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Co-activation of CH4 and CO2 to C2H4 by plasma plasma and Pd-La203/Y-Al203 catalyst

Co-activation of CH4 and CO2 to C2H4 by plasma plasma and Pd-La203/Y-Al203 catalyst

Co-activation of CH4 and CO2 to C2H4 by plasma plasma and Pd-La203/Y-Al203 catalyst: The supported Pd catalyst is a catalyst for the hydrogenation of acetylene, and the micro-loaded Pd can reduce C2H2 to C2H4 or C2H6. When increased to 0.1%, the ethane mole fraction increased from 24.0% to 61.7%. The ethylene mole fraction decreased from 72.3% to 22.1%, while the C3 product mole fraction increased significantly. Therefore, in the reaction of plasma plasma and catalyst co-activated CO2 to oxidize CH4 to C2H4, as long as a trace amount of Pd is loaded on the catalyst, a C2H4 product with greater economic added value can be obtained. The research results of CO2 oxidation of CH to C2 hydrocarbons under the combined action of plasma plasma and catalyst show that La2O3/Y-Al203 can significantly improve the selectivity of C2 hydrocarbon products. Under the same plasma conditions, its C2 hydrocarbon product selectivity is higher than that of Y-Al203. It is higher than 40%, so the yield of C2 hydrocarbon products is high; although the supported metal catalyst Pd/Y-Al2O3 has little effect on the yield of C2 hydrocarbon products, it can obviously change the distribution of C2 hydrocarbon products, and the micro-loaded Pd can obviously Increase the mole fraction of C2H2 in the C2 hydrocarbon product. To this end, the co-activated CO2 oxidation of CH4 to C2H4 by plasma plasma and Pd-La2O3/Y-Al2O3 was studied, and the effects of parameters such as active component loading, feed gas composition, and energy density on the reaction were investigated. When the La2O3 loading was 2%, the C2 hydrocarbon selectivity increased from 30.6% to 72%. Although the methane conversion rate decreased from 43.4% to 24%, the C2 hydrocarbon yield still increased from 13.4% to 17.6%. La2O3 improves the CO2 conversion, but the CO yield decreases: when the La2O3 loading is changed in the range of 2% to 12%, the CH4 conversion and C2 hydrocarbon yield slightly change in peak shape, but the CO2 conversion and CO yield change slightly. The effect of Pd on the conversion rate of CH4 and CO2, and the yield of C2 hydrocarbons and CO basically has no effect when the loading of La2O3 reaches 12%. However, the Pd loading has a great influence on the distribution of C2 hydrocarbon products. When the Pd loading amount is 0.01%, the mole fraction of C2H4 in the C2 hydrocarbon products rises to 78%, that is, the C2 hydrocarbon products are mainly C2H4. C2H2 was detected but C3H8 was produced. When the Pd loading increased from 0.01% to 1%, the mole fraction of C2H4 in the C2 hydrocarbon product gradually decreased, while the mole fraction of C2H6 in the C2 hydrocarbon product gradually increased, indicating that the addition of Pd in ​​the La2O3/Y-Al2O3 catalyst was further increased. It can not increase the mole fraction of C2H4 in C2 hydrocarbon products, but promote the conversion of C2H4 to C2H6 and increase the mole fraction of C2H6 in C2 hydrocarbon products. The recommended loadings of active components Pd and La2O3 are 0.01% and 5%, respectively, that is, the catalyst is 0.01%Pd-5%La2O3/Y-Al2O3.

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Comparison of catalytic activity activation methods for plasma supported catalysts

Comparison of catalytic activity activation methods for plasma supported catalysts

