Microsoft Word - Mamat20-Final.doc IIUM Engineering Journal, Vol. 1, No. 2, 2000 M. F. bin Mamat et al. 1 EFFECT OF LITHIUM CHLORIDE (Licl) DOPANT ON THE PERFORMANCE OF CATALYSTS FOR THE OXIDATIVE COUPLING OF METHANE M. F. Mamat, N. A. Mohd Zabidi, S. Bhatia and M. H. A. Megat Ahmad School of Chemical Engineering, Perak Branch Campus, Universiti Sains Malaysia,31750 Tronoh, Perak, MALAYSIA kkbhatia@kimia.eng.usm.my Abstract: The present study reports effects of lithium chloride (LiCl) doping on MgO, La2O3, SnO2, CaO and ZnO catalysts. All the catalysts were prepared by the impregnation method. The catalysts were tested at reaction temperature of 775oC. The feed flow rate of methane, oxygen and nitrogen was carried out in the ratio of 3:1:2 giving a weight hourly space velocity (WHSV) of 0.375 g.s/cm3. La2O3 showed the highest C2+ selectivity among the undoped catalysts. All the catalysts were doped with LiCl to compare their methane conversion, selectivity and product yield. The 2.0 mol% LiCl doped into La2O3 was the best catalyst formulation having achieved 46.7% of C2+ selectivity with CH4 conversion of 29.0% and the increase in selectivity was attributed to the presence of chlorine. Hydrogen production was more pronounced for MgO based catalysts and believed to be generated by surface- catalyzed reactions. Key Words: Oxidative Coupling, C2+ Selectivity, Hydrogen Production, Ethylene, Chlorine 1. INTRODUCTION Direct conversion of methane to industrial organic compounds is particularly significant especially natural gas, where the major component is methane, is one of the most plentiful fossil fuels available. Industry analysts estimate that the world holds enough readily recoverable natural gas to produce 500 billion barrels of synthetic crude [1]. Perhaps triple that amount of gas can be found in coal seams, natural gas hydrates [2] and in formations that release the gas only slowly. Crude oil is now the main source of chemicals and liquid fuels. However, with the continual depletion of crude oil reserve, the demand for natural gas as a source of chemicals and fuels would certainly increase [3]. One route is the direct dimerization of methane through the catalytic oxidative coupling of methane (OCM) process. The catalytic oxidative coupling of methane (OCM) is represented by the following equation: n4 2 4n-2y 2 y nCH O C H yH O 2 + ® + (1) In most published works in this topic, n would have the optimum value of 2. Oxidant other than O2, such as N2O and O3 have also been shown to facilitate the coupling reaction [4]. The hydrocarbon products are often reported as C2+ products, mostly ethane and ethylene as the major components with ethylene as the target product. C3 hydrocarbons are usually formed but at comparativel y low selectivity. In addition to these products, COx (CO and CO2) are also formed nonselectively. The conversion of CH4 to COx is undesirable since it represents a lower yield of hydrocarbons. The COx may also poison the surface of the catalyst. Another important product from the reaction is hydrogen, which is also a valuable product especially in fuel cells, which is projected to become the main source of energy for automobiles [5]. A large number of compounds, mostly metal oxides has been tested and found capable of facilitating the oxidative coupling reaction. In most of the catalysts studied, reaction temperatures in the range of 700-900oC are needed and products consists of C2+ hydrocarbons, carbon monoxide, carbon dioxide and water are obtained. There appears to be an inverse relation between methane conversion and selectivity to C2 hydrocarbons, resulting in an upper limit of selectivity per pass through the reactor. Indeed, investigation on the thermodynamic feasibility of the reactions, proposed that ethylene yield of 30 per cent is the highest that can be achieved [6]. In earlier studies, the goal of the applied research was often to maximize C2+ yield by varying composition of the catalyst, partial pressures of reactants, etc.; however, even in the best catalytic systems, the C2+ hydrocarbons concentration in the exit gas were quite low making it economically undesirable to extract C2+ from