Influences of preparation methods of ZrO2 support and treatment conditions of Cu/ZrO2 catalysts on synthesis of methanol via CO hydrogenation

ZrO₂ supports were prepared by different methods (conventional precipitation method, shortened as “CP”, and alcogel/thermal treated with nitrogen method, shortened as “AN”), and Cu/ZrO₂ catalysts were prepared by impregnation method. The supports and catalysts were characterized by BET, XRD, TEM and TPR. The effects of the preparation methods of ZrO₂ supports and the treatment conditions (calcination and reduction temperatures) of the catalyst precursors on the texture structures of the supports and catalysts as well as on the catalytic performances of Cu/ZrO₂ in CO hydrogenation were investigated. The results showed that the support ZrO₂-AN had larger BET specific surface area, cumulative pore volume and average pore size than the support ZrO₂-CP. Cu/ZrO₂-AN catalysts showed higher CO hydrogenation activity and selectivity of oxygenates (C₁–C₄ alcohols and dimethyl ether) than Cu/ZrO₂-CP catalysts. Calcination and reduction temperatures of supports and catalyst precursors affected the catalytic performance of Cu/ZrO₂. The conversion of CO and the STY of oxygenates were 12.7% and 229 g/kg h, respectively, over Cu/ZrO₂-AN-550 at the conditions of 300 °C, 6 MPa.     

Solvent effect on synthesis of zirconia support for tungstated zirconia catalysts

Solvothermal reaction of zirconium n-butoxide (ZNB) in different solvent media, such as 1,3-pentanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol resulted in the formation of zirconium dioxide (ZrO₂) nanostructure. Then, the 15%W/ZrO₂ (WZ) catalysts using different zirconia supports were prepared by impregnation method. The effects of solvent on preparation of zirconia on the catalytic performance of WZ catalysts in esterification of acetic acid and methanol at 60 °C were investigated. The experimental results showed that ZrO₂ particles prepared in 1,4-butanediol (ZrO₂-BG) have a spherical shape, while in other glycols the samples were irregularly-shaped particles. The reaction results of esterification illustrated that the W/ZrO₂-BG catalysts had high surface acidity and showed high acetic acid conversion. The W/ZrO₂-PeG catalysts (ZrO₂ particles prepared in 1,5-pentanediol, PeG) exhibited the lowest surface acidity among other samples due to strong interaction of proton species and the zirconia supports as proven by TGA. One of the possible reasons can be attributed to different amounts of carbon residue on the surface of catalysts.     

Promoting effect of rhenium on catalytic performance of Ru catalysts in hydrogenolysis of glycerol to propanediol

Ru/Al₂O₃, Ru/C and Ru/ZrO₂ catalysts were applied to the hydrogenolysis of glycerol to propanediol, and the effect of Re as an additive on the catalytic performance of Ru catalysts was examined. The catalyst systems were characterized by N₂ adsorption/desorption, XRD, TEM-EDX and XPS. The hydrogenolysis of glycerol was carried out under the conditions of 120–180 °C, 4–10 MPa hydrogen pressure and 4–8 h, and the conversion of glycerol varied from 18.7% to 29.7% over Ru/Al₂O₃, Ru/C and Ru/ZrO₂ catalysts. The reaction results indicate that Re possesses high promoting effect on the catalytic performance of Ru catalysts in glycerol hydrogenolysis.     

Dimethyl ether conversion to light olefins over the SAPO-34/ZrO2 composite catalysts with high lifetime

The SAPO-34/ZrO₂ composite catalysts using ZrO₂ as a binder were prepared and their performance was investigated for the dimethyl ether to olefins (DTO) reaction. The composite catalysts showed higher catalytic lifetimes than the free SAPO-34 catalyst, while maintaining high selectivity toward light olefins. This suggests that the binder-filled space between the SAPO-34 crystals can provide additional diffusion paths for mass transfer. In the SAPO-34/ZrO₂ composite catalysts with different ZrO₂ contents, the SAPO-34(11 wt%)/ZrO₂ composite catalyst showed the highest catalytic lifetime. It can be concluded that ZrO₂ is one of the best binders for the preparation of SAPO-34/binder composite catalysts.     

