Temperature-programmed Hydrogenation Research Articles

Preparation and characterization of a plasma treated NiMgSBA-15 catalyst for methane reforming with CO2 to produce syngas

A plasma-assisted method was employed to prepare a NiMgSBA-15 catalyst. The catalytic properties of this catalyst were tested in methane reforming with carbon dioxide. The plasma-treated catalyst exhibited a higher initial catalytic activity and a better stability than those of the untreated counterpart catalyst. To elucidate the effect of the plasma treatment, the catalysts were characterized using XRD, N2 physisorption, XPS, TPR, CO2-TPD, TEM, TGA, Raman and temperature-programmed hydrogenation (TPH) techniques. The results obtained confirmed that the plasma treatment of the Ni precursor had a significant impact on the surface characteristics of the active sites. The plasma treatment reduced the sizes of the Ni clusters and enhanced Ni–support interaction, which enhanced the catalytic performance. The stronger basic sites derived from plasma treatment favored the chemisorption of CO2 and drove the coke elimination. The sintering of the metallic Ni particles did not take place during tests due to the confinement effect of the pore channels of mesoporous material. In addition, the plasma-treated catalyst showed excellent resistance to the deposition of filamentous carbon and encapsulating carbon. This was in contrast to the calcined sample, whose surface was covered by large amounts of graphitic carbon species, resulting in activity loss.

The application of inelastic neutron scattering to investigate the ‘dry’ reforming of methane over an alumina-supported nickel catalyst operating under conditions where filamentous carbon formation is prevalent

The use of CO2 in reforming methane to produce the industrial feedstock syngas is an economically and environmentally attractive reaction. An alumina-supported nickel catalyst active for this reaction additionally forms filamentous carbon. The catalyst is investigated by inelastic neutron scattering as well as elemental analysis, temperature-programmed oxidation, temperature-programmed hydrogenation, X-ray diffraction, transmission electron microscopy and Raman scattering. Isotopic substitution experiments, using 13CO2 for 12CO2, show the oxidant to contribute to the carbon retention evident with this sample. At steady-state operation, a carbon mass balance of 95% is observed. A kinetic scheme is proposed to account for the trends observed.

Effect of cerium on the transformation and reactivity of hematite in a reducing atmosphere

As is well known, cerium compounds are widely used as promoters in iron-potassium catalysts for the dehydrogenation of alkylaromatic and olefinic hydrocarbons. To determine the mechanism and role of cerium oxide in formation of catalytically active phases (potrassium ferrites), we must first study the effect of cerium on transformation and reactivity of iron oxide, which comprises 50 to 80% of the catalyst and participates in ferrite formation. In this work, the thermal behavior of cerium oxalate and the Fe2O3-CeO2 model system, the main components in the production of iron-potassium catalysts, is examined by X-ray diffraction, thermal analysis, particle size distribution analysis, low-temperature nitrogen adsorption, and temperature-programmed hydrogen reduction under heating in air. It is shown that cerianite exhibits greater lability than hematite. It is established that introducing cerium into hematite improves the reactivity of the Fe2O3-CeO2 system, and the partial reduction of Fe2O3 takes place upon its heating. The results from this work will be used in developing new iron-potassium catalysts with enhanced catalytic activity in the dehydrogenation of isoamilenes into isoprene.

A comparison study on methane dry reforming with carbon dioxide over LaNiO3 perovskite catalysts supported on mesoporous SBA-15, MCM-41 and silica carrier

The supported LaNiO3 perovskite catalysts on mesoporous carrier (LaNiO3/SBA-15, LaNiO3/MCM-41 and LaNiO3/SiO2) with different pore structures have been synthesized via filling the pores of mesoporous silica with citrate complex precursors of nickel and lanthanum, with further treatments. The catalysts were characterized by means of N2 physisorption, XRD, HRTEM+EDX, TPR, temperature-programmed hydrogenation (TPH) and TGA techniques, and their catalytic performances were measured in methane dry reforming with carbon dioxide to hydrogen and synthesis gas (syngas). The results of low-angle XRD, N2 physisorption and TEM analysis showed that LaNiO3 perovskite was formed inside the channels of mesoporous supports, and the introduction of LaNiO3 perovskite did not destroy the mesoporous structure of support. The pore structure had a substantial influence on the catalytic performance. LaNiO3/MCM-41 exhibited the higher initial catalytic activity, owing to the higher Ni dispersion, while LaNiO3/SBA-15 was superior to LaNiO3/MCM-41 in the long-term stability, which could be due to the stable silica matrix restricted the agglomeration of nickel species. The hexagonal mesopores of LaNiO3/SBA-15 were still kept intact after reaction, while the mesoporous structure in LaNiO3/MCM-41 was collapsed during the reaction, which resulted in metal particles aggregation to certain extent. For comparison, the carbon deposition was responsible for the remarkable decrease of catalytic activity over LaNiO3/SiO2 sample, evidenced by TGA and TPH results.

