CARBON DEPOSITION AND CATALYST DEACTIVATION OF Sb-Fe OXIDE CATALYST IN THE AMMOXIDATION OF PROPYLENE

Carbon deposition and catalyst deactivation of Sb-Fe oxide catalyst in the ammoxidation of propylenewere investigated by means of a fluidized-bed reactor.The reactivity,surface acidity,specific surfacearea,average pore radius,and electron spin resonance spectrum data were obtained from the catalysts ofincreasing carbon deposition.Chemisorption of oxygen and propylene and thermal programmed desorptionof propylene were carried out on the Sb-Fe oxide catalyst as well as a commercial one,Mo-Bi.Isotopicexperiment using acrylonitrile-2-~(14)C as tracer was also accomplished.It was found that carbon deposition due to intermediates and acrylonitrile on selective oxidation sitescould be the primary reason for catalyst deactivation,and that because of the Sb-Fe oxide catalytspossessing a property of easy reduction and difficult reoxidation,the structure of the FeSbO_4 would bedecomposed under the oxygen-lean condition into Sb_2O_3 and Fe_2O_3 which form the deep oxidation catalystcomponent.According to the above investigation a suggestion for improving catalyst properties has been proposed.     

THE VERTICAL DENSITY PROFILES OF TWOPHASE MIXTURE AND THE FLOW REGIME TRANSITION ON SIEVE TRAYS

The vertical density profiles of the gas-liquid mixture on the flow-guide sieve tray and conventional sieve tray have been studied by gamma-ray absorption technique. It has been found that the inflection points of entrainment rates can be regarded as the criterion of transition of flow regimes and that the operating range between two inflection points is the transition regime. The relationships have been established for the lqiuid hold-up (or clear liquid height), the average dispersion density and the transition of flow regime.     

EFFECT OF SELECTED β-DIKETONES ON THE SYNERGICEXTRACTION OF COBALT(II) BY TRIPHENYL-PHOSPHINE OXIDE IN BENZENE

Abstract

Synergic extraction of Co(ll) by thenoyltrifluoroacetone (HTTA), Pivaroyltrilluoioacetone (HPvTA) or hexafiuoroacetylacetone (HHFA) mixed with triphenyiphosphine oxide (ph₃PO) in benzene from perchlorate media has been investigated. It ’ was found that in all the systems studied, Co(ll) is synergistically extracted as CoL₂.ph₃PO, where L stands for the different chelating ligands. The obtained equilibrum constants for the chelating and adduct systems indicated that: i- the weaker the acidity of the chelating ligand, the higher the overall aqueous phase formation constant of the metal chelate (β₂ ), ii- the sequence of the extraction constants (K_2,1 ) and the organic phase formation constants for the adduct ( β_2,1) as related to the chelating ligands is TTA> HFA > PvTA, iii- the stability of the adduct is related to both the structure and the pK_avalues of the chelating ligands.     

PERIODIC VARIATIONS OF LANTHANIDES YKERGIC EXTRACTION BY THENOYLTRI-FLUOROACETONE AND TRIPHENYLPHOSPHINE OXIDE MIXTURE∗

Abstract

The synergic extraction of the different lanthani-des, except Pm and Lu, by thenoyltrifluoroacetone (HTTA) and triphenylphosphine oxide (TPPO) mixture in benzene from an aqueous perchlorate medium of constant ionic strength of 0·2 was investigated. It was found that the main adduct extracted contains the lanthanide chelates together with two TPPO molecules. The different extraction and formation constants for the lanthanides investigated have been determined. The variations of the logarithmic values of the chelate extraction constant and the adduct formation constant with the different lanthanides was discussed in the light of the tetrad and the inclined-W effects. The experimental results showed that the nature of coordination by adduct formation for the Yb-Sm group is different than that of the Pr-La group.     

STUDIES ON ULTRASONIC DEGRADATION AND BLOCK COPOLYMERIZATION OF POLYACRYLAMIDE AND POLY(ETHYLENE OXIDE)

The kinetics of ultrasonic degradation of aqueous solution of polyacrylamide(PAM)and poly(ethyleneoxide)(PEO)as well as ultrasonic block copolymerization of aqueous solution of the mixture of PAM/PEOwere studied respectively.The degradation reaction of PEO follows a linear relationship between(P_1-P_∞)~(-1)and irradiation time,while that of PAM follows a linear relationship between(P_1-P_∞)~(-1/2)and irradiation time.The structure of the copolymer was identified by IR,NMR and DTA,and the copolymer prepared is a blockone.The copolymer formed by irradiating 1% aqueous solution of PEO/PAM mixture(1:1)for a period of40min.at 18.2 kHz with a sonic intensity corresponding to 2.OA input current on the reversed main circuitamounts to 61.8%.     

