Importance of structural and chemical heterogeneity of activated carbon surfaces for adsorption of dibenzothiophene

The performance of various activated carbons obtained from different carbon precursors (i.e., plastic waste, coal, and wood) as adsorbents for the desulfurization of liquid hydrocarbon fuels was evaluated. To increase surface heterogeneity, the carbon surface was modified by oxidation with ammonium persulfate. The results showed the importance of activated carbon pore sizes and surface chemistry for the adsorption of dibenzothiophene (DBT) from liquid phase. Adsorption of DBT on activated carbons is governed by two types of contributions: physical and chemical interactions. The former include dispersive interactions in the microporous network of the carbons. While the volume of micropores governs the amount physisorbed, mesopores control the kinetics of the process. On the other hand, introduction of surface functional groups enhances the performance of the activated carbons as a result of specific interactions between the acidic centers of the carbon and the basic structure of DBT molecule as well as sulfur-sulfur interactions.     

Interactions of thiophenes with C300 Basolite MOF in solution by the temperature-programmed adsorption and desorption,spectroscopy and simulations

Aromatic sulfur compounds, e.g. thiophene (T), benzothiophene (BT), dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT) are present in petroleum and fossil fuels, and cause air pollution, degradation of catalytic converters, deactivation of fuel-reforming catalysts. In this paper, we report kinetic, thermodynamic, spectroscopic and computational studies of adsorption of T, BT, DBT, and 4,6-DMDBT from solution in n-alkane on metal–organic framework (MOF) Basolite C300 at 25–115 °C. The novel temperature-programmed adsorption/desorption method allows the in situ measurement of an adsorption capacity at the variable temperature, and after the cycle “adsorption/desorption”. Adsorption of BT, DBT and 4,6-DMDBT at 25 °C occurs via the formation of the stoichiometric 1:1 adsorption complexes. BT adsorbs reversibly, while 4,6-DMDBT adsorbs irreversibly. The formation of the adsorption complex of the aromatic sulfur compound with MOF is confirmed by the fluorescence spectroscopy for the first time. The DFT computations of the geometry and energy of dispersive versus electronic interactions of T and DBT with the structural units of the C300 MOF are reported for the first time. The mechanism of adsorption is proposed as a combination of dispersive and electronic interactions of the aromatic sulfur compounds with BTC linker and Cu(II) CUS of C300 MOF.     

Preparation and performance evaluation of resin-derived carbon spheres for desulfurization of fuels

A polystyrene-based ion-exchange resin was employed as the precursor for preparation of resin-derived carbon spheres(RCSs) through KOH activation with various impregnation ratios.Pore structure,yield and hardness,surface functional groups of the samples and their adsorption performance towards dibenzothiophene(DBT) were investigated.The RCSs with large surface areas(up to 2696m2/g) and total pore volumes(up to 1.46 cm3/g) exhibited larger adsorption capacities than a commercial activated carbon,F400.Polanyi-Dubinin-Mane(PDM) model was applied to fit the adsorption data,which proved that micropore filling was involved during the adsorption process.Moreover,a good linear relationship was observed between the extra-micropore volume and adsorption capacity.Intra-particle diffusion(IPD) model was used to describe the kinetic data of DBT onto the adsorbents.The adsorption processes were divided into three stages according to the different diffusion parameter.The selective adsorption towards DBT in the presence of competing compounds was also investigated and the high selectivity of the RSCs towards DBT may be attributed to the large quantity of acidic oxygen-containing groups.     

Preparation and evaluation of a novel surface-imprinted polymer for selective adsorption of dibenzothiophene

We have prepared a novel surface molecular imprinted polymer (S-MIP) using dibenzothiophene (DBT) as the template molecule, 4-vinylpyridine as the functional monomer, and potassium hexatitanate whisker as the carrier. The S-MIP was characterized by Fourier transform infrared spectroscopy and and scanning electron microscopy. The kinetics and isotherms for the adsorption of DBT on the S-MIP followed pseudo-second-order and Freundlich models, respectively. Thermodynamic parameters were determined. The overall adsorption process was endothermic and spontaneous. Selectivity studies showed that the S-MIP selectively adsorbs DBT over its structural analogs and can be regenerated. Its adsorption capacity was still at 84.8% at the sixth cycle.

