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He B.,Chongqing University of Science and Technology | Wang J.,Sichuan Tianyi Science and Technology Co. | You X.,COCC Asphalt Sichuan Ltd | Qiu Z.,Chongqing University of Science and Technology | And 2 more authors.
Shiyou Huagong/Petrochemical Technology | Year: 2013

ZnO/γ-Al2O3 catalyst was prepared by an impregnation method and applied in the deacidification of vacuum gas oil through the esterification with methanol. The effects of the catalyst dosage, methanol dosage, reaction temperature and reaction time on the deacidification were investigated. The vacuum gas oils before and after the deacidification were characterized by means of FTIR. The results showed that the ZnO/γ-Al2O3 exhibited good catalytic activity for the esterification. Under the suitable reaction conditions of vacuum gas oil dosage 40 g, the catalyst dosage 1.25%(w) (based on the vacuum gas oil, the same below), methanol dosage 2.50%(w), reaction temperature 260°C and reaction time 1.00 h, the acid removal rate reached 78%. The FTIR results showed that naphthenic acids in the vacuum gas oil reacted with methanol into corresponding esters, so the acids were eliminated. Compared with the vacuum gas oil before the deacidification, the deacidified oil owned the advantages of low acid value, high kinematic viscosity and high flashing point.

Dai X.,China University of Petroleum - Beijing | Du K.,China University of Petroleum - Beijing | Du K.,Sichuan Tianyi Science and Technology Co. | Li Z.,China University of Petroleum - Beijing | And 5 more authors.
ACS Applied Materials and Interfaces | Year: 2015

Highly active and low-cost catalysts for hydrogen evolution reaction (HER) are crucial for the development of efficient water splitting. Molybdenum disulfide (MoS2) nanosheets possess unique physical and chemical properties, which make them promising candidates for HER. Herein, we reported a facile, effective, and scalable strategy by a deposition-precipitation method to fabricate metal-doped (Fe, Co, Ni) molybdenum sulfide with a few layers on carbon black as noble metal-free electrocatalysts for HER. The CoMoS phase after thermal annealing in Co-doped MoS2 plays a crucial role for the enhanced HER. The optimized Co-doped MoS2 catalyst shows superior HER performance with a high exchange current density of 0.03 mA·cm-2, low onset potential of 90 mV, and small Tafel slope of 50 mV·dec-1, which also exhibits excellent stability of 10000 cycles with negligible loss of the cathodic current. The superior HER activity originates from the synergistically structural and electronic modulations between MoS2 and Co ions, abundant defects in the active edge sites, as well as the good balance between active sites and electronic conductivity. Thanks to their ease of synthesis, low cost, and high activity, the Co-doped MoS2 catalysts appear to be promising HER catalysts for electrochemical water splitting. © 2015 American Chemical Society.

Dai X.,China University of Petroleum - Beijing | Li Z.,China University of Petroleum - Beijing | Ma Y.,China University of Petroleum - Beijing | Liu M.,China University of Petroleum - Beijing | And 7 more authors.
ACS Applied Materials and Interfaces | Year: 2016

Despite being technically possible, the hydrogen production by means of electrocatalytic water splitting is still practically unreachable mainly because of the lack of inexpensive and high active catalysts. Herein, a novel and facile approach by melamine polymerization, exfoliation and Co2+-assisted thermal annealing is developed to fabricate Co nanoparticles embedded in bamboo-like and nitrogen-rich carbonitride nanotubes (Co@NCN). The electronic interaction between the embedded Co nanoparticles and N-rich carbonitride nanotubes could strongly promote the HER performance. The optimized Co@NCN-800 exhibits outstanding HER activity with an onset potential of '89 mV (vs RHE), a large exchange current density of 62.2 ΜA cm-2, and small Tafel slope of 82 mV dec-1, as well as excellent stability (5000 cycles) in acid media, demonstrating the potential for the replacement of Pt-based catalysts. Control experiments reveal that the superior performance should be ascribed to the synergistic effects between embedded Co nanoparticles and N-rich carbonitride nanotubes, which originate from the high pyridinic N content, fast charge transfer rate from Co particles to electrodes via electronic coupling, and porous and bamboo-like carbonitride nanotubes for more active sites in HER. © 2016 American Chemical Society.

