共查询到20条相似文献,搜索用时 70 毫秒
1.
2.
固定化脂肪酶催化菜籽油合成蜡酯 总被引:2,自引:0,他引:2
以菜籽油、鲸蜡醇为原料,采用实验室自制的固定化Candidia sp.99-125脂肪酶分别在有机溶剂和无溶剂体系下合成了蜡酯,在两种体系下对影响蜡酯合成的各种因素进行了比较研究,研究表明:以正己烷为反应介质,在40℃条件下反应12h,油醇摩尔比1∶2,酶量15%(质量分数,上同),水含量7.5%,蜡酯产率可达85.87%;无溶剂体系中在50℃条件下反应20h,油醇摩尔比1∶1.5,蜡酯产率可达80.68%。通过流加鲸蜡醇可以提高酶的使用寿命。 相似文献
3.
制备了三种用于RTM成型工艺的乙烯基酯树脂,分别命名为R-1,R-2,R-3。系统地研究了三种树脂体系的固化反应特性、工艺特性及其树脂浇铸体的力学性能。研究结果表明,三种树脂体系在室温(25℃)下的粘度都很低,分别为350mPa.s、80mPa.s、70mPa.s,一定温度下的粘度均能达到500mPa.s以下,且具有较长的适用期,符合RTM注射工艺的要求。分析树脂浇铸体的力学性能可以看到,弯曲强度最高可达110.05MPa,冲击强度最高可达12.27kJ/m2。最终选定R-3为综合性能最优的树脂体系。 相似文献
4.
5.
以钨酸钠为催化剂、过碳酸钠为氧化剂,选择性氧化乙腈制备乙酰胺.研究了该碱性氧化体系的作用,比较了反应时间、温度对反应的影响.考察了钨酸钠的催化性能以及不同碳酸钠用量在体系中的反应结果.反应时间的延长和温度的升高并不利于提高转化率,因此反应选择在室温条件下进行.碳酸钠和氧化体系碱性的增加能促进产物乙酰胺的生成.以钨酸钠为催化剂,反应条件:室温25℃,时间4 h,V[H2O]/V[methnol]=2/3时,乙腈的转化率可达100%左右,生成的乙酰胺的选择性可达94.3%. 相似文献
6.
以K2Cr2O7/HCI为反应氧化体系,对以催化裂化柴油进行氧化脱硫实验研究,考察了反应时间、反应温度、氧化剂体积分数、反应体系pH值和萃取剂用量对脱硫效果的影响。实验表明,在最佳反应条件下,柴油的脱硫率可达90%以上。 相似文献
7.
以K2Cr2O7/HCI为反应氧化体系,对以催化裂化柴油进行氧化脱硫实验研究,考察了反应时间、反应温度、氧化剂体积分数、反应体系pH值和萃取剂用量对脱硫效果的影响。实验表明,在最佳反应条件下,柴油的脱硫率可达90%以上。 相似文献
8.
采用双硫腙-离子液体[Bmim][PF6](1-丁基-3-甲基咪唑六氟磷酸盐)对水中铅离子的萃取性能及反应条件展开了研究。主要探究了络合剂含量、萃取温度、料液相pH值及萃取体系与水相体积比对萃取效率的影响;此外,在最佳萃取率的前提条件下,进行了反萃剂的筛选,并考察了反萃温度及浓度对反萃效率的影响规律,继而获得最佳反萃条件。研究结果表明,在萃取温度为35 ℃、pH为6、络合剂双硫腙含量为0.5%(w/v)、萃取体系与水相体积比为 1:4 的萃取条件下,该萃取体系对水中铅离子的萃取率高达98.0 %。在35 ℃下,采用1mol/L HNO3对上述负载萃取体系进行反萃,反萃率可达97.0 %。最后,考察了该萃取与反萃体系多次复用的传质效率变化趋势,结果显示三次萃取/反萃后该体系萃取率依然可达80.0 %,反萃率为65.0 %。 相似文献
9.
对加压法二氧化碳与环氧丙烷合成碳酸丙烯酯催化剂进行了研究,实验结果表明:KI/聚乙二醇400催化体系具有很好的催化活性,可在较低温度、压力下短时间高产率的得到碳酸丙烯酯。碳酸丙烯酯得率可达99.8%以上,在一定条件下。经多次循环使用后仍有较高的活性。 相似文献
10.
