Solid Acid Research Articles

3D simulation in a fixed bed coupled pervaporation reactor for biodiesel production

In this study, a solid acid catalyst SO42−/TiO2/ZSM-5 (STZ) was prepared. Biodiesel was synthesized from tall oil fatty acid (TOFA) by the ethanol esterification. The fixed bed and pervaporation (PV) coupling increased the esterification conversion of TOFA and ethanol by about 16 %. The spherical STZ catalyst’s appearance, composition, and catalytic activity were assessed through TGA, XRD, SEM, BET, FTIR, NH3-TPD and XPS analyses. The reaction parameters of ethanol/TOFA molar ratio (10:1–20:1), reaction temperature (75–85 ℃), catalyst dosage (6–12 g) and flow rate (0.3–0.9 mL/min) were optimized by the response surface method (RSM). Under RSM optimization, the TOFA esterification reaction achieved a conversion rate of 99.56 ± 0.23 %. After five cycles of esterification, TOFA conversion remained above 87 %. A computational fluid dynamics (CFD) model was established to predict the esterification reaction behavior in the reactor, and the TOFA conversion rate was found to be close to the experimental results through systematic simulation, by reaction kinetics equation, continuity equation, Navier-Stokes equation, and Brinkman equation. In addition, the TOFA biodiesel prepared by this study complies with EN 14214 and ASTM D6751 standards.

Intensifikasi Sintesis Diasetin dan Triasetin Melalui Esterifikasi Gliserol Dengan Katalis Berbasis Daun Bambu

The synthesis of acetins from glycerol is achieved through esterification assisted by a solid acid catalyst and microwave irradiation. Diacetin and triacetin, suitable as biofuel additives, are produced using biogenic silica from bamboo leaves, which is chemically activated with strong acid and calcined. No research has utilized silica catalysts derived from bamboo leaf ash to produce diacetin and triacetin. This study aims to employ bamboo leaf-based heterogeneous catalysts to enhance triacetin selectivity, simplify product purification and separation, and enable catalyst reuse. Furthermore, microwave application can accelerate the reaction time. The best total selectivity for diacetin and triacetin was obtained under operating conditions of 3% catalyst concentration, a 1:6 molar ratio, and 60 minutes of microwave irradiation. The yields of diacetin and triacetin under these conditions were 65.80% and 18.70%, respectively. GC-MS and FTIR analysis confirm the presence of monoacetin, diacetin, and triacetin, with a total selectivity for diacetin and triacetin of 84,50%.

Friedel Crafts Reactions Revisited: Some Applications in Heterogeneous Catalysis#

Abstract: Important organic reactions require the use of catalysts. The Friedel-Crafts reactions were discovered by Charles Friedel and James Mason Crafts in 1887. They are an essential catalytic process since they are widely applied in different areas such as fuels, cleaning, and pharmacological products. The reaction is usually carried out in the presence of Lewis acids or Brønsted acids in a homogeneous medium, with the nucleophilic aromatic substrate in excess. Although there is still work in the literature on the Friedel- Crafts reaction in a homogeneous medium using metal halides, the tendency is to replace these catalysts, which generate effluents that are harmful to the environment. Heterogeneous catalysts using solid acids show advantages over homogeneous catalysts, especially concerning separating products from the reaction medium, recycling, and reusing. This paper presents a mini-review focusing on the use of solid acids in Friedel-Crafts reactions.

Source and characteristics of inorganic acidic gases and aerosols emission in a semiconductor plant

Inorganic acids, widely used in semiconductor manufacturing processes, have become a concern as improper handling of these acids can have severe environmental impacts. This study investigates the major contamination source of inorganic acids (hydrofluoric acid, hydrochloric acid, nitric acid, phosphoric acid, and sulfuric acid), the different ratios of solid and gaseous inorganic acids, and the particle size distribution of solid particles emitted after local scrubber (LSC) treatment. An assessment of pollutant status revealed that hydrofluoric acid emissions dominate in the chemical vapor deposition (CVD) process at 65%, hydrochloric acid in the diffusion (DIFF) process at 69%, phosphoric acid in the epitaxy (EPI) process at 100%, and sulfuric acid in wet etching at 85%. In contrast, particulate matter constitutes the primary component, ranging from 82% to 99% of the LSC emission. The LSC configuration is then adjusted based on the overview of inorganic acid emissions from different processes to match their characteristics. After related improvement activities, the results presented a significant reduction of 56% to 87% in inorganic acid emissions at the outlet of the LSC, and 18-68% reduction in the stack emissions.

