煤系高岭土水热合成介孔材料

以煤系高岭土为硅源,十六烷基三甲基溴化铵（CTABr）为模板剂,水热合成得到介孔材料。并用傅里叶变换红外光谱（FTIR）、扫描电子显微镜（SEM）、高分辨透射电子显微镜（HRTEM）和N2吸附脱附等测试手段对产物进行表征。结果表明合成的介孔材料骨架上具有Si—O、Si—OH和Si—O—Si等介孔材料特征结构,材料BET比表面积为1070 m2/g,孔径分布在3.82 nm处出现峰值。     

介孔TiO2的水热法制备及表征

以廉价的工业级偏钛酸为原料,采用水热法制备了锐钛矿型介孔TiO2,考察了水热温度和水热时间对TiO2晶粒度的影响,并对TiO2进行了N2吸附-脱附、SEM及TG-DTA表征,结果表明,水热温度对TiO2晶粒度的影响较大而水热时间影响较小,纳米尺寸的TiO2晶体在聚乙二醇模板剂的作用下组装为微米级的介孔TiO2,平均介孔...     

二氧化碳超临界萃取乙基香兰素粗制品的研究

采用二氧化碳超临界萃取乙基香兰素粗品,研究萃取压力、萃取温度、萃取时间、流体流量等工艺条件对萃取效率和产品质量的影响.得出最佳工艺条件,采用萃取压力25～30 MPa,萃取温度55～60℃,流体流量5 L/h,萃取5～6 h,萃取效率可以达到95％,可以得到质量分数大于95％的乙基香兰素产品.     

Continuous extraction of glycerol acetates from their mixture using supercritical carbon dioxide

Supercritical carbon dioxide was used for partially selective extraction of triacetin from a mixture of triacetin, diacetin, and monoacetin with a molar ratio of 1:2:1. The extraction was carried out in two stages. In the first stage, a central composite design was used to optimize the four variables of pressure, temperature, liquid CO₂ flow rate, and extraction time at three levels using a semi-continuous, supercritical carbon dioxide extraction setup. The composition of the extract under the predicted optimum conditions (i.e., 109 bar, 56 °C, 0.86 mL min⁻¹, and 61 min) was about 69% triacetin accompanied by only 30% diacetin and no detectable monoacetin. In the second stage, the effect of the two factors, pressure (100, 109, and 140 bar) and liquid CO₂ flow rates of 0.86 and 1.5 mL min⁻¹ measured at average laboratory temperature (27 °C) and pressure (0.89 bar), were studied using a continuous, supercritical carbon dioxide fractionation setup equipped with a glass-bead packed column kept under a thermal gradient of 56-70 °C. The experimental design was organized as a 3 × 2 general factorial design. Under the best conditions (i.e., 140 bar and 1.5 mL min⁻¹), the extraction yield of triacetin and diacetin were 41.8 and 3.0%, respectively, without any detectable monoacetin as verified by GC-FID.     

Determination and calculation for solubility of m-nitroaniline and its mixture in supercritical carbon dioxide

Equilibrium solubility of m-nitroaniline and p-nitroaniline in supercritical carbon dioxide (SCCO₂) is essential to design the process of SCCO₂ extraction and to investigate the effect of each solute on the solubility in SCCO₂ ternary system. However, the solubility data is not reported so far. We performed the solubility measurements at the temperatures of 308–328 K and in the pressure range of 11.0–21.0 MPa. The experimental results showed the solubility of m-nitroaniline and p-nitroaniline was enhanced in m-nitroaniline + p-nitroaniline + SCCO₂ ternary system. The improvement factor (i), separation factor (μ) and separation efficiency (HE) in the ternary system were defined and calculated, and the best separation result could be obtained at 21.0 MPa and 328 K using SCCO₂ extraction, where the separation efficiency was up to 90.9%. Based on the chemical association theory, a new model was developed to calculate the solubility of mixed solutes in SCCO₂. The correlation result of the new model was tested by about 500 solubility data from 15 kinds of two solutes mixtures in SCCO₂. The correlated result showed that the new model could achieve much better AARD (%) than those of frequently used Sovova and Sovova-T models.     

