Highly dispersed low-leaching cu / sio2 catalyst, its preparation method and application

Abstract

The application provides a high-dispersion and low-leaching Cu / SiO2 catalyst and a preparation method and application thereof. The application realizes controllable process by depositing and precipitating control in a specific weak alkali window (preferably pH=8.2-9.6, and most preferably about pH=8.8-9.2), induces formation of a basic copper nitrate species Cu2(OH)3NO3 containing nitrate, and uses the basic copper nitrate species as a'marker phase' of the deposition structure. Meanwhile, on the basis of the high-dispersion copper species, a super-thin interface layer is constructed TiO2 The super-thin interface layer limits and inhibits migration and leaching, so as to realize the synergistic promotion of 'high dispersion-low leaching', and meet the dual requirements of high activity and high stability in a liquid-phase reaction system. The catalyst is used for catalyzing 1,4-butanediol to prepare gamma-butyrolactone, and the purity and conversion rate of the obtained product are both >99%.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and provides a highly dispersed, low-loss Cu / SiO2 catalyst, its preparation method, and its application. Background Technology

[0002] Existing methods for preparing Cu / SiO2 catalysts mainly include impregnation, deposition-precipitation, co-precipitation, ammonia stripping, and urea homogeneous deposition. While these methods are widely used, they still have the following prominent drawbacks under high copper loading and long-term liquid-phase operation conditions: (1) Copper species are prone to agglomeration and insufficient dispersion. In the existing technology, the copper deposition precipitation process often only roughly controls the pH or the amount of precipitant, which easily leads to local instantaneous over-alkali and oversaturation, resulting in rapid precipitation of the bulk phase and particle growth. This leads to the formation of coarse CuO and Cu crystal phases after calcination and reduction, respectively. The utilization rate of active sites is low, the catalytic performance is unstable, and the batch repeatability is poor.

[0003] (2) It is more difficult to obtain a highly dispersed structure under high copper loading conditions. To improve catalytic activity or production capacity, Cu / SiO2 systems often require a higher copper loading (e.g., 15~35 wt%). However, existing methods are more prone to copper species accumulation and sintering under high loading, which further reduces the dispersibility and leads to faster activity decay, making it difficult to achieve a balance between "high loading and high dispersion".

[0004] (3) Severe copper migration and loss during the liquid-phase reaction process. When Cu / SiO2 is used in aqueous or polar solvent systems, copper species are prone to migration, dissolution, or stripping, resulting in ppm-level metal loss. On the one hand, this causes catalyst deactivation and shortens its lifespan; on the other hand, it introduces metal impurities that contaminate the product, increasing post-processing costs and affecting product quality. Therefore, how to significantly reduce copper loss while ensuring high activity is a key issue that needs to be addressed by existing technologies.

[0005] (4) The deposition process is difficult to control precisely, and batch repeatability is poor. Existing preparation processes rely more on empirical parameter adjustments and lack effective means to induce and determine key sedimentary species such as basic copper nitrate Cu2(OH)3NO3 during the deposition process. This can easily lead to deviations in the deposition path, significant structural differences, and difficulty in stable reproduction, thus limiting the stable preparation and large-scale promotion of highly dispersed structures.

[0006] Therefore, it is necessary to provide a highly dispersed, low-loss Cu / SiO2 catalyst, its preparation method, and its application to meet the needs. Summary of the Invention

[0007] To address the problems mentioned in the background section, this invention provides a Cu / SiO2 catalyst and its preparation method that combine highly dispersed active sites with low copper loss. This invention achieves process control by controlling deposition and precipitation within a specific weakly alkaline window (preferably pH = 8.2~9.6, optimally approximately pH = 8.8~9.2), inducing the formation of basic copper nitrate species Cu2(OH)3NO3 containing nitrate ions, which serves as a "marker phase" for the deposition structure. Simultaneously, an ultrathin TiO2 interfacial layer is constructed on the basis of the highly dispersed copper species to confine and anchor the copper, inhibiting migration and dissolution. This achieves a synergistic improvement in "high dispersion and low loss," meeting the dual requirements of high activity and high stability in liquid-phase reaction systems.

[0008] In a first aspect, the present invention provides a method for preparing a highly dispersed, low-loss Cu / SiO2 catalyst, comprising: Step A: Dissolve the copper salt in a solvent to obtain a copper salt solution; Step B: Add SiO2 to the copper salt solution, stir to disperse, and obtain a solution; Step C: Under stirring conditions, the precipitant is added to the solution obtained in step B to bring the pH of the system into the weakly alkaline range and maintain it for a certain period of time. After aging, a copper-containing deposited slurry is obtained. After adding background electrolyte solution to make the nitrate concentration reach a fixed value, the slurry is solidified. The characteristic peaks or homologous structural signals of basic copper nitrate deposits are detected by XRD to determine the endpoint. Step D: Separate and dry to obtain a solid; Step E: The obtained solid is calcined and reduced to obtain the catalyst precursor Cu / SiO2; Step F: Disperse the catalyst precursor Cu / SiO2 in a solvent, add a titanium source, and heat-treat to solidify to obtain a Cu / SiO2 catalyst coated with a titanium dioxide layer.

