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Cu-based catalysts, modified by gallium addition via the stepwise co-precipitation method, were studied for the liquid phase hydrogenation of hydroxypivalaldehyde (HPA) to neopentyl glycol (NPG). Through physico-chemical techniques, the effects of gallium introduction on the Cu trimetallic catalyst performance and the reaction mechanism of HPA hydrogenation were discussed. The characterization results showed that gallium introduction can influence the dispersion, reduction, and distribution of active Cu species, as well as their reactivity. Herein, the catalyst with 2 wt% gallium addition exhibited excellent catalytic performance with HPA conversion rate and NPG selectivity of 93.5% and 95.5%, at a reaction pressure of 3 MPa, temperature of 110 °C, hydrogen-aldehyde ratio (molar ratio) 10:1, and liquid space-time at a speed of 8.4 h−1. The good performance could be attributed to gallium doping tending to dynamically tune the interaction between the components, increasing Cu dispersion and the distributions of Cu+ and Cu0 species on the catalyst surfaces. [ABSTRACT FROM AUTHOR]

The microstructure changes of unsupported hydrodesulfurization (HDS) catalysts could significantly influence their properties, including the morphology, the dispersity of active components, and HDS activity. In this work, three-dimensionally ordered macroporous (3DOM) NiMo unsupported catalysts were fabricated using the polymethyl methacrylate (PMMA) colloidal crystal template with the assistance of citric acid in 95% ethanol solution. The TG/DTG, XRD, SEM, HRTEM, low-temperature N 2 adsorption-desorption, and H 2 -TPR techniques were employed to intensively characterize the obtained unsupported catalysts. The characterization results indicated that all catalysts possessed a well-defined 3DOM structure, which could not only provide abundant active sites and high specific surface area but also enhance the contact efficiency between the active sites and reactants. Furthermore, among the prepared 3DOM unsupported catalysts, the 3DOM NiMo-1 exhibited an excellent thiophene conversion rate of 99.4% under the reaction conditions of 360 °C and 1.0 MPa. This research provided an evolution direction for designing the high-efficient unsupported HDS catalysts. [Display omitted] • 3DOM NiMo unsupported catalysts were successfully fabricated by employing the PMMA as hard template. • The 3DOM unsupported catalysts possessed high surface area and structure stability. • The prepared NiMo catalysts exhibited excellent catalytic performance of thiophene hydrodesulfurization. [ABSTRACT FROM AUTHOR]

In this work, Zn-modified SSZ-13 catalysts with different spatial distributions of zinc species were prepared by ion exchange (IE), wet impregnation (WI) and in situ synthesis (IS) methods employed for the methanol-to-olefin (MTO) reaction. The reaction results indicate that the initial selectivity towards light olefins significantly enhances from 33% over H-SSZ-13 to 43–70% over Zn-modified catalysts. As for Zn-modified Zn-SSZ-13-IE catalysts, the effect of the zinc content was also investigated and the optimum catalytic performance is obtained over the Zn(1.31)-SSZ-13-IE catalyst with initial and maximum olefin selectivities of 82% and 88% and initial and maximum selectivity ratios of ethylene-to-propylene of 2.21 and 2.14. [ABSTRACT FROM AUTHOR]

The preparation of the supported catalysts with the treatment of various chelating agents would significantly influence their physicochemical properties and corresponding catalytic performance. In the present work, three different methods such as the incipient wetness impregnation method, wet mixing method, and the one‐pot method were employed to prepare the CoMo/Al2O3‐TiO2 hydrodesulfurization (HDS) catalysts. After the comprehensive consideration of the characterization and catalytic performance results, the catalyst prepared by the one‐pot method (OP) was further post‐treated by citric acid (CA) with different concentrations. The thiophene conversion over the CA post‐treated catalysts was significantly improved in comparison with that of the parent catalyst, especially for the OP‐C1.5 catalyst (molar ratio of CA/Mo=1.5) with the thiophene conversion higher than 97.2 %. The CA with the appropriate addition amount in the post‐treatment solution can weaken the MoO3‐Al2O3 interaction for promoting the re‐dispersion of Mo species, which is responsible for the enhanced HDS performance over the CA post‐treated catalysts. [ABSTRACT FROM AUTHOR]

