NaZSM-5 Zeolite Research Articles

Basic thermodynamic characteristics and isotherm of ammonia adsorption in NaZSM-5 and LiZSM-5 zeolites

This paper presents the results of isotherm and basic (ΔH, ΔF,and ΔS) thermodynamic characteristics of ammonia adsorption in Na zeolites2,87ZSM-5 and Li3,37ZSM-5; also the adsorption isotherm is described by the bulk micro-pore filling theory (BFM) equations. The correlation between adsorption-energy characteristics is found, and the molecular mechanism of ammonia adsorption in Na2,87ZSM-5 and Li3,37ZSM-5 zeolites in the whole filling region is revealed. The ammonia adsorbed in NaZSM-5 and LiZSM-5 zeolites is located in the first coordination sphere with Na+and Li+cations, forming octa- and hexaammonia complexes. From the adsorption thermokinetics, it was determined that Li+cations are located in the screened positions of the ZSM-5 zeolite crystal lattice. The adsorption of ammonia molecule results in Li+cations migration from the zeolite lattice into junctions formed by the intersection of straight and zigzag channels and the formation of ion/molecular complexes of various multiplicity in them. It was determined that the average molar entropy of ammonia adsorption on NaZSM-5 and LiZSM-5 zeolites indicates that the mobility of ammonia molecules in the zeolite is below the liquid phase and close to the mobility of the solid phase, indicating a strong limitation of mobility of ammonia adsorbed on the cations.

Catalytic dehydrogenation of ethanol over zinc-containing zeolites

Catalytic dehydrogenation of ethanol produces acetaldehyde, an important precursor for several value-added chemicals such as acetic acid and acetate esters. In this paper, we demonstrate that Zn-containing MFI zeolites are highly active and selective catalysts for this process. Furthermore, we show that their activity and selectivity depend on the chemical composition and preparation of the catalysts. The best catalyst comprises 5 wt% Zn on Silicalite-1 zeolite and results in 65.2% conversion and 94.5% selectivity towards acetaldehyde at 400 ℃. We relate the high selectivity to the absence of Brønsted acidic silanol groups, which suppresses the dehydration of ethanol into ethylene. Furthermore, while pure HZSM-5 and NaZSM-5 zeolites result in dehydration products, such as ethylene and diethyl ether, Zn on NaZSM-5 zeolite also results in acetaldehyde, which confirms that Zn is the active site. Finally, we compare different preparation procedures to show that several Zn-species may be active for the catalytic reaction.

Sustainable sorbent derived from discarded cigarette butts for elimination of tobacco specific nitrosamines carcinogen

In order to control the increasingly serious pollutions of tobacco specific nitrosamines (TSNA) and discarded cigarette butts (DCB) that caused by smoking, new sustainable carbonaceous sorbent was prepared to follow the new idea of “cleaning environment with recycle of waste”. For this propose, DCB was used as the carbon source and aluminum nitrate as the pore-forming agent to form the sorbent with a developed porosity and the well-exposed metal oxides. One-pot synthesis was adopted without template and washing, in order to recycle waste with a sustainable technology. New sorbent could selectively capture 25% of TSNA among hundreds of components in tobacco extract solution or 35 mg g − 1 of 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) in aqueous solution, quite better than activated carbon and zeolite NaZSM-5. In addition, the sorbent was able to catalyze the degradation of the adsorbed NNK in 472–584 K to eliminate the environment carcinogen at relative low temperature. Moreover, cell test demonstrates that the sorbent derived from DCB was cell-safe and therefore widely available. The application of this new sorbent will control both pollutions of TSNA and DCB at the same time, which will protect environment and public health effectively. • Recycle of waste to clean environment was demonstrated in this paper. • Using discarded cigarette butts as the raw material to prepare new sorbent. • One-pot synthesis of the alumina doped carbon without template and washing. • Sustainable sorbent effectively capture tobacco specific nitrosamines carcinogen. • New sorbent is cell-safe and therefore widely available.

