滴流床加氢法生产木糖醇的研究

本文对滴流床中压加氢生产木糖醇的工艺进行了研究,反应温度１２０℃,氢压４．０ＭＰａ,表现液速０．５ｍｍ／ｓ￣２．０ｍｍ／ｓ,Ｒａｎｅｙ－Ｎｉ颗粒催化剂表层活化,床层内径１０ｍｍ。对平均粒径０．４７及０．６７ｍｍ的催化床层在低液速区反应特性进行了初步探讨。用简化模型计算的床层宏观效率因子比实际工业鼓泡床高８￣９倍。其值随液速降低而上升,并存在多稳态的现象,与床层部分润湿现象一致。     

Continuous‐Flow Surface Aeration Systems

An aeration process in an activated sludge plant is a continuous‐flow system. In this system, there is a steady input flow (flow from the primary clarifier or settling tank with some part from the secondary clarifier or secondary settling tank) and output flow connection to the secondary clarifier or settling tank. The experimental and numerical results obtained through batch systems can not be relied on and applied for the designing of a continuous aeration tank. In order to scale up laboratory results for field application, it is imperative to know the geometric parameters of a continuous system. Geometric parameters have a greater influence on the mass transfer process of surface aeration systems. The present work establishes the optimal geometric configuration of a continuous‐flow surface aeration system. It is found that the maintenance of these optimal geometric parameters systems result in maximum aeration efficiency. By maintaining the obtained optimal geometric parameters, further experiments are conducted in continuous‐flow surface aerators with three different sizes in order to develop design curves correlating the oxygen transfer coefficient and power number with the rotor speed. The design methodology to implement the presently developed optimal geometric parameters and correlation equations for field application is discussed.     

Continuous‐Flow Di‐N‐Alkylation of 1H‐Benzimidazole in a Fixed‐Bed Reactor

A new process for a continuous‐flow di‐N‐alkylation of 1H‐benzimidazole to 1H‐benzimidazole‐3‐ium iodide by methylene iodide in the presence of potassium carbonate in a fixed‐bed reactor is presented. The synthesis was transferred from batch to continuous operation with similar yields and conversion rates. Moreover, the influence of temperature and residence time in the continuous flow setup was characterized; optimized conditions led to a doubling of yield. In addition, the continuous flow allowed for a better control of the two‐step reaction by adding an additional tube reactor after the fixed bed that further enhanced the overall performance. With this, the continuous‐flow system presented itself as superior due to higher available temperatures and a better controllability.     

Supported Catalysis in Continuous‐Flow Microreactors

This review surveys the recent developments to perform heterogeneous catalysis in continuous‐flow microreactors. Three different types, namely, (i) packed‐bed, (ii) monolithic, and (iii) wall‐coated approaches are discussed to implement various kinds of catalysts in a microreactor. In addition, the applications of these supported catalysts to perform a variety of organic reactions are described. Furthermore, advantages of catalytic microreactors over classical batch reactors on one or more aspects of the reaction, such as rate, conversion, selectivity, and enantioselectivity are presented.

     

新型合金催化剂用于木糖加氢制木糖醇的研究

采用大连通用化工有限公司研制的三元Raney Ni合金催化剂进行木糖加氢,考察了温度、压力、pH值、剂糖比和反应时间等因素对加氢反应的影响,并与其它Raney Ni类催化剂进行了对比.结果表明,使用大连三元Raney Ni催化剂RTH-311进行木糖加氢,当反应温度为130～140℃、压力为8～10MPa、pH值为6～7、剂糖质量比为2%、反应时间为90～120min时,转化率可达100%,产品色度好.RTH-311催化剂的木糖加氢活性好于其它类催化剂,重复使用时,也可保持较高活性.     

