催化胶凝剂对大掺量电石渣砖强度的影响

利用自制的催化胶凝剂有效激发电石渣和粉煤灰的活性,从而增加电石渣的掺量,研制出大掺量的电石渣砖。试验结果表明,当掺入50%电石渣,另掺入4%Na2SiO3和1%NaAlO2时,所制得的电石渣砖28 d抗压强度达20.23 MPa,并通过XRD图谱对水化产物和水化机理进行了研究。

Photocatalytic activity of TiO_2 supported SiO_2-Al_2O_3 aerogels prepared from industrial fly ash

A ternary composite of TiO2 and a SiO2-Al2O3 aerogel with good photocatalytic activity was prepared by a simple sol-gel method with TiO2 nanoparticles and SiO2-Al2O3 aerogels derived from industrial fly ash.The structural features of the TiO2/SiO2-Al2O3 aerogel composite were investigated by X-ray powder diffraction,Fourier transform infrared spectroscopy,transmission electron microscopy,gas adsorption measurements and diffuse reflectance UV-visible spectroscopy.The optimal conditions for photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol（DNBP],included an initial DNBP concentration of 0.167 mmol/L at pH = 4.86 with a catalyst concentration of 6 g/L,under visible light irradiation for 5 h.A plausible mechanism is proposed for the photocatalytic degradation of DNBP.Our composite showed higher photocatalytic activity for DNBP degradation than that of pure TiO2.This indicates that this material can serve as an efficient photocatalyst for degradation of hazardous organic pollutants in wastewater.

Direct Synthesis of Diphenyl Carbonate with Heterogeneous Catalyst and Optimal Synthesis Conditions of the Support Prepared by Sol-gel Method

The support of catalyst for the direct synthesis of diphenyl carbonate （DPC） by heterogeneous catalytic reaction was prepared by the sol-gel method. Compared with activated charcoal, molecular sieve, porous ceramics, hopcalite, the support prepared by the sol-gel method has higher activity. The characterization of the support by X-ray diffraction （XRD） and transmission electron microscope （TEM） show that the mare crystal phase is Co2MnO4 and the average particle diameter is about 40 nm. The optimum conditions for synthesis of the support were determined by orthogonal experiments, which indicate that the proportion of Cu, Mn, and Co is the first important factor influencing the yield and selectivity of DPC. Temperature of calcination is the second one. The optimum conditions are： molar proportion of Cu, Mn, and Co being 1 ： 1 ： 1, temperature of calcination 700℃, drying at 100~C, temperature of water bath 85~C. The yield and selectivity of DPC in the process can reach 38% and 99% in the batch operation, respectively. The copper cobalt manganese mixed oxides chosen as the support contribute more to the high catalytic activity than the sol-gel method.

Effects of Ni doping contents on photocatalytic activity of B-BiVO_4 synthesized through sol-gel and impregnation two-step method

To enhance the photocatalytic activity of B-BiVO4,Ni-doped B?BiVO4photocatalyst(Ni-B-BiVO4)was synthesized through sol-gel and impregnation method.The photocatalysts were characterized by XPS,XRD,SEM,EDS,BET and UV-Vis DRS techniques.The results showed that single or double doping did not change the crystalline structure and morphology,but the particle size decreased with Ni doping.The band gap energy absorption edge of Ni-B-BiVO4shifted to a longer wavelength compared with undoped,B or Ni single doped BiVO4.More V4+and surface hydroxyl oxygen were observed in BiVO4after Ni-B co-doping.When the optimal mass fraction of Ni is0.30%,the degradation rate of MO in50min is95%for0.3Ni-B-BiVO4sample which also can effectively degrade methyl blue(MB),acid orange(AOII)II and rhodamine B(RhB).The enhanced photocatalytic activity is attributed to the synergistic effects of B and Ni doping.