Reduction of Different GeO2 Polymorphs

A combination of volumetric adsorption, thermal desorption and structure-determining methods was used to study and compare the hydrogen reduction behavior of three different GeO2 polymorphs: tetragonal, water-free hexagonal, and water-containing (hydroxylated) commercial hexagonal GeO2. Marked differences in the onset and extent of reduction between the two water-free polymorphs have been observed. Tetragonal GeO2 adsorbs more hydrogen at temperatures T ≤ 673 K and tends to be more easily reducible at low temperatures, but extended Ge metal formation at elevated temperatures is rather suppressed compared to both hexagonal GeO2 phases. Temperature-programmed hydrogen desorption spectra indicate the reduction-induced formation of weakly bonded hydrogen adsorption sites both on hydroxylated and pure hexagonal GeO2. The existence of the most weakly bonded hydrogen is linked to the transformation of initially present hydroxylated species into a tetragonal structure fraction upon annealing at ∼500 K. Thus, analogous forms of hydrogen were not observed on any of the pure (dehydroxylated) structures.

Methane reforming with carbon dioxide over a Ni/ZiO2–SiO2 catalyst: Influence of pretreatment gas atmospheres

Carbon dioxide reforming of methane to synthesis gas was studied over Ni/ZrO2–SiO2 catalyst under different pretreatment atmospheres. Characterization using powder X-ray diffraction, H2 temperature-programmed reduction, H2 temperature-programmed hydrogenation, TG/DTA, XPS, Raman spectra and transmission electron microscopy techniques revealed that gas atmospheres employed in the catalyst pretreatment have a significant influence on the catalytic performance. The helium-pretreated catalyst was found to be the most suitable catalyst for this application, showing the improved catalytic performance. More specifically, helium pretreatment facilitated the generation of well-distributed active metal sites while the heterogeneity of Ni components upon H2 pretreatment degraded catalytic activity of metal sites considerably. Pretreatment under CO atmosphere resulted in the formation of carbon encapsulated metal species thus causing catalyst deactivation severely. Inefficient reduction under CH4 activation and the presence of a great amount of carbonaceous species, disfavor the production of synthesis gas during the dry reforming.

Effect of Pretreatment Time in Dry Reforming over Ni/TiO2 Catalyst

In this study, the effects of the pretreatment time on the properties of Ni/TiO2 catalysts are examined. The optimum time has been determined to be below 3 h with regard to the catalytic activity. The difference between the CH4 conversion and CO2 conversion drastically increased for a catalyst pretreated for 4 h. The activity tests of the reverse water gas shift reaction (RWGS), temperature-programmed hydrogenation, and elementary reaction of dry reforming over the catalysts showed that the difference between the two conversions was attributed to the high RWGS reaction rate.

Synthesis, characterization and catalytic performances of Ce-SBA-15 supported nickel catalysts for methane dry reforming to hydrogen and syngas

A series of Ce-incorporated SBA-15 mesoporous materials were synthesized through direct hydrothermal synthesis method and further impregnated with 12 wt.% Ni. The samples were characterized by ICP-AES, XRD, N 2 physisorption, XPS, TPR, H 2 chemisorption, TGA, temperature-programmed hydrogenation (TPH) and TEM measurements. The low-angle XRD and N 2 physisorption results showed the Ce successfully incorporated into the framework of SBA-15. The catalytic properties of these catalysts were investigated in methane reforming with CO 2. The Ce/Si molar ratio had a significant influence on the catalytic performance. The highest catalytic activity and long-term stability were obtained over the Ni/Ce-SBA-15 (Ce/Si = 0.04) sample. The improved catalytic behavior could be attributed to the cerium impact in the framework of SBA-15, where cerium promoted the dispersion of nano-sized Ni species and inhibited the carbon formation. In comparison with the effect of CeO 2 crystallites in SBA-15, cerium in the framework of SBA-15 promoted the formation of the nickel metallic particles with smaller size. The XRD and TGA results exhibited that carbon deposition was responsible for activity loss of Ni/SBA-15 and Ni/Ce-SBA-15 (Ce/Si = 0.06) catalysts. TEM results showed that the hexagonal mesopores of SBA-15 were still kept intact after reaction and the pore walls of SBA-15 prevented the aggregation of nickel.

