| With the deepening of the concept green chemistry, near-critical water (NCW) develops quickly due to its function as a green medium and fine solvent. Compared with water at ambient temperature and pressure, NCW possesses its unique performances:high ionization constant, so it has self-acid/base catalysis function; low dielectric constant, so it owns special solubility for both organic and inorganic compounds. These outstanding properties suggest that NCW may play roles as reactant in organic synthesis reactions as well as catalyst and solvent. Its acid/base catalytic ability may reduce or even eliminate the use of traditional acids or bases, and its excellent solubility can replace a large number of toxic and hazardous solvents. In view of its excellent mass transfer performances and green environmental properties, NCW has the potential application in organic synthesis reactions, waste recycling and other areas.The literature review section generalized the physical and chemical properties of NCW, such as dielectric constant, miscibility, ionic product, transport properties, and also made a brief introduction of the research process of organic reactions in NCW. In addition, it summarized systematically the application of NCW in different types of organic reactions, such as dehydration, hydration, elimination, hydrolysis, etc. Up to now, most research on NCW in literature is focused on the role of NCW as reaction medium and the influence of different parameters on reaction. But reactions in NCW assisted with additives were rarely reported. The introduction of additives according to specific reaction reasonably is helpful to reveal general reaction discipline and search the optimal experimental condition to increase the yield of target products. Base on the consideration above, additives-mediated organic reactions of acid catalyzed were studied and details are as follows: 1. Design and feasibility test of reactor in NCWA series of experiments on dehydration of diethylene glycol in the NCW were conducted, in order to investigate whether the self-designed batch reactor could meet the demand for organic reactions in NCW. Variations with or without additives for yield dependence of 1,4-dioxane on temperature, residence time and reactant/water ratio were consistent with the published literature. The satisfactory results demonstrated that the self-designed batch reactor displayed good performance and could be pursued on corresponding reactions in NCW. 2. Research on the dehydration of cyclohexanol in NCWReaction factors on the conversion of cyclohexanol and yield of cyclohexene were investigated, such as temperature (240～320℃), residence time (30～150 min), reactant/water ratio (R/W,1:10-1:30) and additives (Fe2(SO4)3, ZnSO4, NaHSO4). The results suggested that the dehydration of cyclohexanol could carried out successfully without additives, and its best yield 60.31% was obtained at 300℃, with residence time 150 min and R/W ratio 1:20. In the additives-mediated system, the yield of cyclohexene increased. And Fe2(SO4)3 exhibited the best catalytic ability and the yield of cyclohexene was as high as 72.74% at 280℃,120 min and R/W ratio 1:20. According to the results, a possible dehydration mechanism of cyclohexanol in NCW environment was speculated. 3. Research on the hydration of phenylacetylene in NCWFactors on the yield of acetophenone were considered, such as temperature (240～320℃), residence time (60～180 min), reactant/water ratio (R/W,1:10-1:50) and additives (NaHSO4, ZnCl2, FeCl3). The results showed that the hydration of phenylacetylene could be conducted in absence of additives. But the yield of acetophenone increased greatly when additives were introduced to the NCW system. And the three additives exhibited different catalytic performances, and that is FeCl3> ZnCl2>NaHSO4. High yield of 96.68% was obtained at 260℃,120 min, R/W ratio 1:20 in the presence of FeCl3. A possible reaction mechanism was proposed based on the product detected.
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