Ion-exchanged Catalysts Research Articles

Supercritical Fluid Extractive Regeneration of the Ion-Exchange Catalyst KU-2FPP

The process of supercritical fluid extractive regeneration of the ion-exchange catalyst KU-2FPP was studied. The use of pure supercritical carbon dioxide (SC-CO 2 ) and the one modified with a polar additive (H 2 O) as the extractant in the process at T = 383÷393 K and P = 15÷25 MPa provided an effective removal of non-polar organic compounds and the occurrence of the side carboxylation reaction to form dialkylphthalate. The side reaction was supposed to bear responsibility for the ineffective regeneration in the presence of SC-CO 2 as the extractant. The application of supercritical propane-butane mixture as the extractant (T = 393 K, P = 10÷15 MPa) allowed the catalyst activity to be restored to the level appropriate for the industrial application.

Dehydration of 1-octanol to di-n-octyl ether in liquid phase with simultaneous water removal over ion exchange resins: Effect of working-state morphologies

The influence of the concentration of polar reactants and products on the working-state morphology of ion exchange catalysts has been investigated over different acidic ion-exchange resins for di-n-octyl ether (DNOE) synthesis from 1-octanol dehydration at 423–448K and atmospheric pressure in a batch reactor equipped with a Dean & Stark device. By removing water formed 1-octanol conversion was practically complete; the olefin formation being the main secondary reaction. When 1-octanol is completely consumed the working-state morphology of ion exchange resins changes, which influences the selectivities towards products. At this point, for microporous resins all reactions stop while with macroreticular ones DNOE decomposes and significant amounts of olefin dimers appears. The best selectivity to DNOE was found in gel-type and macroreticular resins with low crosslinking degree. Macroreticular resins with medium or high crosslinking give good results in olefin formation.

The oligomerization of high olefin containing hydrocarbon by-products to clean engine fuels

Nowadays it is an important issue in refineries to increase the gasoline/middle distillate flexibility because of the ever-changing engine fuel demands. One possible way is the oligomerization of light olefins (3–6 carbon atoms). The oligomerization of the C4-C6 olefin content of light FCC and more fractions with different composition was investigated on acidic ion exchange resin catalyst and premixed catalyst bed. The favourable application temperature of the ion exchange catalyst was 120–130 °C (P = 30 bar, LHSV = 1.0 h−1). The olefin conversion was also influenced by the composition of the feedstock. The best olefin conversion was achieved in the case of the feedstock with the highest olefin content (olefin conversion: 91.5%, C12+ ratio: 31.2%). Similar results were found with the application of premixed catalysts (B and C) in more oligomerization steps. Olefin conversion and selectivity was depended on the olefin and C12+ content of the feedstock. The total olefin conversion (related to the olefin content of the FCC naphtha feedstock) increased with each oligomerization steps, but it has to be investigated that how many steps could be economic. In the long term experiment (110 °C, 30 bar, 1.0 h−1) it was found that the conversion after 196 h decreased approx. 10% (compared with the initial value) but it was significantly lower after 60 h reaction time at 130 °C. The examined ion exchange resins - in the 100–120 °C temperature range - catalyze the oligomerization reactions for a long time, but an in-situ regeneration should be necessary.

Production of hydrogen from bioethanol in Cu–Ni/NbxOy catalysts obtained by different preparation methods

