查看更多>>摘要：? 2022 Elsevier B.V.Borosilicate zeolite ERB-1 with MWW topological structure was post-processed to prepare deboroned D-ERB-1, pillared layer MCM-36 and delaminated layer structure ITQ-2. Titanium was introduced into MWW structure by atom-planting method. Cr species were loaded by the impregnation for comparison with the one-pot synthesized Cr-MCM-41 and Cr/TS-1. The results show that Cr(Ⅵ) is the active site for oxidative dehydrogenation of ethane with CO2. As the number of hydroxyl groups on the zeolite increases, the content of CrOx and Cr(VI) loaded also increases. The hydroxyl-anchored Cr(VI) on MWW zeolite is easier to be regenerated. The addition of titanium can enhance the dispersion of Cr on the hydrophilic surface of the MWW zeolite and improve the stability of the catalyst. The presence of surface hydroxyl groups is critical to the activity of CrOx-based catalysts. The CO2 can not only promote the reverse water gas shift reaction but also Bouduoard reaction.
查看更多>>摘要：? 2022 Elsevier B.V.CuZn/SiO2 lamellar catalysts are obtained through the introduction of zinc oxide with different amount to Cu/SiO2 prepared by the ammonia-evaporation method and investigated for the dehydrogenation of methanol to methyl formate. The 20CuZn/SiO2 catalyst showed the best catalytic activity with a methanol conversion of 44.5% and a selectivity to methyl formate of ~92.7% at 300 °C and 0.2 MPa. The reason for this excellent activity could be ascribed to the strong interaction between Cu and ZnO, which promoted the decomposition of the copper phyllosilicate precursor to release copper oxide and thereby achieved more active Cu0 species upon reduction on the catalyst surface. In addition, the agglomeration of Cu species was mainly responsible for the slight decline in the methanol conversion in ZnO modified Cu based catalysts for the methanol dehydrogenation reaction.
查看更多>>摘要：? 2022 Elsevier B.V.As the two main components in typical three-way catalysts, Pd-Al2O3 and Pd-Ce0.5Zr0.5O2 usually show different Pd-support interaction strength. Thus, Pd could re-distribute between Al2O3 and Ce0.5Zr0.5O2 upon heating. Here the strategy to mix Pd/La-Al2O3 and Pd/Ce0.5Zr0.5O2 (before or after calcination, or after aging) was researched. The optimal choice was “mixing-calcination-aging”, offering the highest oxygen storage capacity, Pd dispersion and catalytic activity for CO and C3H6 elimination during the three-way catalytic reaction. Thus, the “mixing-calcination-aging” strategy holds promise in industrial applications, as demonstrated at the monolith converter level. The transient drop in conversion with increasing temperature (“kink”) appeared simultaneously for CO, NO and C3H6 over the “mixing-calcination-aging” monolith, but did not over the calcined counterpart “mixing-calcination”. The kinks disappeared for the used “mixing-calcination-aging”, but could be restored upon re-oxidizing. By virtue of the in situ Raman characterization, the reduction of PdO under the reaction conditions was found to cause the kinks.
查看更多>>摘要：? 2022 Elsevier B.V.A series of NiSO4-ReOx/Al2O3 catalysts were synthesized by a co-impregnation method, tested in the conversion of ethylene to propylene at mild conditions, and thoroughly characterized by different spectroscopy techniques. In particular, the attention was focused on the NiSO4 function, which is directly involved in ethylene conversion to 2-butylene, but also drives the catalyst deactivation. Results shows that the sulfate anions increase the surface acidity of alumina, and simultaneously influence the electronic properties of the Ni sites. Indeed, thermal activation of the catalyst promotes the formation of covalent bonds between the sulfate anions and the Ni2+ or Al3+ cations, while keeping constant the + 2 oxidation state of the Ni sites. Studying the initial steps of the ETP reaction reveals the primary acid-catalyzed formation of branched oligomers. Catalyst deactivation could be due to formation and adsorption of long-chain oligomers, or less interaction of sulfate anions with Ni ions.
查看更多>>摘要：? 2022 Elsevier B.V.Catalytic combustion is one of the most effective soot elimination technologies, whereby the development of catalyst with high performance and stability becomes the emphasis. Herein, we elaborately fabricated an innovative catalyst of K-Cu decorated 3DOM La0.8Sr0.2MnO3 perovskite called 5KxCLSM for soot combustion, in which Cu species were introduced via redox precipitation method and K species were loaded by impregnation method. The dispersion and interaction between CuO and perovskite were enhanced by this redox precipitation method. CuO could facilitate the phase transition to form K2?xMn8O16, thereby, the free K species were stabilized. However, excessive CuO would cover the active sites and even destroy 3DOM structure. Among all as-prepared catalysts, 5K2CLSM exhibited the best activity with T50 of 357 ℃ and TOF of 2.97 × 10?3 s?1 (320 ℃) and possessed admirable water-resistance and hydrothermal stability. This work rationalizes an approach to develop an active and stable catalyst for soot combustion or other systems.
