γ-Al2O3 Support Research Articles

Catalysts for selective hydrogenation of furfural derived from the double complex salt [Pd(NH3)4](ReO4)2 on γ-Al2O3

The double complex salt [Pd(NH3)4](ReO4)2 was employed as precursor of supported bimetallic catalysts for selective hydrogenation of furfural. Direct reduction of [Pd(NH3)4](ReO4)2 on γ-Al2O3 in flowing H2 at 400°C yields bimetallic nanoparticles 1–2nm in size that exhibit significant interaction between the metals, as evidenced by temperature-programmed hydride decomposition (complete suppression of β-PdHx formation), extended X-ray absorption fine structure spectroscopy at the Pd K and Re LIII edges (PdRe distance=2.72Å), and scanning transmission electron microscopy with energy dispersive X-ray analysis. In contrast, calcination of [Pd(NH3)4](ReO4)2 on γ-Al2O3 at 350°C in air and subsequent reduction in H2 at 400°C results in metal segregation and formation of large (>50nm) supported Pd particles; Re species cover the Pd particles and γ-Al2O3 support. A PdRe 1:2 catalyst prepared by sequential impregnation and calcination using HReO4 and [Pd(NH3)4](NO3)2 has a similar morphology. The catalyst derived by direct reduction of [Pd(NH3)4](ReO4)2 on γ-Al2O3 exhibits remarkably high activity for selective hydrogenation of furfural to furfuryl alcohol (FAL) at 150°C and 1atm. Suppression of H2 chemisorption via elimination of Pd threefold sites, as evidenced by CO diffuse-reflectance infrared Fourier transform spectroscopy, correlates with increased FAL selectivity.

Structure, activity, and selectivity of bimetallic Pd-Fe/SiO2 and Pd-Fe/γ-Al2O3 catalysts for the conversion of furfural

The conversion of furfural has been investigated in vapor and liquid phases over a series of supported monometallic Pd and bimetallic Pd-Fe catalysts. Over the monometallic Pd/SiO2 catalyst, the decarbonylation reaction dominates, yielding furan as the main product. By contrast, over the bimetallic Pd-Fe/SiO2 catalyst a high yield of 2-methylfuran is obtained with much lower yield to furan. Interestingly, changing the catalyst support affects the product distribution. For instance, using γ-Al2O3 instead of SiO2 as support of the bimetallic catalyst changed the dominant product from 2-methylfuran to furan. That is, Pd-Fe/γ-Al2O3 behaves more like monometallic Pd/SiO2 than bimetallic Pd-Fe/SiO2. A detailed characterization of the catalysts via XPS, XRD, and TEM indicated that a Pd-Fe alloy is formed on the SiO2 support but not on the γ-Al2O3 support. Theoretical density functional theory calculations suggest that on the Pd-Fe alloy binding of the furan ring to the surface is weakened compared to on pure Pd. This weakening disfavors the ring hydrogenation and decarbonylation paths, while the oxophilic nature of Fe atoms enhances the interaction of the CO and the OH groups with the metal surface, which favors the CO hydrogenation and CO bond cleavage paths. The presence of the solvent has a less pronounced effect, but clearly has a stronger inhibition on CC bond cleavage (decarbonylation to furan) than on CO bond cleavage (hydrogenolysis to methylfuran).

Electron microscopic studies of natural gas oxidation catalyst – Effects of thermally accelerated aging on catalyst microstructure

Structural changes of PtPd nanoparticles in a natural gas oxidation catalyst were studied at elevated temperatures in air and low-oxygen conditions and in situ using environmental transmission electron microscopy (ETEM). The fresh catalyst shows <5nm, PtPdOx particles on the γ-Al2O3 support. At 700°C, the noble metal oxide decomposes and Pt gets trapped by PdO particles followed by formation of metallic Pd and Pt containing particles. At 1000°C, the particles had a metallic Pd and Pt containing core surrounded by PdO particles. In addition, the presence of <10nm sized particles was always observed. The activity measurements indicate the decrease in activity at the elevated temperatures. ETEM studies showed significant mobility of the noble metal particles above 850°C. Above 1100°C, PtPd particles were mobile and smaller particles were trapped by larger ones by a particle coalescence mechanism.

