Mohd Asmadi

Optimization of levulinic acid from lignocellulosic biomass using a new hybrid catalyst

Conversion of glucose, empty fruit bunch (efb) and kenaf to levulinic acid over a new hybrid catalyst has been investigated in this study. The characterization and catalytic performance results revealed that the physico-chemical properties of the new hybrid catalyst comprised of chromium chloride and HY zeolite increased the levulinic acid production from glucose compared to the parent catalysts. Optimization of the glucose conversion process using two level full factorial designs (2(3)) with two center points reported 55.2% of levulinic acid yield at 145.2 °C, 146.7 min and 12.0% of reaction temperature, reaction time and catalyst loading, respectively. Subsequently, the potential of efb and kenaf for producing levulinic acid at the optimum conditions was established after 53.2% and 66.1% of efficiencies were reported. The observation suggests that the hybrid catalyst has a potential to be used in biomass conversion to levulinic acid.

Pyrolysis reactions of Japanese cedar and Japanese beech woods in a closed ampoule reactor

The chemical structures of hemicellulose and lignin are different for two distinct types of wood, i.e., softwood and hardwood. Such differences are expected to affect pyrolysis behavior. In this article, the differences are discussed for Japanese cedar wood (a softwood) and Japanese beech wood (a hardwood) pyrolyzed in a closed ampoule reactor (N2/600°C/40–600 s). Oven-dried samples were used to eliminate the influence of initial water. Demineralized samples (prepared by acid washing) were also used to determine the influence of the minerals contained in the wood samples. As a result, some features were disclosed for secondary char (coke) formation, char reactivity, tar formation, and subsequent decomposition.

The effects of combining guaiacol and syringol on their pyrolysis

Abstract Pyrolysis of guaiacol/syringol mixtures was studied in an ampoule reactor (N2/600°C/40–600 s) to understand the reactivities of the aromatic nuclei in hardwood lignins. By comparing the results with those of pure guaiacol or syringol, significant effects of their combination were observed during early stage pyrolysis: charring and gas formation were markedly suppressed. Yields for the tar fractions (MeOH-soluble) were increased by combination but the contents of GC/MS-detectable products with low molecular weight were dramatically decreased in these fractions, especially catechol-type compounds diminished, which are formed through the O-CH3 homolysis reaction and subsequent donation of hydrogen atoms. These observations are discussed at the molecular level. Inhibition of the charring reaction, which can act as a strong hydrogen donor, would increase the probability of radical coupling reactions of the O-CH3 homolysis products instead of the formation of catechol and pyrogallol and their derivatives. The latter compounds are important intermediates for gas formation, especially for CO. Based on these lines of evidence, a hypothesis is proposed according to which poly\xadaromatization during carbonization activates the pyrolytic reactions of guaiacol and syringol.

Synthesis and characterization of carbon cryogel microspheres from lignin–furfural mixtures for biodiesel production

The aim of this work was to study the potential of biofuel and biomass processing industry side-products as acid catalyst. The synthesis of carbon cryogel from lignin-furfural mixture, prepared via sol-gel polycondensation at 90°C for 0.5h, has been investigated for biodiesel production. The effect of lignin to furfural (L/F) ratios, lignin to water (L/W) ratios and acid concentration on carbon cryogel synthesis was studied. The carbon cryogels were characterized and tested for oleic acid conversion. The thermally stable amorphous spherical carbon cryogel has a large total surface area with high acidity. Experimental results revealed the optimum FAME yield and oleic acid conversion of 91.3wt.% and 98.1wt.%, respectively were attained at 65°C for 5h with 5wt.% catalyst loading and 20:1 methanol to oleic acid molar ratio. Therefore, carbon cryogel is highly potential for heterogeneous esterification of free fatty acid to biodiesel.

