Novel sulfonated carbonaceous materials from p-toluenesulfonic acid/glucose as a high-performance solid-acid catalyst

Kinetic and thermodynamic study on the esterification of oleic acid over SO3H-functionalized eucalyptus tree bark biochar catalyst

Herein, esterification of oleic acid (OA) over tosylic acid functionalized eucalyptus bark biochar (TsOH-MBC) to synthesize fatty acid methyl ester (FAME) was investigated. The TsOH-MBC catalyst was prepared via pyrolysis-activation-sulfonation process at various impregnation ratios and was characterized by SEM, FTIR, EDX, XRD, BET, TGA and acid site density techniques. The catalytic performance of the sulfonated biochar catalyst was described in terms of acidity and FAME yield. 6 g of sulfonic acid loaded on 10 g of MBC (6TsOH-MBC) appeared to be most appropriate combination to achieve a highly active catalyst for the esterification of OA with 96.28% conversion to FAME at 80 °C for 5 h with catalyst loading of 4.0 wt% and 8:1 methanol/OA molar ratio. The catalytic reaction kinetic data were very well described by the second-order model, with a rate coefficient of 0.223 mL mol⁻¹ h⁻¹ at 80 °C and activation energy of 81.77 kJ mol⁻¹. The thermodynamic parameters such as \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Delta H$$\end{document}ΔH, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Delta S$$\end{document}ΔS and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Delta G$$\end{document}ΔG were determined to be 78.94 kJ mol⁻¹, 135.3 J mol⁻¹ K⁻¹ and 33.03 kJ mol⁻¹, respectively. This research provided an environmentally friendly procedure for FAME production that could be replicated on a commercial scale.

Sulfonated biochar catalyst derived from eucalyptus tree shed bark: synthesis, characterization and its evaluation in oleic acid esterification

Herein, fatty acid (oleic acid, OA) was upgraded to fatty acid methyl ester (FAME) via esterification reaction using sulfonated biochar obtained from eucalyptus tree shed bark as solid acid catalyst. Under the optimal esterification conditions (i.e., at 65 °C for 2 h using a methanol/OA molar ratio of 10 : 1 with a catalyst dosage of 4 wt%), the FAME yield was 97.05 ± 0.28% when a solid acid catalyst prepared by loading 6 g of p-Toluenesulfonic acid (p-TSA) on 2 g of activated biochar (p-TSA3/ABC) was used. The remarkable performance of the p-TSA3/ABC could be attributed to its high acidity (468.8 μmol g-1) and dominance of the SO3H acid site on the catalyst surface. Experimental findings showed that the p-TSA3/ABC was relatively stable due to its highly functionalized structure. The catalyst was recycled for five successive cycles and exhibited no dramatic decrease in catalytic activity.

Anaerobic digestate as a low-cost nutrient source for sustainable microalgae cultivation: A way forward through waste valorization approach

To suffice the escalating global energy demand, microalgae are deemed as high potential surrogate feedstocks for liquid fuels. The major encumbrance for the commercialization of microalgae cultivation is due to the high costs of nutrients such as carbon, phosphorous, and nitrogen. Meanwhile, the organic-rich anaerobic digestate which is difficult to be purified by conventional techniques is appropriate to be used as a low-cost nutrient source for the economic viability and sustainability of microalgae production. This option is also beneficial in terms of reutilize the organic fraction of solid waste instead of discarded as zero-value waste. Anaerobic digestate is the side product of biogas production during anaerobic digestion process, where optimum nutrients are needed to satisfy the physiological needs to grow microalgae. Besides, the turbidity, competing biological contaminants, ammonia and metal toxicity of the digestate are also potentially contributing to the inhibition of microalgae growth. Thus, this review is aimed to explicate the feasibility of utilizing the anaerobic digestate to cultivate microalgae by evaluating their potential challenges and solutions. The proposed potential solutions (digestate dilution and pre-treatment, microalgae strain selection, extra organics addition, nitrification and desulfurization) corresponding to the state-of-the-art challenges are applicable as future directions of the research.

