Modified Zeolite Catalysts Research Articles

CoB doped acid modified zeolite catalyst for enhanced hydrogen release from sodium borohydride hydrolysis

Cobalt-boron (CoB) catalyst supported on zeolite modified with hydrochloric acid (CoB-zeolite-HCl) and zeolite modified with acetic acid (CoB-zeolite-CH3COOH) is prepared for the hydrogen (H2) release from sodium borohydride (NaBH4). The supported catalyst samples were characterized by X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FTIR), nitrogen adsorption and, inductively coupled plasma optical emission spectroscopy (ICP-OES). The effects of Co metal loading, NaBH4 concentration, NaOH concentration, temperature, and reusability on the catalytic performance of the CoB-zeolite-HCl catalyst were investigated. The completion time of the reaction using the raw zeolite supported CoB catalyst was about 265 min. However, the completion time of the reaction using the CoB-zeolite-HCl catalyst was decreased to about 80 min. BET surface area values showed that there is a 7-fold increase in the specific surface area for the zeolite activated with HCl compared to the BET surface area for the raw zeolite. The activation energy (Ea) of the catalyzed reaction was 42.45 kJ mol−1.

Effect of Stannic Species Modification on the Acidity of Silicalite-1 and Its Enhancement in Transforming Ethylenediamine to Heterocyclic Amines

In this study, a series of SnO2 modified zeolite catalysts (Snx-S-1; x is the weight percentage of Sn) were prepared with SnCl2 and a defective Silicalite-1 (S-1) zeolite via facile deposition–precipitation method. It was found that the stannic species modified all-silica zeolite catalysts were active for the intermolecular condensation of ethylenediamine (EDA) to 1, 2-Diazabicyclo [2, 2, 2] octane (TEDA) and piperazine (PIP). The best catalyst Sn6-S-1 (6 wt.% Sn loading) showed 86% EDA conversion and 93% total selectivity to TEDA and PIP. By contrast, the defective S-1 zeolite parent showed only approximately 9% EDA conversion under the same conditions. With the help of catalyst characterization techniques including hydroxyl vibration and pyridine adsorption FT-IR spectroscopy (transmission mode), the enhancement of the catalytic activity of the SnO2 modified zeolite catalysts (Snx-S-1) was mainly attributed to the formation of mild Lewis acid sites in the siliceous zeolite. Both the hydroxyl nests of the defective S-1 zeolite and the dispersed SnO2 clusters should be the important factors for the formation of mild Lewis acid sites on the modified zeolite. Based on the catalytic performance of the modified zeolite in the conversion of EDA to PIP and TEDA, it is inferred that the mildly acidified defective S-1 zeolite by the SnO2 deposition modification might become a very active and durable catalyst for reactions involving strongly alkaline reactants and products.

One-pot direct conversion of bamboo to aromatics under methane

The direct conversion of bamboo to aromatics was investigated over Zn and/or Ga modified zeolite catalysts under a methane environment. Aromatics are the main liquid products from bamboo conversion on a batch reactor. The reaction over Zn-Ga/ZSM5(30) gives 19.2 wt% yield of aromatics with 55.6% selectivity towards BTEX (benzene, toluene, ethylbenzene, and xylene) at 400 °C. Zn loading promotes the deoxygenation of oxygenated intermediates from bamboo decomposition and favors the formation of BTEX. Ga addition has little effect on BTEX selectivity but improves the aromatics yield. The presence of methane has a negligible impact on residue reduction, however, methane co-existence could benefit the formation of aromatics. Acidity characterization using pyridine and ammonia as probes shows HZSM5 modification with Zn and Ga species significantly increase the number of weak acidic sites. The catalyst with abundant acidic sites, particularly, weak acidic sites, would be beneficial for the conversion of bamboo to aromatics with higher BTEX selectivity. More aromatics with less residue can be produced from bamboo with higher holocellulose content. The results reported in this work could contribute to a better understanding of bamboo conversion into valuable chemicals and cost-efficient utilization of biomass resources.

Ароматизация низкомолекулярных углеводородов на модифицированных цеолитных катализаторах

Новые технологии, Химическая промышленность, Химическая технология, Научные журналы, Защита от коррозии, Технология металлов, Свойства материалов, Технические журналы, Наука и технологии, Справочная литература, Научные разработки

Conversion of the Components of Natural and Associated Petroleum Gases over Modified Zeolite Catalysts

Conversion of the Components of Natural and Associated Petroleum Gases over Modified Zeolite Catalysts

Conversion of the Components of Natural and Associated Petroleum Gases over Modified Zeolite Catalysts

Conversion of the Components of Natural and Associated Petroleum Gases over Modified Zeolite Catalysts

Fundamentals of Heterogeneous Catalysis: a Study of N2O Mitigation Reaction Over Modified Zeolite Catalysts

