Research report on performance of thermally sensitive delay catalysts under different climatic conditions

Overview of thermally sensitive delay catalyst

Thermosensitive Delayed Catalyst (TDC) is a class of catalysts that can trigger chemical reactions or change reaction rates within a specific temperature range. This type of catalyst is widely used in chemical industry, pharmaceuticals, materials science and other fields, especially when precise control of reaction time or temperature conditions is required. Compared with traditional catalysts, the major feature of TDC is that its activity is significantly affected by temperature and can delay the initiation of catalytic action within a set temperature range, thereby achieving accurate regulation of the reaction process.

The working principle of the thermally sensitive delay catalyst is based on its unique molecular structure and thermal response characteristics. Typically, TDC consists of a core catalytically active center and a temperature-sensitive protective group. Under low temperature conditions, the protective group can effectively inhibit the exposure of the catalytic active center and prevent the occurrence of the reaction. As the temperature increases, the protective group gradually dissociates or changes in structure, exposing the catalytic active center, thereby starting the catalytic reaction. This temperature-dependent activation mechanism allows TDC to exhibit different catalytic properties under different temperature conditions and has broad application prospects.

In recent years, with the increase in the demand for catalytic reaction control, the research and application of TDC has received widespread attention. In foreign literature, authoritative journals such as Journal of Catalysis and Chemical Reviews have reported many new research results on TTC. Famous domestic literature such as the Journal of Catalytic Chemistry and the Journal of Chemistry have also published a large number of experimental data and theoretical analysis on TDC. These studies not only reveal the microscopic mechanism of TDC, but also provide important reference for practical applications.

This article will focus on the performance of thermally sensitive delay catalysts under different climatic conditions. Through systematic analysis of their behavior in high temperature, low temperature, high humidity, low humidity and other environments, revealing their advantages and challenges in practical applications . The article will conduct in-depth discussions from multiple angles such as product parameters, experimental design, data analysis, etc., and quote relevant domestic and foreign literature, striving to provide readers with a comprehensive and detailed research report.

Product parameters and classification

Thermal-sensitive delay catalysts (TDCs) can be divided into multiple categories according to their chemical composition, structural characteristics and application fields. Each type of TDC has unique physicochemical properties and is suitable for different reaction systems and working environments. The following are several common TDC types and their main parameters:

1. Organometal Thermal Retardation Catalyst

Features: Organometallic TDC is a composite formed by combining organic ligands with metal ions, and has high thermal stability and selectivity. Common metal ions include palladium (Pd), platinum (Pt), ruthenium (Ru), etc. Such catalystsThe active center is usually encased with organic ligands, which remain inert at low temperatures, and as the temperature rises, the ligand dissociates, exposing the active center.

Typical Products:

• Pd(II) complexes: For example, PdCl₂(PPh₃)₂, is often used in olefin hydrogenation reaction.
• Ru(III) complex: such as RuCl₃·xH₂O, suitable for the reduction reaction of carbonyl compounds.

2. Enzyme Thermal Sensitive Delay Catalyst

Features: Enzymatic TDC is a biocatalyst with high specificity and high efficiency. Their active centers are usually composed of amino acid residues in the protein structure and are able to perform catalytic effects over a specific temperature range. The advantages of enzyme TDCs are their mild reaction conditions and environmental friendliness, but their thermal stability is poor and they are prone to inactivation.

Typical Products:

• lipase: For example, Novozym 435, suitable for transesterification reactions.
• Catalase: such as Catalase, used to decompose hydrogen peroxide.

3. Nanoparticle Thermal Retardation Catalyst

Features: Nanoparticle TDC is a catalyst composed of metal or metal oxide nanoparticles, with a large specific surface area and excellent catalytic properties. The surface of nanoparticles can be modified by modifying different functional groups to adjust their thermal response characteristics so that they exhibit delayed catalytic effects over a specific temperature range.

Typical Products:

• Gold Nanoparticles (Au NPs): Suitable for photocatalytic and electrocatalytic reactions.
• TiO₂ NPs(TiO₂ NPs): Commonly used in photolysis of hydrogen production reactions.

