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Mishakov, Ilya V.; Чесноков, В. В.; Buyanov, R. A.; Пахомов, Н. А.

doi:10.1023/a:1010585808978

Cited by 44 publications

(16 citation statements)

References 3 publications

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“…As follows from the presented data, the value of the equilibrium constant (K p ) exceeds 1 at temperatures above 450 • C. This means that nickel chloride should undergo a reduction with the formation of metal at such temperatures that consequently stabilizes the operation of the catalyst under the conditions of a lack of hydrogen. The obtained theoretical result was earlier confirmed experimentally in the study of the 1,2-DCE decomposition over Fe-, Co-and Ni-containing catalysts [32]. It is worth noting that, among the mentioned metals, Ni had the least tendency to chlorination, which made it possible to use the Ni-based catalysts in the dechlorination reactions in a wider temperature range.…”

Section: (Hydro)dechlorination Of C2h4cl2supporting

confidence: 73%

“…The deactivation process of the nickel catalyst is sensitive to two main factors: temperature and hydrogen concentration (partial pressure) in the reaction mixture. The calculations were carried out in order to define the conditions of nickel resistance towards the chlorination [32]. The reaction of nickel chloride with hydrogen can be represented by the following Equation: As follows from the TGA profile of the sample, the weight loss was represented by at least four peaks in the regions of 120, 255, 320, and 365 • C (Figure 1a).…”

Section: The Features Of Nickel Chloride Interaction With Hydrogenmentioning

confidence: 99%

“…This approach is known as a catalytic chemical vapor deposition (CCVD) technique [31]. CCVD was demonstrated to be very effective for the purposeful catalytic pyrolysis of various chlorinated hydrocarbons and their multicomponent mixtures (waste) [32][33][34][35][36][37][38]. In addition, Ni was found to be the most productive and stable among the other metals of the iron subgroup (Fe, Co, and Ni), which are commonly used in the composition of catalysts for CCVD [32,33].…”

Section: Introductionmentioning

confidence: 99%

“…CCVD was demonstrated to be very effective for the purposeful catalytic pyrolysis of various chlorinated hydrocarbons and their multicomponent mixtures (waste) [32][33][34][35][36][37][38]. In addition, Ni was found to be the most productive and stable among the other metals of the iron subgroup (Fe, Co, and Ni), which are commonly used in the composition of catalysts for CCVD [32,33]. The catalytic pyrolysis of chlorinated organic substances occurs in accordance with the so-called "carbide cycle" mechanism that was earlier revealed for the decomposition of unsubstituted hydrocarbons [39].…”

Section: Introductionmentioning

confidence: 99%

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Two Scenarios of Dechlorination of the Chlorinated Hydrocarbons over Nickel-Alumina Catalyst

et al. 2020

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Dechlorination processes attract great interest since they are involved in environmental protection and waste disposal technologies. In this paper, the process of gas-phase dechlorination of 1,2-dichloroethane, chloroform, and chlorobenzene over Ni/Al2O3 catalyst (90 wt% Ni) prepared by a coprecipitation technique was investigated. The reduction behavior of the oxide precursor NiO/Al2O3 was studied by thermogravimetric analysis in a hydrogen medium. A thermodynamic assessment of the conditions under which metallic nickel undergoes deactivation due to the formation of nickel chloride was performed. The dechlorination of chlorinated substrates was studied using a gravimetric flow-through system equipped with McBain balances in a wide range of temperatures (350–650 °C) and hydrogen concentrations (0–98 vol%). The impact of these parameters on selectivity towards the products of hydrodechlorination (C2H4, C2H6, and C6H6) and catalytic pyrolysis (carbon nanomaterial and CH4) was explored. The relationship between the mechanisms of the catalytic hydrodechlorination and the carbide cycle was discussed, and the specific reaction conditions for the implementation of both scenarios were revealed. According to the electron microscopy data, the carbonaceous products deposited on nickel particles during catalytic pyrolysis are represented by nanofibers with a disordered structure formed due to the peculiarity of the process including the side carbon methanation reaction.

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Section: (Hydro)dechlorination Of C2h4cl2supporting

confidence: 73%

Section: The Features Of Nickel Chloride Interaction With Hydrogenmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Two Scenarios of Dechlorination of the Chlorinated Hydrocarbons over Nickel-Alumina Catalyst

et al. 2020

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“…The reasons for deactivation of hydrodechlorination catalysts may be different. The decrease in the activity of metal catalysts is usually explained by partially blocking of the catalyst surface by the obtaining hydrogen chloride and by the deposition of high molecular weight products and coke [56,58,64,65,67,119,120].…”

Section: Catalyst Deactivation and Stabilitymentioning

confidence: 99%

Theoretical and Applied Aspects of Hydrodechlorination Processes—Catalysts and Technologies