Effect of Pd loading and precursor on the catalytic performance of Pd/WO3–ZrO2 catalysts for selective oxidation of ethylene

The structure and properties of Pd/WO₃–ZrO₂ (W/Zr = 0.2) catalysts with different Pd loadings and precursors were investigated. The results indicate that Pd/WO₃–ZrO₂ prepared from a PdCl₂ precursor was optimum for high activity and selectivity. Moreover, ethylene conversion increased with the Pd loading. The structure and nature of the catalysts were characterized using X-ray diffraction, BET N₂ adsorption, H₂ temperature-programmed reduction and H₂ pulse adsorption techniques. The results reveal that the higher catalytic performance of Pd/WO₃–ZrO₂ prepared from PdCl₂ could be related to the formation of polytungstate species and the existence of well-dispersed Pd particles.     

Effect of the Y2O3–ZrO2 support composition on nickel catalyst evaluated in dry reforming of methane

Nickel catalysts with a load of 5 wt.% Ni, supported on pure ZrO₂ and ZrO₂ stabilized with 4 mol%, 8 mol% and 12 mol% of Y₂O₃, were prepared by the polymerization method. The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (TPR-H₂), specific surface area (BET) and electronic paramagnetic resonance (EPR) and tested as catalysts for carbon dioxide reforming of methane. The XRD patterns showed the presence of the oxide precursor (NiO) and the tetragonal phase of a Y₂O₃–ZrO₂ solid solution. According to the TPR-H₂ analysis, the reduction of various NiO species was influenced by the composition of the support. Catalytic tests were conducted at 800 °C for 6 h, and the composition of the gaseous products and the catalytic conversion rate depended on the composition of the Y₂O₃–ZrO₂ solid solution and its influence on the supported NiO species. A direct relation was observed between the variation in the support, the nickel species supported on it and the performance in the catalytic tests.     

Mesoporous CuO/TixZr1 − xO2 catalysts for low-temperature CO oxidation

Mesoporous CuO/Ti_xZr_1 − xO₂ catalysts were prepared by a surfactant-assisted method, and characterized by N₂ adsorption/desorption, TEM, XPS, in-situ FTIR and H₂-TPR. The catalysts exhibited high specific surface area (S_BET = 241 m²/g) and uniform pore size distribution. XPS and in-situ FTIR displayed that Cu⁺ and Cu²⁺ species coexisted in the catalysts. The CuO/Ti_xZr_1 − xO₂ catalysts presented obviously higher activity in CO oxidation reaction than the CuO/TiO₂ and CuO/ZrO₂ catalysts. Effect of molar ratios of Ti to Zr and calcination temperature on catalytic activity was investigated. The CuO/Ti_0.6Zr_0.4O₂ catalyst calcined at 400 °C exhibited excellent activity with 100% CO conversion at 140 °C.     

Effect of Al Content on the Isomerization Performance of Solid Superacid Pd–S2O82−/ZrO2 –Al2O3

The effect of Al content on the performance of the Pd–S₂O₈²⁻/ZrO₂ –Al₂O₃ solid superacid catalyst was studied using n-pentane isomerization as a probe reaction. The catalysts were also characterized by X-ray diffraction (XRD), Fourier transform Infrared (FTIR), specific surface area measurements (BET), thermogravimetry–differential thermal analysis (TG–DTA), H₂-temperature programmed reduction (TPR) and NH₃ temperature-programmed desorption (NH₃-TPD). The Pd–S₂O₈²⁻/ZrO₂ –Al₂O₃ catalyst made from Al₂O₃ mass fraction of 2.5% exhibited the best performance and its catalytic activity increased by 44.0% compared with Pd–S₂O₈²⁻/ZrO₂. The isopentane yield reached 64.3% at a temperature of 238 °C, a reaction pressure of 2.0 MPa, a space velocity of 1.0 h ^− 1 and a H₂/n-pentane molar ratio of 4.0. No obvious catalyst deactivation was observed within 100 h.     

