丙烷脱氢制丙烯研究新进展

介绍了丙烷催化转化制丙烯的研究状况,综述了丙烷催化脱氢制丙烯的铬系催化剂、铂系催化剂及其助剂Sn的研究进展;评述了丙烷氧化脱氢反应机理低温和高选择性的催化剂及膜反应器在丙烷脱氢反应上所具有的优越性,认为研发具有高稳定性和高透氢性能的氢分离膜,将有望能大幅度提高丙烯的收率。     

Kinetic study of propane dehydrogenation and side reactions over Pt–Sn/Al2O3 catalyst

The kinetics of reactions involved in dehydrogenation of propane to propylene over Pt–Sn/Al₂O₃ catalyst was studied. The simultaneous deactivation of individual dehydrogenation, hydrogenolysis and cracking sites was also studied. A model was developed to obtain the transient conversion of propane, product selectivity and catalytic site activity. The dehydrogenation reaction was considered as the main reaction governing propane and hydrogen concentrations along the reactor. Catalytic test runs were performed in a fixed-bed quartz reactor. The kinetic expressions developed for the main and side reactions were verified by integral and a combination of integral–differential analysis of reactor data, respectively, and the kinetic parameters were obtained. The deactivation of the active sites for the three reactions was found to follow a first-order independent decay law. The rate constants of deactivation were found to decrease in the order of dehydrogenation, hydrogenolysis and cracking. Noncatalytic thermal cracking was found to be comparable to the catalytic route resulting in a very low apparent deactivation rate constant for cracking reaction.     

丙烷脱氢制丙烯技术研究

介绍了几种丙烷脱氢制丙烯技术：催化脱氢、氧化脱氢、膜反应器脱氢。综述了丙烷催化脱氢制丙烯催化剂的研究现状，虽然丙烷催化脱氢生产丙烯虽已实现了工业化，但其催化剂的性能需进一步提高；综述了丙烷氧化脱氢制丙烯反应催化剂的研究现状及膜反应器在丙烷脱氢反应上所具有的优越性，认为研发具有高稳定性和高透氢性能的氢分离膜，将有望能大幅度提高丙烯的收率。     

多孔膜反应器中丙烷催化脱氢制丙烯的模拟研究

针对丙烷高效脱氢制丙烯的多孔膜反应器构建了无量纲数学模型并进行了模拟研究,考察了催化剂活性、透氢膜性能、操作条件对多孔膜反应器中丙烷脱氢的转化率、丙烯收率、氢气收率和纯度的影响。结果表明,移走产物氢气可以有效提升膜反应器的性能,其性能的提升程度由不同温压条件下催化剂和透氢膜性能共同决定。高活性催化剂是丙烷高效转化的基础,催化剂活性越高,膜反应器内的产氢速率越快;其次,膜的选择性和渗透通量越高,氢气的移除效率越高,可在最大程度上打破热力学平衡的限制,使反应向生成丙烯的方向移动。当多孔透氢膜的氢气渗透率在10^-7~10^-6 mol·m^-2·s^-1·Pa^-1,H₂/C₃H₈选择性达到100时,其丙烷转化率可以与Pd膜反应器内的转化率相当,但分离的氢气纯度低于Pd膜反应器。与传统的固定床反应器相比,膜反应器由于促进了化学平衡的移动,可以在较低的反应温度下获得相当高的丙烷转化率,且丙烷转化率随着反应压力的增加呈现出一个最大值。该模拟研究可为实际生产过程中膜反应器用于PDH反应的高效强化提供有益的技术指导。     

Effect of catalytic combustion of hydrogen on the dehydration processes in a membrane reactor. III. calculation of the industrial reactor

This paper describes the mathematical simulation of an industrial membrane reactor for propane dehydrogenation in the thermodynamic coupling with hydrogen combustion (oxidation). Due to the effective removal of hydrogen through a membrane and the heat release as a result of an exothermic reaction, the temperature of the reaction stream at the input could be reduced to 500?C. The fact that the process is carried out on an industrial-level membrane reactor makes it possible to reach a propane conversion of 75% with a propylene selectivity of 97%, which exceeds the figures obtained per pass in existing industrial devices at higher temperatures.     

