Sulfonic Group Content Research Articles

Preparation of Lignin-Based Superplasticizer by Graft Sulfonation and Investigation of the Dispersive Performance and Mechanism in a Cementitious System

A practical graft sulfonation process was developed to synthesize a lignin-based superplasticizer using acid-precipitated lignin from wheat straw black liquor as raw material. The graft-sulfonated lignin, prepared in optimal reaction conditions, was named GSL. The properties of GSL in a cementitious system were investigated. The adsorption isotherms of GSL fractions separated by ultrafiltration and the thickness of their absorbed films on cement particles were measured to reveal the dispersion mechanism. Also, it was found that the molecular weight of graft-sulfonated lignin increased with the dosage of acetone and formaldehyde, but having too high a molecular weight reduced its dispersive performance. High sulfonic group content in graft-sulfonated lignin severely inhibited the increase of molecular weight, resulting in a decrease of dispersive performance. GSL has stronger compressive strength enhancement in concrete and lower hydration heat temperature than the commercial naphthalene-sulfonated formald...

A novel and efficient polymerization of lignosulfonates by horseradish peroxidase/H2O2 incubation

Lignosulfonates(LSs), by-products from chemical pulping processes, are low-value products with limited dispersion properties. The ability of commercially available horseradish peroxidase (HRP) to polymerize LS macromolecules and improve the dispersion properties of LSs was investigated. The polymerization of LSs proceeded efficiently under mild reaction conditions in an aqueous solution with HRP/H2O2. Gel permeation chromatography showed a significant increase in weight-average molecular weight (M w ) of sulfonated kraft lignin and sodium lignosulfonate (NaLS) by 8.5-fold and 4.7-fold, respectively. The mechanism of polymerization was investigated by elemental analysis, surface charge measurement, headspace gas chromatography, infrared spectroscopy (IR), and hydrogen nuclear magnetic resonance spectrometry ((1)H-NMR). The functional group measurements indicated that HRP incubation did not reduce the sulfonic group content. However, it decreased the phenolic and methoxyl group contents. As the phenolic group content decreased, M w increased as a power function. The polymerization was proposed to involve the random coupling of phenoxy radical intermediates. The radicals coupled with each other to form different inter-unit linkages, most of which were the β-O-4' type, as the (1)H-NMR spectra indicated. Moreover, the HRP/H2O2 incubation induced a significant improvement in the adsorption and dispersion properties of LSs. Therefore, the HRP/H2O2 incubation is a promising approach for industrial applications of LSs.

Preparation of solid acid catalyst from rice husk char and its catalytic performance in esterification

A sulfonated carbon-based solid acid catalyst was prepared by sulfonating rice husk char with concentrated sulfuric acid. The as-prepared catalyst was characterized using X-ray diffraction, X-ray photoelectron spectroscopy, ultimate analysis, specific surface area analysis, and thermogravimetry-mass spectrometry. The effects of the sulfonation temperature and time on the catalytic performance were investigated using the esterification of oleic acid and methanol as the probe reaction. The effects of the reaction conditions on the esterification catalyzed by sulfonated rice husk char were also studied. The stability of the catalyst was examined. The results showed that 90 °C and 0.25 h were suitable sulfonation temperature and time, respectively. The catalyst prepared under these conditions had an amorphous carbon structure with a sulfonic group concentration of 0.7 mmol/g. It exhibited high catalytic performance. The conversion of oleic acid was 98.7% under the optimal reaction conditions with a catalyst amount of 5%, a methanol to oleic acid molar ratio of 4:1, and a reaction temperature and time of 110 °C and 2 h, respectively. The esterification conversion still reached 96.0% after seven cycles of successive reuse, which indicated that the catalyst stability was excellent. A solid acid catalyst with high -SO 3 H density and excellent stability was prepared from rice husk char and was used to pre-esterify materials with high fatty acid contents for biodiesel production.

Modification of Cathode Catalyst to Improve PEFC Cell Performance under Low Relative Humidity

Here we report several trials to modify cathode Pt catalysts to improve fuel cell performance under low relative humidity. First approach was to introduce hydrophilic group such as organic sulfonic group to Pt catalyst. The effect of the content of sulfur in cathode catalyst on the cell voltages at RH=31% was examined. Several samples of modified catalysts exhibited better cell voltages than the base catalyst. Nevertheless, the modified catalysts containing excess amount of organic sulfonic group exhibited lower cell voltage at dry condition. The cell voltages were different among the catalysts whose contents of sulfur were almost the same. It indicated that the condition other than the content of organic sulfonic group also affected the cell performance under the lower humidity.