Preparation of molecularly imprinted polymer by surface imprinting technique and its performance for adsorption of dibenzothiophene

The novel surface imprinted polymer composites (MIP/K(2)Ti(4)O(9)) were prepared using dibenzothiophene (DBT) as the template, 4-vinylpyridine as the functional monomer and potassium tetratitanate whisker (K(2)Ti(4)O(9)) as the carrier. The synthetic product was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Parameters influencing DBT adsorption such as contact time, temperature and DBT initial concentration were investigated. The adsorption kinetics were evaluated with the pseudo-first-order and pseudo-second-order models, and the adsorption isotherms were fitted by Langmuir and Freundlich models. Selectivity experiments showed that MIP/K(2)Ti(4)O(9) exhibited excellent recognition capacity and binding affinity to DBT compared with the comparative substrates. MIP/K(2)Ti(4)O(9) could also be easily regenerated and reused ten times with only about 20% loss of adsorption capacity.     

Synthesis and characterization of MFe2O4 sulfur nanoadsorbents

Nanoparticles of ferrites (Fe₃O₄, NiFe₂O₄, CuFe₂O₄, and MnFe₂O₄) were prepared by a reverse (water/oil) microemulsion method. The microemulsion system consisted of cetyltrimethylammonium bromide, 1-butanol, cyclohexane, and a metal salt solution. The procedure was carried out using aqueous ammonia as the coprecipitating agent. Nanosized particles were characterized by thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and pyridine adsorption. The NiFe₂O₄ sample exhibited narrow mesoporous pore size distribution and high surface area ≈233 m²/g. It achieved good adsorption activity towards the dibenzothiophene (DBT) compound (166.3 μmol/g of DBT adsorbent). The structural properties obtained were very interesting for potential applications in the desulfurization process in petroleum refining.     

Liquid-phase adsorption of multi-ring thiophenic sulfur compounds on carbon materials with different surface properties

This work examines the effects of structural and surface properties of carbon materials on the adsorption of benzothiophene (BT), dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT) in the presence of 10 wt % of aromatics in liquid alkanes that simulate sulfur compounds in diesel fuels. The equilibrium-adsorption capacity varies significantly, from 1.7 to 7.0 mg-S/g-A. The results show that different carbon materials have significantly different sulfur-adsorption capacities and selectivities that depend not only on textural structure but also on surface functional groups. The adsorption of multi-ring sulfur compounds on carbon materials was found to obey the Langmuir isotherm. On the basis of adsorption tests and the characterization of carbon materials by BET and XPS, the oxygen-containing functional groups on the surface appear to play an important role in increasing sulfur-adsorption capacity. The adsorption-selectivity trend of the carbon materials for various compounds increases in the order of BT < naphthalene < 2-methylnaphthalene < DBT < 4-MDBT < 4,6-DMDBT, regardless of carbon material types. This selectivity trend for sulfur compounds is dramatically different and almost opposite from that previously observed for adsorption over nickel-based adsorbents. The regeneration of spent activated carbons was also conducted by solvent washing. The high-adsorption capacity and selectivity for methyl DBTs indicate that certain activated carbons are promising adsorbents for selective adsorption for removing sulfur (SARS) as a new approach to ultra deep desulfurization of diesel fuels.     

表面活性剂改性对Zn/Ti-PILCs吸附剂脱硫性能的影响

在柱撑黏土Ti-PILCs的合成过程中,加入各种表面活性剂进行改性,通过负载Zn制备了Zn/Ti-PILCs吸附剂,考察了其对模拟柴油中二苯并噻吩的选择吸附性能。结果表明,经表面活性剂尤其是十六烷基三甲基溴化铵（CTAB）改性制备的Zn/Ti-PILCs其吸附脱硫率得以显著提高。当CTAB/Ti摩尔比为0.5时,Zn/Ti-PILCs-CATB具有最佳的吸附性能,DBT去除率达96.3%。N₂吸附脱附等温线和孔径分布研究表明,CTAB改性可增加1nm～4nm孔的数量,并改善黏土层间柱子的分布,使Ti-PILCs具有更高的比表面及更均匀的孔径分布。     

