Experimental and theoretical investigation of parametric sensitivity and dynamics of a continuous stirred tank reactor for acid catalyzed hydrolysis of acetic anhydride

The continuous stirred tank reactor is a dynamic system exhibiting nonlinear behavior such as multiplicity and oscillations and, in certain range of operating conditions, may exhibit a parametric sensitivity where small changes in one or more of the input parameters lead to large changes in the output variable. In the present work, hydrolysis of acetic anhydride reaction system was used to demonstrate the existence of parametric sensitivity with respect to the input parameter, the cooling water flow rate. The applications of parametric sensitivity analysis were used for detection of parametric sensitivity in a continuous stirred tank reactor using catalyses hydrolysis of acetic anhydride reaction system. Also, theoretical investigation revealed that the effect of wall capacitance has definite influence on the dynamics of continuous stirred tank reactor. The continuous stirred tank reactor showed parametric sensitivity both in the regions of uniqueness and multiplicity, and a mathematical model was developed for the reactor. The numerically simulated results are in satisfactory agreement with the experimental data.     

A novel type of equipment for reactive distillation: Model development,simulation, sensitivity and error analysis

A simulation study of heterogeneously catalyzed reactive distillation experiments carried out with the D + R tray, a novel type of laboratory equipment, is presented. One advantage of the D + R tray is that reaction and distillation are alternating stage‐wise, in a well‐defined way that can be modeled straightforwardly. An equilibrium stage model is used to describe the distillation and a plug flow reactor model to describe the catalyst bed reactors. The model parameters are derived from a systematic experimental characterization of the D + R tray both as a reactor and as a distillation unit. A validated physicochemical fluid property model is used. The primary experimental data are reconciled. Results from the predictive simulations are in good agreement with the experimental results. The influence of errors in the input parameters on the simulation results is investigated by means of a sensitivity and error analysis. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1533–1543, 2013     

Comparative studies on parametric sensitivity analyses using conventional and factorial design methodologies: mathematical modelling of clavulanic acid adsorption on zeolites

BACKGROUND: The main objective of this work was to evaluate the parametric sensitivity of model parameters of clavulanic acid (CA) adsorption in a stirred‐tank reactor using zeolites. The system sensitivity was evaluated in terms of mass transfer and hydrodynamic parameters using two methodologies. First, the sensitivity factors of input variables were evaluated according to a disturbance of ± 20% in the nominal parameter values; second, the factorial design methodology was employed. In both cases, the responses were obtained by means of model simulations. RESULTS: From the sensitivity analysis by experimental design, the best operational conditions for adsorption of CA on zeolites were solid to liquid percentage 7.0%, initial CA concentration 300 mg L^?1 and particle diameter 0.100 mm, which led to a reduction of 25 min in the adsorption time and 9% in the adsorption capacity, increasing the process productivity. CONCLUSION: The use of the factorial design had advantages compared with the conventional method because it provided information regarding the possibility of simultaneous changes in the factors investigated, enabling analyses of system sensitivity regarding operational parameters, as well as the choice of more suitable parameters. Copyright © 2012 Society of Chemical Industry     

The application of dynamic modeling for thermal risks analysis of the acid‐catalyzed hydrolysis of glycidol

The aim of this work was to determine the limits of safe operation of continuous flow stirred‐tank reactor (CSTR) for the acid‐catalyzed hydrolysis of glycidol. The stability analysis was performed by dynamic modelling. The obtained results were compared with the experimental data reported in the open literature. For this purpose, dimensionless variables and parameters were introduced and unstable material and energy balances were defined. The system equations were solved using Matcont (Matlab^® software). Thus, bifurcation diagrams (in one and two dimensions) were mapped. All different dynamic states were identified and studied (thermal stability and instability, with unique and multiple solutions; Hopf bifurcations; turning points and envelope of periodic solutions). Finally, the intrinsic thermal unstable and cycle behavior of the acid‐catalyzed hydration of glycidol to produce glycerol was identified. The appropriate conditions to guarantee safe operation of CSTR were found. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4418–4426, 2016     

Enzymatic hydrolysis of sugarcane bagasse for bioethanol production: determining optimal enzyme loading using neural networks

