Moderate Metal-support Interaction Research Articles

Hydrophobic surface modification and morphology tuning of supported KNiMoS-based catalyst for synergistically enhanced higher alcohols synthesis via CO hydrogenation

MoS2-based catalysts have gained significant attention in higher alcohols synthesis (HAS) via CO hydrogenation. However, the water–gas shift (WGS) to produce CO2 in HAS is undesirable reaction, which will reduce the efficiency of carbon utilization. Here, we provide a facile strategy with hydrophobic surface modification and metal-support interaction modulation to design a series of KNiMoS/MgAl catalysts. The organic modified SiO2 shell with excellent hydrophobicity effectively shortens the residence of water formed in HAS, and further suppress the generation of CO2 and low-chain hydrocarbons. Moreover, the moderate metal-support interaction between MoS2-based active species and MgAl support can regulate the dispersion and sulfidation extent of MoS2 slabs to provide more active sites for alcohol formation. The MoS2 slabs with predominant double-layer structure enhance the C–C propagation and CO insertion in HAS. And as a result, the optimal KNiMoS/MgAl@Si(c)-5 achieves total alcohols selectivity of 74.7 %, C2+OH selectivity of 85.8 % in total alcohols, and C2+ alcohols space–time yield of 107.8 mg gcat-1h−1, where C2+ alcohols space–time yield is 3.50 and 2.71 times than those on KNiMoS/MgAl(H) and KNiMoS/MgAl, respectively. Notably, the total selectivity of CO2 and hydrocarbons is less than 23.2 %, and selectivity ratio of C2-4OH to methanol can be overturned from 1.9 to 6.0. The dependence of HAS performance on the morphology of MoS2 slabs were also demonstrated to get insight into the structure-performance relationship. This work provides a facile strategy with tunable hydrophobic surface and metal-support interaction of MoS2-based catalysts for further improvement of catalytic performance.

Tuning the strong metal support interaction of the Fischer-Tropsch synthesis silica-coated cobalt-based nano-catalyst

The catalyst is crucial in enhancing productivity within the Fischer-Tropsch synthesis (FTS). The metal support interaction (MSI) plays a pivotal role in the FTS catalyst performance, impacting activity, stability, and selectivity. he configuration and composition of the catalyst dramatically impact MSI, with a strong MSI (SMSI) specified for the core-shell structure. In this study, two methods consisting of chemical treatment of etching and adding a promoter (Ru) for tuning the SMSI of the FTS catalyst are presented, and their footprints on the catalysts’ performance are screened by utilizing various characterization tests, molecular dynamic simulation, and catalytic tests. It is recognized that the silica interfacial perimeter acts as a barrier that restricts the charge transfer and boosts the SMSI in the silica-coated catalyst. Conversely, the etched catalyst exhibits a moderate MSI, contributing to increased reducibility, stability, and activity. Furthermore, the Ru-doped etched catalyst represents the optimum MSI, resulting in the highest overall performance.

Al-modified yolk-shell silica particle-supported NiMo catalysts for ultradeep hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene: Efficient accessibility of active sites and suitable acidity

Yolk-shell SiO2 particles (YP) with center-radial meso-channels were fabricated through a simple and effective method. Al-containing YP-supported NiMo catalysts with different Al amounts (NiMo/AYP-x, x = Si/Al molar proportion) were prepared and dibenzothiophene (DBT) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT) were employed as the probes to evaluate the hydrodesulfurization (HDS) catalytic performance. The as-prepared AYP-x carriers and corresponding catalysts were characterized by some advanced characterizations to obtain deeper correlations between physicochemical properties and the HDS performance. The average pore sizes of series AYP-x supports are above 6.0 nm, which favors the mass transfer of organic sulfides. The cavity between the yolk and the shell is beneficial for the enrichment of S-containing compounds and the accessibility between reactants and active metals. Aluminum embedded into the silica framework could facilitate the formation of Lewis (L) and Brønsted (B) acid sites and adjust the metal-support interaction (MSI). Among all the as-synthesized catalysts, NiMo/AYP-20 catalyst shows the highest HDS activities. The improved HDS activity of NiMo/AYP-20 catalyst is attributed to the perfect combination of excellent structural properties of the yolk-shell mesoporous silica, enhanced acidity, moderate MSI, and good accessibility/dispersion of active components.

