Kinetic study of 1‐butanol dehydration to di‐n‐butyl ether over Amberlyst 70

Kinetics of the catalytic dehydration of 1‐butanol to di‐n‐butyl ether (DNBE) over Amberlyst 70 was investigated. Experiments were performed in liquid phase at 4 MPa and 413–463 K. Three elementary reaction mechanisms were considered: a Langmuir–Hinselwood–Hougen–Watson (LHHW) formulation; an Eley–Rideal (ER) formulation in which DNBE remains adsorbed; an ER formulation in which water remains adsorbed. Two kinetic models explain satisfactorily the dehydration of 1‐butanol to DNBE: a LHHW formalism in which the surface reaction between two adjacent adsorbed molecules of 1‐butanol is the rate limiting step (RLS) and where the adsorption of water is negligible, and a mechanism in which the RLS is the desorption of water being the adsorption of DNBE negligible. In both models, the strong inhibiting effect of water was successfully taken into account by means of a correction factor derived from a Freundlich adsorption isotherm. Both models present similar values of apparent activation energies (122 ± 2 kJ/mol). © 2015 American Institute of Chemical Engineers AIChE J, 62: 180–194, 2016     

N‐Methylprolinol Catalysed Asymmetric Baylis−Hillman Reaction

N‐methylprolinol is used as a chiral base catalyst for the Baylis–Hillman reaction to obtain the adducts in good yields with moderate to good enantioselectivities in 1,4‐dioxane:water (1 : 1, v/v) under ambient conditions.     

High catalytic efficiency in liquid‐phase oxidation of 1,4‐dioxane using a Pt/CeO2‐ZrO2‐SnO2/SBA‐16 catalyst

A Pt/CeO₂–ZrO₂–SnO₂/SBA‐16 (SBA‐16: Santa Barbara Amorphous No. 16) catalyst was developed for the efficient removal of 1,4‐dioxane. Because the catalyst showed synergistic action between the high catalytic activity of Pt and the high oxygen release and storage abilities of CeO₂–ZrO₂–SnO₂, high catalytic efficiency in the liquid phase was obtained in an air atmosphere without the supply of any strongly oxidizing additives or photoirradiation. After reaction at 80°C for 4 h, the residual percentage of 1,4‐dioxane reached 31%. Furthermore, the Pt/CeO₂–ZrO₂–SnO₂/SBA‐16 catalyst exhibited high reusability and durability and the rate of net decrease in 1,4‐dioxane reached 44% at 80°C.     

Mechanistic insights into aqueous phase propanol dehydration in H‐ZSM‐5 zeolite

Aqueous phase dehydration of 1‐propanol over H‐ZSM‐5 zeolite was investigated using density functional theory (DFT) calculations. The water molecules in the zeolite pores prefer to aggregate via the hydrogen bonding network and be protonated at the Brønsted acidic sites (BAS). Two typical configurations, i.e., dispersed and clustered, of water molecules were identified by ab initio molecular dynamics simulations of the mimicking aqueous phase H‐ZSM‐5 unit cell with 20 water molecules per unit cell. DFT calculated Gibbs free energies suggest that the dimeric propanol–propanol, the propanol–water, and the trimeric propanol–propanol–water complexes are formed at high propanol concentrations in aqueous phase, which provide a kinetically feasible dehydration reaction channel of 1‐propanol to propene. The calculation results indicate that the propanol dehydration via the unimolecular mechanism becomes kinetically discouraged due to the enhanced stability of the protonated dimeric propanol and the protonated water cluster acting as the BAS site for alcohol dehydration. © 2016 American Institute of Chemical Engineers AIChE J, 63: 172–184, 2017     

Liquid–liquid two‐phase flow in ultrasonic microreactors: Cavitation,emulsification, and mass transfer enhancement

