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Ternary polymer blends of polyamide 6 (PA6), polycarbonate (PC), and phenol novolac (PN) were prepared by a melt mixing process. PN catalyzes the exchange reaction between PA6 and PC and promotes the generation of a copolymer, which improves the compatibility. Herein, the catalytic effect of PN was experimentally supported by an increase in torque during melt mixing and mass signals from copolymer fragments detected by mass spectroscopy. The characteristic behavior of the exchange reaction changed significantly with increasing PN amount. The promotion of in situ copolymer generation led to the formation of ternary blends, which show homogeneous morphologies and superior mechanical properties, such as high stiffness and good elongation, compared with those of the binary blends without PN. Using excess PN causes some drawbacks like brittleness due to the decomposition of the PC component. A loading amount of 1–3 wt % PN was suitable for achieving a ternary blend with improved properties.

1,4,7,10-Tetraazacyclododecane (cyclen) bearing two anthrylmethyl groups (1,7-bis(9-anthrylmethyl)-1,4,7,10-tetraazacyclododecane, L2) was synthesized and used as a fluorescent chemosensor for detection of pH and transition metal cations in aqueous solution. The fluorescent response and complexation properties of L2 were studied in comparison with those of a cyclen with a single anthrylmethyl group that was previously reported (1-(9-anthrylmethyl)-1,4,7,10-tetraazacyclododecane, L1). Although L2 showed a less sharp response than L1, L2 demonstrated fluorescence behavior similar to that of L1, showing strong fluorescence at a low-pH region (pKa = 8.4) and in the presence of Zn2+ and Cd2+ but showing weak fluorescence at a high-pH region and in the presence of Cu2+. Chemical stability test by 1H NMR revealed that L2 is very stable even if left to stand under a humid atmosphere for 30 days, suggesting that L2 may be a potential effective fluorescent chemosensor for detection of pH and transition metal cation...

N-(9-Anthrylmethyl)-1,4,7,10-tetraazacyclododecane (AC), which acts as an efficient fluorescent chemosensor for detection of pH and metal cations in aqueous solution, was covalently grafted on a Na...

An oxidative desulfurization process for light oil has been investigated using a vanadosilicate molecular sieve as the catalyst and H2O2 as the oxidizing agent. The catalytic activities for three k...

S-Methylsulfonium salts, obtained by a desulfurization process for light oil based on the methylation of sulfur-containing compounds using CH3I and AgBF4 and subsequent precipitation, were used as a thermal latent initiator for cationic ring-opening polymerization of epoxide (glycidyl phenyl ether, GPE). The sulfonium salts, obtained from the light oil, showed good thermal latency and demonstrated significantly high initiation activity for the polymerization of GPE. The activity of the salts was rather higher than that obtained using the salts of pure dibenzothiophenes (DBTs) and benzothiophenes (BTs) as the model sulfonium salts. The salts, obtained from light oil, are derived from highly alkyl-substituted DBTs and BTs in light oil, of low nucleophilicity (low electron density on the sulfur atom), and therefore are unstable against thermal stimulation, thus giving the high initiation activity for the polymerization.

The extraction and separation of transition metals has been investigated using several inorganic adsorbents (silica gel, MCM-41, and aluminum oxide), modified with ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) as chelating ligands. The metal ions in aqueous solution were coordinated successfully by the ligands on the surface of the adsorbents under moderate conditions. Metal−ligand complexes formed on the adsorbents effectively in the region of low pH (1−2) but scarcely formed at pH > 4. Silica gel modified with EDTA (silicaED) was shown to be the most effective adsorbent for the extraction of metals and to form specific metal−EDTA complexes, with stability constants lying in the order Cu2+ > Ni2+ > VO2+ > Zn2+ > Co2+ > Mn2+. The relatively good separation of these six adjacent metals was therefore also carried out using the silicaED. The metals coordinated on the silicaED could be desorbed completely by putting the material into contact with 1 mol/L aqueous HCl solu...