丙烷脱氢制丙烯技术研究

介绍了催化脱氢、氧化脱氢、膜反应器脱氢等几种丙烷脱氢制丙烯技术,综述了丙烷催化脱氢制丙烯催化剂的研究现状,虽然丙烷催化脱氢生产丙烯已实现了工业化,但其催化剂的性能需进一步提高;对丙烷氧化脱氢制丙烯反应催化剂的研究现状及膜反应器在丙烷脱氢反应上所具有的优越性进行了描述,认为研发具有高稳定性和高透氢性能的氢分离膜,将有望能大幅度提高丙烯的收率。     

Methylcyclohexane dehydrogenation for hydrogen production via a bimodal catalytic membrane reactor

The dehydrogenation of methylcyclohexane (MCH) to toluene (TOL) for hydrogen production was theoretically and experimentally investigated in a bimodal catalytic membrane reactor (CMR), that combined Pt/Al₂O₃ catalysts with a hydrogen‐selective organosilica membrane prepared via sol‐gel processing using bis(triethoxysilyl) ethane (BTESE). Effects of operating conditions on the membrane reactor performance were systematically investigated, and the experimental results were in good agreement with those calculated by a simulation model with a fitted catalyst loading. With H₂ extraction from the reaction stream to the permeate stream, MCH conversion at 250°C was significantly increased beyond the equilibrium conversion of 0.44–0.86. Because of the high H₂ selectivity and permeance of BTESE‐derived membranes, a H₂ flow with purity higher than 99.8% was obtained in the permeate stream, and the H₂ recovery ratio reached 0.99 in a pressurized reactor. A system that combined the CMR with a fixed‐bed prereactor was proposed for MCH dehydrogenation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1628–1638, 2015     

New Integrated Catalytic Membrane Processes for Enhanced Propylene and Polypropylene Production

Newly reported integrated processes are discussed for aliphatic (paraffin) hydrocarbon dehydrogenation into olefins and subsequent polymerization into polyolefins (e.g., propane to propylene to polypropylene, ethane to ethylene to polyethylene). Catalytic dehydrogenation membrane reactors (permreactors) made by inorganic or metal membranes are employed in conjunction with fluid bed polymerization reactors using coordination catalysts. The catalytic propane dehydrogenation is considered as a sample reaction in order to design an integrated process of enhanced propylene polymerization. Related kinetic experimental data of the propane dehydrogenation in a fixed bed type catalytic reactor is reviewed which indicates the molecular range of the produced C₁-C₃ hydrocarbons. Experimental membrane reactor conversion and yield data are also reviewed. Experimental data were obtained with catalytic membrane reactors using the same catalyst as the non-membrane reactor. Developed models are discussed in terms of the operation of the reactors through computational simulation, by varying key reactor and reaction parameters. The data show that it is effective for catalytic permreactors to provide streams of olefins to successive polymerization reactors for the end production of polyolefins (i.e., polypropylene, polyethylene) in homopolymer or copolymer form. Improved technical, economic, and environmental benefits are discussed from the implementation of these processes.     

Simulation of Propane Dehydrogenation to Propylene in a Radial‐Flow Reactor over Pt‐Sn/Al2O3 as the Catalyst

Catalytic paraffin dehydrogenation for manufacturing olefins is considered to be one of the most significant production routes in the petrochemical industries. A reactor kinetic model for the dehydrogenation of propane to propylene in a radial‐flow reactor over Pt‐Sn/Al₂O₃ as the catalyst was investigated here. The model showed that the catalyst activity was highly time dependent. In addition, the component concentrations and the temperature varied along the reactor radius owing to the occurring endothermic reaction. Moreover, a similar trend was noticed for the propane conversion as for the propylene selectivity, with both of them decreasing over the time period studied. Furthermore, a reversal of this trend was also revealed when the feed temperature was enhanced or when argon was added into the feed as an inert gas.     

Modeling of propane dehydrogenation combined with chemical looping combustion of hydrogen in a fixed bed reactor

A redox process combining propane dehydrogenation(PDH) with selective hydrogen combustion(SHC) is proposed, modeled, simulated, and optimized. In this process, PDH and SHC catalysts are physically mixed in a fixed-bed reactor, so that the two reactions proceed simultaneously. The redox process can be up to 177.0% higher in propylene yield than the conventional process where only PDH catalysts are packed in the reactor. The reason is twofold: firstly, SHC reaction consumes hydrogen and then shift...     

