Effects of Ni–Al2O3 interaction on NiMo/Al2O3 hydrodesulfurization catalysts

Regulation of multilayer long crystalline MoS2 by NiO-modified Al2O3 for improved hydrodesulfurization of COS

Activated alumina-based composite oxide support is a commonly used support in hydrodesulfurization (HDS) catalysts, which not only retains the performance advantages of each component in the composite oxide support, but also significantly improves the defects of a single activated alumina support, such as the strong metal-support force of interaction. In this study, NiO-Al2O3 composite support was prepared by introducing NiO-modified Al2O3, and MoS2/NiO-Al2O3 catalysts were prepared for the hydrodesulfurization of COS by liquid phase reduction method. In the COS hydrogenation reaction, the MoS2/NiO-Al2O3 catalyst achieved complete conversion of COS at 220 °C and showed more than 99.9% H2S selectivity. In stability tests, the catalyst maintained a COS conversion of over 99% throughout the 23-h hydrogenation reaction. Various characterization results show that the NiO-Al2O3 composite support prepared by introducing NiO-modified Al2O3 weakens the metal-support interaction force between MoS2 and NiO-Al2O3 composite support, which is conducive to the synthesis of MoS2 with multilayer and long wafer structures. And it can significantly increase the formation rate of MoS2 to 87.9%, which greatly improves the active site content of the catalyst. Furthermore, the dual modulation of MoS2 and Al2O3 by NiO modulated the surface alkalinity of the catalysts and promoted the formation of a large number of active edge sites in the MoS2/NiO-Al2O3 catalysts, which in turn significantly improved the HDS performance of the catalysts. In addition, EPR characterization combined with experiments showed that the sulfur vacancies are the active sites for catalytic COS hydrodesulfurization over MoS2-based catalysts.

One-pot solvothermal preparation of the porous NiS2//MoS2 composite catalyst with enhanced low-temperature hydrodesulfurization activity

The simple preparation of mesoporous NiS2//MoS2 composite catalyst through a one-pot solvothermal method is presented. The improvement of the specific surface area (220 m2/g) and the construction of the porous structure are realized by this method in the case of no support. The organics acts as a microscopic binder contribute to uniform stacking of MoS2 with NiS2 clusters. The composite structure including NiS2 and MoS2 was obtained (proved by XRD, XPS, TEM, IR, UV-vis and RAMAN) and changed the microelectronic environment of the active metal surface (DFT calculation). The mesoporous NiS2//MoS2 catalyst (Ni1Mo1-200) showed an excellent hydrodesulfurization performance of dibenzothiophene (DBT conversion: 78 % at 260 °C) and a high ratio of direct desulfurization pathway (SDDS/HYD = 16.6) at a low reaction temperature. By combining the characterization and theoretical calculation results, the advantages of this NiS2//MoS2 composite structure in synergistic catalysis was further confirmed.

Study on the Performance of Ni-MoS2 Catalysts with Different MoS2 Structures for Dibenzothiophene Hydrodesulfurization

Hydrodesulfurization (HDS) is an important process for the production of clean fuel oil, and the development of a new environmentally friendly, low-cost sulfided catalyst is key research in hydrogenation technology. Herein, commercial bulk MoS2 and NiCO3·2NiOH2·4H2O were first hydrothermally treated and then calcined in a H2 or N2 atmosphere to obtain Ni-MoS2 HDS catalysts with different structures. Mechanisms of hydrothermal treatment and calcination on Ni-MoS2 catalyst structures were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS). The catalytic performance of Ni-MoS2 catalysts was evaluated by the HDS reaction of dibenzothiophene (DBT) on a fixed bed reactor, and the structure-activity relationship between the structures of the Ni-MoS2 catalyst and the HDS of DBT was discussed. The results showed that the lateral size, the number of stacked layers, and the S/Mo atomic ratio of MoS2 in the catalyst decreased and then increased with the increase of the hydrothermal treatment temperature, reaching the minimum at the hydrothermal treatment temperature of 150 °C, i.e., the lateral size of MoS2 in the catalyst was 20-36 nm, the number of stacked layers of MoS2 was 5.4, and the S/Mo ratio in the catalyst was 1.80. In addition, the effects of different calcination temperatures and calcination atmospheres on the catalyst structures were investigated at the optimum hydrothermal treatment temperature. The Ni-Mo-S and NixSy ratios of the catalysts increased and then decreased with the increasing calcination temperature under a H2 atmosphere, reaching a maximum at a calcination temperature of 400 °C. Therefore, DBT exhibited the best HDS activity over the H-NiMo-150-400 catalyst, and the desulfurization rate of DBT reached 94.7% at a reaction temperature of 320 °C.

