加速溶剂萃取-液相色谱-质谱法分离和鉴定原油中金属卟啉

通过研究萃取溶剂、温度、静态萃取时间和次数对萃取效率的影响,建立了加速溶剂萃取,UV-vis和LC-MS分析原油中金属卟啉的方法。结果表明,加速溶剂萃取原油中金属卟啉的最优条件为:10.3 MPa,80℃,乙腈静态萃取15 min,萃取3次。将该方法应用于孤岛原油,UV-vis结果表明,原油中钒卟啉和镍卟啉含量分别为35.95μg/g和84.48μg/g;两者均以氧化初卟啉(ETIO)和脱氧叶红初卟啉(DPEP)2种类型存在,且主要类型ETIO型分别占71.4%和80.0%。LC-MS结果显示,钒卟啉和镍卟啉的ETIO型和DPEP型系列的碳数分布范围分别是C22～C33、C25～C33和C22～C39、C28～C36,系列中含量最丰富的分别为C34-ETIO、C32-DPEP和C33-ETIO、C32-DPEP。     

大港沥青对正戊烷溶剂中卟啉钒化合物的吸附动力学研究

利用静态实验,研究了在正戊烷溶剂中,大港沥青质对卟啉钒模型化合物的吸附动力学,并对吸附机理进行了探讨。通过对吸附卟啉钒化合物前后的大港沥青质进行FT-ICR MS和元素(C/H/N/O)分析,发现大港沥青质上吸附了一定量的卟啉钒化合物。沥青质对卟啉钒的吸附过程受到沥青质的加入量(0.010 0和0.020 0 g)、戊烷溶液中初始卟啉钒的浓度(10和15μg/mL)以及吸附温度(15、20和25℃)等因素的影响。分别采用拟一级、拟二级、Elovich和粒子内扩散等方程对实验数据进行了拟合,结果发现沥青质对卟啉钒的吸附符合拟二级动力学方程。     

大港沥青对正戊烷溶剂中卟啉钒化合物的吸附动力学研究

利用静态实验,研究了在正戊烷溶剂中,大港沥青质对卟啉钒模型化合物的吸附动力学,并对吸附机理进行了探讨。通过对吸附卟啉钒化合物前后的大港沥青质进行FT-ICR MS和元素（C/H/N/O）分析,发现大港沥青质上吸附了一定量的卟啉钒化合物。沥青质对卟啉钒的吸附过程受到沥青质的加入量（0.010 0和0.020 0 g）、戊烷溶液中初始卟啉钒的浓度（10和15 μg/mL）以及吸附温度（15、20和25 ℃）等因素的影响。分别采用拟一级、拟二级、Elovich和粒子内扩散等方程对实验数据进行了拟合,结果发现沥青质对卟啉钒的吸附符合拟二级动力学方程。     

渣油加氢转化前后沥青质的分子组成变化

沥青质是造成渣油加氢过程中结焦和催化剂失活的主要因素,深入研究渣油加氢转化前后沥青质的分子组成变化对于改进渣油加氢工艺有着重要的指导意义.本文采用傅里叶变换离子回旋共振质谱仪(FT-ICR MS)研究了塔河减渣加氢转化过程中沥青质组分的分子组成差异.为了减少沥青质分子之间的相互干扰和抑制,通过固相萃取技术对渣油加氢前后得到的沥青质进行了分离,并对比了其中主要化合物在分离前后的详细分子组成.利用固相萃取技术分离之后,还可以对加氢后沥青质中微量的卟啉钒化合物进行富集,并研究了在渣油加氢前后沥青质中的卟啉钒化合物的分子组成变化.研究表明,对沥青质样品进行更细致的分离可以得到丰富、全面的沥青质分子组成数据,为石油加工提供更有价值的分子结构信息.     

轮古常渣及其组分中金属钒卟啉的分离与鉴定

采用改进的溶剂萃取方法对轮古常渣及其组分中的金属钒卟啉进行分离。结果表明,从轮古常渣中分离出的卟啉钒的质量分数为18.5%,从轮古常渣正庚烷可溶质和沥青质中分离出的卟啉钒的质量分数分别为68.0%和9.2%。用紫外-可见光谱对萃取出来的金属钒卟啉和甲磺酸脱金属后得到的游离卟啉进行表征。结果表明,轮古常渣及其正庚烷可溶质和沥青质中的金属钒卟啉主要是初卟啉。对轮古常渣中的游离卟啉进行基质辅助激光解吸电离飞行时间质谱分析证明,轮古常渣中的金属钒卟啉主要是初卟啉。     

