Paul A. Webley

Extraction of oil from microalgae for biodiesel production: a review.

The rapid increase of CO(2) concentration in the atmosphere combined with depleted supplies of fossil fuels has led to an increased commercial interest in renewable fuels. Due to their high biomass productivity, rapid lipid accumulation, and ability to survive in saline water, microalgae have been identified as promising feedstocks for industrial-scale production of carbon-neutral biodiesel. This study examines the principles involved in lipid extraction from microalgal cells, a crucial downstream processing step in the production of microalgal biodiesel. We analyze the different technological options currently available for laboratory-scale microalgal lipid extraction, with a primary focus on the prospect of organic solvent and supercritical fluid extraction. The study also provides an assessment of recent breakthroughs in this rapidly developing field and reports on the suitability of microalgal lipid compositions for biodiesel conversion.

Oil extraction from microalgae for biodiesel production

This study examines the performance of supercritical carbon dioxide (SCCO(2)) extraction and hexane extraction of lipids from marine Chlorococcum sp. for lab-scale biodiesel production. Even though the strain of Chlorococcum sp. used in this study had a low maximum lipid yield (7.1 wt% to dry biomass), the extracted lipid displayed a suitable fatty acid profile for biodiesel [C18:1 (∼63 wt%), C16:0 (∼19 wt%), C18:2 (∼4 wt%), C16:1 (∼4 wt%), and C18:0 (∼3 wt%)]. For SCCO(2) extraction, decreasing temperature and increasing pressure resulted in increased lipid yields. The mass transfer coefficient (k) for lipid extraction under supercritical conditions was found to increase with fluid dielectric constant as well as fluid density. For hexane extraction, continuous operation with a Soxhlet apparatus and inclusion of isopropanol as a co-solvent enhanced lipid yields. Hexane extraction from either dried microalgal powder or wet microalgal paste obtained comparable lipid yields.

CO2 capture by adsorption: Materials and process development

Abstract Vacuum swing adsorptive (VSA) capture of CO 2 from flue gas and related process streams is a promising technology for greenhouse gas mitigation. Although early reports suggested that VSA was problematic and expensive, through the application of more logical process configurations that are appropriately coupled to the composition of the feed and product gas streams, we can now refute this early assertion. Improved cycle designs coupled with tighter temperature control are also helping to optimise performance for CO 2 separation. Simultaneously, new adsorbent materials are being developed. These separate CO 2 by selective (acid-base) reaction with surface bound amine groups (chemisorption), rather than on the basis of non-bonding interactions (physisorption). This report describes some of these recent developments from our own laboratories and points to synergies that are anticipated as a result of combining these improvements in adsorbent properties and VSA process cycles.

Highly specific enrichment of glycopeptides using boronic acid-functionalized mesoporous silica.

A novel boronic acid functionalized mesoporous silica, which holds the attractive features of high surface area and large accessible porosity, was developed to enrich glycopeptides. This is the first time that mesoporous material has been introduced into glycoproteome. In comparison to direct (traditional) analysis, this novel method enabled 2 orders of magnitude improvement in the detection limit of glycopeptides. The unbiased nature of organo-boronic acid groups also made this method applicable to all kinds of glycopeptides regardless of their sizes, structures, and hydrophilicities.

General and Controllable Synthesis of Novel Mesoporous Magnetic Iron Oxide@Carbon Encapsulates for Efficient Arsenic Removal

A facile ammonia-atmosphere pre-hydrolysis post-synthetic route that can uniformly and selectively deposit Fe(2) O(3) nanoparticles in the predefined mesopores (5.6 nm) of a bimodal (2.3, 5.6 nm) mesoporous carbon matrix is demonstrated. The mesoporous magnetic Fe(2) O(3) @C encapsulates show excellent performance for arsenic capture with remarkable adsorption capacity, fast uptake rate, easy magnetic separation, and good cyclic stability.

