Multi‐phase electro‐chemical catalytic oxidation of wastewater

The removal of organic pollutants from synthetic wash wastewater by a combined multi‐phase electro‐catalytic oxidation method was evaluated using porous graphite as anode and cathode, and CuO–Co₂O₃–PO₄^3? modified kaolin as catalyst. The synergic effect on COD removal was studied when integrating the electro‐chemical reactor with the effective modified kaolin in a single undivided cell; the results showed that higher COD removal efficiency was obtained than those obtained using the individual processes. Under optimal conditions of pH 3, 30 mA cm^?2 current density, very effective reduction of organic pollutants was achieved with this combined electro‐chemical method. High removal efficiency (90%) of the chemical oxygen demand (COD) was obtained in 60 min in the treatment of simulated wash wastewater (anionic surfactant, sodium dodecyl benzene sulfonate [DBS]). This method was also applied to treat wastewater form paper‐making and resulted in a COD reduction of 84%. Based on the investigation, a possible mechanism of this combined electro‐chemical process was proposed. The pollutants in wastewater could be decreased by the high reactive OH? that were produced via the decomposition of electro‐generated H₂O₂ activated by the synergic effect of electro‐field and catalyst. The results indicate that the multi‐phase catalytic electro‐chemical oxidation process is a promising technique for wastewater treatment. Copyright © 2006 Society of Chemical Industry     

Kinetics of Aqueous‐Phase catalytic dehydration of 2‐Propanol

The aqueous‐phase catalytic dehydration of 2‐propanol was investigated in a batch slurry reactor. Alumina, zeolite 13X, SAPO‐5 and silicalite are all active in the liquid phase dehydration of 2‐propanol at 463 K with silicalite being the most active catalyst. Propylene was found to be the major reaction product, with diisopropyl ether and acetone formed in trace amounts. The reaction kinetics over silicalite was determined at a temperature range of 434 to 463 K and at a concentration range of 4 to 10 mol% 2‐propanol in water. A single site Langmuir‐Hinshelwood‐Hougen‐Watson (LHHW) type mechanism was found to describe the kinetic data well. Water was found to inhibit the dehydration reaction. The activation energy over silicalite was determined to be 226.8 kJ/mol while the heat of adsorption for 2‐propanol and water was –45.5 and –9.6 kJ/mol, respectively.     

Detailed investigation of non‐catalytic DPF regeneration

The present investigation concerns the phenomena that occur during the non‐catalytic regeneration of Diesel Particulate Filters (DPFs). The temperature evolution in the filter has been correlated to the emissions of CO, HC, NO, and NO₂ during the loading and regeneration process. The emissions were assessed over both the diesel oxidation catalyst (DOC) and the DPF, in order to characterise the chemical species evolution inside the after‐treatment line. Different regeneration temperatures, which have been found to have a strong impact on the evolution of the soot oxidation rate, have been assessed. Finally, the particulate emissions during regeneration have been measured on a number and size basis.     

Polyethylene catalytic hydrocracking by PtHZSM‐5, PtHY,and PtHMCM‐41

The mechanisms involved in polyethylene catalytic hydrocracking are investigated by monitoring temperature‐dependent evolution profiles derived from mass spectra obtained while polymer/catalyst samples were heated at a constant rate. Repetitive injection gas chromatography/mass spectrometry (GC/MS) results are used to identify class‐specific fragment ions that represent paraffins, olefins, and alkyl aromatics. Class‐specific ion signals are used to generate isoconversion‐effective activation energy plots from which mechanistic comparisons are made. Studies using PtHZSM‐5, PtHY, and PtHMCM‐41 bifunctional solid acid catalysts in helium and hydrogen are reported. The effects of hydrogen on polyethylene cracking are dramatic and result in significant changes to isoconversion‐effective activation energies. Catalytic cracking mechanisms for the three catalysts are compared and differences are explained by a combination of pore size and acidity effects. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1293–1301, 2004     

Controllable fabrication and catalytic activity of highly b‐oriented HZSM‐5 coatings