Hydrothermal synthesis and characterization of Fe(III)-substituted mordenites

Fe-substituted mordenites were synthesized hydrothermally, partially substituting iron atoms for the framework aluminum of mordenite. XRD, SEM, IR, UV-VIS DRS, ESR, XAS, and catalytic activity studies provided the evidence of Fe³⁺ present in the zeolite framework. The framework IR bands were shifted to lower frequencies as Fe³⁺ ions incorporated into the lattice, and a new Si-O-Fe bond vibration was located near 668 cm^?1. The presence of a signal at g=4.3 in the ESR spectra was assigned to Fe³⁺ isomorphously substituted in the tetrahedral position. EXAFS at the Fe K-edge revealed that the Fe³⁺ ions were present in the zeolite framework in a four-fold coordination with an average Fe-O distance of 1.86 Å. In the UV-vis spectra, an absorption was observed at 375.7 nm which was assigned to the presence of Fe³⁺ in the zeolite framework. A toluene alkylation study reflected that the acidity strength of mordenite is weakened due to the presence of lattice iron species.     

Influence of reaction parameters on synthesis of temperature-sensitive materials in supercritical carbon dioxide by precipitation polymerization

Summary Temperature-sensitive materials were prepared by free radical precipitation copolymerization of N-isopropylacrylamide (NIPA) with acrylic acid (AA) or 1-vinyl-2-pyrrolidone (VP) in supercritical carbon dioxide (scCO₂). Dry, fine, powdered, nano-sized polymer product was produced at 70 °C and pressures ranged from 150 to 400 bar. The resulting high yield (>96%) of temperature-sensitive microgels was obtained in the absence of stabilizer. The effects of comonomer, reaction pressure and reaction time on the yield and morphology of the copolymers have been investigated. It was found that solubility of NIPA in scCO₂ was remarkably enhanced in the presence of comonomers. The morphology of polymers could be controlled conveniently by changing reaction parameters. In addition, the reaction could be completed in short time in the presence of divinyl monomer.     

二氧化碳加氢合成甲醇反应铜基催化剂研究进展

二氧化碳加氢合成甲醇反应是二氧化碳利用的重要途径,其中催化剂的研究是技术的关键。本文针对反应采用的铜基催化剂,从铜基催化剂的制备方法、活性组分铜的分散度、铜粒径以及铜与载体间界面作用等方面,分别对其影响催化剂的活性、甲醇的选择性以及稳定性作用进行研究综述。通过分析认为:催化剂的制备方法影响催化剂的铜分散度、铜粒径及铜与载体间的作用,从而影响催化剂催化性能。其中在共沉淀法的基础上进行改进是目前催化剂制备方法的研究趋势,且增加铜分散度、减小铜粒径及增大铜与载体间作用对二氧化碳加氢合成甲醇反应铜基催化剂的催化性能有不同程度的影响。该综述为进一步研制高活性、高甲醇选择性和优异稳定性的新型催化剂提供参考。     

Hydrogenation of carbon dioxide by hybrid catalysts,direct synthesis of aromatics from carbon dioxide and hydrogen

Direct synthesis of aromatics from carbon dioxide hydrogenation was investigated in a single stage reactor using hybrid catalysts composed of iron catalysts and HZSM-5 zeolite. Carbon dioxide was first converted to CO by the reverse water gas shift reaction, followed by the hydrogenation of CO to hydrocarbons on iron catalyst, and finally the hydrocarbons were converted to aromatics in HZSM-5. Under the operating conditions of 350°C, 2100 kPa, and CO₂/H₅ = 1/2, the maximum aromatic selectivity obtained was 22% with a CO₂ conversion of 38% using fused iron catalyst combined with the zeolite. Together with the kinetic studies, thermodynamic analysis of the CO₂ hydrogenation was also conducted. It was found that unlike Fischer Tropsch synthesis, the formation of hydrocarbons from CO₂ may not be thermodynamically favored at higher temperatures.     

Synthesis, structural characterization and photocatalytic activity of Ti-MCM-41 mesoporous molecular sieves

This paper reports the applicability of hydrothermal synthesis in alkaline medium for preparation of Ti-containing mesoporous MCM-41 materials. The influence of different parameters was investigated, such as the Ti source, the molar ratio between Si and Ti and also the synthesis temperature. Structural analysis shows that the high specific surface area, large pore size and well ordered mesostructure, are partially retained in the titania containing materials. Modifying synthesis temperature, it was shown that MCM-41 isotherms are different for temperatures above or under 140°C. UV-VisDR spectroscopy was used to investigate the local environment of Ti sites. The obtained materials were evaluated for the photocatalytic degradation of Rhodamine 6G in aqueous medium. The best photocatalytic activity was found for the sample prepared at higher ageing temperature of 160°C, at which anatase particles were formed.     

