Preparation of bimodal polypropylene in two‐step polymerization

Polymerization of propylene was carried out by using MgCl₂.EtOH.TiCl₄.DIBP.TEA.cHMDMS catalyst system in n‐heptane, where MgCl₂, EtOH, TiCl₄, DIBP (diisobutyl phthalate), TEA (triethyl aluminum), and cHMDMS (cyclohexyl methyl dimethoxy silane) were support, ethanol for alcoholation, catalyst, external donor, cocatalyst (activator), and internal donor, respectively. The catalyst activity and polymer isotacticity were studied by measuring the produced polymer and its solubility in boiling n‐heptane, respectively. The molecular weight and molecular weight distribution of the polymers were evaluated by gel permeation chromatography. Hydrogen was used for controlling the molecular weight. For producing the bimodal polypropylene, the polymerization was carried out in two steps (i.e., in the presence and absence of hydrogen). It was found that the catalyst showed high activity and stereoselectivity, on the other hand, bimodal polymer could simply be produced in two‐step polymerization by using MgCl₂.EtOH.TiCl₄.DIBP.TEA.cHMDMS catalyst system. Meanwhile, the effect of the step of the hydrogen adding on propylene polymerization was investigated. It was shown that the addition of hydrogen in the second step was more suitable. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1456–1462, 2006     

Selective hydrogenation of nitrile‐butadiene rubber catalyzed by thermoregulated phase transfer phosphine rhodium complex

Hydrogenation of polymer having C?C double bond can be carried out with the metal–organic complex as catalyst, which has the property of themoregulated phase transfer. In this study, a new complex RhCl[PPh[(OCH₂CH₂)_5≤n≤6CH₃]₂]₃ (Rh/AEOPP) was synthesized with a good yield, which was further used as catalyst to selectively hydrogenated nitrile‐butadiene rubber (HNBR). This is the first time that Rh/AEOPP complex was synthesized and applied in nitrile‐butadiene rubber (NBR) hydrogenation. The result shows that hydrogenation degree of product (HNBR) can be extended to 90%, when the condition is [Cat] = 3% (based the weight of NBR), L₂: Cat (Weight Ratio) = 2, [NBR] = 5% (based on the weight of xylene solution), P (H₂) = 1.5 MPa, T = 155°C, and t = 8 h. Also, by adjusting temperature, the catalyst could be easily separated from products with 89% catalyst complex recovery. In addition, ¹H‐NMR and infrared (IR) spectra showed that C?C double bonds in NBR was successfully hydrogenated without causing reduction of the CN group. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polymerization of propylene using the high‐activity Ziegler–Natta catalyst system SiO2/MgCl2 (ethoxide type)/TiCl4/Di‐n‐butyl phthalate/triethylaluminum/dimethoxy methyl cyclohexyl silane

The bisupported Ziegler–Natta catalyst system SiO₂/MgCl₂ (ethoxide type)/TiCl₄/di‐n‐butyl phthalate/triethylaluminum (TEA)/dimethoxy methyl cyclohexyl silane (DMMCHS) was prepared. TEA and di‐n‐butyl phthalate were used as a cocatalyst and an internal donor, respectively. DMMCHS was used as an external donor. The slurry polymerization of propylene was studied with the catalyst system in n‐heptane from 45 to 70°C. The effects of the TEA and H₂ concentrations, temperature, and monomer pressure on the polymerization were investigated. The optimum productivity was obtained at [Al]/[DMMCHS]/[Ti] = 61.7:6.2:1 (mol/mol/mol). The highest activity of the catalyst was obtained at 60°C. Increasing the H₂ concentration to 100 mL/L increased the productivity of the catalyst, but a further increase in H₂ reduced the activity of the catalyst. Increasing the propylene pressure from 1 to 7 bar significantly increased the polymer yield. The isotacticity index (II) decreased with increasing TEA, but the H₂ concentration, temperature, and monomer pressure did not have a significant effect on the II value. The viscosity‐average molecular weight decreased with increasing temperature and with the addition of H₂. Three catalysts with different Mg/Si molar ratios were studied under the optimum conditions. The catalyst with a Mg/Si molar ratio of approximately 0.93 showed the highest activity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1177–1181, 2003     

MgAl2O4 spinel prepared by mechanochemical synthesis used as a support of multimetallic catalysts for paraffin dehydrogenation

