Type Zeolite Catalysts Research Articles

Catalytic conversion of particle board over microporous catalysts

Catalytic pyrolysis of particle board, a type of waste wood that is increasingly produced all over the world, was carried out over three types of zeolite catalysts: HBETA, HZSM-5, and Ga-impregnated HZSM-5 (Ga/HZSM-5). Experiments conducted using a batch reactor showed that the bio-oil yield and gas yield in catalytic pyrolysis were lower and higher than those in non-catalytic pyrolysis, respectively. Analysis of the bio-oil using pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) showed that the yields of high-value-added species such as aromatics and phenolics were increased to a large extent by catalytic upgrading, thus increasing the value of the product bio-oil. In particular, HZSM-5 exhibited high selectivity for aromatic compounds, and impregnation of Ga further increased the selectivity. HBETA could cause levoglucosans to decompose completely owing to its large pore size, resulting in increased yields of low-molecular-mass species.

폴리프로필렌 수지 이용 연료유 생성을 위한 열분해 반응에서 제올라이트계 촉매의 영향

폐 플라스틱을 이용한 연료유 생산 공정을 위한 폴리프로필렌(PP) 수지에 대한 열분해 반응 실험을 하였다. 질소 분위기에서 상온에서 <TEX>$650^{\circ}C$</TEX> 까지의 비등온 조건에서의 열분석기와 <TEX>$420^{\circ}C$</TEX> 등온에서의 Pyrolyser GC-mass 분석기, <TEX>$420^{\circ}C$</TEX>의 배치형 반응기에서 무촉매반응과 천연제올라이트, 폐 FCC 촉매, ZSM-5 등의 제올라이트 계 촉매를 사용한 열분해 실험이 행하여졌다. TGA 실험에서 PP 수지의 열분해반응은 <TEX>$330^{\circ}C$</TEX> 부근에서 시작되어, <TEX>$497^{\circ}C$</TEX>에서 완결되었다. 촉매반응에서 제올라이트 계열 촉매는 폐 FCC 촉매> 천연제올라이트> ZSM-5> PP의 순으로 열분해 반응속도를 높이는데 유효하였다. 열분해가 완료되는 온도도 폐 FCC 촉매 첨가 시 가장 낮게 나타났다. PY-G.C. mass 실험에서 PP 수지 만의 경우에서보다 촉매가 첨가됨에 따라 탄소 수가 낮은 생성물이 생성되는 것을 알 수 있었다. ZSM-5 촉매나 폐 FCC 촉매 첨가 시 특히 낮은 탄소 수의 생성물이 많이 생성되었다. 회분식 반응기에서 초기 오일생성율은 폐 FCC 촉매 첨가시 가장 높지만, 최종 오일전환율은 천연제올라이트 첨가 시가 폐 FCC 촉매 첨가 시보다 2% 정도 높았다. 탄소분석에서도 폐 FCC 촉매 첨가가 경유 성분이 주성분으로 요구되는 연료유 제조에 우수 하였다. The effects of zeolite-type catalysts addition on the thermal decomposition of the PP resin have been studied in a thermal analyzer, a Pyrolyser GC-mass, and a small batch reactor. The zeolite type catalysts tested were natural zeolite, used FCC catalyst, and ZSM-5. As the results of TGA experiments, the pyrolysis starting temperature for PP varied in the range of <TEX>$330{\sim}360^{\circ}C$</TEX> according to the heating rate. Addition of the zeolite type catalysts in the PP resin increased the pyrolysis rate in the order of used FCC catalyst> natural zeolite> ZSM-5 > PP resin. Adding the used FCC catalyst in the PP reduced most effectively the pyrolysis finishing temperature. In the PY-G.C. mass experiments, addition of zeolite type catalysts decreased the molecular weight of pyrolyzed product. In the batch system experiments, the mixing of used FCC catalyst enhanced best the initial yield of fuel oil, but the final yield of fuel oil was 2% higher in the case of mixing of natural zeolite. Also in the carbon number analysis, used FCC catalyst was the most useful one in this experiments for fuel oil.

