201503131148biomass 生物質

biomass : 生物質,相關的網路資源:

國科會化學中心 : 綠色/永續化學網 http://gc.chem.sinica.edu.tw/biomass.html


人類即將面臨的溫室效應、環境惡化、石油能源與化學原料匱乏的問題,促使生物質 (biomass) 之應用成為重要的研究課題。生物質(biomass)顧名思義是指各種有機體的整體質量,亦即太陽能經由光合作用以化學能的形式貯存於生物體中的一種能量 形式,其中包含了相當廣泛的物質,諸如農作物(特別是能源作物 energy crops,可包括玉米、樹藷、小麥、甘蔗、甜菜、或應用於生物柴油 biodiesel 的黃豆、油菜、向日葵等)、草本或木本植物(包括生產速率快的高纖維植物,如芒草 Miscanthus,Switchgrass,混種白楊木 Hybrid poplar 等)、農林畜牧業廢棄物(如玉米稈與葉穗、甘蔗渣、木屑、稻殼、椰殼等)、都會或工業有機廢棄物、廢油、果菜廢棄物,甚至也有更廣泛的說法而包括了沼氣或 甲烷水合物 (methane hydrate) 等資源。

生物質是一種重要的再生資源,與風能、太陽能、地熱等一樣具有取之不盡、用之不竭的特性。而且,所使用材料多為廢棄物,作物的生長還可以吸收二氧化碳,減 少溫室氣體的累積。在此,我們將生物質的相關技術分成三大方向,即:(1) 生質能源 (bioenergy),包括各類的能源形式如生質柴油、生質酒精、生質產氫系統、以及直接燃燒生物質來產生電能等;(2) 生質塑膠 (bioplastics) 主要是轉化生物質成高分子聚合物 polyhroxyalkanoates, PHA;(3) 生質精煉 (Biomass refinery) 與其他,主要是轉化生物質成為化學原料,以取代原來必須利用石油資源來提煉的化學原料。

Wed, 03/11/2015 - 8:21am
by Libby Dowdall, Univ. of Wisconsin-Madison
In a study published in Nature Chemistry, Univ. of Wisconsin-Madison chemistry Prof. Kyoung-Shin Choi presents a new approach to combine solar energy conversion and biomass conversion, two important research areas for renewable energy.
For decades, scientists have been working to harness the energy from sunlight to drive chemical reactions to form fuels such as hydrogen, which provide a way to store solar energy for future use. Toward this end, many researchers have been working to develop functional, efficient and economical methods to split water into hydrogen, a clean fuel, and oxygen using photoelectrochemical solar cells (PECs). Although splitting water using an electrochemical cell requires an electrical energy input, a PEC can harness solar energy to drive the water-splitting reaction. A PEC requires a significantly reduced electrical energy input or no electrical energy at all.
In a typical hydrogen-producing PEC, water reduction at the cathode (producing hydrogen) is accompanied by water oxidation at the anode (producing oxygen). Although the purpose of the cell is not the production of oxygen, the anode reaction is necessary to complete the circuit. Unfortunately, the rate of the water oxidation reaction is very slow, which limits the rate of the overall reaction and the efficiency of the solar-to-hydrogen conversion. Therefore, researchers are currently working to develop more efficient catalysts to facilitate the anode reaction.
Choi, along with postdoctoral researcher Hyun Gil Cha, chose to take a completely new approach to solve this problem. They developed a novel PEC setup with a new anode reaction. This anode reaction requires less energy and is faster than water oxidation while producing an industrially important chemical product. The anode reaction they employed in their study is the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). HMF is a key intermediate in biomass conversion that can be derived from cellulose—a type of cheap and abundant plant matter. FDCA is an important molecule for the production of polymers.
Biomass conversion can offer a viable pathway to generate chemicals used in industrial processes without using petroleum products. Conventional biomass conversion processes use high-pressure oxygen for the conversion of HMF to FDCA at high temperatures. Choi and Cha, however, developed an efficient electrochemical method to oxidize HMF to FDCA at room temperature and ambient pressure using water as the oxygen source. Then they employed this oxidation reaction as the anode reaction of the PEC that produces hydrogen at the cathode. By doing so, they demonstrated the utility of solar energy for biomass conversion as well as the feasibility of using an oxidative biomass conversion reaction as an anode reaction in a hydrogen-forming PEC.
“Since the photoelectrochemical cell is built for the purpose of hydrogen production and HMF oxidation simply replaces oxygen production at the anode, in essence, no resources are used specifically for HMF oxidation,” says Choi.
In other words, FDCA is a bonus byproduct from a PEC that generates hydrogen. The production of FDCA, a valuable chemical, at the anode lowers the production cost for hydrogen. This new approach therefore presents new possibilities for research in both solar conversion and biomass conversion.
“When we first started this study, we were not sure whether our approach could be really feasible,” Choi says. “However, since we knew that the impact of the study could be high when successful, we decided to invest our time and effort on this new research project at the interface of biomass conversion and solar energy conversion.”
Developing and optimizing every piece of the full solar cell setup demonstrated in the study took the researchers about two years. Choi expects that the development of more diverse and efficient electrochemical and solar-driven biomass conversion processes will increase the efficiency and utility of solar-fuel-producing PECs.

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