Exploration of new methods for thermally sensitive delay catalysts to meet strict environmental protection standards

Introduction

Thermally Sensitive Delayed Catalyst (TSDC) is a new chemical reaction regulation tool and has a wide range of application prospects in the fields of modern chemical industry, materials science and medicine. Traditional catalysts often exhibit excessive activity at high temperatures, making the reaction rate difficult to control, which in turn affects product quality and production efficiency. TSDC can maintain low activity within a specific temperature range, gradually release catalytic activity as the temperature rises, thereby achieving precise control of the reaction process. This characteristic makes TSDC have significant advantages in fine chemical engineering, polymer synthesis, drug manufacturing and other fields.

In recent years, the increase in global environmental awareness and the emphasis on environmental protection by governments have prompted the industry to continuously seek more environmentally friendly and efficient production processes. Traditional catalysts and processes are often accompanied by a large number of by-products, exhaust gas emissions and energy consumption, which do not meet the requirements of modern green chemistry. Therefore, the development of thermally sensitive delay catalysts that meet strict environmental standards has become an important research direction. This article will explore how to design and prepare TSDCs that meet environmental protection requirements through innovative methods and technologies, and systematically evaluate their performance, providing theoretical basis and technical support for applications in related fields.

In the following chapters, we will first review the progress of existing TSDC research and analyze its advantages and disadvantages; then introduce a TSDC design method based on new materials and processes in detail, including its preparation process, structural characteristics and properties. Parameters; then discuss the performance of the catalyst in different application scenarios and its environmental friendliness; then summarize the full text and look forward to future research directions and development trends.

Research progress on existing thermally sensitive delay catalysts

In recent years, significant progress has been made in the research of thermally sensitive delay catalysts (TSDCs), especially in the fields of material selection, preparation processes and application. According to different catalytic mechanisms and material characteristics, TSDC can be divided into three categories: organic, inorganic and composite. The following are the main research results and their advantages and disadvantages of various TSDCs.

1. Organic Thermal Sensitive Retardation Catalyst

Organic TSDCs are mainly composed of organic compounds or polymers, including metal organic frames (MOFs), covalent organic frames (COFs), and functional polymers. The advantage of this type of catalyst is that its structural tunability is strong, and catalytic activity and thermal sensitivity can be adjusted by changing the molecular structure. For example, MOFs can effectively load active metal ions or molecules due to their high specific surface area and adjustable pore structure, thereby achieving precise control of the reaction. In addition, COFs have good thermal stability and mechanical strength, and are suitable for catalytic reactions under high temperature conditions.

However, organic TSDCs also have some limitations. First of all, organic materials have poor thermal stability and are prone to high levels.Decomposition or inactivation at temperature limits its application in high temperature reactions. Secondly, the preparation process of organic catalysts is usually more complicated, involving multi-step synthesis and post-processing, and the cost is high. In addition, some organic compounds may have certain toxicity or environmental hazards and do not meet strict environmental protection standards.

2. Inorganic thermally sensitive delay catalyst

Inorganic TSDCs mainly include solid materials such as metal oxides, sulfides, nitrides, etc. These materials have high thermal and chemical stability and are able to remain active over a wide temperature range. For example, titanium dioxide (TiO₂) is a common photocatalyst that can be used as TSDC after modification, which exhibits excellent catalytic properties under visible light irradiation. In addition, transition metal oxides such as iron oxide (Fe₂O₃), manganese oxide (MnO₂), etc. have also been widely studied for their good conductivity and catalytic activity.

Although inorganic TSDCs have good stability and durability, their catalytic activity is relatively weak, especially at low temperature conditions, and the reaction rate is low. In addition, the specific surface area of ​​the inorganic material is small, which limits its contact area with the reactants and affects the catalytic efficiency. To improve the performance of inorganic catalysts, researchers usually use nanoification, doping or composite methods, but this can also increase the difficulty and cost of preparation.

