• Clean Technology
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• v.22 no.4
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• pp.250-257
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• 2016

As an attempt to replacing petroleum-based chemicals with bio-based ones, synthesis of furfural from biomass-derived xylose attracts much attention in recent days. Conventionally, furfural from xylose has been produced via the utilization of highly corrosive, toxic, and environmentally unfriendly mineral acids such as sulfuric acid or hydrochloric acid. In this study, microwave-assisted biphasic reaction process in the presence of novel bio-based heterogeneous acid catalysts was developed for the eco-benign and effective synthesis of furfural from xylose. The microwave was irradiated for reaction acceleration and a biphasic system consisting of $H_2O$ : MIBK (1 : 2) was designed for continuous extraction of furfural into the organic phase in order to reduce the undesired side products formed by decomposition/condensation/oligomerization in the acidic aqueous phase. Moreover, sulfonated amorphous carbonaceous materials were prepared from wood powder, the most abundant lignocellulosic biomass. The prepared catalysts were characterized by FT-IR, XPS, BET, elemental analysis and they were used as bio-based heterogeneous acid catalysts for the dehydration of xylose into furfural more effectively. For further optimization, the effect of temperature, reaction time, water/organic solvent ratio, and substrate/catalyst ratio on the xylose conversion and furfural yield were investigated and 100% conversion of xylose and 74% yield of furfural was achieved within 5 h at $180^{\circ}C$. The bio-based heterogeneous acid catalysts could be used three times without any significant loss of activity. This greener protocol provides highly selective conversion of xylose to furfural as well as facile isolation of product and bio-based heterogeneous acid catalysts can alternate the environmentally-burdened mineral acids.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1085-1089
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• 1998

The well-established nitric acid-sulfuric acid mixed acid process for the nitration of aromatic compounds has serious problems due to the large amount of waste acids and severe reaction conditions. Nitration of toluene can be conducted using nitrogen dioxide and ozone instead of mixed acid. We found that conc. nitric acid increased the reactivity as catalyst and the amount of nitrogen dioxide controlled the extent of nitration. Dinitration proceeded to more than 92 mole % conversion within 2 hr at $0^{\circ}C$ with 6 eq. of nitrogen dioxide and 2 eq./hr of ozone flow. Toluene completed mononitration within 30 min using 3 eq. of nitrogen dioxide, 3 eq. of nitric acid, and 1.5 eq./hr of ozone flow. As a clean process of aromatic nitration, this method is expected to replace the present process which causes the environmental problems.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.266-272
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• 2020

In this study, the production of ethyl levulinate from chitosan using successive acid-catalyzed hydrolysis and esterification was investigated. To optimize and analysis the reaction factors and heir reciprocal interaction, response surface methodology was introduced. In the effect of water content in ethanol solvent, the production yield of ethyl levulinate was high at 5% water content (or 95% ethanol). As a result of optimization of reaction factors, 30.1% ethyl levulinate yield was obtained under the condition of 200 ℃, 3.19% chitosan, 0.49M sulfuric acid, 5% water content, and 58 min. Finally, the formation yield of ethyl levulinate was tended to enhance by increase of combined severity factor. This result indicated that the potential of chitosan as feedstock for production of chemicals and fuels.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.2
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• pp.201-208
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• 2010

The $SO_2$ and $NO_x$ removal with an activated coke catalyst was conducted by a two-stage reaction which first $SO_2$ was oxidized to $H_2SO_4$ and then $NO_x$ was reduced to $N_2$. But if unreacted sulfur dioxide entered in the second stage, the $NO_x$ reduction was hindered by the reaction with ammonia. In this study, experimental investigations by using lab-scale column apparatus on the product and the reactivity of $SO_2$ with ammonia over coke catalyst which was activated with sulfuric acid was carried out through ultimate analysis DTA, TGA and SEM of catalyst before and after the reaction. Also, the effect of reaction emperature on the reactivity of $SO_2$ with ammonia was determined by means of breakthrough curves with time. The obtained results from this study were summarized as following; Activated cokes were decreased carbon component and increased oxygen and sulfur components in comparison with original cokes. The products over coke catalyst were faced fine crystal of $(NH_4)_2SO_4$, which results in the pressure loss of reacting system. The order of general reactivity in terms of the reaction temperature after breakthrough for $SO_2$ was found to be $150^{\circ}C$ > $200^{\circ}C$ > $100^{\circ}C$. This was related to adsorption amounts of ammonia on the activated cokes.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.4
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• pp.21-29
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• 2015

