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Introduction
1. Ionic liquid
1.2 Properties of ionic liquids
1.3 Ionic liquids in science
2. Fine organic synthesis
2.1 Characteristics of TOC
Conclusion
Introduction
Despite the existence of a wide range of known catalysts, chemical engineering and organic synthesis are constantly in need of new, more efficient and environmentally acceptable catalysts, reaction media and solvents. When developing and improving industrial processes for basic and fine organic synthesis, as well as in petrochemistry, new approaches are needed to solve existing economic and environmental problems associated with high energy costs and environmental pollution. A modern approach to solving the problem of replacing volatile organic compounds used as solvents in organic synthesis involves the use of ionic liquids. The use of ionic liquids as new reaction media can solve the problem of solvent emission and the reuse of expensive catalysts.
Fine organic synthesis (TOS) is a huge number of chemical compounds: drugs, dyes, chemical additives, pesticides, surfactants, special polymeric materials, synthetic enzymes, etc. In addition, as a rule, obtaining each product of fine organic synthesis is a complex multi-stage process. It is the subtle transformations in most technological processes, a large number of transitions in the advancement to the target substance that characterize the specifics of this sub-branch of organic chemistry, and not the scale of production.
1. Ionic liquid
1.1 Characterization of ionic liquids
The term "ionic liquids" means substances that are liquids at temperatures below 100 ° C and consist of organic cations, for example, 1,3-dialkylimidazolium, N-alkylpyridinium, tetrakylammonium, tetraalkylphosphonium, trialkylsulfonium and various anions: Cl-, [BF4]-, [PF6]-, [SbF6]-, CF3SO3-, [(CF3SO2) 2N]-, ROSO3-, RSO3-, ArSO3-, CF3CO2-, CH3CO2-, NO3-, [A12C17]-.
The nature of the anion has a great influence on the properties of ionic liquids - melting point, thermal and electrochemical stability and viscosity. The polarity as well as the hydrophilicity or hydrophobicity of ionic liquids can be optimized by appropriate selection of the cation/anion pair, and each new anion and cation provides further possibilities for varying the properties of ionic liquids.
1.2 Properties of ionic liquids
Increased attention to ionic liquids is due to the presence of the following specific properties:
1. Wide range of liquid state (> 300 °C) and low melting points (Tm< 100 °С).
2. High electrical conductivity.
3. Good dissolving power with respect to a variety of inorganic, organometallic and organic compounds and polymers of natural and synthetic origin.
4. Catalytic activity, causing an increase in the selectivity of organic reactions and the yield of the target product.
5. Non-volatile, reusable.
6. Non-combustibility, non-explosion hazard, non-toxicity and the resulting absence of harmful effects on the environment.
7. Limitless possibilities in the directed synthesis of ionic liquids with desired properties.
Qualities 3 and 4 make ionic solvents particularly attractive in polymer synthesis.
1.3 Ionic liquids in science
Ionic liquids are unique objects for chemical research, their use in catalysis, organic synthesis, and other areas, including biochemical processes. The number of ionic liquids described in the literature is currently very large (about 300). Potentially, the number of ionic liquids is practically unlimited and is limited only by the availability of suitable organic molecules (cationic particles) and inorganic, organic and metal complex anions. According to various estimates, the number of possible combinations of cations and anions in such ionic liquids can reach 1018. Figure 1 shows some of the most studied ionic liquids described in the literature.
1.4 Methods for obtaining ionic liquids
The cooking methods are quite simple and can be easily scaled up. There are three main synthesis methods that are most commonly used:
The exchange reaction between a silver salt containing the required B- anion and a halogen derivative with the required cation
A+: Ag+B- + A+Hal- > A+B- + AgHal (1)
Quaternization reaction of an N-alkyl halide derivative with metal halides:
N+ - АlkНal- + MНaln > N+ - АlkМНа1- n+1 (2)
Ion exchange reactions on ion exchange resins or clays.
Rice. 1 - Ionic liquids
(Ri \u003d H, alkyl, aryl, hetaryl, allyl, etc., including functional groups, x \u003d 1-4, m \u003d 2, 3. X- \u003d [BF4] -, [РF6] -, -, -, -, 2-, [AlkSO3] -, [СlO4] -, [СF3SO3] -, [CH3COO] -, [СuСl2] -, [Сu2 Cl3]-, [Cu3Cl4]-, [A1C14]-, [AlBr4]-, [AlI4]-, [AlCl3Et]-, [Al2C17]-, [A13Cl10]-, (CF3S02)2N-, -, -, [Me(CO)n]- etc.)