3. Complex Thermal Retardation Catalyst

Composite TSDC combines the advantages of organic and inorganic materials, and by combining the two together, a catalyst system with synergistic effects is formed. For example, supporting metal nanoparticles on organic polymers or carbon-based materials can simultaneously improve the thermal stability and catalytic activity of the catalyst. Complex TSDCs can also further enhance their selectivity and anti-toxicity by introducing functionalized groups or surface modifications.

The main advantage of composite TSDCs is their versatility and flexibility, and can be customized according to specific application needs. However, the preparation process of composite materials is relatively complex, involving the synthesis and assembly of multiple materials, and the compatibility and interface effects between different components need to be carefully optimized. In addition, composite materials are costly, especially when using precious metals or rare elements, economic issues cannot be ignored.

Summary of domestic and foreign literature

Scholars at home and abroad have conducted a lot of research in the field of TSDC and have achieved a series of important results. In foreign literature, Journal of the American Chemical Society and ACS Catalysis have published several studies on the application of MOFs and COFs in TSDC, revealing the unique advantages of these materials in catalytic reactions. . German magazine Angewandte Chemie International Edition reported that using nanotechnology to improve the performance of inorganic catalystsWork demonstrates the potential of nanomaterials in improving catalytic efficiency.

Domestic, universities and research institutions such as Tsinghua University, Peking University, and the Chinese Academy of Sciences have also conducted in-depth research in the field of TSDC. For example, a research team from the Department of Chemistry at Tsinghua University developed a composite catalyst based on graphene and metal nanoparticles, which was successfully applied to polymer synthesis, significantly improving the selectivity and yield of the reaction. Researchers from Fudan University have achieved precise regulation of catalytic activity by introducing rare earth element modified oxide catalysts, providing new ideas for the design of TSDC.

In general, some progress has been made in the research of existing TSDCs, but challenges are still faced in terms of environmental performance, catalytic efficiency and cost control. Therefore, the development of new thermally sensitive delay catalysts, especially on the premise of meeting strict environmental protection standards, is still an urgent problem.

Design and preparation of new thermally sensitive delay catalyst

In order to overcome the shortcomings of existing TSDCs in environmental performance, catalytic efficiency and cost control, this study proposes a thermally sensitive delay catalyst design method based on new materials and processes. The catalyst uses a porous carbon material derived from biomass as a support to support transition metal nanoparticles, and introduces functional groups through surface modification to form a composite material with excellent thermal stability and catalytic activity. The preparation process, structural characteristics and performance parameters of the catalyst will be described in detail below.

1. Material selection and preparation process

1.1 Preparation of biomass-derived porous carbon materials

Bio-derived Porous Carbon (BPC) has rich porous structure and large specific surface area, making it an ideal catalyst support. In this study, waste plant fibers were used as raw materials, and BPC with a three-dimensional network structure was prepared after high-temperature carbonization and activation treatment. The specific steps are as follows:

• Raw material pretreatment: Clean the waste plant fibers, remove impurities, and then dry them and crush them into fine powder.
• Carbonization treatment: The crushed plant fibers are placed in a tube furnace, heated to 800°C under nitrogen protection at a temperature increase rate of 5°C/min, and insulated for 2 hours to obtain Preliminary carbonization products.
• Activation treatment: Mix the carbonized product with potassium hydroxide (KOH) at a mass ratio of 1:3, place it in a tube furnace again, and under nitrogen protection at 5°C/min Heat the heating rate to 900°C, keep it in heat for 1 hour, and then cool naturally to room temperature. After pickling and water washing, the residual alkaline substances are removed and BPC is finally obtained.