Transformation of carbonaceous species and its influence on catalytic performance for iron-based Fischer–Tropsch synthesis catalyst

Transformation behavior of carbonaceous species over a precipitated iron-based Fischer–Tropsch synthesis (FTS) catalyst was investigated by Mössbauer effect spectroscopy (MES), X-ray photoelectron spectroscopy (XPS), CO temperature-programmed desorption (CO-TPD), temperature-programmed hydrogenation (TPH), high resolution transmission electron microscopy (HRTEM) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The catalytic activities were tested in a fixed bed reactor. It was found that during carburization the fresh catalyst was firstly reduced from α-Fe 2O 3 to Fe 3O 4, accompanied simultaneously with the formation of atomic (C α ) and polymeric (C β ) carbonaceous species on the surface of the catalyst. With time on stream the Fe 3O 4 formed in the near-surface regions was converted gradually to χ-Fe 5C 2, and the amounts of C α and C β species presented an increasing trend. Subsequently, these species were combined partly together to form the graphitic-type (C δ ) carbonaceous species, and the C δ species largely covered on the surface of iron carbides. The formation of iron carbides (especially for χ-Fe 5C 2), C α and C β species on the surface layers promoted the catalytic activity, whereas the C δ species formed restrained the active sites for FTS reaction.

Synergetic Promotional Effects Between Cerium Oxides and Manganese Oxides for NH<SUB>3</SUB>-Selective Catalyst Reduction Over Ce–Mn/TiO<SUB>2</SUB>

Ce and Mn codoped Ce-Mn/TiO2 catalysts were synthesized by sol-gel method and were used as model catalysts to investigate the synergetic promotional effects between cerium oxides and manganese oxides for selective catalytic reduction of NO by NH3. The catalysts were characterized by SEM, XRD, XPS, and temperature-programmed hydrogen reduction (H-2-TPR) and ammonia desorption (NH3-TPD) techniques. The experimental results showed that cerium oxides and manganese oxides affected each other, and their catalystic activities improved both at low and high temperatures. The catalysts yielded more than 90% NOx conversion in the temperature range 250-450 degrees C and W/F of 0.00125 g min mL(-1) (W/F represents the ratio of the catalyst weight to the gas flow rate). It was suggested that the mobility of oxygen species enhanced through the sandwiched structure sic-Mn-O-Ce (sic represents the oxygen vacancy), leading to the enhancement of the NOx conversion over Ce-Mn/TiO2 significantly. Moreover, the Ce and Mn codoping improved the acid concentration with both medium acid sites and strong acid sites. Ce doping inhibited the growth of crystal size of TiO2, while Mn doping had little influence on it.

Hydrogen-assisted dechlorination of 1,2-dichloroethane on active carbon supported palladium–copper catalysts

A series of active carbon supported palladium–copper catalysts with varying amounts of both metal components and overall metal loading 2 wt.%, prepared by incipient wetness impregnation were characterized by temperature programmed reduction (TPR), hydrogen chemisorption, temperature programmed (palladium) hydride decomposition (TPHD), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). TPHD and XRD studies indicated that the bimetallic Pd–Cu/C catalysts exhibited a considerable degree of alloying. Pd/C, Cu/C and Pd–Cu/C catalysts were investigated in the hydrodechlorination (HdCl) of 1,2-dichloroethane in the gas phase at a relatively low reaction temperature (210–230 °C). All catalysts showed fair stability with time on stream (up to ∼15 h). The Pd/C and Pd-rich Pd–Cu catalysts essentially retained their initial activity while the bimetallic samples with higher Cu content exhibited some deactivation at the initial stage of reaction. Cu-rich bimetallic samples exhibited the highest selectivities toward ethene (desired reaction product), >90%. For all bimetallic Pd–Cu/C samples, this selectivity gradually increased with time on stream. XPS studies of freshly reduced and post-reaction catalysts did not support the hypothesis that during hydrodechlorination the surface of Pd–Cu is being gradually enriched in copper, as could be expected of a higher affinity of copper to chlorine. Post-reaction deposits investigated by the temperature programmed hydrogenation (TPH) showed substantial amounts of chlorine on the copper catalyst, whereas all palladium-containing Pd–Cu/C samples exhibited only carbon-containing deposit, with C 2-hydrocarbons desorbing at a relatively low temperature (300 °C). Suggested interpretation of catalytic data includes both the role of C 2H x species building up on catalyst's surface during hydrodechlorination as well as the role of Pd–Cu mixed sites in the mechanism of hydrogen-assisted dechlorination of 1,2-dichloroethane.