Photochemical modulated metal-support-interaction of Pt-rutile TiO2 and the effects on catalytic oxidation of HCHO

The metal-support-interaction (MSI) has been attracting close attention for HCHO oxidation due to its specific electronic and structural effects. Here, we report a mild photochemical strategy for the modulation of the MSI between Pt and rutile TiO2. By increasing the irradiation intensity, more electrons were enriched on Pt and the contact between Pt and TiO2 became stronger, and even induce the encapsulation of Pt nanoparticles by TiO2. The apparent activation energies were 45.4 and 38.8 kJ/mol over the samples with weaker (P40) or stronger (P500) MSI, while decreased to 9.1 kJ/mol on the sample (P120) with moderate MSI. The promoted activity was much higher than that of most reported anatase and P25-based Pt/TiO2 catalysts. The balanced electronic structure and spatial structure favor the activation of oxygen species, thus promoting both the conversion of dioxymethylene to HCOO– species and the following decomposition of HCOO–.

Carbon nanotubes production from catalytic pyrolysis of polyethylene over nickel-based catalysts: The influence of support materials

To understand the influence of support materials on the reactivity of catalysts, four nickel- based catalysts supported on different materials (ZrO2, TiO2, Nb2O5, and Al2O3) were developed and investigated in the carbon nanotubes production from catalytic pyrolysis of polyethylene using two-stage fixed bed reactor. The results showed that the Ni/Al2O3 catalyst generated the highest carbon material yield of 36.5 wt%, while the order of carbon material yield was Ni/Al2O3 > Ni/TiO2 > Ni/ZrO2 > Ni/Nb2O5. To explore the correlation between catalysts properties and carbon products, the essential structural characteristics of fresh catalyst and reacted catalyst were analyzed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM), temperature program oxidation (TPO), nitrogen adsorption measurements and Raman spectroscopy. The Ni/Al2O3 catalyst with the highest surface area, abundant pore structure, and moderate metal-support interaction promoted the decomposition of pyrolysis volatiles to produce carbon nanomaterials, which were consist of carbon nanotubes (CNTs). CNTs are the main component of carbon materials produced, accounting for a relatively high proportion. In comparison, the large metal active particles and weak metal-support interaction of Ni/TiO2 catalyst had a negative impact on the formation of CNTs, generating many fishbone like carbon nanofibers (CNFs). Moreover, the poor pore structure and larger metal active particles for Ni/ZrO2 and Ni/Nb2O5 catalyst led to a low carbon deposition yield and poor quality of CNTs. The results provide valuable data and theoretical support for the research on the preparation of valuable carbon nanotubes from waste plastics.

CO2 methanation over the Ni-based catalysts supported on nano-CeO2 with varied morphologies

A series of CeO2 supports with particular morphologies (nanorods, nanocubes, nanooctas, and nanoparticles) were successfully fabricated by controlling the parameters of the hydrothermal method. The obtained nano-CeO2 materials were utilized as the supports of the Ni-based CO2 methanation catalysts prepared by the incipient impregnation method. It was found that the catalyst supported on the CeO2 nanoparticles (5Ni/NPs) exhibited much higher catalytic activity and better stability than those of catalysts with other morphological CeO2 supports. Thus, the catalytic performance of Ni/CeO2 catalysts could be facilely tuned and optimized by precisely designing the morphology of the CeO2 support. The XPS, CO2-TPD, and H2-TPR characterizing techniques showed that Ni-based catalysts supported on nano-CeO2 with varied morphologies displayed different catalytic performances. It was supposed that the typical merits, such as the abundant oxygen vacancy, medium basic sites, moderate metal-support interaction, excellent reduction ability, etc., were considered as the main origins for the enhancement of the low-temperature catalytic activities. Furthermore, the kinetic study revealed that the Ni-based catalysts supported on the nano-CeO2 with varied morphologies performed the different apparent activation energies toward CO2 methanation. The specific reaction intermediates and possible reaction pathways were carefully investigated through the in-situ DRIFTS and online TPSR techniques. Overall, this work would provide new perspectives that the roles of the morphology effect of the support ought to be emphatically considered when designing new catalysts.

