银离子修饰的介孔磷钨酸/二氧化硅催化剂氧化脱硫性能研究(英文)

采用银修饰介孔磷钨酸/二氧化硅(mesoporous HPW/SiO2)催化剂,并研究了其在模拟柴油和真实柴油氧化脱硫反应中的催化性能.通过银修饰介孔HPW/SiO2,结合银离子对有机硫化物的选择吸附性和HPW对有机硫化物的催化氧化活性,以达到选择氧化脱硫的目的.模拟柴油分别采用石油醚、苯、1-辛烯和二苯并噻吩配制,当银离子与HPW的摩尔比为2时,催化剂具有最高的选择催化氧化活性.采用N2 吸附-脱附、XRD、UV-vis和EDS表征了银修饰的介孔HPW/SiO2催化剂,结果表明,银物种分散均匀且以Ag+形式存在.真实柴油的脱硫研究表明,相比介孔HPW/SiO2催化剂,修饰的催化剂介孔Ag2-HPW/SiO2脱硫率提高了4.6%,初始硫含量为1800×10-6的直馏柴油能被脱除至228×10-6,脱硫率为87.3%.介孔Ag2-HPW/SiO2催化剂具有良好的再生性能,经再生处理后,Ag的损失量极少,其三次脱硫率达到84.8%.     

氨基化中空SiO2杂多化合物复合型催化剂的合成、表征及催化燃油深度脱硫性能

采用分散聚合法制得中空SiO₂微粒,将其氨基化后负载磷钨酸（HPW）,最终制得氨基化中空SiO₂磷钨酸复合型催化剂（NH₄PW-SiO₂）,并对催化剂进行了N₂吸附-脱附、傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）、扫描电子显微镜（SEM）和电感耦合等离子体原子发射光谱（ICP-OES）表征. 考察了以NH₄PW-SiO₂为催化剂,过氧化氢为氧化剂,乙腈为萃取剂的催化氧化萃取燃油深度脱硫性能. 探讨了催化剂用量、氧硫比、催化剂与氧化剂预接触时间、反应温度和初始硫含量对脱硫效果的影响. 结果表明,在催化剂用量为模拟油品质量的1.0%,氧硫摩尔比为15,催化剂与过氧化氢预接触4 min,反应温度为60 ℃,初始硫含量为350 mg/L的条件下,反应180 min时硫含量已降至2.45 mg/L,脱硫率达99.3%. 催化氧化萃取时的脱硫率比单纯萃取时的脱硫率高45.1%. 此外,催化剂用于真实汽油及柴油的催化氧化脱硫也得到了很好的脱硫效果,且催化剂重复使用5次后,脱硫效率未见明显降低.     

介孔硅胶在柴油氧化-吸附组合脱硫中的应用研究

以硅胶(SG)为吸附剂,采用自制的双亲催化剂与H₂O₂组成的催化氧化体系将柴油进行氧化,利用固定床动态吸附法考察了硅胶性质、氧化过程及吸附条件等对硅胶吸附脱硫性能的影响,并对硅胶进行了表征。小角XRD和氮气吸脱附结果表明,实验所用硅胶具有介孔结构。吸附脱硫实验结果表明,在油剂比(柴油与吸附剂的体积比)相同时,氧化-吸附脱硫过程脱硫率明显高于吸附脱硫过程脱硫率;选用硅胶作吸附剂,吸附温度为40℃,吸附空速为6.0 h^-1时脱硫效果较好,当油剂比为1时,脱硫率高达94.57%,且该介孔硅胶具有较大的吸附硫容,随油剂比增大下降缓慢,当油剂比增大到15时,脱硫率仍达85.89%。     

氨基修饰介孔SiO2的合成及对其对Hg2+、 Ni2+和Mn2+的吸附

利用介孔SiO₂微球（MSM）作为基底,对其表面进行氨基修饰,合成了氨基修饰介孔SiO₂微球（MSM/NH₂）,其结构和性能经TEM, XRD和元素分析表征。结果表明：MSM/NH₂ 1.0［3-氨丙基三乙氧基硅烷（APTES）用量为1.0 mL］对Hg²⁺、 Ni²⁺和Mn²⁺的5次循环吸附效率的平均值均超过92.0%。     

