INTEGRATED CATALYTIC MEMBRANE REACTOR PROCESS FOR CO2 REFORMING OF METHANE by Ifeyinwa Orakwe Supervisor: Prof Edward Gobina 7th World Congress on Petrochemistry and Chemical Engineering November 13-14th 2017, Atlanta, Georgia, USA

Outline Introduction: Green house gases CO2 and CH4 Advantages/Applications of membrane technology Aim and Objectives Methodology Results and discussions Conclusion Acknowledgement References

Introduction /Membrane Technology Greenhouse gas (GHG) In recent years, concerns have risen with respect to the effect of rising atmospheric concentration of greenhouse gases which are majorly CO2 and CH4 These greenhouse gas emissions lead to global climatic changes The major source of these GHG emissions are mainly due to human factors as seen in Fig 1.

Introduction /Membrane Technology Sources of green house gases Fig 1: Global human sources of GHG emissions

Fig 2: Percentage composition of compounds in the GHG emissions

Effects of GHG emissions Figures 3 shows some of the effects resulting from GHG emissions b a b. Changes to plant growth and nutrition levels c a. Global warming c. Ocean acidification Figure 3: Effects of GHG emissions

Steam reforming of methane and partial oxidation of methane are the traditional methods of syngas production for many synthetic applications/processes The dry reforming of methane is a new process and can be illustrated in equation 1, in the presence of a noble catalyst e.g. rhodium Instead of steam or oxygen, CO2 can be used to breakdown the methane to yield syngas. Because of the high stability of the CO2 molecule, the reaction is highly endothermic even with the use of catalysts. Hence the need for innovative reactors. (1)

Currently, many studies are being carried out on the development of dry methane reforming methods that could be commercially applicable for the production of syngas from greenhouse gases. Most of the methods under consideration utilize fixed bed tube reactors. These reactors are plagued by mass- transfer limitations in the catalyst bed. Studies have shown that the use of membrane for CO2 reforming can lead to an increase in the yield of syngas and high conversion of CH4 and CO2 This has further led to the consideration of membrane technology and ways of improving the process so that it can be used commercially for syngas production

Advantages Advantages of Membrane process High chemical resistance - Ceramics, Metallic High mechanical strength - Ceramics, Metallic High thermal stability - Ceramics, Metallic Ability to withstand high pressure - Ceramics, Metallic Long life - Ceramics, Metallic Have catalytic property - Ceramics, Zeolite, mixed oxides Compact and has an integral feature-Tubular

Aim and Objectives The aim of this research is to characterize a catalytically impregnated ceramic membrane for CO₂ reduction from flue gas The objectives are: To fabricate a rhodium impregnated membrane To characterize the catalytic membrane using a liquid nitrogen adsorption desorption (BET) analyser to study its surface area and pore size diameter and energy dispersive x-ray (EDAX) analyser to study the presence of rhodium catalysts Carry out flow experiments to measure the conversion of CH4 and CO2 to evaluate the efficiency of the catalytic membrane reactor system

Methodology Two types of Ceramic Supports Used: Membrane A o.d.: 10 mm, id: 7mm, average pore size: 15nm, porosity: 45% Membrane B o.d.: 25 mm, id: 20 mm, average pore size: 6000nm, porosity: 45% Figure 4a shows a picture of these supports, while 4b shows the rhodium impregnated membranes (a) Figure 4: (a) Tubular Ceramic supports, (b) After rhodium impregnation (b)

Methodology Membrane Preparation: Wet impregnation method Figure 5 shows the steps employed in the catalyst deposition process. Figure 5: The dip-coating membrane process. Support dipped in deionised water (a), and RhCl₃ solution (b)

Methodology Membrane holder Reactor cap Graphite Seal Rhodium impregnated membrane Figure 6: Pictorial representation of the platinum membrane being inserted into the membrane holder. The membrane holder is made up of stainless steel material

Methodology Membrane characterization: Liquid Nitrogen adsorption desorption as seen in fig 7a Scanning electron microscopy-EDAX as seen in figure 7b (a) (b) Figure 7: (a) Sample undergoing analysis- Nitrogen Adsorption desorption analyser [Quantachrome®ASiQwinTM ], (b) SEM-EDAX analyser