Investigating the influences of metal-support interaction in Ni[sbnd]Fe catalysts on the quality of carbon nanomaterials from waste polypropylene

Pyrolysis-catalysis is a promising method to realize the recycling of waste plastic. Thereinto, metal-support interaction (MSI) has a crucial impact on the properties and performances of catalysts. Different active metal components (Ni or/and Fe) and pre-reduction process were introduced to adjust the metal-support interaction in this work. The results showed that moderate MSI was obtained from NiFe while Ni presented the weaker MSI and a stronger one was revealed for Fe. After pre-reduction, the promotion of MSI was observed for all catalysts, leading to the increase of active metal particle size. For the carbon deposition process, a higher CNMs yield (44.4 wt%) was obtained from NiFe, followed by 30.0 wt% of Fe and 18.2 wt% of Ni. The moderate MSI and synergistic effects of two metal species contributed to the CNMs production. However, different results were observed after fresh NiFe catalysts were reduced. Less carbon was formed on reduced monometallic Fe or bimetallic NiFe catalyst. This might be ascribed to the stronger MSI promoted by the pre-reduction of Fe-containing catalysts, inhibiting the catalyst activity. In addition, the strengthened MSI made the CNMs growth mechanism shift from tip-model to base-model and the graphitization degree of CNMs was also decreased. Our study may provide specific guidance for the production of high-valued CNMs recycling from waste plastics.

Boosting hydrogen production from steam reforming of glycerol via constructing moderate metal-support interaction in Ni@Al2O3 catalyst

In this manuscript, the relationship between metal-support interaction and the catalytic performance for hydrogen production from steam reforming of glycerol (GSR) over Ni-Al2O3 based catalysts was studied. Pure core–shell structured Ni@Al2O3 and supported Ni/Al2O3 with a fixed medium-sized nickel particle were synthesized without the other additional components to eliminate the influence of other factors. And then the nickel-alumina interaction of Ni@Al2O3 was tuned precisely and the regulatory mechanism of nickel-alumina interaction on catalytic activity was elaborated. The strong nickel-alumina interaction over Ni/Al2O3 and Ni@Al2O3 with high calcination temperature resulted in the formation of NiAl2O4, which was unfavorable to the reduction of nickel species to obtain the more active nickel. Consequently, the poor catalytic performance was caused. The moderate nickel-alumina interaction of Ni@Al2O3 promoted the exposure of the maximum area of active nickel and obtained higher turnover frequency (TOF). Thus, Ni@Al2O3 showed the high catalytic performance in GSR. Additionally, metal-support interaction affected the morphology and growth mechanism of coke deposition. For Ni@Al2O3 with moderate nickel-alumina interaction, the formation of carbon deposition followed the ‘tip-growth’ pattern, and the filamentous coke was mainly formed on catalysts. Conversely, ‘base-growth’ pattern was followed on Ni/Al2O3 with strong nickel-alumina interaction to form mainly encapsulated coke. The research findings of the regulatory role of interaction between nickel and alumina on catalytic performance will provide valuable guidelines for designing effective GSR catalysts.

Role of the solvent evaporating temperature on the NiMo/TiO2-Al2O3 catalyst and the hydrodesulfurization performance for 4,6-dimenthyldibenzothiophehe

