Catalytic combustion of benzene over metal oxides supported on SBA-15

The catalytic combustion of benzene over metal oxides supported on SBA-15 was investigated. The catalysts were prepared by the incipient wetness method and characterized by XRD, BET, TEM, ESR and TPR. The calcined siliceous SBA-15 and CuO/SBA-15 samples displayed well-resolved patterns with a sharp peak at about 1.0°. It is clear that the loading of CuO on the silica matrix drastically decreases the surface area and pore volume of the catalysts, as would be expected for the incorporation of CuO. Among the supported metal oxides, CuO supported on SBA-15 was found to have the highest activity for benzene oxidation. In addition, copper oxide supported on SBA-15 gives higher catalytic activity than copper oxide supported on MCM-41. From the ESR results, the CuO dispersed on the SBA-15 acts as the active site of the CuO/SBA-15 catalysts in the oxidative decomposition of benzene. The catalytic activity gradually increases with increasing CuO loading on SBA-15.     

Phase transition of mesoporous SiO<Subscript>2</Subscript> impregnated with an organic templating agent by post-synthetic microwave heating

Mesoporous silica SBA-15 samples were subjected to microwave heating for 10–40 min at 393 and 443 K after dry-impregnation with TPAOH (tetrapropylammonium hydroxide) to prepare a mesoporous material with zeolytically ordered pore walls. Physicochemical properties of the materials prepared were characterized by XRD, N₂ adsorption at 77 K, SEM, TEM, UV–vis and FT-IR spectroscopies. These investigations revealed that selective transformation of amorphous pore walls of SBA-15 to crystalline zeolytic phase is difficult to be achieved and a mixed phase of mesoporous silica/zeolite composite material was obtained, instead. Microwave heating time, temperature, TPAOH concentration, and hydrothermal stability of the mesoporous host materials tested (MCM-41, HMS, and SBA-15) were important factors to maintain the mesopore structure of the host materials during the post-synthetic microwave heating treatment.     

Stepwise growth of melamine-based dendrimers into mesopores and their CO2 adsorption properties

A series of CO₂ adsorbents were synthesized by functionalizing SBA-15 via stepwise growth of amine-terminated melamine-based dendrimers. The adsorbents contained very high organic loadings (up to 50.3 wt%) relative to previous reports. In addition to that, CO₂ adsorption measurements demonstrated that primary amine groups are the only active groups within these dendritic structures for CO₂ adsorption. The CO₂ adsorption capacities of these adsorbents (except for fourth generation dendrimer functionalized SBA-15) are improved relative to the unfunctionalized SBA-15. The exception is associated with the completely filled pores of this adsorbent.     

Promoting the CO2 adsorption in the amine-containing SBA-15 by hydroxyl group

Novel CO₂ capturer with a high efficiency is fabricated through dispersing the amine mixture of tetraethylenepentamine (TEPA) and diethanolamine (DEA) or glycerol within the as-synthesized mesoporous silica SBA-15, and the resulting sample is characterized by low angle X-ray diffraction and N₂ adsorption to evaluate the distribution of the guest. The influence of hydroxyl group on the CO₂ adsorption capacity of the composite is investigated by using CO₂-TPD and TG–MS techniques. The hydroxyl group of the P123 ((EO)₂₀(PO)₇₀(EO)₂₀, template preserved in as-synthesized SBA-15) and the guest could promote the capture of CO₂ by the amine through changing the interaction mechanism. In addition, the presence of hydroxyl group promotes the formation of the intermediate between CO₂ and the amine with a lower thermal stability hence the CO₂ trapped by the composite is easier to be desorbed and thus the regeneration of adsorbent is facilitated. Therefore, using this mixed amine (TEPA and DEA) modified as-synthesized SBA-15 as CO₂ capturer not only saves the energy for removal of template, but also cut down the cost in the preparation and regeneration of CO₂ capturer, which is critical in CO₂ separation and capture.     

Gold nanoparticles stabilized in a novel periodic mesoporous organosilica of SBA-15 for styrene epoxidation

The stabilization of gold nanoparticles (GNPs) by disulfide groups linked to imidazolium chloride units in a periodic mesoporous organosilica of SBA-15 and their catalytic performances in the epoxidation of styrene were investigated. The mesoporous organosilica (PMO-SBA-15) was synthesized via a one-pot condensation process involving the assembly of ionic liquid silsesquioxane organic precursor containing disulfide group and tetraethoxysilane (TEOS) in the presence of P123 (EO₂₀PO₇₀EO₂₀). Aqueous chloroaurate ions were in situ reduced by the silanol groups presented on the channel surface of the mesoporous organosilica to form GNPs that were subsequently captured by disulfide group to obtain Au-containing mesoporous organosilica (Au-PMO-SBA-15). The PMO-SBA-15 and Au-PMO-SBA-15 were characterized by XRD, ²⁹Si MAS-NMR, FT-IR, UV–vis, TEM and N₂ adsorption–desorption measurements. It was found that both PMO-SBA-15 and Au-PMO-SBA-15 had the typical characteristics of mesoporous SBA-15, and that the GNPs entrapped into the channels of Au-PMO-SBA-15 possessed mean size of ca. 1.8 nm. The Au-PMO-SBA-15 was used as a catalyst in the epoxidation of styrene. 95% of styrene conversion and 75% of selectivity to styrene epoxide were obtained over the novel Au-PMO-SBA-15 catalyst, which were higher than that over the reported nano-Au catalysts. Furthermore, the Au-PMO-SBA-15 could be conveniently recovered for recycled use without significant loss of catalytic activity and selectivity.     