EXTRACTION OF NEPTUNIUM AND PLUTONIUM NITRATES WITH n-OCTYL(PHENYL)-N,N-DIISOBUTYL-CARBAMOYLMETHYLPHOSPHINE OXIDE∗

Distribution equilibria of Np and Pu in various valence states and stripping of Np(V) were studied in a system involving 0.20 M n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide + 1.2 M tributyl phosphate in dodecane as a solvent. Np(V) is weakly extractable at <2 M nitric acid but more effectively extractable at >3 M nitric acid, due to the disproportionation of Np(V) to Np(IV) and Np(VI). Addition of nitrous acid to solutions containing Np(V) increases the over-all extractabllity of Np, due to its partial oxidation to Np(VI). This is also the case In the presence of oxalic acid, both at room temperature and at 40^°C. Both Np(IV) and Np(VI) are highly extractable, but the reduction of Np(V,VI) to Np(IV) is slow even with a reductant as strong as sodium formaldehyde sulfoxylate. Pu(IV) is highly extractable and its reduction to Pu(III) with sulfoxylate Is incomplete in the two-phase system if the aqueous phase contains >0.5 M nitric acid. Extracted Np(VI) can be stripped by reduction to Np(V). The stripping rate is, however, slow with nitrous acid as the reductant at low nitric acid concentration. The reduction of Np(VI) by hydrogen peroxide is fast, but is followed by further reduction to Np(IV). Sulfurous acid reduces Np(VI) rapidly and, if no iron is present, only to Np(V), but Fe(II) induces further reduction to Np(IV).     

CATALYTICALLY ACTIVE COMPONENTS OF Fe_2O_3-Sb_2O_4 MIXED OXIDE CATALYSTS AND THEIR ROLE IN AMMOXIDATION OF PROPYLENE

The catalytically active components of a series of Fe_2O_3-Sb_2O_4 mixed oxide catalysts with differentSb/Fe ratio,calcined at elevated temperature,as well as with or without support,have been investigated byX-ray diffraction analysis,Mossauer spectroscopy and XPS in order to elucidate their catalytic behavior inammoxidation of propylene.Correlations of acrylonitrile yield with Fe~2 and Fe~3 respectively showed that,FeSbO_4 seems to bethe basic active component of catalyst,upon which the formation of new phase containing Fe~3 is responsiblefor a good selective oxidation.     

EXTRACTION OF AMERICIUM(III) FROM CHLORIDE MEDIA BY OCTYL(PHENYL)-N,N-DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE∗

The extraction of Am(III) from chloride media was studied using octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide, Oπ D(iB)CMPO or CMPO, dissolved in tetrachloroethylene. Although the extraction of Am(III) by 0πD(iB)CMPO is many orders of magnitude weaker from chloride than nitrate media, the rapid Increase in the mean activity of chloride in HC1 and in most soluble chloride salts with concentration makes extraction from moderate to concentrated hydrochloric acid and/or concentrated Li, Mg, Ca, and Al chloride salt solutions practical. The stoichiometry of the extractable chloro complex was established by extractant dependency and loading experiments and found to be AmCl₃»3CMPO. Hydrochloric acid appears to be associated with the complex when extraction takes place at high HC1 concentrations. The mode of coordination of OπD(iB)CMPO to AmCl₃appears to be bidentate in marked constrast to its behavior in the corresponding nitrate system.     

THE SEPARATION OF NEPTUNIUM AND PLUTONIUM FROM NITRIC ACID USING n-OCTYL(PHENYL)-N,N DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE EXTRACTION AND SELECTIVE STRIPPING†

The extraction of neptunium and plutonium in several oxidation states was studied as a function of nitric acid concentration for 0.1M n-octyl(phenyl)-N, N-diisobutylcarbamoyl -methylphosphine oxide in 1.4M tributylphosphate with dodecane diluent. Np(V) is only weakly extractable over the range of acid concentrations studied while Np(IV) and Np(VI) are highly extractable. Pu(IV) and Pu(VI) are also highly extractable while Pu(III) was extracted but with lower efficiency. An Fe(II) reductant was used to reduce neptunium to Np(IV) and plutonium to Pu(III) for the initial extraction. Pu(III) was then stripped with dilute HNO₃ in the presence of a holding reductant leaving the Np(IV) in the organic phase. Neptunium may then be recovered to an aqueous phase with one of a number of complexing agents.     

