Selective hydrogenation of benzene to cyclohexene over Ru–Zn/ZrO2 catalysts prepared by a two-step impregnation method

Ru-Zn catalysts for selective hydrogenation of benzene using coprecipitation in low alkalinity

Surface Coordination Decouples Hydrogenation Catalysis on Supported Metal Catalysts

A series of Mg(Ca)Zr-doped acid-base bifunctional mesoporous silica were synthesized to study the impact of the one-step or two-step impregnation method on material structure. The two-step method seems to be a better way to synthesize metal-based functionalized catalyst and their catalytic performance is investigated using deacetalization-Knoevenagel reaction as the probe reaction. The coexisting dual active sites and suitable designing routes endowed highly efficient (Conv. >99.6%, Sel. >99.8%) and robust stability (10 consecutive cycles) of these materials. The present process succeeded in preparing catalysts decorated with acid-base sites by doping acidic and alkali metal species rather than grafting organic groups.

Promotion of manganese on Fe-based catalyst for the production of carbon nanotubes (CNTs) from plastics

Influence factors on activity of Ru–Zn catalysts in selective hydrogenation of benzene

Ru catalyst supported on bentonite for partial hydrogenation of benzene to cyclohexene

Highly dispersed Ni2P clusters inlaid in micropore openings on mesoporous ZSM-5 zeolite and its catalytic performance in the phenylacetylene semi-hydrogenation

CoMo catalysts supported on Beta-MCM-48 were prepared by different impregnation methods and calcination conditions with the addition of citric acid (CA). The addition of citric acid resulted in an increase of the catalytic activities in gasoline hydroupgrading, which was correlated to the formation of Mo–CA complexes, leading to higher MoS2 dispersion degrees and more amounts of Co–Mo–S active phases. The as-synthesized catalysts were characterized by powder X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, and the corresponding catalytic performance of FCC gasoline hydroupgrading was evaluated. The results showed that different impregnation methods and calcination conditions had a certain influence on their catalytic performance. In this research, CA-CoMo/ABM48-S catalyst obtained by two-step impregnation method and air-calcination had the shortest average length of 3.0 nm and the moderate stacking degree of 2.6, therefore, it made a good balance in hydrodesulfurization (HDS), hydroisomerization and aromatization activities, as a result it exhibited the highest HDS efficiency (95.0 %) and the lowest RON loss (0.5 unit).

Effect of magnesia on alumina-supported cobalt Fischer–Tropsch synthesis catalysts

Importance of metal location in M-H zeolite for synergistically catalyzing dimethyl ether carbonylation

Two Ni/Al2O3 catalysts with high Ni loadings of 36 wt% and 48 wt%, which possess high activities for aqueous-phase reforming of glucose, have been successfully prepared by a novel two-step impregnation method. The catalytic performance was investigated at 533 K and autogenous pressure in a batch reactor and a significant enhancement in hydrogen yield was observed over the catalyst prepared by two-step impregnation as compared to the corresponding catalyst prepared by conventional single impregnation. The catalysts were characterized by XRD, N2 adsorption/desorption, H2 chemisorption, O2 uptake, TPO, H2-TPR and TEM. It was found that two-step impregnation yielded catalysts with higher nickel dispersion as well as smaller nickel particle size compared to single impregnation.

Catalytic performance of zirconium-modified Co/Al 2O 3 for Fischer–Tropsch synthesis

