Computational Study of Adsorption and Separation of CO(2), CH(4), and N(2) by an rht-Type Metal-Organic Framework

In this work, a computational study is performed to evaluate the adsorption-based separation of CO(2) from flue gas (mixtures of CO(2) and N(2)) and natural gas (mixtures of CO(2) and CH(4)) using microporous metal organic framework Cu-TDPAT as a sorbent material. The results show that electrostatic interactions can greatly enhance the separation efficiency of this MOF for gas mixtures of different components. Furthermore, the study also suggests that Cu-TDPAT is a promising material for the separation of CO(2) from N(2) and CH(4), and its macroscopic separation behavior can be elucidated on a molecular level to give insight into the underlying mechanisms. On the basis of the single-component CO(2), N(2), and CH(4) isotherms, binary mixture adsorption (CO(2)/N(2) and CO(2)/CH(4)) and ternary mixture adsorption (CO(2)/N(2)/CH(4)) were predicted using the ideal adsorbed solution theory (IAST). The effect of H(2)O vapor on the CO(2) adsorption selectivity and capacity was also examined. The applicability of IAST to this system was validated by performing GCMC simulations for both single-component and mixture adsorption processes.     

Combination of MOFs and zeolites for mixed-matrix membranes

Mixed-matrix membranes (MMMs) were prepared by combinations of two different kinds of porous fillers [metal-organic frameworks (MOFs) HKUST-1 and ZIF-8, and zeolite silicalite-1] and polysulfone. In the search for filler synergy, the MMMs were applied to the separation of CO(2)/N(2), CO(2)/CH(4), O(2)/N(2), and H(2)/CH(4) mixtures and we found important selectivity improvements with the HKUST-1-silicalite-1 system (CO(2)/CH(4) and CO(2)/N(2) separation factors of 22.4 and 38.0 with CO(2) permeabilities of 8.9 and 8.4 Barrer, respectively).     

Synthesis of the phosphino-fullerene PPh2(o-C6H4)(CH2NMeCH)C60 and its function as an η1-P or η3-P,C2 ligand

Following the method of Prato et al., reaction of C(60), N-methylglycine and o-(diphenylphosphino)benzaldehyde affords PPh(2)(o-C(6)H(4))(CH(2)NMeCH)C(60) (1) in moderate yield. Compound 1 reacts with W(CO)(4)(NCMe)(2) to produce W(CO)(4)(η(3)-PPh(2)(o-C(6)H(4))(CH(2)NMeCH)C(60)) (2), through coordination of the phosphine group and one 6 : 6-ring junction of fullerene. Reaction of 1 and Os(3)(CO)(11)(NCMe) affords Os(3)(CO)(11)(PPh(2)(o-C(6)H(4))(CH(2)NMeCH)C(60)) (3), which undergoes a cluster fragmentation reaction in refluxing toluene to produce Os(CO)(3)(η(3)-PPh(2)(o-C(6)H(4))(CH(2)NMeCH)C(60)) (4). Thermal reaction of 1 and Os(3)(CO)(12) affords 3 and 4. On the other hand, reaction of 1 and Ru(3)(CO)(12) yields only the mononuclear complex Ru(CO)(3)(η(3)-PPh(2)(o-C(6)H(4))(CH(2)NMeCH)C(60)) (5). The structures of 1-3 and 5 were determined by an X-ray diffraction study.     

Synthesis and CO2/CH4 separation performance of Bio-MOF-1 membranes

Herein we present the preparation of continuous and reproducible Bio-MOF-1 membranes supported on porous stainless steel tubes. These membranes displayed high CO(2) permeances for equimolar mixtures of CO(2) and CH(4). The observed CO(2)/CH(4) selectivities above one indicate that the separation is promoted by competitive adsorption.     

AlPO-18 membranes for CO2/CH4 separation

The synthesis of reproducible and continuous AlPO-18 membranes is demonstrated. The separation performance of these membranes for equimolar CO(2)/CH(4) gas mixtures is presented. The AlPO-18 membranes displayed CO(2) permeances as high as ~6.6 × 10(-8) mol m(-2) s Pa with CO(2)/CH(4) separation selectivities in the ~52-60 range at 295 K and 138 kPa.     

