Kinetics and Mechanism of Hydration of Acrylic Acid over Ion-exchanged Resin:Experimental Exploration and DFT Calculation

Liquid-phase acrylic acid hydration over solid-phase catalysts is a key reaction for the industrial productionof 3-hydroxypropionic acid. However, the relevant literature primarily focuses on the experimental aspects of catalystscreening and exploring reaction conditions, with few accurate descriptions of the reaction kinetics and determination ofthe reaction mechanism. Here, we combined kinetics experiments and theoretical calculations to elucidate the kinetics andmechanism of acrylic acid hydration on a resin catalyst. The pseudo-homogeneous model, and Langmuir-Hinshelwood-Haugen-Watson and Elie-Riedel (ER) heterogeneous models were used to explain the experimental kinetics data. TheER model can explain the experimental data very well, suggesting strong adsorption of acrylic acid on the surface of theresin catalyst. Furthermore, density functional theory calculations show that the hydration follows a stepwise, rather than aconcerted, reaction pathway. The present study provides theoretical insights into the reaction mechanism and kinetics, fillingthe gap in our understanding of the reaction on a fundamental level.

Purification of Lactic Acid by Heterogeneous Catalytic Distillation Using Ion-exchange Resins

The purification of lactic acid based on the esterification of raw lactic acid from fermentation broth and then the catalytic distillation hydrolysis of methyl lactate simultaneously to achieve pure lactic acid is reported. The esterification kinetics of lactic acid with methanol catalyzed by strong-acid cation-exchange resins (Amberlyst-15,D001, D002, NKC, 002) was studied under the condition that simulates the real catalytic environment. Experimental results were correlated by a Langmuir-Hinselwood model and the nonideality of the solution was taken into account by using activities calculated by the universal quasichemical functional group activity coefficient (UNIFAC) method.A good agreement between the model and the experimental data was achieved. Continuous purification experiments were conducted to find the optimum column configuration and operation condition for the system. The effects of various parameters, e.g. the length of different section of the column, feed rate and ratio of reactants, packing material and catalyst type, were studied. This novel system shows good separation results in lab scale, and is potential for industrial application.

Tungsten removal from molybdate solutions using chelating ion-exchange resin:Equilibrium adsorption isotherm and kinetics

The equilibrium adsorption isotherm and kinetic of the sorption process for W and Mo on macro chelating resin D403 were investigated on single Na2 Mo O4 and Na2WO4 solutions.The sorption isotherm results show that the adsorption process of W obeys the Freundlich model very well whereas the exchange process with Mo approximately follows the Henry model.The kinetic experiments show that the intraparticle diffusion process was the rate-determining step for W sorption on the resin,and the corresponding activation energy is calculated to be 21.976 k J/mol.

Investigation of the Ion-Exchange Behavior of Zeolite Y in the Presence of Resin

Ion-exchange process of zeolite Y using ammonium-type resin as an exchange reagent was successfully carried out. The effect of temperature, space velocity and ion concentration on the breakthrough curves was carefully investigated. At the first exchange section, the maximum proportion of qualified zeolites(QR) was obtained at a temperature of 70 ℃, a weight hourly space velocity of 0.61 h-1, and an ion concentration of 197 mg/L. The minimum length of mass-transfer zone(MTZ) of the resin bed was achieved at a temperature of 70 ℃, a space velocity of 0.61 h-1, and an ion concentration of 423 mg/L. At the second exchange section, the length of MTZ of the resin bed was significantly increased, and the exchange of Na+ ions contained in zeolite Y was more difficult than that achieved at the first exchange section. In both the first and the second exchange sections, the zeolite Y subjected to ion exchange with the resin maintained the similar physical and chemical properties as compared to those exchanged by the conventional approaches, but the zeolite Y, which was obtained after ion exchange, contained a significantly lower content of Na2 O.