A desulfurization and denitrogenation process for light oils has been investigated based on the chemical oxidation of sulfur- and nitrogen-containing compounds using hydrogen peroxide and acetic acid as oxidizing agent. Sulfur and nitrogen compounds, when dissolved in n-tetradecane and xylene, were oxidized under moderate conditions and were removed successfully. By use of this basic process, although nitrogen content of actual light oils was reduced to

A desulfurization process for light oils has been investigated, based on the formation and subsequent adsorption of N-tosylsulfimides, produced by the reaction of the sulfur compounds in the light oils, with chloramine T (sodium N-chloro-p-toluenesulfonamide). Dibenzothiophenes (DBTs) in light oils are converted, by the reaction with chloramine T dissolved in methanol, to form the corresponding sulfimides and are removed into the methanol under moderate conditions, whereas benzothiophenes (BTs) gave rise to the corresponding chlorine-adduct products, on their unsaturated bond. The sulfimides of alkyl-substituted DBTs, formed during the reaction, remained in the resulting light oil, such that the deep desulfurization (0.05 wt %) failed to achieve. These compounds however were removed successfully by the addition of aluminum oxide adsorbent and the sulfur concentration of the light oil was decreased to less than 0.05 wt %. The desulfurization of high-aromatic-content light oil is relatively more difficult, because the aromatic hydrocarbons are chlorinated by reaction with chloramine T, proceeding competitively with chlorination of the sulfur compounds.

The denitrogenation behavior of several model nitrogen compounds has been investigated during a novel desulfurization and simultaneous denitrogenation process based on alkylation using CH 3 I and AgBF 4 (alkylating agents) and subsequent precipitation of the resulting materials. The denitrogenation reactivities obtained for basic nitrogen compounds (aniline, pyridine, quinoline, and acridine) dissolved in xylene solution were compared to those for neutral compounds (pyrrole, indole, and carbazole). The basic compounds and carbazole were removed from xylene by reaction with the alkylating agents as precipitates of the corresponding N-methylated tetrafluoroborates, whereas pyrrole and indole produced insoluble polymerized materials on their unsaturated bonds. It was found that the denitrogenation reactivities lie in the order pyridine > aniline > acridine > quinoline for basic compounds and pyrrole > indole > carbazole for neutral compounds. Semiempirical MO calculations show that the reactivities of the basic compounds depend on the electron density on the π orbital for the nitrogen atom lying perpendicular to the plane of the molecules.

The denitrogenation behavior of light oils, when occurring during a novel desulfurization process based on alkylation and a subsequent precipitation method, using the alkylating agents (CH3I and AgBF4), has been investigated. Denitrogenation results, obtained for three model nitrogen compounds (aniline, indole, and carbazole) in a xylene solution, were compared with the results for three light oils, of differing nitrogen, sulfur, and aromatic concentration. The nitrogen compounds in the light oils were found to be N-methylated by reaction with the alkylating agents, such that they were removed as precipitates under moderate conditions. By use of this process, the nitrogen contents of all of the light oils were reduced successfully to less than 20% of the corresponding feed concentration, thus demonstrating that the present process is satisfactory for the simultaneous denitrogenation of light oils combined with desulfurization. Although the denitrogenation of aniline and indole compounds from the light oil...

The simultaneous removal of sulfur- and nitrogen-containing compounds from vacuum gas oil (VGO), based on alkylation and a subsequent precipitation method using alkylating agents (CH3I and AgBF4), has been investigated. Desulfurization and denitrogenation reactivities for various compounds in VGO have been studied by means of field ionization−mass spectrometry (FI−MS) and gas chromatography−atomic emission detection (GC−AED), respectively. The sulfur and nitrogen compounds in the VGO were found to be methylated by the addition of the alkylating agents under moderate conditions and were removed successfully as the precipitates of the corresponding S-methylsulfonium and N,N-dimethylcarbazolium tetrafluoroborates. By this means, the sulfur and nitrogen concentrations of the VGO were reduced simultaneously to less than 0.1% and 7.0% of the corresponding feed values, in the presence of a 20-fold molar excess of CH3I and a 10-fold molar excess of AgBF4, respectively, based on the initial sulfur concentration of...

Recent developments in an advanced liquid−liquid extraction system for the separation of metal ions by combining a modification or chemical reaction of the metal species in the aqueous and organic phases demonstrate considerable potential. Possible techniques for the chemical conversion of aqueous-phase metal species include redox reactions for the metal ions, masking effects through the addition of water-soluble complexing agents, and complexing reactions with salting-out agents. For the conversion of organic-phase metal species, a synergistic effects through the addition of additional extractants and redox reactions for the extracted species are also useful. The separation of metal ions is effectively improved by the introduction of such chemical reactions to the extraction system.

