The influence of CO2 partial pressure on ethanol dry reforming has been studied over Ce-promoted Co catalyst supported on Al2O3 from 20 to 50 kPa, C2H5OH was kept at 20 kPa and under atmospheric pressure. The catalyst was synthesized using wet impregnation method and tested in a quartz fixed-bed reactor. X-ray diffraction analysis indicated the formation of CeO2, Co3O4 and spinel CoAl2O4 phases on catalyst surface. CoO and Co3O4 and CeO2 phases were formed during temperature–programmed calcination and 5%Ce-10%Co/Al2O3 catalyst has a total high surface area of 137.35 m2 g-1. Both C2H5OH and CO2 conversions was improved with increasing CO2 partial pressure from 20 at 50 kPa and an optimal selectivity of H2 and CO was obtained at 50 kPa

Ahmad Ziad, Sulaiman

Akbari, Sweeta

Fayaz, Fahim

Singh, Sharanjit

UMP Institutional Repository

The National Conference for Postgraduate Research 2016, Universiti Malaysia Pahang  712    Influence of CO2 Partial Pressure on Ethanol Dry Reforming Using 5%Ce-10%Co/Al2O3 Catalyst for Hydrogen Production  Fahim Fayaz*, Ahmad Ziad Sulaiman, Sharanjit Singh, Sweeta Akbari Faculty of Chemical & Natural Resources Engineering Universiti Malaysia Pahang (UMP) Lebuhraya Tun Razak, 26300 Gambang, Kuantan, Pahang, Malaysia *fahimfayaz10@yahoo.com    Abstract— The influence of CO2 partial pressure on ethanol dry reforming has been studied over Ce-promoted Co catalyst supported on Al2O3 from 20 to 50 kPa, C2H5OH was kept at 20 kPa and under atmospheric pressure. The catalyst was synthesized using wet impregnation method and tested in a quartz fixed-bed reactor. X-ray diffraction analysis indicated the formation of CeO2, Co3O4 and spinel CoAl2O4 phases on catalyst surface. CoO and Co3O4 and CeO2 phases were formed during temperature–programmed calcination and 5%Ce-10%Co/Al2O3 catalyst has a total high surface area of 137.35 m2 g-1.  Both C2H5OH and CO2 conversions was improved with increasing CO2 partial pressure from 20 at 50 kPa and an optimal selectivity of H2 and CO was obtained at 50 kPa. Keywords—Ethanol dry reforming; Hydrogen; Ce promoter; Co-based catalyst  1. INTRODUCTION  With rise in world’s population and energy demand  have stimulated an initiative to find the alternative energy source with clean and eco-friendly source. The fossil fuels are accounted more than 80% to meet energy demand of the world. It has created serious environmental problems, such as greenhouse gases and climate changes [1], [2]. In addition, the problems generated by the environmental pollution are considered as a critical challenge for the next generations. Developed countries are investing in the development of fuel processing technology and gaseous fuel for power generation by fuel cells [3]. The production of syngas (a mixture of H2 and CO) by steam reforming and dry reforming has been emerged as a promising method to produce synthetic fuel or a clean energy carrier. In past few decades, numerous research articles have been published on dry reforming of methane. In this process, greenhouse gases (CO2 and CH4) were used as feed-stock to produce eco- friendly syngas [4], [5]. A non-renewable methane, an important component of natural gas is utilized [6]. From the environmental perspective, ethanol is preferred to methane because of easy availability, abundance and cost effectiveness. It is also known as less toxic and renewable fuel [7]. Moreover, ethanol can be produced from biomass, which is one of the most abundantly available renewable resource, can be  obtained from forestry waste and residues [8].The steam reforming of ethanol is also widely acknowledged for syngas production. However, this technique can effectively utilize greenhouse gases (CO2) and also curtail the rise in level of CO2 emission [7]. Therefore, ethanol dry reforming using 5%Ce-10%Co/Al2O3 catalyst for production of syngas has been thoroughly investigated for syngas production because it can minimize the impact of CO2 on the environment, by effectively utilizing the ethanol and CO2 in the reaction [9]. The aim of this research to investigate the physical properties of catalyst and influence of CO2 partial pressure on  ethanol dry reforming for H2 production over 5% Ce-promoted 10%Co/Al2O3 catalyst.    