Co-reporter:Xuezhi Duan;Xinggui Zhou;Jiaqi Lei;De Chen
Industrial & Engineering Chemistry Research October 22, 2014 Volume 53(Issue 42) pp:16309-16315
Publication Date(Web):Publication Date (Web): September 30, 2014
DOI:10.1021/ie502706r
Different sized Pt nanoparticles supported on carbon nanotubes were prepared and then applied in selective oxidation of glycerol in a base-free condition to understand the size effects. It is shown that the turnover frequency of glycerol increases with Pt particle size to a maximum at the mean size of 2.5 nm followed by a decline with a further increase in size, which may be due to strongly adsorbed intermediates blocking Pt active sites for smaller sized Pt catalyst. Moreover, compared with dihydroxyacetone, glyceraldehyde and subsequent glyceric acid (GLYA) are dominating products. In particular, smaller sized Pt catalyst favors the formation of GLYA, which could be related to the stronger oxidation. Unexpectedly, the selectivity of C3 products is insensitive to both Pt particle size and reaction time within 9 h.
Co-reporter:Jian Ji, Xiaodong Yan, Gang Qian, Chong Peng, ... Xinggui Zhou
International Journal of Hydrogen Energy 2017 Volume 42, Issue 27(Volume 42, Issue 27) pp:
Publication Date(Web):6 July 2017
DOI:10.1016/j.ijhydene.2017.04.037
•Fe NPs immobilized on carbon nanofibers are synthesized by CCVD method.•Both morphology and location of Fe NPs in CNFs are sensitive to H2/CO ratio.•The long polyhedron-shaped Fe NPs are highly active for NH3 decomposition.•The possible formation mechanism of shaped Fe nanoparticles is proposed.Ammonia decomposition over Fe-based catalysts is a typical structure sensitive reaction, and the shape-controlled synthesis of Fe nanoparticles based on catalytic chemical vapor deposition (CCVD) method appears to be an effective method toward enhanced catalytic activity. The objective of this work is to understand effects of the reaction parameters on structural and textural properties of the resultant Fe catalysts and thus catalytic ammonia decomposition performance. The as-obtained catalysts are characterized by multiple techniques (N2 physisorption, XRD, SEM, TEM, and Raman spectroscopy). Both the morphology and location of Fe nanoparticles are found to strongly depend on the partial pressure of H2 as well as the growth time of CNFs. The long polyhedron shaped Fe nanoparticles on CNFs exhibit the highest activity among the prepared catalysts, which are relatively higher than the activities of the reported Fe based catalysts. The possible explanation for the good catalytic performance was proposed.
Co-reporter:Shanshan Liang, Xuezhi Duan, Xiangyang Zhang, Gang Qian and Xinggui Zhou
RSC Advances 2016 vol. 6(Issue 78) pp:74700-74703
Publication Date(Web):02 Aug 2016
DOI:10.1039/C6RA11586A
A link between the predominant conformer in supersaturated L-glutamic acid aqueous solution detected by FTIR spectroscopy and the polymorphic outcome is reported. In particular, the supersaturation is found to determine the morphology of the initially crystallized α form and thus to affect the rate for its further transformation to the β form.
Co-reporter:Jiaqi Lei, Hua Dong, Xuezhi Duan, Wenyao Chen, Gang Qian, De Chen, and Xinggui Zhou
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 2) pp:420-427
Publication Date(Web):December 24, 2015
DOI:10.1021/acs.iecr.5b03076
Two kinds of activated carbon (AC)-supported Pt catalysts with similar particle sizes were respectively synthesized using the polyol method and incipient wetness impregnation method, and then tested for glycerol oxidation in a base-free condition. It is revealed that the initial reaction rate on the Pt catalyst prepared by the polyol method (Pt/ACPO) is nearly triple that on the Pt catalyst prepared by incipient wetness impregnation method (Pt/ACIWI), and the Pt/ACIWI catalyst favors further oxidation of glyceraldehyde to glyceric acid and more C–C bond cleavage, which might mainly arise from the difference in relative coverage of oxygen to glycerol caused by the different electronic properties of Pt as well as the difference in the catalyst surface properties. Moreover, the deactivation mechanisms of both catalysts were also investigated. The results show that strongly adsorbed intermediates contribute significantly to the deactivation of the Pt/ACPO catalyst, while both the oxygen poison and the adsorption of intermediates on Pt surfaces cause the deactivation of the Pt/ACIWI catalyst.
Co-reporter:Shanshan Liang;Xuezhi Duan;Xiangyang Zhang;Xinggui Zhou
Chemical Engineering & Technology 2016 Volume 39( Issue 7) pp:1295-1300
Publication Date(Web):
DOI:10.1002/ceat.201500704
Abstract
The role of water in the secondary nucleation of the stable β-form of L-glutamic acid (L-Glu) on three typical surfaces of the metastable α-form is investigated via molecular dynamics simulation. Comparing the simulation results on the surfaces in contact with solution with those on the surfaces in vacuum, it is obvious that water molecules do not cause any change in the order of the adsorption energies for the solute molecules on the three surfaces, but reduce the absolute values of the adsorption energies with the extent increasing in the order of {011} < {111} < {001} and retard the clustering behavior of solute molecules with the same order. Water molecules also weaken the inductive effects of the surfaces on the conformational change of α- to β-form. In general, the impact of water on secondary nucleation of the β-form on the surfaces of the α-form investigated here could provide a better understanding of the polymorphic transformation of L-Glu in solution.