This article provides the fundamental understanding of heterogeneous catalysis and the importance of nitrous oxide (N2O) conversion reactions. Solid catalysts play an important role in the reduction of several greenhouse gases. In developing countries, the topic of N2O mitigation reactions is relatively new and needs review particularly for early stage researchers. In this work, reaction catalysis, zeolite as a prominent catalyst support, and the importance of N2O dissociation reactions are briefly discussed. After an overview of global warming, the discussions continue to introduce the principles of reaction catalysis. Furthermore, N2O is a potent greenhouse gas, whereas its emissions into the environment can be reduced when reacted over active and selective solid catalysts. Presently, Fe-ZSM-5 is commercially used catalyst for N2O conversion reactions. Zeolites, for example, H-ZSM-5 (HnAlnSi96-nO192.16H2O) are aluminosilicate catalyst support with unique physicochemical properties. Catalytic activity of H-ZSM-5 may vary when loaded with metals or treated with acid/base solutions. The selectivity of reaction product changes when the same catalyst support is loaded with different metals.

Conversion of Crude Glycerol from by-Product Biodiesel into Bio-additive of Fuel through Acetylation Reaction based on Modified Zeolite Catalyst

<p class="BodyAbstract">Biodiesel is one of the alternative fuels produced from the transesterification reaction between triglycerides and alcohols with glycerol by-products. So far, the resulting crude glycerol has not been maximally utilized because of its low purity. So, it is necessary to purify glycerol before turning it into a more useful compound. The purified glycerol can be reacted with acetic acid within esterification reaction (acetylation process) using an acid catalyst to produce glycerol triacetate (triacetin). One of the uses of triacetin as an additive in gasoline and biodiesel. The purpose of this study is to utilize glycerol from by-products from biodiesel production to bio-additive materials that can improve fuel quality and are environmentally friendly. The method used in this study begins with the purification of crude glycerol, modification of zeolite catalyst with impregnated of nickel metal followed by an acetylation reaction which held on temperature of 100°C for 60 min. The experimental results are analyzed using base titration to determine the remaining unreacted acids and are applied as bio-additives by adding them to commercial fuels and measured the increasing octane numbers. The result shows that the reaction conversion increases with increasing mole ratio of reactants and catalysts with the best results in the mole ratio of acetic acid and glycerol is 9:1 and catalyst 5% by weight of acetic acid with a conversion of 66.02%. As bio-additives the reaction product could increase the octane number of commercial fuel by 6.5 up to 8.5%.</p><p> </p>Keywords: glycerol, acetylation reaction, mofified zeolite, bio-additive

Influence of Tandem Catalysis and Optimised Parameters on Syngas-Dimethyl Ether Co-fed Process for Ethanol Direct Synthesis in a Dual Bed Reactor

Ethanol use mainly as an alternative green fuel has attracted global attention, hence need for the development of more improved synthesis pathways. In this work, we proposed an in situ direct ethanol synthesis pathway, where dimethyl ether (DME) was co-fed with syngas (CO + H2) over a combination of metal impregnated zeolite (Cu-MOR) and ternary oxide CuO/ZnO/Al2O3 (CZA) catalysts, disjointly packed in a dual bed reactor. The route first transformed DME into an intermediate ester (methyl acetate) by carbonylation reaction on the upper modified zeolite catalyst, followed by hydrogenation of the intermediate ester into ethanol on the lower CZA catalyst. Dimethyl ether conversion reached 75.72% with an ethanol selectivity of 48.05% under Cu loading amount of 13 wt% of zeolite support.

Solvent-free catalytic conversion of xylose with methane to aromatics over Zn-Cr modified zeolite catalyst

One-pot catalytic co-conversion of xylose and methane to aromatics was investigated under solvent-free conditions. Aromatics are the major liquid products from xylose conversion. 57.6% yield of aromatics with 63.1% selectivity of BTEX, and 10.9% yield of solid residue are achieved over HZSM-5 modified with Zn and Cr species. It’s evidenced that methane presence could effectively improve the yield of aromatics and the selectivity of BTEX, and greatly reduce the formation of solid residue. The results of pyridine absorption and NH3-TPD measurements indicate that the distribution of Bronsted and Lewis acidic sites over the catalyst has a negligible effect on xylose conversion to aromatics. More acidic sites with higher ratio of weak acid sites could benefit the formation of aromatics with high BTEX selectivity during the xylose conversion. The possible reaction pathway involved in xylose conversion to aromatics is proposed based on pseudo-situ investigations. The findings in this work lead to a better understanding of the chemistry involved in xylose conversion, which could potentially contribute to the cost-efficient utilization of natural gas and biomass.