Analysis of Membrane Reactors for Integrated Coupling of Oxidative and Thermal Dehydrogenation of Propane

This study presents strategies capable to intensify the thermal dehydrogenation of propane (TDH) using integrated reactor concepts. An inert packed bed membrane reactor for distributed dosing of oxygen to realize the oxidative dehydrogenation (ODH) was studied and compared to a reactor with catalytically active membrane. The latter concept allows to combine TDH and ODH in one apparatus to overcome the chemical equilibrium by in situ conversion of the by‐product H₂ using O₂ or in a reverse water‐gas shift reaction by CO₂. If CO₂ is used as active sweep gas the reactor offered better performance regarding yield and selectivity. Strategies for further thermal integration are discussed.     

Dehydrogenation of propane with selective hydrogen combustion: A mechanistic study by transient analysis of products

The role of lattice and adsorbed oxygen species in propane dehydrogenation in a perovskite hollow fiber membrane reactor containing a Pt–Sn dehydrogenation catalyst was elucidated by transient analysis of products with a sub-millisecond time resolution. Propane is mainly dehydrogenated non-oxidatively to propene and hydrogen over the catalyst, while lattice oxygen of the perovskite oxidizes preferentially hydrogen to water. For achieving high propene selectivity at high propane conversions, the formation of gas phase O₂ on the shell side of the membrane reactor should be avoided. Otherwise, oxygen species adsorbed over the Pt–Sn catalyst participate in non-selective C₃H₈/C₃H₆ transformations to C₂H₄ and CO_x.     

The effects of bimetallic interactions for CO2-assisted oxidative dehydrogenation and dry reforming of propane

The catalytic reduction of CO₂ by propane may occur via dry reforming to produce syngas (CO + H₂) or oxidative dehydrogenation to yield propylene. Utilizing propane and CO₂ as coreactants presents several advantages over conventional methane dry reforming or direct propane dehydrogenation, including lower operating temperatures and less coke formation. Thus, it is of great interest to identify catalytic systems that can either effectively break the C C bond to generate syngas or selectively break C H bonds to produce propylene. In this study, several precious and nonprecious bimetallic catalysts supported on reducible CeO₂ were investigated using flow reactor studies at 823 K to identify selective catalysts for CO₂-assisted reforming and dehydrogenation of propane.     

Model-based Analysis of Fixed-bed and Membrane Reactors of Various Scale

A packed-bed membrane reactor in a distributor configuration is studied theoretically for the oxidative propane dehydrogenation and compared with a fixed-bed reactor. Based on detailed 2D models considering two different heat and mass transport models the reactor scale-up including various reactor-to-particle diameter ratios (D/d_P) is analyzed with respect to reactor performance, heat transfer and hot spot formation. Higher selectivities at lower hot spot temperatures occur in the packed-bed membrane reactor for the same reaction conditions.     

Oxidative Dehydrogenation of Propane on Calcium Hydroxyapatites Partially Substituted with Vanadate

Solid solutions of phosphate and vanadate calcium hydroxyapatites were synthesized and the catalytic activities for the oxidative dehydrogenation of propane to propylene on those catalysts were examined. Although the conversion of propane and the selectivity to propylene were 7.6 and 3.5% on calcium hydroxyapatite (CaHAp), the incorporation of vanadate to CaHAp by V/P=0.05 (atomic ratio) resulted in the enhancement of the conversion and the selectivity to 17.2 and 52.4%, respectively, corresponding to those on Mg₂V₂O₇ under the same reaction conditions (14.0 and 50.9%, respectively).     

Studies on a Membrane Reactor

Abstract

Simulation is used to evaluate the performance of a catalytic reactor with permeable wall (membrane reactor) in shifting the equilibrium of three reversible reactions (cyclohexane dehydrogenation, hydrogen iodide decomposition, and propylene disproportionation). It is found that the preferred choice of cocurrent or countercurrent operation is dependent on the physical properties and operating conditions. Methods of enhancing conversion are suggested and temperature effects are discussed.     

