Development Of Mesoporosity Research Articles

RATIONAL CONDITIONS OF PRODUCING THE ACTIVATED CARBON WITH WELL-DEVELOPED NANOPOROUS STRUCTURE FOR THE TREATMENT OF NATURAL AND WASTE WATERS

Rational conditions for the activation of coal of a high stage of metamorphism (anthracite) have been determined, which allow the development of a nanoporous structure. Obtained activate carbon with nanoporous structure can be use for the treatment of natural and waste waters have been carried out. The structurally sorptive characteristics and granulometric size composition of obtained samples were determined. It was established that in order to obtain a sorbent with specified properties, it is necessary to introduce oxygen into the reacting mixture at the second stage of anthracite activation and control the activation time. The activation in the first stage was carried out with steam at a temperature of 750–800 °C, and in the second stage – with steam in the presence of air oxygen at 280–300 °C. The rational content of oxygen in the activating mixture is in the range of 2.7–4.4 %, while the specific surface area of activated carbon increases, which corresponds to nano-sized pores and, accordingly, the volume of the adsorption space of coal. The process led to the development of mesoporosity ~ 0.2–0.3 cm3/g, after which the microporous sample of activated carbon was impregnated with a surfactant solution. Thus, the rational conditions of activation are the duration of the process of 1.5 hours in the presence of 4.4 % oxygen in the activating mixture. It is shown that the largest values of the total specific surface area and the specific surface area of mesopores are achieved when using ionic surfactants with alkyl chain length n = 10–16 as modifiers. In particular, the use of sodium dodecyl sulfate СН3(СН2)11SO3Na as a modifier allows to obtain the largest value of the total surface Stot 1030 m2/g and the surface of mesopores Smе 334 m2/g. It was established that the activation of modified samples of activated carbon leads to a decrease in the size of granules.The content of fractions with a size of 1.0–2.0 mm and 0.5–1.0 mm is 80–85 %, which are rational for use for water purification from organic compounds.

Time-Dependent Development of Mesoporosity in Ionic Liquid Treated Cellulosic Materials

Natural Fiber Welding (NFW) is process that leverages the unique solvating power of ionic liquids (IL) to mobilize a natural fiber’s outermost polymer strands and enable these mobile polymers to reconfigure and interact with mobilized polymers of adjacent fibers. Upon removal of the ionic liquid via a solvent exchange and drying process, the biopolymer material is welded into a new matrix while still maintaining the vast majority of its native structural hierarchy. Recent work in our laboratory has shown relatively simple modifications to the NFW process can drastically impact the modified matrix morphology, particularly regarding surface structure. Changes in polarity during the solvent exchange process, for instance, can be used to very the surface area over a 1000-fold and produce high surface are materials with tunable mesoporosity. In the present work we investigate the impact of variable ionic liquid treatment time on the development of mesoporosity in fiber welded cotton substrates. Nitrogen gas adsorption/desorption measurements were employed to evaluate changes in surface area and pore size with ionic liquid treatment time. Raman spectroscopy was carried out on epoxy potted material cross sections to assess the impact of treatment time on cellulose decrystallization, and epoxy penetration measured by Raman spectroscopy was used to evaluate the continuity of the mesoporous regions and further asses material porosity.

Premixed precursors to tailor porosity in porous carbons for improved capacitive properties: Towards predicting the texture properties of carbonaceous matter

