半导体气固相光催化氧化反应介绍

介绍了气固光催化氧化过程的基本原理、反应动力学,探讨了反应器模拟和设计计算以及反应器的型式,综述了多相光催化反应半导体光催化剂的制备使用和失活,以及大量的光催化制品。     

环状液-固光催化反应器内流场模拟

多相光催化反应器中,催化剂颗粒在反应器中分布均匀性是衡量多相光催化反应器重要因素.本文用计算流体力学的方法,选用商用软件CFX对液-固光催化反应器内催化剂颗粒分布进行了模拟计算,并进一步对反应器结构进行优化.     

气固相光催化氧化反应动力学分析

对气固相光催化氧化基元反应进行了动力学分析 ,建立了简单适用的动力学模型 .理论分析表明 ,在较低的紫外光强度下 ,光催化反应速率与光强成正比 ;在较高的光强度下 ,速率与光强的平方根成正比 ;在极高光强度下 ,速率与光强无关 .因此将光催化反应简单分解为 3个速率步骤 ,即光子传递步骤、表面作用步骤、扩散步骤 .设计了新颖的气固相光催化反应器 ,采用三氯乙烯 (TCE)为模拟污染物 ,实验结果验证了气固相光催化反应存在光子传递和表面作用控制步骤     

多相光催化反应器的研究进展

介绍了多相光催化反应器的类型、特点和研究现状.围绕光传递限制和传质限制两方面的问题,结合反应器的新型设计和应用情况展开讨论.通过比较悬浮型和负载型光催化反应器,阐明了研究可分离悬浮型和负载型流化床光催化反应器是实现光催化技术工业化的关键所在,指出了光催化反应器设计中存在的问题和今后的研究重点.     

多相光催化反应器数学模型研究进展

本文介绍了当前多相光催化反应体系中反应动力学模型以及反应器数模研究领域内的主要方法及成果。反应动力学方面依据反应机理和动力学方程进行了说明 ;反应器模型则按学术团体各自不同的研究思路及方法分别概述 ,并依照反应器内部的各相的情况作了分类 ,扼要介绍了辐射能分布方程。对未来此领域的研究方向作了展望。     

高固多相生物反应工程

以木质纤维素高固酶解发酵为例,高固形物及其复杂的理化性质会导致体系出现“固体效应”和“水束缚效应”,形成传质速度较低的固液气和微生物复杂多相体系,影响木质纤维素生物转化速率;同时,固形物增加及由此产生的高固酶解发酵流变学特性使以剪切力为主导的机械搅拌在高固多相体系下具有不适应性(会导致酶或微生物活性降低),从而对搅拌方式、反应器及过程设计放大等提出新的要求. 本工作基于课题组多年的研究,提出高固多相生物反应工程的理念,从固体基质特性入手剖析影响高固多相生物反应速率的关键因素,提出了以周期法向力为动力源的过程强化方法,开发出周期蠕动高固多相生物反应系统,以期为高固多相生物反应工程研究提供理论和技术支持.     

气固流化床光催化反应器的欧拉双流体模型模拟

气固流化床光催化反应器的设计是否合理直接影响到反应器的应用,文章选用欧拉双流体模型理论,对煤粉/空气流化体系在一定条件下进行数值模拟,并与实验测定结果比较。研究表明:欧拉双流体模型对于常温常压下反应管内气固两相流动的模拟结果与实验结果吻合较好,可以利用该模型对气固流化床光催化反应器的设计提供相关参数。     

新型气固相光催化反应器的应用研究进展简

本文对气固相光催化反应器的主要类型进行了概述,并较全面的综述了近年来国内外气固相光催化反应器的研制及应用情况,同时探讨了光催化反应器中存在的问题及发展趋势.     

气液固流化床流动介尺度模型研究进展

气液固流化床是一类重要的多相反应器,在化工及相关过程工业中有着广泛的应用。然而,由于对该类反应器内复杂的多相流动结构的定量描述十分有限,目前其设计和放大仍主要依赖经验,致使放大成功率低,反应结果达不到预期效果。因此,建立和完善气液固流化床内的三相流动机理模型,是实现该类反应器科学设计和放大的关键环节。对气液固流化床内的三相流动机理模型的研究进展进行了分析,着重总结了三相流动介尺度机理模型研究的新进展,并指出了存在的问题和进一步研究的方向,希望为该类反应器的基础研究和工业应用提供参考。     

