甲壳素脱乙酰反应的研究

研究了蟹壳甲壳素的脱乙酰反应过程 ,探讨了影响脱乙酰反应的主要影响因素(反应温度、碱液含量和反应时间 )与产物壳聚糖的脱乙酰度和特性粘数之间的关系。确定了制得高脱乙酰度和高粘度的最佳反应条件 :反应时间为 8h,反应温度为 65℃ ,碱液的质量分数为 47%。采用氮气保护与间歇法进行脱乙酰化反应有利于提高产物壳聚糖的脱乙酰度 ,抑制分子链降解。     

高脱乙酰度1，4-2-氨基-2-脱氧-β-D-葡聚糖的制备

研究了3种不同来源甲壳素的脱乙酰反应过程,探讨了脱乙酰反应的主要影响因素(反应时间、碱液浓度和反应温度)与产物1,4-2-氨基-2-脱氧-β-D,葡聚糖(壳聚糖)的脱乙酰度之间的关系。用单因素实验和正交实验确定了制得高脱乙酰度的最佳反应条件：反应时间为90min,反应温度为120℃,碱液的质量分数为40%,料液质量比为1∶30；并用红外光谱对原材料和制备产物进行了表征。     

浸润法制备壳聚糖工艺的研究

提出在浸润的条件下 ,以较少量碱液投加量 ,脱乙酰制备壳聚糖。通过正交实验找到脱乙酰度 85 % ,相对分子质量达 6 8× 10 5的壳聚糖的最佳制备工艺条件 :温度 14 0℃、反应时间 4h、蟹壳与 70 %NaOH水溶液的质量比为 1∶1。同时考察了脱钙、脱乙酰阶段反应条件对壳聚糖质量的影响     

壳聚糖脱乙酰度的实验研究

以虾壳为原料制取甲壳素 ,甲壳素脱乙酰基制备壳聚糖。讨论了影响壳聚糖脱乙酰度的因素。通过正交实验得出了制备壳聚糖的最佳工艺条件为氢氧化钠浓度 4 0 % ,反应温度 90℃ ,反应时间 14h。通过分段碱制得脱乙酰度高达 98.14 %的壳聚糖     

甲壳质制壳聚糖脱乙酰度条件研究

研究了甲壳质分步脱乙酰制壳聚糖反应的温度、时间、NaOH含量和预浸泡时间对脱乙酰度的影响.结果表明,最佳的反应温度为110℃,反应时间为4 h,NaOH的质量分数为47%,预浸泡时间为48 h.在此条件下,可以得到脱乙酰度90%以上的壳聚糖产品.     

微波条件下甲壳素脱乙酰反应的条件研究

研究了微波处理条件下,甲壳素脱乙酰反应条件对壳聚糖脱乙酰度的影响。结果表明:微波甲壳素颗粒大小选择为0.18～0.3mm(过60～80目筛)较利于反应。在料液比小于1∶12(质量∶体积)时,壳聚糖脱乙酰度几乎不变,粘度逐渐增大,之后脱乙酰度随料液比的增大而下降。脱乙酰度随碱液浓度的增大而增大。随微波处理时间的延长,脱乙酰度上升、特性粘度下降。微波功率越高,相同时间下,产品的脱乙酰度越高。经正交试验得出:粒度为0.18～0.3mm的甲壳素原料,按料液比1∶12(质量∶体积)加入浓度为50%(质量分数)的NaOH溶液,在微波功率320W下处理21min,所得产品的脱乙酰度可达85.65%,特性粘度为394.07mL/g,灰分为0.05%。     

微波条件下制备壳聚糖的研究

利用微波技术并通过加入乙醇降低碱浓度的方法制备了壳聚糖。同时对碱浓度、反应时间、碱用量等因素进行研究 ,确定了最优化条件 :甲壳素与碱液体积比为 1∶2 0 ,碱浓度为 30 %,微波功率为 480W ,反应时间为30min。用优化条件制备的壳聚糖的脱乙酰度 >76 %。     

