天然气化学转化新途径

21世纪初将迎来天然气能源时代,作为石油的替代资源,由天然气间接转化(经由合成气)和直接转化为液体燃料或重要化工品原料已成为人们关注的热点。本文简要介绍了80年代以来世界各国和我国有关天然气转化的各种新过程。     

膜分离天然气脱水蒸汽技术的研究现状

天然气脱水蒸汽是天然气净化过程中的必要环节,选择合适的脱水蒸汽技术和工艺至关重要。本文首先简要概述了新兴的膜分离天然气脱水蒸汽方法的特点,然后介绍了膜分离性能的表征参数及测试、膜组件设计及操作条件的选择,重点介绍了近年来膜分离甲烷脱水蒸汽技术中的聚合物膜材料、沸石分子筛膜材料,最后展望了金属有机骨架材料的应用潜力以及天然气脱水蒸汽技术未来的发展趋势。     

The CO2 Reforming of Natural Gas in a Silent Discharge Reactor

The conversion of a 1:1 CH ₄ /CO ₂ mixture to H ₂ and CO was shown to occur at ambient temperature in a silent discharge reactor. Conversions of up to 50% were achieved with two reactors in series with a total residence time of 3 min at 13kV and 25 mA.     

一种天然气直接转化制乙烯的新过程

Many routes for the direct conversion of methane have been explored to utilize a bundant natural gas resources.     

Rational Design of Porous Ionic Liquids for Coupling Natural Gas Purification with Waste Gas Conversion

Removal of trace impurities for natural gas purification coupled with waste gas conversion is highly desired in industry. We here report a type of porous ionic liquids (PILs) that can realize the continuous flow separation of CH₄/CO₂/H₂S and the conversion of the captured H₂S to useful products. The PILs are synthesized through a step-by-step surface modification of ionic liquids (ILs) onto UiO-66-OH nanocrystals. The introduction of free tertiary amine groups on the nanocrystal surface endows these PILs with an exceptional ability to enrich H₂S from CO₂ and CH₄ with impressive selectivity, while the permanent pores of UiO-66-OH act as containers to store an exceptionally higher amount of the selectively captured H₂S than the corresponding nonporous ILs. Simultaneously, the tertiary amines as dual functional moieties offer effective catalytic sites for the conversion of the H₂S stored in PILs into 3-mercaptoisobutyric acid, a key intermediate required for the synthesis of Captopril (an antihypertensive drug). Molecular dynamics, density functional theory calculations and Grand Canonical Monte Carlo simulations help understand both the mechanisms of separation and catalysis performance, confirming that the tertiary amines as well as the permanent pores in UiO-66-OH play vital roles in the whole procedure.     

The CO2 Reforming of Natural Gas in a Pulsed Corona Discharge Reactor

The conversion of CO ₂ and (CH ₄+CO ₂ ) mixtures to CO, at room temperature and atmospheric pressure conditions, in pulsed corona discharges, was investigated. Conversion of pure CO ₂ was 16.8% at 10 cm ³ -min ^–1 flow rate, which corresponds to 75 mol-min ^–1 rate of conversion. The CO ₂ conversion was improved to 38% (85 mol-min ^–1 by feeding the reactor with CH ₄+CO ₂ gas mixture (1:1 ratio), simultaneously with CH ₄ conversion of 46% (102.7 mol-min ^–1 ) at 10 cm ³ -min ^–1 flow rate of feed gases and 9 W power conditions. Rate of CO production is increased from 110 to 180 mol-min ^–1 with the variation of feed gas (CH ₄+CO ₂ mixture, 1:1 ratio) flow rate from 10 to 40 cm ³ -min ^–1 at 9W, which corresponds to energy efficiency of 2.5 to 4.1%. Highest energy yield of 25 g/kWh for CH ₄ conversion, 29 g/kWh for CO ₂ conversion, and 33 g/kWh for CO production were achieved.     