Binary TiO2-Al2O3 serial composites(TA-x) and the NiMo supported catalysts(NiMo/TA-x) were successfully synthesized at different solvent evaporation temperatures,. The materials were characterized by several advanced characterization techniques, and the catalytic hydrodesulfurization (HDS) performances were evaluated. The results revealed that the synthesized TA-x serial composites are amorphous mixtures of TiO2 and Al2O3 with highly ordered two-dimensional hexagonal mesopores. Both the mesostructures and the acidities of the synthesized TA-x composites changed at different evaporation temperature of the solvent. The metal-support interaction(MSI), the existence states and the coordination states of the Mo precursors can be modulated by the changes in the physicochemical property of the TA-x composites caused by the solvent evaporating temperature. A moderate solvent evaporation temperature is favorable for the doping of Ni species into the MoS2 slab and Mo sulfidation degree, thus enhancing the proportion of the NiMoS active phases. Catalyst NiMo/TA-60 exhibits superior activity and the highest direct desulfurization(DDS) pathway selectivity due to the excellent acidity and pore structure property, the highest dispersion and the highest Mo sulfidation degree, a moderate MSI, the highest efficiency in the formation of NiMoS phase and the highest proportion of corner Mo atoms. Moreover, the rate constants of the specific HDS pathways can be correlated with the specific types of active sites: the DDS pathway (kDDS) is closely related to the proportion of corner active sites and the hydrogenation desulfurization pathway (kHYDS) is closely related to the proportion of brim sites. The activity of a single corner active site is found to be approximately 100 times that of a single edge active site. These findings are promising in the design of HDS catalysts for inferior distillates.

Hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene over NiMo supported on yolk-shell silica catalysts with adjustable shell thickness and yolk size

Mesoporous yolk-shell silica spheres with different shell thicknesses and yolk sizes (YxSy) were synthesized by incubating mesostructured silica nanospheres with water. Al-modified YxSy-supported NiMo catalysts were prepared and applied to hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The shell thickness and yolk size have a large effect on the HDS activities. Among the as-made catalysts, NiMo/Al-Y30S13 catalyst with relatively low shell thickness (13 nm), yolk size (30 nm) and proper structural stability exhibit the highest activities for HDS of DBT and 4,6-DMDBT at the weight time of 1.39–13.76 g min mol−1, of which its DBT conversion at 1.39 g min mol−1 (50.4%) is 1.5 times as that of the reference NiMo/Al2O3 (33.6%), four times as that of NiMo/Al-Y83S28 (12.3%) and what’s more, the HDS conversion of Al-Y30S13 could reach 99.5% at 13.76 g min mol−1 (about 2.5 ppm S remained). Its 4,6-DMDBT conversion at 1.39 g min mol−1 (27.1%) is almost 2 times as that over NiMo/Al2O3 (13.8%), and 2.7 times as that over NiMo/Al-Y83S28 (9.9%). Additionally, the 95.7% HDS conversion (about 16.6 ppm S remained) of Al-Y30S13 could be obtained at 13.76 g min mol−1. The good HDS performance of the NiMo/Al-Y30S13 catalyst could be derived from the synergistic effect of moderate shell thickness and relatively small yolk size, proper structural stability, appropriate acidity, moderate metal-support interaction (MSI), suitable dispersion and desirable stacking morphology of the Ni and Mo species. DBT HDS over the NiMo/Al-Y30S13 catalyst shows the lowest direct desulfurization (DDS)/hydrodesulfurization (HYD) ratio (2.70), demonstrating that the increase of HYD proportion could improve the ability of ultra-deep desulfurization of catalysts. 4,6-DMDBT HDS over the NiMo/Al-Y30S13 catalyst shows the highest selectivity of isomerization (ISO) route (69%), illustrating that the ISO route is the dominant pathway. Furthermore, the mechanisms of DBT and 4,6-DMDBT HDS are proposed over NiMo/Al-YxSy materials.

Modulating Fischer-Tropsch synthesis performance on the Co3O4@SixAly catalysts by tuning metal-support interaction and acidity

