近临界水中禽类废弃物超低酸水解加工制备氨基酸的工艺优化

为寻求禽类废弃物的有效利用途径,对其进行在近临界水中超低酸水解加工制备氨基酸的工艺优化。用AAA-Direct氨基酸分析仪对水解产物中的氨基酸进行定性和定量分析。以鸡肠为原料,氨基酸总收率为指标,讨论了反应温度、反应时间、硫酸浓度对氨基酸总收率的影响,并通过正交试验确定了鸡肠近临界超低酸水解的较佳工艺条件。实验结果表明,鸡肠水解后可得17种氨基酸。近临界超低酸水解法高效、工艺简单、对环境友好,在较佳的工艺条件下:T=533K,t=28min,H2SO4=0.02%,氨基酸的总收率可达11.49%。     

近临界水中鱼肉水解制备氨基酸的反应动力学

利用鱼肉蛋白制备氨基酸不但具有经济效益,而且为生物质资源高效利用提供技术支持。采用HL-F(0.2 L+1.5 MG)/30 MPa-IIA超临界水反应装置,在无催化剂、反应温度分别为220,240,260℃,反应时间为30 min条件下,对鱼肉蛋白在近临界水中水解为氨基酸的反应动力学进行了实验研究。用AAA-Direct氨基酸分析仪测定不同反应时间中氨基酸总产率,以酸水解鱼肉蛋白得到的氨基酸量为完全水解标准。在水过量的情况下,得到了鱼肉蛋白水解率宏观反应动力学方程。结果表明鱼肉蛋白水解动力学的级数为1.614 7,220,240,260℃下的反应速率常数分别为0.001 7,0.004 5,0.009 7,活化能为145.125 kJ/mol,前置因子A为9.475 7×109,为工业化生产提供了基础数据。     

近临界水中羽毛水解制备氨基酸的工艺优化研究

研究了近临界水中羽毛水解制备氨基酸的生产工艺及工艺优化.利用氨基酸分析仪对水解产物中的氨基酸进行定性和定量分析.实验结果发现,羽毛水解后可得到16种氨基酸.以氨基酸的总收率为考察指标,反应温度、反应时间、反应压力为考察因素进行正交实验,并考察了他们对氨基酸总收率的影响.研究结果表明,近临界水解法高效,工艺简单,对环境友好,在较佳的水解工艺下:P= (5.0±0.5) MPa,T= 250℃,t=30 min,氨基酸的总收率为6.54%.     

近临界水中低值鱼肉水解制备氨基酸工艺研究

研究了近临界水中低值鱼肉水解制备氨基酸的生产工艺.反应器容积为200 mL,反应温度为180～32℃,反应压力为5～26 MPa,反应时间为5～60 min.利用氨基酸分析仪对水解产物中的氨基酸进行定性和定量分析,实验结果发现,实验所用低值鱼肉水解后可得到17种氨基酸.反应温度、反应压力和反应时间对低值鱼肉近临界水解有影响,其中反应温度影响最大,水解产物中不同种类氨基酸的产率随反应温度、反应压力和反应时间的变化规律各不相同.分别对其中8种含量较高、用途较广、附加值较高的氨基酸,进行了反应温度、反应压力、反应时间对水解液中氨基酸浓度影响的实验,得到了在较低的反应温度、合适的反应压力和一定的反应时间内获得较高氨基酸产率的水解工艺.分别采用空气、氮气和二氧化碳作为反应气氛,进行水解实验,结果表明,对亮氨酸、组氨酸和异亮氨酸,应该采用氮气或二氧化碳反应气氛,对其他氨基酸可以采用空气作为反应气氛.     

近临界水中苯甲醛合成新方法

测定了压力15 MPa下,温度240～320℃范围内肉桂醛水解反应的动力学数据.实验结果表明在无任何外加催化剂的情况下,肉桂醛能够在近临界水中顺利进行水解反应生成苯甲醛,苯甲醛产率随时间的延长先增大后减小.随温度升高,水解反应速率迅速增大,苯甲醛产率达到最大值的时间缩短.得到较佳反应条件为15 MPa、280℃、反应时间6h,此时苯甲醛产率为57.0%(mol).由Arrhenius方程,拟合得到肉桂醛水解反应的活化能为59.8 kJ·mol-1.本方法制备的苯甲醛由于没有引入其它反应物,因此香气品质较佳.     

