Physically activated wheat straw-derived biochar for biomass pyrolysis vapors upgrading with high resistance against coke deactivation

Abstract

Wheat straw-derived biochars (produced through slow pyrolysis at 500 °C and 0.1 MPa) were physically (with CO2) and chemically (with K2CO3) activated to assess their performance as renewable and low-cost catalysts for biomass pyrolysis vapors upgrading. Preliminary cracking experiments, which were carried out at 700 °C using a mixture of four representative model compounds, revealed a clear correlation between the volume of micropores of the catalyst and the total gas production, suggesting that physical activation up to a degree of burn-off of 40% was the most interesting activation route. Next, steam reforming experiments were conducted using the most microporous material to analyze the effect of both the bed temperature and gas hourly space velocity (GHSV) on the total gas production. The results showed a strong dependence between the bed temperature and the total gas production, with the best result obtained at the highest temperature (750 °C). On the other hand, the change in GHSV led to minor changes in the total gas yield, with a maximum achieved at 14500 h-1. Under the best operating conditions deduced in the previous stages, the addition of CO2 into the feed gas stream (partial pressure of 20 kPa) resulted in a total gas production of 98% with a H2/CO molar ratio of 2.16. This good result, which was also observed during the upgrading of the aqueous phase of a real biomass pyrolysis oil, was ascribed to the relatively high coke gasification rate, which refresh the active surface area preventing deactivation by coke deposition.

Activated Biochar-Based Metal Catalysts for Steam Reforming of Pyrolysis Bio-Oil Model Compound

“…The biochar used in this study was produced by slow pyrolysis of binder-free wheat straw pellets (9 mm OD and 10-13 mm long). More details about the pyrolysis set up can be found in our previous work [6]. The pristine biochar, which had an extremely low specific surface area (2 m 2 g -1 ), was physically activated with pure CO2 at 700 °C and 1.00 MPa in order to increase its textural properties (specific surface area and pore size distribution).…”

“…A K-type thermocouple was placed in the center of the catalytic bed to monitor the system temperature. The acetic acid (AcOH) used for the screening of the catalysts performance was diluted with bi-distilled water to achieve a steam to carbon molar ratio (S/C) of 4 [6]. The liquid was stored in a pressurized tank and fed to an evaporator by means of a liquid mass flow controller.…”

Recent Solutions for Efficient Carbonyl Sulfide Hydrolysis: A Review

“…Carbon-Based Materials. The interest toward carbon-based materials has progressively increased in the past 10 years, 37,38 mostly because of the relatively low environmental impact resulting in their employment in a wide number of applications, for example, hydrocarbon conversion 39,40 and synthesis. 41,42 Also, in the scenario of environmental catalysis, activated carbons (AC) and biochar have been extensively studied and applied for removal treatments.…”

“…The interest toward carbon-based materials has progressively increased in the past 10 years, , mostly because of the relatively low environmental impact resulting in their employment in a wide number of applications, for example, hydrocarbon conversion , and synthesis. , Also, in the scenario of environmental catalysis, activated carbons (AC) and biochar have been extensively studied and applied for removal treatments. Activated carbons are well-known coal-derived materials, with a widespread application in wastewater treatment and H 2 S adsorption. − They are actually expensive materials, as they require high energy-intensive thermal activation in order to achieve the desirable adsorption properties. , On the other hand, biochar is less costly, and more important, it is a biomass-derived material, so even more environmentally friendly.…”

Preparation and characterization of powdered and granular activated carbon from Palmae biomass for mercury removal

“…The use of chemical reagents is preferable since low temperature and shorter time is involved. Besides, the extra surface area added to improve on the reactivity of the activated carbon (Di Stasi et al 2019). Among the activating reagents, potassium hydroxide is considered the best since it generates high surface area and high porosity of the activated carbon (Yacob et al 2010;Yang et al 2019;Wan et al 2019;Vazquez et al 2002).…”