[0009] In some embodiments, the copper salt is copper nitrate, copper sulfate, copper chloride, or a combination thereof, preferably copper nitrate.

[0010] In some embodiments, the copper ion concentration in the copper salt solution can be 0.01~3.0 mol / L, preferably 0.05~2.0 mol / L, and preferably any one of the following ranges: 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, or any two of the above values.

[0011] In some embodiments, the solvent is water, ethanol, or a mixture of water and ethanol. In some embodiments, a background anion environment may be introduced into the copper salt solution to regulate the deposition path; the background anion environment is one or more of nitrate, chloride, and sulfate, and the anion concentration may be 0.005~1.0 mol / L, preferably 0.01~0.2 mol / L. It is preferable to introduce nitrate to promote the formation of nitrate-containing transition structures. Preferably, the nitrate concentration is 0.005 mol / L, 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.2 mol / L, or any two of the above values ​​forming any one of the ranges.

[0012] In some embodiments, to improve surface nucleation and inhibit bulk phase precipitation, trace amounts of complexing / slow-release components (such as ammonium salts, weak ligands, buffer systems, or solvent structure modulators) may be added to the copper salt solution. The amount added is limited to not affecting subsequent calcination removal, and preferably the concentration of the trace complexing / slow-release component is in the range of 0.001~0.5 mol / L. Preferably, the concentration of the trace complexing / slow-release component is 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, or any two of the above values ​​forming a range.

[0013] In some embodiments, the SiO2 may be in the form of silica gel, fumed SiO2, sol-gel SiO2, or porous SiO2.

[0014] In some embodiments, the stirring dispersion includes ultrasonic, shearing dispersion or mechanical stirring to achieve uniform dispersion, with a dispersion time of 5 to 180 min (preferably 10 to 120 min), a dispersion temperature of 10 to 60 ℃ (preferably 10 to 40 ℃), and a stirring speed of 100 to 2000 rpm (preferably 300 to 1200 rpm).

[0015] In some embodiments, the SiO2 may be pre-wetted or lightly activated (e.g., water-alcohol pre-wetting, ionic strength pre-adjustment) before deposition to increase the adsorption and nucleation ratio of copper species on the carrier surface.

[0016] In some embodiments, the precipitant is selected from carbonates, bicarbonates, or alkaline complex systems (such as Na2CO3, K2CO3, NH4HCO3, (NH4)2CO3, or combinations thereof).

[0017] In some embodiments, the concentration of the precipitant is 0.05~5.0 mol / L, preferably 0.1~2.0 mol / L. Preferably, it is within the range of 0.05mol / L, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, 0.6mol / L, 0.7mol / L, 0.8mol / L, 0.9mol / L, 1mol / L, 1.1mol / L, 1.2mol / L, 1.3mol / L, 1.4mol / L, 1.5mol / L, 1.6mol / L, 1.7mol / L, 1.8mol / L, 1.9mol / L, 2mol / L, or any two of the above values.

[0018] In some embodiments, in step C, the precipitant is added by continuous dripping, segmented dripping, or co-current dripping. In some embodiments, the rate of continuous dripping is 5-80 drops / min, preferably 10-60 drops / min. To avoid localized over-alkalinity leading to bulk precipitation, it is preferable to control the pH rise process as a gradual change (e.g., through dripping rate, stirring intensity, or solvent system).

[0019] In some embodiments, in step C, the system pH is 8.2–9.6, preferably 8.5–9.5, more preferably 8.8–9.2, and the maintenance time is 2–12 h, preferably 3–8 h. pH control can employ online monitoring closed-loop control or an equivalent segmented control strategy. The maintenance time is to control the formation and detection of basic copper nitrate deposits in the precursor. The copper-containing deposit structure slurry serves as a marker for detecting the deposit structure, such as Cu2(OH)3NO3, which is determined by XRD detection of characteristic peaks or homologous structure signals to ensure consistency between process control and batches.

[0020] In some embodiments, in step C, the background electrolyte solution is an electrolyte solution containing nitrate, preferably an ammonium nitrate solution, preferably with a nitrate concentration of 0.01~0.1 mol / L, preferably 0.05 mol / L, and the pH is adjusted to 8.6~8.9 and cured for 20~60 min, preferably 30 min.

[0021] In some embodiments, in step D, the solid can be obtained by filtration or centrifugation. The separated solid can be further washed with a washing solution containing a background electrolyte, which is a substance consistent with the anion of copper salt or the anion of the background anionic environment, such as NH4NO3 solution. The solid is then washed with water until its pH or conductivity is close to neutral. The concentration of the washing solution is 0.001~0.5mol / L, preferably 0.001~0.1mol / L, and the number of washings is 1~6 times, preferably 2~4 times. The solid is further replaced with an alcohol solvent (e.g., ethanol) to reduce structural collapse or secondary particle aggregation caused by capillary force during the drying process. The number of replacements is 1~3 times.