Enhanced visible-light photocatalytic performance of a monolithic tungsten oxide/graphene oxide aerogel for nitric oxide oxidation

Photocatalysis is considered a promising technique for removal of pollutants from indoor air.However,the low selectivity and limited recyclability of photocatalysts in powder form currently limit their practical application.In this work,we reported the successful preparation of a monolithic tungsten oxide(WO3)/graphene oxide(GO)aerogel photocatalyst through a cost‐effective freeze‐drying method.GO not only acts as a macroscopic support,but also increases the catalyst surface area from 46 to 57 m2/g,enhances the light absorption in the visible‐light region,and raises the separation efficiency of photogenerated electron‐hole pairs.The Obtained WO3/GO aerogel exhibited an outstanding visible‐light photocatalytic degradation rate of nitric oxide of 51%,which was 3.3 times that of pristine WO3 powder.In addition,the aerogel displayed excellent selectivity,with a generation fraction of toxic nitrogen dioxide of as low as 0.5%.This work presents a facile synthesis route to fabricate a monolithic WO3/GO aerogel photocatalyst with great promise for air purification.

Selective catalytic reduction of NO with NH_3 over sol-gel-derived CuO-CeO_2-MnO_x/γ-Al_2O_3 catalysts

Granular CuO-CeO2-MnOx/γ-Al2O3 catalysts were synthesized by the sol-gel method. The performance of the CuO-CeO2-MnOx/γ-Al2O3 catalysts for the selective catalytic reduction (SCR) was studied in a fixed bed system. Preliminary tests were carried out to analyze the behavior of NH3 and NO over catalyst in the presence of oxygen. The optimum temperature range for SCR over the CuO-CeO2-MnOx/γ-Al2O3 catalysts is 300-400 ℃ . The catalysts maintain nearly 100% NO conversion at 350 ℃. The NH3 oxidation experiments show that both NO and N2O are produced gradually with the increase of temperature. The catalysts in this experiment have a stronger oxidation property on NH3, which improves the denitrification activity at low temperature. The over-oxidation of NH3 at high temperature is the main cause leading to a decrease in the NO conversion. The NH3 and NO desorption experiments show that NH3 and NO can be adsorbed on CuO-CeO2-MnOx/γ-Al2O3 granular catalysts. The transient response of NH3 and NO indicates that the SCR reaction proceeds in accordance with the Eley-Rideal mechanism. The adsorbed NO has little influence on the denitrification activity in SCR process.

A new solid acid SO_4^(2-)/TiO_2 catalyst modified with tin to synthesize 1,6-hexanediol diacrylate

A new solid acid catalyst,SO4^2-/TiO2 modified with tin,was prepared using a sol-gel method and its physicochemical properties were revealed by nitrogen adsorption-desorption,X-ray powder diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,infrared spectroscopy of adsorbed pyridine,temperature-programmed desorption of ammonia and thermal gravimetric analysis.The structure,acidity and thermal stability of the SO4^2-/TiO2-SnO2 catalyst were studied.Incorporating tin enlarged the specific surface area and decreased crystallite size of the SO4^2-/TiO2 catalyst.The total acid sites of the modified catalyst increased and Bronsted acid strength remarkably increased with increasing tin content.The decomposition temperature of sulfate radical in the modified catalyst was 100 ℃ greater and its mass loss was more than twice that of the SO4^2-/TiO2 catalyst.The SO4^2-/TiO2-SnO2 catalyst was designed to synthesize 1,6-hexanediol diacrylate by esterification of 1,6-hexanediol with crylic acid.The yield of 1,6-hexanediol diacrylate exceeded 87% under the optimal reaction conditions：crylic acid to 1,6-hexanediol molar ratio = 3.5,catalyst loading = 7%,reaction temperature = 130 ℃ and reaction time = 3 h.The modified catalyst exhibited excellent reusability and after 10 cycles the conversion of 1,6-hexanediol was above 81%.