Ethanol steam reforming for hydrogen production was evaluated using Cu–Ni/NbxOy catalyst prepared by ion exchange (IE), wet impregnation (WI) and co-precipitation (CP). The catalysts were characterized by textural analysis, chemisorption of H2 and N2O for metallic area determination, XDR (calcined and in situ reduced samples), TPR-H2, TPD-NH3, MET/EDX e TPO-O2. Differences in crystal structure and metal-support interaction have altered the reducibility of the catalysts, besides metal surface area and crystallite size of Cu and Ni. The catalytic tests, using ethanol:water molar ratio of 1:10, temperature of 450 and 500 °C, demonstrated high H2 yield and stability, except for the IE catalyst at 500 °C, which favored the ethylene formation by ethanol dehydration. The main route for H2 obtainment in all cases was ethanol decomposition. The temperature increasing up to 500 °C favored the by-product CH4 reforming. The weakest metal-support interaction on WI catalyst provided the fully reduced metal phase, however, support characteristics achieved by this preparation method led to the filamentous coke formation. TEM images showed that different crystalline structures of the support modified the mechanism of the reaction and consequently the type of coke deposited on the surface. The CP catalyst showed low coke deposition and no metal sintering, stoichiometric H2/CO2 ratio, less than 5% of CH4, and no CO, which makes it the best candidate for hydrogen production by ethanol steam reforming.

Catalytic Activity and Accessibility of Acidic Ion-Exchange Resins in Liquid Phase Etherification Reactions

Although macroreticular acidic ion-exchange resins have been widely used as catalysts in the industrial world for decades, their catalytic behavior is still far from being completely understood at a molecular level. Several characterization techniques coexist, which provide information about their properties. Only few of these techniques give an actual picture of their working-state features when swollen in anhydrous polar reactive media such as in etherification processes, where they are extensively used. The inverse steric exclusion chromatography technique, based on modeling the micropores structure, or gel-phase, as a set of discrete volume fractions with a characteristic polymer chain density, constitutes an appropriate procedure to assess the morphology of ion-exchangers in the swollen state. Present work proposes an empirical model to correlate the properties of the volume fractions with their catalytic activity in the etherification reaction rates of isobutene by addition of C1–C4 linear primary alcohols. Sixteen different macroreticular acidic ion-exchange catalysts, both commercial and lab-made, have been used, which differ in acid capacity, sulfonation type, cross-linking degree and swollen-phase volume fractions distribution. Experimental reaction rates have been expressed as a sum of contributions of each individual volume fraction. The contribution of each polymer volume fraction corresponds to the product of the catalyst acidity, the characteristic volume fraction within the gel-phase of the catalyst, and a specific turnover frequency of that fraction. Accessibility of the reacting alcohol, expressed in terms of the Ogston coefficient, has been also included in the empirical dependency equation presented in this work.

Esterification and transesterification of waste cooking oil over Amberlyst 15 and modified Amberlyst 15 catalysts

Biodiesel production via the simultaneous esterification and transesterification reactions of waste cooking oil (WCO) with methanol was investigated. A batch reflux reactor was used in conjunction with acidic ion-exchange catalysts, i.e., Amberlyst 15 and modified Amberlyst 15. The activity of the Amberlyst 15 catalysts could be altered via heat treatment at temperatures that are ≥493K, as a consequence of the reduction of the active surface (SO3H). The hydrogen ion-exchange capacities of the catalysts ranged from 2.5meqH+/g to 5.1meqH+/g. The reaction parameters included the molar ratio of alcohol to oil (6:1–15:1), reaction temperature (298–338K), catalyst concentration (1–9wt.%), reaction time (1–72h) and the free fatty acid content (1.04–8.04%). It was observed that the activities of the Amberlyst 15 and modified Amberlyst 15 catalysts increased linearly with increasing hydrogen ion-exchange capacities of the catalysts. Amberlyst 15 exhibited the highest hydrogen ion-exchange capacity and consequently generated the highest biodiesel yield of (78±3.39%). The esterification reaction of excess fatty acids was also investigated. When the esterification and transesterification reactions were carried out simultaneously, the water generated from the esterification of free fatty acids led to the hydrolysis of triglycerides and reduced the biodiesel yield emphasizing the necessity for the removal of the water during concomitant esterification of excess fatty free acids present and the transesterification of the triglycerides for biodiesel production.

