Hydrogenation of diesters on copper catalyst anchored on ordered hierarchical porous silica: Pore size effect

Polyoxometalate-HKUST-1 composite derived nanostructured Na-Cu-Mo2C catalyst for efficient reverse water gas shift reaction

Transforming CO2 to CO via reverse water-gas shift (RWGS) reaction is widely regarded as a promising technique for improving the efficiency and economics of CO2 utilization processes. Moreover, it is also considered as a pathway towards e-fuels. Cu-oxide catalysts are widely explored for low-temperature RWGS reactions; nevertheless, they tend to deactivate significantly under applied reaction conditions due to the agglomeration of copper particles at elevated temperatures. Herein, we have synthesized homogeneously distributed Cu metallic nanoparticles supported on Mo2C for the RWGS reaction by a unique approach of in situ carburization of metal-organic frameworks (MOFs) using a Cu-based MOF i.e. HKUST-1 encapsulating molybdenum-based polyoxometalates. The newly derived Na-Cu-Mo2C nanocomposite catalyst system exhibits excellent catalytic performance with a CO production rate of 3230.0 mmol gcat-1 h-1 with 100% CO selectivity. Even after 250 h of a stability test, the catalyst remained active with more than 80% of its initial activity.

Cu+-Doped PVA-Derived Mesoporous Carbon@Diatomite Adsorbent for Selective Adsorption Desulfurization

Herein, we successfully constructed a Cu+-doped PVA-derived mesoporous carbon@diatomite (DE) composite by virtue of N2-suffered carbonization and self-reduction at a high temperature. The structure and composition of C/Cu@DE composite adsorbents were determined by a series of characterizations. The results affirmed that Cu+ species are highly scattered in PVA-derived mesoporous carbon, which covered the DE surface. The effect of carbonization temperature on the structure and composition of the C/Cu@DE composite adsorbents were intensively investigated, indicating that the C/Cu@DE composite at an 800 °C carbonization temperature (C/Cu@DE-800 °C) showed the formation of many Cu+ species and preferable hierarchical pore properties. The adsorption experiments of benzothiophene (BT) indicated that C/Cu@DE-800 °C possessed a better adsorption capacity. The adsorption behavior of BT onto C/Cu@DE-800 °C was investigated by a variety of adsorption times, initial concentrations, and recycle times, of which the largest adsorption capacity for BT attained 34.2 mg/g. Furthermore, the adsorption kinetics, intraparticle diffusion, adsorption isotherms, and adsorption thermodynamics of BT onto C/Cu@DE-800 °C was deeply studied, which contributed to the proposed adsorption mechanism.

Highly Enhanced Catalytic Stability of Copper by the Synergistic Effect of Porous Hierarchy and Alloying for Selective Hydrogenation Reaction

Supported copper has a great potential for replacing the commercial palladium-based catalysts in the field of selective alkynes/alkadienes hydrogenation due to its excellent alkene selectivity and relatively high activity. However, fatally, it has a low catalytic stability owing to the rapid oligomerization of alkenes on the copper surface. In this study, 2.5 wt% Cu catalysts with various Cu:Zn ratios and supported on hierarchically porous alumina (HA) were designed and synthesized by deposition–precipitation with urea. Macropores (with diameters of 1 μm) and mesopores (with diameters of 3.5 nm) were introduced by the hydrolysis of metal alkoxides. After in situ activation at 350 °C, the catalytic stability of Cu was highly enhanced, with a limited effect on the catalytic activity and alkene selectivity. The time needed for losing 10% butadiene conversion for Cu1Zn3/HA was ~40 h, which is 20 times higher than that found for Cu/HA (~2 h), and 160 times higher than that found for Cu/bulky alumina (0.25 h). It was found that this type of enhancement in catalytic stability was mainly due to the rapid mass transportation in hierarchically porous structure (i.e., four times higher than that in bulky commercial alumina) and the well-dispersed copper active site modified by Zn, with identification by STEM–HAADF coupled with EDX. This study offers a universal way to optimize the catalytic stability of selective hydrogenation reactions.