The catalytic performance in n-butane dehydrogenation of bimetallic PtSn, PtGa and PtIn, and trimetallic PtSnIn and PtSnGa catalysts (with low metal contents) supported on a MgAl₂O₄ prepared by a novel mechanochemical synthesis was evaluated both in flow and pulse equipment. The influence of the addition of different promoters (Sn, Ga and In) to Pt on the activity, selectivity and deactivation in the n-butane dehydrogenation reaction was studied. Stability experiments through successive reaction-regeneration cycles were carried out for selected catalysts. In order to correlate the properties of the metallic phase of the catalysts with the catalytic behavior, several characterization techniques were used, such as test reactions of the metallic phase (cyclohexane dehydrogenation and cyclopentane hydrogenolysis), TPR, XPS, H₂ chemisorption and TEM. Bimetallic PtSn catalyst has a better catalytic behavior than PtIn and PtGa ones. For PtSnM (M: In or Ga) catalysts, whereas Ga addition to the bimetallic catalyst does not practically modify the dehydrogenation performance, the addition of In produces an increase of the activity and the selectivity to butenes. Characterization results indicate the presence of geometric effects for the PtSn catalyst, and geometric and electronic effects for PtIn and PtGa ones. For trimetallic catalysts, the presence of a close contact between Pt, Sn and In or Ga in both trimetallic catalysts was found, mainly due to geometric effects like blocking and dilution of the active sites by the promoters. In stability experiments, the trimetallic PtSnIn/MgAl₂O₄ catalyst clearly displays the best catalytic performance along reaction-regeneration cycles, though PtSnGa and PtSn catalysts also showed a very good behavior through the successive cycles. The characterization of these catalysts after cycles shows that their metallic phases are slightly modified along the cycles.     

Production of hydrogen over bimetallic Pt–Ni/δ-Al2O3: II. Indirect partial oxidation of LPG

Indirect partial oxidation (IPOX) of a 75:25 propane:n-butane mixture, which was used as a model for LPG, was studied over the bimetallic 0.2 wt%Pt–15 wt%Ni/δ-Al₂O₃ catalyst in 623–743 K temperature range. The effects of steam to carbon ratio (S/C), carbon to oxygen ratio(C/O₂) and residence time (W/F (g cat-h/mol LPG)) on the hydrogen production activity, selectivity and product distribution were studied in detail. The results are compared with the results obtained in the IPOX of pure propane. An Increasing Temperature Program (ITP) was applied during all experiments and the results showed that the presence of n-butane in the feed enhances hydrogen production activity and selectivity. Considering the well established distribution network of LPG and the superior performance of the bimetallic Pt–Ni catalyst in the IPOX of LPG, Pt–Ni system seems a very promising catalyst alternative to be used in commercial fuel processors.     

Evaluation of the Performance of Carbon Supported Pt–Ru–Ni–P as Anode Catalyst for Methanol Electrooxidation

This research is aimed to improve the activity and stability of ternary alloy Pt–Ru–Ni/C catalyst. A novel anodic catalyst for direct methanol fuel cell (DMFC), carbon supported Pt–Ru–Ni–P nanoparticles, has been prepared by chemical reduction method by using NaH₂PO₂ as a reducing agent. One glassy carbon disc working electrode is used to test the catalytic performances of the homemade catalysts by cyclic voltammetric (CV), chronoamperometric (CA) and amperometric i–t measurements in a solution of 0.5 mol L^–1 H₂SO₄ and 0.5 mol L^–1 CH₃OH. The compositions, particle sizes and morphology of home‐made catalysts are evaluated by means of energy dispersive analysis of X‐ray (EDAX), X‐ray diffraction (XRD) and transmission electron micrographs (TEM), respectively. TEM images show that Pt–Ru–Ni–P nanoparticles have an even size distribution with an average diameter of less than 2 nm. The results of CV, CA and i–t curves indicate that the Pt–Ru–Ni–P/C catalyst shows significantly higher activity and stability for methanol electrooxidation due to the presence of non‐metal phosphorus in comparison to Pt–Ru–Ni/C one. All experimental results indicate that the addition of non‐metallic phosphorus into the Pt–Ru–Ni/C catalyst has definite value of research and practical application for enhancing the performance of DMFC.     

