ZrO2 Al2O3 Catalyst Research Articles

Generation of Pure H2 through CH4 Cracking Over Ni Supported on ZrO2 Modified Al2O3 Catalyst

Clean hydrogen formation via CH4 cracking on a zirconia-modified alumina support at 550 ºC and atmospheric pressure with constant Ni loading. The increased H2 yields on 20Ni/3 wt.% ZrO2-Al2O3 are explained by the large Ni surface area. TEM and XRD confirmed the deactivated catalyst’s graphitic origin, while Raman spectroscopy helped distinguish between ordered and disordered carbon. As determined by H2 pulse chemisorption, the high H2 yields produced by 20wt%Ni/3 wt.%ZrO2-Al2O3 catalyst is typified by well- ispersed Ni particles and large Ni metal area.

Synthesis of oxygenated additive fuels from bio-renewable glycerol using sulfated Zr-Al based heterogeneous acid catalyst

The exponential growth of biodiesel production generates an enormous amount of glycerol as a by-product that requires effective strategies to convert it into valuable chemicals to enhance the sustainability of the biodiesel market. Solketal is an interesting compound among various value-added chemicals obtained from waste glycerol produced during biodiesel production. In the present work, highly efficient and economically viable heterogeneous solid acid SO4-2/ZrO2-Al2O3 catalyst was designed via wetness impregnation process. The synthesized catalyst was found to be highly active for acetalization of glycerol with acetone under optimized conditions viz. 1:10 M ratio of glycerol and acetone, 3 wt.% of catalyst loading at 70 °C for 180 min reaction time. The synthesized catalyst is highly selective (98.9%) for solketal synthesis, with 98.1 % yield and 99.2 % glycerol conversion. Green metrics studies were performed to determine the environment-friendly nature of the catalyst and acetalization process. The carbon balance studies were also calculated to show that glycerol is found only in one phase during the overall process of solketal synthesis. The high thermal stability and catalytic activity were retained up to 5th reaction cycle making the catalyst more efficient for its wide application in an industrial level.

Enhanced low-temperature CO2 methanation over Ni/ ZrO2-Al2O3 catalyst: Effect of Al addition on catalytic performance and reaction mechanism

It is desirable but challenging to obtain high CO2 conversion in low-temperature CO2 methanation and elucidate the reaction mechanism on nickel-based catalysts. In this work, we incorporated Al into Ni/ZrO2 to form nickel-based catalysts supported by ZrO2-Al2O3 composite support. The addition of the appropriate amount of Al increased the dispersion of metal Ni on the catalyst surface, promoted the activation and dissociation of H2, and thus significantly improved the activity of CO2 methanation at low-temperature (< 300 °C). The CO2 methanation on nickel-based catalysts supported on ZrO2-Al2O3 composite supports all follow the formate reaction pathway. Since adding Al removes the ability of ZrO2 to activate H2, the active sites of the catalyst change from the surrounding support to the support-Ni interface, which improves the efficiency of the hydrogenation reaction of the active intermediate.

The preparation of Pd/CeO2–ZrO2–Al2O3 catalyst with superior structural stability: effect of zirconia incorporation method

A series of CeO2–ZrO2–Al2O3 (CZA) supports were prepared by coprecipitation method with different mixed modes of precursors, and the corresponding Pd-only catalysts were acquired with incipient impregnation technique. Interestingly, the CZA3 prepared by mixing of Ce(NO3)3·6H2O–ZrO(CO3)2 mixed solution and ZrO(CO3)2–Al(NO3)3·9H2O mixed solution showed better structural stability; meanwhile, the relevant Pd/CZA3 presented better catalytic activity and the operation window. The characterization results displayed that Zr was introduced into Ce and Al, respectively, could enhance the moderate interaction between Pd and support and increase oxygen vacancies as well as inhibit particle growth, agglomeration and phase separation. Moreover, the Pd–O–Ce bond could be weakened for Pd/CZA3 with appropriate Zr content, which was helpful for enhancing redox activity. Combining the results of characterizations and catalytic performance, it is revealed that the Pd/CZA3 possessed the greatest application potential for (three-way catalysts) TWCs.