半导体多相光催化氧化技术

阐述了半导体多相光催化氧化的特点、机理及其应用 ,总结了半导体光催化剂的种类、制备。指出了设计光催化反应器所要考虑的主要方面 ,对影响光催化反应的因素进行了简要分析。     

DESIGN AND APPLICATION OF FLUIDIZED BED PHOTOCATALYTIC REACTOR

Photocatalytic degradation of organic pollutant is a new and potential method to transform it to harmless inorganic material, such as CO2 and H2O. So far, most of photocatalytic reactors were cylinder or tabulate photoreactor. The relevant photocatalyst was TiO2 nanometer powder. Although a few investigators had aimed their research field to fluidized bed reactor, their reaction systems were of biphase, such as solid-liquid or solid-gas. Few people focused their research on the triphasic fluidized bed photocatalytic reactor［1］. Compared with traditional photoreactors, a triphasic fluidized bed photoreactor has more advantages［2］: (1) The solid photocatalyst can be separated easily. (2) Its configuration meets the requirement of higher surface area-to-volume ratio of photocatalytic, which is much lower in a fixed bed or a plate photoreactor. (3) The UV light can be used more efficiently. (4) The mass transfer conditions can be controlled and improved easily. (5) It suited to pilot-scale or large-scale operations. For the UV light penetration and photon efficiency should be considered, the photocatalytic reactor differed greatly from a typical fluidized bed reactor.     

Design of a Multiuse Photoreactor To Enable Visible-Light Photocatalytic Chemical Transformations and Labeling in Live Cells

Despite the growing use of visible-light photochemistry in both chemistry and biology, no general low-heat photoreactor for use across these different disciplines exists. Herein, we describe the design and use of a standardized photoreactor for visible-light-driven activation and photocatalytic chemical transformations. Using this single benchtop photoreactor, we performed photoredox reactions across multiple visible light wavelengths, a high-throughput photocatalytic cross-coupling reaction, and in vitro labeling of proteins and live cells. Given the success of this reactor in all tested applications, we envision that this multi-use photoreactor will be widely used in biology, chemical biology, and medicinal chemistry settings.     

三相流化床中光催化降解反应特性的研究

在设计并建立的流态化光催化反应器中,采用负载型光催化剂对甲基橙水溶液进行了光催化降解实验研究。优化了三相流化状态下光催化反应器的操作条件, 其结果为:气体流量200-250Lh-1,液体流量30 Lh-1,催化剂用量为1.5gkg-1处理液;考察了该反应器中催化剂的使用寿命,为光催化降解技术的工业应用研究提供了参考。     

旋转薄膜浆态光催化反应器

在分析现有光催化反应器特点的基础上,提出了一种新型的旋转薄膜式浆态光催化反应器（RFFS）。用商品化光催化剂Degussa P25,以苯酚模型有机物为降解对象,对比了RFFS与传统鼓泡浆态光催化反应器（TBS）的性能,研究了RFFS的光催化性能。结果表明,与传统浆态光催化反应器相比,RFFS具有较高的光催化性能,尤其是能够在较高的光催化剂浓度下运行。在光催化体系的循环流速大于2.7 L·min-1、供气流量为1.0 L·min-1、催化剂浓度为3.0 g·L-1的条件下,RFFS比传统浆态鼓泡光催化反应器的降解速率提高1.6倍。RFFS利用旋转浆态薄膜强化了光催化反应体系的传质,同时提高了体系中光催化剂对光能的利用率,较好地解决了光在传统浆态体系中的传递问题,为开发新型的具有工业应用前景的光催化反应器提供了方案。苯酚在RFFS中的降解动力学符合表观一级动力学模型,理论值与实验结果吻合较好。     

Non-ideal flow in an annular photocatalytic reactor

This study deals with the modelling of non-ideal flow in a tubular photocatalytic reactor with thin layer of TiO₂ photocatalyst. The objective was to analyse different level of mixing in the photoreactor applying basic principles of chemical reaction engineering. For this purpose photocatalytic oxidation of toluene was used as the model reaction. Photocatalytic reactor was operated in two different flow modes: classic type of an annular reactor with basically ideal (plug) flow with some extent of dispersion and annular flow reactor acted as stirred tank reactor with mixing of reaction mixture accomplished by recirculation. A series of experiments with step input disturbance at the entrance of the reactor with different air flow was performed in order to achieve better understanding of the reactor hydrodynamics. Several reactor models are applied, such as one dimensional model of tubular reactor at the steady state conditions, axial dispersion model at non-stationary conditions and the model of the continuous non-stationary stirred tank reactor. Numerical methods necessary for solving model equations and parameter estimation were described.     

