Investigation of the Adsorption Behavior of Organic Sulfur in Coal via Density Functional Theory (DFT) Calculation and Molecular Simulation.

In this paper, we have investigated the chemical adsorption behavior of O2 on five types of organic sulfur (thiol, sulfoxide, thioether, sulfone, and thiophene) in polycyclic aromatic hydrocarbon (PAH) sheets using density functional theory (DFT) calculations. Here, the adsorption energy of O2-organic sulfur exceeds that of O2-PAH. Sulfone tends to be more favorable for oxidation reactions than other organic sulfur compounds and PAH by energy gap and deformation charge density analyses. A large charge transfer occurs between O2 and organic sulfur compounds by charge analysis. A radical distribution function (RDF) analysis shows that O2/CO2/N2 is preferentially adsorbed on nitrogen/sulfur/oxygen-containing functional groups in coal. To inhibit the reaction of sulfur-containing coal with oxygen, the physical adsorption of pure gas (CO2/O2/N2) and binary mixed gases (CO2 + O2/N2 + O2/CO2 + N2) is conducted at different temperatures and geological depths using molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations. The adsorption capacities of five types of organic sulfur with respect to the pure gases decrease with increasing temperature and increase with increasing depth. For O2/CO2, CO2/N2, and O2/N2 binary gas systems, the order with respect to adsorption amount is CO2 > O2 > N2. The factor of adsorption capacities is also evaluated, and the results show that pore volume plays a key role in adsorption behavior.

Investigation of a Ni-Modified MCM-41 Catalyst for the Reduction of Oxygenates and Carbon Deposits during the Co-Pyrolysis of Cellulose and Polypropylene.

Catalytic fast co-pyrolysis of biomass and plastic is an effective method to achieve high-quality bio-oil production. In this work, (Ni)-MCM-41 catalysts with different Ni loadings were prepared and characterized in detail by using a variety of advanced analytical techniques, and the effects on the catalytic performance were analyzed by micropyrolysis with gas chromatography mass spectrometry (Py-GC/MS) and thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) methods. The results showed that an appropriate amount of Ni addition can effectively modulate the physicochemical properties of MCM-41. For a Ni loading of 25.1 wt % (Cat-C), the catalyst showed an optimal catalytic performance, a decrease in the proportion of oxygenated compounds in the product from 35.6 (MCM-41) to 13.4%, and an increase in the relative total amount of olefins plus aromatics from 62.2 (MCM-41) to 84.6%. The excellent catalytic performance of Cat-C can be ascribed to a balancing of its proper physical structural properties, appropriate acidity, strong metal-carrier interaction, high metal dispersion, and excellent compatibility balance between active and acidic sites.

Catalytic co-pyrolysis of cellulose and polypropylene over all-silica mesoporous catalyst MCM-41 and Al-MCM-41.

Fast pyrolysis is one of the most economical and efficient technologies to convert biomass to bio-oil and valuable chemical products. Co-pyrolysis with hydrogen rich materials such as plastics over zeolite catalysts is one of the significant solutions to various problems of bio-oil such as high oxygen content, low heat value and high acid content. This paper studied pyrolysis of cellulose and polypropylene (PP) separately and co-pyrolysis of cellulose and PP over MCM-41 and Al-MCM-41. The pyrolysis over different heating rates (10K/min, 20K/min, 30K/min) was studied by Thermogravimetry Analysis (TGA) and kinetic parameters were obtained by Coats-Redfern method and isoconversion method. TG and DTG data shows that the two catalysts advance the pyrolysis reaction of PP significantly and reduce its peak temperature of DTG curve from 458°C to 341°C. The activation energy of pyrolysis of PP also has a remarkable reduction over the two catalysts. Py-GC/MS method was used to obtain the product distribution of pyrolysis of cellulose and PP separately and co-pyrolysis of cellulose and PP over MCM-41 and Al-MCM-41 at constant temperature of 650°C. Experiment results proved that co-pyrolysis with PP bring significant changes to the product distribution of cellulose. Oxygenated compounds such as furans are decreased, while yields of olefins and aromatics increase greatly. The yield of furans increases with the catalysis of MCM-41 as for the pyrolysis of cellulose and co-pyrolysis, while the yield of olefins and aromatics both experience significant growth over Al-MCM-41, which can be explained by the abundant acid centers in Al-MCM-41.