Activated biocarbons derived from molasses as new tailored CO2 adsorbents.

An innovative and cost-effective method for enhancing CO2 capture by modifying the textural properties of derived activated biocarbons was explored. A molasses solution was prepared with a sucrose concentration of 1 mol/dm3. A two-step synthesis process was involved, which includes the hydrothermal synthesis of spherical carbonaceous materials from molasses followed by chemical activation. The carbonaceous material to activation agent ratio was studied from 1 to 4. The CO2 adsorption of all activated biocarbons was tested at 0, 10, and 20°C and a pressure of up to 1 bar. The results showed a significant correlation between CO2 adsorption and the textural properties of the activated biocarbons. The activated biocarbon with the highest CO2 adsorption of 7.1 mmol/g at 1 bar and 0°C was successfully produced by modifying with KOH. The selectivity of CO2 over N2 calculated on the basis of the Ideal Adsorbed Solution Theory was excellent (16.5). The Sips model was found to be the most suitable, and the isosteric heats of adsorption were also specified.

Biomass-based activated carbons produced by chemical activation with H3PO4 as catalysts for the transformation of α-pinene to high-added chemicals.

In the era of ecology and careful care for the environment, it becomes important to use renewable raw materials of plant origin, which are often more easily available and cheaper. One of the important and rapidly developing directions of research are works related to the use of waste plant biomass; an example of this trend is the production of activated carbons from food industry waste. One of the examples of the application of derived from biomass activated carbons can be using them as catalysts for the isomerization of terpene compounds. Carbons based on waste biomass are characterized by the minimal amount of waste formation during their manufacture, and their use in the isomerization reaction allows to obtain high conversion of organic raw material and high selectivities of transformation to the desired products, making these carbons environmentally friendly substitutes for the catalysts used usually in this process. In this work, obtained carbonaceous catalysts were tested in the process of isomerization of α-pinene to high value chemicals (mainly camphene and limonene). Under the most favorable conditions (activated carbon from sunflower husks content in reaction mixture 5 wt%, temperature 180 °C, and reaction time 100 min), α-pinene was completely converted (conversion 100 mol%) with high selectivity towards camphene (54 mol%). To prepare activated carbons, biomass precursors (orange peels, sunflower husks, spent coffee grounds) were activated with 85% H3PO4 through the chemical activation. The obtained materials were characterized by such methods as sorption N2 at - 196 °C, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and X-ray fluorescence (XRF) to determine the relationship between their textural-chemical properties and catalysts activity in isomerization process. The synthesized materials were characterized by a specific surface area in the range of 930-1764 m2, total pore volume in the range of 0.551-1.02 cm3/g, and total acid-site concentrations in the range of 1.47-2.33 mmol/g. These results showed that textural parameters of the obtained activated carbons have the important role in the isomerization of α-pinene.

Carbon Dioxide Adsorption over Activated Carbons Produced from Molasses Using H2SO4, H3PO4, HCl, NaOH, and KOH as Activating Agents.

Cost-effective activated carbons for CO2 adsorption were developed from molasses using H2SO4, H3PO4, HCl, NaOH, and KOH as activating agents. At the temperature of 0 °C and a pressure of 1 bar, CO2 adsorption equal to 5.18 mmol/g was achieved over activated carbon obtained by KOH activation. The excellent CO2 adsorption of M-KOH can be attributed to its high microporosity. However, activated carbon prepared using HCl showed quite high CO2 adsorption while having very low microporosity. The absence of acid species on the surface promotes CO2 adsorption over M-HCl. The pore size ranges that are important for CO2 adsorption at different temperatures were estimated. The higher the adsorption temperature, the more crucial smaller pores were. For 1 bar pressure and temperatures of 0, 10, 20, and 30 °C, the most important were pores equal and below: 0.733, 0.733, 0.679, and 0.536 nm, respectively.

FeCl3-Modified Carbonaceous Catalysts from Orange Peel for Solvent-Free Alpha-Pinene Oxidation.