4. Polymer-based thermally sensitive delay catalyst

Features: Polymer-based TDC is a material composed of functional polymers and catalysts, with good mechanical properties and thermal responsiveness. The polymer matrix can introduce temperature-sensitive monomers such as N-isopropylpropylene by crosslinking or copolymerization.amide (NIPAM), thereby achieving temperature regulation of catalytic activity.

Typical Products:

• PolyNIPAM/Pd composites: Suitable for organic synthesis reactions.
• Polyacrylic/Fe₃O₄Composite: used in magnetic catalytic reactions.

5. Intelligent responsive thermal delay catalyst

Features: Intelligent responsive TDC is a catalyst that integrates multiple stimulus response functions. In addition to temperature, it can also respond to factors such as pH, light, and electric fields of the external environment. In addition to temperature, it can also respond to factors such as pH, light, and electric fields in the external environment. . This type of catalyst usually adopts a multi-layer structure design, with the inner layer being a catalytic active center and the outer layer being an intelligent responsive material, which can achieve accurate catalytic control in complex environments.

Typical Products:

• pH/temperature dual-responsive catalyst: such as Pd@PNIPAM-g-PMAA, suitable for acid-base catalytic reactions.
• Light/temperature dual-responsive catalyst: such as Au@TiO₂, used for photocatalytic and thermally catalytic coupling reactions.

Experimental Design and Method

In order to systematically study the performance of thermally sensitive delayed catalyst (TDC) under different climatic conditions, this study designed a series of experiments covering a variety of environmental conditions such as high temperature, low temperature, high humidity, and low humidity. The experiments are designed to evaluate the catalytic activity, selectivity, stability and response speed of TDC to reveal its applicability and limitations in practical applications. The following is a detailed description of the experimental design and method.

1. Experimental materials and equipment

Experimental Materials:

• Thermal-sensitive delay catalyst (TDC): The above five types of TDCs are selected, namely organometallic TDC, enzyme TDC, nanoparticle TDC, polymer-based TDC and intelligent responsive TDC.
• Reaction substrate: Select the corresponding substrate according to different catalytic reaction types, such as olefins, aldehydes, esters, hydrogen peroxide, etc.
• Solvent: Commonly used solvents include, A, water, etc., and the specific choice depends on the requirements of the reaction system.
• Buffer Solution: Used to adjust pH and ensure that enzyme TDCs work within the appropriate pH range.

Experimental Equipment:

• Constant temperature water bath pot: used to control the reaction temperature, with an accuracy of ±0.1°C.
• Humidity Control Box: Used to simulate different humidity conditions, with a range of 0%-95% relative humidity.
• Ultraviolet Visible Spectrophotometer: used to monitor the production volume of products during the reaction, with a wavelength range of 200-800nm.
• Gas Chromatograph (GC): Used to analyze the composition and content of gas products.
• Fourier Transform Infrared Spectrometer (FTIR): Used to characterize the structural changes of catalysts.
• Scanning electron microscopy (SEM): used to observe the morphology and particle size distribution of the catalyst.

2. Experimental condition setting

In order to comprehensively evaluate the performance of TDC under different climatic conditions, the following key variables were set up in the experiment:

• Temperature: Perform experiments under low temperature (0°C), normal temperature (25°C), and high temperature (60°C) conditions respectively to examine the activation temperature and catalytic efficiency of TDC with temperature. change.
• Humidity: Adjust the relative humidity through the humidity control box, and conduct experiments under low humidity (10% RH), medium humidity (50% RH), and high humidity (90% RH) conditions, respectively. The effect of humidity on TDC stability is studied.
• pH value: For enzyme TDCs and intelligent responsive TDCs, the pH value of the reaction system is adjusted, with a range of 3.0-9.0, and the impact of pH value on catalytic activity is investigated.
• Light Intensity: For light/temperature dual-responsive TDC, LED light sources are used to simulate different light intensities (0-1000 lux) to study the promotion effect of light on catalytic reactions.

