Utilization of nickel slag using selective reduction followed by magnetic separation

In order to utilize slag discarded by nickel plants, the selective recovery of nickel and copper versus iron was investigated by selective reduction, which was achieved by controlling the reduction parameters and magnetic separation process on bench scale. The results show that increasing the basicity （mass ratio of CaO to SIO2） of nickel slag facilitates the enrichment of nickel and copper The process parameters for selective reduction were optimized as follows： basicity of 0.15, reducing at 1200 ~C for 20 min, 5% coal on a dried slag mass base. The grinding-magnetic separation results of reduced briquettes show that concentrate containing 3.25%Ni, 1.20%Cu and 75.26%Fe is obtained and selective enrichment is achieved with a recovery of 82.20%, 80.00% for nickel and copper respectively, while the recovery of iron is only 42.17%. The S and P contents are not reduced obviously and further research may be needed to examine the behaviors of S and P in the process.

Thermodynamic of selective reduction of laterite ore by reducing gases

As the sulfide ore deposits become less economical and environmental viable as a source of nickel,increasing attention is being paid to the laterite ores.But in the pyrometallurgical process of laterite,more efforts should be paid to control the reduction of iron oxide in order to get high nickel-content nickeliferous product.For these reasons,equilibrium condition of iron oxide when laterite ore was selectively reduced by CO2/CO,H2O/H2 and CO2/H2 was studied from the perspective of iron activity with an assumption that the activities of Fe O and Fe3O4 equal 1 in this work,and it well accounts for the inescapability of Fe metallization.Activity coefficient of iron in Ni-Fe binary solid alloy was calculated by Miedema model based on the known thermodynamics datum filed.According to Raoult＇s law,the relationship among the Fe/Ni ratio,reduction temperature and reduction gas composition was calculated when laterite ore was selectively reduced by the three different reduction systems.The calculation result was discussed and also compared with the experimental result.The trend of metal iron content in the reduction product of laterite ore varying with temperature and gas composition was well predicted by the calculation result.

Highly dispersed V_2O_5/TiO_2 modified with transition metals(Cu,Fe,Mn,Co) as efficient catalysts for the selective reduction of NO with NH_3

Different transition metals were used to modify V2O5-based catalysts （M-V, M = Cu, Fe, Mn, Co） on TiO2 via impregnation, for the selective reduction of NO with NH3. The introduced metals induced high dispersion in the vanadium species and the formation of vanadates on the TiO2 support, and increased the amount of surface acid sites and the strength of these acids. The strong acid sites might be responsible for the high N2 selectivity at higher temperatures. Among these catalysts, Cu-V/TiO2 showed the highest activity and N2 selectivity at 225-375 ~C. The results of X-ray photo- electron spectroscopy, NH3-temperature-programmed desorption, and in-situ diffuse reflectance infrared Fourier transform spectroscopy suggested that the improved performance was probably due to more active surface oxygen species and increased strong surface acid sites. The outstanding activity, stability, and SO2/H2O durability of Cu-V/TiO2 make it a candidate to be a NOx removal catalyst for stationary flue gas.

Nanocomposites of graphene-CdS as photoactive and reusable catalysts for visible-light-induced selective reduction process

Graphene （GR）-CdS nanocomposites with different weight addition ratios of GR have been assembled by a facile solvothermal treatment. The GR-CdS nanocomposite photocatalyst with an appropriate ratio of GR exhibits enhanced photoactivity for selective reduction of aromatic nitro compounds to the corresponding aromatic amines in water under visible light irradiation as compared with blank-CdS. The characterization of GR-CdS nanocomposite photocatalysts by a collection of techniques discloses that： i） GR can tune the microscopic morphology of CdS nanoparticles and improve light absorption intensity in the visible light region; ii） GR scaffolds act as an electron reservoir to trap and shuttle the electrons photogenerated from CdS semiconductor under the visible light illumination; iii） the introduction of GR enhances the adsorption capacity of GR-CdS nanocomposites toward the substrates, aromatic nitro compounds. The synergistic effect of these factors should account for the photoactivity advancement of GR-CdS nanocomposites toward the probe reactions. Furthermore, because the photogenerated holes in the system are trapped by the quenching agent ammonium oxalate, the as-obtained GR-CdS photocataiyst is stable during the photocatalytic reduction reactions. A reasonable model has also been proposed to illustrate the reaction mechanism.

ZIF-67 derived CoSx/NC catalysts for selective reduction of nitro compounds

Transition metal sulfides(TMSs)-based materials have been extensively investigated as effective non-noble catalysts for various applications.However,the exploration of TMSs-based catalysts for hydrogenation of nitro compounds is limited.Herein,CoSx/NC catalysts were prepared by solvothermal sulfurization of ZIF-67,followed by high-temperature annealing(300–600℃)under NH3 atmosphere.It was found that the structures and compositions of the as-prepared CoSx/NC can be readily tuned by varying the annealing temperature.Particularly,CoSx/NC-500,which possesses higher degree of S defects and larger specific surface areas,can achieve high conversion,selectivity and stability for catalytic reduction of nitro compounds into amines under mild reaction conditions.

