不同载体的TiO2光催化剂降解亚甲基蓝动力学研究

分别以活性炭(AC)和色氨酸(L-Trp)作为两种不同类型载体,通过溶胶-凝胶法制得TiO₂/AC和TiO₂/L-Trp光催化剂,比较了两种载体对亚甲基蓝(MB)吸附和光降解反应的性能影响,分析了其反应机理,并对光催化剂进行了表征分析。实验结果表明,TiO₂/AC和TiO₂/L-Trp的最优煅烧温度均为550℃,最优用量均为1 g/L。表征结果表明,TiO₂/AC和TiO₂/L-Trp均负载了以锐钛矿型存在的TiO₂,TiO₂/AC比表面积大于TiO₂/L-Trp。动力学拟合结果表明TiO₂/AC和TiO₂/L-Trp光催化剂光降解MB受其扩散步骤控制。     

硅酸钠模数对SiO2气凝胶结构和表面改性机制的影响

以粉煤灰为原料制备五种不同浓度的硅酸钠溶液,采用溶胶-凝胶法对硅酸钠溶液进行处理,在常压干燥条件下获得了疏水性SiO₂气凝胶。通过测试气凝胶的密度、比表面积和接触角,研究了硅酸钠溶液模数m对气凝胶结构的影响,阐述了气凝胶表面疏水改性的亲核取代S_N1化学反应机制。研究结果表明,气凝胶的疏水性能与其表面连接的硅甲基—Si—(CH₃)₃数目有直接关系,当硅酸钠模数m=2.50时,气凝胶的疏水性能最佳。气凝胶的密度和比表面积均随硅酸钠模数的增大而增大,当硅酸钠模数m=0.75时,气凝胶的密度和比表面积最小,其值分别为0.073 9 g/cm³和588.5 m²/g。     

半纤维素/TiO2复合凝胶的光催化降解性能

以半纤维素和TiO₂纳米粒子为原料制得半纤维素/TiO₂复合凝胶。分别用红外光谱分析和扫描电镜对复合水凝胶进行了表征,分析表明半纤维素上成功接枝聚丙烯酸,凝胶呈现多孔结构,且随着TiO₂含量的增加凝胶孔径减小。考察了半纤维素/TiO₂复合凝胶的溶胀性能以及对亚甲基蓝的光催化降解性能,研究表明半纤维素/TiO₂复合凝胶的溶胀率随着TiO₂粒子含量的增加而减小,随着pH的增大先增大后减小;对亚甲基蓝染料的降解率随着TiO₂含量的增加先增大后减小,随着pH的增大先增大后减小,随着亚甲基蓝初始浓度的增大而增大。     

乳液法结合溶胶-凝胶法制备多孔TiO2微球

为了进一步提高二氧化钛（ TiO₂）的反射率,采用乳液法结合溶胶 -凝胶法,以聚乙二醇（PEG）为相分离诱导剂,制备了内部具有不连续多孔结构的 TiO₂微球。考察了 PEG的添加量对 TiO₂微球内部孔径大小的影响。研究结果表明： TiO₂微球内部的孔径随 PEG的用量增加而增大。基于溶胶-凝胶转变和相分离过程,详细介绍了多孔 TiO₂微球的形成机理。当 PEG的添加量为 9.0%时,所制备的多孔 TiO₂微球在近红外区的积分平均反射率为 84.9%,比常见钛白粉提高了 5.4%。     

含钛高炉渣制备SCR烟气脱硝催化剂

以含钛高炉渣为原料,稀硫酸为溶剂提取钛液,钛液经水解、高温焙烧后制得高比表面积的TiO₂,并以其为载体采用分步浸渍法制备了V₂O₅-WO₃/ TiO₂催化剂。优化了含钛高炉渣的酸解条件,对所得TiO₂进行了XRD、XRF、BET表征,用自制催化剂评价系统考察了所制备催化剂的脱硝性能及抗硫抗水性能。结果表明：H₂SO₄浓度40%、酸渣比1.5、酸解温度80℃、酸解时间3 h条件下,TiO₂浸出率可达90%,水解产物主要为锐钛型TiO₂,纯度达到74%,含有21.2%无定形SiO₂及少量其他杂质。SiO₂的存在提高了产物的比表面积、孔径,有利于活性组分的负载。以含钛高炉渣基TiO₂为原料制备的V₂O₅-WO₃/TiO₂脱硝催化剂相比于以商业TiO₂和TiOSO₄制备的催化剂,在250～450℃具有更高的催化活性,且在300℃具有较好的抗硫抗水性能。     