It is important to tune the texture properties of porous carbon to improve the specific capacitance and understand the activation behaviors of the carbonaceous matter. Herein, the specific surface area of the porous carbons derived from pine sawdust (PS)/polypyrrole (PPY) blends was higher than that which might be obtained with either precursor alone. Porous carbons characterized by ultrahigh specific surface areas (as high as 3382.60 m2/g) and total pore volumes (as high as 2.12 cm3/g) were prepared from the premixed precursors. The texture properties can be tuned by selecting the ratio of the premixed precursors, which is feasible to yield porous carbon with high specific surface area and high mesoporosity under the same activation conditions. The elemental composition of the precursors, especially the C element content and O/C ratio, are crucial factors in establishing the specific surface area and mesoporosity development. The properties of the as-fabricated porous carbons were studied, and it was observed that when the current density was 0.5 A/g, the specific capacitance of the porous carbon derived from a 1:1 mixture of PPY and PS (PPYPS11C) was 373.75 F/g when determined using the three-electrode system and 242.55 F/g when determined using the two-electrode system. Moreover, PPYPS11C exhibited good cycling stability, with a high energy density of 33.69 Wh/kg at 626.42 W/kg. This work offers a novel approach to tailor the texture properties of porous carbon to match specific applications such as supercapacitors.

Mesoporosity and Acidity Manipulation in ZSM‐23 and theirn‐Hexadecane Hydroisomerization Performance

AbstractThe enhanced mesoporosity in the networks is expected to offer a potential route to surmount mass‐transport constraints within one‐dimensional microporous structural zeolites. Highly crystalized ZSM‐23 zeolite was synthesized and subsequently post‐treated with alkali‐etching and acid‐etching, the effects of post‐treatments on the physical and chemical properties of the parent zeolite were investigated via XRD, N2physical adsorption, FE‐SEM, TEM,27Al MAS NMR, Py‐IR and NH3‐TPD. The catalytic activity of various Pt supported bifunctional catalysts was investigated vian‐hexadecane hydroisomerization. The post‐treated process not only increased the pore volume as well as the specific surface area, which efficiently improved the diffusion efficiency, but also changed the acidity and acid distribution of zeolite: alkali treatment could increase the content of total Brönsted acid while acid treatment exhibited an opposite trend. Acid treatment effectively promoted the density of weak Brönsted acid sites and suppressed the med‐strong Brönsted acid sites. With the manipulation of acidity and development of mesoporosity in zeolite, the formation of isomers and the suppression of cracked products in then‐hexadecane hydroisomerization were accomplished. The catalytic performance of catalysts showed that acid treatment could effectually promote the formation of isomeric products and inhibit cracking reactions. Especially, Pt/Z(1.0 HN) catalyst with suitable distribution of acid sites and textural properties, exhibited an outstandingn‐C16hydroisomerization performance with the highesti‐C16yield of 64 wt.% at 340 °C.

Fabrication of highly mesoporous ZSM-48 zeolite by anionic surfactant-organosilane system for catalytic conversion of methanol to gasoline

A highly mesoporous ZSM-48 zeolite has been prepared using low-cost anionic surfactant sodium dodecylsulphate (SDS) as mesopore-generating agent and short-chain 3-aminopropyltrimethoxysilane (APTMS) as co-structure directing agent. The mesoporosity formation took place through the interaction between the silica species/APTMS and SDS molecules existing in the gel composition. In the synthesis solution with a pH slightly less than ten, the methoxysilyl moiety in APTMS was hydrolysed to the –SiO3 units and became incorporated inside the zeolite crystals while the positively charged ammonium site of APTMS interacted with the negatively charged head group of the SDS. Aggregation of aluminosilicate/APTMS species around the SDS micelles during the crystallization process, led to the formation of a mesoporous zeolite. In this study, a conventional ZSM-48 and seven ZSM-48 zeolites from different mixtures containing SDS, APTMS and SDS-APTMS with different APTMS/SiO2 molar ratios were synthesized. Changes in the properties of the synthesized samples were investigated by XRD, FTIR, SEM, TEM, nitrogen adsorption/desorption isotherms, NH3-TPD and TGA. The optimum ZSM-48/Sur/0.008OS zeolite prepared with APTMS/SiO2 molar ratio of 0.008 exhibited both bundled needle-like and spherical morphologies. The catalytic conversion of methanol to gasoline (MTG) was evaluated in a fixed-bed reactor, and the results revealed that mesoporosity development using Sur-OS system enhanced catalytic activity of ZSM-48/Sur/0.008OS catalyst compared to the other sample. The optimum zeolite showed long stable phase of 40 h and liquid hydrocarbon yield of 42% was achieved for 100% methanol conversion in 22 h of reaction. The proposed method opens a new and simple route for the synthesis of hierarchically porous ZSM-48 with tunable porosity using low-cost anionic surfactants.