[0022] In some embodiments, in step D, the drying temperature is 40~150℃, preferably 60~120℃, and the drying time is 4~24h, preferably 6~16h.

[0023] In some embodiments, in step E, the calcination is carried out in air or an oxygen-containing atmosphere, the calcination temperature is 200~600℃, preferably 300~550℃, and the calcination time is 1~8h, preferably 3~6h.

[0024] In some embodiments, in step E, the reduction is carried out in a hydrogen-containing atmosphere at a reduction temperature of 150-350°C, preferably 250-300°C, and for a reduction time of 1-5 hours, preferably 2-3 hours. In some embodiments, the hydrogen-containing atmosphere is a mixture of hydrogen and H2 / N2 gas.

[0025] In step E, through in-situ transformation via calcination-reduction, the transitional deposition structure, such as Cu2(OH)3NO3, is uniformly converted into highly dispersed CuO / Cu. 0 (Cu + Active sites reduce the formation of coarse crystalline phases.

[0026] In some embodiments, in step F, the solvent is methanol, ethanol, ethyl acetate, dichloromethane, acetone, etc.

[0027] In some embodiments, in step F, the titanium source is at least one of alkoxy titanium (such as TBOT, TEOT), titanium sol, titanate, or hydrolyzable titanium precursor. Tetraethyl orthotitanate (TEOT) or tetrabutyl orthotitanate (TBOT) are examples.

[0028] In some embodiments, in step F, the titanium source coating catalyst precursor Cu / SiO2 can be achieved by controlled hydrolysis deposition (alcohol phase and trace aqueous phase), sol-gel confined deposition, surface adsorption-in-situ conversion deposition, or multi-step composite deposition.

[0029] In some embodiments, in step F, the titanium source is added at an amount of 0.1 to 15 wt% of TiO2 in the total mass of the catalyst, preferably 0.5 to 8 wt%, more preferably 1 to 6 wt%.

[0030] In some embodiments, in step F, the temperature of the heat treatment is 100~450℃, preferably 120~350℃, and the heat treatment time is 1~6h, preferably 2~4h.

[0031] In step F, heat treatment is used to make titanium dioxide a continuous or semi-continuous ultrathin interface layer, forming Ti-O-Si / Ti-O-Cu connection, which provides both anchoring and diffusion barrier to inhibit copper migration / dissolution, and avoids excessive obscuring of active sites, thereby achieving a balance between low loss and high activity.

[0032] Secondly, a highly dispersed, low-loss Cu / SiO2 catalyst is provided, which is prepared by the method described in this invention.

[0033] In some embodiments, the catalyst is based on silicon dioxide, with copper loaded on its surface and an outer layer of titanium dioxide.

[0034] In some embodiments, the copper loading is 15-35 wt%.

[0035] In some embodiments, the coating amount of the titanium dioxide layer accounts for 0.1wt% to 15wt% of the total mass of the catalyst, preferably 0.5wt% to 8wt%, and more preferably 1wt% to 6wt%.

[0036] Thirdly, the invention provides the use of the catalyst described herein in the catalytic preparation of γ-butyrolactone.

[0037] Compared with existing technologies, one of the above technical solutions has the following advantages or beneficial effects: This invention provides a method for preparing a highly dispersed, low-loss Cu / SiO2 catalyst. The method uses a soluble copper salt as the copper source and silica as the support, and performs deposition precipitation or co-precipitation under weakly alkaline conditions. This allows copper species to preferentially nucleate on the support surface and form basic copper nitrate Cu2(OH)3NO3 deposits containing nitrate ions. These deposits undergo in-situ decomposition and rearrangement during subsequent calcination-reduction processes, uniformly transforming into highly dispersed CuO and Cu. 0 / Cu +Active sites. Based on this, an ultrathin TiO2 interface confinement layer is further constructed to form Ti-O-Si / Ti-O-Cu connections, anchoring and blocking the diffusion of active components, thereby inhibiting copper migration and dissolution during liquid-phase operation, achieving a synergistic improvement of "high dispersion-low loss". Specifically, this manifests as follows: (1) During the preparation process, the pH is precisely controlled, and the co-precipitation or deposition process is controlled within a specific weak alkaline window (preferably pH=8.5-9.5, optimal about pH=8.8-9.2). The pH rise rate is limited by slow feeding to avoid rapid precipitation and particle growth in the bulk phase caused by local over-alkali, thereby obtaining more dispersed copper species. After calcination and reduction, Cu active sites with smaller particle size and more uniform distribution are formed.

[0038] (2) Under the preferred pH window and nitrate environment, basic copper nitrate deposit species Cu2(OH)3NO3 can be formed and detected in the precursor. It shows characteristic peaks in the precursor XRD, which can be used to determine that the deposition structure has reached the target state. This transforms the preparation process from empirical control to characterizable control, thereby achieving effective control of the deposition path and improving batch repeatability.