5,10,15,20—四（对—乙酯苯基）卟啉LB膜的结构

对卟啉类化合物LB膜的结构、电性质和气敏性的研究已见报道。本文利用膜天平和UV-Vis分光光度计研究了标题化合物在气-液界面上的成膜特性、分子间相互作用和LB膜的结构。5,10,15,20-四(对-乙酯苯基)卟啉(TPEPP)由5,10,15,20-四(对-氰苯基)卟啉和乙醇酯化得到。元素分析测定值与计算值相符。λ(CHCl_3,nm):421,515,550,590,645;ν(KBr压     

基于临氢热解反应研究石油沥青质中镍和钒化合物的存在形态

本研究通过临氢热解方法处理委内瑞拉减压渣油沥青质,通过电感偶合等离子体质谱仪（ICP MS）、紫外-可见光光谱仪（UV-vis）、高温气相色谱-原子发射检测器联用仪（HT GC-AED）和傅里叶变换离子回旋共振质谱（FT-ICR MS）等手段分析表征反应产物,探究沥青质的分子组成与结构,以及镍和钒化合物的存在形态。实验结果表明,随着临氢热解反应温度从330℃升高至410℃,反应产物的甲苯可溶物收率由64%下降至19%,可被GC-AED检测到的镍、钒化合物的含量大幅度升高,镍和钒卟啉的分子组成分布也随反应温度的升高呈现出规律性的变化。     

几种硝基苯甲酸卟啉酯类化合物的合成

卟啉化合物在模拟光合作用、探索高效利用太阳能等方面具有重要的理论意义和应用前景^[1]。近年来,人们对共价键相连的“卟啉-醌”类化合物研究较多,而关于“卟啉-硝基”类化合物的报道则较少,硝基具有强吸电子等特性,它作为“卟啉-硝基”类化合物的电子受体有利于分子内发生电子传递,可望是光合作用机理研究中的一类较好的模型化合物。为此,我们设计合成了具有不同性质的供体和不同位置的受体的8种新硝基苯甲酸及苯甲酸卟啉酯类化合物,它们的结构已分别通过质谱、核磁、红外、紫外可见光谱以及元素分析确证,结果见表1、2。     

金属卟啉类化合物的催化作用

卟啉是含四个吡咯分子的大环类化合物,母体卟吩自由碱的骨架如图1(1)所示。自然界中分布最广的卟啉化合物是原卟啉Ⅸ(图1(2))、酞菁(图1(3))具有和卟吩核类似的结     

沥青质对塔河稠油黏度的影响机理研究

本文研究了沥青质对塔河稠油黏度的影响机理.首先对不同沥青质含量的稠油的黏度进行了测试,研究结果表明稠油的黏度随沥青质含量的增加而增大;其次,对不同沥青质含量的稠油进行了储能模量的测试,实验结果表明,随着沥青质含量的增加,稠油的储能模量和黏度呈现同步增大的趋势,说明大量的沥青质在稠油内部形成了空间网状聚集体,导致稠油的弹性和黏度增大;最后,对沥青质空间网状结构的成因以及沥青质对稠油黏度的影响机理进行了深入分析.通过甲基化改性实验,脱除沥青质分子上的活泼氢,以此减弱与活泼氢相关的氢键等沥青质分子间作用力,对比了改性前后沥青质分子聚集体的变化以及稠油黏度的变化.实验结果表明,在众多沥青质分子间作用力中,与活泼氢相关的分子间作用力更有利于沥青质空间网状结构的形成,对稠油黏度的影响也更大.     

High temperature gas chromatography – atomic emission detection of metalloporphyrins in crude oils

High temperature gas chromatography-atomic emission spectroscopy is used for the detection of vanadyl, nickel, and iron porphyrins in crude oils. The operational variables are investigated with regard to the effects on performance in high temperature GC-AED. Under optimal conditions, the method provides charactersitic metal distributions for oils from different sources. The method is also advantageous in the study of decomposition of petroleum metal species. Several crude oils were analyzed for the content of the distillable metals in comparison with total metals as determined by a direct spectroscopic method.     

Chromatographic isolation of vanadyl porphyrins from heavy oil resins

A broad fraction of petroleum vanadyl porphyrins of high spectral purity was isolated from heavy oil resins with high vanadium content using a two-step chromatographic method. At the first step, the primary concentrate of vanadyl porphyrins was separated from the resins on the silica gel column. At the second step, it was further purified by the gradient elution through the column packed with sulfo-cationite. According to UV—VIS spectroscopy, this technique allows one to isolate up to 70% of vanadyl porphyrins with the spectral purity corresponding to the best results of other purification methods providing only narrow fractions of vanadyl porphyrins of comparable purity. Deoxophylloerythroetioporphyrin (DPEP) and etioporphyrin (Etio) series of vanadyl porphyrins with the carbon number range of C₂₈—C₄₂ and DPEP/ Etio ratio equal to 1.18 were identified by MALDI-TOF mass-spectrometry.     

