Effect of samarium doping on the activity and sulfur resistance of Ce/MnFeO_(x) catalyst for low-temperature selective catalytic reduction of NO_(x) by ammonia

The self-made MnFeO_(x) catalysts doped with cerium and samarium were prepared by impregnation method for low-temperature selective catalytic reduction(SCR)by NH3.In this work,the surface properties of the series of MnFe-based catalysts were studied.The results indicate Sm-modified catalyst have superior low-temperature SCR activity;NO_(x) conversion maintained at nearby to 100%at 90℃ to 240℃.In addition,The N_(2) selectivity of Sm doping remains above 80%in the range of 60℃ to 150℃.In SO_(2) poisoning test,the NO_(x) conversion can be remained>90%after 10 h of reaction.The XPS,NH_(3)-TPD and H_(2)-TPR results show the catalyst with Sm doping enhances the acid sites and oxidation catalytic sites of mixed oxides serves for improving oxygen vacancies and transfer electrons.In situ diffuse reflaxions infrared Fourier transformations spectroscopy(DRIFTS)results show that NO_(x) is more easily adsorbed on the surface after Sm doping,which provided favorable conditions for the NH_(3)-SCR reaction to proceed.The reaction at the catalyst surface will follow the L-H reaction mechanism by transient reaction test.

Enhancement in the Hg^(0) oxidation efficiency and sulfur resistance of CuCl_(2)-modified MnO_(x)-CeO_(x) nanorod catalysts

In this study,a series of CuCl_(2)-modified MnO_(x)-CeO_(x)nanorods were synthesized for the oxidation of Hg^(0).The addition of CuCl_(2)resulted in an enhancement in the catalyst’s Hg^(0)oxidation ability,and Hg^(0)oxidation efficiency reached>97%from 150 to 250°C.In the MnO_(x)-CeO_(x)catalysts,Mn^(4+)played the role of the active species for Hg^(0)oxidization,but in the CuCl_(2)-doped catalysts Cl−also contributed to Hg^(0)oxidation,conferring the superior performance of these samples.The introduction of SO_(2) led to a decrease in the availability of Mn^(4+),and the Hg^(0)oxidation efficiency of MnO_(x)-CeO_(x)decreased from about 100%to about 78%.By contrast,CuCl_(2)-promoted samples maintained a Hg^(0)oxidation efficiency of about 100%during the SO_(2) deactivation cycle due to the high reactivity of Cl−.

Denitrification performance and sulfur resistance mechanism of Sm-Mn catalyst for low temperature NH_(3)-SCR

MnO_(x)and Sm–Mn catalysts were prepared with the coprecipitation method,and they showed excellent activities and sulfur resistances for the selective catalytic reduction of NO_(x)by NH_(3)between 50 and 300℃in the presence of excess oxygen.0.10Sm–Mn catalyst indicated better catalytic activity and sulfur resistance.Additionally,the Sm doping led to multi-aspect impacts on the phases,morphology structures,gas adsorption,reactions process,and specific surface areas.Therefore,it significantly enhances the NO conversion,N_(2)selectivity,and sulfur resistance.Based on various experimental characterization results,the reaction mechanism of catalysts and the effect of SO_(2)on the reaction process about the catalysts were extensively explored.For 0.10Sm–Mn catalyst,manganese sulfate and sulfur ammonium cannot be generated broadly under the influence of SO_(2)and the amount of surface adsorbed oxygen.The Bronsted acid sites strengthen significantly due to the addition of SO_(2),enhancing the sulfur resistance of the 0.10Sm–Mn catalyst.

SULFUR-RESISTANT BIMETALLIC NOBLE METAL CATALYSTS FOR AROMATIC HYDROGENATION OF DIESEL FUEL

Y zeolite supporting noble metal catalysts, as the important industrial catalysts for aromatics hydrogenation, have received increasing attention in recent years. Pd M/Y bimetallic catalysts, where M is non noble metal element, were prepared to investigate the effects of the addition of a second metal. Pd M/Y catalysts were evaluated under the following conditions: H 2 pressure 4.2 MPa, MHSV 4.0 h -1 , sulfur content in feed 3000 μg/g. The microreactor results indicated that the second metal remarkably affects the hydrogenation activity of Pd/Y catalysts. Among them, Cr and W improve the sulfur resistance of Pd/Y, but La, Mn, Mo and Ag make the sulfur resistance worse and the second metals have no evident influence on product selectivity and acidic properties of the catalysts.