The work presents the synthesis of FeCl3-modified carbonaceous catalysts obtained from waste orange peel and their application in the oxidation of alpha-pinene in solvent-free reaction conditions. The use of waste orange peel as presented here (not described in the literature) is an effective and cheap way of managing this valuable and renewable biomass. FeCl3-modified carbonaceous materials were obtained by a two-stage method: in the first stage, activated carbon was obtained, and in the second stage, it was modified by FeCl3 in the presence of H3PO4 (three different molar ratios of these two compounds were used in the studies). The obtained FeCl3-modified carbon materials were subjected to detailed instrumental studies using the methods FT-IR (Fourier-transform Infrared Spectroscopy), XRD (X-ray Diffraction), SEM (Scanning Electron Microscope), EDXRF (Energy Dispersive X-ray Fluorescence) and XPS (X-ray Photoelectron Spectroscopy), while the textural properties of these materials were also studied, such as the specific surface area and total pore volume. Catalytic tests with the three modified activated carbons showed that the catalyst obtained with the participation of 6 M of FeCl3 and 3 M aqueous solutions of H3PO4 was the most active in the oxidation of alpha-pinene. Further tests (influence of temperature, amount of catalyst, and reaction time) with this catalyst made it possible to determine the most favorable conditions for conducting oxidation on this type of catalyst, and allowed study of the kinetics of this process. The most favorable conditions for the process were: temperature of 100 °C, catalyst content of 0.5 wt% and reaction time 120 min (very mild process conditions). The conversion of the organic raw material obtained under these conditions was 40 mol%, and the selectivity of the transformation to alpha-pinene oxide reached the value of 35 mol%. In addition to the epoxy compound, other valuable products, such as verbenone and verbenol, were formed while carrying out the process.

The Studies on α-Pinene Oxidation over the TS-1. The Influence of the Temperature, Reaction Time, Titanium and Catalyst Content.

The work presents the results of studies on α-pinene oxidation over the TS-1 catalysts with different Ti content (in wt%): TS-1_1 (9.92), TS-1_2 (5.42), TS-1_3 (3.39) and TS-1_4 (3.08). No solvent was used in the oxidation studies, and molecular oxygen was used as the oxidizing agent. The effect of titanium content in the TS-1 catalyst, temperature, reaction time and amount of the catalyst in the reaction mixture on the conversion of α-pinene and the selectivities of appropriate products was investigated. It was found that it is most advantageous to carry out the process of α-pinene oxidation in the presence of the TS-1 catalyst with the titanium content of 5.42 wt% (TS-1_2), at the temperature of 85 °C, for 6 h and with the catalyst TS-1 content in the reaction mixture of 1 wt%. Under these conditions the conversion of α-pinene amounted to 34 mol%, and the selectivities of main products of α-pinene oxidation process were: α-pinene oxide (29 mol%), verbenol (15 mol%) and verbenone (12 mol%). In smaller quantities also campholenic aldehyde, trans-pinocarveol, myrtenal, myrtenol, L-carveol, carvone and 1,2-pinanediol were also formed. These products are of great practical importance in food, cosmetics, perfumery and medicine industries. Kinetic studies were also performed for the studied process.

Activated Carbon Modification towards Efficient Catalyst for High Value-Added Products Synthesis from Alpha-Pinene.

DT0-activated carbons modified with HCl and HNO3 acids, which were used for the first time in the catalytic process of alpha-pinene isomerization, are presented in this study. The carbon materials DT0, DT0_HCl, DT0_HNO3, and DT0_HCl_HNO3 were examined with the following methods: XRF, SEM, EDX, XPS, FT-IR, XRD, and N2 adsorption at -196 °C. It was shown that DT0_HCl_HNO3-activated carbon was the most active material in the alpha-pinene isomerization process. Detailed studies of alpha-pinene isomerization were carried out over this carbon by changing the reaction parameters such as time (5-180 min) and temperature (60-175 °C). The 100% conversion of alpha-pinene was achieved at the temperature of 160 °C and catalyst content of 5 wt% after 3 h over the DT0_HCl_HNO3 catalyst. Camphene and limonene were the main products of the alpha-pinene isomerization reaction.