[0039] (3) The calcination process causes the Cu2(OH)3NO3 formed on the surface of silica to undergo in-situ decomposition and structural rearrangement, and is uniformly transformed into highly dispersed CuO species; further reduction is then carried out to form highly dispersed Cu. 0 / Cu + The active sites are thus constructed through the "basic copper nitrate deposit species-calcination in-situ transformation" site construction pathway. In other words, the calcination in-situ transformation constructs highly dispersed active sites, which can effectively reduce the formation of coarse crystalline phases and improve the utilization rate of copper atoms and catalytic activity.

[0040] (4) Based on the Cu / SiO2 dispersion with deposition structure, a continuous or semi-continuous ultrathin TiO2 interface layer (Ti-O-Si / Ti-O-Cu) is constructed by controlled hydrolysis deposition or sol-gel confined deposition. The ultrathin TiO2 interface layer is coated on the outer layer of the dispersion, which can suppress Cu migration and dissolution without excessively blocking active sites, thus taking into account both activity and stability. As a diffusion barrier and anchoring layer, this interface layer significantly reduces Cu loss during liquid phase operation and extends catalyst lifetime.

[0041] This invention induces the formation of a basic copper nitrate Cu2(OH)3NO3 deposition structure on the SiO2 surface through a pH window. After calcination to obtain a dispersion, the dispersion is synergistically bound and anchored by an ultrathin TiO2 interface layer, constructing highly dispersed Cu active sites and inhibiting copper migration and dissolution, thereby obtaining a Cu / SiO2 catalyst with both high dispersion and low metal loss characteristics.

[0042] The catalyst prepared by this invention exhibits high dispersion and smaller particle size, with a predictable deposition process and high process stability and batch-to-batch consistency. In-situ calcination and reduction can construct highly dispersed sites through in-situ conversion, and coating with a titanium dioxide layer significantly reduces Cu migration and loss, resulting in improved catalyst stability. This invention utilizes a combined technical route of "pH window deposition structure regulation + TiO2 interface confinement" to simultaneously improve the dispersion of active sites and resistance to loss, resolving the contradiction between activity and stability that is difficult to achieve in existing technologies, and realizing a synergistic effect of "high dispersion and low loss." The catalyst is used to catalyze the preparation of γ-butyrolactone from 1,4-butanediol, with both product purity and conversion rate exceeding 99%. Attached Figure Description

[0043] Figure 1 XRD pattern of the dried precursor prepared for the example.

[0044] Figure 2 The image shows the XRD pattern of the catalyst prepared in the example after calcination.

[0045] Figure 3 In the catalytic reaction, the catalyst prepared in Example 1, Cu 2+ A graph showing how the loss changes over time.

[0046] Figure 4 The graph shows the changes in feed conversion rate and product selectivity over time during the catalytic reaction of the catalyst prepared in Example 1.

[0047] Figure 5 The image shows the SEM-EDS spectrum of the catalyst prepared in Example 1.

[0048] Terminology Explanation Certain embodiments of the invention will now be described in detail, examples of which are illustrated by the accompanying structural and chemical formulas. The invention is intended to cover all alternatives, modifications, and equivalents, all of which are included within the scope of the invention as defined in the claims. Those skilled in the art will recognize that many similar or equivalent methods and materials can be used to practice the invention. The invention is by no means limited to the methods and materials described herein. In the event that one or more of the incorporated documents, patents, and similar materials differ from or contradict this application (including, but not limited to, defined terminology, application of terminology, described techniques, etc.), this application shall prevail.

[0049] It should be further appreciated that certain features of the invention, for clarity, have been described in multiple independent embodiments, but may also be provided in combination in a single embodiment. Conversely, various features of the invention, for brevity, have been described in a single embodiment, but may also be provided individually or in any suitable sub-combination.

[0050] Unless otherwise stated, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. All patents and publications related to this invention are incorporated herein by reference in their entirety.

[0051] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0052] In the following content, all numbers disclosed herein, whether or not they use words such as "approximately" or "about," are approximate values. The value of each number may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%. Whenever a number with a value of N is disclosed, any numbers with values ​​of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15%, or N+ / -20% will be explicitly disclosed, where "+ / -" indicates addition or subtraction. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0054] All reagents used in this invention can be purchased commercially or prepared by the methods described in this invention.

[0055] 1. Raw materials and equipment (1) Raw materials: copper nitrate trihydrate Cu(NO3)2·3H2O, silica gel (SiO2), sodium carbonate Na2CO3, ammonium nitrate NH4NO3 (or sodium nitrate NaNO3), anhydrous ethanol, TBOT (tetrabutyl titanate), deionized water.

[0056] (2) Equipment: magnetic stirrer / mechanical stirrer, pH meter, titration device or peristaltic pump, vacuum filter, oven, muffle furnace, tube furnace (reduction).

[0057] 2. Sample Naming Rules Ex: Example sample, x represents the number.

