Hydrogen Production via Sorption Enhanced Steam Methane Reforming Process Using Ni/CaO Multifunctional Catalyst

Abstract

Sorption enhanced steam methane reforming (SESMR) is a promising concept for hydrogen production. The in situ removal of CO 2 shifts the reaction equilibrium toward increased H 2 production as well as H 2 concentration. Generally, most of the previous studies operated the SESMR system using separate materials of a CO 2 adsorbent and a reforming catalyst. In this study, a combined catalyst-adsorbent material (considered as multifunctional catalyst), whose functions are not only to catalyze the reaction but also to adsorb CO 2 simultaneously, was developed and utilized for the SESMR process. CaO and hydrotalcite (MK30-K), wellknown adsorbents for CO 2 capture, were selected as supports to replace a conventional Al 2 O 3 support for Ni catalyst. The material was prepared in the form of powder by incipient wetness technique, and the tests were carried out in the fixed bed reactor system. Experimental results indicated that the activity of Ni/CaO was less than Ni/Al 2 O 3 but high hydrogen concentration in the product stream can be achieved. The effect of Ni loading was investigated, and it was found that at atmospheric pressure, steam to methane ratio of 3 and T = 873 K, 12.5 wt % Ni/CaO was the appropriate ratio, offering high hydrogen concentration (80%). The study also suggested that the use of the multifunctional catalyst eliminates the use of Al 2 O 3 and thus requires a reactor with a smaller size.

High temperature CO2 sorbents and their application for hydrogen production by sorption enhanced steam reforming process

“…Besides a physical admixture of catalyst with sorbent, hybrid catalyst-sorbent patterns which integrate the catalytic reaction and the CO 2 sorption in a single pellet can present some advantages such as the elimination of mass diffusional limitation and the reduction of reactor volume [197,198]. Several studies have been performed on the development of hybrid catalyst-sorbent materials for SESMR process [199][200][201][202][203][204][205]. A first attempt to combine CaO-based sorbent and catalyst in a single pellet was performed by Martavaltzi and Lemonidou [201] who developed a hybrid Ni- …”

Catalytic performance of Ni/CaO-Ca 5 Al 6 O 14 bifunctional catalyst extrudate in sorption-enhanced steam methane reforming

“…3, the CaO utilization efficiency of Ni/CaAl-10 is lower than that of Ni/CaAl-6 in a long-term, multicyclic operation. In addition, too much CaO in the catalyst, e.g., Ni/CaO, would decrease the activity and stability of the catalyst [31,36]. Indeed, a compromise has to be made between the SMR and the carbonation reaction in order to create an effective and stable bifunctional catalyst, in which the reforming rate will ideally match the carbonation rate.…”

“…However, a major challenge to be solved is the stability of catalyst. So far, some CaO-based bifunctional catalysts have been prepared for the SESMR process [28][29][30][31][32][33][34][35], but most of them suffer from poor stability, i.e., the catalyst stability is decreased with the number of reforming-regeneration cycles. Very recently, a Ca 5 Al 6 O 14 -stablized Ni/CaO catalyst prepared in our group [36] equilibrium was reached using this type of catalyst.…”

“…Unfortunately, the catalyst is in the form of powder, which makes it of little practical use. In fact, most CaO-based bifunctional catalysts prepared to date are small unshaped powders [30][31][32][33][34][35][36], with the exception of those reported by Wheelock et al [28,29]. They prepared corein-shell spherical pellets (with an average diameter of 4.5 mm), consisting of a lime or dolomite core and an alumina shell onto which nickel was deposited.…”

Preparation of a mesoporous sorption complex catalyst and its evaluation in reactive sorption enhanced reforming

“…The process of adding CO 2 sorbent during steam methane reforming (SMR) is a potential way of reducing emission of the greenhouse gas CO 2 and enhancing the reforming process for hydrogen production (Han and Harrison, 1994;Carvill et al, 1996;Balasubramanian et al, 1999;Ding and Alpay, 2000;Xiu et al, 2003;Harrison, 2008;Chanburanasiri et al, 2011;Wang et al, 2011). He and Wu (2007) developed a ReSER process that uses nano-CaO as the CO 2 reactive adsorbent in a sorption complex catalyst to produce high-purity hydrogen with control of CO 2 emissions.…”