Advancement in heterogeneous base catalyzed technology: An efficient production of biodiesel fuels

Price fluctuation of petroleum-based diesel, climate change, emerging mandate obligations, availability of new feedstock and the upgrading of conversion technologies are expected to drive biodiesel market to grow robustly in the next coming 10 years. However, the current bottleneck in biodiesel production is the lack of economical sustainable conversion technologies. Generally, industrial production of biodiesel is greatly relied on alkaline homogeneous transesterification reaction. Limitation of the technology, such as multistep process which incur extra pre-step for high acid oil treatment and post-step for biodiesel purification and alkali washing as diminished the economic feasibility and low environmental impact of the entire biodiesel process. Heterogeneous catalysis offers immense potential to develop simple transesterification process, including one step reaction, easy separation, reusability of catalyst, and green reaction. Thus, the aim of this paper is to review the biodiesel production technologies such as blending, micro-emulsion, pyrolysis, and transesterification. Furthermore, recent studies on heterogeneous catalyzed transesterification were presented by discussing the issues such as catalytic performance on different types of biodiesel feedstock, transesterification reaction conditions, limitations encountered by heterogeneous catalysts, and reusability of solid catalysts. The heterogeneous catalysts presented in this review is mainly focused on solid base catalysts, which include single metal oxides, supported metal oxide, binary metal oxide, hydrotalcite, and natural waste shell-based catalyst. Furthermore, current perspectives on application of heterogeneous catalyzed technology in biodiesel industry were discussed herein. (C) 2015 AIP Publishing LLC

Continuously Adjustable, Molecular-Sieving "Gate" on 5A Zeolite for Distinguishing Small Organic Molecules by Size

Zeolites/molecular sieves with uniform, molecular-sized pores are important for many adsorption-based separation processes. Pore size gaps, however, exist in the current zeolite family. This leads to a great challenge of separating molecules with size differences at ~0.01 nm level. Here, we report a novel concept, pore misalignment, to form a continuously adjustable, molecular-sieving “gate” at the 5A zeolite pore entrance without sacrificing the internal capacity. Misalignment of the micropores of the alumina coating with the 5A zeolite pores was related with and facilely adjusted by the coating thickness. For the first time, organic molecules with sub-0.01 nm size differences were effectively distinguished via appropriate misalignment. This novel concept may have great potential to fill the pore size gaps of the zeolite family and realize size-selective adsorption separation

Boehmite-phenolic resin carbon molecular sieve membranes—Permeation and adsorption studies

Publisher Copyright: © 2014 The Institution of Chemical Engineers.Composite carbon molecular sieve membranes (c-CMSM) were prepared in a single dipping-drying-carbonization step from phenolic resin solutions (12.5-15wt.%) loaded with boehmite nanoparticles (0.5-1.2wt.%). A carbon matrix with well-dispersed Al2O3 nanowires was formed from the decomposition of the resin and dehydroxylation of boehmite. The effect of the carbon/Al2O3 ratio on the porous structure of the c-CMSM was accessed based on the pore size distribution and gas permeation toward N2, O2, CO2, He, H2, C3H6 and C3H8. c-CMSM with higher carbon/Al2O3 ratios had a more open porous structure, exhibiting higher permeabilities and lower permselectivities. c-CMSM performance was above the upper bound curves for polymeric membranes for several gas pairs, particularly for C3H6/C3H8 (permeability toward C3H6 of 420 barrer and permselectivity of 18.1 for a c-CMSM with carbon/Al2O3 ratio of 4.4).Unsupported films were also prepared (carbon/Al2O3 ratio 7.3) and crushed into small flakes. Equilibrium isotherms of H2, N2, O2, CO2, C3H8 and C3H6 at 293K were determined on these flakes to obtain the kinetic and adsorption selectivities toward gas pairs of interest; obtained adsorption and diffusion coefficients accurately predicted the permeabilities of all studied gases except CO2 (experimental and predicted permeabilities of 1148 and 154 barrer, respectively).Miguel Teixeira and Margot Tanco are grateful to the Portuguese Foundation for Science and Technology (FCT) for their doctoral grants (references SFRH/BD/24768/2005 and SFRH/BD/61898/2009 , respectively). Marta Campo also acknowledges FCT for her post-doctoral grant (reference SFRH/BPD/65377/2009). The authors also acknowledge financing from FCT through the projects POCTI/EQU/59344/2004, POCTI/EQU/59345/2004 and PTDC/EQU-EQU/114944/2009. Finally, the authors are thankful to CEMUP for the SEM analyses (REEQ/1062/CTM/2005 and REDE/1512/RME/2005 funding provided by FCT).Peer reviewe