Pore Volume Impregnation Research Articles

Enhanced NH3-SCR performance using hydrothermally synthesized cell-like MnOx loaded rectorite catalysts

This study evaluates the catalytic performance of hydrothermally synthesized MnOx loaded rectorite catalysts (MnOx/REC-HP) in the selective catalytic reduction of NH3-SCR. Comparative analyses were conducted with catalysts synthesized via pore-volume impregnation, coprecipitation, and in-situ deposition methods, all yielding comparable manganese mass fractions. Results reveal that catalysts derived from hydrothermal synthesis outperform others in NH3-SCR activity across the 100–300 °C temperature spectrum. MnOx/REC-HP exhibits a distinctive cell-like structure of supported MnOx atop the rectorite substrate, diverging from the particulate patterns observed in other synthesis methods. Hydrothermal synthesis of metal precursors into their respective metal oxides effectively meets the fundamental requirements for SCR composites. This method enables the production of composites that are uniformly attached to nanostructures with high purity and controlled crystallinity. The rectorite surface is embellished with a meticulously arranged honeycomb structure of MnOx, augmenting the BET surface area, intensifying redox capability, enhancing NH3 and NOx adsorption, and amplifying the Mn4+ molar ratio on the catalyst surface. Consequently, MnOx/REC-HP showcases remarkable low-temperature NH3-SCR performance.

Quantifying the modulation of modified ZSM-5 acidity/alkalinity on olefin catalytic pyrolysis to maximize light olefin selectivity

Undesirable side reactions often occur during the catalytic pyrolysis of olefins in FCC gasoline to produce light olefins. We proposed a method to maximize light olefin selectivity by suppressing these side reactions. In this study, P-ZSM-5 and Ce–P-ZSM-5 were prepared by the pore volume impregnation method to investigate the regulatory relationship between their acidity/alkalinity and catalytic pyrolysis. The study found that acid sites could promote the olefin conversion and adjust the cracking pathway. Furthermore, the densities of strong B acid sites and base sites could regulate olefin adsorption, affecting hydrogen transfer activity. Acid strength was crucial in controlling the aromatization reaction. It showed that thermal cracking played a minor role in catalytic pyrolysis, with methane generation mainly resulting from acid sites promoting the cracking of terminal C–C bonds. Loading phosphorus strengthens the acidity of ZSM-5, while loading cerium weakens its acidity and enhances its alkalinity. By optimizing the acidity and alkalinity of ZSM-5, side reactions were suppressed, maximizing the selectivity of light olefins. The results showed that the light olefin selectivity of Ce–P-ZSM-5 increased from 33.2% to over 80%, while the side reaction selectivity decreased from over 60% to below 10%. This work will lay a good foundation for developing catalysts for catalytic pyrolysis of olefins to produce light olefins.

Optimization of Activated Carbon Monolith Co3O4-Based Catalyst for Simultaneous SO2/NOx Removal from Flue Gas Using Response Surface Methodology

ABSTRACTCoal combustion is a primary source of acid gases such as sulfur dioxide (SO2) and nitrogen dioxide (NOx); meanwhile, their effects are detrimental to man and the environment. In this work, three different adsorbents were developed by loading Co3O4 on monolith using pore volume impregnation, deposition precipitation, and hydrothermal methods (HMs) of synthesis. The breakthrough study in the simultaneous SO2 and NOx removal from flue gas revealed that the performance of the adsorbent developed by HM was better than the adsorbents developed by the other methods. Therefore, the characterization analysis and optimization of the variables that affect the adsorption capacity on the best performed adsorbent by response surface methodology were carried out. The model prediction and the experimental results for the adsorption capacity of SO2 are 134.5 and 132.9 mg/g while 152.1 and 151.6 mg/g were obtained for NOx. Furthermore, the optimized independent variables comprising amount of adsorbents, airflow rate, and temperature are 1 mg, 400 mL/min, and 100°C. The regression coefficient of 0.9934 for SO2 and 0.9991 for NOx was obtained which indicates that the interaction between the independent variables and the adsorption capacity of SO2 and NOx is very significant. These results confirmed the suitability of the model for the prediction of the process behavior and the performance of the adsorbent at low temperature with high adsorption capacity emerged as a new finding.