Surface sol–gel modification of mesoporous silica molecular sieve SBA-15 with TiO2 in supercritical CO2

Mesoporous silica molecular sieve SBA-15 has been grafted with monolayer and doublelayer of titanium dioxide via surface sol–gel process in supercritical carbon dioxide (SC CO₂). The materials were characterized by nitrogen adsorption, X-ray photoelectron, X-ray diffraction (XRD), and Raman spectroscopy. The results suggest that the incorporated titanium dioxide is present mainly as anatase phase. The pore diameter decreases with the modification cycle number, and the titanium dioxide exists as a 5 Å thick film chemically anchored on the mesopores of SBA-15.     

二氧化碳催化转化在化学合成中的应用

二氧化碳的转化利用是C1 化学研究的前沿课题之一。综述了近年来CO2 催化转化在开发绿色合成工艺以及制备高附加值化工原料等方面的最新进展。     

Experimental determination and modeling of the phase behavior for the direct synthesis of dimethyl carbonate from methanol and carbon dioxide

This study focuses on the investigation of the phase behavior of mixtures relevant to the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. The bubble points of corresponding quaternary mixtures of varying composition were experimentally determined. The Cubic-Plus-Association (CPA) equation of state was applied to model the phase behavior of the experimentally studied systems. In this regard, the CPA binary interaction parameters were estimated based on experimental data for the corresponding binary systems available in the literature, and subsequently the model was applied to predict the phase behavior of the multicomponent systems. It was shown that CPA is capable of predicting the phase behavior of such complex systems containing polar and associating components at high temperatures and pressures with reasonable accuracy considering the non-ideality of such mixtures. The results reveal P–T regions where the system can exist in one single phase and where it is multiphase, which can be used for further optimization not only of the chemical reaction itself but also subsequent product separation processes.     

模板法制备有序中孔炭材料及其性能

以SBA-15为模板,蔗糖为炭源,在不同的炭化温度下合成了不同比表面积的中孔炭材料。利用红外光谱(IR), 小角X射线衍射(XRD), 透射电镜(TEM),N₂吸脱附及循环伏安测试等技术考察了不同炭化温度对中孔炭材料形貌、比表面积、孔体积及比电容的影响。结果表明：最佳炭化温度为700℃,TEM观测表明,700℃炭化所制备的样品孔结构呈二维六角有序分布,N₂吸脱附测试表明,该样品的孔体积为1.88 cm³•g^-1,比表面积为1394 m²•g^-1,具有典型的中孔结构和集中的中孔分布,它的最可几孔径为3.4 nm;采用循环伏安测试电极及电容器的电化学行为,结果显示,该样品单电极在6 mol•L^-1的KOH电解液中,扫描速度为1 mV•s^-1时,比电容可达212 F•g^-1,是一种理想的超级电容器电极材料。     

Equilibrium solubilities of a p-toluenesulfonamide and sulfanilamide mixture in supercritical carbon dioxide with and without ethanol

Supercritical separation processes for a multi-component mixture of solutes are of practical interest. In this study, the experimental equilibrium solubilities of two solute mixtures, p-toluenesulfonamide (p-TSA) and sulfanilamide (SNA), in supercritical carbon dioxide (SC CO₂) were measured at temperatures of 308, 318 and 328 K and pressures in the range of 11.0-21.0 MPa using a dynamic flow method. The effect of cosolvent on the multi-component system was investigated by the addition of a 3.5 mol% ethanol. In the ternary system (p-TSA + SNA + CO₂), the solubility of SNA increased as compared to its binary system (SNA + CO₂), while the solubility of p-TSA decreased. In the quaternary system (p-TSA + SNA + ethanol + CO₂), a significant solubility enhancement was observed for both p-TSA and SNA. The selectivity, which is thought to imply the intermolecular interactions between p-TSA and SNA, was also enhanced by the presence of ethanol so that the two solutes could be separated by a max. purity of 99.4%. The influence of the hydrogen bond interaction on solubility was discussed. The equations of Chrastil, Méndez-Santiago and Teja, and their modified forms were used to correlate the experimental data.     