BACKGROUND: The efficient production of a fermentable hydrolyzate is an immensely important requirement in the utilization of lignocellulosic biomass as a feedstock in bioethanol production processes. The identification of the optimal enzyme loading is of particular importance to maximize the amount of glucose produced from lignocellulosic materials while maintaining low costs. This requirement can only be achieved by incorporating reliable methodologies to properly address the optimization problem. RESULTS: In this work, a data‐driven technique based on artificial neural networks and design of experiments have been integrated in order to identify the optimal enzyme combination. The enzymatic hydrolysis of sugarcane bagasse was used as a case study. This technique was used to build up a model of the combined effects of cellulase (FPU/L) and β‐glucosidase (CBU/L) loads on glucose yield (%) after enzymatic hydrolysis. The optimal glucose yield, above 99%, was achieved with cellulase and β‐glucosidase concentrations in the ranges of 460.0 to 580.0 FPU L^?1 (15.3–19.3 FPU g^?1 bagasse) and 750.0 to 1140.0 CBU L^?1 (2–38 CBU g^?1 bagasse), respectively. CONCLUSIONS: The dynamic model developed can be used not only to the prediction of glucose concentration profiles for different enzymatic loadings, but also to obtain the optimum enzymes loading that leads to high glucose yield. It can promote both a successful hydrolysis process control and a more effective employment of enzymes. Copyright © 2010 Society of Chemical Industry     

木质纤维素水解制取燃料乙醇研究进展

以木质纤维素生产燃料乙醇具有原料可再生性和环境友好的优点而备受重视.本文介绍了国内外木质纤维素制取燃料乙醇中的水解工艺过程,包括浓酸水解、稀酸水解和酶水解工艺,分析了各工艺的技术特点,同时指出稀酸预处理-酶水解工艺将成为近几年国内外研究和开发的重点.     

Modeling and parametric analysis of hollow fiber membrane system for carbon capture from multicomponent flue gas

The modeling and optimal design/operation of gas membranes for postcombustion carbon capture (PCC) is presented. A systematic methodology is presented for analysis of membrane systems considering multicomponent flue gas with CO₂ as target component. Simplifying assumptions is avoided by namely multicomponent flue gas represented by CO₂/N₂ binary mixture or considering the co/countercurrent flow pattern of hollow‐fiber membrane system as mixed flow. Optimal regions of flue gas pressures and membrane area were found within which a technoeconomical process system design could be carried out. High selectivity was found to not necessarily have notable impact on PCC membrane performance, rather, a medium selectivity combined with medium or high permeance could be more advantageous. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

纤维素酶法水解的研究现状及展望

纤维素是地球上最丰富的天然高分子化合物,可以通过水解的方法将其转化为为人类生产生活服务的能源、食物及化工原料。而早期水解纤维素主要采用酸水解法,但由于要求条件高,产率低, 以及对环境存在污染,现已被淘汰。近年来,随着生物技术的迅速发展以及具有催化高效性的酶的研究,人们开始试图利用纤维素酶来水解纤维素,以期达到充分利用的目的。作者就纤维素酶法水解的研究进展及应用作了简要的概述。     

Process modeling for parametric study on oil palm empty fruit bunch steam gasification for hydrogen production

Biomass steam gasification with in-situ carbon dioxide capture using CaO exhibits good prospects for the production of hydrogen rich gas. The present work focuses on the process modeling for hydrogen production from oil palm empty fruit bunch (EFB) using MATLAB for parametric study. The model incorporates the reaction kinetics calculations of the steam gasification of EFB (C_3.4H_4.1O_3.3) with in-situ CO₂ capture, as well as mass and energy balances calculations. The developed model is used to investigate the effect of temperature and steam/biomass ratio on the hydrogen purity, yield and efficiency. Based on the results, hydrogen purity of more than 76.1 vol.% can be achieved. The maximum hydrogen yield predicted at the outlet of the gasifier is 102.6 g/kg of EFB. It is found that increment in temperature and steam/biomass ratio promotes hydrogen production. However, it is also predicted that the efficiency decreases when using more steam. Due to the still on-going empirical work, the results are compared with published literatures on different systems. The comparison shows that the results are in agreement to some extent due to the different basis.     

