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目前商业溶解木浆纤维素纤维的聚合度多在500~1800左右,这些浆粕的纤维素分子量具有多分散性。因此,本文以不同特征的溶解浆为纤维素纤维原料,结合纤维质量,分析讨论了NaOH水溶液中具有氢键受体物质的添加对其溶解不均一纤维素物料的影响。结果表明,与溶解纯纤维素不同,NaOH/添加剂水溶液对溶解浆纤维素纤维的溶解能力与浆纤维素纤维水溶液体系中纤维的粗度、纤维的刚硬程度和添加剂种类密切相关。混合添加剂的溶剂体系、添加少量氨基磺酸钠和环己基氨基磺酸钠的溶剂体系促进了较长纤维素纤维的溶解。 相似文献
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借助DIS探究甲烷与氯气反应的类型以及外界条件对反应的影响。通过比较实验研究数据表明:甲烷与氯气发生了取代反应,光照有利于甲烷取代反应的进行。 相似文献
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氯氧化镁在水中的溶解行为 总被引:3,自引:0,他引:3
用pH法和氯电位法测定氯氧化镁不同温度下在水中的溶解过程。一定间隔时间分析液样中的Mg^2+、Cl^-、OH^-的浓度,用物化方法鉴定固相。得出不同温度下的相转化、溶解的C ̄t曲线及动力学方程。计算了它们的Ksp和热力学函数。 相似文献
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《高分子通报》2021,(5):29-37
被称之为绿色纤维的Lyocell纤维,其成功开发的基础在于纤维素溶剂N-甲基吗啉-N-氧化物(NMMO)的发现。尽管在发现初期,就有人根据溶解现象和实验证实纤维素在NMMO水溶液中的溶解过程是一个大分子间氢键被破坏的物理过程,但人们对其溶解机理的认识还是经历了一个长期的过程。以往的实验方法局限于纤维素分子与溶剂分子间弱相互作用的研究,随着计算机技术的发展,分子模拟的方法填补了这一空白,使纤维素的溶解机理得到了新的认识,例如纤维素分子和NMMO分子的两亲性,以及疏水缔合相互作用。纤维素溶解机理的深入认识不仅可以促进Lyocell过程稳定性、溶剂回收效率的提升,还会为新溶剂的开发奠定理论基础。本文从NMMO的认识过程、纤维素在NMMO水溶液中溶解过程的实验发现和分子模拟计算等方面,全面总结和理解纤维素在NMMO水溶液中的溶解机理。 相似文献
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丝氨酸在醇-水溶液中的溶解焓 总被引:1,自引:0,他引:1
用RD-496III双热流精密微热量计测量了L-丝氨酸在纯水以及异丙醇、1,2-丙二醇和丙三醇水溶液中的溶解焓, 并计算了从水到醇-水溶液中的迁移焓. 实验发现, L-丝氨酸在水及醇-水溶液中的溶解焓都是正值, 它从水到醇-水溶液中的迁移焓也都是正值, 并且基本上随着醇浓度的增加而增加, 说明在溶解过程中, 溶质与混合溶剂分子的部分去水化吸热过程占主要地位. 另外, 实验还发现L-丝氨酸从水到异丙醇水溶液中的迁移焓大于在1,2-丙二醇水溶液中的, 更大于在丙三醇水溶液中的, 这是由于羟基的减少导致了疏水-亲水作用的增加和亲水-亲水作用的减弱. 相似文献
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钠硼解石——水体系溶解和相平衡的研究(英) 总被引:3,自引:0,他引:3
Ulexite dissolution in water has been studied in the wide temperature range from 10℃ to 93℃ and two higher temperatures at 120 ℃ and 240 ℃. The analytical results showed that ulexite dissolved congruently from 10 ℃ to 35 ℃ and incongruently from 40 to 68 ℃. The solid component of ulexite, NaCaB5O6(OH)6·5H2O was dehydrated to form NaCaB5O6(OH)6·H2O from 50 to 68 ℃ and finally amorphous solid at 68 ℃. This amorphous solid converted into priceite at 71 ℃ and then converted completely to priceite at the boiling point(93℃) of the solution. At both 120 and 240 ℃, the dissolution of ulexite was an incongruent process. Above 120 ℃, ulexite became amorphous solid and then transformed into priceite. In addition to the solid to solid transformation, crystallization of priceite from the solution has also been observed. Based on our experimental results, mechanisms of dissolution, transformation, and crystallization of borate in ulexite-water system are discussed. 相似文献
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The effect of hydrochloric acid concentration and the effect of temperature on the rate of dissolution of Fe2O3 have been investigated. Being heterogeneous, the dissolution reaction has been characterized to have an apparent activation energy of 21.5 Kcal/mol for a 7.11 m aqueous hydrochloric acid solution at temperatures between 273 and 373°K. The rate is linearly correlated to the mean activity of hydrochloric acid in the range from 1.3 to 10.8 m at 300°K. 相似文献
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Changli Ma Taisen Zuo Zehua Han Yuqing Li Sabrina Grtner Huaican Chen Wen Yin Charles C. Han He Cheng 《Molecules (Basel, Switzerland)》2022,27(11)
The atomic picture of cellulose dissolution in alkali/urea aqueous solution is still not clear. To reveal it, we use trehalose as the model molecule and total scattering as the main tool. Three kinds of alkali solution, i.e., LiOH, NaOH and KOH are compared. The most probable all-atom structures of the solution are thus obtained. The hydration shell of trehalose has a layered structure. The smaller alkali ions can penetrate into the glucose rings around oxygen atoms to form the first hydration layer. The larger urea molecules interact with hydroxide groups to form complexations. Then, the electronegative complexation can form the second hydration layer around alkali ions via electrostatic interaction. Therefore, the solubility of alkali aqueous solution for cellulose decreases with the alkali cation radius, i.e., LiOH > NaOH > KOH. Our findings are helpful for designing better green solvents for cellulose. 相似文献