Tailoring surface structure of polymer nanospheres in Pickering emulsion polymerization

A series of surface-functionalized polystyrene (PS) nanospheres with similar particles size of about 100nm and adjusted content of sulfonate groups on the surface are prepared by Pickering emulsion polymerization using titania nanoparticles modified with a mixture of two surfactants as stabilizers. TEM and FE-SEM images indicate that the titania nanoparticles are firmly adsorbed on the surface of polymer nanospheres because of the electric attraction between negative charged surfactant molecules and positive charged titania particles. XPS and electrophoresis measurements confirm that the surfactant with a double bond has been successfully grafted on the surface of PS nanospheres, and the surfactant without a double bond is removed with titania nanoparticles. Polymer nanospheres with appropriate concentration of sulfonate groups on the surface have good colloidal stability in the nonpolar solvent and may be suitable for bistable electrophoretic display application.

Chemical reactivity of alkali lignin modified with laccase

The modification of alkali lignin with laccase was investigated. The structural change of lignin was analyzed. The sulfonation reactivity was measured by the content of sulfonic group. The results showed the sulfonation reactivity increased to some extent under the condition of atmosphere pressure, but decreased under the condition of 0.3 MPa oxygen pressure. The analysis of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) showed the cleavage of various ether linkages and demethylation took place in the structure of lignin to certain extent during modification with laccase, which contributed to the improvement of sulfonation reactivity. Under the condition of 0.3 MPa oxygen pressure, the ratio of s/g (guaiacyl/syringyl) increased after modification, which reduced the sulfonation reactivity of lignin. Simultaneously partial polymerization reaction, such as 4-O-5′, β-5, 5-5 and other reaction in the aromatic ring decreased the activity sites of C2, C5 and C6. Abundant polymerization reaction of α-O increased steric hindrance of C2 and C6 in aromatic ring, resulting in low sulfonation reactivity of lignin.

High performance proton exchange membranes obtained by adjusting the distribution and content of sulfonic acid side groups

The proton conductivity and oxidation resistance as well as dimensional stability of hydrocarbon proton exchange membranes were simultaneously improved, achieving exciting overall properties.

Nanoparticles of Amorphous Cellulose and Their Properties

Method of preparation and some properties of amorphous cellulose nanoparticles (ANP) have been described in this paper. It was shown that ANP have spherical shape and are characterized by high degree of pantamorphia, low DP and increased content of sulfonic groups. The amorphous nanoparticles of cellulose are completely hydrolyzed by cellulolytic enzymes with forming of glucose. Concentrated paste of ANP has expressed thickening properties and therefore its additive can prevent phase separation of water dispersions of various substances. Low-acidic and soft nanoparticles can be used in cosmetic formulation for gentle skin peeling. Moreover, due to increased content of acidic functional groups, ANP can immobilize various therapeutically-active substances (TAS) containing basic functional groups. The ANP-TAS complexes can be used in remedies aimed for effective care and cure of the skin.

Crosslinked PS-DVB microspheres with sulfonated polystyrene brushes as new generation of ion exchange resins

Generation of sulfonated linear polystyrene brushes on poly (styrene–divinylbenzene) (PS-DVB) microspheres and their ion exchange characteristics are reported, for the first time. Two resin materials bearing different chain lengths of sulfonated linear polystyrene brushes were prepared by surface initiated atom transfer radical polymerization (ATRP) of styrene from PS-DVB microbeads (210–420μm) and followed sulfonation. Bromoacetyl groups (0.81mmolg−1) incorporated to the microbeads via acetoxymercuration route were employed as ATRP initiating sites to create non-hydrolyzable linkages between the PS graft chains and bead core. The standard analytical methods and FT-IR spectroscopy techniques were used for characterization of the materials.Ion exchange characteristics (capacity, kinetics and regeneration behaviors) of the resulting materials were investigated in exchange with some divalent metal ions such as Ca (II), Mg (II), Ni (II) and Cu (II) ions in water. Correlation of the exchanged metal concentrations with the sulfonic acid group contents, implied formation of metal mono and disulfonate moieties in the exchange process. High capacities (as high as 1.5–2 times of the commercial resins) and rapid equilibration of the ion exchanges (i.e. less than 1min) were determined as typical characteristics of the newly designed ion exchange materials.

Influence of sulfonated acetone–formaldehyde condensation used as dispersant on low rank coal–water slurry

A water-soluble aliphatic polymer, sulfonated acetone–formaldehyde (SAF) condensation, was developed by sulfonation and polycondensation reaction. To determine the optimum molecular structure of SAF dispersant for preparing the minimum viscosity of highly concentrated low-rank coal–water slurry (CWS), various SAF with different sulfonic group content and different molecular weight were prepared by controlling the quantity of sulfonating agent and the mass concentration of reaction solution. The CWS followed three-parameter Herschel–Bulkley model and behaved as a non-Newtonian fluid in the presence of SAF. Compared with naphthalene sulfonate formaldehyde condensation, SAF had a better effect in reducing the viscosity, especially for the SAF with molecular weight of 31,800–36,800 and the sulfonic group content of 3.53–3.64mmol/g. The effectiveness of viscosity reduction for CWS had been attributed primarily to the diminution of the coal particle–particle interaction because of steric hindrance and electrostatic repulsion, which were offered by adsorbed SAF. The effect was further proved by zeta potential measurements of coal and rheological investigation of slurry in the presence of SAF.