Toward a Continuous‐Flow Synthesis of Boscalid®

A two‐step continuous‐flow protocol for the synthesis of 2‐amino‐4′‐chlorobiphenyl, a key intermediate for the industrial preparation of the fungicide Boscalid^® is described. Initial tetrakis(triphenylphosphine)palladium‐catalyzed high‐temperature Suzuki–Miyaura cross‐coupling of 1‐chloro‐2‐nitrobenzene with 4‐chlorophenylboronic acid in a microtubular flow reactor at 160 °C using the tert‐butanol/water/potassium tert‐butoxide solvent/base system provides 4′‐chloro‐2‐nitrobiphenyl in high yield. After in‐line scavenging of palladium metal with the aid of a thiourea‐based resin, subsequent heterogeneous catalytic hydrogenation is performed over platinum‐on‐charcoal in a dedicated continuous‐flow hydrogenation device. The overall two‐step homogeneous/heterogeneous catalytic process can be performed in a single operation providing the desired 2‐amino‐4′‐chlorobiphenyl in good overall yield and high selectivity.     

Microwave‐Assisted Continuous‐Flow Reactor Based on a Ridged Waveguide

Microwave‐assisted continuous‐flow reactors (MCFRs) are a valuable alternative to conventional reactors for accelerating chemical reactions. However, despite several interesting applications, only little quantitative research has been conducted on the temperature uniformity of the heating load. With water as a common inorganic solvent, a novel MCFR type based on a special ridged waveguide for heating water is studied by optimizing some parameters of micropipes in order to achieve better temperature uniformity. Compared to the original reactor, the standard deviation of the electric field decreased significantly when using the optimized reactor under the same heating conditions while the average electric field density increased. The optimized results were verified by experiments.     

Efficient and General Continuous‐Flow Hydroarylation and Hydroalkylation of Styrenes

A simple and efficient continuous‐flow hydroarylation of arenes and heteroarenes using various styrenes in conjunction with a heterogeneous catalyst has been developed. Additionally, this method has been successfully extended to the hydroalkylation of styrenes by employing 1,3‐dicarbonyl compounds as the nucleophile. Multigram quantities of diarylmethanes have been prepared using this new flow method.     

Practical Continuous‐Flow Controlled/Living Anionic Polymerization

A continuous‐flow reaction system was developed, allowing flow conditions of the entire system to be maintained at a predetermined constant level, which is one of the most significant factors for successful industrial application. Controlled/living anionic polymerization was selected as a model reaction since the characteristics of its polymer products, molecular weights, and molecular weight distributions are highly susceptible to changes in the relative flow rates of a monomer and initiator solutions. In flow microreactors, controlled/living anionic polymerization of styrene in tetrahydrofuran (THF)/hexane initiated by THF‐diluted n‐butyllithium (n‐BuLi) was examined. Poly(styrenes) of larger molecule sizes such as Mn > 15 000 were successfully synthesized. After continuous operation for four hours, ca. 0.5 kg of the polymer was readily produced with narrow molecular weight distribution, demonstrating the applicability of this continuous‐flow system for controlled/living anionic polymerization on considerably large scale with a view to its industrial usage in the future.     

Low‐Temperature Pretreatment of Lignocellulosic Biomass for Enhanced Biogas Production

Readily available lignocellulosic biomass as substrate for biogas plants is gaining popularity amongst biogas plant operators. Results of low‐temperature pretreatment (light cooking) of wheat straw to remove waxes and prepare the biomass for microbial action are described. Benefits of light cooking are low thermal energy demand and low investment cost compared to conventional techniques such as steam explosion. The novelty lies in utilizing the low temperature range 25–100 °C for pre‐soaking the biomass. Two different types of wheat straws were pretreated at varying temperatures and sizes. The results were compared with Buswell's equation for theoretical maximum biomethane yield. Compared to untreated straw, pre‐soaking leads to a significantly higher methane yield. Size reduction combined with light‐cooking does not affect the methane yield in the same manner as pre‐soaking of the biomass.     