Catalytic Fast Pyrolysis of White Oak Wood in a Bubbling Fluidized Bed

Catalytic fast pyrolysis was performed on white oak wood using two zeolite-type catalysts as bed material in a bubbling fluidized bed reactor. The two catalysts chosen, on the basis of a previous s...

The influence of zeolite catalysts on the products of rapeseed oil cracking

The article is devoted to the study of rapeseed oil cracking in the presence of zeolite catalysts in order to prepare the liquid fraction with the properties close to fossil diesel.To evaluate the cracking products, the chromatographic methods GL and GC/MS were used, together with the determination of viscosities, acid values and densities. The cracking of rapeseed oil in the presence of zeolite-type catalysts in batch arrangement at temperatures between 350 and 440 °C gave a yield of liquid condensate 85 to 90 wt.%. After removal of volatile components 3 to 9 wt.% by distillation at the temperatures up to 190 °C, the GL chromatogram of treated condensate was similar to that of fossil diesel fuel. The paper deals with the influence of the kind and amount of catalyst on composition and properties of treated products with the use of GL and GC/MS chromatography and with the tests of blends of fossil diesel fuel with cracking products at contents up to 7 vol.%. The blended fuels meet all parameters specified by standard EN 590 for diesel fuel.

ChemInform Abstract: One-Step Formation of Acetone from Propene and Water on Ultrastable Y- Type Zeolite Catalyst.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Alkylation of Toluene with t-Butyl Alcohol over Zeolite Catalysts

Alkylation of toluene with tert-butylalcohol was investigated over three zeolite catalysts (HY, Hβ, and HMCM-22). The acid properties of zeolites were characterized by FT-IR. The fact that the reaction was influenced by the mount of acid was discussed emphatically, and the reaction temperature on conversion of toluene and selectivity for 4-tert-butyl toluene was also studied. The main products have been identified as 4-tert-butyltoluene and 3-tert-butyltoluene. The best result was obtained when temperature was 473 K, the space velocity was 4.0 h−1, and the mole ratio of toluene to tert-butylalcohol was 6. Zeolite HMCM-22, with the highest total acid and the lowest ratio of the total B acid to the total L acid, possessed high activity for toluene conversion and high paraselectivity over the three types of zeolite catalysts.

Catalytic combustion of polycyclic aromatic hydrocarbons (PAHs) over zeolite type catalysts: Effect of water and PAHs concentration

The catalytic combustion of 1-methylnaphthalene (1-MN), a PAH representative molecule, was carried out over USHY and 0.8%PtUSHY catalysts in presence of steam. These catalysts are able to transform low concentration of 1-MN into carbon dioxide at 300°C over USHY catalyst and at 200°C over PtUSHY, without by-products formation. The presence of platinum on the USHY increases the catalytic activity, hence the reaction rate. The influence of platinum content showed that 0.5% of platinum deposited on the zeolite was sufficient to oxidize 900ppm of 1-MN at 300°C.The influence of water content in the feed was investigated and several assumptions were put forth to explain our results. The carbon dioxide yield decreases in the 0–12% range of relative humidity (RH). When RH increases up to 12% the carbon dioxide yield increases. Over USHY catalyst and for low water content (RH<12%), water could be adsorbed over strong hydrophylic sites of USHY zeolite or via H2O dimer (neutral complex form) formation. Over PtUSHY catalysts, water adsorption over the PtO phase could be considered. For high water content (RH>12%), water cluster formation via H2O dimer (ion-pair complex form) is proposed on both catalysts. This form of H2O dimer (ion-pair complex) could generate an acidity, which facilitates the formation of oxygenated compounds easily degradable into carbon dioxide.

Catalytic activity of Ga-containing zeolite catalysts in the coupled reforming of methanol and C3-C4 alkanes

The catalytic activity of Ca-containing ZSM-5 type zeolite catalysts in the coupled reforming of methanol and the propane-butane fraction is reported. Modification of the high-silica catalyst with Ga or Ga + Pt causes, as the process temperature is raised, an increase in the propane-butane fraction conversion and in the arene yield. This behavior of the modified catalysts is due to the changes in their porous structure and acid properties and to the increase in their methanol and propane adsorption capacities.

