Synthesis of Core@Shell Zeolitic Hydrocarbon Adsorbents for Cold-Start Cold- Emission Control in Automotive Exhaust

MASOUMIRFARD, NIMA; ARNAL PABLO M.; KALIAGUINE, SERGE; KLEITZ, FREDDY

Quebec

Conferencia; 96th Canadian Chemistry Conference and Exhibition; 2013

Elimination of air pollutants from the exhaust gas stream of automobiles is achieved by using catalytic convertors at high temperatures (~>300 oC). However, at lower temperatures of cold-start period, the harmful emissions, like unburned hydrocarbons, cannot be converted to non-toxic gases. Common strategy to solve this problem is to use hydrocarbon traps to retain emissions until the catalyst reaches its ideal working temperature. Recent studies have shown that zeolites are the proper choice among all available sorbents; however, still significant improvements are required. As an efficient modification, synthesizing novel zeolitic architectures, i.e. core@zeolite spheres, is proposed. We report on a layer-by-layer technique to produce nanozeolites-coated cores, along with a secondary hydrothermal treatment step which is performed to strengthen the zeolitic shell and make it uniform (Figure 1(a,b)). In order to determine the best candidate as the core material, which could provide a variety of desirable features; various types of materials are screened. Since the size and monodispersity of the nanozeolites are the most crucial parameters for tuning the zeolitic shell, in terms of crystalline phase, shell-thickness and micropore orientation, different techniques are used to synthesize colloidal nanozeolite solutions. The performance of all products are investigated using a variety of characterization methods, e.g. XRD, TEM, SEM, N2 Sorption, as well as TPD of probe adsorbed molecules.