Selective Reduction of α,β-Unsaturated Amides with NaBH_4/BiCl_3 System

?β-Unsaturated amides with various substitution pattems at the carbon-carbon double And and nitrogen atom can be reduced to the corresponding saturated amides with high selectivity and yields with NaBH4/BiCl3 system.

SELECTIVE REDUCTION OF 3,17—DIOXO—STEROIDS TO 17β-HYDROXY-3-OXO-STEROIDS

11β-Hydroxy-androst-4-en-3,17-dione(1a),androst-4,9(11)-dien-3,17- dione-(2a),androst-4-en-3,11,17-trione(3a),11α-methoxy-androst-4-en-3,17-dione (4a)and 11β-metboxy-androst-4-en-3,17-dione(Sa)were selectively reduced to the corresponding 17β-OH derivatives in one step without the protection of 3- oxo(and 11-oxo,in the case of 3a)group with the yields ranging from 65% to 79%.In these reactions,the ditute NaBH_4(or KBH_4)solution in methanol was added dropwise to the 3,17-dioxo-steroids solution in methanol-benzene-pyridine, while the reaction mixtures were well stirred at -5～5℃.Acid(such as gtacial acetic acid)was added to quench the reactions.The resulted testosterone derivatives(1b～5b)were purified by flash chromatography. This method appties to the reduction of other 3,17-dioxo-steroids such as△~1 -3-one,△^(1.4)-3-one,△^(4.6)-3-one,△^(1.4.6)-3-one containing compounds.

The Selective Reduction of 4-Propylthio-2-nitroaniline with CO Using Ru_3(CO)_(12)/PEDPA Complex as Catalyst

The Ru3(CO)12/PEDPA complex was firstly applied in the CO selective reduction of 4-propylthio-2-mitroaniline. The effects of reaction temperature, the pressure of CO and concentration of catalyst on the reduction were investigated. Under the optimum conditions of T=140℃, Pco=5.0MPa and substrate/catalyst = 300 (molar ratio), the conversion and selectivity were 70% and 98%, respectively. After simple phase separation, the catalyst could be recycled.

The Novel Selective Reduction of the C-C Triple Bond

A novel reduction system is reported here in which the compounds with terminal C-C triple bond and disubstituted C-C triple bond react with NaBH4/Pd(PPh3)(4) in a base condition and only terminal C-C triple bond is reduced.

A STUDY ON THE SELECTIVE REDUCTION OF AROMATIC AMIDE WITH LiAlH_4

In the synthesis of l-phenyl-5-substituted amino-4-pyrazole N-alkyl amide, it was found for the first time that one of the two aromatic amido groups in the molecule of 1-phenyl-5-benzoyl amino-4-pyrazole N-alkyl amide was reduced selectively by LiAlH_4. new conclusion was drawn after several experiments have been done that ortho-amino(or substituted amino)aryl amide or the aryl amide with its ortho substituent which can be reduced into an amino group(or substituted amino group)can not be reduced by LiAlH_4. It was further rationalized by quantum chemical calculation.

Plasma-catalytic Selective Reduction of NO with C_(2)H_(4)in the Presence of Excess Oxygen

This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250 °C in the presence of excess oxygen by using a one-stage plasma-over-catalyst (POC) reactor. With the reactant gas mixture of 530 ppm NO, 650 ppm C2H4, 5.8% O2 in N2 and GHSV = 12000 h-1, the pure catalytic, pure plasma-induced (discharges over fused silica pellets) and plasma- catalytic (in the POC reactor) NOx conversion are 39%, 1.5% and 79%, respectively. The in-situ optical emission spectra of the reactive systems imply some short-lived active species formed from plasma-induced and plasma-catalytic processes may be responsible to the observed synergistic effects in this one-stage POC system.

Molecular engineering binuclear copper catalysts for selective CO_(2) reduction to C_(2) products

Molecular copper catalysts serve as exemplary models for correlating the structure-reaction-mechanism relationship in the electrochemical CO_(2) reduction(eCO_(2)R),owing to their adaptable environments surrounding the copper metal centres.This investigation,employing density functional theory calculations,focuses on a novel family of binuclear Cu molecular catalysts.The modulation of their coordination configuration through the introduction of organic groups aims to assess their efficacy in converting CO_(2) to C_(2)products.Our findings highlight the crucial role of chemical valence state in shaping the characteristics of binuclear Cu catalysts,consequently influencing the eCO_(2)R behaviour,Notably,the Cu(Ⅱ)Cu(Ⅱ)macrocycle catalyst exhibits enhanced suppression of the hydrogen evolution reaction(HER),facilitating proton trans fer and the eCO_(2)R process.Fu rthermore,we explo re the impact of diverse electro n-withdrawing and electron-donating groups coordinated to the macrocycle(R=-F,-H,and-OCH_3)on the electron distribution in the molecular catalysts.Strategic placement of-OCH_3 groups in the macrocycles leads to a favourable oxidation state of the Cu centres and subsequent C-C coupling to form C_(2) products.This research provides fundamental insights into the design and optimization of binuclear Cu molecular catalysts for the electrochemical conversion of CO_(2) to value-added C_(2) products.