Effect of Support on the Performance of CoMoRe Catalyst in Thiophene and Benzothiophene Hydrodesulfurization

This work is aimed at selection of a suitable support for CoMoRe catalyst in hydrodesulfurization (HDS) of thiophenes. g-Al2O3 and g-Al2O3-HMS were used as a support for CoMoRe catalyst with 4%Co, 8%Mo and 0.5%Re loading. The metal loading was incorporated by using the pore volume impregnation method, employing aqueous solutions of cobalt (II) nitrate, ammonium molibdate and rhenium (VII) oxide. The catalysts were sulfided with dimethyl disulphide at 250 �C for 10 h and finally tested in the HDS reaction of thiophene and benzothiophene in different temperature and pressure conditions. The catalysts were characterized by determining the adsorption isotherms, the pore size distribution and the acid strengt, FTIR, XRD and S EM. T he catalyst supported on g - Al2O3 displayed higher activity than catalyst supported on g-Al2O3-HMS. The results suggest that activity is favoured by the suitable textural and acidic properties of the support.

Activated carbon monolith Co3O4 based catalyst: Synthesis, characterization and adsorption studies

Abstract The multi-step SO2 and NOx removal techniques is complex process with high capital cost, high risk in solvent losses, unwanted foaming, flooding, and equipment fouling. Therefore, the simultaneously SO2/NOx removal from flue gas by adsorption alternative offers economical and environmental benefits. In this study, the surface area of monolith was improved by acid modification, furfuryl alcohol coating, carbonization (at 800 o C) and subsequent activation under CO2 atmosphere. The activated carbon monolith (ACM) was impregnated with tricobalt tetraoxide (Co3O4) catalyst by three different synthesis methods namely hydrothermal, deposition precipitation and the pore volume impregnation. The fixed bed adsorption test for simultaneous SO2/NOx removal showed that the adsorbent synthesized by hydrothermal method (HM-Co3O4/ACM) exhibited high adsorption capacity (123.1 and 130.2 mg/g for SO2 and NOx) with the breakthrough times of 86 and 124 min respectively. This finding indicated that the adsorbent’s unique ability to high NOx adsorption affinity a major breakthrough. About 1.1% Co3O 4 was impregnated in the ACM mesoporous ( ≈ 38 nm) dominated adsorbents meanwhile, thermal decomposition that may be attributed to the oxidation of carbonaceous species and Co3O4 occurred. The regeneration study and characterization of the HM-Co3O4/ACM adsorbent proved its stability and potentiality to industrial application.

Breakthrough studies of Co3O4 supported activated carbon monolith for simultaneous SO2/NOx removal from flue gas

This work investigates the deposition precipitation, pore volume impregnation and hydrothermal methods of synthesizing activated carbon monolith supported metal oxide adsorbent (Co3O4/ACM). The hydrothermally synthesized Co3O4 activated carbon monolith adsorbent (Hm-Co3O4/ACM) demonstrate better adsorption capacity (SO2 is 123.1, NOx is 130.2 mg/g) than the adsorbents synthesized by the other methods. The adsorbent displayed high affinity to NOx adsorption where this influence was associated to operation conditions, physical and chemical properties of the adsorbent which were expressed in the plot of the breakthrough curve. Moreover, the surface properties (BET), thermal decomposition (TGA), functional groups (FTIR), chemical composition (XRD) and surface morphology (FESEM) of the adsorbent were investigated. The Langmuir adsorption isotherm fitted the experimental results meanwhile, the thermal regeneration of the adsorbent over two cycles showed an average regeneration efficiency of 94.4% for SO2 and 94.8% for NOx. Finally, the post regeneration characterization analyses were discussed.

