Co-reporter:Wenqian Fu;Lei Zhang;Quanyong Yu;Tiandi Tang;Ting Tang
Industrial & Engineering Chemistry Research July 6, 2016 Volume 55(Issue 26) pp:7085-7095
Publication Date(Web):2017-2-22
DOI:10.1021/acs.iecr.6b01583
Mesoporous zeolite ZSM-5 (ZSM-5-M) was synthesized and used as support for the preparation of highly efficient nickel phosphide catalyst (Ni2P/ZSM-5-M) in the deep hydrogenation of phenanthrene and in the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DM-DBT). Compared with Ni2P catalysts supported silica and high surface area hexagonal mesoporous silica (HMS) (Ni2P/SiO2 and Ni2P/HMS), Ni2P/ZSM-5-M exhibits higher hydrogenation and HDS activity. The phenanthrene conversion and deep hydrogenation products selectivity over Ni2P/ZSM-5-M (95% and 83%) are much higher than those over Ni2P/SiO2 (61% and 73%) and Ni2P/HMS (69% and 45%) under mild conditions. The 4,6-DM-DBT conversion over Ni2P/ZSM-5-M (93%) was higher than that over Ni2P/SiO2 (62%). This feature is attributed to the difference in surface properties of support. A large amount of acidic hydroxyl groups on the zeolites can interact strongly with catalyst precursor, resulting in the formation of highly dispersed Ni2P particles with small sizes, which provide abundant hydrogenation active sites.
Co-reporter:Fanghua Wu, Dongfang Wu
Powder Technology 2017 Volume 305() pp:289-296
Publication Date(Web):January 2017
DOI:10.1016/j.powtec.2016.09.077
•The effects of particle properties on attrition characteristics are investigated.•New methods including nanoindentation and particle strength tests are employed for characterization.•Attrition resistances are mainly influenced by the particle hardness and strength.•Attrition mechanisms are influenced by particle surface properties.•Literature attrition models are applied to analyze the experimental data, the results are satisfactory.Attrition tests of three fluid catalytic cracking (FCC) catalyst samples, named here as sample A, B and C, were carried out in an ASTM (American Society for Testing and Materials) design fluidized bed test unit. The results showed sample A is the most easy to be attrited while sample B has the best attrition resistance. Factors which affect the attrition characteristics including hardness, mechanical strength and surface properties were investigated with particle size distribution (PSD) analysis, scanning electron microscope (SEM), nanoindentation and particle strength tests. The results of the PSD test showed that the attrition mechanisms of the three samples were a mixture of abrasion and fragmentation. Fragmentation of samples B and C was more severe than that of sample A. The nanoindentation and particle strength tests proved that hardness and mechanical strength are the dominant factors of attrition resistances. The combination of attrition tests, SEM images and PSD analyses showed that surface properties such as shapes and surface roughness have weak impacts on attrition resistance, but they can influence attrition mechanisms. Fragmentation was found to occur to particles which have irregular shapes while abrasion generally takes place when surfaces are rough. These findings are important for the manufacture of some solid catalysts.The physical unit of data is millimeter. Material construction is stainless steel.
Co-reporter:Dongfang Wu, Yanhong Zhang, Yongdan Li
Journal of Industrial and Engineering Chemistry 2017 Volume 56(Volume 56) pp:
Publication Date(Web):25 December 2017
DOI:10.1016/j.jiec.2017.07.010
Alumina-washcoated FeCrAl alloy sheets are prepared to investigate the effects of metallic substrate pretreatments on the mechanical stability of monolithic catalysts. It is shown that chemical and thermal pretreatments produce different effects on the metallic surface morphology and phase, and different mechanisms are involved in their ways of improving the washcoat adhesion. Combination of chemical and thermal pretreatments leads to the formation of α-alumina whiskers on corroded and rough metallic surface, thus giving the most satisfactory washcoat adhesion. It is also pointed out that not only mechanical shock resistance but also thermal shock resistance is crucial to metallic monolithic catalysts.Download high-res image (267KB)Download full-size image
Co-reporter:Xue Zhang, Dongfang Wu
Ceramics International 2016 Volume 42(Issue 15) pp:16563-16570
Publication Date(Web):15 November 2016
DOI:10.1016/j.ceramint.2016.07.076
Abstract
The MOx (M=Cu, Ni or Co) modified manganese-cerium mixed-oxide catalysts supported on ceramic monolith were prepared by sol-gel method and examined for the catalytic combustion of o-xylene. Results show that the addition of CuOx could significantly enhance the catalytic properties of the monolithic catalysts, which may be correlated with the Mn-Cu synergistic interaction. The effects of the preparation parameters including the Cu content, the total amount of active phase and the calcination temperature and time, as well as the reaction conditions, i.e., the space velocity and concentration of o-xylene, on the catalytic performance for the combustion of o-xylene were also investigated. It is shown that the MnCeCu0.4/monolith catalyst with the active phase loading of 11.4 wt% and calcined at 500 °C for 3 h displays the highest catalytic activity. When the concentration of o-xylene is 1000 ppm and the space velocity is 10,000 h−1, the temperature at which 90% o-xylene conversion is reached is 277 °C. It is also seen that the optimum catalyst has a good catalytic stability and exhibits an excellent activity not only at a rather high space velocity but also within a wide range of o-xylene concentration. Furthermore, the optimum catalyst also show the high combustion performance for other hydrocarbons, e.g., n-butanol and styrene.
