Nanocrystalline ZSM-5 Research Articles

Friedel-Crafts Acylation of Aromatics with Acetic Anhydrideover Nano-Sized Rare Earth Cation Exchanged ZSM-5 Catalysts

Friedel-crafts acylation of aromatic compounds used to synthesize aromatic ketones and significance has commercial importance in diverse areas of fine chemical synthesis and pharmaceutical manufacturing industry. Conventionally, acylation reactions are catalysed by corrosive metal halides or mineral acids. The present work reports on the catalytic activity of nanocrystalline ZSM-5 and rare earth metal cation such as La3+, Ce3+ and Nd3+ exchanged ZSM-5 in the liquid phase acylation of veratrole with acetic anhydride. The catalyst was thoroughly characterized for its structure. The nanocrystalline Ce-ZSM-5 displayed highest activity towards the acylation of veratrole. The catalytic performance of Ce-ZSM-5 was used to compare its activity for the acylation of other aromatics; such as toluene, anisole and veratrole. The nanocrystalline Ce-ZSM-5 shows highest activity over nanocrystalline ZSM-5 in acylation reactions of aromatics. It was established that smaller size crystal of Ce-ZSM-5showed superior activity, which is due to the enhanced density of acidic sites along with increased external surface area of smaller crystal which facilitate the activity of the acylation reaction. The catalysts used in this study are reusable without any loss of activity.

Enhanced monoaromatic hydrocarbons production via pressurized catalytic pyrolysis of end-of-life tires

One of the most active research lines in the area of end-of-life tires (ELT) recycling is pyrolysis, which consists of a thermal decomposition at moderate temperatures and in absence of oxygen. This process was initially focused on the recovery of carbon black and energy, this last by combustion of both the gas and liquid fractions obtained. However, its rentability and alignment to the circular economy goals would be improved if added-valuable chemicals were produced from the pyrolytic oil. For this purpose, the application of catalysts (catalytic pyrolysis) and modification of some operation conditions have been approached in previous works. However, pressure has been missed until now despite the important role it may play affecting the volatilization process, the vapors residence time and the pyrolytic compounds-catalyst contact. This work reports for first time a comprehensive study that demonstrates that carrying out catalytic pyrolysis under moderate pressure (10 bar) is very beneficial to improve the quality of the oil. Thermal and ex-situ catalytic pyrolysis have been performed in a fixed-bed reactor using a real scrap tire as feedstock. Both pressure and catalyst/tire ratio have been modified, using a nano-crystalline ZSM-5 zeolite as catalyst. Increasing the pressure from 1 to 10 bar leads to a slight reduction in the oil yield, which is somewhat more remarkable in the presence of catalyst. Nevertheless, the resulting pyrolysis oil was enriched in marketable monoaromatics (benzene, toluene, xylenes, ethylbenzenes and cymenes) due to a promotion of hydrogen transfer and aromatization reactions. In the case of pressurized catalytic tests, there was a drastic increase in the monoaromatic mass yields, reaching values up to 23–26 % and concentrations in the oil of 50–56 wt%. Finally, the feasibility to regenerate and reuse the catalyst by thermal treatment has been also approached, observing minor changes in its structural and activity properties.

Propane dehydrogenation over Pt and Ga-containing MFI zeolites with modified acidity and textural properties

A variety of oxides (titanium, tin, calcium, magnesium, and gallium) were supported over nano-crystalline ZSM-5 zeolite (n-ZSM-5) by wet impregnation, characterized and evaluated for propane dehydrogenation (PDH) reaction. To enhance the catalytic performance of the oxide-modified n-ZSM-5, Pt nanoparticles were also dispersed over the oxides-supported zeolite catalysts by wet impregnation. Finally, Ga-containing MFI zeolites were used as catalysts in the PDH. Ga was incorporated into the zeolite by two different methods, via hydrothermal synthesis and via wet impregnation. In the PDH reaction, Pt-containing samples exhibited a high initial catalytic activity although they suffered a fast deactivation by coke deposition. On the contrary, Ga-containing MFI catalysts showed a remarkable stability in the PDH reaction. In particular, the catalyst in which Ga was incorporated into the MFI structure by hydrothermal synthesis (Ga-MFI (nSH)) achieved the highest catalytic performance in PDH (9% conversion and 80% propylene selectivity) due to the synergy between the Brønsted and Lewis acid sites (BAS and LAS) and the optimal strength of its LAS sites. These results denote the great potential of Ga-MFI zeolites as catalysts in PDH reactions.