Effect of promoters on hydrogenation of diethyl malonate to 1,3-propanediol over nano copper-based catalysts

Copper-based catalysts were prepared via ammonia evaporation co-precipitation method. Structure evolutions of the catalysts were systematically characterized by XRD, FTIR, TG, SEM, N₂-physisorption, ICP-AES, N₂O chemisorption and XPS focusing on the influence of promoters on the catalytic behavior in the hydrogenation of diethyl malonate to 1,3-propanediol. The results showed that diethyl malonate conversion and 1,3-propanediol selectivity could reach 96.71% and 29.76% respectively at 473 K with 2.0 MPa and 1.8 h^− 1 with boron as promoter. The improved catalytic performance of Cu-B/SiO₂ catalyst could be attributed to more Cu⁰ formed with the inhibition of copper phyllosilicate and better dispersion of copper species.     

The CO methanation over NaY-zeolite supported Ni/Co3O4, Ni/ZrO2, Co3O4/ZrO2 and Ni/Co3O4/ZrO2 catalysts

The CO methanation was studied over zeolite NaY supported Ni, Co₃O₄, ZrO₂ catalysts. The XRD, N₂ physisorption and SEM analysis were used in order to characterize the catalysts. Catalytic activities were carried out under a feed composition of 1% CO, 50% H₂ and 49% He between the 125 °C to 375 °C. Except for the Ni/Co₃O₄/NaY catalyst, all catalysts gave high surface area because of the presence of zeolite NaY. Average pore diameter of the catalysts fell into the mesopore diameter range. The highest CO methanation activity was obtained with Ni/ZrO₂/NaY catalyst at which the CO methanation was started after 175 °C and 100% CO conversion was obtained at 275 °C using the same catalyst.     

n-Hexane isomerization over copper oxide-promoted sulfated zirconia supported on mesoporous silica

Copper oxide-promoted sulfated zirconia (CuSZ) was supported on MCM-41 by the direct impregnation method. n-Hexane isomerization was investigated over the CuSZ/MCM-41 catalysts. 2-MP, 3-MP and 2,3-DMB are the major isomerization products, besides a small amount of 2,2-DMB. The product distribution is comparable to that reported for Pt based catalysts. The optimal CuO loading in these catalysts calcined at 700 °C is around 3.2 wt% and only leads to the formation of catalytic active metastable tetragonal ZrO₂. The improved performance of CuO-promoted SZ/MCM-41 is a trade-off between the sulfur amount and the content of tetragonal ZrO₂ phase.     

Catalytic performance and characterization of Ni-doped HZSM-5 catalysts for selective trimerization of n-butene

A series of Ni-doped HZSM-5 catalysts were prepared and the catalytic performance of these catalysts in n-butene trimerization was investigated. The Ni-loading, the Si/Al ratio of HZSM-5 and the reaction conditions (temperature, pressure and WHSV) played great influences on the catalytic performance of these catalysts in the reaction. 77.5 wt.% conversion of n-butene and 50.5 wt.% selectivity of trimers as well as 19.6 × 10^? 2 g_trimers/(g_cat h) yield of trimers were obtained on 1NiHZSM-5(320) catalyst up to 148 h at 420 °C, WHSV = 2 h^? 1 and 1.0 MPa. In addition, the physicochemical properties of these catalysts were comparatively characterized by powder X-ray diffraction (XRD), N₂ isothermal adsorption–desorption, infrared red spectroscopy (IR) and pyridine adsorbed infrared red spectroscopy (Py-IR) techniques. The doping of Ni into HZSM-5(320) modified the specific surface area and the acidity of these catalysts, which in turn affected the catalytic performance of these catalysts in n-butene trimerization. The acidic amount and the ratio of Lewis/Brönsted acid sites (L/B) on the external surface of these catalysts were close relative to the catalytic performance of these catalysts. 1NiHZSM-5(320) catalyst showed the highest catalytic performance in n-butene trimersization among the investigated catalysts because it had the proper acidic amount and the proper L/B ratio on its external surface.     