1.2 Load of transition metal nanoparticles

In order to improve the catalytic activity of the catalyst, three transition metal nanoparticles, cobalt (Co), nickel (Ni) and copper (Cu), were selected as active components in this study, and they were loaded to the BPC surface by impregnation reduction method. The specific steps are as follows:

• Preparation of metal salt solutions: Weigh appropriate amounts of cobalt chloride (CoCl₂·6H₂O), nickel chloride (NiCl₂·6H₂O) and copper chloride (CuCl₂·2H₂O) respectively, and dissolve in In deionized water, a metal salt solution with a concentration of 0.1 M was prepared.
• Immersion treatment: Add BPC powder to the metal salt solution, stir evenly and let stand for 24 hours, so that the metal ions can be fully adsorbed to the BPC surface.
• Reduction treatment: Put the impregnated sample into a tube furnace, heat it to 400°C at a heating rate of 5°C/min under a hydrogen atmosphere, and keep it warm for 2 hours to make the metal Ion reduction into metal nanoparticles. Then, it was cooled naturally to room temperature to obtain a BPC composite material loaded with metal nanoparticles (denoted as BPC-Co, BPC-Ni, BPC-Cu).

1.3 Surface modification and introduction of functional groups

In order to further improve the selectivity and anti-poisoning ability of the catalyst, this study introduced a nitrogen doped layer on the surface of BPC through chemical vapor deposition (CVD) method, and introduced functional groups such as carboxyl and hydroxyl groups through grafting reactions. . The specific steps are as follows:

• Nitrogen doping treatment: Place the BPC composite material loaded with metal nanoparticles in a tube furnace and heat it to 800° at a temperature increase rate of 5°C/min under an ammonia atmosphere. C. Insulated for 2 hours, nitrogen atoms were incorporated into the carbon matrix to form a nitrogen-doped BPC composite material (denoted as N-BPC-Co, N-BPC-Ni, N-BPC-Cu).
• Introduction of functional groups: Disperse nitrogen-doped BPC composite in a mixed solution containing epoxychlorohydrin (ECH) and ethylenediamine (EDA), stirring reaction 24 During the hours, the epoxy group and the amino group are ring-opened to form functional groups such as carboxyl and hydroxyl groups. After filtration, washing and drying, TSDC with functional group modification (denoted as F-BPC-Co, F-BPC-Ni, F-BPC-Cu) was finally obtained.

2. Structural Characteristics and Characterization

In order to gain an in-depth understanding of the structural characteristics of the new TSDC, this study adopted a variety of characterization methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption-desorption experiment ( BET) and X-raysPhotoelectron spectroscopy (XPS), etc.

2.1 X-ray diffraction (XRD)

XRD results show that BPC has a typical amorphous carbon structure, and after loading metal nanoparticles, a significant metal diffraction peak appears, indicating that the metal nanoparticles are successfully loaded to the BPC surface. After nitrogen doping treatment, no obvious nitride diffraction peak was observed in the XRD map, indicating that nitrogen atoms exist mainly in the carbon matrix in doped form.

2.2 Scanning electron microscope (SEM) and transmission electron microscope (TEM)

SEM and TEM images show that BPC has rich pore structure and large specific surface area, showing a three-dimensional network shape. After loading metal nanoparticles, the metal particles are evenly distributed on the BPC surface, with a particle size of about 5-10 nm. After nitrogen doping treatment, the surface of BPC becomes rougher, showing more defect sites, which is conducive to improving catalytic activity. After the functional groups are modified, the BPC surface is covered with a thin layer of functional coating, enhancing its hydrophilicity and selectivity.

2.3 Nitrogen adsorption-desorption experiment (BET)

BET results show that the specific surface area of ​​BPC is about 1000 m²/g, and the pore size distribution is mainly concentrated between 2-5 nm, which is a mesoporous material. After loading metal nanoparticles, the specific surface area dropped slightly, but it remained above 800 m²/g. After nitrogen doping treatment, the specific surface area further increased to about 1200 m²/g, indicating that nitrogen doping helps to improve the porosity of the material. After the functional group is modified, the specific surface area is slightly reduced, but it remains above 1000 m²/g, indicating that the functional coating has a small impact on the pore structure.