共聚法制备疏水性SiO2气凝胶

以正硅酸乙酯为原料,应用溶胶-凝胶两步催化,甲基丙烯酸基丙基三甲氧基硅烷作为改性剂,无水乙醇为溶剂,共聚法常压下制备疏水性SiO₂气凝胶。运用原位红外在线监测反应历程,确定制备工艺步骤。运用N₂吸附仪、扫描电镜、红外光谱、TG-DSC对SiO₂气凝胶孔径分布、形貌、表面官能团及热稳定性进行分析。结果表明,经甲基丙烯酸基丙基三甲氧基硅烷改性的SiO₂气凝胶疏水性能良好,疏水的耐温性可达到407℃,比表面积为877.17 m²·g^-1, 由球形纳米颗粒堆积而成,颗粒尺寸范围在10～50 nm,孔径集中分布在1.9相似文献   

Mn、Ce负载顺序对催化剂Mn-Ce/TiO2低温脱硝活性的影响

采用溶胶凝胶法制备了一系列Mn-Ce/TiO₂催化剂样品, 并用比表面积及孔径分析仪(BET)、X射线衍射仪(XRD)和扫描电子显微镜(SEM)等对催化剂进行了表征, 考察了活性组分Mn、Ce负载顺序对催化剂结构的影响, 并在固定床连续流动反应器上对其催化活性进行了评价。结果表明, 催化剂晶相均为锐钛矿型结构, Mn、Ce活性组分在载体表面高度分散或形成了无定形结构;Mn、Ce同时负载时催化剂表面活性组分分布均匀, 比表面积最大, 为97.6m²/g, 且催化剂孔径分布以中孔为主;Mn、Ce同时负载时催化剂活性最好, 反应温度为200℃时, NO转化率达到90%以上。     

分子印迹-TiO2光电催化降解增溶PHE废水性能研究

分别以菲(PHE)、非离子表面活性剂曲拉通X-100及两者的混合物作为模板,钛酸正丁酯为功能单体,通过溶胶-凝胶法,制备得到三种分子印迹-TiO₂[MIP-(TX-100)TiO₂,MIP-(PHE)TiO₂,MIP-(TX-100+PHE)TiO₂],并且制备对应的薄膜电极,用于光电催化处理模拟土壤淋洗增溶废水PHE。通过XRD、氮气吸附脱附、SEM对MIP-TiO₂材料及其薄膜电极进行性能表征。结果表明,MIP-(TX-100)TiO₂中,TX-100印迹分子的引入会改变晶体结构,出现金红石晶相TiO₂,且其比表面积达到63.533 m²/g,TiO₂颗粒大小及分散性较为良好,团聚现象也得到了一定的改善,其对TX-100 (5 g/L)增溶的PHE (30 mg/L)溶液光电催化降解率可达74.45%。MIP-(TX-100)TiO₂电极对增溶废水PHE的吸附过程更...     