EPR spectra of V(IV) complexes and the structure of oil porphyrins

For natural bitumoids, the effects of the structure of vanadyl-porphyrin complexes on the EPR spectra were investigated. The ambiguity of the hyperfine structure (its presence or absence) corresponding to four nitrogen atoms in the spectra of oil vanadyl porphyrins correlates with the changes in the second coordination sphere of the nearest environment of the metal ion, namely, in methine bridges.     

Observation of vanadyl porphyrins and sulfur-containing vanadyl porphyrins in a petroleum asphaltene by atmospheric pressure photonionization Fourier transform ion cyclotron resonance mass spectrometry

Vanadyl (VO) porphyrins and sulfur-containing vanadyl (VOS) porphyrins of a wide carbon number range (C(26) to C(52)) and Z-number range (-28 to -54) were detected and identified in a petroleum asphaltene by atmospheric pressure photonionization (APPI) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). APPI provides soft ionization of asphaltene molecules (including VO and VOS porphyrins), generating primarily molecular ions (M(+.)). The ultra-high mass resolving power (m/Delta m(FWHM) approximately 500 K) of FTICR-MS enabled resolution and positive identification of elemental formulae for the entire family of VO and VOS porphyrins in a complicated asphaltene matrix. Deocophylerythro-etioporphyrin (DPEP) is found to be the most prevalent structure, followed by etioporphyrins (etio)- and rhodo (benzo)-DPEP. The characteristic Z-distribution of VO porphyrins suggests benzene and naphthene increment in the growth of porphyrin ring structures. Bimodal carbon number distributions of VO porphyrins suggest possible different origins of low and high molecular weight species. To our knowledge, the observation of VOS porphyrins in a petroleum product has not previously been reported. The work is also the first direct identification of the entire vanadyl porphyrin family by ultra-high resolution mass spectrometry without chromatographic separation or demetallation.     

Axial ligand coordination in sterically strained vanadyl porphyrins: synthesis, structure, and properties

A hitherto unknown family of six-coordinate vanadyl porphyrins of the sterically crowded, nonplanar 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetranitroporphyrin incorporating axial ligand L [where L is pyridine, tetrahydrofuran (THF), or methanol (MeOH)] has been isolated as VO(tn-OEP)(L) in the solid phase for the first time and also structurally characterized. The presence of four electron-withdrawing, bulky nitro groups at the meso positions of vanadyl octaethylporphyrins severely distorts the porphyrin macrocycles and significantly enhances the affinity for the axial ligands, where even weak sigma-donating ligands, such as MeOH, bind strongly enough to be isolable in the solid phase and that too under the offset effects of the macrocyclic distortions. Thus, the axial ligand affinity is influenced by both the electronic and conformational effect, which cannot be separated completely in this series. The solid-state magnetic measurements and their typical electron paramagnetic resonance (EPR) spectrum show the presence of a single, unpaired electron, consistent with V(IV) formulation. The VO stretching frequency for VO(tn-OEP) occurs as a sharp, strong peak at 1008 cm(-1), which is consistent with five-coordinate vanadyl porphyrins, while VO(tn-OEP)(L) displays a strong band at lower wavenumbers. The downshift in nu(VO) upon axial coordination increases with increasing donor strength of the axial ligands; for pyridine, the downshift is 30 cm(-1), while for THF and MeOH, the downshifts are nearly 18 cm(-1). X-ray structure determinations authenticate axial coordination in a purely saddle-distorted porphyrin macrocycle for all of the complexes reported here in which V-Np distances are significantly shorter, while the porphyrin cores have been expanded on axial ligand coordination. As a result, vanadium atoms are more inplane than in a five-coordinate species. The binding of L does not change the spin or metal oxidation states (V(IV), d(1)-system) of the complexes; therefore, the changes observed are truly the reflections of axial ligand coordination. Electrochemical data obtained from cyclic voltammetric studies reveal that the complexes are much easier to reduce (by approximately 1200 mV) but more difficult to oxidize (by approximately 500 mV) as compared to nearly planar VO(OEP). The complexes undergo two one-electron oxidations due to pi-cation radical and dication formation and three one-electron reductions. The first two reductions are because of pi-anion radical and dianion formation, while the third quasi-reversible reduction is assigned to a metal-centered process (V(IV) --> V(III)). These results can be useful for identifying the interaction of the vanadyl porphyrins with the biological targets in their reported involvement in potent insulinomimetic activity and in anti-HIV agents.     