Producing gasoline-like hydrocarbons by cracking crude soybean oil: tuning the NaZSM-5 zeolite’s acidity for increasing the catalyst lifetime

This work investigates the effect of NaZSM-5 zeolite’s acid properties on the catalytic cracking of crude soybean to produce gasoline-like hydrocarbons. We modified both the acid concentration and the acid strength of the NaZSM-5(60) zeolite (where 60 denotes the SiO2/Al2O3 molar ratio) either by varying the SiO2/Al2O3 ratio (i.e., 30, and 90) or by exchanging the compensation cation (i.e., from Na+ to H+). Given the ammonia temperature-programmed desorption and temperature-programmed oxidation tests, we observed that the acid strength of the catalyst is associated not only with the distribution of the cracking products, but also with the nature of the carbonaceous deposits formed during the reaction. Weak, medium, and strong acidity were associated with the formation of heavy hydrocarbon species, soft, and hard coke, respectively. The NaZSM-5 zeolites exhibited weak and medium acidity, while the HZSM-5(60) zeolite exhibited weak and strong acidity. Although both NaZSM-5(30) and HZSM-5(60) zeolites delivered higher gasoline yield than the NaZSM-5(60) zeolite due to its higher acid concentration, the HZSM-5(60) zeolite formed carbonaceous deposits with lower reactivity (i.e., hard coke). Therefore, low values of SiO2/Al2O3 ratio in the NaZSM-5 zeolite drive the reaction products towards gasoline-like hydrocarbons and favor the catalyst reactivation through the formation of more reactive carbonaceous deposits.

New versatile zincic sorbent for tobacco specific nitrosamines and lead ion capture

New carbon-doped ferric zinc oxide sorbents were fabricated to capture the environment carcinogen tobacco specific nitrosamines (TSNA) efficiently in solution, following new adsorption model of electrostatic attraction instead of traditional geometric constraints. The influence of ferric content on the structure-property of the sorbents was systemically studied with XRD, N2 adsorption-desorption and SEM methods combined with the adsorption of TSNA in different solutions. New sorbent captured 99% of 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) in simulated surface water and 40% of TSNA in the tobacco extract solution, more than activated carbon or zeolites. Ferric ZnO sorbent took about 15 min to reach the adsorption equilibrium in the NNK or Pb(Ⅱ) solution, faster than NaZSM-5 zeolite. Moreover, the adsorbed NNK on ferric ZnO sorbent decomposed at mild conditions for the first time, providing a new way to control environment pollution.

#42 Maternal exposure to venlafaxine during the first trimester: 10-years experience of the Florence Teratology Information Service

New carbon-doped ferric zinc oxide sorbents were fabricated to capture the environment carcinogen tobacco specific nitrosamines (TSNA) efficiently in solution, following new adsorption model of electrostatic attraction instead of traditional geometric constraints. The influence of ferric content on the structure-property of the sorbents was systemically studied with XRD, N2 adsorption-desorption and SEM methods combined with the adsorption of TSNA in different solutions. New sorbent captured 99% of 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) in simulated surface water and 40% of TSNA in the tobacco extract solution, more than activated carbon or zeolites. Ferric ZnO sorbent took about 15 min to reach the adsorption equilibrium in the NNK or Pb(Ⅱ) solution, faster than NaZSM-5 zeolite. Moreover, the adsorbed NNK on ferric ZnO sorbent decomposed at mild conditions for the first time, providing a new way to control environment pollution.