Hierarchical Catalysts Prepared by Interzeolite Transformation.

Interzeolite transformation has been used to produce a novel family of hierarchical catalysts featuring excellent textural properties, strong acidity, and superior catalytic performance for the Friedel–Crafts alkylation of indole with benzhydrol, the Claisen–Schmidt condensation of benzaldehyde and hydroxyacetophenone, and the cracking of polystyrene. Intermediate solids of the FAU interzeolite transformation into BEA display both increased accessibility—due to the development of mesoporosity—and strong acidity—caused by the presence of ultrasmall crystals or zeolitic fragments in their structure. The use of surfactants allows for the development of the hierarchical catalysts with very narrow pore size distribution. The properties of interzeolite transformation intermediates (ITIs) can be fine-tuned simply by stopping the interconversion at different times.

Impact of Hierarchization on the Textural Properties of MCM‐22 Based Zeolites

AbstractThe impact of zeolite hierarchization is often highlighted in terms of increased mesopore volume or specific surface area and preservation of micropore volume. Yet, although these targets may be achieved, the accessibility to certain micropores might be negatively affected during hierarchization. A set of hierarchical MCM‐22 based materials is prepared based on desilication treatments of MCM‐22, of the layered precursor MCM‐22(P) and of the hexadecyltrimethylammonium bromide (CTAB) swollen precursor swMCM‐22(P), and by the pillaring of swMCM‐22(P) leading to MCM‐36. A new methodology is presented based on comparing the micropore volume of pristine materials with their n‐nonane retaining counterparts. A definition of the accessible micropore volume fraction is given, which relates to the amount of surface 12‐MR cups. This approach hence allows quantifying which type of microporosity is preferentially destroyed during hierarchization treatments of MCM‐22. Besides comparing the development of mesoporosity, specific surface area, and the evolution of micropore volume during hierarchization treatments, the accessible micropore volume fraction allows for a distinct definition of the hierarchization quality for MCM‐22 based materials. Despite an important increase in interlayer‐mesopore volume and specific surface area for MCM‐36, the accessible micropore volume fraction is found to be just 3% higher than for MCM‐22.

Synergistic performance of simply fabricated polyaniline/carbon xerogel composite as supercapacitor electrode

Abstract This work involves preparation of loaded polyaniline (PANI)/carbon xerogel (CX) composites with different mass ratios. The effect of PANI loading on the porosity and electrochemical activity of the composites is studied. Surface characterization analysis of studied samples reveals that incorporation of PANI onto the CX network reduces its specific surface area with a simultaneous expansion of the average pore diameter from the microporous to the mesoporous range. The prepared composites are tested as supercapacitor electrodes, and their electro-capacitive properties are studied by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy in a two-electrode cell using 1 M H2SO4 electrolyte. Results show that introducing PANI into CX network enhances the gravimetric capacitance from 156 to 612 F ∙ g−1 at current density of 0.1 A ∙ g−1 with reasonable stability. For instance, sample composite of PANI:CX = 5:1 w/w displays a retention percentage of 87.6% after 1500 repetitive cycles. In general, this synergy between PANI and CX in the prepared composites is attributed to the development of mesoporosity and the lowering of electrode resistance.