二苯并噻吩分子印迹功能化MOF199吸附剂的制备及性能

结合分子印迹技术,MOF199为基体,以二苯并噻吩(DBT)为模板分子,甲基丙烯酸(MAA)为功能单体,制备了新型表面分子印迹聚合物材料MOF@SMIP。采用SEM、BET、FT-IR等对其结构和形貌进行表征,在模拟油样中进行吸附评测,吸附平衡时间为1.5 h。MOF@SMIP对DBT吸附量为130.73 mg/g较MOF199吸附量37.79 mg/g有很大提升,同时MOF@SMIP吸附量对比MOF@NIP吸附量(57.13 mg/g)优势明显,印记因子f_(imp)为2.29。吸附行为遵循伪一阶动力学模型说明吸附主要为物理过程。选择性吸附实验表明,MOF@SMIP对目标分子DBT表现出比对结构类似物苯并噻吩(BT)和联苯更高的亲和力,吸附DBT对干扰物BT和联苯的相对选择系数k'分别达到2.55和2.14。     

Sn和Si掺杂AlPO4-5分子筛及其加氢脱硫反应性能研究

直接在AlPO4-5凝胶中加入Si和Sn2+源成功制备SAPO-5和SnSAPO-5分子筛。采用XRD、低温N2物理吸附、SEM、NMR、Py-IR、NH3-TPD等表征对分子筛物理化学性质进行分析。随Sn含量的增多,杂原子SnSAPO-5分子筛表面更光滑,外貌呈现更规则的六棱柱;Sn和Si更多的富集于表面;并且Sn2+同晶取代Al3+,骨架产生缺陷,电荷不平衡,进而产生更多的酸性位点。将分子筛用于NiW催化剂的改性,以脱除模拟油中二苯并噻吩（DBT）为探针,评价其改性加氢催化剂的加氢脱硫（HDS）反应性能。SnSAPO-5分子筛的添加在催化剂上引入了更多的酸性中心;改善载体与活性金属的相互作用;促进活性金属的硫化;形成更多的金属活性相,进而提高NiW催化剂的加氢脱硫能力。因而SnSAPO-5改性催化剂表现出比其他改性催化剂更好的HDS活性,具有良好的应用前景。     

纳米MoS_2催化剂的合成及其在加氢脱硫反应中的应用

通过羰基钼和升华硫反应制备了晶片层数为3～5,比表面积为71m2/g的纳米MoS2催化剂,并考察了其催化十二硫醇或二苯并噻吩的加氢脱硫活性.结果表明,在3.0MPa初始氢气压力下,该催化剂在200C和280C就可使十二硫醇和二苯并噻吩转化接近100%.     

Surface properties of yeast cells during heavy metal biosorption

Properties of metal solution, environmental conditions and the type of biomaterials (microorganism genus, species or even strain) influence the mechanism of metal biosorption and consequently metal adsorption capacity, affinity and specificity. Cell surface properties determine the metal-microorganism interactions to a large extent. In this work the relationship between yeast surface properties and yeast’s ability to bind cadmium, lead and copper was studied. Surface charge and hydrophobicity before and after biosorption were determined using dye retention and solvent partition assays, respectively. There were differences in the surface charge and relative hydrophobicity among different yeast strains. A higher metal adsorption capacity for more negatively charged yeast cells was observed. Biosorption of heavy metals resulted in modifications to the surface charge and hydrophobicity of yeast cells. However, there were not statistically significant changes in the yeast surface charge and hydrophobicity after binding of heavy metals depending on the nature of the metal, initial metal concentration and solution pH.     

Cadmium and lead recovery from yeast biomass

Properties of metal solution, environmental conditions and the type of biomaterials (microorganism genus, species or even strain) influence the mechanism of metal biosorption and consequently metal adsorption capacity, affinity and specificity. Cell surface properties determine the metal-microorganism interactions to a large extent. In this work the relationship between yeast surface properties and yeast’s ability to bind cadmium, lead and copper was studied. Surface charge and hydrophobicity before and after biosorption were determined using dye retention and solvent partition assays, respectively. There were differences in the surface charge and relative hydrophobicity among different yeast strains. A higher metal adsorption capacity for more negatively charged yeast cells was observed. Biosorption of heavy metals resulted in modifications to the surface charge and hydrophobicity of yeast cells. However, there were not statistically significant changes in the yeast surface charge and hydrophobicity after binding of heavy metals depending on the nature of the metal, initial metal concentration and solution pH.     

