• Energy Research

Abstract The power conversion efficiency (PCE) of TiO2-based dye-sensitized solar cells (DSSCs) could be enhanced by modification of photoanodes. The effective blocking layer addition, one-dimensional nanostructure architecture, and scattering material design are the most important approaches to provide the high PCE of DSSCs and are critically reviewed in this work. The blocking layer generated the energy barrier can suppress the recombination of an electron in photoanode. One-dimensional (1D) nanostructures of a nanorod, nanotube and nanowire, promote the enhanced electron transport of DSSCs. The PCE of 1D nanostructure based DSSCs can potentially be improved by incorporating high surface area TiO2 nanoparticles and constructing the multilayered 1D nanostructure arrays photoanodes. The scattering effect can be generated by mesoporous, core-shell and yolk-shell materials with the sizes architecture corresponding to the wavelength of incident light, enhancing the light harvesting. The high efficiency of TiO2-based photoanodes could be realized by optimizing the composition, size of materials, and thickness of photoanodes.

Abstract Glycerol emerges as a significant worth chemical that can be converted into high value products. In the prospect of biorefinery industries and great demand towards renewable sources, glycerol has proved to have tremendous potential to be transformed, thus supersede conventional petroleum derived fuel additive. Various types of oxygenated biocomponents and rigorous studies of glycerol transformation into fuel additives are presented in this review paper. Particular focus is given to etherification, acetylation and acetalation processes with specific behaviors in the respective reaction system.

This paper critically reviews the impacts of supplementing trace elements on the anaerobic digestion performance. The in-depth knowledge of trace elements as micronutrients and metalloenzyme components justifies trace element supplementation into the anaerobic digestion system. Most of the earlier studies reported that trace elements addition at (sub)optimum dosages had positive impacts mainly longer term on digester stability with greater organic matter degradation, low volatile fatty acids (VFA) concentration and higher biogas production. However, these positive impacts and element requirements are not fully understood, they are explained on a case to case basis because of the great variance of the anaerobic digestion operation. Iron (Fe), nickel (Ni) and cobalt (Co) are the most studied and desirable elements. The right combination of multi-elements supplementation can have greater positive impact. This measure is highly recommended, especially for the mono-digestion of micronutrient-deficient substrates. The future research should consider the aspect of trace element bioavailability.

Abstract This paper addresses B5 biodiesel programs in Malaysia, global challenges on the production of palm oil. Protective measures for future efficiency as well as continued viability of this renewable energy sector are also discussed. Crude palm oil (CPO) prices are currently suppressed because of high palm oil inventory. Malaysian government has taken a pro-active step in implementing the B5 biodiesel for transportation and industrial sectors through the introduction of B5 biodiesel. The B5 Biodiesel Program which was initially targeted at selected government agencies has been fully implemented for subsidized sectors in the Central Region. The promotion of B5 development is highly attractive due to its potential local feedstock from palm oil industry and the availability of production technologies that offer opportunities for the sustainable development in energy entrepreneurships. Nationally, produced B5 will improve the access to alternative energy services and is expected to help in improving productivity and sustainability. Despite successful local B5 implementation, Malaysia is recently facing global challenges on the biodiesel production which currently remains stagnant due to weak domestic demand and uncompetitive export tax structure.

Sonocatalytic degradation of various organic dyes (Congo Red, Reactive Blue 4, Methyl Orange, Rhodamine B and Methylene Blue) catalyzed by powder and nanotubes TiO(2) was studied. Both catalysts were characterized using transmission electron microscope (TEM), surface analyzer, Raman spectroscope and thermal gravimetric analyzer (TGA). Sonocatalytic activity of powder and nanotubes TiO(2) was elucidated based on the degradation of various organic dyes. The former catalyst was favorable for treatment of anionic dyes, while the latter was more beneficial for cationic dyes. Sonocatalytic activity of TiO(2) nanotubes could be up to four times as compared to TiO(2) powder under an ultrasonic power of 100 W and a frequency of 42 kHz. This was associated with the higher surface area and the electrostatic attraction between dye molecules and TiO(2) nanotubes. Fourier transform-infrared spectrometer (FT-IR) was used to identify changes that occurred on the functional group in Rhodamine B molecules and TiO(2) nanotubes after the reaction. Sonocatalytic degradation of Rhodamine B by TiO(2) nanotubes apparently followed the Langmuir-Hinshelwood adsorption kinetic model with surface reaction rate of 1.75 mg/L min. TiO(2) nanotubes were proven for their high potential to be applied in sonocatalytic degradation of organic dyes.

