【作者】 马云倩；

【导师】 王睿；

【作者基本信息】 山东大学 ， 环境工程， 2014， 博士

【摘要】 硫化氢(H2S)是天然气、炼厂气、合成气等工业气体中的一种有害物质,它的存在不仅会腐蚀生产设备和管路,导致催化剂中毒,而且还是引起大气污染、温室效应、破坏臭氧层以及形成酸雨的主要物质之一,是必须消除或控制的环境污染物。在工业脱除H2S的众多方法之中,绿色湿法脱硫工艺因脱硫剂可循环使用,并且能够从废气中回收硫磺、无二次污染等优点,已成为当今研究的热点。而杂多酸化合物用于脱除硫化氢是一种面向天然气净化与硫磺回收的新方法。长期以来杂多化合物一直被用作特定反应的催化剂,无直接利用其氧化还原性能进行污染物治理研究的先例。鉴于钼钨为我国丰产元素,本文合成了Dawson结构钒取代的磷钼酸以及掺杂过渡金属的Keggin结构磷钼钒酸,进行湿法氧化脱除H2S的研究,并且将脱硫扩展到了作为绿色溶剂的离子液体的领域,构建了多酸及功能化离子液体绿色脱硫体系,主要研究内容为以下五个方面：一、采用乙醚萃取法制备了一系列Dawson结构磷钼钒酸H6+n[P2Mo18-nVnO62](n=1～4),考察了不同钒原子取代数目、吸收温度、H2S浓度、杂多酸浓度条件下,Dawson结构磷钼钒酸水溶液对H2S的吸收效率。吸收H2S后采用微波辐照下携带水汽的空气对脱硫剂进行再生,与单纯空气再生进行了比较,并进一步分析了再生性能。结果表明,脱硫性能随着钒原子的增加而降低,随着温度的升高而降低,随着气速的增大而降低,并且随着杂多酸浓度的减小而降低。微波辅助空气再生温度越高,微波辐照时间越长,微波功率越大,吸收剂再生效果越好,微波辅助空气再生条件推荐为：再生温度55℃,微波辐照时间为60min,微波功率695W。吸收前、吸收后以及微波辅助空气再生后H7[P2Mo17VO62]的红外谱图表明,吸收H2S后Mo元素有价态降低的趋势,而再生后Mo元素有价态升高的趋势。对微波再生前后H7[P2Mo17VO62]中Mo和V元素的XPS表征中,未监测到Mo元素吸收前后价态的变化,而V元素由于含量很少也未监测到。通过氧化还原电位以及溶液化学需氧量的测定,定量揭示了整个过程的氧化还原情况,比较了微波辅助空气再生与单纯空气再生的效果。结果表明,随着脱硫的进行,H7[P2Mo17VO62]水溶液的氧化还原电位逐渐降低,当通入空气进行再生时,氧化还原电位逐渐升高,而微波辅助空气再生过程,杂多酸水溶液的氧化还原电位要高于单纯空气再生。对吸收后、微波辅助空气再生和单纯空气再生后的COD值分别为187.2mg O2/L、120.1mg O2/L和136.8mg O2/L,表明微波辅助空气再生的程度要大,微波能够活化空气中氧气从而促进脱硫后吸收剂的再生,是优于单纯空气再生的一种新的再生方法。二、采用水热合成法制备了H4PMo11VO40(M11PV1)以及五种过渡金属Cu, Fe, Zn, Mn和Cr掺杂的H4PMo11VO40(M11PV1Cu, M11PV1Fe, M11PV1Zn, M11PVIMn和M11PVlCr),并且通过FT-IR、XRD和TGA-DSC表征确认了其Keggin杂多酸结构和热稳定性,同时比较了五种过渡金属掺杂的杂多化合物与M11PV1的循环伏安曲线,得到M11PV1Cu和M11PV1Fe能够明显的观察到Cu(0)到Cu(Ⅱ)以及Fe(0)到Fe(Ⅲ)的还原峰,说明掺杂Cu2+和Fe3+的杂多化合物中,Cu2+/Fe3+与PMo11VO404-存在一种特殊的连接。首次研究了六种杂多化合物水溶液对H2S的吸收性能,并进一步分析了氧化脱硫机理。实验结果表明,M11PVlCu水溶液脱硫效率最高(>87%),并且最高时可达到98%,与其他吸收剂不同的是其效率曲线呈现“桥形”,即脱硫效率先升高并保持一段时间后降低,M11PV1Fe, M11PV1Zn, M11PVIMn和M11PV1Cr水溶液脱硫效率在85%-50%之内逐渐降低,而M11PV1水溶液的脱硫效率相对稳定,即保持在70%-65%之间。在吸收前、吸收90min和吸收300min后,分别对M11PV1Cu中元素Mo、 Cu和V进行XPS表征,结果表明,在吸收300min后,Cu2+全部被还原成Cu+,而Mo6+和Vs+分别被部分还原成Mo5+和V4+,此时Cu元素已无法提供氧化能力的情况下,脱硫效率仍然非常高(达到85%以上),显然高于M11PV1的脱硫效率(70%～65%),由此推断Cu2+或Cu+能够以物理吸附或化学结合形式储存H2S,然而在高价态Mo和V存在的情况下,其储存形式则极有可能为CuS和Cu2S化学性的结合,而高价态Mo和V有能力氧化S2-时,最终会将CuS和Cu2S氧化为硫磺。而M11PV1Cu水溶液呈现“桥形”脱硫效率则进一步证明Cu+存在储存H2S的能力或者能力比Cu2+更强。三、通过沉淀法制备了杂多酸离子液体[Bmim]3PMo12O40(简写为[Bmim]3PM),通过红外和XRD表征确定了其仍然具有Keggin杂多酸结构,TGA-DSC表征则说明[Bmim]3PM具有良好的热稳定性。将[Bmim]3PM溶解于四种离子液体[Bmim]Cl,[Bmim]BF4,[Bmim]PF6和[Bmim]NTf2中得到[Bmim]3PM-IL脱硫剂,首次研究了其吸收H2S的性能。结果表明,80℃下,0.005mol/L的脱硫剂吸收H2S的效率为：[Bmim]3PM-[Bmim]Cl＞[Bmim]3PM-[Bmim]BF4＞H3PM012O40-H2O＞[Bmim]3PM-[Bmim]PF6>[Bmim]3PM-[Bmim]NTf2＞[Bmim]3PM-H2O＞H2O,并且研究了80℃不同[Bmim]3PM浓度(0,0.001,0.005和0.01nol/L)[Bmim]3PM-[Bmim]Cl和[Bmim]3PM-[Bmim]BF4脱硫剂吸收H2S的效率,结果表明,当[Bmim]3PM浓度为0nol/L时,两种脱硫剂吸收H2S的效率都很低,但是当[Bmim]3PM浓度为0.001mol/L时,[Bmim]3PM-[Bmim]Cl在60min内的脱硫效率接近100%,而此时[Bmim]3PM-[Bmim]BF4的脱硫效率在60min时只有40%左右,当[Bmim]3PM浓度增大为0.01mol/L时,[Bmim]3PM-[Bmim]BF4的脱硫效率才能基本达到100%。