Synthesis of a sulfated-group-riched carbonaceous catalyst and its application in the esterification of succinic acid and fructose dehydration to form HMF

A novel sulfated-group-riched sulfonated carbonaceous catalyst with high acidic strength and adjustable ratio of acidic groups was designed in the paper, where glucose and benzyl chloride were hydrothermally carbonized first followed by sulfonation treatment. Various physicochemical techniques were used to characterize the catalyst such as IR, 13C MAS NMR and XPS spectra, NH3-TPD, XRD patterns and TG curve. Then, it was applied in the esterification of succinic acid and fructose dehydration to form HMF. Compared to commercial Amberlyst-15 catalyst, such carbonaceous solid acid exhibited excellent catalytic activity and thermal stability, which was attributed to its higher amount of sulfonic acid group.

Pretreatment of Switchgrass for Production of Glucose via Sulfonic Acid-Impregnated Activated Carbon

In the present research, activated carbon-supported sulfonic acid catalysts were synthesized and tested as pretreatment agents for the conversion of switchgrass into glucose. The catalysts were synthesized by reacting sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid with activated carbon. The characterization of catalysts suggested an increase in surface acidities, while surface area and pore volumes decreased because of sulfonation. Batch experiments were performed in 125 mL serum bottles to investigate the effects of temperature (30, 60, and 90 °C), reaction time (90 and 120 min) on the yields of glucose. Enzymatic hydrolysis of pretreated switchgrass using Ctec2 yielded up to 57.13% glucose. Durability tests indicated that sulfonic solid-impregnated carbon catalysts were able to maintain activity even after three cycles. From the results obtained, the solid acid catalysts appear to serve as effective pretreatment agents and can potentially reduce the use of conventional liquid acids and bases in biomass-into-biofuel production.

One-step synthesis of biomass-based sulfonated carbon catalyst by direct carbonization-sulfonation for organosolv delignification

Biomass-based sulfonated carbon catalyst (SCC) was prepared from corncob via direct sulfuric acid carbonization-sulfonation treatment. Central composite design was used to evaluate temperature and time for optimizing SCC yield and sulfonic acid (SO₃H) density. The SO₃H groups were successfully introduced to the SCC as evidenced by FTIR and sulfur analysis. Numerical optimization results showed that 100 °C and 5.78 h are the optimal conditions for maximizing yield (61.24%) and SO₃H density (1.1408 mmol/g). The highest ethanol organosolv lignin (EOL) yield of 63.56% with a substrate yield of 39.08% was achieved at 20% SCC loading in the ethanol organosolv delignification of lignocellulosic biomass. The FTIR spectra of the isolated lignin revealed typical features of G-lignin, indicating that no drastic changes took place in the lignin structure during the process. This study developed a simple one-step preparation method of SCC, which was successfully used as a catalyst in an organosolv delignification of biomass.

Conversion of biochar to sulfonated solid acid catalysts for spiramycin hydrolysis: Insights into the sulfonation process

Biochar has been recognized as a sustainable platform for developing functional materials including catalysts. This work demonstrated a method of converting biochar to sulfonated solid-acid catalysts, and the effectiveness of the catalysts for spiramycin hydrolysis was examined. Two biochar samples (H and X) were sulfonated with three reagents (concentrated H₂SO₄, ClSO₃H and p-toluenesulfonic acid (TsOH)) under hydrothermal, simple heating, ambient temperature, and CHCl₃-assisted treatments. The effect of elemental compositions and structural characteristics of the feeding materials (H and X) on the acidic properties of the sulfonated biochars were investigated. The results showed that the sulfonation ability of the three reagents was in the order of ClSO₃H > H₂SO₄ > TsOH, while hydrothermal treatment provided the highest total acidity, and largest amount of acidic groups (e.g., SO₃H, COOH and Ar-OH). Biochar X with higher O/C and N contents, and less graphitic features showed superior acidic properties than biochar H under all the employed treatments. The hydrolytic efficiencies of the sulfonated biochars under 200 W of microwave irradiation increased with increasing total acidity, and the amount of SO₃H and COOH groups. After sulfonation, the O/C of biochars increased, while H/C decreased, and the aromatic and graphitic features did not change. The electromagnetic energy absorbed by the sulfonated biochars did not notably contribute to spiramycin hydrolysis. Thus, this work demonstrated an effective and promising method for maneuvering biochar-based functional solid-acid catalysts for antibiotic remediation in contaminated water.