Influence of sulfating method on La–Ni–S2O82–/ZrO2–Al2O3 solid superacid catalyst for n-pentane isomerization

La–Ni–S2O82–/ZrO2–Al2O3 catalysts were successfully prepared by two different methods of sulfate impregnation, and the physico-chemical properties of the catalysts were characterized by X-ray diffraction, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, pyridine adsorption–infrared spectroscopy, and X-ray photoelectron spectroscopy techniques. Catalytic activities were evaluated in a fixed-bed flow reactor using n-pentane isomerization as the probe reaction. Compared with catalyst La–Ni–S2O82–/ZrO2–Al2O3-I, prepared by the traditional impregnation method, the catalyst La–Ni–S2O82–/ZrO2–Al2O3-W, prepared by the incipient-wetness impregnation method, possessed higher pore volume, pore size, sulfur content, and stronger Brønsted acid sites. The catalytic activity for La–Ni–S2O82–/ZrO2–Al2O3-W was maintained at around 56% within 3000 min with an isopentane selectivity of 88% which showed much greater stability than that of La–Ni–S2O82–/ZrO2–Al2O3-I. This can be attributed to the fact that (1) the large pore size and pore volume of La–Ni–S2O82–/ZrO2–Al2O3-W can largely suppress carbon deposition and (2) the more numerous and stronger Brønsted acid sites for La–Ni–S2O82–/ZrO2–Al2O3-W guaranteed to provide enough acid sites for isomerization during the reaction process.

Conversion of Cellulose to Lactic Acid by Using ZrO2–Al2O3 Catalysts

Lactic acid has a wide range of applications in many industries, both as an ingredient and as an intermediate. Here, we investigated the catalytic conversion of cellulose to lactic acid by using heterogeneous mixed-oxide catalysts containing ZrO2. Although pure ZrO2 has catalytic activity for the conversion of cellulose to lactic acid, the yield of lactic acid obtained is not satisfactory. In contrast, a series of ZrO2–Al2O3 catalysts containing various percentages of ZrO2 provided higher yields of lactic acid. The ZrO2–Al2O3 catalysts had more Lewis acid sites and far fewer base sites than ZrO2. This suggests that the Lewis acid sites on ZrO2–Al2O3 catalysts are more important than the base sites for the conversion of cellulose to lactic acid.

Consequence of heterogeneity of active sites for reactivity mechanism of n-butane isomerization over SO42−/ZrO2-Al2O3 catalyst

The relationship between the heterogeneity of active sites and isomerization mechanism of n-butane over alumina-promoted sulfated zirconia (SZA) was elucidated by two series of catalysts with different surface properties. The incomplete removal of coke deposition leads to a decrease in overall activity without the reduction of the rate of isobutane formation. Subjecting the fresh SZA catalyst to the thermal treatment at 650°C causes a striking decrease in activity, resulting from the decrease in the superacidity and oxidizability of the catalyst. While the thermal treatment at 600°C only selectively suppresses the side reactions. It is found that the peaks in NH3-TPD profiles at 500–700°C are caused by a redox reaction between strongly adsorbed ammonia and superacid sites by in situ NH3-TPD-MS measurements. Thus, this peak reflects the strength of superacidity and oxidizability. At the beginning of the reaction, the effective oxidative and protonative activation routes result in the higher concentration of intermediates, which facilitates the “dimerization-isomerization-cracking” reactions. The incomplete removal of coke and the appropriate decrease in the density of sulfate species on the surface selectively promoted the monomolecular pathway.