Sulfidation of Supported Ni, Mo and NiMo Catalysts Studied by In Situ XAFS

Active sites in Mo-based hydrotreating catalysts are produced by sulfidation. To achieve insights that may enable optimization of the catalysts, this process should be studied in situ. Herein we present a comparative XAFS study where the in situ sulfidation of Mo/δ-Al2O3 and Ni/δ-Al2O3 is compared to that of δ-Al2O3 supported NiMo catalysts with different NiMo ratios. The study also covers the comparison of sulfidation of Ni and Mo using different oxide supports as well as the sulfidation conditions applied in the reactor. The XAFS spectra confirms the oxide phase for all catalysts at the beginning of the sulfidation reaction and their conversion to a sulfidized phase is followed with in situ measurements. Furthermore, it is found that the monometallic catalysts are less readily sulfidized than bimetallic ones, indicating the importance of Ni-Mo interactions for catalyst activation. Mo K-edge XAFS spectra did not show any difference related to the support of the catalyst or the pressure applied during the reaction. Ni K-edge XAFS spectra, however, show a more complete sulfidation of the Ni species in the catalyst when SiO2 is used as a support as compared to the Al2O3. Nevertheless, it is believed that stronger interactions with Al2O3 support prevent sintering of the catalyst which leads to its stabilization. The results contribute to a better understanding of how different parameters affect the formation of the active phase of the NiMo catalysts used in the production of biofuel.

A Highly Active NiMoAl Catalyst Prepared by a Solvothermal Method for the Hydrogenation of Methyl Acrylate

In this study, a series of Ni10MoxAl composite metal oxide (Ni10MoxAl, NiO = 10 wt.%, x = 2.5, 5, 10, 15, 20 wt.%) catalysts with different Mo content were prepared by a solvothermal method using a water—ethanol system. By employing various characterization technologies, it was confirmed that the suitable amount of the Mo element can not only promote the dispersion of the Ni species but also inhibit the formation of the inactive NiAl2O4 phase. Consequently, the hydrogenation activity of the Ni10MoxAl catalysts was affected by the particle size of the active components and the amount of the NiAl2O4 phase. As a result, the Ni10Mo10Al catalyst showed the best catalytic performance on methyl acrylate hydrogenation, and the yield of methyl propionate can be increased from 53.7% to 89.5% at 100 °C and 1 MP H2, compared with the Ni10Mo10/γ–Al2O3 catalyst prepared by a traditional impregnation method. The stability of the Ni10Mo10Al catalyst was also investigated, and the catalyst can run stably for 23 h. The novel strategy adopted in this article provides a new direction for the preparation of high activity Ni–Mo catalysts.

Catalytic Hydrotreating of Crude Pongamia pinnata Oil to Bio-Hydrogenated Diesel over Sulfided NiMo Catalyst

This work studied the catalytic activity and stability of Ni-MoS2 supported on γ-Al2O3, SiO2, and TiO2 toward deoxygenation of different feedstocks, i.e., crude Pongamia pinnata oil (PPO) and refined palm olein (RPO). PPO was used as a renewable feedstock for bio-hydrogenated diesel production via catalytic hydrotreating under a temperature of 330 °C, H2 pressure of 50 bar, WHSV of 1.5 h−1, and H2/oil (v/v) of 1000 cm3/cm3 under continuous operation. The oil yield from a Soxhlet extraction of PPO was up to 26 wt.% on a dry basis, mainly consisting of C18 fatty acids. The catalytic activity in terms of conversion and diesel yield was in the same trend as increasing in the order of NiMo/γ-Al2O3 > NiMo/TiO2 > NiMo/SiO2. The hydrodeoxygenation (HDO) activity was more favorable over the sulfided NiMo supported on γ-Al2O3 and TiO2, while a high DCO was observed over the sulfided NiMo/SiO2 catalyst, which related to the properties of the support material and the intensity of metal–support interaction. The deactivation of NiMo/SiO2 and NiMo/TiO2 occurred in a short period, due to the phosphorus and alkali impurities in PPO which were not found in the case of RPO. NiMo/γ-Al2O3 exhibited the high resistance of impure feedstock with excellent stability. This indicates that the catalytic performance is influenced by the purity of the feedstock as well as the characteristics of the catalysts.

Phosphomolybdic acid encapsulated in ZIF-8-based porous ionic liquids for reactive extraction desulfurization of fuels

Phosphomolybdic acid was encapsulated within a ZIF-8-based porous ionic liquid (HPMo@ZIF-8-PIL) for ultradeep reactive extraction desulfurization.