首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 69 毫秒
1.
介绍了夹带剂在超临界CO2萃取中的作用和原理,分析了夹带剂分子极性、相对分子质量、分子体积及特殊分子结构等性质对超临界CO2萃取的影响,总结出夹带剂性质对萃取率的变化规律:夹带剂的分子极性越大,溶质在超临界CO2中的溶解度越大;夹带剂的相对分子质量、分子体积的增大,其在超临界CO2中的溶解度减小,萃取率减小;夹带剂中易形成氢键的特殊分子结构,可提高萃取率。  相似文献   

2.
郭楠楠  魏龙  李利民 《工业催化》2016,24(11):10-13
由于超临界流体的特殊性质,研究超临界流体在不同领域的应用越来越广泛,如超临界萃取技术、超临界流体色谱技术、超临界流体反应技术和超临界水氧化技术等。活性炭由于巨大的比表面积及特殊的表面结构可使催化剂的活性组分得到充分分散,活性炭的表面结构和性质则直接关系到由其制备的催化剂上活性组分分散度及活性等,因此,对活性炭表面进行适当的改性处理并研究处理方法对活性炭表面性质及催化活性的影响意义重大。  相似文献   

3.
超临界流体技术在绿色化学化工中的应用   总被引:1,自引:0,他引:1  
本文介绍了超临界流体的特殊性质,以及超临界条件下的绿色化学反应。综述了超临界流体技术在萃取分离、材料制备及化学分析等领域的应用。  相似文献   

4.
超临界流体技术在绿色化工中的应用   总被引:8,自引:0,他引:8  
简要介绍了超监界流体的特殊性质,综述了作为新兴绿色技术的超临界流体技术在化学反应、萃取分离、化学分析、材料制造、石油化工及环保等领域的应用。  相似文献   

5.
重点介绍了超临界流体的特殊理化性质,主要包括密度、粘度、扩散系数、介电常数等,对超临界流体技术在萃取、颗粒制造、环境治理、化学反应等领域的应用现状进行了综述,并对该技术的未来发展趋势进行了展望。  相似文献   

6.
超临界流体技术的应用   总被引:3,自引:0,他引:3  
钟宏  梁璀 《精细化工中间体》2006,36(1):11-13,20
简要介绍了超临界流体的特殊性质,从超临界流体在萃取、高分子科学、制备超细颗粒材料、精密仪器清洗、化学分析、化学反应及环保领域几个方面着重介绍了超临界流体的应用。  相似文献   

7.
超临界水氧化技术处理污泥的研究与应用进展   总被引:2,自引:0,他引:2       下载免费PDF全文
超临界水氧化技术是一种新型且高效的废物处理技术,利用水在超临界状态下的特殊性质使其在处理含有机物及难降解有机污染物的城市污泥、工业污泥等时具有独特的优势。介绍了超临界水氧化技术机理的研究进展,介绍了国内外近年来超临界水氧化技术在污泥处理领域的研究进展,从反应时间、反应温度、体系压力、催化剂、氧化剂、共氧化剂等影响因素系统总结。介绍了该技术在国内外污泥处理领域的实际应用现状、具体工艺流程及成本效益,并针对目前存在的问题对超临界水氧化处理技术处理污泥的前景方向进行了展望。  相似文献   

8.
介绍了超临界二氧化碳的特殊性质,综述了超临界二氧化碳为介质的高分子合成方面的应用进展情况.皿示出超临界二氧化碳是一种对环境无污染且价廉的绿色介质,具有广阔的应用前景。  相似文献   

9.
超临界流体是一种具有特殊物理特性和热力学性质的绿色溶剂,可表现出液体与气体的性质;超临界流体萃取技术是一种新型、清洁、高效的绿色分离、提取技术,是国内外研究的热点之一。对超临界流体萃取技术的基本原理、发展过程和特点进行了介绍,并对超临界萃取技术在食品工业、制药工业、天然香料领域和环境保护领域的应用进展进行了综述,为超临界流体萃取技术的进一步应用提供参考。  相似文献   