Ti3+ Tuning the Ratio of Cu+ /Cu0 in the Ultrafine Cu Nanoparticles for Boosting the Hydrogenation Reaction

Hydrogenation of diesters to diols is a vital process for chemical industry. The inexpensive Cu⁺ /Cu⁰ -based catalysts are highly active for the hydrogenation of esters, however, how to efficiently tune the ratio of Cu⁺ /Cu⁰ and stabilize the Cu⁺ is a great challenge. In this work, it is demonstrated that doped Ti ions can tune the ratio of Cu⁺ /Cu⁰ and stabilize the Cu⁺ by the TiOCu bonds in Ti-doped SiO₂ supported Cu nanoparticle (Cu/Ti-SiO₂ ) catalysts for the high conversion of dimethyl adipate to 1,6-hexanediol. In the synthesis of the catalysts, the Ti⁴⁺ OCu²⁺ bonds promote the reduction of Cu²⁺ to Cu⁺ by forming Ti³⁺ O_V Cu⁺ (O_V : oxygen vacancy) bonds and the amount of Ti doping can tune the ratio of Cu⁺ /Cu⁰ . In the catalytic reaction, the O vacancy activates CO in the ester by forming new Ti^{3+ δ} O_R Cu^{1+ δ} bonds (O_R : reactant oxygen), and Cu⁰ activates hydrogen. After the products are desorbed, the Ti^{3+ δ} O_R Cu^{1+ δ} bonds return to the initial state of Ti³⁺ O_V Cu⁺ bonds. The reversible TiOCu bonds greatly improve the activity and stability of the Cu/Ti-SiO₂ catalysts. When the content of Ti is controlled at 0.4 wt%, the conversion and selectivity can reach 100% and 98.8%, respectively, and remain stable for 260 h without performance degradation.

Effects of calcination temperature on physicochemical property and activity of CuSO4/TiO2 ammonia-selective catalytic reduction catalysts

CuSO₄/TiO₂ catalysts with high catalytic activity and excellent resistant to SO₂ and H₂O, were thought to be promising catalysts used in Selective catalytic reduction of nitrogen oxides by NH₃. The performance of catalysts is largely affected by calcination temperature. Here, effects of calcination temperature on physicochemical property and catalytic activity of CuSO₄/TiO₂ catalysts were investigated in depth. Catalyst samples calcined at different temperatures were prepared first and then physicochemical properties of the catalyst were characterized by N₂ adsorption-desorption, X-ray diffraction, thermogravimetric analysis, Raman spectra, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption of NH₃, temperature-programmed reduction of H₂ and in situ diffuse reflectance infrared Fourier transform spectroscopy. Results revealed that high calcination temperature had three main effects on the catalyst. First, sintering and anatase transform into rutile with increase of calcination temperature, causing a decrement of specific surface area. Second, decomposition of CuSO₄ under higher calcination temperature, resulting in disappears of Brønsted acid sites (S-OH), which had an adverse effect on surface acidity. Third, CuO from the decomposition of CuSO₄ changed surface reducibility of the catalyst and favored the process of NH₃ oxidation to nitrogen oxides (NO_x). Thus, catalytic activity of the catalyst calcined under high temperatures (≥600°C) decreased largely.

Highly dispersed Pt catalyst supported on nanoporous carbon derived from waste PET bottles for reductive alkylation

Nanoporous carbon (NPC) derived from waste polyethyleneterephthalate (PET) bottles was prepared by a MgO-templated method and employed as a support for a highly dispersed platinum catalyst. The NPCs and Pt/NPCs catalysts were characterized by BET, SEM, TEM, XRD and ICP-OES. The catalytic performance of the NPC supported Pt catalysts for reductive alkylation of p-aminodiphenylamine (p-ADPA) with methyl isoamyl ketone (MIAK) was investigated. The textural properties of the NPC prepared could be tailored by changing the size of the MgO-template and the MgO/waste PET powder mass ratio. When the pore size was below 14 nm, the catalytic performance of the Pt/NPCs for the reductive alkylation could be improved with increasing the pore size of the NPCs. Profiting from the higher mechanical strength and the ideal pore structure, Pt/O@NPC50(1/1)–PTA had excellent reusability, which could maintain 98% conversion of p-ADPA after reused 10 times.

Nanoporous carbon (NPC) derived from waste polyethyleneterephthalate (PET) bottles was prepared by a MgO-templated method and employed as a support for a highly dispersed platinum catalyst.

Activated carbon aerogel supported copper catalysts for the hydrogenation of methyl acetate to ethanol: effect of KOH activation

Methyl acetate (MA) hydrogenation is crucial for indirect ethanol synthesis through syngas (CO + H₂).

Effects of pore structure of MgO-templated mesoporous carbon on its supported Pt catalysts for reductive alkylation of p-aminodiphenylamine with methyl isobutyl ketone

Mesoporous carbon (MC) was prepared by the nano-MgO template method and used as a support for the preparation of a Pt-based reductive alkylation catalyst.

Bio-MCM-41: a high-performance catalyst support derived from pyrolytic biochar

Bio-MCM-41 was produced from pyrolytic rice husk char in a sequential stepwise method and then used to prepare Cu/Bio-MCM-41 catalyst with good performance.