Preparation of porous spherical MgCl2/SiO2 complex support as precursor for catalytic propylene polymerization

The MgCl₂/SiO₂ complex support was prepared by spray drying using alcoholic suspension, which contained MgCl₂ and SiO₂. The complex support reacted with TiCl₄ and di‐n‐butyl phthalate, giving a catalyst for propylene polymerization. The catalyst was spherical and porous with high specific surface area. TEA was used as a cocatalyst, and four kinds of alkoxysilane were used as external donors. The bulk polymerization of propylene was studied with the catalyst system. The effect of the reaction conditions and external donor on the polymerization were investigated. The results showed that the catalyst had high activity, high stereospecificity, and sensitive hydrogen responsibility. Polypropylene has good grain morphology because of duplicating the morphology of the catalyst. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1296–1299, 2005     

Copolymerization of ethylene–propylene using high‐activity bi‐supported Ziegler–Natta TiCl4 catalyst

Heterogeneous Ziegler–Natta TiCl₄ catalyst using MgCl₂ and SiO₂ as supports was prepared under controlled conditions. Mg(OEt)₂ was used as a starting material and was expected to convert to active MgCl₂ during catalyst preparation. Due to the high surface area and good morphological control, SiO₂ was chosen as well. Slurry copolymerization of ethylene and propylene (EPM) was carried out in dry n‐heptane by using the catalyst system SiO₂/MgCl₂/TiCl₄/EB/TiBA or TEA/MPT/H₂ at temperatures of 40–70°C, different molar ratios of alkyl aluminum : MPT : Ti, hydrogen concentrations, and relative and total monomers pressure. Titanium content of the catalyst was 2.96% and surface area of the catalyst was 78 m²/g. Triisobutyl aluminum (TiBA) and triethyl aluminum (TEA) were used as cocatalysts, while ethyl benzoate (EB) and methyl p‐toluate (MPT) were used as internal and external donors, respectively. H₂ was used as a chain‐transfer agent. Good‐quality ethylene propylene rubber (EPR) of rubber was obtained at the ratio of [TiBA] : [MPT] : [Ti] = 320 : 16 : 1 and polymerization temperature was 60°C. When TiBA was used as a cocatalyst, a higher and more rubberlike copolymer was obtained. For both of the cocatalysts, an optimum ratio of Al/Ti was obtained relative to the catalyst productivity. Ethylene content of the copolymer obtained increased with increasing TiBA concentration, while inverse results were obtained by using TEA. Addition of H₂ increased the reactivity of the catalyst. The highest product was obtained when 150 mL H₂/L solvent was used. Increasing temperature from 40 to 70°C decreased the productivity of the catalyst, while irregular behavior was observed on ethylene content. Relative pressure of P_P/P_E = 1.4 : 1 and total pressure of 1 atm was the best condition for the copolymerization. Polymers with ethylene contents of 25–84% were obtained. Increasing ethylene content of EPR decreased T_g of the polymer obtained to a limiting value. Viscosity‐average molecular weight (M_v) decreased with increasing temperature and TiBA and H₂ concentration. However, increasing the polymerization time increased the M_v. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2597–2605, 2004     

Surface species structure and activity in NO decomposition of an anatase-supported V–O–Mo catalyst

The paper concerns the evolution of surface species of a V–O–Mo/anatase catalyst in the course of its thermal treatment in oxidising and/or reducing conditions. The catalyst was obtained by the sol–gel method. The structure of its surface was investigated by XPS and Raman spectroscopy. The fresh catalyst consists of anatase nanocrystallites with some vanadium and molybdenum ions substituted for titanium ones and molybdenum oxide islands on their surfaces. A V/Mo₅O₁₄ solid solution-containing V atoms in its channels, as well as MoO₃ and anatase with some surface vanadia species are present on the catalyst surface.The reduction of anatase to TiO_2−x and of MoO₃ to Mo₅O₁₄, accompanied by inward vanadium diffusion occurs during the catalyst interaction with ammonia at 523 K. The oxidation of the TiO_2−x but not Mo₅O₁₄ and V reappearance in the surface channels take place during the interaction of the reduced catalyst with molecular oxygen.However, the oxidation of Mo₅O₁₄ to MoO₃ occurs under the influence of atomic oxygen, formed by NO decomposition at 423 K. It is accompanied by the surface vanadia species formation. The activity of V ions of these species in NO decomposition is lower than of the surface interstitial ones.     