Multilayer b‐orientated HZSM‐5 catalytic coating is controllably synthesized by repeated growth of zeolite layer on Ti?OH‐modified surface of sublayer. The as‐prepared zeolite coating shows performance enhancement up to 110% in catalytic cracking of n‐dodecane ascribed to enhanced mass transfer in its straight and short pathway along the b‐axis. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1964–1968, 2014     

Mathematical modelling of fluidized‐bed reactors for non‐catalytic gas–solid reactions

Mathematical modelling of a continuous fluidized‐bed reactor has been carried out for non‐catalytic gas–solid reactions. The two‐phase bubbling bed model has been used and the elutriation phenomenon for the fine particles has been investigated. The feed stream consisting particles with size distribution and reversible or irreversible first‐order kinetics can be treated by the model. The reduction behaviour of solid reactants was described by the grain model. A program was developed in MATLAB software for solving the governing equations at conditions of different temperatures and pressures. The model was validated using experimental data and simulation results available in the literature for the iron ore reduction with a gas mixture containing hydrogen [Srinivasan and Staffansson, Chem. Eng. Sci. 45(5), 1253–1265 (1990)]. The mathematical modelling was also used for predicting the extent of reaction for reduction of cobalt oxide by methane.     

Environment‐friendly silicone sealants by self‐catalytic cross‐linking reaction of α‐aminomethyl triethoxysilanes

On the basis of the self‐catalytic characteristic of α‐aminomethyl triethoxysilanes, (diethyl) aminomethyl triethoxysilane, cyclohexylaminomethyl triethoxysilane, and anilinomethyl triethoxysilane were used as self‐catalytic cross‐linkers to prepare a series of environmental friendly, nano‐CaCO₃ reinforced silicone sealants based on poly(dimethylsiloxane) (PDMS). The tensile properties, hardness, adhesive properties, hot‐air aging resistance, and oil‐resistance properties of these materials were studied by universal electronic tensile machine, scanning electron microscope, and atomic force microscopy, etc. Results show that the comprehensive properties of the self‐catalytic cross‐linking PDMS sealants are much better than that of the traditional ones. The chemical structure and reactivity of the α‐aminomethyl triethoxysilanes have a great effect on the properties of PDMS sealants. The tensile strength of the reinforced sealants with 100 phr (100 parts per hundreds of PDMS) nano‐CaCO₃ is about 4.4 times than that of the unreinforced ones, and the elongation at break is about three times. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Chemical kinetic modeling of i‐butane and n‐butane catalytic cracking reactions over HZSM‐5 zeolite

A chemical kinetic model for i‐butane and n‐butane catalytic cracking over synthesized HZSM‐5 zeolite, with SiO₂/Al₂O₃ = 484, and in a plug flow reactor under various operating conditions, has been developed. To estimate the kinetic parameters of catalytic cracking reactions of i‐butane and n‐butane, a lump kinetic model consisting of six reaction steps and five lumped components is proposed. This kinetic model is based on mechanistic aspects of catalytic cracking of paraffins into olefins. Furthermore, our model takes into account the effects of both protolytic and bimolecular mechanisms. The Levenberg–Marquardt algorithm was used to estimate kinetic parameters. Results from statistical F‐tests indicate that the kinetic models and the proposed model predictions are in satisfactory agreement with the experimental data obtained for both paraffin reactants. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2456–2465, 2012     

Theoretical investigation of a water‐gas‐shift catalytic membrane for diesel reformate purification