Catalytic oxidative desulfurization performance of immobilized NMP.FeCl3 ionic liquid on γ-Al2O3 support

NMP.FeCl3 (NMP=N-methyl-2-pyrrolidone, C5H9NO) ionic liquid (IL) was effectively immobilized on γ-Al2O3 as a support and examined in the catalytic oxidative deep desulfurization (ODS) of BT, DBT and 4,6-DMDBT from model oil employing 30 wt.% H2O2 as the oxidant reagent. The supported catalyst was prepared via a simple wet impregnation and the effective immobilization of IL was confirmed by FTIR, SEM, EDS, XRD, BET and BJH analysis. The maximum efficiency of 99% was achieved for ODS of DBT using supported IL at the loading amount of 10 wt.%, H2O2/sulfur molar ratio of 4, temperature of 40°C, and duration of 90min. The use of support material in this study resulted in using a lower amount of IL in ODS process. The ODS reactivity of the thiophenic compounds changed in the order of DBT>4,6-DMDBT≫BT. The catalyst was recycled for several times and showed no significant loss in the activity. Furthermore, based on GC–MS analysis of the products, desulfurization mechanism was surveyed and a reasonable pathway was proposed.

Real-Time Scattering-Contrast Imaging of a Supported Cobalt-Based Catalyst Body during Activation and Fischer–Tropsch Synthesis Revealing Spatial Dependence of Particle Size and Phase on Catalytic Properties

A combination of time-resolved synchrotron μ-X-ray diffraction computed tomography (μ-XRD-CT) and μ-pair distribution function computed tomography (μ-PDF-CT) has been applied for the study of an individual Co/γ-Al2O3 catalyst pellet during reduction and the early stages of the Fischer–Tropsch synthesis (FTS) reaction, revealing insight into the solid-state changes occurring from within such crystalline materials. Both sets of data were of sufficient quality so as to be able to follow the spatial dependency of Co speciation evolution from Co3O4 to CoO to face-centered cubic (fcc) Co metal nanoparticles. These data revealed the samples to be highly heterogeneous and contain two types of Co species: small (≤6.5 nm) nanoparticles that interact strongly with the γ-Al2O3 support which are difficult to reduce (remaining as CoO) and nanoparticles that agglomerate and have little interaction or else are weakly interacting with the support but readily reduce in H2. The Co phase evolution under FTS conditions shows ...

Influence of Mixed Supports on the Steam Catalytic Reforming of Wood Vinegar

Obtaining hydrogen from renewable energy is a novel method. Instead of single support catalysts, mixed zeolite supports were used in this study to obtain hydrogen by steam catalytic reforming of wood vinegar. This technique improves the activity and extends the life of catalysts. The results show that, compared with a single support catalyst, mixed supports are beneficial for improving H2 concentration and anticarbon ability. H2 content and yield increased from 54.77% to 60.32% and 18.91 mg/g sample to 22.47 mg/g sample, respectively, when γ-Al2O3 mixed MCM-41 supports were used instead of single γ-Al2O3. Moreover, the amount of carbon deposition significantly decreased from 9.79% to 5.85%. The admixture of support γ-Al2O3 with MCM-41 optimized the diversity of acidic intensity, structure, pore characteristics, and heat and mass transfer ability of mixed catalysts, and improved the reactivity and resistance to carbon deposition of catalysts.

Removal of NOx in the presence of oxygen over Mn/BaO/Al2O3 catalysts.

In this study, the influence of Mn content on the NOx decomposition in the presence of oxygen over xMn/BaO/Al2O3 catalysts (x is molar ratio of Mn/Ba) was investigated. Samples were characterized by N2 adsorption, XRD and SEM-EDX. The Mn loading, the dispersion of Ba on the surface and the BET surface area are the key factors affecting the NOx removal activity of the catalysts. The maximum conversion of NOx was obtained with 0.5 MnBa/Al sample. Lower and higher Mn loading resulted in a significant loss of the overall efficiency of NOx conversion. The lower NOx conversion at lower Mn loading (x=0.1) demonstrated that oxide manganese is the catalyst active site. The loss in efficiency observed at higher Mn loading is attributed to the lower dispersion of Ba on the surface, which could decrease the NOx storage ability, and the lower BET surface. There is no NOx conversion on support γ-Al2O3 or Ba/γ-Al2O3.