Carbon dioxide in the dehydrogenation of isobutane over VMgOx

On the basis of catalytic tests and kinetic investigations, the role of carbon dioxide in the conversion of isobutane to isobutene over VMgO_x catalyst was studied. It was shown that both the high temperature (>826 K) and the presence of VMgO_x catalyst are required for activation of CO₂ molecule. Presented results stay in agreement with thermodynamic analysis of the isobutane dehydrogenation process, where the two-step dehydrogenation pathway (i.e., simple dehydrogenation followed by reverse water gas shift reaction) was the most favorable way of isobutene synthesis. Moreover, insufficient oxidizing property of carbon dioxide allows to exclude possibility of the redox-cycle mechanism over VMgO_x catalyst.     

Changes in Physico-Chemical Properties of Iron-Based Fischer–Tropsch Catalyst Induced by SiO2 Addition

The effect of adding SiO₂ to a precipitated Fe-based Fischer–Tropsch catalyst was investigated. Silica was added to the catalyst either during or after precipitation. The iron-based Fischer–Tropsch catalysts were studied using Mössbauer spectroscopy, BET surface area, XRD and SEM characterization methods. Adding SiO₂ to the catalyst during precipitation or immediately after precipitation (i.e., precipitated SiO₂) results in the formation of Fe crystallites with an average diameter less than 3 nm, which have high surface areas and exhibit a strong interaction with the SiO₂ matrix. Consequently, these crystallites are resistant to reduction and carburisation. When SiO₂ was added to the catalyst after heat treatment (i.e., binder SiO₂), the resulting catalyst was observed to consist of segregated SiO₂-rich and Fe-rich phases. The distribution of K₂O in both these phases indicates that the amount of effective K₂O, i.e., that associated with Fe, is less when SiO₂ is added as a binder. The low extent of reduction and carburisation observed with catalysts that contain precipitated SiO₂ results in catalysts with low % CO conversion. A positive correlation between the amount of iron carbides present in the catalyst and the % CO conversion was observed in these studies.     

Silica‐supported (nBuCp)2ZrCl2: effect of catalyst active center distribution on ethylene–1‐hexene copolymerization

Metallocenes are a modern innovation in polyolefin catalysis research. Therefore, two supported metallocene catalysts—silica/MAO/(ⁿBuCp)₂ZrCl₂ (Catalyst 1) and silica/ⁿBuSnCl₃/MAO/(ⁿBuCp)₂ZrCl₂ (Catalyst 2), where MAO is methylaluminoxane—were synthesized, and subsequently used to prepare, without separate feeding of MAO, ethylene–1‐hexene Copolymer 1 and Copolymer 2, respectively. Fouling‐free copolymerization, catalyst kinetic stability and production of free‐flowing polymer particles (replicating the catalyst particle size distribution) confirmed the occurrence of heterogeneous catalysis. The catalyst active center distribution was modeled by deconvoluting the measured molecular weight distribution and copolymer composition distribution. Five different active center types were predicted for each catalyst, which was corroborated by successive self‐nucleation and annealing experiments, as well as by an extended X‐ray absorption fine structure spectroscopy report published in the literature. Hence, metallocenes impregnated particularly on an MAO‐pretreated support may be rightly envisioned to comprise an ensemble of isolated single sites that have varying coordination environments. This study shows how the active center distribution and the design of supported MAO anions affect copolymerization activity, polymerization mechanism and the resulting polymer microstructures. Catalyst 2 showed less copolymerization activity than Catalyst 1. Strong chain transfer and positive co‐monomer effect—both by 1‐hexene—were common. Each copolymer demonstrated vinyl, vinylidene and trans‐vinylene end groups, and compositional heterogeneity. All these findings were explained, as appropriate, considering the modeled active center distribution, MAO cage structure repeat units, proposed catalyst surface chemistry, segregation effects and the literature that concerns and supports this study. While doing so, new insights were obtained. Additionally, future research, along the direction of the present work, is recommended. © 2013 Society of Chemical Industry     

