Mn Promoter Research Articles

Pore size effects on Ru/SiO2 catalysts with Mn and Zr promoters for Fischer–Tropsch synthesis

The effects of pore size on Ru/SiO2 catalyst performance were investigated for Fischer–Tropsch synthesis under the conditions of 503K, 20bar and 1800h−1. Ru/SiO2 with 10nm pore size catalyst showed higher catalytic activity than Ru/SiO2 catalysts with 3, 6 and 30nm pore sizes. The 10nm pore size, Ru/SiO2 catalyst exhibited uniform pore diameter, an increased surface concentration of active Ru metals, and the increased dispersion of Ru on the surface compared to the other pore diameters. Deactivation was clearly observed for all Ru/SiO2 catalysts during the reaction. The addition of small amounts of Zr and Mn (1:30, Zr or Mn:Si) improved catalytic activity and stability for Fischer–Tropsch synthesis. The deactivation rate of Ru/Zr/Q10 was about 21% at 51h time on stream and this rate was much lower than Ru/Q10 (57%). Ru/Mn/Q10 showed higher catalytic activity than Ru/Q10 and Ru/Zr/Q10, and its deactivation rate was much lower ~9% after 51h time on stream. The small amount of Mn added to the Ru/SiO2 increased the concentration of active Ru metals and enhanced their dispersion on the support surface.

Ethanol synthesis from syngas on Mn- and Fe-promoted Rh/γ-Al2O3

Abstract The catalytic hydrogenation of CO was studied over Mn- and/or Fe-promoted Rh/γ-Al2O3 catalysts. The catalysts were characterized by means of XRD, BET, H2-TPR·H2-TPD, XPS and DRIFTS. CO hydrogenation results showed that the doubly Mn- and Fe-promoted Rh/γ-Al2O3 catalysts exhibited superior catalytic activity and better ethanol selectivity. The DRIFTS results showed that Mn promoter stabilized the adsorbed CO on Rh+ and Fe stabilized adsorbed CO on Rh+ and Rh0, especially Rh0. The fact that doubly Mn- and Fe-promoted Rh/γ-Al2O3 owned more (Rhx0–Rhy+)–O–Fe3+·(Fe2+) active species was proposed to be a crucial factor accounting for its higher ethanol selectivity.

Effect of Mn and Pb Promoters on the Performance of Cu/ZnO-Catalyst in CO<sub>2</sub> Hydrogenation to Methanol

The influences of Mn or Pb promoters on the catalytic performance of Cu/ZnO-SBA-15 catalyst in the methanol synthesis from CO2 hydrogenation were studied. The catalytic performances of the prepared catalysts were investigated in a stirred high pressure reactor under conditions of T = 483K, P = 2.25 MPa, and H2:CO2 = 3:1 (volume ratio). The experimental results showed that the promoted catalysts exhibited higher catalytic performance. The Mn promoted catalyst resulted in 36% of CO2 conversion and 67% of methanol selectivity, whereas the unpromoted catalyst showed 26% of CO2 conversion and 58% of methanol selectivity.

High temperature water gas shift reaction over promoted iron based catalysts prepared by pyrolysis method

In this work the effects of different promoters (Cr, Al, Mn, Ce, Ni, Co and Cu) on the structural and catalytic properties of Nanocrystalline iron based catalysts for high temperature water gas shift reaction were investigated. The catalysts were prepared in active phase (Fe3O4) via a facile direct synthesis routs without any additive and characterized using X-ray diffraction (XRD), N2 adsorption (BET), temperature-programmed reduction (TPR), transmission and scanning electron microscopies (TEM,SEM) techniques. The obtained results indicated that synergic effect of Mn and Ni promoters can lead to obtain a Cr-free catalyst with high activity. In addition, the effect of Ni content on the structural and catalytic properties of the Fe–Mn–Ni catalysts was investigated. It was found that Fe–Mn–Ni catalyst with Fe/Mn = 10 and Fe/Ni = 5 weight ratios showed the highest catalytic activity among the prepared catalysts and possessed a stable catalytic performance without any decrease during 10 h time on stream. Moreover, the effect of GHSV and steam/gas ratio on the catalytic performance of this catalyst was investigated.