Solid acid catalysts produced by sulfonation of petroleum coke: Dominant role of aromatic hydrogen

Carbon based solid waste materials have been intensively investigated for the preparation of solid acid catalysts through sulfonation, but the acidity varies significantly depending on the material. In this study, the role of aromatic hydrogen in sulfonation with concentrated H₂SO₄ was investigated using petroleum coke (petcoke), graphite, and biochar as the carbon materials. Through ball milling and calcination, the amount of aromatic hydrogen on the petcoke could be increased or decreased, respectively. After sulfonation at 80 °C with concentrated H₂SO₄, the produced acidity (i.e., -SO₃H groups) increased as the amount of aromatic hydrogen increased from essentially no acidity on graphite to 0.55 mmol/g on biochar and 1.25 mmol/g on petcoke (particle sizes of 45-90 μm) indicating the importance of aromatic hydrogen during sulfonation. Calcination (350 °C for 1 h) of the petcoke before sulfonation decreased the acidity to 0.59 mmol/g, while ball milling (with isopropanol and silica for 24 h) increased the acidity to 3.73 mmol/g. The sulfonated petcoke samples were used as catalysts for the esterification reaction between octanoic acid and methanol at 60 °C and the turnover frequencies were 48-85 h^-1. The results give insights on the preparation of solid acid catalysts from carbon materials and highlight the application of petcoke without activation as a feedstock for esterification catalysts.

Halloysite nanotubes based heterogeneous solid acid catalysts

Taking into account the excellent catalytic performance of halloysite nanotubes, the main focus of this review article is to unveil the research on halloysite nanotubes for the preparation of solid acids and their applications in acid catalysis.

A green approach for the preparation of a surfactant embedded sulfonated carbon catalyst towards glycerol acetalization reactions

A surfactant embedded carbon-based acid catalyst was prepared via simple physical mixing and thermal treatment to establish the relationship between hydrophobicity and acidic site density for efficient glycerol acetalization reaction.

Direct Production of 2,5-Dimethylfuran with High Yield from Fructose over a Carbon-Based Solid Acid-Coated CuCo Bimetallic Catalyst

A carbon-based solid acid, which functionalized with p-toluenesulfonic acid (TsOH), an encapsulated non-noble CuCo multifunctional heterogeneous catalyst was for the first time developed and used to catalyze the one-pot direct conversion of fructose into 2,5-dimethylfuran (2,5-DMF) without purification of 5-hydroxymethylfurfural (5-HMF) from the reaction solutions. Fructose was first transformed into intermediate 5-HMF over the outer shell carbon-based solid acid sites via dehydration, and subsequently 5-HMF was further converted to produce 2,5-DMF over the non-noble metal active sites in the core. As high as 71.1 mol % yield of 2,5-DMF was achieved in tetrahydrofuran at 220 °C and 3 MPa H₂ for 10 h, which is higher than the yield reported for the direct conversion of fructose to 2,5-DMF. Besides, the carbon-based solid acid-coated CuCo catalyst could be reused up to five times.

Microwave-Assisted Homogeneous Acid Catalysis and Chemoenzymatic Synthesis of Dialkyl Succinate in a Flow Reactor

Two new continuous flow systems for the production of dialkyl succinates were developed via the esterification of succinic acid, and via the trans-esterification of dimethyl succinate. The first microwave-assisted continuous esterification of succinic acid with H2SO4 as a chemical homogeneous catalyst was successfully achieved via a single pass (ca 320 s) at 65–115 °C using a MiniFlow 200ss Sairem Technology. The first continuous trans-esterification of dimethyl succinate with lipase Cal B as an enzymatic catalyst was developed using a Syrris Asia Technology, with an optimal reaction condition of 14 min at 40 °C. Dialkyl succinates were produced with the two technologies, but higher productivity was observed for the microwave-assisted continuous esterification using chemical catalysts. The continuous flow trans-esterification demonstrated a number of advantages, but it resulted in lower yield of the target esters.

