Conversion of glycerol to acrolein by mesoporous sulfated zirconia-silica catalyst

A mesoporous sulfated zirconia-silica catalyst bearing only Br？nsted acid sites converted glycerol to acrolein in 81%yield with 82% selectivity.Space time yield as high as 9.0 mmol h^（-1） g_（cat）^（-1） was achieved even at a low reaction temperature of 523 K.The catalytic activity and selectivity were higher than those of typical sulfated zirconia.It is proposed that the milder acidity due to dilution of zirconium species by silica and large pore size for faster diffusion contributed towards the better catalytic performance.

Preparation and characterization of mesoporous tetragonal sulfated zirconia

Mesoporous tetragonal sulfated zirconia with high surface area and narrow pore-size distribution was prepared using Zr（O-nPr）4 as zirconium precursor, sulfuric acid as sulfur source and triblock copolymer poly（ethylene glycol）-poly（propylene glycol）- poly（ethylene glycol） （P123） as the template. The samples were characterized by X-ray diffraction, N2 sorption, TEM, and NH3- TPD. A phase transformation from monoclinic sulfated zirconia to tetragonal sulfated zirconia is observed. The product shows strong acidity.C2009 Bin Yue. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Polyoxymethylene dimethyl ethers synthesis from methanol and formaldehyde solution over one-pot synthesized spherical mesoporous sulfated zirconia

The synthesis of polyoxymethylene dimethyl ethers as an ideal diesel fuel additive is the current hot topic of modern petrochemical industry for their expedient properties in mitigating air pollutants emission during combustion.In this work,a series of spherical sulfated zirconia catalysts were prepared by a one-pot hydrothermal method assisted with surfactant cetyltrimethylammonium bromide(CTAB).The prepared sulfated zirconia catalysts were used to catalyze PODEn synthesis from methanol and formaldehyde solution.Various characterization(XRD,BET,SEM,TGA,NH_(3)-TPD,FTIR,and Py-IR)were employed to elaborate the structure–activity relationship of the studied catalytic system.The results demonstrated that S/Zr molar ratio in precursor solution played an effective role on catalyst morphology and acidic properties,where the weak Brønsted acid sites and strong Lewis acid sites were favorable to the conversion of methanol and formation of long-chain PODEn,respectively.The reaction parameters such as catalyst amount,molar ratio of FA/MeOH,reaction time,temperature and pressure were optimized.The speculated reaction pathway for PODEn synthesis was proposed based on the synergy of Brønsted and Lewis acid sites,which suggested that Brønsted and Lewis acid sites might be advantageous to the activation of polyoxymethylene hemiformals[CH_(3)(OCH_(2))_(n)OH]and methylene glycol(HOCH_(2)OH),respectively.

The optimum conditions for methanol conversion to dimethyl ether over modified sulfated zirconia catalysts prepared by different methods

Sulfated zirconia(SZ)and two promoted 1% Mn/SZ catalysts which have been prepared via sol gel(Mn/SZ-S)and impregnation(Mn/SZ-I)methods were studied.The morphology of the catalysts was characterized by XRD,BET,NH3-TPD,ICP,SEM and FT-IR analysis.The conversion of methanol to dimethyl ether and hydrocarbons was carried out in the temperature range of 120−300℃.The Mn/SZ-S showed the highest activity due to the high surface area with suitable acidity.The optimum condition of Mn/SZ-S catalyst was investigated at 200℃ and LHSV of 0.02 h^−1 in a time range from 30 to 210 min.It was found that the total conversion decreased from 80.18% to 53.26% at 210 min.The reusability of this catalyst was studied at the optimum condition up till four cycles for 1 h.The characterization of the reused catalyst showed a significant change in the structure and surface acidity due to the blockage of the surface acid sited by carbonaceous materials.

One-pot Green Synthesis of Pyrrole Derivatives Catalyzed by Nano Sulfated Zirconia as a Solid Acid Catalyst

A new and efficient method for the preparation of N-substituted pyrroles from one-pot Paal-Knorr condensation has been accomplished using nano-crystalline sulfated zirconia （SZ） as the catalyst in ethanol at moderate temperature. This new protocol has the advantages of easy availability, stability, reusability and eco-friendliness of the catalyst, high to excellent yields, simple experimental and work-up procedure. The synthesized compounds were confirmed through spectral characterization using IR, 1H NMR, 13C NMR and mass spectra.

Promoting di-isobutene selectivity over ZnO/ZrO_(2)-SO_(4) in isobutene oligomerization

Isooctane attracts great interest in recent years because of its promising potential as friendlyenvironmental gasoline,which is obtained by dimerization of isobutene with a hydrogenation step.Herein,a solid acid catalyst sulfated zirconia modified by ZnO was prepared.The oligomerization of isobutene had been investigated over ZrO_(2)-SO_(4) and ZnO(X)/ZrO_(2)-SO_(4) catalyst in order to find efficient catalysts for the production of isobutene oligomers.The presence of ZnO obviously enhanced the dimerization of isobutene and ZnO(X)/ZrO_(2)-SO_(4) exhibited the highest di-isobutene yield of 60%.Kinetic studies showed the higher trimerization-to-dimerization activation energy ratios of ZnO(X)/ZrO_(2)-SO_(4) than those of ZrO_(2)-SO_(4) from 353 to 393 K.In addition,reaction rate of dimerization was higher than trimerization over ZnO(X)/ZrO_(2)-SO_(4).The high L/B ratio manifested the capability to enhance the selectivity of C8 in isobutene dimerization.Furthermore,ZnO(X)/ZrO_(2)-SO_(4) exhibited stable conversion for the dimerization of isobutene.

Liquid-phase a-Pinene Isomerization over Fe-doped Sulfated Zirconia Prepared by a Hydrothermal Treatment-assisted Process

A series of Fe-doped （0.5%--3%） sulfated zirconia have been prepared by a hydrothermal treatment-assisted process. Textural and structural characterizations of the as-synthesized materials were performed by means of N2 adsorption, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and thermogravimetric analysis. Temperature-programmed desorption of ammonia was used to determine the acidity of the samples. The effects of Fe-doping on the structure, acidity and catalytic activity of sulfated zirconia for liquid-phase a-pinene isornerization were investigated. The incorporation of small amounts of Fe into sulfated zirconia results in the increase of sulfate content and the number of acid sites, which is responsible for the enhanced activity of Fe-doped catalysts in comparison with the undoped one. Meanwhile, hydrothermal treatment helps to improve the activity of the catalyst.

Simultaneous Al2O3 Doping and Sulfation in Hierarchically Porous ZrO2 Solid Acids by an One-pot Synthesis for Enhanced Recycling Catalytic Performances

Alumina doping and sulfation in hierarchically porous zirconia solid acids have been achieved simultaneously via one-pot and bi-surfactant-assisted self-assembly process, using aluminum sulfate as both Al and SO^2- sources. The prepared composite solid acids showed much enhanced acidity and recycling catalytic activity for an esterification reaction compared with sulfated zirconia without alumina doping and Al-doped sulfated zirconia without hierarchically porous structure.