The synthesis of nylon 6 and nylon 66 can be performed, starting with the selective hydrogenation of benzene to cyclohexene, which is deemed to be environmentally friendly and cost-saving and to have higher atom efficiency. Nano-Ru catalyst was synthesized via a precipitation method. The prepared catalyst was evaluated in the selective hydrogenation of benzene toward cyclohexene generation in the presence of ZnSO4 in a liquid batch reactor. The promotion effect of the addition of amines, i.e., ethylenediamine, ethanolamine, diethanolamine, and triethanolamine, was investigated. The fresh and spent catalysts were thoroughly characterized by XRD, TEM, AES, N2-sorption, FT-IR, and TPR. It was found that the addition of amines could significantly improve the catalytic selectivity toward cyclohexene formation in the presence of ZnSO4. This was attributed to the formation of (Zn(OH)2)5(ZnSO4)(H2O)x (x = 0.5, 3 or 4) through the reaction between ZnSO4 and the amines, which could be chemisorbed on the Ru surface. This led to retarding the formation of cyclohexane from the complete hydrogenation of benzene and, thus, increased the catalytic selectivity toward cyclohexene synthesis. Therefore, with the presence of ZnSO4, the amount of chemisorbed (Zn(OH)2)5(ZnSO4)(H2O)x increased with increasing amounts of added amines, leading to a decline in the catalytic activity toward benzene conversion and selectivity toward cyclohexene generation. When 7.6 mmol of diethanolamine and 10 g of ZrO2 were applied, the highest cyclohexene yields of 61.6% and 77.0% of benzene conversion were achieved over the Ru catalyst. Promising stability was demonstrated after six runs of catalytic experiments without regeneration. These achievements are not only promising for industrial application but also beneficial for designing other catalytic systems for selective hydrogenation.

How to control the size and morphology of metal nanocatalysts is of vital importance in enhancing their catalytic performance. In this work, uniform and ultrafine Ru–B amorphous alloy nanoparticles (NPs) supported on titanate nanosheets were fabricated via a confined synthesis in titanate nanotubes (TNTs) followed by unwrapping the tube to sheetlike titanate (TNS) (denoted as Ru–B/TNS), which exhibit excellent catalytic performance toward the selective hydrogenation of benzene to cyclohexene (yieldcyclohexene: 50.7%) without any additives. HRTEM images show the resulting Ru–B NPs are highly dispersed on the titanate nanosheets (particle size: 2.5 nm), with a low Ru–Ru coordination number revealed by EXAFS. Moreover, XPS demonstrates the surface-enriched B element and a strong electron transfer from B to Ru, which facilitates the formation and desorption of cyclohexene on the Ru active-sites, accounting for the significantly enhanced catalytic behavior. The surfactant-free confined synthesis and additive-free catalytic system make the Ru–B/TNS catalyst a promising candidate for the selective hydrogenation of benzene.

Organozirconium complexes are chemisorbed on Brønsted acidic sulfated ZrO2 (ZrS), sulfated Al2O3 (AlS), and ZrO2-WO3 (ZrW). Under mild conditions (25 °C, 1 atm H2), the supported Cp*ZrMe3, Cp*ZrBz3, and Cp*ZrPh3 catalysts are very active for benzene hydrogenation with activities declining with decreasing acidity, ZrS ≫ AlS ≈ ZrW, arguing that more Brønsted acidic oxides (those having weaker corresponding conjugate bases) yield stronger surface organometallic electrophiles and for this reason have higher benzene hydrogenation activity. Benzene selective hydrogenation, a potential approach for carcinogenic benzene removal from gasoline, is probed using benzene/toluene mixtures, and selectivities for benzene hydrogenation vary with catalyst as ZrBz3(+)/ZrS(-), 83% > Cp*ZrMe2(+)/ZrS(-), 80% > Cp*ZrBz2(+)/ZrS(-), 67% > Cp*ZrPh2(+)/ZrS(-), 57%. For Cp*ZrBz2(+)/ZrS(-), which displays the highest benzene hydrogenation activity with moderate selectivity in benzene/toluene mixtures. Other benzene/arene mixtures are examined, and benzene selectivities vary with arene as mesitylene, 99%, > ethylbenzene, 86% > toluene, 67%. Structural and computational studies by solid-state NMR spectroscopy, XAS, and periodic DFT methods applied to supported Cp*ZrMe3 and Cp*ZrBz3 indicate that larger Zr···surface distances are present in more sterically encumbered Cp*ZrBz2(+)/AlS(-) vs Cp*ZrMe2(+)/AlS(-). The combined XAS, solid state NMR, and DFT data argue that the bulky catalyst benzyl groups expand the "cationic" metal center-anionic sulfated oxide surface distances, and this separation/weakened ion-pairing enables the activation/insertion of more sterically encumbered arenes and influences hydrogenation rates and selectivity patterns.