Pervaporation dehydration of ethylene glycol by NaA zeolite membranes

Home-made NaA zeolite membranes were used for pervaporation dehydration of ethylene glycol (EG)/water mixtures. Hydrothermal stability of the membranes in pervaporation was investigated for industrial application purpose. The membranes exhibited good stability for water content of less than 20 wt.% at 100 °C. The reduction of operating temperature was effective to improve membrane stability for operating at high feed water content (e.g. 30 wt.%). The influence of feed water content and operating temperature on dehydration of EG was extensively investigated. A permeation flux of 4.03 kg m⁻² h⁻¹ with separation factor of >5000 was achieved at 120 °C for the separation of the solution with 20 wt.% water content. A pilot-scale pervaporation facility with membrane area of 3 m² was built up for dehydration of EG with the water content of 20 wt.%, which showed technical feasibility for industrial application.     

A型分子筛膜在分离乙二醇水溶液中的应用

采用抽空涂晶二次生长法成功地合成出了A型分子筛膜,研究了乙二醇水溶液在A型分子筛膜上的渗透气化和蒸气渗透分离性能,考察了温度、浓度对渗透通量的影响,完成了1000 h的稳定性实验。结果表明,A型分子筛膜对EG水溶液具有非常高的分离选择性和稳定性,分离系数达到10000,在120 ℃透量达到10 kg/(m2•h)。     

环氧乙烷催化水合生产乙二醇工艺技术研究

非催化水合生产乙二醇工艺具有能耗大、成本高的缺点。笔者采用树脂类催化剂进行了环氧乙烷化水合生产乙二醇工艺技术研究,并考察了温度、空速、n(H2O)∶n(EO)、压力及进料方式等工艺条件对催化剂性能的影响,催化剂经过了800 h稳定性考察,研究结果表明,在温度100℃、压力1.0MPa、空速1.5 h-1、n(H2O)∶n(EO)=6.5条件下,不仅具有很稳定的性能,而且环氧乙烷(EO)转化率和乙二醇(EG)选择性最高都可以达到100%。     

One-pot synthesis of ethylene glycol and its mono-methyl ether from ethylene using Al-TS-1 catalyst

Ethylene glycol (EG) and its mono-methyl ether (MME) were synthesized directly from ethylene and hydrogen peroxide under mild conditions using Al–TS-1 as the bifunctional catalyst. The progressive incorporation of Al into the framework increased the catalytic capacity of Al–TS-1 until a maximum was reached (SiO₂/Al₂O₃ molar ratio: 504), whereas further Al incorporation decreased the catalytic activity to even lower values than in TS-1. Under the optimum conditions, the conversion and utilization of H₂O₂ reached 95% and 90%, respectively, while the total concentration of EG and MME reached to above 10 wt.%.     

环氧乙烷催化水合生产乙二醇动力学研究

在温度为70~105℃,压力为0.7~1.5 MPa,n(H2O)∶n(环氧乙烷)=6~8的条件下,以阴离子交换树脂为催化剂,研究了环氧乙烷(EO)催化水合生产乙二醇(EG)反应动力学特性,建立了动力学模型.研究结果表明,EG的生成速率对EO浓度具有一级反应特征.对试验数据进行了回归,得到了动力学模型参数,其反应活化能为42.4 kJ/mol,指前因子为5.48×106h-1。回归数据的线性相关系数均大于0.96,说明该模型能够充分体现反应特征。     

Controlled synthesis of high performance carbon/zeolite T composite membrane materials for gas separation

A simple approach has been developed to synthesize the carbon/zeolite T composite membrane materials with the high gas separation performance. The precursors of the composite membrane are composed of polyimide matrix and dispersed zeolite T particles. The composite membranes prepared by pyrolysis at 973 K show excellent gas (H₂, CO₂, O₂, N₂, and CH₄) permeability and selectivity (O₂/N₂, CO₂/CH₄) for both single gas and mixed-gas. The gas separation performance of the composite membranes can be controlled in a wide range by only changing the zeolite T particle size. The maximum selectivity of O₂ over N₂ (21/79 mol%) for the composite membranes with the least zeolite T particle (0.5 μm) is 15 with an O₂ permeability of 347 Barrers (1 Barrer = 7.5 × 10⁻¹⁸ m² s⁻¹ Pa⁻¹) and the selectivity of CO₂ over CH₄ (50/50 mol%) reaches a value of 179 with a CO₂ permeability of 1532 Barrers. It is believed that the increase of gas permeability is attributed to the ordered microchannels in the zeolite and the interfacial gaps formed between zeolite and carbon matrix in the composite membranes. And the gas selectivity is tuned by the size of interfacial gaps which are varied with the zeolite particle size. This technique will provide a simple and convenient route to efficiently improve the trade-off relationship between the permeability and the selectivity and enable the construction of carbon-based composite materials with novel functionalities in membrane science.     

