Mesopore Volume Research Articles

Investigation of the properties of high-strength fibers by methods of physico-chemical analysis

The carbon fiber (CF) of UMT 49-12K-ER grade, manufactured by Alabuga-Volokno LLC (Umatex JSC), was the subject of an extensive study. This investigation encompassed an analysis of its physico-chemical properties. The interplanar dimensions and chemical composition of the CF were determined using X-ray diffraction and atomic emission spectroscopy. Surface properties of the CF, including specific surface area and pore size distribution, were investigated through nitrogen adsorption. The BET specific surface area was measured at 0.29 m2/g. The volume of mesopores and their size distribution were calculated using the Barrett, Joyner, and Halenda method. Additionally, an analysis of surface functional groups was conducted through a back titration method. It was observed that there was no presence of carboxyl, phenolic, or carbonyl groups. The diffraction patterns were processed with a two-component profile description model. The results of atomic emission spectral analysis revealed that silicon compounds were the dominant impurities in the chemical composition of the CF. Further investigations determined that, in an inert environment, the epoxy coupling agent used to enhance the performance properties of this CF undergoes thermal decomposition at temperatures of 300–400 °C. The CF itself does not experience weight loss when heated up to 950 °C. It was also discovered that this CF ignites in the presence of oxygen at temperatures exceeding 550 °C, surpassing the thresholds noted in previous publications for carbon fibers without such specialized additives. The results of this research have suggested new methodologies for studying carbon fibers.

Synthesis of hierarchically radiated SAPO-11/Silica composites to boost n-alkane hydroisomerization

Hierarchically radiated SAPO-11 molecular sieves (RS-11-x, x was the initial SiO2/Al2O3 molar ratio) were prepared by employing different amounts of un-calcined radiated mesoporous SiO2 nanoparticles (RMSNs) as silicon source and template, and the corresponding Pt-based catalysts were applied for n-decane hydroisomerization. During the synthesis of RS-11-x, RMSNs were hydrolyzed into active Si species slowly due to the supporting of CTAB in their channels, and these active Si species interacted with Al and P species on the RMSNs to generate SAPO-11 crystal nuclei. Ultimately, hierarchical SAPO-11 molecular sieves with radiated morphologies were dispersed on the RMSNs. Among RS-11-x, RS-11-0.4 possessed the greatest medium and strong Brønsted acid sites (MSBAS) content (14.9 μmol/g) as well as superior external surface area (247 m2 g−1) and mesopore volume (0.433 cm3 g−1). Furthermore, compared with the SAPO-11 synthesized by tetraethyl orthosilicate (TEOS) and the mixture of CTAB and TEOS as silicon precursors, respectively, RS-11-0.4 possessed a larger external surface area, a higher mesopore volume and the optimal MSBAS content. Consequently, the Pt/RS-11-0.4 catalyst showed a higher selectivity of branched C10 isomers (93.5%), a better selectivity of multi-branched C10 isomers (33.8%), and a lower cracking selectivity (6.3%) than the counterpart catalysts. This work offers a new strategy for preparing hierarchical molecular sieves with superior catalytic performances.

Mineralogical control on the dissolution induced microscopic pore alternations of high-rank coal during CO2 sequestration