Preparation of CeO2–ZrO2–Al2O3 composite with layered structure for improved Pd-only three-way catalyst

In this study, two CeO2–ZrO2–Al2O3 composites with layered structure were prepared by sequential precipitation route (SP) and compared with that obtained from conventional coprecipitation method (CC). The structural, textural and redox properties of the Pd-supported three-way catalysts were investigated by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, CO chemical adsorption, H2-temperature-programmed reduction and oxygen storage capacity (OSC). By adjusting the precipitation sequence of CZ and Al2O3 components, different combination styles of CZ and Al2O3 as well as different interaction between the two components are obtained, which consequently modifies the physicochemical properties, catalytic performance along with the thermal stability of the supported Pd/CeO2–ZrO2–Al2O3 catalysts. The catalysts derived from SP present comparable structural and textural thermal stability compared to that obtained from CC. From the aspects of XPS, TPR and OSC, more Ce3+ and improved redox properties are created by SP with respect to CC. In addition, the dispersion of palladium is enhanced due to the strong metal–support interaction. The catalytic performance evaluation results reveal that SP method leads to the formation of three-way catalysts with advanced catalytic activities for C3H8, CO and NO conversions especially when CZ is enriched in the outer layer.

Synthesis of nickel catalysts supported on Zr-doped ordered mesoporous Al2O3 and their catalytic performance for low-temperature CO2 reforming of CH4

A series of Zr-doped ordered mesoporous Al2O3 with various Zr contents were synthesized by evaporation-induced self-assembly strategy and the Ni-based catalysts supported on these Al2O3 materials were prepared by impregnation method. These catalysts with large specific surface area, big pore volume, uniform pore size possess excellent catalytic performance for the low-temperature carbon dioxide reforming of methane. The activities of these catalysts were tested in carbon dioxide reforming of methane reaction with temperature increasing from 500 to 650 °C and the stabilities of these catalysts were evaluated for long time reaction at 650 °C. It was found that when Zr/(Zr + Al) molar ratio = 0.5%, the Ni/0.5ZrO2–Al2O3 catalyst showed the highest activity, and exhibited superior stabilization compared to the Ni-based catalyst supported on traditional ordered mesoporous Al2O3. The “confinement effect” from mesoporous channels of alumina matrix is helpful to stabilize the Ni nanoparticles. As a promoter, Zr could stabilize the ordered mesoporous framework by reacting with Al2O3 to form ZrO2–Al2O3 solid solution. Since ZrO2 enhances the dissociation of carbon dioxide, more oxygen intermediates are given to remove the carbon formed during the reaction.

Isomerization of n-pentane over La-Ni-S2O82−/ZrO2-Al2O3 solid superacid catalysts: Deactivation and regeneration

A La-Ni-S2O82−/ZrO2-Al2O3 (La-Ni-SZA) catalyst was prepared and studied in the isomerization of n-pentane. The mechanisms of deactivation and methods for regeneration of the La-Ni-SZA catalyst were explored. The results revealed that the yield of isopentane using fresh La-Ni-SZA was maintained above 65% in the first 1000min. However, the yield fell sharply from 65% to 25% during the subsequent 2000min. The decline in pentane isomerization activity was slow initially, but increased significantly after 1000min. The deactivation of the La-Ni-SZA catalyst may be due to a combination of carbon deposition, loss of Brønsted acidity, removal of sulfur entities. Based on this analysis, two regeneration methods were proposed. It was found that catalytic activity of the spent catalyst could be partially recovered (58%) by calcination. Resulfating the calcined catalyst with 0.5molL−1 (NH4)2S2O8 increased the acidity significantly, especially Brønsted acidity, compared with fresh catalyst. The isopentane yield using the resulfated La-Ni-SZA was maintained at about 58%, with isopentane selectivity above 90%, during the tested 3000min. Compared with fresh catalyst, the resulfated catalyst showed sustained excellent stability, although the initial activity was slightly lower. The improved stability of the resulfated catalyst can be explained by: (1) suppression of carbon deposition to some extent; (2) formation of improved acidic nature by resulfation, favoring isomerization on acidic sites; (3) restructuring of the acid and metal sites via the calcination-resulfation procedure.