Modeling and optimization of dilute nitric acid hydrolysis on corn stover

BACKGROUND: Because of its high cost, nitric acid has not been widely employed as the catalyst for hydrolysis of lignocellulosic biomass to obtain fermentable sugars. However, recently more and more research results have reported that nitric acid was more effective than other acids for the hydrolysis of lignocellulose. Therefore, it is necessary to find an optimum condition for nitric acid pretreatment and a means of reducing the cost. RESULTS: In this work, low concentrations of nitric acid and short reaction times were considered to optimize the pretreatment process. The kinetic parameters of models to predict the concentrations of xylose, glucose, arabinose, acetic acid and furfural in the hydrolysates were obtained. Applying the kinetic models, the optimum conditions were: 150 °C, 0.6% HNO₃ and 1 min, which yielded a solution containing up to 22.01 g L^?1 xylose, 1.91 g L^?1 glucose, 2.90 g L^?1 arabinose, 2.42 g L^?1 acetic acid and 0.21 g L^?1 furfural, which were consistent with the predicted values. The influence of temperature was also studied using the Arrhenius equation. CONCLUSIONS: A combination of experimental data and model analysis suggested that 96% xylose yield can be achieved by using low concentration nitric acid for a short reaction time, which could greatly reduce the pretreatment cost. Therefore, dilute nitric acid could be considered a good choice for the hydrolysis of corn stover. Copyright © 2010 Society of Chemical Industry     

羰基硫水解催化剂失活研究的现状与进展

介绍目前国内外对羰基硫水解催化剂机理及催化剂失活原因的研究进展与发展趋势。     

不同粒度HMX的重结晶制备和机械感度研究

采用微团化动态结晶方法和溶剂/非溶剂滴加重结晶方法制备出中位径d50分别为0.472、6.266、36.75μm的HMX颗粒,并采用粒度分析仪和扫描电子显微镜（SEM）对3种试样的粒度进行了表征。测定了3种试样的撞击感度（特性落高H50）和摩擦感度（爆炸百分数）值。测试结果表明,撞击感度随粒度减小逐渐降低,并且在粒度降至亚微米级时降到最低;摩擦感度随粒度减小先升高再降低,而且粒度在10μm～50μm时最为钝感。     

Exothermic oxidations in supercritical CO2: effects of pressure-tunable heat capacity on adiabatic temperature rise and parametric sensitivity

Many oxidation reactions, including H₂ combustion with O₂, have been shown to admit the phenomenon of parametric sensitivity. Given its inertness to oxidation and non-flammable nature, supercritical CO₂ (scCO₂) is a desirable solvent for performing oxidations. Further, for oxidations that employ H₂O₂ as an oxidant, the use of scCO₂ as a solvent has been suggested for producing H₂O₂ in situ by reacting H₂ and O₂. Another significant, and as yet not fully understood, advantage of using scCO₂ is the ability to exploit its liquid-like heat capacity, which exhibits a maximum in the near-critical region (1.01-1.2T_c and 0.9-2.0P_c). It is shown in this modeling study that by performing an oxidation reaction in scCO₂, the temperature rise accompanying the highly exothermic reaction can be effectively controlled. To demonstrate this concept, we simulated the maximum temperature rise (ΔT_ad) for H₂ combustion with O₂ in CO₂ in a constant-pressure adiabatic reactor, at feed temperatures ranging from 300 to and reactor pressures from 1 to . At a feed temperature of , a five-fold reduction in ΔT_ad value (from 209 to ) is predicted by tuning the operating pressure from 1 to . In contrast, the ΔT_ad in N₂ medium is relatively insensitive in the 1- pressure range and is six times greater (roughly ) compared to the value predicted with CO₂ medium at . Further, the values of β (the dimensionless temperature rise parameter) may also be sensitively tuned with pressure in the near-critical region such that parametric sensitivity is minimized. These results indicate that the liquid-like heat capacities of scCO₂ may be exploited to control the adiabatic temperature rise and to ameliorate parametric sensitivity during exothermic reactions, a problem of fundamental and practical significance.     

