•Cyclohexane dehydrogenation under “wet–dry” multiphase reaction conditions was optimized.•Effects of the process parameters on several responses depicted visually.•The optimal energy balance point was obtained.•Provide valuable information for efficient and economical hydrogen production.Hydrogen production via cyclohexane dehydrogenation catalyzed by a Raney-Ni catalyst under multiphase reaction conditions was investigated in this study. The uniform design (UD) method was employed to optimize the performance of the dehydrogenation reaction system of cyclohexane under “wet–dry” multiphase reaction conditions and to evaluate the effects of the process parameters on several response functions, such as the total amount of hydrogen produced in 2 h, the dehydrogenation conversion of cyclohexane and the relative activity of the catalyst. The results indicated that the data were well fitted by the regressed second-order polynomial models. Optimum reaction conditions for each response were obtained, under which the total amount of hydrogen produced in 2 h reached 9280 ml, the hydrogen produced through the conversion of cyclohexane was 18.63 and the relative activity of the catalyst maintained 0.91. In addition, the optimum reaction conditions for multi-response optimization were obtained, under which all three responses were expected to exhibit a relatively good performance. Confirmation experiments demonstrated that the UD method is a powerful and useful approach for optimizing the system of cyclohexane dehydrogenation under multiphase reaction conditions and is expected to provide valuable information for both efficient and economical hydrogen production.Hydrogen production via cyclohexane dehydrogenation catalyzed by Raney-Ni under multiphase reaction conditions was investigated and optimized using the uniform design method.

•A novel technical route was put forward to construct OTS SAM on SS316L surface.•The OTS SAM constructed on SS316L surface was well-ordered and integrated.•No corrosion spot could be found on sample surface even in 1 μm × 1 μm scale.•OTS SAM on SS316L exhibited an excellent stability under physiological conditions.Alkyltrichlorosilane self-assembled monolayer (SAM) was regarded as the most stable SAM on silicon/silica substrate, but it was rarely coated on stainless steel 316L (SS316L) substrate surface due to the serious surface corrosion caused by the hydrochloric acid released during the hydrolysis process of alkyltrichlorosilane molecules. In this paper, a novel technical route aiming at constructing solid octadecyltrichlorosilane (OTS) SAM on SS316L surface was put forward. By prolonging the storage time of OTS–toluene reaction solution and adding a moderate amount of alkali into the reaction solution, a well-ordered and integrated OTS SAM was successfully coated on SS316L surface. The obtained OTS SAM was characterized by contact angle, atomic force microscopy (AFM), scanning electron microscope (SEM) and attenuated total reflectance Fourier transform infrared (ATR-FTIR). The long-term in vitro stability study of OTS SAM on SS316L showed that, even immersed in physiological saline or phosphate buffered saline (PBS) solution at 37 °C for up to 60 days, the sample surface still kept a typical hydrophobicity.

•The kinetics of dehydrogenation reaction of cyclohexane was studied.•The nature of “wet–dry” multiphase reaction was discussed.•The dynamic energy balance control is important to the multiphase reaction system.•The conversion of cyclohexane was up to 72.7% and purity of evolved H2 was 100%.The kinetics of dehydrogenation reaction of cyclohexane catalyzed by Raney-Ni under “wet–dry” multiphase reaction conditions was studied in this paper. The influences of the heating temperature, feeding amount of cyclohexane and catalyst dosage on conversion of cyclohexane, apparent rate constant of reaction and retardation constant for aromatic product were investigated systematically. The experimental studies indicate that the control of the dynamic energy balance of reaction system is very important, there exists an optimal energy balance point in “wet–dry” multiphase reaction system, which depends on the combined action of heating temperature, feeding amount of cyclohexane and catalyst dosage. It was found that, with 0.5 ml cyclohexane feeding amount and 7 g catalyst dosage, at 320 °C the reaction system approached its optimal energy balance point, and the dehydrogenation conversion of cyclohexane reached its highest value of 72.7%.

The (3-aminopropyl)triethoxysilane (APTES) self-assembled monolayer (SAM) has been widely used in fundamental research and engineering applications; however, characterization of its surface wetting properties remains problematic. Surface wetting properties of the APTES SAM were systematically investigated using different contact angle measurement techniques. The observed unique nonideal wetting was related to the APTES SAM structure, including surface hydrogen bond formation, the surface roughness, and the effect of water penetration. The contact angle decreased dramatically with the residence time on the APTES SAM surface, and a special contact angle hysteresis phenomenon was observed. The contact angle could be distorted by the calculation method used for the nonideal APTES SAM surface. Values calculated by the tangent-leaning method were thought to be more accurate and credible. Our findings demonstrated that static advancing contact angles were the most stable and credible for characterizing the APTES SAM surface wettability.

Dehydrogenation of methyl-cyclohexane (MCH) catalyzed by Raney-Ni under a multiphase reaction condition was studied in this paper. The evolved gases were continuously separated from the reaction system through a condenser during the reaction, and the influences of the reaction temperatures (483–573 K), the amounts of the reactant (0.2–4.0 ml) feed and the catalyst (2–10 g) dosages on the conversion had been investigated. The mechanism of the multiphase reaction was analyzed from the viewpoints of the dynamic energy balance. Our experimental results showed that there existed an optimal energy balance point, which guaranteed not only the efficient contact between the reactant and catalyst, but also the higher conversion of the MCH dehydrogenation. At 523 K, with 0.5 ml MCH amount feed and 8 g Raney-Ni dosages, the dehydrogenation conversion of MCH could reach ∼65%∼65%.

The structure and effects of mechanical ball-milling on hydriding behavior of LaMg11Ni were studied. Structures of the alloys and the hydrides were determined by X-ray diffraction (XRD). By measuring hydrogen-storage capacity and hydrogen absorption kinetics of the material, hydriding behaviors of LaMg11Ni prepared by different mechanical ball-milling time were compared. In this work, there is a 20% increase of hydrogen absorption capacity after 20 h milling, and the kinetics of hydrogen absorption was markedly improved. Nevertheless, further milling does not make good. When the milling time is too long, the situation will be deteriorated. For example, after 120 h milling, the material has very poor hydrogen-storage capacity and is difficult to activate. Explanation of the phenomenon is proposed on the basis of microstructure analysis.

Hydrogen production via dehydrogenation of cyclohexane is regarded as one of the most promising on-board hydrogen supplier system for hydrogen vehicles. In this study, the deactivation mechanism of Raney-Ni catalyst under “wet-dry” multiphase reaction conditions was studied by means of characterizations. The fresh and deactivated Raney-Ni catalyst was characterized by scanning electron microscope (SEM), thermogravimetry analysis (TGA), X-ray spectroscopy (XRD), Brunauer-Emmett-Teller (BET), mercury porosimetry and granularity analysis. It was found that the deposition of the filamentous carbon, which came from the side reactions of cyclohexane, on the outer layers of Raney-Ni particles was the main reason for the catalyst deactivation. Due to the strong external diffusion resistance during the multiphase reaction process, the carbon was concentrated in the orifices, and the amount of carbon was about 3.25 wt.% of the catalyst. The decay of Raney-Ni was a typical orifice coking deactivation. The experimental study also showed that the deactivated Raney-Ni catalyst could be regenerated by coke elimination with water and recovered its activity. In addition, a regeneration mechanism of the deactivated catalyst by coke elimination was proposed.Deactivation and Regeneration of Raney-Ni Catalyst during Multiphase Dehydrogenation of CyclohexaneDownload high-res image (224KB)Download full-size image