Cation Anion Double Hydrolysis Research Articles

Facile one-pot synthesis of Ni-based catalysts by cation-anion double hydrolysis method as highly active Ru-free catalysts for green H2 production via NH3 decomposition

A series of Ni/Al1CeaOx composites prepared by various synthetic methods, including one-pot anion-cation double hydrolysis (CADH), co-precipitation (CP), CADH followed by wet impregnation (CADH-WI), and CP followed by wet impregnation (CP-WI) were employed as catalysts for ammonia (NH3) decomposition to generate hydrogen. The results revealed that the catalyst prepared by the one-pot CADH method exhibited outstanding catalytic performance (complete NH3 decomposition at around 550 °C) mainly because of significant enhancement in Ni dispersion, Ni reducibility, the quantity of surface oxygen vacancy, and NH3 adsorption affinity. The superior catalytic performance of Ce-containing catalysts over Ni/Al2O3 catalyst was ascribed to the synergistic effects of NiO reducibility, surface oxygen vacancies, basicity, and Ni-support interaction. The selected catalysts demonstrated excellent stability during 100 h continuous operation, without any obvious decrease in NH3 conversion. Overall, the proposed one-pot CADH method offers great advantages in preparing highly active and stable Ni-based catalysts for NH3 decomposition.

CO2 Reforming of Methane over a Highly Dispersed Ni/Mg–Al–O Catalyst Prepared by a Facile and Green Method

A novel Ni/Mg–Al–O catalyst has been successfully synthesized by the cation–anion double hydrolysis (CADH) method for carbon dioxide (CO2) reforming of methane. Compared with the Ni/MgO–Al2O3 catal...

Adsorption of 4,6-dimethyldibenzothiophene and collidine over MoO3/γ-Al2O3 catalysts with different pore structures

Mesoporous γ-Al2O3 supports with different pore structures were prepared by the cation-anion double hydrolysis method. Based on these samples, MoO3/γ-Al2O3 catalysts were made via impregnation. The adsorptions of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and collidine over the supports and catalysts were studied by FT-IR. The supports or catalysts with larger pores can adsorb more 4,6-DMDBT. The methyl groups on adsorbate molecules are very close to the sulfur atom, resulting in apparent steric hindrance. Increasing the pore size can promote the interaction between the adsorbates and supports or catalysts, enhancing the CC bond and weakening the CS bond of 4,6-DMDBT. 4,6-DMDBT molecules were coordinated with the unsaturated Mo atoms over the catalysts to form π-complexation adsorption. There was much difference between thiophene and 4,6-DMDBT adsorption. The adsorption of collidine over the catalysts also illustrated that there existed steric hindrance. Significantly, the catalyst with hierarchical mesopores was beneficial for the adsorbates with larger molecular dynamics diameter. Compared with the pore size, the specific surface area was not the key factor to affect the adsorptions of 4,6-DMDBT and collidine. The hydrodesulfurization reaction of 4,6-DMDBT illustrated that the catalysts with larger pore size or hierarchical pore structure presented higher desulfurization efficiency (above than 80%).

A facile one-pot cation-anion double hydrolysis approach to the synthesis of supported MgO/γ-Al2O3 with enhanced adsorption performance towards CO2

A series of supported MgO/γ-Al2O3 composites (denoted as Mg/Al-x) with enhanced adsorption performance towards CO2 were successfully synthesized via a facile one-pot cation-anion double hydrolysis approach. Their phase structures, morphologies, textural properties and basic properties were comparatively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), N2 adsorption-desorption, in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) and CO2 temperature programmed desorption (CO2-TPD). Three kinds of carbonates including bicarbonate, bidentate and monodentate carbonate are formed during the adsorption process, indicating a synergistic adsorption mechanism for CO2. For the dynamic CO2 adsorption without water vapor, the adsorption capacity decreases in the order of Mg/Al-0.2>Mg/Al-0.3>Mg/Al-0.1>Mg/Al-0, which coincides with the trend of the amount of basic sites; especially, Mg/Al-0.2 with the Mg/Al molar ratio of 0.2 shows a stable adsorption capacity of 1.60mmol/g without loss after 11 cycles at 60°C. Furthermore, water vapor shows a positive effect on their adsorption, and Mg/Al-0.2 reaches an adsorption capacity of 2.10mmol/g for the simulated flue gas with 10vol% water vapor at 60°C. Its relatively high adsorption capacity, excellent cyclic adsorption/desorption stability and facile preparation process make it an attractive candidate for CO2 capture with flue gas conditions.