Production of aromatic compounds from catalytic fast pyrolysis of Jatropha residues using metal/HZSM-5 prepared by ion-exchange and impregnation methods

Metal based-zeolite catalysts were successfully prepared by two different methods including ion-exchange and wet impregnation. HZSM-5 synthesized by hydrothermal method at 160 °C was used as a support for loading metals including Co, Ni, Mo, Ga and Pd. The metal/HZSM-5 had surface area and pore size of 530–677 m2/g and 22.9-26.0 Å. Non- and catalytic fast pyrolysis of Jatropha residues using metal/HZSM-5 were studied using an analytical pyrolysis-GC/MS at 500 °C. Non-catalytic pyrolysis vapors contained primarily high levels acid (50.7%), N-containing compounds (20.3%), other oxygenated compounds including ketones, alcohols, esters, ethers, phenols and sugars (25.0%), while generated small amount of aromatic and aliphatic hydrocarbons of 3.0% and 1.0%. The addition of synthesized metal/HZSM-5 improved the aromatic selectivity up to 91–97% and decreased the undesirable oxygenated (0.6–4.0%) and N-containing compounds (1.8–4.6%). The aromatic selectivity produced by metal-ion exchanged catalysts was slightly higher than that produced by impregnated ones. At high catalyst content (biomass to catalyst ratio of 1:10), Mo/HZSM-5 showed the highest aromatic selectivity of 97% for ion-exchanged catalysts and Ga/HZSM-5 revealed the highest aromatics of 95% for impregnated catalysts. The formation of aromatic compounds could be beneficial to improve calorific values of bio-oils. The presence of metal/HZSM-5 from both preparation methods greatly enhanced MAHs selectivity including benzene, toluene, and xylene (BTX), while substantially reduced unfavorable PAHs such as napthalenes.

The Oligomerisation of High Olefin Containing Hydrocarbon Fractions on Ion Exchange Resin Catalyst

Nowadays there is an increasingly important issue in refineries to increase the gasoline / middle distillate flexibility because of the ever-changing motor fuel demands. One possible way is to oligomerize light olefins (3-6 carbon atoms). There is a further advantage of the oligomerization technology that with the hydrogenation of the olefin-isoolefin mixture, formed as an intermediate product, high paraffin-isoparaffin containing products can be produced. In our experimental work we investigated the conversion possibilities with oligomerization of the C4-C6 olefin content of light FCC and more fractions with different composition on acidic ion exchange resin catalyst. The favourable application temperature of the ion exchange catalyst was 120-130 °C (P= 30 bar, LHSV= 1.0 h -1 ). The available olefin conversion was also influenced by the composition of the feedstock. We achieved the best olefin conversion in the case of the feedstock with highest olefin content (olefin conversion: 91.5 %, C12+ selectivity: 31.2 %).

SYNTHESIS OF ZEOLITE FROM INORGANIC WASTES

The synthesis of zeolite in forms suitable for indu strial applications is of great importance, mainly as ion exchange material, molecular sieves, adsorbents and catalyst. In the p resent investigation an effort has been made to syn thesize zeolite from glaze free ceramic (inorganic) wastes (porcelain bodies) such as broken stoneware pipe and washbasin. Porcelain m ainly is composed of amorphous glass phase and crystalline phases such aquartz and mullite. Most of the amorphous and cry stalline phases are converted into soluble phases by alkali fusion and transformed into zeolite crystals with high specifi c area and unique micro-pores. The synthesized zeolites were characterized using X -ray powder diffraction.

A mechanism for the hydrazinolysis of benzoic acid in the presence of ion-exchange catalyst

A mechanism for the hydrazinolysis of benzoic acid via cyclic transition states is proposed on the basis of kinetic and IR spectroscopic studies.

