Text|Jane is hardcore
Editor|Hardcore
preface
As a renewable energy source, biomass has a wide range of resource potential and environmental advantages, and its effective conversion into high value-added products is essential for achieving sustainable development, and biomass "hot dissolution and carbon-rich" technology has received widespread attention as an emerging transformation method.
This technology uses the solvent effect in the pyrolysis process to convert biomass raw materials into carbon-rich products, which has the advantages of high carbon yield, low energy consumption, and multi-product regulation, and is regarded as a biomass conversion pathway with great potential.
The key to biomass "hot dissolution and carbon rich" technology is to understand and master the influence of physical parameters on the transformation process and product properties, and carry out process design and optimization on this basis.
Effect of chemical composition of biomass on the "hot dissolved carbon-rich" process
Biomass is a complex mixture of cellulose, hemicellulose, lignin and other chemical components, and the content and proportion of these components have an important impact on the "hot-soluble carbon-rich" process of biomass.
Effect of cellulose content
Cellulose is the main component of biomass, and its content has a significant impact on the effect of the "hot dissolved carbon-rich" process, and higher levels of cellulose can provide more carbon sources, thereby increasing the carbon content of the product.
Cellulose also has a higher melting point and pyrolysis temperature, which requires higher temperature and energy to achieve adequate pyrolysis, so an increase in cellulose content may require an increase in reaction temperature or an extended reaction time.
Effects of hemicellulose and lignin
Hemicellulose and lignin are other important components in biomass, and hemicellulose can be rapidly pyrolyzed in the "hot dissolved carbon-rich" process to produce soluble products and promote the formation of carbon products.
Lignin has a high melting point and pyrolysis temperature, and requires higher energy to achieve full pyrolysis, but can generate carbon-rich products, and the content and characteristics of hemicellulose and lignin have a significant impact on product distribution and carbon yield.
Influence of other components
In addition to cellulose, hemicellulose and lignin, biomass also contains some other components, such as ash, water, volatile substances, etc., which may produce some by-products or affect the progress of the reaction in the "hot dissolved carbon-rich" process.
Ash may react with the catalyst, affecting the activity of the catalyst; The presence of water and volatile substances may lead to more gaseous products in the product, and the understanding and control of the content and characteristics of these other components is also an important factor to achieve efficient "hot dissolved carbon-rich" conversion.
Effect of reaction temperature on product mass and carbon yield
The effect of temperature on product distribution
Reaction temperature is one of the important factors to regulate the distribution of products, generally speaking, with the increase of reaction temperature, the amount of gas products will increase, while the amount of solid and liquid products may decrease, higher temperature is conducive to the pyrolysis and gasification reaction of biomass, resulting in the increase of gas products (such as CO, CO2, CH4, etc.).
Lower temperatures may favor the formation of carbon-rich products such as carbon black or tar, and the selection of reaction temperatures requires a combination of product characteristics and yield requirements.
Effect of temperature on carbon yield
The reaction temperature has an important influence on the carbon yield, and the higher reaction temperature can improve the carbon yield, because the high temperature is conducive to the pyrolysis and carbonization reaction of biomass, and under high temperature conditions, the carbon element in the biomass is easier to form solid carbon products, thereby improving the carbon yield.
Excessive temperature may lead to excessive combustion and pyrolysis of the product, reducing the carbon yield, and it is necessary to find the best balance point in the right temperature range to achieve high carbon yield and ideal product quality.
At different reaction temperatures, it may also lead to changes in the chemical structure and properties of the product, and the pyrolysis of cellulose and hemicellulose in biomass may be promoted at higher temperatures to generate more soluble products and gas products, while lower temperatures may be conducive to retaining more cellulose and hemicellulose to form solid products with higher carbon content.
Influence of catalyst on reaction process and product structure
Catalysts play a key role in the process of "hot dissolution and carbon enrichment" of biomass, which can regulate the reaction rate, promote the conversion reaction and adjust the product structure, and explore the selection of catalyst types, the optimization of catalyst dosage and the regulation of product structure by catalysts, so as to reveal the influence of catalysts on the reaction process and product structure.
Selection of catalyst type
The types of catalysts have an important influence on the reaction process and product structure, and common catalysts include metal catalysts (such as nickel, iron, molybdenum, etc.), oxide catalysts (such as titanium dioxide, alumina, etc.) and acid-base catalysts (such as zinc chloride, phosphoric acid, etc.).
Different kinds of catalysts have different catalytic activity and selectivity, which can guide different reaction pathways and product formation, and the characteristics of the required products and the requirements for optimizing yield need to be considered when selecting catalysts.
Optimization of catalyst dosage
The optimization of catalyst dosage is very important for reaction efficiency and economy, the right amount of catalyst can improve the reaction rate and conversion rate, but excessive catalyst may increase the cost and processing difficulty, and even negatively affect the product structure and quality, it is necessary to determine the optimal catalyst dosage through experiments and optimization to balance the reaction effect and economy.
