Journal of Applied Research in Chemical-Polymer Engineering

Abstract Research subject: One of the common problems in natural gas transmission lines is congestion and pressure drop in gas transmission pipes due to the formation of gas hydrates. Gas hydrates are stable crystalline compounds that are formed from the contact of water molecules with some gas molecules of the right size and under the right thermodynamic conditions (low temperature and high pressure). These compounds are studied from both thermodynamic and kinetic perspectives. Despite many studies in the thermodynamic part of hydrates, the kinetics of hydrates require further study.
Research approach: To this end, in order to determine the equilibrium conditions of natural gas hydrate, 5 different experiments were conducted with a natural gas sample from Gas and Liquefied Gas Refinery 1300 in the temperature range of 285.5, 281.5, 276.21, 275.59, 273.92 Kelvin and pressure of 41.1, 28.2, 18.84, 13.4, 11.5 bar in a reactor using the constant volume method.
Main results: Based on the experimental data, the mass transfer coefficient was 0.243, 0.159, 0.153, 0.094, 0.131 meters per second, respectively, and the molecular diffusion coefficient was 4.516(×10-09), 4.785(×10-09), 1.175(×10-09), 2.847(×10-09), 1.147(×10-09) m2/s. These results show that with increasing reactor temperature (at constant pressure), the mass transfer coefficient decreases and the molecular diffusion coefficient increases. Also, with increasing pressure (at constant temperature), the mass transfer coefficient increases and the molecular diffusion coefficient decreases, which is consistent with empirical equations. Statistical analysis of the results revealed that the reactor pressure parameter has a greater effect on the mass transfer coefficient than temperature. Furthermore, statistical examination showed that temperature is a more influential parameter on the molecular diffusion coefficient (DAB) of natural gas in water.

Abstract Research subject: Synthesis and characterization of a functionalized magnetic nanosorbent (cobalt ferrite–triaminopropyltriethoxysilane–chitosan), optimization and modeling of adsorption conditions, and investigation of the kinetics of monoethylene glycol removal from wastewater.
Research approach: In this research, a functionalized magnetic nanosorbent was used to remove the pollutant monoethylene glycol (MEG) from wastewater. This adsorbent was synthesized by attaching chitosan to the surface of magnetic cobalt ferrite nanoparticles (CoFe2O4) using triaminopropyltriethoxysilane (APTES) as a coupling agent. Chitosan has a high ability to absorb organic pollutants such as monoethylene glycol due to its amino and hydroxyl functional groups. Furthermore, the use of chitosan enhances the surface area and consequently improves the adsorption capacity. The magnetic properties of cobalt ferrite enable easy separation of the adsorbent from the wastewater sample using an external magnetic field. The properties of the synthesized adsorbent were investigated using Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The optimal adsorption conditions, including pH, contact time, and adsorbent recovery over adsorption–desorption cycles, were also determined.
Main results: The optimal pH value for glycol adsorption from wastewater by the functionalized magnetic nanosorbent was determined to be 6, and the equilibrium contact time was 5 minutes, indicating the high availability of active adsorption sites. Furthermore, the change in adsorption capacity after 10 adsorption–desorption cycles was less than 21%, indicating the high recovery capability and economic feasibility of the adsorbent. Adsorption kinetic data were analyzed using three kinetic models: pseudo-first-order, pseudo-second-order, and intraparticle diffusion. Given the higher correlation coefficient for the pseudo-second-order model (R2 = 0.9951), the adsorption of glycol on the synthesized adsorbent is best described by this model.

Abstract Research subject:
The kinetics of xylene isomerization reaction on Mo-Pt @ZSM5 catalyst has not been investigated so far. In this research, the single reversible reaction of meta-xylene to para-xylene has been studied to model this process. Considering that the feed of the industrial unit has only small amounts of non-xylene compounds, it seems reasonable regardless of other reactions and the results of this research also confirm it.
Research approach:
The desired reaction was carried out in the gas phase and constant temperatures of 375 ^oC and 378 ^oC on Mo-Pt @ZSM5 catalyst. The feed is taken from an industrial unit. In each test, the temperature is considered constant. In this research, in order to obtain a simple model, only the reversible reaction of meta-xylene to para-xylene is considered. The forward speed constant is considered as an adjustable parameter, and the backward reaction speed constant is calculated from the (meta-xylene)-(para-xylene) equilibrium constant reported in the literature. Since other reactions are neglected, the total mole fraction of meta-xylene and para-xylene is assumed to be constant and equal to their sum in the feed, and the mole fraction of ortho-xylene is calculated from the (meta-xylene)-(ortho-xylene) equilibrium constant reported in the literature. Using the mass balance and performance equation of the packed column as well as Ergun's equation to estimate the pressure changes along the column, a suitable differential equation system was proposed in this research and solved numerically using the ode45 function in MATLAB.
Main results: both the experimental data and the simulation results with the Aspen HYSYS software show that the temperature has little effect on the obtained results in the investigated temperature range. The optimal value of the reaction rate constant of metaxylene to paraxylene for the forward reaction is 1340 cm³ of product per gram of catalyst per hour. For the reverse reaction, it is obtained from the equilibrium constant data in terms of temperature. The results and the proposed simple kinetic model give a good prediction of the experimental data.