Mass transfer mechanisms in fixed-bed adsorption of erythromycin

The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined. The equilibrium data in a batch system was well described by a Langmuir isotherm. The separation performance was investigated in a fixed-bed system with respect to the adsorption superficial velocity, ionic strength and pH. A mathematical model was used to simulate the mass transfer mechanism, taking film mass transfer, pore diffusion and axial dispersion into account. The model predictions were consistent with the experimental data and were consequently used to determine the mass transfer coefficients.     

离子液体[Bmim]PF6萃取红霉素动力学机理

研究探讨离子液体[Bmim]PF6萃取红霉素过程的动力学行为和特征,考察了温度以及传质界面积对萃取速率的影响。结果表明,离子液体[Bmim]PF6萃取红霉素的过程为化学反应控制过程,并确定萃取平衡方程式。一级反应动力学模型能很好的描述实验条件下离子液体对红霉素的萃取分离过程。     

Determination of parameters in a two-dimensional model for fixed-bed adsorbers

A new method is proposed for the determination of the parameters in a two-dimensionalmodel which characterizes the properties of axial and radial mixing and mass transport in afixed-bed adsorber.Parameter estimation for the model is carried out with methane-air-5A molecularsieve in a bed under the condition of step injection of tracer from a point on the main axis of thebed by the curve fitting method in the time domain.     

大孔吸附树脂对红霉素的平衡吸附行为及其热力学性质

引言 红霉素(EM)是临床应用较多的一种大环内酯类抗生素,随着一些疗效更好的半合成衍生物的开发,红霉素原料需求呈现增长趋势.     

耦合传质的羰基化固定床反应器传热模拟分析

固定床反应器中进行强放热反应时, 反应器的热点温度对操作参数变化敏感,容易引起飞温,导致转化率下降,影响催化剂寿命。为强化羰基化固定床反应器内热质传递与化学反应的协同性,建立考虑颗粒内扩散影响的羰基化固定床反应器拟均相一维传热模型,考察操作参数对床层热点温度、反应转化率、床层温升的影响。不仅体现传热传质和反应的协同作用,而且影响关系明晰、求解方便。为保证反应转化率,本实验条件下确定催化剂颗粒直径小于等于1.5 mm。反应器入口温度/冷却剂油温既要满足床层热稳定性需求,又要使反应转化率和床层温升都在合理范围内。模拟结果表明在床层入口温度升高的同时,可通过降低冷却剂油温获得良好的反应转化率和较小的床层温升。在此基础上,考察入口环氧乙烷浓度对反应转化率和床层温升的影响。本研究可为固定床反应器满足转化率要求、床层合理温升而选择催化剂颗粒直径、床层入口温度、冷却剂油温和床层入口浓度等操作参数提供计算依据。     

微波辅助离子液体测定环境中残留红霉素的研究

用微波辅助疏水性离子液体[Bmim]PF6萃取分离红霉素,考察了微波辐射功率、辐射时间、离子液体用量、pH值对红霉素萃取率的影响。结果表明,微波辅助离子液体萃取分离红霉素的最佳工艺条件为:在303.15 K的温度下,调节体系pH=6～7,微波辐射功率为210 W,采用间歇辐射的方式,单次辐射时间为20 s,辐射3次,离子液体的用量为3 g,萃取率为90.7%。同时,建立微波辅助离子液体富集分离分析牛奶中红霉素的方法,该方法的检出限为4μg/kg,线性范围在5～50μg/L,RSD=1.7。     

Multicomponent mass transfer in fixed-bed carbon adsorption columns

The technique based upon the constant pattern model was extended to evaluate mass transfer coefficients for multicomponent (binary) adsorption by carbons. The mass transfer coefficient of the lesser adsorbed component was essentially the same for both single component and binary systems. The mass transfer coefficient of the more strongly adsorbed component was significantly lower in the binary case, indicating interference between components. The mass transfer coefficients obtained were used in a computer simulation of fixed bed adsorption columns, and experimental data were successfully predicted.     

固定床雷尼金属催化剂研究进展

雷尼金属催化剂具有价格低廉、工艺可控性强、技术成熟等优势,广泛用于各种有机合成加氢反应。但是雷尼型粉末催化剂存在容易粉化流失而活性降低、反应完毕后需要过滤分离催化剂等固有的缺点,仅能应用于小批量生产。固定床雷尼金属催化剂在工业装置上的应用进展较快,但现有文献散见于专利技术和新闻报道。本文介绍了固定床雷尼金属催化剂国内外的应用进展,总结了固定床雷尼金属催化剂的制备方法,主要有块状雷尼金属破碎、雷尼合金粉成型和热喷射镀层方法。分析了各种固定床雷尼金属催化剂制备方法的特点和创新点,指出国内外固定床雷尼金属催化剂已经取得一定进展,正在逐渐取代基于传统釜式工艺的粉末雷尼镍催化剂。     