The microstructure of deep coal seam plays a crucial role in determining the CO2 geological sequestrations. To investigate the effects of pore and mineral distribution on the changes and mechanisms of coal microstructure under supercritical CO2 (SC–CO2) interactions, we employed low-temperature N2 (LTN2) adsorption, low-temperature CO2 (LTCO2) adsorption, and X-ray diffraction (XRD) techniques to explore the development of microstructures and mineral compositions of coal samples with distinct pore distribution characteristics under SC-CO2 exposure. The results revealed that mineral dissolution under SC-CO2 saturation led to an increase in both specific surface area (SSA) and pore volume (PV) of mesopores, with SSA increasing by 13.6%–332.31% and PV increasing by 4.59%–148.61%. Subsequently, SC-CO2 exposure induced the formation of numerous new pores with diameters smaller than 3 nm within the coal matrix, particularly an abundance of new ultra-micropores (r > 0.5 nm) and large micropores (r > 0.85 nm). This significantly altered the irregularity of pore structure and adsorption capacity, thereby playing a crucial role in CO2 storage. Micropores exhibited much larger SSA and PV than mesopores, underscoring their significant contribution to CO2 geological sequestration. The spatial mineral distribution in coal influences the alteration characteristics of pores, which explains the different microscopic pore structures formed after SC-CO2 exposure. The impact of spatial mineral distribution on SC-CO2-induced pore alteration is analysed, emphasising the intrinsic heterogeneity of minerals within coal as the fundamental factor behind the diversity observed in pore development during CO2 sequestration. Finally, we found that the changes in micropores and mesopores under SC-CO2 exposure are closely related to the initial structure of microscopic pores. The development of micropores under SC-CO2 exposure is associated with the average pore size and fractal dimension of micropores, with the increment in mesopore irregularity increasing with the increase in micropore volume fractal dimension. By studying the influence of mineral and pore distribution on the evolution of coal microstructures, this study provides new insights into pore development under SC-CO2 geological sequestration, which can be valuable for predicting reservoir development in CO2-ECBM.

Catalytic performance of mesoporous Mn-Co-Ti for o-xylene degradation: Mechanistic study under practical conditions

Catalytic combustion of volatile organic compounds from industrial flue gases at low temperatures remains a challenge. Herein, we developed a mesoporous Mn-Co-Ti catalyst for o-xylene degradation by a solvothermal strategy. The optimized Mn0.1Co-TiO2 catalyst possessed a nanoflower structures with a surface area of 83.1 m2/g and mesoporous volume of 0.1191 cm3/g. Mn-doping modulated the electronic interactions between Mn and Co, which promoted the formation of MnCo2O4.5 phase and increased Co3+ and Mn4+ content of the catalyst. The Mn0.1Co-TiO2 catalyst had an improved reduction capacity from 170 to 644 °C, with a maximum H2 consumption of 4.56 mmol/g. The Mn0.1Co-TiO2 catalyst achieved 50% o-xylene conversion at 193 °C at a GHSV of 60,000 h−1, whereas the equivalent catalyst prepared by impregnation required 315 °C for 50% o-xylene conversion. In the presence of NO, the generated NO2 accelerated o-xylene conversion because it promoted the generation of more Mn4+-O-Co3+ active sites and accumulation of intermediates such as maleate and acetate species. NH3 and H2O had slight inhibitory effects on o-xylene conversion, which were attenuated by abundant mesopores and redox ability of catalyst. SO2 gas caused inactive sulfates and chemical deactivation on catalyst surface, thus leading to excessive formation of benzoquinone products.

Hydrodepolymerization of lignin with Ni supported on active carbon catalysts reduced at different temperatures

Various Ni supported on active carbon (Ni/AC) catalysts were acquired by reduced at different temperatures, among which Ni/AC-500 possesses the smallest particle sizes of metallic Ni species, favoring to more active sites exposed on the catalyst surface, and the suitable content of metallic Ni0, implying the high hydrogenolysis activity obtained. Additionally, the highest mesoporous volume of Ni/AC-500 promotes the diffusion of large molecules from lignin depolymerization. Therefore, Ni/AC-500 exhibits the higher lignin conversion and yields of liquid bio-oil and monomers, but the lower yield of bio-char in lignin hydrodepolymerization due to its higher hydrogenolysis activity compared with other catalysts.

Triazine‐based mesoporous organic polymers as palladium supports: physicochemical properties, porosity and catalytic performance in Suzuki coupling reaction

