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Research on the conversion of propane and butane under the action of plasma

Research on the conversion of propane and butane under the action of plasma

Research on the conversion of propane and butane under the action of plasma: Propane is the main component of natural gas, oilfield gas and refinery gas. Propane is a saturated alkane, and its economic value is low when it is directly utilized. However, propylene has a large gap, so it is necessary to study the olefination of propane. my country has abundant natural gas and petroleum resources. With their continuous development and utilization, propane in natural gas, oil field gas and refinery gas has increased sharply. Therefore, the development of propane production of propylene technology is of great importance for the rational use of propane and the development of new sources of propylene. Significance. At present, there are three main ways of propane dehydrogenation: propane high temperature steam cracking, propane catalytic deradon and propane oxidative dehydrogenation. The propylene yield of propane high temperature steam cracking dehydrogenation is too low, and the propane conversion rate of propane catalytic dehydrogenation reaction is too low; propane oxidative dehydrogenation can break the thermodynamic barrier of the reaction, and theoretically can obtain higher selectivity and yield. Rate. The current oxidants are mainly O2 and CO2. O2 is used as an oxidant for oxidative dehydrogenation. Due to the high activity of oxygen, there are many by-products. The selectivity of propylene is low, and the milder oxidant CO2 is often used, which can make full use of abundant The CO2 resource can reduce environmental pollution, so it has received more attention in recent years. Coupling the reverse water gas shift reaction with the direct dehydrogenation of propane, that is, using CO2 as the oxidant to oxidize propane to propylene, on the one hand, the thermodynamic equilibrium of the direct dehydrogenation of propane can be shifted, and it is possible to obtain higher olefin selectivity; Therefore, it has a strong application prospect because of CO2 that causes the global greenhouse effect. But the important problem at present is to find a suitable catalyst to make the reaction of CO2 oxidation of C3H8 better. The main product of propane under the action of pure plasma is C2H2 propane conversion and C2H2 yield increase with the increase of plasma energy density. The active species detected by 0ES online are mainly H and methyl radicals, indicating that the C-C bond is mainly broken in propane in the plasma, followed by the C-H bond. The main product of propane under the combined action of plasma and Ce4.34-Ni2.75-Zn-O/Y-Al2O3 catalyst is still acetylene, but a small amount of propylene is generated, indicating that plasma activation plays a leading role in this reaction, while Ce4 The .34-Ni2.75-Zn-O/Y-Al2O3 catalyst only plays the role of modulation. The main product of n-butane under the action of pure plasma plasma is C2H2, which is because the bond energy of CC bond is lower than that of CH bond. Under the action of atmospheric plasma plasma, the CC bond is preferentially broken to form CHx active species, which further reacts C2H2 is preferentially generated.

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Under the action of plasma plasma, CH4 and CO2 are the raw material gas to synthesize C2 hydrocarbon reforming reaction

Under the action of plasma plasma, CH4 and CO2 are the raw material gas to synthesize C2 hydrocarbon reforming reaction