Flash hydrolysis of microalgae (Scenedesmus sp.) for protein extraction and production of biofuels intermediates

The present study on flash hydrolysis under subcritical water medium capitalizes on the difference in reaction kinetics of algae polymeric components and fractionates proteins in liquid phase in seconds of residence time. All the experiments were conducted using flocculated Scenedesmus sp. cultivated in the laboratory using photobioreactors. The effect of temperature and residence time on protein hydrolysis to water-soluble fractions (algal hydrolyzate) and yield of lipid-rich solids (biofuels intermediate) was studied using a lab-scale continuous flow reactor.More than 60 wt% of the total nitrogen content (dry basis) in Scenedesmus sp. was extracted within 10 s of residence time above 240 °C. The ion chromatography and NMR spectra of the algal hydrolyzate showed that the extracted proteins were present both as free amino acids and peptides. The carbon content of biofuels intermediate increased up to 66 wt% making it lipid- and energy-dense feedstock suitable for biofuels production. The scanning electron microscope image of biofuels intermediate indicated that the solids were globular and smaller in size as compared to the untreated microalgae.     

Study on the acid hydrolysis of Peat: 1. extraction of carbohydrates

Peat and its derived products such as peat extracts or hydrolysates offer a variety of possibilities as raw materials for the development of chemical and biochemical processes. Acid hydrolysis of peat yields soluble carbohydrates which can be utilised as fermentation media. In this work, Sphagnum peat moss was hydrolysed under various conditions of H₂SO₄ concentration, retention time, temperature, peat concentration, peat particle size distribution and original moisture content in the peat. The results suggest that mild conditions of hydrolysis, which will minimise possible negative effects on other nutrients available in peat, are adequate for the release of the carbohydrates present in peat. It was found that peat particle size distribution and original moisture content as well as peat concentration will also affect the yield of carbohydrates obtained.     

水解酸化-缺氧法处理采油废水的试验研究

针对采油废水水质复杂、可生化性差的特点,试验采用水解酸化-缺氧法处理采油废水,取得了较为合适的处理工艺参数.试验结果表明:水解酸化-缺氧法对采油废水具有较好的处理效果,缺氧段各工况的出水COD均能达到<国家石油开发工业水污染物排放标准>(GB 3550-1983)第一级Ⅰ类标准.     

白腐菌预处理甘蔗渣促进水解的研究

利用一株产木质素降解酶的白腐菌Ceripriopsis sp.,以固态发酵形式对甘蔗渣进行预处理,选择性降解其中的木质素,从而提高其水解效率。甘蔗渣固态发酵过程中,发酵温度、培养基成分、含水量和初始pH值对酶活和糖收率都有影响。含水量是对糖收率影响最大的因素,其次是麸皮添加量,再次是温度,而初始pH值影响最小。甘蔗渣固态发酵的最佳条件为:培养基中含水量为80%,麸皮含量为5%,初始pH=4.0时28℃发酵14d,获得的糖产率最大,达20.6%。     

Acid hydrolysis of glycosidic bonds in oat β‐glucan and development of a structured kinetic model

Homogeneous acid‐catalyzed hydrolysis of oat β‐glucan, which contains β‐(1,4) and β‐(1,3) glycosidic bonds in a nonrandom order, was studied at 353 K using HCl and H₂SO₄. A new structured kinetic model was developed that takes into account the difference in the reactivity of β‐(1,4) and β‐(1,3) glycosidic bonds as well as their positions in the polysaccharide chain. To minimize the correlation of adjustable parameters in the new model, the reactivities of these bonds were studied independently (T = 313…363 K; c_H+ = 0.1…2 mol/L) using cellobiose and laminaribiose. The difference in kinetic parameters (e.g., T = 338 K: k_β‐(1,4) = 0.693 × 10^?3 L/mol/min, k_β‐(1,3) = 1.027 × 10^?3 L/mol/min) was found to be statistically significant (P < 0.0001), which emphasizes the need for the structured model for oat β‐glucan hydrolysis. The simulation of β‐glucan hydrolysis with the new model was in good agreement with the experimental data and shows improvement over existing nonstructured models. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2570–2580, 2018