Acidic and Catalytic Properties of Zeolites Modified by Zinc in the Conversion Process of Lower C3–C4 Alkanes

The acid and catalytic properties of the modified MFI zeolite catalysts during the conversion of the propane–butane fraction of the associated petroleum gases into the aromatic hydrocarbons were studied. It was established that the high-silica zeolites synthesized with the new structure-forming additive of the alcohol fraction (ZKE-AF) belong to the high-silica MFI zeolites. The resulting zeolites were modified by 1–5 wt. % additives consisting of zinc oxide and sulfide. The influence of the modifying additive concentration containing zinc oxides and sulfides in an amount of 1–5% on the acid and catalytic properties of the catalysts in the conversion process of lower C3–C4 alkanes into liquid hydrocarbons was studied. The research of the acid properties of the modified zeolite catalysts by thermal desorption of ammonia showed that the total concentrations of the acidic centers of H-ZKE-AF modified by 3% and 5% ZnO increased. It was found that the highest yield of liquid hydrocarbons was on the zeolite catalysts modified by 3% and 5% ZnS, and is 60.6% and 60.5%, respectively, which is 9% more than in the initial H-ZKE-AF. The activity of the zeolite catalysts modified by zinc oxide and zinc sulfide was in correlation with their acid properties.

Copper-Exchanged Philippine Natural Zeolite as Potential Alternative to Noble Metal Catalysts in Three-Way Catalytic Converters

Natural and synthetic zeolites are microporous hydrated aluminosilicate minerals known for their high thermal stability and their use in various catalytic applications. In this study, the potential of modified Philippine natural zeolite as a cheap alternative to noble metal catalysts in three-way catalytic converters was investigated. The natural zeolite (Z) of the heulandite variety was treated using hydrochloric acid and then ion-exchanged with sodium (NaZ) and copper (CuZ) ions in succession. Energy-dispersive X-ray spectroscopy analysis revealed successful replacement of sodium and other exchangeable cations by copper in the zeolite at 1.19%. Morphological features using scanning electron microscope have shown uniform dispersion of copper as well as uniform particle distribution. In the emission study, a stationary two-stroke 125 cm3 spark-ignition gasoline engine motorcycle at three different speeds of 10 (low), 40 (medium) and 70 (high) kilometers per hour (kph) was used to investigate the catalytic properties of CuZ with the non-catalytic setup as baseline. Using the modified zeolite catalyst, emission test results have shown significant reduction in carbon monoxide (CO) and hydrocarbon (HC) emissions in all speeds, while nitrogen monoxide (NO) emission was significantly reduced from medium to high speeds, suggesting that NO reduction was highly influenced by reaction temperature. Highest reduction in CO emission was 59.61% at medium speed, while highest HC and NO emissions were 66.52% and 76.63%, respectively, at high speed. While further tests are recommended, results show the potential of modified Philippine natural zeolite as a cheap alternative material for three-way catalytic converters.

Oxidative conversion of isopropyl alcohol to acetone over modified zeolite catalysts

Oxidative conversion of isopropyl alcohol to acetone over modified zeolite catalysts

Mechanistic Investigation on Catalytic Deoxygenation of Phenol as a Model Compound of Biocrude Under Methane

A novel hydrogen-free approach is developed to effectively convert phenolic compounds into aromatics including benzene, toluene, ethylbenzene, and xylene (BTEX), a very important and widely used class of petrochemical intermediates, and naphthalene. High yield and selectivity of BTEX are achieved over Zn modified zeolite catalyst during phenol deoxygenation under a methane environment at 400 °C and 2 MPa. Methane can greatly enhance the liquid yield and selectivity of BTEX, but also improve the catalyst activity. Experimental analysis and mechanistic studies reveal that methane is incorporated into both the methyl group and aromatic ring. The embedding of methane into aromatic compounds is achieved via C-alkylation of phenyl ring, coaromatization with hydrocarbon radicals, and a ring-expansion/contraction mechanism. Liquid- and solid-state NMR investigations make evident the phenyl ring-opening in the reaction. Our mechanistic understanding of this process will provide valuable insights into the chemistry...

Conversion of Associated Petroleum Gas (APG) to Aromatic Hydrocarbons

The studies demonstrated the possibility of effective catalytic synthesis of aromatic hydrocarbons over a zinc oxide modified zeolite catalyst during several reaction-regeneration cycles. The service cycle was shown to be no less than 130–150 hours – a good parameter for the high temperature process. Dependencies of the conversion of fatty C3–C4 constituents of APG on the reaction temperature and time were determined.