[0058] Cx: Comparative sample, where x represents the sample number.

[0059] pH7 / 8 / 9 / 10: refers to the pH controlled during the coprecipitation stage.

[0060] 30Cu, 20Cu: Indicates the theoretical copper loading (wt%).

[0061] 3. In this invention, room temperature refers to 15~35℃, preferably 25℃.

[0062] Example 1 A method for preparing a highly dispersed, low-loss Cu / SiO2 catalyst, comprising: Step A: Preparation of copper salt solution: Dissolve 11.4 g Cu(NO3)2·3H2O in deionized water (about 150 mL).

[0063] Step B: Addition of carrier and pre-dispersion / pre-adsorption: Add 7.0 g of porous SiO2 to the solution obtained in step A, sonicate for 10 min and stir for 60 min.

[0064] Step C: Weak base window precipitation / coprecipitation: Continuously add 0.5 mol / L Na2CO3 solution at a rate of 1 drop / second to slowly raise the pH to and maintain it at 9.0±0.1, and age for 4 h; add NH4NO3 to reduce NO3-. - With a concentration of approximately 0.05 mol / L, adjust the pH back to 8.6-8.9 and cure for 30 minutes.

[0065] Step D: Solid-liquid separation and fractional washing: Filter by suction, wash the solid twice with 10 mL of 0.05 mol / L NH4NO3 solution, then wash with water until pH neutral; replace twice with 10 mL of ethanol, and dry at 80℃ for 12 h to obtain the E-1 precursor.

[0066] Step E: Drying and heat treatment: The precursor is calcined in air at 450°C for 4 h; then reduced in H2 / N2 at 250°C for 2 h to obtain Cu / SiO2.

[0067] Step F: Construction of TiO2 interface confinement layer: The above Cu / SiO2 was dispersed in 20 mL of ethanol, TBOT (3 wt% based on the theoretical amount of TiO2 introduced) was added and TiO2 thin layer was deposited by controlled hydrolysis, and the interface layer was cured by heat treatment at 200℃ to obtain 10 g of catalyst E-1, which theoretically has 30 wt% Cu based on metallic Cu.

[0068] Figure 5 The SEM-EDS image of catalyst E-1 is shown in Table 1 below, where the elemental distribution is as follows: Table 1 Number of element distributions

[0069] Example 2 (E-2): 30Cu, pH=8.8 The sample was prepared using the same steps as in Example 1, but the pH was controlled at 8.8 ± 0.1 during the deposition stage. The rest were the same, resulting in sample E-2.

[0070] Example 3 (E-3): 30Cu, pH=9.2 The sample was prepared using the same steps as in Example 1, but the pH was controlled at 9.2 ± 0.1 during the deposition stage. The rest were the same, resulting in sample E-3.

[0071] Example 4 (E-4): 20Cu, pH=9 window + TiO2 coating Prepared using the same steps as in Example 1, except that the target theoretical load of Example 1 was changed to 20 wt% (approximately 7.6 g of Cu(NO3)2·3H2O and approximately 8.0 g of SiO2), and the remaining steps were the same as in Example 1, to obtain sample E-4.

[0072] Example 5 (E-5) Prepared using the same steps as in Example 1, except that the copper salt in Example 1 was replaced with 42.2g of copper chloride, and the remaining steps were the same as in Example 1, to obtain sample E-5.

[0073] Example 6 (E-6) Prepared using the same steps as in Example 1, except that the copper salt in Example 1 was replaced with 50.2g of copper sulfate, and the remaining steps were the same as in Example 1, to obtain sample E-6.

[0074] Example 7 (E-7) Prepared using the same steps as in Example 1, except that the target copper theoretical load in Example 1 was changed to 40 wt%, and the remaining steps were the same as in Example 1, to obtain sample E-7.

[0075] Example 8 The sample was prepared using the same steps as in Example 1, except that the precipitant used in step C of Example 1 was different. The remaining steps were the same as in Example 1. The specific parameters and corresponding catalyst numbers are shown in Table 2 below.

[0076] Table 2. Changes with different precipitants

[0077] Example 9 The sample was prepared using the same steps as in Example 1, except that the aging time in step C of Example 1 was different, while the other steps were the same as in Example 1. The specific parameters and corresponding catalyst numbers are shown in Table 3 below.

[0078] Table 3. Variations at different aging times

[0079] Example 10 The sample was prepared using the same steps as in Example 1, except that the dropping rate in step C of Example 1 was different. The remaining steps were the same as in Example 1. The specific parameters and corresponding catalyst numbers are shown in Table 4 below.

[0080] Table 4. Variations at different dropping rates

[0081] Example 11 Prepared according to the same steps as in Example 1, except that the TBOT used in step F of Example 1 was replaced with other titanium sources, and the remaining steps were the same as in Example 1. The specific parameters and corresponding catalyst numbers are shown in Table 5 below.