Enhanced catalytic activity in propene oxidation over NaZSM-5 zeolite-supported Pt nanoparticles by increasing the zeolite Si/Al ratio

A series of zeolite-supported Pt nanoparticles (Pt/NaZSM-5) have been prepared by adjusting Si/Al ratio of NaZSM-5 zeolite from 60 to pure silica. Catalytic tests in propene oxidation as an important model reaction for removal of hydrocarbons emitted from automobiles during cold-start, show that the catalytic activities significantly increase with Si/Al ratios of NaZSM-5 zeolite in these Pt/NaZSM-5 catalysts. As a typical example, Silicalite-1 supported Pt nanoparticles exhibits the highest activity, giving the 50% conversion temperature (T50) and 90% conversion temperature (T90) at 112 °C and 118 °C, respectively. Characterizations of these catalysts with multiple techniques show that the enhanced catalytic activities are strongly related to the zeolite Si/Al ratios of the catalysts, where an increase of zeolite Si/Al ratio is favorable for the adsorption of propene, promoting the propene oxidation. This feature might offer a good opportunity to design and prepare highly efficient heterogeneous catalysts for removal of light olefins in the future.

Catalytic Ozonation of Recalcitrant Organic Chemicals in Water Using Vanadium Oxides Loaded ZSM-5 Zeolites.

The discharge of wastewater having recalcitrant chemical compositions can have significant and adverse environmental effects. The present study investigates the application of a catalytic ozonation treatment for the removal of recalcitrant organic chemicals (ROCs) from the water. Novel catalytic materials using vanadium (V) oxides deposited onto the surface of NaZSM-5 zeolites (V/ZSM) were found to be highly efficient for this purpose. The highly-dispersed V oxides (V4+ and V5+) and Si-OH-Al framework structures were determined to promote the surface reaction and generation of hydroxyl radicals. The constructed V1/ZSM450 (0.7 wt% of V loading and 450°C of calcination) exhibited the highest activity among the developed catalyst compositions. The V1/ZSM450-COP increased the mineralization rate of nitrobenzene and benzoic acid by 50 and 41% in comparison to single ozonation. This study demonstrates the enhanced potential of V/ZSM catalysts used with catalytic ozonation process (COP) for the treatment of chemical wastewaters.

Non-thermal Plasma Technology for the Effective Regeneration of Macroscopic Adsorbent Materials Used in the Removal of Patent Blue V Dye from Aqueous Solutions

In this work, two different commercial macroscopic adsorbent materials (Na-ZSM5 zeolite in spherical pellets and TiO2 cylindrical pellets) has been tested in the removal of model organic food dyes (Patent blue V, E131) and they were regenerated using an innovative techniques based on non-thermal plasma process. The adsorption experiments were carried out using a pyrex cylindrical reactor and liquid samples were analyzed in continuous mode by spectrophotometric measurement at ? = 636 nm. The results demonstrated that these materials were able to remove Patent blue V dye, with removal efficiency equal to 80% for the zeolite and 95% for TiO2 pellets after 400 min of treatment time. The adsorbent materials have been used for several cycles until their saturation. In particular, after seven adsorption cycles, the adsorbing capacity was reduced of about 60 and 20% for zeolite and TiO2 pellets, respectively. Subsequently, the materials were regenerated by non-thermal plasma and reused in the adsorption system. The results evidenced that the regeneration by non-thermal plasma was able to induce the complete degradation of the absorbed organic substance and consequently restoring the initial adsorption capacity of both macroscopic adsorbent materials

Synthesis, characterization and CO2 adsorption of NaA, NaX and NaZSM-5 from rice husk ash

NaA, NaX and NaZSM-5 zeolites were prepared by using silica extracted from rice hull ash as a raw material, and they were investigated for CO2 adsorption performance as an adsorbent in order to solve the problem of suppressing the global warming. Three zeolites were synthesized by hydrothermal methods with seed technology, and a series of characterization methods, including XRD, FTIR, nitrogen adsorption-desorption and SEM, were used to demonstrate their advantages compared to traditional hydrothermal methods. The maximum equilibrium adsorption capacity of NaA-RS, NaX-RS and NaZSM-5-RS was 1.46, 3.12 and 2.20 mmol/g at 0 °C and 101.3 kPa, respectively. The CO2 and N2 adsorption isotherms recorded at different temperatures were perfectly fitted by the Dual-site Langmuir model. The CO2/N2 selectivity and Henry's law constants were calculated to demonstrate that the samples have a stronger affinity for CO2, especially at low pressures. The isosteric heat of CO2 and N2 adsorption of the three zeolites was calculated, which was indicated that they were in an excellent potential for adsorption and separation of CO2 in industrial flue gas.