Heterogeneous acid catalyst preparation from olive pomace and its use for olive pomace oil esterification

Solid acid catalyst was produced from olive pomace (OP), characterized and used for the esterification of OP oil. OP was pyrolyzed, physical activated by steam and sulfonated using sulfuric acid. Commercial, coconut husk-based, activated carbon (CHAC) was also sulfonated for comparison. The activation has shown a significant increase in olive pomace activated carbon (OPAC) surface area by developing simultaneously its micro and meso-porosity. The sulfonation has further increased OPAC BET surface area to reach 618.18 m2/g and has changed its structure to become microporous. Sulfonation also removed tar residues and aliphatic hydrocarbons from OPAC’s surface. Tendencies observed with carbon CHAC, used for comparison, are slightly different with a mesoporosity development. Although its higher surface area (1227.01 m2/g), CHAC has fixed three times less sulfur than OPAC, which can be attributed to its higher hydrophobicity or pore distribution. Sulfur was mainly fixed in the form of sulfonic acid (SO3H). Esterification with methanol using produced solid catalysts decreased OPO acidity below the 2 mgKOH/g threshold after 5 h of reaction and reduced mono, di and triglycerides to levels close to the ones required by European norm EN14214.

The order of addition and time matters: Impact of electrolyte processing on micelle-assisted electrosynthesis of mesoporous alloys

Mesoporous thin films are currently awaking a considerable interest for their prospective use in applications ranging from catalysis to energy storage. Yet, some of the synthetic parameters enabling a reproducible development of mesoporosity remain uncontrolled. In this research, we demonstrate that a subtle change in the procedure for the electrolyte preparation for the electrosynthesis of mesoporous Co‒Pt films is critical for reproducing the mesoporosity of the alloys. Specifically, we show that dissolution of the platinum salt (Na2PtCl6·6H2O) in water and storage of the solution (referred to as ‘equilibration time’) before adding the remaining reagents and additives (CoCl2 and P-123) are imperative to consistently reproduce the films mesoporosity. Highly mesoporous Pt-rich Co‒Pt films (10–23 at.% Co), with a pore diameter of 10‒17 nm, were obtained from an electrolyte that involved an equilibration time, while mesoporosity was often absent in films grown from a freshly prepared electrolyte (i.e., upon dissolving all chemicals immediately before electrodeposition). The results suggest that pore formation is governed by the complexation dynamics of Pt(IV) in water, which was investigated by UV–vis spectroscopy. Namely, the concentration of hydroxochloroplatinate complexes ([PtCl6-x(OH)x]2–) originating from the exchange of Cl– by OH– ions increase during the equilibration time. [PtCl6-x(OH)x]2– species would interact more favorably with the hydrophilic poly(ethylene oxide) moieities of P-123 micelles than [PtCl6]2–. The distinct interaction between micelles and the complexes of platinum is key for the reproducible generation of a mesoporous network. Our finding highlights the relevant role of electrolyte processing for the control of mesoporosity in metallic systems prepared by micelle-assisted electrodeposition, which we believe can be extended to many electrolytic processes.

Heteroatom doped carbon nanosheets from waste tires as electrode materials for electrocatalytic oxygen reduction reaction: Effect of synthesis techniques on properties and activity

The effective method for synthesis of heteroatom doped carbon nanosheets (CNS) from waste tires was developed. The process employed NiO loaded CaCO3 catalyst for catalytic chemical vapor deposition (CCVD) of the CNS from the non-condensable pyrolysis gas. The promotion of CaCO3 with NiO had beneficial effect on carbon growth compared to pure CaCO3, increasing the carbon yield by 2.8 and 8.0 times for the CCVD at 700 and 750 °C, respectively. On the contrary, the morphology and structure of synthesized S,O-doped CNS as well as oxygen reduction reaction (ORR) electrocatalytic activity were not influenced by the NiO addition. Based on the carbon yields and ORR electrocatalytic activities, the preferred CCVD temperature was 700–750 °C, resulting in the CNS with the ORR peak reduction potentials of −0.217 V to −0.220 V (versus −0.167 V for Pt electrode). The improvement of CCVD process was proposed decreasing the ORR peak reduction potential to −0.191 V. A mixture of NH3 and H2O was added to pyrolysis gas, promoting the development of mesoporosity and incorporation of N into the material structure. The developed technique is a viable solution for the conversion of non-condensable gases from tire pyrolysis into S,N,O-doped CNS for ORR.