钯/聚苯胺纳米多层膜的制备及对抗坏血酸和多巴胺的催化氧化

采用脉冲电位法(PPSM)结合聚苯胺(PANI)的层层自组装制备了Pd/PANI交替沉积纳米多层膜, 并用于抗坏血酸(AA)和多巴胺(DA)的检测. 实验发现, 多层膜结构形貌及催化性能受前躯体K₂PdCl₆浓度、 脉冲条件及膜厚度等影响. 当K₂PdCl₆浓度为2×10^-3 mol/L, 阴极脉冲电位为-0.3 V, 阶跃次数为17时, 5层Pd/PANI修饰玻碳电极对AA和DA的催化性能最佳; 在0.1 mol/L磷酸盐缓冲液中, AA和DA的氧化峰明显分离[ΔE_p(AA, DA)=160 mV], 其峰电流与浓度分别在5×10^-5～4×10^-4和4×10^-5～1×10^-4 mol/L范围内呈较好线性关系, 实现了对AA和DA的同时测定. 该修饰电极具有良好的抗干扰性和稳定性.     

新型钳状芳杂环杯[4]芳烃修饰电极对银离子的分子识别研究

合成了25,27-二羟基-26,28-双(3-苯并噻唑基硫代丙氧基)-5,11,17,23-四叔丁基杯[4]芳烃,并将其研制成PVC膜化学修饰电极.探讨了膜电极的修饰方法及伏安性能对金属离子的识别及其识别机理.结果表明,采用涂层-刻痕法制备的修饰电极在0.2mol/LHNO₃溶液中对银离子有很灵敏的伏安响应,在5.0×10^-8～1.3×10^-6mol/L范围内氧化峰电流与银离子呈线性关系,检测限为3.8×10^-8mol/L.用该法测定了一些实际样品,结果令人满意.     

硫堇衍生化自组装膜修饰金电极的电化学性质及其对抗坏血酸的电催化氧化

将硫堇共价键合到自组装在金电极表面的半胱胺单分子层上,制成了衍生化自组装单分子膜修饰电极,并用电化学方法研究了它的电化学性质.循环伏安图显示其在pH＝7.7的磷酸盐缓冲液中,于－0.45～＋0.50V(vs.SCE)范围内有2对氧化还原峰.峰电位分别为E_pa¹＝214mV。E_pc¹＝82mV,E_pa2＝－75mV,E_pc2＝－160mV(vs.SCE).pH在5.0～9.0范围内,峰1有2个质子参与反应,峰2有1个质子参与反应.它的表面电子转移速率常数k_s＝0.02S^－1.此膜对抗坏血酸的氧化有催化作用,其氧化过电位较在裸金电极上降低了约250mV.催化电流与抗坏血酸的浓度在1.0×10^-6～4.0×10^-3mol/L范围内呈良好的线性关系.抗坏血酸催化氧化的异相速率常数为2.68×10^-3cm/s.     

汽油活性炭基脱硫吸附剂的制备与评价

以250℃温度下浓硫酸改性后的活性炭为载体,采用浸渍法制备了以MnO₂为活性组分的活性炭基的汽油脱硫吸附剂MnO₂/AC,考察了吸附剂的制备条件及脱硫条件对脱硫效果的影响。研究结果表明,适宜的吸附剂制备条件为,以Mn(NO₃)₂为活性组分前驱物,Mn(NO)₂浸渍液浓度0.15mol/L、常温下浸渍24h、焙烧温度350℃、焙烧时间2h。该吸附剂在静态吸附温度120℃、吸附时间2h、剂油质量比0.10的条件下可使原料油硫的质量分数从628.6×10^-6降至221.5×10^-6,脱硫率达到64.8%;在动态吸附温度60℃、空速1.76h^-1的条件下,初始流出汽油硫的质量分数降至21.8×10^-6,初始脱硫率达到96.5%。     

