THE AIM OF THIS PROJECT IS TO DEVELOP AN IMPROVED PROCESS FOR THE OXIDATIVE COUPLING OF METHANE WITH A VIEW TO OBTAINING MORE VALUABLE C2 HYDROCARBONS
New catalysts were developed exhibiting high selectivity, activity and stability during operation; furthermore, already known catalysts were improved. From the results obtained fundamental factors affecting the selectivity and yield of hydrocarbons with 2 or more carbons (C2+) were derived. Since ethane and ethylene, being the desired products of the oxidative coupling of methane (OCM) reaction, are oxidized to carbon oxides in consecutive reaction steps, the oxidative dehydrogenation of ethane to ethylene was additionally studied in order to elucidate whether high C2+ selectivity can be obtained by suppressing the nonselective oxidation step of the C2+ hydrocarbons by applying several of the OCM catalysts.
Kinetic studies were performed to investigate the primary catalytic reaction steps, the homogeneous gas phase and the simultaneous catalytic and homogeneous gas phase reaction.
Chemical reaction engineering work was focused on the testing of different types of reaction for the OCM reaction and optimization of operating conditions to achieve maximum C2+ selectivity or yield respectively, set up of suitable reactor models as a basis for process optimization and scale up; and evaluation of the economics of a potential OCM process.
4 different laboratory scale reactors were tested applying catalysts which have been studied in microscale reactors:
isothermal fixed bed reactor;
applied: PbO/gamma-Al2O3, La2O3/CaO, NaOH/CaO nonisothermal fixed bed reactor;
fluidized bed reactors;
packed fluidized bed reactor (di = 50 mm, Hcat approximately equal to 100 mm, catalysts applied: NaOH/CaO).
THE PROJECT IS INTENDED TO COVER TWO MAIN AREAS:
A.- A SEARCH FOR AN IMPROVED CATALYST FOR THE CONVERSION REACTION OF CH4 INTO C2 HYDROCARBONS
B.- A SEARCH FOR OPTIMUM REACTION CONDITIONS AND REACTOR CONFIGURATION. EACH AREA ENCOMPASES SEVERAL INTERRELATED SUBPROJECTS. THE RESEARCH ON THE DEVELOPMENT OF A NEW, EFFICIENT CATALYST WILL BE CARRIED OUT IN THE FOLLOWING STAGES:
1) EMPIRICAL OPTIMIZATION OF CATALYSTS AND REACTION CONDITIONS THROUGH A LARGE NUMBER OF SHORT EXPERIMENTS ON FIXED-BED MICRO REACTORS.
2) EMPIRICAL STUDY ON DEACTIVATION KINETICS AND ON THE DEACTIVATION-DEPENDENCE OF ACTIVITY AND SELECTIVITY, THROUGH SEVERAL LONG-TERM EXPERIMENTS CARRIED OUT SIMULATNEOUSLY.
3) BASIC RESEARCH ON THE ACTION MECHANISM OF SELECTED CATALYSTS, WITH THE SPECIFIC AIM OF DETERMINING THE OXYGEN SPECIES INVOLVED AND ELUCIDATING THE ROLE PLAYED BY THE ACIDITY-BASICITY OF THE SUPPORT AND THE STRUCTURE OF THE CATALYST SURFACE.
AS REGARDS THE SECOND AREA, FIVE ETAGES ARE ENVISAGED:
1) DETERMINATION OF OPTIMUM REACTION CONDITIONS ON 5 TO 10 SELECTED NEW CATALYSTS ON SPECIALLY DESIGNED BENCH-SCALE FLUIDIZED-BED AND FIXED MULTIBED REACTORS.
2) DEVELOPMENT OF MATHEMATICAL MODELS FOR EACH KIND OF REACTOR WITH A VIEW TO SCALING-UP.
3) DETERMINATION OF KINETIC DATA FOR 3 TO 5 SELECTED CATALYSTS.
4) CHECKING THE RELIABILITY OF THE MODELS IN 10 LONG-TERM RUNS ON SEMI-PILOT SCALE REACTORS.
5) DEVELOPMENT OF ALTERNATIVE PROCESS DESIGNS AND ESTIMATION OF INVESTMENT COSTS.