Li Z.,China University of Petroleum - Beijing | Dai X.,China University of Petroleum - Beijing | Du K.,China University of Petroleum - Beijing | Du K.,Sichuan Tianyi Science and Technology Co. | And 5 more authors.
Journal of Physical Chemistry C | Year: 2016

Efficient hydrogen evolution through water splitting at low overpotentials is crucial to develop renewable energy technology, which depends on the design of efficient and durable electrocatalysts composed of earth-abundant elements. Herein, a highly and stable electrocatalyst for hydrogen evolution reaction (HER) has been developed on the basis of MoS2 on p-phenylenediamine (PPD)-functionalized reduced graphene oxide/O-containing carbon nanotubes (rGO/O-MWCNT) hybrids via facile and green hydrothermal process. Among the prepared catalysts, the optimized MoS2/rGO/PPD/O-MWCNT with nanosized and highly dispersed MoS2 sheets provides a large amount of available edge sites and the improved electron transfer in 3D conductive networks. It exhibits excellent HER activity with a low overpotential of 90 mV and large current density of 47.6 mA·cm-2 at 200 mV, as well as excellent stability in an acidic medium. The Tafel slope of 48 mV·dec-1 reveals the Volmer-Heyrovsky mechanism for HER. Thus, this work paves a potential pathway for designing efficient MoS2-based electrocatalysts for HER by functionalized conductive substrates. © 2016 American Chemical Society.

Dai X.,China University of PetroleumBeijing | Du K.,China University of PetroleumBeijing | Du K.,Sichuan Tianyi Science and Technology Co. | Li Z.,China University of PetroleumBeijing | And 4 more authors.
International Journal of Hydrogen Energy | Year: 2015

Abstract The oxygen- or nitrogen-functionalized multiwalled carbon nanotubes (O- or N-MWCNT) coated with few-layer MoS2 nanosheets (MoS2/MWCNTs) were successfully synthesized by a facile hydrothermal method. The results suggest that the N-MWCNT is favorable for the dispersion of few-layer MoS2 nanosheets due to the strong interaction between the N-containing groups and Mo precursor. The N-MWCNT coated with few-layer MoS2 (MoS2/N-MWCNT) exhibits the highest HER activity: onset potential of 90 mV vs. reversible hydrogen electrode, Tafel slope of 40 mV dec-1, high current density of 80.3 mA cm-2 at overpotential 0.2 V, together with excellent stability during 10,000 cycles. Such high HER activity is superior to most of MoS2-based catalysts reported so far, and attributed to the intimate contacts between highly conductive network of N-MWCNT and thin MoS2 nanosheets, the high quantity of unsaturated sulfur atoms or the bridging S22-, and high pyridinic and graphitic N concentrations. This work shows that the few-layer MoS2 nanosheets coated on conductive N-doped MWCNT has a great potential for electrocatalytic hydrogen evolution. © 2015 Hydrogen Energy Publications, LLC.

Zou C.,Southwest Petroleum University | Zhao P.,Southwest Petroleum University | Wang M.,Southwest Petroleum University | Liu D.,Southwest Petroleum University | And 2 more authors.
Engineering Failure Analysis | Year: 2013

Natural gas dehydration by molecular sieves is one of the most promising processes. However, the sharply declined dehydration capability of the regenerative molecular sieve has become a serious problem for molecular sieve recycling. A series of experiments is carried out to investigate the failure factors, such as pH analysis, thermogravimetry, differential thermogravimetry, scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectrum characterizations. The results indicate that there are four main aspects for the unavailability of the regenerative molecular sieve. First, the pH values and surface alkalinity decrease. Second, the secondary pore structure is diminished and blocked. Third, the crystallite size increases, and the crystals are agglomerated. Finally, not only are the hydrocarbons adsorbed, but also alcohols, ethers and carbonyl sulfides are generated in pores. © 2013 Elsevier Ltd.

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