Hydrogen chemical ionization mass spectrometry of metalloporphyrins

The hydrogen chemical ionization (H₂ CI) mass spectra of a range of metal(II) (Ni, Cu, Co, Pt), metal (III) (Al, Mn, Ga, Fe (bearing a single axial ligand)) and metal(IV) (Si, Ge, Sn (bearing two axial ligands) and V (as V?O²⁺)) porphyrins have been determined, The spectra are highly dependent on the coordinated metal, rather than the axial ligand(s) (where present). Ni(II), Cu(II), Mn(II or III), Ga(III), Ge(IV), Fe(III) and Sn(IV) porphyrins fragment via hydrogenation and demetallation, followed by cleavage of the resulting porphyrinogens at the meso(bridge) positions to give mono- and di-pyrrolic fragments. Tripyrrolic fragments are also observed in the case of Ni(II), Cu(II) and Sn(IV). Fragmentations of this type are similar to those observed for free-base porphyrins. In the case of Pt(II), Co(II), Al(III), Si(IV) and V(IV) (as vanadyl), the dipyrrolic fragment ions are either very weak or completely absent; hence their H₂CI spectra contain limited structural information. This variable CI behaviour may be related to the relative stabilities of the metalloporphyrins together with the multiple stable valency states exhibited by several metals.     

Chemistry of Vanadyl Porphyrins

The chemistry of vanadyl porphyrins has been explored using vanadyl octaethylporphyrin as the type substance, and with special reference to the occurrence of such substances in petroporphyrins. Spectroscopic properties (electronic spectra, IR spectra, mass spectra) are described, and electronic spectra are employed to detect the occupation of the vacant axial coordination site. Direct substitution of vanadyl octaethylporphyrin furnishes meso-substituted products: various nitro, chloro and benzoyloxy derivatives are characterised. Trans alkylation is observed when vanadyl octaethylporphyrin is heated in vacuo on various supports, including clay minerals: the reaction provides a model for the generation of the homologous series of vanadyl polyalkylporphyrins found in crude oils and bitumens.     

A Highly Efficient Chelating Polymer for the Adsorption of Uranyl and Vanadyl Ions at Low Concentrations

A new polymer containing double amidoxime groups per repeating unit was synthesized to enhance the metal ion uptake capacity. The adsorption properties of this new polymeric adsorbent, amidoximated poly(N,N-dipropionitrile acrylamide), for U(VI), V(V), Cu(II), Co(II) and Ni(II) ions were investigated by batch and flow-through processes at very low concentration levels (ppb). The chelating polymer showed high adsorption capacity for uranyl as well as vanadyl ions. In selectivity studies from a mixture of metal ions in aqueous solutions, the adsorbent showed high selectivity for uranyl and vanadyl ions in the following order: U(VI) > V(V) Co(II) = Cu(II) Ni(II) as determined by calculating the distribution coefficients D, of corresponding ions. The adsorption of uranyl and vanadyl ions from natural seawater by the new adsorbent was also examined in flow through mode.     

Speciation of heavy metals in environmental water by ion chromatography coupled to ICP–MS

Biogenic (e.g. phytochelatins, porphyrins, DOM) as well as anthropogenic (e.g. NTA, EDTA, phosphonates) chelators affect the mobility and cycling of heavy metals in environmental waters. Since such chelators can form strongly bound anionic heavy metal complexes that are stable and highly mobile, anion-exchange chromatography coupled to ICP-MS was investigated. A narrow bore HPLC system was connected to a micro concentric nebuliser for in-line sample introduction. A new chromatographic procedure based on a synthetic hydrophilic quaternary ammonium anion exchanger in combination with nitrate as a strong eluent anion, and gradient elution, provided high separation selectivity and a large analytical window. Low detection limits (nmol L(-1)) were achieved by on-column matrix removal and sample preconcentration. This allowed the method to be successfully applied to different environmental research areas. In ecotoxicological studies of heavy metal effects on algae low concentrations of metal EDTA complexes were determined in nutrient solutions without interference from high (buffer) salt concentrations. In groundwater, infiltrated by a polluted river, mobile metal EDTA species were observed. In river water of different pollution levels beside CuEDTA other anionic Cu-complexes were found in nmol L(-1) concentrations.