Gasification and Syngas Reforming of City Waste Papers for Solid Oxide Fuel Cells

This study has investigated the thermal processes of three types of Municipal Solid Wastes (MSW) in Taipei. Three key properties of the processes are concerned, the formation of tar, the sulfur content, and the reforming of CH4 as the syngas is used for Solid Oxide Fuel Cells (SOFCs). K2CO3 is used as a catalyst to reduce the amount of tar. One of tar production from MSW is reduced from 37.2 wt% to 13.7 wt%. The raw syngas from gasification is then reformed using a Ni-CeO2 catalyst on a γ-Al2O3 support to optimize the quantity of H2 and reduce the CH4 content. H2S generated by waste paper is in a level of 1.83 ppm, and reduced to 0.04 ppm by CaCO3. Syngas with a composition of 51.3 vol% H2, 44.8 vol% CO and 3.4 vol% CH4 is used for the power generation by a selfassembled SOFC. The best power density is 269 mW.cm-2 at 800°C, which is inferior to the maximum value of 326 mW.cm-2 for a cell that uses H2 as the fuel.

Synthesis Of Nano Ni-Mo/γ-Al2O3 CatalystSynthesis Of Nano Ni-Mo/γ-Al2O3 Catalyst

Nano γ-Al2O3 support was prepared by co-precipitation method by using different calcination temperatures (550, 600, and 750) oC. Then nano NiMo/γ-Al2O3 catalyst was prepared by impregnation method were nickel carbonate (source of Ni) and ammonium paramolybdate (source of Mo) on the best prepared nano γ-Al2O3 support at calcination temperature 550 oC. Make the characterizations for prepared nano γ-Al2O3 support at different temperatures and for nano NiMo/γ-Al2O3 catalyst like X-ray diffraction, X-ray fluorescent, AFM, SEM, BET surface area, and pore volume.&#x0D; The Ni and Mo percentages in the prepared nano NiMo/γ-Al2O3 catalyst determined by X-ray fluorescence were 2.924 wt % and 12.9 wt %, respectively. SEM of prepared nano γ-Al2O3 support at calcination temperature 550 oC. The average particles diameter of prepared γ-Al2O3 support determined by AFM at calcination temperatures 550, 600, and 750 oC and for prepared nano NiMo/γ-Al2O3 catalyst at calcination temperature 550 oC.

The role of tungsten oxide in the selective hydrogenolysis of glycerol to 1,3-propanediol over Pt/WOx/Al2O3

Bi-functional heterogeneous catalysts combining a noble metal with an oxophilic metal (mainlyW or Re) were reported to be selective for the CO hydrogenolysis of glycerol to the high added-value 1,3-propanediol. Despite intensive research work carried out, there is a great deal of controversy about the role of the oxophilic metal. In this work, the hydrogenolysis of glycerol over Pt/WOx/Al2O3 catalysts was studied in real time by in-situ attenuated total reflection infrared (ATR-IR) spectroscopy. Moreover, ex-situ ATR-IR spectroscopic studies were also used to study the interactions between glycerol and the different catalytic surfaces. The results obtained indicate a stronger adsorption of glycerol through the primary hydroxy group/s when tungsten oxides are grafted onto the γ-Al2O3 support. The competitive adsorption between the reactant and the main reaction products for the same active sites, and the effect of the hydrogen availability were also studied. The evidences found in this work point out a triple role of tungsten oxide in the reaction, acting as: (i) a strong anchoring site for the primary hydroxy group/s of glycerol, (ii) a supplier of protons, and (iii) a stabilizer of the secondary carbocation. Under the best conditions, a remarkable high yield of 1,3-propanediol of 38.5% was obtained after only 4h of reaction time.