Co-reporter:Wenhui Tan;Xiangyu Yang;Xuezhi Duan;Xiangyang Zhang;Xinggui Zhou
Crystal Research and Technology 2016 Volume 51( Issue 1) pp:23-29
Publication Date(Web):
DOI:10.1002/crat.201500108
The dependence of crystal growth rate of L-alanine on solution supersaturation was investigated by combining experiments and molecular dynamics (MD) simulations. The experimental results show that lower supersaturated solution yields more elongated L-alanine crystals along the c-axis, i.e., the aspect ratio (c/b) of the crystal decreases with the increase of solution supersaturation, which is due to the higher supersaturation inducing a rise in the relative growth rate between the main side surface (the (120) surface) and the main end surface (the (011) surface). MD simulations on the two surfaces in contact with different supersaturated solutions revealed that the solute molecules tend to be more efficiently attached to the (011) surface than to the (120) surface at both supersaturations studied, as the interaction between the solute molecules and the L-alanine molecules in the first layer of the (011) surface is stronger than that of the (120) surface. However, higher supersaturation leads to larger relative interaction energy between the (120) and (011) surfaces, suggesting an increase in the relative growth rate of the two surfaces (R(120)/R(011)) with supersaturation, which is in agreement with the experimental results.
Co-reporter:Shanshan Liang, Xuezhi Duan, Xiangyang Zhang, Gang Qian, and Xinggui Zhou
Crystal Growth & Design 2015 Volume 15(Issue 8) pp:3602
Publication Date(Web):July 7, 2015
DOI:10.1021/cg501833u
Solution-mediated polymorphic transformation of l-glutamic acid (l-Glu) from α to β form was studied by combining experiments and molecular simulation. Experimental results show that the β form mainly nucleates on the three surfaces of the α form during the transformation, and the corresponding probability follows the order of {011} > {111} > {001}. Molecular simulation of the adsorption of molecule initially with α or β conformation on the three surfaces indicates that regardless of the initial conformation, the adsorption energies decrease in the order of {011} > {111} > {001}, which is consistent with the experimental results. Moreover, it reveals that the three surfaces have different abilities to induce the conformational change of α to β. Especially, for a molecule adsorbed on the {011} surface initially with α conformation, it will evolve into the β conformation. These findings provide insights about the crucial role of α form surfaces in the polymorphic transformation of l-Glu.
Co-reporter:Xiangyang Zhang, Gang Qian, Rui Wang, Xiaowu Yang, Lin Hao, Hongyuan Wei, Xinggui Zhou
Fluid Phase Equilibria 2015 Volume 388() pp:59-65
Publication Date(Web):25 February 2015
DOI:10.1016/j.fluid.2014.12.037
•Solubility of GN in five different solvents was determined using gravimetric method.•Dissolution enthalpy and entropy of GN in five different solvents were estimated.•Activity coefficient in different solvents was calculated.To realize the rapid solvent screening and further crystallization process optimization, experimental determination of accurate solubility data of target solute in potential solvents is necessary. Using a gravimetric method, solubilities of guanidine nitrate in water, methanol, ethanol, n-propanol and acetone at temperature ranging from 278.05 K to 332.85 K at pressure p = 0.1 MPa were experimentally measured. Melting temperature, Tm, and fusion enthalpy, ΔHf, of guanidine nitrate were determined using differential scanning calorimetry. Subsequently, Apelblat equation, van’t Hoff equation, λh equation, and Wilson model were used to correlate the measured solubility data, respectively. Dissolution of guanidine nitrate in all examined solvents was found to be endothermic and entropically favorable. Moreover, the measured solubility data were combined with calculated ideal solubility data to calculate activity coefficients at infinite dilution based on the assumption of ΔCp = 0, which were then fitted to a van’t Hoff like regular solution equation.
Co-reporter:Xiangyang Zhang, Gang Qian, Xinggui Zhou
Journal of Crystal Growth (1 April 2017) Volume 463() pp:162-167
Publication Date(Web):1 April 2017
DOI:10.1016/j.jcrysgro.2017.02.023
•Effect of malic acid on crystallization kinetics of zinc lactate has been studied.•A PBE model was used to estimate the nucleation and crystal growth kinetics.•Malic acid decreased nucleation and crystal growth rates of zinc lactate.•Crystal habit and purity of final products were also investigated.Influence of malic acid, which acts as an impurity, on the crystallization kinetics of zinc lactate has been investigated in this work. Crystallization of zinc lactate with a linear cooling profile was carried out in a batch crystallizer and a population balance model was used to estimate the crystallization kinetics for each studied system by using the nonlinear optimization method. The predicted results related to the concentration profile of zinc lactate are in good agreement with the experimental data. The influence of malic acid on the crystallization of zinc lactate is discussed herein.