Influence of synthesis parameters of SBA-15 supported palladium catalysts for methane combustion and simultaneous NOx reduction

Several synthesis routes were followed to prepare ordered mesoporous silica, SBA-15, and alumino-silica, Al–SBA-15, supported palladium catalysts. Synthesis method as well as the nature of precursor used in the preparation of these catalysts strongly determined their physico-chemical features which were evaluated by means of XRD diffraction, N2 sorption, temperature programmed reduction, UV–visible spectroscopy, and transmission electron microscopy. Their activity in simultaneous NOx reduction and methane combustion was assayed by means of temperature-programmed surface reaction and steady-state measurements. The catalyst prepared by means of incipient wetness impregnation using an ammine palladium precursor exhibited the highest deNOx activity together with substantial activity in methane combustion. Adequately dispersed PdO active phase, located inside the pores of the ordered structure of the silica support, as well as relative stronger interaction active phase-support in this case resulted in this higher activity. However, methane oxidation reaction seemed to be somehow hindered by such enhanced dispersion and stronger palladium-support interactions. Therefore higher activity towards methane oxidation, both in terms of set-off temperature and maximal conversion achieved, was observed for the ion-exchanged catalyst, containing less dispersed and more weakly bonded palladium phase.

Migration of Cu species in Cu/SAPO-34 during hydrothermal aging

In the present work, we report the migration of copper species in Cu/SAPO-34 during hydrothermal aging and its role in selective catalytic reduction (SCR) of NOx. Two Cu/SAPO-34 catalysts, prepared by ion-exchange and precipitation methods, were hydrothermally aged at 700°C for 48h and characterized in detail. The aged ion-exchanged catalyst exhibited little deterioration in NH3-SCR activity; however, the catalytic activity of the precipitated catalyst, which showed inferior activity for the fresh sample, was markedly improved after hydrothermal treatment and became comparable to that of the ion-exchanged sample. A detailed characterization of the Cu species before, during, and after the hydrothermal treatment using a combination of experimental techniques clearly demonstrated that the copper species in the precipitated sample, which initially existed as CuO clusters on the external surface of SAPO-34, migrated to the ion-exchanged sites as isolated ions after aging. The change in copper oxidation states and coordination environment during the aging process was probed by in situ X-ray absorption spectroscopy, and a possible mechanism of Cu migration involving metallic Cu species was proposed.

Reactive Distillation Using an Ion-Exchange Catalyst: Experimental and Simulation Studies for the Production of Methyl Acetate

In this study, the performance of a packed-bed reactive distillation (RD) column for the production of methyl acetate (MeOAc) using an ion-exchange catalyst and simulation of the same using CHEMCAD were analyzed. An ion-exchange catalyst, Indion 190, was used in this study. The performance of the RD column was evaluated based on the MeOAc concentration in the top product. Both steady- and unsteady-state behavior of the column was simulated using CHEMCAD, and the results were experimentally validated. The process parameters, viz., reboiler temperature, enriching temperature, reactor temperature, catalyst loading, molar ratio of the reactant, and flow rate of reactants, were studied, and the optimal values were found to be 73 °C, 56 °C, 72 °C, 100 g, 1:2, and 15 mL/min, respectively. Feed locations of acid and alcohol to the reactor that gave maximum MeOAc concentration in the top product were determined. A mathematical model based on the rigorous calculation using SCDS (used to calculate the nonideal K val...

Novel Ion-Exchange Catalysts for Reactions Involving Lipophilic Reagents: Perspectives in the Reaction of Esterifications of Fatty Acids with Methanol

New catalysts for the esterification of fatty acids with methanol have been obtained from a gel type polystyrene-divinylbenzene resin (2 % cross-linked). To this purpose the starting resin was first acylated with either acetyl, butyrroyl or capryloyl groups and then sulfonated with concentrated sulfuric acid. The acylation degree ranged from 51 to 82 % and the ion exchange capacity ranged from 2.87 to 4.16 mmol/g. These catalysts were tested in the esterification of stearic acid with methanol (solution in edible oil: 5 % for the acid, 5 or 20 % for the alcohol) in a continuous glass reactor at 85 °C. At high relatively methanol concentration the catalytic activity is mainly correlated to the degree of swelling of the catalysts and the best one was the non-acylated benchmark (hence the most hydrophilic) material. At low methanol concentration the swelling is smaller and practically the same for all the catalysts. In spite of this their activity does not level down to the same value. Under these conditions the capryloyl functionalized catalysts, the most lipophilic ones, by far outperform the benchmark catalyst and in general the activity increases with the increasing lipophilic character of the catalyst. This is likely caused by the enhanced adsorption of the fatty acid close to the acidic active site, assisted by the lipophilic acyl groups.