Effects of K<sub>2</sub>O and SO<sub>2</sub> on the selective catalytic reduction of NO by NH<sub>3</sub> over CuO/Al<sub>2</sub>O<sub>3</sub> catalyst

CuO/Al 2 O 3 catalyst containing 2 wt% CuO was prepared by pore volume impregnation of γ-Al 2 O 3 with an aqueous solution of Cu(NO 3 ) 2 and then calcination. K 2 O was loaded onto the catalyst with an aqueous solution of KNO 3 as the precursor. The catalysts were sulphated before being subjected to an activity test. Activity test was performed at 400 o C to investigate the effect of K 2 O and SO 2 on the selective catalytic reduction of NO by NH 3 over CuO/Al 2 O 3 catalyst. The catalyst samples were characterized by ICP-MS, XRD, IS-FTIR, NH 3 -TPD and H 2 -TPR to elucidate the possible poisoning reason. Results indicate that in the absence of SO 2 , K 2 O promotes conversion of CuSO 4 to water-insoluble copper, possibly due to reduction of CuSO 4 to Cu 3 N by NH 3 . This reaction consumes the NH 3 for SCR reaction and weakens acidity of the catalyst, which are responsible for the reduced SCR activity by K 2 O. In the presence of SO 2 , conversion of CuSO 4 to water-insoluble copper is inhibited, and the net influence of SO 2 on the SCR activity is determined by the promotion of SO 4 2− on the acidity of the catalyst, the competitive adsorption between SO 2 and NH 3 , and the weakened acidity of the catalyst caused by K 2 O. SO 2 reduces the SCR activity of the catalyst without K 2 O, has no influence at K/Cu ratio of 0.13, and promotes the SCR reaction at K/Cu ratios of higher than 0.13.

Vanadium poisoning of FCC catalysts: A quantitative analysis of impregnated and real equilibrium catalysts

Amongst the contaminant transition metals Fe, Ni, V that deposits onto the fluid catalytic cracking (FCC) catalyst and promote unwanted secondary reactions, vanadium is the most deleterious one because not only acts as undesired dehydrogenation site but also migrates deeper inside the catalyst particles under the FCC regeneration conditions, stabilizing in different phases that attack the crystalline structure of the catalyst, thus resulting in its irreversible loss of activity. The mechanisms through which vanadium affect the catalyst during its use in the FCC process remain under debate and the accurate determination of the chemical species involved and of their concentration is of paramount importance for the investigations in this field. In this work, a quantification methodology for contaminant vanadium in FCC catalysts was developed based on X-ray fluorescence (XRF) and electron paramagnetic resonance (EPR). A commercial FCC catalyst was artificially contaminated with vanadium at different loads by pore volume impregnation with aqueous vanadyl sulfate solution, in the presence or not of a complexing agent, followed by steam deactivation at 788 °C/5 h, and the samples were compared to spent FCC catalysts from different Brazilian refineries. It has been shown that EPR is a very sensitive and reliable technique to quantify vanadyl ions (V4+) in FCC catalysts while lower valence states such as V3+ have not been detected in any of the samples studied. Vanadyl ions (VO2+) deposited onto the catalyst are mostly oxidized to higher valence state species and the extent of this oxidation in equilibrium catalysts from FCC units was calculated and related to the combustion mode at which the FCC regenerators operate. The artificial vanadium contamination and deactivation protocol adopted in this work resulted in a proportion of V4+/Vtotal of nearly 10%, similar to that of equilibrium catalysts sampled from FCC units with full combustion regeneration. The present study brings a new interpretation for the EPR signal detected as a broad unstructured line, with evidences of some vanadium existing as a ferri-/ferromagnetic surface phase in the catalyst particles, likely formed by induced oxygen vacancies during reaction (reducing atmosphere) and quite resistant to the regeneration step.