Direct Lanthanide-Transition Metal Interactions: Synthesis of (NH(3))(2)YbFe(CO)(4) and Crystal Structures of {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity) and [(CH(3)CN)(3)YbFe(CO)(4)](infinity)

The heterometallic complex (NH(3))(2)YbFe(CO)(4) was prepared from the reduction of Fe(3)(CO)(12) by Yb in liquid ammonia. Ammonia was displaced from (NH(3))(2)YbFe(CO)(4) by acetonitrile in acetonitrile solution, and the crystalline compounds {[(CH(3)CN)(3)YbFe(CO)(4))](2).CH(3)CN}(infinity) and [(CH(3)CN)(3)YbFe(CO)(4)](infinity) were obtained. An earlier X-ray study of {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity) showed that it is a ladder polymer with direct Yb-Fe bonds. In the present study, an X-ray crystal structure analysis also showed that [(CH(3)CN)(3)YbFe(CO)(4)](infinity) is a sheetlike array with direct Yb-Fe bonds. Crystal data for {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity): monoclinic space group P2(1)/c, a = 21.515(8) ?, b = 7.838(2) ?, c = 19.866(6) ?, beta = 105.47(2) degrees, Z = 4. Crystal data for [(CH(3)CN)(3)YbFe(CO)(4)](infinity): monoclinic space group P2(1)/n, a = 8.364(3) ?, b = 9.605(5) ?, c = 17.240(6) ?, beta = 92.22(3) degrees, Z = 4. Electrical conductivity measurements in acetonitrile show that these acetonitrile complexes are partially dissociated into ionic species. IR and NMR spectra of the solutions reveal the presence of [HFe(CO)(4)](-). However, upon recrystallization, the acetonitrile complexes show no evidence for the presence of [HFe(CO)(4)](-) on the basis of their IR spectra. The solid state MAS (2)H NMR spectra of deuterated acetonitrile complexes give no evidence for [(2)HFe(CO)(4)](-). It appears that rupture of the Yb-Fe bond could occur in solution to generate the ion pair [L(n)Yb](2+)[Fe(CO)(4)](2-), but then the highly basic [Fe(CO)(4)](2-) anion could abstract a proton from a coordinated acetonitrile ligand to form [HFe(CO)(4)](-). However, upon crystallization, the proton could be transferred back to the ligand, which results in the neutral polymeric species.     

Adsorption of CH4 and CO2 on Zr-metal organic frameworks

Zirconium-metal organic frameworks (Zr-MOFs) were synthesized with or without ammonium hydroxide as an additive in the synthesis process. It was found that addition of ammonium hydroxide would change the textural structure of Zr-MOF. The BET surface area, pore volume, and crystal size of Zr-MOF were reduced after addition of ammonium hydroxide. However, the crystalline structure and thermal stability were maintained and no functional groups were formed. Adsorption tests showed that Zr-MOF presented much higher CO(2) adsorption than CH(4). Zr-MOF exhibited CO(2) and CH(4) adsorption of 8.1 and 3.6 mmol/g, respectively, at 273 K, 988 kPa. The addition of ammonium hydroxide resulted in the Zr-MOF with a slight lower adsorption of CO(2) and CH(4), however, the selectivity of CO(2)/CH(4) is significantly enhanced.     

冷等离子体作用下CH_4-CO_2转化制合成气

在常温常压条件下 ,利用电晕放电 ,使 CH4 - CO2 混合气转化生成合成气 .结果表明 ,该过程中 CH4 和 CO2 的转化率与反应体系能量密度、原料气配比和流速等有关 .在 0 .1MPa气压 ,能量密度为 10 50 k J/ mol(反应体系温度低于 50 0 K) ,n( CH4 )∶ n( CO2 ) =1∶ 2条件下 CH4 和 CO2 的转化率分别超过 60 %和 50 % ,超出了热力学平衡转化率的限制 .通过调配原料的配比 ,可以得到不同 n( H2 ) / n( CO)比值的产物 .对该体系的反应机理进行了探讨 .     

(CH3)4N][(C5H5NH)0.8((CH3)3NH)0.2]U2Si9O23F4 (USH-8): an organically templated open-framework uranium silicate

The open-framework uranium fluorosilicate [(CH3)4N][(C5H5NH)0.8((CH3)3NH)0.2]U2Si9O23F4 (USH-8) has been synthesized hydrothermally by using tetramethylammonium hydroxide and pyridine-HF. The compound has a framework composition U2Si9O23F4 based on silicate double layers that are linked by chains of UO3F4 pentagonal bipyramids. The framework has 12-ring channels along [010] and 7-ring channels along [100]. The [010] 12-ring channels have a calabash-shape with the middle part partially blocked by the uranyl oxygen atoms. The narrow side of the 12-ring channels is occupied by well-ordered TMA cations while the wide side is occupied by disordered pyridinium and trimethylammonium cations.     