The effects of ultrasound on the hydrodynamic and mass transfer behaviors of immiscible liquid–liquid two‐phase flow was investigated in a domestic ultrasonic microreactor. Under ultrasonic irradiation, cavitation bubble was generated and underwent violent oscillation. Emulsification of immiscible phases was initiated by virtue of oscillating bubbles shuttling through the water/oil interface. The pressure drop was found to decrease with increasing ultrasound power, with a maximum decrement ratio of 12% obtained at power 30 W. The mass transfer behavior was characterized by extraction of Rhodamine B from water to 1‐octanol. An enhancement factor of 1.3–2.2 on the overall mass‐transfer coefficient was achieved under sonication. The mass transfer performance was comparable to passive microreactor at similar energy dissipation rate (61–184 W/kg). The extraction equilibrium was reached under a total flow velocity 0.01 m/s and input power 20 and 30 W, exhibiting its potential use in liquid‐liquid extraction process. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1412–1423, 2018     

Methanol synthesis in a three‐phase catalytic bed under nonwetted condition

To overcome the heat removal problem encountered in methanol synthesis at high syngas concentrations in the gas phase, a three‐phase nonwetted catalytic system was established by introducing an inert liquid medium into a fixed‐bed reactor. To form a repellent interface between the liquid and the catalyst, the catalyst was modified into hydrophobic, while the liquid medium was chosen as a room temperature ionic liquid with hydroxyl groups. The liquid‐solid contact angle was measured to be 115°, and only 20% of the catalyst external surface was wetted by the liquid. Under three‐phase condition, the reaction rate was measured to be 60%–70% of gas‐phase reaction, while it was merely 10%–20% for the fully wetted catalyst. From the resistance analysis on the mass transfer and reaction steps, the overall reaction rate is expected to increase further if the surface could be more wet proofed. © 2016 American Institute of Chemical Engineers AIChE J, 63: 226–237, 2017     

Electrochemical oxidation of 1,4‐dioxane at boron‐doped diamond electrode

BACKGROUND: The electrochemical oxidation of 1,4‐dioxane at a boron doped diamond (BDD) surface on a niobium substrate anode was studied because (i) 1,4 dioxane is a resistant contaminant in waste‐waters and ground‐waters which needs to be removed/oxidized and (ii) most of the currently applied techniques for removal/oxidation require chemicals. RESULTS: Results show that in the potential region supporting electrolyte stability 1,4‐dioxane can be oxidized directly. Adhesive products, which cause electrode fouling, are also formed during oxidation in this potential region. The BDD anode can be restored to its initial activity by simple anodic treatment in the potential region of electrolyte decomposition. In this region, oxidation reactions leading to complete oxidation of 1,4‐dioxane, can take place due to electro‐generated hydroxyl radicals. Therefore, dioxane can only be effectively oxidized at these potentials. The effect of current density on the oxidation of 1,4‐dioxane has been investigated. The experimental results have also been compared with a theoretical chemical oxygen demand (COD)–instantaneous current efficiency (ICE) model. At a current density above 32 mA cm^?2, the oxidation process is completely controlled by mass transfer and no intermediates are formed. 92% of the COD can be removed with a total consumption of 7 Ah L^?1. CONCLUSIONS: Results show that dioxane can be effectively and completely oxidized at a BDD anode. Copyright © 2010 Society of Chemical Industry     

Comparitive study on facilitated pertraction of succinic acid using TRI‐n‐octylamine without and with 1‐octanol

Succinic acid has been pertracted with TOA using free liquid membranes without or with 1‐octanol. The addition of the alcohol led to the increase of up to 2.8–3 times of the acid's initial and final mass flows. At the same time, the influence of 1‐octanol on the transport capacity of the pertraction system was negative, its addition inducing the accumulation of succinic acid into the liquid membrane. A mathematical model describing the acid accumulation inside the liquid membrane has been developed for pertraction systems without and with 1‐octanol and offers good concordance with the experimental data. © 2012 Canadian Society for Chemical Engineering     

Liquid‐phase axial dispersion of turbulent gas–liquid co‐current flow through screen‐type static mixers