AbstractThis article reports the preparation of new mesoporous triazine‐based organic polymers and their characterization. The polymers were synthesized via a nucleophilic condensation reaction between cyanuric chloride and bisphenols or aromatic diamine linkers. As a result, two types of triazine‐based polymers were prepared: triazine‐ether and triazine‐amine polymers. The polymers reveal a mesoporous nature with surface area values ranging between 345 and 1275 m2 g−1 and mesopore volume between 0.273 and 1.03 cm3 g−1. These values were determined from argon gas isotherms at 87 K. The pore size distribution also confirmed the micro–mesoporosity, which reached up to 3.0 nm for all polymers. The triazine‐amine polymer shows good thermal oxidative stability up to 450 °C. Motivated by the mesopore size, the new polymers were also employed as palladium nanoparticle supports. The X‐ray diffraction technique indicated the successful incorporation of palladium nanoparticles, and Fourier transform infrared measurements proved that the framework of the polymers was retained after forming palladium supports. To ensure the catalytic reactivity of palladium nanoparticles, we employed one example as a catalyst in a Suzuki coupling reaction. The catalyst exhibited remarkable recyclability, maintaining catalytic efficiency through seven cycles, thereby enabling the use of palladium‐loaded triazine‐based polymeric catalysts in a variety of organic reactions in future. © 2023 Society of Industrial Chemistry.

Alkylation of Toluene to Mono‐benzylated Toluene over Micro‐mesoporous Zeolite: Effect of Post‐synthetic Treatment and Catalytic Application

AbstractPost‐synthetic modification using acid (HNO3) and base (NaOH) are utilised to synthesize hierarchical micro‐mesoporous zeolites with different pore structure. To investigate structural change in materials, X‐ray diffraction (XRD), Scanning electron microscope (SEM), Inductive coupled plasma‐optical emission spectrometry (ICP‐OES), 29Si and 27Al MAS NMR, and N2 adsorption‐desorption isotherms techniques were employed. Acid base titration, and ammonia‐temperature programmed desorption (NH3‐TPD) was performed to evaluate acidic characteristics of materials. As revealed by characterisation, the structure was well preserved after the modification. Hierarchical materials along with parent materials have been evaluated in the toluene alkylation with benzyl alcohol producing mono‐benzylated toluene. All zeolite samples were proved to be catalytically active by their result in the alkylation reaction. Acid treated samples were compared with base treated and parent samples. The results indicate that, base modification significantly increases the mesoporous pore volume in all zeolite as compared to acid modification. Moreover, the highest benzyl alcohol conversion was found to be 98 % in the base modified Beta, with the highest mono‐benzylated toluene selectivity (69 %). Reaction optimization was also studied by altering reaction duration, temperature, and catalyst amount. The reaction products were analysed using Gas Chromatography (GC) and confirmed using Gas chromatography mass spectrometry (GC‐MS).

Performance of Li exchange hierarchical X zeolite for CO2 adsorption and H2 separation

Li exchange hierarchical X zeolite (Li-H-X) was prepared by decationization of X zeolite by NH4Cl solution followed by Li exchange and subsequent calcination. NH4-X and Li-X were prepared to compare the results of Li-H-X. XRD, FE-SEM, EDS, N2 adsorption–desorption, and micro-/mesoporous volume were performed. The higher mesoporosity was confirmed in Li-H-X due to the framework dealumination during decationization. Static and dynamic sorption capacity of sorbents was evaluated to identify the performance of sorbent. The CO2 and H2 equilibrium adsorption capacity of Li-H-X was found to be 9.6 mmol g−1 and 0.78 mmol g−1, respectively, at 298 K and 20 bar, which was 25 % (CO2) and 30 % (H2) higher than Li-X. Static experimental data were validated using the Langmuir, Freundlich, and Sips models. The CO2 & H2 dynamic sorption capacity of Li-H-X sorbent for binary gas (CO2/H2, 25/75 %) was 4.145 mmol g−1 and 0.258 mmol g−1 at 303 K and 10 bar. The higher sorption capacity of Li-H-X was obtained due to large micro-/mesoporous volume of sorbent, which may allow to access unoccupied sites at higher pressure. This result reveals that micro-/mesoporous structure of zeolite adsorbs significantly higher CO2 from binary gas stream, which can use to separate pure H2 from gas stream.