Development of Solid Acid Catalysts for Synthesis of Chemicals from Sugars and Sugar Alcohols

Development of Solid Acid Catalysts for Synthesis of Chemicals from Sugars and Sugar Alcohols

Covalent organic frameworks with tunable Co–N–C for high-performance carbamate decomposition via sulfonic modification in amine-based CO2 capture

Nanowire-like COF support with sulfo group (-SO3H) decoration was designed and synthetized, to offer favourable conditions for atomically dispersing Co atoms (S–Co/NC). The ingenious coordination of sulfo group synergistically improved COF structure and Co–N–C scheme, creating high surface area and excellent catalytic activity. Lab-scale experimental evaluations confirmed that the maximum CO2 desorption rate of spent MEA-solvent increased significantly by 733 % (3.74 CO2 mmol/min) after introducing S–Co/NC catalysts, ascribed to its contribution for proton transfer and C-N break. Bench-scale experiments demonstrated that a mere 0.0125 wt% of catalyst in MEA-solvent substantially decreased the CO2 loading of lean solvent by 17.7 % at low desorption temperatures (120→110 °C), resulting in a 28.8 % reduction in energy consumption. Furthermore, the negligible degradation of catalytic performance during 100-h testing wall-validated the stability and durability of the S–Co/NC catalysts. This work provided a prominent COF-based solid acid catalysts for energy-saving solvent regeneration during amined-based CO2 capture.

Unlocking new potentials in energy-efficient carbon dioxide capture: How catalyst-phthalocyanine is leading the way

Addressing the high energy demand of amine-based carbon dioxide capture systems is crucial for achieving carbon neutrality. While enhancing energy efficiency with solid acid catalysts in amine regeneration is promising, developing more efficient catalysts remains a critical challenge. In this study, we introduce the innovative use of a robust, metal-free phthalocyanine as a catalyst to facilitate amine regeneration. Distinctively, phthalocyanine features a macrocyclic ring with an extensive π-conjugated system that functions as Lewis acid sites, diverging from conventional methods that rely on metal atoms for this role. Additionally, the nitrogen and hydrogen atoms on the macrocyclic ring act as Brönsted base sites and Brönsted acid sites, respectively. These sites collectively contribute to a significant acceleration in the CO2 desorption rate, achieving an increase of 1679% at approximately 67 ℃, which far surpasses the performance of previously investigated catalysts. Furthermore, phthalocyanine catalyzes the decomposition of carbamate and protonated monoethanolamine more efficiently than bicarbonate. This research lays the groundwork for next-generation catalysts in amine solvent regeneration of the carbon dioxide capture process.

Valorization of Bambusa striata shavings into functional superparamagnetic material and its application in biodiesel production: Response surface optimization, kinetics, thermodynamics and economic assessment

Herein, a novel highly porous biomass-based (Bambusa vulgaris striata) magnetic solid acid catalyst was developed for the first time via simultaneous activation and magnetization followed by acid functionalization. The sulfonated magnetic porous carbon was utilized as a catalyst for transesterifying Jatropha curcas oil (JCO) to biodiesel under microwave irradiation. The synthesized catalyst was extensively characterized using VSM, XRD, FTIR, SEM, EDS, TGA, XPS, Raman spectroscopy, and AFM techniques. Through Response Surface Methodology (RSM), a maximal biodiesel yield of 98.8 % was achieved over optimal optimal parametric states (catalyst loading 8 wt%, MOMR 24:1, 50 min, 80 °C). NMR confirmed JCO biodiesel formation with a FAME content of 98.04 %, and GCMS provided insight into its chemical composition. A pseudo-first-order kinetic study revealed an activation energy (Ea) of 28.734 kJ mol1. Thermodynamic analysis showed endothermic and non-spontaneous behavior with ΔH#, ΔS#, and ΔG# values of 25.928 kJ mol1, −0.193 kJ mol1 K1, and 94.251 kJ mol1, respectively. The catalyst displayed good reusability, easy recoverability, and stability, maintaining 75.4 % oil conversion even after ten consecutive cycles. Life cycle cost analysis (LCCA) estimates biodiesel production cost of $0.60 per liter, emphasizing high commercial viability.