Improvement of porous polyvinylidene fluoride-co-hexafluropropylene hollow fiber membranes for sweeping gas membrane distillation of ethylene glycol solution

Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N₂ permeation, overall porosity, critical water entry pressure (CEP_w), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N₂ permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m⁻¹. CEP_w of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m⁻²·h⁻¹ which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.     

Dehydration of acetic acid/water mixtures by pervaporation with a modified poly(4-methyl-1-pentene) membrane

The dehydration of acetic acid/water mixtures by pervaporation with a EVA/TPX membrane has been studied. The membrane exhibited water selectivity during all process runs. Investigations were focused on the effects of heat treatment temperature on membrane formation, membrane thickness, feed solution concentration, EVA content, and feed solution temperature. Compared with pure TPX membrane, the EVA/TPX blend membrane effectively improved the pervaporation performances. The permeation rate decreases with increasing heat treatment temperature during the membrane formation. Optimum pervaporation results were obtained by EVA/TPX membrane with 12.5 wt % EVA content, giving a separation factor of 606 and permeation rate of 215 g/m²h.     

Dehydration of water/1-1-dimethylhydrazine mixtures by zeolite membranes

In this research, dehydration of water/1-1-dimethylhydrazine (UDMH) mixtures by zeolite NaA and hydroxy sodalite membranes has been investigated. Support of these membranes has been tubular mullites that have been made by extruding a mixture of about 67–75% kaolin clay and 33–25% distilled water using an extruder. Zeolite NaA and hydroxy sodalite membranes have been coated on the external surface of the porous supports by the hydrothermal synthesis.

UDMH/water mixtures have been separated at ambient temperature and pressure by pervaporation (PV) using these zeolite membranes. These membranes showed very high selectivity of water for all UDMH mixtures. For the UDMH/water mixtures, separation factor as high as 10 000 has been obtained for UDMH feed concentration of 2%. Total mass fluxes of 1.05–0.2 kg/(m² h) have been also obtained.     

Simultaneous synthesis of dimethyl carbonate and ethylene glycol dimethacrylate using homogenous basic catalyst

A novel method simultaneously to prepare dimethyl carbonate and ethylene glycol dimethacrylate from ethylene carbonate and methyl methacrylate has been demonstrated in the presence of catalyst sodium methoxide and polymerization inhibitor ZJ-705. The effect of reaction parameters such as catalyst loading, polymerization inhibitor loading, concentration of reactants, reaction time, etc., on synthesis of dimethyl carbonate and ethylene glycol dimethacrylate was investigated. A reaction mechanism has been discussed with catalyst sodium methoxide.     

Synthesis of full interpenetrating network membranes of poly(acrylic acid-co-acrylamide) in the matrix of polyvinyl alcohol for dehydration of ethylene glycol by pervaporation

Polyvinyl alcohol (PVOH) has been chemically modified by crosslink copolymerization of acrylic acid (AA) and acrylamide (AM) in aqueous solution of PVOH and finally crosslinking the copolymer with methylene bis acrylamide (MBA) and PVOH with glutaraldehyde to produce a full interpenetrating network (FIPN) membrane. Accordingly, three such fully crosslinked IPNs i.e. FIPN25, FIPN50 and FIPN75 have been synthesized with different mass ratio of PVOH:copolymer i.e. 1:0.25 (FIPN25), 1:0.50 (FIPN50) and 1:0.75 (FIPN75). These full IPN membranes were used for pervaporative dehydration of ethylene glycol (EG). All of these IPN membranes were characterized with various conventional methods like FTIR, mechanical properties, DTA and SEM. The performances of the membranes were evaluated in terms of sorption and pervaporative dehydration of EG. The IPN membranes were found to show preferential sorption and diffusion for water. Flux and water selectivity of these membranes were found to increase with increasing amount of copolymer in PVOH matrix. However, among the three membranes, FIPN75 were found to show the highest flux but lower selectivity for water while FIPN50 membrane showed optimum performance in terms of both flux and selectivity. Diffusion coefficient and plasticization interaction of water and EG through all the IPN membranes were determined using modified solution-diffusion model.     

Synthesis of MCM-41 using microwave heating with ethylene glycol

Mesoporous material MCM-41 with hexagonal arrangement is obtained by microwave treatment of precursor gel at 100–120°C for 1 h or less, a very short period of time compared with the hydrothermal method. In addition to shorter synthesis time, microwave radiation in the synthesis of MCM-41 provides a way to control its crystallinity and morphology. Especially the addition of small amount of ethylene glycol (EG) in synthetic mixture contributes to improving crystallinity, forming homogeneous particle shape and reducing particle size of MCM-41 under microwave radiation. Attenuated total reflectance (ATR)/FTIR and photoluminescence (PL) spectroscopy have been used to monitor intermediate step of microwave preparation of MCM-41.     