such a mixture. The more effective catalysts may be divided into five groups a) highly basic pure oxides, of which the early members of the lanthanide oxides series (excluding CeO2) are the best, b) Group IA or IIA ions supported on basic oxides (for example, Li/MgO, Ba/MgO and Sr/La2O3), c) monophasic oxides, d) a few transition metal oxides that contain Group IA ions, and e) any of these materials that are promoted with chloride ions. It is very unlikely that only a single type of site is responsible for the activation of methane as can be seen in the diversity of the catalysts used in the oxidative coupling reaction. It is difficult to determine the nature of the active sites as most characterization methods are IIUM Engineering Journal, Vol. 1, No. 2, 2000 M. F. bin Mamat et al. 2 applicable only at conditions far removed from those used in the actual catalytic reaction. Nonetheless, rational hypothesis can be made concerning the species that might exist on the surface of the functioning catalysts. The addition of chloride ions to an oxidative coupling catalyst can have a marked effect on its properties, particularly with respect to the ethylene (C2H4) to ethane (C2H6) product ratio. The chloride may be introduced either initially as a part of the catalyst or through organo chlorine compounds, for instance CCl4, that are added to the reagents [7]. Because chlorine is known to dehydrogenate C2H6 in the gas phase, it has been suspected that homogenous reactions may be responsible for the large C2H4/C2H6 ratios that are observed in these chlorine containing systems [8]. In this study, the effects of LiCl on different oxide catalysts such as MgO, La2O3, SnO2, CaO and ZnO are reported. 2. EXPERIMENTAL Catalysts were prepared through the wet impregnation method. Powdered MgO (Merck, extra high purity), La2O3 (Fluka, purity 97%), CaO(BDH), ZnO (Merck, 99.0%) and SnO2 (Merck, 99.0%) were used directly from supplier's package without any treatment. For doping the catalysts with LiCl, desired amount of LiCl (Merck, 98.0%) was dissolved in deionized water. The supports were then poured into the solution and stirred. The resulting paste was dried in an oven for 12 hrs at 110oC-120oC. The dried paste was then crushed to powder and calcined at 950oC for 4 hour. The calcined material was then pelletized at 5 tons/m2 for each 5 gm of catalyst. The pellet was then calcined again at 950oC for another 8 hrs. After calcination, the pellets were crushed and sieved to 40-60 mesh size. The same procedure was applied with the other dopant (Li2CO3, Ajax, 99.5%) used before testing. The catalysts were tested in a stainless steel microreactor (O.D. 12.7 mm, I.D. 10.92 mm and length 600 mm) situated vertically in a tubular furnace (Carbolite VST 12). The catalyst layer was placed in the center of the microreactor. The free space below and above the catalyst layer was filled with quartz particles (RDH) of 40-60 mesh size in order to minimize the dead volume of the reactor. Methane (Malaysian Oxygen, purity 99.99%), Oxygen (99.8%) and Nitrogen (99.99%) were passed through the microreactor. Flow of the gases was controlled using mass flow controllers (Brooks 5850E for both nitrogen and oxygen and MKS for methane). Outlet gas flow rate was monitored using a gas flowmeter (Alexander Wright DM3 B). The gaseous products were analyzed using an on-line gas chromatograph (Hewlett-Packard 6890). Porapaq N column was used to separate carbon dioxide, ethane, ethylene and propylene and Molecular Sieve 5A was used for separation of hydrogen, oxygen, carbon monoxide, nitrogen and methane. Water, a by-product of the reaction, was trapped in a gas trap before gaseous product sampling was carried out. The gas chromatograph was calibrated using a standard gas mixture supplied by BOC Gases, U.K. The catalyst was first heated in O2 at a flow rate of 10 ml/min at 800oC for half an hour to oxidize adsorbed components. It was then cooled down to 700oC before mixture of reactants was fed through the microreactor with CH4:O2:N2 ratio of 3:1:2 giving a total flow rate of 240 ml/min. A 1.5 gm of catalyst was used for each experimental run. Furnace temperature was