Highly Efficient and Selective CH Activation in Gallium-Containing Molten-Salt Systems

in an ionic liquid or molten salt medium with very high selectivities (up to 98 % of gaseous products) to form isobutane. During the reaction, hydrogen and anionic chlorogallate species of Ga I and Ga III are formed. The latter can be electrochemically reduced to Ga 0 in a subsequent step. The chlorine liberated in the regeneration of Ga 0 can be used for the synthesis of the chloromethane feedstock from methane, thus making this new reaction a potential key step in a fundamentally new process chain for increasing the value of methane in a closed chlorine/chloride cycle. Rational and efficient conversion of methane to more useful higher hydrocarbons is a very important topic in natural gas utilization. Today, methane activation is mostly carried out indirectly by transformation of methane to syngas (a mixture of CO and hydrogen), which then is converted into higher hydrocarbons (olefins, gasoline, and waxes) by Fischer–Tropsch synthesis. Alternatively, syngas can be used to synthesize methanol, which later can be converted into hydrocarbons using methanol-to-olefins (MTO) or methanolto-gasoline (MTG) catalysts. [1–4] In both routes, a great part of the overall cost stems from production of syngas. [5] Another problem of Fischer–Tropsch synthesis and methanol conversion processes is that it is not possible to produce a single product with high selectivity, as distributions of products with different chain lengths are obtained. A true alternative for indirect methane conversion is the use of chloromethane as the activated intermediate. Chloromethane is obtained both from radical chlorination of methane and from oxyhydrochlorination [6] of methane. In 1988, Taylor and Noceti published a process for the production of gasoline from chloromethane in an MTG-like process. [7] The byproduct HCl of the MTG-like step can be recycled back to the production of chloromethane by oxyhydrochlorination, thus making the overall process attractive for technical use. In the following years, different types of zeolite catalysts were applied in this kind of chloromethane transformation, showing different performance with respect to catalytic activity, coke formation, and the distribution of hydrocarbons produced. [8–12] Recently, the application of SAPO-34-type molecular sieve catalysts was found to be promising (SAPO = silicon aluminum phosphates). With this type of catalyst, light alkenes (ethene, propene, butenes) can be produced at temperatures of 350–5008C in 70–80 % selectivity in a temperature-dependent mix in which the maximum selectivity for one individual product hardly reaches 45 %. [13] Only minor amounts of light alkanes are obtained, while 15–20 % of the products are heavier than C5. Herein, we describe a new, highly efficient and selective

Pyrolysis of waste tyres with zeolite USY and ZSM-5 catalysts

Pyrolysis of waste tyres was carried out with a two-stage bed reactor. The waste tyres were first pyrolysed in a fixed bed reactor, and then the evolved pyrolysis gases were passed through a secondary catalytic reactor filled with two types of zeolite catalysts, which were ultrastable Y-type (USY) and ZSM-5 catalyst. The catalytic temperatures were examined to determine their influence on the yield of product from the pyrolysis–catalyst of waste tyres. The results indicated that with the increase of catalytic temperature, the gas yield increased at the expense of oil yield. The light fractions (<220°C) distilled from the derived oils with the two catalyst were analyzed by gas chromatography/mass spectrometry (GC/MS). It showed that there was a dramatic increase in the concentration of single ring aromatic compounds in the light fractions of the derived oils after catalysis. For example, toluene reached a value in the light fraction of 11.62wt%, benzene 1.6wt%, m/p-xylene 12.27wt% and o-xylene 4.42wt%, with the catalysis of USY catalyst, at the pyrolysis temperature, catalysis temperature and catalyst/tyre ratio of 500, 400°C and 0.5, where the light fraction was about 71wt% in the derived oil. The yield of aromatic hydrocarbons in the derived oils were related to the different properties of the two catalysts such as the pore size which influenced the selectivity, and the silica/alumina (Si/Al) ratio which influenced the number of active sites on the catalyst surface.