[0082] Table 5. Changes in Titanium Source

[0083] Comparative Example 1 (C-1): 30Cu, pH=7 The sample was prepared using the same steps as in Example 1, but the pH was controlled at 7.0 ± 0.1 during the deposition stage. The rest were the same, resulting in sample C-1.

[0084] Comparative Example 2 (C-2): 30Cu, pH=8 The sample was prepared using the same steps as in Example 1, but the pH was controlled at 8.0 ± 0.1 during the deposition stage. The rest were the same, resulting in sample C-2.

[0085] Comparative Example 3 (C-3): 30Cu, pH=10 The sample was prepared using the same steps as in Example 1, but the pH was controlled at 10.0 ± 0.1 during the deposition stage. The rest were the same, resulting in sample C-3.

[0086] Under the conditions of Comparative Example 3, the concentration of copper ions in the supernatant after precipitation was much higher than in other examples. The precipitate dissolved again in the liquid phase, and phenomena such as blue supernatant and increased soluble copper species were easily observed. Solid XRD showed no obvious Cu2(OH)3NO3 marker peak, and it was more prone to agglomeration after calcination.

[0087] Comparative Example 4 (C-4): 30Cu conventional rapid alkali addition co-precipitation The same formulation as in Example 1 was used, but Na2CO3 was added to the reaction system all at once to make the target pH≈9. The window aging and closed-loop back-off curing control steps were not performed. The rest were the same, and sample C-4 was obtained.

[0088] Comparative Example 5 (C-5): 30Cu, pH=9 window After preparing Cu / SiO2 according to Example 1 and reducing it, TiO2 coating was not performed (i.e., step F was omitted), and the rest were the same, resulting in sample C-5.

[0089] Comparative Example 6 (C-6): 30Cu, conventional rapid alkali addition co-precipitation The same formulation as in Example 1 was used, but Na2CO3 was added to the reaction system rapidly at 3~4 drops / s (almost in a line) to make the target pH≈9. The window aging and closed-loop back-off curing control steps were not performed. The rest were the same, and sample C-6 was obtained.

[0090] Example 1 (1) XRD detection: XRD tests were performed on the dried precursor, with a focus on determining whether the characteristic peak of Cu2(OH)3NO3 appeared; XRD tests were performed on the calcined samples, focusing on the intensity and full width at half maximum (FWHM) of the CuO diffraction peaks, which reflect the grain size and dispersion.

[0091] The results are as follows Figure 1 and Figure 2 As shown.

[0092] Figure 1 XRD results showed that the precursor sample prepared under the pH window and nitrate environment conditions described in this invention exhibited a distinct diffraction peak at 2θ≈12.8°, which was completely consistent with the (001) crystal plane in the basic copper nitrate Cu2(OH)3NO3 standard card (PDF#15-014). Simultaneously, synergistic diffraction peaks appeared at 2θ≈25.7°, 36.5°, 39.8°, and 43.5°, further confirming the formation of a basic copper nitrate phase with complete lattice characteristics in the deposited structure. The aforementioned characteristic peaks were significantly weakened or absent in the comparative samples (C1, C2, C3), indicating that this deposited structure did not form, thus proving that the technical solution of this invention can effectively induce copper species on the carrier surface.

[0093] Figure 2 The XRD patterns of the calcined samples show significant differences in the crystallization state of copper species under different preparation conditions. The comparative samples (C1, C2, C3) exhibit distinct and sharp diffraction peaks at 2θ≈35.5° and 38.7°, corresponding to the (-111), (002), and (111) crystal planes of CuO, respectively. Matching peaks were observed at 48.7°, 53.4°, and 58.2°, indicating that CuO has high crystallinity and a large grain size, characteristic of bulk crystallization. In contrast, the characteristic peaks of CuO in the E1 sample prepared in this embodiment are significantly weakened or even difficult to distinguish. The spectrum mainly shows an amorphous background envelope of SiO2 and weak scattering signals, without strong narrow diffraction peaks. This indicates that the CuO grain size is significantly reduced in Example 1, and the copper species exist in a highly dispersed state on the SiO2 surface, without forming obvious bulk agglomerated crystals. This phenomenon is consistent with the XRD characteristics of highly dispersed metal oxides at the nanoscale. That is, when the particle size is reduced to the nanometer scale, the diffraction peak intensity decreases, the half-peak width increases, and it partially overlaps with the background of the carrier. This proves that the process of the present invention can effectively suppress the agglomeration of copper species during the calcination process and achieve the construction of a highly dispersed structure.

[0094] like Figure 1 and Figure 2 As shown, the XRD pattern of the E-1 precursor should show characteristic peaks of Cu2(OH)3NO3 (marker phase); after calcination, it is converted into highly dispersed CuO, and after coating, it still maintains a highly dispersed structure.