The catalytic dehydrogenation of propane to propene is an alternative technique to supplement the traditional steam cracking and catalytic cracking process for satisfying the continuously increasing demand for propylene downstream products. In this study, the parent PtSn/γ-Al2O3 catalyst was fabricated via the one-step method for the subsequent La post-modification to prepare the catalysts for propane dehydrogenation. The prepared and spent catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscope (SEM), NH3 temperature-programmed desorption (NH3-TPD), H2 temperature-programmed desorption (H2-TPR), and thermogravimetric (TG) analysis. The catalytic performance and characterization results demonstrated that the addition of La into the parent catalyst could significantly improve the catalytic performance of the prepared catalyst. Especially, the PtSn-La2.2 catalyst with the 2.2 wt.% La addition exhibited the stable and highest propylene selectivity (>84%) under the investigation time of 800 min. The introduced La exhibits the ability to adjust the textural properties of the obtained catalysts, curb the acidity of support, promote the reduction of Pt species, and reduce the carbon accumulation on the prepared catalysts. [ABSTRACT FROM AUTHOR]

The dehydrogenation of low-carbon alkane to obtain olefins is an effective way to meet the steadily increasing demand of these building blocks in chemical industry. In this study, Ca-doped CrOx/γ-Al2O3 catalysts were fabricated via a one-pot method by employing Cr(OH)3 as the precursor, and their catalytic performances were tested in the dehydrogenation of isobutane to isobutene (DITI) process. The prepared catalysts were intensively characterized by XRD, SEM, NH3-TPD, H2-TPR, low-temperature N2 adsorption–desorption, etc. These characterization results indicated that the doping of Ca into the CrOx/γ-Al2O3 catalysts could tune the acidity properties of the prepared catalysts and enhance the interaction between the active species and support. The Ca-doped CrOx/γ-Al2O3 catalysts, especially the Ca2-Cr/γ-Al2O3 catalyst with a Ca doping of 2 wt%, exhibited a superior catalytic performance in the DITI process in comparison with the undoped catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • CoMo supported catalysts were successfully fabricated by using the melamine foam as support. • The supported HDS catalysts possessed three-dimensional macropores and high structure stability. • The prepared CoMo catalysts exhibited excellent catalytic performance of thiophene hydrodesulfurization. The performance of the hydrodesulfurization (HDS) catalysts is generally subjected to the characteristics of supports. In this work, the melamine foam (MF) was employed as the support for fabricating a series of three-dimensional porous (3DP) Co x Mo/MF supported HDS catalysts. The properties of the obtained HDS catalysts were characterized by XRD, TG, SEM, TEM, and low-temperature N 2 adsorption–desorption techniques. The characterization results demonstrated that the Co x Mo/MF supported catalysts possessed the 3DP structure, in which the metal oxides were attached to the prismatic pillars of the MF framework. The activity test results illustrated that the thiophene conversion over the Co 2.0 Mo/MF catalyst could reach 96.96% under 1 MPa and 360 °C. The unique 3DP structure with rich meso -/macropores, low average length and average stacking of crystalline MoS 2 promoted the HDS activity of the Co 2.0 Mo/MF catalyst. This research shows the potential application of MF support in the field of catalysis and provides the possible direction for the further development of the supported HDS catalysts. [ABSTRACT FROM AUTHOR]

With the increasingly prominent concerns on the environmental pollution from vehicles, the sulfur content in fuels must be limited to < 10 ppm around the world. The hydrodesulfurization (HDS) technology still is the dominant hydrorefining process of fuels. Traditional supported HDS catalysts usually refer to the Co(Ni)Mo/Al 2 O 3 with the shortages of low loading of active metals and strong metal-support interaction. Thus, the unsupported (or bulk) HDS catalysts without support have received increasing attention both from academia and industry in recent years. This review provides the research progress of unsupported catalysts for the HDS of fuel. Firstly, the overview of the HDS process was introduced, followed by the developments of template-free methods and template methods for preparing unsupported HDS catalysts. Finally, some crucial issues and the perspective of future development of unsupported HDS catalysts were summarized to achieve the goal of the production of ultra-low sulfur fuels. [Display omitted] • The theory of the HDS process and the composition of unsupported catalysts were introduced. • The template-free and template methods for preparing unsupported HDS catalysts were summarized. • The analysis of structure-activity relationship over unsupported HDS catalysts was conducted. [ABSTRACT FROM AUTHOR]