ZIF-67 derived catalysts for Fischer-Tropsch synthesis have attracted much attention in recent years, while there is still a potential to improve their activity and selectivity. In this work, we prepared Si/Al co-immobilized Co 3 O 4 @Si x Al y catalysts by in-situ doping tetraethylorthosilicate and aluminum nitrate during the synthesis of ZIF-67. The effects of different Si/Al ratios on the metal-support interaction, acidity and FTS performance were explored. Results indicated that the Co 3 O 4 @Si 0 Al 4 catalyst exhibited the best FTS performance with the CO conversion as high as 79.9% and CTY (cobalt time yield) value of 19.5 × 10 −5 mol CO ·g Co −1 ·s −1 , which was ascribed to the moderate metal-support interaction and the most active Co sites. Meanwhile, the Co 3 O 4 @Si 3 Al 1 and Co 3 O 4 @Si 2 Al 2 catalysts exhibited higher iso-paraffin and olefin selectivity due to more acidic sites. The Co 3 O 4 @Si 0 Al 4 catalyst exhibited the highest FTS activity due to the moderate metal-support interaction (MSI), while the Co 3 O 4 @Si 3 Al 1 and Co 3 O 4 @Si 2 Al 2 catalysts showed certain hydrocracking and isomerization ability due to the formation of acidic sites. • Co 3 O 4 @Si x Al y catalysts were prepared by in-situ doping method based on ZIF-67. • The Co 3 O 4 @Si 0 Al 4 exhibited the highest Fischer-Tropsch synthesis (FTS) activity. • The high activity was due to moderate metal-support interaction and most active sites. • Acidic sites promoted the hydrocracking and isomerization of long chain hydrocarbons.

Tuning Metal-Support Interaction of Pt-CeO2 Catalysts for Enhanced Oxidation Reactivity.

Metal-support interaction (MSI) has been widely recognized to be playing a pivotal role in regulating the catalytic activity of various reactions. In this work, the degree of MSI between Pt and CeO2 support was finely tuned by adjusting the activation condition, and the obtained catalysts were tested for the oxidative abatement of CO and HCHO under ambient conditions. The characterization of catalysts shows that activation of strongly interacting Pt-CeO2 at higher temperatures by H2 leads to a weaker MSI with increased electron density of Pt, and this modification of local electronic properties is demonstrated to result in enhanced O2 adsorption/activation to prevent the CO self-poisoning effect, while it abates the activity of CO adsorption/activation and oxidation of adsorbed CO. The Pt-CeO2 catalyst with a moderate MSI, which is able to balance each step in the catalytic cycle over Pt and Pt-CeO2 interface domains, displays the highest activity for CO/HCHO oxidation under ambient conditions.

Study of the Metal-Support Interaction and Electronic Effect Induced by Calcination Temperature Regulation and Their Effect on the Catalytic Performance of Glycerol Steam Reforming for Hydrogen Production.

Steam reforming of glycerol to produce hydrogen is considered to be the very promising strategy to generate clean and renewable energy. The incipient-wetness impregnation method was used to load Ni on the reducible carrier TiO2 (P25). In the process of catalyst preparation, the interaction and electronic effect between metal Ni and support TiO2 were adjusted by changing the calcination temperature, and then the activity and hydrogen production of glycerol steam reforming reaction (GSR) was explored. A series of modern characterizations including XRD, UV-vis DRS, BET, XPS, NH3-TPD, H2-TPR, TG, and Raman have been applied to systematically characterize the catalysts. The characterization results showed that the calcination temperature can contribute to varying degrees of influences on the acidity and basicity of the Ni/TiO2 catalyst, the specific surface area, together with the interaction force between Ni and the support. When the Ni/TiO2 catalyst was calcined at 600 °C, the Ni species can be produced in the form of granular NiTiO3 spinel. Consequently, due to the moderate metal–support interaction and electronic activity formed between the Ni species and the reducible support TiO2 in the NiO/Ti-600C catalyst, the granular NiTiO3 spinel can be reduced to a smaller Ni0 at a lower temperature, and thus to exhibit the best catalytic performance.

