Wei-Ping Pan

Bio: Wei-Ping Pan is an academic researcher from North China Electric Power University. The author has contributed to research in topics: Mercury (element) & Coal. The author has an hindex of 45, co-authored 250 publications receiving 8121 citations. Previous affiliations of Wei-Ping Pan include University of Montana & Chinese Academy of Sciences.

Thermal Degradation Chemistry of Alkyl Quaternary Ammonium Montmorillonite

Abstract: The thermal stability of organically modified layered silicate (OLS) plays a key role in the synthesis and processing of polymer-layered silicate (PLS) nanocomposites. The nonoxidative thermal degradation of montmorillonite and alkyl quaternary ammonium-modified montmorillonite were examined using conventional and high-resolution TGA combined with Fourier transform infrared spectroscopy and mass spectrometry (TG−FTIR−MS) and pyrolysis/GC−MS. The onset temperature of decomposition of these OLSs was approximately 155 °C via TGA and 180 °C via TGA−MS, where TGA−MS enables the differentiation of water desorbtion from true organic decomposition. Analysis of products (GC−MS) indicates that the initial degradation of the surfactant in the OLS follows a Hoffmann elimination reaction and that the architecture (trimethyl or dimethyl), chain length, surfactant mixture, exchanged ratio, or preconditioning (washing) does not alter the initial onset temperatures. Catalytic sites on the aluminosilicate layer reduce ther...

Thermal Stability of Quaternary Phosphonium Modified Montmorillonites

Abstract: Organically modified layered silicates (OLS) with high thermal stability are critical for synthesis and processing of polymer layered silicate nanocomposites (PLSN). In the current study, the non-oxidative thermal degradation chemistry of alkyl and aryl quaternary phosphonium-modified montmorillonites (P-MMT) was examined using TGA combined with pyrolysis/GC-MS. The morphology evolution at elevated temperature was investigated using in-situ high-temperature X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The onset decomposition temperature via TGA of these P-MMTs ranged from 190 to 230 °C. The initial degradation of the alkyl P-MMTs follows potentially two reaction pathways - ‚-elimination [E‚] and nucleophilic displacement at phosphorus [SN(P)] reflecting the multiple environments of the surfactant in the silicate. Aryl P-MMT decomposition proceeds via either a reductive elimination through a five-coordinate intermediate or radical generation through homologous cleavage of the P-phenyl bond. Overall, the interlayer environment of the montmorillonite has a more severe effect on stability of the phosphonium surfactant than previously reported for ammonium-modified montmorillonite (N-MMT). Nonetheless, the overall thermal stability of P-MMT is higher than that of N-MMT. These observations indicate that, in addition to their conventional purpose as stabilizers, phosphonium salts offer unique opportunities for melting processing polymer layered silicate nanocomposites.

Investigation of chemical looping combustion by solid fuels. 1. Process analysis

Abstract: To concentrate CO2 in combustion processes by efficient and energy-saving ways is a first and very important step for its sequestration. Chemical looping combustion (CLC) could easily achieve this goal. However, only limited references are available that use coal as the energy resource in a CLC process even though the development of CLC of solid fuels follows the trend of energy utilization. This paper is the first in a series of two, where we present the concept of a CLC process of solid fuels using a circulating fluidized bed with three loop seals. The riser of this circulating fluidized bed was used as the oxidizer of the oxygen carrier; one of the loop seals was used as the reducer of the oxygen carrier and the separator for ash and oxygen carrier, and the other two loop seals were used for pressure balance in the solid recycle process. Pressure profiles of recycled solids using this process are presented in detail. For the development of an oxygen carrier, we focused on the establishment of a theoret...

Pyrolysis of Wood/Biomass for Bio-oil: A Critical Review

Abstract: Fast pyrolysis utilizes biomass to produce a product that is used both as an energy source and a feedstock for chemical production. Considerable efforts have been made to convert wood biomass to liquid fuels and chemicals since the oil crisis in mid-1970s. This review focuses on the recent developments in the wood pyrolysis and reports the characteristics of the resulting bio-oils, which are the main products of fast wood pyrolysis. Virtually any form of biomass can be considered for fast pyrolysis. Most work has been performed on wood, because of its consistency and comparability between tests. However, nearly 100 types of biomass have been tested, ranging from agricultural wastes such as straw, olive pits, and nut shells to energy crops such as miscanthus and sorghum. Forestry wastes such as bark and thinnings and other solid wastes, including sewage sludge and leather wastes, have also been studied. In this review, the main (although not exclusive) emphasis has been given to wood. The literature on woo...

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Abstract: Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.