Sulfur poisoning mechanism of three way catalytic converter and its grey relational analysis

Combining a detailed catalytic surface reaction mechanism with noble metal and promoter elementary reactions, a new three-way catalytic converter(TWC) reaction mechanism is established. Based on the new mechanism, steady condition numerical simulation is carried out, and the change of light-off temperatures and conversion efficiency with various SO2 contents is obtained. By grey relational analysis(GRA), the relational grade between conversion efficiency and SO2 content is obtained. And, the result shows that SO2 content has the most important influence on C3H6 and NOX conversion efficiency. This provides an important reference to the improvement of activity design of TWC, and may provide guidance for the condition design and optimization of TWC.

Molecular Simulation Study on Interaction of Thiophene Sulfides with Transition Metals

The computer molecular simulation technique was applied to study the chemisorption of thiophene and tetramethylthiophene as the model sulfides on the simple oxides and complex oxides of some transition metals as the catalytic materials. The study disclosed that the thiophene sulfides could enter into chemisorption with metal oxides such as VO, ZnO, NiO and Zn-Al-spinel. This interaction could lead to thiophene molecular structure deformation to be in an activated adsorption state, which could help to promote the conversion of thiophene sulfides in the course of catalytic cracking. The VO with a valence of 2 could provide relatively strong selective adsorption sites for the conversion of thiophene sulfides to apparently transform the molecular structures and electron cloud states of such heterocyclic sulfur compounds such as thiophene and tetramethylthiophene into an activated adsorption state. The effect of this interaction was more pronounced with respect to tetramethylthiophene.

An isotope study of the accumulation mechanisms of high-sulfur gas from the Sichuan Basin, southwestern China

The mechanism of hydrogen sulfide(H_2S) generation plays a key role in the exploration and development of marine high-sulfur natural gas, of which the major targets are the composition and isotope characteristics of sulfur-containing compounds.Hydrocarbon source rocks, reservoir rocks, natural gases and water-soluble gases from Sichuan Basin have been analyzed with an online method for the content of H_2S and isotopic composition of different sulfur-containing compounds. The results of comparative analysis show that the sulfur-containing compounds in the source rocks are mainly formed by bacterial sulfate reduction(BSR), and the sulfur compounds in natural gas, water and reservoir are mainly formed by thermal sulfate reduction(TSR). Moreover, it has been shown that the isotopically reversion for methane and ethane in high sulfur content gas is caused by TSR. The sulfur isotopic composition of H_2S in natural gas is inherited from the gypsum or brine of the same or adjacent layer,indicating that the generation and accumulation of H_2S have the characteristics of either a self-generated source or a near-source.

Genetic relationships between swamp microenvironment and sulfur distribution of the Late Paleozoic coals in North China

The genetic relationships between microenvironment of the Late Paleozoic peat-forming swamp and the sulfur contents of coal in North China have been studied by using coal-facies parameters involving gelification degree, tissue preservation index, vegetation index, transportation index, groundwater influence index, water medium indicator and swamp type index, etc. Among the various controlling factors of swamp microenvironment, swamp water medium elaborates a dominant action to sulfur accumulation in the marine-influenced coals; while coal-forming plant type, hydrodynamic state and water covering depth are more important to sulfur accumulation in the fresh water-influenced coals. Geological fractionation of sulfur isotopes reflects that sulfur accumulation experienced multi-stages evolution. Pyrite sulfurs formed earlier than organic sulfur and the sulfur isotopic δ34Sp shows lower values than organic sulfur isotopic δ34So. In the brine-influenced coals, sulfur accumulation processed relatively a long time span, the distribution of sulfur isotopes dispersed, and the coals are provided with high sulfur contents. In the fresh-water-influenced coals, sulfur accumulation occurred mainly at the syngenetic-penesyngenetic stage and the early diagenetic stage, and the total sulfur is lower and mainly composed of organic sulfur.

Application of MXenes in lithium-sulfur batteries

Although lithium-sulfur batteries are considered one of the most potential next-generation energy storage systems owing to their high-energy density, the dissolution and shuttle of intermediate lithium polysulfides primarily limit their commercial applications. Currently, the search for new materials for high-performance lithium-sulfur batteries has become a global research hotspot.MXenes, two dimensional inorganic compound comprising several layers of transition metal carbide, nitride, or car-bonitride,are actively investigated owing to their large specific surface area, good conductivity, and excellent cycle and rate performance.This article firstly reviews the breakthrough of MXenes in lithium-sulfur batteries, introduces the preparation methods and structural characteristics, and summarizes the specific applications and modification mechanisms in lithium-sulfur batteries.Then, the characteristics and advantages of MXenes as a composite electrode material for lithium-sulfur batteries are highlighted. Finally, the potential in future commercial applications is summarized.

Sulfur retention efficiency of clean coke produced by co-pyrolysis of coal with CaCO_(3) to substitute household coal

Raw coal is used by many suburban and rural households for cooking and heating and results in severe air pollution,especially problematic SO_(2) emissions.A source treatment strategy was proposed to reduce SO_(2) emissions,which used the co-pyrolysis of raw coal with a CaCO3 additive to produce clean coke.The effect of Ca/S molar ratio on the SO_(2) capture efficiency of clean coke was investigated,and the SO_(2) retention efficiency was optimized at a Ca/S molar ratio of 1.5.The sulfur retention mechanism of clean coke was attributed to:(1)CaCO3 decomposition to CaO and partial reaction of CaO with H2S to generate CaS during pyrolysis.(2)Transformation of the remaining sulfur in the clean coke to SO_(2) during combustion,capture by unreacted CaO to form CaSO_(4),and direct oxidation of CaS to CaSO_(4).The feasibility of SO_(2) emission reduction by clean coke in a practical household stove was verified.