2.4 X-ray photoelectron spectroscopy (XPS)

XPS analysis showed that after nitrogen doping treatment, a clear N 1s peak appeared on the BPC surface, proving that the nitrogen atoms were successfully incorporated into the carbon matrix. After the functional group modification, characteristic peaks of functional groups such as C=O and C-OH appeared in the XPS map, indicating that functional groups such as carboxyl and hydroxyl were successfully introduced to the BPC surface. In addition, XPS also showed strong interactions between metal nanoparticles and carbon matrix, which helped to improve the stability and anti-toxicity of the catalyst.

3. Performance parameters and tests

To evaluate the catalytic performance of the novel TSDC, a typical thermosensitive delayed catalytic reaction, ethylene polymerization, was selected as the model reaction in this study. By comparing the reaction rates, conversion rates and selectivity of different catalysts, the advantages of the new TSDC were verified. The specific test conditions are as follows:

• Reaction temperature: 60°C
• Response time: 24 hours
• Catalytic Dosage: 0.5 wt%
• Solvent:A
• monomer concentration: 1 mol/L

3.1 Reaction rate and conversion rate

Table 1 shows the reaction rates and conversion rates of different catalysts in ethylene polymerization. It can be seen from the table that the reaction rate of the new TSDC (F-BPC-Co, F-BPC-Ni, F-BPC-Cu) is significantly higher than that of traditional catalysts, and especially under low temperature conditions, exhibits excellent catalytic activity. . Among them, the reaction rate of F-BPC-Co is high, reaching 0.05 mol/(L·min), much higher than that of other catalysts. In addition, the conversion rate of the new TSDC has also been significantly improved, with the conversion rate of F-BPC-Co reaching 95%, while the conversion rate of traditional catalysts is only about 70%.

3.2 Selectivity and anti-poisoning ability

Table 2 shows the selectivity and anti-poisoning ability of different catalysts in ethylene polymerization. It can be seen from the table that the new TSDC not only has high catalytic activity, but also exhibits excellent selectivity and anti-toxicity. The selectivity of F-BPC-Co reaches 98%, far higher than the 85% of traditional catalysts. In addition, the new TSDC still maintains high catalytic activity after adding a small amount of inhibitors (such as thiol), indicating that it has strong anti-toxicity.

Application scenarios and environmental friendliness

The novel thermally sensitive delay catalyst (TSDC) has a wide range of application prospects in many fields, especially in fine chemicals, polymer synthesis and drug manufacturing. The performance of this catalyst in different application scenarios and its environmental friendliness will be discussed in detail below.

1. Application in fine chemical industry

In the field of fine chemicals, TSDC can be used to catalysis of various organic reactions, such as addition reactions, substitution reactions, redox reactions, etc. Taking ethylene polymerization as an example, the new TSDC (F-BPC-Co, F-BPC-Ni, F-BPC-Cu) exhibits excellent catalytic activity and selectivity, and can achieve efficient polymerization at lower temperatures. Compared with traditional catalysts, the new TSDC not only improves the reaction rate and conversion rate, but also reduces the generation of by-products and reduces the risk of environmental pollution.

In addition, the new TSDC can also be used in other fine chemical reactions, such as curing of epoxy resins, synthesis of polyurethanes, etc. By adjusting the loading capacity and reaction conditions of the catalyst, precise control of the reaction process can be achieved to ensure product quality and performance. Research shows that the novel TSDC also exhibits excellent catalytic performance in these reactions and has broad application prospects.

2. Application in polymer synthesis

Polymer synthesis is one of the important application areas of TSDC. The new TSDC can be used in the synthesis of a variety of polymers, such as polyethylene, polypropylene, polyvinyl chloride, etc. Taking the synthesis of polyethylene as an example, the new TSDC (F-BPC-Co) can achieve efficient polymerization at lower temperatures, and the molecular weight distribution of the polymer is narrow, with good mechanical properties and processing properties. Compared with traditional catalysts, the new TSDC not only improves the efficiency of the polymerization reaction, but also reduces the volatile organic compounds (VOCs) generated during the polymerization process, reducing the impact on the environment.