Co-reporter:Yiran Gu, Qian Zhuo, Dongfang Wu
Materials Science in Semiconductor Processing 2016 Volume 53() pp:18-27
Publication Date(Web):October 2016
DOI:10.1016/j.mssp.2016.05.016
Developing highly active photocatalysts for water treatment is of vital importance. A large-mesopore hierarchical WO3 hydrate photocatalyst with exposed high energy facets was synthesized via a facile hydrothermal method using sodium chloride as structure-directing agent. The forming model of the hierarchical structure was discussed, and photogenerated oxide species were investigated. It is shown that the orthorhombic WO3·1/3H2O photocatalyst is of a hierarchical structure assembled by various 2-dimension nanosheets and that its average pore diameter reaches approximately 33.2 nm. Besides, it could decompose 92% of rhodamine B (Rh B) under visible light irradiation within four hours. The enhanced photocatalytic efficiency is attributed to the exposed high energy (002) crystal facets of hierarchical structure, and to the large mesopores existing between crossed nanosheets which help to charge carriers separation, adsorption of reactants and desorption of product molecules. Furthermore, the catalyst displays an excellent photocatalytic stability, indicating its broad application in water pollution treatment.
Co-reporter:Weiwei Guo, Dongfang Wu
International Journal of Hydrogen Energy 2014 Volume 39(Issue 30) pp:16832-16840
Publication Date(Web):13 October 2014
DOI:10.1016/j.ijhydene.2014.08.088
•We have synthesized VS4/graphene composites via a one-step hydrothermal route successfully.•The morphology, structure and interaction between VS4 and graphene are studied by a series of characterization methods.•Graphene accelerates the nucleation during the growth period of VS4.•The photocatalytic properties are tested by water splitting reaction under visible-light irradiation.•We report the formation of C–S bond account for the superior photocatalytic activity of VS4/graphene nanocomposites.VS4/reduced graphene oxide (VS4/rGO) composites are successfully synthesized via a one-step hydrothermal route. Then their photocatalytic activities are examined by water splitting reaction, and the morphology and structure are characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy and thermo gravimetric analysis, respectively. It is shown that graphene accelerates the nucleation during the growth period of VS4. Main product is VS4, not VS2. Monoclinic VS4 particles interact with graphene through chemical action. VS4/rGO composites show excellent photocatalytic water splitting activities under visible-light irradiation. This excellent performance is due to the formation of π-conjugated structure, which can transmit electrons from S2p to graphene rapidly. However, composites with excess graphene show poor dispersion, which leads to the best doping ratio of graphene is 5 wt%.
Co-reporter:Dongfang Wu;Wangbing Li ;Rui Gao
Journal of Chemical Technology and Biotechnology 2014 Volume 89( Issue 10) pp:1559-1564
Publication Date(Web):
DOI:10.1002/jctb.4239
Abstract
BACKGROUND
An efficient, quick and simple preparation method is of great importance for mass production of monolithic catalysts in industry. This paper reports a comparison of three methods used to prepare a monolithic Cu–Mn mixed-oxide/γ-alumina/cordierite catalyst.
RESULTS
The catalysts obtained by different methods have significant differences in catalytic activity and mechanical stability, although their chemical crystalline phases are identical. Similar to a conventional two-step method, the simple one-step sol dipping method leads to homogeneous distribution of active phase and hence to greater o-xylene combustion activity, compared with the one-step solution impregnation method. Furthermore, the one-step sol dipping method results in the strongest adhesion and cohesion of catalytic material on to the monolithic substrate, followed by the one-step solution impregnation method and then the conventional two-step method.