Characteristics of copper ion exchanged mordenite catalyst deactivated by HCl for the reduction of NOx with NH3

The deactivation characteristics of copper ion exchanged mordenite type zeolite catalyst (CuHM) by HCl for the reduction of NOx, particularly from an incinerator with NH3, have been investigated over a fixed bed flow reactor system. X-ray absorption near edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), synchrotron radiation X-ray diffraction (SR-XRD), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD) have been employed to illustrate the deactivation mechanism of CuHM by HCl due to the formation of the deactivation precursor through the reaction between HCl and Cu on the catalyst surface. Cu2Cl(OH)3 has been identified as the precursor for the present reaction system and can also be converted to CuCl2·2H2O during the course of the reaction, particularly at high reaction temperature. XANES and EXAFS analyses reveal that the oxidation state of Cu ion on CuHM catalyst is mainly divalent, regardless of the degree of the catalyst deactivation. However, XPS study provides evidence for an increase of the content of Cu(I) ion on the surface of the catalyst deactivated at 450°C for 110h. Moreover, CuCl2·2H2O that forms on the catalyst surface during the course of the reaction evaporates at a reaction temperature higher than 350°C. It eventually converts to CuCl and then it may evaporate to the bulk gas stream and/or introduce a copper ion onto the zeolite surface again through solid-state ion exchange.

Kinetic Experiments and Modeling of a Complex DeNOx System: Decane Selective Catalytic Reduction of NOx in the Gas Phase and over an Fe-MFI Type Zeolite Catalyst

The reduction of NOx in the gas phase (in a NO−NO2−decane−water−O2 mixture) and over a Fe-MFI type zeolite catalyst was extensively studied under a wide range of temperatures, gas hourly space velocities, and concentrations. The Fe-MFI zeolite (Si/Al 12.5 and Fe/Al 0.31) was prepared by solid-state ion exchange. The decane selective catalytic reductions (decane-SCRs) of NO and NO2 were carried out with a reaction mixture consisting of 1000 ppm NOx, 300 ppm C10H22, 6.0% O2, and 0 or 12.0% H2O at gas hourly space velocity values of 15 000−60 000 h-1 and temperatures of 150−450 °C. Under the experimentally investigated reaction conditions, there was no N2 formation in the bulk gas phase. Water vapor had little effect on the N2 yield in decane-SCR of NOx. The kinetic description of the homogeneous system included reactions between NO2 and decane with the formation of NO, CO, and CO2 and a pseudocompound “C3H6O1.8” lumping all oxygenated, olefinic, and paraffinic hydrocarbon products. The heterogeneous system ...

Perturbation and Tracer Chromatography Study of Hydrocarbon Adsorption from Simulated Exhaust Gas on Fe-MFI and MOR Type Zeolite Catalysts

Hexane and propene fully penetrate within the micropores of the Fe-MFI zeolite and strongly adsorb. Decane, tetradecane, isooctane and toluene have a very limited access to the micropores and probably adsorb at the micropore mouths where then can act as reducing agents for NO. Linear alkanes (C6–C8), isoheptane and toluene have an easy access to the micropores of the mordenite MSM-20. Henry constants, adsorption enthalpies and entropies have been estimated. Pre-adsorbed carbon dioxide inhibits adsorption of propene and hexane on the Fe-MFI.

Activity and basicity of BaO modified zeolite and zeolite-type catalysts

BaO modified zeolite and zeolite-type catalysts provide new and valuable data about the alternative reaction for ethylbenzene and styrene formation—the oxidative methylation of toluene with methane. Over BaO modified X, Y, mordenite, ZSM-5, silicalite and AlPO 4-5 catalysts, the toluene conversion, selectivity and yield of C 8 hydrocarbons (ethylbenzene and styrene) are affected to a different degree by the reaction temperature. Both activity and basicity (measured by TPD of CO 2) are resultant from the combined effect of chemical composition and geometry of zeolite and zeolite-type structures, as well as from the accessibility of BaO modifier to the reagents. The Si/Al atomic ratio determines the catalytic and basic properties within a series of the same structural type. The zeolite and zeolite-type structural geometry determines the accessibility of the introduced BaO. Higher accessibility of BaO used for modification favors the activity. Basicity measurements by X-ray photoelectron spectroscopy (XPS) are mainly sensitive towards the chemical composition of the zeolite and zeolite-type framework.