Rare earth metal doped nickel catalysts supported on exfoliated graphitic carbon nitride for highly selective CO and CO2 methanation

Rare earth metals like Ce and La oxides have emerged as potential promoter candidates for CO and CO2 methanation due to their unique properties. Herein, we report the synthesis by a facile impregnation method of nickel catalysts supported on exfoliated graphitic carbon nitride with cerium (Ni-Ce/eg-C3N4) and lanthanum (Ni-La/eg-C3N4) as promoters. Compared to Ni/eg-C3N4, the promoted catalysts showed an increased number of mesopores, a higher degree of dispersion of Ni nanoparticles, moderate metal-support interaction, and more surface basic sites. In terms of catalytic performance, Ni-Ce/eg-C3N4 catalyst exhibited the best CO methanation (XCO = 72%, SCH4 = 89%) and CO2 methanation (XCO2 = 83%, SCH4 > 99%) activities at ca. 279 °C and 297 °C, respectively. Considering the very high thermodynamic stability of the CO2 molecule, the temperature to achieve maximum conversion of CO2 was only 18 °C higher than CO, demonstrating the significant effect of the Ce promoter in the adsorption and activation of CO2 molecules. This can be attributed to the generation of sufficient active sites of surface defects or oxygen vacancies originating from the reduction of the CeO2 and Ni-Ce-O solid solution. Additionally, the creation of abundant mesopores in eg-C3N4 support increased the capacity of surface basic sites to promote the adsorption of CO2 molecules. The enhancement of CO2 adsorption and activation sites by the Ce promoter and eg-C3N4 support could be the key factor for the high catalytic activity of CO2 methanation at low temperatures.

Biosugarcane-based carbon support for high-performance iron-based Fischer-Tropsch synthesis

SummaryExploiting new carbon supports with adjustable metal-support interaction and low price is of prime importance to realize the maximum active iron efficiency and industrial-scale application of Fe-based catalysts for Fischer-Tropsch synthesis (FTS). Herein, a simple, tunable, and scalable biochar support derived from the sugarcane bagasse was successfully prepared and was first used for FTS. The metal-support interaction was precisely controlled by functional groups of biosugarcane-based carbon material and different iron species sizes. All catalysts synthesized displayed high activities, and the iron-time-yield of Fe4/Cbio even reached 1,198.9 μmol gFe−1 s−1. This performance was due to the unique structure and characteristics of the biosugarcane-based carbon support, which possessed abundant C−O, C=O (η1(O) and η2(C, O)) functional groups, thus endowing the moderate metal-support interaction, high dispersion of active iron species, more active ε-Fe2C phase, and, most importantly, a high proportion of FexC/Fesurf, facilitating the maximum iron efficiency and intrinsic activity of the catalyst.

Promising Biosugarcane-Based Carbon Support for High Performance Iron-Based Fischer–Tropsch Synthesis

Exploiting new carbon supports with adjustable metal-support interaction and low price is of prime importance to realize the maximum active iron efficiency and industrial-scale application of Fe-based catalysts for Fischer−Tropsch synthesis (FTS). Herein, a simple, tunable and scalable biochar support with 3D hierarchical pore structure, deriving from the sugar cane bagasse, was successfully prepared and first for FTS. The metal-support interaction was precisely controlled by functional groups of the biosugarcane-based carbon material and different iron species sizes introduced by iron loadings. All catalysts synthesized displayed greatly high activities, and the FTY of Fe4/Cbio even reached 1198.9 μmol gFe−1s−1, remaining an excellent stability for 150 h. The superior performance was belong to the unique structure and characteristics of the biosugarcane-based carbon support, which possessed abundant C−O, C=O (η1(O) and η2(C, O)) functional groups, thus endowed the moderate metal-support interaction, high dispersion of active iron species, more active e-Fe2C phase, and most importantly, high proportion of FexC/Fesurf, facilitating the maximum iron efficiency and intrinsic activity of the catalyst.

In situ grown metallic nickel from X–Ni (X=La, Mg, Sr) oxides for converting plastics into carbon nanotubes: Influence of metal–support interaction