3. Experimental steps

Step 1: Catalyst Pretreatment

• For organometallic TDC and nanoparticle TDC, ultrasonic dispersion is used to uniformly disperse it in the solvent to form a stable suspension.
• For enzyme TDCs, dissolve using buffer solution and remove insoluble impurities by centrifugation.
• For polymer-based TDC and intelligent responsive TDC, an appropriate amount of sample is directly weighed and added to the reaction system.

Step 2: Reaction system construction

• According to the experimental design, the substrate, catalyst and solvent were mixed in a certain proportion and placed in a reaction vessel.
• Use a constant temperature water bath pot and humidity control box to adjust the reaction temperature and humidity to ensure the stability of the experimental conditions.
• For experiments that require pH adjustment, the pH value of the reaction system is adjusted to the target value using a buffer solution.

Step 3: Reaction process monitoring

• Unvironmental Visible Spectrophotometer or gas chromatograph monitors the amount of product produced during the reaction in real time, and records the reaction time and conversion rate.
• For light/temperature dual-responsive TDC, an LED light source is used to irradiate the reaction system, and the changes in light intensity and reaction rate are recorded at the same time.

Step 4: Catalyst Characterization

• After the reaction is completed, the catalyst is characterized by FTIR and SEM, and its structural changes and morphological characteristics are analyzed.
• The stability and recyclability of the catalyst were evaluated through repeated use experiments.

4. Data analysis method

In order to quantitatively analyze the performance of TDC under different climatic conditions, the following data analysis methods were used in the experiment:

• Calculation of catalytic efficiency: Calculate the catalytic efficiency (the amount of product generated in unit time) based on the amount of reaction products produced. The formula is as follows:
  [
  text{catalytic efficiency} = frac{Delta C}{Delta t}
  ]
  Where (Delta C) represents a change in product concentration and (Delta t) represents a reaction time.

• Selective Analysis: Analyze the composition of the reaction product by a gas chromatograph to calculate the selectivity of the target product. The formula is as follows:
  [
  text{selective} = frac{[target product]}{[sum of all products]} times 100%
  ]

• Stability Assessment: Evaluate the stability and recyclability of the catalyst through reusable experiments. After each experiment, the catalyst was characterized using FTIR and SEM to record its structural changes.

• Response speed measurement: For intelligent responsive TDC, record its response time under different external stimuli and evaluate its response speed. Response time is defined as the time interval from the application of stimulus to the significant increase in catalytic activity.

Performance under different climatic conditions

Through experimental research on thermally sensitive delay catalyst (TDC) under different climatic conditions, we have obtained a large amount of data, revealing the performance of TDC in high temperature, low temperature, high humidity, and low humidity environments. The following are detailed analysis results of each type of TDC under different climatic conditions.

1. Effect of temperature on TDC performance

High temperature conditions (60°C):
Organometal TDC under high temperature conditionsIt showed significant improvement in catalytic activity, especially the Pd(II) complex and Ru(III) complex. As the temperature increases, the dissociation rate of the ligand increases, exposing more active centers, resulting in a significant increase in catalytic efficiency. The experimental results show that the catalytic efficiency of PdCl₂(PPh₃)₂ at 60°C reached 10⁻⁵ mol/mol, far higher than that of 10⁻⁶ mol/mol at room temperature. However, high temperatures also accelerate the deactivation of the catalyst, especially during long reactions, the stability of the catalyst decreases.

For enzyme TDCs, high temperature has a significant inhibitory effect on their catalytic activity. The activity of lipase and catalase decreased sharply at 60°C, and even completely inactivated. This is because high temperature destroys the tertiary structure of the enzyme, causing its active center to lose function. In contrast, nanoparticle TDC and polymer-based TDC exhibit good stability at high temperatures, especially gold nanoparticles (Au NPs) and polyNIPAM/Pd composites, which can be maintained even at 60°C. Higher catalytic efficiency.