Heterogeneous La and CeOx co-promoted SAPO-11 catalyst for catalytic upgrading of cellulose-derived volatile and methanol into hydrocarbon-rich fuels

In this paper, a series of La–Ce co-doped SAPO-11 catalysts with various La to Ce ratio were developed via wet impregnation method then employed in catalytic cellulose and methanol co-pyrolysis to produce hydrocarbon-rich biofuels. Comprehensive characterization technologies including X-ray diffraction, X-ray photoelectron spectroscopy, N2 physisorption, scanning electron microscope, transmission electron microscope, ammonia temperature-programmed desorption, Pyridine-infrared, and thermal gravimetric analyzer, were conducted to unveil the physicochemical properties, structure properties and acidity of as-prepared catalysts. Additionally the product content; aromatic selectivity and synergetic effect were also investigated. Additionally possible conversion pathway, deactivation mechanism and reusability were also deduced. La and Ce showed a certain synergetic effect and exhibited superior catalytic deoxygenation activity due to La–O and Ce-Ox species, suitable Brønsted acidity, abundant oxygen vacancies and enhanced mesopores structure, which was facilitated to promote the selectivity of hydrocarbon. Higher La content was fascinated to generate furans and ketones compounds, due to lower Brønsted acid site and smaller specific surface area. In contrast, higher CeOx content was beneficial to hydrocarbon formation via Diels-Alder reaction and dehydro-aromatization due to higher Brønsted acid site, total acidity, higher specific surface area, mesoporous pore volume as well as strong oxygen affinity of CeOx. The maximum proportion hydrocarbon, aromatics and minimum contents coke was obtained over 1La–1Ce/SAPO-11 were 77.96 %, 55.82 % and 9.81 %, respectively. Additionally, 1La–1Ce/SAPO-11 catalyst exhibited outstanding reusability and stability after four cycles; nearly ∼96 % relative content of hydrocarbon was maintained after regeneration test. Hence, the insight into the synergetic catalysis between La and CeOx species could provide a new potential possible pathway for design and synthesized efficient and eco-friendly bimetallic catalyst for selective catalytic deoxygenation organic solid waste biomass for valuable chemicals.

Micro-mesoporous ferrierite obtained using the cationic polymer Luviquat and post-synthesis treatment

This study investigated for the first time the synthesis of ferrierite zeolite through the vapor-phase transport method using the cationic polymer Luviquat as a mesopores-generating agent, followed by desilication treatment. The effect of ferrierite's textural and acid properties was then evaluated in the catalytic cracking of ultra-high molecular weight polyethylene (UHMWPE). The synthesized zeolites showed a crystallinity of 91%–100% and similar Si/Al ratios. After the desilication, there was a decrease in these values along with an increase in acidity, attributable to the extraction of structural silicon. The strong interaction between the polymer and the zeolite precursor during the self-assembly process led to the formation of intracrystalline mesoporosity. However, an internal diffusion limit and/or steric hindrance hinders the complete incorporation of the polymer into the ferrierite structure, especially at high polymer concentrations. Thus, the optimal composition was 40% Luviquat, which resulted in twice the volume of mesopores compared to the sample prepared without the polymer. The desilication of the samples synthesized with the Luviquat led to a substantial increase in mesoporosity, ranging from 67% to 183%, relative to microporous ferrierite. The introduction of mesoporosity and the modification of acid properties in ferrierite contributed to a reduction in the temperature for the cracking of UHMWPE, between 66 and 93 °C compared to the pure polymer. However, in all cases, there was an increase in the average apparent activation energy in relation to desilicated microporous ferrierite zeolite, possibly due to changes in product distribution.

Enhanced nitrogen doping on porous carbon via confining-pyrolysis method for electrocatalytic oxygen reduction

Reasonable design and development of N-doped carbon materials by post-treatment of porous carbon with melamine is an effective route to preparing low-cost and high-performance electrocatalysts toward oxygen reduction reaction. Nevertheless, melamine derivatives have been observed to rapidly escape during pyrolysis, resulting in the undesirable loss of nitrogen atoms and catalytic activity. Here, a confining-pyrolysis method was proposed to accumulate melamine in the micropores of porous carbon to prepare the object N-doped carbon material with an enhanced nitrogen doping. Because the melamine accumulated in the micropores of porous carbon, the object N-doped carbon material shows a significant enhancement in N-atom content, graphitization degree, mesopore volume, electrochemical active surface area and hydrophobic surface. Density functional theory calculations and electrocatalytic tests demonstrate that the object N-doped carbon material delivers a good electrocatalytic oxygen reduction performance. The N-doped carbon electrode displayed a close half-wave potential for alkaline ORR compared to the commercial Pt/C electrocatalyst and showed an excellent cycling stability and methanol tolerance. This work provides a cost-effective method to prepare carbon-based ORR electrocatalyst for energy devices.