Structural changes of Rh-Mn nanoparticles inside carbon nanotubes studied by X-ray absorption spectroscopy

Supported Rh-based catalysts such as Rh-Mn nanoparticles (NPs) have potential use in the synthesis of ethanol from syngas. The structure of Rh-Mn NPs in multi-walled carbon nanotubes under different atmospheres and temperatures was studied by X-ray absorption spectroscopy (XAS). TEM images showed that the NPs dispersed in the carbon nanotubes had a uniform size of 2 nm. XAS data revealed that the Rh-Mn NPs before reduction were composed of Rh2O3 clusters and mixed Mn oxide species. After reduction in a 10% H2-90% He atmosphere, the mixed Mn oxides were converted into nearly pure MnO. In contrast, the Rh2O3 clusters were easily decomposed to metallic Rh clusters even under a He atmosphere at 250 °C. The Rh clusters remained in the metal state under the next reduction atmosphere, but their dispersion in the Rh-Mn NPs increased with increasing temperature. No significant Mn-Rh or Mn-O-Rh interaction in the reduced NPs was observed in the extended X-ray absorption fine structure analysis. The results showed that there was no interaction between the MnO particles and Rh clusters and the role of the Mn promoter was mainly to improve Rh dispersion.

Enhancement of the Partial Oxidation of Methanol Reaction over CuZn Catalyst by Mn Promoter

A series of in situ experiments on mechanisms and top-down LHHW (Langmuir–Hinshelwood–Hougen–Watson) microkinetic analysis were conducted for the partial oxidation of methanol on CuMnZn (ca. 28.0 wt % Cu, 23 wt % Mn, and 49 wt % Zn) catalyst. In comparison with CuZn (ca. 29 wt % Cu and 71 wt % Zn), CuMnZn catalyst with the structure of copper–manganese spinel CuMn2O4 enhanced the turnover frequency (TOF) for methanol conversion at a lower temperature (from 4.2 to 10.1 s–1 at 150 °C). Mn also played a role in electronic charge transfer, which could enhance formate decomposition and mitigate the accumulation of carbonate species at high temperature. From a kinetic modeling analysis, the activation energy of CuZn-based catalyst was apparently reduced from 22.4 to 16.5 kcal/mol by the Mn promoter.

12wt% Co 담지 촉매에서 합성오일 제조시 조촉매 효과 및 반응조건 영향 분석

Abstract >> The synthesis of Fischer-Tropsch oil is the catalytic hydrogenation of CO to give a range of products,which can be used for the production of high-quality diesel fuel, gasoline and linear chemicals. Our cobalt basedcatalyst was prepared Co/alumina, silica and titania by the incipient wet impregnation of the nitrates of cobalt and promoter with supports. Cobalt catalysts was calcined at 350°C before being loaded into the FT reactors. Afterthe reduction of catalyst has been carried out under 450°C for 24hrs, FT reaction of the catalyst has been carriedout at GHSV of 4,000/hr under 200°C and 20atm. From these test results, we have obtained the results as following; in case of 12wt% Co-supported Al 2 O 3 , SiO 2 and TiO 2 catalysts, maximum activities of the catalysts were appearedat the promoters of Mn, Mo and Ce respectively. The activity of 12wt% Co/Al 2 O 3 added a Mn promoter wasabout 3 times as high as that of 12wt% Co/Al 2 O 3 catalyst without promoters. When it has been the experiment at the range of reaction temperature of 200~220°C and GHSV of 1,546~5,000/hr, the results have shown generallyincreasing the activities with the increase of reaction temperature and GHSV.

