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In this paper, hydrophobic treatment by hexadecetyltrimethoxysilane (HDTMS) on the surface of Sn–Ti submicrospheres with regular morphology and uniform size prepared via a simple PVP-assisted sol-gel method was firstly reported. Their physical and chemical properties were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), N2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FI-IR), Uvioletvisible diffuse reflection spectroscopy (UV-vis DRS), Water contact angle (WCA), Thermogravimetric analysis (TG), Inductively coupled plasma-Atomic emission spectrometry (ICP-AES), C elemental analysis and Transmission electron microscope (TEM) techniques, and the catalytic performance in the Baeyer-Villiger (B-V) oxidation of cyclohexanone in the oxygen-benzaldehyde system was also investigated. The regular submicrospheres with anatase crystal phase can be kept well by the successful grafted hydrophobic layer. When the weight ratio of HDTMS to 12%-ST submicrospheres was 1, the maximum hydrophobic angle of 126.0º for 12%-1-C16-ST catalyst can be obtained. The cyclohexanone conversion and caprolactone yield over the 12%-1-C16-ST catalyst was highest, whose value was 2.32 and 3.44 times, respectively, than that of 12%-ST without hydrophobic treatment. The 12%-1-C16-ST catalyst also showed good stability with only a 3.74% drop of caprolactone yield after repeated use for 5 times. This method can provide a valuable reference and potential catalyst for the industrial application in the production of caprolactone. [ABSTRACT FROM AUTHOR]

The impregnation of the exterior surface of a masonry wall with a water repellent is a common intervention in (historic) building renovation and maintenance. Such treatments, whilst degrading at the surface with time under influence of ultra violet light, remain effective below the surface several decades after their application. During renovation works of masonry previously treated with a water repellent, the question arises whether it is necessary to repeat the hydrophobic treatment of the entire masonry after repointing. Opposing opinions exist with this regard, but no research clearly supporting one or the other. This research investigates for the first time the effect of hydrophobic treatment when applied on previously treated and repointed masonry walls. Small masonry walls were subjected to rain periods in the laboratory and their water uptake and drying behaviour were studied. Moreover, this laboratory research was followed by 30 months of outdoor exposition of the masonry specimens. The following cases were considered: (1) wall treated with water repellent, (2) wall treated with water repellent, followed by repointing but without new water repellent treatment, (3) wall treated with water repellent, followed by repointing and retreatment. This was done for three different types of pointing mortar: ordinary Portland cement and natural hydraulic lime with standard sand, and natural hydraulic lime with sand with one grain size. The results show that, after prolonged rain periods, the water uptake by repointed but not retreated masonry is comparable to that of untreated, non-hydrophobic masonry, whereas drying is considerably slower. This leads to a high saturation degree in repointed but not retreated masonry, which, in turn, increases the risk of damage to the masonry by e.g. frost. Therefore, retreating repointed hydrophobic masonry should definitively be considered. • A rain test was performed in laboratory. • Repointed but not retreated masonry, and untreated masonry had similar water uptake. • Repointed but not retreated masonry dried much slower than untreated masonry. • A high saturation degree was measured in repointed but not retreated masonry. • Retreatment of repointed hydrophobic masonry reduces potential risk of damage. [ABSTRACT FROM AUTHOR]

CO 2 hydrogenation to methanol is an efficient way to utilize CO 2 and store hydrogen. However, realizing high activity and methanol selectivity as well as excellent stability are still challenges due to the competitive reverse water-gas shift (RWGS) reaction and the accumulation of water on the catalyst surface. Herein, Cu/ZnO catalyst was prepared by oxalic acid-assisted solid-state grinding method and then was subjected to hydrophobic treatment using stearic acid as a functionalization agent. The effect of stearic acid concentration on the physicochemical properties of Cu/ZnO catalysts and the catalytic activity for low-temperature CO 2 hydrogenation to methanol was investigated and discussed in detail. Detailed catalyst characterizations disclosed that hydrophobic treatment using suitable concentration of stearic acid removed residues from the decomposition of oxalic acid and also increased specific surface area, surface basicity, reducibility and hydrogen adsorption strength on Cu/ZnO catalysts, leading to the enhanced catalytic performance and methanol selectivity. Among all the catalysts, Cu/Zn-2 mM catalyst exhibited methanol selectivity and methanol space time yield (STY) of 78.8% and 87.17 g/kg·h−1 at 200 ℃, much higher than those of untreated Cu/ZnO catalyst (71.7% and 68.93 g/kg·h−1). The hydrophobic Cu/Zn-2 mM catalyst also exhibited outstanding stability for low-temperature CO 2 hydrogenation to methanol, keeping its activity for 100 h without obvious deactivation when compared to untreated Cu/ZnO catalyst. This facile hydrophobic treatment using stearic acid not also enhanced catalytic activity, methanol selectivity and stability of Cu/ZnO catalysts for low-temperature methanol synthesis, but also enlightened the invention of more hydrophobic materials in the near future. [Display omitted] • Hydrophobic Cu/ZnO catalyst was successfully prepared using stearic acid. • The effect of stearic acid concentration was disclosed. • Hydrophobic treatment enhanced catalytic performance and methanol selectivity. • The hydrophobic Cu/Zn-2 mM catalyst kept its activity for 100 h without deactivation. [ABSTRACT FROM AUTHOR]