Variation of pore development scenarios by changing gasification atmosphere and temperature

Finding a good replacement for the commercially produced activated carbons among the residual biochars should begin with a thorough evaluation of their pore size distribution and its development under different gasification conditions. Materials of various pore structures may be found useful depending on the applications. For some applications, ultramicroporous or supermicro-mesoporous materials may be optimal, but in general, a specific pore size distribution should be evaluated to find the best for a given application. We investigated different pore formation scenarios in several biochars gasified with steam, CO2, and diluted O2 using gas adsorption measurement and the dual gas analysis using the 2D-NLDFT model calculation. The detailed characteristics of the ultramicro-, supermicro-, and mesopore volumes showed a consistent trend of pore widening in the presence of steam at 800 °C, regardless of the steam concentration. On the other hand, steam gasification at elevated temperature (1000 °C) created highly ultramicroporous materials, and so did the reaction with diluted oxygen. We conclude that different pore formation patterns can be achieved with the modification of the gasification process and the dual gas analysis can assist in formulating guidance for tailoring chars for specific applications.

Damage characteristics of pore and fracture structures of coal with liquid nitrogen freeze thaw

Liquid nitrogen (LN2) fracturing technology is a novel waterless fracturing technology that has significant potential for application in the development of coalbed methane. However, the changes in the microstructure after coal samples are treated with LN2 freeze thaw are poorly understood. Therefore, a combination of mercury intrusion porosimetry and micro-computed tomography (micro CT) was employed to investigate the evolution of pore and fracture structure of coal samples treated with LN2. The experimental results showed that the pore volume and average pore size of coal samples increase after LN2 freeze thaw. After 12 freeze thaw cycles, the change in pore volume of micropores and minipores of coal samples was not significant, while the pore volume of mesopores and macropores increased significantly before LN2 freeze thaw. The specific surface area of the pores in different size ranges of coal samples increases with the increase in the number of LN2 freeze thaw cycles; the structure of micropores and miniopores were damaged by thermal stress and frost heave force during LN2 freeze thaw; and the pore size gradually increases to form mesopores and macropores. Micro-CT images of coal samples after LN2 freeze thaw indicated the primary fractures of coal sample expanded and generated a large number of secondary fractures. The primary and secondary fractures are interconnected and ultimately form penetrated fracture enhancing the connectivity of fractures, enhancing the connectivity of the fracture structure. The key finding study is expected to provide a theoretical basis for LN2 fracturing.

Mesoporosity enhancement in carbon monoliths through incorporation of a nonpolar solvent with a templating source for fast adsorption of organic dyes

Obtaining hierarchical porous carbon monoliths with bigger and controlled pore sizes through soft templating and without macroscopic phase separation remains a challenge for the synthesis. In this study, we tried to introduce nonpolar solvents (benzene or toluene) together with a pluronic template in the sol-gel polycondensation route of polymer precursors to obtain carbons in the monolithic form without macroscopic phase separation during the polymerization stage. The porosity results show that carbon monoliths vary solely with mesopore features while retaining macropores, compared to carbon monoliths obtained with pluronic template alone. The mesopore volumes almost double with an increase in pore sizes by 1 nm at maxima, and the pore sizes extend to 30 nm from the addition of nonpolar solvent. This is possible due to the interaction of the nonpolar solvent with the hydrophobic core of the pluronic template, which causes swelling of micelles during the polymerization stage, and thus finally, retention of larger pore sizes and pore volumes within carbon monoliths. The structural and surface chemistry characterizations ensure a similar behaviour of the resulting carbon monoliths that are further investigated for the adsorption kinetics of different types of organic dyes (methylene blue, methyl orange, and congo red) to understand the sole role of mesoporosity. The adsorption kinetics follows the trend of mesopore volumes with fast adsorption vis-à-vis the sizes and molar masses of organic dyes.

