Breakthrough Studies of Methyl Salicylate and DMMP Mixed in Methyl Salicylate with Pressure Swing Adsorption Composed of 13X Molecular Sieves

A test procedure for pressure swing adsorption (PSA) was established and elucidated for the air purification using methyl salicylate (MeS) and 5% (v/v) dimethyl methyl phosphonate (DMMP) in MeS containing air stream as feed. The effect of feed flow rate was studied by varying the flow from 5 lpm to 20 lpm, for both the molecules at 25 oC and 4 kg/cm2. The results revealed that the flow rate had a significant influence on the breakthrough time. A method was developed for the determination of feed, purge, and dry air composition, by the solvent extraction method using the XAD-2 and the average concentrations reported. The 13X molecular sieves were characterised for its structural and textural properties such as BET- SA, XRD, and FT-IR. The temperature programmed desorption of DMMP and MeS on 13X clearly demonstrated that it was easily regenerated at ~320 °C after prolonged field operation of PSA. The PSA results obtained with PSA composed molecular sieves appeared to give promising technology for air purification and specifically to the chemical warfare agents simulants

Ozone catalytic oxidation of toluene over 13X zeolite supported metal oxides and the effect of moisture on the catalytic process

AbstractThis paper reports the behavior of 13X zeolite supported Ce, Cu, Co, Ag and Mn metal oxides toward ozone catalytic oxidation (OZCO) of toluene and the influence of moisture on the decomposition process. The simple impregnation method was adapted to disperse the metal oxides and found highly active for toluene oxidation in the presence of ozone. The steady-state activities and ozone decomposition data reveal that the activity is in the order of Mn/13X>Ce/13X>Cu/13X>Ag/13X>Co/13X and Mn/13X>Cu/13X>Ce/13X>Ag/13X>Co/13X, respectively. The extent of ozone decomposition is responsible for the degree of oxidative decomposition of toluene over the Mn/13X catalyst. The addition of moisture (Relative Humidity of 25%) to the reaction mixture considerably enhanced the conversion of toluene and selectivity to carbon oxides from 49% to 61% and 38% to 53% respectively, on the Mn/13X catalyst. The two sets of experiment results reveal that the surface adsorbed by-products such as benzene, benzaldehyde, p-methyl phenol and oxalic acid are considerably oxidized to CO2 in the presence of moisture whereas in the absence of moisture these by-products are slowly oxidized. The activity data in the presence of ozone and moisture also reveal that the moisture has considerably enhanced the activation of surface adsorbed by-products than that of initial toluene oxidation. Based on the temperature programmed desorption and temperature programmed oxidation studies, the addition of moisture decreased the by-products accumulation thereby, reduced the catalyst deactivation and enhanced the extended oxidation of toluene on the Mn/13X zeolite

Application of pressure swing adsorption technology combined with 13X molecular sieves for the regenerative air cleaning systems with a dimethyl sulfide as a contaminant

353-360The use of pressure swing adsorption (PSA) system in the air cleaning technology for the application of regenerative air cleaning systems, which have wide applications in the defence sector has been reported. For this, a test procedure has been established and is elucidated for air purification using dimethyl sulfide (DMS) as a contaminant with 13X molecular sieves as the adsorbent at 4 kg/cm2. The dynamic adsorption capacities of 13X molecular sieves for DMS decreases from 14 to 0.3 wt% by increasing the flow rate from 3 to 15 lpm at 25°C, and at 4 kg/cm2. The flow rate and contact time are optimized as 6.5 lpm and 5.8 s, respectively for a selected PSA system. No DMS break through has been observed in 80 hr of continuous operation at an average feed concentration of 130 ppm. The 13X molecular sieves are further characterized by BET-SA, FT-IR, XRD and TPD. The TPD data reveal that the regeneration of 13X molecular sieves can be effectively achieved at ~180°C. The PSA system combined with 13X molecular sieves appears to be the promising technology for regenerative air purification applications and specific to the reduced sulfur compounds