Tailoring the Stabilization and Pyrolysis Processes of Carbon Molecular Sieve Membrane Derived from Polyacrylonitrile for Ethylene/Ethane Separation

For ethylene/ethane separation, a CMS (carbon molecular sieve) membrane was developed with a PAN (polyacrylonitrile) polymer precursor on an alumina support. To provide an excellent thermal property to PAN precursor prior to the pyrolysis, the stabilization as a pre-treatment process was carried out. Tuning the stabilization condition was very important to successfully preparing the CMS membrane derived from the PAN precursor. The stabilization and pyrolysis processes for the PAN precursor were finely tuned, and optimized in terms of stabilization temperature and time, as well as pyrolysis temperature, heating rate, and soaking time. The PAN stabilized at >250 °C showed improved thermal stability and carbon yield. The CMS membrane derived from stabilized PAN showed reasonable separation performance for ethylene permeance (0.71 GPU) and ethylene/ethane selectivity (7.62), respectively. Increasing the pyrolysis temperature and soaking time gave rise to an increase in the gas permeance, and a reduction in the membrane selectivity. This trend was opposite to that for the CMS membranes derived from other polymer precursors. The optimized separation performance (ethylene permeance of 2.97 GPU and ethylene/ethane selectivity of 7.25) could be achieved at the pyrolysis temperature of 650 °C with a soaking time of 1 h. The separation performance of the CMS membrane derived from the PAN precursor was comparable to that of other polymer precursors, and surpassed them regarding the upper bound trade off.

Physicochemical Characterization of Cherry Pits-Derived Biochar

Although the suitability of some biochars for contaminants’ sorption separation has been established, not all potential feedstocks have been explored and characterized. Here, we physicochemically characterized cherry pit biochar (CPB) pyrolyzed from cherry pit biomass (CP) at 500 °C, and we assessed their As and Hg sorption efficiencies in aqueous solutions in comparison to activated carbon (AC). The basic physicochemical and material characterization of the studied adsorbents was carried out using pH, electrical conductivity (EC), cation exchange capacity (CEC), concentration of surface functional groups (Boehm titration), and surface area (SA) analysis; elemental C, H, N analysis; and Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX). AsO43− anions and Hg2+ cations were selected as model contaminants used to test the sorption properties of the sorption materials. Characterization analyses confirmed a ninefold increase in SA in the case of CPB. The total C concentration increased by 26%, while decreases in the total H and N concentrations were observed. The values of carbonate and ash contents decreased by about half due to pyrolysis processes. The concentrations of surface functional groups of the analyzed biochar obtained by Boehm titration confirmed a decrease in carboxyl and lactone groups, while an increase in phenolic functional groups was observed. Changes in the morphology and surface functionality of the pyrolyzed material were confirmed by SEM–EDX and FTIR analyses. In sorption experiments, we found that the CPB showed better results in the sorption separation of Hg2+ than in the sorption separation of AsO43−. The sorption efficiency for the model cation increased in the order CP < CPB < AC and, for the model anion, it increased in the order CPB < CP < AC.

Numerical Study of Cylindrical Tropical Woods Pyrolysis Using Python Tool

In this paper, the thermal behavior of large pieces of wood pyrolysis has been modeled. Two mathematical models coupling heat transfer equations to chemical kinetics were used to predict the pyrolytic degradation of a 25 mm radius wood sample, assumed to be dry in the first model and wet in the second, when heated to 973.15 K. The reactions involved in the pyrolysis process are assumed to be endothermic. The diffusion of bounded water during the process is taken into account in the second model, where the heat transfer equation has been coupled to that of the diffusion of moisture. This model, although simple, provides more information on the drying and pyrolysis processes during the heating of wood, which is its originality. It can therefore be advantageously used to calculate the temperature distribution in a pyrolysis bed. The equations of the two models, discretized by an explicit finite difference method, were solved numerically by a program written in Python. The validation of both models against experimental work in the literature is satisfactory. The two models allow examination of the temperature profile in the radial direction of wood samples and highlighting of the effect of temperature on some thermal, physical and physicochemical characteristics.

Modeling of mechanism of obtaining mesostructural coal matrix in pyrolysis processes.

Reducing the role of coal in the energy balance of countries and the whole world sets the task of improving coal combustion technologies and creating new environmentally friendly processes for deep processing of coal. The production of high-quality raw materials for the metallurgical industry and other industries is a strategic task for the development of the country. In this study we try to use an Monte Carlo method to analyze and modeling of coke producing process in the device for continuous pyrolysis of organic materials in a thermally loaded layer.

Study of the Combustion , Pyrolysis Characteristics and Synergistic Effect of Co-hydrocharsation Products of Oil Shale and Rice HuskStudy of the Combustion , Pyrolysis Characteristics and Synergistic Effect of Co-hydrocharsation Products of Oil Shale and Rice Husk

Under the pressure of environmental problems and fossil energy shortage, countries all over the world are looking for fuel to replace fossil energy. Oil shale and rice husk are potential fuels, but they both have some problems, such as high ash content and low calorific value .In the present study,oil shale and rice husk were used as feedstock for the high quality fuel through hydrothermal approach,it provides a new way for the resource utilization of oil shale and rice.Thermogravimetric method was used to analyze the functional groups change and thermal transformation characteristics of mixed hydrochars prepared for oil shale(OS) and rice husk(RH) at different hydrothermal temperatures(150,200 and 250℃), including combustion and pyrolysis processes, and analyze the synergistic effects. Results showed that the co-hydrocharsization pretreatment had a significant effect on the thermal transformation behavior of oil shale and rice husk.On the one hand, the mixture of hydrocar has higher volatile content than its calculated value.On the other hand,a synergistic effect(promoting combustion and pyrolysis behavior) was found in both combustion and pyrolysis processes, and this effect was the most obvious when the hydrothermal temperature was around 200℃,and the characteristic peak of functional groups vibration was strong.Since the synergistic effect of pyrolysis process is lower than that of combustion process, co-hydrocharsation products are considered to be more suitable for combustion.These findings have positive significance of energy generation and utilization of organic waste by the combination of co-hydrocharsization modification and subsequent thermochemical process.

Activated carbon from agave wastes (agave tequilana) for supercapacitors via potentiostatic floating test

To prepare an efficient supercapacitor, an activated carbon from agave wastes was prepared and their electrochemical performance was evaluated as a novel electrode for supercapacitor. The carbon was prepared by two thermal pyrolysis processes under nitrogen atmosphere. The first pyrolysis was achieved at 500°C until the charring of the bagasse, in the second pyrolysis step, the char was impregnated with different mass ratios of KOH (1:2 − 1:4) and thermally treated at 800 or 900°C, for 1 h under N2 flow. The textural analysis showed that the activated carbon had a specific surface area of 1462 m2 g− 1 and depicted a type I isotherm (IUPAC) characteristic of a microporous carbon. Raman spectroscopy and XRD measurements confirm that the activated carbon contains a small graphitization degree and a disordered structure. The electrochemical study of the symmetric carbon supercapacitor was carried out in 1M Li2SO4 solution as the electrolyte. The electrochemical performance of the coin cell supercapacitor was evaluated under an accelerated ageing floating test consisting of potentiostatic steps at different voltages (1.5, 1.6 and 1.8 V) for 10 h followed by galvanostatic charge/discharge sequences, the overall procedure summarized a floating time up to 200 h. The highest capacitance was observed at a floating voltage of 1.5 V, with a large initial specific capacitance of 297 F g− 1.