The novel application of a catalytic water‐gas‐shift membrane reactor for selective removal of CO from H₂‐rich reformate mixtures for achieving gas purification solely via manipulation of reaction and diffusion phenomena, assuming Knudsen diffusion regime and the absence of hydrogen permselective materials, is described. An isothermal, two‐dimensional model is developed to describe a tube‐and‐shell membrane reactor supplied with a typical reformate mixture (9% CO, 3% CO₂, 28% H₂, and 15% H₂O) to the retentate volume and steam supplied to the permeate volume such that the overall H₂O:CO ratio within the system is 9:1. Simulations indicate that apparent CO:H₂ selectivities of 90:1 to >200:1 at H₂ recoveries of 20% to upwards of 40% may be achieved through appropriate design of the catalytic membrane and selection of operating conditions. Under these conditions, simulations predict an apparent hydrogen permeability of 2.3 × 10^?10 mol m^?1 Pa, which compares favorably against that of competing hydrogen‐permselective membranes. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4334–4345, 2013     

Temperature‐responsive catalytic performance of Ag nanoparticles endowed by poly (N‐isopropylacrylamide‐co‐acrylic acid) microgels

In this study, we facilely introduce silver nanoparticles into Poly(N‐isopropylacrylamide‐co‐acrylic acid)(Poly(NIPAM‐co‐AA)) microgels and specially focus on the effect of hydrophilic acrylic acid segments on the responsive catalytic performance of silver nanoparticles. The obtained Poly(NIPAM‐co‐AA)/AgNPs composites are characterized by Fourier transform infrared spectra, X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission electron microscopy. The composites as catalysts are applied to the hydrogenation reaction of p‐nitrophenol and the related conditions such as reaction temperature, concentration of p‐nitrophenol, and the loadings of Ag nanoparticles are studied in detail. NIPAM segments of composites conveniently give silver nanoparticles a controllable characteristic for catalytic reaction by their conformation variation. AA segments of composites not only provide good stability and dispersibility for silver nanoparticles but also favor an easier diffusion of p‐nitrophenol to Ag NPs. POLYM. COMPOS., 38:708–718, 2017. © 2015 Society of Plastics Engineers     

Homogeneous catalytic hydrogenation of hydroxyl‐terminated liquid nitrile rubber

It was difficult to obtain high degree of hydrogenation of hydroxyl‐terminated liquid nitrile rubber (HTBN) by using homogeneous noble metal catalyst because the hydroxyl (? OH) in HTBN was likely to cause catalyst poisoning. In this study, with hexamethyl disilylamine protecting ? OH, a good yields of hydrogenated HTBN was synthesized through the use of homogeneous metal catalyst. The effects of catalyst concentration, reaction time, hydrogen pressure, and temperature on the hydrogenation of HTBN were investigated and obtained the following optimum process parameter values: catalyst mass fraction of 0.8%, reaction time of 8 h, pressure of 1.6 MPa, and temperature of 100°C. Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy were used to characterize the hydrogenation product of the protected HTBN, indicating that under certain conditions a high degree of hydrogenation of HTBN can be achieved. Only the carbon–carbon double bonds (C?C), not the ? CN bonds, are subject to hydrogenation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Gas‐solid catalytic reactions with an extended DSMC model

An algorithm of diffusive gas transport in porous solids based on random collisions of molecules (DSMC) is extended to include basic heterogeneous reaction mechanisms (adsorption, coadsorption, desorption, and reaction of gas species on the surface of the solid). With this model, we study the catalytic oxidation of CO inside highly porous nanoparticle layers in the transition regime using kinetic parameters from Pd(111) surfaces at ultra high vacuum conditions. Investigation of the reaction at different temperatures reveals a clear transition between a kinetic limit (low temperatures) and a diffusion limit (high temperatures). At high temperatures and under steady‐state conditions, the porous layer shows three distinct regions with different reaction rates (reactor poisoning, an effective reaction region, and a region with CO depletion), whose extends are determined by CO concentration and mass‐transport limitation. We expect that similar investigations help optimizing the structure of gas sensor elements based on nanoparticle layers fabricated with flame spray pyrolysis. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2092–2103, 2015     

Preparation of polyelectrolyte‐stabilized silver nanoparticles for catalytic applications