在45～180℃之间,脱硫效率基本不受温度变化影响,但是温度过低,离子液体粘度越大,影响脱硫剂对气体的吸收,因此该脱硫剂更适用于高温脱硫。[Bmim]3PM-[Bmim]Cl的硫容为230.9g·L-1,高于[Bmim]3PM-[Bmim]BF4(62.2g·L-1)和H3PMo12O40-H2O(59.0g·L-1)的硫容,说明[Bmim]Cl离子液体作为溶剂,能够有效地促进[Bmim]3PM氧化H2S。[Bmim]3PM-[Bmim]Cl优异的脱硫性能与[Bmim]3PM在[Bmim]Cl中的溶解、H2S与[Bmim]Cl的相互作用有着极其重要的关系。浊度测试,显微镜测试均表明[Bmim]3PM在[Bmim]Cl中的溶解最好,并且H2S与Cl之间的相互作用最强。氧化产物不易物理性分离,因此用CS2萃取出来,通过与标准硫磺的紫外光谱作对比得到氧化产物为硫磺。[Bmim]3PM-[Bmim]Cl可以通入空气24h得到再生并能够循环使用六次以上,但是再吸收保持100%脱硫效率的时间减半。四、合成并通过FT-IR和TG-DSC表征了有机胺型铁基离子液体1.6Et3NHCl·FeCl3,确定了其结构和良好的热稳定性,与现有的水相铁法吸收剂相比,脱硫剂体系无蒸发损失。研究了H2S浓度为832mg/m3,温度为40-180℃,气速分别为100、300、400和500mL/min的条件下,H2S的去除率,并计算了硫容。结果表明,有机胺型铁基离子液体适用于气速小于300nl/min、温度大于80℃的高温脱硫,其硫容为6.36g/L,远高于氯化咪唑铁基离子液体。通过XRD分析,确定了脱硫产物为斜方晶体硫磺(α),与传统水相湿法氧化脱硫得到的产物相同,但是不同于氯化咪唑铁基离子液体的脱硫产物,产物硫磺易于分离。采用密度泛函理论从分子水平上研究了H2S与1.6Et3NHCl·FeCl3、[Bmim]FeCl4两种铁基离子液体以及Fe3+水溶液的相互作用,从理论上比较了脱硫剂中的基质对H2S吸收的影响,确定了胺基对H2S吸收的促进作用。通入空气可以快速有效地对脱硫剂进行再生。五、合成并通过FT-IR和TGA-DSC表征了3种功能化离子液体[Bmim]HCO3,[TMG]L和[MEA]L,确定了其结构和良好的热稳定性,并将其与包括传统离子液体([Bmim]Cl和[Bmim]BF4)在内的5种离子液体分别与N-甲基二乙醇胺(MDEA)水溶液混合,得到新型复配脱硫剂,考察了离子液体的消泡性能,以及复配脱硫剂吸收H2S和再生性能。实验结果表明,低温有利于复配脱硫剂对H2S的吸收；室温下,10mL相同质量配比(IL:MDEA=1:3)的复配脱硫剂吸收H2S的效率为[Bmim]Cl-MDEA-H2O＞[Bmim]HCO3-MDEA-H2O＞[Bmim]BF4-MDEA-H2O＞MDEA-H2O＞[TMG]L-MDEA-H2O＞[MEA]L-MDEA-H2O。单一MDEA水溶液60min后的脱硫效率为87%,添加[Bmim]Cl、[Bmim]HCO3和[Bmim]BF4离子液体的脱硫效率可高达97%,优于单—MDEA水溶液；添加[MEA]L和[TMG]L离子液体的复配体系,其脱硫效率反而下降。除了[TMG]L,其他离子液体均起到不同程度的消泡作用,其中[Bmim]HC03离子液体消泡效率最高,为46.4%,并且随着[Bmim]HCO3在脱硫剂中比例的增加而提高。采用密度泛函理论计算了离子液体、MDEA和H2S两者之间结合后释放的热量,通过与实验结果比较,结果表明,在H2S的吸收效率方面,离子液体和MDEA结合的稳定性为主要因素。在60℃下,向吸收H2S饱和的复配脱硫剂[Bmim]BF4-MDEA-H2O,[Bmim]HCO3-MDEA-H2O和[Bmim]Cl-MDEA-H2O中通入空气可基本再生,但是H2S并无法完全被吹除,再生效率分别为94.89%,94.74%和94.66%,这与H2S和离子液体的结合能大小有关,结合能越大说明结合越稳定,越有利于吸收,但是不利于H2S与离子液体的分离,使得再生程度降低。更多还原

【Abstract】 Hydrogen sulfide (H2S) is a hazardous substance of industrial gas such as natural gas, refinery gas, synthesis gas and so on. H2S cannot only cause catalyst poisoning and corrosion to pipelines in the process of transport, but also it is considered as one of the main contaminants leading to air pollution, greenhouse effect and ozone depletion. Therefore, H2S is one of the environmental pollutants that should be removed and controlled. Refer to the removal of H2S, green wet desulfurization has now become a hot research with some advantages, such as recycle of desulfutization agent, recovery of sulfur from the exhanst gas and no secondary pollution. H2S removal by heteropolycompounds (HPCs) is a