Zhongkui Zhao

Nitrogen-doped nanotubes-decorated activated carbon-based hybrid nanoarchitecture as a superior catalyst for direct dehydrogenation

A novel N-doped activated carbon (AC) based nanostructure decorated with nanotubes (N-CNT-AC) has been successfully fabricated through a facile and scalable approach involving the mechanical milling and subsequent solid pyrolysis of the low-cost and commercially available AC and melamine. Various characterization techniques including high resolution transmission electron microscopy, X-ray diffraction, nitrogen adsorption, X-ray photoelectron spectroscopy, Raman spectroscopy and Fourier transform infrared spectroscopy were employed to reveal the relationship between catalyst features and catalytic performance in the oxidant- and steam-free direct dehydrogenation (DDH) of ethylbenzene to styrene. Although the as-synthesized AC-based hybrid nanostructure has a much lower surface area (397.0 cm2 g−1) and pore volume (0.17 cm3 g−1) than the parent AC (777.1 cm2 g−1 surface area and 0.4 cm3 g−1 pore volume), it demonstrates 1.74 and 3.67 times the steady-state styrene rate of the per gram parent AC and the industrially-used K–Fe catalyst, respectively, for the DDH reaction, which is ascribed to the promoting effect of the unique hybrid microstructure, the surface rich CO group and defect/edge feature, the increased basic properties through N-introduction into the hybrid nanostructure, the small size of the graphitic crystallite, as well as the inherent high surface and large porosity of the AC-based materials. The in situ Fourier transform infrared spectroscopy measurement suggests a lower activation energy over the developed novel N-doped AC-based hybrid nanostructure for the DDH reaction than over the parent AC. Interestingly, the developed hybrid nanocomposite exhibits a much superior selectivity for styrene production compared to the parent AC, which is ascribed to the N-doping into the AC-based matrix. The developed N-doped AC-based hybrid nanostructure catalyst could be a potential candidate for catalytic styrene production via steam- and oxidant-free direct dehydrogenation of ethylbenzene.

A Facile Approach to Fabricate an N‐Doped Mesoporous Graphene/Nanodiamond Hybrid Nanocomposite with Synergistically Enhanced Catalysis

Owing to their unique structural features and surface properties, graphene and nanodiamond have attracted tremendous attention in diverse fields. However, restacking of graphene and reagglomeration of dispersed nanodiamond inevitably depress their catalytic properties. Herein, inspired by the historic discovery of “pillared clay”, we successfully realized the simultaneous inhibition of their restacking by fabricating a N‐doped mesoporous graphene/nanodiamond (N‐RGO/ND) nanocomposite by a facile wet‐chemical approach. The electrocatalytic oxygen reduction reaction (ORR) and the thermocatalytic oxidant‐free and steam‐free direct dehydrogenation (DDH) of ethylbenzene were used to examine its catalytic properties. The nanocomposite showed synergistically improved catalytic DDH and electrocatalytic ORR activity relative to that of the individual components, which can be ascribed to synergy between graphene and nanodiamond and to the large surface area, well‐ordered mesoporous structure, small crystalline size, and rich defect and CO surface features. Moreover, the developed synthetic strategy in this work can be extended to diverse N‐doped nanocomposites from dispersion‐required carbon precursors.

Guanidine Nitrate Enhanced Catalysis of Nitrogen‐Doped Carbon Nanotubes for Metal‐Free Styrene Production through Direct Dehydrogenation