Effect of boron promotion on the stability of cobalt Fischer–Tropsch catalysts

Density functional theory (DFT) calculations indicate that boron atoms are thermodynamically stable at step, p4g clock, and subsurface sites of a Co catalyst under Fischer–Tropsch synthesis (FTS) conditions. Moreover, the presence of boron at step and clock sites is calculated to destabilize the adsorption of carbon atoms at neighboring sites by +160 and +108 kJ/mol, respectively. The calculations hence suggest that boron promotion can selectively block the deposition, nucleation, and growth of resilient carbon species. To experimentally evaluate this concept, the deactivation of a 20 wt.% Co/γ-Al 2O 3 catalyst promoted with 0.5 wt.% boron was studied for 200 h during FTS at 240 °C and 20 bar. Boron promotion was found to reduce the deactivation rate more than six-fold, without affecting the initial activity or selectivity. Characterization with X-ray photoelectron spectroscopy (XPS) and temperature-programmed hydrogenation (TPH) confirms that boron promotion reduces the deposition of resilient carbon species.

Mechanism of Biogas Reforming for Hydrogen Production over Ni-Co Bimetallic Catalyst

Ni-Co bimetallic catalysts supported on commercial γ-Al2O3 modified with La2O3 were prepared by conventional incipient wetness impregnation for biogas reforming. The catalysts were characterized using temperature-programmed hydrogenation (TPH), temperature-programmed oxygenation (TPO), temperature-programmed surface reaction (TPSR), temperature-programmed desorption (TPD), and a pulse experiment. During biogas reforming the surface carbon species on Ni-Co/La2O3-γ-Al2O3 originated mainly from the cracking of CH4 and the contribution of CO2 was insignificant. Cracking of CH4 results in three carbon species of Cα, Cβ, and Cγ, which have different reaction activities. During the reaction, the amount of Cα decreased but Cβ and Cγ increased. In addition, Cγ could be changed into inactive graphite carbon. The activation of CH4 and CO2 was mutually promoted in the reforming reaction. It was revealed that the controlling step for biogas reforming over the Ni-Co/La2O3-γ-Al2O3 catalyst could be the reaction of the surface species of O with C to form CO or with CHx to give CHxO followed by the formation of CO and adsorbed H.

Manganese promoting effects on the Co–Ce–Zr–O x nano catalysts for methane dry reforming with carbon dioxide to hydrogen and carbon monoxide

The Mn doping nanocrystalline Co–Ce–Zr–O x catalysts were prepared by the co-precipitation method and characterized by various physico-chemical characterization techniques such as X-ray diffraction (XRD), temperature- programmed reduction (TPR), O 2 temperature-programmed desorption (O 2-TPD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed hydrogenation (TPH). Their catalytic performances for methane reforming with CO 2 to hydrogen and carbon monoxide were investigated. Adding Mn remarkably enhanced the catalytic activity and stability of the Co–Ce–Zr–O x catalyst. The highest catalytic activity and long-term stability was obtained when the molar ratio of Mn/(Ce + Zr + Mn) was 10%. The improved catalytic behavior was closely related to the surface oxygen species and oxygen mobility. In comparison with that of Co–Ce–Zr–O x catalyst, the migration of bulk lattice oxygen species became easier, and the content of surface oxygen species was higher for the Mn-doped nanocrystalline Co–Ce–Zr–O x samples. TPH characterization showed that the surface coke species could be easily oxidized into CO x for the Mn-doped nano cobalt-composite catalyst due to the higher amount of mobile oxygen. The Mn incorporation promoted the dispersion of the nano-sized CoO x crystallites. In comparison with the impregnated samples, CoO x species dispersed better in the co-precipitated catalysts.