缓冲盐溶液反萃分离红霉素A、C的研究

用NaH2PO4-Na2HPO4缓冲盐溶液反萃醋酸丁酯相中的红霉素,以纯化酯相中的红霉素A。分别考察了缓冲盐pH值、相比(体积比)、温度对红霉素A、C反萃取的影响。实验结果表明:随着pH值的增加,红霉素A的反萃率大大减少,红霉素C的反萃率先增加后减小,当pH=8时,酯相中红霉素A纯度最高且损失最低;随着相比(A/O)的增加,红霉素A、C的反萃率及酯相中的红霉素A纯化效果都略有提高,但综合考虑反萃剂用量和红霉素A损失,可知相比(A/O)为2∶1时较优;随着温度的增加,红霉素A、C的反萃率都大大减小,且酯相中的红霉素A纯度略有下降,但因红霉素A反萃损失较少,可考虑在328 K时,反萃2次,除去大量红霉素C的同时损失较少的红霉素A。     

新型固定床Raney催化剂的制备进展

综述了固定床Raney催化剂的多种制备方法,该类型催化剂主要用于不饱和化合物的加氢反应。Raney催化剂用于固定床连续使用有多种方法,可采用粗Raney合金颗粒,控制活化条件仅溶除合金颗粒外层的金属铝;另外也可将Raney合金粉末添加其他物质成型,或者将适当金属气相沉积于其他材料上,再经高温焙烧、碱液浸取活化后使用,其中后者可以获得形状统一、强度较高、催化活性和活性稳定性较好的固定床Raney催化剂。     

Mass transfer limitations on fixed-bed reactor for Fischer-Tropsch synthesis

Mass transfer limitations on fixed-bed for Fischer-Tropsch synthesis were investigated by changing synthesis gas superficial velocity, catalyst pellet size, and catalyst amount. To study external mass transfer limitation, synthesis gas superficial velocity was changed from 8.47 × 10^− 4 m s^− 1 to 3.39 × 10^− 3 m s^− 1. As a result, the synthesis gas superficial velocity of 3.39 × 10^− 3 m s^− 1 was most suitable for hydrocarbon chain growth resulting to liquid hydrocarbon formation. In case of internal mass transfer limitations, the effects of catalyst pellet size and catalyst amount (W_cat/F) were discussed. The large catalyst pellet showed higher C₅₊ selectivity and a lower α value compared to the small pellet because of more severe internal mass transfer limitations of α-olefin and long-chained hydrocarbons in the large pellet, respectively. Catalyst amount (W_cat/F) was inversely proportional to the internal mass transfer limitation because increased catalyst amount gave more time for liquid hydrocarbon products to diffuse from the catalyst pellet and, therefore, the catalyst amount of 4.5 g (W_cat/F = 45 g_cat min L^− 1) was most appropriate for liquid hydrocarbon formation.     

三相连续环流反应器中氧的液相传质过程

在空气-水-玻璃珠三相连续操作环流反应器中,利用动态溶氧方法研究了表观气速(Ug=0.01~0.13 m/s)、进料浆速(USL=0.001~0.011 m/s)、浆相质量固含率(es=0~30%, w)和固相颗粒大小(dp=59, 200 mm)对环流反应器内氧的液相传质性能的影响. 结果表明,在考察范围内,环流反应器传质系数随表观气速增大而增大,受进料浆速变化的影响较小,随浆相固含率增大呈现先增大后减小的趋势,但在高固含率下(es≥10%, w)的影响不显著;随固相颗粒粒径增大而减小. 同时得到了液相体积传质系数的经验关联式.     

分子筛吸附脱除芳烃中的环状烯烃

以Y型分子筛为吸附剂脱除甲苯中的环状烯烃化合物（二聚环戊二烯,DCPD）。采用NH3-TPD测试方法分析了USY和HY分子筛的酸性中心性质。通过间歇吸附实验考察了USY和HY分子筛对甲苯中DCPD的吸附脱除能力以及温度对USY分子筛吸附能力的影响,结果表明,USY分子筛的烯烃吸附量是HY分子筛的1.68倍;当温度由30℃升至50℃时,USY分子筛的吸附速率增大。采用固定床连续实验考察了温度、体积空速和原料中烯烃浓度对USY分子筛吸附效果的影响,当温度为80℃、空速为0.133h?1时,分子筛的穿透吸附量最大;分子筛处理具有较高初始浓度的原料时得到较高的穿透吸附量,且对工业焦化甲苯溶液的处理效果明显,具有较好的工业应用前景。TGA热重分析结果表明,USY分子筛对DCPD的选择性吸附能力强于甲苯。     