A Study on Modified HZSM-5 Aromatization for FCC Light Gasoline

In this article, the HZSM-5 type zeolite catalysts modified with zinc nitrate and calcium nitrate are prepared by impregnation method. The FCC gasoline (<75°C fraction) is observed and studied on the modified HZSM-5 type zeolite catalysts. The results are that the Z x -HZSM-5 type zeolite catalysts have a high initial aromatic yield but a rapid deactivation. The C y -HZSM-5 type zeolite catalysts have a lower aromatic yield and a familiar deactivation comparing to Z x -HZSM-5. The HZSM-5 type zeolite catalysts modified with bimetal zinc nitrate and calcium nitrate have a rather low initial aromatic yield but a long catalyst life; among them, the C3.5Z2.0HZSM-5 has the best performance. And also, the C3.5Z2.0HZSM-5 type zeolite catalyst has demonstrated good regenerated performance. After regenerated three times, the catalyst still has a good stability. The reaction operational conditions are also observed and studied. The results are that the optimal reaction temperature is 450–490°C, the liquid hours space velocity (LHSV) is 1 h−1 and the reaction pressure is 0.1 MPa.

Basic zeolite and zeolite-type catalysts for the oxidative methylation of toluene with methane

The oxidative methylation of toluene with methane is used as a test reaction for determining the activity, selectivity and yield of C8 hydrocarbons (ethylbenzene and styrene) over different zeolite and zeolite-type catalysts, viz., X, Y, mordenite, ZSM-5, silicalite and AlPO4-5. Selectivity and basicity increase with decreasing Si/Al atomic ratio within the series of the same structural type. The basicity, surface structure and structural integrity are characterized by TPD of CO2, XPS and IRS, respectively.

DIRECT MECHANISMS CHALLENGED

IN A REPORT THAT'S SURE TO spark controversy in catalysis circles, researchers at the University of Southern California say methanol-to-olefin chemistry does not occur directly on solid acid catalysts when all reagents are highly purified. Rather, they claim, the widely studied conversion process is a result of reactions initiated by low-level organic impurities { J. Am. Chem. Soc. , 124 , 3844 (2002)}. Discovered some 25 years ago by scientists at Mobil, zeolite-catalyzed reactions that convert methanol to olefins and other hydrocarbons have been the focus of many research programs because of their industrial importance. Having the technical know-how to convert abundant feed materials like methanol to valuable chemicals or fuels can reduce a country's dependence on imported oil, for example. But figuring out precisely how simple compounds like methanol or dimethyl ether are converted to more complex hydrocarbons in the microscopic pores of zeolite-type catalysts has proven challenging. Proponents of so-c...

Aromatization of methane over zeolite supported molybdenum: active sites and reaction mechanism

The conversion of methane to aromatics, mainly benzene, has been studied. Zeolite type catalysts, ZSM-5, MCM-22, containing molybdenum were used. The reaction was carried out at 973–1073 K and atmospheric pressure. Aromatics were formed after an induction period during which molybdenum carbide was formed. Induction period was followed by analyzing infrared (IR) band of the acidic OH. Zeolite plays an important role for increasing Mo dispersion. Comparison between ZSM-5 and MCM-22 showed that Mo/MCM-22 was twice more active than Mo/ZSM-5. This was attributed to more open topoly of MCM-22 which facilitated the migration of Mo ions towards exchangeable positions thus favoring Mo dispersion, and also reduced diffusion limitation of the aromatic products. Analysis of the products at high space velocity showed that acetylene was formed as primary product along with possibly ethylene. Acetylene was converted into aromatics (benzene, naphthalene) as the space velocity decreased. IR analysis in the OH stretching vibrations showed that H + ions, in H-ZSM-5, are progressively exchanged during the calcination of Mo/HZSM-5, and almost completely removed after the induction period following CH 4 reaction at 823 K. At high temperature in O 2 molybdenum species, possibly MoO 2 + (Mo 2O 5) 2+, migrate in the zeolite framework and replace H +. These species were further converted into Mo 2C by reaction with methane, residual carbon species (coke) poisoning the residual zeolite protons. The reaction of CH 4, C 2H 2 and C 2H 4 over acidic H-ZSM-5, H + poisoned Mo 2C/H-ZSM-5 and non-acidic Mo 2C/SiO 2 was studied. It resulted that H + sites are not prerequisite for aromatization of C 2H 2 or C 2H 4. It was concluded that the principal route for the aromatization of CH 4 is the formation of C 2H 2 over Mo 2C which again over the molybdenum carbide forms benzene. The bifunctional mechanism apparently was less important.