Another practically important direction in the synthesis of ionic liquids is their preparation directly in the reactor. In this case, the corresponding N-alkyl halide and the metal halide are mixed in the reactor and an ionic liquid is formed just before starting the chemical process or catalytic reaction. Most often, ionic liquids are prepared on the basis of a mixture of aluminum chloride with organic chlorides. When two solids are mixed, an exothermic reaction occurs and eutectic mixtures are formed with melting points down to -90 °C. It is, as a rule, a transparent colorless or yellow-brown liquid (the color is due to the presence of impurities and local overheating of the reaction mass during the preparation of the ionic liquid). Ionic liquids, due to the diversity and peculiarities of their properties, have proved to be very attractive for catalysis and organic synthesis.
As for the “environmental friendliness” of ionic liquids, much should and will be reassessed in subsequent studies, although, in general, the fact that they are recyclable, non-flammable, and have a low vapor pressure makes them full participants in “green” chemistry, even without taking into account those gains in productivity and selectivity, examples of which were given in the review. Obviously, due to their high cost, ionic liquids are unlikely to find wide application in large-scale processes, unless additional advantages of heterogenized systems are found. At the same time, low-tonnage chemistry, primarily metal complex catalysis, may turn out to be a fertile area for their use, as well as electrochemistry in general and electrocatalysis in particular.
2. Fine organic synthesis
2.1 Characteristics of TOC
Fine organic synthesis (TOS) is an industrial low-tonnage production of complex organic substances.
The main sources of raw materials are products of basic organic synthesis. Fine organic synthesis is characterized by a multistage nature, difficulties in large-scale transition and relatively high specific energy and labor costs, often due to low product removal per unit volume of reactors, a significant amount of waste, the complexity of solving environmental issues, etc. The efficiency of fine organic synthesis processes is increased mainly through the use of flexible block-modular schemes, automatic control systems, the use of biotechnology methods (for obtaining intermediate products and waste conversion), laser chemistry, etc.
The main products of fine organic synthesis are dyes, drugs, pesticides, textile auxiliaries and fragrances, chemical additives for polymeric materials, chemicals for film and photographic materials, chemical reagents, etc.
2.2 History of progress in organic synthesis
Progress in the organic synthesis industry is largely dependent on the development of new reactions. Often a fundamentally new reaction creates a new era in organic chemistry. For example, in 1928, a diene synthesis reaction was discovered (O. Diels and K. Alder), consisting in the addition of substances containing a double or triple bond (dienophiles) in the 1,4-position to conjugated diene systems with the formation of six-membered rings:
Figure 1 - Scheme of the reaction of diene synthesis
This reaction has become the basis for the production of many new synthetic substances from a wide variety of cyclic compounds to complex polycyclic systems, such as steroid and further heterocyclic systems.
The Wittig reaction became the basis of a new method for the synthesis of olefins, with the help of which a large number of complex analogs of natural compounds were obtained, Figure 2.
Figure 2 - Scheme of the Wittig reaction
2.3 Enzyme immobilization method
The development of the synthesis of olefins was promoted by the development of reagents immobilized on polymeric carriers. In this case, the second reagent is in solution. The reaction proceeds in such a way that the product remains on the polymer and is easily separated by filtration and washing from the excess of the second reactant and by-products. The final product is then cleaved from the polymer matrix and purified. This makes it possible to carry out multi-stage and labor-intensive syntheses without complex purification at intermediate stages. This method is especially successfully used for the synthesis of peptides and proteins.
A very effective method is the immobilization of enzymes on an insoluble carrier. The enzyme is isolated from a natural source, purified, fixed on an inorganic or polymeric carrier by covalent bonding or by adsorption. A solution of a substance is passed through a column filled with such an immobilized enzyme. At the outlet of the column, the product is separated by conventional methods. Thus, it is possible to carry out multi-stage processes by passing the solution sequentially through several columns with different enzymes.
