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。     

冷管型甲醇合成反应器浅识

铜催化剂甲醇合成反应器床层温度接近等温分布有利于催化剂寿命长、产率高、操作稳定和产品质量好。本文介绍了冷管型甲醇合成反应器床层温度分布现状，并探讨了适应铜催化剂特点的冷管传热方式。     

流化床串联多段绝热床HCl氧化反应器模拟优化

以Ce Cu K/Y为催化剂,提出了一种由流化床与多段绝热床串联的新型反应器用于HCl催化氧化过程。假设HCl年处理量为12万t/a,通过物料、能量、动量衡算建立反应器的数学模型,对HCl氧化工艺的操作参数进行优化。在不考虑床层压降的情况下,考察绝热床段数NAR及流化床出口HCl转化率xA,f对绝热床的最佳操作曲线和催化剂用量的影响。当NAR为3,xA,f为60%时,绝热床的最佳操作温度在380—430℃,满足了催化剂活性要求,催化剂总用量也较少。在考虑床层压降情况下,考察绝热床入口压强pin和内径Di对其催化剂用量WAR、床层压降Δp和床层高度Hi等的影响。综合反应器的操作难度及成本等因素,优选绝热床入口压强为500 k Pa,内径为1.6 m。在最佳操作条件下流化床和固定床所需催化剂分别为3.1 t和8.5 t。该研究为氯资源循环利用工业反应器的开发提供了理论依据。     

径向流固定床反应器的流动特性研究及结构参数的合理选择

径向流固定床反应器的操作状态和反应效果在很大程度上取决于反应器内穿越催化剂床层径向气流沿反应器轴向分布的均匀程度，亦即床层内催化剂负荷的均布程度。本文对此类反应器内的流动特性进行了研究，对立了描述反应器内流动规律的基本运动方程。研究结果表明，径向气流的轴向分布情况与反应器的流动结构型式、反应器内分流流道与合流流道截面积的比值、催化剂床层的阻力系数以及反应器的高径比等参数有关。并提出了如何合理选择反     

小型反应器内气相甲醇制二甲醚操作优化与分析

通过对小型反应器内气相甲醇催化制二甲醚反应进行高温热态实验,探究了反应温度与甲醇质量空速对催化剂床层轴向温度分布的变化规律,同时分析了不同的操作条件对甲醇转化率和二甲醚选择性的影响,从而优化小型反应器的操作参数。研究结果表明：当甲醇质量空速为1 h^-1时,在不同反应温度条件下,催化剂床层会出现约1.7～2.9℃的轴向绝热温升,且催化剂床层热点温度接近于催化剂床层轴向中部位置;当反应温度为250℃,甲醇质量空速为1 h^-1时,催化剂床层轴向温度分布曲线较为平缓,且甲醇转化率和二甲醚收率均较高,即反应温度为250℃及甲醇质量空速为1 h^-1可视为该小型反应较优的操作条件。     

变床层高度固定床反应器的分析

在分子筛催化剂苯气相乙基化制乙苯过程开发中,根据该反应过程的特点,提出了变床层高度固定床反应器的构想。利用催化剂失活动力学模型,通过模拟计算,对常规固定床反应器和变床层高度固定床反应器的性能进行比较,结果表明后者对延长反应器操作周期和改善反应选择性均有显著作用。上述分析已在300吨乙苯/年中试反应器的运转中得到证实。     

延长PTA Pd/C催化剂使用寿命方法分析

在精对苯二甲酸的生产中,有多种原因可能导致催化剂失活,影响其使用寿命。根据近几年Pd/C催化剂的使用状况的分析,找出影响Pd/C催化剂使用寿命的因素,并探讨延长Pd/C催化剂使用寿命的方法。通过在装卸、工艺操作中精心操作,平稳生产,避免波动,及时碱洗,严格控制氢气和脱离子水纯度,避免催化剂中毒等一系列的延长Pd/C催化剂使用寿命的方法。     

热壁式加氢反应器工艺设计

热壁式加氢反应器的设计,主要依据厂方提供的现场操作奈件和技术要求,对新反应器反-101的大小及高径比、催化剂床层和液体分布板等进行计算和设计。     

变床层高度固定床反应器的分析

在分子筛催化剂苯气相乙基化制乙苯过程开发中，根据该反应过程的特点，提出了变床层高度固定床反应器的构想。利用催化剂失活动力学模型，通过模拟计算，对常规固定床反应器和变床层高度固定床反应器的性能进行比较，结果表明后者对延长反应器操作周期和改善反应选择性均有显著作用。上述分析已在３００吨乙苯／年中试反应器的运转中得到证实。     