In this study, the feasibility of utilizing wood chips from pitch pine (Pinus rigida) was evaluated for bioethanol production by an organosolv pretreatment and enzymatic saccharification. When wood chips from pitch wood were pretreated with 75% (v/v) ethanol and 1.7% sulfuric acid as a catalyst at H-factor 2000, average pulp yield was 43.3%, which pretreated wood fibers showed higher glucan (55.8%) and lower lignin (12.2%) contents than untreated control (43.9% glucan and 27.8% lignin). After enzymatic saccharification, the organosolv pulps with 56.2% delignification rate reached above 97% conversion rate of cellulose to glucose. These results indicated that increasing the delignification rate causes micro pores on the surface of organosolv pulps resulting in improved the accessibility of enzyme onto the substrate. Moreover, it was in agreement with the SEM examination of wood fibers.

• Journal of the Korean Wood Science and Technology
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• v.39 no.6
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• pp.459-468
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• 2011

The main purpose of this study was to examine the influence of treatment amounts of Slurry Composting and Biofiltration liquid fertilizer (SCBLF) on biomass growth of Yellow poplar (Liriodendron tulipifera) and to compare bioethanol production from the harvested wood. Relative growth rate, biomass production and leaf characteristics were significantly enhanced by SCBLF treatment and medium treatment plot showed highest value. Nitrogen compounds and water content in SCBLF affected to increase chlorophyll contents which led improving biomass production (64.67%) and glucose contents (6.07%) than control. Organosolv and dilute acid pretreatments were preliminarily carried for bioethanol production, and the pretreatment processes were conducted at all the same solid to liquid ratio (1 : 10), reaction temperature ($150^{\circ}C$), preheating time (40 min) and residence time (10 min). The water insoluble solid recovery of Organosolv pretreatment with 1% sulfuric acid as a catalyst was the lowest and that of medium treatment plot was 44.81%. Exchangeable cations in SCBLF might be affected to increase pretreatment effect. The simultaneous saccharification and fermentation process was followed to determine the ethanol production of the pretreated biomass. The highest ethanol production yield based on initial weight was obtained from high treatment plotby Organosolv pretreatment with 1% sulfuric acid (16.11%). But regarding biomass production, medium treatment plot produced most, and bioethanol production was increased by 72.93% than control.

• Journal of the Korean Chemical Society
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• v.20 no.6
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• pp.469-478
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• 1976

Clinoptilolite zeolite samples were treated with hydrochloric acid, sulfuric acid and phosphoric acid of different strength and the adsorption characteristics and crystal structures of the original and acid-treated clinoptilolites were studied. By treating with hydrochloric acid, the adsorbed amount increased to 5-fold for nitrogen, to 3-fold for benzene, but for methanol no significant change was observed. As acid strength increased further, there were declines both in adsorption capacity and crystallinity. The results showed that the increase of adsorbed amount was caused by the rearrangement of the pore entrance and cation exchange. A method for determination of clinoptilolite content in natural mineral based on benzene adsorption on acid-treated sample is proposed. By this method, the original sample used in this study was found to contain approximately 40% of clinoptilolite. Using pulse technique in micro-catalytic reactor system, the catalytic activities of hydrochloric acid-treated clinoptilolites in cumene cracking and toluene disproportionation reactions were measured. For cumene cracking reaction, the maximum conversion was observed for the 0.5 N hydrochloric acid-treated sample. It is instructive to note that the maximum benzene adsorption was also observed for the sample treated with 0.5 N HCl. This suggest that the conversion rate was determined mainly by the rate of transport of reactants and the products through the pore structure. In the toluene disproportionation reaction, the same trend was observed. But the rate of deactivation was high for samples with strong acid sites. Since catalyst having higher activity was deactivated more easily, the conversion maximum was shifted to the sample treated with higher concentration of acid, -1N. The catalytic activity of $Ca^{2+} and La^{3+} ion exchanged samples for the toluene disproportion was much lower than that of acid-treated samples. Introduction of Ca^{2+} and La^{3+}$ into the pore structure apparently decreases the effective pore diameter of acid-treated clinoptilolite thus limiting the diffusion of reactants and products.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.189-194
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• 2013