高脱乙酰度壳聚糖的制备

以甲壳素为原料,以异丁醇为溶剂,氢氧化钠为亲核试剂,探讨了一种制备高脱乙酰度壳聚糖的新方法.研究了投料比、反应温度、反应时间、反应方法等对脱乙酰度的影响.结果表明,在反应温度为110℃,反应时间2.5h,壳聚糖∶NaOH∶醇=1∶5∶12(质量比)条件下制得脱乙酰度为93.2%的壳聚糖,而传统水溶剂脱乙酰度小于50%.另外间歇法处理样品可以在较短的时间里制备出脱乙酰度较高的壳聚糖,并用红外谱图对壳聚糖进行了表征.     

壳聚糖碱液法制作工艺的优化试验

以天然虾壳为原料,对碱液法制备甲壳素、壳聚糖的工艺进行了优化试验.结果表明,二次酸碱法反应制备甲壳素的常规工艺中盐酸的使用浓度为3%～8%,在此范围盐酸使用浓度愈高甲壳素的品质越好;在壳聚糖的制作过程中,当反应温度为100 ℃,反应时间为8 h,氢氧化钠溶液浓度为60%时,得出的壳聚糖产品脱乙酰度高.     

不同脱乙酰度壳聚糖的制备及其聚集行为研究

壳聚糖的脱乙酰度直接影响壳聚糖的物理化学和生物特性。在乙酸-水-甲醇体系中研究壳聚糖的乙酰化反应工艺,考察了反应时间、壳聚糖质量浓度对乙酰化反应的影响,优化了反应条件。研究表明,反应时间为6h时,壳聚糖乙酰化反应基本完全,乙酰化反应后,相对重均分子质量基本不变,壳聚糖相对分子质量分布变宽。在优化后的反应条件下,改变乙酸酐加入量分别制备了脱乙酰度为76%,64%和54%的不同脱乙酰度的壳聚糖。芘荧光光谱研究表明,壳聚糖的临界聚集浓度(CSC)随脱乙酰度的降低而增加。     

微波场中KCl浓度对几丁质脱乙酰反应的影响

研究了KCl浓度对几丁质在微波场中脱乙酰反应的影响. 结果表明，引入盐离子促进了反应的进行. 随着反应时间的延长，几丁聚糖的脱乙酰度上升，但上升速度逐渐变慢，呈一级反应特征；分子量随时间延长而降低. 脱乙酰度随KCl浓度上升而减小，但在实验范围内，均高于对照组. 当[KCl]=0.05 mol/L时脱乙酰度达到79.26%，与对照组相比(脱乙酰度=69.84%)提高了13.5%. 随KCl浓度的上升，分子量开始减小，当KCl浓度上升到0.2 mol/L附近时，分子量又呈上升趋势. 这是由于KCl浓度影响体系介质损耗角正切值，在较高KCl浓度时降低了体系对微波的吸收能力.     

常压和加压浸渍法制备壳聚糖性能对比

研究了常压和加压条件下碱液浓度和反应时间对壳聚糖性能的影响。与传统工艺相比,在不改变壳聚糖化学结构、晶型结构的条件下,压力浸渍法反应时间由6 h降到1 h,耗碱量降低了65%。结果表明,压力浸渍法可得到更高脱乙酰度和更高分子量的壳聚糖产品。     

2-羟丙基三甲基氯化铵壳聚糖的制备及其表征

以脱乙酰度为90%的壳聚糖(CTS)为原料,异丙醇为溶剂,w(NaOH)=40 0%的水溶液为催化剂,3 氯 2 羟丙基三甲基氯化铵(CTA)为改性剂,在m(NaOH)∶m(CTS)=1 0∶1 0,m(CTA)∶m(CTS)=4 0∶1 0,反应温度65 0℃下制备了2 羟丙基三甲基氯化铵壳聚糖(HTCC)。实验结果表明,在反应时间达到或超过9 0h时,得到的HTCC产品的接枝度超过90 0%,在pH=6 7～7 0的水中可完全溶解形成w(HTCC)=3 0%的溶液。IR和1HNMR的结果表明,接枝反应主要发生在CTS的氨基上。     

