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排序方式: 共有1139条查询结果,搜索用时 31 毫秒
101.
Ronny Purwadi Tomas Brandberg Mohammad J. Taherzadeh 《International journal of molecular sciences》2007,8(9):920-932
The cultivation of toxic lignocellulosic hydrolyzates has become a challenging research topic in recent decades. Although several cultivation methods have been proposed, numerous questions have arisen regarding their industrial applications. The current work deals with a solution to this problem which has a good potential application on an industrial scale. A toxic dilute-acid hydrolyzate was continuously cultivated using a high-cell-density flocculating yeast in a single and serial bioreactor which was equipped with a settler to recycle the cells back to the bioreactors. No prior detoxification was necessary to cultivate the hydrolyzates, as the flocks were able to detoxify it in situ. The experiments were successfully carried out at dilution rates up to 0.52 h−1. The cell concentration inside the bioreactors was between 23 and 35 g-DW/L, while the concentration in the effluent of the settlers was 0.32 ± 0.05 g-DW/L. An ethanol yield of 0.42–0.46 g/g-consumed sugar was achieved, and the residual sugar concentration was less than 6% of the initial fermentable sugar (glucose, galactose and mannose) of 35.2 g/L. 相似文献
102.
Laura Prati Alberto Villa Francesca Porta Di Wang Dangsheng Su 《Catalysis Today》2007,122(3-4):386-390
The liquid phase oxidation of glycerol with oxygen has been studied using mono and bimetallic catalysts based on Au and Pd metals supported on activated carbon, in order to study the effect of the metal on the distribution of the products and on activity of catalysts. It was found that by using bimetallic catalysts (Au–Pd) a strong synergistic effect was shown. By using a preformed nucleating centre we were able to obtain a single alloyed phase, which allowed us to address the synergistic effect to the presence of alloyed Au/Pd. The advantage of using this latter catalyst lies not only in the high activity but also in a prolonged catalyst life. Although a partial leaching of palladium and assembling of the particles have been revealed by ICP and HRTEM respectively, activity after 10 re-cycles decreased less than expected (about 10%). 相似文献
103.
Victor T. Wyatt Alberto Nuñez Thomas A. Foglia William N. Marmer 《Journal of the American Oil Chemists' Society》2006,83(12):1033-1039
Novel oligomeric prepolymers were synthesized by acid-catalyzed condensation of glycerol with iminodiacetic, azelaic, or succinic
acid. The prepolymers were obtained, on average, in 62% yield and were characterized by 13C NMR, 1H NMR, matrix-assisted laser desorption ionization-time of flight-mass spectrometry, and gel permeation chromatography. The
synthesized oligomers had an average M.W. of 1543 Daltons (average polydispersity (PD)=1.34, average degree of polymerization
(DOP)=5.5). Hyperbranching was evident in the oligomers produced when using azelaic acid and succinic acid as co-monomers
with glycerol, whereas the reaction between iminodiacetic acid and glycerol resulted in linear products bearing cyclic urethane
structures. 相似文献
104.
利用pH值的测定和凝胶转化率的计算,研究了醋酸甘油酯(三醋酸甘油酯、二醋酸甘油酯、一醋酸甘油酯)对甲阶酚醛树脂交联反应的催化作用,以及体系pH值对催化作用的影响。结果表明:在同样条件下催化速度:三醋酸甘油酯〉二醋酸甘油酯〉一醋酸甘油酯。体系的pH值对催化作用有重要的影响,pH值〉12.5时交联反应不能进行,pH值越低,交联反应的速度越快;pH值对一醋酸甘油酯的催化作用影响最大,二醋酸甘油酯次之,三醋酸甘油酯最小。增加醋酸甘油酯的浓度和升高反应温度使交联反应的速度加快。 相似文献
105.
106.
甘油法制备环氧氯丙烷中间体二氯丙醇催化剂的研究 总被引:3,自引:0,他引:3
对甘油制环氧氯丙烷中间体二氯丙醇的催化剂进行了研究。考察了以冰醋酸、草酸、丁二酸、己二酸、辛酸五种有机酸为催化剂时,时间、温度、催化剂用量对目的产物二氯丙醇的收率以及反应速率的影响。研究结果表明,以己二酸为催化剂,甘油用量为3mol/kg,反应温度为110℃,反应时间为3h左右时达到平衡,二氯丙醇收率可达到85%。 相似文献
107.
甘油与环己酮缩合反应催化剂的研究 总被引:1,自引:0,他引:1
通过比较Lewis酸、质子酸、无机酸酐、分子筛、酸化蒙脱土在催化甘油与环己酮缩合反应中的活性,研究了催化剂结构和性质对环己酮转化率和反应选择性的影响。结果表明,Lewis酸有较高的催化活性和稳定性,而且表现为L酸和B酸两种酸的催化形式。催化剂结构对环己酮转化率和反应选择性的影响为:(1)Lewis酸的构成:对相同阴离子的Lewis酸而言,其阳离子的L酸酸强度越强或水解程度越大,催化活性和2-羟甲基-1,4-二氧杂螺环[4,5]癸烷(产物a)的选择性越高;对相同阳离子的Lewis酸而言,其盐酸盐型的催化活性和产物a的选择性要高于硫酸盐型的;(2)水合硫酸盐的催化活性与其煅烧温度有关。催化活性和产物a的选择性最好的Lewis酸为AlCl3。当n(AlCl3)∶n(环己酮)∶n(甘油)=1∶10 000∶15 000,带水剂环己烷加入量为反应物总体积的47%,92℃回流反应2 h,环己酮转化率为97.9%;最终产物中产物a的选择性为97.8%。 相似文献
108.
Crude glycerol, a waste stream of the biodiesel production process, is low-cost renewable feedstock for the production of chemicals and polymers. In this study, polyurethane (PU) adhesives were synthesized from crude glycerol-based polyols (CG-based polyols) for wood bonding applications. Effects of different variables, including hydroxyl values of CG-based polyols, chain extenders, and the molar ratio of NCO/OH on the properties of PU adhesives were investigated. The chemical structures of PU adhesives were characterized, and their thermal, mechanical, and chemical resistance properties were evaluated. The experimental results indicated that an increase of the NCO/OH molar ratio (1.3) substantially improved bonding strength by up to 38 MPa. Higher thermal stability and stronger chemical resistance to hot and cold water and to alkali and acid solutions were observed comparing to vegetable oil-based adhesives. However, the effect of the hydroxyl value of polyols on bonding strength was not significant. Additionally, bond strength of crude glycerol-based PU adhesives was comparable to that of some commercial PU wood adhesives. All these properties demonstrated the potential of CG for PU wood adhesive applications, particularly for fast-curing uses. 相似文献
109.
110.