Formation Of Acrylonitrile Research Articles

Propane ammoxidation to acrylonitrile - an overview

The main aspects of the new reaction of direct (one-stage) propane ammoxidation to acrylonitrile (ACN) are analyzed with reference to the development of the catalysts for this reaction, the main technological options for the process and relationship with reaction conditions, the reaction network and kinetics of the reaction. In particular it is shown that i) V-Al-antimonate based mixed oxides are promising catalytic systems for the selective formation of ACN from propane in the absence of gas-phase additives, ii) ACN forms through the intermediate formation of propylene and the factor controlling the selectivity to ACN is the rate of the reaction for the formation of ACN from the intermediate propylene (rate which critically depends on the availability of ammonia on the catalyst surface), and iii) kinetic and economic analyses suggest the use of a process involving a high propane concentration with O 2 and NH 3 as limiting reagents to recycle unreacted propane.

Stereospecific Polymerization of Acrylonitrile Using Acrylonitrile–Urea Canal Complex Initiated by γ-Ray Irradiation: Roles of Radical Chain Transfer Reagents

An attempt was made to clarify the effect of polymerization conditions (e.g., the content of chain transfer reagent, irradiation dose, acrylonitrile (AN)–urea ratio, aging time) on the stereoregularity, the viscosity-average molecular weight Mv, and the conversion in the radiation-induced polymerization of AN–urea canal complex in the presence of radical chain transfer reagent including alkyl mercaptans, alkylamines, alkyl alcohols and chloroform. The addition of n-butyl mercaptan (n-BM) to AN–urea system slowed down the rate of the canal complex formation and decreased the amount of the canal complexes formed. The role of n-BM on the formation of AN–urea canal complex was also examined by DSC. The enthalpy of fusion (ΔH) of AN solid in AN–n-BM–urea system decreased with elapse of aging time, although ΔH of n-BM was almost constant in the whole range of aging time. From these findings, it was concluded that n-BM is not included in the AN–urea canal complex. The conversion decreased remarkably with an increase in n-BM content. When 2 mol%/AN of n-BM was added to AN, Mv was almost constant (ca. Mv=2.0×105), irrespective of the amount of n-BM added. Addition of n-BM to AN–urea system brings about a small, but significant increase in the content of isotactic triad (mm) by 5 to 14%.

Atmospheric Chemistry of Toxic Contaminants. 3. Unsaturated Aliphatics: Acrolein, Acrylonitrile, Maleic Anhydride

Detailed mechanisms are outlined for the chemical reactions that contribute to In-situ formation and atmospheric removal of the unsaturated aliphatic contaminants acrolein, acrylonitrile, and maleic anhydride. In-situ formation of small amounts of acrolein and maleic anhydride may Involve the reaction of OH (and O3) with 1,3-dienes and the reaction of OH with aromatic hydrocarbons, respectively. There is no known pathway for In-situ formation of acrylonitrile. Rapid removal of acrolein (half-life = less than one day) and of maleic anhydride (half-life = several hours) is expected from their rapid reactions with OH (major), O3, and NO3. These reactions lead to formaldehyde and glyoxal from acrolein and to dicarbonyls from maleic anhydride. Acrylonitrile is removed at a slower rate (half-life = 2–7 days) by reaction with OH, leading to formaldehyde and formyl cyanide.

TRANSIENT RESPONSE ANALYSIS IN THE DETERMINATION OF ADSORPTION RATE COEFFICIENTS FOR PROPYLENE AND NITRIC OXIDE ON NiO/Al203 AEROGEL CATALYSTS

Nickel oxide on alumina aerogel catalysts are known to be active and selective for the formation of acrylonitrile from nitric oxide and propylene. During an effort to investigate the mechanism of this reaction some transient feed experiments were carried out. The results obtained from these transient experiments were used to calculate the adsorption coefficients of propylene and nitric oxide on a NiO/Al2O3 aerogel catalysts with 1:1 Ni to Al atomic ratio. Adsorption coefficients of nitric oxide and propylene was determined by independently flowing the respective gases over the catalyst in a stream of helium at 410° C. Adsorption coefficient of nitric oxide on the catalyst at an oxidized state has been found to be less than that of propylene. When the two reactant gases flowed across the catalyst together the rate of adsorption of nitric oxide increased as the catalyst was reduced by propylene adsorption. The increased rate of adsorption of nitric oxide does not, however, influence the overall rate of formation of acrylonitrile.