Investigation of Catalytic Ozonation of Recalcitrant Organic Chemicals in Aqueous Solution over Various ZSM-5 Zeolites

Catalytic ozonation processes (COPs) are an emerging technology for wastewater treatments. NaZSM-5 zeolites in three different SiO2/Al2O3 ratios (31, 45, and 120) and their metallic oxides loaded samples were compared for COP of nitrobenzene solution. NaZSM-5(120) showed high total organic carbon (TOC) removals (70.2–74.0%) by adsorption relative to NaZSM-5(45) (0.4–0.6%) at various initial pH conditions. NaZSM-5(31) was obtained by NaOH treatment of NaZSM-5(45) and displayed 20.9–23.8% of TOC removals by adsorption. In COPs, the different ZSM-5 zeolites exhibited various TOC removals and different reaction pathways. COP-NaZSM-5(120) showed high TOC removals compared to COP-NaZSM-5(45) and COP-NaZSM-5(31). The repeated uses of zeolites in COPs were performed to understand the reaction pathways and contribution of adsorption versus ozonation (i.e., catalytic oxidation and/or direct ozonation). Both adsorption and direct ozonation in COP-NaZSM-5(120) contributed TOC removal for the first use, whereas direct ozonation and •OH mediated oxidation dominated the process for eight repeated uses. Direct ozonation and •OH-mediated oxidation controlled the COP-NaZSM-5(45) process for the first and eight repeated uses. Adsorption and direct ozonation governed the COP-NaZSM-5(31) process for the first use, whereas the direct ozonation dominated it for eight repeated uses. In COPs, NaZSM-5(120) and NaZSM-5(45) showed the catalytic activity, whereas NaZSM-5(31) displayed negligible catalytic activity. The high catalytic activity of NaZSM-5(120) may be due to more Si-O bonds on zeolite surfaces. The results revealed that loading of Mg oxide on ZSM-5 zeolites can increase catalytic activity in COPs. These results show the application potential of ZSM-5 zeolites in ozonation of recalcitrant chemical wastewaters.

A novel CuO NPs/AgZSM-5 zeolite composite adsorbent: Synthesis, identification and its application for the removal of sulfur mustard agent simulant

In this investigation, the parent NaZSM-5 zeolite has been successfully fabricated by the hydrothermal route and then to enhance the catalytic performance of this zeolite, silver ions (Ag+) and copper oxide nanoparticles (CuO NPs) were loaded in its structure through the ion exchange and impregnation methods to attain the novel CuO NPs/AgZSM-5 zeolite composite adsorbent. The parent and modified samples were comprehensively analyzed and identified by using the FESEM-EDX, TEM, XRD, and FTIR techniques. This is the first time that the CuO NPs/AgZSM-5 (containing 3.4 wt% Ag and 12.6 wt% CuO) has been utilized for the removal (adsorption and degradation) of 2-chloroethyl phenyl sulfide (2-CEPS) as a toxic sulfur mustard agent simulate, and its applicability was proved according to the GC-FID, GC-MS, and FTIR results. Moreover, the consequences of several experimental factors such as contact time, initial concentration, adsorbent dose, and adsorbent type on the removal efficiency of 2-CEPS were also surveyed. The GC-FID analysis data confirmed that the maximum removal yield of 2-CEPS was 100%. Besides, the parameters of contact time (120 min), initial concentration (25 mg/L), and adsorbent dose (0.3 g) were perused and optimized for the subsequent reaction. The reaction kinetic status was also studied employing first order model. The quantities of the half-life (t1/2) and rate constant (k) were indicated as 26.25 min and 0.0264 min−1, respectively. The product obtained from the degradation and hydrolysis reaction between the 2-CEPS and CuO NPs/AgZSM-5 was 2-hydroxy ethyl phenyl sulfide (2-HEPS) which is substantially less toxic than original pesticide.