Aging and Thermal Stability of the Mixed Product of the Ether‐Soluble Fraction of Bio‐Oil and Bio‐Diesel

The storage and thermal stability of blends of the ether‐soluble fraction of bio‐oil (ES) and bio‐diesel are reported. Fuel properties such as viscosity, water content, acid number and average molecular weight of the ES/bio‐diesel blends were measured before and after aging. Compared to the aging properties of bio‐oil alone, very small changes in water content and viscosity were shown for the blends aged at 80 °C for 180 h. Chemical changes were characterized using gel permeation chromatography, showing a slight increase in the molecular weight over time. Further confirmation of the changes was provided through Fourier transform infrared spectrometry, thermal decomposition analysis using a thermogravimetric analyzer, proton assignment using proton nuclear magnetic resonance, and carbon assignment using carbon nuclear magnetic resonance. Overall, the study indicates that ES/bio‐diesel blends are stable as fuel under the conditions tested in this paper.     

Subcritical Water Reaction Behavior of D‐Glucose as a Model Compound for Biomass Using Two Different Continuous‐Flow Reactor Configurations

Recently, cellulosic materials have been considered as a useful resource for the recovery of valuable chemicals and liquid fuels, etc. Cellulose is a homopolymer of D ‐glucose, which is often used as a model compound for biomass. Reactions of D ‐glucose in subcritical water as the reaction solvent were conducted using a single‐flow‐type reactor ( S1 ) and an admixture‐type reactor with feed and preheated‐water flow ( S2 ) at temperatures from 200 to 240 °C, pressures from 15 to 20 MPa, residence times from 40 to 120 s, and initial feed concentrations of 1.5–10 wt %. D ‐Glucose was converted into aldehydes, organic acids and furans, with mainly organic acids obtained at 240 °C. D ‐Glucose decomposition using reactors S1 and S2 revealed that the conversion rate of D ‐glucose was promoted more using S2 than by S1 . The yield of furans with S1 was higher than with S2 , while the yield of organic acids from S1 was lower than that from S2 .     

Catalytic Hydrogenation for Bio‐Oil Upgrading by a Supported NiMoB Amorphous Alloy

A method of ultrasound‐assisted reduction of a nickel‐ammonia complex with borohydride in aqueous solution was used to prepare NiMoB/MCM‐41 and NiMoB/SBA‐15 supported amorphous alloy catalysts. These catalysts were used to upgrade bio‐oil at mild temperatures ranging from 100 to 160 °C and recycling of these two supported catalysts and of unsupported NiMoB was carried out. Then, fresh and third time used catalysts were characterized by X‐ray diffraction, X‐ray photoelectron spectra, and transmission electron microscopy. Quantitative results were obtained from the analysis of gas chromatography/mass spectrometry. Through mild upgrading, 1‐hydroxy‐2‐propanone, furfural, and 2‐methoxy‐4‐vinylphenol in the bio‐oil were converted to relevant alcohols and saturated phenols. The conversion rates were 45.7, 71.5, and 57.1 %, respectively, when crude bio‐oil was upgraded using NiMoB/MCM‐41 at 160 °C. The two supported catalysts, especially NiMoB/MCM‐41, had smaller amorphous NiMoB particles and exhibited more uniform dispersion on mesoporous silica, leading to higher reaction activity and stability than unsupported NiMoB. Deactivation of these catalysts resulted from the reduction of Ni⁰, B⁰, and Mo⁴⁺ species on the surface, the transition from the amorphous to the crystalline state, particle agglomeration, and coke deposition on the surface.     

Automatic Low‐Cost Method to Determine the Solubility of Liquid‐Liquid Mixtures by Continuous‐Flow Cloud Point Titration

A low‐cost, accurate, and fast technique to determine the solubility of liquid‐liquid mixtures by continuous cloud point titration is demonstrated. A light‐emitting diode (LED) is employed to illuminate the mixing liquids during the continuous‐flow titration process, and the transmitted light as well as Mie scattering from droplets is monitored using a simple webcam image sensor. The time‐resolved evolution of the signal allows the determination of the solubility. In order to prove the concept and to evaluate its accuracy and reproducibility, experimental results from the binary systems butan‐1‐ol/water and pentan‐1‐ol/water are presented and compared with literature data. The entire setup can be realized with a low investment and delivers results virtually identical to those in literature with established techniques. The approach is suitable for academic and industrial, but due to its simplicity also for educational purposes.     