Promotion effect of cerium and lanthanum oxides on Ni/SBA-15 catalyst for ammonia decomposition

CeNi/SBA-15 and LaNi/SBA-15 catalysts were prepared by deposition–precipitation (DP) method and characterized by N₂ physical adsorption, XRD, H₂-TPR, H₂-chemisorption and TEM. Their catalytic performances in the ammonia decomposition reaction were tested and compared with Ni/SBA-15 catalyst. Addition of cerium and lanthanum oxides to the Ni/SBA-15 catalyst caused some decrease of BET surface area and pore volume of the catalysts, but led to a promotion effect to their catalytic activity which was closely related to the ratio of Ce (La)/Ni. The highest conversion of ammonia could be obtained when the Ce (La)/Ni ratio was around 0.3. The promotion effect is more evident on CeNi/SBA-15(0.3) than on LaNi/SBA-15(0.3) catalyst under identical reaction conditions. The CeNi/SBA-15 and LaNi/SBA-15 catalysts show smaller nickel particle size and easier reducibility in comparison with the Ni/SBA-15 catalysts.     

EA-MS测试过程中添加助燃剂的影响效应研究

利用元素分析-质谱仪(EA-MS)联用系统,探讨对高C/N植物样品测试过程中添加助燃剂对样品氮同位素比值、氮含量和仪器本底的影响。在植物样品中添加CuO或者V₂O₅,测定的氮同位素组成结果表明：添加助燃剂导致样品测试的结果偏差更小,这与测试过程中植物样品能够完全燃烧有关;添加助燃剂使测试的氮含量高于不添加助燃剂的情况,同时仪器本底也能迅速降低,说明助燃剂的添加有助于样品在瞬间燃烧,因此使测试结果更为精确;不同助燃剂的添加对植物氮同位素比值结果的影响程度不同,与不添加助燃剂的情况相比,CuO的添加使得同位素比值偏正,而V₂O₅的添加结果不具有规律性;在样品中添加CuO助燃剂（和植物样品以4∶1的质量比混合）,样品测试的同位素值偏差最小,测试结果也更加可信,样品本底可以达到连续做样而不影响测定下一样品的氮同位素组成。该方法简单、有效、投入较少,可以用于难以反应的样品分析中。     

A land use model of the effects of eco-labeling in coffee markets

International non-profit organizations have started to implement eco-labeling for credence attributes programs aimed to inform consumers about environmentally sound or “sustainable” production standards for various products. Using coffee labeled as “shade grown” or “bird friendly” as an example, this paper describes the impact such labeling programs may have on local land use patterns in coffee producing regions. Shade grown coffee farms should provide a variety of external benefits, including the preservation of biodiversity, carbon sequestration, the prevention of soil erosion and aquifer recharge. Those externalities, however, are not expected to have observable land use impacts unless they are capitalized in the coffee market. The prospect of market capitalization of externalities suggests the extension of the conventional von Thünen model to the calculation of social location rent. Using the maximization of social location rent as a criterion allows the externality effect to play a direct role in market-based land use allocation of land between eco-labeled shade grown coffee production and other activities.     

除氢处理对1Cr15Ni4Mo3N钢锻件疲劳性能的影响

研究了除氢处理对1Cr15Ni4Mo3N钢锻件疲劳性能的影响.1Cr15Ni4Mo3N钢锻造时可从加热气氛(油炉或天然气炉)中吸入氢,并导致锻件疲劳性能显著降低.结果表明:在淬火之前进行520℃×8h的除氢处理,可使1Cr15Ni4Mo3N钢锻件疲劳性能恢复至正常水平.     

冷压烧结制备Cu-15%Cr_2AlC复合材料的组织与性能研究

以自制的高纯Cr_2AlC陶瓷粉体为原料,采用冷压真空烧结技术制备了Cu-15%Cr_2AlC(质量分数)复合材料。研究了不同压制压力、烧结温度及烧结时间对复合材料的电阻率、热导率、摩擦因数以及材料的断裂方式和组织结构的影响。结果表明:随着压制压力的增大、烧结温度的升高,复合材料的电阻率、摩擦因数呈下降趋势,热导率逐渐升高;随着烧结时间延长,复合材料的电阻率逐渐降低,摩擦因数先降低后升高,热导率先升高后降低;复合材料的断裂方式均为脆性断裂;随着烧结温度的提高、烧结时间的延长,Cr_2AlC与Cu发生固溶强化效应,引起Cr_2AlC晶格常数畸变。