Charge transfer and formation of reduced Ce3+ upon adsorption of metal atoms at the ceria (110) surface

The modification of cerium dioxide with nanoscale metal clusters is intensely researched for catalysis applications, with gold, silver, and copper having been particularly well studied. The interaction of the metal cluster with ceria is driven principally by a localised interaction between a small number of metal atoms (as small as one) and the surface and understanding the fundamentals of the interaction of metal atoms with ceria surfaces is therefore of great interest. Much attention has been focused on the interaction of metals with the (111) surface of ceria, since this is the most stable surface and can be grown as films, which are probed experimentally. However, nanostructures exposing other surfaces such as (110) show high activity for reactions including CO oxidation and require further study; these nanostructures could be modified by deposition of metal atoms or small clusters, but there is no information to date on the atomic level details of metal-ceria interactions involving the (110) surface. This paper presents the results of density functional theory (DFT) corrected for on-site Coulomb interactions (DFT+U) calculations of the adsorption of a number of different metal atoms at an extended ceria (110) surface; the metals are Au, Ag, Cu, Al, Ga, In, La, Ce, V, Cr, and Fe. Upon adsorption all metals are oxidised, transferring electron(s) to the surface, resulting in localised surface distortions. The precise details depend on the identity of the metal atom. Au, Ag, Cu each transfer one electron to the surface, reducing one Ce ion to Ce(3+), while of the trivalent metals, Al and La are fully oxidised, but Ga and In are only partially oxidised. Ce and the transition metals are also partially oxidised, with the number of reduced Ce ions possible in this surface no more than three per adsorbed metal atom. The predicted oxidation states of the adsorbed metal atoms should be testable in experiments on ceria nanostructures modified with metal atoms.     

Theoretical study of interaction of heteroaromatic compounds with a cluster model of kaolinite tetrahedral surface

Heteroaromatic hydrocarbons (including thiophene [TH], benzothiophene [BT], and dibenzothiophene [DBT]) do not have apparent functional groups capable of interacting with the silica‐oxide tetrahedral surface of kaolinite. Thus, question remains concerning what would be the driving forces for the adsorption. Here, the Si₁₃O₃₇H₂₂ cluster model for the surface is constructed, and the interactions of the surface with three heteroaromatic compounds are studied at the MP2/6‐31G(d,p)//B3LYP/6‐31G(d) level. The computed properties characterizing the complexes include optimized structural parameters, electron density characteristics (the ρ and ? ²ρ values for C? H…O bonds), adsorption energies, vibration frequencies and electrostatic potential maps. The results suggest that the C? H…O hydrogen bonding interactions between the heteroaromatic compounds and tetrahedral surface are likely among the important interactions for the adsorption. The order of the stability of the cluster model of kaolinite complexed with the heteroaromatic compounds is found to be 3Si? O? DBT > 3Si? O? BT > 3Si? O? TH based on the calculations.     

Effect of reduction treatment on copper modified activated carbons on NO(x) adsorption at room temperature

Activated carbon was impregnated with copper salt and then exposed to reductive environment using hydrazine hydrate or heat treatment under nitrogen at 925 °C. On the obtained samples, adsorption of NO(2) was carried out at dynamic conditions at ambient temperature. The adsorbents before and after exposure to nitrogen dioxide were characterized by X-ray diffraction (XRD), thermal analysis, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS), N(2)-sorption at -196 °C, and potentiometric titration. Copper loading improved the adsorption capacity of NO(2) as well as the retention of NO formed in the process of NO(2) reduction on the carbon surface. That improvement is linked to the presence of copper metal and its high dispersion on the surface. Even though both reduction methods lead to the reduction of copper, different reactions with the carbon surface take place. Heat treatment results in a significant percentage of metallic copper and a reduction of oxygen functional groups of the carbon matrix, whereas hydrazine, besides reduction of copper, leads to an incorporation of nitrogen. The results suggest that NO(2) mainly is converted to copper nitrates although the possibility to its reduction to N(2) is not ruled out. A high capacity on hydrazine treated samples is linked to the high dispersion of metallic copper on the surface of this carbon.     