2.4 Interfacial catalyst method
A new stage in the development of fine organic synthesis was the use of the so-called interfacial catalysis, when special substances are added to the reaction mixture - catalysts for interfacial transfer (ammonium, phosphonium salts, crown ethers). These substances facilitate the transfer of, for example, anions from the aqueous or solid phase to the organic phase, where they react.
The number of reactions for which interfacial catalysts are effective is very large and includes almost all reactions involving carbanions (Claisen, Michael, Wittig, Horner reactions, and others, C-alkylations, additions, etc.). It is promising to use interfacial catalysis in oxidation reactions, when the organic substance is insoluble in water, and the oxidizing agent is in the organic solvent. For example, potassium manganate, insoluble in benzene, upon addition of small amounts of crown ether, gives the so-called raspberry benzene, which contains the MnO4- ion, which serves as a strong oxidizing agent. In modern methods of organic synthesis, the planning of complex multistage processes is now successfully used. As a rule, the transition from initial to target products of complex composition and structure can be carried out in different ways, among which there are more or less rational ones. As the synthesized compounds become more complex, certain methodological principles for choosing the most efficient scheme are formed.
Conclusion
ionic liquid organic synthesis
At the moment, the study of ionic liquids and their properties is a very promising and very important branch in world science. Particularly interesting is the area of interaction of ionic liquids with various substances, with the further production of new substances.
Ionic liquids play a very important role in the simplification of fine organic synthesis technologies. Since TOC is a labor-intensive process, the scientific community is interested in the invention of new catalysts, such as ionic liquids.
List of sources used
1. Yagfarova, A.F., Methodological manual on ionic liquids / A.R. Gabdrakhmanova, L.R. Minibaeva, I.N. Musin. - Bulletin: KTU, 2012, 192-196.
2. Gabdrakhmanova, A.R., Methodological manual on ionic liquids / A.F. Yagfarova, L.R. Minibaeva, A.V. Klinov. - Bulletin: KTU, 2012, 63-66.
3. Bykov, GV History of organic chemistry. - M., 1976. 360 s
4. Reichsfeld, V.O., Erkova L.N., Equipment for the production of basic organic synthesis and synthetic rubbers / Reichsfeld V.O., Erkova L.N. - M. - Spt., 1965.
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The miscibility of ionic liquids with various solvents is presented in Table 1.4.
Table 1.4. Miscibility of IL with various solvents. No. Solvent e I
A1C13 - base - AICI3 - acid 1 Water 80.1 Immiscible Reacting Reacting 2 Propylene carbonate 64.4 Miscible Miscible Miscible 3 Methanol 33.0 Miscible Reacting Reacting 4 Acetonitrile 26.6 Miscible Miscible Miscible 5 Acetone 20.7 Miscible Miscible Reacting 6 Methylene chloride 8.93 C Miscible Miscible Miscible 7 THF 7.58 Miscible Miscible Reacting 8 Trichlorethylene 3.39 Immiscible Not
miscible Not
miscible 9 Carbon disulfide 2.64 Not miscible Not
miscible Not
miscible 10 Toluene 2.38 Immiscible Miscible Reacts 11 Hexane 1.90 Immiscible Not
miscible Not
mixed up
Ionic liquid (+PF) Typically, processes in ionic liquids are compared with those in typical organic solvents. From this point of view, with respect to compounds that exhibit weak basic properties, the basic IL will behave like DMF. On the other hand, acid-type ILs behave like trifluoroacetic acid in acidity. At room temperature, ionic liquids are excellent solvents and, at the same time, are able to play the role of catalysts for a number of reactions, such as Friedel-Craft reactions sa, Diels-Alder, isomerization and reduction reactions.
[EM1sh]C1-A1C13 and other haloaluminate ionic liquids have Lewis acidity, which can be controlled by changing the molar ratio of the two components A1C13A1C13. All this makes ionic liquids interesting as non-aqueous reaction media. The Lewis acidity of these systems is determined by the activity of chloride. Equilibrium in a chloraluminate liquid at room temperature can be described by two equations:
AICI4" + AICI3 AI2C17*
The first describes the process in basic melts, when the molar ratio A1C13AmC1 is less than one, and the second - in acidic ones, where the ratio is greater than one. This means that more anions C G, AICI4", AI2CI7" are formed, and their relative amounts are determined by the equilibrium: 2A1SC" *
ACL" + SG Heptachloroaluminate ion is a strong Lewis acid, due to the chlorine ion in the conjugate Lewis base. A neutral ionic liquid is a liquid where the molar ratio of A1C13LmC1 is equal to unity and only the AICI4 * ion is present. At present, it has become possible to neutralize buffer acidic ILs with solid metal alkyl chlorides.
