Leonila C. Abella

Kinetic study on the dehydration of tert‐butyl alcohol catalyzed by ion exchange resins

The dehydration of tert-butyl alcohol (TBA) in the liquid phase was studied by using an ion exchange resin, Amberlyst 15 (A15) in the H+ form. Experiments were carried out both in a semi-batch reactor and in a continuous stirred tank reactor (CSTR) with wet or dry resins. The results with the dry resin in the semi-batch reactor were different from those with the wet resin due to the swelling of resin in the presence of water. However, the results in CSTR agreed well with those in the semi-batch reactor using the wet resin. A rate equation that considered the inhibition of water was formulated. The experimental results agreed well with the calculated ones.

Effect of Cu on Ni Catalyst for the Thermal Decomposition of Methane: A Molecular Dynamics Investigation

investigated via ab initio DMol 3 molecular dynamics simulation. Initial simulation used the Local Density Approximation (LDA) with the Perdew-Wang 1992 (PWC) specific local exchange correlation functional, Gaussian double zeta plus polarization function basis set (DNP) at gamma (1x1x1) k-point calculation and orbital cut-off of 3.4 A, with additional parameters: T = 1300K, time step = 2.5 fs, simulation time of 0.25 ps, with canonical NVT (constant amount (N), volume (V) and temperature) thermodynamic ensemble and Generalized Gradient Moment (GGM) thermostat. Results demonstrate the capacity of Ni for carbon deposition, whereas the addition of Cu resulted in the following: promoted the disjoining of the H atoms from the C atom allowing the C atom to form more bonds with the metal surface; accelerated the initial catenation of the CH4 atom (Ni = 12.5 fs; Ni-Cu = 10.0 fs); and delayed the initial deposition of C atom on the metal surface (Ni = 30.0 fs; Ni-Cu = 37.5 fs). Examination of the decomposition mechanism revealed the initial formation of a metal-H bond between one of the H atoms of the CH4 molecule and one of the metal atoms, followed by the re-formation of a transition bond between the C atom and the H atom bonded to the metal. This brings the C atom towards the metal surface for deposition after which the transition C-H bond is broken. This implied role of hydrogen in the deposition of carbon agrees with experimental results in literature.

Hydrogen Production via Thermo Catalytic Decomposition of Methane over Bimetallic Ni-Cu/AC Catalysts: Effect of Copper Loading and Reaction Temperature

 Abstract—This study investigated on the effect of copper loading on the catalytic performance of Ni/AC catalysts at various reaction temperatures. Cu loading was varied from 0%, 5%, 10% and 15%, and the reaction temperatures tested were 600° C, 750° C and 900° C. The reaction was carried out in a U-tube quartz plug flow micro-reactor, and allowed to proceed for 8 hours. The highest initial methane conversion of 29.95% was observed on the Ni/AC catalyst without Cu loading at 900° C. However, this catalyst rapidly deactivated after only 3 hours. On the other hand, the 6.7Ni-5Cu/AC catalyst at 900° had an initial methane conversion of 27%, but slower catalyst deactivation was observed. This is due to the positive effect of copper on the metallic Ni particles, enhancing the ability of the catalyst to accumulate carbon, thus increasing stability at high temperatures. Statistical analysis of the experimental data using two-way ANOVA method determined that for a 95% confidence interval, only reaction temperature had a significant effect on the activity of the Ni-Cu/AC catalysts, while Cu loading was an insignificant factor. XRD results showed the formation of Ni3C crystallite for all catalyst samples except 6.7Ni-5Cu/AC, which may have contributed to catalyst deactivation. Also, SEM images of the spent 6.7Ni-5Cu/AC catalyst, which exhibited the best catalytic performance, showed the formation of valuable filamentous carbon, which may be used extensively in many other fields of application.

CNT Production through the Catalytic Decomposition of Methane on Ni-Cu/γ-Al2O3 at Varying Ni-Cu Ratios: An Ab Initio and Empirical Investigation

The decomposition of a single CH4 molecule on Ni-Cu/γ-Al2O3 catalyst surface with varying Ni-Cu ratios for CNT production was determined through ab initio calculations with experimental verification. The structural model was based on empirical XRD characterization data from experimentally-prepared catalysts. Structural relaxation and ab initio molecular dynamics simulations were performed using Materials Studio 2016 DMol with the Local Density Approximation – Vosko-Wilk-Nusair (LDA-VWN) exchange correlation functional, Gaussian double zeta plus polarization function basis set (DNP) at 2 × 2 ×1 k-point calculation and orbital cut-off of 3.5 Å, with simulation parameters: T = 1,148 K, time step = 1.9 fs (78.5 a.u.), simulation time of 0.38 ps, with the canonical NVT (constant amount (N), volume (V) and temperature (T)) thermodynamic ensemble and Generalized Gaussian Moment (GGM) thermostat. Ab initio simulation data predicted a decrease in C deposition time with 1:1 Ni-Cu/γ-Al2O3. Empirical data from TGA and SEM analyses confirmed higher CNT yield on 1:1 Ni-Cu/γ-Al2O3. Ab initio calculations indicated an increase in binding energy magnitude with the formation of a Ni-Cu alloy. This increase in energy is attributed to the calculated decrease in crystal size, and was verified by the decrease in average CNT diameter produced on 1:1 Ni-Cu/γ-Al2O3. These findings demonstrate the viability of CTDM as a technology for CNT production, as well as its adaptability to simpler catalytic systems for industrial or commercial applications.

Catalytic Dry Reforming of Methane Using Ni/MgO-ZrO2 Catalyst

Publisher Summary This study focuses on the use of 15% Ni/MgO-ZrO2 as a catalyst for CH4 dry reforming where the high basicity of MgO and the mobile oxygen species provided by ZrO2 are expected to provide high catalyst activity and stability. Methane dry reforming is one of the important routes in natural gas processing. Here, CH4 and CO2 are converted into syngas CO and H2 which later can be used as feedstock for the processing of other chemicals such as CH3OH and NH3. Methane dry reforming requires the use of catalysts, often nickel-based, to increase the reaction rate. To date, the dry reforming of methane has limited commercial application due to the rapid deactivation of the catalysts. The reactants contain carbon species that has a high potential of blocking active sites on the catalyst surface, deactivating them.