Pt-modulated Cu/SiO2 catalysts for efficient hydrogenation of CO2-derived ethylene carbonate to methanol and ethylene glycol

Copper-based catalysts were widely used in the heterogeneous selective hydrogenation of ethylene car-bonate (EC),a key step in the indirect conversion of CO2 to methanol.However,a high H2/EC molar ratio in feed is required to achieve favorable activity and the methanol selectivity still needs to be improved.Herein,we fabricated a series of Pt-modulated Cu/SiO2 catalysts and investigated their catalytic perfor-mance for hydrogenation of EC in a fixed bed reactor.By modulating the Pt amount,the optimal 0.2Pt-Cu/SiO2 catalyst exhibited the highest catalytic performance with ～99％ EC conversion,over 98％ selectiv-ity to ethylene glycol and 95.8％ selectivity to methanol at the H2/EC ratio as low as 60 in feed.In addition,0.2Pt-Cu/SiO2 catalyst showed excellent stability for 150 h on stream over different H2/EC ratios of 180-40.It is demonstrated a proper amount of Pt could significantly lower the H2/EC molar ratio,promote the reducibility and dispersion of copper,and also enhance surface density of Cu+ species.This could be due to the strong interaction of Cu and Pt induced by formation of alloyed Pt single atoms on the Cu lattice.Meanwhile,a relatively higher amount of Pt would deteriorate the catalytic activity,which could be due to the surface coverage and aggregation of active species.These findings may enlighten some fundamen-tal insights for further design of Cu-based catalysts for the hydrogenation of carbon-oxygen bonds.     

Fabrication of cobalt nanowires from mixture of 1-ethyl-3-methylimidazolium chloride ionic liquid and ethylene glycol using porous anodic alumina template

Porous anodic alumina template is synthesized by electrochemical anodization of aluminum and used to grow cobalt nanowires. The cobalt nanowires produced by direct current electrodeposition are characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and physical property measurement system. Test results indicate that the average diameter of cobalt nanowires is about 45 nm, which is generally the same as the pore diameter of porous anodic alumina template, and the cobalt nanowires electrodeposited from mixture of 1-ethyl-3-methylimidazolium chloride ionic liquid and ethylene glycol have a smoother surface and better magnetic properties than cobalt nanowires electrodeposited from aqueous solution, and they show a better squareness. Therefore it can be concluded that the cobalt nanowires electrodeposited from mixture of 1-ethyl-3-methylimidazolium chloride ionic liquid and ethylene glycol using porous anodic alumina template can be used as a perpendicular magnetic recording film.     

天然气路线合成乙二醇新技术

综合分析了采用天然气为原料合成乙二醇(EG)的工艺新技术,其中甲醇乙烯法工艺技术成熟,具备建设大规模工业装置的技术条件,合成气草酸酯法及甲醛羰基化法尚有待进一步提高技术经济性,其它路线仍存在重大技术难点。     

Sustainable hydrogen production via reforming of ethylene glycol using a novel spouted bed reactor

Hydrogen produced from renewable energy sources is of great interest as an alternative to fossil fuels and as a means for clean power generation via fuel cells. The aqueous fraction of bio-oil can be effectively reformed to hydrogen rich streams in the presence of active catalytic materials. In this paper we present the experimental work carried out in a novel spouted bed reactor for the reforming of bio-oil. The use of a specially designed injection nozzle in combination with the particular hydrodynamic characteristics of the spouted bed resulted in efficient processing of the organic feed. The known problem of coking was notably avoided regardless of the loading material of the reactor. The effect of reaction temperature and steam to carbon ratio in the feed was investigated in the presence of various catalytic and non-catalytic particles. Runs were conducted with ethylene glycol as a representative model compound of the aqueous phase of bio-oil. Olivine, when associated with nickel, proved to be a very suitable catalytic material for the process combining high activity in reforming, anti-coking characteristics combined with exceptional mechanical strength.     