Fe-Mn/Al_2O_3 catalysts for low temperature selective catalytic reduction of NO with NH_3

A series of Fe‐Mn/Al2O3 catalysts were prepared and studied for low temperature selective catalytic reduction （SCR） of NO with NH3 in a fixed‐bed reactor. The effects of Fe and Mn on NO conversion and the deactivation of the catalysts were studied. N2 adsorption‐desorption, X‐ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, H2 temperature‐programmed reduction, NH3 temperature‐programmed desorption, X‐ray photoelectron spectroscopy （XPS）, thermal gravimetric analysis and Fourier transform infrared spectroscopy were used to character‐ize the catalysts. The 8Fe‐8Mn/Al2O3 catalyst gave 99%of NO conversion at 150？？ and more than 92.6%NO conversion was obtained in a wide low temperature range of 90–210？？. XPS analysis demonstrated that the Fe3＋was the main iron valence state on the catalyst surface and the addition of Mn increased the accumulation of Fe on the surface. The higher specific surface area, enhanced dispersion of amorphous Fe and Mn, improved reduction properties and surface acidity, lower binding energy, higher Mn4＋/Mn3＋ratio and more adsorbed oxygen species resulted in higher NO conversion for the 8Fe‐8Mn/Al2O3 catalyst. In addition, the SCR activity of the 8Fe‐8Mn/Al2O3 cata‐lyst was only slightly decreased in the presence of H2O and SO2, which indicated that the catalyst had better tolerance to H2O and SO2. The reaction temperature was crucial for the SO2 resistance of catalyst and the decrease of catalytic activity caused by SO2 was mainly due to the sulfate salts formed on the catalyst.

Performances of CuSO_4/TiO_2 catalysts in selective catalytic reduction of NO_x by NH_3

A series of CuSO4/TiO2 catalysts were prepared using a wet impregnation method.The activity of each sample in the selective catalytic reduction of NO by NH3（NH3-SCR） was determined.The effects of SO2 and H2O,and their combined effect,on the activity were examined at 340 ℃ for 24 h.The catalysts were characterized using N2 adsorption-desorption,X-ray diffraction,X-ray photoelectron spectroscopy,temperature-programmed reduction of H2（H2-TPR）,temperature-programmed desorption of NH3（NH3-TPD）,and in situ diffuse-reflectance infrared Fourier-transform spectroscopy（DRIFTS）.The CuSO4/TiO2 catalysts had good activities,with low production of N2O above 340 ℃.SO2 or a combination of SO2 and H2O had little effect on the activity,and H2O caused only a slight decrease in activity during the experimental period.The NH3-TPD and H2-TPR results showed that CuSO4 increased the amounts of acid sites and adsorbed oxygen on the catalyst.In situ DRIFTS showed that the NH3-SCR reaction on the CuSO4/TiO2 catalysts followed an Eley-Rideal mechanism.The reaction of gaseous NO with NH3 adsorbed on Lewis acid sites to form N2 and H2O could be the main reaction pathway,and oxygen adsorption might favor this process.

Promotional effects of Zr on K^+-poisoning resistance of CeTiO_x catalyst for selective catalytic reductionof NO_x with NH_3

CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 （NH3‐SCR）. Various amounts of KNO3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K＋‐poisoning resistance of the CeTiOx catalyst. The NH3‐SCR performance of the catalysts showed that the NOx removal activity of the Zr‐modified catalyst after poisoning was better than that of the CeTiOx catalyst. Brunau‐er‐Emmett‐Teller data indicated that the Zr‐containing catalyst had a larger specific surface area and pore volume both before and after K＋poisoning. X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO3 was inhibited. The Ce 3d X‐ray photoelectron spectra showed that the Ce3＋/Ce4＋ratio of CeZrTiOx decreased more slowly than that of CeTiOx with increasing K＋loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH3‐SCR performance; the temperature‐programmed desorption of NH3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K＋‐poisoning resistance of the CeTiOx catalyst.