Oxidative Coupling of Methane over Li/MgO： Catalyst and Nanocatalyst Performance

The Li/MgO catalyst and nanocatalyst were prepared by the incipient wetness impregnation and sol-gel method, respectively. The catalytic performance of the Li/MgO catalyst and nanocatalyst on oxidative coupling of methane was compared. The catalysts prepared in two ways were characterized by X-ray powder diffraction, Brunauer-Emmett-Teller surface and transmission electron microscope. The catalyst was tested at temperature of 973-1073 K with constant total pressure of 101 kPa. Experimental results showed that Li/MgO nanocatalyst in the oxidative coupling of methane would result in higher conversion of methane, higher selectivity, and higher yield of main products （ethane and ethylene） compared to ordinary catalyst. The results show the improved influence of nanoscale Li/MgO catalyst performance on oxidative coupling of methane.

Nitrogen‐doped graphene aerogel‐supported ruthenium nanocrystals for pH‐universal hydrogen evolution reaction

The design and synthesis of high‐performance and low‐cost electrocatalysts for the hydrogen evolution reaction(HER),a key half‐reaction in water electrolysis,are essential.Owing to their modest hydrogen adsorption energy,ruthenium(Ru)‐based nanomaterials are considered outstanding candidates to replace the expensive platinum(Pt)‐based HER electrocatalysts.In this study,we developed an adsorption‐pyrolysis method to construct nitrogen(N)‐doped graphene aerogel(N‐GA)‐supported ultrafine Ru nanocrystal(Ru‐NC)nanocomposites(Ru‐NCs/N‐GA).The particle size of the Ru‐NCs and the conductivity of the N‐GA substrate can be controlled by varying the pyrolysis temperature.Optimal experiments reveal revealed that 10 wt%Ru‐NCs/N‐GA nanocomposites require overpotentials of only 52 and 36 mV to achieve a current density of 10 mA cm^(−2) in 1 mol/L HClO4 and 1 mol/L KOH electrolytes for HER,respectively,which is comparable to 20 wt%Pt/C electrocatalyst.Benefiting from the ultrafine size and uniform dispersion of the Ru‐NCs,the synergy between Ru and the highly conductive substrate,and the anchoring effect of the N atom,the Ru‐NCs/N‐GA nanocomposites exhibit excellent activity and durability in the pH‐universal HER,thereby opening a new avenue for the production of commercial HER electrocatalysts.

Promoting Xylene Production in Benzene Methylation using Hierarchically Porous ZSM-5 Derived from a Modified Dry-gel Route

Methylation of benzene is an alternative low-cost route to produce xylenes, but selectivity to xylene remains low over conventional zeolitic catalysts. In this work, a combined dry-gel-conversion and steam-assisted- crystallization method is used to synthesize hierarchically porous zeolite ZSM-5 with varied Si/AI malar ratios. X-ray diffraction （XRD）, N2 physisorption, NH3-temperature programmed desorption （TPD）, scanning electronic microscopic （SEM） measurement and Fourier transform infrared （FT-IR） are employed to characterize the struc- ture and acidity of both hierarchically porous zeolites and their conventional counterparts. The method is found to be applicable to ZSM-5 with molar ratios of Si/A1 from 20 to 180. The ZSM-5 zeolites are used as catalysts for benzene methylation at 460 ℃ to investigate the effect of additional porosity and Si/A1 ratios. At low Si/AI ratios, the benzene conversions over conventional and hierarchical ZSM-5 are close, and selectivity to toluene is high over hierarchical ZSM-5. It is found that hierarchical porosity markedly enhances the utility of zeolite and the se- lectivity towards xylenes via improved mass transport at higher Si/Al ratios. Under an optimized hierarchical ZSM-5 catalvst, xvlene selectivity reaches 34.9% at a Si/AI ratio of 180.