近临界水中乙烯-醋酸乙烯酯共聚物水解反应动力学

为了开发聚醋酸乙烯酯绿色水解工艺,以聚乙烯醋酸乙烯酯为原料,研究了其在近临界水中的水解反应动力学。在考察了实验数据的重现性和物料配比对聚乙烯醋酸乙烯酯水解反应的影响之后,系统地测定了483.15～623.15K下聚醋酸乙烯酯的无催化和醋酸催化下水解反应动力学数据,并采用元素分析仪、傅立叶变换红外光谱仪、凝胶色谱仪、热重分析仪、示差扫描量热仪对水解产物进行了表征。结果表明,近临界水中聚醋酸乙烯酯水解改性是可行的,通过改变水解工艺条件可获得一系列不同醋酸乙烯酯、乙烯醇含量的水解产物;温度、物料配比以及原料不同酯基含量是影响水解速率的主要因素,同时在聚乙烯醋酸乙烯酯水解反应中醋酸的引入可大大提高反应速度。以自催化反应动力学模型对实验数据进行了拟合,得到了无催化和1mol·L-1醋酸催化下聚乙烯醋酸乙烯酯水解反应活化能分别为51.8kJ·mol-1和41.6kJ·mol-1。研究建立了一个近临界水中聚乙烯醋酸乙烯酯水解改性的新方法,方法具有绿色、可控等优点。     

近临界水中薯蓣皂苷的水解反应

在近临界水中研究了薯蓣皂苷水解成薯蓣皂苷元的工艺和反应动力学,分别考察了反应温度、压力、时间等因素对薯蓣皂苷元收率的影响。实验结果表明,近临界水解法的较佳工艺条件为260℃,25 MPa,反应10 min。在此条件下,薯蓣皂苷元收率为1.46%。动力学研究结果表明,薯蓣皂苷在近临界水中水解是一级反应,活化能为76.7 kJ/mol,指前因子k0为5.99×104s-1。     

近临界水中苯乙腈无催化水解反应动力学

为了开发苯乙酸的绿色制备工艺,系统地研究了近临界水中苯乙腈的无催化水解反应动力学.在研究了实验数据的重现性以及苯乙腈初始浓度对反应动力学影响之后,系统地测定了523.15～563.15 K下苯乙腈及其分解的中间产物苯乙酰胺的水解反应动力学数据,结果表明苯乙腈水解反应是典型的连串反应,以苯乙酰胺为中间产物.且能高选择性地得到最终产物苯乙酸.并以一级连串反应动力学模型对实验数据进行了拟合,得到了苯乙腈和苯乙酰胺水解反应活化能分别为64.4 kJ·mol-1和82.4 kJ·mol-1.论文工作为苯乙酸的绿色制各提供了重要的基础数据,同时能为其他腈类物质在近临界水中的水解提供参考.     

亚临界水中大豆渣水解制备氨基酸工艺研究

豆渣是大豆加工过程中的主要副产物。今在亚临界水中对豆渣水解制备氨基酸的生产工艺进行了研究,为大豆的综合利用开辟了一条新的途径。利用氨基酸分析仪对水解产物中的氨基酸进行定性和定量分析,实验结果发现,大豆渣水解后可得到17种氨基酸。考察了反应温度、反应时间、物料浓度以及CO2分压对氨基酸总收率的影响,并进行正交试验。研究结果表明,亚临界水解法高效快速,工艺简单,CO2气体的加入有利于增加氨基酸总收率,较佳的水解工艺条件为:T=200℃,P(CO2)=3.0 MPa,w=5.0 mg mL 1,t=15 min,氨基酸的总收率为14.25%。     

近临界水中鱼蛋白水解及水解液脱色研究

鱼类蛋白包括鱼肉及鱼类加工过程中产生的废弃物,文中采用近临界水技术,在反应温度180—320℃,反应压力5—26 MPa,反应时间5—60 min,无催化剂条件下将其制备成氨基酸,不但能提高附加值,而且有利于环境保护。实验结果发现,水解物含17种氨基酸,水解物中不同种类氨基酸的产率随反应温度、反应压力和反应时间的变化规律各不相同。对其中8种含量高、用途广、附加值高的氨基酸,分别得到了最佳水解工艺。以颗粒状活性炭为脱色剂,对水解液在不同pH值、活性炭用量、吸附温度和吸附时间条件下进行脱色实验,并考察脱色率和氨基酸损失率,结果表明,较好的脱色工艺条件为:pH=4.0,活性炭用量为0.020 g/mL,吸附温度45℃,吸附时间25 min,脱色率90%。被活性炭吸附的氨基酸,可以通过解吸附得到回收。     

近临界水中水解鱼蛋白制备氨基酸

The hydrolysis technology and reaction kinetics for amino acids production from fish proteins in subcritical water reactor without catalysts were investigated in a reactor with volume of 400 ml under the conditions of reaction temperature from 180-320℃, pressure from 5-26 MPa, and time from 5-60 rain. The quality and quantity of amino acids in hydrolysate were determined by bioLiquid chromatography, and 17 kinds of amino acids were obtained. For the important 8 amino acids, the experiments were conducted to examine the effects of reaction temperature, pressure and time on amino acids yield. The optimum conditions for high yield are obtained from the experimental results. It is found that the nitrogen and carbon dioxide atmosphere should be used for leucine, isoleucine and histidine production while the air atmosphere might be used for other amino acids. The reaction time of 30 rain and the experimental temperature of 220℃, 240℃ and 260℃ were adopted for reaction kinetic research. The total yield of amino acids versus reaction time have been examined experimentally. According to these experimental data and under the condition of water excess, the macroscopic reaction kinetic equation of fish proteins hydrolysis was obtained with the hydrolysis reaction order of 1.615 and the rate constants being 0.0017, 0.0045 and 0.0097 at 220℃, 240℃ and 260℃ respectively. The activation energy is 145.1 kJ·mol^- 1.     