Synergy between Brønsted Acid Sites and Carbonaceous Deposits during Skeletal 1-Butene Isomerization over Ferrierite.

During skeletal 1-butene isomerization over ferrierite carbonaceous deposits block 98% of the micropores within 24 h, rendering them effectively inaccessible to reactants, while the catalytic activity improves continuously for 100 h on stream. Ex-situ pyridine adsorption shows that the concentration of conventional Brønsted acid sites in the 10-R channels decreases below the detection threshold of infrared spectroscopy within 2 h. However, the operando addition of the base triethyl amine to the feed quenches the reaction, showing that mediated acidity is necessary. The larger base 2,2,6,6-tetramethyl piperidine only deactivates catalytic activity after several hours because it cannot directly bind to active sites at the sterically restricted pore mouths. The communication of internal Brønsted acid sites to the external reactants via a concerted mechanism involving protonated monoaromatic deposits trapped in the pore mouths explains the promoting effects of coke species in zeolite-catalyzed skeletal butene isomerization. This work presents a consolidated explanation of the synergy of solid acidity, structural confinement, and carbonaceous deposits in zeolites.

A highly efficient Lewis acid catalyst of F-doped activated carbon for acetylene dimerization

Doping carbon-based materials with heteroatoms is considered an effective strategy to enhance their catalytic activity by altering their electronic structure and chemical properties. In this study, fluorine doped activated carbon was synthesized and used in acetylene dimerization reaction. Fluorine has the highest electronegativity (3.98) and can induce neighboring carbon atoms to possess a stronger positive charge, thereby generating Lewis acid sites between the two atoms. The resulting carbon material exhibited abundant Lewis acid sites ensuring the ample exposure and availability of catalytic sites to facilitate notable activity in acetylene dimerization. Theoretical calculations indicated that the introduction of F could help to alleviate the progression of polymers. This research provides a promising approach to the development of solid acid catalysts with excellent catalytic performance by incorporating Lewis acid sites onto carbon materials.

Fabrication of Keggin heteropolyacid modified macroporous covalent triazine frameworks with cyano group-rich defects for high-value utilization of carbohydrates

Designing an efficient, stable and recyclable solid acid for catalytic conversion of biomass and its derived compounds to synthesize high value-added organic chemicals could effectively alleviate the environmental problems caused by the energy crisis and carbon dioxide emissions. We prepared a Keggin heteropolyacid modified macroporous covalent triazine frameworks (PW12-MCTF) catalyst using a simple template method and post-impregnation technology for efficient conversion of carbohydrates to produce 5-hydroxymethylfurfural (HMF). Abundant structural defects of MCTF can be constructed in situ through incomplete polymerization, which can firmly bind H3PW12O40 through physical confinement effect and bonding interactions. Under optimized conditions, PW12-MCTF exhibited high HMF yield (79.4 % or 44.4 %) and the highest turnover frequency (4.39 min−1 or 1.86 min−1) in microwave-assisted catalytic conversion of fructose or inulin, respectively. Its catalytic activity surpassed that of bulk PW12-CTF and commercial acid zeolite and resin catalysts, due to its appropriate acid properties, well-dispersed nature in DMSO, inter-connected pore structure and outstanding nucleophilic effect of N-rich units. Density Functional Theory (DFT) study provides a plausible mechanism in PW12-CTF-catalyzed fructose dehydration. The catalytic performance of PW12-MCTF remained unchanged after three cycles due to strong bonding interaction between the Keggin units and framework of MCTF. This study will provide a new strategy for the fabrication of heteropolyacid modified covalent organic frameworks with structural defects to achieve the high-value utilization of carbohydrates.

