The Effects of Material Properties on the Activity of Sol‐Gel Entrapped Perruthenate under Supercritical Conditions

Silica gels organically modified and doped with the ruthenium species tetra‐n‐propylammonium perruthenate (TPAP) are leach‐proof, selective catalysts for the aerobic oxidation of alcohols to carbonyl compounds with dioxygen at low pressure in compressed carbon dioxide. The catalytic sol‐gels are recyclable and the correlation between the reactivity of the materials and their surface polarity and textural properties suggests valuable information on the chemical behaviour of sol‐gel entrapped silica catalysts in oxidation catalysis which is of relevant interest considering the importance of heterogeneous oxidative dehydrogenation of alcohols in fine chemistry. An explanation of the structure‐activity relationship is proposed to provide guidelines for the further development of efficient solid oxidation catalysts for conversions in supercritical carbon dioxide.     

Sol‐Gel Ormosils Doped with TEMPO as Recyclable Catalysts for the Selective Oxidation of Alcohols

Organically modified silicas doped with TEMPO prepared via the sol‐gel method are highly recyclable catalysts of the selective Montanari‐Anelli oxidation of 1‐nonanol; They show a notable ”positive feedback” effect of matrix alkylation on the catalyst activity which is typical of doped sol‐gel materials and markedly differentiates the behaviour of these materials from that of analogous silica‐supported TEMPO.     

涤纶织物超临界二氧化碳染色研究

分散染料在120℃、30MPa条件下溶解在超临界二氧化碳中，将涤纶织物在此条件下循环染色50分钟；与水介质中染色的涤纶织物进行结果比较：前者无需清洗即可获得很高的色牢度但染色深度偏低，并需25～30MPa的压力。在实验条件下，超临界二氧化碳流体循环压力、流量、介质均匀程度直接影响染色织物的色深度、牢度和匀染性。     

岩蔷薇超临界二氧化碳萃取研究

采用超临界二氧化碳萃取技术 ,研究了岩蔷薇的萃取工艺。探讨了温度、压力、时间及CO2 流量等因素对萃取物得率的影响 ,采用四因素四水平的正交设计 ,得出超临界二氧化碳萃取最佳工艺条件为 :压力 2 8MPa、温度 40℃、时间 3h、流量 3 0L/h ,萃取物得率为 6.6%。产品质量优于有机溶剂萃取法。     

超临界二氧化碳中气体参与的有机化学反应

综述了超临界二氧化碳作为反应介质的最新研究进展,特别介绍了有气体(氢气,一氧化碳,氧气)参与的有机化学反应,即催化氢化反应、羰基化反应、氧化反应。     

超临界CO2介质中反应气体参与的催化反应研究进展

在反应气体参与的催化反应中,超临界CO2作为溶剂的主要优势是消除气体的溶解性能差所带来的传质问题,同时提高实验室和化工生产中的安全系数。介绍了超临界CO2介质中气体参与的催化反应的特点以及在催化加氢、羰基化和催化氧化等反应中的研究进展,并对未来的发展提出展望。     

间三氟甲基硝基苯的超临界催化加氢

研究了用超临界二氧化碳作为反应介质来提高间三氟甲基硝基苯的加氢反应速度和选择性。实验考察了二氧化碳压力、加氢反应温度、氢气浓度、反应空速等因素对超临界加氢反应的影响。结果表明，在二氧化碳压力为9．5MPa,反应温度为45℃，氢气浓度为0．6molL^-1,反应空速为1．0min^-1的条件下，间三氟甲基硝基苯的转化率为99．5％，选择性为100％。同时，在45℃时超临界催化加氢反应速度是液相加氢时的29倍。     

Dealcoholisation of Cider by Supercritical Extraction with Carbon Dioxide

A study of cider dealcoholisation by supercritical extraction with carbon dioxide using pilot-plant-scale equipment has been carried out. The effects of pressure, temperature and solvent to feed ratio have been examined. Supercritical and liquid carbon dioxide have been used to extract ethanol and aromas from cider at pressures of 80–250 bar and temperatures of 20 and 40°C.     

