Shuqi Fang,Kang Bi,Qiao Zhang,Lingpeng Chen,Yongming Sun,Hongyu Huang,Longlong Ma,Chenguang Wang
Layered double hydroxide (LDH) is a layered solid containing positively charged layers with negatively charged anions as an interchangeable interlayer. In this research, Mg(Al)O supports were synthesized with three different Mg:Al molar ratios, and bimetallic PtSn catalysts were loaded onto the supports via the anion exchange method. The properties of ethane dehydrogenation of the PtSn/Mg(Al)O catalysts were investigated. The results show that the structure and properties of the PtSn/Mg(Al)O catalysts were influenced by the Mg:Al molar ratio of the hydrotalcites, which consequently influenced the ethane dehydrogenation performance. When the Mg:Al ratio was 5:1, the ethane dehydrogenation performance was optimal, relative to the Mg:Al ratios of 2:1 and 10:1.Keywords:hydrotalcite;Mg:Al molar ratio;anion exchange method;ethane dehydrogenation
Poorly ordered Al/Si phases are widely distributed across the surface of Mars, among which allophane and amorphous silica are the two main constituents. Both allophane and amorphous silica can form in Al-Si systems through surface chemical weathering or subsurface hydrothermal alteration of volcanic materials. Nevertheless, our comprehension of the products derived from Al-Si hydrolysis systems remains poorly constrained. Hydrolysis experiments were conducted on Al-Si systems across an unprecedentedly wide range of Si/(Al + Si) molar ratios ( n , 0 ≤ n ≤ 0.9), followed by characterizing the products using multiple techniques. At n ≤ 0.1, the products consist predominantly of Al 30 (an Al polycation with a Keggin structure) and poorly ordered Al hydroxides. The introduction of Si resulted in formation of a small amount of proto-allophane. At n = 0.2 and 0.3, poorly ordered materials were still dominant, along with the presence of well-crystallized bayerite and gibbsite. The proto-allophane increased in quantity and began to assemble into allophane. At n = 0.5, well-crystallized minerals were absent and allophane dominated the product. At n = 0.7, the amount of allophane decreased significantly and at n = 0.8 and 0.9, allophane was probably absent, although proto-allophane still formed. Meanwhile, an increasing amount of amorphous silica was formed. X-ray diffraction, Fourier transform infrared, and VNIR provide information for differentiating Al-rich phases and Si-rich phases but show limited capability in identifying poorly ordered Al/Si-rich phases. NMR is powerful for identifying poorly ordered Al/Si phases, although widespread iron on the martian surface and the large instrument pose challenges to its application on Mars.
Huiyue Xin,Wenbo Zhang,Xixi Xiao,Li Chen,Peng Wu,Xiaohong Li
Due to coexistence of two conjugated unsaturated functional groups in cinnamaldehyde (CAL), exploring efficient catalysts with desirable selectivity to highly value-added products is still challengeable for the selective hydrogenation of CAL. Herein, Ni x Fe 1- x Al 2 O 4+ δ spinel composite metal oxides (SCMOs) supported Pt catalysts were developed and proved to be active and selective for the selective hydrogenation of CAL. Moreover, the selectivity switch can be realized just by changing the Ni/(Fe + Ni) molar ratios in Ni x Fe 1- x Al 2 O 4+ δ SCMOs. As a result, the excellent cinnamyl alcohol (COL) selectivity (~92.2%) and hydrocinnamaldehyde (HCAL) selectivity (~80.7%) were achieved on Pt/FeAl 2 O 4+ δ and Pt/NiAl 2 O 4+ δ , respectively. Based on the kinetic investigation of further hydrogenation of semi-hydrogenated product, the reason for the selectivity switch with Pt/Ni x Fe 1- x Al 2 O 4+ δ was revealed. In combination with detailed characterization, the excellent COL selectivity on Pt/FeAl 2 O 4+ δ can be attributed to more Pt(1 1 1) facets and FeO x species which can facilitate the preferential activation of C O bonds; while the high HCAL selectivity on Pt/NiAl 2 O 4+ δ is owing to the fact that there are more low coordinated active sites and two neighbouring Pt sites.
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