Theoretical Study on the Catalytic Activity and Sulfur Resistibility of Amorphous Alloy Ni-B-P

In the present paper, one hundred cluster models NinBP （n = 1-6） have been designed and studied by density functional theory （DFT） to get an insight into the local structure, catalytic properties and sulfur resistibility of amorphous alloy Ni-B-P. The configurations in triplet state are found more stable than those in the singlet state. It is found： that as the content of Ni in the clusters increases, the value of Fermi level in clusters fluctuated, which shows that the content of Ni can influence the Fermi level to a certain extent. Based on the Fermi level and DOS, we consider the activity of catalyst in hydrogenation reaction is the best in cluster Ni3BP. On the basis of the charge of clusters NinBP （n = 1 -6）, we conclude the amorphous alloy Ni-B-P with high Ni content has better sulfur resistibility and the best hydrogenation activity, strong sulfur resistibility appears in clusters Ni3BP, and the amorphous alloy Ni60B20P20 with similar proportion is expected to prepare in the future.

Synthesis of N-type semiconductor diamonds with sulfur,boron co-doping in FeNiMnCo-C system at high pressure and high temperature

A series of diamonds with boron and sulfur co-doping were synthesized in the Fe Ni Mn Co-C system by temperature gradient growth（TGG） under high pressure and high temperature（HPHT）. Because of differences in additives, the resulting diamond crystals were colorless, blue-black, or yellow. Their morphologies were slab, tower, or minaret-like. Analysis of the x-ray photoelectron spectra（XPS） of these diamonds shows the presence of B, S, and N in samples from which N was not eliminated. But only the B dopant was assuredly incorporated in the samples from which N was eliminated. Resistivity and Hall mobility were 8.510 Ω·cm and 760.870 cm^2/V·s, respectively, for a P-type diamond sample from which nitrogen was eliminated. Correspondingly, resistivity and Hall mobility were 4.211×10^5 Ω·cm and 76.300 cmΩ2/V·s for an N-type diamond sample from which nitrogen was not eliminated. Large N-type diamonds of type Ib with B–S doping were acquired.

A confined growth strategy to construct 3DOM SiO_(2) nanoreactor insitu embedded Co_(3)O_(4) nanoparticles catalyst for the catalytic combustion of VOCs:Superior H_(2)O and SO_(2) resistance

SO_(2)poisoning is a common problem in the catalytic combustion of volatile organic compounds(VOCs).In this work,we took three-dimensionally ordered macroporous and mesoporous(3DOM)SiO_(2)as the nanoreactor to protect active sites from SO_(2)erosion in the catalytic combustion of benzene.Simultaneously,the confined growth of metal active nanoparticles in the multi-stage pore is also full of challenges.And we successfully confined Co_(3)O_(4)nanoparticles(NPs)in macroporous and mesoporous channels.Interestingly,the precursors’growth in the pore was controlled and nanoreactors with different pore sizes were prepared by adjusting the loading amount and preparation methods.It is discovered that the Co_(3)O_(4)NPs confined in 3DOM SiO_(2)nanoreactor showed superior sulfur and water resistance.Density functional theory(DFT)calculations verified that the Co-Si catalyst had high SO_(2)adsorption energy(-0.48 eV),which illustrated that SO_(2)was hard to attach to the surface of the Co-Si catalyst.The SiO_(2)nanoreactor had low SO_(2)adsorption energy(-5.15 eV),which indicated that SO_(2)was easily absorbed on SiO_(2)nanoreactor.This illustrated that the SiO_(2)nanoreactor could protect effectively active sites from SO_(2)erosion.

Propene and CO oxidation on Pt/Ce-Zr-SO_4^(2-) diesel oxidation catalysts:Effect of sulfate on activity and stability

Platinum/cerium-zirconium-sulfate（Pt/Ce-Zr-SO_4^（2-）） catalysts were prepared by wetness impregnation.Catalytic activities were evaluated from the combustion of propene and CO.Sulfate（SO_4^（2-））addition improved the catalytic activity significantly.When using Pt/Ce-Zr-SO_4^（2-） with 10 wt%SO_4^（2-）,the temperature for 90%conversion of propene and CO decreased by 75℃ compared with Pt/Ce-Zr.The conversion exceeded 95%at 240℃ even after 0.02%sulfur dioxide poisoning for 20 h.Temperature-programmed desorption of CO and X-ray photoelectron spectroscopy analyses revealed an improvement in Pt dispersion onto the Ce-Zr-SO_4^（2-） support,and the increased number of Pt particles built up more Pt^（-）-（SO_4^（2-））^（-） couples,which resulted in excellent activity.The increased total acidity and new Bronsted acid sites on the surface provided the Pt/Ce-Zr-SO_4^（2-） with good sulfur resistance.