10.
造纸黑液的无害化资源化利用对造纸工业减少环境污染、缓解能源短缺具有重要意义。超临界水气化技术是一种新型且高效的有机废水无害化资源化利用技术,利用水在超临界状态下的特殊性质使其在无害化资源化处理造纸黑液时具有独特的优势。回顾了近年来造纸黑液超临界水气化制氢与高附加值化学品回收的进展,介绍了制氢反应机理,系统总结了温度、压力、浓度、停留时间和催化剂等因素对黑液超临界水气化制氢的影响,介绍了造纸黑液里各类有用无机盐在超临界水条件下的反应、分离回收及造纸黑液超临界水气化反应装置的发展现状。针对现存问题对造纸黑液超临界水气化制氢和资源化无害化处理回收有用成分进行了展望。  相似文献   

11.
Phosphor yttrium aluminum garnet (Y3Al5O12, YAG) doped with Eu (10 at%) was synthesized by supercritical water (SCW) and solid-state methods in a batch reactor. The crystals, morphologies and luminescent properties of the phosphors obtained from different pH conditions in the SCW were studied. Pure YAG phase was successfully synthesized at the alkaline condition in the SCW without formation of intermediate phases, while the size and luminescent property of YAG: Eu were strongly affected by pH condition. The luminescent intensity of YAG: Eu by the SCW method without further thermal treatment is stronger than that by the solid-state method with thermal treatment.  相似文献   

12.
The influence of reaction pressure, reaction time, reaction temperature, and biomass‐to‐water mass ratio R on the conversion of miscanthus biomass to biofuels under sub‐ and supercritical water (SCW) conditions was investigated. The highest total conversion was obtained under SCW conditions and the heating value increased under subcritical and SCW conditions. The findings herein show that near‐supercritical and supercritical water at 400 °C and high pressure can be an effective reaction medium for converting biomass to oils with relatively low oxygen contents in high yields.  相似文献   

13.
Dodecane cracking and aromatization over ZSM-5 was studied in the presence and absence of supercritical water (SCW). A group-type model was used to determine five best-fit rate constants to describe yields to aliphatics, aromatics, coke, and gases. SCW accelerated gas formation while suppressing coke formation. CO and CO2 were formed in the presence of SCW, but not in its absence; a new, low-temperature coke gasification pathway was suggested to account for this observation. Similarly, a low-temperature alkane reforming pathway was hypothesized to explain the increased relative rate constant for production of gases in the presence of SCW compared with its absence. Additional tests and analysis indicated that these effects could not be ascribed solely to zeolite degradation in the presence of SCW, implying that water directly influences the reaction mechanism. These results provide new insights into the role(s) of water during oil cracking under supercritical conditions.  相似文献   

14.
Interactions of supercritical water (SCW) with several carbon (including polycrystalline graphite, highly ordered pyrolytic graphite (HOPG), pyrolytic carbon, and diamond) and selected ceramic materials under oxic or anoxic conditions are investigated. Wettability and surface/material properties of samples, before and after the SCW exposure, are characterized with sessile drop contact angle measurement, profilometry, XPS, XRD, and ToF-SIMS. All tested ceramic materials became more hydrophilic during the SCW exposure, mainly due to hydrolysis reactions. Carbon samples exposed to oxic SCW became more hydrophilic as a result of surface oxidation. Carbon materials, except HOPG and diamond, became more hydrophobic when exposed to anoxic SCW because of degradation of hydrophilic oxygen functionalities. HOPG and diamond became more hydrophilic after anoxic SCW exposure mainly due to the removal of hydrophobic hydrocarbon contaminants. Hydrophobicity of different carbon samples exposed to SCW are explained based on the abundance of surface hydrophilic sites (i.e., oxygen functionalities, reactive carbon dangling bonds or defects), hydrocarbon impurities, and surface roughness.  相似文献   