adjusted to the desired reaction temperature. Catalyst bed temperature was monitored using a Chromel-Alumel thermocouple inserted into the catalyst bed. Once the bed temperature stabilized for 15 mins, the sample was drawn. The activity of the catalysts was expressed in terms of methane conversion, selectivity and yield for C2+ hydrocarbon and hydrogen. A carbon balance of 100+2% was obtained for every run over the catalysts. The conversion of methane or oxygen was defined as 4 2 4 2 4 2 X(CH or O ) moles CH or O conver t ed 100% moles CH or O fed = ´ (2) The selectivity for Cn products was calculated as n n 4 S(C ) n moles C in product s 100% moles CH convert ed t o all product s = ´ ´ (3) The yield for Cn product was given by n n 4 n moles C in pr oduct s Y(C ) 100% moles CH fed ´ = ´ (4) The selectivity for H2 product was calculated as 2 2 4 S(H ) 2 moles H in product s 100% 4 moles CH convert ed t o all product s = ´ ´ ´ (5) The yield for H2 product was given by 2 n 4 2 moles H in pr oduct s Y(C ) 100% moles CH fed ´ = ´ (6) 3. RESULTS In most of experimental runs, methane to oxygen mole ratio was more than 2. A 100% O2 conversion was achieved in most of experiments. Figure 1 shows the methane conversion, selectivity and yield of C2+ hydrocarbons for undoped catalysts. La2O3 gives the highest activity in terms of selectivity and yield of C2+ hydrocarbons, which were 44.8% and 12.4% respectively, followed by MgO with 39.4% selectivity and yield of 11.3% of C2+ hydrocarbons. ZnO gave 18.8% selectivity OF C2+ hydrocarbons and yield of 4.0%. Catalytic performance of both SnO2 and CaO show that they are nonselective catalysts. All these results are in line with literature findings. Both the La2O3 and MgO have been known to be good coupling catalysts especially when doped with alkaline earth oxides [9]. IIUM Engineering Journal, Vol. 1, No. 2, 2000 M. F. bin Mamat et al. 3 Fig. 1 Performance of undoped catalyst Figure 2 shows the selectivity and yield of hydrogen for the undoped catalysts. MgO showed the highest activity with H2 selectivity of 19.1% and yield of 5.5%. Compared to the selectivity and yield of hydrocarbons product, CaO showed significant selectivity and yield of H2 relative to MgO. A selectivity of 12.0% and 2.7% yield of hydrogen were obtained. Both SnO2 and ZnO gave low activity to H2 formation. The ratios of C2H4/C2H6 and CO/CO2 are shown in Figure 3. From these results, it appeared that higher C2+ selectivity leads to higher C2H4/C2H6 ratio, nevertheless a small degree of variation in catalytic activity among the catalysts was observed. MgO produced higher ethylene relative to ethane as compared to La2O3 even though La2O3 gave the highest selectivity to C2+ hydrocarbons. The C2H4/C2H6 ratio did not correlate with H2 selectivity and yield. Fig. 2 Activity of undoped catalyst for selectivity and yield of hydrogen production Fig. 3 Ethylene to ethane ratio and carbon monoxide to carbon dioxide ratio over undoped catalyst Doping the catalysts with 1 mol% LiCl did not result in an apparent increase in terms of C2+ selectivity and yield for any of the catalysts except CaO, as shown in Figure 4. The C2+ selectivity of 1 mol% LiCl/CaO increased much higher compared to the other catalysts but the methane conversion decreased. The C2+ selectivity increased from 7.6% to 17.2% wihile methane conversion dropped 22.8% to 18.8%. No marked changes in the measured parameters were observed for other 1 mol% LiCl doped catalysts. Figure 5 shows the selectivity and yield of H2 on the 1 mol% LiCl doped catalysts. Again, except for 1 mol% LiCl/CaO, there are no significant changes in both the H2 selectivity and yield for the other catalysts. The H2 selectivity and yield for 1 mol% LiCl/CaO catalysts decreased from 12.0% to 0.9% and from 2.7% to 0.2%, respectively. Fig. 4 Activity of 1 mol% of LiCl doped catalysts IIUM Engineering Journal, Vol. 1, No. 2, 2000 M. F. bin Mamat et al. 4 Fig. 5 Hydrogen production over 1 mol% LiCl doped catalyst Figure 6 shows the ratios of C2H4/C2H6 and CO/CO2 against the 1 mol% LiCl doped catalysts. The presence of LiCl appears to have a conspicuous influence to the product ratios, especially doped