Resin-Based Catalysts for the Hydrogenolysis of Glycerol to Propylene Glycol

Three alkysulfonic resins were obtained by co-polymerization of 2-acrylamido-2-methyl-propansulfonic acid with N,N-dimethylacrylamide and ethylene dimethacrylate (the cross-linker), with respectively 4, 20 and 40 mol% cross-linking degree (DAE26-4, DAE26-20, DAE26-40). These resins were employed as acidic components in physical mixtures with Ru/C (5 %, w/w) or as supports for bifunctional ruthenium and copper catalysts, to be used in the hydrogenolysis of glycerol (20 %, w/w, in water). The physical mixtures were more efficient than the bifunctional catalysts, but temperatures as high as 200 °C are required to obtain an appreciable activity. However, in view of their relatively high thermal stability in comparison with the sulfonated polystyrene-divinylbenzene ion-exchange catalysts employed so far they can withstand this temperature, while Amberlyst 70 cannot be employed above 180–190 °C. Interestingly, the catalytic systems based on physical mixtures of DAE with Ru/C resins at 200 °C are much more selective towards propylene glycol than those containing A70 are at 180 °C.

Changes in Ion Exchanger Catalysts after Extremely Long Exposure to the Reactor Environment

This study involved the investigation of morphological changes in ion exchanger catalysts after more than 12 years in an industrial reactor for esterification of acrylic acid with methanol. The results showed that both desulfonation and de/cross-linking of the polymer was quite extensive. These changes were detected to a higher extent in test polymer samples located near the reactor input than in the sample obtained from main reactor charge, indicating that impurities in the reaction mixture, probably peroxidic compounds, could be responsible for the splitting of C–S and C–C bonds.

Studies on some economic and effective Ion exchange Resin used as catalyst in the synthesis of terpene derivative Isolongifoline Ketone

Terrenes are the abundant group of natural compounds that can be transformed into products of higher commercial value by organic reaction under the influence of suitable catalyst. Isolongifoline ketone was synthesized by Isolongifoline with the application of ion exchange catalyst viz. Tulsion T-421, Tulsion T-521, Indion 225, Indion 770.It is evident that Tulsion T-421 & T-521 shows higher yield of Isolongifoline ketone due to its characteristics. Characterization of resin was done by determine the elemental analysis, ion exchange capacity, FTIR analysis, TGA and SEM analysis. The significance of the ion exchange resin is revealed by the conversion of Isolongifoline to Isolongifoline ketone.Thermax T-421was finding to possess the higher selectivity for isolongifoline ketone and high thermal stability.

Regulation of the copper-oxide cluster structure and DeNOx activity of Cu-ZSM-5 catalysts by variation of OH/Cu2+