Under the action of plasma plasma, CH4 and CO2 are the raw material gas to synthesize C2 hydrocarbon reforming reaction: Synthesis of C2 hydrocarbons with CH4 and CO2 as feed gas is a very interesting reaction. The first complete reduction product of CO2 hydrogenation is CH4, and the partial reduction product is C2 hydrocarbon; secondly, the complete oxidation product of CH4 is CO2, the partial oxidation product is C2 hydrocarbon, and the intermediate product is CHx. Obviously, these two reactions are mutually reversible. , such as co-activation of CH4 and CO2, that is, the presence of CO2 will be beneficial to the partial oxidation of CH4, and the presence of CH4 will inhibit the deep reduction of CO2, the result of the joint action will be conducive to the formation of C2 hydrocarbons. The significance of studying the CH4 coupling reaction with CO2 as the oxidant is that: first, a method to solve the difficult activation of CH4 is proposed, which provides an effective way to make full use of natural gas: Secondly, the conversion and utilization of CO2 can reduce greenhouse gases to a certain extent. emission. Therefore, this research has important academic value and broad application prospects. The synthesis route of CO2 oxidation of CH4 to C2 hydrocarbons has been reported. Under the action of plasma plasma, CO2 oxidation of CH4 to C2 hydrocarbons can be divided into indirect method and direct method. Synthetic system of C2 hydrocarbons. Zhou et al. used the dielectric barrier discharge method to realize the CO2 reforming CH4 reaction. When the injection energy was 87kW.h/(N∙m3), the conversion rate of methane was 64%, and the conversion rate of carbon dioxide was 54%. Gallon et al. and Pinhao et al. respectively investigated the reforming reaction of CH4 and CO2 under the action of DBD discharge plasma, and the results showed that the main product of the reforming reaction was syngas, and only a small amount of hydrocarbons (mainly C2H6) were generated. However, under the action of DBD discharge plasma, the reactant conversion of CH4 and CO2 reforming reaction is relatively low and the reaction energy consumption is high. Li et al. investigated the reforming reaction of CH4 and CO2 under the action of DC and AC corona discharge respectively. The experimental results show that the reformation reaction of CH4 and CO2 under the action of corona discharge plasma can obtain higher conversion rate of reactants, H2 selectivity and CO selectivity, compared with that obtained by DC positive corona discharge. , followed by AC corona, low DC negative corona. Malik et al. and Gesser et al. realized CO2 reforming CH4 reaction under pulsed corona plasma and silent discharge plasma conditions, respectively. The direct method is to prepare C2 hydrocarbons from CH4 and CO2 in one step, and the reaction can be realized under the action of microwave, flow column discharge and radio frequency plasma. Liu uses the flow column discharge method, with He as the balance gas (accounting for 60%~80% of the total gas flow), under a certain discharge power, according to the different molar ratios of CO2 and CH4, the methane conversion rate is between 20%~80% , the conversion rate of carbon dioxide is between 8% and 49%, and the yield of C2 hydrocarbons is between 20% and 45%. Chen Dongliang et al. directly converted CH4 and CO2 under the action of microwave plasma, and produced C2 hydrocarbons in one step. The main C hydrocarbon products in the reaction were C2H2 and C2H6. The increase of plasma power is conducive to the generation of C2H2. Yao et al. used radio frequency plasma to realize the reaction of CO2 oxidation of CH to C2 hydrocarbons, the methane conversion rate was 31%, the carbon dioxide conversion rate was 24%, and the C2 hydrocarbon selectivity was 64%.

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Under the action of plasma plasma, CH4 and CO2 are the raw material gas to synthesize C2 hydrocarbon reforming reaction

Under the action of plasma plasma, CH4 and CO2 are the raw material gas to synthesize C2 hydrocarbon reforming reaction

Under the action of plasma plasma, CH4 and CO2 are the raw material gas to synthesize C2 hydrocarbon reforming reaction: Synthesis of C2 hydrocarbons with CH4 and CO2 as feed gas is a very interesting reaction. The first complete reduction product of CO2 hydrogenation is CH4, and the partial reduction product is C2 hydrocarbon; secondly, the complete oxidation product of CH4 is CO2, the partial oxidation product is C2 hydrocarbon, and the intermediate product is CHx. Obviously, these two reactions are mutually reversible. , such as co-activation of CH4 and CO2, that is, the presence of CO2 will be beneficial to the partial oxidation of CH4, and the presence of CH4 will inhibit the deep reduction of CO2, the result of the joint action will be conducive to the formation of C2 hydrocarbons. The significance of studying the CH4 coupling reaction with CO2 as the oxidant is that: first, a method to solve the difficult activation of CH4 is proposed, which provides an effective way to make full use of natural gas: Secondly, the conversion and utilization of CO2 can reduce greenhouse gases to a certain extent. emission. Therefore, this research has important academic value and broad application prospects. The synthesis route of CO2 oxidation of CH4 to C2 hydrocarbons has been reported. Under the action of plasma plasma, CO2 oxidation of CH4 to C2 hydrocarbons can be divided into indirect method and direct method. Synthetic system of C2 hydrocarbons. Zhou et al. used the dielectric barrier discharge method to realize the CO2 reforming CH4 reaction. When the injection energy was 87kW.h/(N∙m3), the conversion rate of methane was 64%, and the conversion rate of carbon dioxide was 54%. Gallon et al. and Pinhao et al. respectively investigated the reforming reaction of CH4 and CO2 under the action of DBD discharge plasma, and the results showed that the main product of the reforming reaction was syngas, and only a small amount of hydrocarbons (mainly C2H6) were generated. However, under the action of DBD discharge plasma, the reactant conversion of CH4 and CO2 reforming reaction is relatively low and the reaction energy consumption is high. Li et al. investigated the reforming reaction of CH4 and CO2 under the action of DC and AC corona discharge respectively. The experimental results show that the reformation reaction of CH4 and CO2 under the action of corona discharge plasma can obtain higher conversion rate of reactants, H2 selectivity and CO selectivity, compared with that obtained by DC positive corona discharge. , followed by AC corona, low DC negative corona. Malik et al. and Gesser et al. realized CO2 reforming CH4 reaction under pulsed corona plasma and silent discharge plasma conditions, respectively. The direct method is to prepare C2 hydrocarbons from CH4 and CO2 in one step, and the reaction can be realized under the action of microwave, flow column discharge and radio frequency plasma. Liu uses the flow column discharge method, with He as the balance gas (accounting for 60%~80% of the total gas flow), under a certain discharge power, according to the different molar ratios of CO2 and CH4, the methane conversion rate is between 20%~80% , the conversion rate of carbon dioxide is between 8% and 49%, and the yield of C2 hydrocarbons is between 20% and 45%. Chen Dongliang et al. directly converted CH4 and CO2 under the action of microwave plasma, and produced C2 hydrocarbons in one step. The main C hydrocarbon products in the reaction were C2H2 and C2H6. The increase of plasma power is conducive to the generation of C2H2. Yao et al. used radio frequency plasma to realize the reaction of CO2 oxidation of CH to C2 hydrocarbons, the methane conversion rate was 31%, the carbon dioxide conversion rate was 24%, and the C2 hydrocarbon selectivity was 64%.