Pd Pt VO_(x)/CeO_(2)-ZrO_(2):Highly efficient catalysts with good sulfur dioxide-poisoning reversibility for the oxidative removal of ethylbenzene

The PdPtVO_(x)/CeO_(2)-ZrO_(2)(PdPtVO_(x)/CZO)catalysts were obtained by using different approaches,and their physical and chemical properties were determined by various techniques.Catalytic activities of these materials in the presence of H_(2)O or SO_(2)were evaluated for the oxidation of ethylbenzene(EB).The PdPtVO_(x)/CZO sample exhibited high catalytic activity,good hydrothermal stability,and reversible sulfur dioxide-poisoning performance,over which the specific reaction rate at 160℃,turnover frequency at 160℃(TOF_(Pd or Pt)),and apparent activation energy were 72.6 mmol/(g_(Pt)·sec)or 124.2 mmol/(g_(Pd)·sec),14.2 sec^(-1)(TOF_(Pt))or 13.1 sec^(-1)(TOF_(Pd)),and 58 k J/mol,respectively.The large EB adsorption capacity,good reducibility,and strong acidity contributed to the good catalytic performance of PdPtVO_(x)/CZO.Catalytic activity of PdPtVO_(x)/CZO decreased when 50 ppm SO_(2)or(1.0 vol.%H_(2)O+50 ppm SO_(2))was added to the feedstock,but was gradually restored to its initial level after the SO_(2)was cut off.The good reversible sulfur dioxide-resistant performance of PdPtVO_(x)/CZO was associated with the facts:(i)the introduction of SO_(2)leads to an increase in surface acidity;(ii)V can adsorb and activate SO_(2),thus accelerating formation of the SO_(x)^(2-)(x=3 or 4)species at the V and CZO sites,weakening the adsorption of sulfur species at the PdPt active sites,and hence protecting the PdPt active sites to be not poisoned by SO_(2).EB oxidation over PdPtVO_(x)/CZO might take place via the route of EB→styrene→phenyl methyl ketone→benzaldehyde→benzoic acid→maleic anhydride→CO_(2)and H_(2)O.

Promoting Effects of Pt on the Catalytic Performance of Supported NiB Amorphous Alloy Catalysts for Benzene Hydrogenation

A support(denoted AM) was prepared using pseudo-boehmite and mordenite.Ni-B and NiPtB amorphous catalysts were prepared on the support by the impregnation method followed by chemical reduction with a KBH4 solution.And the catalysts were characterized by X-ray diffraction(XRD),environment scanning electron microscope(ESEM),inductively coupled plasma(ICP),H2-temperature programmed reduction(H2-TPR),differential thermal analysis(DTA),and BET.Benzene hydrogenation was used as a probe reaction to evaluate the effect of addition of small quantities of Pt on the NiB/AM catalyst.The results show that Pt can promote the reduction of NiO and the formation of active sites,leading to smaller catalyst particles and better dispersion of active metal particles on the support.The catalytic activity,sulfur resistance and thermal stability were remarkably improved by Pt doping of the NiB/AM catalyst.

Study on Corrosion Protection Method of Reinjection Water Treatment System in a Natural Gas Processing Plant