Abstract In the current era of energy crises, alternative feedstock such as methanol are commonly used as fuels and solvents in various industries. Methanol is commonly produced from non-renewable sources. Recently, sustainable methanol synthesis via innovative and efficient catalytic processes has drawn a lot of attention and research is currently aimed at finding a suitable catalyst for optimized production at commercial scale. Nowadays, one of the main interests is catalytic synthesis of methanol from CO2. This work presents a critical review on innovative catalysts for methanol synthesis, research progress for their development and their use in the catalytic process. It also provides an overview on recent development in methanol synthesis from syngas, CO2 hydrogenation and photo-catalytic reduction of CO2. The use of various reactors, the influence of preparation method, support, promoter, different type of catalysts used, their properties and performance during methanol synthesis are also thoroughly reviewed.

Waste cooking oil is increasingly becoming a significant component of biodiesel feedstock and its conversion to FAME requires coupling of esterification and transesterification processes. In this study, new environmentally benign catalysts were prepared from oil palm trunk and sugarcane bagasse, which are sustainable because of the superfluity of oil palm trunk and abundant supply of bagasse. Effect of preparation variable, surface acidity and textural properties, pre-esterification of FFA in oil matrices and transesterification of waste oil under pseudo-infinite methanol and conventional methods were investigated. The preparation variable, H2SO4 impregnation time showed marginal effect on sulfonic acid density after 6 h, and the corresponding values for 6-10 h impregnations were 1.33 +/- 0.01-1.41 +/- 0.01mmol g(-1) for OPT and 1.44 +/- 0.01-1.48 +/- 0.01mmol g(-1) for SCB catalysts. In esterification of palmitic acid, activity of catalysts with different H2SO4 impregnation time correlates with their sulfonic acid density. The catalysts demonstrated rapid esterification of FFA in oil matrices under pseudo infinite methanol, reducing its content from 42 wt.% to l1 wt.% in just 15 min. Similarly, the conversions of waste oil by OPT and SCB derived catalysts were 80.6% and 83.2%, respectively after 4 h under pseudo-infinite methanol, and 43.7% and 45%, respectively after 6 h under conventional method. These catalysts have shown remarkable properties that are suitable for biodiesel production from waste oil. (C) 2014 Elsevier Ltd. All rights reserved.