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The effect of CO2 addition on CH4 conversion reaction under the action of plasma

The effect of CO2 addition on CH4 conversion reaction under the action of plasma

The effect of CO2 addition on CH4 conversion reaction under the action of plasma:     In the O2 plasma methane oxidative coupling reaction, the amount of O2 added will directly affect the conversion rate of CH4 and the selectivity of C2 hydrocarbons. is COx(x=1, 2). For the CO2 oxidative CH conversion reaction under the action of plasma plasma, there is also a suitable amount of CO2 addition. The effect of CO2 addition on the conversion rate of CH4, CO2 and product yield can be seen from the results: when the CO2 concentration in the feed gas increases from 15% to 85%, the conversion rate of CH4 increases gradually, and the conversion rate of CO2 changes in a peak shape. When the CO2 concentration is 50%~65%, it reaches as high as about 24%. The research shows that the key step in the oxidation of CH4 by CO2 under the action of plasma plasma is the generation of active species, that is, the high-energy electrons generated by the plasma have elastic or inelastic collisions with CH4 and CO2 molecules, so that CH is successively broken. , generate CHx (x=1～3) free radicals; CO2 breaks C-0 bond to generate reactive oxygen species, which react with CH4 or methyl radicals to generate more CHx (x=1～3) free radicals. The higher the CO2 concentration in the feed gas, the higher the number of reactive oxygen species provided and the higher the CH conversion rate. Therefore, the CH conversion rate is related to two factors, the number of high-energy electrons in the system and the concentration of reactive oxygen species. The CO2 conversion rate is related to collisions between energetic electrons and CO2 molecules, which elastic or inelastic collisions promote: (1) C-O cleavage of CO2 generates CO and O: CO2 + e* → CO2 + O + e (4-1) The depletion of oxygen-reactive species by CH4 favors a rightward shift of the reaction. (2) The ground state CO2 molecules absorb energy and transform into excited state CO2 molecules. Obviously, the CO2 conversion mainly depends on the former. Under the same plasma conditions, the conversion rates of pure CH4 and pure CO2 were 10.9% and 9.4%, respectively. The conversion rates of CH4 and CO2 were higher than the above values ​​when CH4 and CO2 were co-fed, indicating that CH4 and CO2 were co-fed. It is favorable for the co-activation of the two. When the CO2 concentration in the system increased from 15% to 35%, the C2 hydrocarbon yield increased slightly; with the further increase of the CO2 concentration in the system, the C2 hydrocarbon yield gradually decreased. This is because at high CO2 concentration, too many reactive oxygen species in the system interact with CH4 molecules to generate oxidation products on the one hand, and on the other hand, they interact with the generated C2 hydrocarbon products to promote the conversion of C2H6, C2H4, and C2H2 into oxidation products. The CO yield increases with the increase of CO2 concentration, and becomes a constant value when the CO2 concentration is higher than 50%. At the same time, as the CO2 concentration in the system increased from 15% to 85%, the molar ratio of H2 and CO in the product decreased from 3.5 to 0.6. The above research results show that: under certain plasma conditions, in order to obtain a higher C2 hydrocarbon yield and a suitable H2/CO ratio, a lower amount of CO2 addition should be selected. Under the experimental conditions, its value should be 20% to 35%. The distribution of C2 hydrocarbons decreased with the increase of CO2 concentration in the system, and the mole fraction of C2H2 decreased; while the mole fractions of C2H6 and C2H4 showed a rising trend. The possible reasons are: 1. More and more CO2 molecules in the system will absorb more energy, reduce the number of high-energy electrons, and prevent the CH bond of the CH3(CH2) radical from being further broken, resulting in the concentration of CH3, CH2, and CH radicals. distribution changes. The free radical coupling reaction changes the distribution of C2 hydrocarbons in the system; 2. Just as inert gases such as N2 and He play a role in the methane coupling reaction under plasma plasma conditions, the CO2 molecules in the system also play a role as a diluent gas. effect. It is generally believed that methane generates acetylene through the following two paths under plasma conditions: 1. The coupling reaction of CH radicals; 2. The dehydrogenation reaction of C2H6 and C2H4. With the continuous increase of CO2 concentration in the system, a large number of high-energy electrons are consumed, and the collision probability between C2H6, C2H4 and high-energy electrons decreases continuously, further dehydrogenation reaction is hindered, and the generation of C2H4 is further reduced. Therefore, with the increase of CO2 concentration in the system, the mole fractions of C2H6 and C2H4 show a rising trend, while the mole fraction of C2H2 decreases.