Maximizing the production of aromatic hydrocarbons from lignin conversion by coupling methane activation

Maximizing the production of aromatic hydrocarbons from lignin conversion by coupling methane activation without solvent was investigated over Zn-Ga modified zeolite catalyst. The co-loading of Zn and Ga greatly improves lignin conversion, arene yield along with BTEX (i.e., benzene, toluene, ethylbenzene, and xylene) selectivity, which gives 37.4 wt% yield of aromatic hydrocarbons with 62.2 wt% selectivity towards BTEX at 400 °C and 3.0 MPa. Methane presence has a negligible impact on lignin conversion, but improves arene yield and BTEX selectivity. Liquid 13C, 1H and 2H NMR investigations confirm the incorporation of methane into the final arene products. The NMR results reveal that methane might be incorporated into both the methyl group and aromatic ring, possibly via methylation of aryl moieties and co-aromatization of alkyl moieties. Pyridine and ammonia as probes for surface acidity analysis of the developed catalysts demonstrate that HZSM5 modification with Zn and Ga species could redistribute BAS (Brønsted acid sites) and LAS (Lewis acid sites) and significantly increase the fraction of weak acidic sites on the catalyst, rendering better catalytic performance on the depolymerization of lignin to arene products with higher BTEX selectivity. The results reported in this work may open a novel route to a promising technique for lignin valorization into aromatics and cost-efficient utilizations of biomass and natural gas resources.

Catalytic Valorization of Furfural under Methane Environment

The technical feasibility of developing a novel process for coupling bioderived furans (furfural) with methane was investigated at mild reaction conditions (400 °C and 2.5 MPa) over modified zeolite catalysts. Monoaromatics are the main liquid products with high yield, and the oxygen of furfural is removed in the form of CO and CO2. Compared to other zeolite-supported metal catalysts developed in this study, Zn–Ga/ZSM5 shows better catalytic performance on furfural conversion in terms of a higher yield of aromatics, particularly benzene, toluene and xylene (BTX), slightly lower gas yield and higher methane conversion. The presence of methane provides carbon atoms that are effectively utilized in the formation of aromatics, and further significantly enhances the yield of aromatics under the facilitation of the charged catalyst. Direct evidence of methane participation in the formation of aromatic products is witnessed by liquid 1H, 2H and 13C NMR investigations, which reveal that methane tends to be incorp...

Catalytic co-aromatization of methane and heptane as an alkane model compound over Zn-Ga/ZSM-5: A mechanistic study

The joint conversion of methane and heptane, a model compound of paraffin-rich raffinate oil, over a Zn-Ga modified zeolite catalyst has been investigated at various reaction times. In comparison with the performance from a N2 environment, the introduction of methane highly promotes the formation of light aromatic compounds with a single phenyl ring, and increased carbon number and substitution index of chemical constituents formed are indicative of methane incorporation into the liquid product. In addition, with prolonged time, the interaction between catalyst and methane molecules is enhanced. Through cleavage of methane molecules, the formed moieties likely participate in the aromatization reaction, which results in the growth of larger aromatic components through further condensation. According to the NMR spectra, witnessing methane engagement into the phenyl carbon and alkyl carbon sites of the formed liquid aromatics along with increasing reaction time is evidenced 13C-methane incorporation into aromatics. The excellent catalytic performance of Zn-Ga/ZSM-5 might be ascribed to the greatly dispersed metal species on the catalyst surface as well as a certain amount of medium and weak acid sites. With regards to the spent catalyst, the presence of methane could inhibit the aggregation of loaded active metals and coke formation during the co-aromatization process. The elucidation on the co-conversion of methane and high alkane provides great potential for the utilization of natural gas resources and intermediates formed from petrochemical industries.

Kinetics and Mechanism of the Oxidative Conversion of n-Amyl Alcohol to Valeric Acid on a Modified Zeolite Catalyst

The catalytic activity of natural and synthetic mordenites modified with Cu2+, Zn2+, and Pd2+ cations via ion exchange was studied in the oxidative conversion of n-amyl alcohol to valeric acid under the action of oxygen. It is established that the highest activity and selectivity in this reaction is exhibited by mordenite hydrothermally synthesized from kaolinite and containing 3.0 wt % Cu2+, 0.1 wt % Pd2+, and 2.0 wt % Zn2+. The kinetics of this catalytic reaction is studied. Based on the experimental data, a possible stepwise mechanism is proposed, and a theoretically grounded kinetic model of the process is developed.

Influence of UV-Activation of Modified Zeolite Catalysts on Their Physicochemical and Catalytic Properties in Their Process of Getting High-Octane Gasoline Components

The influence of UV-irradiation by an XeCl excimer lamp on the physicochemical and catalytic properties of MFI-type high-silica zeolites modified by cobalt tungsto- and molybdobismuthates in the process of getting high-octane gosoline components is studied. It is show that the concentration of acidic centers can be increased by 76%; the arene yield, by 4-13 wt%; and the octane number of the products, by 2-3 points as compared with starting zeolite if cobalt tungstobismuthate heteropoly compound (1 wt%) is used as the modifier and the material is activated by UV-irradiation for 24 min. It is established that UV-irradiation of modified zeolites increases the concentration of acidic centers and decreases the adsorption capacity and specific surface area.