Correlating the degree of metal–promoter interaction to ethanol selectivity over MnRh/CNTs CO hydrogenation catalysts

Multi-walled carbon nanotubes (MCNTs) were used as a support for Rh-based catalysts for high pressure (20bar) CO hydrogenation. 3wt% Rh/CNTs catalysts were loaded with 1wt% and 2wt% Mn promoter, respectively, in order to study the effect of metal–promoter interactions for ethanol synthesis. Both STEM and EXAFS results showed ∼1nm Rh particles in promoted as well as the unpromoted catalysts, STEM and EELS results verified the enhanced metal–promoter interaction when the amount of Mn promoter increased from 1wt% to 2wt%. The enhancement in the degree of metal–promoter interaction leads to an increase in the ethanol selectivity. Moreover, due to the nature of CNTs (low Z number), the Mn–Rh interactions could be observed at atomic resolution during the STEM–EELS characterization, and the promoter phase is confirmed as Mn(II) oxide by XANES and EELS.

Influence of Mn Promotion on CO Hydrogenation over Rh/CNTs Catalyst

The influence of manganese promotion on the catalytic performance of Rh/CNTs catalyst for ethanol production from syngas was investigated. With the addition of manganese, CO conversion and ethanol yield increased significantly. The effects of reaction temperature, pressure, and H2/CO molar ratio on the manganese-promoted Rh/CNTs catalyst were studied. With pressure increase, alcohol selectivity increased, while methane selectivity decreased. The high H2/CO molar ratio improved CO conversion and suppressed the formation of CO2. The catalysts were characterized by Brunauer–Emmett–Teller method, X-ray diffraction, transmission electron microscopy, temperature-programmed desorption experiment, and X-ray photoelectron spectroscopy to clarify their physical and chemical properties. It was found that the high activity of the Mn–Rh/CNTs catalyst and the corresponding high ethanol yield were attributed to the small and well dispersed active components and the enhancement of CO dissociation.

La and Mn Promotion of Ni/Al2O3 Catalysts for Syngas Methanation

24Ni-2La, 24Ni-2Mn, and 24Ni-2La-2Mn catalysts were prepared by co-impregnation method for syngas methanation, and were characterized by N2 adsorption-desorption, XRD, H2-TPR, and TEM. The addition of La and/or Mn as promoters can decrease the crystal size of Ni particles and prevent the growth of Ni particles during calcination and reduction. 24Ni-2La, 24Ni-2Mn, and 24Ni-2La-2Mn have similar average Ni particle size, which is in the range of 12.8–13.2 nm. For syngas methanation, 24Ni-2La presents a better synergism effect than both 24Ni-2Mn and 24Ni-2La-2Mn.

Mn(IV) promotion mechanism for the photocatalytic oxidation of arsenite by anatase-TiO2

Abstract A Ti–Mn hybrid oxide (Ti–Mn–HO) that simultaneously contained anatase-TiO 2 and Mn 3 O 4 was prepared and applied to arsenite photocatalytic oxidization (PCO) under UV irradiation. X-ray diffraction (XRD), scanning electron microscopy with an energy dispersive spectrometer (SEM/EDS), transmission electron microscopy (TEM) and a N 2 adsorption–desorption method were employed to characterize the morphology of the catalyst. Kinetics experiments indicated that Mn 3 O 4 promoted the PCO-adsorption process of arsenite [As(III)] better than either pure anatase-TiO 2 under UV irradiation or Ti–Mn–HO without UV exposure. The cause of this phenomenon was investigated using Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Finally, a synergistic effect for the transformation of photoproduct holes and electrons between the TiO 2 and Mn 3 O 4 phases is assumed.