Gas permeation characteristics of silica/alumina composite membrane prepared by chemical vapor deposition

Amorphous silica membranes were deposited by thermal decomposition of tetraethoxysilane at 600–650 ‡C on a porous α-alumina tube with pore size of 110–180 nm or γ-alumina coated α-alumina tube with pore size of 6–8 nm.The forced cross-flow through the porous wall of the support was very effective in plugging macropores. The membranes formed on γ-alumina coated oc-alumina tube showed H₂ permeances much higher than the SiO₂ membranes formed on the α-alumina tube. This indicated that the γ-alumina film was effective in improving the H₂ permeance and H₂/N₂ selectivity. The permeation tests with CO₂, N₂, CH₄, C₃H₈ and i-C₄H₁₀ showed that a very small number of mesopores remained unplugged by the CVD. Permeation of hydrogen was explained by activated diffusion, and that of the other gases by Knudsen diffusion through the unplugged pores. Thus, the total permeance was composed of permeances due to the activated and Knudsen diffusion mechanisms. The contribution of Knudsen diffusion pores decreased to 0.02 when the γ-alumina film was modified at 650 ‡C until P_fe=50 Pa.     

A novel method of surface modification on thin-film composite reverse osmosis membrane by grafting poly(ethylene glycol)

A novel method of surface modification by grafting hydrophilic poly(ethylene glycol) (PEG) chains onto the surface of a thin-film composite (TFC) polyamide reverse osmosis (RO) membrane was performed. Aminopolyethylene glycol monomethylether (MPEG-NH₂) was used as grafting monomer. The membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The changes in chemical composition and morphology of the membranes' surface indicated the successful grafting process. Furthermore, a preliminary experiment confirmed that the grafting of PEG chains improved membrane antifouling property.     

Formation of soluble hyperbranched polymer through the initiator-fragment incorporation radical copolymerization of ethylene glycol dimethacrylate with N-methylmethacrylamide

The copolymerization of ethylene glycol dimethacrylate (EGDMA) as a divinyl monomer with N-methylmethacrylamide (NMMAm) as a water-soluble monomer was carried out at 70 and 80 °C in N,N-dimethylformamide (DMF) using dimethyl 2,2′-azobisisobutyrate (MAIB) of high concentrations as initiator. When the concentrations of EGDMA, NMMAm and MAIB were 0.15, 0.50 and 0.35 mol/l, the copolymerization proceeded homogeneously with no gelation at 80 °C to give soluble copolymer in a yield of 50%. EGDMA was polymerized more rapidly than NMMAm as shown by Fourier-transform near infrared spectroscopy. The copolymer formed for 8 h consisted of 20 mol% of EGDMA unit, 47 mol% of NMMA unit and 33 mol% of methoxycarbonylpropyl group unit as MAIB-fragment. The copolymer formed at 80 °C for 30 min showed an upper critical solution temperature (34 °C on cooling) in methanol. The intrinsic viscosity of the copolymer formed for 2 h was very low (0.11 dl/g) at 30 °C in DMF despite high weight-average molecular weight [3.1×l0⁶ by multi-angle laser light scattering (MALLS)]. The copolymer exhibited a very low second virial coefficient (4.2×l0⁻⁶) as determined at 25 °C in DMF by MALLS. The individual copolymer molecules were observed as nanoparticles of 7-20 nm diameter by a transmission electron microscope. These results show that the resulting copolymers are of hyperbranched structure.     

An examination of the role of plasma treatment for lean NOx reduction over sodium zeolite Y and gamma alumina Part 2: Formation of nitrogen

NO_x reduction with NO₂ as the NO_x gas in the absence of plasma was compared to plasma treated lean NO_x exhaust where NO is converted to NO₂ in the plasma. Product nitrogen was measured to prove true chemical reduction of NO_x to N₂. With plasma treatment, NO as the NO_x gas, and a NaY catalyst, the maximum conversion to nitrogen was 50% between 180 and 230 °C. The activity decreased at higher and lower temperatures. At 130 °C a complete nitrogen balance could be obtained, however between 164 and 227 °C less than 20% of the NO_x is converted to a nitrogen-containing compound or compounds not readily detected by gas chromatograph (GC) or Fourier transform infrared spectrometer (FT-IR) analysis. With plasma treatment, NO₂ as the NO_x gas, and a NaY catalyst, a complete nitrogen balance is obtained with a maximum conversion to nitrogen of 55% at 225 °C.

For γ-alumina, with plasma treatment and NO₂ as the NO_x gas, 59% of the NO_x is converted to nitrogen at 340 °C. A complete nitrogen balance was obtained at these conditions. As high as 80% NO_x removal over γ-alumina was measured by a chemiluminescent NO_x meter with plasma treatment and NO as the NO_x gas.

When NO is replaced with NO₂ and the simulated exhaust gases are not plasma treated, the maximum NO_x reduction activity of NaY and γ-alumina decreases to 26 and 10%, respectively. This is a large reduction in activity compared to similar conditions where the simulated exhaust was plasma treated. Therefore, in addition to NO₂, other plasma-generated species are required to maximize NO_x reduction.