Cet article analyse les domaines techniques critiques qui limitent actuellement le succès du biodiesel en tant que carburant. Le processus de production passe actuellement d'homogène à hétérogène en utilisant des catalyseurs solides pour un processus plus propre et une séparation plus facile des produits. Les teneurs en acides gras libres et en humidité des matières premières doivent être suffisamment faibles pour éviter la formation de savon. La production de biodiesel en pleine conformité avec la norme ASTM D6751-07 ou EN 14214:2003 est une tâche ardue. Les technologies actuelles de production de biodiesel ne fournissent toujours pas un surplus d'énergie plus important. Le biodiesel a un contenu énergétique relativement plus faible, ce qui entraîne une consommation de carburant plus élevée. Le biodiesel présente un inconvénient en termes de propriétés d'écoulement à froid. Un indice d'iode élevé peut entraîner la dégradation et la polymérisation des composants du biodiesel. Les impuretés monoglycérides, diglycérides et triglycérides non converties affecteront les performances du moteur. La teneur en alcool du biodiesel peut attaquer les joints en caoutchouc et les joints. Le biodiesel peut également subir des modifications chimiques et biologiques pour affecter sa qualité dans le stockage à long terme. Le biodiesel est également associé à des émissions élevées de NOx, un fait qui nécessite une attention particulière. En este artículo se analizan las áreas técnicas críticas que actualmente limitan el éxito del biodiesel como combustible. El proceso de producción está cambiando actualmente de homogéneo a heterogéneo utilizando catalizadores sólidos para un proceso más limpio y fácil de separar el producto. El contenido de ácidos grasos libres y humedad en las materias primas debe ser lo suficientemente bajo como para evitar la formación de jabón. La producción de biodiesel con pleno cumplimiento de ASTM D6751-07 o EN 14214:2003 es una tarea cuesta arriba. Las tecnologías actuales para la producción de biodiesel aún no proporcionan un excedente de energía más significativo. El biodiésel tiene un contenido energético relativamente bajo, lo que provoca un mayor consumo de combustible. El biodiesel tiene un inconveniente en cuanto a sus propiedades de flujo en frío. Un alto valor de yodo puede causar la degradación y polimerización de los componentes del biodiesel. Las impurezas de monoglicéridos, diglicéridos y triglicéridos no convertidos afectarán el rendimiento del motor. El contenido de alcohol en el biodiesel puede atacar los sellos y juntas de goma. El biodiesel también puede sufrir modificaciones químicas y biológicas para afectar su calidad en el almacenamiento a largo plazo. El biodiesel también se asocia con emisiones de NOx de alto nivel, un hecho que requiere una atención especial. This article analyses critical technical areas that currently limit the success of biodiesel as a fuel. The production process is currently shifting from homogeneous to heterogeneous using solid catalysts for a cleaner process and ease of product separation. The free fatty acid and moisture contents in the raw materials must be sufficiently low to avoid soap formation. The production of biodiesel with full compliance with ASTM D6751-07 or EN 14214:2003 is an uphill task. Current technologies for biodiesel production still do not provide more significant energy surplus. Biodiesel has relatively lower energy content, causing higher fuel consumption. Biodiesel has a drawback in terms of its cold flow properties. A high iodine value can cause degradation and polymerization of biodiesel components. Unconverted monoglyceride, diglyceride and triglyceride impurities will affect the engine performance. The alcohol content in biodiesel can attack rubber seals and gaskets. Biodiesel also can undergo chemical and biological modification to affect its quality in long-term storage. Biodiesel is also associated with high-level NOx emission, a fact that needs special attention. تحلل هذه المقالة المجالات التقنية الحرجة التي تحد حاليًا من نجاح الديزل الحيوي كوقود. تتحول عملية الإنتاج حاليًا من متجانسة إلى غير متجانسة باستخدام محفزات صلبة لعملية أنظف وسهولة فصل المنتج. يجب أن تكون محتويات الأحماض الدهنية الحرة والرطوبة في المواد الخام منخفضة بما يكفي لتجنب تكوين الصابون. يعد إنتاج الديزل الحيوي مع الامتثال الكامل للمواصفة ASTM D6751 -07 أو EN 14214:2003 مهمة شاقة. لا تزال التقنيات الحالية لإنتاج الديزل الحيوي لا توفر فائضًا أكبر في الطاقة. يحتوي الديزل الحيوي على محتوى طاقة أقل نسبيًا، مما يتسبب في زيادة استهلاك الوقود. الديزل الحيوي له عيب من حيث خصائص التدفق البارد. يمكن أن تتسبب القيمة العالية لليود في تدهور وبلمرة مكونات الديزل الحيوي. ستؤثر شوائب أحادي الغليسريد وثنائي الغليسريد وثلاثي الغليسريد غير المحولة على أداء المحرك. يمكن أن يهاجم محتوى الكحول في الديزل الحيوي موانع التسرب المطاطية والحشيات. يمكن أن يخضع الديزل الحيوي أيضًا لتعديل كيميائي وبيولوجي للتأثير على جودته في التخزين طويل الأجل. يرتبط الديزل الحيوي أيضًا بانبعاثات أكاسيد النيتروجين عالية المستوى، وهي حقيقة تحتاج إلى اهتمام خاص.

Abstract This paper addresses the challenges in developing a sustainable biodiesel industry especially in Malaysia. The challenges discussed in this paper are divided into three main sections covering issues before, during and after biodiesel processing. The pre-processing problems concern the feedstock market, legislation through policies, fuel–food competition, deforestation issue and alternative feedstock conflict. Problems with regards to the uncontrollable glycerol production and its global market crisis are also reviewed. Besides, some suggestions on poising back the glycerol market stability are reviewed through several upgrading processes and methods that can convert glycerol to its functional chemicals. The last section covers the social issue of biodiesel in obtaining people׳s acceptance and capability of this industry to cultivate the sustainable practices along the processing line. Moreover, challenges in verifying its commercial value by fulfilling the global biofuel standards are also highlighted.