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Plasmon-enhanced InAs Single Quantum Dot Fluorescence Radiation Changes Nanoscale Size Tuning Wavelength Research

Plasmon-enhanced InAs Single Quantum Dot Fluorescence Radiation Changes Nanoscale Size Tuning Wavelength Research

Plasmon-enhanced InAs Single Quantum Dot Fluorescence Radiation Changes Nanoscale Size Tuning Wavelength Research: Semiconductor quantum dots are quantum structures with limited three-dimensional dimensions, which restrict the spatial distribution and motion of carriers, and thus have some unique physical properties, such as discrete energy levels, density of states similar to functions, etc. Quantum dots have good application prospects in single-photon emitting devices. After the surface plasmon treatment of metal nanostructures, it has rich and unique physical properties, which makes the optical field localized in the sub-wavelength size range, and has a strong localized electromagnetic field enhancement effect. Changing the nanometer size of metals can tune the resonant wavelength of surface plasmons. At the same time, metal nanostructures will also reduce the lifetime of fluorescence, reduce the intensity of fluorescence, or cause fluorescence quenching. When the nanostructures only resonate with the excitation light field, the fluorescence lifetime of the quantum dots remains unchanged; when the nanostructures resonate with the fluorescence of the quantum dots, the quantum yield can be improved, while the fluorescence lifetime of the quantum dots is reduced. The luminescence lifetime, luminescence intensity and saturation excitation power of the obtained quantum dots are all modulated by the gold island film. This is mainly manifested in the following three aspects: One is the enhancement of the localized laser field. The nanostructure of the gold island film allows the optical field to be localized in the sub-wavelength size, especially at some sharp corners or slits, which increases the localized strength of the electric field, which will lead to saturated excitation power. reduce; 2. The coupling between the quantum dot dipole transition and the gold island film leads to a decrease in the fluorescence lifetime, which belongs to the non-radiative recombination process of excitons. At the same time, the luminous energy is absorbed by the gold island film and lost, resulting in a decrease in the luminous intensity and an increase in the saturation excitation power; 3. The gold island film structure is used as a directional coupling-out antenna for quantum dot light emission, which increases the PL collection efficiency, resulting in a higher spectral collection efficiency, but has little effect on the saturated excitation power and fluorescence lifetime. The coupling between the gold island film and the quantum dot emission is related to the emission wavelength of the quantum dot and the specific nanostructure of the gold island film in the quantum dot sample. The metal nanostructure can change the radiation direction of the light field to form the directional emission of the light field. Therefore, metal nanostructures are widely used to study excitation light field enhancement, fluorescence emission coupling and their interaction with dipole luminescence, such as using Tam plasmon modes, nanoparticles, nanoantennas, metal films, nanostructures And plasmon resonance, etc., improve the fluorescence radiation intensity of quantum dots, form fluorescence directional emission, improve fluorescence collection efficiency, etc. Plasma enhances the fluorescence radiation of single quantum dots and improves the quality of the luminous effect of the product. The main physical mechanism of the fluorescence enhancement effect is that the gold island film structure acts as an effective directional coupling output of quantum dots, and the antenna increases the PL collection efficiency of the quantum dots, thereby obtaining a higher spectral collection efficiency. The gold island film structure mainly enhances the collection efficiency of quantum dot spectra, providing an efficient method for preparing bright single-photon sources. At the same time, it is also observed that a small number of quantum dots like QD2 have the phenomenon that the luminescence lifetime is shortened (about 270ps), the saturation excitation power is increased (about 1nW), and the total fluorescence intensity is weakened. This is because the luminescence energy is reduced by gold. The island film is absorbed and lost, and no radiation recombination plays a major role. The gold island film has a certain modulation effect on the luminescence lifetime, luminescence intensity and saturation excitation power of quantum dots. The gold island film nanostructure is beneficial to improve the collection efficiency of PL spectra of quantum dots, which provides an efficient method for fabricating bright single-photon sources.