Roles of phosphorous-modified Al2O3 for an enhanced stability of Co/Al2O3 for CO hydrogenation to hydrocarbons

A phosphorous-modified γ-Al2O3 (P-Al2O3), where γ-Al2O3 support was prepared by sol-gel method with a high surface area of ∼350m2/g, has been applied for a preparation of cobalt-supported Co/P-Al2O3 catalysts. The Co/P-Al2O3 catalysts having a different P/Al molar ratio were investigated to elucidate the roles of phosphorous species on the γ-Al2O3 to the catalytic stability and product distribution for CO hydrogenation to hydrocarbons. The γ-Al2O3 surface was partially transformed to aluminum phosphates after phosphorous modification, and the newly formed aluminum phosphate phases simultaneously altered the surface hydrophilicity and cobalt dispersion as well. The partial formation of tridymite aluminum phosphate (AlPO4) phases on the P-Al2O3 support eventually enhanced the dispersion of the supported cobalt crystallites and suppressed the aggregation of cobalt nanoparticles by forming the strongly interacted cobalt crystallites on the P-Al2O3 surfaces. The phosphorous-modified Fischer-Tropsch synthesis (FTS) catalyst also significantly suppressed heavy hydrocarbon depositions due to an increased surface hydrophilicity originated from partially formed SiO2-like tridymite AlPO4 surfaces. A higher stability of the Co/P-Al2O3 catalyst at an optimal phosphorous content in the range of 0.5–1.0 mol% was attributed to homogeneously distributed cobalt crystallites and less deposition of heavy hydrocarbons by forming macro-emulsion droplets with the help of trace amount of alcohols formed during FTS reaction. This was confirmed by in-situ analysis of adsorbed intermediates with surface hydrophilicity and some surface characterizations such as crystallite size, reducibility, and electronic state of the supported cobalt nanoparticles.

NO reduction by CO over TiO2-Γ-Al2O3 supported In/Ag catalyst under lean burn conditions

TiO2/Γ-Al2O3 supported In/Ag catalysts were prepared by impregnation method, and investigated for NO reduction with CO as the reducing agent under lean burn conditions. The microscopic structure and surface properties of the catalysts were studied by N2 adsorption-desorption, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, H2 temperature-programmed reduction and Fourier transform infrared spectroscopy. TiO2/Γ-Al2O3 supported In/Ag is a good catalyst for the reduction of NO to N2. It displayed high dispersion, large amounts of surface active components and high NO adsorption capacity, which gave good catalytic performance and stability for the reduction of NO with CO under lean burn conditions. The silver species stabilized and improved the dispersion of the indium species. The introduction of TiO2 into the Γ-Al2O3 support promoted NO adsorption and improved the dispersion of the indium species and silver species.

Acid-Modified Natural Bauxite Mineral as a Cost-Effective and High-Efficient Catalyst Support for Slurry-Phase Hydrocracking of High-Temperature Coal Tar

In this paper, we present a novel kind of supported Mo catalyst for hydrocracking high-temperature coal tar (HTCT), a byproduct of coal carbonization/gasification that has an abundant supply and is considered as a potential feedstock to refineries in the future. The catalysts are featured by their supports derived from a natural bauxite that has a low price and abundant reserves in the earth. The natural bauxite was modified via acid treatments with different acids (i.e., HCl, H2C2O4, H3PO4, HNO3, and H3BO3), and different supports were obtained. The physicochemical properties of the supports were systematically characterized, and the slurry-phase hydrocracking performance of the corresponding catalysts was assessed in a batch autoclave reactor. The results show that the modifications of the calcined natural bauxite with both HCl and H2C2O4 yield two supports with an enlarged specific surface area and pore volume and enhanced acidity as a result of the leaching of Fe2O3 and the enrichment of Al2O3. Such characteristics are responsible for the outstanding catalytic performance of the derived catalysts. Moreover, the bauxite-derived support can reduce the total catalyst cost by 50–60% compared to a conventional γ-Al2O3 support. Our success provides an economic and effective catalyst for refiners to convert unconventional heavy feedstocks to value-added products.