绿色合成介孔碳负载(Ni)MoS2加氢脱硫催化剂

以Anderson结构Ni-Mo杂多酸簇(NH₄)₄[NiMo₆O₂₄H₆]·5H₂O、硫脲、柠檬酸、氯化钠为原料,采用冻干法得到前驱体后焙烧、洗涤得到介孔碳骨架负载(Ni)MoS₂纳米颗粒的加氢脱硫催化剂,考察了其对二苯并噻吩的加氢脱硫活性,并采用X射线衍射、N₂低温吸附-脱附、拉曼光谱、X光电子能谱、扫描电子显微镜、高分辨透射电镜、程序升温还原等表征手段对催化剂进行了分析。结果表明,介孔碳骨架负载(Ni)MoS₂纳米颗粒催化剂具有较弱的载体-金属相互作用,MoS₂纳米颗粒平均长度较短(4.9 nm),层数适宜(4.8),NiMoS活性相含量较高,二苯并噻吩的转化率可达94.1%,反应速率常数及活性位转换频率分别可达1.7×10^-6 mol/(g·s)和2.8×10^-3 s^-1。该方法利用原位生成的氯化...     

利用H2O2-KI-鲁米诺体系化学发光法测定痕量钼

钼(Ⅵ)可以催化H₂O₂氧化I^-的反应,生成的I₂在碱性水溶液中能氧化鲁米诺而产生化学发光^[1],本文将这两个反应结合起来,建立了铝的化学发光分析法,方法有较高的灵敏度,检出限为6×10^-10g/cm³Mo,测定的相对标准偏差小于6%,工作曲线的线性范围是1×10^-9～1×10^-7g/cm³Mo,用EDTA作掩蔽剂,排除了大多数金属离子的干扰,方法有较好的选择性,应用此法对一些粮食样品中的痕量钼进行了测定,结果比较满意。     

Oxidative Desulfurization of Diesel Oil Using Mesoporous Phosphotungstic Acid/SiO2 as Catalyst

Ordered mesoporous phosphotungstic acid/SiO₂ (HPW/SiO₂) with Keggin‐type heteropolyacids (HPAs) encapsulated into a SiO₂ framework has been synthesized and used as the catalyst for oxidative desulfurization of diesel fuel. The sulfur compounds in diesel were oxidized and removed at a temperature range of 50–80 °C with H₂O₂ as the oxidant and acetonitrile as the extraction agent. The sulfur content in diesel was reduced to as low as 48–86 μg/g from the initial level of 438 μg/g. The loss in catalytic activity was negligible even after five cycles of use, and the reduction of the sulfur content was enhanced with increasing the immobilized phosphotungstic acid (HPW) concentration. Oxidation of model compounds showed that in the heterogeneous system both the electron density and the steric hindrance affected the reactivity of these sulfur compounds. The reactivities of these sulfur compounds studied in this work followed the order of dibenzothiophene > 4,6‐dimethydibenzothiophene > benzothiophene.     

银含量对二氧化硅固载磷钨酸银催化四氢呋喃聚合反应性能的影响

通过共浸渍法合成了一系列担载型杂多酸银盐催化剂Ag_xH_3-xPW/SiO₂ (x=0.5, 1.0, 1.5, 2.0, 2.5, 3.0),由于催化剂在极性溶剂中的不溶性, 在合成聚四氢呋喃的反应中显示了高反应活性和稳定性能. Ag离子取代含量和银盐的担载量对催化剂活性会产生显著影响. Ag 离子含量的不同会导致磷钨酸银盐的晶相结构和催化剂的酸性质发生变化. x=2.0 时, 催化剂Ag₂HPW/SiO₂达到最大酸强度和最高催化聚合反应活性. 当银盐Ag₂HPW的担载量为30% (质量分数)时, 催化剂能达到高分散度和高的四氢呋喃聚合反应活性. 与普通二氧化硅担载的磷钨酸催化剂HPW/SiO₂对比, 担载型磷钨酸银盐30%Ag₂HPW/SiO₂拥有优异的重复使用性能, 循环4 次后催化活性只有轻微下降. 通过引入Ag离子合成的新型担载磷钨酸银盐30%Ag₂HPW/SiO₂, 反应稳定性能明显改进, 得到拥有稳定平均分子量的产物聚四氢呋喃.     

