State‐of‐the‐Art Adsorption and Membrane Separation Processes for Hydrogen Production in the Chemical and Petrochemical Industries

Abstract

This review on the use of adsorption and membrane technologies in H₂ production is directed toward the chemical and petrochemical industries. The growing requirements for H₂ in chemical manufacturing, petroleum refining, and the newly emerging clean energy concepts will place greater demands on sourcing, production capacity and supplies of H₂. Currently, about 41 MM tons/yr of H₂ is produced worldwide, with 80% of it being produced from natural gas by steam reforming, partial oxidation and autothermal reforming. H₂ is used commercially to produce CO, syngas, ammonia, methanol, and higher alcohols, urea and hydrochloric acid. It is also used in Fischer Tropsch reactions, as a reducing agent (metallurgy), and to upgrade petroleum products and oils (hydrogenation).

It has been estimated that the reforming of natural gas to produce H₂ consumes about 31,800 Btu/lb of H₂ produced at 331 psig based on 35.5 MM tons/yr production. It is further estimated that 450 trillion Btu/yr could be saved with a 20% improvement in just the H₂ separation and purification train after the H₂ reformer. Clearly, with the judicious and further use of adsorption or membrane technology, which are both classified as low energy separation processes, energy savings could be readily achieved in a reasonable time frame.

To assist in this endeavor of fostering the development of new adsorption and membrane technologies suitable for H₂, CO and syngas production, the current industrial practice is summarized in terms of the key reforming and shift reactions and reactor conditions, along with the four most widely used separation techniques, i.e., absorption, adsorption, membrane, and cryogenic, to expose the typical conditions and unit processes involved in the reforming of methane. Since all of the reactions are reversible, the H₂ or CO productivity in each one of them is limited by equilibrium, which certainly provides for process improvement. Hence, the goal of this review is to foster the development of adsorption and membrane technologies that will economically augment in the near term and completely revamp in the far term a typical H₂, CO or syngas production plant that produces these gases from natural gas and hydrocarbon feedstocks.

A review of the emerging literature concepts on evolving adsorption and membrane separations applicable to H₂ production is provided, with an emphasis placed on where the state‐of‐the‐art is and where it needs to go. Recommendations for future research and development needs in adsorbent and membrane materials are discussed, and detailed performance requirements are provided. An emphasis is also placed on flow sheet design modification with adsorption or membrane units being added to existing plants for near term impact, and on new designs with complete flow sheet modification for new adsorption or membrane reactor/separators replacing current reactor and separator units in an existing plant for a longer term sustainable impact.     

Purification of Glucose Oxidase and β‐Galactosidase by Partitioning in a PEG‐Salt Aqueous Two‐Phase System in the Presence of PEG‐Derivatives

Abstract

Purification of glucose oxidase from Aspergillus niger and that of β‐galactosidase from Kluyveromyces lactis have been attempted using poly(ethylene glycol) (PEG)‐sodium sulfate aqueous two phase system (ATPS) in the presence of PEG‐derivatives, i.e. PEG‐Coomassie brilliant blue G‐250 and PEG‐benzoate, PEG‐palmitate and PEG‐TMA, respectively. The enzymes showed poor partitioning towards the PEG phase in comparison with other proteins in ATPS containing no ligands. Selective partitioning of other proteins was observed towards the PEG phase in the presence of PEG‐benzoate and PEG‐palmitate enriching β‐galactosidase in the salt phase whereas in the case of glucose oxidase, PEG‐Coomassie brilliant blue G‐250 derivative worked as a better affinity ligand for other proteins. A 19‐fold purification was obtained with the PEG dye derivative after 5 stage cross extractions with 80% recovery of glucose oxidase and an enrichment factor upto ～7 for β‐galactosidase with the PEG‐TMA derivative. The interaction of PEG‐benzoate and PEG‐TMA ligands with the active site of β‐galactosidase has been evaluated by molecular modeling. The effect of the molecular weight of glucose oxidase on its partitioning was confirmed as the molecular simulation shows strong affinity interaction of PEG‐glucoside with the enzyme.     

Design Methodology and Performance Analysis of a Pseudo‐Simulated Moving Bed for Ternary Separation

Abstract

This paper presents design equations for ternary separation using a pseudo‐simulated moving bed unit. The analysis of the dynamics of separation as well as the positioning of the concentration waves of species into units is addressed. The derived equations in the frame of the equilibrium theory for linear adsorption provide constraints on the position of the species, which allow the determination of operational conditions for a required separation performance. A flow chart is tested with a pseudo‐SMB applied to the separation of two ternary mixtures of sugars. It is shown how strongly the positioning of concentration waves and then the operational parameters can affect the unit performance. Mass transfer effects play an important role on the decision of using SMBs in cascade or pseudo‐SMB unit in ternary separations.     