Superior performance of freeze-dried Ni/ZnO-Al2O3 adsorbent in the ultra-deep desulfurization of high sulfur model gasoline

Reactive adsorption desulfurization (RADS) is an effective approach to the ultra-deep desulfurization under mild conditions. The sulfur adsorption capacity of the adsorbents strongly depends on the pore structure, the chemical states and the dispersion of active species. In this work, ZnO-Al2O3 mixed oxides with an improved structure were synthesized via a freeze-drying modified cation-anion double hydrolysis (CADH) technique and used as the support. The fresh and spent catalysts were characterized through N2 adsorption-desorption, H2-temperature programmed reduction, X-ray diffraction, UV–vis diffuse reflection spectroscopy, Fourier transformed infrared spectroscopy and transmission electron microscopy (TEM). Freeze drying technique provided the adsorbent with a smaller sized ZnO and an improved pore structure compared with the normal oven drying method. Evaluation results in the RADS of a high sulfur model gasoline reveals that the freeze-dried Ni/ZnO-Al2O3 (40°C) with a crystallization temperature of 40°C exhibits a superior RADS performance with an accumulative sulfur adsorption capacity of 90mgS/g, which is 5.3% and 118% higher than those of adsorbents prepared by the normal oven drying and the conventional kneading methods. A high amount of small ZnO particles, improved textural properties and the absence of inactive NiAl2O4 phase are among the factors accounting for the superior RADS performance of Ni/ZnO-Al2O3 adsorbent prepared by the freeze-drying method. Upon four RADS-regeneration cycles, sample Ni/ZnO-Al2O3 (40°C) exhibited a high stability without evident activity loss.

Relationship between Surface Chemistry and Catalytic Performance of Mesoporous γ-Al2O3 Supported VOX Catalyst in Catalytic Dehydrogenation of Propane

Mesoporous γ-Al2O3 was synthesized via a cation-anion double hydrolysis approach (CADH). The synthesized mesoporous alumina displayed a relatively high surface area, a large pore volume and a narrow pore size distribution. By applying the mesoporous alumina as a support, supported vanadium catalysts were prepared and evaluated in the dehydrogenation of propane, exhibiting a superior catalytic performance over that supported on a commercial alumina. Materials were characterized with a variety of techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, 51V magnetic angle spinning nuclear magnetic resonance, Raman spectroscopy, Fourier transformed infrared spectroscopy of pyridine adsorption and thermogravimetric-differential thermal analysis. The correlated structure-performance relationship of catalysts reveals that a higher crystallization temperature endows mesoporous alumina materials with more surface acid sites, favoring the formation of polymerized VOX species, which are more active than isolated ones in the propane dehydrogenation, resulting in a better catalytic performance. The established relationship between surface chemistry and catalytic performance of supported VOX catalysts suggests that a superior vanadium catalyst for propane dehydrogenation could be achieved by rationally enriching the concentration of polymeric VOX species on the catalyst, which can be realized by tuning the surface acidity of alumina support.

Comparison of the Reactive Adsorption Desulfurization Performance of Ni/ZnO–Al2O3 Adsorbents Prepared by Different Methods

In this study, a series of Ni/ZnO–Al2O3 mixed oxide (MO) adsorbents were prepared by the one-step homogeneous precipitation method and the cation–anion double hydrolysis (CADH) method for reactive adsorption desulfurization (RADS) using thiophene as a model fuel in a fixed bed reactor. The synthesized adsorbents were characterized by N2 sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS), and Raman spectroscopy. Results show that both Ni loading and the preparation method have a significant effect on the RADS activities of the adsorbent. Among the studied adsorbents, 10% Ni/ZnO–Al2O3 prepared by the one-step urea precipitation method showed the best RADS performance, with a thiophene conversion up to 96% and a sulfur adsorption capacity of 86 mg of S/g, which is 34% larger than that of CADH adsorbents. In addition, upon five RADS–regen...