Mesoporous zirconium–silica nanocomposite modified with heteropoly tungstophosphoric acid catalyst for ultra-deep oxidative desulfurization

An adsorbent catalyst was proposed to reduce the leaching of active species of the catalyst and enhance the kinetics of the oxidative desulfurization (ODS) reaction of dibenzothiophene (DBT) from model diesel fuel. By loading phosphotungstic acid (HPW) species onto a zirconium-modified hexagonal mesoporous silica (Zr-HMS), a novel catalyst was synthesized and utilized for the ODS process. An ultrafast ODS kinetics was specifically identified using 20%HPW/Zr-HMS as catalyst. Within 30 min, more than 95% of the 350 ppm DBT content of the model fuel was oxidized by H₂O₂. The synthesized catalyst retained its sulfur removal ability even after five subsequent ODS reactions and the leaching of HPW species was found to be suppressed successfully. Overall, this new reusable catalyst provided an alternative for highly efficient ultra-deep desulfurization process.     

Promotion of oxidative desulfurization performance of model fuel by 3DOM Ce-doped HPW/TiO2 material

Phosphotungstic acid (HPW) supported on Ce-doped three-dimensional ordered macroporous (3DOM) TiO₂ catalysts are studied in catalytic oxidation desulfurization (ODS) of model oil. The structural and textural of as-synthesized catalysts are characterized by N₂ adsorption, XRD, Raman spectroscopy, SEM-EDS, TEM, FT-IR, XPS, UV–Vis and ICP. These results upheld the existence of periodically arranged macroporous structure of catalyst, with Keggin-type of HPW dispersed homogeneously on TiO₂ matrix. Among these 3DOM Ce-doped HPW/TiO₂ materials, catalyst with 15 wt.% cerium dosage exhibits best ODS performance, which oxidized 99.8% of dibenzothiophene (DBT) into corresponding sulfone within 40 min. The excellent ODS performance of 3DOM Ce-doped HPW/TiO₂ catalyst is related to the common influence of more oxygen vacancies produced by electron transformation between Ce³⁺ and Ce⁴⁺. The chemisorbed oxygen on the surface catalyst will facilitate the selective oxidation of sulfides to sulfones. Moreover, the 3DOM structure of catalyst will further promote the mass transfer of reactants and products on the pore channel. The as-prepared catalyst shows excellent reusability in the ODS system, no obviously decrease in catalytic activity even after 6 runs.     

AgCeY分子筛吸附剂的制备及性能研究

以NaY分子筛为载体,通过液相离子交换法制备了经Ag、Ce双金属离子改性的AgCeY吸附剂,并利用UV-vis、XRD、BET、ICP、XPS和FT-IR技术对吸附剂进行了表征。以噻吩/苯并噻吩/正辛烷/甲苯体系为汽油模拟体系,考察了制备条件和吸附条件对吸附剂脱硫性能的影响以及吸附剂再生性能。结果表明,AgCeY吸附剂上Ag、Ce这两种金属元素分别以Ag⁺、Ce⁴⁺形式存在,AgCeY吸附剂具有类似于AgY的高的脱硫性能,又具有类似于CeY的高的吸附选择性,AgCeY对噻吩(TP)和苯并噻吩(BT)的吸附选择性顺序为BT > TP;最适宜的制备条件为先交换Ag后交换Ce离子、离子交换24 h、Ce/Ag物质的量比为2.5、500 ℃焙烧;在原料20 mL、AgCeY吸附剂用量0.2 g、吸附温度50 ℃、吸附时间60 min下,噻吩脱硫率可达到59.0%,苯并噻吩脱硫率达到96.5%。     

Membrane-Supported Layered Coordination Polymer as an Advanced Sustainable Catalyst for Desulfurization

The application of a catalytic membrane in the oxidative desulfurization of a multicomponent model diesel formed by most refractory sulfur compounds present in fuel is reported here for the first time. The catalytic membrane was prepared by the impregnation of the active lamellar [Gd(H₄nmp)(H₂O)₂]Cl·2H₂O (UAV-59) coordination polymer (CP) into a polymethyl methacrylate (PMMA, acrylic glass) supporting membrane. The use of the catalytic membrane in the liquid–liquid system instead of a powder catalyst arises as an enormous advantage associated with the facility of catalyst handling while avoiding catalyst mass loss. The optimization of various parameters allowed to achieve a near complete desulfurization after 3 h under sustainable conditions, i.e., using an aqueous H₂O₂ as oxidant and an ionic liquid as extraction solvent ([BMIM]PF₆, 1:0.5 ratio diesel:[BMIM]PF₆). The performance of the catalytic membrane and of the powdered UAV-59 catalyst was comparable, with the advantage that the former could be recycled successfully for a higher number of desulfurization cycles without the need of washing and drying procedures between reaction cycles, turning the catalytic membrane process more cost-efficient and suitable for future industrial application.     

