A series of silica supported Pd (Pd/SiO 2 ) catalysts were prepared in various HCl concentrations ( C HCl ) of the impregnation solution with different electrostatic interactions between Pd precursor and support, and their catalytic properties were evaluated by the selective hydrogenation of nitrile butadiene rubber (NBR). The results show that with the C HCl increasing from 0.1 to 5 M, the particle size of Pd nanoparticles dramatically decreases from 24.2 to 5.1 nm and stabilizes at ∼5 nm when C HCl is higher than 2 M. Using the catalysts prepared with a high C HCl (>2 M), an excellent hydrogenation degree (HD) of ∼94% with 100% selectivity to C=C can be acquired under mild conditions. Interestingly, the HD could be remarkably increased from 65 to 92% by increasing only C Cl – from 0.1 to 2 M with the addition of NaCl while keeping C H + at 0.1 M. This is because PdCl 4 2– is the predominant existing form of precursor at high C Cl – , which has a strong electrostatic attraction with the positively charged support favorable for the formation of small-sized Pd nanoparticles over silica. Notably, Pd leaching behavior during the hydrogenation reaction is closely related to C H + , and the higher the C H + , the less Pd residues are detected in the hydrogenated NBR. Our contribution is to provide a facile strategy to synthesize effective and stable Pd/SiO 2 catalysts via adjusting the electrostatic interaction, which exhibits a high activity and selectivity for NBR hydrogenation.

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a b s t r a c tA MnCl 2 /CaCl 2 -NH 3 two-stage solid sorption freezing system consisting of a MnCl 2 sorption bed, a CaCl 2 sorption bed, an evaporator and a condenser is established for a refrigerated truck, for which the required refrigerating capacity is 1.13 kW at a refrigerating temperature of À5 C. Composite adsorbents of MnCl 2 and CaCl 2 developed by expanded natural graphite treated with sulfuric acid are utilized. The sorption/desorption process and the resorption process are coupled in the two-stage cycle. The experimental results show that the maximum refrigerating capacity of 1.25 kW and COP (coefficient of performance) of 0.143 are obtained at a resorption time of 120 min when the hot air and refrigerating temperatures are 230 C and À5 C, respectively. In addition, the refrigerating capacity of 1.19 kW is achieved even when the hot air temperature is as low as 210 C, and such a result can satisfy the requirement for transporting fresh goods. The refrigerating capacity is 1.32 kW when the hot air and refrigerating temperatures are 270 C and À10 C, respectively, and the data are higher than the required refrigerating capacity. However, for refrigerating temperatures of À15 C and À18 C, the refrigerating capacity experimentally obtained could meet the requirement only when a truck is utilized for longdistance transportation.

The oxidation of TH to SP by H2O2 with the assistance of IL experiences two steps via two transition states.