Kinetics of thiophene hydrodesulfurization over a supported Mo–Co–Ni catalyst

In this study, the kinetics of thiophene (TH) hydrodesulfurization (HDS) over the Mo–Co–Ni-supported catalyst was investigated. Trimetallic catalyst was synthesized by pore volume impregnation and the metal loadings were 11.5 wt % Mo, 2 wt % Co, and 2 wt % Ni. A large surface area of 243 m 2 /g and a relatively large pore volume of 0.34 cm 3 /g for the fresh Mo–Co–Ni-supported catalyst indicate a good accessibility to the catalytic centers for the HDS reaction. The acid strength distribution of the fresh and spent catalysts, as well as for the support, was determined by thermal desorption of diethylamine (DEA) with increase in temperature from 20 to 600 °C. The weak acid centers are obtained within a temperature range between 160 and 300 °C, followed by medium acid sites up to 440 °C. The strong acid centers are revealed above 440 °C. We found a higher content of weak acid centers for fresh and spent catalysts as well as alumina as compared to medium and strong acid sites. The catalyst stability in terms of conversion as a function of time on stream in a fixed bed flow reactor was examined and almost no loss in the catalyst activity was observed. Consequently, this fact demonstrated superior activity of the Mo–Co–Ni-based catalyst for TH HDS. The activity tests by varying the temperature from 200 to 275 °C and pressure from 30 to 60 bar with various space velocities of 1–4 h −1 were investigated. A Langmuir–Hinshelwood model was used to analyze the kinetic data and to derive activation energy and adsorption parameters for TH HDS. The effect of temperature, pressure, and liquid hourly space velocity on the TH HDS activity was studied.

In Situ DRIFTS Study of the Low Temperature Selective Catalytic Reduction of NO with NH3 over MnOx Supported on Multi-Walled Carbon Nanotubes Catalysts

MnOx supported on multi-walled carbon nanotubes (MWCNTs) catalysts were prepared by the pore volume impregnation method and used for low-temperature selective catalytic reduction (SCR) of NO with NH3. Based on the previous study, 10 wt.% loading MnOx/MWCNTs were then selected for investigation of the reaction mechanism by in situ Diffuse Reflectance Infrared Fourier Transform spectroscopy (in-situ DRIFTS). The important intermediates in the SCR of NOx process at 210°C were discussed based on the DRIFTS results. Furthermore, the NH3-SCR reaction pathways over MnOx/MWCNTs catalysts were proposed. The results showed that NH4 + species on Bronsted acid sites and coordinate ammonia species on Lewis acid sites existed during the SCR reaction. NH4 + species was more active than coordinate ammonia species over the catalysts at 210°C. Most of NOx ad-species would react with NH3 ad-species. However, nitrite species, bidentate and monodentate nitrates contributed to the SCR reaction over the catalysts mostly. Two possible reaction pathways were proposed. One was that NOx ad-species could react with NH4 + to form intermediate of NH4N2O4 (a), NH4NO2 (a) or NH4NO3 (a), then to produce N2 and H2O as the final products. The other pathway was that NH3 was initially adsorbed on active site and NH2 was formed, then NH2 reacted with NOx ad-species to produce intermediate NH2NO2 or NH2NO3 which were unstable and would decompose into N2 and H2O.

