Low-temperature catalytic dechlorination of model plastic pyrolytic oil over zeolite catalysts

Although most of the applications of the zeolites are closely connected with their structural and chemical properties (i.e., type of zeolite, modification by ion exchange and/or isomorphous substitution, etc.), size and morphology of zeolite crystals can play a significant role in the mode and efficiency of their application (1,2). Here are shown some characteristic examples of the influence of size and shape of zeolite crystals in their applications as ion exchangers, catalysts, adsorbents, coatings, and so forth. In order to control particle properties such as size and shape, it is necessary to understand crystal growth, which is the focus of this chapter.

Introduction: Soil structural stability affects the profitability and sustainability of agricultural systems. Particle size distribution (PSD) and aggregate stability are the important characteristics of soil. Aggregate stability has a significant impact on the development of the root system, water and carbon cycle and soil resistance against soil erosion. Soil aggregate stability, defined as the ability of the aggregates to remain intact when subject to a given stress, is an important soil property that affects the movement and storage of water, aeration, erosion, biological activity and growth of crops. Dry soil aggregate stability (Mean Weight Diameter (MWD), Geometric Mean Diameter (GMD)) and Wet Aggregate Stability (WAS) are important indices for evaluating soil aggregate stability.To improve soil physical properties, including modifying aggregate, using various additives (organic, inorganic and chemicals), zeolites are among what has been studied.According to traditional definition, zeolites are hydratealuminosilicates of alkaline and alkaline-earth minerals. Their structure is made up of a framework of[SiO4]−4 and [AlO4]−5 tetrahedron linked to each other's cornersby sharing oxygen atoms. The substitution of Si+4 by Al+3 intetrahedral sites results inmore negative charges and a high cation exchange capacity.Zeolites, as natural cation exchangers, are suitable substitutes to remove toxic cations. Among the natural zeolites,Clinoptilolite seems to be the most efficient ion exchanger and ion-selective material forremoving and stabilizing heavy metals.Due to theexisting insufficient technical information on the effects of using different levels of zeolite on physical properties of different types of soils in Iran, the aim of this research was to assess the effects of two different types of zeolite (Clinoptilolite natural zeolite, Z4, and Synthetic zeolite, A4) on aggregate stability indicesof soil. Materials and Methods: In this study at first, after preparation of two different types of soil with light and medium texture and doing identification tests such as determination of gradation and hydrometer tests and Atterberg limits, zeolite in four levels, 0 (control), 1%, 5%, and 10%w/w, was mixed with two soil textures (sandy loam and silty loam) in three replications. Then, each treatment was saturated for 48 hours in each month, during 6 months. Dry soil aggregate stability (Mean Weight Diameter (MWD), Geometric Mean Diameter (GMD), and Wet Aggregate Stability (WAS)), were determined. The experiment was carried out using factorial method in a randomized complete design. Results and Discussion:The results showed that, in sandy loam texture, there was no significant difference between two types of zeolites, their level of using and their interaction on MWD (p

Preparation and preliminary testing of MnO 2 prepared on different types of zeolites as support Part I

The combination of advantages of using zeolites and gold nanoparticles were aimed to be used for the first time to improve the characteristic properties of ion selective field-effect transistor (ISFET)-based creatinine biosensors. The biosensors with covalently cross-linked creatinine deiminase using glutaraldehyde (GA) were used as a control group, and the effect of different types of zeolites on biosensor responses was investigated in detail by using silicalite, zeolite beta (BEA), nano-sized zeolite beta (Nano BEA) and zeolite BEA including gold nanoparticle (BEA-Gold). The presence of gold nanoparticles was investigated by ICP, STEM-EDX and XPS analysis. The chosen zeolite types allowed investigating the effect of aluminium in the zeolite framework, particle size and the presence of gold nanoparticles in the zeolitic framework.After the synthesis of different types of zeolites in powder form, bare biosensor surfaces were modified by drop-coating of zeolites and creatinine deiminase (CD) was adsorbed on this layer. The sensitivities of the obtained biosensors to 1 mM creatinine decreased in the order of BEA-Gold > BEA > Nano BEA > Silicalite > GA. The highest sensitivity belongs to BEA-Gold, having threefold increase compared to GA, which can be attributed to the presence of gold nanoparticle causing favourable microenvironment for CD to avoid denaturation as well as increased surface area. BEA zeolites, having aluminium in their framework, regardless of particle size, gave higher responses than silicalite, which has no aluminium in its structure. These results suggest that ISFET biosensor responses to creatinine can be tailored and enhanced upon carefully controlled alteration of zeolite parameters used to modify electrode surfaces.