Comparison of Response Surface Methodology and Artificial Neural Network for Modeling Xylose‐to‐Xylitol Bioconversion

Previous experimental data of xylose‐to‐xylitol bioconversion by Debaryomyces hansenii carried out according to a 3³ full factorial design were used to model this process by two different artificial neural network (ANN) training methods. Models obtained for four responses were compared with those of response surface methodology (RSM). ANN models were shown to be superior to RSM in the predictive capacity, whereas the latter showed better performance in the generalization capability step. RSM with optimization using a genetic algorithm was revealed as a whole to be the best modeling option, which suggests that the comparative performances of RSM and ANN may be a highly problem‐specific issue.     

Homogeneous Catalytic Hydrogenation of Bio‐Oil and Related Model Aldehydes with RuCl2(PPh3)3

A homogeneous RuCl₂(PPh₃)₃ catalyst was prepared for the hydrogenation of bio‐oil to improve its stability and fuel quality. Experiments were first performed on three model aldehydes of acetaldehyde, furfural and vanillin selected to represent the linear aldehydes, oxygen heterocyclic aldehydes and aromatic aldehydes in bio‐oil. The results demonstrated the high hydrogenation capability of this homogeneous catalyst under mild conditions (55–90 °C, 1.3–3.3 MPa). The highest conversion of the three model aldehydes was over 90 %. Furfural and acetaldehyde were singly converted to furfuryl alcohol and ethanol after hydrogenation, while vanillin was mainly converted to vanillin alcohol, together with a small amount of 2‐methoxy‐4‐methylphenol and 2‐methoxyphenol. Further experiments were conducted on a bio‐oil fraction extracted by ethyl acetate and on the whole bio‐oil at 70 °C and 3.3 MPa. Most of the aldehydes were transformed to the corresponding alcohols, and some ketones and compounds with C–C double bond were converted to more stable compounds.     

Thermochemical Processing of Miscanthus through Fluidized‐Bed Fast Pyrolysis: A Parametric Study

Thermochemical processing of agriculture waste not only provides surrogates for combustion fuel but also reduces the environmental issues of waste. Miscanthus has been viewed as one of the largest agriculture wastes in Taiwan and a proper process for turning Miscanthus into a valuable product has become a significant subject. Here, fluidized‐bed fast pyrolysis was applied to convert Miscanthus into bio‐oil, bio‐char, and pyrolytic gases as the products. The product distributions were examined depending on various reaction parameters such as reaction temperature, carrier gas flow rate, feedstock feeding rate, and feedstock size. The chemical compositions of the bio‐oil, bio‐char, and product gases were analyzed and the properties of the bio‐oil were also tested via standard methods. So far, bio‐oil derived from Miscanthus is unfavorable for application in combustion engines without further upgrading processes.     

Development of a Continuous‐Flow Microreactor for Asymmetric Sulfoxidation Using a Biomimetic Manganese Catalyst

Asymmetric sulfoxidation catalyzed by a biomimetic manganese complex under continuous‐flow microreactor is described. The reaction is conducted in microreactor, it can rapidly (<4 min) oxidize a wide scope of sulfides with high yield (up to 91%) and excellent enantioselectivity (up to 99% ee), and allows shorter reaction times, easier scale‐up and lower catalyst loadings than its batchwise counterpart. Additionally, a convenient numbering‐up strategy for the scale‐up of asymmetric sulfoxidation has been developed which enables a direct scaling of the reaction to 5 g affording the corresponding sulfoxides within 20 min.

     

Deoxygenation of Bio‐oil from Calcium‐Rich Paper‐Mill Waste

De‐inking sludge, an ash‐rich recycling paper solid waste, is generated in huge amounts. The catalytic deoxygenation potential of calcium‐based de‐inking sludge in co‐pyrolysis mode with wood and its neat thermal conversion to sustainable biofuels are investigated. Wood, de‐inking sludge, and their blends are processed in a thermocatalytic reforming (TCR) system. In the presence of de‐inking sludge, the oxygen content in the organic phase decreases and the bio‐oil calorific value improves as compared to the neat wood‐derived bio‐oil. The TCR processing of neat de‐inking sludge produces a bio‐oil with low oxygen content and higher calorific value.