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Plasmon-enhanced InAs Single Quantum Dot Fluorescence Radiation Changes Nanoscale Size Tuning Wavelength Research

Plasmon-enhanced InAs Single Quantum Dot Fluorescence Radiation Changes Nanoscale Size Tuning Wavelength Research

Plasmon-enhanced InAs Single Quantum Dot Fluorescence Radiation Changes Nanoscale Size Tuning Wavelength Research: Semiconductor quantum dots are quantum structures with limited three-dimensional dimensions, which restrict the spatial distribution and motion of carriers, and thus have some unique physical properties, such as discrete energy levels, density of states similar to functions, etc. Quantum dots have good application prospects in single-photon emitting devices. After the surface plasmon treatment of metal nanostructures, it has rich and unique physical properties, which makes the optical field localized in the sub-wavelength size range, and has a strong localized electromagnetic field enhancement effect. Changing the nanometer size of metals can tune the resonant wavelength of surface plasmons. At the same time, metal nanostructures will also reduce the lifetime of fluorescence, reduce the intensity of fluorescence, or cause fluorescence quenching. When the nanostructures only resonate with the excitation light field, the fluorescence lifetime of the quantum dots remains unchanged; when the nanostructures resonate with the fluorescence of the quantum dots, the quantum yield can be improved, while the fluorescence lifetime of the quantum dots is reduced. The luminescence lifetime, luminescence intensity and saturation excitation power of the obtained quantum dots are all modulated by the gold island film. This is mainly manifested in the following three aspects: One is the enhancement of the localized laser field. The nanostructure of the gold island film allows the optical field to be localized in the sub-wavelength size, especially at some sharp corners or slits, which increases the localized strength of the electric field, which will lead to saturated excitation power. reduce; 2. The coupling between the quantum dot dipole transition and the gold island film leads to a decrease in the fluorescence lifetime, which belongs to the non-radiative recombination process of excitons. At the same time, the luminous energy is absorbed by the gold island film and lost, resulting in a decrease in the luminous intensity and an increase in the saturation excitation power; 3. The gold island film structure is used as a directional coupling-out antenna for quantum dot light emission, which increases the PL collection efficiency, resulting in a higher spectral collection efficiency, but has little effect on the saturated excitation power and fluorescence lifetime. The coupling between the gold island film and the quantum dot emission is related to the emission wavelength of the quantum dot and the specific nanostructure of the gold island film in the quantum dot sample. The metal nanostructure can change the radiation direction of the light field to form the directional emission of the light field. Therefore, metal nanostructures are widely used to study excitation light field enhancement, fluorescence emission coupling and their interaction with dipole luminescence, such as using Tam plasmon modes, nanoparticles, nanoantennas, metal films, nanostructures And plasmon resonance, etc., improve the fluorescence radiation intensity of quantum dots, form fluorescence directional emission, improve fluorescence collection efficiency, etc. Plasma enhances the fluorescence radiation of single quantum dots and improves the quality of the luminous effect of the product. The main physical mechanism of the fluorescence enhancement effect is that the gold island film structure acts as an effective directional coupling output of quantum dots, and the antenna increases the PL collection efficiency of the quantum dots, thereby obtaining a higher spectral collection efficiency. The gold island film structure mainly enhances the collection efficiency of quantum dot spectra, providing an efficient method for preparing bright single-photon sources. At the same time, it is also observed that a small number of quantum dots like QD2 have the phenomenon that the luminescence lifetime is shortened (about 270ps), the saturation excitation power is increased (about 1nW), and the total fluorescence intensity is weakened. This is because the luminescence energy is reduced by gold. The island film is absorbed and lost, and no radiation recombination plays a major role. The gold island film has a certain modulation effect on the luminescence lifetime, luminescence intensity and saturation excitation power of quantum dots. The gold island film nanostructure is beneficial to improve the collection efficiency of PL spectra of quantum dots, which provides an efficient method for fabricating bright single-photon sources.

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