One-Pot Cation–Anion Double Hydrolysis Derived Ni/ZnO–Al2O3 Absorbent for Reactive Adsorption Desulfurization

In this study, a series of Ni/ZnO–Al2O3 adsorbents were synthesized by a one-pot cation–anion double hydrolysis (CADH) method. The materials were characterized by N2 sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible diffuse reflectance spectroscopy (UV–vis), Raman spectroscopy, and H2 temperature-programmed reduction (H2-TPR). The reactive adsorption desulfurization (RADS) performance of the adsorbents was evaluated in a fixed bed reactor using thiophene in n-octane as a model fuel. Results showed that the adsorbents exhibited better RADS performance than those prepared using the conventional kneading method. The thiophene conversion and sulfur capacity of adsorbents decreased with increasing the crystallization temperature. Among all tested adsorbents, the Ni/ZnO–Al2O3 sample prepared at 28 °C presented the largest adsorption capacity and highest RADS reactivity. Textual characterization results indicated that the sample Ni/...

Adsorption of thiophene compounds on MoO3/γ-Al2O3 catalysts with different mesopore sizes

γ-Al2O3 without amorphous domains was synthesized by cation-anion double hydrolysis method. The mesopore size in the range of 3.9–8.5 nm was easily controlled by regulating crystallization temperature, solution pH value and the concentration of NaAlO2. The introduction of MoO3 to the γ-Al2O3 via impregnation method can lead to a decrease of specific surface areas, pore sizes and pore volumes of the supports. The less steric hindrance of the larger mesopores (particularly 8.5 nm) exhibits the more Lewis acid sites over the γ-Al2O3. The MoO3/γ-Al2O3 possesses more Bronsted acid sites compared to Lewis. The thiophene compounds can be adsorbed both on the supports and catalysts. The acid sites can facilitate the interaction between the thiophene compounds and catalysts (or supports). The more adsorbed thiophene and dibenzothiophene on the catalysts is attributed to the coordinately unsaturated metal sites and Bronsted acid sites on the surface of the catalysts. Of note is the supports and catalysts with larger pore size (especially 8.5 nm) could promote the adsorption of thiophene compounds. It demonstrates that there is pore confinement effect in the hydrodesulfurization catalysts.

Cation–anion double hydrolysis derived mesoporous mixed oxides for reactive adsorption desulfurization

Mesoporous ZnO–Al2O3 mixed oxides (MO) were synthesized by double hydrolysis method at different temperatures and used as the support for the preparation of Ni/MO adsorbents. The reactive adsorption desulfurization (RADS) performance of adsorbents was evaluated in a fixed bed microreactor using thiophene as a model compound. The adsorbents before and after RADS were characterized by X-ray diffraction, N2 adsorption/desorption, thermogravimetric analysis, Fourier transformed infrared spectrometry and transmission electron microscopy techniques. Results show that Ni/MO samples exhibited much higher RADS activity and larger accumulative sulfur capacity than sample NZA-K prepared using the conventional kneading method. The desulfurization activity of Ni/MO adsorbents decreased with increasing the crystallization temperature of MO. As a result, sample Ni/ZnO–Al2O3-60 °C synthesized at 60 °C showed the best desulfurization performance among all Ni/MO adsorbents. Detailed characterization results revealed that the high dispersion of NiO and ZnO, the absence of inactive NiAl2O4 and high concentration of surface Lewis acid sites may account for the superior RADS performance of Ni/MOs samples. Furthermore, based on the experimental results, a mechanism is proposed for the RADS process with Ni/MO adsorbents.