超临界二氧化碳中的甲苯选择性氧化反应

考察了甲苯选择性氧化反应中反应物及产物在超临界二氧化碳中的溶解性质。结果表明,甲苯在超临界二氧化碳中的溶解度较大,在反应条件下能与二氧化碳形成均相;苯甲醇、苯甲醛和苯甲酸在超临界二氧化碳中的溶解度随着物质极性的增强而降低。利用不同产物的溶解性差异,可实现超临界二氧化碳中甲苯的选择性氧化。同时考察了超临界二氧化碳中甲苯选择性氧化反应过程中,反应时间、反应压力、反应温度以及n(甲苯)/n(氧气)对反应选择性的影响。     

萃取八角茴香精油的研究

用超临界CO₂萃取八角茴香精油。采用4因素4水平的正交试验,得出超临界CO₂萃取八角茴香精油的最佳工艺条件为:压力16 MPa、温度35℃、时间2 h、CO₂流量30 L/h。在此条件下,八角茴香萃取物得率为10.5%。采用水蒸气蒸馏提取精油,得率为7.5%。对两种不同提取方法得到的精油的品质和得率进行了比较。超临界CO₂萃取方法得到的八角茴香精油产品得率比水蒸气法高出40%,并且香气更全面。     

超临界CO_2萃取芹菜籽油研究

用超临界ＣＯ２萃取技术对广东白芹菜籽进行了萃取研究。结果表明，萃取压力低于１５ＭＰａ时，较重的油树脂等成分难以被萃取出来；萃取温度为３０８Ｋ时对萃取最有利；解析温度对萃取效率影响较小；ＣＯ２流量对萃取效率的影响比床层高度引起的扩散阻力的影响大得多。超临界ＣＯ２萃取所得芹菜籽油品质优越，且其中的药用有效成分（３－正丁基－４，５－二氢苯并呋喃酮）含量比水汽法所得芹菜籽油的高五倍多。     

对羟基苯甲酸甲酯在含夹带剂超临界CO2中溶解度的研究

采用流动法测定了对羟基苯甲酸甲酯在含和不舍夹带剂的超临界CO2中的溶解度,实验所用夹带剂分别为正己烷、乙醇、丙酮及混合夹带剂正己烷 丙酮(摩尔比为1：1),夹带剂的摩尔分数均为0．035。论述了温度、压力和夹带剂对固体溶解度的影响,然后用化学缔合模型关联了实验数据,实验值与计算值吻合良好。     

Density‐Dependent Formation of the Pure trans‐Isomer of the Unsaturated Alcohol by Selective Hydrogenation of Citral in Supercritical Carbon Dioxide

Selective hydrogenation of citral to unsaturated alcohol [geraniol (trans) + nerol (cis)] was carried out in supercritical carbon dioxide (scCO₂) using an MCM‐41 supported plantinum catalyst (∼1 wt% Pt). A remarkable rate of isomerization of the unsaturated alcohol [nerol (cis) to geraniol (trans)] during the hydrogenation of citral was achieved simply by tuning the density of CO₂. Optimum reaction conditions were developed to obtain only geraniol (trans) with a selectivity of 98.8% and citral conversion of 99.8%. A significant change in the cis:trans ratio of the product (1:82.3) from the substrate (1:1.3) was observed depending on the various reaction parameters like carbon dioxide and hydrogen pressure, reactant concentration, reaction time and, particularly, the total selectivity for unsaturated alcohol [geraniol (trans) +nerol (cis)]. It has been observed that the presence of hydrogen is necessary for isomerization. Our results were explained in terms of a density‐dependent, two‐step model. The kinetic behaviour shows that the rate of isomerization was higher in scCO₂ compared to other organic solvents and the pure form of geraniol (trans) was obtained exclusively. A probable reaction pathway was proposed in order to explain the isomerization during hydrogenation of citral in scCO₂ medium.     

香附的超临界二氧化碳萃取研究

分别用超临界二氧化碳萃取和水蒸气蒸馏法对中药香附进行了提取研究 ,并用GC MS对两种提取产物进行了化学成分分析。结果表明 :与水蒸气蒸馏法相比 ,超临界二氧化碳萃取法的出油率增加了 3倍 ,提出的主要药用有效成分如香附子烯、香附酮等的总量增加了 1.3倍 ,而萃取时间仅为水蒸气蒸馏法的 1/ 3;用超临界二氧化碳萃取时 ,较高的萃取温度 (5 5℃ )和中等的萃取压力对萃取有利 ,当压力高于 15MPa时 ,压力越高出油率越低     