[0095] (2) Cu loss (ICP): The prepared catalyst was simulated by soaking in the target liquid phase system for 40 h, and the liquid phase was collected. The Cu content (ppm) was determined by ICP. The results are shown in Table 6. Table 6 Cu 2+ Loss

[0096] As can be seen, the catalyst prepared in this application exhibits low copper loss and low loss performance. Compared with E-1 and C-5, the TiO2 interface layer can further reduce copper migration and loss, and improve stability. Catalysts C-1, C-2, and C-3, with different pH controls during the deposition stage, resulted in samples with high final copper loss rates. Using a one-time or rapid addition of the precipitant, C-4 and C-6 also showed high copper loss rates. Compared with the catalyst prepared in the comparative examples, the catalyst prepared in the examples of this application demonstrates better low loss performance.

[0097] (3) Catalytic performance: Catalyst evaluation was conducted using a fixed-bed reactor with an inner diameter of 80 mm, a catalyst loading of 3 mL, and a set temperature of 250 °C; a hydrogen-to-ethanol molar ratio of 40:1; a reaction pressure of atmospheric pressure; and a mass hourly space velocity (WHSV) of 1,4-butanediol (BDO) of 1 h⁻¹. -1 After the reaction feed stabilized, samples were taken for analysis to determine the yield of the product γ-butyrolactone (GBL). The target reaction conversion, selectivity, and cycling stability were recorded for correlation with loss / structure.

[0098] The results are shown in Table 7. Figure 3 and Figure 4 As shown.

[0099] Table 7 Catalyst performance

[0100] As can be seen from the catalytic performance of catalysts E-1, E-2 and E-3 recorded in Table 7, the catalyst prepared by changing the pH has a significant impact on the catalytic performance, with the catalyst prepared at pH 9 showing the best performance.

[0101] As can be seen from the catalytic performance of catalysts E-1, E-4 and E-7 recorded in Table 7, the catalyst prepared by changing the copper loading has a significant impact on the catalytic performance, and the catalyst prepared with a copper loading of 30 wt% has the best performance.

[0102] As can be seen from Table 7, the use of different copper salts in the preparation of catalysts E-5 and E-6 slightly affects the performance of the catalysts.

[0103] The different alkaline systems used in the preparation processes of catalysts E-8-1, E-8-2, and E-8-3 slightly affected their performance.

[0104] The different aging times used in the preparation processes of catalysts E-9-1, E-9-2, and E-9-3 slightly affected their performance.

[0105] The different pH control rates used in the preparation processes of catalysts E-10-1 and E-10-2 slightly affected the catalyst performance.

[0106] The use of different titanium sources in the preparation process of catalysts E-11-1, E-11-2, E-11-3, E-11-4, and E-11-5 slightly affected the catalyst performance.

[0107] Compared with the catalysts prepared in the comparative example, the catalysts prepared in the embodiments of this application have better catalytic performance.

[0108] Figure 3 For E1 catalyst during the reaction, Cu 2+ Trend of churn over timeFigure 4 The table shows the trends of substrate conversion and product selectivity of the E1 catalyst over time. In the initial stage of the liquid-phase reaction, a relatively high copper loss rate is observed, while the catalytic activity is at a low level. This stage corresponds to the structural rearrangement and interfacial adaptation process of copper species on the catalyst surface: some weakly bound or unstable coordination environments of copper species migrate or dissolve in the reaction medium, causing the distribution of active components in the system to tend towards reequilibrium. As the reaction proceeds, the remaining copper species gradually form a more stable anchoring structure under the action of the support interface and the TiO2 confinement layer, and the distribution of active sites tends to be uniform, indicating that the system enters a stable operating stage. At this time, the copper loss rate decreases significantly, while the catalytic activity gradually increases and remains stable, indicating that the catalyst structure has transitioned from an initial adjusted state to a stable active structure. Therefore, the copper loss behavior and catalytic performance are not simply negatively correlated, but rather reflect the transition process of the catalyst from structural adjustment to stable operation. This invention, through interfacial confinement and deposition structure regulation, enables this stable stage to appear earlier and be maintained for a long time, thereby achieving synergistic stable operation with low loss and high activity.

[0109] The method of this invention has been described through preferred embodiments. Those skilled in the art will readily be able to modify or appropriately alter and combine the methods and applications described herein within the scope, spirit, and context of this invention to implement and apply the technology of this invention. Those skilled in the art can refer to the content herein to appropriately improve process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of this invention.

Claims

1. A method for preparing a highly dispersed, low-loss Cu / SiO2 catalyst, characterized in that, include: Step A: Dissolve the copper salt in a solvent to obtain a copper salt solution; Step B: Add SiO2 to the copper salt solution, stir to disperse, and obtain a solution; Step C: Under stirring conditions, add the precipitant to the solution obtained in step B, so that the pH of the system enters the weakly alkaline range and is maintained for a certain period of time, and then age to obtain a copper-containing deposited slurry. After adding background electrolyte solution to bring the nitrate concentration in the system to a fixed value, solidification was carried out. The characteristic peaks or homologous structural signals of basic copper nitrate sediment species were detected by XRD to determine the endpoint. Step D: Separate and dry to obtain a solid; Step E: The obtained solid is calcined and reduced to obtain the catalyst precursor Cu / SiO2; Step F: Disperse the catalyst precursor Cu / SiO2 in a solvent, add a titanium source, and heat-treat to solidify to obtain a Cu / SiO2 catalyst coated with a titanium dioxide layer.