CONCLUSIONS
The one-step sol dipping method is superior to the other two methods and is therefore recommended for use in the future preparation of monolithic catalysts, especially for mass production of monolithic catalysts in industry. © 2013 Society of Chemical Industry
Co-reporter:Kai Huang, Yulong Liu, Dongfang Wu
Progress in Organic Coatings 2014 Volume 77(Issue 11) pp:1774-1779
Publication Date(Web):November 2014
DOI:10.1016/j.porgcoat.2014.06.001
•A novel and relatively more convenient method to prepare core–shell particles was proposed.•The morphology of latex and the property of the film were noticeably influenced with the content of siloxane.•It was of vital importance to control the pH of system in faintly acid condition.•The mechanism of ring opening polymerization between A-151 and D4 was discussed.In this paper, a new method was designed to prepare polyacrylate modified by polysiloxane latex particles, with methyl methacrylate (MMA) and butyl acrylate (BA) as main monomers, vinyltriethoxysilane (A-151) as functional monomer and octamethylcyclotetrasiloxane (D4) as grafting agent. The chemical structure and morphology of the latexes were characterized by FTIR, TEM, and particle size analyzer. The properties of the films were tested in terms of static contact angle, water absorption and TGA. The results showed that uniform spherical structure and narrow particle size distribution could be obtained in the latexes. Furthermore, the hydrophobicity, low surface free energy and thermal stability were also noticeably increased with the content of polysiloxane. The mechanism of ring opening polymerization between D4 and A-151 was also discussed; it turned out that it was quite important to control the pH under faintly acid conditions.
Co-reporter:Dongfang Wu and Hua Zhang
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 41) pp:14713-14721
Publication Date(Web):2017-2-22
DOI:10.1021/ie402546q
Alumina washcoated cordierite monoliths are prepared to investigate mechanical stability of monolithic catalysts by ultrasonic vibration and thermal shock. It is shown that mechanical failure of monolithic catalysts is a stress-induced fatigue damage process, i.e., microcracks are first initiated at the pre-existing flaws and then propagate to form macrocracks, leading to the washcoat surface cracking, interconnection between large cracks, and consequent spalling of active material. It is also found that the washcoat adhesion of mini-monolithic catalysts is distributed over a wide range of values, resulting from fatigue failure of active material. Statistics indicates that the measured weight losses follow a bimodal Weibull distribution, attributed to the transition in the type of the flaws that control fatigue, i.e., the transition in the two spalling modes, interior spalling (cohesive failure) and interface spalling (adhesive failure). Furthermore, it is recommended that at least five monolithic specimens be used to obtain a reliable mechanical stability of monolithic catalysts.
Co-reporter:Dongfang Wu, Yali Guo, Shu Geng, and Yinghao Xia
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 3) pp:1216
Publication Date(Web):December 11, 2012
DOI:10.1021/ie302108r
A monolithic stirrer reactor, in which the cordierite monolith-supported metal oxide and mixed-metal oxide catalysts are used as stirrer blades, is applied for the alcoholysis of urea with 1,2-propylene glycol to synthesize propylene carbonate. It is shown that the mixed-metal oxides give much higher urea alcoholysis performances than the metal oxides, arising from the existence of a strong synergetic effect in the mixed-metal oxides. The zinc–chromium mixed oxide not only shows an excellent catalytic performance but also has extremely strong adhesion strength on the monolithic substrate. For the monolith-supported zinc–chromium mixed oxide catalyst, the monolithic stirrer reactor performs very well, and the highest yield of propylene carbonate reaches 97.8%. The performance is comparable to that of a conventional mechanically agitated slurry reactor, revealing the monolithic stirrer reactor can be an attractive alternative to the slurry reactor for heterogeneously catalyzed liquid–liquid reactions.
Co-reporter:Dongfang Wu;Wei Jiang ;Jiancheng Zhou
Journal of Chemical Technology and Biotechnology 2010 Volume 85( Issue 4) pp:569-576
Publication Date(Web):
DOI:10.1002/jctb.2346
Abstract
BACKGROUND: This paper presents a mathematical modeling and factorial analysis of the toluene combustion activity of a cordierite monolith supported copper–manganese–silver mixed-oxide catalyst in the drying and calcination processes, using response surface methodology. A central composite rotatable design is performed to collectively study the effect of drying temperature, calcination temperature and calcination time. Experimental results are provided to confirm the validity of the models developed.