Benzylation of benzene by benzyl chloride over Fe-, Zn-, Ga- and In-modified ZSM-5 type zeolite catalysts

Liquid phase benzylation of benzene by benzyl chloride to diphenylmethane over H-ZSM-5, H-gallosilicate (MFI), H-galloaluminosilicate (MFI), H-ferrosilicate (MFI), H-ferroaluminosilicate (MFI), Fe2O3/H-ZSM-5, ZnO/H-ZSM-5, Ga2O3/H-ZSM-5 and In2O3/H-ZSM-5 zeolites (at 60 and 80°C) has been investigated. A complete or partial substitution of Al in H-ZSM-5 zeolite by Fe or Ga or an impregnation of the zeolite by Fe2O3, ZnO, Ga2O3 or In2O3 makes the zeolite highly active in the benzylation process. The redox function created due to the modification of the H-ZSM-5 zeolite by Fe, Zn, Ga or In seems to play very important role in the benzylation process. However, all these catalysts show a significant induction period for the reaction. The Ga2O3/H-ZSM-5 catalyst showed high benzene benzylation activity even in the presence of moisture in the catalyst and/or in the substrate. However, the reaction induction period is increased markedly with increasing the moisture and it is reduced by removing the moisture from the catalyst by refluxing with moisture-free benzene. It is also reduced by the HCl gas pretreatment to the catalyst before the benzylation reaction. The Ga2O3/H-ZSM-5 and In2O3/H-ZSM-5 catalysts showed excellent reusability in the benzene benzylation. Kinetics of the benzene benzylation (using an excess of benzene) over the H-GaMFI, H-GaAlMFI, H-FeMFI, Ga2O3/H-ZSM-5 and In2O3/H-ZSM-5 catalysts have also been thoroughly investigated. A plausible reaction mechanism for the reaction over the modified ZSM-5 zeolite catalysts is proposed.

Aromatization of dilute ethylene over Ga-modified ZSM-5 type zeolite catalysts

Aromatization of dilute ethylene (5 mol% ethylene in N 2) over different Ga-modified H-ZSM-5 type zeolite catalysts (viz. Ga/H-ZSM-5 (Ga loading=0%, 1.4% and 4.7%), H-GaMFI and H-GaAlMFI (with different bulk and framework compositions of Si, Ga and Al)) at 400°C and atmospheric pressure was investigated at different space velocities (3100–24,600 cm 3 g −1 h −1). The product selectivity and the distribution of aromatics and xylene isomers are strongly influenced by the space velocities and consequently show a strong dependence on the ethylene conversion. With decreasing the conversion, the selectivity for propylene is increased but that of aromatics is decreased, the concentration of C 8-aromatics and that of p- and o-xylene in xylenes are increased but that of benzene and toluene are decreased. Based on these observations a simplified reaction path for aromatization process is proposed. Because of their uniform distribution of non-framework (non-FW) Ga-species in the zeolite channels, the H-GaMFI and H-GaAlMFI zeolite catalysts show higher aromatics selectivity and/or higher ethylene-to-aromatics conversion activity in the ethylene aromatization than the Ga/H-ZSM-5 zeolite catalysts. The high zeolitic acidity is essential for the high ethylene conversion activity of the zeolite catalysts, but the high acidity alone is not enough for obtaining high aromatics selectivity or high ethylene-to-aromatics conversion activity. The aromatics selectivity does not show direct dependence on the acidity or non-FW Ga of the zeolite catalyst. For a Ga-modified ZSM-5 zeolite catalyst to be highly active and also highly selective in the ethylene aromatization, it should have both high acidity and an optimum ratio of non-FW Ga to strong acid sites, which is close to 1.0.