Development of the Al2O3-supported NaNO3-Na2Mg(CO3)2 sorbent for CO2 capture with facilitated sorption kinetics at intermediate temperatures

For the development of a dry solid sorbent having quite fast CO2 sorption kinetics in an intermediate temperature range of 245–300 °C to be applicable to a riser-type fluidized bed carbonator, samples of Al2O3-supported MgCO3 (1.2 mmol/g) promoted with different molar amounts of Na2CO3 (1.2, 1.8 mmol/g) and/or NaNO3 (0.6 mmol/g) were prepared by incipient wetness pore volume impregnation. For a reference, an unsupported bulk phase sorbent of NaNO3-Na2Mg(CO3)2 was also prepared. From the sorption reaction using a gas mixture containing CO2 by 2.5–10% at 1 bar for the sorbents after their activation to MgO, Al2O3-supported sorbents were featured by their rapid carbonation kinetics in contrast to the unsupported sorbent showing a quite slow carbonation behavior. The addition of Na2CO3 to the MgCO3/Al2O3 sorbent made MgO species more reactive for the carbonation, bringing about a markedly enhanced kinetic rate and conversion, as compared with the unpromoted MgCO3/Al2O3 sorbent having a small negligible reactivity. The addition of NaNO3 to MgCO3/Al2O3 or to Na2CO3-MgCO3/Al2O3 induced the same promotional effects, but to a lesser magnitude, as observed for the Na2CO3 addition. It was also characteristic for all these MgCO3-based sorbents that initial carbonation conversions with time appeared as sigmoid curves. For the Al2O3-supported sorbent comprised of NaNO3, Na2CO3, and MgCO3 by 0.6, 1.8, and 1.2 mmols, respectively, per gram sorbent, showing the best kinetic performance, a kinetic equation capable of reflecting such sigmoid conversion behavior was established, and its applicability to a riser carbonator was examined throughout a simple model calculation based on the kinetics obtained.

Pd/activated carbon sorbents for mid-temperature capture of mercury from coal-derived fuel gas

Higher concentrations of Hg can be emitted from coal pyrolysis or gasification than from coal combustion, especially elemental Hg. Highly efficient Hg removal technology from coal-derived fuel gas is thus of great importance. Based on the very excellent Hg removal ability of Pd and the high adsorption abilities of activated carbon (AC) for H2S and Hg, a series of Pd/AC sorbents was prepared by using pore volume impregnation, and their performance in capturing Hg and H2S from coal-derived fuel gas was investigated using a laboratory-scale fixed-bed reactor. The effects of loading amount, reaction temperature and reaction atmosphere on Hg removal from coal-derived fuel gas were studied. The sorbents were characterized by N2 adsorption, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicated that the efficiency of Hg removal increased with the increasing of Pd loading amount, but the effective utilization rate of the active component Pd decreased significantly at the same time. High temperature had a negative influence on the Hg removal. The efficiency of Hg removal in the N2–H2S–H2–CO–Hg atmosphere (simulated coal gas) was higher than that in N2–H2S–Hg and N2–Hg atmospheres, which showed that H2 and CO, with their reducing capacity, could benefit promote the removal of Hg. The XPS results suggested that there were two different ways of capturing Hg over sorbents in N2–H2S–Hg and N2–Hg atmospheres.

Preparation of iron oxide-impregnated spherical granular activated carbon-carbon composite and its photocatalytic removal of methylene blue in the presence of oxalic acid

The spherical granular activated carbon-carbon composites (GAC-Fe) with different iron oxide contents (Fe mass% = 0.6–10) were prepared by a pore volume impregnation method. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and N2-adsorption results confirm the presence of amorphous iron oxide, pyrolytic carbon, and graphitized globular carbon nanoparticles covered with amorphous carbon in the CAG-Fe. The rate of photodegradation of methylene blue (MB) in aqueous solution under UV light in the presence of oxalic acid correlates with porosity of the prepared materials. The total MB removal includes the combination of adsorption and photodegradation without the addition of H2O2. The results of total organic carbon (TOC) analysis reveal that the decolorization of MB in aqueous solution containing oxalic acid corresponds to the decomposition of organic compounds to CO2 and H2O.