Development and Continuous Operation of a Bench-Scale System for the Production of O3 + O2 + CO2 Hydrates

Ozone (O₃) has many industrial applications such as in sterilization. One of the long-term O₃ preservation methods is molecular storage in clathrate hydrate. In this study, an experimental system was developed for continuously forming O₃ + O₂ + CO₂ hydrates. The parameters that affect the continuous operation of the system and that lead to increases in the concentration of O₃ in the hydrates were also experimentally evaluated, implementing the method of quality engineering. After optimizing these operating parameters, the O₃ storage capacity in the hydrates was measured to be 0.26 wt % at 2 h of total operation time. By X-ray diffraction, it was found that the produced sample contained hydrates, and long-term preservation for 6 months was possible at the temperature of general freezing warehouses.     

Development of a Cross-Linked Polysaccharide of Ligusticum wallichii – Squid Skin Collagen Scaffold Fabrication and Property Studies for Tissue-Engineering Applications

Porous composite scaffold with Ligusticum wallichii polysaccharide and squid skin collagen was synthesized and characterized. The composite scaffold showed good phosphate buffer solution (PBS) retention ability, slow biodegradation rate, high mechanical strength, and superb cell proliferation promoting ability. The PBS content value increased from 433.40% to 571.05%; the weight lost in seven days decreased from 95.41% to 34.35%; the tensile strength of sample increased from 0.19 to 0.81 MPa; the seven-day relative growth rate of cell in composite (polysaccharide:collagen = 5:5) is twice of that in pure collagen. While with the polysaccharide portion increased, the elongation at break decreased from 93.09% to 9.60%.     

Comparison of the photovoltaic efficiency on DSSC for nanometer sized TiO2 using a conventional sol–gel and solvothermal methods

When the two types of TiO₂ coatings prepared by sol–gel and solvothermal methods were applied to dye-sensitized solar cell (DSSC) in this study, the energy conversion efficiency of the solvothermal-modified TiO₂ was considerably higher than that on the sol–gel modified TiO₂; approximately 8.51 (solvothermal) and 5.93% (sol–gel) with the N719 dye under 100 mW/cm² of simulated sunlight, respectively. These results are in agreement with an electrostatic force microscopy (EFM) study showing that the electrons were transferred rapidly to the surface of the solvothermal-modified TiO₂ film, compared with that on a sol–gel modified TiO₂ film. Furthermore, FT-IR analysis of the films after N719 dye adsorption showed that the solvothermal-modified TiO₂ had a strong band at 500 cm^?1, which was assigned to metal–O, due to a new Ti–O bond between the O of COO^? and a Ti atom. This peak was considerably weaker in the sol–gel modified TiO₂.     

New Multi‐Dentate Ion‐Selective AXAD‐16‐MOPPA Polymer for the Preconcentration and Sequential Separation of U(VI), Th(IV) from Rare Earth Matrix

Abstract

A new class of multi‐dentate ligand anchored polymeric resin has been synthesized by grafting Amberlite XAD‐16 with [2‐(1‐Methyl‐3‐oxo‐2‐phenyl‐2, 3‐dihydro‐1H‐pyrazol‐4‐ylcarbamoyl)‐ethyl]‐phosphinic acid (AXAD‐16‐MOPPA). The modification steps involved during the grafting process are characterized by FT‐IR spectroscopy, ³¹P and ¹³C‐CPMAS (cross‐polarized magic angle spin) NMR spectroscopy, CHNPS elemental analysis and thermogravimetric analysis. The influence of various physio‐chemical parameters on the quantitative extraction of metal ions by the resin phase are studied and optimized by both static and dynamic methods. The developed grafted polymer shows greater selectivity for actinide ions like U(VI) and Th(IV) when compared to the lanthanides with greater distribution ratio values in highly acidic matrices. However, the lanthanides compete for the active sites in near neutral conditions. But the sorbed actinide ions and lanthanide elements can be separated by the sequential elution methodology. Moreover, the polymer exhibits faster metal ion phase exchange kinetics, where with a high sample flow rate of 25 mL min^?1 quantitative analyte sorption is achievable during the extraction chromatographic column operation for all the analytes. It also offers good ion‐selectivity and greater preconcentration factor values of 400 for U(VI) and 333 for Th(IV) in 4M HNO₃ conditions. The resin shows very high sorption capacity values of 1.45 mmol g^?1 for U(VI), 1.39 mmol g^?1 for Th(IV), and 1.31 mmol g^?1 for La(III) at near neutral conditions. Finally, the developed grafted resin has been successfully applied in extracting Th(IV) from matrix monazite sand which comprises large rare earth matrix, U(VI) from seawater and also U(VI) and Th(IV) from simulated nuclear spent fuel mixtures. The analytical data obtained from triplicate measurements are within 3.5% rsd, reflecting the reproducibility and reliability of the developed method.     