Synthesis and characterization of mesoporous Si-modified alumina with high thermal stability

Mesoporous alumina with pseudo-boehmite phase modified by water glass was prepared by using the cation–anion double hydrolysis method from mixed aqueous solution of aluminum sulfate and sodium aluminate. The texture structure and acidity of these samples was studied with the assistance of characterization techniques, such as X-ray diffraction (XRD), N2 adsorption–desorption isotherms, 27Al and 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) and Fourier transform infrared (FTIR) spectroscopy. The XRD and N2 adsorption–desorption results show that the addition of sodium silicate can decrease the crystallinity of alumina, but greatly improve pore volume and surface area. The highest pore volume (1.46 cm3/g) and surface area (427.69 m2/g) can be simultaneously obtained when the adding amount of silica is up to 12 wt%. The NMR and FTIR results display that the presence of a certain amount of silicon can generate AlV in alumina, which is considered to be related with strong acid sites. In addition, the acidity of the Si-modified alumina samples can be adjusted by changing the amount of silica.

Ni–Al composite hydroxides fabricated by cation–anion double hydrolysis method for high-performance supercapacitor

Abstract Chemical doping of nickel hydroxide with other cations ( e.g. Al 3+ ) is an efficient way to enhance its electrochemical capacitive performances. Herein, a simple cation–anion (Ni 2+ and AlO 2 − ) double hydrolysis method was developed toward the synthesis of nickel–aluminum (Ni–Al) composite hydroxides. The obtained composite hydroxides possesses a porous structure, large surface area (121 m 2 /g) and homogeneous element distribution. The electrochemical test shows that the obtained composite hydroxides exhibits a superior supercapacitive performances (specific capacitance of 1670 F/g and rate capability of 87% from 0.5 A/g to 20 A/g) to doping-free nickel hydroxide (specific capacitance of 1227 F/g and rate capability of 47% from 0.5 A/g to 20 A/g). Moreover, the galvanostatic charge/discharge test displays that after 2000 cycles at large current density of 10 A/g, the composite hydroxides achieves a high capacitance retention of 98%, indicative of an excellent electrochemical cycleability.

Effects of synthetic conditions on the textural structure of pseudo-boehmite

Mesoporous alumina with pseudo-boehmite phase was prepared by using the cation–anion double hydrolysis method from mixed aqueous solution of aluminum sulfate and sodium aluminate. The effect of synthetic conditions on the crystal structure and textual properties of pseudo-boehmite was investigated, such as synthetic temperature, pH value and the addition of sodium silicate. With the assistance of characterization techniques, such as X-ray diffraction (XRD), N2 adsorption–desorption isotherms (BET) and 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR), the relationship between textural properties of the mesoporous alumina samples and their synthetic conditions was discussed. The results displayed that an increase in synthesis temperature promoted the formation of higher crystalline pseudo-boehmite with the increase of its surface area and pore volume. Pure pseudo-boehmite phase could be obtained in the pH value range from 6.0 to 9.0, while bayerite phase occurred when the pH value was over 10.0. The introduction of sodium silicate could greatly improve the pore volume (1.20cm3/g) and surface area (480.2m2/g) of pseudo-boehmite. Interestingly, pure pseudo-boehmite phase was obtained at very high pH value without formation of bayerite phase when sodium silicate was initially added into the aluminum hydroxide colloid.

Size-controlled synthesis of alumina nanoparticles through an additive-free reverse cation–anion double hydrolysis method

Size-controlled alumina (Al2O3) nanoparticles have been successfully synthesized for the first time via a reverse cation–anion double hydrolysis (CADH) method without any additive, employing the starting material of NaAlO2 and Al(NO3)3·9H2O, AlCl3·6H2O, Al2(SO4)3·18H2O. The structures and properties of as-obtained samples were well characterized by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The Al2O3 samples prepared by CADH method using different aluminum salts have three different nanostructures. The as-synthesized clew-like Al2O3 was self-assembled by uniform nanosized cubic platelets with the side-length of 100–150nm, thickness of about 20nm. The length of these as-synthesized Al2O3 nanorods is about 150nm. The side-length of as-prepared irregular Al2O3 nanosheets is less than 50nm.