The research investigated the corrosion of the reinjection water system to ensure the safe production of the system.By analyzing the composition of the methanol-containing wastewater,the corrosion status of the injection water system was studied by the on-site materials 20#steel,Q235B steel and L316 steel for that the methanol-containing wastewater of a natural gas processing plant in northern Shaanxi had high acidity,Cl-and sulfide contents,salinity and corrosion.Then the grey system theory modeling software 3.0 was used to study the influence degree of various corrosion factors on the corrosion rate and depth of Q235B steel.The most important factors were determined,and countermeasures against corrosion were proposed.The results showed that L316 steel was more resistant to corrosion,and the corrosion rate was 0.0015 mm/a,which was less than the national standard(0.0760 mm/a).The maximum corrosion depth was 47.63μm,which was the lowest among the three materials.The corrosion rate and depth were the parent factors.Among the four factors of sulfide,Cl-,salinity and pH,grey relational degrees of sulfide were 0.75 and 0.80,respectively,which was the most important factor causing corrosion;using sulfur corrosion inhibitor protection method,TS-792C was selected by electrochemical method from three corrosion inhibitors.The impedance data simulation software ZSimpWin was used to simulate the equivalent circuit diagram,and the impedance of Q235B steel was the largest.The corrosion inhibition rate was up to 90.26%when corrosion rate was 0.0130 mm/a under the fitting of Tafel polarization curve,with the best anti-sulfur effect.At 80℃and a sulfide content of 300 mg/L,the corrosion rate of Q235B steel was less than 0.0760 mm/a.When the added amount was 100 mg/L,the corrosion current density and corrosion rate of the reinjection sewage was 0.462 mA/cm 2 and 0.0505 mm/a,both at the lowest values and with good temperature and sulfur resistance.

High CO methanation activity on zirconia-supported molybdenum sulfide catalyst

In this study, different methods were used to prepare MoO3/ZrO2 catalysts for sulfur resistant methanation reaction. It was found that MoO3/ZrO2 catalyst prepared by one-step co-precipitation method achieved high methanation performance. CO conversion could reach up to 90% on 25 wt% MoO3/ZrO2 catalyst, much higher than that on the conventional 25 wt% MoO3/Al2O3 catalyst. The Mo-based catalysts were characterized by XRF, XRD, Raman, BET, TEM and H2-TPR etc. It was found that MoO3 particles were highly dispersed on ZrO2 support for 25 wt% MoO3/ZrO2 catalyst prepared at 65-85℃ because of its relatively larger pore size, which contributed to a high CO conversion. Meanwhile, when MoO3 loading exceeded the monolayer coverage, the formed crystalline MoO3 and ZrM020g might block the micropores of the catalyst and make the methanation activity declined. These results are useful for preparing highly efficient catalyst for CO methanation process.

Fabrication of wide temperature lanthanum and cerium doped Cu/TNU-9 catalyst with excellent NH_(3)-SCR performance and outstanding SO_(2)+H_(2)O tolerance

The effects of La on the catalytic performance,SO_(2)and H2O resistance of Cu-Ce/TNU-9 catalyst were studied in the selective catalytic reduction of NO_(x)via ammonia(NH_(3)-SCR).The results show that the La doped Ce-Cu/TNU-9(CCL/T9)catalyst exhibits better SCR performance than Ce-Cu/TNU-9(CC/T9)and Cu/TNU-9(C/T9)in the wide temperature window(200-450℃)due to La benefiting from enhancing Cu^(+)+Ce^(4+)?Cu^(2+)-+Ce^(3+)to facilitate the electron transfer,which further accelerates the oxidation of NO into NO_(2)that leads to the"Fast SCR".The La can also enhance the surface acidic,redox property and is beneficial to the formation of oxygen vacancy.Meanwhile,the larger co ntent of Ce^(3+) can produce oxygen vacancy,resulting in rising SCR activity.The CCL/T9 has outstanding water and SO_(2) resistance,which may be due to the adso rbed S on the surface of these catalysts mainly existing in the form of a small amount of sulfate and sulfite,the decomposition of ammonium bisulphite under high temperature and the hydrophobicity of TNU-9 zeolite.

Promoting effect of vanadium on catalytic activity of Pt/Ce–Zr–O diesel oxidation catalysts

A series of Pt-V/Ce-Zr-O diesel oxidation catalysts was prepared using the impregnation method. The catalytic activity and sulfur resistance of Pt-V/Ce-Zr-O were investigated in the presence of simulated diesel exhaust. The effect of vanadium on the structure and redox properties of the catalysts was also investigated using the Brunauer-Emmett-Teller method,X-ray diffraction, H2temperature-programmed reduction, CO temperature-programmed desorption, X-ray photoelectron spectroscopy, and Energy Dispersive Spectroscopy. Results showed that the Pt particles were well dispersed on the Ce-Zr-O carrier through the vanadium isolation effect, which significantly improved the oxidation activity toward CO and hydrocarbons. An electron-withdrawing phenomenon occurred from V to Pt, resulting in an increase in the metallic nature of platinum, which was beneficial to hydrocarbon molecular activation.

