English abstract
The achievement of the overarching goal of eliminating all greenhouse gas (GHG)
emissions worldwide by the year 2050 requires industry to embrace alternative fuels that
can replace diesel and are environmentally friendly. One such fuel is dimethyl ether. The
main aim of this study is to examine the production of dimethyl ether through the process
of methanol dehydration, using a new formulating catalyst consisting of metal oxide
supported on activated carbon.
The synthesis of the activated carbon catalyst included the use of date seeds, a readily
available and sustainable natural waste resource. The carbonized date seeds were enriched
with metal oxides including molybdate, tungstate, and cobalt, comprising around 4% of
the total composition. A range of analytical techniques, such as X-ray diffraction (XRD),
Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy with
energy-dispersive X-ray spectroscopy (SEM/EDS), Brunauer-Emmett-Teller (BET)
analysis, and X-ray photoelectron spectroscopy (XPS), were used to conduct a thorough
characterization of the catalysts that were synthesized. The characterization data obtained
in this study provide prove of the successful impregnation of metal oxides into the
activated carbon substrate. To determine the optimal catalyst for the process of methanol
dehydration, four types of catalysts, namely AC, AC-4% Mo, AC-4% W, and AC-4% Co,
were used in a controlled experimental setting. The results of this investigation suggest
that the catalyst including activated carbon supported by 4% molybdate exhibits enhanced
efficacy in comparison to other catalysts, leading to a higher concentration of dimethyl
ether. The production of dimethyl ether was modelled and optimized using the most
efficient catalyst using response surface methodology (RSM) with the assistance of the
Design Expert program. The investigation included several process parameters, including
temperature (varying from 150 to 250 °C), reaction residence time (ranging from 1 to 3
hr), and catalyst weight (ranging from 1 to 3 g). Based on the 2FI model postulated by
RSM, it was determined that the variable with the most significant impact among the
tested parameters was the process temperature. Increasing in the reaction temperature was
found to be associated with a concomitant elevation in the concentration of dimethyl ether.
The best conditions for dimethyl ether synthesis were determined to be a process
temperature of 249.63 °C, a residence time of 1.00 hr, and a catalyst weight of 1.03 g.
Additionally, a study was undertaken to test the effects of temperatures beyond 250°C on
the synthesis of dimethyl ether, which indicated a decrease in its production beyond this
temperature threshold. While increasing the loading of metal oxide above 4%w/w results
in an enhanced production of dimethyl ether. The results indicate that the most favorable
ratio of metal oxide to activated carbon is 6% w/w. Moreover, the recycled catalysts were
regenerated and used again in methanol dehydration reaction. The evaluation findings
revealed a reaction that may be deemed effective, but with a reduced performance of 73%
when compared to the performance shown by the original catalyst.