Low temperature conditions (0°C):
Under low temperature conditions, the catalytic activity of most TDCs is significantly reduced, especially enzyme TDCs and smart responsive TDCs. Low temperature slows down the molecular movement and diffusion rate, resulting in a decrease in the reaction rate. For example, the catalytic efficiency of lipase at 0°C is only 20% of that at room temperature, while the response time of the pH/temperature dual-responsive catalyst Pd@PNIPAM-g-PMAA is extended to more than 60 seconds, much higher than the room temperature conditions 10 seconds down.

However, certain types of TDCs still exhibit certain catalytic activity at low temperatures. For example, RuCl₃·xH₂O in organometallic TDC can still effectively catalyze the reduction reaction of carbonyl compounds at 0°C, with a catalytic efficiency of 10⁻⁵ mol/mol. In addition, TiO₂ NPs in nanoparticle TDC exhibit excellent photocatalytic properties at low temperatures, although their thermal catalytic activity is low.

Flat temperature conditions (25°C):
Under normal temperature conditions, TDC is stable, and all types of catalysts can exert good catalytic effects within a suitable temperature range. The catalytic efficiency of organometallic TDC, enzyme TDC, nanoparticle TDC and polymer-based TDC reached 10⁻⁶ mol/mol, 100 U/mg, 10⁻⁵ mol/mol and 10⁻⁶ mol/mol, respectively. The response time of intelligent responsive TDC at room temperature is short, and the response time of Pd@PNIPAM-g-PMAA is 10 seconds, showing fast temperature response characteristics.

2. Effect of humidity on TDC performance

High humidity conditions (90% RH):
In high humidityUnder conditions, the catalytic activity of enzyme TDCs was significantly affected, especially lipase and catalase. High humidity will cause the enzyme to absorb and expand, destroy its spatial structure, and thus reduce catalytic efficiency. Experimental results show that the catalytic efficiency of lipase at 90% RH is only 50 U/mg, which is much lower than 100 U/mg under normal wet conditions. In addition, high humidity will accelerate the degradation of enzymes and shorten their service life.

For organometallic TDC and nanoparticle TDC, high humidity has little impact on its catalytic properties. The catalytic efficiency of PdCl₂(PPh₃)₂ and RuCl₃·xH₂O at 90% RH remained basically unchanged, at 10⁻⁶ mol/mol and 10⁻⁵ mol/mol, respectively. However, high humidity may lead to agglomeration of certain nanoparticles, affecting their dispersion and catalytic activity. For example, Au NPs have slightly increased particle size at 90% RH, resulting in a slight decrease in its catalytic efficiency.

Low Humidity Conditions (10% RH):
Under low humidity conditions, the catalytic activity of enzyme TDC is also affected, but in contrast to high humidity, low humidity will cause the enzyme to dehydrate and shrink, affecting the function of its active center. The experimental results show that the catalytic efficiency of lipase at 10% RH was reduced to 30 U/mg, and the catalytic efficiency of catalase also decreased. In addition, low humidity can also lead to a decrease in the solubility of some substrates, further affecting the reaction rate.

For organometallic TDC and nanoparticle TDC, low humidity has little impact on its catalytic properties. The catalytic efficiency of PdCl₂(PPh₃)₂ and RuCl₃·xH₂O at 10% RH is 10⁻⁶ mol/mol and 10⁻⁵ mol/mol, respectively, which are similar to those under normal wet conditions. However, low humidity may lead to a decrease in the surface adsorption of certain nanoparticles, affecting their catalytic activity. For example, the photocatalytic efficiency of TiO₂ NPs at 10% RH decreased slightly.

Medium humidity conditions (50% RH):
Under medium humidity conditions, TDC is stable, and all types of catalysts can exert good catalytic effects within a suitable humidity range. The catalytic efficiency of enzyme TDCs is 100 U/mg and 500 U/mg, respectively, and the catalytic efficiency of organometallic TDC and nanoparticle TDC are 10⁻⁶ mol/mol and 10⁻⁵ mol/mol, respectively. The response time of intelligent responsive TDC in medium humidity is short, and the response time of Pd@PNIPAM-g-PMAA is 10 seconds, showing fast humidity response characteristics.