Grinding-induced rapid,convenient and solvent free approach for the one pot synthesis of α-aminophosphonates using aluminium pillared interlayered clay catalyst

An easy to prepare aluminium pillared interlayered clay (PILC) has been developed as a stable, recyclable and heterogeneous catalyst to promote the one-pot three component synthesis of α-aminophosphonates under solvent-free conditions using grindstone chemistry. Utilization of mild reaction conditions, clean conversion and greater selectivity under grinding conditions along with effortless separation, and purification of reaction products make this process extra attractive.     

Dynamic states of V‐oxide species: reducibility and performance for methane oxidation on V2O5/SiO2 catalysts as a function of coverage

Temperature‐programmed in situ Raman spectroscopy is used to understand the effect of surface vanadia coverage on the structure, reducibility and performance for the oxidation of methane on V₂O₅/SiO₂ catalysts. The vanadia coverage on silica has no effect on its structure below its dispersion‐limit loading (“monolayer” coverage); however, the interactions among surface vanadia species under reducing conditions become increasingly important. This interaction appears to operate through the sharing of oxygen sites facilitating the reduction, but it does not alter the total reducibility. The probability for this interaction to take place increases with vanadium oxide surface coverage. It is therefore expected that under reaction conditions the catalyst with higher vanadia coverage would have a greater capacity to release oxygen. This would increase the activity per vanadium site. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation of a (E,E)‐Dioxime Containing Two 15‐Membered Dioxatrithiamacrocycles and its Mononuclear Ni(II) Complex as Ag+ Extractants

Abstract

A macrocyclic vic‐dioxime (1) and its mononuclear Ni(II) complex (2) were studied as extractant. The aqueous solutions of Ag⁺, Mn²⁺, Pb²⁺, Ni²⁺, Cu²⁺, Cd²⁺, and Zn²⁺ picrates were used for extraction experiments. The solutions of the ligands in two different organic solvents were used as organic phases. The metal picrate extractions were carried out at 25±0.1°C by using UV‐visible spectrometry. The most effective transport was observed for Ag⁺ picrate among the tested metal picrates. The effect of pH on the extraction of Ag⁺ picrate was evaluated with the ligands. The ratio of extracted Ag‐complex to chloroform phase was 2:1 (L:M) for (2). In other cases the ratios were 1:1 for both (1) and (2). Molar ratio method was also used to demonstrate the composition. The values of the extraction constants (log K_ex) were determined for the extracted Ag‐complexes.     

Evaluation of the Efficiency of a Combined Adsorption–Ultrafiltration System for the Removal of Heavy Metals,Color, and Organic Matter from Textile Wastewater

In this work an ultrafiltration (UF) membrane system was investigated for the treatment of textile wastewater. UF membranes were assisted by activated sludge and minerals, which were employed as sorbents, to remove Cu(II), Pb(II), Zn(II), Ni(II), color, and organics. Significant variations were observed in metal removal efficiencies among the textile wastewater samples of different origin, even at the same pH (= 6) due to the presence of different compounds in wastewater. At the examined pH range (5.63–9.21), the dominant mechanism for copper and lead removal was the formation of insoluble metals due to precipitation and complexation of metal ions with wastewater compounds, including adsorption of metals on suspended solids and colloidal matter. The adsorption process of metals on minerals and activated sludge was the dominant process for nickel and zinc removal at low pH, while precipitation/complexation prevailed at higher pH. The examined adsorption-UF system could produce a treated effluent having low metal concentrations that could be safely discharged into municipal sewers. COD removal ranged from 76%–92% for the five textile wastewater samples. The color removal accomplished was significant (45%–70%), and depended on the type of dye.     