Optimum parameters for production of chitin and chitosan from squilla (S. empusa)

Chitin and chitosan of high quality were produced from squilla, a by‐catch of Indian Ocean fisheries, by demineralization, deproteination, and deacetylation. Optimum conditions for the production of chitin and chitosan were determined. The quality of chitin was assessed from its ash and protein content. Ash content was below 1% after treatment with 4% HCl for 12 h at 50°C. A protein content of less than 1% could be achieved by treatment with 4% NaOH in 12 h but only at a temperature of 70°C or higher. Production of chitin was also tested by a three‐stage treatment with altering sequence of sodium hydroxide and hydrochloric acid (HCl–NaOH–HCl or NaOH–HCl–NaOH). This three‐step treatment appeared to be successful to achieve a mineral content and protein content below 1% within 30 h and at a temperature not exceeding 50°C. The chitin obtained under optimum conditions was tested for deacetylation using NaOH concentrations of 40 and 50% for 12–44 h at 30, 50 and 70°C. The chitosan obtained had a degree of deacetylation of 77–86%, a viscosity of 8.2–16.2 × 10² cps, solubility of 98%, and molecular weight of ? 1 × 10⁶ dalton. The data show that processing of squilla waste can lead to a high quality chitosan, useful for a broad range of applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 103: 3694–3700, 2007     

The effect of reaction time and temperature during heterogenous alkali deacetylation on degree of deacetylation and molecular weight of resulting chitosan

The objective of the study is to elucidate the effect of reaction time and temperature during heterogenous alkali reaction on degree of deacetylation (DD) and molecular weight (MW) of the resulting chitosans, and to establish the reaction conditions to obtain desired DD and MW chitosan products. Chitin was extracted from red shrimp process waste. DDs and MWs were determined by infrared spectroscopy (IR) and static light scattering, respectively. The results are as follow: The DD and MW of chitin obtained were 31.9% and 5637 kDa, respectively. The DD of the resulting chitosan increased along with reaction time and/or reaction temperature. The DDs of the resulting chitosan that were obtained from 140°C were higher than those reacted at 99°C. The highest DD of the resulting chitosans after alkali deacetylation at 99 and 140°C were 92.2 and 95.1%, respectively. The DDs of chitosans increased fast at the beginning of reaction process then slowed over time. The reaction rate and rate constant of the deacetylation reaction decreased with increasing DD of the reactant. The MWs of chitosans decreased along with the deacetylation time. MW of those chitosans reacted at 140°C are smaller than those at 99°C. The rate of chitosan degradation was above 43.6%/h in the initial stage, then decreased to about 20%/h. The degradation rate constants raised substantially in the late stage. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2917–2923, 2003     

Deacetylation of β‐chitin. I. Influence of the deacetylation conditions

The influences of the deacetylation temperature, deacetylation time, and NaOH concentration on the degree of deacetylation (DD) of deacetylated products prepared from β‐chitin are discussed. The DD values of deacetylated products are related to the ratio of the signal intensities of methyl on acetyl groups and the first anomeric carbon, which are obtained from ¹³C‐NMR spectra. The results show that the DD values of deacetylated product increase as the NaOH concentration, deacetylation time, or deacetylation temperature increases. The thermal properties, chemical structures, and crystalline characteristic of deacetylated products are significantly related to their DD values. Differential scanning calorimetry shows that the peak temperature is slightly increased as the DD values of deacetylated products of β‐chitin increase. Thermogravimetric analysis shows that the thermal degradation onset temperature of deacetylated products decreases as the DD values increase. Fourier transform infrared spectra show that the intensity of a specific absorption peak of ? NH₂ in deacetylated products significantly increases as DD increases. X‐ray diffraction patterns of deacetylated products with DD values of 17.5 and 44.7% have three significant diffraction peaks. However, there are only two diffraction peaks found in products with higher DD values of 76.5 and 94.7%. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2416–2422, 2004