Acid-driven architecture of hierarchical porous ZSM–5 with high acidic quantity and its catalytic cracking performance

Controllable synthesis of ZSM–5 zeolites with hierarchical pores and high acidities is an efficient way for cracking of naphtha to produce light olefins. Here, nanocrystalline ZSM-5 aggregates (NCs) with n(Si)/n(Al) of ∼18 were hydrothermally synthesized via acid hydrolysis of a silicon source for the cracking of n–pentane. Compared with conventional microporous ZSM–5 zeolite, NCs catalysts with preserved micropores and newly generated intercrystalline mesopores promote cracking conversion as well as selectivity of light olefins. Moreover, enhanced acidities with high Al concentration in zeolite benefit the conversion of n–pentane. Interestingly, it is found that with moderate amount of framework Fe, the strength of the Brønsted acid sites of the catalysts increases and Lewis acid sites are formed in zeolite, while maintaining the total acidities. Owing to the restricted bimolecular reaction of the olefins on the adjacent acid sites, the catalysts with an Al–Fe co–framework (NC–5Al–1Fe) affords increased yield of light olefins (ethylene and propylene) up to ∼40 wt% with enhanced catalytic stability after 16 h reaction at 600 °C.

Upgrading of solid recovered fuel (SRF) by dechlorination and catalytic pyrolysis over nanocrystalline ZSM-5 zeolite

Globally increasing concern related to municipal solid waste generation is encouraging research efforts on developing alternative routes to valorize mixed refused wastes. In this way, catalytic pyrolysis is emerging as an interesting and efficient technology due to its great flexibility in terms of feedstock. In the current work, upgrading of a Solid Recovered Fuel (SRF) has been investigated by catalytic pyrolysis over nanocrystalline ZSM-5 zeolite (n-ZSM-5), paying special attention to dechlorination effects due to the high Cl content of the raw waste. Thus, pretreatment of the SRF by water washing and mild thermal processing allows for a significant reduction of the Cl concentration. Regarding the catalytic pyrolysis step, the best conditions correspond with a temperature of 400 °C in the catalyst bed and 0.50 catalyst/SRF mass ratio, which lead to ca. 30 wt% oil yield (rich in aromatic hydrocarbons) together with about 40 wt% gas yield (rich in C3–C4 olefins). Accordingly, these products could find use as raw chemicals or for the production of advanced fuels. In addition, zeolite reutilization has been tested for several cycles, denoting a progressive modification of the products distribution because of coke deposition. However, an almost total recovery of the n-ZSM-5 zeolite catalytic performance is achieved after regeneration by air calcination, affording the production of an oil fraction with a Cl content as low as 40 ppm.

Steam catalytic cracking and lump kinetics of naphtha to light olefins over nanocrystalline ZSM-5 zeolite.

This study investigates the reaction pathways and kinetics to comprehend the catalytic cracking of dodecane, a heavy naphtha model compound, over the nanocrystalline ZSM-5 catalyst in the presence and absence of steam with the aim of increasing olefin production. The nanocrystalline zeolite was characterized using XRD and BET, and the surface acidity was measured by NH3-TPD and Py-FTIR. The steam treated ZSM-5 contributed to an increase in pore volume with extra-framework alumina, resulting in highly catalytic active sites and hence higher olefin selectivity. The high conversion of dodecane (>90%) was achieved during catalytic cracking in the presence and absence of steam. In the presence of steam, the short pores of nano ZSM-5 led to an increase in the naphtha-to-olefin conversion with lesser dry gas and coke formation. The activation energies of primary cracking in the presence and absence of steam were slightly different. Lower activation energies through secondary cracking routes and higher reaction rate constants were obtained via assisted-steam catalytic cracking, promoted the selectivity towards light olefin products. Meanwhile the hydrogenation and alkylation reactions toward LPG and C5+ were favored in the absence of steam. Moreover, the ZSM-5 nano zeolite pores promoted more β-scission reactions, resulting in higher selectivity towards ethylene and dry gas.