Influence of sulfur on the carbon deposition in steam reforming of liquid hydrocarbons over CeO 2–Al 2O 3 supported Ni and Rh catalysts

This study was performed to elucidate the influence of sulfur on the carbon deposition in steam reforming of liquid hydrocarbons over CeO 2–Al 2O 3 supported Ni and Rh catalysts at 800 °C. The characteristics of the carbon deposits on the used catalysts after the reactions without and with sulfur were investigated by temperature-programmed oxidation (TPO), transmission electron microscopy (TEM), scanning transmission X-ray microscopy (STXM), temperature-programmed hydrogenation (TPH), X-ray absorption near edge structure (XANES), and scanning electron microscopy (SEM). Though abundant carbon deposits can accumulate on the pure CeO 2–Al 2O 3 support due to fuel thermal cracking, the addition of Ni or Rh metal greatly reduced the carbon deposition in the sulfur-free reaction. The presence of sulfur increased the carbon deposition on both catalysts, which has a much more significant impact for the Ni catalyst. Carbon XANES study on the used catalysts revealed that graphitic carbon was dominant in the presence of sulfur, while oxidized carbon species (quinone-like carbon, carboxyl and carbonate) prevailed without sulfur. Meanwhile, the formation of carboxyl and carbonate more dramatically dropped on the Ni catalyst than that on the Rh catalyst. Our results strongly suggest that (I) the presence of sulfur can suppress carbon gasification and promote the formation of graphitic carbon on reforming catalysts due mainly to its poisoning effect on metals, and (II) Rh catalyst possesses stronger capability to maintain carbon gasification activity than Ni catalyst in the presence of sulfur.

Correlation of Oxygen Storage Capacity and Structural Distortion in Transition-Metal-, Noble-Metal-, and Rare-Earth-Ion-Substituted CeO2 from First Principles Calculation

Oxygen storage/release (OSC) capacity is an important feature common to all three-way catalysts to combat harmful exhaust emissions. To understand the mechanism of improved OSC for doped CeO2, we undertook the structural investigation by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2-TPR (temperature-programmed hydrogen reduction) and density functional theoretical (DFT) calculations of transition-metal-, noble-metal-, and rare-earth (RE)-ion-substituted ceria. In this report, we present the relationship between the OSC and structural changes induced by the dopant ion in CeO2. Transition metal and noble metal ion substitution in ceria greatly enhances the reducibility of Ce1−xMxO2−δ (M = Mn, Fe, Co, Ni, Cu, Pd, Pt, Ru), whereas rare-earth-ion-substituted Ce1−xAxO2−δ (A = La, Y) have very little effect in improving the OSC. Our simulated optimized structure shows deviation in cation−oxygen bond length from ideal bond length of 2.34 Å (for CeO2). For example, our theoretical calculation for Ce28Mn4O62 structure shows that Mn−O bonds are in 4 + 2 coordination with average bond lengths of 2.0 and 3.06 Å respectively. Although the four short Mn−O bond lengths spans the bond distance region of Mn2O3, the other two Mn−O bonds are moved to longer distances. The dopant transition and noble metal ions also affects Ce coordination shell and results in the formation of longer Ce−O bonds as well. Thus longer cation−oxygen bonds for both dopant and host ions results in enhanced synergistic reduction of the solid solution. With Pd ion substitution in Ce1−xMxO2−δ (M = Mn Fe, Co, Ni, Cu) further enhancement in OSC is observed in H2−TPR. This effect is reflected in our model calculations by the presence of still longer bonds compared to the model without Pd ion doping. The synergistic effect is therefore due to enhanced reducibility of both dopant and host ion induced due to structural distortion of fluorite lattice in presence of dopant ion. For RE ions (RE = Y, La), our calculations show very little deviation of bonds lengths from ideal fluorite structure. The absence of longer Y−O/La−O and Ce−O bonds make the structure much less susceptible to reduction.