Functionalization of alkanes by heterogeneous vapour-phase oxidation.: II. Propane ammoxidation

Propane ammoxidation to acrylonitrile was studied on (VO) 2P2O 7, on vanadium—titanium mixed oxide, on vanadium—antimonate with different Sb:V atomic ratios and on iron—antimonate (Sb:Fe=2.0) catalysts. The results showed a strong deactivation effect of ammonia on propane conversion, interpreted as a competitive adsorption of ammonia on the sites for activation of propane by oxidative dehydrogenation to propylene. Selectivity to acrylonitrile behaves in a complex waywith respect to ammonia concentration showing a maximum value for an NH 3 concent around 15% followed by a decrease with a parallel increase in propylene selectivity. The effect was interpreted considering a double effect of ammonia that (i) transforms total oxidation sites to selective sites for acrylonitrile synthesis and (ii) reduces these sites due to its oxidation to nitrogen oxides. V P O and V Sb O systems show the higher selectivities in acrylonitrile formation from propane.

Etude expérimentale de l'ammoxydation catalytique du propène dans un réacteur différentiel

The kinetics of ammoxidation of propene has been studied over an industrial Sn/Sb oxides catalyst in a differential reactor at 490 °C. Factorial design of experiments leads to reliable rate equations over the range of partial pressures encountered in a fluidized bed reactor. The rate of disappearance of propene may be represented by the equation r 1 = 1.497 × 10 −7 P C 3H 6 0.48 P O 2 0.48 P NH 3 0.19 and the rate of formation of acrylonitrile by r 4 = 1.287 × 10 −7 P C 3H 6 0.43 P O 2 0.52 P NH 3 0.47 A best fit is obtained by the addition of some empirical pressure interaction terms. Catalytic activity is about the same as for other Sn/Sb oxides catalysts and maximum selectivity at 490 °C is at least 82%.

Surface Composition of SnO2–ZrO2 Binary Oxide Catalyst and Its Selectivity for C3H6–NO Reaction

Abstract The relation between the composition of outermost surface layer on SnO2–ZrO2 binary oxide catalyst and catalytic selectivity in the C3H6–NO reaction has been investigated by XPS technique. The composition of outermost surface layer was estimated from a comparison of the intensity ratios of X-ray induced Auger peak or XPS peak of Sn to XPS peak of Zr. A superficial enrichment of Zr was observed in these catalysts calcined at 600 °C in the air, while surface enrichment of Sn took place during the course of evacuation at 450 °C. The catalytic selectivity for formation of acrylonitrile showed a maximum with the catalyst containing Sn and Zr in the same concentration at the outermost surface layer of catalyst.

Aspects of selective oxidation and ammoxidation mechanisms over bismuth molybdate catalysts

The interaction of allyl radicals, generated in situ by thermal nitrogen extrusion from 3,3′-azopropene, was studied at 320°C. The catalyst systems were MoO3, Bi2O3·nMoO3 (where n = 1, 2, and 3), a multicomponent Bi-molybdate, and Bi2O3. Allyl radicals gave significantly more byproducts (e.g., CO2, acetaldehyde, benzene) than did allyl iodide or propylene under corresponding reaction conditions. When allyl radicals were generated from azopropene over MoO3, and in the presence of ammonia, substantial yields of acrylonitrile were obtained. In the absence of ammonia, acrolein was the major useful product. The results for propylene oxidation and ammoxidation over Bi-molybdates are interpreted in terms of a concerted chemisorption, α-hydrogen abstraction mechanism, with subsequent oxygen (or NH) insertion, which does not proceed via a free allyl radical as the major pathway. Allyl radicals can, however, favorably compete with ammonia for oxygen (or NH) insertion sites over MoO3 at 320°C. The proposed mechanism involves the formation of a π-allylic Mo (V) intermediate as the rate-determining step, in rapid equilibrium with a σ-bonded Mo (V) ester, the acrolein precursor. Acrylonitrile formation is explained by reaction of the initially formed π-allylic intermediate with ammonia, loss of water, and subsequent H-abstraction from the thus formed σ-bonded Mo (V) amide.