Preparation and characterization of CuO-CoO-MnO/SiO_2 nanocomposite aerogels as catalyst carriers

CuO-CoO-MnO/SiO2 nanocomposite aerogels were prepared by using tetraethyl orthosilicate(TEOS) as Si source,and aqueous solution of Cu,Co and Mn acetates as the precursors via sol-gel process and ethanol supercritical drying technique.The gelatination mechanism was investigated by nuclear magnetic resonance(NMR) and X-ray photoelectron spectroscopy(XPS).The microstructure and composition of the CuO-CoO-MnO/SiO2 nanocomposite aerogels were characterized by field emission scanning electron microscopy(FE-SEM),transmission electron microscopy(TEM),electron dispersive spectroscopy(EDS) and XPS.The specific surface area,pore size and pore size distribution of the nanocomposite aerogels were determined by the Brunauer–Emmett–Teller(BET) method.The products were analyzed by gas chromatography(GC).The results show that the CuO-CoO-MnO/SiO2 nanocomposite aerogels are porous,with a particle size distribution of 10–150 nm,a pore size distribution of 2–16 nm,an average pore size of 7.68 nm,and a specific surface area of 664.4-695.8 m2/g.The molar fraction of transition metals in the nanocomposite aerogels is 0.71%-13.77%.This kind of structure is favorable not only to increase the loading of catalysts,but also to make full use of the effect of transition metal oxides as cocatalysts;CuO-CoO-MnO/SiO2 nanocomposite aerogels can be used as a novel catalyst carrier in the safer and environment-friendly synthesis of diphenyl carbonate and other fields of catalysis.

Preparation and characterization of La_(1-x)Ce_xFe_(1-y-n)Co_yRu_nO_3 compounds

The mixed oxides La1 -xCexFe1-y-nCOyRunO3 were prepared by sol-gel method and used as catalysts for NO direct decomposition. The catalysts were characterized by DTA - TG, XRD, IR and BET. XRD analysis reveals that the samples are in a pure perovskite phase in 550 - 650 ℃, and catalyst structure keeps long else 20 decrease, and lattice parameters enhance when Ru is introduced. The characteristic peaks of samples are stronger during a temperature increase, and the particle size grows faster. IR analysis shows that the position and shape of adsorption peaks are almost the same among all samples, but with the Ru content increasing, 600 cm^-1 peak stretches to a high frequency and changes to disorder. The wave numbers move to low frequency when n = 0. 05, yet it doesn＇ t vary obviously when n 〉 0. 05. The BET surface area testifies that particle sizes of all catalysts increase with temperature increasing.

Selective oxidation of methanol to dimethoxymethane over V_2O_5/Ti O_2–Al_2O_3 catalysts

This paper describes the effect of the prepara- tion method of binary oxide supports （TiO2-Al2O3） on catalytic performance of V2O5/TiO2-Al2O3 catalysts for methanol selective oxidation to dimethoxymethane （DMM）. The TiO2-A1203 supports are synthesized by a number of methods including mechanical mixing, ball milling, precipitation, co-precipitation, and sol-gel method, which is followed by incipient wetness impregnation to produce V2O5/TiO2-Al2O3 catalysts. Among these samples, the V2O5/TiO2-Al2O3 catalyst prepared by the sol-gel method has the best catalytic performance with a maximum methanol conversion of 48.9 % and a high DMM selectivity of 89.9 % at 393 K, showing superior performance than V2O5/TiO2 and V2O5/Al2O3. The excellent catalytic performance of V2O5/TiO2-Al2O3 is attributed to the effective interaction between the active component and the mixed support. Such interaction changes the chemical states of supported active V components, produces an increased amount of V^4＋ species, and facilitates the electron transfer between support and active component. Additionally, the incorporation of titanium cation into the alumina structure could also help produce an appropriate amount of acidic sites, which increases the DMM selectivity. The coordinated environment of the dispersed vanadia on TiO2-Al2O3 mixed support improves the catalytic efficiency on methanol oxidation to DMM.