Spray pyrolysis synthesis of γ-Al2O3 supported metal and metal phosphide catalysts and their activity in the hydrodeoxygenation of a bio-oil model compound

In this study, spherical γ-Al2O3 supported metal and metal phosphide (Ni, Co, Ni2P and CoP) catalysts were successfully prepared by combining sol-gel and spray pyrolysis methods. First boehmite sol was prepared based on the Yoldas process and then the corresponding metal salts were added to the sol at the desired concentration, followed by spray pyrolysis of the mixed solution. As the well-mixed solution was transformed to spherical γ-Al2O3 supported metal and metal phosphide catalysts during spray pyrolysis process, the metal species were uniformly distributed in the mesoporous γ-Al2O3 supports. The product catalysts were investigated under different conditions for hydrodeoxygenation of bio-oil model compound, 2-furyl methyl ketone (FMK), which is the main component of the bio-oil product from pyrolysis of Saccharina japonica. Among the investigated catalysts, the 10wt% Ni/γ-Al2O3 catalyst after calcination at 800°C showed the highest FMK conversion of 83.02% at the reaction temperature of 400°C. The gas and liquid products were analyzed by gas chromatography (GC) with TCD/FID detectors and GC–MS, respectively, to determine the product compositions.

Development of Low-Temperature Methane Gas Sensors By Using Cup-Stacked Carbon Nanofilament-Supported Pd Catalyst

Methane gas is found in environment, industrial and domestic areas. On the other hand, methane can cause explosions due to its inflammability. Thus, detection of methane gas in the environment is very important to avoid any accidental explosion. Catalytic combustion-type methane gas sensors can detect methane gas immediately. This type of methane gas sensors utilizes heat from catalytic combustion of methane by Pd-loaded catalysts. To indicate high catalytic activity, it is necessary for catalyst to heat around 250 ~ 600 °C because of thermochemical stability of methane. Consequently, electrical power consumption on the sensors is large. Hence development of efficient methane sensors that could work even at low temperatures is required. In this work, cup-stacked carbon nanofilament (CSCNF) was used for Pd support material. γ-Al2O3 was used for general catalytic combustion-type methane gas sensors. Relatively large amount of Pd is required to indicate catalytic activity in using γ-Al2O3 support. On the other hand, CSCNF has functional groups such as C=O carbonyl-type structures and C-O-C ether-type structures on its edge surface regularly. These functional groups interact with metallic ion in preparing catalysts by impregnating method. Therefore, Pd can be discretely distributed in small particles on the surface of CSCNF. CSCNF supported catalysts are considered to indicated high activity with even small amount of Pd. Therefore, low-temperature combustion of methane is expected. Moreover, sensors can detect heat of methane combustion immediately because CSCNF has good thermal conductivity. Catalytic activity of Pd/CSCNF was evaluated by temperature programmed reaction (TPR). This catalyst combusted 1 % methane in air at relatively low temperature 270 °C. Pd/γ-Al2O3, which was reference, combusted methane at 330 °C. CSCNF support was able to upgrade catalytic activity of Pd nanoparticles. Pd/CSCNF could reduce methane combustion temperature 60 °C lower than that of Pd/γ-Al2O3. It seems that CSCNF supported catalysts are attractive for methane combustion at low temperatures. CSCNF-loaded catalysts are more efficient for catalytic combustion-type methane gas sensors than the conventional sensors.

Determination of the surface area and sizes of supported copper nanoparticles through organothiol adsorption—Chemisorption

The mechanisms involving the nanoparticle surfaces in catalytic reactions are more difficult to elucidate due to the nanoparticle surface unevenness, size distributions, and morphological irregularity. True surface area and particle sizes determination are key aspects of the activity of metal nanoparticle catalysts. Here we report on the organothiol adsorption-based technique for the determination of specific surface area of Cu nanoparticles, and their resultant sizes on γ-Al2O3 supports. Quantification of ligand packing density on copper nanoparticles is also reported. The concentration of the probe ligand, 2-mercaptobenzimidazole (2-MBI) before and after immersion of supported copper catalysts was determined by ultraviolet-visible spectrometry (UV–vis). The amount of ligand adsorbed was found to be proportional to the copper nanoparticles surface area. Atomic absorption spectrometry (AAS), N2-physisorption (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used for the characterization of the catalysts. A fair agreement was found between particle sizes obtained from ligand adsorption and TEM methods. The catalytic activity of the copper nanoparticles related to their inherent surface area was evaluated using the model reaction of the oxidation of morin by hydrogen peroxide.