Glucose isomerisation into fructose over Mg-impregnated Na-zeolites: Influence of zeolite structure

Magnesium-impregnated NaY, NaMOR, NaBEA, NaZSM-5 and NaFER zeolites have been prepared and investigated for glucose isomerisation into fructose. It was shown that better magnesium dispersion and smaller reduction of textural properties were obtained with three-dimensional rather than with mono- and two-dimensional zeolites. MgO particle size was also observed to be dependent on the zeolite structure. Various contributions were found to affect the final catalyst performances: availability of MgO, the strength of basic sites, location where the reaction takes place, and the extent of homogeneous reaction due to Na and Mg leaching. Higher glucose conversions were achieved over the MOR, BEA and ZSM-5 zeolites (37–39%), while Y and FER zeolites presented a relatively moderate performance (28 and 27%). In general, lower fructose selectivities were reached for the most active samples, except for the ZSM-5 zeolite. For this catalyst, the reaction appeared to take place mostly on the external surface due to the smaller pore size. Among the various structures investigated, 5%MgNaY zeolite revealed the most resistance to MgO particle size agglomeration during consecutive reaction runs. In addition, 5%MgNaY was found to be the only catalyst capable of recovering its initial activity when regenerated at high temperature. Thus, the type of zeolite structure selected as support for MgO appears to have a significant effect on the catalyst performance for the glucose isomerisation into fructose, with Y zeolite being the most attractive choice for this application.

Impact of proton: Capturing tobacco specific N-nitrosamines (TSNA) with HZSM-5 zeolite

HZSM-5 zeolite was used to conquer the challenge of liquid adsorption of tobacco specific N-nitrosamines (TSNA), either in aqueous solution or tobacco extract solution, offering a candidate with an optimal Si/Al ratio and channel structure to capture the carcinogens. It could trap 84% of N′-nitrosonornicotine (NNN) and 99% of 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) in aqueous solution, much better than that by NaZSM-5 zeolite. Both FTIR and TG/MS technologies were employed to study the adsorption and catalytic degradation of NNN and NNK by HZSM-5 zeolite. The N–N bond of NNK was broken in the range of 423–573K and the pyridine fragments appeared at 630K due to the breakage of C–C bond between pyridine and carbonyl groups. Besides, HZSM-5 zeolite was sprayed on the rod of cigarette and smoked with different manners for the first time, in order to assess its function of reducing TSNA content in mainstream smoke and compared with that of liquid adsorption.

Liquid adsorption and catalytic degradation of 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) by zeolite

Adsorption of 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) along with N’-nitrosonornicotine (NNN) in water is studied for the first time with the monitoring of LC-MS/MS. In the mixed aqueous solution of NNK and NNN, NaZSM-5 zeolite uniquely captured NNK but refused NNN. And the influence of initial concentration, adsorption time and type of sorbents were systemically investigated. Degradation of NNK adsorbed on zeolite is studied with TG/MS and FTIR methods for the first time. It was degraded to NO, pyridine, amine and propanal at around 600 K, avoiding formation of volatile nitrosamines and secondary pollution.

Acid-Free Nitration of Benzene and Toluene in Zeolite NaZSM-5

The syntheses of nitrobenzene and p-nitrotoluene directly from benzene, toluene, and NO2 within the pore network of the initially acid-free zeolite NaZSM-5 are reported for the first time. The active species , formed by the interaction of NO2 with the Na+ cations present on the internal surface, results in the acid-free electrophilic substitution of the aromatic ring. There are two distinct reservoirs for the reagents: one associated with close proximity to the cation sites and the other associated with the siliceous areas of the pore network. Up to 34% of the hydrocarbon and 70% of the available NO2 are reacted at 50°C. Only the cation associated sites are reactive at low temperature, and there appears to be little mobility between the sites under the reaction conditions. There is no evidence of a second nitration occurring. This represents a novel route to the single nitration of benzene and toluene and for toluene, the generation of the para isomer exclusively. The pore network of the NaZSM-5 restricts the available reaction volume and transition state geometry allowing only the para-substituted product.