Facile and controllable preparation of nanocrystalline ZSM-5 and Ag/ZSM-5 zeolite with enhanced performance of adsorptive desulfurization from fuel

The diffusion limitation owing to the long and narrow pore structure in traditional ZSM-5 zeolite could restrain the adsorptive desulfurization performance towards thiophene sulfur compounds from fuels. Herein, ZSM-5 zeolite nanocrystals were successfully fabricated using steam-assisted gel crystallization strategy to control the size of zeolite particles within 70 ∼ 160 nm. Compared to traditional micron ZSM-5, ZSM-5 zeolite nanocrystals could effectively reduce the diffusion pathway, enlarge the specific surface area, and increase exposure of adsorption sites, which could enhance the desulfurization performance. ZSM-5 nanocrystals with a mole ratio SiO2/Al2O3 of 200 exhibited a satisfactory desulfurization efficiency, and the breakthrough capacity attained 0.0509 mmol S/g adsorbent. After ZSM-5 nanocrystals were ion-exchanged with NH4+ and Ag+, both mesoporous characteristics and the Lewis acid (L-acid) sites were enhanced, which promoted the adsorption desulfurization performance. Furthermore, nanocrystalline ZSM-5 and Ag/ZSM-5 also exhibited acceptable regeneration performance. This study is expected to provide an effective strategy and a facile method to prepare nanocrystalline ZSM-5 based adsorbents for the development of efficient desulfurization materials.

Preparation of nanocrystalline ZSM-5 and its catalytic performance in fast pyrolysis of cellulose to produce aromatic hydrocarbons

A series of nanocrystalline ZSM-5 zeolites with abundant intercrystalline mesopores was fabricated by a hydrothermal crystallization method without any mesopore template. The ZSM-5 zeolite was characterized by XRD, XRF, N2 adsorption, NMR, SEM, TEM and NH3-TPD and used for the catalytic fast pyrolysis (CFP) of cellulose. The external surface area of the nanocrystalline ZSM-5 zeolite reached 146.6 m2/g, larger than the external surface area of conventional ZSM-5 (57.9 m2/g). The product yields of the CFP reaction were studied over different Si/Al ratios of nanocrystalline ZSM-5, and the aromatic yield of nanocrystalline ZSM-5 was generally higher than the aromatic yield of conventional ZSM-5. The relationship between the surface area, acid amounts and product yields was established by drawing a linear fitting curve. The results show that both pore structure and acidity have important effects on aromatic yield and coke yield. Aromatics are generated in micropores, and the increase in external surface area caused by reducing the particle size improves the pyrolysis of cellulose to generate bio-oil vapours, which further diffuse into micropores to generate aromatics.

Novel hierarchical core-shell BEA@NanoZSM-5 zeolite for improved cracking performance for 1,3,5-triisopropylbenzene and n-hexadecane

To overcome diffusional limitations associated with the catalytic cracking of large hydrocarbons, a novel core-shell hierarchical zeolite has been developed and evaluated. Large, branched hydrocarbons encounter diffusional limitations in micropores of zeolites for cracking reactions, a limitation overcome by improved textural properties of hierarchical zeolites, leading to enhanced cracking activity. This will result in an improvement in deactivation rate, cracking activity, and enhanced product selectivity towards light hydrocarbon products. The impact of chain length involving a long chain paraffin (hexadecane) and a highly branched aromatic (1,3,5-TIPB) was also investigated to study the influence of the presence of the micro-mesopore network in overcoming diffusion limitations. This paper investigates the use of hierarchical core-shell [email protected] in the catalytic cracking of 1,3,5 triisopropylbenzene (1,3,5-TIPB), and n-hexadecane (C16). The novel hierarchical composite was synthesized by preliminary seeding of the core BEA crystals and subsequent growth under hydrothermal conditions leading to the formation of an intergrown and distinctive nanocrystalline ZSM-5 shell zeolite. Evidence of the existence of a hierarchical structure was probed by Ar sorption utilising non-local density functional theory (NLDFT) pore size distribution analysis.

Highly Efficient Nanocrytalline Zeolite Catalyst for the Hydroxyalkylation of Anisole with Benzaldehyde

The heterogeneous solid acid catalyzed hydroxyalkylation of arenes with benzaldehyde yields triarylmethane (TRAM) compounds which have gained significant attention due to their notable application in dyes, pharmaceuticals and the synthesis of various functional materials. In the present study the activity of nanocrystalline Beta and ZSM-5 zeolites was studied in the liquid phase hydroxyalkylation of anisole with benzaldehyde. The catalysts were characterized by Dynamic Light Scattering measurements, an X-ray diffraction study and scanning electron microscope and transmission electron microscope analyses. The reaction parameters, such as-catalyst loading, mole ratio, reaction temperature, and catalyst reusability were optimized. The efficiency of zeolite catalysts having different pore sizes was tested under the optimum reaction conditions. The results showed that the larger pore of nanocrystalline Beta exhibited the highest activity, which was due to the increased pore size of the crystal for the easy adsorption of reactants and the desorption of bulky products. It is important to highlight that the nanocrystalline Beta catalysts showed higher efficiency compared to other reported results in the literature, with the advantage of high activity, selectivity, separation of the catalyst and excellent reusability. Therefore, these catalysts can be used instead of conventional homogeneous catalysts such as AlCl3, ZnCl2 and H2SO4 for an eco-friendly selective production of tri aryl methane compounds.