Kinetic Study of Esterification of Lactic Acid with Isobutanol and n-Butanol Catalyzed by Ion-exchange Resins

The esterification reactions of lactic acid with isobutanol and n-butanol have been studied in the presence of acid ion-exchange resin Weblyst D009. The influences of catalyst loading, stirrer speed, catalyst particle size, initial reactant molar ratio and temperature on the reaction rate have been examined. Experimental kinetic data were correlated by using the pseudo-homogeneous, Langnluir-Hinshelwood and Eley-Rideal models. Nonideality of the liquid phase was taken into account by using activities instead of molar fractions. The activity coefficients were calculated according to the group contribution method UNIFAC. Provided that the nonideality of the liquid is taken into account, the esterification kinetics of lactic acid with isobutanol and n-butanol catalyzed by the acid ion-exchange resin can be described using all threemodels with reasonable errors.

The Desalting Property of Ion-Exchange Resins in Organic Solvent

the desalting property of ion-exchange resins in organic solventis reported by using potassium acetate as a model compound. Theexperimental results show that solvability of the solvent, stirringspeed, and temperature are the factors which influence theion-exchange rate. The increase of solvability, stirring speed andtemperature will speed up the ion-exchange process.

Modified DIX model for ion-exchange equilibrium of L-phenylalanine on a strong cation-exchange resin

L-phenylalanine, one of the nine essential amino acids for the human body, is extensively used as an ingredient in food, pharmaceutical and nutrition industries. A suitable equilibrium model is required for purification of L-phenylalanine based on ion-exchange chromatography. In this work, the equilibrium uptake of L-phenylalanine on a strong acid-cation exchanger SH11 was investigated experimentally and theoretically. A modified Donnan ion-exchange （DIX） model, which takes the activiW into account, was established to predict the uptake of L-phenylalanine at various solution pH values. The model parameters including selectivity and mean activity coefficient in the resin phase are presented. The modified DIX model is in good agreement with the experimental data. The optimum operating pH value of 2.0, with the highest t-phenylalanine uptake on the resin, is predicted by the model. This basic information combined with the general mass transfer model will lay the foundation for the prediction of dynamic behavior of fixed bed separation process.

Study on the Stability of Ion-exchange Resin Catalysts:Ⅰ. TGA as a Rapid Evaluating Method

The thermal stability of five commercial ion-exchange resin catalysts was studied by means of thermal gravimetric analysis （TGA） at elevated temperatures of up to 600℃ and isothermal temperatures in the range of 150℃ and 200 ℃. Resin samples with different initial water contents were also investigated. The study indicated that TGA, as a complementary evaluating method for the plug flow reactor system approach, could be used as a fast analyzing means for study on the thermal stability of ion-exchange resin catalysts. The stoichiometric calculation of the isothermally treated resin catalysts based on the FTIR analysis and acid capacity confirmed that the weight loss of the resins at 150℃ and 200℃ was caused by the desulfonation process and that desulfonation occurred mainly at the para-position of the benzene ring in the resins. H＋ ions and moisture played an important role in the desulfonation process.

Study on Stability of Ion-exchange Resin Catalysts:Ⅱ. Desulfonation during Isobutylene Dimerization

The performance of ion-exchange resin catalysts during isobutene (IB) dimerization was investigated under different IB contents,temperatures and liquid-volume hourly space velocity (LHSV) using a plug flow reactor in the absence of any selectivity enhancing component.High IB content and temperature resulted in a high conversion and C12 selectivity bu low C8 selectivity.The influence of LHSV was related with the IB content:LHSV had great effect at high IB content,while the performance of ion-exchange resin changed little with LHSV if IB content was low.The effect of water on the stability of resins was also studied.Desulfonation was observed during the C4 dimerization reaction when water was added to the feed.Chlorinated resin was more stable than conventional polystyrene-based resins during the test.

Taste masking of ciprofloxacin by ion-exchange resin and sustain release at gastric-intestinal through interpenetrating polymer network