A facile and green method is developed for the preparation of polyelectrolyte‐stabilized silver nanoparticles (AgNPs ) using dopamine as a reducing agent. The AgNPs were prepared in the presence of the polyelectrolyte poly[acrylamide‐co ‐(diallyldimethylammonium chloride)] (PADA ) and amine‐functionalized silane matrices. Interestingly, only amine‐functionalized silanes led to AgNPs in the presence of PADA , whereas silane without amine functionalization failed to produce them. The catalytic ability of the AgNPs was investigated by adopting a benchmark reaction, i.e. reduction of 4‐nitrophenol in the presence of sodium borohydride. It was found that PADA ‐Ag(0.1)‐TPDT (TPDT = N ‐[3‐(trimethoxysilyl)propyl]diethylenetriamine) showed better catalytic activity when compared to other silver concentrations of 0.05, 0.5 and 1 mmol L^?1. Remarkably, a very high normalized rate constant, 20 374 s^?1 g^?1, was observed for PADA ‐Ag(0.1)‐TPDT . © 2016 Society of Chemical Industry     

High‐conversion catalytic chain transfer polymerization of methyl methacrylate

In this work the effects of conversion on the apparent catalyst activity in the catalytic chain transfer polymerization of methyl methacrylate are reported. Several mechanisms are discussed that may explain the experimental observations. The discussion is supported with computer simulations using Predici software. It is shown that the experimental decrease in weight average molecular weight with conversion is smaller than the decrease obtained in simulations. The most likely cause for this discrepancy is slow catalyst deactivation. The half‐life of CoBF under the reported conditions was determined to be about 10 h. Furthermore, the effect of acetic acid (HAc) and benzoyl peroxide (BPO) on the evolution of the molecular weight distribution is investigated. Both HAc and BPO enhance catalyst deactivation. For HAc, catalyst deactivation scales with the square root of its concentration. BPO‐ enhanced deactivation depends linearly on its concentration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1375–1388, 2004     

A review of catalytic approaches to waste minimization: case study—liquid‐phase catalytic treatment of chlorophenols

Effective waste management must address waste reduction, reuse, recovery/recycle and, as the least progressive option, waste treatment. Catalysis can serve as an integral green processing tool, ensuring lower operating pressures/temperatures with a reduction in energy requirements while providing alternative cleaner synthesis routes and facilitating waste conversion to reusable material. The case study chosen to illustrate the role that catalysis has to play in waste minimization deals with the conversion of toxic chlorophenols in wastewater. The presence of chloro‐organic emissions is of increasing concern with mounting evidence of adverse ecological and public health impacts. A critical overview of the existing treatment technologies is provided with an analysis of the available literature on catalytic dechlorination. The efficacy of Pd/Al₂O₃ to promote the hydrogen‐mediated dechlorination of mono‐ and dichlorophenols is demonstrated, taking account of both the physical and chemical contributions in this three‐phase (solid catalyst and liquid/gaseous reactants) system. Hydrodechlorination activity and selectivity trends are discussed in terms of chloro‐isomer structure, the influence of temperature is discussed, the role of base (NaOH) addition is examined and the feasibility of catalyst reuse is addressed. Copyright © 2005 Society of Chemical Industry     

Selective removal of 1,2‐propanediol and 1,2‐butanediol from bio‐ethylene glycol by catalytic reaction

Ethylene glycol (EG), synthesized from biomass, frequently contains refractory 1,2‐propanediol (PDO) and 1,2‐butanediol (BDO). Selective removal of PDO and BDO was realized herein by catalytic dehydration to form volatile aldehydes, ketones, and acetals. Various acidic and basic catalysts were screened under a range of conditions for the conversion of a mixture containing 73 wt % EG, 20 wt % PDO, and 7 wt % BDO. Over H‐Beta 26 zeolite, the most selective catalyst among tested, PDO and BDO conversions reached 99.1 and 99.3%, respectively, after 4 h reaction at 453 K, with separation factors over 2. The activation energies for EG, PDO, and BDO dehydration were ca. 99.3, 69.9, and 54.0 kJ/mol, respectively, accounting for the high reactivity of PDO and BDO. The dehydration largely proceeded in the micropores of H‐Beta and depended on the number of strong Brønsted acid sites, but excessively strong acid sites enhanced the polymerization of EG. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4032–4042, 2017     

