Xiuyang Lu

Adsorption of CO2 and CH4 on a magnesium-based metal organic framework

A magnesium-based metal organic framework (MOF), also known as Mg-MOF-74, was successfully synthesized, characterized, and evaluated for adsorption equilibria and kinetics of CO(2) and CH(4). The Mg-MOF-74 crystals were characterized with scanning electron microscopy for crystal structure, powder X-ray diffraction for phase structure, and nitrogen adsorption for pore textural properties. Adsorption equilibrium and kinetics of CO(2) and CH(4) on the Mg-MOF-74 adsorbent were measured in a volumetric adsorption unit at 278, 298, and 318 K and pressures up to 1 bar. It was found that the Mg-MOF-74 adsorbent prepared in this work has a median pore width of 10.2 Å, a BET specific surface area of 1174 m(2)/g, CO(2) and CH(4) adsorption capacities of 8.61 mmol g(-1) (37.8 wt.%) and 1.05 mmol g(-1) (1.7 wt.%), respectively, at 298 K and 1 bar. Both CO(2) and CH(4) adsorption capacities are significantly higher than those of zeolite 13X under similar conditions. The pressure-dependent equilibrium selectivity of CO(2) over CH(4) (q(CO2)/q(CH4)) in the Mg-MOF-74 adsorbent showed a trend similar to that of zeolite 13X and the intrinsic selectivity of Mg-MOF-74 at zero adsorption loading is 283 at 298 K. The initial heats of adsorption of CO(2) and CH(4) on the Mg-MOF-74 adsorbent were found to be 73.0 and 18.5 kJ mol(-1), respectively. The adsorption kinetic measurements suggest that the diffusivities of CO(2) and CH(4) on Mg-MOF-74 were comparable to those on zeolite 13X. CH(4) showed relatively faster adsorption kinetics than CO(2) in both adsorbents. The diffusion time constants of CO(2) and CH(4) in the Mg-MOF-74 adsorbent at 298 K were estimated to be 8.11 × 10(-3) and 4.05 × 10(-2) s(-1), respectively, showing a modest kinetic selectivity of about 5 for the separation CH(4) from CO(2).

Adsorption of Ethane, Ethylene, Propane, and Propylene on a Magnesium-Based Metal–Organic Framework

Separation of olefin/paraffin is an energy-intensive and difficult separation process in petrochemical industry. Energy-efficient adsorption process is considered as a promising alternative to the traditional cryogenic distillation for separating olefin/paraffin mixtures. In this work, we explored the feasibility of adsorptive separation of olefin/paraffin mixtures using a magnesium-based metal-organic framework, Mg-MOF-74. Adsorption equilibria and kinetics of ethane, ethylene, propane, and propylene on a Mg-MOF-74 adsorbent were determined at 278, 298, and 318 K and pressures up to 100 kPa. A dual-site Sips model was used to correlate the adsorption equilibrium data, and a micropore diffusion model was applied to extract the diffusivities from the adsorption kinetics data. A grand canonical Monte Carlo simulation was conducted to calculate the adsorption isotherms and to elucidate the adsorption mechanisms. The simulation results showed that all four adsorbate molecules are preferentially adsorbed on the open metal sites where each metal site binds one adsorbate molecule. Propylene and propane have a stronger affinity to the Mg-MOF-74 adsorbent than ethane and ethylene because of their significant dipole moments. Adsorption equilibrium selectivity, combined equilibrium and kinetic selectivity, and adsorbent selection parameter for pressure swing adsorption processes were estimated. The relatively high values of adsorption selectivity suggest that it is feasible to separate ethylene/ethane, propylene/propane, and propylene/ethylene pairs in a vacuum swing adsorption process using Mg-MOF-74 as an adsorbent.

Enrichment and purification of madecassoside and asiaticoside from Centella asiatica extracts with macroporous resins.