Propane Dehydrogenation over a Commercial Pt-Sn/Al2O3 Catalyst for Isobutane Dehydrogenation: Optimization of Reaction Conditions

The applicability of a commercial Pt-Sn/Al₂O₃ isobutane dehydrogenation catalyst in dehydrogenation of propane was studied. Catalyst performance tests were carried out in a fixed-bed quartz reactor under different operating conditions. Generally, as the factors improving propane conversion decrease the propylene selectivity, the optimal operating condition to maximize propylene yield is expected. The optimal condition was obtained by the experimental design method. The investigated parameters were temperature, hydrogen/hydrocarbon (H₂/HC) ratio and space velocity, being changed in three levels. Constrains such as the susceptibility of the catalyst components to sintering or phase transformation were also taken into account. Activity, selectivity and stability of the catalyst were considered as the measured response factors, while the space-time-yield (STY) was considered as the variable to be optimized due to its commercial interest. A STY of 16 mol·kg^-1·h^-1 was achieved under the optimal conditions of T 620℃, H₂/HC 0.6 and, weight hourly space velocity (WHSV) 2.2 h^-1. Single carbon-carbon bond rupture was found to be the main route for the formation of lower hydrocarbon byproducts.     

Catalytic oxidation of hydrogen over Au/TiO2 catalysts

Selective catalytic oxidation of hydrogen in the presence of hydrocarbons was studied in a fixed bed quartz reactor, over 3 wt%Au/TiO₂ and 5 wt%Au/TiO₂ catalysts. This reaction can be utilised in the production of light alkenes via catalytic dehydrogenation, providing in situ heat to the endothermic dehydrogenation reaction and simultaneously removing a fraction of the produced hydrogen. It is important to avoid the non-selective combustion of the hydrocarbons in the mixture. Both 3 wt%Au/TiO₂ and 5 wt%Au/TiO₂ are active for the combustion of hydrogen, but in a gas mixture with propane and oxygen the selectivity is dependent upon the feed ratio of hydrogen and oxygen. At 550 °C, with propane present, no carbon oxides are formed when the H₂:O₂ ratio is four, but at lower ratios some CO₂ and some CO is formed.     

In situ encapsulated subnanometric CoO clusters within silicalite-1 zeolite for efficient propane dehydrogenation

Cobalt-based catalysts are promising alternatives to replace Pt- and Cr-based catalysts for propane dehydrogenation (PDH). However, the sintering and reduction of unstable Co sites cause fast deactivation. Herein, the ultrasmall cobalt oxide clusters encapsulated within silicalite-1 zeolites (CoO@S-1) has been obtained via a ligand assistance in situ crystallization method. This CoO@S-1 catalyst exhibits an attractive propylene formation rate of 13.66 mmol_C3H6·g_cat⁻¹·h⁻¹ with selectivity of >92% and is durable during 120-h PDH reaction with five successive regeneration cycles. The high PDH activity of CoO@S-1 is assigned to the encapsulated CoO clusters are favorable for propane adsorption and can better stabilize the detached H* species from propane, leading to the lower dehydrogenation barriers than framework Co²⁺ cations and Co₃O₄ nanoparticles. Additionally, the π-binding propylene on CoO clusters can prevent the over-dehydrogenation reaction compared with the di-σ binding propylene on metallic Co, leading to the superior propylene selectivity and catalytic stability.     

Comparison of different methods for quantitative analysis of TAP pulse-response data for propane dehydrogenation over Pt–Sn–K/γ–Al2O3

Propane dehydrogenation over a Pt–Sn–K/γ–Al₂O₃ catalyst has been studied in the TAP reactor. Qualitative analysis of the pulse responses reveals part of the reaction network. Dissociative adsorption of propane yields propylene and hydrogen. Propylene is further converted into coke. Hydrogen and propylene compete for the same active sites.The first order rate constant for the propane conversion has been evaluated by moment analysis, the thin-zone model and regression analysis of the full pulse response for different catalyst bed lengths and temperatures. This has shown that the three methods yield comparable results for both the values of the rate constant and the corresponding activation energies. However, the expression derived from the thin-zone model is the easiest to use and gives a reasonable order of magnitude estimate of the first order rate constant.