Influence of the degree of acetylation of o-cresol resin on its molecular conformation in solution

o-Cresol-formaldehyde resin (OC) and five kinds of acetylated OC (AC-X-OC; X is the degree of acetylation) were prepared. The Θ-temperature for each resin was determined by means of the Shultz-Flory method, and their molecular conformations in both tetrahydrofuran (THF) and Θ-solvent were estimated from the values of the exponents in the Mark–Houwink–Sakurada equations. The effect of the degree of acetylation on the exponent was negligible in THF, but was remarkable in Θ-solvent. In THF, the molecular chains of these resins are relatively extended, because the hydrogen bond between phenolic hydroxyl groups is loosely formed. In Θ-solvent, however, the molecular conformation is compact and the resins are considered to form a pseudo cross-linked network structure through inter- and/or intra-molecular hydrogen bonds. The Mark–Houwink–Sakurada equation for AC-100-OC in 2-ethoxyethanol at 92.0°C was found to be [η]_θ = 0.0773 M?^0.50_n, where [η]₀ is the limiting viscosity number under the Θ-condition, and M?_n is the number-average molecular weight. The unperturbed dimension, (〈r²₀〉/M?_n)^1/2, 〈r²₀〉 being the unperturbed mean square end-to-end distance, for AC-100-OC was found to be 0.659×10^?8 cm g^?1/2 mol^1/2.     

Effect of fatty amine and perfluorocarbon as anti‐fouling agent on the catalyst activity and titanium oxidation state in slurry polymerization of ethylene

In this work, the effect of two antifouling materials on the activity of catalyst used to produce polyethylene in a 1‐L slurry reactor and on the titanium oxidation state of the catalyst was investigated. Armostat 300 with the formula alkyl C₁₄‐C₁₈ bis(2‐hydroxyethyl)amine is an antistatic agent that reduces static electricity of the polymer particles. It was found that within the concentration of 0.16–1.32 g/mmol Ti, Armostat 300 helps to increase the catalyst activity to 1.3–2 times. The variation of the titanium oxidation state of the catalyst in the presence of Armostat 300 at 80°C with Al/Ti molar ratio of 100 showed that Ti (III) species increased. The effect of Armostat 300 on T_m, % X_c, density, bulk density, and MFI of polymer was insignificant. In this work, Zonyl FSN‐100 with the formula R_f(CH₂CH₂O)_xH, R_f = F(CF₂CF₂)_y, y = 1–9, x = 1–26 was used as antifouling agent in copolymerization of ethylene with 1‐butene. It was found that Zonyl FSN‐100 at the concentration range of 5–20 ppm reduces the catalyst activity to 1.11–1.9 times. It was also shown that Ti (III) species in the presence of Zonyl FSN 100 decreased. This antifouling agent slightly decreased the properties of polymer including % X_c, density, and M_w. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 257–260, 2006     

Nanosized Pt-Perovskite Catalyst for the Regeneration of a Wall-Flow Filter for Soot Removal from Diesel Exhaust Gases

Perovskite-type catalysts have been investigated for diesel soot combustion: (i) the LaCr_0.9O_3– substoichiometric perovskite, (ii) K–La partially substituted chromites; (iii) Pt added ii-type perovskites. The catalysts prepared showed a progressively higher activity and potential for practical application in diesel particulate traps. Engine bench tests performed on a SiC wall-flow trap (Ibiden) lined with the La_0.9K_0.1Cr_0.9O_3– + 1 wt%Pt catalyst showed that the catalyst not only speeds up soot combustion on occasional trap heating (regeneration phase) but also prolongs the trap loading phase (soot accumulation during normal operation) as Pt active sites promote NO–NO₂ oxidation, followed by the non-catalytic reaction of NO₂ with the trapped soot.     

Intrinsic viscosity–number average molecular weight relationship for poly(1,4‐butylene adipate) diol

The relationship between number average molecular weight (M_n) and intrinsic viscosity ([η]) was studied for poly(1,4‐butylene adipate) diol (PBAD) in tetrahydrofuran, toluene, and ethyl acetate at 25°C. Thus, a series of PBAD samples were prepared by polymerization between 1,6‐adipic acid and 1,4‐butanediol. The values of M_n for the samples were determined by end‐group analysis as well as by ebulliometry, and the average difference of M_n between the two analysis ways was about 2.69%. The Mark–Houwink–Sakurada equations for PBAD were obtained to relate [η] with M_n in the range of 1900–10,000. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of ultra‐high‐molecular‐weight polyethylene and its morphological study with a heterogeneous Ziegler–Natta catalyst