A sulfonated activated carbon (AC-$SO_3H$) was used as a solid acid catalyst for dehydration of sorbitol to isosorbide and its catalytic performance was compared with the commercial solid acid such as acidic ion exchange resin, Amberlyst-36, and sulfated copper oxide. The catalytic performance with 100% sorbitol conversion and 52% isosorbide selectivity was obtained over AC-$SO_3H$ at 423.15 K. Although AC-$SO_3H$ possessed only 0.5 mmol/g of sulfur content, it showed the similar dehydration activity of sorbitol to isosorbide with Amberlyst-36 (5.4 mmol/g) at 423.15 K. Based on the high thermal and chemical stability of AC-$SO_3H$, one-step reactive distillation, where isosorbide separation can be carried out simultaneously with sorbitol dehydration, was tried to increase the recovery yield of isosobide from sorbitol. The reactive distillation process using AC-$SO_3H$, the turnover number of AC-$SO_3H$ was 4 times higher than the conventional two-step process using sulfuric acid.

• Journal of Korea Foresty Energy
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• v.19 no.2
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• pp.86-92
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• 2000

The liquefactions of $\alpha$-cellulose(Sigma Chemical, C-8002, 47H0383) was prepared in the presence of phenol using sulfuric acid as a catalyst under $N_2$ gas protection at $180^{\circ}C$ for 60minutes to examine its components. The ratio of $\alpha$-cellulose to phenol was 1: 6.2(w/w), and that to sulfuric acid was 1: 0.05(g/$m\ell$). The yields of liquefaction were calculated after the liquefied mixtures were passed through 1G4 glass filter. The luquefied product of $\alpha$-cellulose was analyzed using GC-MS Spectormeter. The 12 compounds identified by GC-MS Spectrometer, of which peak area covers 54% as 2,4-dimethyl phenol, p-isopropyl phenol, 1-ethyl-3,5-dimethyl benzene, o-isopropyl phenol, (E)-2,4\` dihydroxy-stilbene, 2,2\`-methylene-bisphenol, 4,4\`-methylenebisphenol, 3-methyl-2-hydroxyphenyl-(E)-2-hydroxyl-4\`-methoxy-stilbene, 1-phyenyl-1-(4\`hydroxyphenyl)methanol phenol derivatives. From this results, the reaction pathways of the liquefaction of cellulose were proposed through electrophilic substitution reaction. Phenol as a solvent might react with the reaction intermediates as well in the cellulose liquefaction.

• Journal of the Korean Wood Science and Technology
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• v.43 no.5
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• pp.600-612
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• 2015

We investigated the optimization of the organosolv pretreatment of yellow poplar for bioethanol production. Response surface methodology was used to determine the optimal conditions of three independent variables (reaction temperature, reaction time, and sulfuric acid (SA) concentration). Reaction temperature is the most significant variable in the degradation of xylan and lignin in the presence of an acid catalyst, and ethanol production increased with a decrease in the lignin content. The highest ethanol concentration ($42.80g/{\ell}$) and theoretical ethanol yield (98.76%) were obtained at $152^{\circ}C$ (2.5 bar) with 1.6% SA for 16 min. However, because of excessive degradation of the raw material, the overall ethanol yield was less than under other pretreatment conditions which has approximately 50% of WIS recovery rate after pretreatment. The optimal conditions for the maximum overall ethanol yield ($146^{\circ}C$ with 1.22% SA for 15.9 min) were determined with a predicted yield of 17.11%, and the experimental values were very close (17.15%). Therefore, the quadratic model is reliable.