Adsorption and photodegradation of methylene blue with Fe2O3-activated carbons under UV illumination in oxalate solution

Materials based on iron oxide (Fe2O3) and activated carbons (Fe-ACs) were prepared by pore volume impregnation of activated carbon in an iron nitrate solution followed by heat treatment at 250 °C. The Fe-AC materials were amorphous and microporous, and the specific surface areas (SBET) values were higher than 1000 m2/g. The effects of Fe content, porous properties, pH of the treatment solution, oxalic acid (OA) and MB concentrations were systematically investigated. The increase of the Fe content caused a significant decrease in the SBET values, lowering of the MB adsorption capacity and the photodegradation rate constant of the Fe-AC samples. The simultaneous processes of MB adsorption–photodegradation samples were complex owing to a strong influence of MB desorption during the photodegradation experiments under UV illumination. The MB decomposition was intensified by the enhanced simultaneous heterogeneous and homogeneous catalytic reactions. The almost complete simultaneous mineralization of MB and OA was confirmed by total organic carbon (TOC) analysis. The present system has advantages on the viewpoint of no hydrogen peroxide in operation, the low Fe leaching near neutral pH, no sludge formation, the possibility to recycle the iron promoter and cyclic usage.

Effect of CuSAPO-34 catalyst preparation method on NOx removal from diesel vehicle exhausts

CuSAPO-34 samples prepared by hydrothermal synthesis (HS), pore-volume impregnation (PVI), and ion-exchange (IE) methods were characterized using X-ray diffraction, scanning electronic microscopy, atomic absorption spectroscopy, temperature-programmed reduction with hydrogen, X-ray absorption near-edge structure spectroscopy, X-ray photoelectron spectroscopy, and N 2 adsorption. The selective catalytic reduction (SCR) ability over CuSAPO-34 for NO x from a simulated diesel exhaust was investigated through C 3 H 6 -SCR and NH 3 -SCR, before and after aging of the CuSAPO-34 catalyst. The results indicated that the sample prepared by IE had significantly better activity compared with those prepared using HS and PVI, especially in C 3 H 6 -SCR at temperatures below 300 °C. The activity of CuSAPO-34 in NO SCR was affected by the preparation method as a result of changes in the specific area ( A BET ), pore-size distribution, and the valence state of the active component. The active component of the catalyst prepared by HS was mainly Cu 2+ , whereas those of samples prepared by IE and PVI were mainly Cu + . Aging treatment can destroy the structure of the catalyst, decrease its surface area, and reduce the number of active Cu components on the catalyst surface, leading to a visible decrease in catalytic activity. The CuSAPO-34 prepared using the PVI method had the smallest decrease in NO SCR activity after aging, showing that it had better anti-aging properties. 用一维CeO 2 纳米管替代非一维结构的商用CeO 2 , 用于负载Pd而制得的催化剂在空气气氛下高温煅烧过程中Pd纳米粒子的团聚受到明显抑制, 在选择性有氧氧化苯甲醇生成苯甲醛反应中, 所制CeO 2 纳米管负载的Pd催化剂表现出更高的催化活性. 可见, 一维金属氧化物材料有望用作载体以抑制贵金属纳米粒子的团聚, 从而提高其催化性能. CuSAPO-34 catalysts were prepared by hydrothermal synthesis, ion exchange, and pore-volume impregnation. The de-NO x activity of CuSAPO-34 strongly depended on the preparation method, and the sample prepared using ion exchange performed best in selective catalytic reduction in both NH 3 -SCR and C 3 H 6 -SCR.

Effects of cerium on the selective catalytic reduction activity and structural properties of manganese oxides supported on multi-walled carbon nanotubes catalysts

