Recently, the team of Xiao Jianping, a researcher of the Research Group of Theoretical Catalytic Innovation Special State of the State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, teamed up with Professor Xiao Fengshou of Zhejiang University and Wang Liang, a team of researchers, to make new progress in the study of one-step synthesis of ethanol from syngas .
Ethanol is an important chemical and fuel. Efficient and highly selective direct production of ethanol via synthesis gas is currently a hotspot in the field of energy research. If the catalyst is too reactive or too weak, the selectivity of by-products will be too high, so it is also difficult to directly produce ethanol from syngas. A thorough understanding of the reaction mechanism of synthesis gas conversion is of great significance for the subsequent improvement of catalyst activity and the search for non-noble metal catalysts. There are dozens of intermediates and transition states and thousands of reaction paths in the synthesis gas conversion process, and the traditional theoretical methods cannot well understand this process. Based on this, the team of Xiao Jianping has developed a new method of reaction path research and product selectivity analysis, which can simplify the adsorption energy of dozens of intermediates and transition states to two dimensions-the adsorption energy of CO and OH, and to This is to describe the selectivity of different catalysts to products (such as the two-dimensional reaction phase diagram above), and to understand and guide the design of the catalyst. This method can also integrate thermodynamic and kinetic effects to automatically search for the optimal reaction path for ethanol production.
In the synthesis gas conversion process, if the CO molecule and the catalyst (such as pure Rh, Co catalyst, etc.) are too strongly combined, the carbon-oxygen bond is basically broken, and then methane is selectively obtained; if the CO and the catalyst (such as the Cu catalyst) are combined Too weak, the carbon-oxygen bond cannot be broken at all, so only methanol can be obtained. Only when there is a very small energy window between CO and catalyst, the intermediate (CHx *) after CO dissociation and undissociated CO * / CHO * can coexist to have better ethanol selectivity. Theoretical calculations show that the coupling of CH2 * and CO / CHO * intermediates is the most critical step. The MnOx structure and the restricted environment provided by the molecular sieve affect the electronic structure of the Rh atom at the interface (near MnOx), making RhMn @ S The -1 catalyst happens to fall in this range, and ultimately allows CH2 * and CO * / CHO * intermediate substances to coexist in large quantities, resulting in higher ethanol selectivity. This work provides new ideas for the design of catalysts for the preparation of ethanol with highly selective synthesis gas.
Related results were published in Chem. This work was supported by the National Major R & D Program, the National Natural Science Foundation of China, the key deployment project of the Chinese Academy of Sciences, and the "Xingliao Talent Program" in Liaoning Province.
PEEK Plastics,Polyether ether ketone, known in English as polyetheretherketone plastic (PEEK Plastics), is a linear aromatic polymer containing chain sections in the main chain of molecules.Its constituent units are oxygen-pairs of phenyl-oxycarbonyl - pairs of phenyl, semi-crystalline, thermoplastics.
Product name: polyether ether ketone (PEEK Plastics) resin is a kind of excellent special engineering plastics, PEEK Plastics has more significant advantages compared with other special engineering plastics, resistance to high temperature is 260 degrees, mechanical performance, good self-lubrication, resistance to chemical corrosion, flame retardant, stripping resistance, abrasion resistance, no strong sulfuric acid, nitric acid resistance, radiation resistance, strong mechanical properties can be used for high-end technology such as mechanical, nuclear engineering and aviation.
PEEK Plastics has heat resistance, chemical stability and the forming process of thermoplastic plastic. PEEK Plastics has excellent heat resistance.Its thermal deformation temperature of 160 ℃, with 20% ~ 30% Glass Fiber reinforced, heat distortion temperature can be increased to 280 ~ 300 ℃.Polyether ether ketone is good, the thermal stability of 420 ℃ in air.2 h under weightlessness is only 2%, at 500 ℃ was 2.5%, significantly thermo-gravimetric 500 ℃.Polyether ether ketone of long-term use of temperature is about 200 ℃, under this temperature, still can keep the high tensile strength and bending modulus, PEEK Plastics is also a kind of very strong material, has excellent resistance to creep and fatigue performance for a long time.
PEEK Plastics electrical insulating performance is very excellent, volume resistivity of about 10 ~ 10 Ω · cm.It still has small dielectric constant and dielectric loss in high frequency range.For example, in 10Hz, the dielectric constant in the room is only 3.2 and the dielectric loss is only 0.02.
The chemical stability of polyether ether ketone is also very good. In addition to concentrated sulfuric acid, almost any chemical reagent is very stable, even at high temperature, PEEK Plastics can maintain good chemical stability.In addition, PEEK Plastics has excellent heat resistance and steam resistance.In 200 ~ 250 ℃ steam can be used for a long time.
PEEK Plastics with good flame retardancy, in normal circumstances it is difficult to burn, even burning, smoke and harmful gas release a quantity to also is very low, even lower than low smoke volume of polymer such as ptfe.In addition, PEEK Plastics has excellent radiation resistance.Its resistance to alpha rays, beta gamma rays and gamma rays is the best current polymer material.The wire products covered with it can withstand gamma rays of 1.1 x 10Gy.
The polyether ether ketone has good fluidity and thermal stability at the melting point.Therefore, PEEK Plastics has the typical processing performance of thermoplastic plastic. Therefore, it can be used for injection molding, extrusion, blow molding and laminating, and also spinning and making films.Although the polyether ether ketone melt processing temperature range is 360 ~ 360 ℃, but because of its thermal decomposition temperature above 520 ℃, and it still has the very wide processing temperature range.
Although the development history of PEEK Plastics is only a short 20 years, but because PEEK Plastics has the outstanding heat resistance, chemical corrosion resistance, radiation resistance and high strength, easy to machining, PEEK Plastics is currently in the nuclear industry, chemical industry, electronic appliances, machinery, instrument, automobile industry, and has been widely used in aerospace field.In particular, thermoplastic resin, which is excellent in heat resistance, can be used as the base material of high performance composite materials.
modified
PEEK Plastics performance of the pure material is difficult to meet the different needs of different industries, in special working environment need to modification of PEEK Plastics, its main means blending modification, copolymerization modification, reinforced composite, infill modification, nanometer modification and surface modification technology.The modification can increase the performance of PEEK Plastics, such as wear resistance, impact strength, etc., thereby extending the application range of PEEK Plastics, reducing the cost of materials and improving the processing performance of PEEK Plastics.
Application
PEEK Plastics has been widely used in aerospace, automotive manufacturing, electronics, medical and food processing.
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