Regulation of product structure by catalysts
The catalyst can regulate the product structure, affect the carbon content, molecular structure and distribution of the product, the acid-base properties, surface activity and pore structure of the catalyst can affect the polymerization, cracking and oxidation processes in the reaction, and the acid catalyst can promote the cracking of cellulose and hemicellulose and increase the formation of soluble products.
Basic catalysts are conducive to the formation of gas products and acid neutralization reactions, and the selection and use of catalysts can also regulate the molecular weight distribution, aromaticity and oxygen content of products.
The mechanism of action of catalysts involves the formation of active sites and the adsorption and dissociation of reactants, and in the design and preparation of catalysts, it is necessary to comprehensively consider the physical and chemical properties, surface activity and stability of catalysts to improve the catalytic effect and catalyst life.
Effect of reaction time on product properties
Effect of reaction time on product yield
Reaction time refers to the duration of the reaction, it and the product yield has a close relationship, usually, with the extension of the reaction time, the product yield will gradually increase, because the longer reaction time can provide a fuller chance of reaction, so that the chemical bonds in the biomass to a greater degree of rupture and transformation.
However, there is also a limit to the reaction time, after which the increase in product yield will tend to saturate, and a balance between product yield and reaction time needs to be balanced when determining the optimal reaction time.
Effect of reaction time on product structure
The reaction time also has an important influence on the formation and regulation of the product structure, in the short reaction time, the polymer in the biomass mainly undergoes a cracking reaction, and more low molecular weight compounds and gas products may appear in the product.
The reaction time is prolonged, and the cracking reaction gradually tends to equilibrium, so that the cracking degree of the polymer is reduced, and the formation of carbon-rich products is increased, and the longer reaction time helps to form solid products with high carbon content.
The reaction time can also affect the molecular weight distribution and structural characteristics of the product, under the short reaction time, the molecular weight of the polymer in the product is lower, and with the extension of the reaction time, the molecular weight of the polymer gradually increases, and the molecular weight distribution of the product gradually becomes wider.
Effect of raw material particle size on reaction process and product quality
Selection of raw material particle size
The choice of raw material particle size is crucial for the "hot dissolution carbon-rich" reaction process, and smaller raw material particle size can increase the reaction surface area, improve the contact area and mass transfer efficiency between biomass and solvent or catalyst, which helps to improve the reaction rate and conversion efficiency.
Larger raw material particle size may lead to limited mass and heat transfer within the reactant, reduce reaction rate and conversion efficiency, and consider reaction rate, conversion efficiency and operating cost when selecting raw material particle size.
Effect of raw material particle size on product yield
Raw material particle size has a certain influence on product yield, smaller raw material particle size can increase the contact area between reactants and solvent or catalyst, enhance the progress of the reaction, thereby improving product yield, too fine raw material particle size may lead to agglomeration and accumulation of reactants, increase the difficulty of solid-liquid separation and product separation, and limit the improvement of product yield.
The effect of raw material particle size on product structure
Raw material particle size also has a certain influence on the formation and regulation of product structure, smaller raw material particle size helps to improve the uniform heating and mass heat transfer efficiency of reactants, promote the pyrolysis and cracking reaction of biomass, thereby facilitating the formation of carbon-rich substances (such as carbon black or tar) in the product.
While larger raw material particle size may lead to incomplete pyrolysis reaction and polymer accumulation, resulting in more low molecular weight compounds and gas products, the choice of raw material particle size can regulate the carbon content and molecular structure of the product.
Need to pay attention to the selection of raw material particle size also need to consider the specific reaction system and operating conditions, different reaction devices and solvent systems may have different requirements for raw material particle size, in the process design, should comprehensively consider product properties, reaction rate and process feasibility, select the appropriate raw material particle size.
Author's point of view
The chemical composition of biomass has an important impact on the "hot dissolution carbon-rich" process, the increase of cellulose content can increase the carbon content of the product, while the characteristics of hemicellulose and lignin play an important role in the product distribution and carbon yield, and the presence of other components may also affect the reaction process and product properties.
Reaction temperature is a key parameter to regulate product quality and carbon yield, appropriate reaction temperature selection can improve product quality and carbon yield, but too high temperature may lead to excessive combustion and pyrolysis of the product.
Catalyst plays a key role in the process of "hot dissolution and carbon enrichment" of biomass, which can regulate the reaction rate, promote the conversion reaction and adjust the product structure, and the type selection, dosage optimization and regulation of the product structure of the catalyst are important factors to be considered in the process design.
The reaction time has a significant impact on the properties of the product, and the appropriate reaction time can improve the product yield and regulate the product structure, but the long reaction time may reach the limit of the benefit.
Raw material particle size also has an important influence on the reaction process and product quality, and appropriate raw material particle size selection can improve the reaction rate and conversion efficiency, but too fine or too large particle size will bring difficulties to the formation and separation of products.
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