MgO catalyst. The ratio of C2H4/C2H6 increased from 1.14 for MgO catalyst to 1.38 for 1 mol% LiCl/MgO whereas the CO/CO2 increased from 0.14 to 0.25. For the other catalysts, no significant changes were observed in C2H4/C2H6 ratio but the CO/CO2 ratio for CaO and SnO2 reduced markedly due to total oxidation to CO2. Because of its high selectitivity to C2+ hydrocarbons, both the La2O3 and MgO have been doped with 2 mol% LiCl. Table 1 shows the results of these catalysts together with pure and 1 mol% LiCl doped catalysts for comparison purpose. Fig. 6 Products ratio over 1 mol% LiCl doped catalyst From Table 1, increasing LiCl concentration on MgO resulted in a negative effect where the C2+ selectivity decreased from 39.6% for 1 mol% LiCl/MgO catalyst to 34.7% for 2 mol% LiCl/MgO. The conversion also decreased from 27.6% to 24.7%. The most marked change was observed on the C2H4/C2H6 ratio, which decreased from 1.38 to 0.29. This was observed when Li2CO3 was used as a precursor. The C2+ selectivity increased to 42.6% with methane conversion of 29.7%, resulting in C2+ yield of 12.7%. The C2H4/C2H6 ratio also increased to 1.5. All the other measured parameters were kept constant. For La2O3, doping it with 2 mol% LiCl caused an increase in C2+ selectivity and yield which were the highest among all the catalysts studied. Table 1: Catalytic activity of La2O3 and MgO based catalysts Catalysts %CH4 conversion %C2+ hydrocarbons %C2+ yield %H2 selectivity %H2 yield C2H4/C2H6 CO/CO2 MgO 28.8 39.4 11.3 19.1 5.5 1.14 0.14 1 mol% LiCl/MgO 27.6 39.6 10.9 16.3 4.5 1.38 0.25 2 mol% LiCl/MgO 24.7 34.7 8.6 20.6 5.1 0.29 0.32 2 mol% Li/MgO * 29.7 42.6 12.7 17.0 5.1 1.5 0.25 La2O3 27.7 44.8 12.4 15.8 4.4 0.95 0.11 1 mol% LiCl/La2O3 28.5 44.3 12.6 14.0 4.0 0.99 0.12 2 mol% LiCl /La2O3 29.0 46.7 13.5 15.5 4.5 1.05 0.10 2 mol% Li/La2O3* 27.8 42.8 11.9 12.9 3.4 0.81 0.05 *Prepared by using Li2CO3 as a precursor for Li dopant IIUM Engineering Journal, Vol. 1, No. 2, 2000 M. F. bin Mamat et al. 5 The C2+ selectivity and yield of 2 mol% LiCl/La2O3 were 46.7% and 13.5%, respectively. The H2 selectivity and yield together with the C2H4/C2H6 and CO/CO2 ratios did not change significantly. The activity of 2 mol% LiCl/La2O3 also was better than 2 mol% Li/La2O3 catalyst prepared by using Li2CO3 as the Li dopant precursor, where the C2+ selectivity obtained was 42.8% with methane conversion of 27.8%. The conversion, yield and selectivity values were reproducible within experimental error of 5%. 4. DISCUSSIONS It is generally accepted that the oxidative coupling of methane to C2 hydrocarbons and subsequently to C3 and higher hydrocarbons is initiated by the generation of gas-phase methyl radicals [10]. This is accomplished through the abstraction of hydrogen atom from methane, which has been proposed as follows: - - s4 3CH O CH OH+ ® + (7) where the surface oxygen species, O-s is the active site. The OH- would be converted to water through subsequent reactions that regenerate the O-s with the help of gas-phase oxygen. Ethane is formed via the coupling of methyl radicals in the gas phase, whereas ethylene is believed to be originated from the thermal dehydrogenation of ethane or the surface-catalyzed oxidative dehydrogenation of ethane. Both CO and CO2 come from the gas-phase or surface catalyzed oxidation of methane, hydrocarbon intermediate species and hydrocarbons final product. The latter two may contribute more significantly than the former for this non-selective reactions [11]. The production of hydrogen may be invoked by these possible paths of consecutive reactions [12]: Water gas-shift reaction (referred to as WGS) 2 2 2CO H O CO H+ ® + (8) Thermal cracking of ethane 2 6 2 4 2C H C H H® + (9) Steam reforming of hydrocarbons n 2n+ 2 2 2C H nH O nCO (2n+ 1)H+ ® + (10) Partial oxidation of hydrocarbons n 2n+ 2 2 2 1 C H nO nCO (n+ 1)H 2 + ® + (11) Ethane dehydrogenation in the presence of steam is an un-catalyzed commercial process, whereas WGS and steam reforming of hydrocarbons do not proceed without a catalyst. Partial oxidation can occur both thermally and catalytically. From the figures and table presented, it is noticeable that when the C2+ selectivity increases, the C2H4/C2H6 would also increase but not the H2 selectivity. This indicates that the catalytic oxidative dehydrogenation of ethane and the thermal dehydrogenation of ethane are the sources of ethylene and the water gas-shift reaction (Eq. 8) is the main source of hydrogen production. The catalytic influence on these reactions is clearly shown by the differences in activity of CaO and 1 mol% LiCl/CaO. The relative importance of the catalytic oxidative dehydrogenation of ethane and the thermal dehydrogenation of ethane is, however, difficult to determine. The low CO/CO2 ratio recorded on all the catalysts indicates that the steam reforming of hydrocarbons (Eq. 10) and the partial oxidation of hydrocarbons (Eq. 11) do not proceed to a significant extent. The absence of steam reforming reaction is in line with kinetics observation by Stansch[11] on La2O3/CaO catalyst which stated that the reaction was not observed for reaction temperatures below 800oC but become significant above 800oC. This is because the reaction of C2+ hydrocarbons with water is much slower as compared with oxygen. Investigation by Hargreaves, et. al.[12] showed that partial oxidation of hydrocarbons was found to be the dominant route to H2 only at low oxygen conversion. In the present study, a 100% of oxygen conversion was achieved on all the catalysts system. For the catalysts studied, the positive influence of LiCl on La2O3 is much more pronounced. The increase in the C2H4/C2H6 ratio may indicate the participation of chlorine in dehydrogenating ethane in the gas phase. As the calcination and reaction temperature used in this study are relatively high, significant loss of chlorine from the catalyst may occur before and definitely after the reaction. This is believed to happen because of the evaporative nature of chlorine. During experimentation, chlorine may react with water vapors resulting in the formation of HCl. If chlorine induced dehydrogenation of ethane occurred, it is projected that MgO when doped with 2 mol% of LiCl should give a much higher C2H4/C2H6 ratio as compared to 1 mol% of LiCl/MgO. However, this is not the case in our present study. This suggests that other factor, which was influenced by the presence of Cl plays a part in the catalyst selectivity. The negative effect of chlorine on MgO is proved further when Li2CO3 was used as a precursor to prepare 2 mol% Li/MgO, and the C2+ selectivity increased together with the C2H4/C2H6 ratio. The presence of chlorine, however, possibly enhanced the C2H4/C2H6 ratio only at a much lower temperature. A study on LiCl/MgO catalyst showed the catalysts to be effective in increasing the ratio of C2H4/C2H6 up to 5 with C2 yield of 20% at 640oC[7]. For La2O3, higher doping concentration of LiCl gives a positive effect to the C2+ selectivity but the C2H4/C2H6 ratio remains to be similar. Again, the presence of chlorine is the main factor in the increase of C2+ selectivity as doping the La2O3 with the same Li concentration using Li2CO3 as the precursor do not give a similar result but a decrease in C2+ selectivity as observed. The different behavior of La2O3 and MgO based catalysts may be attributed to the influence of chlorine on the active sites of the catalysts. The chlorine seems to affect the catalysts activity more than that of lithium. IIUM Engineering Journal, Vol. 1, No. 2, 2000 M. F. bin Mamat et al. 6 5. CONCLUSIONS Results obtained show that the presence of LiCl has a marked influence on the activity of all the catalysts studied. The function of the chlorine atom is related more to the active sites on the surface of the catalysts rather than involved in facilitating ethylene formation via gas-phase dehydrogenation reaction of ethane, as previously suggested. It is also discovered that hydrogen is mainly produced through the water gas- shift reaction. ACKNOWLEDGEMENTS This research has been supported by Universiti Sains Malaysia under long-term IRPA grant (Project No. 02- 02-05-7003). Megat Harun Al Rashid bin Megat Ahmad acknowledges Ministry of Science, Technology and Environment, Malaysia for award of postgraduate scholarship. REFERENCES [1] S. A. Fouda, "Liquid