Effect of Additives on Cracking Characteristics of Dust-Containing Tar over Nickel-Based Catalysts

To develop tar-cracking catalysts with an industrial application value and to study the effect of dust species on the cracking characteristics of dust-containing tar, four kinds of modified nickel (Ni)-based catalysts were prepared by the incipient wetness impregnation method. Alkali and alkaline earth metal oxides K2O and MgO and transition metal oxides CeO2 and ZrO2 were used as additives. The activities and stability performances of these catalysts were investigated in a fixed-bed apparatus. The additions of K2O and MgO neutralized the acidity of the catalysts and reduced carbon deposition on the catalyst surface, and the additions of CeO2 and ZrO2 improved active ingredient dispersion. X-ray diffraction studies revealed that the (Zr0.85Ce0.15)O2 solid solution has good stability. The 2% NiO/1% CeO2/2% ZrO2–Al2O3 catalyst shows the highest activity and stability among the four modified Ni-based catalysts. Depositions of different species of dust on the catalyst surface have different influences on the ...

The effect of Zn–Fe modified S2O8 2−/ZrO2–Al2O3 catalyst for n-pentane hydroisomerization

Fe–Zn-doped S2O82−/ZrO2–Al2O3 (SZA) catalysts were synthesized and characterized by using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis, Fourier transform infrared (FT–IR) measurements, hydrogen temperature-programmed reduction (H2–TPR), and pyridine infrared (Py–IR) measurements. The effects of Fe and Zn on the structure and isomerization performance of SZA were studied using n-pentane as a probe reaction. Results showed that all of the samples show the pure peaks of tetragonal ZrO2. The addition of Zn can improve the redox performance of the catalysts, while Fe can lead to a better dispersion of sulfate ions on the surface of the catalysts. As a result, an improvement in the redox performance of the Zn–Fe–SZA catalyst was observed. The Zn or Fe can increase mainly Lewis acidity of the SZA, and the total acidity of samples decrease in the following order: Zn–Fe–SZA > Zn–SZA > Fe–SZA > SZA. The Fe–Zn–SZA catalyst exhibits the best catalytic activity for n-pentane isomerization. The isopentane yield of the Zn–Fe–SZA catalyst reaches 67.2 % at 443 K, which is an increase of 44.2 % when compared with that found for SZA at its optimum temperature of 573 K.

Lignin conversion in supercritical ethanol in the presence of solid acid catalysts

The effects of sulfated ZrO2 and ZrO2-Al2O3 catalysts and acidic zeolite catalysts with various Si/Al ratios on the thermal conversion of alkali lignin in supercritical ethanol at 300–400°C and on the composition of the resulting products have been investigated. All of the catalysts enhance lignin conversion into liquid products. The strongest effect with the catalysts based on sulfated ZrO2 is attained at 400°C; with the zeolites, at 350°C. The catalysts diminish the concentration of phenol and its derivatives and increase the concentration of ethers (mainly the 1,1-diethoxyethane concentration) in the liquid products. The zeolite catalysts are preferable, since the reaction over the ZrO2-containing catalysts produces gaseous compounds in higher yields. The maximum lignin conversion and a high yield of low-boiling liquid products are achieved at 350°C with the zeolite catalyst with Si/Al = 30, which contains a high concentration of acid sites that are stable at elevated temperatures. The most abundant phenolic liquid products of lignin conversion over the zeolite catalysts at 350°C are methoxyphenols and their methylated and ethylated derivatives.

Effect of Pd content on the isomerization performance over Pd-S2O8 2−/ZrO2-Al2O3 catalyst

The effect of Pd content on the performance of the Pd-S2O8 2−/ZrO2-Al2O3 solid superacid catalyst was studied using n-pentane isomerization as a probe reaction, and the catalysts were characterized by FTIR, BET, TG-DTA, H2-TPR, NH3-TPD and XPS. The results showed that an appropriate amount of Pd could promote the formation of acid sites, enhance the acidity of catalyst, improve the redox properties of the catalyst, and delay the decomposition of S2O8 2− effectively. The Pd-S2O8 2−/ZrO2-Al2O3 catalyst with 0.05 wt % Pd exhibited the best catalytic activity for n-pentane isomerization. At the reaction temperature of 200 °C, reaction pressure of 2.0 MPa, weight hourly space velocity of 1.0 h−1, H2/n-pentane molar ration of 4.0, the n-pentane conversion, iso-pentane selectivity and yield reached 61.1, 96.7, and 59.1 %, respectively, the isopentane yield with the Pd-S2O8 2−/ZrO2-Al2O3 increased by 39.1 % compared to S2O8 2−/ZrO2-Al2O3, and no obvious catalyst deactivation was observed within 100 h.

