Cellulose ethanol produced from fibers such as straws, crop husks and stems, leaves, forestry corner residues, and urban and rural organic waste has solved the problem of biofuels competing for land and food, and is known as the first Second-generation biofuels. Not to mention that its raw materials are cheap and readily available, and its preparation process is not simple. Recently, Zhang Tao, academician of the Chinese Academy of Sciences and Wang Aiqin, researcher of the Dalian Institute of Chemical Physics, the Chinese Academy of Sciences have developed a new chemical catalysis method based on the multi-step tandem reaction strategy, which can efficiently convert cellulose in one pot into ethanol. Related results were recently published in "Joule". The "darling" of biofuels As the most abundant biomass resource in nature, a large amount of cellulose and hemicellulose derived from agricultural and forestry wastes are widely used. Due to its inedible characteristics, it has attracted much attention in renewable carbon resources and has become a "darling" for scientists to produce biofuels and chemicals. Cellulose ethanol made from this is one of them. "Cellulosic ethanol is an important biofuel. Mixing it with gasoline in a certain ratio can form a new generation of clean and environmentally friendly vehicle fuel, which can reduce the emission of car exhaust such as carbon monoxide, hydrocarbons and other pollutants." Wang Aiqin Tell the China Science News. Cellulose is a polymer composed of glucose as the basic structural unit and formed by β-1,4 glycosidic bonds. Due to the large number of hydrogen bonds between and within the cellulose molecules, a natural network structure can be formed to protect the internal β-1,4 glycosidic bonds from attack. Although it has natural resistance, it also greatly hinders its biotransformation. Wang Aiqin said that traditionally scientists used bio-fermentation methods for conversion, but cellulase is expensive and easily poisoned, so the commercialization process has always faced technical and economic challenges. Among various biomass conversion routes, chemical catalytic conversion has the unique advantages of high efficiency and easy docking with existing chemical infrastructure, and it is favored by researchers. "In the study of the catalytic conversion of biomass, one of the main research directions is to selectively break the CC and CO bonds in the macromolecules of biomass, thereby obtaining important small molecule compounds, including alcohols, aldehydes, and acids. This is also our The research direction of the group for many years. "Wang Aiqin introduced that the team first created the catalytic conversion reaction of hydrogenolysis of cellulose to ethylene glycol in 2008, and discovered the unique role of W-containing compounds in catalyzing the selective cleavage of cellulose CC bonds. A two-step method for preparing ethanol by oxidative esterification of cellulose and then hydrogenation reduction is proposed. Subsequently, the team found that the metal-acid bifunctional catalyst supported on platinum by tungsten oxide can effectively hydrogenolyze the CO bond in glycerol, which provides a theoretical basis for the preparation of a new catalyst. So, is it possible to design such a multi-functional catalyst that will couple the reaction of the cellulose CC bond to ethylene glycol and the ethylene glycol CO bond to ethanol, so as to efficiently catalyze cellulose to ethanol in one pot? Scientists look forward to the answer. Ethanol conversion "full power" Based on this concept, the team first designed and prepared a Pt / WOx metal-acid bifunctional catalyst. The performance of the catalyst for the hydrogenolysis of cellulose was investigated under the reaction conditions of 250 ℃ and 6 MPa hydrogen in the reactor. The results show that the catalyst can indeed hydrolyze cellulose to produce ethanol, but the ethanol yield is not ideal. The first author of the paper, Yang Man, Ph.D., Dalian Institute of Chemistry, Chinese Academy of Sciences, told the China Science Journal that after many attempts, the experimenters found that the introduction of the transition metal Mo can increase the yield "horsepower", and the catalytic activity of the catalyst and the load of Mo The quantity and load sequence are closely related. "Only when the Mo / Pt atomic ratio is 0.1, and when Pt is loaded first and then Mo, can a high ethanol yield be obtained (the optimal ethanol yield is 41.3%). Moreover, the" one-pot "reaction of cellulose-made ethanol The dependence on the Mo / Pt atomic ratio is completely consistent with the law of hydrogenolysis of ethylene glycol to ethanol, indicating that the latter is a kinetic rate-determining step and is a structure-sensitive reaction. "She said. In order to explore the structure-activity relationship, the experimental staff then carried out various spectral characterizations such as XAFS and Raman, and proposed the active site structure of MoO5-Pt-WOx. According to Yang Man, MoO5 presents a monodisperse form of coordinated unsaturation. Through the interaction with the surface of nano-Pt, the electronic interaction of Pt-WOx is modulated to promote the hydrogenolysis of glycol to ethanol. Too much Mo forms Pt active sites on the surface covered by Mo-O-Mo species, thus reducing the reactivity. Although the problem has been solved, what restricts the ethanol yield? To this end, the team turned its attention to the catalytic conversion of primary biomass. The experiment found that when corn stalks, miscanthus and birch wood chips were used as raw materials, the ethanol yields were 25.2%, 26.3% and 29.0% respectively without any pretreatment-indicating that the presence of lignin affected Conversion of cellulose. When the appropriate pretreatment method is used to remove most of the lignin in Miscanthus, the ethanol yield can reach more than 40%. Subsequently, the experimenters studied the anti-CO poisoning performance and cycle stability of the catalyst. "Interestingly, when using H2 with 0.5% CO, the Mo / Pt / WOx catalyst showed excellent resistance to CO poisoning, and the ethanol yield could still be maintained at 41%, which is mainly due to the Pt and WOx The strong electronic interaction between them inhibits the adsorption of CO. In the cycle stability test, the instability of the WOx structure in the Mo / Pt / WOx catalyst led to the aggregation of Pt. "Wang Aiqin said. In the end, the experimenters used Pt / WOx / Al2O3 catalyst with better stability. By matching with tungstic acid, the catalyst can be cycled 5 times to keep the ethanol yield unchanged, and has the characteristics of high efficiency and continuous production. "Urgent" the new future of production It is understood that as of 2018, China's fuel ethanol production capacity has reached 2.9 million tons. However, in 2018, China's total gasoline consumption reached 130 million tons. If all the current 10% blending standards are used, the demand for biofuel ethanol will reach 13 million tons, and the gap between supply and demand is extremely large. Wang Aiqin said that the new catalyst created by the team can catalyze the cleavage of the CC bond and CO bond in cellulose at the same time, so that direct hydrogenolysis of cellulose can be used to obtain ethanol, which greatly improves the conversion efficiency. At the same time, the catalyst's excellent anti-CO poisoning performance and cycle stability make it have great potential in future practical applications. However, if you want to invest in industrial applications, you need to create a "full chain" preparation system. "The industrialization of cellulose ethanol is a typical system engineering, from raw material collection to straw pretreatment, from catalyst screening to reactor structure design, from cellulose / hemicellulose conversion to straw full-scale utilization, from process route Design to engineering enlargement involves many disciplines and fields, and requires systematic technical integration and comprehensive integration of resources. "Wang Aiqin said. "We will further optimize the catalyst and process conditions on the basis of existing research, and strive to obtain practically useful catalysts with high activity, high selectivity, and high stability." She said that the team is committed to working with related companies to Technology is applied to the market. (■Our newspaper trainee reporter Cheng Weijia reporter Liu Wansheng correspondent Yang Man) 3Pc Flanged Ball Valves,3Pc Flanged Ball Valve ,3 Flanged Ball Valve,3 Piece Flanged Ball Valve WENZHOU DIYE VALVE&FITTINGS CO.,LTD , https://www.diye-valve.com