Characterization and catalytic properties of Ni and NiCu catalysts supported on ZrO2–SiO2 for guaiacol hydrodeoxygenation

ZrO₂–SiO₂ complex oxides with Si/Zr mole ratio of 3 (SZ-3) were synthesized. ZrO₂–SiO₂ supported Ni and NiCu catalysts were prepared by impregnation method. Their catalytic performances were evaluated in the hydrodeoxygenation (HDO) upgrading of model reactant guaiacol to hydrocarbons. The physicochemical properties of the support materials and catalysts were characterized by FTIR, XRD, TPD, TPR, and BET techniques. The addition of Cu significantly affected the acidity, and thus influenced their catalytic performance for product distributions. Over the Ni5Cu/SZ-3 catalyst, the cyclohexane selectivity of 80.8% and the methylcyclohexane selectivity of 12.4% were obtained with complete conversion of guaiacol under the 300 °C, 5.0 MPa H₂ pressure.     

Ageing mechanisms on PdOx-based catalysts for natural gas combustion in premixed burners

The ageing effect induced by S-compounds over 2%Pd/CeO₂·2ZrO₂, 2%Pd/LaMnO₃·2ZrO₂ and 2%Pd/BaCeO₃·2ZrO₂ catalysts for CH₄ combustion was investigated; S-compounds are in fact added as odorants in the natural gas network for safety purposes. Pd-based catalysts were prepared by solution combustion synthesis (SCS), starting from metal nitrates/glycine mixtures. Basic characterization (XRD, BET, FESEM analysis), FT–IR studies and catalytic activity tests were performed on powders and after accelerated ageing carried out up to 2 weeks (hydro-thermal treatment at 900 °C under a flow rate with typical domestic boiler exhaust gas composition, 9% CO₂, 18% H₂O, 2% O₂ in N₂, containing also 200 ppmv of SO₂ to emphasize any poisoning effect). Over fresh catalysts, IR analysis of CO adsorption evidenced the formation of highly dispersed Pd metal clusters and Pd ions. With ageing, 2%Pd/CeO₂·2ZrO₂ increased its CH₄ combustion half-conversion temperature (T₅₀, regarded as an index of catalytic activity) from 382 °C—recorded for fresh sample—to 421 °C, attained with the same sample aged two weeks. An unexpected improvement was found instead in the overall performance of 2%Pd/LaMnO₃·2ZrO₂ and 2%Pd/BaCeO₃·2ZrO₂: the T₅₀ in fact lowered from 570 to 450 °C for the first one, and from 512 to 443 °C for the second one, after two weeks ageing. S-hydro-thermal treatment provoked bulk and surface sulfates formation on all aged samples, with a concentration increasing with the exposure time. Prevailing ageing mechanisms seemed to be Pd metallic clusters coalescence, detected over the Ce–Zr system, and surface-bulk sulfates formation, the latter destroying the initial crystallographic structure. In 2%Pd/LaMnO₃·ZrO₂ and 2%Pd/BaCeO₃·ZrO₂ powders the amount of the perovskite phase strongly decreased during ageing, in favor of the formation of bulk sulfate and of oxides.     

Highly selective vapor phase Fries rearrangement of phenyl acetate to 2-hydroxyacetophenone using H3PO4/ZrO2–TiO2

ZrO₂–TiO₂ mixed oxides with a Ti and Zr molar ratio of 1/1 were prepared with and without surfactant by the sol–gel method. Catalysts containing 5–35% H₃PO₄ were prepared using these mixed oxides and the catalytic performance of each material for vapor phase Fries rearrangement of phenyl acetate (PA) to 2-hydroxyacetophenone (2-HAP) was determined. At optimized conditions, the conversion of PA over 15 wt.% H₃PO₄/TiO₂–ZrO₂-surf and 15 wt.% H₃PO₄/TiO₂–ZrO₂varied between 91% and 85.2% and selectivity to 2-HAP was between 81.9% and 48.3%, respectively. In all cases, the formation of 2-HAP was clearly favored in comparison to that of para isomer. The 4-HAP in the improved conditions was about 1.1%. In comparison with other catalysts, the percentage of phenol in the optimized condition was lower than 16%. The solvent effect on Fries rearrangement was investigated and dichloromethane showed better results. The Fries rearrangement was carried out in the temperature range of 473–673 K.     

Enhanced catalytic performance over Fe2O3-doped Pt/SO42 −/ZrO2 in n-heptane hydroisomerization

A series of Fe₂O₃-doped (1–5%) Pt/SO₄^2 −/ZrO₂ were prepared by a co-precipitation method. The incorporation of small amounts of Fe₂O₃ into Pt/SO₄^2 −/ZrO₂ results in an enhanced Brønsted acidity in the presence of H₂, which makes the Fe₂O₃-doped catalysts much more active than the undoped one for n-heptane hydroisomerization. A maximal yield of C₇ isomers appears at 3.5% Fe₂O₃.     