毛竹纳米纤丝化纤维素球形气凝胶的制备和表征

以毛竹(Phyllostachys heterocycla cv.Pubescens)为原料,采用落球法制备纳米纤丝化纤维素(NFC)球形水凝胶,溶剂置换和超临界CO2干燥后得到了NFC球形气凝胶。通过透射电子显微镜(TEM)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)和BET对NFC球形气凝胶的微观形貌、化学态、结晶结构和孔隙结构进行表征分析。研究结果表明,NFC水凝胶和气凝胶均为球形,其化学组成和结晶结构均与天然纤维素一致,NFC气凝胶的骨架通过丝状纳米纤丝化纤维素缠绕和聚集形成三维网络结构,NFC气凝胶具有较高的比表面积和孔隙体积,分别为173 m2/g和0.62 cm3/g。     

多级孔ZrO2/TiO2/ZSM-5分子筛的合成及吸附-光催化协同性能

以碱酸改后的凹凸棒土为硅源,利用溶胶-凝胶法将 TiO₂和 ZrO₂负载于一步水热合成的多级孔 ZSM-5 分子筛表面,形成多级孔 ZrO₂/TiO₂/ZSM-5 分子筛。通过 XRD、SEM 和 N₂吸附-脱附仪等手段对样品进行表征,研究 TiO₂和 ZrO₂掺杂对多级孔 ZSM-5骨架结构、形貌及孔道的影响,并对亚甲基蓝溶液进行实验,探究其吸附-光催化协同性能。结果表明：ZrO₂负载促进了锐钛矿 TiO₂的形成,同时利用分子筛的多级孔道和比表面积提高了底物富集能力。当反应进行 20 min时,TiO₂掺杂量为 10% 的 TiO₂/ZSM-5 分子筛光催化降解效率达 73%;进一步掺杂 ZrO₂,ZrO₂/TiO₂/ZSM-5 分子筛光催化反应效率提高至 96.2%,说明 ZrO...     

Preparation and characterization of nitrogen-doped mesoporous titania with high specific surface area

Nitrogen-doped mesoporous titania aerogel photocatalysts were prepared by supercritical drying technique with carbon dioxide (SCCO₂) and calcination the urea impregnated TiO₂ aerogel at 773 K under NH₃ or N₂ + NH₃aq gaseous atmosphere. The pore properties were investigated from nitrogen adsorption measurement at 77 K. The prepared N-doped TiO₂ aerogel had a high specific surface area (116 m²/g), a total pore volume (0.33 cm³/g) and a sharp pore radius distribution (r_peak = 4.2 nm). The doping of the nitrogen atom into the TiO₂ lattice is expected from X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), and UV–Vis spectroscopy. Nitrogen states in the lattice and crystalline structure were measured using X-ray photoelectron spectroscopy and X-ray diffractometry. The N-doped TiO₂ aerogel absorbed well into the visible region up to 600 nm.     

Maya crude hydrodemetallization and hydrodesulfurization catalysts: An effect of TiO2 incorporation in Al2O3

Hydrotreating of Maya heavy crude oil over high specific surface area CoMo/TiO₂–Al₂O₃ oxide supported catalysts was studied in an integral reactor close to industrial practice. Activity studies were carried out with Maya crude hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodenitrogenation (HDN), and hydrodeasphaltenization (HDAs) reactions. The effect of support composition, the method of TiO₂ incorporation, and the catalyst deactivation are examined. Supported catalysts are characterized by BET specific surface area (SSA), pore volume (PV), pore size distribution (PSD), and atomic absorption. It has been found that sulfided catalysts showed a wide range of activity variation with TiO₂ incorporation into the alumina, which confirmed that molybdenum sulfided active phases strongly depend on the nature of support. The pore diameter and nature of the active site for HDS, HDM, HDN, and HDAs account for the influence of the large reactant molecules restricted diffusion into the pore, and/or the decrease in the number of active sites due to the MoS₂ phases buried with time-on-stream. The textural properties and hysteresis loop area of supported and spent catalysts indicated that catalysts were deactivated at the pore mouth due to the metal and carbon depositions. The atomic absorption results agreed well regarding the textural properties of spent catalysts. Thus, incorporation of TiO₂ with γ-Al₂O₃ alters the nature of active metal interaction with support, which may facilitate the dispersion of active phases on the support surface. Therefore, the TiO₂ counterpart plays a promoting role to HDS activity due to the favorable morphology of MoS₂ phases and metal support interaction.     