Development of intracrystalline mesoporosity in NH4HF2-etched NaY zeolites by surfactant-templating and its effect on toluene adsorption

Volatile organic compounds have seriously affected the natural environment and human health, and adsorption is one of the most effective method for controlling VOCs pollution. In this work, the NH4HF2-etched NaY-s-x zeolites with intracrystalline mesoporosity are obtained via the surfactant-templating process in weak base NH4OH solution. The morphology, microstructure, and toluene adsorption property of as-prepared hierarchical Y zeolites are systematically characterized. It is found that the structural and textural properties of NH4HF2-etched NaY samples are significantly changed by the simple surfactant-templated approach and the large-sized mesopores inside NH4HF2-etched NaY sample disappear to form the surfactant-templated mesoporosity with a size of ~4 nm. It is demonstrated that the intracrystalline mesoporosity obviously improves the toluene molecular adsorption properties of zeolite samples. Moreover, the mechanism of the surfactant-templating process is elucidated.

Role of Nitrogen on the Porosity, Surface, and Electrochemical Characteristics of Activated Carbon.

Surface functionalities of activated carbon can be affected by the presence of heteroatoms such as oxygen, sulfur, and nitrogen. In this work, nitrogen-doped activated carbons (NACs) were prepared from shrimp shells, and the effects of the mixing ratio (raw material to an activating agent) on the porous texture and surface functionalities were investigated. It was found that, with increasing the mixing ratio (resulting in increasing N/C), the development of mesoporosity was significantly observed. This led to decreasing microporosity and specific surface areas (SSAs). The obtained NACs exhibited nitrogen functionalities in the forms of pyridinic and pyrrolic groups. It was found that although the pyridinic-N has a detrimental effect on the SSA, it does favor the pseudocapacitance, leading to an enhancement in the ion storage capability regardless of the low SSA.

Catalytic activity of facilely synthesized mesoporous HZSM-5 catalysts for optimizing the CO2 desorption rate from CO2-rich amine solutions

Post-combustion CO2 capture using aqueous alkanolamine solutions has a great potential to reduce anthropogenic CO2 emissions but the large-scale deployment of this technique is hindered due to a highly energy-intensive solvent regeneration mainly because of poor CO2 desorption kinetics. To overcome this limitation, we synthesized a series of mesoporous HZSM-5 catalysts through facile alkaline desilication and surfactant-induced re-assembly of dissolved species originating from the parent HZSM-5 crystals, and evaluated their performance to optimize the CO2 desorption rate from benchmark 30 wt% monoethanolamine (MEA) solution under mild temperature condition (40–82 °C). X-ray diffraction (XRD) patterns showed that the synthesized catalysts retained their crystallinity. Desilication by treatment in the alkaline medium led to a remarkable development of mesoporosity, with an increase in the Brunauer–Emmett–Teller (BET) surface area as well. The experimental results suggested that the synthesized catalysts significantly enhanced the CO2 desorption rate at low temperatures (up to 350–580% at ≤82 °C), improved the total amount of desorbed CO2 up to 60%, and minimized the heat duty by 24–37%. Detailed characterization revealed that the synergistic effect of higher mesoporosity and increased number of Lewis acid sites (LAS) and Brønsted acid sites (BAS) was crucial to improve the CO2 desorption rate. Based on the characterization and experimental results, a plausible reaction mechanism for catalyst aided CO2 desorption was also presented. This investigation highlights the role of catalysts in optimizing the CO2 capture process and presents new understanding for the design of high-performance catalysts for this purpose.