2. The preparation method according to claim 1, characterized in that, The copper salt is copper nitrate, copper sulfate, copper chloride, or a combination thereof; Preferably, the concentration of copper ions in the copper salt solution can be 0.01~3.0 mol / L; Preferably, the solvent is water, ethanol, or a mixture of water and ethanol.

3. The preparation method according to claim 1, characterized in that, The SiO2 may be in the form of silica gel, vapor phase SiO2, sol-gel SiO2 or porous SiO2; Preferably, the stirring and dispersing includes using ultrasonic, shearing, or mechanical stirring to achieve uniform dispersion, with a dispersion time of 5-180 min, a dispersion temperature of 10-60 ℃, and a stirring speed of 100-2000 rpm.

4. The preparation method according to claim 1, characterized in that, The precipitant is selected from carbonates, bicarbonates or alkaline compound systems. Preferably, the precipitant is selected from Na2CO3, K2CO3, NH4HCO3, (NH4)2CO3 or a combination thereof. Preferably, the concentration of the precipitant is 0.05~5.0 mol / L, and more preferably 0.1~2.0 mol / L.

5. The preparation method according to claim 1, characterized in that, In step C, the precipitant is added by means of continuous dripping, segmented dripping, or co-current dripping; preferably, the rate of continuous dripping is 5-80 drops / min, more preferably 10-60 drops / min; Preferably, in step C, the pH of the system is 8.2~9.6, more preferably 8.5~9.5, more preferably 8.8~9.2, and the maintenance time is 2~12h, more preferably 3~8h; Preferably, in step C, the background electrolyte solution is an electrolyte solution containing nitrate, preferably ammonium nitrate, with a preferred nitrate concentration of 0.01~0.1 mol / L, and the pH is adjusted to 8.6~8.9 for 20~60 min to solidify. Preferably, the basic copper nitrate deposit species is Cu2(OH)3NO3.

6. The preparation method according to claim 1, characterized in that, In step D, a solid is obtained by filtration or centrifugation; preferably, the separated solid is further washed with a washing solution containing a background electrolyte, wherein the background electrolyte is a substance consistent with the anion of copper salt or the anion of background anionic environment, and then further washed with water until the pH or conductivity of the solid is close to neutral. The concentration of the washing solution is 0.001~0.5mol / L, preferably 0.001~0.1mol / L, and the number of washing cycles is 1~6, preferably 2~4; further, the washing is carried out by alcohol solvent replacement, with the replacement cycle being 1~3 times; In step D, the drying temperature is 40~150℃, preferably 60~120℃, and the drying time is 4~24h, preferably 6~16h.

7. The preparation method according to claim 1, characterized in that, In step E, the calcination is carried out in air or an oxygen-containing atmosphere, the calcination temperature is 200~600℃, preferably 300~550℃, and the calcination time is 1~8h, preferably 3~6h. Preferably, in step E, the reduction is carried out in a hydrogen-containing atmosphere, the reduction temperature is 150~350℃, preferably 250~300℃, and the reduction time is 1~5h, preferably 2~3h; preferably, the hydrogen-containing atmosphere is hydrogen or an H2 / N2 mixture.

8. The preparation method according to claim 1, characterized in that, In step F, the solvent is methanol, ethanol, ethyl acetate, dichloromethane, or acetone; Preferably, in step F, the titanium source is at least one of alkoxy titanium, titanium sol, titanate, or hydrolyzable titanium precursor; the titanium source is preferably TBOT or TEOT. Preferably, in step F, the titanium source coating catalyst precursor Cu / SiO2 is carried out in the following ways: controlled hydrolysis deposition, sol-gel confined deposition, surface adsorption-in-situ conversion deposition, or multi-step composite deposition. Preferably, in step F, the titanium source is added at an amount of 0.1-15 wt% of TiO2 in the total mass of the catalyst, more preferably 0.5-8 wt%, and more preferably 1-6 wt%. Preferably, in step F, the temperature of the heat treatment is 100~450℃, more preferably 120~350℃, and the heat treatment time is 1~6h, more preferably 2~4h.

9. A highly dispersed, low-loss Cu / SiO2 catalyst, characterized in that, Prepared by the method according to any one of claims 1 to 8; The catalyst is based on silicon dioxide, with copper loaded on the surface and coated with a titanium dioxide layer on the outside. Preferably, the theoretical copper loading is 15-35 wt%; Preferably, the coating amount of the titanium dioxide layer accounts for 0.1wt% to 15wt% of the total mass of the catalyst, more preferably 0.5wt% to 8wt%, and even more preferably 1wt% to 6wt%.

10. The use of a catalyst comprising the method of any one of claims 1 to 8 or the catalyst of claim 9 in the catalytic preparation of γ-butyrolactone.

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