Effects of SO2 and H2O on low-temperature NO conversion over F-V2O5-WO3/TiO2 catalysts

F-V2 O5-WO3/Ti02 catalysts were prepared by the impregnation method.As the content of F ions increased from 0.00 to 0.35 wt.%,the NO conversion of F-V2 O5-WO3/TiO2 catalysts initially increased and then decreased.The 0.2 F-V2 O5-WO3/TiO2 catalyst(0.2 wt.%F ion)exhibited the best denitration(De-NOx)performance,with more than 95%NO conversion in the temperature range 160-360℃,and 99.0%N2 selectivity between 110 and 280℃.The addition of an appropriate amount of F ions eroded the surface morphology of the catalyst and reduced its grain size,thus enhancing the NO conversion at low temperature as well as the sulfur and water resistance of the V2 O5-WO3/Ti02 catalyst.After selective catalytic reduction(SCR)reaction in a gas flow containing SO2 and H2 O,the number of NH3 adsorption sites,active component content,specific surface area and pore volume decreased to different degrees.Ammonium sulfate species deposited on the catalyst surface,which blocked part of the active sites and reduced the NO conversion performance of the catalyst.On-line thermal regeneration could not completely recover the catalyst activity,although it prolonged the cumulative life of the catalyst.In addition,a mechanism for the effects of S02 and H2 O on catalyst NO conversion was proposed.

Cobalt doped Fe-Mn@CNTs catalysts with highly stability for lowtemperature selective catalytic reduction of NO_(x)

In this paper,we report the fabrication of cobalt-doped de-NO_(x)catalyst by pyrolyzing an analogous metal-organic framework-74(MOF-74)containing Fe&Mn.The resulted catalyst exhibits distinctive microstructures of manganese,cobalt,and iron immobilized on N-doped carbon nanotubes(CNTs).It is found through experiments that the trimetallic catalyst Fe_(2)Mn_(1)Co_(0.5)/CNTs-50 has the best NH_(3)-selective catalytic reduction(SCR)performance.The Fe_(2)Mn_(1)Co_(0.5)/CNTs-50 exhibited excellent water and sulfur resistance and good stability under the harsh gas environment of 250℃ and/or 170℃,NO=NH_(3)=1,000 ppm,8 vol.%O_(2),20 vol.%H2O,1,000 ppm SO_(2),and gas hourly space velocity(GHSV)=75,000 h^(-1).The de-NO_(x)conversion was maintained about 55%and 25%after 192 h.The water and sulfur resistance performance were much higher than commercial vanadium series catalyst.The highly water and sulfur resistance performance may be attributed to the unique core-shell microstructure and the synergistic effect of manganese,cobalt,and iron which helps reduce the formation for byproducts(NH_(4)HSO_(4)).This study may promote to explore the development of a high stability catalyst for low-temperature selective catalytic reduction of NO_(x)with NH_(3).

Effects of SO2 on the low temperature selective catalytic reduction of NO by NH3 over CeO2-V2O5-WO3/TiO2 catalysts

The CeO2-V2O5-WO3/TiO2 （CeO2-VWT） catalysts were prepared by one-step and two-step impregnation methods. The effects of different loading of CeO2 and different preparation methods on De-NOx activity of catalysts had been investigated. CeO2 helped to improve the De-NOx activity and sulfur resistance. The optimal loading of CeO2 was 3% with the De-NOx efficiency reached 89.9% at 140℃. The results showed that the De-NOx activity of 3% CeO2-VWT catalysts by one-step method was the same as two-step method basically and reached the level of industrial applications, the N2 selectivity of catalysts was more than 99.2% between 110℃ and 320℃. In addition, CeO2 promoted the oxidation of NO to NO2, which adsorbed on the Lewis acid site （V5＋-O） to form V5＋-NO3 and inspired the fast SCR reaction. Not only the thermal stability but also the De-NOx activity of catalysts decreased with excess CeO2 competed with V2O5. Characterizations of catalysts were carried out by XRF, BET, XRD, TG and FT-IR. BET showed that the specific surface area of catalysts decreased with the loading of CeO2 increased, the active components content and specific surface area of catalysts decreased slightly after entering SO2. Ammonium sulfate species were formed in poisoned catalyst which had been investigated by XRF, BET, TG and FT-IR. The largest loss rate of weight fraction was 0.024%.℃-1 at 380℃ 390℃, which was in accordance with the decomposition temperature of NH4HSO4 and （NH4）2SO4,