Qingxin Guan

Bio-aviation fuel production from hydroprocessing castor oil promoted by the nickel-based bifunctional catalysts

Bio-aviation fuel was firstly synthesized by hydroprocessing castor oil in a continuous-flow fixed-bed microreactor with the main objective to obtain the high yield of aviation fuel and determine the elemental compositions of the product phases as well as the reaction mechanism. Highest aviation range alkane yields (91.6 wt%) were achieved with high isomer/n-alkane ratio (i/n) 4.4-7.2 over Ni supported on acidic zeolites. In addition, different fuel range alkanes can be obtained by adjusting the degree of hydrodeoxygenation (HDO) and hydrocracking. And the observations are rationalized by a set of reaction pathways for the various product phases.

Low-Temperature Selective Catalytic Reduction of NO with NH3 over Mn2O3-Doped Fe2O3 Hexagonal Microsheets

Mn2O3-doped Fe2O3 hexagonal microsheets were prepared for the low-temperature selective catalytic reduction (SCR) of NO with NH3. These hexagonal microsheets were characterized by SEM, TEM, XRD, BET, XPS, NH3-TPD, H2-TPR, and in situ DRIFT and were shown to exhibit a considerable uniform hexagonal microsheet structure and excellent low temperature SCR efficiency. When doped with different Mn molar ratios, Mn2O3 was detected in the Fe2O3 hexagonal microsheets based on the XRD results without the presence of other MnOX species. In addition, the hexagonal microsheets with a Mn/Fe molar ratio of 0.2 showed the best SCR removal performance among the materials, where a 98% NO conversion ratio at 200 °C at a space velocity of 30,000 h(-1) was obtained. Meanwhile, excellent tolerances to H2O and SO2, as well as high thermal stability, were obtained in Mn2O3-doped Fe2O3 hexagonal microsheets. Moreover, on the basis of the XPS and in situ DRIFT results, it can be suggested that coupled Mn2O3 nanocrystals played a key role at low temperatures and produced a possible redox reaction mechanism in the SCR process.

Effect of template in MCM-41 on the adsorption of aniline from aqueous solution

The effect of the surfactant template cetyltrimethylammonium bromide (CTAB) in MCM-41 on the adsorption of aniline was investigated. Various MCM-41 samples were prepared by controlling template removal using an extraction method. The samples were then used as adsorbents for the removal of aniline from aqueous solution. The results showed that the MCM-41 samples with the template partially removed (denoted as C-MCM-41) exhibited better adsorption performance than MCM-41 with the template completely removed (denoted as MCM-41). The reason for this difference may be that the C-MCM-41 samples had stronger hydrophobic properties and selectivity for aniline because of the presence of the template. The porosity and cationic sites generated by the template play an important role in the adsorption process. The optimal adsorbent with moderate template was achieved by changing the ratio of extractant; it has the potential for promising applications in the field of water pollution control.

Nitrogen-doped Carbon Derived from ZIF-8 as a High-performance Metal-free Catalyst for Acetylene Hydrochlorination

Acetylene hydrochlorination is a major industrial technology for manufacturing vinyl chloride monomer in regions with abundant coal resources; however, it is plagued by the use of mercury(II) chloride catalyst. The development of a nonmercury catalyst has been extensively explored. Herein, we report a N-doped carbon catalyst derived from ZIF-8 with both high activity and quite good stability. The acetylene conversion reached 92% and decreased slightly during a 200 h test at 220 °C and atmospheric pressure. Experimental studies and theoretical calculations indicate that C atoms adjacent to the pyridinic N are the active sites, and coke deposition covering pyridinic N is the main reason for catalyst deactivation. The performance of those N-doped carbons makes it possible for practical applications with further effort. Furthermore, the result also provides guidance for designing metal-free catalysts for similar reactions.

Structure–performance relationships of MnO2 nanocatalyst for the low-temperature SCR removal of NOX under ammonia

To investigate the corresponding relationship between catalytic efficiency and structure, MnO2 nanomaterials (nanospheres, nanosheets, nanorods) have been prepared successfully, and were thoroughly characterized by SEM and TEM. Furthermore, the selective catalytic reduction (SCR) performance of NOX under ammonia was used as an indicative reaction. Among the MnO2 nanomaterials with different morphologies, it was found that their SCR activities showed an interesting variation tendency: nanospheres > nanosheets > nanorods of MnO2. The NO conversion ratio of the MnO2 nanospheres could reach 100% from 200 to 350 °C. Moreover, in order to study the probable mechanism for the best removal efficiency of the nanospheres, XRD, H2-TPR, NH3-TPD, BET, XPS and in situ DRIFTS were performed in detail. It is found that surface chemisorbed oxygen, specific surface area, reducibility and acid sites have great influence on the NO removal efficiency in the SCR reaction. In addition, how several process parameters affect the NOX removal efficiency was carried out, such as time, H2O and SO2.