Dependence of the catalytic activity of Ag/Al2O3 on the silver concentration in the selective reduction of NOx with n-hexane in the presence of H2

The activity of 0.25–5% Ag/Al₂O₃ catalysts in the selective catalytic reduction of nitrogen oxides with n-hexane under the conditions of promotion with a small amount of H₂ was studied. It was found that, upon the introduction of ∼1000 ppm of H₂ into the reaction mixture, the Ag/Al₂O₃ samples containing 1–2% Ag exhibited optimum activity and selectivity. It was established that, in the presence of 1000 ppm of H₂, the rate of the selective catalytic reduction of NO _x was higher by a factor of 10–13, and the onset temperature of the reaction was lower by approximately 100°C. It was found by X-ray photoelectron spectroscopy, temperature-programmed reduction, and UV spectroscopy that the high activity of 1–2% Ag/Al₂O₃ catalysts was due to the presence of small Ag _n ^δ+ and Ag _m ⁰ clusters on their surface. A decrease in the concentration of Ag below the optimum value resulted in the predominance of an inactive ionic form on the catalyst surfaces. As the concentration of Ag was increased (>2%), large particles of Ag₂O and Ag⁰, which facilitate the oxidation of n-C₆H₁₄, were formed to lead to a decrease in selectivity and in the degree of reduction of nitrogen oxides.     

Deep desulfurization of diesel by selective oxidation using amphiphilic paradodecatungstate catalyst

An amphiphilic paradodecatungstate catalyst, [(C₁₈H₃₇)₂N(CH₃)₂]₉[NaH₂W₁₂O₄₂] was prepared and characterized by Fourier transform infrared spectroscopy, UV–visible spectrum, differential thermal analysis, and thermogravimetric analysis. The amphiphilic catalyst exhibits very high catalytic activity that dibenzothiophene (DBT) in model diesel can be oxidized into dibenzothiophene sulfones using hydrogen peroxide as an oxidant. The reactivity of sulfur compounds decreased in the order of DBT > 4,6-DMDBT > BT > 5-MBT. The reaction rates of these sulfur compounds are sensitive to the electron density on sulfur atoms and the steric hindrance of the substituted groups of sulfur compounds. The sulfur level of a commercial diesel after desulfurization can drop from 200 ppm to about 12 ppm.     

An Effective Hybrid Heterogeneous Catalyst to Desulfurize Diesel: Peroxotungstate@Metal–Organic Framework

A peroxotungstate composite comprising the chromium terephthalate metal–organic framework MIL-101(Cr) and the Venturello peroxotungstate [PO₄{WO(O₂)₂}₄]³⁻ (PW₄) has been prepared by the impregnation method. The PW₄@MIL-101(Cr) composite presents high catalytic efficiency for oxidative desulfurization of a multicomponent model diesel containing the most refractory sulfur compounds present in real fuels (2000 ppm of total S). The catalytic performance of this heterogeneous catalyst is similar to the corresponding homogeneous PW₄ active center. Desulfurization efficiency of 99.7% was achieved after only 40 min at 70 °C using H₂O₂ as an oxidant and an ionic liquid as an extraction solvent ([BMIM]PF₆, 2:1 model diesel/[BMIM]PF₆). High recycling and reusing capacity was also found for PW₄@MIL-101(Cr), maintaining its activity for consecutive oxidative desulfurization cycles. A comparison of the catalytic performance of this peroxotungstate composite with others previously reported tungstate@MIL-101(Cr) catalysts indicates that the presence of active oxygen atoms from the peroxo groups promotes a higher oxidative catalytic efficiency in a shorter reaction time.