微波复合直流等离子体转化天然气制乙炔的研究

利用微波复合直流等离子体对天然气转化制乙炔反应进行了研究. 考察了氢烷比、气体流量、功率等参数对装置的能量利用率以及天然气转化反应的影响, 并考核了微波复合直流等离子体转化天然气制乙炔工艺的稳定性. 实验结果表明: 微波复合直流等离子体装置的能量利用率随等离子体工作气体的流量的增加而提高; 由于微波的作用使传统直流柱状等离子体分化为多根丝状等离子体, 从而使得电极的烧蚀方式由传统的点烧蚀变为面烧蚀, 并大幅度提高等离子体转化天然气工艺的稳定性和电极寿命; 甲烷的转化率和乙炔的收率随功率的增加而提高, 随CH₄/H₂比和气体流量的增加而降低, 在氢烷比为0.9、总气体流量为760 L/min、微波源输出电功率6 kW、直流电源输出功率90 kW时, 甲烷转化率可达84.4%, 乙炔选择性为75.6%, 乙炔收率为63.8%, 乙炔能耗达10.8 kWh•kg^－1; 电极寿命超过200 h.     

Oxidative Conversion of Methane/Natural Gas into Higher Hydrocarbons

Oxidative coupling of methane (OCM) to ethylene and ethane is a futuristic process of great practical importance for the effective utilization of methane/natural gas. A brief summary of the work carried out at National Chemical Laboratory (Pune) for the development of catalyst and catalytic process for OCM, particularly addressing the major issues/limitations of the OCM process and efforts made to overcome the problems is presented. This review particularly covers the development of a number of highly active/selective and stable unsupported and supported (using commercial catalyst carriers) catalysts for the OCM process and also the process of improvements/modifications to overcome most of the limitations of OCM.     

Conversion Natural Gas to Ci Hydrocarbons via Cold Plasma Reaction

Natural gas is not only an increasing important role in energy and chemicals supplies in 21st century but also the second most important of the greenhouse gases^[1]. For the past 200 years atmospheric methane concentrations have increased from 0.8 to 1.65ppm. This change in methane concentration had been led to an estimated increase in radiative forcing of climate of 0.47 W/m² compared to the increase of 1.56 W/m² due to the change in carbon dioxide concentration over a comparable time period^[2]. With large increases in natural gas reserves proven worldwide, it can be expected that natural gas will play an increasing important role in humanity future. Cold plasma chemical processing is a promising route for synthesis of chemicals that have high activation energies, because electric field can be excite reactant to the plasma and many kinds of reactive particles, electrons, free radicals, ions metastable species and photons are produced in a plasma chemical processing system.     

Catalytic Conversion of Simulated Biogas Mixtures to Synthesis Gas in a Fluidized Bed Reactor Supported by a DBD

The catalytic conversion of methane and carbon dioxide was studied in a fluidized bed reactor supported by a 13.56?Hz driven coaxial DBD-reactor. Palladium or cupper catalyst which are covered on Al₂O₃ particles were used. The goal was to test whether biogas can be used for the production of synthesis gas. The influences of discharge power, catalysts and temperature of the catalyst bed on the product yield were studied. The starting material and product stream was analyzed by quadrupole mass spectrometry and infrared spectroscopy. H₂/CO ratios can be adjusted in a range between 0.65 (without a catalyst) and 1.75 (using a copper catalyst). The process is highly selective for hydrogen production (up to 83%, using a Palladium catalyst). A copper catalyst increases the H₂/CO ratio can from 1.04 to 1.16 and the palladium catalyst from 1.11 to 1.43 by heating the catalyst to a temperature of 250°C.     

基于压电陶瓷的A型分子筛膜合成与吸附性能

无铅压电陶瓷0.8Na_0.5Bi_0.5TiO₃-0.2K_0.5Bi_0.5TiO₃表面采用化学改性预涂晶种作为基底,分别以微乳和澄清溶液法在基底上水热晶化合成了A型分子筛膜.通过XRD、SEM和FTIR对晶种及分子筛膜进行了表征,通过压电谐振法测量甲烷吸附性能.结果表明:微乳和澄清溶液法均合成单一A型分子筛相,1次合成分子筛膜的时间分别为6、9 h,通过不同镀膜次数生成A型分子筛膜的形貌、膜厚不同.经A型分子筛膜修饰压电振子后,其对甲烷气体的灵敏度可分别达到59 Hz/1%CH₄、68 Hz/1%CH₄.     

Gas to Liquid Conversion for Australian Stranded Gas

Australia has large reserves of natural gas but much of these are offshore. Conversion of gas to liquids, needed to meet an impending shortage of liquid fuels, must be carried out within the constraints of space available on an offshore platform. Research intended to meet these demands is outlined.     