A series of manganese and cerium oxides supported on multi-walled carbon nanotubes (MWCNTs) catalysts for low-temperature NH 3 selective catalytic reduction (SCR) of NO x were prepared by the pore volume impregnation method. The SCR activity of Mn-Ce/MWCNTs catalysts was compared with that of Mn/MWCNTs catalyst. The effects of Ce were characterized by transmission electron microscopy, N 2 adsorption-desorption, H 2 temperature-programmed reduction, X-ray photoelectron spectroscopy and X-ray powder diffraction. The results show that the addition of cerium oxides could improve the SCR activity of Mn/MWCNTs catalysts. Mn-Ce/MWCNTs catalyst with a Ce/Mn ratio of 0.6 was found to have the highest activity. The addition of cerium oxides enhanced the dispersion of metal oxides on the MWCNTs. It could also increase the specific surface area and total pore volume, and decrease the average pore size of the catalysts. Ce would improve the concentration of oxygen and the valence of manganese. Furthermore, from the XRD results, it was obvious that the crystalline MnO x disappeared because of the introduction of Ce to the catalyst. MnO x mainly existed in an amorphous state or microcrystal structure in the Mn-Ce/MWCNTs catalysts. CeO 2 was found to be the main phase for CeO x . 采用等体积浸渍法制备多壁碳纳米管(MWCNTs)负载Ce-Mn的催化剂, 考察了Ce掺杂对Mn/MWCNTs催化剂上NH 3 选择性催化还原(SCR)NO x 反应活性的影响. 并运用透射电镜扫描/N 2 吸附-脱附/程序升温还原/X射线光电子能谱/X射线衍射等手段, 重点考察了Ce掺杂对Mn/MWCNTs催化剂结构性质的影响. 结果表明, Ce掺杂能显著提高催化剂的SCR活性, 其活性增量随着Ce含量的增加先增大后减小; 当Ce/Mn为0.6时, 催化剂活性最佳. 表征结果显示, Mn/MWCNTs中添加Ce后, 金属氧化物在MWCNTs上的分散程度提高; 催化剂的比表面积和孔体积增大, 平均孔径减小; 氧化能力提高; 表面氧含量增加, Mn化合价升高; 结晶度降低, Mn主要以无定形或微晶形式存在, Ce主要以CeO 2 物相存在. This study examines the effects of cerium on the selective catalytic reduction (SCR) activity and the structure of Mn/MWCNTs by comparing SCR activity, specific surface area, crystallization, oxidizability, and superficial species and elements.

Progress in the deactivation of metals contaminated FCC catalysts by a novel catalyst metallation method

The artificial deposition of contaminant metals on FCC catalysts by pore volume impregnation methods (Mitchell) followed by hydrothermal deactivation in small scale units are the most common techniques for the deactivation of FCC catalysts in the laboratory due to the simplicity and robustness of such methods. However, such methods do not match the deposition of the metals on the outer surface of the FCC catalyst particles as observed for equilibrium catalysts (FCC catalysts equilibrated in FCC units).A new method of catalyst metallation has been developed using a spray impregnation technique, where the contaminant metals vanadium and nickel are deposited on the outer surface area of the FCC catalyst particles. Using this novel technique nickel remains primarily on the surface of the particles under severe hydrothermal conditions whilst vanadium migrates into the bulk of the particles and from particle to particle as observed in equilibrium catalysts. This dispersion of the contaminant metals occurs simultaneously with zeolite degradation and thus leads to different effects on the physical and catalytic properties of FCC catalysts compared to a Mitchell-type method where the contaminant metals already penetrate the FCC catalyst particles during the impregnation step. Such differences in physical and catalytic properties are shown by numerous examples. It is also demonstrated that the hydrothermal deactivation of catalysts metallated by the spray impregnation method results in catalyst properties being closer to those of equilibrium catalysts than the deactivation after metallation by the Mitchell method. Hence the catalytic testing of spray impregnated and deactivated samples provides more realistic results than the testing of Mitchell impregnated catalysts.