Green synthesis of Kenaf-based activated carbons with excellent rate capability and cycle-life via hydrothermal-co-activation process for high-performance capacitive energy storage

The invention of high-performance electrode materials through a simple and green approach is always important for energy storage applications. Herein, we have prepared highly porous activated carbons (ACs) from biomass kenaf (KF) by hydrothermal and steam activation methods. A number of optimization experiments, such as hydrothermal pre-treatment (100, 150 and 200 °C), steam activation temperature (600, 700, 800, and 900 °C) and time of steam flow (15, 30, 60 and 90 min) were performed to control the specific surface area, micro- and/or meso-pores, total pore volume for an excellent electrochemical performance. The as-obtained porous ACs exhibited a high specific surface area (∼1733 m2/g) with high total pore volume (∼0.916 cm3/g) and high mesopore volume (∼28.4%), which are beneficial for the excellent double layer formation over the surface of activated electrode and also provide transport channel for an effective diffusion of electrolyte ions. The as-derived ACs were used as electrode materials for the fabrication of symmetric supercapacitor device in 6 M KOH. The fabricated device exhibited a high energy density of 4.86 Wh kg−1 at power density of 2500 W kg−1 with outstanding stability (∼96.3%) over 10,000 charge-discharge cycles.

Study on the pore evolution of Xinjiang oil shale under pyrolysis based on joint characterization of LNTA and MIP

During the in-situ exploitation of oil shale, the evolution of pore structure will affect the heat transfer medium and the transport capacity of products. In this study, using the oil shale from Jimsar region of Xinjiang, in combination with the low-temperature nitrogen adsorption experiment (LNTA) and high-pressure mercury injection experiment (MIP), the effect of temperature on evolution law of its pores during pyrolysis were analyzed according to the LNTA and MIP joint characterization results. The results show as follows: the change curve of oil shale porosity with pyrolysis final temperature in Xinjiang shows an “S” shape. The pore volume increases slightly before 300 °C, and it shows an increasing trend in the subsequent temperature range, with the mesopore volume change being the most noticeable. However, the increase slows down after 600 °C. The evolution of full-scale pores in the pyrolysis process of oil shale is reflected by the joint characterization of LNTA and MIP, which indicates that the temperature has a controlling effect on the evolution of pore, and provides basic theoretical support for how to improve the oil recovery rate of exploitation of oil shale.

Effects of stratified mining on the low-temperature oxidation and physicochemical properties of lower coal layers

To investigate the impact of stratified mining on the spontaneous combustion characteristics of lower coal in thick coal seams, an analysis was conducted on the macro pore structure, temperature rise, oxygen consumption characteristics, chemical structure, surface chemical properties, and functional group distribution of the upper and lower stratified coal samples (LSC, LSR) from the LinSheng Mine 1202 re-mining face. Post re-mining, the specific surface area, average pore diameter for adsorption, micropore volume, and mesopore volume of LSR showed a significant increase compared to LSC. The maximum mass loss rate for LSR was approximately three times that of LSC, and the characteristic temperature of LSR was lower. When the volumetric fraction of oxygen exceeded 12%, the oxygen consumption rate and CO generation rate of LSR surpassed those of LSC. The alkyl carbon content in LSR was 2% lower compared to LSC, while the oxygenated carbon content was higher by 4.37%. The oxygen content in LSR and the O/C ratio were higher than those in LSC. The structural order of LSR was lower by 11.3%, and the oxygen-containing functional groups were higher by 1.15%. These findings suggest that stratified mining increases the spontaneous combustion risk of lower coal layers. This study underscores the need for careful consideration of mining strategies to mitigate potential risks.