Comparison of FeMn, FeMnNa and FeMnK Catalysts for the Preparation of Light Olefins from Syngas

The influence of sodium and potassium promoters on the structure and reaction behavior of an FeMn catalyst toward light olefin synthesis from syngas was investigated by N2 adsorption, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), CO/CO2 temperature-programmed desorption (CO/CO2-TPD), Mossbauer spectroscopy (MES) and CO+H2 reaction. We found that an increase in manganese improves the dispersion of the active Fe component and light olefin selectivity; however, excessive enrichment with the Mn promoter on the catalyst surface suppresses CO conversion. Potassium and sodium inhibit the reduction of the catalyst in H2 and improve the adsorption of CO2 and CO because of the enhanced surface basicity of the catalysts. After reduction with syngas (nH2/nCO=20) and reaction with syngas (nH2/nCO=3.5), the analysis of the bulk structure was compared with those of the FeMn, FeMnNa, and FeMnK catalysts. The results show that FeCx is found in relatively high levels in the FeMnK 1932 LI Jiang-Bing et al.: Comparison of FeMn, FeMnNa and FeMnK Catalysts for the Preparation of Light Olefins No.10

An Approach to Benzophosphole Oxides through Silver‐ or Manganese‐Mediated Dehydrogenative Annulation Involving CC and CP Bond Formation

Benzophosphole construction was achieved through the Ag(I) -mediated dehydrogenative annulation of phenylphosphine oxides with internal alkynes in a process involving CC and CP bond formation. A wide range of asymmetrical phenylacetylenes could be employed and the reactions proceeded with perfect regioselectivity. Moreover, the annulation could be conducted even at room temperature when a Mn(III) promoter was used in place of Ag(I) .

Manganese-promoted nickel/alumina catalysts for hydrogen production via auto-thermal reforming of ethanol

Abstract The manganese-promoted nickel-based catalysts were prepared via wet-incipient impregnation, and tested in auto-thermal reforming (ATR) of ethanol for hydrogen production. The Ni/Al 2 O 3 catalyst, in which Ni existed as NiAl 2 O 4 , produced a low H 2 yield near 1.85 mol H 2 /mol ethanol. The Ni–Mn/Al 2 O 3 catalyst showed a better performance in a 30-h test: the conversion of ethanol reached 100%, and a higher H 2 yield remained stable near 3.1–3.2 mol H 2 /mol ethanol. This improvement can be attributed to the promotion of Mn: With Mn, the ilmenite-type NiMnO 3 was formed, the reducibility of Ni–Mn/Al 2 O 3 was thus improved, and there were more Ni 0 over the surface of catalysts. Moreover, these Ni 0 species were stable in the ATR test, as indicated by XRD and XPS.

Investigation of Cu-Based Catalyst for Direct Synthesis of Ethyl Acetate from Ethanol: Improvement of Thermal Stability of Cu–Cr–Zr Composite Oxide Catalyst by Addition of Mn Promoter

A Mn promoter was introduced into a Cu–Cr–Zr composite oxide catalyst for the direct synthesis of ethyl acetate from ethanol dehydrogenation by means of coprecipitation method. The effects of the Mn promoter on the structure and catalytic performance of the catalyst were investigated with characterization techniques including XRD, TPR, XPS, and N2O TPD. An interaction between the Mn promoter and the CuO in the catalyst was found to exist, and it improved the dispersion of the Cu component on the catalyst surface and decreased the size of CuO crystal particles, thereby increasing the thermal stability of the catalyst. The results of long-duration activity tests indicated that the Mn-promoted CCZ (Cu–Cr–Zr) catalyst maintained its activity and showed good stability.

Ni/Al2O3 catalysts for syngas methanation: Effect of Mn promoter

Ni/Al2O3 catalysts with different amounts of manganese ranging from 1 to 3 wt% as promoter were prepared by co-impregnation method. The catalysts were characterized by N2 physisorption, XRD, TPR, SEM and TEM. Their catalytic activity towards syngas methanation reaction was also investigated using a fixed-bed integral reactor. It was demonstrated that the addition of manganese to Ni/Al2O3 catalysts can increase the catalyst surface area and average pore volume, but decrease NiO crystallite size, leading to higher activity and stability. The effects of reaction temperature, pressure and weight hourly space velocity (WHSV) on carbon oxides conversion and CH4 formation rate were also studied. High carbon oxides conversion, CH4 selectivity and formation rate were achieved at the reaction temperature range of 280–300 °C.