The complete solubility of ionic liquids in solvents makes them convenient for spectrophotometric measurements, especially in the visible and UV regions. They can be used together with organic solvents; in this case, as a result of solvation, IL ions are dispersed and, as a result, some physicochemical properties change: a decrease in viscosity and an increase in the conductivity of the solution. When comparing the IR spectra of acidic and basic ionic liquids, a slight distortion of the aromatic ring is found, which is less stressed in contrast to the salt, which has a smaller cation. This means that the hydrogen bond between the hydrogen atom on the second carbon atom of the ring and the chloride ion is either very weak or non-existent. In basic type ILs, the hydrogen bond tension is still significant. One of the advantages of ILs is their thermal stability over a wide temperature range, which makes it possible to successfully control the reactions occurring in these liquids. Thus, +PF6" begins to decompose at a temperature of ~620 K, and with a noticeable rate at 670 K. Decomposition of IL proceeds according to the same mechanism both in air and in a nitrogen atmosphere. It was found that when heated in air, IL oxidation does not occur.
Ionic liquids are convenient to use and inexpensive to produce. They are good solvents, and the possibility of creating catalytic systems on their basis makes them preferable for carrying out catalytic reactions. By selecting ionic liquids, it is possible to achieve the separation of reaction products into another phase.
The behavior of ILs under the action of ionizing radiation has practically not been studied. A preliminary assessment of the radiation stability of one of the most well-known ILs based on 1,3 dialkylimidazole cation (+PF6") shows that it is relatively resistant to ionizing radiation (similar to benzene) and more stable than a system based on a mixture of tributyl phosphate and kerosene. It was shown that under the studied conditions, ionic liquids under the action of ionizing radiation in detectable amounts do not decompose into their constituent organic components.
More on the topic 1.5.2. Properties of ionic liquids:
- 3.5. Study of the radiation-chemical process of polymerization of elemental phosphorus in organic solvents in the presence of ionic liquids 3.5.1. Dielectric Properties of Initial Solutions
A. S. Solodov, M. S. Solodov, S. G. Koshel
Supervisor - S. G. Koshel, Dr. of Chem. sciences, professor
Yaroslavl State Technical University
Ionic liquids belong to the so-called "green solvents", which correspond to the principles of green chemistry. Ionic liquids are low-temperature molten salts that have a number of properties, such as: non-volatility, chemical stability, environmental safety, high ionic conductivity, good dissolving power, electrochemical "window" width.
Ionic liquids are used as a component of electrolytes for various electrochemical devices of a new type (in lithium batteries, capacitors, solar batteries). It is possible to use ionic liquids as active components of membranes. Membranes are the main components of fuel cells that can operate in harsh environments.
A significant advantage of using ionic liquids in electrochemical processes in comparison with traditional electrolytes has been established. The use of ionic liquids as non-aqueous polymer solutions for electrochemical and electrocatalytic reactions is promising: electrooxidation, electroreduction. Many organic substrates are more soluble in ionic liquids than in water. The precipitation of metal from ionic liquids containing the same metal in the composition of the cation occurs quite easily.
The main advantage of using ionic liquids - electrolytes in electroplating industries is that they are not aqueous solutions, that is, there is no hydrogen release during electrodeposition of coatings. Thus, it is essentially possible to obtain crack-free and more corrosion-resistant coatings.
From the point of view of research, ionic liquids based on choline chloride eutectics are of interest. Ionic liquids based on eutectic - teak choline chloride can be easily operated in ambient conditions. We have obtained and studied the following eutectic mixtures of choline chloride with ethylene glycol, with urea, with oxalic acid and with chromium chloride. The temperature dependence of the electrical conductivity of these eutectics has been established.
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Scientific adviser - A. A. Kiselev, Ph.D. ped. Sci., Professor Yaroslavl State Technical University The development of market relations requires the implementation of a new financial policy, the growth of production efficiency at each specific chemical enterprise ...