Catalytic cracking of heavy oil over catalysts containing different types of zeolite Y in active and inactive matrices

The development of selective adsorbents has become very important for the effective multi-nuclide decontamination. In this study, the selective adsorption properties of 26 nuclides for different types of zeolites (A, L, natural mordenite (NM), Ag-NM) were examined in the presence of boric acid. The batch adsorption experiments were carried out using four kinds of test solutions containing boric acid and calcium hydroxide; (1)DW (distilled water) + H3BO4: 3,000 ppm + LiOH: 10 ppb, (2)DW + Ca(OH)2: 500 ppm + H3BO4: 3,000 ppm + LiOH: 10 ppb, (3)Seawater (30% diluted) + H3BO4: 3,000 ppm, (4)Seawater + H3BO4: 3,000ppm. The uptake (%) of Sr2+ for zeolite A (A-51J), Cs+ for natural mordenite (NM, 2460#, Ayashi, Sendai), and I− for Ag-NM was determined under the following conditions; Concentration of Sr2+, Cs+ and I− ions: 10 ppm, V/m = 100 cm3/g, 25°C, 24 h. The uptake (%) of Sr2+, Cs+ and I− ions was estimated to be above 90%, while tended to decrease in the presence of seawater. Especially, the uptake (%) of I− ions for Ag-NM markedly decreased in the presence of seawater. As for the zeolites A and L, the uptake (%) of 26 elements was determined by using two kinds of test solutions; (1)DW (distilled water) + H3BO4: 3,000 ppm + LiOH: 10 ppb + 26 nuclides: 10 ppm, (2)Seawater (30% diluted) + H3BO4: 3,000 ppm + 26 nuclides: 10 ppm. Zeolite A has relatively large uptake percentage for Sr, Co, Ni and Zn, and zeolite L has high adsorbability to lanthanoid group of Eu, Ce and Pr. The increase in pH led to the enhancement of uptake (%), while the hydrolysis of metal ions should be also considered. The multi-nuclides separation is thus expected by considering the difference in uptake properties of zeolite A, L and natural mordenite.

Adsorption of H2, N2, and CO on four different protonated zeolitesH-ZSM-5, H-β, H-Y, and dealuminated H-Yat low temperatures was studied by transmission Fourier transform infrared spectroscopy. The introduction of the basic probe molecules caused a red-shift of the IR stretching bands of the zeolitic acidic OH groups. This perturbation, which is commonly interpreted as a hydrogen bonding between the acidic OH group and the adsorbate and often taken as a measure of the acidic strength, was then compared with intrinsic activities for the acid-catalyzed cracking of n-hexane previously published for the same zeolite samples. Catalytic and spectroscopic characterization of the acidity is consistent only within the same class of zeolites, e.g. comparison of differently pretreated faujasites. Spectroscopic and catalytic observations for different types of zeolites do not match perfectly, because additional effects, such as interactions of larger molecules with pore walls and the stabilization of transition state...

Isomerization of cyclopropane on H+-exchanged zeolites of different types: An in situ drift spectroscopic study

Biomass ash is a huge potential resource that needs to be exploration and utilization. The ash which is usually rich in silica has been used to synthesize zeolites. The aim of this work was to summarize the condition of synthesis, characterization, and application on the different types of zeolites prepared from biomass ash. In general, crystallization time (t), crystallization temperature (T) and alkaline concentration (C) were considered in the experiments. The physicochemical characteristics of zeolites were mainly analyzed by XRD, FTIR, SEM and nitrogen porosimetry. Meanwhile, the catalytic and adsorptive applications were pointed out. It’s possible to obtain the interesting information about relevant researches from this work. The mechanism of zeolite formation needs to be further clarified and reach a consensus.

To solve the environmental problems caused by greenhouse gas emissions, porous materials based on alkaline solid wastes (fly ash and slag) were prepared in this study. Besides, the preparation scheme of the porous materials was optimized through an orthogonal test by taking the compressive strength and static CO2 adsorption capacity as the target parameters. The two target parameters of the porous materials prepared under the optimal ratio are 15.395N and 0.83mmol/g. On the basis of the optimal ratio, zeolite composite porous materials were prepared by adding different types of zeolite, which further improves the CO2 adsorption capacity of the porous materials. Furthermore, the micro-morphologies, CO2 adsorption performances, and mechanical properties of the porous materials were analyzed by a scanning electron microscope (SEM), the Brunauer-Emmett-Teller (BET) method, and a universal testing machine. It is discovered that the addition of different types of zeolite decreases the compressive strength but significantly improves the CO2 adsorption performance as it can promote the specific surface area and the pore volume. Moreover, the best performance is achieved with the addition of 13X zeolite. In this case, the adsorption capacity reaches 2.68mmol/g, about 3.2 times greater than that of the porous materials without zeolite. The CO2 adsorbent proposed in this study, which boasts excellent mechanical property and CO2 adsorption performance, is applicable to goafs and has a bright prospect in the comprehensive utilization of solid wastes and the control of global warming.