Synthesis, characterization and evaluations of micro/mesoporous ZSM-5 zeolite using starch as bio template

We report a simple and economical method to synthesis hierarchical ZSM-5 zeolite using a natural polymer, soluble starch, as a mesotemplate. The synthesized samples were characterized with X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, nitrogen sorption, ammonia temperature-programmed desorption and thermogravimetric analysis. The crystallinity and Mordenite Framework Inverted structure of the samples was confirmed by X-ray diffraction and Fourier transform infrared spectroscopy analysis. Scanning electron microscopy and transmission electron microscopy images revealed the presence of mesopores in the synthesized samples. The nitrogen adsorption/desorption results of the hierarchical samples have been found to be in agreement with the scanning electron microscopy and transmission electron microscopy results and support the development of mesoporosity. The acidity of the hierarchical zeolite was studied using ammonia temperature-programmed desorption. The thermogravimetric analysis confirmed the thermal stability of the synthesized samples up to 750 °C. The catalytic activities of the modified and unmodified zeolites were specifically tested for the esterification of acetic acid with benzyl alcohol. The results indicate that the hierarchical ZSM-5 catalyst offers a better catalytic yield (76%) than the unmodified systems.

Carbon Xerogels Hydrothermally Doped with Bimetal Oxides for Oxygen Reduction Reaction.

A total of two carbon xerogels doped with cobalt and nickel were prepared by the sol–gel method. The obtained carbon xerogels underwent further surface modification with three binary metal oxides namely: nickel cobaltite, nickel ferrite, and cobalt ferrite through the hydrothermal method. The mesopore volumes of these materials ranged between 0.24 and 0.40 cm3/g. Moreover, there was a morphology transformation for the carbon xerogels doped with nickel cobaltite, which is in the form of nano-needles after the hydrothermal process. Whereas the carbon xerogels doped with nickel ferrite and cobalt ferrite maintained the normal carbon xerogel structure after the hydrothermal process. The prepared materials were tested as electrocatalysts for oxygen reduction reaction using 0.1 M KOH. Among the prepared carbon xerogels cobalt-doped carbon xerogel had better electrocatalytic performance than the nickel-doped ones. Moreover, the carbon xerogels doped with nickel cobaltite showed excellent activity for oxygen reduction reaction due to mesoporosity development. NiCo2O4/Co-CX showed to be the best electrocatalyst of all the prepared electrocatalysts for oxygen reduction reaction application, exhibiting the highest electrocatalytic activity, lowest onset potential Eonset of −0.06 V, and the lowest equivalent series resistance (ESR) of 2.74 Ω.

Optimization of desilication parameters in fabrication of mesoporous ZSM-48 zeolite employed as excellent catalyst in methanol to gasoline conversion

Mesoporous ZSM-48 zeolite was prepared by alkaline desilication at optimized conditions using central composite design (CCD) under response surface methodology (RSM). Statistical models were designed to predict high BET surface area, high mesopore volume and specified mean pore diameter. The desilication temperature and NaOH solution concentration were varied in the ranges 0.1–0.3 M and 60–80 °C respectively. It was found that the NaOH concentration was more effective factor than temperature for mesoporosity development in ZSM-48 zeolite. Variance analysis showed that CCD equations were significant for the desilication parameters (R2 = 0.98 for mesopore volume, R2 = 0.95 for BET surface area and R2 = 0.98 for mean pore diameter). The influence of the post-synthesis desilication on the pore characteristics, crystallinity, morphology and acidity of the optimized zeolite was examined using N2-adsorption, XRD, SEM and NH3-TPD respectively. The optimal mesoporous ZSM-48 zeolite had a BET surface area of 154 m2 g−1, mesopore volume of 0.22 cm3g-1 and mean pore diameter of 6.93 nm. The MTG reaction was performed in a fixed-bed stainless-steel reactor at 390 °C and weight hourly space velocity of 4.75 h−1. The catalytic results illustrated that the modification of the catalyst extensively influenced the liquid hydrocarbons distribution. Over mesoporous ZSM-48 catalyst, the selectivity to branched alkanes, alkenes and cyclic non-aromatic compounds partly decreased while that to aromatics substantially increased relative to parent catalyst. The aromatics yield reached up to 78%. Furthermore, the yield of liquid hydrocarbons and catalyst life time increased about 29% and 34% respectively relative to microporous ZSM-48.