In present study, the performance and separation characteristics of five macroporous resins for the enrichment and purification of asiaticoside and madecassoside from Centella asiatica extracts have been evaluated. The adsorption and desorption properties of total triterpene saponins (80% purity) on macroporous resins including HPD100, HPD300, X-5, AB-8 and D101 have been compared. According to our results, HPD100 offered higher adsorption and desorption capacities and higher adsorption speed for asiaticoside and madecassoside than other resins. Column packed with HPD100 resin was used to perform dynamic adsorption and desorption tests to optimize the separation process of asiaticoside and madecassoside from C. asiatica extracts. After the treatment with gradient elution on HPD100 resin, the content of madecassoside in the product increased from 3.9 to 39.7%, and the recovery yield was 70.4%; for asiaticoside the content increased from 2.0 to 21.5%, and the recovery yield was 72.0%. The results showed that HPD100 resin revealed a good ability to separate madecassoside and asiaticoside, and the method can be referenced for the separation of other triterpene saponins from herbal raw materials.

Catalytic hydrothermal deoxygenation of palmitic acid

We herein report a new approach to convert fatty acids to hydrocarbons in near- or supercritical water. We tested several different metal salts, bases, and high-surface-area supported metal catalysts for activity toward deoxygenation of palmitic acid in a hydrothermal reaction medium. Two heterogeneous catalysts, 5% platinum on activated carbon (Pt/C) and 5% palladium on activated carbon (Pd/C), proved to be very effective for hydrothermal deoxygenation of palmitic acid. The reactions were done in water with no added H2. The catalysts can be reused without significant activity loss, and the selectivity was more than 90% toward pentadecane, the deoxygenation product. We examined the effect of the catalyst loading, reactant loading, batch holding time, and reaction temperature on the Pt/C-catalyzed deoxygenation rate. The results show that the reaction is first-order in palmitic acid, and the rate constants displayed Arrhenius behavior with an activation energy of 79 kJ mol−1.

Hydrothermal Decarboxylation and Hydrogenation of Fatty Acids over Pt/C

We report herein on the conversion of saturated and unsaturated fatty acids to alkanes over Pt/C in high-temperature water. The reactions were done with no added H(2) . The saturated fatty acids (stearic, palmitic, and lauric acid) gave the corresponding decarboxylation products (n-alkanes) with greater than 90 % selectivity, and the formation rates were independent of the fatty acid carbon number. The unsaturated fatty acids (oleic and linoleic acid) exhibited low selectivities to the decarboxylation product. Rather, the main pathway was hydrogenation to from stearic acid, the corresponding saturated fatty acid. This compound then underwent decarboxylation to form heptadecane. On the basis of these results, it appears that this reaction system promotes in situ H(2) formation. This hydrothermal decarboxylation route represents a new path for using renewable resources to make molecules with value as liquid transportation fuels.

In situ ethyl ester production from wet algal biomass under microwave-mediated supercritical ethanol conditions

An in situ transesterification approach was demonstrated for converting lipid-rich wet algae (Nannochloropsis salina) into fatty acid ethyl esters (FAEE) under microwave-mediated supercritical ethanol conditions, while preserving the nutrients and other valuable components in the algae. This single-step process can simultaneously and effectively extract the lipids from wet algae and transesterify them into crude biodiesel. Experimental runs were designed to optimize the process parameters and to evaluate their effects on algal biodiesel yield. The algal biomass characterization and algal biodiesel analysis were carried out by using various analytical instruments such as FTIR, SEM-EDS, TLC, GC-MS and transmission electron microscopy (TEM). The thermogravimetric analysis (TGA) under nitrogen and oxygen environments was also performed to examine the thermal and oxidative stability of ethyl esters produced from wet algae. This simple in situ transesterification process using a green solvent and catalyst-free approach can be a potentially efficient route for algal biodiesel production.

