Ultrasound-assisted extraction of pomegranate seed oil – Kinetic modeling

In this work, ultrasound-assisted extraction was employed to extract oil from pomegranate seeds. Seed particle size, extraction temperature, solvent/solid ratio, amplitude level, and pulse duration/pulse interval ratio were the factors investigated with respect to extraction yield using a central composite design. The optimum operating conditions were found to be: seed particle size, 0.2 mm; extraction temperature, 20 ^oC; solvent/solid ratio, 20/1; amplitude level, 60%; pulse duration/pulse interval ratio, 5/15. Under these optimized conditions, the predicted value for extraction yield was 59.8%. A second-order kinetic model was successfully developed for describing the mechanism of ultrasound extraction under different processing parameters.     

New kinetic models for the crystallization of anatase nanoparticles from amorphous titania (TiO2)

In this article, amorphous Titania (TiO₂) nanoparticles were crystallized both in a solution environment and by a dry heat treatment using new kinetic models with the capabilities of more accurately predicting the polymorphic transformation behavior of TiO₂. In these models, both the nucleation and growth processes were simultaneously taken into account. The results were indicative of the Surface Nucleation (SN) of anatase occurring in a hydrothermal treatment process through the phase transformation. Also, both the surface and interface nucleation processes were found to play significant roles in the phase transformation kinetics when dealing with dry heat treatments at low temperatures. The proposed models were advantageous to any other published models, in which the nucleation mechanisms had been incorporated with suitable growth expressions. In other words, no experimental data of a particle size were required to investigate the phase transformation kinetics of TiO₂ nanoparticles in the models presented in this article.     

A kinetic model involving oxidation and volatilization in SiC-B4C-xAl2O3 ceramics system

In this paper, a new kinetic model considering both oxidation and volatilization kinetics is established and applied to analyze the oxidation of SiC-B₄C-xAl₂O₃ ceramics and other systems in various oxidation conditions. The effects of diffusion area and volume changes during the oxidation process are considered in this model. The physical meaning of each parameter in this model is explicit and simple. According to this model, the diffusion coefficient of species and the corresponding diffusion activation energy are easily available. The practicability of this model is well verified by the experimental data of SiC-B₄C-xAl₂O₃ and other systems oxidized under different conditions. In addition, the practice shows that the model is applicable not only to the systems where oxidation and volatilization coexist, but also to the system where only oxidation plays a major role. We hope the model proposed in this work can be used in other materials with more complex environments.     

分子筛ZSM-5对海藻酸钠热分解的影响

本研究采用热重分析法研究了分子筛ZSM-5填充海藻酸钠在空气中的热分解过程,升温速率分别为5K/min、10K/min、15K/min、20K/min和30K/min,温度范围为室温（298K）至1250K,并利用TGA曲线分析了复合材料的热分解特性。热重分析结果显示,热分解反应最剧烈的温度介于450～650K之间,热分解动力学分析表明,该热分解过程为一级反应,可通过最大失重速率温度法和Ozawa等失重率法分别计算求得活化能和频率因子。结果表明,活化能和频率因子随着失重率的增加而增大,分子筛ZSM-5的加入有利于海藻酸钠的热分解。     

肌苷发酵过程的动力学研究

采用枯草杆菌(Bacillus Subtilis)突变株,以葡萄糖为碳源进行间歇发酵研究,得到肌苷发酵过程受底物抑制的动力学关系。在肌苷代谢机理简化的基础上推导建立了工程上适用的菌体增殖动力学方程(dx)/(dt)=0.00266(Sx)/(20.3+s+s~2/76.4+I/6.03)肌苷生成的动力学方程为(dp)/(dt)=0.1791((Sx)/(67.76+s))-8.40(dx)/(dt)基质糖消耗的动力学方程为-(ds)/(dt)=(1/1.017)((dx)/(dt))+(1/0.1207)((dp)/(dt))+(0.3188x)     

A KINETIC STUDY OF THE SULPHURIZATION OF RESIDUAL ASPHALTS

The kinetics of the sulphurization reaction of residual asphalts were investigated at temperatures of 220^°-250^°C and reaction time of 1 hr. The apparent reaction order varied from 1.40-3.50 for the range of temperature studied. The maximum reaction order was obtained at 24O^°C which appeared to be the optimum reaction temperature. The apparent kinetic rate parameters estimated for the sulphurization reactions were activation energy of 99.5 kJ/mol and a frequency factor of 15.48 × 10⁸. The rate parameters show some good agreement with other work reported in the literature.     

茜素红褪色动力学光度法测定痕量钴

在pH 8.0的氨-氯化铵介质中,以聚氧乙烯醚-200（PEG-200）为活化剂,Co催化溴酸钾氧化茜素红褪色,建立了动力学光度法测定痕量Co的新方法。该方法检出限为2.0×10-7g/L;线性范围0.01~0.21μg/50 mL;最大相对标准偏差为4.3%。该法用于湖水及生产排水的测定,结果满意;加标回收率在96.0%~105.0%。     

不同渣油加氢级配体系脱硫性能研究

在固定床连续操作装置进行渣油加氢中试试验。试验过程考察三种不同渣油加氢催化剂级配的稳定性。同时,运用反应动力学模型对不同反应条件的中试数据进行了归一化对比研究。研究结果表明,在相同操作条件下级配体系1和级配体系3中试试验的加氢脱硫活性、稳定性相近,均高于级配体系2中试试验结果。该研究结果可为工业装置的催化剂级配选择提供参考。     

高氮量硝化棉的脱硝反应动力学研究(英文)

用实时测定凝聚相分解产物的固体原位反应池/快速扫描傅立叶变换红外光谱热技术研究了高氮量硝化棉(14.14%N)的脱硝反应动力学。该反应的动力学参数(活化能和指前因子)用改良的Coats-Redfern法计算。根据所得结果,提出了在403～465K温度范围内描述高氮量硝化棉脱硝反应的微分动力学方程。     

硫化橡胶的压缩应力松弛

本文进行了丁腈,氯丁、天然以及氯醇/丁腈并用胶等六种实用配方硫化橡胶,在40-110℃不同温度范围内的压缩应力松驰研究。应力松弛动力学变化不能用人所共知的Maxwellian衰减公式描述,可用下列经验公式:σ/σ_0=B·exp(-kt~α)描述化学应力松驰变化,式中α用逼近法确定,在全部实验情况下得到令人满意的结果。