Novel approach to the application of unsteady state catalysis for advanced reactor and process design

• Research unit: EU RFP
• Project number: 97.0191

Key words (English)

Oxidative methane conversion; partial oxidation; mixed oxide catalysts; aromatics oxidation; vanadium based catalysts; periodic reactor operation; two zone fluidised bed reactor; reversed flow reactor; bifurcation analysis; SSITKA; TAP; FTIR; DRIFTS;

Alternative project number (English)

EU project number: IC15-CT97-0709

Research programs (English)

EU-programme: 4. Frame Research Programme - 8.1 Cooperation with 3rd countries & intern. organisations

Short description (English)

See abstract

Partners and International Organizations (English)

Institute of Applied Chemistry, Berlin, University of Gent, Boreskov Institute of Catalysis, Novosibirsk, Institute of Chemical Physics, Moscow, Pisarzhevsky Institute of Physical
Chemistry, Kiev

Abstract (English)

Environmental, safety, economic and technical demands require new approaches in chemical manufacturing. In the heterogeneous catalytic transformation of chemical raw materials into useful industrial products it is the reactor operation which often determines the economic feasibility of a processes. The aim of the project was it to investigate how unsteady-state cata-lysis can lead to an in-crease in process efficiency. The approach of unsteady state cata-lysis was applied to several reactions: oxidative conversion of methane to C2-hydro-carbons, partial oxidation of methane to synthesis gas, oxidation of aromatics (o-xylene and toluene) over vanadium based catalysts and CO-Oxidation. Since the understanding of the reac-tion me-cha-nism and the dynamics of individual reaction steps is crucial for process opti-mization and reactor design the project linked experimental studies of kinetics and mathe-matical modelling of reac-tion kinetics. The following results were obtained:
Oxidative conversion of methane to C2-hydrocarbons.The work was focused on a comparative study of different catalytic oxide systems for oxidative coupling of methane in the periodic operation mode. Mechanistic kinetic models were developed based on transient and steady-state experiments. Kinetic constants were correlated with the catalyst composition in order to de-rive the optimal solid properties and reaction conditions for unsteady-state operation. Accor-dingly, the catalysts 1Na%Mn/4Na%Na2WO4 and KNaSrCoO3 revealed the highest selectivity in the periodic reactor operation. For technical application, the redox stability as well as the capacity of the catalytic solids for selective oxygen species has to be further optimized.
Partial oxidation of methane to syngas. The feasibility of the reversed flow partial oxidation of methane with air over a Rh-catalyst was studied in a bench scale unit. Semi-cycle times of more than 0.5h were possible. The time ave-raged conversions and selectivities over a semi-cycle in the permanent regime are rather low, but these are the consequence of the relatively low temperatures in the catalyst bed (order 900°C) due to the application of the nitrogen dilution. Yet, the selectivities and the conver-sions are comparable to those in a steady state reactor. The advantages of the reversed flow reactor are the autothermal operation and the fact that external heat exchangers are no longer required.
Oxidation of aromatics (o-xylene and toluene) over vanadium based catalysts. From transient technique on a V/Ti oxide catalyst kinetic data and mechanistic insight of oxidation reactions of aromatic compounds on vanadium catalysts was obtained. On the basis of mathematical modeling of response experiments kinetic constants and ac-tivation energies of the particular steps of the reaction mechanism were determined. The partial oxidation of o-xylene into phthalic anhydride and toluene into benzoic acid in a two zone lab. scale fluidized bed reactor has been investigated. It has been demonstrated that the selectivity of reactions is increased due to catalyst circulation between zones with different temperatures. By model simulation the unsteady state performance of the catalyst was analyzed. Accor-dingly, the reaction can be influenced by periodic operations of reactor and by spatial regulation in a dual-reactorsystem. It was pre-dicted that under periodic operations and in dual-reactor system averaged reaction rates can exceed the steady state value by several times. The optimization of the reaction parameters might increase the selectivity towards the desired product from 66.7% up to 90%.
CO-Oxidation. Mathematical model, describing oscillatory behaviour during CO oxidation over Pd Glass Fibre Catalyst has been developed. It was demonstrated, that the origin of oscillations in this system is due to periodic oxidation-reduction of supported Pd. Mathe-matical model can simulate the main properties of observed oscillations, namely the observed oscillatory behavior in T - CCO,in parameter space, the waveform of oscillations, the period and the amplitude variation with temperature and inlet CO concentration.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 97.0191