Highly tritiated water (HTW) may be generated at ITER by various processes and, due to the excessive radio toxicity, the self-radiolysis and the exceedingly corrosive property of HTW, a potential hazard is associated with its storage and process. Therefore, the capture and exchange method for HTW utilizing Molecular Sieve Beds (MSB) was investigated in view of adsorption capacity, isotopic exchange performance and process parameters. For the MSB, different types of zeolite were selected. All zeolite materials were additionally platinized. The following work comprised the selection of the most efficient zeolite candidate based on detailed parametric studies during the H2/D2O laboratory scale exchange experiments (~25 g zeolite per bed) at the Tritium Laboratory Karlsruhe (TLK). For the zeolite, characterization analytical techniques such as Infrared Spectroscopy, Thermogravimetry and online mass spectrometry were implemented. Followed by further investigation of the selected zeolite catalyst under full technical operation, a MSB (~22 kg zeolite) was processed with hydrogen flow rates up to 60 mol h-1 and deuterated water loads up to 1.6 kg in view of later ITER processing of arising HTW.

Methyl α-Hydroxyisobutyrate Dehydration over Zeolite Catalysts

The so-called mechanochemical method for the synthesis of zeolites reduces the generation of liquid residues and gaseous pollutants as compared to the conventional solvothermal method. Different types of zeolites have been synthesized at the laboratory scale with this method using mostly pestle and mortar. However, such an approach hinders both the systematic comprehension of the effects of the input variables of the milling process and its further scale-up towards the synthesis of the zeolites and their catalytic application. This work investigates the influence of key factors involved in the ball milling stage of the mechanochemical route for the synthesis of MFI done with the assistance of a commercial MFI seed and in the absence of solvents over the most salient physicochemical properties of this type of materials, i.e. the recovery percentage, production cost, morphology, surface area and porosity, crystallinity, acidity of the protonated MFI and catalytic performance. The synthesis of the materials was planned and executed following a full 24 factorial experiment whose input variables were the Na2O/SiO2 and H2O/SiO2 molar ratios and the milling time and speed. The effects of both main and interaction factors over key physicochemical properties, and catalytic behavior of the synthesized materials on the alkylation of phenol with tert-butyl alcohol were established within the explored sampling space. Results showed that the Na2O/SiO2 molar ratio plays a key role for the mechanochemical synthesis of MFI, since this variable may direct the synthesis to the preferential production of MOR instead of MFI. On the other hand, it was found that the milling time and speed and their interactions markedly impact the textural properties of MFI. Furthermore, the triple interaction between the input variables affected the concentration of Lewis acid sites of the produced materials. These effects were rationalized by considering that sodium can act as a structure directing agent during the mechanochemical synthesis of MFI and also can promote the incorporation of aluminum to its structure. On the other hand, the milling time and speed are non-linearly correlated to the milling energy required for forming the aluminosilicate precursor that crystallizes during the hydrothermal stage of the process. Overall, all the zeolites synthesized by the mechanochemical route were less crystalline than both the MFI used as seed and an MFI synthesized by sol-gel. This was associated to the formation of amorphous agglomerates around the zeolitic crystals. Finally, the catalytic behavior of the mechanochemical MFI zeolites in the studied reaction was found to be linearly and positively correlated with both the concentration of BrØnsted of sites and with the density of acid sites. The catalytic tendencies were consistent with the proposal of a stepwise Langmuir-Hinshelwood mechanism for the alkylation of phenol with tert-butyl alcohol.

The effect of the active site and substrate structure in preparation of substituted tetrahydropyrans via intramolecular cyclization

Cold VCl3-plasma is employed for the preparation of highly dispersed vanadium oxide clusters on nanosized zeolite. Different types of zeolites, such as EMT, FAU (z.X), and Beta, are used. The activity of the prepared catalysts is studied in the selective photooxidation of methanol under polychromatic visible and UV irradiations. The physicochemical properties and catalytic performance of plasma-treated zeolite Beta (P-V2O5@Beta) catalyst is compared with zeolite Beta (V2O5@Beta) and amorphous silica (V2O5@SiO2) impregnated vanadium oxide catalysts. Pure V2O5 is used as a reference material. The set of catalytic data shows that plasma-prepared zeolite Beta based catalyst displays the highest activity. Complementary characterization techniques including XRD, N2-sorption, FTIR, ionic exchange, pyridine adsorption, Raman, NMR, TPR, and EDX-TEM are used to study the impact of the preparation approach on the physicochemical properties and catalytic performance of photocatalysts.