以钨酸钠为催化剂、过碳酸钠为氧化剂,选择性氧化乙腈制备乙酰胺。研究了该碱性氧化体系的作用,比较了反应时间、温度对反应的影响。考察了钨酸钠的催化性能以及不同碳酸钠用量在体系中的反应结果。反应时间的延长和温度的升高并不利于提高转化率,因此反应选择在室温条件下进行。碳酸钠和氧化体系碱性的增加能促进产物乙酰胺的生成。以钨酸钠为催化剂,反应条件:室温25℃,时间4h,V[H2O]/V[methanol]=2/3时,乙腈的转化率可达100%左右,生成的乙酰胺的选择性可达94.3%。 相似文献
11.
铜绿假单胞菌脂肪酶无溶剂催化棕榈油甘油解Ⅱ.进一步提高单甘酯产率的研究 总被引:3,自引:0,他引:3
以自产铜绿假单胞菌脂肪酶为催化剂 ,通过无溶剂法棕榈油甘油解反应催化合成了单脂肪酸甘油酯。考察了反应温度程序以及加酶方式对最终产物中单甘酯质量分数的影响。结果表明程序降温和批次加酶更有利于反应 ,产物中单甘酯质量分数可增大 1 0 %~ 2 0 % ,实验条件下反应 48h后单甘酯质量分数可达 65 % ,脱酶后达 77%。 相似文献
12.
Li Deng Tianwei Tan Fang Wang Xuebing Xu 《European Journal of Lipid Science and Technology》2003,105(12):727-734
A lipase preparation developed from Candida sp. 99‐125 was used for fatty acid alkyl ester synthesis by both enzymatic esterification of fatty acids, and transesterification of oils and fats. The lipase preparation was chosen based on screening of lipases from commercial sources as well as those produced in the laboratory. The effects of enzyme dosage, solvent types, water absorbent additions, inhibition of short‐chain alcohols, alcohol and acid types, molar ratio of substrates, and reusability of the lipase preparation in esterification were studied. Degree of esterification between oleic acid and methanol under optimal conditions reached 92%. Purity of the methyl ester after washing with water and distillation was 98%. Half‐life of the lipase preparation was calculated to be approximately 340 h. For transesterification of rapeseed oil with the same lipase preparation, the amount of methanol and mode of methanol addition to the reaction were also conducted. Transesterification of the oil with stepwise methanol addition reached 83% after 36 h reaction time. 相似文献
13.
14.
Lipase from Candida antarctica was entrap-immobilized in cellulose acetate-TiO2 gel fiber (fiber-immobilized lipase) by the sol-gel method. Syntheses of geranyl acetate and citronellyl acetate catalyzed
by the fiber-immobilized lipase were studied in heptane solution. Conversions reached 85% for geranyl acetate after 100 h,
and 75% for citronellyl acetate after 80 h, and these values were almost identical to those for syntheses catalyzed by nonimmobilized
lipase, although the reaction rate was decreased by immobilization. Compared to those of the non-immobilized lipase and commercially
available immobilized lipase (Novozyme 435), the activity of the fiber-immobilized lipase was not particularly affected by
changes in reaction conditions, such as bulk water content or substrate concentration. The fiber-immobilized lipase retained
a high level of activity after six repeated uses, and almost no enzyme leakage from fiber was observed. However, the reactivity
of the fiber-immobilized lipase was depressed at higher temperature, presumably due to dehydration by thermal contraction
of the gel fiber. 相似文献
15.
16.
17.
Yomi?Watanabe Yoshie?Yamauchi-Sato Toshihiro?Nagao Takaya?Yamamoto Kentaro?Tsutsumi Akio?Sugihara Yuji?Shimada
We attempted to produce MAG of CLA through lipase-catalyzed esterification of a FFA mixture containing CLA (referred to as
FFA-CLA) with glycerol. Screening of lipases showed that MAG-CLA was produced efficiently at 5°C with Penicillium camembertii, Rhizopus oryzae, and Candida rugosa lipases. Among them, C. rugosa lipase was selected because the lipase is widely used as a catalyst for oils and fats processing. The reaction was conducted
with agitation of a 300-g mixture of FFA-CLA/glycerol (1∶5, mol/mol), a 200-U/g mixture of C. rugosa lipase, and 2% water. When the reaction was conducted at 30°C, the esterification scarcely proceeded, owing to inhibition
of the reaction by glycerol. But the reaction at 5°C eliminated the inhibition and produced MAG efficiently: The degree of
esterification reached 93.8% after 58 h, and MAG content in the reaction mixture was 88.4 wt%. To reduce the reaction time,
the reactor was connected with a vacuum pump after 24 h, and the reaction was continued with dehydration at 5 mm Hg. The degree
of esterification reached 94.7% after 24 h of dehydration (48 h in total), and MAG content increased to 93.0 wt%. Candida rugosa lipase acted a little more strongly on cis-9, trans-11 CLA than on trans-10,cis-12 CLA, but the contents of the two isomers in MAG obtained from a 48-h reaction were the same as the contents in FFA-CLA. 相似文献
18.