The National Conference for Postgraduate Research 2016, Universiti Malaysia Pahang  713  2. EXPERIMENTAL  A.  Catalyst preparation  The Gamma-Al2O3 support was purchased from Sasol (PURALOX SCCa150/200) and calcined in air at 1023 K for 5 h with heating rate of 5 K min-1 to ensure thermal stability. The 5%Ce-10%Co/Al2O3 catalyst was prepared by using the wet impregnation method. Then, accurately weighted amount of Ce(NO3)3.6H2O and Co(NO3)2.6H2O aqueous solutions (supplied by Sigma-Aldrich) were mixed with calcined alumina support and magnetically stirred for 3 h at room temperature and followed by drying at 383 K overnight and dried sample was calcined at 773 K for 3 h in air.   B. Catalyst characterization  The catalyst surface area, pore volume and pore diameter were determined in a Thermo Scientific Surfer unit using N2 physisorption at 77 K. The crystal structures of γ-Al2O3 support and 5%Ce-10%Co/ Al2O3 catalyst were investigated using the X-ray diffraction (XRD), in a Rigaku Miniflex II system with wavelength, λ = 1.5418 Å at 30 kV and 15 mA. The diffraction patterns were recorded from  2θ = 3° to 80° with 1° min-1 scan speed and a step size of 0.02°.  Temperature-programmed calcination (TPC) runs was performed for uncalcined 5%Ce-10%Co/ Al2O3 catalyst using TGA Q500 unit (TA Instrument). For complete removing of moisture and volatile compounds, sample was initially preheated at 373 K with 10 K min-1 heating rate for the 30 min in the flow of N2 as flow of 100 ml min-1. The sample was heated at 1023 K with different heating rates of 10-20 K min-1 in the gas mixture of 4N2:1O2 (100 ml min-1) for 30 min kept isothermally and subsequently sample was cooled down at room temperature in the same gas mixture.  C. Catalytic tests  The catalytic activity test have been performed in a quartz fixed-bed reactor (L = 17 inches and O.D. = 3/8 inches) placed vertically in a split tubular furnace with varying CO2 partial pressure from 20-50 kPa and C2H5OH was kept at 20 kPa during reaction and  reaction temperature of 973 K under atmospheric pressure. Approximately, 0.1 gcat of catalyst with average particle size of 125-160 μm was mounted by quartz wool in the center of quartz reactor. The inlet flow of gas hourly space velocity, GHSV = 42 L gcat-1 h-1  was used for all runs to minimize both internal and external transport resistances. The C2H5OH was fed into the reactor by using the syringe pump (KellyMed KL-602). Both CO2 and N2 flow rates were controlled through the Alicat mass flow controllers. The total flow rate of CO2, C2H5OH, and N2 gas employed to the reactor was 70 ml min-1. The collected gas from the reactor was analysed using an Agilent GC 6890 series gas chromatograph provided with thermal conductivity detector (TCD) and flame ionization (FID) detectors.   3. RESULTS AND DISCUSSION   A.  BET Surface area   The physical properties of γ-Al2O3 support and 5%Ce-10%Co/Al2O3 catalyst were obtained from N2 physisorption measurements summarized in Table 1. The BET surface area of 5%Ce-10%Co/Al2O3 catalyst was 137.35 m2 g-1 and lower than the BET surface area of γ-Al2O3 support 175.29 m2 g-1. After impregnation and calcination, the reduction in surface area and average pore volume from 0.46 cm3 g-1  to 0.37 cm3 g-1 was observed with presence of active metal on the surface of catalyst. This result was due to pore blockage with the presence of Ce and Co metal oxide phases.  Table 1: Textual properties of γ-Al2O3 support and 5%Ce-10%Co/Al2O3 catalyst.     