Tuning the structure of alumina

Using aluminum nitrate as aluminum source, mesoporous alumina was respectively synthesized via cation–anion double hydrolysis method, sol–gel method and hydrothermal method. The pore structure, acidic property and microstructure etc. can be controlled by different methods and synthesis conditions. Different formation mechanisms induce different average crystallite sizes. The samples obtained from sol–gel and cation–anion double hydrolysis method have mono-modal mesopores with pore size in the range of 3.5–20.6 nm, while samples derived from hydrothermal method show bimodal mesoporous structure. There are more Lewis acid sites on the surface of the samples synthesized by sol–gel method. Nanorod morphology was observed in all the samples. Of note is that samples prepared with hydrothermal method show some irregular nanoparticles among the rods and samples synthesized by other methods bear pure nanorod structure. Moreover, there is more six-coordination aluminum (AlO6) in the framework of alumina prepared with hydrothermal method compared to that of samples synthesized by other methods.

Cation–anion double hydrolysis derived layered single metal hydroxide superstructures for boosted supercapacitive energy storage

A double hydrolysis reaction provides a simple strategy to construct layered single hydroxides with superstructures for electrochemical energy storage.

A Generalized Approach to the Synthesis of Mesoporous Mixed Metal Oxides Using the Cation-Anion Double Hydrolysis Method

A series of mesoporous mixed metal oxide were prepared by using a cation-anion double hydrolysis method, which was demonstrated to be a generalized approach for the synthesis of meso-porous mixed metal oxides. The mesoporous mixed oxide were characterized by N adsorption, X-ray diffraction, transmission electronic microscopy and energy dispersive X-ray analysis techniques. Results showed that thus obtained mixed metal oxide catalysts possess a high surface area, high loading of active component together with high dispersion, verifying that this approach is advantageous over the conventional wet impregnation method. The prepared mesoporous mixed oxides exhibit a great potential in replacing the traditional catalysts currently used in many important chemical processes.

An excellent Au/meso-γ-Al2O3 catalyst for the aerobic selective oxidation of alcohols

Alumina is traditionally considered to be inappropriate as a support for high-performance gold catalysts. Here, a highly active Au/meso-AlO catalyst for liquid-phase alcohol oxidations was synthesized using a home-made mesoporous γ-Al2O3 (meso-AlO) via a cation–anion double hydrolysis (CADH) method.

Cation–anion double hydrolysis derived mesoporous γ-Al2O3 as an environmentally friendly and efficient aldol reaction catalyst

Download options Please wait... Article information DOI https://doi.org/10.1039/B819993K Article type Paper Submitted 10 Nov 2008 Accepted 09 Dec 2008 First published 29 Jan 2009 Download Citation J. Mater. Chem., 2009,19, 1554-1563 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Cation–anion double hydrolysis derived mesoporous γ-Al2O3 as an environmentally friendly and efficient aldol reaction catalyst P. Bai, P. Wu, Z. Yan and X. S. Zhao, J. Mater. Chem., 2009, 19, 1554 DOI: 10.1039/B819993K To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Peng Bai Pingping Wu Zifeng Yan X. S. Zhao

A reverse cation–anion double hydrolysis approach to the synthesis of mesoporous γ-Al 2O 3 with a bimodal pore size distribution

Mesoporous γ-Al 2O 3 with a bimodal pore size distribution was synthesized using a reverse cation–anion double hydrolysis method (CADH). The effect of various synthesis parameters, including crystallization temperature, pH and P123 content on the structural properties of the resultant mesoporous alumina samples was examined. The texture and crystalline phase of the prepared alumina samples were characterized using N 2 adsorption, X-ray diffraction and transmission electron microscope. The results showed that the mesoporous aluminas samples prepared in this work exhibited a bimodal pore size distribution with a high surface area (up to 371 m 2/g). The chemistry of the synthesis system was found to be crucial in determining the structure of the final solid products.