Thermodynamic analysis of methanation of palm empty fruit bunch (PEFB) pyrolysis oil with and without in situ CO2 sorption

Thermodynamic equilibrium analysis for conversion of palm empty fruit bunch (PEFB) bio-oil to methane using low-temperature steam reforming (LTSR) process was conducted by assuming either isothermal or adiabatic condition, with and without sorption enhancement (SE-LTSR), with CaO(S) or Ca(OH)2(S) as CO2 sorbent. Temperatures of 300-800 K, molar steam to carbon (S/C) ratios of 0.3-7.0, pressures of 1-30 atm and molar calcium to carbon ratios (Ca:C) of 0.3-1.0 were simulated. For reasons of process simplicity, the best conditions for CH4 production were observed for the adiabatic LTSR process without sorption at S/C between 2.5 and 3 (compared to the stoichiometric S/C of 0.375), inlet temperature above 450 K, resulting in reformer temperature of 582 K, where close to the theoretical maximum CH4 yield of 38 wt % of the simulated dry PEFB oil was obtained, resulting in a reformate consisting of 44.5 vol % CH4, 42.7 vol % CO2 and 12.7 vol % H2 and requiring only moderate heating mainly to partially preheat the reactants. Temperatures and S/C below these resulted in high risk of carbon by-product

Bioreactor for microalgal cultivation systems: strategy and development

Microalgae are important natural resources that can provide food, medicine, energy and various bioproducts for nutraceutical, cosmeceutical and aquaculture industries. Their production rates are superior compared to those of terrestrial crops. However, microalgae biomass production on a large scale is still a challenging problem in terms of economic and ecological viability. Microalgal cultivation system should be designed to maximize production with the least cost. Energy efficient approaches of using light, dynamic mixing to maximize use of carbon dioxide (CO2) and nutrients and selection of highly productive species are the main considerations in designing an efficient photobioreactor. In general, optimized culture conditions and biological responses are the two overarching attributes to be considered for photobioreactor design strategies. Thus, fundamental aspects of microalgae growth, such as availability of suitable light, CO2 and nutrients to each growing cell, suitable environmental parameters (including temperature and pH) and efficient removal of oxygen which otherwise would negatively impact the algal growth, should be integrated into the photobioreactor design and function. Innovations should be strategized to fully exploit the wastewaters, flue-gas, waves or solar energy to drive large outdoor microalgae cultivation systems. Cultured species should be carefully selected to match the most suitable growth parameters in different reactor systems. Factors that would decrease production such as photoinhibition, self-shading and phosphate flocculation should be nullified using appropriate technical approaches such as flashing light innovation, selective light spectrum, light-CO2 synergy and mixing dynamics. Use of predictive mathematical modelling and adoption of new technologies in novel photobioreactor design will not only increase the photosynthetic and growth rates but will also enhance the quality of microalgae composition. Optimizing the use of natural resources and industrial wastes that would otherwise harm the environment should be given emphasis in strategizing the photobioreactor mass production. To date, more research and innovation are needed since scalability and economics of microalgae cultivation using photobioreactors remain the challenges to be overcome for large-scale microalgae production