Comparison of catalytic activity activation methods for plasma supported catalysts: In the reaction of CO2 oxidation of CH4 to C2 hydrocarbons, the currently used methods for activating reactants methane and carbon dioxide include catalytic activation method and plasma plasma activation method, and the plasma catalytic activation method is introduced. For the convenience of comparison, the results of CO2 oxidation of CH4 to C2 hydrocarbons under three activation conditions are listed in Table 4-3. It can be seen from Table 4-3 that in the catalytic activation method, when the reaction temperature is as high as 1100K, methane can Converted to C2 hydrocarbons, although the selectivity of C2 hydrocarbons is high, the conversion rate of methane is very low, so the yield of C2 hydrocarbons is only 2%. Plasma activation can significantly improve the methane conversion rate. When the plasma plasma injection power is 30W, the methane conversion rate reaches 26.5%, due to the lack of choice between the reactions between free radicals in the plasma plasma space and the decomposition effect of the plasma on the products. , resulting in a low C2 hydrocarbon selectivity (47.9%), and with the increase of plasma injection power, the C2 hydrocarbon selectivity decreases rapidly, so it is difficult to improve the C2 hydrocarbon yield under a certain plasma plasma injection power. In the reaction of plasma catalytic activation of CO2 oxidation of CH4 to C2 hydrocarbons, the activation of plasma can fully activate methane and improve the conversion rate of methane. The surface is selectively adsorbed and compounded to generate C2 hydrocarbon products, which improves the C2 hydrocarbon selectivity and C2 hydrocarbon yield. Because it is still difficult to study the mechanism of the plasma-catalytic activation reaction using the existing detection instruments, the research on this reaction is still in the initial stage of speculation and exploration based on the experimental results. Comparing the three activation methods, plasma catalytic activation of CO2 oxidation of CH4 to C2 hydrocarbons should have application potential and is worthy of further study. Table 4-3 Comparison of activation methods (unit: %) Activation method Xcog XcH Sc Yc Yc, H Yco Plasma 20.2 26.5 47.9 12.7 1.6 33.2 Catalysis 3.7 2.1 97.0 2.0 >2.0 Plasma-Catalysis 22.0 24.9 72.7 18.1 13.8 28.6

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Vacuum plasma surface cleaning machine circuit board plasma treatment changes in chemical and physica

Vacuum plasma surface cleaning machine circuit board plasma treatment changes in chemical and physica

Vacuum plasma surface cleaning machine circuit board plasma treatment changes in chemical and physical: The operation process, timeliness and treatment plan of the processing line of the vacuum plasma surface cleaning machine, the high-energy plasma is generated by the radio frequency power supply under a certain pressure, and then the surface of the processed surface object is bombarded by the plasma to produce a microscopic surface peeling effect. In the vacuum chamber, a high-energy plasma is generated by the radio frequency power supply under a certain pressure, and then the surface of the machined object is bombarded by the plasma to produce a microscopic surface peeling effect (the peeling depth can be adjusted by adjusting the plasma bombardment time. , The role of plasma is nano-scale, so it will not damage the processing object) to achieve the purpose of operation. Vacuum plasma surface cleaning machine reactive plasma means that the active particles in the plasma can chemically react with the surface of the refractory material, thereby introducing a large number of polar groups, making the surface of the material change from non-polar to polar, and increasing the surface tension , the bondability is enhanced. Reactive plasma active gases are mainly O2, H2, NH3, CO2, H20, S02, HVH20, air, glycerol vapor and ethanol vapor. Under the action of the plasma, some active atoms, free radicals and unsaturated bonds appear on the surface of the refractory plastic. These active groups will react with the active particles in the plasma to generate new active groups. However, materials with active groups will be affected by the action of oxygen or the movement of molecular segments, causing the surface active groups to disappear. Before the circuit board (FPC/PCB) is shipped, the surface will be cleaned with a vacuum plasma surface cleaning machine plasma. Under normal circumstances, downstream customers of circuit boards will conduct incoming inspections of products, such as Wire Bonding Test, Wire Pull Test, etc. When the surface is not cleaned, there are often some contaminations that lead to testing. Fail. In order to avoid the above problems, surface plasma cleaning before shipment has become a trend in this era of increasing pursuit of quality. Because the plasma treatment of vacuum plasma surface cleaning machine is manifested in chemical changes and physical changes. In the physical change, the surface of the material is modified and roughened, and the number of protrusions on the surface after etching increases, increasing the surface area. If exposed to polluted air, mixed with dust, oil, impurities, the surface energy will gradually decrease. During chemical changes, oxygen-containing polar groups, such as hydroxyl and carboxyl groups, are introduced during plasma treatment. These active molecules are time-sensitive and are prone to chemical changes with other substances. The surface energy retention time after treatment is not easy to determine. Different gases, power, processing time, and placement environment will have an impact on the surface aging of the material. The proven aging of FPC products after cleaning is: 1 week (confirmed with contact angle measurement data, the smaller the contact angle value, the higher the dyne value).