This article discusses the characteristics of turbulent gas–liquid flow through tubular reactors/contactors equipped with screen‐type static mixers from a macromixing perspective. The effect of changing the reactor configuration, and the operating conditions, were investigated by using four different screen geometries of varying mesh numbers. Residence time distribution experiments were conducted in the turbulent regime (4500 < Re < 29,000). Using a deconvolution technique, the RTD function was extracted to quantify the axial/longitudinal liquid‐phase dispersion coefficient. The findings highlight that axial dispersion increases with an increasing flow rate and/or gas‐phase volume fraction. However, regardless of the number and geometry of the mixing elements, reactor configuration, and/or operating conditions, the recorded liquid‐phase axial dispersion coefficients in the presence of screens was lower than that for an empty pipe. Furthermore, the geometry of the screen was found to directly affect the axial dispersion coefficient in the reactor. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1390–1403, 2017     

Effect of various additives on pore size of polysulfone membrane by phase‐inversion process

The phase‐inversion process was used to prepare integrally skinned asymmetric polysulfone (PSf) membranes with different pore sizes. Membranes were prepared from a casting solution of PSf; N‐methyl‐2‐pyrrolidone (NMP) as solvent; and 1,4‐dioxane, diethylene glycol dimethyl ether (DGDE), acetone, and γ‐butyrolactone (GBL) as additives by immersing them in water as a coagulant. The effect of the additives on membrane performance and structure was investigated. The low miscibility of 1,4‐dioxane, DGDE, and acetone with the coagulant resulted in reduced membrane pore size. However, by using GBL as additive pore size of the membrane was slightly increased because of its higher miscibility with the coagulant than NMP. Changing the amount of additives in the casting solution could control the molecular‐weight cutoff values of asymmetric membranes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2562–2566, 2003     

Influence of Gas Injection on the In‐Situ Oil Fraction of an Oil‐Water Flow in Horizontal Pipes

In this work, an experimental study was made on gas injection into an oil‐water flow in horizontal pipes with two unequal pipe diameters. Special attention was given to the influence of gas injection on the average in‐situ oil fraction. Measurements were made for input water flow rates of 1.25–5 m³/h, input oil flow rates of 0–8 m³/h and input gas flow rates of 0–9 m³/h. It was found that gas injection has a considerable influence on the in‐situ oil fraction. In general, a small increase in the rate of air injection leads to greatly decreasing in‐situ oil fractions. The in‐situ oil fraction with gas injection decreases to a greater extent than that without gas injection, at the same input liquid flow rates. At a given input water flow rate, the value of the in‐situ oil fraction in the pipe with the larger diameter is higher than that in the pipe with the smaller diameter. Furthermore, the drift flux models were extended to predict the average in‐situ fractions of the oil phase in the intermittent three‐phase flow regimes. A good agreement is obtained between theory and data, especially for the in‐situ oil fraction range of 0.2–1.0.     

Formation of integrally skinned asymmetric polyetherimide nanofiltration membranes by phase inversion process

Integrally skinned asymmetric polyetherimide (PEI) membranes were prepared by the phase inversion process from casting solution containing dimethylformamide (DMF) as a solvent and 1,4‐dioxane as a cosolvent. Deionized water was used as a coagulation medium in preparing asymmetric membranes. The effect of 1,4‐dioxane was investigated by measuring casting solution properties, permeation properties, and membrane structures. Various effects of polymer concentration, evaporation time, and coagulation bath temperature were also studied. Low miscibility of 1,4‐dioxane with coagulant (water) resulted in reducing membrane pore size. The molecular weight cutoff values of asymmetric membranes could be controlled by changing the amount of 1,4‐dioxane in the casting solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1300–1307, 2002; DOI 10.1002/app.10452     

Synthesis,characterization, and properties of thermosets based on the cocuring of an acetylene‐terminated liquid‐crystal and silicon‐containing arylacetylene oligomer