RESULTS: The calcination temperature is the most significant process factor affecting the catalytic combustion activity. It is also shown that the combustion activity increases in most cases with decreasing calcination time and that a moderate calcination or drying temperature is required to increase the combustion activity. The optimal factor levels are drying temperature 160 °C, calcination temperature 500 °C, and calcination time 3 h.
CONCLUSIONS: There is significant scope to improve the combustion activity of the monolithic catalyst through the optimization of the drying and calcination process factors. Response surface methodology is an effective technique for mathematical modeling and factorial analysis of the catalytic activity of monolithic catalysts. Copyright © 2010 Society of Chemical Industry
Co-reporter:Jiancheng Zhou;Dongsheng Guo
Journal of Chemical Technology and Biotechnology 2010 Volume 85( Issue 10) pp:1402-1406
Publication Date(Web):
DOI:10.1002/jctb.2446
Abstract
BACKGROUND: The Taguchi method, a powerful tool for the optimization of quality, was used to improve the yield of thiocarbohydrazide in its synthetic process. An orthogonal array was selected to analyze the effects of the process factors, i.e. reflux time, molar ratio of hydrazine to carbon disulfide and reflux temperature. Experiments were undertaken to confirm the effectiveness of the Taguchi method.
RESULTS: Through this study, the main factors that affect the yield of thiocarbohydrazide were found, together with the optimal factor levels. It was shown that the reflux temperature was the most significant factor affecting the yield of thiocarbohydrazide, followed by the molar ratio of hydrazine to carbon disulfide. The optimum factor levels were a reflux time of 6 h, molar ratio of hydrazine to carbon disulfide 3.0 and reflux temperature 70 °C. A 92.3% yield of thiocarbohydrazide was obtained at these optimal factor levels.
CONCLUSIONS: The yield of thiocarbohydrazide can be significantly improved by optimization of the synthetic process factors. The Taguchi method provided a systematic and efficient methodology for this optimization, with far less effort than would be required for most other optimization techniques. Copyright © 2010 Society of Chemical Industry
Co-reporter:J.-C. Zhou;D.-F. Wu;W. Jiang;Y.-D. Li
Chemical Engineering & Technology 2009 Volume 32( Issue 10) pp:1520-1526
Publication Date(Web):
DOI:10.1002/ceat.200900151
Abstract
Monolithic catalysts were prepared by washcoating an alumina sol and then impregnating Cu-Mn-Ag mixed oxides onto cordierite substrates. The effects of the preparation parameters including the Ag/Cu/Mn ratio, the total amount of active phase and the loading of washcoat, and the reaction conditions, e.g., the space velocity and the oxygen/toluene ratio on the catalytic performance for the combustion of toluene were investigated. It is shown that the Cu-Mn-Ag oxides are very active for the combustion of toluene and that the highest catalytic activity is achieved over a monolithic catalyst containing 14.7 wt % of washcoat and 21.2 wt % of active phase with a Ag/Cu/Mn molar ratio of 13.8/43.1/43.1. It is also seen that the optimum catalyst has a good catalytic stability and exhibits an excellent activity not only at a rather high space velocity but also within a wide range of oxygen/toluene ratios.
Co-reporter:Dongfang Wu, Jiancheng Zhou, Yongdan Li
Chemical Engineering Science (January 2009) Volume 64(Issue 2) pp:198-206
Publication Date(Web):1 January 2009
DOI:10.1016/j.ces.2008.10.014
Mathematical models for the mechanical properties of a CoMoP/Al2O3 hydrotreating catalyst in the sulfidation process are developed with response surface methodology. A Doehlert design is performed to collectively study the effects of sulfidation temperature, time and heating rate on the mean strength, Weibull modulus and pellet density. Analysis of variance reveals that the models developed for the mean strength and Weibull modulus are adequate. The validity of the models is also verified by experimental data. Analyses of response surfaces show that in the great part of the experimental domain examined, as the sulfidation temperature increases the mean strength decreases, while the Weibull modulus increases at first and then decreases. The middle level of the sulfidation time results in smaller mean strength and higher Weibull modulus. The Weibull modulus decreases with increasing heating rate; however, the effect of the heating rate on the mean strength is statistically less pronounced. It is concluded that there is a great potential for improving the catalyst mechanical reliability in the sulfidation process, while the pellet density does not vary significantly.