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Research on the application of low temperature plasma radical chemical reaction in polysilicon industry

Research on the application of low temperature plasma radical chemical reaction in polysilicon industry

Research on the application of low temperature plasma radical chemical reaction in polysilicon industry: A chemical reaction is a recombination at the level of atoms or groups of atoms, which requires the necessary activation energy for the reaction from the outside world. Compared with plasma, the reactants produced in industry are mostly in a dense condensed state. Most of the participating gases are dense layers of "high concentration", which makes it difficult to continuously transfer large excitation energy to the reaction system, and some chemical reactions that require extremely large activation energy are difficult to achieve under conventional technical conditions. There is a close connection between chemistry and physics. Microscopic forms such as electron movement, interatomic interaction force, and excitation and ionization of atoms and molecules in molecules determine the physicochemical properties and chemical reaction capabilities of substances. Therefore, applying physical methods to change the state of matter can lead to chemical changes or affect the progress of chemical reactions. For this reason, the electric field directly transfers energy to the gas molecules in the reaction chamber, generating electrons with sufficient energy to inelastically collide with the gas molecules, transferring almost all the energy of the electrons to the gas molecules participating in the reaction, so that a large number of photons are generated in the gas in the reaction chamber. , electrons, ions, free radicals and active atoms excited state atoms and active molecules provide extremely active active particles for their chemical reactions, thereby making many chemical reaction conditions milder and improving chemical reaction efficiency. In nature, substances exist in solid state, liquid state and gaseous state. Among them, solid particles are closely bound together, followed by liquid state, and gaseous state is dispersed. To achieve the transformation of substances from a dense to a dispersed aggregate state, it is necessary to provide additional energy to destroy the larger binding energy between the original particles. In the same way, when the substance is in a gaseous state, it continues to provide energy to form the ionization of the gaseous substance particles to form a plasma. The difference between a low temperature plasma and a high temperature plasma is the temperature of the ions and the ion channel. The electron motion temperature of low temperature plasma is as high as 10~10K, while the ion and neutral ion temperature of gas is close to the ambient temperature, which is much lower than the electron motion temperature. Therefore, low temperature plasma is also called non-equilibrium plasma. Low temperature plasma can be generated under normal temperature and pressure, and its industrial application prospect is broad. The test data shows that the power parameters have a great influence on the primary conversion rate of STC. The lower the power frequency and the higher the voltage within a certain range, the more conducive to the chlorosilane hydrogenation reaction. The low-temperature plasma generator generated by the power frequency through the DBD discharge method is safe, reliable, economical, environmentally friendly and easy to implement. For the promotion effect in the hydrogenation of silicon tetrachloride, the primary conversion efficiency of STC of more than 5% can be achieved by using plasma assistance under normal temperature and pressure conditions. Plasma contains a large number of photons, electrons, ions, free radicals, and active atomic excited state atomic excited state molecules and active molecules, etc., which provide extremely active active particles for chemical reactions, so that many usually cannot occur or require extremely harsh conditions to occur. The chemical reaction becomes easy to carry out at close to room temperature, which provides a new realization method for chemical reaction. For the polysilicon chemical industry, considering hydrogenation, vapor deposition and other processes in terms of energy consumption control and efficiency improvement, the use of plasma to promote the reaction process has great practical value and scientific research value.

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Research on the modification of vanadium catalyst carrier diatomite performance index modified by plasma technology

Research on the modification of vanadium catalyst carrier diatomite performance index modified by plasma technology

Research on the modification of vanadium catalyst carrier diatomite performance index modified by plasma technology: The vanadium catalyst used in the production of sulfuric acid is a catalyst with vanadium oxide as active component, alkali metal oxide as co-catalyst and diatomaceous earth as carrier. The diatom shell in diatomite has a special microporous structure and a shell wall composed of amorphous silica. These small pores distributed on the shell wall can provide good conditions for uniform adsorption or coating of catalyst active components In addition, diatomite itself has good permeability, so that the fluid can pass through at a larger flow rate, so diatomite becomes an important carrier for vanadium catalysts. The reserves of diatomite in my country are very rich, but there are not many high-quality diatomite that can be used as vanadium catalyst carrier. In recent years, due to the protective mining measures adopted by the government, fewer and fewer high-quality diatomite mines are allowed to be mined. Many catalyst factories have begun to use imported diatomite to improve the quality of vanadium catalysts, but imported diatomite has gradually formed a monopoly in China. , the price is expensive, and the domestic catalyst factory is unbearable. How to improve the quality of domestic diatomite and make it meet or exceed the quality of imported diatomite has always been the direction of domestic catalyst factories. The pore size distribution of the carrier has an important relationship with the performance of the vanadium catalyst. In general, the important characteristics of good quality vanadium catalysts are large pore volume and reasonable pore size distribution. It is required that the number of pores with a pore size between 100 and 1000 nm accounts for more than 50% to ensure that there are enough internal diffusion channels for gas molecules in the catalytic reaction. Under the reaction conditions, the pores below 100 nm basically do not exist, and mainly become the storage unit of active substances, while the macropores with a pore size above 100 nm are not only unobstructed, but also provide an active surface. Domestic diatomite has a relatively large proportion of micropores with a pore diameter of less than 1 nm, and a relatively small proportion of mesopores with a pore diameter of 1 to 1000 nm and large pores above 1000 nm, resulting in a small pore volume and high bulk density of the vanadium catalyst, which is not conducive to the reaction. Diffusion of gases. Changing the pore size distribution of diatomite, increasing the pore volume and reducing the bulk density are important ways to improve diatomite in China. The diatomite is modified by plasma technology, the diatomite is treated by the active substance of the plasma, and the surface and internal impurities of the pore channel are cleaned by physical and chemical effects, so as to increase the pore size of the diatomite. Plasma bombardment of diatomite can make diatomite generate local high temperature, and the organic impurities in the pores are removed by high temperature pyrolysis, thus leaving more effective space, which is manifested as the increase of BJH adsorption pore volume. This also shows that plasma technology can be used as an effective method for diatomite modification. The increased pore volume of diatomite can make the reaction gas pass more smoothly and the catalytic efficiency is higher. Modified by plasma technology, a considerable number of micropores in diatomite may be converted into mesopores. The treatment has both physical effect (non-elastic collision effect) and chemical effect (active substance reacts with functional groups on the surface of diatomite), so as to achieve the effect of cleaning the surface of the pores and the internal organic impurities and some inorganic impurities.