Sulfonated polyethersulfone directly synthesized through sulfonic monomer as a new stable solid acid catalyst for esterification

A new stable solid acid catalyst, functional polyethersulfone containing high content of sulfonic acid group was directly synthesized from sulfonic monomer. This new catalyst was characterized by nuclear magnetic resonance (NMR), thermo-gravimetric analysis, acid-base titration and reagent uptake. The results showed that the new polymer catalyst had higher swelling of reagent and sulfonic group stability than conventional solid acid catalyst Amberlyst 15. Meanwhile, the polymer catalyst exhibited higher activity and stability than Amberlyst 15 in the esterification reactions. The superior performance of new catalyst is attributed to its unique features, including swelling property as well as thermal stability.

The Influence of Laccase Modification on the Adsorption of Lignosulfonate

The ability of commercial laccase to improve the adsorption of sodium lignosulfonate (SL) without any mediator was studied. When SL are modified by laccase, gel permeation chromatography (GPC) shows an initial decrease followed by an extensive increase in molecular weight (Mw). Furthermore, the decrease in Mw is accompanied by an increase in phenolic hydroxyl groups, while the increase in Mw is accompanied by the decrease in phenolic hydroxyl groups. The laccase modification does not affect the content of the sulfonic group. Furthermore, the electrostatic self-assembly technology indicates that the adsorbed amount and the root-mean-square (RMS) of SL/PDAC multilayers increase obviously with the increase of the incubation time, which might be due to the influence of the Mw and the adsorption configuration.

Oxidation and sulfomethylation of alkali-extracted lignin from corn stalk

A lignosulfonate was prepared from alkali-extracted corn stalk lignin (AEL) by oxidation under mild conditions and sulfomethylation. The oxidized AEL exhibited lower molecular weight, narrower molecular weight distribution, and higher phenolic hydroxyl content than AEL, demonstrating that oxidized AEL was more reactive than those before oxidation. The content of sulfonic groups was significantly increased with the increase in sodium sulphite to AEL ratio, while the content slightly decreased when the ratio was above 1:1. During the sulfomethylation, the content of sulfonic groups increased with time and then achieved a constant level with the increase in time. The content of sulfonic groups reached 1.29 mmol/g, the maximum value, at 5 h and a sodium sulphite to AEL ratio of 1:1. The solubility of AEL was obviously improved by sulfomethylation with the increase in the content of sulfonic groups. The surface activity of AEL was improved after sulfomethylation. The sulfomethylation products exhibited good dispersibility and showed potential for use as a dye dispersant.

Application Property and Structural Characteristics of Bark Lignosulfonate Superplasticiser

The application property and structural characteristics of bark lignosulfonate (LS) was studied. Results showed that bark LS had perfect application property in concrete. The fluidity of cement paste was 214mm, which was 87.0% of commercial superplasticiser of naphthalene sulfonate; the loss on fluidity of cement paste of bark LS was very small, which was much better than that of naphthalene sulfonate. The loss on fluidity of cement paste of bark LS after 60 min was only 5.6%, but that of naphthalene sulfonate was 30.6%. Bark LS had low foaming capacity and high foam stability. Surface tension of 1% bark LS solution was 48.1 mN/m. Structural characteristics of bark LS was also studied. It showed that the reason that bark LS had good application property was that it had high content of hydrophilic sulfonic group, carboxyl group and phenolic hydroxyl group, and uniform molecular weight distribution.

Studies on Preparation of Concrete Water Reducer from Xylitol Residue of Corn Cob

Xylitol residue from corn cob was modified by alkaline sulfonation to produce lignosulfonate with good properties for concrete water reducing agent. Results showed that the optimum condition for lignin sulfonation was: total alkaline charge (calculated by Na2O) 16%, cooking temperature 170°C, holding time 3h, degree of sulfitation 80%. The yield of lignosulfonate at this condition was 68.1%. The fluidity of cement paste could reach 124mm when lignosulfonate dosage was 0.35% (on the base of solids). The surface tension of 1% lignosulfonate solution was 46.1 mN/m, and the content of sulfonic group was 2.16 mmol/g.