The synthesis and evaluation of highly active Ni2P–MoS2 catalysts using the decomposition of hypophosphites

This paper presents the synthesis and evaluation of highly active Ni2P–MoS2 catalysts using the decomposition of hypophosphites. A family of catalysts have been prepared, whose activities were tested using the hydrodesulfurization of 4,6-dimethyldibenzothiophene. Furthermore, the synergy between Ni2P/Al2O3 and MoS2/Al2O3 beds was explained by the remote control model through a migration of hydrogen spillover.

Catalytic performance and deoxygenation path of methyl palmitate on Ni2P/SiO2 synthesized using the thermal decomposition of nickel hypophosphite

In this paper, the catalytic performance and deoxygenation path of methyl palmitate on Ni2P/SiO2 catalysts were systematically studied in a continuous flow fixed-bed reactor. A series of Ni2P/SiO2 catalysts (with different molar ratios of P/Ni and Ni2P loadings) were synthesized at 300 °C using the thermal decomposition of nickel hypophosphite. The increased molar ratio of P/Ni generates phosphate-rich nickel phosphide catalysts and increasing conversion. Interestingly, Ni2P/SiO2 showed significantly higher conversion of methyl palmitate in comparison with Ni/SiO2. Furthermore, an activation temperature higher than 500 °C would significantly reduce the catalytic activity, as a result of the sintering of Ni2P. The pressure in a range of 3.0 to 0.5 MPa almost has no effect on the deoxygenation of methyl palmitate, but significantly affects the reaction path and product distribution. Finally, a possible deoxygenation path over Ni2P/SiO2 was proposed based on a GC-MS investigation.

The synthesis and mechanistic studies of a highly active nickel phosphide catalyst for naphthalene hydrodearomatization

Although HDS and HDN reactions over transition metal phosphides have been widely studied, few publications about aromatic hydrodearomatization (HDA) over transition metal phosphides are found. Using ordered mesoporous Al-MCM-41 (Al-M) as the support, a series of supported nickel phosphide catalysts with different Ni/P molar ratios and loadings have been prepared by a temperature-programmed reduction and characterized. The HDA activity of naphthalene was measured in a fixed bed reactor at 250–330 °C and 3 MPa. The results showed that the catalyst with initial Ni/P molar ratio of 1.25 and 15 wt% loading displayed the highest HDA activity as well as 99.0% of selectivity of decalin at 270 °C, which is even higher than that of 0.5 wt% Pt–Al-M catalyst. As a comparison, the HDA performance of various catalysts was also examined. The results revealed that the presence of framework aluminum favors HDA processes and a synergistic effect between nickel phosphide and the suitable acidity resulted in an improvement of the catalytic activity. Finally, the possible reaction pathway of naphthalene hydrogenation (HYD) on nickel phosphide catalysts was proposed. Taking into consideration the high catalytic activity, Al-M supported nickel phosphide can be considered as a very efficient HDA catalyst to decrease the contents of aromatics in the fuels.

Comparison of four different synthetic routes of Ni2P/TiO2–Al2O3 catalysts for hydrodesulfurization of dibenzothiophene

Ni2P/TiO2–Al2O3 is a very promising hydrodesulfurization catalyst, however the catalysts reported so far all use the temperature-programmed reduction (H2-TPR) method and the reduction temperature can be as high as 973 K. It is important to develop more feasible methods to prepare this material. Herein, Ni2P/TiO2–Al2O3 catalysts were successfully synthesized at a low reduction temperature (573 K) based on NiCl2·6H2O and NH4H2PO2 (method I). Three other methods were also used to prepare the Ni–P/TiO2–Al2O3 catalysts in this work. The catalysts were characterized using XRD, TEM, FT-IR, XPS, CO uptake, and N2 sorption measurements. Experimental results indicate that the preparation method had a major influence on the physicochemical properties of the catalysts and the HDS activity. Among the four methods examined, method I could more effectively suppress the formation of AlPO4 and favor the formation of Ni2P, which can be attributed to the relatively low reduction temperature and the flowing hydrogen used in this method. The hydrodesulfurization activity results indicate that the Ni2P/TiO2–Al2O3 catalyst prepared by method I gave a high HDS conversion of 100.0% at a reaction temperature of 583 K. The results suggest that method I provides a simple and energy-efficient route for the preparation of the Ni2P/TiO2–Al2O3 catalyst with excellent catalytic performance for the HDS of dibenzothiophene.

Synthesis of bulk and supported nickel phosphide using microwave radiation for hydrodeoxygenation of methyl palmitate

In this paper, we proposed a novel method for preparing bulk and supported Ni2P catalysts under mild conditions. Ni2P and Ni2P/SiO2 were synthesized from nickel hypophosphite precursors at 230 °C for 5 min using a CEM Discover microwave reactor, and the initial reaction temperature is about 202 °C. The catalysts were characterized using XRD, TEM, SEM, XPS, BET, carbon monoxide chemisorption, and the catalytic performance was tested for hydrodeoxygenation (HDO) of methyl palmitate in a fixed-bed reactor. Interestingly, microwave irradiation does not result in sintering of Ni2P particles. The principal products of the HDO reaction for both catalysts are pentadecane and hexadecane. Isomerization products were not detected, and other by-products content is very low (<1%). The HDO results demonstrate that the catalyst prepared using a microwave has better activity than that prepared using calcination.