Selective oxidation of hydrogen sulfide containing excess water and ammonia over vanadia–titania aerogel catalysts

A series of V₂O₅–TiO₂ aerogel catalysts were prepared by sol–gel method with subsequent supercritical drying with CO₂. The aerogel catalysts showed much higher surface areas and total pore volumes than V₂O₅–TiO₂ xerogel and impregnated V₂O₅–TiO₂ catalysts. Two species of surface vanadium in the aerogel catalysts were identified by Raman measurements: monomeric vanadyl and polymeric vanadates. The selective oxidation of hydrogen sulfide in the presence of excess water and ammonia was studied over these catalysts. Aerogel catalysts showed very high conversion of H₂S without harmful emission of SO₂. Temperature programmed reduction (TPR), XRD and Raman analyses revealed that the high catalytic performance of the aerogel catalysts originated from their highly dispersed VO_x species and high reducibility.     

Effects of hydrothermal temperature and time on the photocatalytic activity and microstructures of bimodal mesoporous TiO2 powders

Bimodal nanocrystalline mesoporous TiO₂ powders with high photocatalytic activity were prepared by a hydrothermal method using tetrabutylorthotitanate (TiO(C₄H₉)₄, TBOT) as precursor. The as-prepared TiO₂ powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and N₂ adsorption–desorption measurements. The photocatalytic activity of the as-prepared TiO₂ powders was evaluated by the photocatalytic degradation of acetone (CH₃COCH₃) under UV-light irradiation at room temperature in air. The effects of hydrothermal temperature and time on the microstructures and photocatalytic activity of the TiO₂ powders were investigated and discussed. It was found that hydrothermal treatment enhanced the phase transformation of the TiO₂ powders from amorphous to anatase and crystallization of anatase. All TiO₂ powders after hydrothermal treatment showed bimodal pore-size distributions in the mesoporous region: one was intra-aggregated pores with maximum pore diameters of ca. 4–8 nm and the other with inter-aggregated pores with maximum pore diameters of ca. 45–50 nm. With increasing hydrothermal temperature and time, the average crystallite size and average pore size increased, in contrast, the Brunauer-Emmett-Teller (BET) specific surface areas, pore volumes and porosity steadily decreased. An optimal hydrothermal condition (180 °C for 10 h) was determined. The photocatalytic activity of the prepared TiO₂ powders under optimal hydrothermal conditions was more than three times higher than that of Degussa P25.     

钛-硅复合氧化物比表面积的影响因素研究

以无机盐为原料采用溶胶-凝胶法制备了钛-硅复合氧化物（TiO₂-SiO₂）。利用氮气吸附-脱附法对复合氧化物进行了比表面积分析。考察了原料配比、加料方式、表面活性剂、反应温度、老化温度、老化时间、焙烧温度等因素对复合氧化物比表面积的影响。综合结果表明：当二氧化钛质量分数为22%、添加剂为十六烷基三甲基溴化铵（CTAB）、反应温度为30 ℃、老化温度为70 ℃、老化时间为1 h、焙烧温度为150 ℃时,制备的复合氧化物的比表面积为361.4 m²/g、孔容为1.18 cm³/g、平均孔径为13.0 nm。不同因素对比表面积均有一定的影响,依据规律可以实现复合氧化物比表面积的可控调变。     

羟甲基化木质素/纤维素气凝胶粒子的制备、表征及吸附性能

以羟甲基化木质素和纤维素为原料,NaOH/尿素水溶液为溶解体系,采用冷冻干燥法制备羟甲基化木质素/纤维素气凝胶粒子。采用扫描电子显微镜（SEM）、傅里叶变换红外光谱（FT-IR）仪、X射线衍射（XRD）仪、比表面积及孔径分析仪等对其结构进行了表征。研究结果表明：羟甲基化木质素分子通过氢键作用附着在纤维素骨架上,气凝胶内部仍保持三维网状结构,羟甲基化木质素的引入使得气凝胶表面出现明显收缩,网状结构的致密度随着羟甲基化木质素用量提高而逐渐降低;同时气凝胶粒子具有纤维素Ⅱ型红外吸收峰和XRD衍射峰;粒子表现出Ⅱ型吸附/脱附等温线,孔径均在15 nm以下,且随着羟甲基化木质素用量不断提高,比表面积、孔容均有所减小,HKL-4的比表面积为105.3m²/g,孔容为0.336 6cm³/g,孔径为13.67nm。吸附性能分析表明在25℃下吸附5 h,HKL-4气凝胶粒子对金胺O、亚甲基蓝和罗丹明B的吸附量分别为33.06、96.06和43.26mg/g,对亚甲基蓝的饱和吸附量可达208.7 mg/g,吸附过程更符合Langmuir等温吸附模型,主要为单分子层吸附。     