Valorisation of a lignin-rich residue via catalytic pyrolysis over ZrO2/ZSM-5 technical catalyst

The thermochemical valorisation of a lignin-rich residue has been investigated by thermal and catalytic pyrolysis. The catalyst, based on nanocrystalline ZSM-5, has been modified with ZrO2 and agglomerated with attapulgite (ZrO2/n-ZSM-5-ATP). Firstly, the effect of the temperature in thermal pyrolysis has been explored, establishing 600 °C as the optimal temperature to thermally decompose the lignin-rich feedstock, yielding 53.7 wt% of bio-oil* (water-free bio-oil). In contrast, the incorporation of the technical catalyst using an ex-situ reactor, as well as the increase in the catalyst/lignin ratio, strongly affected the mass and energy yields of products. Thus, a significant decrease of the bio-oil* yield was observed, although its composition was significantly improved, with a reduction of the oxygen content from 30 to 10 wt%. Comparing the parent zeolite with the technical catalyst, the latter afforded a bio-oil* production with lower oxygen content, a higher share of aromatics and lower concentration of heavy species (non-detected by GC–MS). In particular, the technical catalyst allows increasing the concentration in bio-oil* of GC–MS detected compounds, which are the most valuable for commercial applications, by a factor of 2.5 regarding the thermal test. Interestingly, these remarkable results are obtained despite working under mild catalytic conditions (450 °C, catalyst/lignin = 0.2 g/g).

Rice husk ash derived nanocrystalline ZSM-5 for highly efficient removal of a toxic textile dye

Synergistic solution of two different environmental issues such as solid waste management and wastewater treatment is not just a sustainable solution but also adds to circular economy. In this study, a novel nano ZSM-5 zeolite (nZSM-5) was synthesized from agro-waste rice husk ash by two-step method for removal of industrial toxic dye crystal violet (CV) from water using ultrasonic-assisted adsorption process. The physico-chemical properties of as-synthesized nZSM-5 was examined by means of TEM, XRF, FESEM, XRD, FTIR, and BET analysis. Surface area, average pore volume, average crystal size, and product yield of nZSM-5 were found as 608.93 m2/g, 0.245 cm3/g, and 8.5 nm, 87% respectively. Also, from FESEM analysis, the average particle size was found to be 32.42 nm. Effect of solution pH (3–11), sonication time (0–60 min), adsorbent dose (50–250 mg/100 ml), and initial CV dye concentration (25–125 mg/L) on nZSM-5 was analyzed in ultrasound-assisted adsorption process. Pseudo-second order kinetic (R2 = 0.994) model and Langmuir isotherm (R2 = 0.991) model were best fitted for the adsorption of CV on nZSM-5 with maximum Langmuir adsorption capacity of 125.43 mg/g. The removal efficiency of nZSM-5 zeolite for CV dye was estimated as 99.99%. This study suggests that the synthesized novel nZSM-5 zeolite is a highly efficient adsorbent for CV dye under ultrasonication.

Cerium Incorporated Nanocrystalline ZSM-5: An Efficient Catalyst for Friedel Crafts Acylation of Toluene.

In this paper, the application of cerium modified nanocrystalline zeolite ZSM-5 as catalyst for Friedel Crafts acylation of toluene was investigated and compared with nanocrystalline ZSM-5. The acylating agent used was acetic anhydride. The zeolite samples were characterized by means of Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Thermal analysis, ammonia temperature-programmed desorption (NH₃-TPD) and Nitrogen sorption analysis. The results show an enhanced Lewis acidity, pore volume and surface area for cerium modified ZSM-5 providing a superior accessibility for acetic anhydride and toluene to the active sites compared to the unmodified one, thereby leading to 93% conversion of acetic anhydride, which was higher than that of unmodified ZSM-5 sample.

