01 | 2008-07-23 | 汉能科技有限公司 | Catalyst for hydrogen production from methane vapor reforming and preparing method thereof |
| CN106807387A (en) * | 2017-01-17 | 2017-06-09 | 陕西师范大学 | A kind of bifunctional catalyst for absorption enhancement hydrogen production by bio-oil steam reforming and preparation method thereof |
| CN107252689A (en) * | 2017-07-19 | 2017-10-17 | 太原理工大学 | A kind of composite catalyst and its preparation method and application |
-
2019
- 2019-07-31 CN CN201910704434.2A patent/CN110433811B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB916216A (en) * | 1961-08-16 | 1963-01-23 | Ici Ltd | Steam reforming of hydrocarbons and catalyst therefore |
| GB1064481A (en) * | 1963-01-28 | 1967-04-05 | Ici Ltd | Improvements in or relating to catalysts useful in the steam reforming of hydrocarbons |
| JP2002126529A (en) * | 2000-10-18 | 2002-05-08 | Japan National Oil Corp | Method for preparing reforming catalyst |
| CN101224427A (en) * | 2008-02-01 | 2008-07-23 | 汉能科技有限公司 | Catalyst for hydrogen production from methane vapor reforming and preparing method thereof |
| CN106807387A (en) * | 2017-01-17 | 2017-06-09 | 陕西师范大学 | A kind of bifunctional catalyst for absorption enhancement hydrogen production by bio-oil steam reforming and preparation method thereof |
| CN107252689A (en) * | 2017-07-19 | 2017-10-17 | 太原理工大学 | A kind of composite catalyst and its preparation method and application |
Non-Patent Citations (2)
| Title |
|---|
| MgO负载Ni催化剂催化水蒸气重整生物醇制氢;王雪;《中国学位论文全文数据库》;20151229;摘要、第2.2.1节 * |
| 助剂MgO、CaO对甲烷水蒸气重整Ni/γ-Al_2O_3催化性能的影响;赵云莉等;《燃料化学学报》;20100415(第02期);第92-96页 * |
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