Pollution Control Meets Sustainability: Structure-Activity Studies on New Iron Oxide-Based CO Oxidation Catalysts.

A new class of catalysts for the oxidation of CO based on iron oxide as a biocompatible, earth-abundant and non-toxic metal is presented. The catalytic activities achieved with these catalysts provide promising milestones towards the substitution of noble metals in CO oxidation catalysts. The catalysts can be obtained by using iron core-shell nanoparticle precursors. The metal used for the shell material determines whether the iron core is integrated in or isolated from the support. The active iron site is effectively integrated into the γ-Al2 O3 support if an aluminum shell is present in the core-shell precursor. When the metal used for the shell is different from the support, an isolated structure is formed. Using this directed synthesis approach, different iron oxide species can be obtained and their structural differences are linked to distinct catalytic activities, as demonstrated by combined in-depth analytical studies using XRD, X-ray absorption spectroscopy (XAS), UV/Vis, and Brunauer-Emmett-Teller (BET) analysis. The key species responsible for high catalytic activity is identified as isolated tetrahedrally coordinated Fe(III) centers, whereas aggregation leads to a reduction in activity.

Performance Comparison of Spray-dried Mn-based Oxygen Carriers Prepared with γ-Al2O3, α-Al2O3, and MgAl2O4as Raw Support Materials

Performance Comparison of Spray-dried Mn-based Oxygen Carriers Prepared with γ-Al2O3, α-Al2O3, and MgAl2O4as Raw Support Materials

Catalytic conversion of stearic acid to fuel oil in a hydrogen donor

Stearic acid (SA) was dispersed in tetralin (a hydrogen donor) and hydrotreated in a batch reactor over a fabricated sulfided NiMo/γ-Al2O3-β-zeolite catalyst to obtain a diesel-range fuel product. NiMo/γ-Al2O3-β-zeolite catalysts were prepared by loading the active components NiO and MoO3 onto a mechanically mixed γ-Al2O3 and β-zeolite support, followed by a sulfurization procedure. The effects of the catalytic properties and reaction conditions on the hydrodeoxygenation of SA were investigated. The results showed that increasing the β-zeolite in the support leads to a decrease in SA conversion and an increase in the isomerization of products; increasing the NiO and MoO3 mass fraction tends to promote the formation of alkene hydrocarbons and increase the level of isomerization; increasing the Ni molar fraction helps to promote both conversion and isomerization; and temperatures above 330 °C promoted the activities of the catalysts and tetralin. A nearly 90% SA conversion was achieved at 350 °C under H2 at a pressure of 0.8 MPa for 2 h in tetralin. The total content of C16C18 alkanes and alkenes in the products was about 98%, and the isomerized compounds accounted for 10–40 wt%.

The preparation of Mo/γ-Al2O3 catalysts with controllable size and morphology via adjusting the metal-support interaction and their hydrodesulfurization performance

In this work, a series of Mo/γ-Al2O3 catalysts have been prepared by using Mo species enwrapping with dodecyltrimethylammonium bromide (DTAB) as the novel precursors for the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The objective of this work is to get a deep insight into the effect of the Mo precursors on the size and morphology of the active phases and HDS activity. DTAB as the organic additive for the preparation of Mo precursors can dominate the nature of precursor solution and adjust the metal-support interaction so as to control the dispersion and morphology of the active phases. It is clearly shown that the addition of DTAB can effectively decrease the strong interaction between the Mo species and γ-Al2O3 support and favor to tune the size and morphology of MoS2 nanoparticles. The optimum molar ratio of DTAB/Mo is 3/5 and the corresponding catalyst shows the highest sulfidation degree with the most suitable stacking layer numbers and the shortest length of MoS2 and thus exhibits the best HDS performance. Our work explores the important roles of organic additive to adjust the metal-support interaction and control the morphology of active phases and provides an effective precursor which can be used widely to prepare supported catalysts.