Enzymatic synthesis of high-purity structured lipids with caprylic acid at 1,3-positions and polyunsaturated fatty acid at 2-position 总被引:2,自引:0,他引:2
Akiko Kawashima Yuji Shimada Miwa Yamamoto Akio Sugihara Toshihiro Nagao Sadao Komemushi Yoshio Tominaga 《Journal of the American Oil Chemists' Society》2001,78(6):611-616
We attempted to synthesize high-purity structured triacylglycerols (TAG) with caprylic acid (CA) at the 1,3-positions and
a polyunsaturated fatty acid (PUFA) at the 2-position by a two-step enzymatic method. The first step was synthesis of TAG
of PUFA (TriP), and the second step was acidolysis of TriP with CA. Candida antarctica lipase was effective for the first reaction. When a reaction medium of PUFA/glycerol (3∶1, mol/mol) and 5% immobilized Candida lipase was mixed for 24 h at 40°C and 15 mm Hg, syntheses of TAG of γ-linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic
acids reached 89, 89, 88, and 83%, respectively. In these reactions, the lipase could be used for at least 10 cycles without
significant loss of activity. In the second step, the resulting trieicosapentaenoin was acidolyzed at 30°C for 48h with 15
mol parts CA using 7% of immobilized Rhizopus delemar lipase. The CA content in the acylglycerol fraction reached 40 mol%. To increase the content further, the acylglycerols were
extracted from the reaction mixture with n-hexane and were allowed to react again with CA under conditions similar to those of the first acidolysis. After three successive
acidolysis reactions, the CA content reached 66 mol%. The content of dicapryloyl-eicosapentaenoyl-glycerol reached 86 wt%
of acylglycerols, and the ratio of 1,3-dicapryloyl-2-eicosapentaenoyl-glycerol to 1(3),2-dicapryloyl-3(1)-eicosapentaenoyl-glycerol
was 98∶2 (w/w). In this reaction, the lipase could be used for at least 20 cycles without significant loss of activity. Repeated
acidolysis of the other TriP with CA under similar conditions synthesized 1,3-dicapryloyl-2-γ-linolenoyl-glycerol, 1,3-dicapryloyl-2-arachidonoyl-glycerol,
and 1,3-dicapryloyl-2-docosahexaenoyl-glycerol in yields of 58, 87, and 19 wt%, respectively. 相似文献
19.
Wax esters were synthesized in a solvent free system catalyzed by immobilized lipase from Candida sp. 99-125, with oleic acid and cetyl alcohol. The effects of substrate molar ratio, lipase dosage and water removal were investigated in a 50 ml flask incubated in a thermostatic cultivation cabinet. The optimized conditions were: temperature 40 ℃, shaking at 170 r·min-1, acid/alcohol molar ratio 1:0.9, lipase dosage in 10% (by mass) of oleic acid, and open reaction for water removal. As a result, the conversion rate reached 98% for reaction of 8 h. The volume of reactor was scaled up to 1 L three-neck flask. The optimized parameters were: 200 r·min-1 agitation speed, 2.5% (by mass) lipase dosage, others were the same as the parameters described above. The conversion rate reached 95% for reaction of 24 h. The lipase retained 46% conversion rate after reuse for 6, 7 batches. The products were purified by removing remained cetyl alcohol and fatty acids with ethanol and saturated sodium carbonate so-lution, respectively. The purity of the wax ester, cetyl oleate, was 96%. The physical and chemical properties of cetyl oleate were tested and compared with those of jojoba oil. The results show that the product cetyl oleate has great potential to use as the substitute of natural jojoba oil. 相似文献