A thermotropic acetylene‐terminated liquid‐crystal monomer, 2‐methyl‐1,4‐phenylene bis(4‐ethynylbenzoate) (MPBE), was prepared and used as a modification composition to react and cocure with a silicon‐containing arylacetylene (PSA) oligomer for improving PSA resin. The curing behavior of the PSA–MPBE resins were characterized by differential scanning calorimetry and Fourier transform infrared spectroscopy. The microstructure and morphology of the PSA–MPBE resins were investigated by scanning electron microscopy (SEM) and transmission electron microscopy. Their dynamic mechanical properties and thermostability were measured by dynamic mechanical analysis (DMA) and thermogravimetric analysis. The results indicate that the thermotropic acetylene‐terminated liquid‐crystal monomer melted into a schlieren texture. MPBE and PSA could copolymerize to fix the mesogenic domain in the crosslinked network and form a homogeneous‐phase sea‐island structure, which improved the rigidity and toughness of the materials. DMA showed that the storage modulus of the PSA–MPBE resins increased by about 400 MPa compared to the those of the pure components. The SEM experiments showed a noticeable change in the morphology, from a typical brittle fracture for the pure PSA to microplastic deformation behavior for the PSA–MPBE resins. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45141.     

Computer simulation and comparative study on the pervaporation separation characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) to separate aqueous mixtures of 1,4‐dioxane or tetrahydrofuran

A comparative study on the pervaporation separation has been attempted for water + 1,4‐dioxane and water + tetrahydrofuran mixtures using sodium alginate and blend membranes of sodium alginate with 5, 10, and 20 mass % of poly(vinyl alcohol). Pure sodium alginate membrane has a selectivity of 111 to water at 0.35‐mol fraction of water in the feed mixture containing 1,4‐dioxane while for water + tetrahydrofuran mixture, the membrane selectivity to water was 291 at 0.31‐mol fraction of water in the feed mixture. Pervaporation results have been discussed using the solution–diffusion principles. Arrhenius activation parameters for diffusion and permeation have been computed from the temperature‐dependent pervaporation results. Furthermore, experimental results have been analyzed using the complete mixing and plug flow models to compute membrane area as well as design parameters that are useful in scale‐up operations. The plug flow model is more appropriate than the complete mixing model to analyze the pervaporation results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1827–1840, 2004     

13C‐NMR study on cure‐accelerated phenol‐formaldehyde resins with carbonates

Both liquid‐ and solid‐state carbon‐13–nuclear magnetic resonance (¹³C‐NMR) spectroscopies were used to investigate the cure acceleration effects of three carbonates (propylene carbonate, sodium carbonate, and potassium carbonate) on liquid and cured phenol‐formaldehyde (PF) resins. The liquid‐phase ¹³C‐NMR spectra showed that the cure acceleration mechanism in the propylene carbonate‐added PF resin seemed to be involved in increasing reactivity of the phenol rings, whereas the addition of both sodium carbonate and potassium carbonate into PF resin apparently resulted in the presence of ortho–ortho methylene linkages. Proton spin‐lattice rotating frame relaxation time (T_1ρH) measured by solid‐state ¹³C cross polarization/magic‐angle spinning NMR spectroscopy was smaller for the cure‐accelerated PF resins than that of the control PF resin. The result indicated that the cure‐accelerated PF resins are less rigid than the control PF resin. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1284–1293, 2000     

Activated charcoal‐loaded composite membranes of sodium alginate in pervaporation separation of water‐organic azeotropes

Composite membranes of sodium alginate prepared by incorporating nanosized‐activated charcoal particles were prepared and characterized for the extent of cross‐linking, thermal stability, and mechanical strength properties using Fourier transform infrared, differential scanning calorimetry, and universal testing machine, respectively. The membranes were tested for pervaporation (PV) dehydration of isopropanol (IPA), ethanol (EtOH), 1,4‐dioxane (1,4‐D), and tetrahydrofuran (THF) at their azeotropic compositions. Improved PV performances of the composite membranes were observed compared with plain sodium alginate membrane for all the azeotropes. Sorption was studied to evaluate the extent of interactions between liquids and membranes as well as degree of swelling of the membranes in the chosen aqueous‐organic mixtures. Adding different amounts of activated charcoal into NaAlg offered high water selectivity values of 99.7, 99.1, 99.4, and 99.41%, respectively, for IPA, THF, 1,4‐D, and EtOH. Arrhenius activation parameters were computed from the temperature versus flux plots, which showed systematic trends for different liquids that depended upon their interactions with membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of emulsion‐type curing agent of water‐borne epoxy resin