MOLECULAR MODELLING AND SPECTROSCOPIC STUDIES OF THE INTERACTIONS BETWEEN CHELATING AND ELECTRON-DONOR METAL EXTRACTANTS: THE SYSTEM TRI-N-OCTYLPHOSPHINE OXIDE - 3-PHENYL-4-BENZOYL-ISOXAZOL-5-ONE ( ‘HPBI‘ ) IN WET TOLUENE AND CHLOROFORM.

ABSTRACT

IR, NMR (^H, ¹³C and ³¹P) and electronic spectroscopies have been used to study the tautomeric forms of 3-phenyl-4-benzoyl-isoxazol-5-one, "HPBI", and its interaction with tri-rc-octylphosphine oxide, ‘TOPO’, in wet toluene or benzene, and in chloroform. These metal extracting media have been compared with analogous solutions containing l-phenyl-3-methyI-4-acyI-pyrazoI-5-oIs. The spectroscopic results are compared with those of molecular modelling studies. Spectroscopic criteria that allow a choice between the various tautomeric forms of pyrazolones or isoxazolones are briefly reviewed.

In the solid, in wet toluene, benzene or chloroform solutions, HPBI mainly exists as a fi-keto-enol chelate, quite different from its tautomeric form in methanol, which is most probably a diketone-enamine. Molecular modelling studies show that the energy difference between the chelated 5-hydroxy- and 5-one- tautomeric forms of the free molecule is rather low. They cannot be discriminated by spectroscopy

As shown by UV and PMR spectroscopies, the interaction of TOPO with HPBI is stronger than with 4-acyl-5-hydroxypyrazoles (acyl: lauroyl, benzoyl, thenoyl). The most likely tautomeric form for HPBI in the H-bonded [TOPO.HPBI] moiety is the diketone-enamine (b’). Accordingly, molecular modelling studies show that the R3PO-H-NHPBI hydrogen bond is 0.15A shorter than the R3PO-H-OHPBI one, when comparing two isomeric forms of the 1:1 [TOPO.HPBI]complex.     

THE SYNTHESIS AND ACTINIDE AND LANTHANIDE COMPLEXATION OF“ SOFT” DONOR LIGANDS: COMPARISON BETWEEN 4-BENZOYL-2,4-DIHYDRO-5-METHYL-2-PHENYL-3H-PYRAZOL-3-THIONE ( HBMPPT) AND 4-THIOBENZOYL-2,4-DIHYDRO-5-METHYL-2-PHENYL-3H-PYRAZOL-3-ONE ( HTBMPP) WITH TRI-n-OCTYLPHOSPHINE OXIDE (TOPO) SYNERGIST FOR Am( III) AND Eu( III) EXTRACTION

A comparison study between two “ soft” donor ligand isomers, 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione ( HBMPPT) and 4-thiobenzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one ( HTBMPP), both with tri-n-octylphosphine oxide ( TOPO) synergist in toluene, is reported for the extraction of Am( III) and Eu(UI). The more stable ligand, HBMPPT, gave no detectable extraction, but when HBMPPT and TOPO were combined, substantial extraction occurred with selectivity for Am( UI) over Eu( III) in three acid systems HC1, HCIO4, and HNO3. A maximum separation factor ( SF = DAm/ DEu) of 125 was obtained at pH 3.0 for the HBMPPT/ TOPO/ HCIO4 system. The other less stable ligand isomer, HTBMPP, did extract Am( m) to a small extent but combination with TOPO greatly enhanced the extraction. A maximum SF of 15 at pH 3.0 was observed for the HTBMPP/ TOPO/ HCIO4 system. Comparison of HBMPPT/ TOPO among the acids studied indicated different extraction mechanisms in the linear region in each system for Eu( ID) extraction, whereas the Am( m) extraction mechanism remained nearly constant and the same as Eu( m) in chloride media. The large difference in the selectivity and extraction behavior between the two ligands appears to be related to charge density distribution on the donor heteroatoms