•ZnO-Al2O3 mixed oxides were synthesized using a freeze drying modified cation-anion double hydrolysis method•Freeze dried adsorbents exhibited a superior performance in reactive adsorption desulfurization•A large amount of small sized ZnO gives rise to a large sulfur capacity•The absence of the inactive NiAl2O4 phase in the adsorbents allows the fast cleavage of C-S bond in thiophene•High surface area and large pore volume facilitate the mass transfer of reactants and accommodate more sulfurReactive 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 90 mg S/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.

•ZnO–Al2O3 mixed oxides were synthesized using a cation–anion double hydrolysis method.•Mixed oxide based adsorbents exhibited high activity and large sulfur capacity in reactive adsorption desulfurization.•The absence of the inactive NiAl2O4 phase in the adsorbents allowed the fast cleavage of C–S bond in thiophene.•The high concentration of surface Lewis acid sites in mixed oxides favored the adsorption of thiophene.•The high dispersion of ZnO in mixed oxides led to high diffusion rate of sulfur in ZnO particles.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.

In this study, a clew-like ZnO superstructure was synthesized by a copolymer-controlled self-assembly homogeneous precipitation method. Ni was impregnated to the clew-like ZnO superstructure to obtain Ni/ZnO adsorbents. The synthesized materials were characterized by scanning electron microscopy, transmission electron microscopy, N2 sorption, X-ray diffraction, Fourier transform infrared spectrometry, and H2-temperature programmed reduction techniques. 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. Sample Ni/ZnO-4h exhibits a remarkably high performance with a sulfur capacity of 189.1 mg S g–1, which is above 6 times that of the one prepared with commercial ZnO. Characterization results show that the morphology changes from micro-clews to large solid sticks with the increase of the crystallization time. The loose and open architecture of the clew-like ZnO superstructure facilitates the diffusion of reactants/products, and prevents the adsorbent particles from breakage by supplying space for the volume expansion during the RADS process. The small nanoparticles in ZnO nanostrips result in a high sulfur adsorption capacity and also favor the dispersion of Ni, leading to an excellent RADS performance.本文利用共聚物控制均匀沉淀法自组装合成了一种毛线球状ZnO超结构. 通过将Ni浸渍于该氧化锌材料上制备了一系列Ni/ZnO吸 附剂. 其中, 样品Ni/ZnO-4h在反应吸附脱硫中表现出极高的硫容量(189.1 mg S g–1), 是相同条件下使用普通商业ZnO制备的Ni/ZnO-C样 品的6倍. 毛线球状ZnO疏松开放的结构能够促进反应物/产物的扩散, 并抑制体积膨胀对吸附剂结构的破坏. 较小的ZnO颗粒在提供较高 的硫容量的同时还能促进活性组分Ni的分散, 从而导致吸附剂具有较高的反应吸附脱硫性能.

Monodispersed colloidal particles have received continuously increasing attention due to their unique physicochemical properties for applications in many technological areas, especially in nanotechnology. The size and morphology of the colloid particles produced in a homogeneous solution are very sensitive to the synthesis conditions. Thus, it has been a great challenge to generalize the synthesis of monodispersed colloidal particles. In this work, a hydrothermally promoted double hydrolysis approach (HPDH) was found to be effective in the synthesis of monodispersed colloidal particles of different compositions. Several types of colloids were synthesized to demonstrate the feasibility and versatility of this novel approach. The monodispersity of the colloids was examined by scanning electron microscopy, transmission electron microscopy and particle size distribution analysis. The crystalline structure and porosity of the colloids were investigated by X-ray diffraction, selected area-electron diffraction and N2 adsorption methods. Results show that the HPDH derived colloids have a high monodispersity, which may render these materials highly potential in numerous emerging applications.

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.Keywords: mesoporous γ-Al2O3; polymerized VOX species; propane dehydrogenation; surface acidity; vanadium-based catalyst

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/ZnO–Al2O3(28 °C) possessed relatively bigger pore size and larger pore volume than other samples, which may alleviate the pore shrinkage/blockage during the RADS process. A combination of XRD, UV–vis, and H2-TPR characterization results demonstrate that a high crystallization temperature favors the growth of inactive ZnAl2O4 crystals and induce the formation of more less-reducible Ni2+ ion, causing the loss of active ZnO phase and Ni0 atoms, which may be the reason for the lower RADS activity of the adsorbent synthesized at higher crystallization temperatures.

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–regeneration cycles, sample 10% Ni/ZnO–Al2O3 exhibited a drop of only 3% in thiophene conversion, indicating the high stability of the Ni/ZnO–Al2O3 adsorbent prepared by homogeneous precipitation. Characterization results show that the one-step homogeneous precipitation method could facilitate the formation of small ZnO particles while suppressing the formation of inactive ZnAl2O4. On the other hand, by decreasing the formation of NiAl2O4, the homogeneous precipitation method could also generate high concentration of Ni0 sites, which are the active centers for the hydrogenolysis of C–S bonds. These findings indicate that a high-performance adsorbent for RADS can be obtained by employing a proper preparation method with good control on the adsorbent structure.