Phenomenological-based model of direct blue 2 adsorption on corncob in a fixed-bed

This work presents a phenomenologically based semi-physical model (PBSM) for the liquid–solid adsorption process, which has been experimentally validated. Two modes of operation of adsorption of direct blue 2 dye (DB2) on corn cobs in a fixed bed are discussed by applying the PBSM. The first mode of operation is the typical continuous liquid flow, whereas the second is a semicontinuous mode with the recirculation of liquid leaving the column. These modes of operation were used to illustrate different ways in which the system reaches equilibrium conditions. The equilibrium distribution curve (EDC) for low DB2 concentration was reached with the best fit using the Langmuir–Freundlich model ( $R^2=0.998$). The local mass transfer coefficient for the solid phase was evaluated by the PBSM deduction, and subsequently, the diffusivity of the surface solid was experimentally evaluated through comparison in terms of the PBSM. Regardless of the mode of operation, surface diffusion is associated with only the nature of the adsorbent material rather than the concentration of the liquid phase. In addition, the PBSM exhibited liquid and solid concentration changes at different points in the column. Moreover, different operating curves of the process were constructed and validated, exhibiting similar results when comparing the predictions of the model and the experimental data. These findings support the strength of the constructed model, enabling its extension to other adsorbent–dye systems.     

固定层制气技术的发展及问题探讨

介绍了固定层制气技术的发展过程,指出了今后固定层制气的发展方向。针对目前固定层制气生产过程中存在的工艺配套、设备及操作等问题,提出了解决问题的方法和思路:①增大炉径,提高单个煤气发生炉的产气量;②在解决好工艺配置的前提下,大胆使用先进技术和设备;③采用富氧空气进行加氮。     

烷烃中少量芳烃的固定床和模拟移动床吸附

在实验研究烷烃中少量芳烃的固定床吸附动态过程和模拟移动床吸附动态过程的基础上,用固定床和模拟移动床线性推动力模型进行了模拟计算,可得到如下结论:在本文的实验条件下,固定床吸附动态模型和模拟移动床吸附动态模型拟合的结果均与实验值相符;但从技术性能指标和技术经济指标两个角度都反映出对脱除烷烃中的少量芳烃的吸附分离过程,用固定床吸附过程比模拟移动床吸附过程更具有可行性。这些结果为在直链烷基苯的生产过程中,降低循环烷烃中芳构化物的含量,实现延长脱氢催化剂的寿命,提高烷基苯的产量提供了技术基础。     

Mass transfer kinetics in pressure swing adsorption

Many mass transfer kinetic models are used to study varying pressure steps of a pressure swing adsorption (PSA) cycle, namely pressurization and blowdown steps. It is shown that the choice of an appropriate model to account for intra-particle diffusional limitations is essential to simulate accurately PSA processes. It has been demonstrated that, besides mathematical approximations (parabolic profile within the particle), a very important factor that can affect simulation results remarkably is the correctness of the mass transfer kinetic model when regarded as being a mass balance for the adsorbent particle. In fact, neglecting intra-particle gas phase leads to erroneous simulations. Some models widely used in the literature, such as the classic linear driving force (LDF) and the solid diffusion models prove inadequate. It is recommended to use pore diffusion model as well as a new version of the solid diffusion model to get reliable predictions.     

Effect of particle size on lignite devolatilization in a fixed-bed reactor

A fixed-bed coal gasification reactor was set up which specifically simulated the devolatilization zone in a gasifier. Samples (100 g) of lignite coal in three size ranges; ?2+1 mm, ?3+2 mm and ?4+3 mm, were devolatilized in the temperature range 350–550 °C with a steam-oxygen mixture, at 1 atm. The effect of these operating variables on tar yield and composition, melting point, viscosity, specific gravity, and molecular weight distribution was determined. A first-order reaction model was fitted to the experimentally observed total loss in weight of the lignite.     

工业级错流列管式固定床反应器的CFD模拟

工业级大型列管式固定床反应器壳程温度场与流场的均匀程度与反应的转化率及选择性密切相关。通过添加阻力源项和分散热源项,对工业级全尺寸错流列管式固定床壳程流场及温度场进行了CFD模拟研究,并进一步考察了折流板窗口区大小及其位置对壳程压降与温度分布的影响。结果表明,模拟得到壳程压降与由经验公式计算得到的压降较为接近,且壳程温度分布与工业实际数据吻合;增大窗口区面积,壳程压降呈现指数下降,同时高温差区（径向温差大于2 K）的范围与径向温差变大;随着第1块折流板位置降低,高温差区范围及径向温差均减小,但压降并不呈现规律性变化。模拟方法可用于工业级大型列管式固定床反应器的优化及设计。