Kinetic studies and mechanism of the reaction of propylene with nitric oxide for acrylonitrile synthesis in the presence of nickel oxide on alumina catalysts

The reaction of propylene with nitric oxide for the synthesis of acrylonitrile has been studied over nickel oxide supported on alumina as catalyst. A xerogel catalyst of composition 2NiO, Al 2O 3 was prepared by thermal decomposition, under vacuum at 400 °C, of a nickel hydroaluminate, 2NiO, Al 2O 3, 8H 2O. Aerogel catalysts NiOAl 2O 3 and NiOAl 2O 3SiO 2 of variable compositions were prepared by the autoclave method (hypercritical conditions). All these solids are selective (80%) in the formation of acrylonitrile at 410 °C. The best catalytic activity and selectivity are observed after a previous activation of the catalyst by oxygen at 410 °C for 48 hr. The kinetic studies reveal that the mechanism of the reaction is of the “redox” type. First there is reduction of the catalyst by propylene with formation of dehydrogenated radicals; these then form acrylonitrile with atomic nitrogen released by the dissociation of nitric oxide which reoxidizes the catalyst. The behavior of xerogel catalyst ( Ni Al = 1 ) and of aerogel catalysts ( Ni Al varying between 0.2 and 1) is similar for the same composition. The formation of acetonitrile is attributed to the oxidation of acrylonitrile over a fresh catalyst (barley reduced). The formation of carbon dioxide devolves from the oxidation of acrolein.

Electron microscope observation of microtexture and craze formation of acrylonitrile–EPT–styrene copolymer

Electron microscope observation of microtexture and craze formation of acrylonitrile–EPT–styrene copolymer

Molecular complexes. Part 11.—Some comments on electrostatic and steric effects in the formation of acrylonitrile + aromatic complexes

The interactions between acrylonitrile and various alkylbenzenes have been studied by 1H n.m.r. at several temperatures. The equilibrium quotients, Kx, and aromatic induced shifts, Δc, at a particular temperature, as well as ΔG°, ΔH° and ΔS° appear superficially to show an almost random variation with the degree of alkylation of the aromatic nucleus. However, the data have been rationalized in a quantitative fashion by considering that the reaction and complex parameters are governed by three factors. These are due to an intermolecular electrostatic effect and two steric features of the aromatic compounds due to the “blocking” and “trapping” effects of the alkyl substituents.

CNDO/2 calculations and energy partitioning in the formation of acrylonitrile and propiolonitrile from acetylene and hydrocyanic acid

Calculations within the CNDO/2 approximation have been performed on HCN and HCCH oriented in a variety of ways with respect to each other. Total electronic energies and partitioned energies have been obtained which predict that an intermediate forms. Additional calculations on a variety of related configurations have also been carried out and a qualitative mechanism for the homogeneous, high temperature formation of both acrylonitrile and propiolonitrile from HCN and HCCH has been proposed.

Mechanism of [3-13C]propene ammoxidation on bismuth molybdate catalyst

To study the mechanism of acrylonitrile formation, the ammoxidation of [3-13C]propene was studied in the presence of a bismuth molybdate catalyst on a silica support. The reaction was carried out at 723 K with a conversion of about 40 vol % of the propene to acrylonitrile and a small amount of acetonitrile. The 13C distribution among the reaction products was examined quantitatively with a high-resolution mass spectrometer. Half of the 13C in the acrylonitrile was found to be in the CN-group and the other half in the C2H3-group. This result points to a symmetrical intermediate, such as an allylic species, in the ammoxidation reaction. A similar intermediate was observed in the catalytic oxidation of propene to acrolein. The total 13C content in the acetonitrile amounted only half that of the acrylonitrile, which indicates carbon-carbon bond fissure of the allylic intermediate in the mechanism of acetonitrile formation. Ammoxidation of propene does not seem to involve acrolein as an intermediate. As a matter of fact, the addition of ammonia to a mixture of propene + oxygen + helium completely suppresses acrolein formation at 623 K.

