Acid Mesoporous Carbon Monoliths from Lignocellulosic Biomass Waste for Methanol Dehydration

Abstract

Activated carbon monoliths (ACMs), with 25 cells/cm2, were prepared from the direct extrusion of Alcell, Kraft lignin and olives stones particles that were impregnated with phosphoric acid, followed by activation at 700 °C. These ACMs were used as catalysts for methanol dehydration reaction under air atmosphere. ACM that was prepared from olive stone and at impregnation ratio of 2, OS2, showed the highest catalytic activity, with a methanol conversion of 75%, a selectivity to dimethyl ether (DME) higher than 90%, and a great stability under the operating conditions studied. The results suggest that the monolithic conformation, with a density channel of 25 cells/cm2 avoid the blockage of active sites by coke deposition to a large extent. Methanol conversion for OS2 was reduced to 29% in the presence of 8%v water, at 350 °C, although the selectivity to DME remained higher than 86%. A kinetic model of methanol dehydration in the presence of air was developed, while taking into account the competitive adsorption of water. A Langmuir-Hinshelwood mechanism, whose rate-limiting step was the surface reaction between two adsorbed methanol molecules, represented the experimental data under the conditions studied very well. An activation energy value of 92 kJ/mol for methanol dehydration reaction and adsorption enthalpies for methanol and water of −12 and −35 kJ/mol, respectively, were obtained.

Kinetic modeling of CO2+CO hydrogenation to DME over a CuO-ZnO-ZrO2@SAPO-11 core-shell catalyst

“…The implementation of the CZZr@S-11 catalyst on a larger scale requires having a kinetic model suitable for the design of the reactor, which allows assessing the effects of the process conditions on products yields and distribution. Given the industrial relevance of the main reactions involved, the mechanisms and kinetic models for methanol synthesis [46][47][48][49][50]; its dehydration [51][52][53][54] and WGS reaction [55][56][57][58][59] are well established in the literature. However, these kinetic equations have been obtained under the suitable conditions (pressure, temperature) for each of these reactions and with a composition of the reaction medium that is also different from that in the direct synthesis of DME.…”

Biomass—a Renewable Resource for Carbon Materials (2nd Edition)

“…They are easily produced by pseudo-sintering dehy- Correlation between S u and S BET of the selected carbon monoliths made from whey (black squares). The red symbols are results of other activated carbon monoliths found in the literature: (Liu, 2006) [19]; (Rangel-Sequeda, 2022) [20]; (Du, 2020) [57]; (Li, 2024) [58]; (Ibeh, 2019) [59]; (Guo, 2019) [60]; (Tang, 2020) [61]; (Gadkaree, 1998) [62].…”

Customised Microporous Carbon 3D Structures with Good Mechanical Properties and High Nitrogen Content Obtained from Whey Powders

“…Strategies based on binder-free monoliths from biomass precursors are scarce. Indeed, a very interesting methodology comprises the formation of slurries from activating agents such as H 3 PO 4 or ZnCl 2 and lignocellulosic precursors [23][24][25]. These slurries are prone to be either uniaxially compressed or extruded to obtain monoliths that withstand carbonisation and washing of the activation by-products.…”