催化剂撇头和压降超高原因分析

对固定床反应器催化剂进行撇头是对床层压降超高后有效的处理措施,影响催化剂床层压上升的原因有原料保护、油溶性金属、原料杂质、操作波动等多个因素,生产运行中必须有针对性的实施管理,才能有效的抑制催化剂床层压降的快速上升。     

PTA加氢精制Pd/C催化剂活性降低原因及处理

洛阳PTA装置氧化母液回收系统投用后,进口钯/碳(Pd/C)催化剂使用过程中活性降低,对其原因进行分析和探讨,通过对催化剂床层进行翻床处理,并使用脱离子水清洗,确保该床催化剂的正常使用。     

Continuous mode linoleic acid hydrogenation on Pd/sibunit catalyst

Catalytic hydrogenation of linoleic acid and oleic acid to stearic acid over palladium on mesoporous carbon sibunit (Pd/sibunit) catalyst was studied in a continuous trickle-bed reactor with the weight hourly space velocity 5.4 h⁻¹ at 120°C and 30 bar using tall oil fatty acid (TOFA) as reactor feed. Stearic acid preparation using TOFA as a raw material is of industrial importance. Pd/sibunit catalysts with spherical particle shape of the size 1.62 mm were synthesized with the palladium loadings 0.5, 1, and 2 wt %. The metal dispersion (%), metal particle size (nm), as well as metallic surface area (m²/g metal) of the three synthesized Pd/Sibunit samples were measured by CO chemisorption. The Pd/C catalysts were tested in linoleic acid hydrogenation, showing promising behavior in terms of activity, selectivity and stability to be used in fixed bed applications. The product stream from the fixed bed reactor was saved and analyzed by X-ray fluorescence (XRF) and direct current plasma (DCP) spectroscopy. The catalyst activity increased with the Pd loading. The lowest metal loading of 0.5 wt % gave the least prone to initial deactivation and thus the most stable catalyst. This catalyst can be recommended for farther pilot testing.     

Pd/HZSM-5催化剂催化加氢丙酮合成甲基异丁基酮

以HZSM-5为载体,采用浸渍法制备系列Pd/HZSM-5催化剂,在高压连续流动固定床反应器中考察Pd/HZSM-5催化剂催化加氢丙酮一步法合成甲基异丁基酮性能,并对工艺条件进行优化。结果表明,当HZSM-5载体上Pd负载质量分数为0.5%时,在反应温度140 ℃、氢压1 MPa、空速0.48 h^-1和氢酮物质的量比为1条件下,Pd/HZSM-5催化剂催化活性较高,丙酮转化率为45.91%,甲基异丁基酮选择性为94.33%。采用XRD、H₂-TPD、SEM、EDS和TGA等对催化剂进行表征,结果表明,负载质量分数0.5%的Pd在HZSM-5分子筛表面分散均匀,且0.5%Pd/HZSM-5催化剂具有较高氢吸附能力,失活的主要原因为催化剂表面积炭,采用流化床反应器取代传统的固定床反应器可以很好的解决催化剂积炭问题。     

二氯乙酸选择性加氢脱氯制备高纯氯乙酸

以Pd/C为催化剂,通过固定床反应器对含氯乙酸、二氯乙酸以及乙酸的氯化液进行选择性催化加氢脱氯研究,使氯化液中的大部分或全部二氯乙酸转化为一氯乙酸或乙酸。考察催化剂制备条件对催化性能的影响,结果表明,在Pd负载质量分数0.9%、浸渍液浓度4.5 g·L-1和浸渍温度20℃条件下制备的催化剂,催化活性和产物选择性最佳,运行时间超过1 500 h活性未出现明显衰减。     

Catalytic hydrogenation in a packed bed bubble column reactor

The cocurrent downflow contactor reactor (CDCR) has been found to give low mass transfer resistances both in slurry and packed bed catalytic operation. The hydrogenation of propan-2-ol solutions of itaconic acid in the range 100–300 kPa and 20–70°C and of soyabean oil in the range 100–500 kPa and 130–160°C was studied using slurry (5% w/w Pd/C) and packed bed (3% w/w Pd/Al₂O₃ Raschig ring) catalyst. Mass transport and kinetic parameters were evaluated for both operational modes and while the slurry CDCR gave better mass transfer properties than the packed bed CDCR, the latter gave better mass transfer than conventional reactors and superior selectivity to the slurry CDCR. As has been observed with the slurry CDCR, the packed bed CDCR was found to operate under surface reaction rate control with negligible transport resistances. This was particularly evident for soyabean oil hydrogenation, which is well known to be transport controlled in conventional reactors.     