基于压电陶瓷的A型分子筛膜合成与吸附性能

无铅压电陶瓷0.8Na0.5Bi0.5TiO3-0.2K0.5Bi0.5TiO3表面采用化学改性预涂晶种作为基底,分别以微乳和澄清溶液法在基底上水热晶化合成了A型分子筛膜。通过XRD、SEM和FTIR对晶种及分子筛膜进行了表征,通过压电谐振法测量甲烷吸附性能。结果表明:微乳和澄清溶液法均合成单一A型分子筛相,1次合成分子筛膜的时间分别为6、9h,通过不同镀膜次数生成A型分子筛膜的形貌、膜厚不同。经A型分子筛膜修饰压电振子后,其对甲烷气体的灵敏度可分别达到59Hz/1%CH4、68Hz/1%CH4。     

Thermodynamic Assessment of a Solar-Driven Integrated Membrane Reactor for Ethanol Steam Reforming

To efficiently convert and utilize intermittent solar energy, a novel solar-driven ethanol steam reforming (ESR) system integrated with a membrane reactor is proposed. It has the potential to convert low-grade solar thermal energy into high energy level chemical energy. Driven by chemical potential, hydrogen permeation membranes (HPM) can separate the generated hydrogen and shift the ESR equilibrium forward to increase conversion and thermodynamic efficiency. The thermodynamic and environmental performances are analyzed via numerical simulation under a reaction temperature range of 100–400 °C with permeate pressures of 0.01–0.75 bar. The highest theoretical conversion rate is 98.3% at 100 °C and 0.01 bar, while the highest first-law efficiency, solar-to-fuel efficiency, and exergy efficiency are 82.3%, 45.3%, and 70.4% at 215 °C and 0.20 bar. The standard coal saving rate (SCSR) and carbon dioxide reduction rate (CDRR) are maximums of 101 g·m⁻²·h⁻¹ and 247 g·m⁻²·h⁻¹ at 200 °C and 0.20 bar with a hydrogen generation rate of 22.4 mol·m⁻²·h⁻¹. This study illustrates the feasibility of solar-driven ESR integrated with a membrane reactor and distinguishes a novel approach for distributed hydrogen generation and solar energy utilization and upgradation.     

Oxidative Conversion of Wood Gasification Products in a Mixing Reactor

Russian Journal of Applied Chemistry - The results of thermodynamic calculations and experimental data on conversion of wood gasification tars in pyrolysis gas to tar-free fuel gas by partial...     

透氧膜反应器内NiO/MgO催化焦炉煤气重整反应途径

对透氧膜反应器内焦炉煤气(COG)重整反应模型进行分析.通过H2+N2、CH4+N2、CO+N2和H2+CH4+N2混合气在透氧膜反应器内重整反应,以及有无催化剂下重整反应和催化剂床层厚度重整反应实验,推测焦炉煤气重整反应模型:首先焦炉煤气中H2在催化剂活性金属镍颗粒上吸附解离,解离后的氢向高活性位迁移"(三相界面")并与膜表面侧晶格氧(或O2-)反应生成H2O.同时CH4也可能在活性镍颗粒上裂解生成CH3*和H*,反应生成的H2O与膜表面催化剂上裂解的碳反应生成H2和CO.未反应完的H2O在催化剂床层内与剩余CH4反应生成H2和CO.     

T型及KA分子筛膜的制备、修复及其天然气脱水蒸气性能研究

天然气在长距离输送之前必须进行脱水蒸气,膜分离法是天然气脱水蒸气的有效方法,其中膜材料是关键,而分子筛膜因具有均一的孔径、规则的孔道、良好的稳定性而备受关注。本研究选择孔径为3-5 μm,直径为2 cm的圆片状多孔氧化铝陶瓷作为成膜基底,通过在基底上预涂晶种后原位生长得到了T型和NaA分子筛膜,NaA分子筛膜进一步经过金属离子交换获得了KA分子筛膜,最后将两种分子筛膜应用于水蒸气含量为3.5%的甲烷气体(作为模型天然气)进行天然气脱水蒸气实验。研究结果表明,T型及KA分子筛膜对模型天然气脱水蒸气的H₂O/CH₄选择性分别为2.80和3.16。进而采用表面涂层法对分子筛膜中的缺陷进行了修复,从而有效提高了其模型天然气脱水蒸气性能,修复后的T型及KA分子筛膜的H₂O/CH₄选择性分别达到了10.52和17.71,水蒸气的渗透系数分别为104397 Barrer和28200 Barrer,甲烷损失率分别仅为2%和1%,修复后的两种分子筛膜皆具有良好的稳定性。