new method faced on natural gas purification and recovery of sulfur. HPCs have been used as a catalyst in some certain reactions for a long period, but not been applied to contaminants treatment for their oxidation-reduction. Based on the abundance of Mo and W element, V-substitued phosphomolybdic acid and transition metal doped HPC solutions were developed as the desulfurizers, and it is also extended to the field of ionic liquid (IL) which is used as a green solvent. HPC and functionalized ionic liquid green desulfurization were constructed. The content of this thesis contains the following five parts:Ⅰ) Synthesis, Desulfuration and Air Regeneration of Dawson-type Molybdovanadophosphoric HeteropolyacidDawson-type molybdovanadophosphoric heteropolyacids H6+n[P2Mo18-nVnO62](n=1～4) were prepared using the method of ethyl ether extraction, and the absorption efficiency of H2S by their solutions was measured under different conditions reflecting the effects of the number of vanadium, absorption temperature, concentrations of H2S gas and heteropolyacid. Then, desulfurizer was regenerated by air with steam under microwave irradiation, and the regenerability was investigated, compared with single air regeneration. As a result, H2S removal efficiency decreases with the number of V atom, temperature and gas flow increasing, and with the concentration of HPA decreasing. Microwave-assisted air regeneration improves with the temperature, irradiation time and power increasing, therefore, the conditions of microwave-assisted air regeneration were proposed that the temperature, irradiation time and power was intended to be55℃,2h and695W, respectively. Characterized by FT-IR, the characteristic peak of desulfurizer H7[P2Mo17VO62] was found to be changed after H2S absorption and microwave-assisted air regeneration, which indicates that the valence state of Mo decreases and increases, respectively. The changes of the valence state for Mo and V during absorption and regeneration did not be detected by XPS. The absorbents were tested by redox potentiometry and chemical oxygen demand (COD), which revealed that the redox in absorption and regeneration, and microwave-assisted air regeneration was further compared with single air regeneration. The result shows that the redox potential of HPA solution decreases in the process of absorption, and increases in the process of regeneration, and the redox potential for microwave-assisted air regeneration is higher than that for single air regeneration. The COD value after absorption, microwave-assisted