Effects of Mn promotion on the activity and selectivity of Co/SiO2 for Fischer–Tropsch Synthesis

An investigation has been carried out of the effects of Mn promotion on the activity and product selectivity of Co/SiO2 for Fischer–Tropsch Synthesis (FTS). All experiments were conducted with an H2/CO feed ratio of 2.0 at either 1atm or 10atm and a temperature of 493K. At 1atm, the rate of CO consumption decreased with CO conversion, whereas the selectivities to all products were unaffected. However, the olefin to paraffin (O/P) ratio of the C2C4 fraction decreased with increasing CO conversion due to increased hydrogenation of olefins with increasing space time. Mn promotion increased the rate of CO consumption at Mn/Co ratios of 0.05, decreased the selectivity to methane, and increased the selectivity to C5+ products, but had no effect on the selectivity to C2C4 products. Raising the pressure to 10atm increased the CO consumption rates for both unpromoted and Mn-promoted Co/SiO2, but the rate of reaction was lower for the Mn-promoted catalyst due to a higher level of CO inhibition. CO conversion at 10atm had no effect on the rate of CO consumption for Co/SiO2 and caused a slight increase in the rate for Mn-promoted Co/SiO2. The intrinsic O/P ratio was higher at 10atm than at 1atm. In contrast to what was observed at 1atm, at 10atm, C2C4 of the C2C4 fraction incorporated into growing hydrocarbon chain, leading to a decrease in C1C4 selectivities and an increase in C5+ selectivities with increasing CO conversion. The observed effects of Mn promotion on catalyst activity and product selectivity are discussed in terms of the mechanisms for CO hydrogenation and hydrocarbon chain growth.

Mn monolayer modified Rh for syngas-to-ethanol conversion: a first-principles study

Rh is unique in its ability to convert syngas to ethanol with the help of promoters. We performed systematic first-principles computations to examine the catalytic performance of pure and Mn modified Rh(100) surfaces for ethanol formation from syngas. CO dissociation on the surface as well as CO insertion between the chemisorbed CH(3) and the surface are the two key steps. The CO dissociation barrier on the Mn monolayer modified Rh(100) surface is remarkably lowered by ~1.5 eV compared to that on Rh(100). Moreover, the reaction barrier of CO insertion into the chemisorbed CH(3) group on the Mn monolayer modified Rh(100) surface is 0.34 eV lower than that of methane formation. Thus the present work provides new mechanistic insight into the role of Mn promoters in improving Rh's selectivity to convert syngas to ethanol.

Effects of Promoters on Properties of Cu-Zn-Al Catalyst for Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

Cu-Zn-Al catalyst was modified by the additives such as Ni and Mn, and the prepared catalyst was employed in the selective catalytic hydrogenation of cinnamaldehyde. The results showed that the addition of Ni could improve catalytic activity significantly, moreover, the improving effect was highest when Zn was replaced by Ni, simultaneously leading to excessive hydrogenation. The Cu-(5%)Mn-Zn-Al catalyst exhibited a higher selectivity of 93.6% for C = O bond to cinnamyl alcohol and hydrogenation activity of 33.0% conversion at 130°C under 1.0 MPa of H2 pressure with the reaction time of 1 h. TPR and XRD characterization showed that Mn promoter was favorable for the growth of Cu0 fine grains on the surface of catalyst, which not only led to steric effect which improved the selectivity for cinnamyl alcohol, but also reduced the numbers of active centers, consequently decreased the reaction rate.

EXAFS and FT-IR Characterization of Mn and Li Promoted Titania-Supported Rh Catalysts for CO Hydrogenation

The effect of Li and Mn promoters on the structure and selectivity of supported Rh catalysts for CO hydrogenation reaction was examined. Infrared spectroscopy and X-ray absorption were used to inve...