Ordered Mesoporous Platinum@Graphitic Carbon Embedded Nanophase as a Highly Active, Stable, and Methanol-Tolerant Oxygen Reduction Electrocatalyst

Highly ordered mesoporous platinum@graphitic carbon (Pt@GC) composites with well-graphitized carbon frameworks and uniformly dispersed Pt nanoparticles embedded within the carbon pore walls have been rationally designed and synthesized. In this facile method, ordered mesoporous silica impregnated with a variable amount of Pt precursor is adopted as the hard template, followed by carbon deposition through a chemical vapor deposition (CVD) process with methane as a carbon precursor. During the CVD process, in situ reduction of Pt precursor, deposition of carbon, and graphitization can be integrated into a single step. The mesostructure, porosity and Pt content in the final mesoporous Pt@GC composites can be conveniently adjusted over a wide range by controlling the initial loading amount of Pt precursor and the CVD temperature and duration. The integration of high surface area, regular mesopores, graphitic nature of the carbon walls as well as highly dispersed and spatially embedded Pt nanoparticles in the mesoporous Pt@GC composites make them excellent as highly active, extremely stable, and methanol-tolerant electrocatalysts toward the oxygen reduction reaction (ORR). A systematic study by comparing the ORR performance among several carbon supported Pt electrocatalysts suggests the overwhelmingly better performance of the mesoporous Pt@GC composites. The structural, textural, and framework properties of the mesoporous Pt@GC composites are extensively studied and strongly related to their excellent ORR performance. These materials are highly promising for fuel cell applications and the synthesis method is quite applicable for constructing mesoporous graphitized carbon materials with various embedded nanophases.

Comprehensive Study of Pore Evolution, Mesostructural Stability, and Simultaneous Surface Functionalization of Ordered Mesoporous Carbon (FDU-15) by Wet Oxidation as a Promising Adsorbent

Fuctionalization of porous carbon materials through chemical methods orientates the development of new hybrid materials with specific functions. In this paper, a comprehensive study of pore evolution, mesostructural oxidation resistance, and simultaneous surface functionalization of ordered mesoporous carbon FDU-15 under various oxidation conditions is presented for the first time. The mesostructure and pore evolution with increasing oxidative strength are retrieved from XRD, TEM, and N(2) sorption techniques. The textural properties can be conveniently manipulated by changing the oxidation parameters, including different oxidative solution, temperature, and duration. It is revealed that the mesoporous carbon FDU-15 shows excellent structural stability under severe oxidation treatments by acidic (NH(4))(2)S(2)O(8), HNO(3), and H(2)O(2) solutions, much more stable than the mesostructural analogue CMK-3 carbon prepared by the nanocasting method. The surface area and porosity deteriorate to a large extent compared to the pristine carbon, with the micropores/small mesopores as the major contribution to the deterioration. The micropore/small mesopore can be blocked by the attached surface oxides under mild oxidation, while reopened with more carbon layer dissolution under more severe conditions. Simultaneously, high densities of surface oxygen complexes, especially carboxylic groups, can be generated. The contents and properties of the surface oxygen-containing groups are extensively studied by FTIR, TG, elemental analyses, and water and ammonia adsorption techniques. Such surface-functionalized mesoporous carbons can be used as a highly efficient adsorbent for immobilization of heavy metal ions as well as functional organic and biomolecules, with high capacities and excellent binding capabilities. Thus, we believe that the functionalized mesoporous carbon materials can be utilized as a promising solid and stable support for water treatment and organic/biomolecules immobilization and may be applicable in drug delivery, separation, adsorption technology, and columns for GC and HPLC systems in the near future.