air regeneration and single air regeneration is187.2,120.1and136.8mg O2/L, respectively, and this indicates that the regeneration of heteropolyacid is promoted by foregoing microwave assisted air regeneration method which can activate O2. In summary, microwave assisted air regeneration is proved to be a new method superior to single air regeneration and recyclable forever without any change in the structure of this absorbent.II) Effects of Fe-, Cu-, Zn-, Mn-and Cr-doped H4PMo11VO40for the removal of H2S in wet oxidationA series of new transition metal (Cu, Fe, Zn, Mn and Cr)-doped H4PMo11VO40(M11PV1) were prepared by the method of hydrothermal synthesis and the synthetic heteropolycompounds were abbreviated as M11PV1Cu, M11PV1Fe, M11PV1Zn, M11PV1Mn and M11PV1Cr. Their structures and thermostability were confirmed by FT-IR, XRD and TGA-DSC techniques. The CV curves of M11PV1Cu, M11PV1Fe, M11PV1Zn, M11PV1Mn and M11PV1Cr were compared with M11PV1, and the deoxidization peaks of Cu (0) to Cu (Ⅱ) and Fe (0) to Fe (Ⅲ) were only observed, and the result shows that a special connection is set up between Cu2+/Fe3+and PMo11VO404-. H2S removal efficiency of M11PVlCu, M11PVlFe, M11PV1Zn, M11PV1Mn, M11PV1Cr and M11PV1was studied, and the mechnism of oxidation desulfurization was analyzed. The experimental results demonstrates that M11PV1Cu has the best H2S absorption efficiency (＞87%, and the top efficiency is nearly100%) which presents in ’bridge type’, and it shows that the efficiency increases firstly and then keeps one value for some time and at last decreases. The H2S absorption efficiency of M11PVlFe, M11PV1Zn, M11PV1Mn and M11PV1Cr decreases between85%～50%, while that of M11PV1is stable between70%～65%. The XPS spectra of elements Mo, Cu and V shows that after300-min absorption, all of Cu2+ions have already been reduced to Cu+, whilst Mo6+and V5+have been partly reduced to Mo5+and V4+, and the H2S absorption efficiency of M11PV1Cu is still very high (＞85%), and higher than that of M11PV1, even Cu+did not have oxidizability with H2S, and it indicates that Cu2+/Cu+can adsorb or store H2S. The XPS spectra of S yielded indicates that H2S can be oxidized to sulfur, and no S2-suggests that there is no Cu2S, and all of H2S are oxidated to S by Mo and V elements. The’bridge type’ also suggests that Cu+can adsorb or store H2S, or its capacity is better than Cu2+.