Self‐emulsified water‐borne epoxy curing agent of nonionic type was prepared using triethylene tetramine (TETA) and derivative of epoxy resin as a capping agent, which was synthesized by liquid epoxy resin (E51) and polyethylene glycol (PEG), and the curing agent possessed emulsification and curing properties at the same time. The curing agent with good property of emulsifying liquid epoxy resin could be obtained under the condition of the molar ratio of PEG : E51 : TETA as 0.8 : 1 : 3.5 at 80°C for 5 h. The mean particle size of the emulsion liquid was about 220 nm with the prepared curing agent and epoxy resin at the mass ratio of 1 : 3. The structure of the emulsion‐type curing agent was confirmed by FTIR and ¹H NMR spectra, and the mechanism of cured film formation was also analyzed by SEM photographs. The cured film prepared by the emulsion‐type curing agent and epoxy resin under ambient cure conditions showed good properties even at high staving temperature. This study provides useful suggestions for the application of the water‐borne epoxy resins in coating industry. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2652–2659, 2013     

Equilibrium and non‐equilibrium gas–liquid two phase flow in long and short pipelines following a rupture

The two‐phase flow following the blowdown of pipeline carrying flashing liquid is numerically investigated by using thermodynamic equilibrium and non‐equilibrium models. Model equations are solved numerically by the finite volume method. The values of fluxes at cell boundaries are obtained by AUSM+‐up. To obtain proper values for the coefficients of dissipation, both single phase liquid and two phase shock tube problems are investigated. The transient release from the pressurized pipeline is studied for two cases of long and short pipes. Comparison of the predictions against experimental data reveals non‐equilibrium model performs a little better than equilibrium model in the prediction of temporal variations of pressure and void fraction of the long pipe. However, equilibrium model totally overestimates pressure and void fraction of the short pipe. The relative error of equilibrium model in the prediction of pressure variation with time exceeds 50% and it is 20% for non‐equilibrium model. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3214–3223, 2017     

Phase separation of gas–liquid two‐phase stratified and plug flows in multitube T‐junction separators

Using air and water as the working fluids, phase separation phenomena for stratified and plug flows at inlet were investigated experimentally, at a simple T‐junction and specifically designed multitube T‐junction separators with two or three layers. The results show that for these two flow patterns the separation efficiency of the two phases for any multitube T‐junction separator is much higher than that of the simple T‐junction. Increasing the number of connecting tubes in the multitube T‐junction separator can increase the separation efficiency. Generally, for stratified flow, complete separation of the two phases can be achieved by the two‐layer multitube T‐junction separator with five or more connecting tubes and by the three‐layer separator; increasing the gas flow rate, the liquid flow rate, or the mixture velocity under plug flow is detrimental to phase separation with a drop in peak separation efficiency. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2285–2292, 2017     

13C‐NMR study on cure‐accelerated phenol–formaldehyde resins with carbonates

Both liquid‐ and solid‐state ¹³C‐NMR spectroscopies were employed to investigate the cure‐acceleration effects of three carbonates [propylene carbonate (PC), sodium carbonate (NC), and potassium carbonate (KC)] on liquid and cured phenol–formaldehyde (PF) resins. The liquid‐phase ¹³C‐NMR spectra showed that the cure‐acceleration mechanism in the PC‐added PF resin seemed to be involved in increasing reactivity of the phenol rings, while the addition of both NC and KC into PF resin apparently resulted in the presence of ortho–ortho methylene linkages. Proton spin‐lattice rotating frame relaxation time (T_1ρH) measured by solid‐state ¹³C‐CP/MAS‐NMR spectroscopy was smaller for the cure‐accelerated PF resins than for that of the control PF resin. The result indicated that cure‐accelerated PF resins are less rigid than the control PF resin. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 841–851, 2000