Trickle bed reactor diluted with fine particles and coiled tubular flow-type reactor for kinetic measurements without external effects

Gas and liquid velocities in laboratory scale trickle bed reactors are one or two orders of magnitude lower than those in commercial reactors. Then, the kinetic data may include the external effects. This shortcoming of laboratory scale trickle bed reactor can be resolved by diluting the catalyst bed with fine inert particles. The catalyst bed dilution increases dynamic liquid holdup, pressure drop, gas–liquid mass transfer coefficient. Hydrogenation of 2-phenylpropene on Pd/Al₂O₃ was performed with the trickle bed reactor diluted with fine inert particles and the coiled tubular flow-type reactor to compare the kinetics with that of the basket type batch reactor. The trickle bed reactor diluted with fine inert particles is suitable to obtain the reaction rate without external effects even if the liquid velocity is low. The coiled tubular flow-type reactor should be used at high gas velocities.     

固定床“一步法”连续合成对乙酰氨基酚的研究

:采用钯炭颗粒催化剂 ,研究了固定床“一步法”连续合成对乙酰氨基酚的工艺条件。在催化剂重 0 .50 g,对硝基酚质量分数 5.0 % ,醋酐与对硝基酚的摩尔比为 1 .2～ 1 .4,液时空速 0 .50～ 3.0 0 /h,氢压 1 .0～ 1 .4MPa,反应温度 1 60～ 1 80°C等条件下 ,对硝基酚转化率 1 0 0 % ,成品对乙酰氨基酚选择性达 95.0 %以上。     

Transient modeling of combined catalytic combustion/CH4 steam reforming

This paper presents an investigation into the complex interactions between catalytic combustion and CH₄ steam reforming in a co-flow heat exchanger where the surface combustion drives the endothermic steam reforming on opposite sides of separating plates in alternating channel flows. To this end, a simplified transient model was established to assess the stability of a system combining H₂ or CH₄ combustion over a supported Pd catalyst and CH₄ steam reforming over a supported Rh catalyst. The model uses previously reported detailed surface chemistry mechanisms, and results compared favorably with experiments using a flat-plate reactor with simultaneous H₂ combustion over a γ-Al₂O₃-supported Pd catalyst and CH₄ steam reforming over a γ-Al₂O₃-supported Rh catalyst. Results indicate that stable reactor operation is achievable at relatively low inlet temperatures (400 °C) with H₂ combustion. Model results for a reactor with CH₄ combustion indicated that stable reactor operation with reforming fuel conversion to H₂ requires higher inlet temperatures. The results indicate that slow transient decay of conversion, on the order of minutes, can arise due to loss of combustion activity from high-temperature reduction of the Pd catalyst near the reactor entrance. However, model results also show that under preferred conditions, the endothermic reforming can be sustained with adequate conversion to maintain combustion catalyst temperatures within the range where activity is high. A parametric study of combustion inlet stoichiometry, temperature, and velocity reveals that higher combustion fuel/air ratios are preferred with lower inlet temperatures (≤500 °C) while lower fuel/air ratios are necessary at higher inlet temperatures (600 °C).     

Katalytische Abluftreinigung: Verfahrenstechnische Aufgaben und neue Lösungen

Catalytic air purification; Challenges and new solutions. The integration of regenerative heat exchange into the catalyst bed allows for the autothermal operation of catalytic air purification with a low content of combustible gas. Concentrations corresponding to an adiabatic temperature rise of less then 20 °C can be processed without an additional heat source; in case of higher concentratons a side stream withdrawal allows for the utilization of the total heat of combustion at the highest reactor temperature. The feedback of heat due to the integrated heat exchange gives rise to an unusual reactor behaviour. An analogy of fixed bed reactor operation with countercurrent heat exchange is used to derive simple equations for reactor design and operation. If conventional catalyst packings are replaced by monolithic catalysts, substantial reduction in pressure loss and/or packed bed volume can be obtained. The corresponding relations are briefly discussed.     

环已烯基环已酮催化合成邻苯基苯酚的研究

研究了环己烯基环己酮用合成的Pd-C催化剂气相催化脱氢制邻苯基苯酚,反应温度,表面酸碱性、空速等条件对反应有影响.同时设计试验了Ni、Cu负载于Al2O3上的催化剂用于脱氢反应.在一定条件下,以Pd-C作催化剂,产物中邻苯基苯酚含量可高达78%.