Ⅲ) An excellent recycling strategy for highly efficient removal of H2S by [Bmim]3PMo12O40dissolved in [Bmim]ClA kind of functionalized ionic liquid [Bmim]3PMo12O40([Bmim]3PM) was prepared by the method of precipitation. The structure and thermostability of [Bmim]3PM was confirmed by FT-IR, XRD and TGA-DSC. An environmentally benign approach has been proposed for the removal of H2S using a Keggin-type heteropolyanion-based ionic liquid [Bmim]3PM dissolved in a green solvent-ionic liquid (IL). The results show that80℃, H2S removal efficiency by [Bmim]3PM-IL of0.005mol/L is in the following sequence:[Bmim]3PM-[Bmim]Cl＞[Bmim]3PM-[Bmim]BF4＞H3PM012O40-H2O＞[Bmim]3PM-[Bmim]PF6＞[Bmim]3PM-[Bmim]NTf2＞[Bmim]3PM-H2O＞H2O. In the condition of80℃, different concentration of [Bmim]3PM (0,0.001,0.005and0.01mol/L), H2S removal efficiency by [Bmim]3PM-[Bmim]Cl and [Bmim]3PM-[Bmim]BF4was investigated, and the result shows that when the concentration of [Bmim]3PM is0mol/L, the H2S removal efficiency of the two desulfurizers is very low; when the concentration is0.001mol/L, H2S removal efficiency of [Bmim]3PM-[Bmim]Cl is nearly100%, but that of [Bmim]3PM-[Bmim]BF4is only40%; when the concentration is0.01mol/L, that of [Bmim]3PM-[Bmim]BF4reaches100%. The temperature (45～180℃) does not affect the H2S removal efficiency, but the viscosity of ionic liquids at low temperature affects the removal of H2S. Therefore,[Bmim]3PM-ILs are suitable to desulfurization at high temperature. The sulfur capacity of [Bmim]3PM-[Bmim]Cl (230.9g·L-1) is higher than that of [Bmim]3PM-[Bmim]BF4(62.2g·L-1) or H3PMo12O40-H2O (59.0g·L-1), which indicates that [Bmim]Cl as a solvent can improve the oxidation of H2S by [Bmim]3PM. Microscopic observation, turbidity measurement and quantum chemical calculations were used to analyse the factors (solubility of [Bmim]3PM in ILs and stabilization energy for H2S-Anion) that influence H2S removal efficiency, the results suggest that [Bmim]3PM is well dissolved in [Bmim]Cl and high stabilization energy for H2S-Cl-increases the residence time of H2S in [Bmim]Cl, which makes the reaction between H2S and [Bmim]3PM more sufficient. H2S is oxidated to elemental S and Mo6+is reduced to lower valence state in the absorption stage according to UV-vis and FTIR data, respectively. Using air,[Bmim]3PM-[Bmim]Cl can be recycled for more than six times without any obvious decrease in the removal efficiency of H2S, but the time for keeping100%reduces to the half.IV) H2S Absorption Capacity and Regeneration Performance of Amine Fe-based Ionic LiquidAmine Fe-based ionic liquid1.6Et3NHCl·FeCl3was synthetized with ideal H2S absorption capacity and good thermostability. H2S removal efficiency was tested under the condition with