Two routes for the direct synthesis of light olefins from syngas. [Display omitted] • Recent advances on the direct synthesis of light olefins from syngas was reviewed. • Co 2 C nanoprisms showed superior C 2 =-C 4 = selectivity at mild reaction conditions. • A landmark breakthrough was achieved by designing a novel OX-ZEO catalyst concept. • The core-shell structured catalyst enhanced the C 2 =-C 4 = yield by inhibiting the WGS. The direct synthesis of light olefins (C 2 H 4 , C 3 H 6 and C 4 H 8) from syngas (a mixture of H 2 and CO) could supply the extra resources of these platform building blocks for the subsequent production of various chemicals, which has attracted wide interest in recent years. The Fischer-Tropsch synthesis (FTS) has become a classic process for the syngas transformation since 1925. However, the products selectivity, especially for the light olefins, still remains a great challenge owing to the limitation of the Anderson-Schulz-Flory (ASF) distribution. The present review highlights the recent advances on the state-of-the-art catalyst development (from 2016 to 2021) for the direct conversion of syngas to light olefins with the selectivity far more than the theoretical limit of ASF model, including the Co 2 C quadrangular nanoprisms, metal oxides and zeolite (OX-ZEO) bifunctional catalysts. The active components and catalytic performances of those high-efficient catalysts, in particular the selectivity of light olefins, were compared and discussed in detail. Moreover, the established relationships between catalytic performance and active sites provided insights for designing catalysts with superior selectivity of desired light olefins. Finally, a comprehensive conclusion on the advantages and disadvantages of each catalyst system and perspectives for further optimization of the catalyst compositions and structure were discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cu–La2O3–ZrO2/γ-Al2O3 hybrid catalysts were prepared by four different methods. [•] Smaller particle size and highly dispersed Cu species are favorable for STD process. [•] The acidic site with medium strength is active phase for methanol dehydration. [•] The catalyst prepared by mixing both fresh precursors showed better STD performance. [ABSTRACT FROM AUTHOR]

An efficient approach for the rapid synthesis of nanosized SSZ-13 zeolite with hierarchical structure was rationally developed by the combination of additive and seed induced crystallization. Compared with the conventional hydrothermal synthesis, the addition of additive and seed during the synthesis of SSZ-13 could significantly shorten the crystallization time from 144 h to 6 h. The obtained nanosized SSZ-13 with average crystal size of ca. 400 nm possessed abundant mesopores within the crystals. The crystal size could also be regulated in the range of 400–6000 nm by adjusting the crystallization time and the type and amount of the additives. UV–Vis results showed that the strong chelation ability of citric acid to Al ions as well as the formation of new metastable phase accelerated the crystallization rate in the synthesis of SSZ-13. The fast-synthesized hierarchical nanosized SSZ-13 exhibited prolonged catalytic lifetime and improved selectivity to light olefins in comparison with the conventional SSZ-13 catalyst in the MTO reaction. This work not only provides a simple and facile approach for the rapid synthesis of hierarchical nanosized aluminosilicate zeolite, but also might help to develop the fast synthesis methods for other aluminosilicate zeolites. [Display omitted] • Rapid synthesis of hierarchical nanosized SSZ-13 with the addition of additive and seed. • SSZ-13 crystal size could be regulated in the range of 400–6000 nm. • Hierarchical nanosized SSZ-13 exhibited superior MTO catalytic performance. [ABSTRACT FROM AUTHOR]

The microstructure tuning of bulk catalysts would significantly influence their physical/chemical properties for the subsequent applications. In this work, the three-dimensionally ordered macroporous (3DOM) bulk catalysts (CoMo, CoMoW and CoW) were successfully fabricated by employing the poly-(methyl methacrylate) (PMMA) as hard template. The prepared bulk catalysts were characterized by means of techniques, such as TG/DTG, XRD, low-temperature N 2 adsorption-desorption, SEM, etc. The characterization and catalytic performance evaluation results indicated that the unique hierarchical pore system of the 3DOM bulk catalysts could not only supply more available surface area, thus more active sites, but also facilitate the diffusion of the reactants/products to/from the active sites of the bulk catalyst. Moreover, the 3DOM structure of the bulk catalysts was retained after the pre-sulfurization process and hydrodesulfurization reaction, illustrating the relatively high stability of prepared bulk catalysts in the experimental investigation. The 3DOM CoMo bulk catalyst exhibited superior catalytic performance with thiophene conversion of 99.2% at 360 °C in comparison with the CoW and CoMoW bulk catalysts. • 3DOM bulk catalysts were successfully fabricated by employing the PMMA as hard template. • The unique pore system could supply available active sites and facilitate the diffusion process. • The prepared 3DOM bulk catalysts exhibited relatively high surface area and structure stability. • The preparation process and structure-activity correlation of catalysts were investigated. [ABSTRACT FROM AUTHOR]