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A set of nearly NS-trending rifts developed in the Himalayan orogen and southern Tibet, which are the large-scale extensional structures formed under the continuous compression of the Indo-Eurasia continent, playing a significant role in revealing the post-collisional evolution of the Tibetan Plateau. Different predictions have been made on the spatiotemporal distribution of these rifts through the existing hypothesis models, constituting the key factors constraining the formation system of the rifts. In this study we synthesized previous studies on the initiation time of rifting, and further clarified the spatiotemporal trend. The analysis results showed that the rifting initiated progressively earlier westward, which is consistent with the evolution of post-collisional magmatism in the Lhasa Terrain. Moreover, combined with the geophysical observations, it is inferred that the geodynamic mechanism of the nearly NS-trending rifts accords closely with the hypothesis model concerning the eastward-propagating lateral detachment of the subducted Indian slab. The Indian slab detachment resulted in asynchronous gravitational potential energy gradients, which drove the lithosphere flow eastward and eventually caused the eastward development of the rifting.

Due to the particularity of the carburizing process, it is unavoidable to generate deposited carbon on the surface of molybdenum carbide, which has a negative effect on its catalytic performance. In this paper, the molybdenum carbide catalyst was prepared by CH4 and H2 plasma and modified by O2 plasma (0.5 vol % O2/Ar) to reduce deposited carbon on its surface. Besides, the effect of discharge time on the amount of deposited carbon and the states of molybdenum active sites were investigated at 16 W. The results of XRD shows that the Mo2C modified by O2 plasma had little influence in their particles size but Mo2C was gradually oxidized with the extension of discharge time. The characterizations by means of H2-TPR, XPS, Raman, CO2-TPO and TGA revealed that the amount of deposited carbon on the surface of Mo2C after O2 plasma treatment was significantly reduced. It was found that the disordered carbon could be removed more easily than the ordered graphitic carbon. H2-TPD characterization revealed that Mo2C after O2 plasma treatment exposed more active sites. Mo2C-x were evaluated in the hydrodeoxygenation of o-cresol, and the results showed that the Mo2C after O2 plasma treatment for 1 h showed the highest catalytic performance and the toluene yield was nearly 80%. [ABSTRACT FROM AUTHOR]

Unsupported molybdenum carbide catalyst was prepared by a nonthermal plasma carburization (PC) method. The input voltage (50, 60, 70, 80, 90, 100, and 110 V) and discharge time (2, 3, and 4 h) were optimized. Pure β-Mo2C was prepared at input voltage of 90 V for 4 h (Mo2C-PC). In comparison, a molybdenum carbide catalyst (Mo2C-TPC) was prepared by the conventional temperature-programmed reduction carburization. Mo2C-PC had smaller crystal size (7.4 nm), as estimated by the Scherrer equation (XRD), and more active sites (Mo2+), as determined by XPS. TEM characterization revealed that there was no obvious agglomeration of Mo2C-PC particles, whereas agglomerative particles and a carbon layer could be observed in Mo2C-TPC. Mo2C-PC and Mo2C-TPC were evaluated in the hydrodeoxygenation (HDO) of guaiacol, phenol, and anisole, using a stainless-steel tubular reactor. The results showed that both the conversion of phenolic compounds and the selectivity to aromatic hydrocarbons over Mo2C-PC were higher than those of Mo2C-TPC at low temperatures (< 300 °C). The TOF of Mo2C-PC(0.37 s−1) was close to that of Mo2C-TPC (0.32 s−1) in HDO of guaiacol, suggesting that the enhanced performance could be ascribed to reduced particles, increased Mo sites (Mo2+) and suppressed carbon deposit. [ABSTRACT FROM AUTHOR]

Citric acid (CA) modified Ni3P catalysts with small particle sizes were prepared by H2 temperature-programmed reduction (H2-TPR) of the precursors, which were prepared by co-precipitation with Ni(NO3)2·6H2O and (NH4)2HPO4, using citric acid as the chelating agent and calcining under a N2 atmosphere. The catalytic activity of the prepared catalysts was tested in the aqueous phase reforming (APR) and hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO). The effects of the CA/Ni molar ratio and reaction conditions (temperature, pressure, and time) on APR and hydrogenolysis of glycerol were investigated. The CA(1)–Ni3P catalyst exhibited the best performance at 220 °C, 0.5 MPa N2, and 8 h with 74.6% glycerol conversion and 43.2% selectivity of 1,2-PDO. The prepared CA(x)–Ni3P catalysts were characterized by XRD, N2 adsorption, Raman spectroscopy, CO-chemisorption and TEM. The addition of CA significantly enhanced the dispersion of Ni species in the precursors and enlarged the surface area of the catalyst. The residual carbonaceous species after calcination in N2 prevented the aggregation of Ni3P particles and promoted the reduction of the precursors. Compared with the unmodified Ni3P and CA(x)–Ni3P calcined in air, the CA(x)–Ni3P calcined in N2 with a smaller average particle size exhibited higher catalytic activities. [ABSTRACT FROM AUTHOR]