Nitrogen‐doped carbon nanotubes (CNTs) with defect‐ and CO‐group‐rich surface features were fabricated through a facile and scalable physical dry milling and subsequent pyrolysis approach of carbon nanotubes and melamine in the presence of guanidine nitrate. The catalytic performance of the as‐prepared N‐doped CNTs with diverse guanidine nitrate dosages and pyrolysis temperatures for direct dehydrogenation of ethylbenzene to styrene under oxidant‐ and steam‐free conditions was measured. Various characterization techniques including high‐resolution transmission electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, nitrogen–adsorption and thermogravimetric analysis, and Raman spectroscopy were employed to investigate the structure and surface properties, as well as to explore the relationship between catalyst nature and catalytic performance. It is found that the addition of guanidine nitrate in the pyrolysis process of CNT with melamine significantly affects the structure, surface properties, and catalytic performance. The optimized N‐doped CNTs demonstrate steady‐state styrene production rates 1.56 and 1.60 times higher than those of the parent CNTs and the established nanodiamond, as well as 6.49 times the rate of commercially available K–Fe catalyst without compromising the selectivity to styrene. The much superior catalytic performance in metal‐free catalytic direct dehydrogenation can be ascribed to the CO group‐ and defect‐rich surface nature, the basic properties resulted from N‐doping, the larger surface area and pore volume, and smaller graphitic carbon crystallites. The fabricated novel N‐doped CNTs can be considered as a promising candidate for sustainable production of styrene through oxidant‐ and steam‐free direct dehydrogenation of ethylbenzene with energy‐saving and environmentally benign features. The developed defect‐formation strategy in this work can be used for preparation of other metal‐free carbocatalysts.

Facile simultaneous defect production and O,N-doping of carbon nanotubes with unexpected catalytic performance for clean and energy-saving production of styrene

O,N-doped carbon nanotubes with increased structural defects and enriched surface ketonic CO groups (MN-CNT), prepared by a facile and low-cost one-step strategy, demonstrate unexpected catalytic performance in direct dehydrogenation of ethylbenzene for styrene production with clean and energy-saving features. This work paves a new avenue for preparing other highly-efficient carbocatalysts in diverse organic transformations.

Explosive decomposition of a melamine-cyanuric acid supramolecular assembly for fabricating defect-rich nitrogen-doped carbon nanotubes with significantly promoted catalysis.

A facile and scalable approach for fabricating structural defect-rich nitrogen-doped carbon nanotubes (MCSA-CNTs) through explosive decomposition of melamine-cyanuric acid supramolecular assembly is presented. In comparison to pristine carbon nanotubes, MCSA-CNT exhibits significantly enhanced catalytic performance in oxidant- and steam-free direct dehydrogenation of ethylbenzene, demonstrating the potential for metal-free clean and energy-saving styrene production. This finding also opens a new horizon for preparing highly-efficient carbocatalysts rich in structural defect sites for diverse transformations.

Dynamic Interfacial Tension Between Crude Oil and Novel Surfactant Flooding Systems Without Alkali

Abstract The surface tensions of tetradecylmethylnaphthalene sulfonate (TMNS) surfactant aqueous solution and the dynamic interfacial tension (DIT) between crude oil, from Shandong Shengli oil field of China, and the surfactant solution without alkaline, was measured. Results indicate that the TMNS surfactant had great capability and efficiency of lowering the solution surface tension. The critical micelle concentration (cmc) is 0.001 mass% and the surface tension at this concentration is 28.19 mN.m−1. It was also found that the TMNS surfactant is greatly effective in reducing the interfacial tensions and can lower the tension of crude oil-water interface to ultra-low at very low concentration, 0.002 mass%, without alkali and other additives. Both chromatogram separation of flooding and breakage of stratum are avoided effectively. The lower salinity is favorable for the flooding systems, lowering the DIT. The synthesized TMNS surfactant flooding systems without alkali and sodium chloride, decreasing the cost of oil recovery and avoiding the stratum being destroyed, would have a great prospect for enhanced oil recovery (EOR).

Mesostructured Co–Ce–Zr–Mn–O composite as a potential catalyst for efficient removal of carbon monoxide from hydrogen-rich stream