Efficient catalytic conversion of corn stalk and xylose into furfural over sulfonated graphene in γ-valerolactone

Sulfonated graphene (SG) was prepared and employed to convert corn stalk and xylose into furfural. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize SG. The effects of reaction time, temperature, substrate loading, catalyst dosage and solvents on the reaction were researched and optimized. SG exhibited high catalytic activity in the conversion of xylose and corn stalk to furfural. A fairly high furfural yield of 96% was achieved at 150 °C from xylose and a 71.9% furfural yield was obtained when using a 10.7 ratio (mass ratio: xylose to SG) at 140 °C. While a 48% furfural yield was obtained from corn stalk (based on the starting combined moles of xylan and glucan in corn stalk; yield was >100%, if based on only xylan) using a substrate loading (corn stalk to catalyst mass ratio) of 2.14 and a 19% 5-hydroxymethylfurfural (5-HMF) yield was obtained. What's more, a 43.9% yield of furfural was obtained in only 20 min. In addition, the reusability of SG was also investigated and shown to have good stability for xylose dehydration.

Catalytic conversion of corn stalk over sulfonated graphene.

Microwave-Assisted Conversion of Fructose to 5-Hydroxymethylfurfural Using Sulfonated Porous Carbon Derived from Biomass

In this study, a series of sulfonated carbon solid acid catalysts was prepared by a template method using fructose as the carbon source and zinc chloride as the catalyst and template. The reaction involving fructose dehydration to 5-hydroxymethylfurfural (5-HMF) was investigated using these catalysts with microwave assistance in dimethyl sulfoxide. The influence of different catalysts, catalyst amount, microwave power, fructose content, and reaction temperature, as well as the reusability of the catalyst, were investigated. The prepared catalysts were characterised by X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, nitrogen adsorption–desorption measurement, and temperature-programmed desorption of ammonia gas, and the total numbers of surface acid sites of these carbon-based solid acid catalysts were analysed by chemical adsorption–desorption of ammonia along with the standard curve for ammonia. The results revealed that the C2-SO3H catalyst exhibited the best activity. A 5-HMF yield of 87 % and fructose conversion of 99 % were achieved at 170°C in DMSO after 3 min. The microwave-assisted synthetic strategy was advantageous compared with the traditional method because this approach could shorten the total reaction time.

Preparation and investigation of highly selective solid acid catalysts with sodium lignosulfonate for hydrolysis of hemicellulose in corncob

Saccharification of lignocellulose is a necessary procedure for deconstructing the complex structure for building a sugar platform that can be used for producing biofuel and high-value chemicals. In this study, a carbon-based solid acid catalyst derived from sodium lignosulfonate, a waste by-product from the paper industry, was successfully prepared and used for the hydrolysis of hemicellulose in corncob. The optimum preparation conditions for the catalyst were determined to be carbonization at 250 °C for 6 h, followed by sulfonation with concentrated H₂SO₄ (98%) and oxidation with 10% H₂O₂ (solid–liquid ratio of 1 : 75 g mL⁻¹) at 50 °C for 90 min. SEM, XRD, FT-IR, elemental analysis and acid–base titration were used for the characterization of the catalysts. It was found that 0.68 mmol g⁻¹ SO₃H and 4.78 mmol g⁻¹ total acid were loaded onto the catalyst. When corncob was hydrolyzed by this catalyst at 130 °C for 12 h, the catalyst exhibited high selectivity and produced a relatively high xylose yield of up to 84.2% (w/w) with a few by-products. Under these conditions, the retention rate of cellulose was 82.5%, and the selectivity reached 86.75%. After 5 cycles of reuse, the catalyst still showed high catalytic activity, with slightly decreased yields of xylose from 84.2% to 70.7%.

A novel carbon-based catalyst with high catalytic ability and xylose selectivity was prepared from sodium lignosulfonate.

Catalyst design for biorefining

The quest for sustainable resources to meet the demands of a rapidly rising global population while mitigating the risks of rising CO2 emissions and associated climate change, represents a grand challenge for humanity. Biomass offers the most readily implemented and low-cost solution for sustainable transportation fuels, and the only non-petroleum route to organic molecules for the manufacture of bulk, fine and speciality chemicals and polymers. To be considered truly sustainable, biomass must be derived from resources which do not compete with agricultural land use for food production, or compromise the environment (e.g. via deforestation). Potential feedstocks include waste lignocellulosic or oil-based materials derived from plant or aquatic sources, with the so-called biorefinery concept offering the co-production of biofuels, platform chemicals and energy; analogous to today's petroleum refineries which deliver both high-volume/low-value (e.g. fuels and commodity chemicals) and low-volume/high-value (e.g. fine/speciality chemicals) products, thereby maximizing biomass valorization. This article addresses the challenges to catalytic biomass processing and highlights recent successes in the rational design of heterogeneous catalysts facilitated by advances in nanotechnology and the synthesis of templated porous materials, as well as the use of tailored catalyst surfaces to generate bifunctional solid acid/base materials or tune hydrophobicity.