超临界CO_2辅助UHMWPE/PP挤出成型研究

对超临界CO2辅助UHMWPE/PP共混体系的挤出成型进行了研究。结果表明,在挤出成型过程中,超临界CO2对UHMWPE/PP体系起到一定的增韧作用,使其力学性能有所改善。同时超临界CO2作为一种增塑剂,降低了UHMWPE/PP体系的黏度,改善了体系的流动性和加工性能。     

超临界CO_2发泡聚苯乙烯工艺研究

以超临界CO_2为发泡剂,采用釜压法在不同发泡工艺条件下制备了聚苯乙烯(PS)发泡试样,通过扫描电子显微镜对PS发泡试样的泡孔形貌进行了表征,探讨了不同发泡工艺对PS发泡试样发泡性能的影响。结果表明,随发泡温度的升高,PS发泡试样泡孔尺寸增大,泡孔密度下降,而泡沫密度呈现先降低后升高的趋势,发泡倍率与此相反;增大保压时间和保压压力,可提高试样的发泡效果。当发泡温度为136℃,保压压力为20 MPa,保压时间为4 h时,PS发泡试样的发泡效果最好,其泡沫密度为0.043 g/cm~3,发泡倍率为24.4,泡孔尺寸为59.8μm,泡孔密度为6.20×107个/cm~3。     

超临界CO2萃取山苍子核仁油的工艺研究

研究了用超临界CO2流体萃取山苍子核仁油的萃取工艺,探讨了各种影响因素对山苍子核仁油萃取率的影响,通过正交试验确定了超临界萃取的最佳工艺为：萃取温度45℃、萃取压力25 MPa、CO2流量220 L/h、萃取时间80 min。在此条件下,山苍子核仁油萃取率84.5%。研究证明了加入溶剂和剥壳均可提高山苍子核仁油的萃取率。     

超临界CO2和植物油脱臭馏出物相平衡研究

研究了植物油脱臭馏出物在超临界CO2中的相平衡问题。基于组分的相似性把含有复杂组分的植物油脱臭馏出物简化为两种虚拟组分,用改进的混合规则和超临界组分的能量参数计算式,结合PR状态方程进行计算：理论计算与实验数据相吻合,为间歇式或连续逆流式超临界CO2萃取分离的设计提供了依据。     

合成纤维的超临界二氧化碳染色

传统染色工艺使用大量的水,存在环境污染严重及资源消耗、浪费大的问题,有机溶剂作染色介质也存在生态、成本问题等,很难工业化应用。超临界二氧化碳流体染色作为一种新型染色技术越来越得到关注。本文介绍了超临界流体的性质及其染色工艺的特点,讨论了分散染料在超临界二氧化碳中的溶解和分散性,分析了三种合成纤维在超临界二氧化碳流体中染色研究现状、应用趋势和存在问题。     

Rapid Hydrogenation of Aromatic Nitro Compounds in Supercritical Carbon Dioxide: Mechanistic Implications via Experimental and Theoretical Investigations

An exceptionally rapid hydrogenation of nitrobenzene to aniline [TOF=252,000 h⁻¹] over palladium containing MCM‐41 (Pd/MCM‐41) with excellent yield of >99% can be achieved in supercritical carbon dioxide at 50 °C and a hydrogen pressure of 2.5 MPa. It has been observed that this promising method preferred a single phase between liquid substrate and carbon dioxide‐hydrogen system. The ascendancy of the supercritical carbon dioxide medium is established in comparison with the conventional organic solvent and solvent‐less conditions. Changes in the reaction parameters such as carbon dioxide and hydrogen pressure, temperature and the reaction time do not affect the selectivity. A combined experimental and theoretical study has elucidated the mechanism under the studied reaction condition because experimental observations revealed a direct conversion of nitrobenzene to aniline. However, density functional theory (DFT) calculation shows that the direct conversion is energetically unfavourable; hence, a stepwise mechanism has been proposed. Theoretical predictions and experimental observations suggested that the rate‐limiting step of nitrobenzene conversion is different from that of the liquid phase hydrogenation. This catalytic process can also be successfully extended to the hydrogenation of other aromatic nitro compounds with different substituents. Easy separation of the liquid product from catalyst and the use of an environmentally friendly solvent make this procedure a viable and an attractive green chemical process.