Studies on Preparation of Concrete Water Reducer from Xylitol Residue of Corn Cob

Xylitol residue from corn cob was modified by alkaline sulfonation to produce lignosulfonate with good properties for concrete water reducing agent. Results showed that the optimum condition for lignin sulfonation was: total alkaline charge (calculated by Na2O) 16%, cooking temperature 170°C, holding time 3h, degree of sulfitation 80%. The yield of lignosulfonate at this condition was 68.1%. The fluidity of cement paste could reach 124mm when lignosulfonate dosage was 0.35% (on the base of solids). The surface tension of 1% lignosulfonate solution was 46.1 mN/m, and the content of sulfonic group was 2.16 mmol/g.

Sulfated graphene as an efficient solid catalyst for acid-catalyzed liquid reactions

Graphene with its two-dimensional sheet of sp2-hybridized carbon is a hot topic in the fields of materials and chemistry due to its unique features. Herein, we demonstrate that sulfated graphene is an efficient solid catalyst for acid-catalyzed liquid reactions. The sulfated graphene was synthesized from a facile hydrothermal sulfonation of reduced graphene oxide with fuming sulfuric acid at 180 °C. Combined characterizations of XRD, Raman, and AFM techniques show that G-SO3H has a sheet structure (1–4 layers). IR spectroscopy shows that G-SO3H has a SO bond, and the XPS technique confirms the presence of an S element in G-SO3H. Acid–base titration indicates that the acidic concentration of sulfonic groups in the sulfated graphene is 1.2 mmol g−1. TG curves shows that the decomposition temperature (268 °C) of the sulfonic groups on the sulfated graphene is much higher than that of conventional SO3H-functionalized ordered mesoporous carbon (237 °C). Catalytic tests of the esterification of acetic acid with cyclohexanol, the esterification of acetic acid with 1-butanol, the Peckmann reaction of resorcinol with ethyl acetoacetate, and the hydration of propylene oxide show that sulfated graphene is much more active than the conventional solid acid catalysts of Amberlyst 15, OMC-SO3H, SO3H-functionalized ordered mesoporous silica (SBA-15-SO3H), graphene oxide, and reduced graphene oxide, which is attributed to the fact that the sulfated graphene almost has no limitation of mass transfer due to its unique sheet structure. Very importantly, the sulfated graphene has extraordinary recyclability in these reactions, which is attributed to the stable sulfonic groups on the sulfated graphene. The advantages, including high activities and good recyclability as well as simple preparation, are potentially important for industrial applications of the sulfated graphene as an efficient heterogeneous solid acid catalyst in the future.

Concrete Superplasticizer Prepared from Catalytic Oxidation of Lignosulfonate

Bamboo lignosulfonate was modified under the role of H2O2 and catalyst in order to improve the dispersing property of lignosulfonate. Results show that the amount of H2O2 and pH value have strong influences on characteristics of lignosulfonate. Cement paste fluidity of lignosulfonate modified at pH5 and 11% H2O2 is 178mm, which is 68% higher than that of unmodified lignosulfonate. Both of oxidative degradation and condensation occur during catalytic oxidation reaction, but oxidation is the main reaction when high amount of H2O2 is applied. The structure of lignosulfonate has some relationship to water reducing property. High molecular weight, high carboxylic content and proper sulfonic group content are the main reasons that enhance water reducing property of lignosulfonate.

General Performance of Sulfonic Group Modified Polycarboxylate-Type Superplasticizer

The polycarboxylate-type superplasticizers (PCS) modified by sulfonic group were prepared. The influence of sulfonic group content on the performance of cement admixtures when using sulfonic group modified PCS was discussed. Some physical properties such as dispersion, cement paste fluidity, mortar fluidity, compressive strength ratio and flexural strength ratio were investigated. The results show that when using PCS with sulfonic group content 20%~25% (mol/mol of total carboxyl group), the dispersion and fluidity of concrete can be distinctly improved, meanwhile the strength properties can be maintained.

A novel β-cyclodextrin polymer modified by sulfonate groups

Based on the special properties and advantages of β-cyclodextrin (β-CD), β-CD polymers have been widely studied and used in recent years. A lot of researches have focused on the adsorption and separation properties of β-CD polymers. In this paper, β-CD polymer modified by sulfonate groups, which was named S-β-CDP, was prepared using epichlorohydrin as crosslinker and tiron (1,2-dihydroxybenzene-3,5-disulfonic acid disodium salt) as modifier. β-CD polymer without modification, which was named β-CDP, was also prepared for comparison. Infrared spectra, elemental analysis and adsorption tests of S-β-CDP were carried out and compared with β-CDP. The content of sulfonate groups in S-β-CDP was obtained from elemental analysis. The dramatically increased adsorption capability toward methylene blue and basic magenta confirmed the existence and chemical activity of sulfonate groups in S-β-CDP. Due to the convenient preparation process and modified adsorption properties, S-β-CDP will find its applications in various fields such as water purification, drug loading, separation and analysis.