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PETROCHEMISTRY, 2007, Volume 47, No. 5, p. 339-348
UDC 541.48-143:542.97
F. A. Nasirov, F. M. Novruzova, A. M. Aslanbeyli, and A. G. Azizov
Institute of Petrochemical Processes, National Academy of Sciences of Azerbaijan, Baku E-mail: [email protected] Received February 6, 2007
Data on the processes of catalytic conversion of olefins and dienes using ionic liquids (ILs) as solvents are summarized. The role of these compounds in solving environmental problems from the point of view of green chemistry is discussed. Some industrial processes involving ionic liquids are considered.
The general definition of "green chemistry" is the design and development of chemical products and processes that reduce or eliminate the use and production of hazardous substances. Any substance and the method of obtaining it through chemical transformations can be considered in connection with their possible impact on the environment. The task of "green chemistry" is reduced to the development of chemical processes, on the one hand, economically acceptable, on the other - minimally polluting nature. When developing such "clean" industrial processes, one should be guided by the 12 principles of "green chemistry" given in the works.
The use of environmentally friendly solvents or the conduct of processes without solvents at all is one of the most important areas of "green chemistry". Typical organic solvents are often sufficiently volatile compounds that, in addition to being hazardous air pollution, they tend to be highly flammable, toxic, or carcinogenic. The use of ILs instead of them is of great scientific and practical interest in the development of new "green chemistry" processes.
Advances in the application of ILs in catalysis are described in detail in numerous books and review articles, including .
Significant progress has been made using ILs in such processes of the catalytic conversion of olefins and dienes as dimerization, oligomerization, alkylation, and metathesis. The potential of ILs as new media for the mentioned reactions of homogeneous catalysis was fully appreciated thanks to the pioneering work and in-depth studies of a whole group of chemists.
CONCEPT OF IONIC LIQUIDS
Ionic liquids, as a new class of alternative solvents, are attracting much attention due to their low vapor pressure, lack of toxicity, and the possibility of interaction with organometallic compounds, which opens up wide prospects for their use in catalysis. In principle, a huge variety of ILs is achieved by varying the combination of cation and anion, which, in turn, can be chosen for each specific reaction. At the same time, the toxicity and cost issues of this new class of solvents must be evaluated on a case-by-case basis.
ILs, consisting of a large nitrogen-containing organic cation and a much smaller inorganic anion, are compounds with Gm usually below 100-150°C.
Numerous cation–anion associations capable of forming room temperature ILs (RBIs) have been mentioned in the literature. This circumstance distinguishes them from classical molten salts (e.g., NaCl with Mm = 801°C, Na3AlF3 with Mm = 1010°C, tetrabutylphosphonium chloride with Mm = 80°C, LiCl:KCl = 6:4 mixtures with Mm = 352°C, etc.). IZHKT - liquids Ch. arr. with large asymmetric cations in the molecule preventing close packing of anions. ILs contain ammonium, sulfonium, phosphonium, lithium, imidazolium, pyridinium, pi-colinium, pyrrolidinium, thiazolium, triazolium, oxazolium and pyrazolium cations with various substituents.
Of particular interest are liquid salts based on ^^ dialkylimidazolium cation, from -
characterized by a wide range of physicochemical properties, which are usually obtained by anion exchange from imidazole halides.
IL anions are divided into two types. The first is composed of polynuclear anions (for example,
A12 C1-, A13 C1 10, Au2C17, Fe2C17 and 8b2B-!), formed by the interaction of the corresponding Lewis acid with a mononuclear anion (for example,
A1C1-) and are especially sensitive to air and water. The second type is mononuclear anions that are part of neutral stoichiometric ILs,
e.g., VB4, RB6, 2pS133, SiS12, 8pS1-,
N#802)-, N(#802)-, C(SBz802)3, SBzS02,
SB3803, CH380- etc.
By changing the alkyl groups of the starting compound (imidazole, pyridinium, phosphonium, etc.), as well as the type of associated anions, the synthesis of a huge variety of ILs with different physicochemical properties is theoretically possible. The authors of the work suggest the existence of up to one trillion (1018) possible cation/anion combinations in ILs.
The most commonly used are chloraluminate, tetrafluoroborate, or hexafluorophosphate ILs based on N-alkylpyridinum or 1,3-dialkylimidazolium. Organochloraluminate ILs obtained from N-alkylpyridinium or 1,3-dialkylimidazolium chlorides and aluminum trichloride have a wide liquid phase limit up to 88°C.