Selective Nitration of Chlorobenzene by NO2 in the Alkali Zeolite NaZSM-5

Chlorobenzene was reacted with NO2, in the initially acid-free zeolite NaZSM-5, to yield para-chloronitrobenzene exclusively. The precursors were loaded sequentially into self-supporting pellets of the zeolite, contained within a stainless steel cell, from the gas phase. The reaction proceeds spontaneously at room temperature. It is, however, very temperature dependent and effectively ceases at zero degrees Celsius. The reaction was monitored in situ using FT-IR. The active nitrating agent is formed from the partial electron donation by the NO2 to the Na+ cations present in the zeolite lattice. Under the reaction conditions, chlorobenzene is not readily mobile through the pore system; thus, only the molecules adsorbed near a cation site react to form para-chloronitrobenzene.

Phosphoric acid treating of ZSM-5 zeolite for the enhanced photocatalytic activity of TiO2/HZSM-5

NaZSM-5 zeolite was modified by phosphoric acid and a sol–gel method was used to prepare the supported TiO2/HZSM-5. The composite photocatalysts were characterized by XRD, SEM, BET, FT-IR and XPS measurements. The TiO2 existed as anatase phase in both pure TiO2 and supported TiO2/ZSM-5. The TiO2 crystallite size became smaller after loading TiO2 on the zeolite. The surface areas of the composite 50%TiO2/χHZSM-5 were much higher than that of pure TiO2, while the surface areas of the composites decreased with increasing TiO2 loading contents. The TiO2/0.5HZSM-5 composites had higher photocatalytic activity than the pure TiO2. The maximum degradation rate was 49.7% on the 50%TiO2/0.5HZSM-5 using the support of 0.5HZSM-5 which was treated with 0.5mol/L phosphoric acid. Nearly all of the absorption peaks of Reactive Brilliant Red X-3B disappeared after 2h of degradation on 50%TiO2/0.5HZSM-5.

Synthesis, Characterization and Catalytic Fast Pyrolysis of Jatropha Waste Over Synthesized NaZSM-5 and HZSM-5 Zeolites

Synthesis, Characterization and Catalytic Fast Pyrolysis of Jatropha Waste Over Synthesized NaZSM-5 and HZSM-5 Zeolites

Transesterification of soybean oil to biodiesel using zeolite supported CaO as strong base catalysts

A series of supported CaO catalysts with NaY, KL and NaZSM-5 zeolites as supports were prepared by microwave irradiation and used to catalyze the transesterification of methanol with soybean oil. The activities of synthesized catalysts were investigated compared to pure CaO. It was found that the activity of CaO catalyst increased after supported on zeolites, and the CaO/NaY exhibited the best performance. The improved catalytic activity was attributed to the increase of BET values and the concomitant increase of basic strength and basicity after dispersed on NaY zeolite through microwave irradiation. The prepared catalysts were characterized by several techniques such as X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, scanning electron microscopy (SEM) and the Hammett indicator method. In addition, the factors affecting biodiesel yield were investigated to optimize the reaction conditions. A biodiesel yield of 95% was achieved (using the CaO/NaY catalyst) with 30wt.% of CaO loading on NaY zeolite, methanol/soybean oil molar ratio 9, reaction temperature 65°C, reaction time 3.0h and catalyst/oil mass ratio 3%. The results indicated that the supported catalyst had the capacity of water resistance and acid resistance. A high yield (more than 80%) could be obtained when the acid value and the water content of oil were less than 4mg KOH/g and 1.5%, respectively.