Fine-tuning hierarchical ZSM-5 zeolite by controlled aggregation of protozeolitic units functionalized with tertiary amine-containing organosilane

Abstract Hierarchical ZSM-5 zeolite has been synthesized by hydrothermal crystallization of protozeolitic nanounits previously functionalized with two types of commercially available organosilanes. The first one (N,N-diethyl-3-aminopropyl-trimethoxysilane, DEAMP) is a monopodal organosilane that contains a tertiary amine group, whereas the second one (1,2-bis(trimethoxysilyl)decane, BTMDC) includes a long aliphatic chain and two tri-alkoxysilyl groups (dipodal organosilane). The properties of the samples obtained have been compared with two nanocrystalline ZSM-5 materials as references. While both organosilanes are effective in generation of a secondary porosity, enhancing strongly the textural properties of ZSM-5 zeolite, DEAMP affords for more uniform nanounits in the aggregates with narrower mesopore size distribution compared to BTMDC. On the other hand, varying the concentration of DEAMP during the silanization step (in the range of 2.5–10 mol%, referred to the silica content of the synthesis gel) it has been possible to synthesize hierarchical ZSM-5 samples showing progressively smaller size of the nanounits in the aggregates. This fact has led to important changes in both the textural and acid properties of the zeolite samples. In particular, a decrease in the Bronsted/Lewis acid sites ratio has been observed with increasing the concentration of DEAMP introduced in the synthesis gel. These materials have been tested as catalysts for low-density polyethylene (LDPE) cracking, showing enhanced catalytic activity in comparison with the two reference nanocrystalline ZSM-5 samples. A maximum of the LDPE conversion has been obtained with the h-ZSM-5 zeolite prepared with 5 mol% of silanization agent as this material exhibits an optimum combination of acidic features and accessibility.

Improved biofuel quality in catalytic cracking of triglyceride-rich biomass over nanocrystalline and hierarchical ZSM-5 catalysts

Improved biofuel quality in catalytic cracking of triglyceride-rich biomass over nanocrystalline and hierarchical ZSM-5 catalysts

Hydrotreating of Guaiacol and Acetic Acid Blends over Ni2P/ZSM-5 Catalysts: Elucidating Molecular Interactions during Bio-Oil Upgrading.

Catalytic hydrodeoxygenation (HDO) is an effective technology for upgrading pyrolysis bio-oils. Although, in the past years, this process has been extensively studied, the relevance of the cross-reactivity between the numerous chemical components of bio-oil has been scarcely explored. However, molecular coupling can be beneficial for improving the bio-oil characteristics. With the aim of gaining a better understanding of these interactions, this work investigates the catalytic hydrodeoxygenation of mixtures of two typical components of pyrolysis bio-oils: guaiacol and acetic acid. The catalytic tests were carried out employing a bifunctional catalyst based on nickel phosphide (Ni2P) deposited over a commercial nanocrystalline ZSM-5 zeolite. The influence of both hydrogen availability and temperature on the activity and product distribution, was evaluated by carrying out reactions under different H2 pressures (40–10 bar) and temperatures (between 260 and 300 °C). Using blends of both substrates, a partial inhibition of guaiacol HDO occurred because of the competence of acetic acid for the catalytic active sites. Nevertheless, positive interactions were also observed, mainly esterification and acylation reactions, which could enhance the bio-oil stability by reducing acidity, lowering the oxygen content, and increasing the chain length of the components. In this respect, formation of acetophenones, which can be further hydrogenated to yield ethyl phenols, is of particular interest for biorefinery applications. Increasing the temperature results in an increment of conversion but a decrease in the yield of fully deoxygenated molecules due to the production of higher proportion of catechol and related products. Additional experiments performed in the absence of hydrogen revealed that esterification reactions are homogeneously self-catalyzed by acetic acid, while acylation processes are mainly catalyzed by the acidic sites of the zeolitic support.

Heterogeneity of nano-sized zeolite crystals

Abstract Analytical characterization and evaluation of performance of zeolite catalysts are normally done under the assumption of a homogeneous batch. However, it is known that in the same batch particles of the zeolite ZSM-5 can be very different one from another, regarding their aluminum content and catalytic performance. Here, we quantify the extent of this heterogeneity within a singular synthesis batch of nanocrystalline ZSM-5, through the analysis of single crystalline individua. We found that the overall aluminum content was distributed unequally between two kinds of crystal populations. Cornered crystals contained three times more aluminum than round-shaped crystals. This observation connects morphological differences to the chemical composition of each zeolite crystal for the first time. This finding could provide a means for performance optimization in zeolite synthesis.