The process of pyrolysis and in-line catalysis was employed for converting plastics into value-added carbon nanotubes (CNTs). The metallic nickel catalysts Ni/X (X = La, Mg, Sr) were prepared through in situ growth from parent X–Ni oxides under reductive conditions and used for the catalytic synthesis of CNTs. The results showed that the activities of nickel catalysts decreased in the order of Ni/La > Ni/Sr > Ni/Mg, which strongly depended on the degree of metal–support interaction. The strong metal–support interaction in Ni/Mg catalyst was not favorable for the exsolution of large amount of metallic Ni, resulting in the lowest yield of CNTs. On the other hand, the weak metal–support interaction in Ni/Sr was unfavorable for the high coverage of Ni nanoparticles, leading to the simultaneous growth of carbon nano-onions and CNTs. The Ni/La catalyst with moderate metal–support interaction exhibited the highest yield of CNTs due to optimized amount, size and surface coverage of Ni nanoparticles. The microstructure, graphitization degree, quality and purity of obtained carbon products were characterized using X-ray diffraction, electron microscopy, Raman spectroscopy and thermogravimetric analysis. This study demonstrated an effective and delicate approach to tune the supported metal nanoparticles, leading to enhanced catalytic activity.

Hierarchically Ordered Micro-/Mesoporous Material Assembled by a Zeolite W Nanocrystal and Its Hydro-Upgrading Performance for FCC Gasoline

A novel micro-/mesoporous composite material W-MCM-41 was synthesized through self-assembly of the zeolite W nanocrystal precursor. The hierarchical structure material inherited the combining advantages of the ordered mesopores of MCM-41 and the modulated acid properties of zeolite W. Different crystallization times of zeolite W and various molar ratios of CTAB/SiO2 were optimized to achieve good physicochemical properties of micro-/mesoporous materials, which were used to prepare the corresponding CoMo-supported catalysts. Various characterization methods were adopted to analyze the relationship between the catalytic performance and physicochemical properties of series catalysts. The CoMo/WMA catalyst presented the highest hydrodesufurization activity (93.4%) and the best octane number preservability (ΔRON = −1.3 unit), which could be attributed to desirable texture of support, moderate metal–support interaction, and highest sulfidation degree of active phases. The distribution of sulfide compounds in hy...

Dry reforming of methane over La2O2CO3-modified Ni/Al2O3 catalysts with moderate metal support interaction

The modulation of the interaction between the active metal and the underlying support material plays a key role and remains a challenge in many important catalytic reactions. This paper describes a new method for the modification of Ni/Al2O3 by La2O2CO3, which is responsible for modulating the interaction between Ni and the Al2O3 support. When La2O2CO3 is loaded on the Al2O3 support as a La2O3 precursor, combined with XRD, H2-TPR, H2-pluse chemisorption, Raman spectroscopy and TEM characterization, it is found that La2O2CO3 can prevent Ni from entering the alumina support and forming NiAl2O4. This strategy allows more Ni to be reduced and exposed as active sites. Consequently, the La2O2CO3 modified Ni/Al2O3 exhibited superior activity with respect to the reference La2O3 modified Ni/Al2O3 and original Ni/Al2O3 in dry reforming of methane (DRM). At the same time, La can cover the acidic sites of alumina and increase the alkalinity of the catalyst, thereby promoting carbon dioxide adsorption and activation, and inhibiting carbon deposition. In addition, the introduction of La also inhibits the sintering of Ni under harsh reaction conditions by enhancing the interaction between Ni metal and the support. This modification method can simultaneously improve the reactivity and stability of the catalyst by altering the interaction between the metal and the support.

Stabilizing Optimal Crystalline Facet of Cobalt Catalysts for Fischer–Tropsch Synthesis

Developing efficient catalysts with a stable optimal crystalline facet is highly promising yet challenging for the Fischer-Tropsch synthesis (FTS). Here, we demonstrate a coating strategy to fabricate a stable optimal cobalt-facet catalyst. The catalyst (Co@C-SiO2) is composed of a single crystalline core, a wrapped carbon layer, and an amorphous silica shell. The moderate metal-support interaction endowed by carbon, combining the confined effect of the silica shell, protects and maintains the single-crystal structure and optimal crystalline facet of the core, that is, Co(10-11). Due to the unique core-shell nanostructure and optimal cobalt facets, our Co@C-SiO2 catalyst shows a remarkable low methane selectivity (5.3%), high activity (TOF = 4.0 × 10-2 s-1), C5+ selectivity (88.9%), and more importantly, excellent stability (TOS = 168 h) in FTS.