Graphene wrapped phthalocyanine: Enhanced oxidative desulfurization for dibenzothiophene in fuel

Graphene wrapped metal phthalocyanine (MPc/RGO, M = Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) composites are synthesized by a facile ‘in situ hydrothermal’ method, using graphene oxide, M (CH₃COO)₂ and phthalic anhydride as the precursors. A biomimetic catalytic system of MPc/RGO and molecular O₂ have high activity for ultra‐deep removal of dibenzothiophene (DBT) in model oil containing n‐octane. Compared with pure graphene oxide and MPc, MPc/RGO composites displayed highly enhanced catalytic activity for the oxidation of dibenzothiophene in n‐octane. The conversion ratio of DBT was up to 97.51% after 180 min treatment at 60 °C and atmospheric pressure. The photostability of RGO/MPc composites photocatalystic degradation of dibenzothiophene was investigated. Mechanistic studies revealed that the RGO/MPc ? O₂ · species were the main active intermediate via the π‐π stacking interaction of MPc and RGO. The RGO wrapped phthalocyanine materials offer great potential as active photocatalysts for degradation of thiophene derivatives in fuel.     

CuHY分子筛中铜离子的分布与吸附脱硫性能

采用等体积浸渍法制备具有不同Cu担载量的CuHY 分子筛吸附剂. 用X射线衍射(XRD)、比表面积(BET)和氨程序升温脱附(NH3-TPD)技术对分子筛吸附剂进行了表征, 并测定了CuHY 分子筛吸附剂在含二苯并噻吩(DBT)模拟柴油中的吸附脱硫性能; 通过多晶XRD确定了Cu2+在Cu8HY 分子筛笼内的结构与分布. 实验结果表明, 分子筛的骨架结构没有发生改变, 部分Cu2+进入Y型分子筛笼内, 分子筛样品强酸中心有所减少, 中强酸中心有所增加; 进入Y型分子筛笼内的Cu2+, 一部分处于β 笼的SI' 位, 另一部分位于分子筛超笼中的SIII位上, 并与笼内的水分子配位. 处于超笼中的SⅢ位Cu2+对模拟柴油中的DBT分子具有吸附作用, 是吸附脱硫的中心. 而当模拟柴油中存在萘时, 与DBT分子会产生竞争吸附.     

A surface-imprinted polymer for removing dibenzothiophene from gasoline

A surface-imprinted polymer for the adsorption of dibenzothiophene (DBT) was obtained from DBT (the template), titanium dioxide (the support), methacrylic acid (the functional monomer), ethylene glycol dimethacrylate (the cross-linker), 2,2´-azobisisobutyronitrile (the initiator) and toluene (the porogen). The material was characterized by Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller model and Scanning electron microscopy. Batch adsorption experiments were performed to study the adsorption of the material in terms of adsorption kinetics, isotherms, and thermodynamic parameters. The adsorption follows pseudo-second-order kinetics, the Freundlich adsorption equation fits the experimental data well, and there is strong evidence for multiple layer adsorption. The negative values of the Gibbs free energy (ΔG₀) range from -6.04 kJ?mol^-1 to -7.69 kJ?mol^-1 between 298 and 318 K, which reveals that the adsorption is endothermic. The material can selectively recognize DBT over similar compounds present in gasoline (such as benzothiophene and 4-methyldibenzothiphene).     

四钛酸钾晶须表面二苯并噻吩印迹聚合物的制备及其性能研究

以二苯并噻吩为模板,4-乙烯基吡啶为功能单体,四钛酸钾晶须为载体,合成了对二苯并噻吩具有特异吸附的四钛酸钾表面分子印迹聚合物.采用红外光谱、扫描电镜、氮气吸附对其形貌和结构进行表征,利用气相色谱法研究其吸附性能.结果表明:在318 K,吸附时间为240 min时,吸附效果最佳.在初始浓度500 mg/L的二苯并噻吩溶液...