FeCl_3·6H_2O-catalyzed selective reduction of allylic halides to alkenes with concomitant oxidation of benzylic alcohols to aldehydes

Iron-catalyzed direct reduction of allylic halides with benzylic alcohol was achieved,providing a new,simple,and efficient method for conducting highly regioselective hydrodehalogenation.This method not only features a readily available reductant,an inexpensive catalyst,simple manipulation,and good tolerance of functional groups including nitriles,nitro,esters,and methoxyl groups,it also has mild reaction conditions and shows complete regioselectivity in that only halides sited at the allylic position are reduced.Alternatively,this method can be applied in the selective transformation of benzylic alcohols to aromatic aldehydes without overoxidation to carboxylic acids.

Synthesis of a chabazite-supported copper catalyst with full mesopores for selective catalytic reduction of nitrogen oxides at low temperature

A series of meso‐microporous copper‐supporting chabazite molecular sieve（CuSAPO‐34） catalysts with excellent performance in low‐temperature ammonia selective catalytic reduction（NH3‐SCR）have been synthesized via a one‐pot hydrothermal crystallization method. The physicochemical properties of the catalysts were characterized by scanning electron microscopy, transmission electron microscopy, N2 adsorption‐desorption measurements, X‐ray diffraction, 27 Al magic angle spinning nuclear magnetic resonance, diffuse reflectance ultraviolet‐visible spectroscopy, inductively coupled plasma‐atomic emission spectroscopy, X‐ray photoelectron spectroscopy, temperature‐programmed reduction measurements, and electron paramagnetic resonance analysis. The formation of micro‐mesopores in the Cu‐SAPO‐34 catalysts decreases diffusion resistance and greatly improves the accessibility of reactants to catalytic active sites. The main active sites for NH3‐SCR reaction are the isolated Cu^2＋ species displaced into the ellipsoidal cavity of the Cu‐SAPO‐34 catalysts.

Promotional effect of H_3PO_4 on ceria catalyst for selective catalytic reduction of NO by NH_3

A series of H3PO4-modified CeO2 samples were prepared by impregnation of CeO2 with H3PO4solution,and evaluated for the selective catalytic reduction of NOx by NH3.The samples were characterized by X-ray diffraction,N2 adsorption-desorption,infrared spectroscopy,Raman spectroscopy,X-ray photoelectron spectroscopy,temperature-programmed desorption of NH3,and temperature-programmed reduction of H2.The results showed that more than 80%NO conversion was achieved in the temperature range 250-550℃ over the H3PO4-CeO2 catalyst.The enhanced catalytic performance could be ascribed to the increase in acidic strength,especially Bronsted acidity,and reduction in redox properties of the CeO2 after H3PO4 modification.

Resistance to SO_2 poisoning of V_2O_5/TiO_2-PILC catalyst for the selective catalytic reduction of NO by NH_3

A titania pillared interlayered clay（Ti-PILC） supported vanadia catalyst（V2O5/TiO2-PILC） was prepared by wet impregnation for the selective catalytic reduction（SCR） of NO with ammonia. Compared to the traditional V2O5/TiO2 and V2O5-MoO3/TiO2 catalysts, the V2O5/TiO2-PILC catalyst exhibited a higher activity and better SO2 and H2O resistance in the NH3-SCR reaction. Characterization using TPD, in situ DRIFT and XPS showed that surface sulfate and/or sulfite species and ionic SO4^（2-）species were formed on the catalyst in the presence of SO2. The ionic SO4^（2-） species on the catalyst surface was one reason for deactivation of the catalyst in SCR. The formation of the ionic SO4^（2-） species was correlated with the amount of surface adsorbed oxygen species. Less adsorbed oxygen species gave less ionic SO4^（2-） species on the catalyst.

Kinetic Model and Simulation of Promoted Selective Non-catalytic Reduction by Sodium Carbonate

Abstract The detailed kinetic model of selective non-catalytic reduction （SNCR） of nitric oxide, including so-dium species reactions, was deyeloped on the basis of recent studies on thermal DeNOx mechanism, NOxOUTmechanism and promotion mechanism of Na2CO3. The model was validated by comparison with several experi-mental findings, thus providing an effective tool for the primary and promoted SNCR process simulation. Experimental and simulated results show part-per-million level of sodium carbonate enhances NO removal efficiency andextend the effective SNCR temperature range in comparison with use of a nitrogen agent alone. The kinetic modeling, sensitivity and rate-of-production analysis suggest that the performance improvement can be explained as ho-mogeneous sodium species reactions producing more reactive OH radicals. The net result of sodium species reac-tions is conversion of H2O and inactive HO2 radicals into reactive OH radicals, i.e. H2O＋HO2=3OH, which enhances the SNCR performance of nitrogen agents by mainly increasing the production rate of NH2 radicals. More-over, N2O and CO are eliminated diversely via the reactions Na＋N20=NaO＋N2, NaO＋CO=Na＋CO2 andNaO2＋CO =NaO＋CO2, in.the pro.moted SNCR process, especially in the NOxOUT process.