Mesostructured CoxCe0.85Zr0.15MnyOe composites were firstly prepared by a simple one-pot surfactant-assisted co-precipitation (SACP) method and then employed to catalyze the CO preferential oxidation (CO PROX) reaction in an H2-rich stream. Effects of the Co and Mn contents (x and y, respectively) in the formula, as well as the presence of H2O and CO2 in feed were investigated. The as-synthesized Co0.4Ce0.85Zr0.15Mn0.10Oe catalyst showed excellent catalytic performance in the CO PROX reaction: 100% CO conversion could be observed in a wide temperature range of 140–200 °C; even in the simulated syngas, the almost complete CO removal could still be achieved at 175–225 °C; no obvious change in both CO conversion and CO2 selectivity over the catalyst took place during the CO PROX process with simulated syngas as feed. N2 physisorption (BET), temperature-programmed reduction (TPR), X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopic (XPS) characterization techniques were employed to reveal the relationship between the catalyst nature and catalytic performance. The outstanding catalytic performance in CO PROX reaction was remarkably dependent on a larger specific surface area, more reducible Co3+ and the high dispersity of the Co3O4, affected by the Co and Mn contents through strong Co–Ce–Zr–Mn interactions. The mesostructured Co0.4Ce0.85Zr0.15Mn0.10Oe catalyst prepared by the simple one-pot SACP protocol can be a promising candidate for CO PROX reaction in excess H2.

Increased active sites and their accessibility of a N-doped carbon nanotube carbocatalyst with remarkably enhanced catalytic performance in direct dehydrogenation of ethylbenzene

This work presents an efficient and low-cost one-step strategy for simultaneously N-doping and increasing surface ketonic CO groups and structural defects of a N-doped carbon nanotube (HN-CNT) through the explosive decomposition of hexamethylenetetramine (HTA) nitrate, a low-cost N,O-containing organic compound. The as-synthesized HN-CNT demonstrates a 1.64 and 2.19 times higher steady-state styrene rate with 98.5% selectivity towards styrene for direct dehydrogenation (DDH) than that of the parent CNT and H-CNT prepared by the similar pyrolysis procedure to that for the HN-CNT except for replacing HTA nitrate with HTA.

Dynamic Interfacial Behavior of Decyl Methylnaphthalene Sulfonate Surfactants for Enhanced Oil Recovery

Abstract The high purity decyl methylnaphthalene sulfonate (DMNS) was synthesized, the purity was determined by HPLC and the structure was confirmed by IR, UV and ESI-MS. Dynamic interfacial tensions (DIT) between DMNS flooding systems and crude oil were measured and the effects of sodium carbonate concentration, surfactant concentration and sodium chloride concentration on the DIT behaviors were investigated. Its found that the surfactant concentration, alkali concentration and the salinity have obvious influences on DIT behaviors. DMNS possessed outstanding capacity and efficiency of lowering the DIT between oil and water. The minimum dynamic interfacial tension could reach 6.35×10−6 mNm−1 at a lowconcentration for added surfactant. DMNS might be used in Enhanced Oil Recovery with lowcosts and high efficiency.

Supported Ni catalyst on a natural halloysite derived silica–alumina composite oxide with unexpected coke-resistant stability for steam-CO2 dual reforming of methane

The natural halloysite derived silica–alumina composite oxides (SA–H) through calcination at diverse temperatures were employed as supports for synthesizing novel supported Ni catalysts towards steam-CO2 dual reforming of methane (SCRM) for the production of synthesis gas. The effect of calcination temperature on the nature of the as-prepared supports and the supported Ni catalysts was investigated by using various characterization techniques including transmission electron microscopy (TEM), N2 adsorption–desorption (BET), X-ray diffraction (XRD), CO chemisorption, thermogravimetric analysis (TGA), and H2 temperature-programmed reduction (H2-TPR). The supported Ni catalyst on the halloysite derived silica–alumina nanorod (Ni/SANR–H) prepared by calcination at 1000 °C exhibited higher catalytic activity with similar selectivity in comparison with the ones prepared with the other temperatures, ascribed to higher Ni dispersity. More interestingly, the robust Ni/SANR–H catalyst exhibited unexpectedly catalytic stability for a SCRM reaction with much higher coke and Ni-sintering resistance than the supported Ni catalyst on traditional silica alumina prepared by a precipitation method (Ni/SA-P). The unexpected coke-resistant capacity of the Ni/SANR–H catalyst endows it to be a promising candidate for synthesis gas production through a SCRM reaction.