Study of intermediate species involved in the formation of acrylonitrile—II : Charge and spin-polarizations and their relation to chemical structure and activity

We present several charge and spin density graphs for the different species involved in the formation of acrylonitrile through the reactions C 2H 2 + HCN and C 2H 3 + CN. These graphs were plotted using a modified version of the ISODENS program. Some interesting aspects of polarization shown by comparing charge densities in the different fragments and in acrylonitrile itself are discussed. We also analyse total and individual MO spin polarizations in the C 2H 3 and CN radicals.

The Reaction between Hydrocarbon and Hydrogen Cyanide in Silent Electrical Discharge. II. The Formation of Acrylonitrile from Ethylene and Hydrogen Cyanide

Abstract The present investigation was undertaken to examine the possibility of the direct introduction of a cyano radical into ethylene by means of a silent discharge. When a mixture of ethylene and hydrogen cyanide was discharged in an ozonizer under atmospheric pressure, the main liquid product was acrylonitrile, though the formation of telomers, such as ethyl cyanide, n-butyl cyanide and n-hexyl cyanide, was also observed. Besides these compounds, the reaction products were confirmed to consist of s-butyl, n-propyl, isopropyl, n-amyl, and isoamyl cyanides, and a gaseous product. The yield of acrylonitrile was affected by the temperature and voltage of the discharge. It has been found that the yields of the liquid products and the gaseous product increase with the rise in the temperature and voltage of the discharge, while the relative ratio of acrylonitrile to the other liquid product decreases. Judging from the relative concentration of each compound in the reaction products, it may be said that the vinyl radical and the cyano radical are the main intermediates in this reaction system.

Studies on the Intoxication of Acrylonitrile : Mercaptide Formation of Acrylonitrile with SH-Compounds in the Body

Studies on the Intoxication of Acrylonitrile : Mercaptide Formation of Acrylonitrile with SH-Compounds in the Body

Polarography of halogen organic compounds communication 2. determination of reaction stoichiometry by means of latent limiting currents

1. Using the equations for latent limiting currents, given by Kemula and Grabowski, expressions are found for determining the stoichiometric coefficients of a reaction which is capable of reducing a substance with the reduction products of another substance. 2. The correctness of the relations derived is shown with several organic compounds, and the proposal is made to use latent limiting hydrogen currents to identify the products of electroreduction. 3. This method has been used to demostrate the reduction mechanism of 2,3-dibromopropionitrile with formation of acrylonitrile in the first wave.

Studies on Direct Synthesis of Acrylonitrile. IX

The effects of change in concentration of NH4C1, CuCl, and HCl in CuC1-NH4C1 catalyst pretreated with HCN on the loss of HCN by evolution, thevelocity of formation of acrylonitrile (AN) and an induction period for formationof AN have been investigated.An increase in concentration of NH4Cl in Newland's catalyst accelerated thevelocity of evolution of HCN and the induction period for formation of AN wasgradually increased. Although the velocity of formation of AN was increasedup to a certain concentration of NH4Cl, it decreased gradually thereafter. A peakfor formation of AN was appeared by the presence of an equimolar mixture of NH4Cl and CuCl after passing through the induction period. Also, NH4Cl in thepresence of CuCN had no direct relation in the synthetic reaction of AN atany stage of reaction.There was no parallelism between the velocity of lossof HCN by evolution and the velocity of formation of AN.An increase in concentration of CuCl caused the loss of HCN by evolutionin an inversely related way and this was inversely relatad to the reaction of NH4Cl. The induction period for AN formation was shortened in such a way asinversely related to the concentration of CuCl, but the velocity of formationof AN was increased up to a certain cencentration of CuCl and became constantthereafter. An increase in concentration of HCl caused an increase in the loss of HCN by evolution and this was accompanied with an increase in the velocity off ormation of AN as well as an increase in induction period for its formationsimilar to that of NH4Cl but it showed no peak in the formation of AN asshown by NH4Cl.