A desulfurization process, based on the formation and subsequent precipitation of S-alkylsulfonium salts using alkylating agents (CH3I and AgBF4), has been applied to the desulfurization of catalytic-cracked gasoline (CCG). The desulfurization reactivity of each sulfur compound (thiol, disulfide, benzothiophene, tetrahydrothiophene, and thiophenes) in n-decane solution, as a model gasoline, was compared with that obtained from actual CCG. The sulfur compounds in CCG are methylated by the addition of the alkylating agents under moderate conditions and are removed as the precipitates of the corresponding S-alkylsulfonium salts. By employing this new process, the sulfur content of the CCG was decreased from 100 ppm to less than 30 ppm. The benzothiophene in CCG was found to be the most difficult compound to desulfurize, whereas the thiophenes were the most difficult compounds for the model gasoline. Although the olefin concentration was decreased significantly following desulfurization, the resulting CCG dem...

A novel desulfurization process for light oils has been investigated, based on the precipitation of S-alkylsulfonium salts produced by the reaction of sulfur-containing compounds with alkylating ag...

The simultaneous removal of sulfur- and nitrogen-containing compounds from vacuum gas oil (VGO), based on the combination of UV irradiation and liquid−liquid extraction using an oil/acetonitrile two-phase system, has been investigated. Detailed desulfurization and denitrogenation reactivities for the various compounds in VGO have also been studied by means of field ionization mass spectrometry (FI-MS) and gas chromatography with atomic emission detection (GC-AED), respectively. When VGO and acetonitrile are mixed and photoirradiated, the sulfur and nitrogen compounds in the VGO are distributed into the acetonitrile phase and photodecomposed there to form highly polarized compounds, which do not distribute into the lower-polarity VGO. The successive removal of these compounds from VGO to acetonitrile can therefore be carried out under moderate conditions, such that the sulfur and nitrogen contents for the VGO are decreased simultaneously to less than 1% of the feed values. FI-MS and GC-AED analyses reveal ...

The photoreductive stripping of cobalt from hydroxyoxime extractants was investigated, employing 2-hydroxy-5-nonylacetophenone oxime (LIX-84I) and 2-hydroxy-5-nonylbenzophenone oxime (LIX-65N) as extractants, n-dodecane as the diluent, and a halogen lamp as the light source. The stripping of cobalt is barely achieved by conventional stripping, in this extraction system, because of the oxidation of the cobalt-hydroxyoxime complex by electron attraction with the O 2 molecule. The stripping of cobalt is, however, substantially improved by photoirradiation using light of visible radiation wavelength. The organic solution obtained following photoirradiation can be reused for repeated extraction and photoreductive stripping processing.

The selective extraction of Y from Ho/Y/Er solution by liquid−liquid extraction using (2-ethylhexyl)phosphonic acid mono(2-ethylhexyl) ester (EHPNA), in the presence of a water-soluble complexing agent (ethylenediaminetetraacetic acid, EDTA), has been investigated. The extraction behavior of the ternary system for Ho, Y, and Er, in the presence of EDTA can be expressed using extraction equilibrium formulations, applying for the EDTA free system and consistent with the assumption that the rare-earth metals, when complexed with EDTA, do not take part in the extraction (masking effect). The extraction of Ho and Er in the presence of EDTA is suppressed when compared to that of Y because of the masking effect, and the selective extraction of Y is enhanced. Simulation studies for the separation of Y from a Ho/Y/Er mixture, by the use of a countercurrent mixer−settler cascade, show that the separation is enhanced by the addition of EDTA in both extraction and scrubbing sections.

The mechanism for the extraction of V, when effected by the photochemical reduction of V(V) to V(IV), was investigated, employing bis(2-ethylhexyl)phosphoric acid as the extractant, n-dodecane as the diluent, and a xenon lamp as the light source. The photochemical reduction of V(V) progresses at a rate that is first order with respect to the concentration of V(V) in both aqueous and organic solutions. Reduction also occurs, in the extraction system, at the interface between the aqueous and organic phases. The observed time-course variation in the distribution ratio with respect to photoirradiation is expressed successfully by a proposed scheme, in which the photochemical reduction of V(V) is a rate-determining step. The organic solution obtained following photoirradiation can be reused for repeated photoreductive extraction−stripping processing.