Fe-Mo Catalysts with High Resistance to Carbon Deposition During Fischer–Tropsch Synthesis

Effects of Mo addition on the Fischer–Tropsch synthesis (FTS) performance of precipitated Fe and FeCu catalysts were tested at 280 °C, 1.5 MPa, H2/CO = 2.0, 2,000 h−1. Reaction results in fixed-bed reactor indicate that Mo addition stabilizes the selectivity to higher molecular-weight hydrocarbons of Fe and FeCu catalysts. Carbonaceous species over the spent catalysts were studied by Mossbauer effect spectroscopy (MES) and temperature-programmed hydrogenation (TPH). It is found that Mo addition inhibits the carbon deposition on iron catalysts surface during the FTS reaction and thus probably protects the active sites for producing heavy hydrocarbons. Mo addition inhibits the carbon deposition on iron catalysts surface during the Fischer–Tropsch synthesis and thus protects the sites for production of heavy hydrocarbons and stabilizes the selectivity to higher molecular-weight hydrocarbons (C5 +).

Carbon deposition on Co catalysts during Fischer–Tropsch synthesis: A computational and experimental study

The deactivation of a 20 wt% Co/γ-Al 2O 3 catalyst during Fischer–Tropsch Synthesis (FTS) at 240 °C, 20 bar, and a H 2:CO ratio of 2 was studied in a fixed-bed micro-reactor. The CO conversion had reduced by 30% after 200 h, and both carbidic and polyaromatic carbon species could be detected on the catalyst using a combination of Temperature-Programmed Hydrogenation (TPH), X-ray Photoelectron Spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM). Using Density Functional Theory (DFT), the relative stability of different types of deposited carbon on the Co catalyst was evaluated. Extended layers of graphene were the most stable form, followed by a p4g surface carbide phase initiating from the step edges. Both are more stable than surface CH 2 groups by 99 and 79 kJ/mol. The calculated C 1s core-level binding energies of 284.5 and 283.4 eV further support the presence of polyaromatic carbon and of a surface carbide.

Understanding the Effect of Cobalt Particle Size on Fischer−Tropsch Synthesis: Surface Species and Mechanistic Studies by SSITKA and Kinetic Isotope Effect

Co/γ-Al(2)O(3) catalysts with particle sizes in the range of 4-15 nm were investigated by isothermal hydrogenation (IH), temperature programmed hydrogenation (TPH), and steady-state isotopic transient kinetic analysis (SSITKA). Kinetic isotope effect experiments were used to probe possible mechanisms on Co/γ-Al(2)O(3) with different particle size. It was found that CO dissociated on Co/γ-Al(2)O(3) catalysts at 210 °C. The total amount of CO(2) formed following the dissociation depends on the cobalt crystal size. O-Co binding energy was found to be highly dependent on the Co metal particle size, whereas similar C-Co binding energy was found on catalysts with different Co particle size. Very strongly bonded carbon and oxygen surface species increased with decreasing particle size and acted as site blocking species in the methanation reaction. SSITKA experiments showed that the intrinsic activity (1/τ(CH(x))) remained constant as the particle size increased from 4 to 15 nm. The number of surface intermediates (N(CH(x))) increased with increasing particle size. The apparent activation energies were found similar for these catalysts, about 85 kJ/mol. D(2)-H(2) switches further confirmed that the particle size did not change the kinetically relevant steps in the reaction. The reactivity of the active sites on the 4 nm particles was the same as those on the 8, 11, and 15 nm particles, and only the number of total available surface active sites was less on the 4 nm particles than on the others.

Nickel-grafted TUD-1 mesoporous catalysts for carbon dioxide reforming of methane

The nickel active sites were introduced into TUD-1 mesoporous molecular sieve via grafting, direct synthesis, and impregnation methods. These samples were characterized using powder X-ray diffraction, N2 physisorption, H2 temperature-programmed reduction, H2 chemisorption, TG/DTA, temperature-programmed hydrogenation, Raman spectra and transmission electron microscope to give the insight of physicochemical properties. Catalytic tests probed by the carbon dioxide reforming of methane revealed that Ni-grafted TUD-1 exhibited the highest catalytic activity and long-term stability among these catalysts. Further studies implied catalytic activity, stability and carbon formation were highly sensitive to the metallic nickel particle size which was significantly affected by the introduction method of Ni active sites. Strong anchoring effect inherent to the grafting method was suggested to be the underlying reason for the small Ni particle size and improved catalytic performance.