Conversion of Stearic Acid into Bio-Gasoline over Pd/ZSM-5 Catalysts with Enhanced Accessibility

Palladium supported on nanocrystalline ZSM-5 (n-ZSM-5, Si/Al = 32) and hierarchical ZSM-5 (h-ZSM-5) with different acidity (Si/Al = 33, 51, 122) were tested in the liquid-phase conversion of stearic acid under nitrogen atmosphere (6 bar). The incorporation of Pd into ZSM-5 zeolite increased significantly the share of gasoline in the reaction products due to the promotion by this metal of both decarboxylation and hydrogen transfer reactions. Likewise, the Pd nanoparticles dispersed over the zeolitic support favored the conversion of light olefins formed by end-chain cracking reactions into gasoline-range hydrocarbons according to an oligomerization/cyclization/aromatization pathway. Additionally, Pd/h-ZSM-5 gave rise to higher conversion and selectivity towards gasoline than Pd/n-ZSM-5, due mainly to the enhanced accessibility and improved Pd dispersion achieved when using the hierarchical zeolite. The decrease in the Si/Al atomic ratio in Pd/h-ZSM-5 samples resulted in a rise in the stearic acid conversion, although it was lower than expected. This finding denotes that, for supports with high acid sites concentration, the Pd availability became the limiting factor as the metal was loaded in similar amounts in all catalysts. Finally, the increase of the reaction temperature with the Pd/h-ZSM-5 (122) catalyst augmented both stearic acid conversion and gasoline selectivity, since it enhanced the conversion of the light olefins, formed as primary cracking products, into liquid hydrocarbons. Therefore, it can be concluded that Pd supported on hierarchical ZSM-5 zeolite is a convenient catalyst for obtaining bio-gasoline from oleaginous feedstock.

Scaling-Up of Bio-Oil Upgrading during Biomass Pyrolysis over ZrO2 /ZSM-5-Attapulgite.

Ex situ catalytic biomass pyrolysis was investigated at both laboratory and bench scale by using a zeolite ZSM-5-based catalyst for selectively upgrading the bio-oil vapors. The catalyst consisted of nanocrystalline ZSM-5, modified by incorporation of ZrO2 and agglomerated with attapulgite (ZrO2 /n-ZSM-5-ATP). Characterization of this material by means of different techniques, including CO2 and NH3 temperature-programmed desorption (TPD), NMR spectroscopy, UV/Vis microspectroscopy, and fluorescence microscopy, showed that it possessed the right combination of accessibility and acid-base properties for promoting the conversion of the bulky molecules formed by lignocellulose pyrolysis and their subsequent deoxygenation to upgraded liquid organic fractions (bio-oil). The results obtained at the laboratory scale by varying the catalyst-to-biomass ratio (C/B) indicated that the ZrO2 /n-ZSM-5-ATP catalyst was more efficient for bio-oil deoxygenation than the parent zeolite n-ZSM-5, producing upgraded bio-oils with better combinations of mass and energy yields with respect to the oxygen content. The excellent performance of the ZrO2 /n-ZSM-5-ATP system was confirmed by working with a continuous bench-scale plant. The scale-up of the process, even with different raw biomasses as the feedstock, reaction conditions, and operation modes, was in line with the laboratory-scale results, leading to deoxygenation degrees of approximately 60 % with energy yields of approximately 70 % with respect to those of the thermal bio-oil.

Starch Coated Silica Nanospheres Parenting the Growth of Trimodal Porous Zeolites for Catalysis Involving Large Molecules

A simple method for the synthesis of nanocrystalline ZSM-5 and Beta zeolites with trimodal porosity was developed using starch coated silica nanospheres (as silica precursor) for generating interparticle porosity (50–200 nm); propyltriethoxysilane was used as an additive for generating intercrystalline mesopores (2–50 nm) in the presence of microporous zeolite porogen. Loading of starch and propyltriethoxysilane additive played a pivotal role in obtaining trimodal porosity with very small size zeolite nanoparticles having high surface area and pore volume. The possible growth mechanism for the fabrication of trimodal porous zeolite is presented. The resultant zeolite demonstrated excellent acidity and activity in the liquid phase acid catalyzed reactions such as esterification of hexanoic/oleic acid with benzyl alcohol, condensation of benzaldehyde and 2-hydroxyacetophenone, and Friedel–Crafts alkylation followed by ring closure reaction for the synthesis of vitamin E when compared to conventional zeolite with excellent recyclability. Such an economical starch mediated synthesis strategy can be extended to other zeolite frameworks and similar heterogeneous catalytic materials.