Catalysts BET surface area (m2 g-1) Average pore volume (cm3 g-1) Average pore diameter (Å) γ-Al2O3 175.29 0.46 92.96 5%Ce-10%Co/Al2O3 137.35 0.37 82.8 The National Conference for Postgraduate Research 2016, Universiti Malaysia Pahang  714    B. X-ray diffraction measurments  The XRD patterns of calcined gamma-Al2O3 and 5%Ce-promoted 10%Co/Al2O3 catalyst are shown in Fig. 1. The formation of gamma-Al2O3 phase was detected at 2θ = 32.73º, 36.79º, 44.20º, 45.62º, 55.40º and 67.06º whilst almost same peaks were observed on the surface of 5%Ce-promoted 10%Co/Al2O3 catalyst. Additionally, the peaks were identified on the surface of 5%Ce-promoted catalyst at 2θ = 31.15º and 36.97º belonged to Co3O4 phase whilst 2θ of 59.38º and 65.33º formation of spinel CoAl2O4. The peak was detected 2θ = 28.50º corresponded to the formation of CeO2 phase for 5%Ce-promoted catalyst. These results were in agreement with other finding [10].     C. Thermogravimetric studies  The derivative weight profiles of 5%Ce-10%Co/Al2O3 catalyst during the temperature-programmed calcination are shown in Fig. 2. The peak P1 positioned at low temperature of 420-495 K with high intensity was due to the metal nitrates decomposition to the metal oxides equations (1) and (2), respectively.                                                                        3 2 2 2( ) 2 0.5Co NO CoO NO O  23 52 332 ( ) 3Ce NO Ce O N O              During the air calcination, the second peak (P2) at high temperature of 500-550 K was ascribed to the oxidation of CoO to Co3O4 and Ce3+ to Ce4+ equations (3) and (4), respectively. Furthermore, beyond 550 K, there were no peak observed for all three heating ramps due to the completed decomposition of metal precursors to metal oxides (CoO and Co3O4) on catalyst surface during the temperature-programmed calcination analysis. This result in good agreement with Mahadi et al. [11].  2 3 43 0.5CoO O Co O         2 3 2 20.5 2Ce O O CeO  D. Influence of CO2 partial pressure  The influence of CO2 partial pressure on ethanol dry reforming was performed at temperature of 973 K with varied CO2 partial pressure from 20 to 50 kPa and kept C2H5OH at 20 kPa. The C2H5OH and CO2 conversions of 5%Ce-10%Co/Al2O3 catalyst was shown in Fig. 3. Both C2H5OH and CO2 conversions with increasing of PCO2 increased to about 43.96%, and 35.13%, respectively. This result was due to the existence of extra CO2 Partial pressure in feed which improved the secondary reaction i.e. CH4 dry reforming for converting CH4 intermediate product to syngas [12]. Jankhah et al. have studied that the ethanol dry reforming conversions obtained at high ratio of CO2 and C2H5OH [13].  Furthermore, the properties of high oxygen storage capacity of Ce loading in the catalyst to enhanced the catalytic activity and stability in the reaction [14]. The influence of CO2 partial pressure on selectivity of H2, CO and CH4 exhibited in Fig. 4. The selectivity of H2 and CO increased linearly with growing CO2 partial pressure from 18.03-26.64% and13.93-20.24%, respectively whilst the selectivity of CH4 was decreased from 25 to 18% with growing CO2 partial pressure. This result indicated that the CH4 and CO2 reacted through the secondary reaction, i.e. dry reforming of CH4. Additionally, CH4 and CO can produced a synthetic gas and improve the H2 and CO selectivity [15].    4. CONCLUSIONS  5%Ce-10%Co/Al2O3 catalyst was prepared using a wet impregnation method and examined for ethanol dry reforming reaction in a quartz fixed-bed reactor at PCO2 (20-50 kPa), PC2H5OH = 20 kPa and 973 K. Both γ-Al2O3 support and 5%Ce-10%Co/Al2O3 catalyst possessed that high surface area of 175.29 and 137.35 m2 g-1, respectively. The formation of Co3O4, CeO2 and CoAl2O4 phases on surface of catalyst indicted by XRD measurements. The complete decomposition of metal precursors to metal oxides (CoO and Co3O4) observed at temperature beyond 550 K during the TGA analysis. The optimal C2H5OH and CO2 conversions were obtained at PCO2 = 50 kPa. Significantly, with rising CO2 partial pressure from 20-50 kPa, H2 and CO selectivity was increased whilst CH4 selectivity decreased at the same condition.  The National Conference for Postgraduate Research 2016, Universiti Malaysia Pahang  715   Figure 1: X-ray diffractograms of (a) γ-Al2O3 support and (b) 5%Ce-10%Co/Al2O3 catalyst.   