Ultra‐high‐molecular‐weight polyethylene (PE) with viscosity‐average molecular weight (M_v) of 3.1 × 10⁶ to 5.2 × 10⁶ was prepared with a heterogeneous Ziegler–Natta MgCl₂ (ethoxide type)/TiCl₄/triethylaluminum catalyst system under controlled conditions. The optimum activity of the catalyst was obtained at a [Al]/[Ti] molar ratio of 61 : 1 and a polymerization temperature of 60°C, whereas the activity of the catalyst increased with monomer pressure and decreased with hydrogen concentration. The titanium content of the catalyst was 2.4 wt %. The rate/time profile of the catalyst was a decay type with a short acceleration period. M_v of the PE obtained decreased with increasing hydrogen concentration and polymerization temperature. The effect of stirrer speeds from 100 to 400 rpm did not so much affect the catalyst activity; however, dramatic effects were observed on the morphology of the polymer particles obtained. A stirrer speed of 200 rpm produced PE with a uniform globulelike morphological growth on the polymer particles. The particle size distributions of the polymer samples were determined and were between 14 and 67 μm. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Complexation of Zirconium Alkoxides with 3-Pentenoic Acid and Hydrolytic Stability of Their Products

Reactions of Zr(OPr ⁿ )₄ and Zr(OBu ⁿ )₄ with 3-pentenoic acid (PA) in 1:1 molar ratio were studied in propanol and butanol solution at room temperature by the sol–gel process. The complexations were investigated by ¹³C{¹H}, ¹H-NMR and FTIR spectroscopy. The ¹³C{¹H}, ¹H-NMR and FTIR spectra showed that PA completely reacted with Zr(OPr ⁿ )₄ and Zr(OBu ⁿ )₄. The new products were hydrolyzed by water in a ratio of 1:4 (Zr(OR ⁿ )₄/ H₂O, R = propyl, butyl). The stability of hydrolyzed products was investigated spectroscopically. After hydrolysis, it was observed that no PA was released from the complexes, [Zr(OPr ⁿ )₃(PA)] and [Zr(OBu ⁿ )₃(PA)], under the reaction conditions.     

Hydrogen production by steam reforming of methanol over Cu–CeZrYOx-based catalysts

Active and selective Cu_x(CeZrY)_1−xO_y catalysts (pure and with addition of Al₂O₃ and Cr) for the steam reforming of methanol were synthesized via the urea–nitrate combustion method. Structural, surface and redox characteristics of these catalysts were investigated by XRD, BET, IR spectroscopy, differential dissolution (DD), H₂-TPR and XPS methods. It was shown that addition of alumina and Cr leads to the steep increase in H₂ production due to appearance of highly dispersed copper species and stabilizes their activity. The parallel change of SRM rate constants and maximal rates of reduction with hydrogen characterizing mobility of lattice oxygen at variation of the catalyst composition was revealed that shows the importance of lattice oxygen mobility for steam reforming of methanol.     

Catalytic behavior of hybrid Co/SiO2-(medium-pore) zeolite catalysts during the one-stage conversion of syngas to gasoline

The catalytic properties of 10-MR (membered ring) zeolites (ZSM-5, MCM-22, IM-5, ITQ-2, all with a similar Si/Al ratio of ca. 15) in hybrid Co/SiO₂-zeolite catalysts for the direct conversion of syngas to mainly high-octane gasoline-range hydrocarbons has been studied under typical Fischer-Tropsch (FT) conditions: 250 °C, 2.0 MPa, and H₂/CO = 2. Special emphasis has been given to the deactivation behavior and the characterization of the amount and nature of the carbonaceous deposits formed by a combination of techniques (elemental analysis, TGA (thermogravimetric analyses), GC–MS, and DR (diffuse reflectance) UV–vis spectroscopy). The presence of the medium-pore zeolite increases the gasoline yield by about 20–50%, depending on the particular zeolite, and enhances the formation of branched products with respect to the base Co/SiO₂ catalyst, which is explained by the promotion of isomerization and cracking of long-chain (C₁₃₊) n-paraffins formed on the FT component. The initial zeolite activity is mostly determined by the surface acidity rather than by the total amount of Brønsted acid sites, pointing out to the existence of limitations for the diffusion of the long-chain n-paraffins through the 10-MR channels under FT conditions. Thus, ITQ-2 bearing the largest surface area presents the highest initial yield of branched gasoline-range products, followed by ZSM-5, IM-5, and MCM-22. All zeolites experience a loss of activity with TOS, particularly during the initial reaction stages. This deactivation is governed by the morphological and structural properties of the zeolite, which finally determine the amount and location of the coke species, and not by the acidity.