HYDROFORMYLATION OF ALPHA-PINENE AND BETA-PINENE CATALYZED BY RHODIUM AND COBALT CARBONYLS

Alpha- and beta-Pinene were hydroformylated to their respective aldehydes and alcohols at 60-130-degrees-C and 600 psi of CO/H-2. Employing Rh6(CO)16 as a catalyst precursor the main product is 10-formylpinane, 2. In contrast, mononuclear rhodium complexes containing phosphine ligands typically give 3-formylpinane, 1, as the major product. 3-Formylpinane, 1, was also the main product upon employing either Co2 (CO)8 or phosphine-modified Rh6(CO)16. The turnover frequency drops sharply as the total rhodium concentration increases upon using Rh6(CO)16, to catalyze alpha-pinene hydroformylation at 130-degrees-C and 600 psi of H-2/CO (1:1). This shows that cluster fragmentation occurs to generate the active catalytic species of lower nuclearity. Furthermore, the product distribution at equivalent alpha-pinene conversions remains the same at different total rhodium concentrations under Rh6(CO)16 catalysis, suggesting there is only (predominantly) one catalytically active species operating in the reaction. Hydroformylation with triphenylphosphite-modified Rh6(CO)16 was initially faster but the catalyst life is short due to hydrogenolysis of triphenylphosphite which produces phenol. Hydrogenation of alpha- and beta-pinene (Pd/C, 1 atm H-2, ambient temperature) generated the two pinane isomers, 10 and 11, which result from the hydrogen addition to the two faces of the double bond. The only hydrogenation byproduct detected during Rh6(CO)16-catalyzed hydroformylations was 11 where hydrogen addition occurred to the face of the double bond which was cis to the C(CH3)2 bridge. Use of the mixed metal carbonyl systems: Co2(CO)8/Rh6(CO)16, Co2(CO)8/Ru3(CO)12, Rh6(CO)16/RU3(CO)12/PPh3 and Co2(CO)12/Rh6(CO)16/PPh3 in toluene at 100-degrees-C and 600 psi H-2/CO=1:1 did not lead to any synergistic rate enhancements in the hydroformylation of alpha-pinene.8341671516

Chiral ligands derived from abrine. Part 7: Effect of O, S, N in aromatic ring substituents at C-1 on enantioselectivity induced by tetrahydro-beta-carboline ligands in diethylzinc addition to aldehydes

The effect or O, S and N atoms in aromatic ring substituents at C-1 position of tetrahydro-B-carboline ligands on the enantioselectivity of diethylzinc additions to benzaldehyde was studied when esters or tertiary alcohol functions were present at C-3. A mechanism is proposed to explain why the ester ligands 2c and 2d, in which the pyridyl N atom is at C'-2 in 2c and at C'-3 in 2d, catalyzed the addition of diethylzinc to benzaldehyde to form the (R)- and (S)-enantiomers of 1-phenyl-1-propanol, respectively. An explanation was also proposed for the moderate enantioselectivity induced by tert-alcohol 3c versus the very small enantioselectivity induced by 3d. containing a 3-pyridyl function at C-1, during diethylzine additions. A -CH2-t-Bu substituent at C-1 leads to very high enantio selectivities. (C) 2001 Elsevier Science Ltd. All rights reserved

Activation of methane to syngas over a Ni/TiO2 catalyst

Partial oxidation of methane (POM) to syngas and CH4/CO2 reforming have been investigated over a Ni/TiO2 catalyst in a fixed-bed reactor. The Ni/TiO2 catalyst has high initial activity but undergoes significant deactivation during the partial oxidation of methane reaction. Deactivation is due largely to the oxidation of Ni(0) to NiTiO3. After the partial oxidation of methane at 700degreesC the catalyst was pale yellow. XRD confirmed that Ni(0) had been converted to NiTiO3 and oxygen pulse reactions found only traces of carbon were present after the POM reaction. The Ni/TiO2 catalyst has a high activity and a long term stability in the CO2 reforming reaction. XRD found Ni(0) was present after the reforming reaction but NiO and NiTiO3 were absent. Activation of methane over Ni/TiO2 was also investigated using pulse reaction techniques in the absence of gas phase oxygen. Methane pulse reactions demonstrated that the mechanism of methane oxidation changes as the oxidation state of nickel changes. CH4 may have been oxidized by oxygen from solid NiO or by active oxygen within the TiO2 Support via the non-selective Rideal-Eley mechanism over the oxidized Ni/TiO2 catalyst surface. In contrast, CH4 is efficiently converted to CO and H-2 via a direct oxidation mechanism when Ni/TiO2 is reduced. Pulse reaction studies provide evidence that the oxidation state of nickel controls the methane activation mechanism and the product distribution. (C) 2002 Elsevier Science B.V. All rights reserved