Development of functional mesoporous microparticles for controlled drug delivery

Mesoporous microbeads can be easily obtained by radical polymerization of biocompatible glycerol dimethacrylate (GDMA) in supercritical carbon dioxide. Small mass density microparticles (ρ = 0.19-0.37 g cm⁻³) with controlled size (1-3 μm) and homogeneous morphology are obtained by the addition of different stabilizers to the polymerization media. The microbeads were obtained in quantitative yield as white, dry powders directly from the reaction vessel possessing a pollen-like morphology. The (S)-ibuprofen loading (up to 120 mg g⁻¹) and release profile from the PGDMA microbeads is highly promising which makes them potential drug delivery vehicles.     

Preparation, characterization, and supercritical carbon dioxide foaming of polystyrene/graphene oxide composites

Graphene oxide (GO) was prepared by oxidation of graphite using the Hummers method, and was modified by isocyanate to obtain dispersed GO sheets in dimethylformamide. Polystyrene (PS)/GO composites were prepared by solution blending, and their morphologies and properties were characterized. The addition of GO increased the glass transition temperature of the PS/GO composites. The storage modulus and thermal stability of the composites were also improved compared with PS. Foams of PS and PS/GO composites were prepared by supercritical carbon dioxide foaming. The composite foams exhibited slightly higher cell density and smaller cell size compared with the PS foam, indicating the GO sheets can act as heterogeneous nucleation agents.     

Cu基CO2合成甲醇催化剂载体的研究进展

氧化物载体与Cu之间的相互作用、CO₂的活化位点、表面反应机理、表面反应路径直接影响CO₂催化加氢的产物分布。因此,探明不同金属–载体的相互作用和界面微观结构至关重要。本文综述了CO₂催化加氢合成甲醇Cu基催化剂载体的研究现状,重点综述了ZnO、ZrO₂、CeO₂、TiO₂这4种具有氧空位的载体,并简单总结了SiO₂、Al₂O₃、Zn-Zr、Ce-Zr、钙钛矿等其他氧化物载体。Cu与ZnO之间的强金属相互作用（SMSI）所形成的Cu/ZnO_x是主要的活性位点,对其微观结构与反应机理研究得较为充分;对Cu/ZrO₂的研究主要集中在ZrO₂晶相的影响,不同的研究者所获得的结论尚存在争议;对Cu/CeO₂的机理研究停留在反向CeO₂/Cu(111)模型表面,负载型催化剂上不同晶面的CeO₂与Cu的相互作用强度不同,并影响反应性能;Cu/TiO₂中TiO₂的影响因素较多,如晶型、晶面等,目前对其研究尚不全面。最后,本文分析并展望了CO₂加氢制甲醇催化剂载体的研究方向,未来将采用与实际催化剂一致的正向模型表面进行基础研究,并基于原位表征手段对反应过程中催化剂的结构变化进行探索,最终设计高效、低成本的多元复合物载体的Cu基催化剂。     

Hydrothermal conversion of glucose in multiscale batch processes. Analysis of the gas,liquid and solid residues

Hydrothermal conversion is an interesting process to transform (very) humid biomass into high energy vectors or valuable products in the liquid or solid state. In the supercritical domain, water becomes a solvent for organics as well as a reactant, and thus the cellulosic content is effectively hydrolyzed into glucose, largely considered as its model molecule.The kinetics of glucose decomposition during the heating step in the batch reactor were investigated through the analysis of glucose concentration. Glucose reacts totally before reaching the supercritical point of water. Among the operating parameters that influence supercritical water gasification, this paper presents only the effect of reaction temperature through gas composition, liquid carbon content and structure of the solid. Glucose gasification in a batch process (5 wt% glucose, 0.5 wt% catalyst, 600 °C, 25 MPa, 60 min) produced 1.5 mol of hydrogen per mol of glucose. The gas has energetic properties (H₂, CH₄, C₂H₆) while the liquid contains substances that could be used as platform molecules (5-HMF). The solid phase is composed of carbon (almost pure) in two distinct phases: spherical nanoparticles and an amorphous phase.