Synthesis and biological evaluation of imidazol-2-one derivatives as potential antitumor agents

A new series of aryl substituted imidazol-2-one derivatives structurally related to combretastatin A-4 (CA-4) were synthesized and evaluated for their cytotoxic activities in vitro against various human cancer cell lines including MDR cell line. The cytotoxic effects of compounds 7b and 7i proved to be similar to or greater than that of docetaxel. The highly active compound 7b also exhibited excellent inhibitory activity on tumor growth in vivo.

One-pot preparation of methyl levulinate from catalytic alcoholysis of cellulose in near-critical methanol.

One-pot preparation of methyl levulinate (MLA) from cellulose in near-critical methanol was studied. Acids containing SO(3)H group were proven to be effective catalysts for the production of MLA from celluloses catalytic alcoholysis. The effects of different reaction conditions, such as an initial cellulose concentration of 10-30 g/L, a temperature range from 170 to 190°C, and a sulfuric acid concentration of 0.01-0.03 mol/L, on the production of MLA were investigated. The results showed the reaction temperature and acid concentration significantly affected the process of cellulose alcoholysis and the yield of MLA. A high yield of up to 55% MLA was achieved at 190°C for 5h, using 0.02 mol/L H(2)SO(4) as a catalyst.

Production of aviation fuel via catalytic hydrothermal decarboxylation of fatty acids in microalgae oil

A series of fatty acids in microalgae oil, such as stearic acid, palmitic acid, lauric acid, myristic acid, arachidic acid and behenic acid, were selected as the raw materials to produce aviation fuel via hydrothermal decarboxylation over a multi-wall carbon nanotube supported Pt catalyst (Pt/MWCNTs). It was found that Pt/MWCNTs catalysts exhibited higher activity for the hydrothermal decarboxylation of stearic acid with a 97% selectivity toward heptadecane compared to Pt/C and Ru/C under the same conditions. And Pt/MWCNTs is also capable for the decarboxylation of different fatty acids in microalgae oil. The reaction conditions, such as Pt/MWCNTs loading amount, reaction temperature and time were optimized. The activation energy of stearic acid decarboxylation over Pt/MWCNTs was calculated (114 kJ/mol).

Adsorption of alkaloids on ordered mesoporous carbon

An ordered mesoporous carbon (OMC) adsorbent was synthesized, characterized, and evaluated for effective separation and purification of alkaloid compounds from aqueous solutions. The OMC adsorbent has a large BET specific surface area (1532.2m(2)/g), large pore volume (2.13cm(3)/g), and narrow pore diameter distribution with a median pore diameter of 4.21nm. Berberine hydrochloride, colchicine, and matrine were selected as the model compounds for evaluating the adsorption properties of the OMC adsorbent for alkaloid purification. Batch adsorption experiments of pure components in water were carried out to measure both adsorption equilibria and kinetics, and column breakthrough and desorption experiments were performed to validate the separation and regeneration efficacy of the OMC adsorbent. The adsorption equilibrium capacities of berberine hydrochloride, colchicine, and matrine on the OMC adsorbent at 0.100mg/L and 298K are 450, 600, and 480mg/g, respectively, which are more than double the adsorption capacities of these compounds on two commonly used commercial resins (HPD300 and HPD100B) at similar conditions. Adsorption equilibrium of all three alkaloids could be obtained within 120min at 298K. The dynamic adsorption capacities determined from the breakthrough experiments are within 12% of the estimated equilibrium capacities from the Langmuir isotherms; and 74.3-92.8% of the adsorbed amounts could be recovered by desorbing with a 70% alcohol solution. The adsorption isotherms are analyzed with both Langmuir and Freundlich models, the adsorption kinetic data with the pseudo-first-order and pseudo-second-order models, and the breakthrough curves with four breakthrough models. The large adsorption capacity, fast adsorption rate, and easy regeneration make the ordered mesoporous carbon a promising adsorbent for adsorption and purification of alkaloid compounds from the extracts of herbal plants.