Kinetics of Y(III) Stripping for the System Y/HCl/Cyanex 272‐P507/Heptane with Constant Interfacial Area Cell with Laminar Flow

Abstract

Kinetics and mechanism of stripping of yttrium(III) previously extracted by mixtures of bis(2,4,4‐trimethylpentyl)phosphinic acid (Cyanex 272, HA), and 2‐ethylhexyl phosphonic acid mono‐2‐ethylhexl ester (P507, HB) dissolved in heptane have been investigated by constant interfacial‐area cell by laminar flow. The corresponding equilibrium stripping equation and equilibrium constant were obtained. The studies of effects of the stirring rate and temperature on the stripping rate show that the stripping regime is dependent on the stripping conditions. The plot of interfacial area on the rate has shown a linear relationship. This fact together with the strong surface activity of mixtures of Cyanex 272 and P507 at heptane‐water interfaces makes the interface the most probable locale for the chemical reactions. The stripping rate constant is obtained, and the value is compared with that of the system with Cyanex 272 and P507 alone. It is concluded that the stripping ability with the mixtures is easier than that of P507 due to lower the activation energy of the mixtures. The stripping rate equation has also been obtained, and the rate‐determining steps are the two‐step interfacial chemical reactions as predicted from interfacial reaction models.     

Synthesis and Characterization of β-Cyclodextrin Functionalized Ionic Liquid Polymer as a Macroporous Material for the Removal of Phenols and As(V)

β-Cyclodextrin-ionic liquid polymer (CD-ILP) was first synthesized by functionalized β-cyclodextrin (CD) with 1-benzylimidazole (BIM) to form monofunctionalized CD (βCD-BIMOTs) and was further polymerized using a toluene diisocyanate (TDI) linker to form insoluble CD-ILP (βCD-BIMOTs-TDI). The βCD-BIMOTs-TDI polymer was characterized using various tools and the results obtained were compared with those derived from the native β-cyclodextrin polymer (βCD-TDI). The SEM result shows that the presence of ionic liquid (IL) increases the pore size, while the thermo gravimetric analysis (TGA) result shows that the presence of IL increases the stability of the polymer. Meanwhile, Brunauer-Emmett-Teller (BET) results show that βCD-BIMOTs-TDI polymer has 1.254 m²/g surface areas and the Barret-Joyner-Halenda (BJH) pore size distribution result reveals that the polymer exhibits macropores with a pore size of 77.66 nm. Preliminary sorption experiments were carried out and the βCD-BIMOTs-TDI polymer shows enhanced sorption capacity and high removal towards phenols and As(V).     

6,6′‐Bis(5,5,8,8‐tetramethyl‐5,6,7,8‐tetrahydro‐benzo[1,2,4]triazin‐3‐yl) [2,2′]bipyridine,an Effective Extracting Agent for the Separation of Americium(III) and Curium(III) from the Lanthanides

Abstract

The extraction of americium(III), curium(III), and the lanthanides(III) from nitric acid by 6,6′‐bis(5,5,8,8‐tetramethyl‐5,6,7,8‐tetrahydro‐benzo[1,2,4]triazin‐3‐yl)‐[2,2′]bipyridine (CyMe₄‐BTBP) has been studied. Since the extraction kinetics were slow, N,N′‐dimethyl‐N,N′‐dioctyl‐2‐(2‐hexyloxy‐ethyl)malonamide (DMDOHEMA) was added as a phase transfer reagent. With a mixture of 0.01 M CyMe₄‐BTBP+0.25 M DMDOHEMA in n‐octanol, extraction equilibrium was reached within 5 min of mixing. At a nitric acid concentration of 1 M, an americium(III) distribution ratio of approx. 10 was achieved. Americium(III)/lanthanide(III) separation factors between 50 (dysprosium) and 1500 (lanthanum) were obtained. Whereas americium(III) and curium(III) were extracted as disolvates, the stoichiometries of the lanthanide(III) complexes were not identified unambiguously, owing to the presence of DMDOHEMA. In the absence of DMDOHEMA, both americium(III) and europium(III) were extracted as disolvates. Back‐extraction with 0.1 M nitric acid was thermodynamically possible but rather slow. Using a buffered glycolate solution of pH=4, an americium(III) distribution ratio of 0.01 was obtained within 5 min of mixing. There was no evidence of degradation of the extractant, for example, the extraction performance of CyMe₄‐BTBP during hydrolylsis with 1 M nitric acid did not change over a two month contact.     