Agro-waste derived sulfonated biochar material as a sustainable heterogeneous catalyst for conversion of fructose to 5-hydroxymethylfurfural

BackgroundDevelopment of biomass derived solid acid catalysts has the advantage to conform the green chemistry protocol for production of 5-hydroxymethylfurfural (HMF) by dehydration of fructose. MethodWe have reported waste cashew nut shell produced char as a biochar to prepare sulfonated biochar (SBC) catalyst by incorporating –SO3H group through treatment of concentrated sulfuric acid. Significant findingsDifferent methods of characterization including XRD, FT-IR, XPS, FESEM-EDS, TEM, TPD and BET analysis, were used to study the structure, morphology, chemical compositions, acidity and porosity of the produced SBC catalysts. The mesoporous nature of the material was confirmed by the powder X-ray diffraction patterns (PXRD), type IV isotherm (BET), and flakes-like structure was observed in TEM analysis. The catalyst showed high yield of HMF (92%) under optimum conditions of 120 °C in 60 min under biphasic solvent mixture of water and toluene (1:2). High yield could be explained by high acid strength of catalyst as observed by NH3-TPD analysis. Leaching test by Sheldon's method and recyclability experiment proved the need and heterogeneity of the present catalyst.

Analysis of the region-specific characteristics of traditional Korean doenjang produced in Gyeonggi-do.

Doenjang is traditional soybean fermented food in Korea, and traditional doenjang on the market has different qualities like aroma, taste. This study is a preliminary study to investigate the quality characteristics of doenjang produced in each region of Korea. The objective of this study was to analyze the region-specific characteristics of traditional Korean doenjang produced in Gyeonggi-do. Physiochemical characteristics including pH, moisture content, soluble solid content, salinity, color, acid value, titratable acidity, NH2-N, total/reducing sugar, and alcohol contents, and enzymatic activities such as acidic/neutral protease and α/β-amylase activities, were analyzed. Doenjang produced in Gyeonggi-do was classified into two groups (GDG-A and GDG-B), and the distinction between two groups were the aging period: doenjang samples in GDG-A groups were aged over 3 yrs, while samples in GDG-B groups were aged less than 3 yrs. The results of this study provided the physicochemical characteristics and enzymatic activities of traditional doenjang produced in Gyeonggi-do.

Comparative study of mango cultivars at the ready-to-eat stage: The case of Western Crete, Greece, a cool subtropic region of the Mediterranean

With the expansion of the mango consumer market, exports of the product have increased. The harvest time effects quality characteristics, which identify the quality and consequently the price of the product. Greece is very close to the European markets, so mango fruits can be transferred at a ready-to-eat stage and minimize the distance between harvest maturity and edibility. On this research we studied the characteristics of twelve mango cultivars (‘Carrie’, ‘Keitt’, ‘Kensington’, ‘Kent’, ‘Lippens’, ‘Osteen’, ‘Palmer’, ‘Sabre’, ‘Sensation’, ‘Tommy Atkins’, ‘Van Dyke’ and ‘Zill’) in Greece. The parameters measured were the harvest time, fruit weight and size, fruit firmness, juice pH, soluble solid components, dry matter, ascorbic acid, total sugars and acidity. The first fruits were harvested ready-to-eat, at the first days of August. Fruit firmness was from 4.28 K/cm2 (‘Sensation’), to 1.55 (‘Lippens’). The pH level ranged from 3.64 (‘Van Dyke’) to 4.52 (‘Osteen’). Total soluble solids were 19.84% Brix in ‘Kent’, different from ‘Osteen’ (16.33%). ‘Kent’ had the highest dry matter concentration (25.3%). The higher amount of ascorbic acid (Vit C) was measured in ‘Palmer’ (82.79 mg/100 g juice). Total sugar was the highest in ‘Tommy Atkins’ (24.82 g glucose/100 g juice) and the lowest in ‘Palmer’ (6.51 g glucose/100 g juice). The lowest acidity was observed in ‘Lippens’ (0.16%). Our results indicate that Greece can offer fruit production of high quality, at the ready-to-eat stage. Our results are the first data of mango cultivation in Greece, a region of Europe where mango crop is gaining ground on the market.