Spectroscopic tracking of mechanochemical reactivity and modification of a hydrothermal char

A glucose hydrothermal char (HTC) was synthesized and ball milled to break chemical bonds, generate defects, and form new chemical structures.

Sulfonated carbon/nano-metal oxide composites: a novel and recyclable solid acid catalyst for organic synthesis in benign reaction media

A novel catalytic system based on the use of nano-metal oxides and carbon has been designed and exhibits excellent catalytic activity for acid catalyzed organic reactions.

Catalytic acetoxylation of lactic acid to 2-acetoxypropionic acid, en route to acrylic acid

We present an alternative synthetic route to acrylic acid, starting from the platform chemical lactic acid and using heterogeneous catalysis.

Biobased catalyst in biorefinery processes: sulphonated hydrothermal carbon for glycerol esterification

The better performance of sulphonated hydrothermal carbon (SHTC) in glycerol esterification is attributed to cooperative effects. High conversions and high selectivity towards triesters are achieved and SHTC could be reused after regeneration.

Efficient solid acid catalyst containing Lewis and Brønsted Acid sites for the production of furfurals

Self-assembled nanoparticulates of porous sulfonated carbonaceous TiO2 material that contain Brønsted and Lewis acidic sites were prepared by a one-pot synthesis method. The material was characterized by XRD, FTIR spectroscopy, NH3 temperature-programmed desorption, pyridine FTIR spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, N2 -sorption, atomic absorbance spectroscopy, and inductively coupled plasma optical emission spectroscopy. The carbonaceous heterogeneous catalyst (Glu-TsOH-Ti) with a Brønsted-to-Lewis acid density ratio of 1.2 and more accessible acid sites was effective to produce 5-hydroxymethylfurfural and furfural from biomass-derived mono- and disaccharides and xylose in a biphasic solvent that comprised water and biorenewable methyltetrahydrofuran. The catalyst was recycled in four consecutive cycles with a total loss of only 3 % activity. Thus, Glu-TsOH-Ti, which contains isomerization and dehydration catalytic sites and is based on a cheap and biorenewable carbon support, is a sustainable catalyst for the production of furfurals, platform chemicals for biofuels and chemicals.

Oil palm trunk and sugarcane bagasse derived solid acid catalysts for rapid esterification of fatty acids and moisture-assisted transesterification of oils under pseudo-infinite methanol

The use of pseudo-infinite methanol in increasing the rate of esterification and transesterification reactions was studied using oil palm trunk (OPT) and sugarcane bagasse (SCB) derived solid acid catalysts. The catalysts were prepared by incomplete carbonisation at 400°C for 8h, followed by sulfonation at 150°C for 15h and characterised using TGA/DTA, XRD, FT-IR, SEM-EDS, EA and titrimetric determinations of acid sites. Under optimal reaction conditions, the process demonstrated rapid esterification of palmitic acid, with FAME yields of 93% and 94% in 45min for OPT and SCB catalysts, respectively. With the process, moisture levels up to 16.7% accelerated the conversion of low FFA oils by sulfonated carbon catalysts, through moisture-induced violent bumping. Moisture assisted transesterification of palm olein containing 1.78% FFA and 8.33% added water gave FAME yield of 90% in 10h, which was two folds over neat oil.

Conversion of Fructose to 5-hydroxymethylfurfural Catalyzed by Coaled Carbon-Based Solid Acid

Coaled carbon-based solid acid (Coal-SO3H) was prepared by sulfonating ultra-low ash Taixi coal and characterized by XPS, IR and PXRD. It was used as a new, efficient and recyclable catalyst for fructose dehydration to form 5-hydroxymethylfurfural (5-HMF) in dimethyl sulfoxide (DMSO). Reaction time, temperature and catalyst amounts were investigated respectively. The results showed that 81.6 % yield of 5-HMF achieved in dimethyl sulfoxide (DMSO) at 140 °C after 140min using the Coal-SO3H as catalyst. The ash, carbonization temperature and sulfonated way which could influence the catalyst performance for preparing 5-HMF had been investgated.