查看更多>>摘要：? 2022 Elsevier B.V.The cuprous oxide/copper/titanium tin solid solution(Cu2O/Cu/T60S1) composite photocatalyst was synthesized by first preparing Sn-doped titanium dioxide by sol-hydrothermal method, and then depositing Cu2O and Cu on its surface by photochemical reduction method. The crystal structure and properties of the synthesized photocatalysts were investigated by various characterization techniques. The activity of the photocatalyst was evaluated by degrading the mixed pesticides (Pirimicarb and Fenitrothion) and tetracycline hydrochloride(TC-HCl) under simulated natural light. The results showed that Cu2O and Cu were successfully deposited on the surface of T60S1, the introduction of Cu2O and Cu significantly improved the photocatalytic activity of T60S1 in the degradation of TC-HCl and organic pesticides under visible light. The degradation rate of TC-HCl of sample 3Cu2O/Cu/T60S1 was as high as 98.2% within 60 min, the degradation rate of mixed pesticides reached more than 95% within 180 min. Combined with density functional theory(DFT) calculations, discussed the photocatalytic degradation mechanism of 3Cu2O/Cu/T60S1.
查看更多>>摘要：? 2022 Elsevier B.V.Herein, K+ was added in the synthesis gel to regulate the distribution of acid sites in the ITQ-13 zeolite and enhance its catalytic performance in the conversion of methanol to olefins (MTO). The results indicate that a proper content of K+ ions in the synthesis gel can not only expedite the crystallization of ITQ-13 zeolite, but also significantly decrease the proportion of paired Al and distribute more Al atoms in the 10-ring sinusoidal channel out from the intersection cavity. Accordingly, over the H-ITQ-13(0.3 K) zeolite prepared using the synthesis gel with a KCl/Al2O3 molar ratio of 0.3, the alkene cycle of MTO keeping to the dual cycle hydrocarbon pool (HCP) mechanism is preferably enhanced, whereas the hydride transfer and aromatization reactions are substantially suppressed. As a result, H-ITQ-13(0.3 K) exhibits much longer catalytic lifetime and higher selectivity to propene and butene, in comparison with the H-ITQ-13 counterpart obtained without adding K+.
查看更多>>摘要：? 2022 Elsevier B.V.Currently, NOx emission control by the selective catalytic reduction of NOx with NH3 (NH3?SCR) technology for the cement industry has become urgent in China. The poisoning effect of Ca species from cement flue gas on V2O5/TiO2(V/Ti) catalysts still faces severe challenges. For the first time, CuO was investigated for the possibility of Ca resistance enhancement on V/Ti catalysts. The activity tests show that the Ca?CuV/Ti catalyst maintains a good performance with an NO conversion above 80% between 260 ? 330 °C, while the highest NO conversion of Ca?V/Ti in the test temperature range is only 52.4%. According to the characterization results, CaO is easier to adsorb on CuO than V2O5, thus retaining the V active sites. Due to the cycles of 2Cu2+ + V3+ ? 2Cu+ + V5+, CuO modification can significantly improve the redox ability of the V/Ti catalyst. In situ DRIFTS results show that the effect of CaO poisoning on the adsorption rate and reactivity of NHx over Ca?CuV/Ti is less than that of Ca?V/Ti. CaO even promotes the formation of the active nitrate species over CuV/Ti, which is the main reason for its strong Ca resistance. This study provides theoretical support for the industrial application of anti?Ca poisoning SCR catalysts.
查看更多>>摘要：? 2022 Elsevier B.V.The CrOx-based catalysts supported on Zn-modified alumina were prepared for propane dehydrogenation. The CrOx/Zn-Al2O3 catalysts possess uniform foamed pores with high specific surface area and large pore size. The zinc enriched on the surface of alumina changes the surface energy and acid sites, which decreases interaction between chromium and support so that increases the particle size of crystal Cr2O3 and changes the distribution of Cr species. The dispersion of Cr6+ species on the Zn-modified alumina is improved, and the zinc promotes the formation of more active oligomeric and polymeric chromate on the surface and highly dispersive non-redox Cr3+ species in pore channel simultaneously, which chromium species exhibit high propane conversion and propylene yield. The zinc modifier obviously inhibits the formation of coke deposition to increase catalyst stability.
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