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排序方式: 共有706条查询结果,搜索用时 532 毫秒
1.
Nagendranath Mahata V. Vishwanathan 《Journal of molecular catalysis. A, Chemical》1997,120(1-3):267-270
Kinetics of vapor phase hydrogenation of phenol to cyclohexanone over Pd/MgO system has been studied in a flow microreactor under normal atmospheric pressure. The reaction rate is found to be negative order with respect to the partial pressure of phenol and has increased from −0.5 to 0.5 with increasing temperature (473 to 563 K). The apparent activation energy (Ea) of the process is found to be close to 65 kJ per mol. On the basis of kinetic results a surface mechanism is proposed. 相似文献
2.
Two new compounds have been isolated from the whole plant of Monochoria vaginalis and characterized as: (10Z)‐1‐(2,6‐dihydroxyphenyl)octadec‐10‐en‐1‐one ( 1 ) (20R, 24R)‐campest‐5‐ene‐3β, 4β‐diol ( 2 ) together with nine known ones. The structures of these compounds were elucidated on the basis of spectral data and chemical evidence. 相似文献
3.
以合成土样为对象,研究了超声波辅助提取苯酚的条件及其提取效率。用中档超声波场辐射试样2×30s,30ml丙酮-正己烷(体积比1:1)分两次萃取10.0g合成土样中的苯酚,这时所获收率最高。在选定条件下用于实际土样分析,以索氏萃取4h的结果为对照基准,本方法的平均回收率为97.8%,RSD为1.5%。 相似文献
4.
纳米羟基磷灰石制备及其对溶液中苯酚吸附的优化设计 总被引:3,自引:0,他引:3
采用化学沉淀法制备得到纳米羟基磷灰石(n-HAp)粉体,研究了n-HAp粉体对水溶液中苯酚的吸附性能,并初步探讨了其在粉体上的吸附机理,在低浓度(5~30mg/L)时的吸附符合Freundlich等温吸附模型。实验结果表明,n-HAp粉体对苯酚具有较好的吸附效果,2h可基本达到吸附平衡。利用正交设计实验探讨了粉体煅烧温度、吸附温度、吸附时间、溶液pH等因素对吸附效果的影响。正交实验结果统计分析表明,各种因素对吸附的影响程度依次为:溶液pH>煅烧温度>振荡温度>振荡时间。pH对吸附性能的影响最明显,强酸和强碱环境能有效提高n-HAp对苯酚的吸附量。 相似文献
5.
6.
The [4+2] cyclodimerization of cyclohexa-2,4-dienone derivatives of the orthoquinone monoketal and orthoquinol types has been the topic of numerous investigations over the last 50 years in the aim of rationalizing the extraordinary level of regio-, site-, and stereoselectivities observed in these processes. In particular, the double diastereo-π-facial differentiation expressed in cyclodimerizations of chiral orthoquinols (i.e., 6-alkyl-6-hydroxycyclohexa-2,4-dienones) is an important aspect of these transformations, for they relate to the construction of several natural products. The experimental and theoretical results that are described in this article offer a comprehensive understanding of the factors controlling these site-specific regio- and diastereoselectivities. Our interpretation of these results relies on a combination of Woodward-Hoffmann and Salem-Houk secondary orbital interactions and Cieplak-type hyperconjugative effects in bispericyclic C2-symmetric transition states. 相似文献
7.
Halina Y. Neujahr 《Applied biochemistry and biotechnology》1982,7(1-2):107-111
The enzyme phenol 2-hydroxylase was immobilized on Sepharose and used in conjunction with an O2 electrode for quantitating phenol. Similarly, catechol 1,2-oxygenase was used for quantitating catechol. A third probe was
prepared by immobilization ofTrichosporon cutaneum cells rather than purified phenol 2-hydroxylase for phenol quantitation. The whole cell system gave results comparable to
the immobilized enzyme system. 相似文献
8.
Yasuhiro Aoki 《Tetrahedron》2005,61(22):5219-5222
Synthesis of phenol and cyclohexanone in one pot was examined by means of the NHPI-catalyzed aerobic oxidation of cyclohexylbenzene. The aerobic oxidation of cyclohexylbenzene catalyzed by NHPI followed by treatment with sulfuric acid afforded phenol and cyclohexanone in good selectivities. Thus, the reaction of cyclohexylbenzene under atmospheric dioxygen (1 atm) by NHPI at 100 °C for 3 h followed by treatment with 0.3 M sulfuric acid at room temperature for 2 h resulted in phenol and cyclohexanone in 96 and 91% selectivity, respectively, at 25% conversion. This method was successfully extended to the one-pot synthesis of 4-hydroxyacetophenone and cyclohexanone. 相似文献
9.
流动注射化学发光法测定工业废水中苯酚 总被引:2,自引:0,他引:2
采用流动注射技术,研究了高锰酸钾-过氧化氢-苯酚的化学发光行为,对影响化学发光强度的因素进行了试验,建立了流动注射化学发光法测定苯酚的方法。方法的检出限为3×10-5g.L-1,线性范围为1.0×10-4~1.0×10-1g.L,对浓度为4.0×10-4g.L的苯酚作试验,求得其相对标准偏差(n=11)值为1.6%。方法用于废水中苯酚含量的测定,结果与分光光度法测得值一致。 相似文献
10.
This study aims to clarify the effects of carbon activation type and physical form on the extent of adsorption capacity and
desorption capacity of a bi-solute mixture of phenol and 2-chlorophenol (2-CP). For this purpose, two different PACs; thermally
activated Norit SA4 and chemically activated Norit CA1, and their granular countertypes with similar physical characteristics,
thermally activated Norit PKDA and chemically activated Norit CAgran, were used. The thermally activated carbons were better
adsorbers for phenol and 2-CP compared with chemically activated carbons, but adsorption was more reversible in the latter
case. 2-CP was adsorbed preferentially by each type of activated carbon, but adsorption of phenol was strongly suppressed
in the presence of 2-CP. The simplified ideal adsorbed solution (SIAS) model underestimated the 2-CP loadings and overestimated
the phenol loadings. However, the improved and modified forms of the SIAS model could better predict the competitive adsorption.
The type of carbon activation was decisive in the application of these models. For each activated carbon type, phenol was
desorbed more readily in the bi-solute case, but desorption of 2-CP was less compared with single-solute. This was attributed
to higher energies of 2-CP adsorption. 相似文献