Efficient solid dielectric electrochemical polishing with minimal electrolyte consumption and reusable conductive media

Electrochemical polishing finds wide application across various industries, including manufacturing, biomedicine, and semiconductors. However, this technology requires substantial water usage and results in environmental pollution due to the generation of waste electrolytes containing highly corrosive acids and heavy metal ions. Herein, we propose an electrochemical polishing method (SDEP) that employs solid dielectrics consisting of macroreticular ion exchange resin (MIER) solid particles and phosphoric acid electrolyte as an alternative to traditional liquid conductive media. Maintaining a polishing current of 0.4–0.5 A requires only an electrolyte consumption of 10–20 mL/h, leading to a more than 65% reduction in electrolyte usage compared to liquid electrochemical polishing. Meanwhile, this method can be applied to polish additively manufactured metal parts with an initial roughness Ra>10 μm. The achievable surface finish features Ra = 0.778 ± 0.078 μm, Rq = 0.960 ± 0.121 μm, and Rz = 4.175 ± 1.111 μm after 1-h polishing, with a material removal rate of 0.15–0.19 mm3/min. The improvement of Ra, Rq, and Rz are 92.3%, 92.1%, and 92.0%, respectively. With the EDS and XPS analysis, rod-shaped by-products adhering to the surface of MIER particles generated during the SDEP process are confirmed as Fe3+, PO43−, and PO3−. Furthermore, the MIER particles can be reused after cleaning, exhibiting polishing performance comparable to fresh MIER. This method reduces the use of electrolytes at the source of electropolishing, and MIER particles can be recycled, pointing towards the development of eco-friendly electrochemical polishing.

Preparation of a magnetic solid acid Fe3O4@PS‐SO3H and its use in hydrolysis of cellulose

AbstractBACKGROUNDIn order to improve the catalytic performance and stability of magnetic solid acid for cellulose hydrolysis in the aqueous phase, this study first modified the surface of magnetite (Fe3O4) nanoparticles (NPs) with oleic acid. Then, in an oil‐in‐water (O/W) emulsion system, polystyrene (PS) was coated on the Fe3O4 NPs through emulsion polymerization. Finally, magnetic solid acid Fe3O4@PS‐SO3H was prepared by sulfonation.RESULTSThe obtained Fe3O4@PS‐SO3H was characterized by transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, infrared, X‐ray diffraction, X‐ray photoelectron spectroscopy and thermogravimetric analysis, and its acid densityand magnetic properties determined. Applied to cellulose hydrolysis, it exhibited 35.28 emu·g−1 saturation magnetization and 3.56 mmol·g−1 maximum acid density. At 140 °C and 1:1 acid to substrate ratio, cellulose hydrolysis with Fe3O4@PS‐SO3H gave a glucose yield of ≤64.14% in 10 h. The solid acid was conveniently recycled with a magnet and reused for further cellulose hydrolysis. It maintained good catalytic activities after five cycles.CONCLUSIONThe magnetic solid acid with a polystyrene backbone prepared by emulsion polymerization exhibits efficient and stable catalytic performance, in line with the trend of green development in ‘bio‐refining’, and lays the foundation for the development of composite solid acids. © 2024 Society of Chemical Industry (SCI).

The studies on dehydration reaction mechanism of irradiated solid acid - nanostructured sodium - bentonite clay

Research findings can offer data and a theoretical framework for a quantitative examination of the bentonite dehydration mechanism. The reasons for changes in pore’ water under the influence of gamma rays in vacuum and in the presence of oxygen was discussed using TGA and DTA, FT-IR spectroscopy. It was revealed that dehydration and pore characteristics are mutually dependent. A question about the associated evolution of dehydration pore‘s water in nanostructured sodium – bentonite clay under the influence of ionizing rays with and without oxygen has been comparatively studied. The article is devoted to a discussion of how ionizing radiation, passing through nanoclays, produces, or rather begins to produce, chemical effects. It was used Infrared spectroscopy as the method for determining structural responses of natural clay from the Alpoid deposit in the Republic of Azerbaijan, to gamma rays exposure. It was found that under influence of ionizing rays in vacuum obtained hydrogen peroxide. It is of great interest for the study of the dehydration reaction mechanism and its role in formation of H2 under gamma irradiation.