Catalytic Performance and Synergetic Effect of Mo-V/Al2O3 in Residue Hy-drotreatment

Mo-V/Al 2 O 3 catalyst samples with different atom ratios of Mo/(Mo+V) were prepared by pore volume impregnation. The catalyst samples were characterized by Raman spectroscopy, H 2 temperature-programmed reduction, and high resolution transmission electron microscopy. The catalytic performance of Mo-V/Al 2 O 3 samples for model molecules (naphthalene) and for real feedstock (Kuwait atmosphere residue) was measured after sulfidation. Hydrogenation (HYD), hydrodemetallization (HDM), and hydrodesulfurization (HDS) were assessed. It can be concluded that Mo and V exhibited a synergetic effect in model molecules HYD and residue HDM reactions. Because the metals and sulfurs exist in different forms in residue and the V–S and V–Mo–S phases are more active for HDM than HDS, it is observed that the Mo-V/Al 2 O 3 catalyst exhibited higher HDM activity and lower HDS activity compared with the Ni-Mo/Al 2 O 3 catalyst.

Adsorption kinetics of phenol from water on Fe/AC

Activated carbon (AC)-supported iron adsorbents (Fe/AC) were prepared using pore volume impregnation with ferric nitrate. The effect of iron doping on the physicochemical properties of AC as well as the effects of the contact time, initial phenol concentration, and Fe doping mass fraction on phenol adsorption by AC and Fe/AC from water were investigated. The adsorption kinetics was also analyzed using pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models. The adsorbents were characterized using elemental analysis, X-ray diffraction, N2 adsorption, and Boehm titration. The results show that the AC pore properties after Fe doping were not significantly changed. But Fe doping introduced a significant number of acidic oxygenated groups (mainly carboxylic groups, phenolic groups, and lactones) onto the AC surface. In addition, the number of acidic O-containing groups of Fe/AC increased with increasing doped Fe mass fraction. The adsorption of phenol on the adsorbents can be separated into rapid adsorption, slow adsorption, and equilibrium periods. Fe doping did not significantly affect the adsorption capacity of a low-concentration phenol solution. However, the adsorption of high-concentration phenol showed that Fe doping clearly reduced the phenol uptake and that the uptake decreased with increasing doped Fe mass fraction because of the decrease in the dispersive interaction between phenol and AC surface. The uptake of each adsorbent increases with increasing the initial phenol concentration. A pseudo-second-order model better describes the adsorption of low-concentration phenol on AC and Fe1/AC (AC doped with low-mass fraction Fe). The adsorption of low-concentration phenol by Fe5/AC (AC with high-mass fraction doped Fe) is consistent with the Elovich model due to a major decrease in the adsorption sites on the AC surface after Fe doping. The AC adsorption before and after Fe doping followed the Elovich model when high-concentration phenol was adsorbed. The rate-controlling steps during early and middle adsorption are primarily intraparticle and film diffusions, respectively.

Manganese oxides supported on multi-walled carbon nanotubes for selective catalytic reduction of NO with NH3: Catalytic activity and characterization

A series of catalysts of manganese oxides supported on multi-walled carbon nanotubes (MWCNTs) modified by oxygen dielectric barrier discharge plasma were prepared by the pore volume impregnation method, and the catalysts were characterized by TEM, XRD, XPS, N2 adsorption, H2-TPR, and Raman spectroscopy methods. The effects of Mn loading, calcination temperature, and MWCNTs outer diameter on selective catalytic reduction (SCR) of NO with NH3 were investigated, and the SCR activity tests were carried out in a fixed-bed reactor. The results showed that MnOx dispersion on MWCNTs varied with the Mn loading, calcination temperature, and MWCNTs outer diameter. Three states of manganese species (MnO2, Mn3O4, and MnO) coexisted in MnOx/MWCNTs catalysts, and most of the Mn existed as MnO2 and Mn3O4. Additionally, among the MnOx/MWCNTs catalysts prepared, MWCNTs (60–100nm) supported 10wt.% manganese calcined at 400°C catalyst presented the best SCR activity under the conditions of 1000ppm NH3, 1000ppm NO and 5vol.% O2. Well dispersed MnOx on MWCNTs, high concentration of MnO2 and low concentration of MnO would lead to high SCR activity.