Figure 2: Derivative weight profiles for temperature-programmed calcination runs of 5%Ce-10%Co/Al2O3 catalyst.    Figure 3: Influence of PCO2 on C2H5OH and CO2 conversions of 5%Ce-10%Co/Al2O3 catalyst at PC2H5OH = 20 kPa and 973 K.  2-theta Angle (o)20 30 40 50 60 70Intensity (a.u. )2 3γ-Al O2 4CoAl O 3 4Co O2CeO (a)(b) Temperature (K)400 500 600 700 800 900 1000Deriv. Weight ( mg min-1)  10 K min-1 15 K min-1 20 K min-1P1P2PCO2 (kPa) Conversion (%)202530354045C2H5OH  CO220 30 40 50The National Conference for Postgraduate Research 2016, Universiti Malaysia Pahang  716   Figure 4: Influence of PCO2 on selectivity of  H2, CO and CH4 at PC2H5OH = 20 kPa and 973 K.   ACKNOWLEDGMENT  The authors would like to appreciate for the financial support from UMP Research Grant Scheme (RDU130376) to conduct this study. Fahim Fayaz is also thankful for the Graduate Research Scheme Award (GRS) from Universiti Malaysia Pahang (UMP).  REFERENCES  [1] D. Das, and T. N. Veziroglu, “Hydrogen production by biological processes: a survey of literature,” Int. J. Hydrogen Energy, vol. 26, pp. 13–28, 2001. [2] M. Ball and M. Wietschel, “The future of hydrogen - opportunities and challenges,” Int. J. Hydrogen Energy, vol. 34, pp. 615–627, December 2009. [3] F. Joensen and J. R. Rostrup-Nielsen, “Conversion of hydrocarbons and alcohols for fuel cells,” J. Power Sources, vol. 105, pp. 195–201, 2002. [4] K. Selvarajah, N. H. H. Phuc, B. Abdullah, F. Alenazey, and D.-V. N. Vo, “Syngas production from methane dry reforming,” Res. Chem. Intermed., vol. 42,  pp. 269–288, January 2016. [5] M. C. J. Bradford and M. a. Vannice, “CO2 Reforming of CH4,” Catal. Rev., vol. 41, pp. 1–42, February 2007. [6] F. Barbir, “Transition to renewable energy systems with hydrogen as an energy carrier,” vol. 34, pp. 308–312, August 2009. [7] A. N. Fatsikostas, D. I. Kondarides, and X. E. Verykios, “Production of hydrogen for fuel cells by reformation of biomass-derived ethanol,” Catal. Today, vol. 75, pp. 145–155, 2002. [8] M. Ni, D. Y. C. Leung, M. K. H. Leung, and K. Sumathy, “An overview of hydrogen production from biomass,” Fuel Process. Technol., vol. 87, pp. 461–472, November 2006. [9] W. Wang and Y. Wang, “Dry reforming of ethanol for hydrogen production: Thermodynamic investigation,” Int. J. Hydrogen Energy, vol. 34, 13, pp. 5382–5389, May 2009. [10] M. S. Batista, R. K. S. Santos, E. M. Assaf, J. M. Assaf, and E. a. Ticianelli, “High efficiency steam reforming of ethanol by cobalt-based catalysts,” J. Power Sources, vol. 134, pp. 27–32, June 2004. [11] M. B. Bahari, N. H. H. Phuc, B. Abdullah and D.-V. N. V. Vo, “Ethanol dry reforming for syngas production over Ce-promoted Ni/Al2O3 catalyst,” J. Environ. Chem. Eng. In press [12] X. Hu and G. Lu, “Syngas production by CO2 reforming of ethanol over Ni/Al2O3 catalyst,” Catal. Commun. vol. 10, pp. 1633–1637, May 2009. [13] S. Jankhah, N. Abatzoglou, and F. Gitzhofer, “Thermal and catalytic dry reforming and cracking of ethanol for hydrogen and carbon nanofilaments’ production,” Int. J. Hydrogen Energy, vol. 33, pp. 4769–4779, August 2008. [14] W. Hong, Z. Lijuan, LI. Miao, L. Yuan, and B. Xue, “Co/CeO2 for ethanol steam reforming: Effect of ceria morphology,” J. Rare Earths, vol. 31, pp. 565–571, June 2013. [15] M. B. Bahari, F.-L. W. Ming, F. Fayaz, N. Ainirazali, N. H. H. Phuc, and D.-V. N. Vo, “Evaluation of Co-promoted Ni/Al2O3 Catalyst for CO2 Reforming of Ethanol,” J. Eng. Appl. Sci., vol. 11, pp. 7249-7253, June 2016.  PCO2 (kPa)Selectivity (%)2030405060H2 CO CH4 20 30 40 50

Influence of CO2 Partial Pressure on Ethanol Dry Reforming Using 5%Ce-10%Co/Al2O3 Catalyst for Hydrogen Production

http://umpir.ump.edu.my/id/eprint/15771/1/P096%20pg712-716.pdf

Influence of CO2 Partial Pressure on Ethanol Dry Reforming Using 5%Ce-10%Co/Al2O3 Catalyst for Hydrogen Production

Abstract

Similar works

Full text

Available Versions

UMP Institutional Repository