Carborane-based metal-organic frameworks as highly selective sorbents for CO(2) over methane

Separation of CO(2)/CH(4) mixtures was studied in carborane-based metal-organic framework materials with and without coordinatively unsaturated metal sites; high selectivities for CO(2) over CH(4) ( approximately 17) are obtained, especially in the material with open metal sites.     

High CO2 uptake and selectivity by triptycene-derived benzimidazole-linked polymers

Successful incorporation of triptycene into benzimidazole-linked polymers leads to the highest CO(2) uptake (5.12 mmol g(-1), 273 K and 1 bar) by porous organic polymers and results in high CO(2)/N(2) (63) and CO(2)/CH(4) (8.4) selectivities.     

Kinetic separation of carbon dioxide and methane on a copper metal-organic framework

Separation of carbon dioxide and methane is an important issue in upgrading low-quality natural gas. Adsorption equilibria and kinetics of CO(2) and CH(4) on a copper metal-organic framework (MOF), Cu(hfipbb)(H(2)hfipbb)(0.5) [H(2)hfipbb=4,4'-(hexafluoroisopropylidene) bis(benzoic acid)], were investigated to evaluate the feasibility of removing CO(2) from CH(4) in a pressure swing adsorption process using this new MOF adsorbent. The heat of adsorption of CO(2) on the Cu-MOF at zero-coverage (29.7 kJ/mol) is much lower than those on a carbon molecular sieve and a zeolite 5A adsorbent; and the heat of adsorption of CH(4) on the Cu-MOF (21.4 kJ/mol) is similar to that on the zeolite 5A adsorbent and smaller than that on a carbon molecular sieve. The Cu-MOF being investigated has apertures of (~3.5 × 3.5 ?), which favors the kinetically controlled separation of CO(2) and CH(4). The kinetic selectivity is found to be 26 at 298 K, and the overall selectivity (combining the equilibrium and kinetic effects) is about 25 for an adsorption separation process. These results suggest that the Cu-MOF adsorbent is an attractive alternative adsorbent for the CO(2)/CH(4) separation.     

Ni/γ-Al2O3催化剂上CH4-CO2重整体系中积碳-消碳的研究

用动态热重技术和色谱技术联用以及XRD和TEM等表征手段,研究了Ni/γ-Al2O3催化剂上甲烷－二氧化碳重整体系的积碳和消碳及其与一氧化碳产率之间的关系。结果表明,二氧化碳与甲烷有不同的活性中心,二氧化碳的存在不改变甲烷活化积碳的本质,但可通过及时将表面含碳物种转化为一氧化碳而降低积碳速率,二氧化碳能消去活泼的须状碳,但不易消去惰性的石墨碳。等摩尔条件下二氧化碳消碳能力弱于甲烷活化积碳,二氧化碳适度过量可有效抑制积碳,n(CO2)/n(CH4)≈1.3为进料比最佳值,此时积碳－消碳达到动态平衡,可获得最高的一氧化碳产率和较低的积碳速率,且该值不受温度影响。Ni/γ-Al2O3催化剂有很强的再生能力,但反复积碳－消碳会使催化剂镍晶粒度增大,分散度下降,从而导致不可逆失活。     

An ionic porous coordination framework exhibiting high CO2 affinity and CO2/CH4 selectivity

An ionic porous coordination polymer possessing partially exposed uncoordinated nitrogens exhibits strong interaction with CO(2) and high CO(2)/CH(4) selectivity, and the adsorption mechanism is illustrated by the structure of its CO(2)-loaded single-crystal.     

High and selective CO2 capture by two mesoporous acylamide-functionalized rht-type metal-organic frameworks

Two mesoporous and flexible acylamide-functionalized rht-type MOFs exhibit not only high excess unsaturation CO(2) uptake (157 wt%) at 20 bar and 273 K, but also good selectivity of CO(2)/CH(4) (8.6) and CO(2)/N(2) (34.3). The advantages of acylamide groups for CO(2) capture have been further confirmed by GCMC and first-principles calculations.     