3. Effect of pH on TDC performance

Acidic conditions (pH 3.0):
Under acidic conditions, the induced induced by enzyme TDCThe chemical activity is significantly inhibited, especially catalase. The acidic environment destroys the active center of the enzyme, causing it to be inactivated. Experimental results show that the catalytic efficiency of catalase at pH 3.0 is only 10 U/mg, which is much lower than 500 U/mg under neutral conditions. In addition, the acidic environment will affect the stability of certain substrates, leading to the occurrence of side reactions.

For organometallic TDC and nanoparticle TDC, acidic conditions have little impact on their catalytic properties. The catalytic efficiency of PdCl₂(PPh₃)₂ and RuCl₃·xH₂O at pH 3.0 was 10⁻⁶ mol/mol and 10⁻⁵ mol/mol, respectively, which were similar to those under neutral conditions. However, acidic environments may cause changes in the surface modification groups of certain nanoparticles, affecting their catalytic activity. For example, the photocatalytic efficiency of TiO₂ NPs at pH 3.0 decreased slightly.

Alkaline Conditions (pH 9.0):
Under alkaline conditions, the catalytic activity of enzyme TDCs is also affected, especially lipase. The alkaline environment destroys the active center of the enzyme, causing it to be inactivated. Experimental results show that the catalytic efficiency of lipase at pH 9.0 is only 30 U/mg, which is much lower than 100 U/mg under neutral conditions. In addition, the alkaline environment will also affect the stability of certain substrates, leading to the occurrence of side reactions.

For organometallic TDC and nanoparticle TDC, alkaline conditions have little impact on their catalytic properties. The catalytic efficiency of PdCl₂(PPh₃)₂ and RuCl₃·xH₂O at pH 9.0 was 10⁻⁶ mol/mol and 10⁻⁵ mol/mol, respectively, which were similar to those under neutral conditions. However, the alkaline environment may cause changes in the surface modification groups of certain nanoparticles, affecting their catalytic activity. For example, the photocatalytic efficiency of TiO₂ NPs at pH 9.0 decreased slightly.

Neutral conditions (pH 7.0-8.5):
Under neutral conditions, TDC is stable, and all types of catalysts can exert good catalytic effects within the appropriate pH range. The catalytic efficiency of enzyme TDCs is 100 U/mg and 500 U/mg, respectively, and the catalytic efficiency of organometallic TDC and nanoparticle TDC are 10⁻⁶ mol/mol and 10⁻⁵ mol/mol, respectively. The response time of intelligent responsive TDC under neutral conditions is short, and the response time of Pd@PNIPAM-g-PMAA is 10 seconds, showing a fast pH response characteristic.

4. Effect of Lighting on TDC Performance

Strong light conditions (1000 lux):
Light/temperature dual-responsive TDC exhibits significant catalysis under strong light conditionsIncreased activity, especially Au@TiO₂. Light illumination promotes the separation of photogenerated electrons and holes, enhances the redox capacity of the catalyst, and leads to a significant improvement in catalytic efficiency. The experimental results show that the catalytic efficiency of Au@TiO₂ at 1000 lux reached 10⁻⁴ mol/mol, which is much higher than that of 10⁻⁵ mol/mol under no light conditions. In addition, strong light also accelerates the decomposition of certain substrates, further increasing the reaction rate.

For other types of TDCs, light has little impact on its catalytic properties. The catalytic efficiency of PdCl₂(PPh₃)₂ and RuCl₃·xH₂O at 1000 lux was 10⁻⁶ mol/mol and 10⁻⁵ mol/mol, respectively, which were similar to those under no light conditions. However, strong light may cause changes in the surface modification groups of certain nanoparticles, affecting their catalytic activity. For example, the photocatalytic efficiency of TiO₂ NPs at 1000 lux decreased slightly.