The aim of the study was to taste mask ciprofloxacin(CP)by using ion-exchange resins(IERs)followed by sustain release of CP by forming interpenetrating polymer network(IPN).IERs based on the copolymerization of acrylic acid with different cross linking agents were synthesised.Drug-resin complexes(DRCs)with three different ratios of drug to IERs(1:1,1:2,1:4)were prepared&evaluated for taste masking by following in vivo and in vitro methods.Human volunteers graded ADC 1:4,acrylic acid-divinyl benzene(ADC-3)resin as tasteless.Characterization studies such as FTIR,SEM,DSC,P-XRD differentiated ADC 1:4,from physical mixture(PM 1:4)and confirmed the formation of complex.In vitro drug release of ADC 1:4 showed complete release of CP within 60 min at simulated gastric fluid(SGF)i.e.pH 1.2.IPN beads were prepared with ADC 1:4 by using sodium alginate(AL)and sodium alginate-chitosan(AL-CS)for sustain release of CP at SGF pH and followed by simulated intestinal fluid(SIF i.e.pH 7.4).FTIR spectra confirmed the formation of IPN beads.The release of CP was sustain at SGF pH(<20%)whereas in SIF media it was more(>75%).The kinetic model of IPN beads showed the release of CP was non-Fickian diffusion type.

SIMULTANEOUS ION-EXCHANGE AND ADSORPTION OF LACTIC ACID ON D354 RESIN

From a number of ion-exchange resins and adsorbents,a macro-pore weak-base type anionion-exchange resin,D354,was selected for the separation of lactic acid.Experimental data showedthat simultaneous ion-exchange and physical adsorption existed in the lactic acid-D354 system.Amathematical model was suggested to simulate the experimental data.Also,the effects of inorganicsalts on the ion-exchange.equilibrium were studied.The difference in ion-exchange equilibrium be-tween DL-and L-lactic acid was observed.

Elution Behaviour of Monocarboxylic Acids on a Cation-exchange Resin Column

The retention mechanism of monocarboxylic acids on a cation-exchange resin column was investigated. It was assumed that both Donnan membrane equilibrium and adsorption equilibrium were involved in the chromatographic process. On the basis of the proposed mechanism, an equation was derived for correlating distribution coefficient, Kd, dissociation constant, Aa, and adsorption equilibrium constant, K, of the analyzed acid. By this approach, retention data for some aliphatic acids under different operating conditions were predicted. Results are reasonably in agreement with experiment.

Liquid-phase esterification of methacrylic acid with methanol catalyzed by cation-exchange resin in a fixed bed reactor:Experimental and kinetic studies

The kinetic behavior of esterification between methacrylic acid and methanol catalyzed by NKC-9 resin was studied in a fixed bed reactor.The reaction was conducted in the temperature range of 323.15 to 368.15 K with the molar ratio of reactants from 0.8 to 1.4 under certain pressure.The measurement data were regression with the pseudo-homogeneous(P-H),Eley-Rideal(E-R),and Langmuir-Hinshelwood(L-H)heterogeneous kinetic models.Independent adsorption experiments were implemented to gain the adsorption equilibrium constants of four components.Among the above three models,the L-H model exhibited the best fitting results.The stability of NKC-9 was evaluated by long-term running with the yield of methyl methacrylate no decrease during 3000 h operation.The structure and physicochemical properties of the new and used catalyst were performed by several characterizations including thermogravimetric analysis(TG),scanning electron microscope(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)and so on.

Adsorption properties of Ag(Ⅰ),Au(Ⅲ),Pd(Ⅱ)and Pt(Ⅳ)ions on commercial 717 anion-exchange resin

The adsorption properties of the four precious metal ions(Ag(Ⅰ),Au(Ⅲ),Pd(Ⅱ)and Pt(Ⅳ))on the commercial Cl--form 717 strongly basic anion-exchange resin were studied in detail.The effects of the contact time,solution acidity,and concentrations of Cl - and Pb 2+ ions on the adsorption properties were studied by the batch method.Then,the column method was conducted under the optimized adsorption conditions(pH=3.0).The effects of the sample loading flow rate and the length-to-diameter ratios of the columns were investigated.The precious metal ions adsorbed could not be eluted completely after the saturated adsorption because the precious metal ions were found to be reduced to their metallic states during the adsorption process.So,it is recommended that the commercial Cl--form 717 strongly basic anion-exchange resin should be decomposed directly to recovery the precious metals after the saturated adsorption.