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 2.0MPa, a space velocity of 1.0h−1 and a H2/n-pentane molar ratio of 4.0. No obvious catalyst deactivation was observed within 100h.

Hydroisomerization of benzene-containing gasoline fractions on Pt/SO 4 2− -ZrO2-Al2O3 catalyst: Conversion of model and real feedstocks

The conversion of benzene-containing gasoline fractions on the bifunctional Pt/SO42−-ZrO2-Al2O3 catalytic system with different compositions of the support is studied. Using the results from hydroisomerization of a heptane-benzene model mixture, it is shown that a system with 67.8 wt % of aluminum oxide in its support has the best catalytic properties. For the IBP-85°C industrial benzene-containing fraction (23.7 wt % of benzene), it is established that the given catalyst ensures the complete removal of arenes from the benzene-containing fraction while raising its research octane number by 2.2–3.3 points and retaining a high yield of liquid products at levels of 98.7 wt % and higher.

Synthesis of acetic acid from ethanol–water mixture over Cu/ZnO–ZrO2–Al2O3 catalyst

It was shown that acetic acid can be obtained from aqueous ethanol (6–40mol%) solutions over Cu/ZnO–ZrO2–Al2O3 catalyst at 250–320°C and atmospheric pressure. Selectivity of 80–90% and space-time yield of acetic acid up to 9mmolgcat−1h−1 at 60–80% ethanol conversion were obtained while processing 14–37mol% aqueous ethanol solutions. Hydrogen was generated in an amount ~2moles per 1mole of acetic acid as a co-product.

Normal Hexane Hydroisomerization Over Alumina Modified Pt/SO4 2−/ZrO2 Catalyst

Pt/SO4 2−/ZrO2-Al2O3 (PSZA) catalysts were prepared by extruding sulfated hydroxide zirconium with SB powder. The n-hexane hydroisomerization reaction was performed in a continuous flow fixed-bed reactor. Isomerization activities under varying pretreatment parameters (including catalyst storage time before use, activating temperature, and reduction temperature) and reaction conditions (including reaction temperature, space velocity, and the molar ratio of hydrogen to n-hexane) were investigated. The results indicated the optimum pretreatment conditions for the PSZA catalyst is as follows: five days of storage, 350°C of the activation temperature, and 250°C of the reduction temperature. In addition, the optimum reaction conditions contained the reaction temperature ranging from 200 to 210°C, space velocity of 1 hr−1, and hydrogen to hexane mole ratio of 5.

One-pot synthesis of 5-hydroxymethylfurfural directly from starch over [formula omitted]/ZrO2–Al2O3 solid catalyst

The synthesis of 5-hydroxymethylfurfural (HMF) directly from starch was studied in dimethyl sulfoxide–water. The effects of catalyst variation, reaction time, water content, catalyst loading and temperature on the reaction were investigated. The SO42-/ZrO2–Al2O3 catalyst was found to act as a bifunctional catalyst with high activity for both hydrolysis and dehydration of starch. HMF yield of 55% was obtained after 6h at 423K for the reaction of starch (the molar ratio of water to glucose in starch is 44/1) over the SO42-/ZrO2–Al2O3 catalyst, which bears high acidity and moderate basicity with Zr/Al molar ratio of 1:1.

Hydroisomerization of benzene-containing gasoline fractions on a Pt/SO 4 2− -ZrO2-Al2O3 catalyst: III. The hydrogenating properties of the catalyst

The properties and state of platinum in Pt/SO 4 2− -ZrO2-Al2O3 catalysts with various alumina contents have been investigated in benzene hydrogenation as a model reaction using IR spectroscopy, temperature-programmed reduction, and H2 chemisorption. As the Al2O3 content is raised, the hydrogenating activity of the catalyst increases, which is due to the increasing proportion of metallic platinum on the surface.