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Dissolution of Cellulose in Aqueous NaOH Solutions 总被引:10,自引:0,他引:10
Dissolution of a number of cellulose samples in aqueous NaOH was investigated with respect to the influence of molecular weight, crystalline form and the degree of crystallinity of the source samples. A procedure for dissolving microcrystalline cellulose was developed and optimized, and then applied to other cellulose samples of different crystalline forms, crystallinity indices and molecular weights. The optimum conditions involved swelling cellulose in 8–9 wt % NaOH and then freezing it into a solid mass by holding it at –20°C. This was followed by thawing the frozen mass at room temperature and diluting with water to 5% NaOH. All samples prepared from microcrystalline cellulose were completely dissolved in the NaOH solution by this procedure. All regenerated celluloses having either cellulose II or an amorphous structure prepared from linter cellulose and kraft pulps were also essentially dissolved in the aqueous NaOH by this process. The original linter cellulose, its mercerized form and cellulose III samples prepared from it had limited solubility values of only 26–37%, when the same procedure was applied. The differences in the solubility of the celluloses investigated have been interpreted in terms of the degrees to which some long-range orders present in solid cellulose samples have been disrupted in the course of pre- treatments. 相似文献
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聚氯乙烯(PVC)管材中氯乙烯单体的溶解沉淀-顶空-气相色谱法测定 总被引:1,自引:0,他引:1
建立了聚氯乙烯(PVC)管材中氯乙烯单体的溶解沉淀-顶空-气相色谱法。选择HP-Wax毛细管柱为分离色谱柱,4mL含水量为37.5%(体积分数)的N,N-二甲基乙酰胺(DMA)溶液溶解PVC管材,在75℃平衡35min的条件下顶空进样进行气相色谱分析。结果显示,氯乙烯在0.025~2.50mg/L范围内线性关系良好,相关系数r=0.9993。以3倍信噪比计算,该方法的检出限为4.75μg/L。对样品加标测定6次,加标回收率为90%~96%,相对标准偏差(RSD)小于6.0%。该方法比常规的顶空进样方法的灵敏度提高了近9倍,具有操作简单、快速、灵敏度高、准确度和精密度好等优点,适合于PVC管材中氯乙烯单体的检测。 相似文献
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Shinnya Chiyokawa Kyouzou Suyama Katsuko Takaizumi 《Journal of solution chemistry》2003,32(8):743-752
We are interested in polyvinylpyrrolidone as an analog for the D-state proteins. In a volumetric study, the interactions between polyvinylpyrrolidone (PVP) and sodium-, potassium-, calcium-, and tetrabutylammonium chloride at 35°C in a series of aqueous PVP solutions over a concentration range of PVP up to 20 wt.% was performed. The volumes of transfer at infinite dilution tr
V
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0 from water to the PVP solutions were determined for the salts; their decreasing order showed a parallel relation to the Hoffmeister series. The tr
V
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0 data were analyzed by applying the McMillan–Mayer method to obtain the volumetric interaction coefficients between the ions and the polymer unit. 相似文献
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纯铝在强碱溶液中阳极溶解的电化学阻抗谱解析 总被引:2,自引:0,他引:2
依据曹楚南提出的法拉第导纳表达式,拟合了纯铝在强碱溶液中的阳极溶解过程的电化学阻抗谱,并据此提出了这一反应进行的机理.结果表明,阻抗谱中的低频容抗弧是由表面裸露的Al转变为中间产物Al(OH)ads的反应引起的,而中频感抗弧则由Al(OH)ads转变为Al(OH)3,ads的反应引起.法拉第导纳的时间常数τ1和τ2的物理意义是物种Al(ss)和Al(OH)ads在单位表面活性位上的转化时间. τ1 >0和τ2 >0是符合稳定性条件的,也能够满足Kramers-Kronig转化的必要条件. g1和g2是与物种Al(ss)和Al(OH)ads在电极表面的覆盖密度随电位E变化有关的参数,由g1< 0可知随电位升高,纯铝表面的活性位面积减小. 相似文献
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氯化钙/水-醇溶液稀释热 总被引:3,自引:0,他引:3
电解质溶液稀释热是溶液的重要热性质之一.由它可计算不同浓度下电解质的溶解热、表现相对摩尔焓、溶液中反应热和化合物生成热等.在电解质溶液理论研究中,稀释热也是重要的基础数据.由稀释热可推算溶液中组分的活度系数、渗透系数、相对偏摩尔焓及表观摩尔热容等[1-3].在化工生产中,稀释热是化工过程能量计算不可缺少的数据.电解质水溶液稀释热已有不少研究[2,4].但电解质混合溶剂体系稀释热报导甚少.随着加盐精馏技术、海水淡化技术等研究的进展,急需这方面数据.本文作者已报告了CaCl2/C2H5OH-H2O体系[5]和CaCl2/n-C… 相似文献