Activated Carbons Obtained from Orange Peels, Coffee Grounds, and Sunflower Husks-Comparison of Physicochemical Properties and Activity in the Alpha-Pinene Isomerization Process.

This work presents studies on the preparation of porous carbon materials from waste biomass in the form of orange peels, coffee grounds, and sunflower seed husks. The preparation of activated carbons from these three waste materials involved activation with KOH followed by carbonization at 800 °C in an N2 atmosphere. This way of obtaining the activated carbons is very simple and requires the application of only two reactants. Thus, this method is cheap, and it does not generate much chemical waste. The obtained activated carbons were characterized by XRD, SEM, XPS, and XRF methods. Moreover, the textural properties, acidity, and catalytic activity of these materials were descried. During catalytic tests carried out in the alpha-pinene isomerization process (the use of the activated carbons thus obtained in the process of alpha-pinene isomerization has not been described so far), the most active were activated carbons obtained from coffee grounds and orange peels. Generally, the catalytic activity of the obtained materials depended on the pore size, and the most active activated carbons had more pores with sizes of 0.7-1.0 and 1.1-1.4 nm. Moreover, the presence of potassium and chlorine ions in the pores may also be of key importance for the alpha-pinene isomerization process. On the other hand, the acidity of the surface of the tested active carbons did not affect their catalytic activity. The most favorable conditions for carrying out the alpha-pinene isomerization process were the same for the three tested activated carbons: temperature 160 °C, amount of the catalyst 5 wt.%, and reaction time 3 h. Kinetic studies were also carried out for the three tested catalysts. These studies showed that the isomerization over activated carbons from orange peels, coffee grounds, and sunflower seed husks is a first-order reaction.

CO2 Adsorption on Activated Carbons Prepared from Molasses: A Comparison of Two and Three Parametric Models.

Activated carbons with different textural characteristic were derived by the chemical activation of raw beet molasses with solid KOH, while the activation temperature was changed in the range 650 °C to 800 °C. The adsorption of CO2 on activated carbons was investigated. Langmuir, Freundlich, Sips, Toth, Unilan, Fritz-Schlunder, Radke-Prausnitz, Temkin-Pyzhev, Dubinin-Radushkevich, and Jovanovich equations were selected to fit the experimental data of CO2 adsorption. An error analysis (the sum of the squares of errors, the hybrid fractional error function, the average relative error, the Marquardt's percent standard deviation, and the sum of the absolute errors) was conducted to examine the effect of using various error standards for the isotherm model parameter calculation. The best fit was observed to the Radke-Prausnitz model.

Studies of the kinetics of ammonia decomposition on promoted nanocrystalline iron using gas phases of different nitriding degree.

Promoted nanocrystalline iron was nitrided in a differential reactor equipped with systems that made it possible to conduct both thermogravimetric measurements and hydrogen concentration analyses in the reacting gas mixture. The nitriding process, particularly catalytic ammonia decomposition reaction, was investigated under an atmosphere of ammonia-hydrogen mixtures, under atmospheric pressure. Ammonia concentrations, and so nitriding potentials, were changed gradually from 0 to 100% at the inlet of reactor. The temperature was changed in the range of 475-500 degrees C. While values of nitriding potential were increasing, the rate of catalytic ammonia decomposition on alpha-Fe(N) was increasing too, but on mixture of alpha-Fe(N) with gamma'-Fe(4)N nitride the rate was decreasing. The obtained results were interpreted on the basis of the adsorption range model. New equations describing the catalytic ammonia decomposition reaction rate as a function of the logarithm of the nitriding potential of the gas phase, temperature, and nitriding degree of solid samples were proposed.