Template-free synthesis of Ta3N5 hollow nanospheres as a visible-light-driven photocatalyst

Ultrathin mesoporous Ta3N5 hollow nanospheres were synthesized via a facile and orchestrated template-free solution-based synthesis followed by thermal nitridation. A systematic investigation of structural evolution with annealing revealed a progressive crystallization with concurrent development of mesoporosity and modification of chemical composition with nitridation time. Subsequent performance of as-prepared photocatalysts were evaluated by the degradation of methylene blue under visible light irradiation (λ > 400 nm). Ta3N5 hollow nanospheres exhibited higher photocatalytic activity than Ta3N5 nanorods or bulk Ta3N5, which can be attributed to their engineered structure as well as the oxygen and nitrogen content.

Synthesis and Characterization of Fe-Co/meso-HZSM-5: Effect of Impregnated Ratio of Iron and Cobalt

The combination of bimetallic Fe-Co (as polymerization catalyst) and HZSM-5 (as cracking catalyst) could convert synthesis gas to biofuel in one-step Fischer-Tropsch synthesis. Mesoporous HZSM-5 gave better conversion, because it increased reactants and products diffusivity. The effect of impregnated ratio of iron and cobalt on characterization of Fe-Co/meso-HZSM-5 catalyst had been studied. HZSM-5 was made from ammonium ZSM-5 through calcination process, then it was desilicated with NaOH and impregnated with 10% metal loading and 0-100% Fe content in Fe-Co (%w). The material results were reduced continuously by hydrogen at 400° for 10 hours. Treatment of HZSM-5 in various ratio of iron and cobalt leads to mesoporosity development. The iron and cobalt impregnation decreased the total surface area from 350.859 m2/g (on HZSM-5) to 231.852-329.606 m2/g (on Fe-Co/HZSM-5). Increasing cobalt content in Fe-Co impregnation on HZSM-5 decreased total surface area and increased average pore diameter. Impregnation process lowered the crystallinity but still maintained the material crystal structure. The catalyst reduction produced Fe, Co, alloy Fe-Co and less oxides of Fe2O3 and Co3O4. The largest alloy Fe-Co could be found in 30Fe-70Co/HZSM-5. Iron and cobalt impregnation occupied the active sites formed from alcohol groups function that was indicated with decreasing alcohol groups area in FTIR spectra.

Engineering the Catalytic Properties of HZSM5 by Cobalt Modification and Post-synthetic Hierarchical Porosity Development

Hierarchical zeolites have been identified as special catalytic materials with improved catalytic properties. In this study, hierarchical bifunctional ZSM5 based catalysts were prepared by desilication for controlled mesoporosity development and have been modified by Co doping. Their performance in the catalytic pyrolysis of oak in a lab scale reactor was evaluated. Desilicated counterparts were proven more active in deoxygenation of bio oil, while carbon deposition on the catalysts reduced compared to non-desilicated counterparts. Increased Lewis acidity favors decarboxylation reactions, while higher olefins as well as PAH content indicate easier diffusion within and from the porous network and interactions in the mesopores. The conversion of bulky lignin molecules (alkoxy phenols) is enhanced by the mesopores, while acidity is of secondary importance. Coke deposition inside the pores is more profound in the desilicated catalysts due to larger pore size. Carbon deposition on the catalysts is reduced in the following order: HZSM5 > Co/HZSM5 > Ds-HZSM5 > Co/Ds-HZSM5. GC–MS characterization of the CH2Cl2 soluble coke indicated that for the desilicated counterparts the main coke precursors are the bulky lignin molecules which are partially deoxygenated.