A novel demetalation process for residue oils, based on a combination of photochemical reaction and liquid−liquid extraction, has been investigated. A simultaneous photoreaction and extraction process, employing an oil/water two-phase system, was first studied. The results for the demetalation, obtained for vanadyl(IV)- and nickel(II)tetraphenylporphyrin dissolved in tetralin, were compared with those obtained for actual atmospheric residue oil. It was found that this first process was able to demetalize “free”-type metalloporphyrins, but had difficulty in the demetalation of “bound”-type metalloporphyrins, which are associated strongly with the asphaltenic molecules in residue oil. To weaken this association and thus convert the bound-type metalloporphyrins to the free-type ones, a hydrogen-donating polar solvent, 2-propanol, was added to the residue oil and photoirradiated. The 2-propanol was then removed by evaporation, and the resulting residue oil was contacted with aqueous HCl solution, into which t...

The mechanism of the photoreductive stripping of iron(III) in the liquid−liquid extraction process was investigated by employing (2-ethylhexyl)phosphonic acid mono(2-ethylhexyl) ester (EHPNA) and bis(2-ethylhexyl)phosphoric acid (D2EHPA) as extractants, n-dodecane and kerosene as diluents, and a xenon lamp as the light source. The photoreductive stripping of iron(III) progressed by photoirradiation following an initial induction period caused by dissolved oxygen in the extraction system. The iron(III)−extractant complex was photoexcited in the organic phase and photoreduced to the iron(II) complex by electron donation from the water at the aqueous/organic interface. A kinetic study of the photoreductive stripping of iron(III) revealed that the photochemical reduction of iron(III) was the rate-determining step. The removal of iron from a simulated zinc refinery residue solution by using liquid−liquid extraction combined with photochemical reduction of iron was also investigated, showing that the rare metal...

A desulfurization process, based on photoinduced electron-transfer oxidation using 9,10-dicyanoanthracene (DCA) and organic two-phase extraction, has been applied to the desulfurization of catalytic-cracked gasoline (CCG). Sulfur-containing compounds (thiol, disulfide, and thiophenes), in acetonitrile solution, are photooxidized by photoirradiation, at wavelengths of λ>400 nm in the presence of DCA, to form highly polarized compounds (sulfoxide, sulfone, and sulfate anion), and these compounds do not distribute into the CCG. Thus, when CCG and acetonitrile solution are mixed and are photoirradiated with DCA, the sulfur-containing compounds are extracted into the acetonitrile phase and are photooxidized, thus providing the successive removal of sulfur from CCG to acetonitrile under moderate conditions. In this way, the sulfur content of CCG is reduced successfully from 100 ppm to less than 30 ppm. The large quantity of olefins contained in the CCG is minimally photooxidized, owing to their small fluorescence quenching rate with DCA, and thus the desulfurized CCG has the same high octane number as that of the feed CCG.

The desulfurization products of benzothiophenes (BTs) and dibenzothiophenes (DBTs), produced during a new photochemical desulfurization process, employing an organic two-phase liquid−liquid extraction system, have been identified. The acidic products were converted to their corresponding methyl esters by reaction with diazomethane and were then analyzed. In acetonitrile, BT is converted first to benzothiophene-2,3-dione, followed by hydrolysis, loss of carbon monoxide, and oxidation of the sulfur atom, to be converted finally to 2-sulfobenzoic acid. 3-Methyl BT and 2,3-dimethyl BT produce 2-sulfobenzoic acid and two other products, benzenesulfonic acid and 2-acetylbenzenesulfonic acid. DBT is first photooxidized to DBT sulfoxide, which is then further oxidized to form DBT sulfone or dibenz[c,e][1,2]oxathiin-6-oxide. The latter is then oxidized and finally converted to 2-sulfobenzoic acid via dibenz[c,e][1,2]oxathiin-6,6-dioxide. Benzothiophene-2,3-dicarboxylic acid is likely to be formed directly by the o...