In silico screening of metal-organic frameworks in separation applications

Porous materials such as metal-organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs) offer considerable potential for separating a variety of mixtures such as those relevant for CO(2) capture (CO(2)/H(2), CO(2)/CH(4), CO(2)/N(2)), CH(4)/H(2), alkanes/alkenes, and hydrocarbon isomers. There are basically two different separation technologies that can be employed: (1) a pressure swing adsorption (PSA) unit with a fixed bed of adsorbent particles, and (2) a membrane device, wherein the mixture is allowed to permeate through a micro-porous crystalline layer. In view of the vast number of MOFs, and ZIFs that have been synthesized there is a need for a systematic screening of potential candidates for any given separation task. Also of importance is to investigate how MOFs and ZIFs stack up against the more traditional zeolites such as NaX and NaY with regard to their separation characteristics. This perspective highlights the potency of molecular simulations in determining the choice of the best MOF or ZIF for a given separation task. A variety of metrics that quantify the separation performance, such as adsorption selectivity, working capacity, diffusion selectivity, and membrane permeability, are determined from a combination of Configurational-Bias Monte Carlo (CBMC) and Molecular Dynamics (MD) simulations. The practical utility of the suggested screening methodology is demonstrated by comparison with available experimental data.     

A triply interpenetrated microporous metal-organic framework for selective sorption of gas molecules

A microporous metal-organic framework Zn(ADC)(4,4'-Bpe)(0.5).xG [1; ADC = 4,4'-azobenzenedicarboxylate, 4,4'-Bpe = trans-bis(4-pyridyl)ethylene, G = guest molecules] with a triply interpenetrative primitive cubic net was synthesized and characterized. With pores of about 3.4 x 3.4 A, the activated 1a exhibits highly selective sorption behavior toward H(2)/N(2), H(2)/CO, and CO(2)/CH(4).     

制备方法对Ni/MgO/Al2O3催化剂在甲烷与二氧化碳重整反应活性的影响

采用浸渍－还原法制备的Ｎｉ／ＭｇＯ／Ａｌ２Ｏ３在ＣＨ４与ＣＯ２重整制合成气反应中显示出良好的催化性能和一定的抗积炭能力;在１０２３Ｋ下流动反应气氛中连续运转１００ｈ,未见活性下降,ＣＨ４及Ｃ弦均为９０％左右,ＣＯ收率高于９０％,实验还发现,ＣＨ４转化率随着原料气中ＣＯ２浓度的增加而升高,当Ｖ（ＣＯ２）／Ｖ（ＣＨ４）＝２时ＣＨ４转化率可达１００％,通过ＢＥＴ比表面积测定及ＸＲＤ,ＴＥＭ等分析手段,比     

Microporous polystyrene particles for selective carbon dioxide capture

This study presents the synthesis of microporous polystyrene particles and the potential use of these materials in CO(2) capture for biogas purification. Highly cross-linked polystyrene particles are synthesized by the emulsion copolymerization of styrene (St) and divinylbenzene (DVB) in water. The cross-link density of the polymer is varied by altering the St/DVB molar ratio. The size and the morphology of the particles are characterized by scanning and transmission electron microscopy. Following supercritical point drying with carbon dioxide or lyophilization from benzene, the polystyrene nanoparticles exhibit a significant surface area and permanent microporosity. The dried particles comprising 35 mol % St and 65 mol % DVB possess the largest surface area, ～205 m(2)/g measured by Brunauer-Emmett-Teller and ～185 m(2)/g measured by the Dubinin-Radushkevich method, and a total pore volume of 1.10 cm(3)/g. Low pressure measurements suggest that the microporous polystyrene particles exhibit a good separation performance of CO(2) over CH(4), with separation factors in the range of ～7-13 (268 K, CO(2)/CH(4) = 5/95 gas mixture), which renders them attractive candidates for use in gas separation processes.     

CH2+O2反应的反应机理

The mechanisms of the CH2＋ O2→ H2O＋ CO and CH2＋ O2→ H2＋ CO2 reactions have been studied by performing ab initio CAS(8,8)/6-31G(d,p) calculations, and five intermediates(IMn) and eight transitions(TSn) have been located along the reaction paths. The predicted path for the CH2＋ O2→ H2O＋ CO is: CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS4→ IM4a→ TS5→ H2O＋ CO. For the CH2＋ O2→ H2＋ CO2 reaction, there are two paths: (i) CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS6→ H2＋ CO2 and (ii) CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS4→ IM4a→ TS7→ IM4b→ TS8→ H2＋ CO2, with the latter path more favorable energetically.