Flid¹,

Kartashov²,

Treger³

2020

Catalysts

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The commercial implementation of hydrodechlorination processes will be an essential step in resolving the problem of environmentally sound organochlorine wastes processing. By now, there is a number of fundamental, applied, and process elaborations of such processes, in which chlorine is almost completely removed from wastes. The review article contains a significant number of results including basic regularities of thermal hydrodechlorination, comprehensive and selective catalytic hydrodechlorination. It discusses thermodynamics, kinetics, and catalysts of gas and liquid phase processes. Considerable attention is paid to hydrodechlorination of vinyl chloride production wastes and utilization of tetrachloromethane, which is the ozone-depleting substance. It also discusses hydrodechlorination of mono-and (poly)chlorobenzenes. The important examples of liquid phase data include hydrogenation using complex hydrides of elements. It also includes several flow sheets of hydrodechlorination processes.Various methods for C-Cl bonds reduction in non-cyclic organochlorine compounds can be divided into the following groups:Catalysts 2020, 10, 216 3 of 52 one should note the reviews [4,10] published in the 1990s. It is noted that catalytic methods are more widely used for hydrodechlorination. Electrochemical ReductionElectrochemical reduction is a complex process in which the speed and direction of reactions depend on many factors. It is characterized by the following features. Two electrons are spent for breaking the C-Cl bond; the half-wave potential in most cases does not depend on the pH of the medium; in general, the electrode reaction is irreversible [1]. There is an approximate linear relationship between the half-wave potential of the reactionsIn [12], a scheme was proposed describing the mechanism of electrochemical reduction of the C-Cl bondRClHowever, there is another point of view, according to which there is a simultaneous transfer of a pair of electrons, similar to that for nucleophilic substitution reactions [1].Electrochemical reduction is carried out on cathodes of copper, zinc, amalgamated zinc, palladium, cadmium, mercury, and lead [13]. The cathodic dechlorination proceeds in an alkaline environment more efficiently than in an acidic one; however, in most cases, acidic electrolytes are used to avoid such side reactions as saponification [13,14]. The recovery is usually carried out in inert solvents, in particular in alcohols. In [13], the influence of the reduction conditions-the cathode material, current density, the nature of electrolyte and solvent, the concentration of the reducible substance, and temperature-on the course of the reaction is described.The recovery of monochlorohydrocarbons is difficult and results mainly in the replacement of chlorine by hydrogen in accordance with the overall equationIn some cases, dimeric compounds (R-R) are formed according to the schemeThe recovery of vinyl chlorine is difficult, and that of the allyl one is facilitated in comparison with chlorine in saturated com...

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A Biomass‐Derived Non‐Noble Cobalt Catalyst for Selective Hydrodehalogenation of Alkyl and (Hetero)Aryl Halides

et al. 2017

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Hydrodehalogenation is astraightforwardapproach for detoxifications of harmful anthropogenic organohalidebased pollutants,aswell as removal of halide protecting groups used in multistep syntheses.An ovel sustainable catalytic material was prepared from biowaste (chitosan) in combination with an earth-abundant cobalt salt. The heterogeneous catalyst was fully characterized by transmission electron microscope,X -rayd iffraction, and X-ray photoelectron spectroscopym easurements,a nd successfully applied to hydrodehalogenation of alkyla nd (hetero)aryl halides with broad scope (> 40 examples) and excellent chemoselectivity using molecular hydrogen as ar eductant. The general usefulness of this method is demonstrated by successful detoxification of non-degradable pesticides and fire retardants.M oreover,t he potential of the catalyst as adeprotection tool is demonstrated in am ultistep synthesis of (AE)-peronatin B( alkaloid).Hydrodehalogenation constitutes an important organic transformation where ahalogen atom is formally substituted with ahydrogen atom. It has become an enabling technology for degradation of anthropogenic and environmentally deleterious chemicals into their less noxious congeners.T he former are often produced in industrial processes and can include polyhalogenated organic pollutants (such as,p olychlorodioxins and polychlorophenols), toxic and persistent pesticides,and fire retardants. [1,2] Furthermore,hydrodehalogenation reactions are often used in organic synthesis for deprotection chemistry,s ince halides can selectively block one of two reaction sites with similar reactivity without strongly influencing the electronics of the system. [2,3] Additionally,s tereoselective hydrodehalogenation of prochiral gem-dihalo-organic compounds affords chiral halo-organic compounds. [4] Hydrodehalogenation reactions have been performed with various methods,s uch as metal-halogen exchange, [2, 5] metal-mediated reduction, [2,6] photochemical reduction, [7] and reductive radical dehalogenation. [8] Some of these reactions are marred by the use of toxic and explosive reagents, production of stoichiometric metal waste,poor selectivity,and low functional-group tolerance.Nevertheless,there has been an intense research interest in developing more efficient and reliable transition-metal-catalyzed hydrodehalogenation processes (mostly involving,Pd, [9] Rh, [10] Ru, [11] Ni, [4,12] and Fe [13] ) using Grignard reagents, [12c,13] alcohol and base, [9a, 10c, 11a,c] hydrides, [4,9b,c, 12b,d,14] formic acid [9h] or its salt, [9e] hydrazine, [9d] and molecular hydrogen. [9c,f,g,10a,b, 11b,12a] Obviously,f rom an ecological perspective,t he later reagent is considered to be the most efficient, clean, and atom-economical reductant. [15] Fort he last decade,t he implementation of cheap,e arth abundant, non-noble metals for (de)hydrogenation reactions has attracted significant interest in homogeneous and heterogeneous catalysis. [16] As acomplement to molecularly defined organometallic complexes,heterogeneous mat...

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Untitled

Cited by 44 publications

References 3 publications

Two Scenarios of Dechlorination of the Chlorinated Hydrocarbons over Nickel-Alumina Catalyst

Two Scenarios of Dechlorination of the Chlorinated Hydrocarbons over Nickel-Alumina Catalyst

Theoretical and Applied Aspects of Hydrodechlorination Processes—Catalysts and Technologies

A Biomass‐Derived Non‐Noble Cobalt Catalyst for Selective Hydrodehalogenation of Alkyl and (Hetero)Aryl Halides

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