Performance assessment of novel catalytic spouted-bed vapor jet flow heat exchanger in amine-based carbon capture process

This study introduced a spouted bed and jet flow catalytic heat exchanger (SBJ-EX). This novel non-agitated technology can potentially integrate with a conventional desorption column to enhance heat transfer and CO2 desorption performance in amine-based post-combustion carbon capture systems. As its first research in the carbon capture field, this work experimentally evaluated key factors including overall heat transfer coefficient, logarithmic mean temperature difference, temperature distribution along the reactor, and cyclic loading under varied parameters such as inlet temperature of the heating oil, inlet solvent temperature, rich CO2 loadings, and mass of catalysts to simulate real-world operating conditions using benchmark MEA solvent and solid acid catalyst HZSM-5. Compared to conventional plate heat exchangers, the SBJ-EX demonstrated over a 70 % enhancement in heat transfer performance due to its effective overall heat transfer coefficient. It also exhibited impressive CO2 desorption performance even at lower temperatures with sufficient catalysts. Unlike agitated-type heat exchangers, the SBJ-EX could minimize catalyst attrition and offer more excellent stability. In contrast to fixed-bed catalyst desorbed columns, this equipment offered a more compact design for quicker and simpler catalyst replacement to reduce downtime for operators significantly. The SBJ-EX can also function as an optional backup or add-on unit to provide operators with flexibility. This work further discussed advantages and challenges of the SBJ-EX operation. This work enriched the future research outlook for this technology, and contributed a commercially viable approach to catalysts in carbon capture processes.

Alcohol formaldehyde resin solid acid catalytic conversion of biomass into furan compounds

The conversion of waste lignocellulosic biomass into biomass platform chemicals is very promising. In this work, a novel resin-based solid acid catalyst was obtained by condensation of furfuryl alcohol with furfural, and mild calcination and sulfonation process. Then it was used to convert sugars and biomass to obtain furan compounds. Results showed that the solid acid with a furfural to furfuryl alcohol molar ratio of 3:1 is an irregular mesoporous material, with a specific surface area of 134.18 m2/g and an acid content of 2.723 mmol/g, which is extremely stable below 200 °C. 82.2 % (from fructose), 15.8 % (from glucose), 10.0 % (from cellobiose) yields of 5-HMF and 35.5 % (from xylose) yield of furfural could be obtained at 160 °C for 2 h. It can be reused more than 5 times and can restore the best catalytic effect after re-sulfonation. Notably, in the catalytic conversion of rice husk, rice straw, camphor tree branch and leaves under typical reaction conditions, 5-HMF and furfural was in yields of 9.4–24.5 % and 20.3–47.9 %, respectively. Moreover, a 10 % water dropwise to solvent can effectively promote the catalytic conversion of biomass, while there is a significant inhibitory effect after it exceeds 20 %.

Low-cost and green straw derived hierarchical porous carbon as support to phosphotungstic acid for efficient and clean production of α-terpineol

This study developed a novel reciprocal template method to prepare MgO@Carbon micrometre tubes directly from straw-based biomass. Biomass carbon with a rich hierarchical porous structure (MRSC30) was obtained by acid-washing the MgO@Carbon micrometre tubes. The pore formation mechanism of MRSC30 was systematically analyzed using Density Functional Theory calculations and various characterization methods. The in situ growth of Mg(OH)Cl/MgO inside the biomass promotes the polymerized carbon precursors to be tightly affixed to the templating agent and provides exfoliation, support, and catalysis (i.e., electrostatic attraction, nucleophilic substitution, and electrophilic addition), which effectively promotes the formation of hierarchical porous carbon. The continuous release of light gases from the inside out during the prolongation of the decomposition temperature of the biomass by Mg(OH)Cl or/and MgO helps to promote the formation of stomata in the biomass carbon. The results showed that the method minimized the consumption of chemicals, energy consumption, and the time required to prepare HPC by 35.75%, 67.57%, and 52.38%, respectively. The phosphotungstic acid-loaded MRSC30 was successfully prepared as a highly amphiphilic and highly acidic solid acid catalyst and applied to the hydration of α-pinene to prepare superior performance gasoline additives (α-terpineol). Under optimal process conditions obtained in a batch reactor, the catalytic performance of the catalyst could be further improved by alternating flow using a novel semi-batch unsteady-state reactor developed in this institute, and the α-pinene conversion and the α-terpineol selectivity reached a maximum of 95.53% and 65.75%, respectively. At the same time, the reactor was able to substantially reduce the time required for hydration and the amount of moderately toxic acetone used compared to the conventional batch reactor by 20.83% and 62.50%, respectively.