A novel deep desulfurization process for light oils, based on visible light-induced electron-transfer oxidation using 9,10-dicyanoanthracene (DCA) in an organic two-phase liquid−liquid extraction system, has been investigated. Sulfur-containing compounds, when dissolved in acetonitrile, are successfully oxidized by photoirradiation at wavelengths of λ > 400 nm in the presence of DCA, to form highly polarized compounds, which do not distribute into the nonpolar light oil. When light oil and acetonitrile are mixed and are photoirradiated with DCA, the sulfur-containing compounds are extracted successively and are photooxidized in the acetonitrile phase. In this way, a deep desulfurization is achieved: the sulfur content in light oil being reduced from 0.18 wt % to less than 0.005 wt %. The DCA and the aromatic hydrocarbons in the acetonitrile are able to be recovered by the addition of water, followed by extraction with n-hexane. The DCA distributed into the light oil is strongly adsorbed by silica gel and...

A deep desulfurization process for light oil has been investigated, on the basis of photosensitized oxidation using a triplet photosensitizer and hydrogen peroxide in an oil/water two-phase liquid−liquid extraction system. Dibenzothiophene (DBT) in tetradecane was effectively desulfurized. This was achieved via the indirect photoexcitation of DBT, using benzophenone (BZP) under photoirradiation conditions of wavelength λ > 280 nm, and the effective oxidation of the excited DBT by H2O2, suppressing the photodecomposition of H2O2. The desulfurization of commercial light oil was also achieved in this process by the addition of both BZP and H2O2, and the sulfur content was reduced from 0.2 to 0.05 wt % by 48 h of photoirradiation, to meet with the new regulation in Japan. Although C5 and C6 alkyl-substituted DBTs were found to be the most difficult components to be desulfurized, they too were desulfurized effectively in the presence of BZP and H2O2. The photodecomposed sulfur-containing compounds removed into...

The separation and recovery of gallium and indium from zinc refinery residue, using liquid−liquid extraction, has been investigated. The major components with the exception of zinc can be removed by extraction with tri-n-butyl phosphate at low aqueous acidity, and gallium and indium can be separated from the remaining major component, zinc, by extraction with bis(2-ethylhexyl)phosphoric acid (D2EHPA) using the correct conditions, at which effective separation may be feasible. Extraction equilibrium formulations for the ternary system containing gallium, indium, and zinc have been established up to high conversion conditions of the extractant to metal complexes, when D2EHPA is employed as the extractant and kerosene as the diluent. The scrubbing behavior for the process can also be expressed by the proposed extraction scheme. Simulation work based on the equilibrium studies shows that indium may be recovered effectively from the mixture of gallium and zinc with 98.9% overall fractional recovery and 100% pu...

A novel deep desulfurization process of light oil, effected by a combination of photochemical reaction and organic two-phase liquid−liquid extraction, has been investigated. The process is comprised of two stages. The first consists of the transfer of the sulfur-containing compounds from the light oil to an aqueous-soluble polar solvent. This is then followed by the photooxidation and photodecomposition of the sulfur-containing compounds in the solvent by UV irradiation, using a high-pressure mercury lamp. The operations are carried out under conditions of room temperature and atmospheric pressure. Acetonitrile was found to be the most suitable polar solvent for the process. In acetonitrile, dibenzothiophene (DBT) is converted to DBT 5-monoxide and then to DBT 5,5-dioxide, dibenz[c,e][1,2]oxathiin 6-oxide, and aromatic sulfonate or sulfinate anion by the UV irradiation. These products are highly polarized and are therefore not distributed into the nonpolar light oil phase. An adverse effect of naphthalene...

A desulfurization process for dibenzothiophene (DBT) by a combination of photochemical reaction and liquid-liquid extraction has been investigated. The DBT dissolved in tetradecane was photodecomposed by the use of a high-pressure mercury lamp and removed into the water phase at conditions of room temperature and atmospheric pressure. The addition of benzophenone (BZP), a triplet photosensitizer, enhanced the removal of DBT from tetradecane. This reaction, however, hardly proceeded in the presence of naphthalene (NP), probably because of triplet energy transfer from photoexcited DBT or BZP to ground-state NP. The addition of hydrogen peroxide enhanced the desulfurization of commercial light oil as well as the removal of DBT from tetradecane, since H{sub 2}O{sub 2} acted as a weak oxidizing agent for photoexcited DBT and interrupted the energy transfer from excited DBT to NP to some extent. In the case using a 30% H{sub 2}O{sub 2} solution, the desulfurization yield of commercial light oil was 75% following 24 h of photoirradiation and the sulfur content in the light oil was reduced from 0.2 wt % to less than 0.05 wt %.