15.
In the presence of supercritical water (SCW) and N2, the pyrolysis of heavy oil was investigated to distinguish the difference in the reaction kinetics between the upgrading in the SCW and oil phases. The pyrolysis in the SCW phase is faster than that in the oil phase, but the reaction in whichever phase is retarded by vigorous stirring. The pyrolysis can be preferably described by a four‐lump kinetic model consisting of the condensation of maltenes and asphaltenes in series. In the SCW phase, highly dispersed asphaltenes are isolated by water clusters from maltenes dissolved in SCW surroundings, by which the condensation of asphaltenes is drastically accelerated. Benefited from excellent mass transfer environments in SCW, the condensation of maltenes is promoted simultaneously. The introduction of SCW into the pyrolysis of heavy oil results in an effectively increased upgrading efficiency, but its influence on the properties of equilibrium liquid products is minor. © 2014 American Institute of Chemical Engineers AIChE J, 61: 857–866, 2015  相似文献   

16.
The treatment of coals of various degrees of metamorphism in supercritical water (SCW) over the temperature region 380–800°C was studied. The yields and compositions of liquid products obtained by treatment in SCW were determined. These data were compared with the results of the semicoking of the above coals.  相似文献   

17.
Effect of supercritical water on upgrading reaction of oil sand bitumen   总被引:1,自引:0,他引:1  
The advantages of supercritical water (SCW) as a reaction medium for upgrading oil sand bitumen were investigated through a comprehensive analysis of the output product, which includes gaseous products, middle distillate, distillation residue, and coke. Canadian oil sand bitumen mined by the steam assisted gravity drainage method was treated in an autoclave at 420-450 °C and 20-30 MPa for up to 120 min with three kinds of reaction media: SCW, high-pressure nitrogen, and supercritical toluene. The yields of gaseous products indicated that a very small amount of water was involved in the upgrading reaction. The analytical results of the middle distillate fractions were almost the same using water and nitrogen at 450 °C. The distillation residues produced in SCW had lower molecular weight distributions, lower H/C atomic ratios, higher aromaticities, and consequently more condensed structures compared to those produced in nitrogen. The coke produced using SCW also had lower H/C values and higher aromaticities. Judging from all the analytical results, the upgrading of bitumen by SCW reaction was primarily considered to be physical in nature. As a result, it is possible to highly disperse the heavy fractions by SCW. This dispersion effect of SCW led to intramolecular dehydrogenation of the heavier component and prevention of recombination reactions, and consequently gave the highest conversion.  相似文献   

18.
Use of supercritical water (SCW) as a medium for oxidation reactions, conversion of organic materials to gaseous or liquid products, and for organic and inorganic synthesis processes, has been the subject of extensive research, development, and some commercial activity for over 25 years. A key aspect of the technology concerns the identification of materials, component designs, and operating techniques suitable for handling the moderately high temperatures and pressures and aggressive environments present in many SCW processes. Depending upon the particular application, or upon the particular location within a single process, the SCW process environment may be oxidizing, reducing, acidic, basic, nonionic, or highly ionic. Thus, it is difficult to find any one material or design that can withstand the effects of all feed types under all conditions. Nevertheless, several approaches have been developed to allow successful continuous processing with sufficient corrosion resistance for an acceptable period of time. The present paper reviews the experience to date for methods of corrosion control in the two most prevalent SCW processing applications: supercritical water oxidation (SCWO) and supercritical water gasification (SCWG).  相似文献   

19.
超临界水中萘酚氧化分解的研究   总被引:16,自引:0,他引:16  
建立了超临界水中有机物连续氧化分解的实验装置。初步探索了超临界水中β-萘酚氧化分解的影响因素及主要残留物。  相似文献   

20.
Luminescent yttrium aluminum garnet (YAG, Y3Al5O12) nanoparticles doped with Eu (10 at%) were synthesized in batch-type and continuous-type supercritical water (SCW) reactors. In the case of the continuous-type SCW method, the particles of YAG: Eu phosphors were much smaller and demonstrated a uniform spherical-like shape. Inversely, in the case of the batch-type SCW method, a needle-like or elliptical-like shape was formed because a finite amount of time was required to reach SCW conditions from ambient conditions. However, the emission intensity of YAG: Eu phosphors synthesized by using the batch-type SCW method was stronger. Therefore, it is concluded that the continuous-type SCW method is superior to the batch-type SCW method from the viewpoint of the particle size and shape, but the luminescence property of phosphors in the continuous-type SCW method needs to be improved. In addition, a calcination process slightly improved the luminescence intensities of YAG: Eu phosphors generated by using either the batch-type or continuous-type SCW methods.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号