Optimization of amino acids production from waste fish entrails by hydrolysis in sub and supercritical water

A resource recovery technique using sub‐ and supercritical water hydrolysis was applied to convert waste fish entrails into amino acids. The effect of reaction parameters such as temperature and time necessary for the control of reaction towards optimum yield of amino acids was investigated. Results showed a maximum yield of total amino acids (137 mg/g dry fish) from waste fish entrails at T= 523 K (P = 4 MPa) and reaction time of 60 min in a batch reactor. Under supercritical conditions (e. g., T= 653 K, P = 45 MPa), the yield decreases due to rapid decomposition compared to production rate of amino acids. The results suggest operation of the system at short reaction time and mild temperature condition.     

Hydrolysis of fatty acid esters in subcritical water

Hydrolysis of esters of higher fatty acids by subcritical water, performed in a flow‐through tubular reactor, was investigated at temperatures from 280 up to 340 °C and pressures exceeding 12 MPa, using an ester/water ratio of 1 : 2 or 1 : 4 (vol/vol). The kinetics of the hydrolysis of both the triacylglycerols and the methyl esters obeyed the rate equation valid for first‐order reactions. Conversion of the esters to free fatty acids exceeding 95% was reached at the temperature of 340 °C during 12 min. IR spectroscopy revealed structural changes in the chains of the unsaturated fatty acids and their partial polymerization during the hydrolysis.     

有机酸对甜高粱渣亚临界水解产物的影响

半纤维素的高效转化是提高甜高粱渣原料全组分利用的关键技术之一。采用亚临界水热预处理方法,并将强度因子R₀引入研究过程,考察了不同温度（160~200℃）和反应时间（10~60 min）对甜高粱渣水解反应的影响。在这基础上,进一步考察了多种有机酸（乳酸、醋酸及乳酸+醋酸）对亚临界水解效果的影响。实验表明,当强度因子lgR₀=3.96（180℃,40 min）时,采用不外加酸的亚临界水热预处理工艺得到的最大木糖浓度为4.79 g·L^-1;有机酸的加入可强化水解反应,提高木糖浓度;与单一乳酸或醋酸处理方法相比,加入同浓度的乳酸+醋酸既可以促进半纤维素水解,又可以抑制副产物生成;在温度180℃,时间40 min,乳酸+醋酸（乳酸：醋酸=6：4）的浓度1%（质量）的条件下,木糖浓度为7.92 g·L^-1。     

Supercritical hydrolysis of cellulose for oligosaccharide production in combined technology

A combined supercritical/subcritical technology was used as a pre-treatment and hydrolysis method for ethanol production from cellulose/lignocelluloses. In a batch study for supercritical hydrolysis, which is the primary step of the combined technology, 60 mg of microcrystalline cellulose in 2.5 ml deionized water was loaded into each reactor and heated in a salt bath at a selected temperature for a specified reaction time. Cellulose was quickly hydrolyzed to oligosaccharides, hexoses and other small molecular products at temperatures above the critical point of water. Temperature and reaction time were the two key parameters that determined the products of cellulose hydrolysis. The highest yield of oligosaccharides (approximately 40%) was obtained at optimum conditions of 380 °C and a reaction time of 16 s. The corresponding yield of hexoses was 24%, giving a maximum yield of hydrolysis products of approximately 63%. A complete decomposition of hydrolysis products occurred at higher temperatures and/or longer reaction times. A kinetic analysis was performed to explain the reaction of cellulose in supercritical water. The results presented here provide a rigid framework for the use of combined supercritical/subcritical technology in subsequent research.     

Solubility of fatty acids in subcritical water

A phase equilibrium apparatus was designed to determine the solubilities of stearic acid and palmitic acid in subcritical water at different temperatures and pressures. The dissolution equilibrium time was measured. The effect of an ultrasonic field on dissolution equilibrium was also studied. The results showed that the maximum solubilities of stearic acid and palmitic acid were 0.136 g/100 g and 0.178 g/100 g in subcritical water at temperatures of 180 °C and 160 °C, respectively, and a pressure of 15 MPa for 30 min. An ultrasonic field also clearly promoted the dissolution of fatty acids in subcritical water. The dissolution equilibrium time was shortened to 20 min using ultrasonic oscillation (250 W, 20 kHz).