Simulation of a multi-annular photocatalytic reactor for degradation of perchloroethylene in air: Parametric analysis of radiative energy efficiencies

A multi-annular photocatalytic reactor was designed, that shows good effectiveness for perchloroethylene (PCE) removal from contaminated air streams. In a previous work, a rigorous physical and mathematical model of the photocatalytic reactor was developed and experimentally verified. In this work, this mathematical model was used to study the radiative energy efficiency of the multi-annular photoreactor. The total quantum efficiency is defined as the ratio of the number of molecules of PCE reacted to the number of photons emitted by the lamp, and it is expressed as the product of the following factors: the reactor radiation incidence efficiency, the catalyst radiation absorption efficiency, and the overall reaction quantum efficiency. For the employed reactor, the numerical values of each one were 83%, 92%, and <2.5%, respectively. Particularly, the dependence of the overall reaction quantum efficiency upon operating variables such as the PCE feed concentration, gas flow rate, irradiation level and relative air humidity was analyzed. These results are useful to optimize the operating conditions and design parameters of the photocatalytic reactor.     

A new combination of a membrane and a photocatalytic reactor for the depollution of turbid water

This paper describes the combination of a dialysis membrane and a photocatalytic reactor into an original membrane photoreactor (MPR) to mineralize organic compounds contained in artificial turbid waters which are obtained by using natural clay named bentonite. Various systems have been described in the literature, combining photocatalysis with pressure-driven membrane techniques, such as nanofiltration (NF) and ultrafiltration (UF), but these systems can lead to membrane fouling. Only the combination of photocatalysis and membrane distillation avoids this problem, but it needs energy to reach pervaporation phenomena. The MPR system presented here works at ambient temperature, with the membrane used as a barrier for particles and to extract the organic compounds from the turbid water without transmembrane pressure. Thus, we were able to separate the polluted turbid water from the photoreactor compartment and to separate TiO₂ continuously from the treated water. The photocatalytic reaction and dialysis were studied separately before the MPR process was developed. A model pollutant, 2,4-dihydroxybenzoic acid (2,4-DHBA), was mineralized from turbid waters by photocatalysis. By means of the membrane, the TiO₂ remained in the photoreactor compartment without filtration and bentonite was kept away from the photoreactor.A mathematical model, based on diffusion through the membrane, with zero-order reaction in the reactor, is in good agreement with the experimental data.     

Wastewater treatment using photo-impinging streams cyclone reactor: Computational fluid dynamics and kinetics modeling

A photo impinging streams cyclone reactor has been used as a novel apparatus in photocatalytic degradation of organic compounds using titanium dioxide nanoparticles in wastewater. The operating parameters, including catalyst loading, pH, initial phenol concentration and light intensity have been optimized to increase the efficiency of the photocatalytic degradation process within this photoreactor. The results have demonstrated a higher efficiency and an increased performance capability of the present reactor in comparison with the conventional processes. In the next step, residence time distribution (RTD) of the slurry phase within the reactor was measured using the impulse tracer method. A CFD-based model for predicting the RTD was also developed which compared well with the experimental results. The RTD data was finally applied in conjunction with the phenol degradation kinetic model to predict the apparent rate coefficient for such a reaction.     

基于固定相二氧化钛薄膜的新型多重石英管分布式光催化反应器及其水处理应用

A novel multi-tube photoreactor with 0.0188m3 valid reaction volume was constructed in pilot-scale. This rectangular reactor consisted of 13 regularly distributed silica glass tubes coating with TiO2 thin film photo-catalyst. Total active area of TiO2 thin film is 0.3916m2. The ratio of surface area to volume achieves 20.8m-1. Photocatalytic experiment of phenol red demonstrates that the apparent reaction rate constant (k) is 0.074 65 h-1 and 0.16502h-1 for reaction system with and without micro-bubbles mixing. The corresponding apparent quantum efficiency (a) is 8.1771 X 10-7g.J-1 and 4.9036 x 10-7g-J-1, respectively. COD value of reactant could decrease to 17mg.L-1 and high performance liquid chromatography (HPLC) only shows two absorption peaks in 24 h pho-tocatalytic process time, so this photoreactor has good photomineralization effect. Experimental results reveal that photocatalytic destruction of organics is possible by using the multi-tube photoreactor.