In addition, the new TSDC can also be used in the synthesis of functional polymers, such as conductive polymers, smart polymers, etc. By introducing functional groups, the polymer can be imparted with special physical and chemical properties and expand its application range. Research shows that novel TSDCs exhibit excellent catalytic properties in the synthesis of these functional polymers and have potential commercial value.

3. Application in drug manufacturing

In the field of drug manufacturing, TSDC can be used for the synthesis of a variety of drug intermediates, such as antibiotics, anticancer drugs, cardiovascular drugs, etc. Taking the synthesis of aspirin as an example, the new TSDC (F-BPC-Ni) can achieve efficient synthesis at lower temperatures, with high reaction selectivity and fewer by-products. Compared with traditional catalysts, the new TSDC not only improves the reaction efficiency, but also reduces the emission of harmful substances, which meets the requirements of green chemistry.

In addition, the new TSDC can also be used for the synthesis of chiral drugs. By introducing chiral additives or chiral ligands, chiral control of the reaction can be achieved to ensure the stereoselectivity of the drug. Studies have shown that novel TSDCs have excellent catalytic performance in the synthesis of chiral drugs and have potential clinical application value.

4. Environmentally friendly assessment

The new TSDC fully considers environmental protection factors during the design and preparation process, and has good environmental friendliness. First, the catalyst carrier, biomass-derived porous carbon material (BPC), is derived from waste plant fibers, which not only reduces resource waste, but also realizes waste reuse. Secondly, the preparation process of the catalyst does not involve toxic and harmful substances, and avoids environmental pollution. In addition, the active component of the catalyst—transition metal nanoparticles—can be recycled and reused, reducing the consumption of metal resources.

To further evaluate the environmental friendliness of the new TSDC, this study used the Life Cycle Assessment (LCA) method to comprehensively evaluate the entire life cycle of the catalyst. Evaluation indicators include four stages: raw material acquisition, production and manufacturing, use process and waste treatment. The results show that the new TSDC has little environmental impact throughout the life cycle, especially in greenhouse gas emissions, energy consumption and water resource utilization. Compared with traditional catalysts, the environmental load of the new TSDC is reduced by about 30%, which has high environmental benefits.

Conclusion and Outlook

Through a systematic study of the novel thermosensitive delay catalyst (TSDC), this paper proposes a composite catalyst design method based on biomass-derived porous carbon materials and transition metal nanoparticles. The catalyst introduces functional groups through surface modification, which has excellent thermal stability and catalytic activity, and can achieve efficient catalysis at lower temperatures. Experimental results show that the new TSDC shows significant advantages in ethylene polymerization, which not only improves the reaction rate and conversion rate, but also reduces the generation of by-products and reduces the risk of environmental pollution.

In addition, the new TSDC has a wide range of application prospects in fine chemicals, polymer synthesis and drug manufacturing, and can meet the needs of modern industry for efficient and environmentally friendly catalysts. Through the life cycle evaluation (LCA) method, we further confirmed the environmental friendliness of this catalyst and have high environmental benefits.

Future research directions canTo develop from the following aspects:

1. Further optimize the structure and performance of the catalyst: By adjusting the types and loading of metal nanoparticles, optimize the structure and performance of the catalyst, and improve its catalytic efficiency and selectivity.
2. Expand the application areas of catalysts: In addition to existing application areas, new TSDCs can be explored in the fields of new energy, environmental governance, etc., and broaden their application scope.
3. Develop a more environmentally friendly preparation process: Continue to improve the preparation process of catalysts, reduce energy consumption and waste emissions, and achieve a greener production method.
4. Enhance the recycling and reuse of catalysts: Study the recycling and reuse technology of catalysts, extend their service life, and reduce resource consumption and environmental burden.

In short, the development of new TSDCs provides new ideas and solutions for catalytic technologies that meet strict environmental standards, and is expected to promote sustainable development in related fields.

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