Activity of a Sulfonated Carbon-Based Catalyst Derived from Organosolv Lignin toward Esterification of Stearic Acid under Near-Critical Alcohol Conditions.

In this study, an environmentally benign carbon-based catalyst derived from extracted bagasse lignin (EL) was successfully synthesized by solvothermal carbonization and sulfonation with methane sulfonic acid (MSA). Interestingly, the results indicated that the use of MSA as a sulfonation agent made a catalyst with higher thermal stability than conventional sulfuric acid. Thus, in comparison to the catalyst prepared by using sulfuric acid, the catalyst prepared by using MSA (EL-MSA) exhibited higher catalytic activity in the esterification of stearic acid under near-critical methanol conditions. Under optimum conditions (260 °C for 5 min, a 9:1 methanol-to-stearic-acid molar ratio, 5 wt % catalyst loading, and 10% v/v toluene), the esterification over the EL-MSA catalyst promoted a 91.1% methyl stearate yield. Moreover, the results also revealed that the high thermal stability of the EL-MSA catalyst not only affects its great catalytic activity, but it also prevents damage to the porous structure and decomposition of acidic surface oxygen-containing functional groups. It contributes to the excellent reusability of the catalyst. After the fifth run, a high yield of 82.8% was obtained. The effect of alcohol type on the catalyst performance was also studied. It was found that the EL-MSA catalyst also presented good performance toward esterification with ethanol and propanol, from which ethyl stearate and propyl stearate with a more than 80% ester yield can be achieved.

Effects of Kraft lignin on hydrolysis/dehydration of sugars, cellulosic and lignocellulosic biomass under hot compressed water.

The effect of Kraft lignin presenting on the hydrolysis and dehydration of C5 and C6 sugars, cellulose, hemicelluloses and biomass under hot compressed water (HCW) in the presence of H3PO4 catalyst was intensively studied. The lignin strongly inhibited the acid hydrolysis of cellulose and hemicellulose to glucose and xylose, respectively. Interestingly, the admixed lignin markedly promoted the isomerization of glucose to fructose, and dehydration of fructose (except at the low catalyst loading), resulting in high 5-hydroxymethylfurfural yields. Nonetheless, lignin inhibited the hydrolysis of xylan to xylose and dehydration of xylose to furfural. Moreover, the acidity of the system significantly affects the hydrolysis/dehydration of biomass. It was revealed that the presence of lignin strongly interfered the yields of sugars and furans produced from raw corncob, while the delignified corncob provided significant improvement of product yields, confirming the observed role of lignin in the biomass conversion system via sugar platforms.

Conversion of fructose, glucose, and cellulose to 5-hydroxymethylfurfural by alkaline earth phosphate catalysts in hot compressed water.

The phosphates of alkaline earth metals (calcium and strontium) synthesized by precipitation process in acetone-water media system were used as catalysts for converting fructose, glucose, and cellulose to 5-hydroxymethylfurfural (HMF) under hot compressed water condition. It was found that the phosphates of calcium and strontium effectively catalyzed the HMF formation from fructose and glucose dehydration and cellulose hydrolysis/dehydration reaction, as compared with the non-catalytic system. The XRD analysis confirmed the CaP(2)O(6) and α-Sr(PO(3))(2) crystalline phases of the catalyst samples, while acid strength of both catalysts was in a range of +3.3 ≤ H(0) ≤ +4.8. From the study, CaP(2)O(6) and α-Sr(PO(3))(2) showed similar catalytic performance toward the dehydration of sugars, providing the HMF yields of 20-21% and 34-39% from glucose and fructose, respectively; whereas the total yield of glucose and HMF from the hydrolysis/dehydration of cellulose over α-Sr(PO(3))(2) (34%) was higher than that over CaP(2)O(6) (17.4%).

Multi-element preconcentration of heavy metal ions from aqueous solution by APDC impregnated activated carbon.

Ammonium pyrrolidinedithiocarbamate impregnated activated carbon (APDC-AC) has been used for the preconcentration of Cd(II), Cu(II), Ni(II), and Zn(II) from aqueous solution by column solid phase extraction (SPE) technique. Trace metal ions in aqueous solution were quantitatively sorbed onto APDC-AC packed in a SPE column at pH 5.0 with a flow rate of 1.0mLmin(-1). The sorbed metals were eluted with 1M nitric acid in acetone solution at a flow rate of 0.6mLmin(-1) and analyzed by flame atomic absorption spectrometry. The effects of sample volume, amount of APDC-AC, volume of eluent and ionic strength of working solution on metal ion recovery have been investigated. The present methodology gave recoveries from 90 to 106% and R.S.D. from 0.6 to 5.5%.