Post-enrichment of nitrogen in soft-templated ordered mesoporous carbon materials for highly efficient phenol removal and CO2 capture

Control of porosity and structure and modification of surface and framework are the golden rules to adapt carbon materials to targeted applications. The former has been fairly well developed for the soft-templated FDU-type mesoporous carbons while there is still a large need for the latter. In this paper, a simple post-synthetic route is adopted to incorporate nitrogen-containing functionalities into the frameworks of these carbon materials. The basic principle relies on the confinement of melamine molecules in the mesochannels of an ordered mesoporous carbon matrix such that they self-condense into carbon nitride uniformly dispersed under a heat treatment at ∼500 °C and subsequently lead to the formation of mesoporous nitrogen-enriched carbon materials at 700–900 °C with well-retained ordered mesostructure and high surface area. The structure, porosity, composition and the nitrogen-containing functionalities are extensively studied. The integration of regular and open mesostructure, uniform and large mesopore size, high mesoporosity, and nitrogen enrichment makes these materials highly efficient for phenol removal, not only through physisorption with fast adsorption kinetics and large capacity but also by a newly found photo-degradation property with remarkable catalytic activity. Furthermore, the mesoporous nitrogen-enriched carbons deliver promising properties for CO2 capture with greatly enhanced heats of adsorption and well-retained high capacity. Given that the FDU-type mesoporous carbon materials hold variable structures, tunable pore sizes, flexible morphologies and an ease for large-scale synthesis, the success in nitrogen-enrichment would significantly accelerate the progress of their practical applications in pollution control, environment management, supercapacitors and fuel cells.

Ordered Mesoporous Crystalline γ-Al2O3 with Variable Architecture and Porosity from a Single Hard Template

In this paper, an efficient route is developed for controllable synthesis of ordered mesoporous alumina (OMA) materials with variable pore architectures and high mesoporosity, as well as crystalline framework. The route is based on the nanocasting pathway with bimodal mesoporous carbon as the hard template. In contrast to conventional reports, we first realize the possibility of creating two ordered mesopore architectures by using a single carbon hard template obtained from organic-organic self-assembly, which is also the first time such carbon materials are adopted to replicate ordered mesoporous materials. The mesopore architecture and surface property of the carbon template are rationally designed in order to obtain ordered alumina mesostructures. We found that the key factors rely on the unique bimodal mesopore architecture and surface functionalization of the carbon hard template. Namely, the bimodal mesopores (2.3 and 5.9 nm) and the surface functionalities make it possible to selectively load alumina into the small mesopores dominantly and/or with a layer of alumina coated on the inner surface of the large primary mesopores with different thicknesses until full loading is achieved. Thus, OMA materials with variable pore architectures (similar and reverse mesostructures relative to the carbon template) and controllable mesoporosity in a wide range are achieved. Meanwhile, in situ ammonia hydrolysis for conversion of the metal precursor to its hydroxide is helpful for easy crystallization (as low as approximately 500 degrees C). Well-crystallized alumina frameworks composed of gamma-Al(2)O(3) nanocrystals with sizes of 6-7 nm are obtained after burning out the carbon template at 600 degrees C, which is advantageous over soft-templated aluminas. The effects of synthesis factors are demonstrated and discussed relative to control experiments. Furthermore, our method is versatile enough to be used for general synthesis of other important but difficult-to-synthesize mesoporous metal oxides, such as magnesium oxide. We believe that the fundamentals in this research will provide new insights for rational synthesis of ordered mesoporous materials.

Adsorption technology for CO2 separation and capture: a perspective

The capture of CO2 from process and flue gas streams and subsequent sequestration was first proposed as a greenhouse gas mitigation option in the 1990s. This proposal spawned a series of laboratory and field tests in CO2 capture which has now grown into a major world-wide research effort encompassing a myriad of capture technologies and ingenious flow sheets integrating power production and carbon capture. Simultaneously, the explosive growth in materials science in the last two decades has produced a wealth of new materials and knowledge providing us with new avenues to explore to fine tune CO2 adsorption and selectivity. Laboratory and field studies over the last decade have explored the synergy of process and materials to produce numerous CO2 capture technologies and materials based on cyclic adsorption processes. In this brief perspective, we look at some of these developments and comment on the application and limitations of adsorption process to CO2 capture. We identify major engineering obstacles to overcome as well as potential breakthroughs necessary to achieve commercialization of adsorption processes for CO2 capture. Our perspective is primarily restricted to post-combustion flue gas capture and CO2 capture from natural gas.