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This study is one of the few to develop a strategy that inhibits coke deposition by loading Cr on zeolite defects. We revealed that Cr6+ species, which interacted with hydroxyl groups in the zeolite framework inhibited coke deposition.

Extensive effort has been focused on the advancement of an efficient catalyst for CO2 reforming of CH4 to achieve optimum catalytic activity together with cost-effectiveness and high resistance to catalyst deactivation. In this study, for the first time, a new catalytic support/catalyst system of bifunctional NiO/dolomite has been synthesized by a wet impregnation method using low-cost materials, and it shows unique performance in terms of amphoteric sites and self-reduction properties. The catalysts were loaded into a continuous micro-reactor equipped with an online GC-TCD system. The reaction was carried out with a gas mixture consisting of CH4 and CO2 in the ratio of 1 : 1 flowing 30 ml min−1 at 800 °C for 10 h. The physicochemical properties of the synthesized catalysts were determined by various methods including X-ray diffraction (XRD), N2 adsorption–desorption, H2 temperature-programmed reduction (H2-TPR), temperature-programmed desorption of CO2 (TPD-CO2), and temperature-programmed desorption of NH3 (TPD-NH3). The highest catalytic performance of the DRM reaction was shown by the 10% NiO/dolomite catalyst (CH4 & CO2 conversion, χCH4; χCO2 ∼ 98% and H2 selectivity, SH2 = 75%; H2/CO ∼ 1 : 1 respectively). Bifunctional properties of amphoteric sites on the catalyst and self-reduction behaviour of the NiO/dolomite catalyst improved dry reforming of the CH4 process by enhancing CH4 and CO2 conversion without involving a catalyst reduction step, and the catalyst was constantly active for more than 10 h.

Propane dehydrogenation (PDH) is one of the most promising candidates for the propylene production process to meet the growing demand of propylene for the future. There is an urgent need to develop catalysts for PDH. In this work, we have synthesized high silica Ga-Beta as a new candidate for a catalyst from dealuminated zeolite using the dry gel conversion method. A high silica Ga-Beta catalyst with a Si/Ga ratio of up to 177 can be synthesized. In the PDH reaction, the synthesized Ga-Beta showed the highest propane conversion and the highest propylene yield amongst the Ga-based zeolites. The combination of the Ga species being incorporated into zeolite frameworks, its large microporosity and Bronsted acidity is likely to lead to the excellent catalytic performance of Ga-Beta. Moreover, Ga-Beta with a higher Si/Ga ratio shows a longer catalyst lifetime for the PDH reaction, since the coke deposition rate decreased with the decrease in the amount of acid. This work provides new insights for the PDH reaction over Ga-based zeolite catalysts, and contributes to the progress in the activation and transformation of light alkenes to value-added chemicals.

We have synthesized MFI type ferrisilicate zeolite (Fe-MFI) nanocrystals with a crystal size smaller than 100 nm by a dry gel conversion (DGC) method using a sole template (tetrapropylammonium hydroxide). The crystal size of Fe-MFI synthesized by the DGC method was much smaller than that of Fe-MFI synthesized by a conventional hydrothermal synthesis (HTS) method despite using the same precursor solution. The catalytic performance of the nano-sized Fe-MFI in methanol to olefin (MTO) reactions was investigated. The Fe-MFI catalysts showed higher propylene to ethylene (P/E) ratios and lower light paraffin yields compared with MFI type aluminosilicate zeolites (Al-MFI) for both the synthesis methods. In addition, nano-sized Fe-MFI showed a higher P/E ratio (ca. 30) and a longer catalyst lifetime than macro-sized Fe-MFI synthesized by the HTS method.

Zeolites have been widely applied as sophisticated solid acid catalysts in chemical industries. Tuning the acidic properties of zeolites is very important to improve their catalytic performances and expand their utilization. Herein, we synthesized AEI-type Ge-incorporated aluminophosphate, GeAPO-18, by a dry gel conversion method in order to generate new acidity. GeAPO-18 had weaker Bronsted acid sites than the conventional SAPO-18. To confirm the effect of the substitution of Ge, we carried out the methanol to olefin (MTO) reaction over GeAPO-18 and the conventional SAPO-18. The catalyst lifetime of GeAPO-18 in the MTO reaction was longer than that over the conventional SAPO-18. The rate of coke deposition on GeAPO-18 was slower than that on the conventional SAPO-18. These results indicated that the decreased acid strength of GeAPO-18 could retard the coke formation via undesired successive reactions. The incorporation of Ge into the aluminophosphate zeolite framework was a crucial method for tuning the acid strength, which provides a new direction for the design of solid acid catalysts.

A highly oriented UiO-66 film, with a monocrystalline layer, was successfully prepared by the solvothermal method. Acetic acid, which served as a modulator, was essential to achieve high film orientation. Water played an important role in promoting the intergrowth of UiO-66 crystals.

Pure silica CHA type zeolite (Si-CHA) was used in a high pressure swing adsorption for CO2 separation in the presence of water. The effective CO2 adsorption capacity was much higher than that of zeolite 13X, and was not influenced by coexisting water. The breakthrough curve gave an effective CO2 adsorption capacity of 3.1 mol kg−1 and CO2–N2 selectivity of >31.