A desulfurization process for dibenzothiophene (DBT) and its derivatives such as 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) by combination of photochemical reaction and liquid−liquid extraction has been investigated. In this, the DBTs dissolved in tetradecane were quantitatively photodecomposed by the use of a high-pressure mercury lamp and were removed to the water phase as SO42- at conditions of room temperature and atmospheric pressure. The order of reactivity for the DBTs was DBT < 4-MDBT < 4,6-DMDBT, thus indicating a different tendency from that reported for the hydrodesulfurization method. The desulfurization yield of commercial light oil, however, by the proposed method was only 22% following 30 h irradiation and was caused mainly by the depression of the photoreaction of DBT by the presence of aromatic compounds in the light oil.

The mechanism of formation of composite cadmium sulfide and zinc sulfide ultrafine particles (Cd{sub 1{minus}x}Zn{sub x}S) by simultaneous precipitation of cadmium sulfide and zinc sulfide in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles has been studied. The particle formation process was followed by the change in UV-visible absorption spectra. The effects of the reactant concentration, the molar ratio of cadmium to zinc ions, and the water content on the particle formation process were investigated. The resultant particles were richer in CdS than the feed composition of the cadmium to zinc ions in the reaction solution. The particle composition was found to be controlled by the solubility of the CdS and ZnS ultrafine particles. The particle coagulation process was analyzed on the basis of a statistical distribution of particles among the reverse micelles. The coagulation rate constant was controlled by the composition and the size of the particles and by the size of the reverse micelles.

The photoreductive stripping of Eu from an organic phase (xylene, cyclohexane, or hexane) containing Sm[sup 3+], Eu[sup 3+], Gd[sup 3+], and bis(2-ethylhexyl)phosphoric acid as an extractant has been investigated. The organic phase and an aqueous 1 M (NH[sub 4])[sub 2]SO[sub 4] solution were agitated in a glass cell and irradiated with a low-pressure mercury lamp (LPML) or high-pressure mercury lamp (HPML) in the presence of a radical scavenger (isopropyl formate, formic acid, or 2-propanol). The trivalent Eu was photoreduced to the divalent state in the organic phase and precipitated selectively as EuSO[sub 4] in the aqueous phase. The effects of organic solvent, radical scavenger, and UV wavelength on the recovery and separation of Eu were studied. The recovery of Eu as EuSO[sub 4] from the organic solution initially containing equal amounts (4.5--5 mM) of the three elements reached 93%, and a purity of Eu in the precipitate was about 99% when LPML and 2-propanol were used.

The mechanism of formation of cadmium sulfide and zinc sulfide ultrafine particles in reverse micelles has been studied, using sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane as a reverse micellar solution. The particle formation process was followed by the change in UV-visible absorption spectra. The effects of reactant concentration and water content on the particle diameter were also investigated. Particle formation by nucleation and growth occurred very rapidly and was complete within 0.02 s, followed by particle coagulation. The particle coagulation rate constant was found to be controlled only by the intermicellar exchange rate, in the initial stage. With increasing particle diameter, the coagulation was dominated by the statistical distribution of particles among the reverse micelles. As the diameter of particle approached that of the water core in reverse micelle, the coagulation became restricted by the micellar size

The mechanism of the formation of titanium dioxide ultrafine particles in reverse micelles by the hydrolysis of titanium tetrabutoxide (TTB) was studied, using sodium bi(2-ethylhexyl) sulfosuccinate (AOT)/isooctane as a reverse micellar solution. The effects of water, TTB, and surfactant concentrations were investigated. The particle formation process was followed by the change of UV-visible absorption spectra. The conditions for the formation of particles were studied, and the particle formation was found to be controlled by the TTB concentration and the number of micelles. A reaction scheme for the particle formation, based on the number of micelles, was proposed, which successfully explained the data for the combined stages