The physical and chemical properties of ILs (density, electrical conductivity, viscosity, Lewis acidity, hydrophobicity, ability to form hydrogen bonds) can be controlled by changing the type and ratio of cationic and anionic components. In this case, it becomes possible to create ILs with desired properties suitable for use in catalysis.
ILs are called "green solvents" - due to their low vapor pressure, they are not volatile and therefore do not ignite; moreover, they are immiscible with a number of common organic solvents, which provides a real alternative for creating two-phase systems. This property makes it easier to separate the products from the reaction mixture, as well as to regenerate the catalyst and return it to the system together with the IL. Two-phase liquid-liquid catalysis promotes the "heterogenization" of a homogeneous catalyst in one phase (usually polar, in this case in an IL), and organic products in another. The product is separated from the catalyst solution by simple decantation, and the catalyst is used repeatedly without reducing the efficiency.
efficiency, selectivity and activity of the process. An ionic type catalyst can be easily retained in the IL phase without the need for the synthesis of special purpose ligands. In the case when the catalyst is not charged, the transition (washout) of an expensive transition metal into the organic phase can be limited by using functional ligands specially introduced into the structure of the IL. The thermodynamic and kinetic characteristics of chemical reactions carried out in IL differ from those in traditional volatile organic solvents, which is also of great interest.
The literature reports on many chemical reactions in which ILs are used as a medium. Such reactions include cracking, hydrogenation, isomerization, dimerization, oligomerization, etc. It is known that ILs used in a number of catalytic systems exhibit greater activity, selectivity, and stability than in the case of conventional solvents. They often provide better yields, highly selective distribution of reaction products, and in some cases faster process kinetics. Reactions in IL also proceed at lower pressures and temperatures than conventional reactions, thus leading to a significant reduction in energy and capital costs.
IONIC LIQUIDS IN CATALYTIC PROCESSES OF OLEFIN AND DIEN CONVERSION
The catalytic processes of dimerization, oligomerization, alkylation, and metathesis of olefins and dienes in IL open up new opportunities for their conversion into more valuable olefins and other products. The role of the solvent in these homogeneous catalytic processes is to dissolve and stabilize the molecules of monomers, ligands, and catalysts without interaction with them and without competition with monomers for a vacant coordination center.
As solvents, ILs are unique in their weak coordination ability, which, with respect to the catalytic complex, depends on the nature of the anion. ILs with low nucleophilicity do not compete with the organic molecule for coordination in the electrophilic center of the metal. In some cases, their role is simply to provide a polar, weakly coordinating environment for an organometallic complex catalyst (as a "harmless" solvent) or as a cocatalyst (for example, in the case of chloroaluminate or chlorostannate ILs), so they can be used
act as a direct solvent, co-solvent and catalyst.
It is known that most ILs form two-phase mixtures with many olefins, and these systems have all the advantages of both homogeneous and heterogeneous catalysis (e.g., mild process conditions, high efficiency/selectivity ratio characteristic of homogeneous catalysts, easy separation of reaction products, optimal consumption of heterogeneous catalysts).
At present, the most studied reaction in IL is the dimerization of lower olefins catalyzed by nickel compounds using a chloraluminate type of solvent.
The French Petroleum Institute (FIN) has developed a catalytic process of propylene dimerization in a chloraluminate IL based on 1-bu-
tyl-3-methylimidazolium chloride (bmimCl) - so-called. nickel process. The catalyst consists of L2NiCl2 (L = Ph3P or pyridine) in combination with EtAlCl2 (bmimCI/AlQ3/EtAlQ2 = 1/1.2/0.25) and active catalytic
ionic complex of nickel(II) +AlCl– formed in situ upon alkylation of L2NiCl2 with EtAlCl2 in acidic alkyl chloroaluminate ILs. Since the latter promote the dissociation of ionic metal complexes, it was assumed that they have a beneficial effect on this reaction. At 5°C and atmospheric pressure, the productivity of the process reaches ~250 kg dimer/g Ni, which is much higher than
For further reading of the article, you need to purchase the full text ELISEEV O.L., LAPIDUS A.L. - 2010
A. G. Azizov, R. V. Alieva, F. M. Velieva, B. V. Guliyev, M. D. Ibragimov - 2008