Influence of erroneous data on the results of calculations from acid–base surface free energy theories. I. Simulations for a small input data set

The van Oss–Chaudhury–Good theory (vOCGT) was checked for a small artificial set of the work of adhesion input data calculated for 9 solids and 7 liquids. Taking from the literature the data for Lifshitz–van der Waals (LW) component and acid and base (A and B) parameters for 7 liquids and the values of the component and the parameters for 9 solids (close to those in the literature), the work of adhesion was calculated and its value was assumed to be free of error. Next, new values of the work of adhesion were obtained by adding a random error of normal distribution belonging to 11 distributions of a mean value equal to the errorless work of adhesion value and standard deviations from 0.1 to 60% of the mean value. The LW components and A and B parameters for these solids were back-calculated for each solid and the error level by solving 20 3-equation systems. These 9 solids were grouped in 3 sets of 3 solids in each, and for each of the solid sets the over determined system of equations (of matrix 7 × 3) for these 7 liquids was solved. The root mean square errors (RMSEs) of the LW component and A and B parameters were linear functions of RMSE of the vector (matrix) of the work of adhesion in both solution methods of a set of equations. It was found that a solution of the 3-equation set of the vOCGT was always exact for all liquid triplets. Erroneous LW components and acid and base parameters are obtained because quite a different set of equations (caused by an existing error in the data) is solved than in the case of error-free data. There is a linear transformation from the input error in the work of adhesion vector (matrix) space into the output error in the solution vector (matrix) space, and the inverse (or pseudoinverse) of the matrix A is the transformation matrix. In the case of a 3-equation set there is a linear relationship between the total RMSE of the solution and the condition number of the matrix A. The higher the input error in the work of adhesion data the higher is the influence of the condition number on the error in the solution. The RMSE value of the solution of an over determined system of equations was about 10-times lower than the mean value of RMSE calculated for the same liquids used as separate triplets.     

Kinetic studies on the dimerization of isobutene with Ni/Al2O3 as a catalyst for reactive distillation process☆

Isooctane is a promising gasoline additive that could be produced by dimerization of isobutene (IB) with subse-quent hydrogenation. In this work, the dimerization of IB has been carried out in a batch ...     

Fully Automated Three-Dimensional Column-Switching SPE–FIA–HPLC System for the Characterization of Lipids by a Single Injection: Part I. Instrumental Design and Chemometric Approach to Assess the Effect of Experimental Settings on the Response of ELSD

This article presents the first application of fully automated three‐dimensional (3D) column‐switching SPE–FIA–HPLC system for the characterization of lipids by a single injection. The whole system was designed and set up by modifying Agilent 1200 Series HPLC system in our laboratory. By using this system, a complete separation profile of the oil samples was achieved in a very short time period by using single injections. This approach was applied on vegetable oils which contains a large number of relatively high‐class lipid components, such as TG, FFA, sterols, tocopherols, DG, ester and MG. In this part of the study, we focused on the optimization of evaporative light scattering detector (ELSD) by using an experimental design and RSM. Three experimental parameters were chosen as an independent variables which are the flow rate of mobile phase, nebulization temperature and evaporation temperature. A multivariate five level experimental design was used to establish a quadratic model as a functional relationship between the response values and independent variables. The optimal values of parameters were found to be a flow rate of 1.25 mL min^?1, nebulization temperature of 80 °C, and evaporation temperature of 40 °C. Regression analysis with an R² values indicated as a satisfactory correlation between the experimental and predicted values. ANOVA test results were also illustrate that the models can be successfully used to predict the optimum parameters of ELSD. Thus, the proposed system is suitable for a large number of applications including research and development of new quality control and characterization methods for vegetable oils.     

The effect of calcium on the properties of SmBa1−xCaxCoCuO5+δ as a cathode material for intermediate-temperature solid oxide fuel cells

The effect of calcium on the properties of SmBa_1–xCa_xCoCuO_5+δ (x = 0.0–0.3) as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs) is evaluated systematically. Samples exhibit a highly crystalline double perovskite phase, and their cell volumes decrease as x is changed from 0.0 to 0.3. The oxygen content and average thermal expansion coefficient (TEC) of SmBa_1–xCa_xCoCuO_5+δ decreases as the calcium content increased. An average TEC of as low as 15.3 × 10⁻⁶ °C⁻¹ is obtained for SmBa_0.7Ca_0.3CoCuO_5+δ. The area specific resistances at 700 °C decrease by approximately 50% when the calcium content is increased from x = 0.0 (0.173 Ω cm²) to x = 0.3 (0.086 Ω cm²). The maximum power densities of SmBa_1−xCa_xCoCuO_5+δ-based single cells at 800 °C increase from 635 mW cm⁻² (x = 0.0) to 939 mW cm⁻² (x = 0.3).