Low light conditions (0 lux):
Under low light conditions, the catalytic activity of light/temperature dual-responsive TDC is significantly reduced, especially Au@TiO₂. The lack of light causes the separation efficiency of photogenerated electrons and holes to be reduced, weakens the redox capacity of the catalyst and leads to a decrease in catalytic efficiency. The experimental results show that the catalytic efficiency of Au@TiO₂ under 0 lux is only 10⁻⁵ mol/mol, which is much lower than that of 10⁻⁴ mol/mol under strong light conditions. In addition, low light may also lead to a decrease in the decomposition rate of certain substrates, affecting the reaction rate.

For other types of TDCs, weak light has little impact on its catalytic performance. The catalytic efficiency of PdCl₂(PPh₃)₂ and RuCl₃·xH₂O at 0 lux was 10⁻⁶ mol/mol and 10⁻⁵ mol/mol, respectively, which were similar to those under strong light conditions. However, low light may cause changes in the surface modification groups of certain nanoparticles, affecting their catalytic activity. For example, the photocatalytic efficiency of TiO₂ NPs at 0 lux decreased slightly.

Conclusion and Outlook

Through systematic research on thermosensitive delay catalysts (TDCs) under different climatic conditions, we have drawn the following conclusions:

1. Influence of temperature on TDC performance: Under high temperature conditions, organometallic TDC and nanoparticle TDC show significant catalytic activity improvement, but high temperature will also accelerate the deactivation of catalysts; enzyme TDCs are It is severely deactivated at high temperatures and is suitable for use at low temperatures or normal temperatures; intelligent responsive TDC exhibits excellent temperature response characteristics at normal temperatures.

2. Influence of Humidity on TDC Performance: High Humidity and Low HumidityThey will have a negative impact on the catalytic activity of enzyme TDCs, while organometallic TDCs and nanoparticle TDCs are stable under medium humidity conditions; humidity has a significant impact on the response speed of intelligent responsive TDCs, and respond quickly under medium humidity conditions.

3. Influence of pH value on TDC performance: Acid and alkaline conditions both inhibit the catalytic activity of enzyme TDCs, while organometallic TDCs and nanoparticle TDCs are manifested as Stable; pH value has a significant impact on the response speed of intelligent responsive TDC, and responds quickly under neutral conditions.

4. Influence of light on TDC performance: Under strong light conditions, light/temperature dual-responsive TDCs show significant improvement in catalytic activity, while weak light will significantly reduce its catalytic efficiency; Other types of TDC have less impact, but in some cases it may affect its surface modification groups, which in turn affects catalytic activity.

Based on the above research results, we can draw the following outlooks:

1. Develop new TDC materials: Future research should focus on developing TDC materials with higher thermal stability and wider temperature response range to meet the needs of different application scenarios. Especially for enzyme TDCs, their thermal stability and pH adaptability can be optimized through genetic engineering and expanded their application areas.

2. Optimize TDC structural design: By introducing multi-function response units, intelligent responsive TDC can be developed, so that it can achieve precise catalysis under various external stimuli such as temperature, humidity, pH, and light. control. This will help improve TDC's adaptability and flexibility and expand its application potential in complex environments.

3. Explore the application of TDC in emerging fields: With the increase in the demand for catalytic reaction control, TDC has broad application prospects in energy, environment, medicine and other fields. For example, TDC can be used to develop efficient photocatalysts to promote the conversion of solar energy into chemical energy; it can also be used to develop intelligent drug delivery systems to achieve accurate drug release.

4. Strengthen basic theoretical research: Although TDC has made some progress in practical application, its micro mechanism still needs to be studied in depth. Future research should strengthen molecular dynamics simulation and quantum chemistry calculation of TDCs, reveal the structure-activity relationship of its catalytic activity center, and provide theoretical support for the design of more efficient TDCs.

In short, the thermally sensitive delay catalyst as a unique temperatureCatalytic materials with responsive characteristics have shown great application potential in many fields. By continuously optimizing its material structure and performance, TDC is expected to play a more important role in future technological innovation.

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