Pyrolysis and Secondary Reaction Mechanisms of Softwood and Hardwood Lignins at the Molecular Level

Primary pyrolysis and secondary reactions of Japanese cedar (Cryptomeria japonica, a softwood) and Japanese beech (Fagus crenata, a hardwood) wood lignins were studied with open-top and closed-ampoule reactors in N2 at 400–600°C. Milled wood lignins (MWL) isolated from these wood samples were used along with several model aromatic compounds (guaiacol and syringol and their pyrolysis intermediates). Although the low molecular weight products from beech MWL included more syringyl-type of aromatic rings in primary pyrolysis, in the secondary reaction step, the yields of syringyl-characteristic products were quite lower than those of guaiacyl-characteristic products. Contrary to this, the beech MWL and syringol produced more coke. These results suggest that the syringyl-characteristic products are converted preferentially into coke, instead of other low MW products. The molecular mechanisms of these tar conversions are also discussed with the model compound data. Additional OCH3 group in syringyl-unit enhances the coke formation through double opportunity of the OCH3 rearrangement pathway, which includes o-quinonemethide as a key intermediate step for coke formation.

Dry Reforming of Methane Over Oil Palm Shell Activated Carbon and ZSM-5 Supported Cobalt Catalysts

ABSTRACT In this study, cobalt supported oil palm shell activated carbon (Co/OPS-AC) and ZSM-5 zeolite (Co/ZSM-5) catalysts have been prepared for dry reforming of methane. Cobalt ratios of 6.0 and 14.0 wt% were deposited via wet impregnation method to the OPS-AC and ZSM-5 catalysts. The catalysts were characterized by XRD, N2 adsorption--desorption isotherms, BET surface area, SEM, FESEM-EDX, TPR-H2, and TPD-NH3. The dry reforming of methane was performed using a micro reactor system under the condition of 10,000 ml/h.g-cat, 3 atm, CH4/CO2 ratio of 1.2:1.0 and temperature range from 923 K to 1023 K. The gaseous products were analyzed by gas chromatography (GC) with thermal conductivity detector (TCD) and further quantified to determine the conversions of CH4 and CO2, and the yields of CO and H2. Experimental results revealed both catalysts exhibited lower conversions of CO2 and CH4 with the increase in temperature from 923 K to 1023 K. The reduced conversions may be due to the formation of carboneous substance on the catalyst known as coking. Comparatively, Co/OPS-AC gave higher conversions of CO2 and CH4 as well as higher yields of H2 and CO as it has a higher surface area than Co/ZSM-5 which subsequently rendered higher activity for the reforming of methane. With the increasing cobalt loadings and reaction temperature, OPS-AC(14) catalyst exhibited improved activity and H2/CO ratio. Based on these results, cobalt supported OPS activated carbon catalyst was suggested to be more effective for CO2 and CH4 conversions.

Carbon Cryogel from Lignin-Furfural as Acid Catalyst in Esterification of Oleic Acid

Carbon cryogel (CC) has been synthesized from commercial lignin with furfural via acid catalyzed sol-gel polycondensation reaction step. Freeze drying and carbonization were performed on the gels for preparation of the CC. Effect of water and H2SO4 concentration on carbon synthesis was studied where lignin to water (L/W) ratio and acid concentration of 1.0 and 8 M, respectively were found suitable for CC synthesis. The selected CC exhibited higher thermal stability which can be used in thermal reaction process. CC has potential as super acid solid catalyst with acidity and surface area of 14.07 mmol/g and 330.35 m2/g, respectively for esterification of free fatty acid to produce 91.3 wt.% FAME yield.

Primary Pyrolysis and Secondary Reaction Behaviors as Compared Between Japanese Cedar and Japanese Beech Wood in an Ampoule Reactor

The purpose of this work is to understand the primary pyrolysis and secondary reaction behaviors of two distinct groups of woody biomass, i.e., softwood and hardwood by using Japanese cedar wood (a softwood) and Japanese beech wood (a hardwood). Their demineralized samples were also used in order to understand the influences of inorganic substance. Heat-treatment was conducted under the conditions of N2 / 600°C / 40–600 s in an ampoule reactor. In this paper, some characteristic features of these wood samples are reported and discussed with the different chemical structures of lignin and hemicellulose as their composing polymers.