•Zeolite Y with interconnected mesoporous was prepared by post synthesis modification.•Modified catalysts showed improved catalytic behavior in the presence of contaminant metals.•The introduction of mesopores increased yields of light oil product with lower coke and gas yields.•Improved structural properties caused superior performance.It is well known that pores in catalysts larger than reactant molecules in dimension can ease flow resistance and enhance desorption of the molecules. In this work, mesoporosity was introduced into ultra-stable Y zeolite (USY) via a soft-templating method and the resulting zeolite was applied for preparation of fluid catalytic cracking (FCC) catalysts. The zeolite was extensively characterized by methods including N2 sorption, X-ray Diffraction (XRD), magic angle spinning nuclear magnetic resonance (MAS NMR), Fourier transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Results show that the resulting zeolite pores were highly interconnected. Aluminum atoms were re-distributed within the framework while the crystallites were maintained. The effect of contaminant metals (vanadium and nickel) on the activity and product distribution of the prepared catalysts containing modified zeolite was investigated using the micro activity test (MAT). Compared with the parent USY, the modified USY exhibited higher yields of light oil products, much lower coke formation, and lower dry gas yield. Furthermore, the catalysts containing modified USY-10 possessed a higher stability toward metal deactivation than the parent USY. This improved catalytic behavior could be attributed not only to the enhanced diffusion and faster desorption of the adsorbed oil molecules within the pores, but also to the increased accessibility to the acidic sites due to well interconnected pore structures and the large mesopore size.Modification of a commercial USY introduces interconnected mesopores with bimodal pore size distribution. This developed features cause improvement in the fluid catalytic cracking performance of the zeolite catalyst. Generally, light oil yields increased, while coke and gas yields decreased.

ZSM-5 samples with hierarchical pores (macropores, mesopores and micropores) were synthesized in the presence of n-hexyltrimethylammonium bromide (HTAB) and tetrapropylammonium hydroxide (TPAOH). The effect of synthesis conditions including the Si/Al ratio, crystallization temperature and time, and the amount of HTAB added to the synthesis system on the final products was examined. The catalytic properties of the hierarchical zeolite were investigated in reactions of Claisen–Schmidt condensation of benzaldehyde and acetophenone, self-condensation of cyclohexanone and methanol conversion. The hierarchical zeolite exhibits superior catalytic performance in Claisen–Schmidt condensation of benzaldehyde and acetophenone and self-condensation of cyclohexanone and has a remarkably high selectivity for dimethyl ether in the methanol conversion reaction at relatively low temperatures, which was attributed to the fast mass transport in the three-dimensional hierarchical pore network. A cooperative assembly mechanism accounting for the formation of the hierarchical zeolite was proposed based on experimental results.

Alumina is commonly used as a catalyst binder together with aluminum sol in modern fluid catalytic cracking (FCC) catalysts. The surface acidity properties of alumina strongly affect the catalytic performance of FCC catalysts. Lewis acid sites tend to produce coke because of their dehydrogenation activity, while Brönsted ones produce less coke. Thus, it is beneficial to convert the surface Lewis acid sites into Brönsted type. Fluorine-containing modifiers have been demonstrated to be effective to generate Brönsted acid sites on alumina surface. However, different types of fluorine-containing compounds may have different modification effects. In this work, three fluorine-containing compounds, ammonium fluoroborate (NH4BF4), ammonium fluorosilicate [(NH4)2SiF6], and ammonium fluoride (NH4F), were tested and compared in the modification of alumina surface acidity. Results show that NH4BF4 and (NH4)2SiF6 perform equally well in the generation of Brönsted acid sites, while NH4BF4 is more effective in the reduction of Lewis acid sites. In comparison, NH4F is not so effective in the generation of Brönsted acid sites as the other two compounds.

ZSM-5 samples with hierarchical pores (macropores, mesopores and micropores) were synthesized in the presence of n-hexyltrimethylammonium bromide (HTAB) and tetrapropylammonium hydroxide (TPAOH). The effect of synthesis conditions including the Si/Al ratio, crystallization temperature and time, and the amount of HTAB added to the synthesis system on the final products was examined. The catalytic properties of the hierarchical zeolite were investigated in reactions of Claisen–Schmidt condensation of benzaldehyde and acetophenone, self-condensation of cyclohexanone and methanol conversion. The hierarchical zeolite exhibits superior catalytic performance in Claisen–Schmidt condensation of benzaldehyde and acetophenone and self-condensation of cyclohexanone and has a remarkably high selectivity for dimethyl ether in the methanol conversion reaction at relatively low temperatures, which was attributed to the fast mass transport in the three-dimensional hierarchical pore network. A cooperative assembly mechanism accounting for the formation of the hierarchical zeolite was proposed based on experimental results.