Synthesis of polymer‐supported quaternary ammonium salts and their phase‐transfer catalytic activity in halogen‐exchange reactions

Polymer‐supported quaternary ammonium salts were prepared, and their applications as phase‐transfer catalysts in aqueous organic systems were investigated. The polymer‐bound phase‐transfer catalysts were prepared with polystyrene resins crosslinked with the bifunctional monomers divinylbenzene and 1,4‐butanediol dimethacrylate. The polymers were functionalized with chloromethyl groups and quaternized with trialkylamines having different alkyl chains. The obtained phase‐transfer catalysts were characterized with IR spectroscopy and elemental analysis. The thermal stability was also determined by the thermogravimetric method. The catalytic properties of the phase‐transfer catalysts were studied in halogen‐exchange reactions. The effects of the nature and extent of crosslinking of the polymer support, the alkyl groups of the trialkylamine, and the reaction conditions were investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci 2009     

Preparation of polymer‐supported polyethylene glycol and phase‐transfer catalytic activity in benzoate synthesis

The crosslinked polymeric microspheres (GMA/MMA) of glycyl methacrylate (GMA) and methyl methacrylate (MMA) were prepared by suspension polymerization. Polyethylene glycol (PEG) was grafted on GMA/MMA microsphers via the ring‐opening reaction of the epoxy groups on the surfaces of GMA/MMA microspheres, forming a polymer‐supported triphase catalyst, PEG‐GMA/MMA. The Phase‐transfer catalytic activity of PEG‐GMA/MMA microspheres was evaluated using the esterification reaction of n‐chlorobutane in organic phase and benzoic acid in water phase as a model system. The effects of various factors on the phase transfer catalysis reaction of liquid–solid–liquid were investigated. The experimental results show that the PEG‐GMA/MMA microspheres are an effective and stable triphase catalyst for the esterification reaction carried out between oil phase and water phase. The polarity of the organic solvent, the ratio of oil phase volume to water phase volume and the density of the grafted PEG on PEG‐GMA/MMA microspheres affect the reaction rate greatly. For this investigated system, the solvent with high polarity is appropriate, an adequate volume ratio of oil phase to water phase is 2:1, and the optimal PEG density on the polymeric microspheres is 15 g/100 g. Triphase catalysts offer many advantages associated with heterogeneous catalysts such as easy separation from the reaction mixture and reusability. The activity of PEG‐GMA/MMA microspheres is not nearly decreased after reusing of 10 recycles. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Bio‐ and auto‐catalytic esterification of high acid mowrah fat and palm kernel oil

An alternative process for the deacidification of high acid palm kernel oil (PKO) and mowrah fat, MF, was investigated by autocatalytic and enzyme (Mucor miehei)‐catalyzed esterification of free fatty acids (FFA). In the process monoglyceride (MG) or glycerol was used as esterifying agent. The results of the autocatalytic esterification process were compared with that of bioesterification with respect to reduction of FFA. For the former process the optimum reaction temperature and oil to MG or glycerol proportion were established. The optimum reaction temperature for PKO free fatty acids with stoichiometric quantity of glycerol is 160—165 °C (at 10 mm Hg pressure (1.33 kPa)) and after 6 h the FFA content is reduced to 1.6%, w/w, (from 25.0%, w/w, original). However, if a stoichiometric amount of MG is used as an esterifying agent the optimum esterification temperature is found to be 195—200 °C (at 10 mm Hg pressure (1.33 kPa)), and after 8 h the FFA content is reduced to 3.4%, w/w. On the contrary, biorefining of PKO at 60 °C temperature and 10 mm Hg pressure (1.33 kPa) using optimum (40% excess) quantity of glycerol or 50% excess MG reduces the FFA level to 1.2% and 0.7%, w/w, respectively. Similar study on bio‐ and auto‐catalytic esterification of MF was also carried out and got comparable results. The final products were then characterized.