fuels from natural gas", Scientific American, pp. 74-77, March 1998. [2] M. Max, and W. Dillon, "Natural gas hydrate: a frozen asset?", Chemistry and Industry., pp. 16-18, January 2000. [3] G. J. Hutchings, J. S. J. Hargreaves, R.W. Joyner and C. J. Kiely, C. J., "Towards understanding of methane coupling" ChemTech, Vol. 24, pp. 25-29, 1994. [4] A. G. Anshits, E.V. Kondratenko, E. N. Voskresenskaya, L. I. Kurteeva, and N. I., Pavlenko, "The influence of O2 on oxidative coupling of methane over oxide catalysts using N2O as oxidant", Catalysis Today, Vol. 46(2-3), pp. 211-216, 1998. [5] T. Brousas, P. H. Chiang, D. Eng and M. Stoukides, "Technical and economic evaluation of a methane solid oxide fuel cell", Ionics, Vol. 1, pp. 328-337, 1995. [6] M. Baerns, O. Buyevskaya and L. Mleczko, "Direct conversion of methane to C2 hydrocarbons-Is there a prospect for the future?", Proceedings from the European Applied Research Conference on Natural Gas-Eurogas 94-Sintef, Trondheim, pp. 93-113, 1995. [7] J. H. Lunsford, "The catalytic oxidative coupling of methane", Angewandte Chemie, Vol. 34, pp. 970-980, 1995. [8] S. Ahmed and J. B. Moffat, "The oxidative coupling of methane on Mn/SiO2 and the effect of solid- and gas- phase doping", Journal of Catalysis, Vol. 171, pp. 439- 448, 1999. [9] J. Zaman, "Oxidative processes in natural gas conversion", Fuel processing Technology, Vol. 58, pp. 61-81, 1999. [10] N. W. Cant, E. M. Kennedy and P. F. Nelson, "Magnitude and origin of the deuterium kinetic isotope effect during methane coupling and related reactions over Li/MgO catalysts", Journal of Physical Chemistry, Vol. 97, pp. 1445-1450, 1993. [11] Z. Stansch, L. Mleczko and M. Baerns, "Comprehensive kinetics of oxidative coupling of methane over the La2O3/CaO catalyst", Industrial Engineering and Chemistry Research, Vol. 36, pp. 2568-2579, 1997. [12] J. S. J. Hargreaves, J. G. Hutchings and R. W., Joyner, “Hydrogen production in methane coupling over magnesium oxide”, Natural Gas Conversion, Elsevier, pp. 155-159, 1991. BIOGRAPHIES Muhammad Fadzli bin Mamat received his Diploma in Chemical Engineering from Universiti Teknologi Malaysia in 1993. He worked as a technician at Mobil Malaysia before furthering his study in Chemical Engineering at the School of Chemical Engineering, Universiti Sains Malaysia. He carried out his final year project on the development of catalysts for the oxidative coupling of methane(OCM) under the supervision of Dr. Noor Asmawati and graduated with honors recently. Dr. Noor Asmawati binti Mohd. Zabidi received her B.S. in chemistry from Nebraska Wesleyan University, Lincoln, USA in 1986. She carried out research in photocatalysis under the supervision of Prof. Timothy F. Thomas at the University of Missouri-Kansas City, USA where she received her Ph.D. in 1995. She has been a lecturer at the School of Chemical Engineering, Universiti Sains Malaysia, Perak Branch Campus since 1996. Megat Harun Al Rashid bin Megat Ahmad received his B.App.Sc. in analytical chemistry from the School of Chemical Sciences, Universiti Sains Malaysia in 1997. He conducted his MSc. research project on the development of catalyst for the oxidative coupling of methane under the supervision of Dr. Noor Asmawati and Prof. Subhash Bhatia. Previously he has undertaken research on the DPASV and DPP under the supervision of Dr. Sulaiman Ab. Ghani (USM), EIA on Tasik Bera, Pahang, Malaysia (Universiti Malaya-Wetlands International) and the determination of marker for p53 mutation for colon cancer research at the Institute of Medical Research, Malaysia. Prof. Subhash Bhatia joined School of Chemical Engineering, Universiti Sains Malaysia, Perak Branch Campus, in 1995. He was a Full Professor at the Department of Chemical Engineering, Indian Institute of Technology, Kanpur (India). Prof. Bhatia was a visiting faculty at the University of Queensland, Australia from 1988-89 and 1994-95. His research interests are zeolite catalysis, chemical reaction engineering and environmental catalysis. He has written a book on Zeolite Catalysis that was published by CRC Press, USA and has published more than 60 papers in national and international journals.