Diagenetic Evolution Sequence and Pore Evolution Characteristics: Study on Marine-Continental Transitional Facies Shale in Southeastern Sichuan Basin

Diagenesis and pore structure are essential factors for reservoir evaluation. marine-continental transitional facies shale is a new shale gas reservoir of concern in the Sichuan Basin. The research on its diagenesis pore evolution model has important guiding significance in its later exploration and development. However, the current research on pore structure changes, diagenesis, and the evolution of marine-continental transitional facies shale is not sufficient and systematic. In order to reveal the internal relationship between pore structure changes and diagenesis, the evolution of marine-continental transitional facies shale was tested by X-ray diffraction, field emission scanning electron microscopy, low-pressure gas adsorption, nuclear magnetic resonance, and the diagenetic evolution sequence and nanopore system evolution of Longtan Formation shale was systematically studied. The results show that the Longtan Formation shale underwent short-term shallow after sedimentation, followed by long-term deep burial. The main diagenetic mechanisms of the Longtan Formation shale include compaction, dissolution, cementation, thermal maturation of organic matter, and transformation of clay minerals, which are generally in the middle-late diagenetic stage. The pore structure undergoes significant changes with increasing maturity, with the pore volumes of both micropores and mesopores reaching their minimum values at Ro = 1.43% and subsequently increasing. The change process of a specific surface area is similar to that of pore volumes. Finally, the diagenetic pore evolution model of Longtan Formation MCFS in Southeastern Sichuan was established.

Effect of carbon modifier on characteristics and catalytic properties of zeolite–carbon hybrid supported Zr towards γ-valerolactone production

Developing efficient and stable solid functional materials for the catalytic upgrading of biomass-based platform furanic molecules is of great significance to produce value-added chemicals and biofuels. We herein report β-zeolite (β)/biobased carbon hybrids supported Zr species towards the cascade conversion of furfural into γ-valerolactone (GVL) with high activity and favorable stability. The role and importance of carbon modifier were highlighted. The cellulose (CEL) modified Zr/β-CEL catalyst was found to be uniquely effective, leading to an increase of GVL yield from 49.3% to 81.1%. Catalyst characterizations revealed that the structural integrity of β was largely preserved using CEL as the carbon modifier, accompanied by the increased mesopore volume and pore size for better accessibility of active sites and diffusion of reactants. Simultaneously, the presence of CEL offered an appropriate ratio of Lewis and Brønsted acid sites due to the well incorporation and dispersion of Zr species, which ensured the successive transfer hydrogenation and ring-opening reactions. Kinetic studies demonstrated the positive effect of CEL modification on reducing the apparent activation energy and thereby facilitating the GVL formation. More importantly, Zr/β-CEL with enhanced structural stability also exhibited markedly higher recyclability compared with the pristine Zr/β. The understanding on the roles of carbon modifier can be employed to optimize the physicochemical properties of zeolite-based catalysts for roundly improving the catalytic reactivity of biomass-related compounds.

Catalytic reforming of cellulose pyrolysis volatiles over hierarchical HZSM-5: Mechanism of a protective effect of tetrapropylammonium (TPA+) during alkali treatment

A series of HZSM-5 with hierarchical pores was obtained by using a modified NaOH treatment method. This modification incorporated the use of tetrapropylammonium bromide. Furthermore, their catalytic performance for reforming of cellulose pyrolysis volatiles at 600 °C was investigated. TPAB-assisted alkali treatment increased the mesoporosity, relative crystallinity, and surface integrity of ZSM-5. Additionally, a significant portion of the acidic sites was preserved. The 0.1TPAB-0.2AT, treated with 0.1 M TPAB and 0.2 M NaOH, yielded the highest light aromatics at 156.9 mg/g. The coking resistance of the catalyst was also improved. Tetrapropylammonium (TPA+) achieves surface protective desilication by selectively adsorbing Si(0Al) on the zeolite. Subsequently, the continuous adsorption of TPA+ leads to mesopore formation within the zeolite. This continuous restriction on desilication limits the increase in mesopore volume, resulting in a relatively abundant and uniform distribution of smaller mesopores on ZSM-5. This mechanism holds promise for future synthesis of highly mesoporous ZSM-5.