Methodology Catalytic Performance Measurement: A flue gas with a gas composition of CO2-12.5%, CH4-2.5%, CO-50ppm, N2-80.595%, O2-4.4% was used as feed at 700 and 900°C in catalytic membrane reactors as seen in fig 7a and analysed in an Agilent GC-MS [figure 7b] (b) (a) Fig. 8 (a) Pictorial representation of the reactor setup, (b) Analysis done using an Agilent GC-MS

Methodology Equations 2 and 3 were used for calculating the percentage conversion for each of the gases (2) (3)

Results and Discussions The following parameters are discussed in relation to the results obtained The specific surface area and pore diameter of the catalytic membrane The Scanning electron microscope photographs and EDXA analysis Conversion results

Results and Discussions Table 1 shows a summary of the results obtained from the adsorption desorption analysis   Type BET (surface area) m2.g-1 Pore volume cc.g-1 Pore diameter nm Alumina support Membrane A (15nm) 12.144 0.001 3.305 Rh/Al2O3 0.092 0.011 3.136 Membrane B (6000nm) 13.477 0.012 4.176 2.872 0.003 3.137

Results and Discussions The morphological structure of the Rh/Al2O3 membranes are seen in fig 9. The EDXA also confirms the presence of Rh on the surface and pores of the membranes. Rh metal Fig 9 Scanning electron micrographs of (a) Membrane A (Rh/Al2O3 15nm membrane), (b) Membrane B (Rh/Al2O3 6000nm membrane)

Results and Discussions EDXA for the membranes showing the chemical components present in the membrane samples are shown in figure 10 Rh Rh Fig 10 EDXA analysis for (a) Membrane A (Rh/Al2O3 15nm membrane), (b) Membrane B (Rh/Al2O3 6000nm membrane)

Results and Discussions The performance of the membrane were evaluated at 700 and 900oC at a flowrate of 1,500 ml.min-1. Operations at 900oC increased the flue gas conversion to over 94% for both CH4 and CO2 gases. Results are shown in figure 11 (a) (b) Fig. 11 Reactant conversions for CH4 and CO2 for (a) Membrane A (15 nm membrane), and (b) Membrane B (6000nm membrane)

Conclusion Rh/Al2O3 prepared by wet impregnation method was characterised by nitrogen adsorption desorption method and EDAX. Results showed a decrease in the membrane’s surface area when compared to that of the fresh support. A catalytic membrane reactor process with Rh/Al2O3 membranes were used to convert flue gas into synthetic gas by a dry reforming process. The performance of the membrane were evaluated at 700 and 900oC at a flowrate of 1,500 ml.min-1. Operations at 900oC increased the flue gas conversion to over 94% for both CH4 and CO2 gases. A 40,000% scale-up has been achieved in the pore size and 2,500% in o.d. respectively which is sufficient to initiate a pilot plant study of the process.

Acknowledgement The authors wish to acknowledge the financial support from CCEMC which presently operates as Emissions Reduction Alberta (“ERA”). The authors are also grateful to the staff of Centre for Process Integration and Membrane Technology, Robert Gordon University for their support.  

References ATASHI, H. et al., 2017. Thermodynamic analysis of carbon dioxide reforming of methane to syngas with statistical methods. International Journal of Hydrogen Energy, 42(8), pp. 5464-5471   CHEN, Q. et al., 2017. Temperature-dependent anti-coking behaviors of highly stable Ni-CaO-ZrO2 nanocomposite catalysts for CO2 reforming of methane. Chemical Engineering Journal, 320, pp. 63-73 https://whatsyourimpact.org/effects-increased-greenhouse-gas-emissions EL HASSAN, N. et al., 2016. Low temperature dry reforming of methane on rhodium and cobalt based catalysts: Active phase stabilization by confinement in mesoporous SBA-15. LI, D. et al., 2017. Preparation of supported Co catalysts from Co–Mg–Al layered double hydroxides for carbon dioxide reforming of methane. International Journal of Hydrogen Energy, 42(8), pp. 5063-5071 MOVASATI, A., ALAVI, S.M. and MAZLOOM, G., 2017. CO2 reforming of methane over Ni/ZnAl2O4 catalysts: Influence of Ce addition on activity and stability. International Journal of Hydrogen Energy, PRABHU, A.K. and OYAMA, S.T., 2000. Highly hydrogen selective ceramic membranes: application to the transformation of greenhouse gases. YANG, W. et al., 2016. CO2 reforming of methane to syngas over highly-stable Ni/SBA-15 catalysts prepared by P123-assisted method.

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