Effective adsorptive denitrogenation from model fuels over yttrium ion-exchanged Y zeolite

The adsorption removal of indole and quinoline in octane with and without toluene over zeolites NaY and Yttrium Ion-exchanged Y(YY)using batch adsorption experiments was studied at 25℃and 0.1 MPa.YY was prepared by treating NaY with Y(NO3)3 solution twice via liquid ion-exchange method.NaY and YY were both characterized by XRD,SEM,N2 adsorption,XRF,NH3-TPD,and pyridine-FTIR techniques.Adsorption isotherms of indole,quinoline and toluene in octane were conducted at 25.0℃to explain the influence of toluene on nitrogen removal over NaY and YY.The partial destruct of the crystalline structure of NaY was observed after the introduction of yttrium ion,which led to an evident decline in BET surface area and pore volume of YY.Strong Br?nsted acidity and medium Lewis acidity were introduced by yttrium ion-exchange.Though the specific surface area and pore volume of YY were much lower than those of NaY,YY exhibited equivalent adsorption capacities for indole and quinoline as NaY in model fuels without toluene.In the presence of 20 vol%toluene,however,YY exhibited much higher adsorption capacities for indole and quinoline than NaY,especially in the case of quinoline.The improved toluene-tolerant of YY was ascribed to the strong acid–base interaction between YY and quinoline and the decreased adsorption strength between YY and toluene.

Tribological Properties of Magnesium Ion-exchanged α-Zirconium Phosphate as a Solid Lubricant Additive in Lithium Grease

Magnesium ion-exchanged a-zirconium phosphates(Mg-α-ZrP) with particle sizes of 600 and 80 nm were prepared through the sealed ion-exchange and one-step hydrothermal synthesis methods, respectively. It was found that larger particles of Mg-α-ZrP had a higher load-carrying capacity than that of smaller particles, whereas smaller Mg-α-ZrP particles had better anti-wear properties than that of larger Mg-α-ZrP particles under mild loads. The correlation between the particle size of the sample and the surface roughness of the friction pair thus seems to be a key factor influencing the performance.

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl_4 and SbCl_3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using： （1） an ion-exchange hydrolysis to remove chlorine ions, and （2） isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.

L-LACTIC ACID FERMENTATION IN A ROTATING-DISC CONTACTOR WITH SIMULTANEOUS PRODUCT SEPARATION BY ION-EXCHANGE

A rotating disk contactor（RDC）was designed to perform L-lactic acid fermentation with afilamentous fungi,Rhizopus oryzae,which was immobilized on the surfaces of the rotating discs.Thebioreactor was operated using repeated-batch method as well as continuous feeding method.Ananionic resin,D354,slightly basic in nature and of high selectivity and capacity was chosen for lacticacid separation.A coupled process of L-lactic acid fermentation and ion-exchange separation wasevaluated experimentally.The results indicated that the pH value of the fermentation broth could bemaintained at about 3-3.5 without any addition of alkali.The conversion ratio of glucose to L-lacticacid was about 0.7 g·g-1 and the fermentation rate reached as high as 62.5 g·h-1·m-2.

Study on Removal of Trace Lead from Nickel Sulphate Solution by Ion-exchange Method

By comparing the adsorption capacity of several kinds of resins, D363 resin is regarded as the most suitable one for removing lead from nickel sulphate electrolyte. The effects of pH, temperature and contact time on exchange adsorption during removing trace lead from industrial nickel sulphate solution with D363 large pore weak alkali anion exchange resin are discussed. Optimum conditions of adsorption of lead from nickel electrolyte by D363 resin are at room temperature, pH 1 2, contact time 30 min.

Influence of earth gravity on reaction engineering of tubular reactor for high concentration tungsten ion-exchange

The influence of gravity on the reaction engineering of tubular reactor is studied by analyzing the residence time distribution curves.The results show that upflow-feeding mode is more beneficial compared with downflow-feeding mode,since the flow pattern of the fluid in the reactor is closer to plug flow.The result of dynamic experiment conducted in ion-exchange of tungsten metallurgy is as good as that in reaction engineering of ion-exchange column.Whether downflow-feeding or upflow-feeding mode is adopted,breakthrough time decreases when solution concentration increases.Upflow-feeding mode has longer breakthrough time and greater improvement in adsorption capacity especially with high WO3 concentration in ion-exchange.