High Surface-Area Ceria Aerogel

Ceria (CeO₂) aerogels with high surface area and high porosity have been prepared. Ce-methoxyethoxide diluted in excess methoxyethanol was slowly hydrolyzed to yield a gel, which was then supercritically dried in CO₂. Both as-synthesized and annealed aerogels were examined by X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy, and BET surface area and pore-size analyses. Thermal analysis of the as-synthesized gel showed it to contain only ∼5 wt% residual organics, which were removed by 300°C under oxygen. The unheated ceria aerogel was crystalline and exhibited a specific surface area of 349 m²/g with average pore diameter of ∼21.2 nm and 90% porosity. Heat treatment led to a reduction of porosity and pore size, as would be expected, but the extremely narrow pore-size distribution of the aerogel was retained.     

Structure and photocatalytic performance of TiO2/clay nanocomposites for the degradation of dimethachlor

In the present study TiO₂/clay composites were synthesized by dispersion of TiO₂ on the surfaces of a natural montmorillonite and a synthetic hectorite in order to increase the sorption ability of TiO₂ and therefore its photocatalytic action. Six materials with different loading in TiO₂ (15, 30 and 55 wt%) were prepared and characterized by several analytical techniques including XRD, BET and SEM analysis. The synthetic procedure allows the development of delaminated layers for hectorite–TiO₂ samples, while in the case of montmorillonite–TiO₂ composites we have the formation of a more lamellar-like aggregation. It was found that, the greater the percentage of TiO₂, the greater the pore volume and the specific surface area of the montmorillonite–TiO₂ samples. On the contrary, in the case of hectorite–TiO₂ samples, as the content of TiO₂ increases, the surface area and pore volume decreases. The photocatalytic efficiency of the nanocomposite catalysts was evaluated using a chloroacetanilide herbicide (dimethachlor) in water as model compound. The primary degradation of dimethachlor followed pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. All supported catalysts exhibit good photodegradation efficiency and their overall removal efficiency per mass of TiO₂ was better than that of bare TiO₂ produced by the sol–gel method. In conclusion, together with their good sedimentation ability the composite materials could be considered as a promising alternative for the removal of organic water contaminants.     

用废弃煤矸石制备高比表面积的SiO2-Al2O3二元复合气凝胶

以兖州煤矸石为原料,经过低温焙烧、酸浸除杂、碱熔活化,采用溶胶-凝胶法和真空干燥法制备完整的块状SiO₂-Al₂O₃二元复合气凝胶。通过X射线衍射、扫描电镜、傅里叶变换红外光谱、氮气吸附等检测手段对原料、SiO₂-Al₂O₃气凝胶及其制备过程中得到的中间产物的物理、化学特性进行表征,研究SiO₂-Al₂O₃凝胶的形成机制。实验结果表明,煤矸石经过酸浸除去了大部分的铁、钾、碱土金属等杂质。在经过碱熔活化后,煤矸石主要组分石英和高岭石均转化为非晶态,反应活性提高。制备得到的SiO₂-Al₂O₃气凝胶是以Si-O-Si、Si-O-Al网络结构为骨架的非晶态纳米颗粒聚集体,其堆积密度0.37 g·cm^-3,比表面积483 m²·g^-1,比孔容1.87 cm³·g^-1,平均孔径10.29 nm,最可几孔径9.32 nm,具有较好的介孔特征。