The present work studies RedOx properties and reactivity in N2O decomposition and selective catalytic reduction of NO (NO-SCR) by propane of Cu-modified ZSM-5 catalysts prepared by hydrolytic polycondensation (HPC). Their characteristics are compared with properties of Cu-ZSM-5 samples having the same copper content (1wt.%) and produced by ion exchange (IEX) with water–ammonia solutions of copper chloride at NH4OH/Cu2+ equal to 6–30.The HPC method consists in the treatment of the copper-impregnated zeolite by water–ammonia solution for polycondensation of hydrolyzed copper ions in the zeolite pores. It is shown that varying the NH4OH/Cu2+ ratio allows a regulation of the size and structure of copper active complexes. The copper-impregnated zeolite contains copper as CuO-like particles after calcination. At NH4OH/Cu2+ equal to 1–3, active sites in dried samples are disordered polynuclear copper-hydroxo complexes, which are characterized by symmetric ESR signal with g0=2.18. Increase of NH4OH/Cu2+ to 6–30 lead to the orbital ordering of Cu2+ ions in the copper–ammoniate complexes, observed as the rhombic ESR signals (gzex,1=2.18, gyex,1=2.08, gxex,1=2.03 and g∥ex,2=2.24, g⊥ex,2=2.03), and to dispersion of CuO-like particles during following thermal treatment at 500°C. The dried 1%Cu(30)ZSM-5-HPC sample prepared at NH4OH/Cu2+=30 has a higher amount of isolated tetraammine–copper complex and a lower number of weak associates of Cu2+ ions among samples.The addition of ammonia solution to the copper-impregnated zeolite for hydrolytic polycondensation has a favorable impact on the Cu-ZSM-5 activity in DeNOx processes. In N2O decomposition, the ion-exchanged CuZSM-5 catalysts were more reactive in the low-temperature region, while the ex-polycondensation catalysts provided a high N2O conversion at high temperatures. In NO-SCR by propane, the more reactive were the ion-exchanged catalysts, and NO reduction rate increased with NH4OH/Cu2+ grew for 10. It is suggested that the ordered associated Cu2+ ions of ex-polycondensation and ion-exchanged catalysts have higher reactivity and selectivity in both DeNOx processes as compared to the isolated copper ions.

Cu-zeolite NH3-SCR catalysts for NOx removal in the combined NSR–SCR technology

The challenge of efficient NOx removal from diesel and lean-burn engine exhaust gas by combining NSR and SCR catalyst is studied. Several Cu exchanged zeolites have been prepared, varying the preparation method (ion exchange and impregnation), the copper content (1–6%) and the zeolite (BETA and ZSM5). The prepared catalysts have been characterized, and acidity, surface area, crystallinity and metal reducibility have been compared. SCR experiments under 750ppm NO, 750ppm NH3 and 9.5% O2 (Ar to balance) discriminated low copper loading, prepared by ion exchange catalyst (Z-IE-1.4 and B-IE-2.1) as the most active for NOx conversion (>95%) in ample temperature range (280–450°C). These active SCR catalysts were placed downstream a monolith NSR Pt–BaO/Al2O3 catalyst, running under cycled lean–rich conditions, and the improvement on NOx removal and selectivity to only N2 were determined. In an ample range of temperature, from 200 to 400°C, NOx conversion was increased in more than 30%, also notably increasing the production of nitrogen, and reducing production of ammonia and N2O below 3% and 2%, respectively, when comparing the combined NSR–SCR configuration versus the single NSR catalyst.

Evaluation of strongly acidic ion‐exchange catalysts and the desulfonation study in the isobutylene dimerization reaction

AbstractThree commercial ion‐exchange resin based catalysts were compared under different temperature and liquid‐volume hourly space velocity (LHSV) in the isobutene (IB, C4) dimerization reaction using a plug flow reactor in the absence of any selectivity enhancing component. High IB conversion for all catalysts was obtained at or higher than 50°C. But, diisobutene (DIB, C8) selectivity decreased with the increase of temperature. High C8 selectivity was observed with LHSV higher than 1.5 at 50°C. The best catalytic performance of the three resins did not show obvious differences. The effect of the selectivity enhancers on the stability of the resins was also studied. Desulfonation was observed in the C4 dimerization reaction when water or the commonly used enhancer tert‐butyl alcohol (TBA) was added to the feed. The deactivation of catalyst resulted in decrease of both IB conversion and C8 selectivity. Fourier Transform Infrared spectroscopy showed that desulfonation happened in both para and ortho positions of the sulfonated benzene rings. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013