Linlin Yi,Huan Liu,Kangxin Xiao,Geyi Wang,Qiang Zhang,Hongyun Hu,Hong Yao
The fast pyrolysis of biomass with catalysts is a promising route for producing upgraded bio-oil as an alternative energy source . A CaO catalyst prepared from organic calcium compounds (Org-CaO) was first used to upgrade the pyrolysis oil of Jatropha curcas seeds in situ. Calcium d -gluconate monohydrate, calcium citrate tetrahydrate, and calcium acetate hydrate were employed as the organic precursors in this work. The results showed that Org-CaO exhibited better deoxygenation ability to produce more hydrocarbons than conventional CaO derived from Ca(OH) 2 (CH CaO). Acids accounted for 83% of the oxygenated compounds in the raw bio-oil and were almost completely removed via CaO. For bio-oil catalyzed by Org-CaO, the fraction of esters in the oxygenated compounds was only ∼9%, which was 20% less than that in CH CaO bio-oil. The relative content of ketones and alcohols in Org-CaO bio-oil increased by 16% versus that in CH CaO bio-oil. Org-CaO exhibited a remarkably larger pore size and much smaller particle sizes. Thus, Org-CaO entered into the fuel through the pore channels, and this promoted the formation of chemical crosslinking points between CaO and oxygenated groups. In addition, the basicity and the amount of basic sites for Org-CaO increased versus CH CaO. Thus, the adsorption forms of oxygen-containing groups in the bio-oil on the basic sites of CaO changed: the carboxyl groups were removed from the acids and were absorbed in a stable form of unidentate carbonate on oxygen vacancies (O 2− ). The stable form was bidentate carbonate on Ca 2+ –O 2− . In addition, oxygen vacancies on Org-CaO extracted more hydroxyl groups from the acids, resulting in dehydroxylation of acids to form ketones and alcohols.
Xi Liu,Shuai Zhang,Qing-Wen Song,Xiao-Fang Liu,Ran Ma,Liang-Nian He
A bifuncational catalytic system consisting of CaBr2 and 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) was developed for the efficient fixation of CO2 with epoxides to cyclic carbonates. Such a dual catalysis facilitates the reaction to proceed smoothly at atmospheric CO2 pressure, presumably due to the simultaneous activation of CO2 by DBU and epoxides by CaBr2. In addition, the activation role of CaBr2 was also studied using density functional theory (DFT) calculations. A plausible mechanism involving the DBU–CO2 adduct-assisted ring opening path and the bromide anion-promoted ring opening path is proposed, in combination with the activation of epoxides by the calcium cation. This process represents a simple, cost-effective and biocompatible route to obtain cyclic carbonates from CO2 under mild conditions, especially at atmospheric CO2 pressure.
Mengjie Zhang,Xiangpu Jiao,Dezhang Ren,Chenxin Huang,Yang Li,Duofu Chen,Zhibao Huo
The rapid development of the biodiesel industry is of significant importance for achieving carbon emission reduction in the transportation sector. However, the presence of trace amounts of water in the feedstock during biodiesel synthesis may lead to severe saponification reactions, thereby reducing the yield of fatty acid methyl esters. In this study, based on our exploration of the characteristic of porous carbon to absorb moisture from the environment, we synthesized a CaO catalyst with porous carbon coating via discarded shrimp shell biomass. Because the carbonization temperature of organic matter in shrimp shells is lower than the decomposition temperature of CaCO 3 , the CO 2 generated during pyrolysis can erode the pyrolytic carbon and form porous structure. The mesoporous carbon shell facilitates the diffusion of oil and methanol molecules while adsorbing moisture in the alcohol phase. This structure effectively minimizes the interaction between CaO and water, thereby suppressing saponification reactions and ensuring the smooth progression of the desired transesterification reaction. Through a series of physicochemical characterizations, the structure and water absorption performance of the catalyst were confirmed. The as-prepared CaO@PC-900 catalyst demonstrated the ability to maintain a biodiesel yield of over 85% in a reaction system with a water content of 3%, significantly surpassing the performance of commercial CaO and previously reported Ca-based solid bases. This work provides a new approach to the design of anti-saponification transesterification catalysts, while also offering a novel pathway for the synthesis of porous carbon from discarded crustacean biomass.
Several rare earth-doped, calcium-based magnetic catalysts were prepared for the synthesis of glycerol carbonate. The basicity and basic strength analysis of the catalysts showed that the doping of rare earth improved the basicity of the catalysts, and the doping of lanthanum maximized it. In addition, with the doping of lanthanum, the particle size of the catalyst became smaller to promote the organic reactants near the active sites of catalysts, thereby effectively improving the performance. NiFe 2 O 4 @[CaO-La 2 O 3 ] shows better catalytic performance with 99.0% yield of glycerol carbonate compared to the other catalysts. The NiFe 2 O 4 @(CaO-La 2 O 3 ) could be reused in six cycles without significant loss in activity.
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