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Preliminary discussion on the co-action mechanism of plasma and catalyst

Preliminary discussion on the co-action mechanism of plasma and catalyst

Preliminary discussion on the co-action mechanism of plasma and catalyst: The research results of the reaction of CO2 oxidation of CH4 to C2 hydrocarbons under the action of plasma plasma and various catalysts show that the co-action mechanism of plasma plasma and catalyst is different from that of pure plasma or ordinary catalytic activation. The oxidation of CO2 under the action of pure plasma plasma The CH4 conversion reaction is a free radical process, and the selectivity of the target product is low; the catalyst does not show catalytic activity below 80 °C. When a catalyst is introduced into the plasma, the catalyst adsorbs reactants through adsorption, and free radicals participate in the surface reaction, which affects the conversion rate of reactants and the yield of products; plasma plasma is introduced into the catalytic process, and the plasma provides the necessary energy for catalyst activation. , and will also have direct and indirect effects on reactant adsorption, surface reactions, and product desorption processes. According to the experimental results, the co-action of the plasma and the catalyst is manifested in the following aspects. (1) The plasma plasma continuously activates the catalyst. There are a large number of high-energy particles in the plasma, and these high-energy particles mainly transfer energy to the catalyst through collision and activate the catalyst. Therefore, even at lower experimental temperatures (below 100 °C), the catalysts studied in the experiments still show high catalytic activity. (2) The catalyst has a certain influence on the plasma discharge state. Different catalyst types have different influences. Marafee et al. studied the effect of metal oxide catalysts with OH groups on the oxidative coupling reaction of methane in corona discharge plasma, and the results showed that the catalysts with OH groups could enhance the gas discharge effect and lead to methane conversion and C2 hydrocarbon yield increased significantly. The research shows that the basicity of the catalyst is beneficial to the formation of C2 hydrocarbons. (3) The catalyst has an activating effect on the reactants. The catalyst activates the reactant by adsorption, and promotes the conversion of the reactant. The study on the activation and conversion mechanism of methane under catalysis shows that the C-H bond of methane adsorbed on the active center of the catalyst is activated due to the filling of electrons by the anti-bond σ* orbital electrons, and the C-H bond energy is reduced. In the joint action of the plasma and the catalyst, the catalyst activated by the plasma may activate the CH bond and CO bond of the reactant in the same way, and the high-energy electrons with lower energy in the plasma interact with the activated reactant to promote the conversion of the reactant. . It is worth pointing out that under the same plasma plasma injection power, the conversion rate of reactants under the joint action of some catalysts and plasma is lower than that of pure plasma experiments under the same conditions, which may be due to the fact that catalyst activation consumes more energy. (4) Another function of the catalyst may be to selectively adsorb the active species, promote the reaction of the active species, remove the excess energy of the new material to prevent its decomposition, improve the product yield, and reduce the formation of carbon deposition. Therefore, the joint action of plasma and catalyst is a potential enhanced reaction process and a brand-new research direction. Once a breakthrough is made, it is bound to promote the development of the emerging interdisciplinary field of plasma. Thank you for your attention and support to Chengfeng Zhizao atmospheric plasma cleaning machine. The company is committed to providing users with comprehensive surface performance treatment and testing solutions, and independently develops, produces and sells plasma surface treatment equipment. Dedicated to the research of surface properties for many years, adhere to the tenet of continuous innovation, and professional quality service, it has won the unanimous recognition of users at home and abroad.

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