Stanislav Jašo

Experimental investigation of fluidized-bed reactor performance for oxidative coupling of methane

Performance of the oxidative coupling of methane in fluidized-bed reactor was experimentally investigated using Mn-Na2WO4/SiO2, La2O3/CaO and La2O3-SrO/CaO catalysts. These catalysts were found to be stable, especially Mn-Na2WO4/SiO2 catalyst. The effect of sodium content of this catalyst was analyzed and the challenge of catalyst agglomeration was addressed using proper catalyst composition of 2%Mn-2.2%Na2WO4/SiO2. For other two catalysts, the effect of Lanthanum-Strontium content was analyzed and 10%La2O3–20%SrO/CaO catalyst was found to provide higher ethylene yield than La2O3/CaO catalyst. Furthermore, the effect of operating parameters such as temperature and methane to oxygen ratio were also reviewed. The highest ethylene and ethane (C2) yield was achieved with the lowest methane to oxygen ratio around 2. 40.5% selectivity to ethylene and ethane and 41% methane conversion were achieved over La2O3-SrO/CaO catalyst while over Mn-Na2WO4/SiO2 catalyst, 40% and 48% were recorded, respectively. Moreover, the consecutive effects of nitrogen dilution, ethylene to ethane production ratio and other performance indicators on the down-stream process units were qualitatively discussed and Mn-Na2WO4/SiO2 catalyst showed a better performance in the reactor and process scale analysis.

Oxidative Coupling of Methane: Reactor Performance and Operating Conditions

Abstract In this work, the achievable performance in case of desired-product selectivity, yield and conversion are evaluated systematically for different reactors in order to find the optimum range of operation for the OCM process. This approach is applied to a nonisothermal plug flow reactor and a nonisothermal porous packed bed membrane reactor using different types of catalysts in the wide range of operating conditions. Moreover, a fluidized bed reactor is also considered. The results show that tracking the optimum area of operation has a monotonic direction under some range of operating conditions, whereas it reflects a qualitative trade-offs under some other ranges of operating conditions. For all investigated reactor concepts the likelihood of optimal operating conditions are found, and the best corresponding performance for all of them are reported.

Feasibility study of the Mn–Na2WO4/SiO2 catalytic system for the oxidative coupling of methane in a fluidized-bed reactor

The catalytic system Mn–Na2WO4/SiO2, known for its relatively stable performance for oxidative coupling of methane (OCM), has been thoroughly investigated in the past. In order to evaluate its catalytic performance, micro-fixed-bed reactors were used almost exclusively. This study aims to answer the question of whether this catalytic system would be applicable on a larger scale using a miniplant fluidized-bed quartz glass reactor. Special consideration was given for finding the optimal operating conditions and investigating whether catalyst abrasion and agglomeration could be limiting factors. In this study different compositions of the Mn–Na2WO4/SiO2 catalyst were tested. High sodium content catalysts were difficult to fluidize at the optimal reaction temperature due to severe agglomeration by melting. Low sodium content catalysts showed low selectivity to C2+ hydrocarbons. Catalysts containing intermediate levels of sodium were used for detailed testing as they showed promising performance as well as good fluidizability. The influence of the different reaction parameters on performance was tested, resulting in 19.4% C2 yield at 40% C2 selectivity. Catalysts before and after reaction were characterized regarding composition, crystalline phases, surface morphology and thermal stability. After time on stream, all catalysts exhibited a reduction in specific surface area, changes in Mn valence state (Mnδ+ (2 ≤ δ ≤ 3)) and changes in morphology due to grain growth.

Process development in a miniplant scale - A multilevel - multiscale PSE approach for developing an improved Oxidative Coupling of Methane process

The oxidative coupling of methane (OCM) is a promising alternative route to olefins that converts methane to higher hydrocarbons and open up a new feedstock for the oil based industry. However, due to yield limitations of available catalysts and high separation costs for conventional gas processing, the OCM process has not been applied yet in the industry. Starting with process simulation and sensitivity studies a flexible mini-plant was built in this research so as to demonstrate technical feasibility of an efficient OCM process, model validity and to study long term effects. By this means a concurrent engineering approach was applied for the whole process while investigating each unit parallel. Moreover, catalyst with several reactor concepts like the fluidized bed and membrane reactor were investigated by CFD simulation, process simulation and experiments, in order to study catalyst life time, operation conditions and technical feasibility. Thus, the reaction section was improved from 16% yield to 18%. Furthermore, the separation part of the OCM process was energetically improved by an integrated down streaming unit for the CO2. Thus, an energetic improvement of more than 40% in comparison to a benchmark absorption - desorption based CO2 separation process was achieved. In addition to this, novel absorbents were studied starting with molecular simulation up to process simulation and experimental validation for the CO2 separation. The results of the integrated process development and optimization process for the OCM will be presented and an overview of the multi scale and multilevel Process System Engineering (PSE) approach will be given for the case study.

A Novel Design Concept for the Oxidative Coupling of Methane Using Hybrid Reactors

In this work, the relevance of hydrodynamics, reactor geometry, and feeding policy on the performance of a hybrid fluidizedbedmembrane reactor for the Oxidative Coupling of Methane (OCM) is shown. For this purpose, several case studies are simulated in full 3D geometry under the same reaction conditions, but with different reactor geometries and feeding policies. These studies show the significance of hydrodynamic parameters for the reactor performance, and moreover, how reactor performance can be improved by a careful study of coupled momentummass transport reaction phenomena. Furthermore, it can be demonstrated that a suitable distributed feeding policy of oxygen provides a significant improved of yield compared to traditional reactor concepts.