Intramolecular selective hydrogenation of cinnamaldehyde over CeO2–ZrO2-supported Pt catalysts

Selective liquid phase hydrogenation of cinnamaldehyde is reported, for the first time, over CeO₂, ZrO₂, and CeO₂–ZrO₂-supported Pt catalysts. Cinnamyl alcohol is the selective product. These catalysts are highly active and selective even at 25 °C and found to be superior to most of the hitherto known supported Pt catalysts. Alkali addition (NaOH) has enhanced the performance of these catalysts. At an optimized reaction condition, 95.8% conversion of cinnamaldehyde and 93.4% selectivity of cinnamyl alcohol have been obtained. Acidity of the support (due to the presence of ZrO₂ component) and higher electron density at Pt (due to CeO₂ component) are attributed to be responsible for the superior catalytic activity of Pt supported on CeO₂–ZrO₂ composite material.     

Ru/CexZr1−xO2, a novel and effective catalyst for the catalytic wet air oxidation of 2-chlorophenol

We report for the first time the use of Ce_xZr_1−xO₂ solid solutions as supports for Ru catalysts to be implemented in the catalytic wet air oxidation of 2-chlorophenol. Such catalytic systems appeared to be very efficient, even at low temperature (393 K) and low pressure (3 MPa), and exhibited a great advantage over Ru/CeO₂ or Ru/ZrO₂.     

Characterization and oxidation states of Cu and Pd in Pd–CuO/ZnO/ZrO2 catalysts for hydrogen production by methanol partial oxidation

Copper and zinc oxide based catalysts prepared by coprecipitation were promoted with palladium and ZrO₂, and their activity and selectivity for methanol oxidative reforming was measured and characterized by N₂O decomposition, X-ray absorption spectroscopy, BET, X-ray photoelectron spectroscopy, X-ray diffraction, and temperature programmed reduction. Addition of ZrO₂ increased copper dispersion and surface area, with little effect on activity, while palladium promotion significantly enhanced activity with little change of the catalytic structure. A catalyst promoted with both ZrO₂ and palladium yielded hydrogen below 150 °C. EXAFS results under reaction conditions showed that the oxidation state of copper was influenced by palladium in the catalyst bulk. A palladium promoted catalyst contained 90% Cu⁰, while the copper in an unpromoted catalyst was 100% Cu¹⁺ at the same temperature. Palladium preferentially forms an unstable alloy with copper instead of zinc during reduction, which persists during reaction regardless of copper oxidation state. A 100-h time on stream activity measurement showed growth in copper crystallites and change in copper oxidation state resulting in decreasing activity and selectivity. A kinetic model of the reaction pathway showed that palladium and ZrO₂ promoters lower the activation energy of methanol combustion and steam reforming reactions.     

Efficient and selective conversion of hexose to 5-hydroxymethylfurfural with tin–zirconium-containing heterogeneous catalysts

Efficient and selective production of 5-hydroxymethylfurfural (HMF) from the hexose is achieved in the presence of heterogeneous Sn-based catalyst. The mixed SnO₂–ZrO₂ is prepared from zirconium n-propoxide and different metal Sn precursors using Sol–gel method. The sulfated SnO₂–ZrO₂ (SO₄^2 −/SnO₂–ZrO₂) is obtained by the impregnation method with H₂SO₄ solution. All catalytic materials are detected with XRD, TG, SEM, TEM and BET techniques in order to reveal the physical properties and structures of these materials. When these materials were used in the dehydration of fructose, it was found that the suitable ratio of Sn/Zr is 0.5, and the catalytic activity of SO₄^2 −/SnO₂–ZrO₂ is higher than that of SnO₂–ZrO₂ where more than 75.0% yield of HMF was obtained for 2.5 h at 120 °C. The effects of reaction temperature and reaction time were also investigated. Moreover, the recycling experiment of catalyst shows that the catalytic activity can be almost kept unchanged after being used five times.