concentration of H2S being832mg/m3, temperature ranging from40to180℃, and gas flow of100,300,400or500mL/min. The results show that when the gas flow is less than400mL/min, H2S removal efficiency can reach100%; H2S removal efficiency increases with the increasing in temperature and tends to approach an asymptotic value. Under the optimal conditions, the sulfur capacity of1.6Et3NHCl·FeCl3is6.36g/L, higher than that of [Bmim]FeCl4. Comparing the FT-IR spectra before and after H2S absorption, redox reaction between1.6Et3NHCl·FeCl3and H2S is confirmed. The interaction between H2S and1.6Et3NHCl·FeCl3/[Bmim]FeCl4/H2O has been studied at the molecular level using density functional theory, and the influence of the substrate on H2S absorption was illustrated to be responsible for the enhancement of H2S absorption by aminal group. The product after H2S absorption is orthorhombic crystal sulfur (α), which is the same as the product from traditional aqueous phase oxidation desulfurization.1.6Et3NHCl·FeCl3ionic liquid can be reused efficiently after quick regeneration by air flow.V) H2S Absorption Capacity Studies of Ionic Liquid-MDEA-H2O Combined DesulfurizersThree kinds of functionalized ionic liquids [Bmim]HC03,[TMG]L and [MEA]L were synthetized which was referred to previous methods. The structure and thermostability of the synthetic ionic liquids (ILs) was confirmed by FT-IR spectrum and thermogravimetry characterization, respectively. The new combined deoxidizer was prepared by mixing ionic liquid ([Bmim]HC03,[TMG]L,[MEA]L,[Bmim]Cl or [Bmim]BF4) with methyldiethanolamine (MDEA) aqueous solution according to certain proportion. In the conditions of different ionic liquids, absorption temperature and combined proportion, H2S absorption and bubble eliminated capacity by deoxidizers and ILs were measured, and regeneration performance of optimized deoxidizer was studied. The concentration of SO42-in regenerated deoxidizer was analyzed by ion chromatography after deeply oxidation by O3, and the mechanism of absorption was analyzed by density functional theory. The results show that absorption capacity is in the sequence that [Bmim]Cl-MDEA-H2O＞[Bmim]HCO3-MDEA-H2O＞[Bmim]BF4-MDEA-H2O＞MDEA-H2O＞[TMG]L-MDEA-H2O＞[MEA]L-MDEA-H2O, and the major factor is attributed to the the stability of IL-MDEA;[Bmim]HCO3performs the best capacity of bubble eliminated;[Bmim]Cl-MDEA-H2O,[Bmim]HCO3-MDEA-H2O and [Bmim]BF4-MDEA-H2O can be regenerated by air basicly, and high stability of IL-H2S brings higher the absorption efficiency, but smaller regeneration.更多还原