română ADRIAN VOLCEANOV, RĂZVAN STATE, COSMIN MĂRCULESCU, ENIKÖ VOLCEANOV
Abstract
Pyrolysis and gasification as well as the product upgrading can be performed by conventional heating or microwave heating, the latter being preferred lately due to its advantages, such as fast heating and start-up or short processing time. The resulting products from gasification and pyrolysis have certain limitations and cannot be used for application in their current state. Pyrolysis and gasification are accompanied using catalysts to improve the yields or quality of reaction products.
The main goal of our research was to study the synthesis and structural characterization of ZSM-5 zeolite type catalysts, as well as to simulate their potential behavior in pyrolysis and gasification process of different vegetal waste.
As starting raw material has been used ZSM-5 zeolite that was subjected to protonation to obtain HZSM-5 form of zeolite. Then, substitution of H from protonated form with different transitional metals (Me = Ni, Mo, Co, Fe2+, Fe3+) was employed. The purpose was to establish the catalytic ability of Me-ZSM-5 substituted zeolite during pyrolysis.
To establish composition and structural-morphological characteristics of Me-ZSM-5 catalysts there were performed X-ray analysis and Fourier Transformed Infrared (FTIR) spectroscopy before and after pyrolysis process. The results have shown the preservation of structural features even after use, confirming their good stability after calcination at 6000C, the simulated temperature of pyrolysis. Morphological analyses have been done using Scanning Electron Microscopy (SEM) together with Energy Dispersive X-ray Analysis (EDAX) for elemental distribution and analysis.
The results were considered satisfactory and the first tests on both thermochemical and microwave assisted pyrolysis seem to be very promising.
Keywords
pyrolysis, catalyst, zeolite, synthesis ZSM-5
DOREL RADU, OVIDIU DUMITRESCU, IRINA PINCOVSCHI
Abstract
In the Na2O–Al2O3 system, six glasses were synthesized having the (35–x)Na2O·xAl2O3·65B2O3 molar composition, where x = 0; 5; 10; 12.5; 15; 17.5. For these synthesized glasses the following physical properties were measured: density; refractive index; linear thermal expansion coefficient; glass transition temperature. The structural compactness, the molar volume and the volume of oxygen ion, considered as structural characteristics for the first level of analysis (atomic), at a sub-nanometric scale, were also calculated. The correlation analysis of the properties indicated that these structural characteristics, even at this atomic level, sub-nanometric, influence the physical properties considered at a macroscopic scale. Moreover, the dependency graphs show a series of particular points (return points) that suggest structural transformation areas generated by the [BO3]-> [BO4] and [AlO6] -> [AlO4] transformations, according to the chemical composition of the glasses.
Keywords
Na2O–Al2O3 glasses, structural compactness, properties, correlations, sub-nanometric scale
CHUNQUAN DAI , YANXIA LONG, ZEJUN SHI, GUANGXUE XING, WENZENG HOU
Abstract
Considering the high permeability and low strength of weathered granite in tunnelling and underground projects, this paper develops strong permeability grouting (SPG) materials with good fluidity, excellent impermeability and long durability based on the features of the weathered granite formation. The materials can repair and reinforce the weathered granite formation through permeation grouting. Besides, the author tested the basic mechanical properties of the proposed SPG materials, and applied them to a tunnelling project of Qingdao Metro. The test and application results show that the SPG materials enjoy great wettability and permeability to granite; the SPG materials can meet the requirements for grouting projects in granite formation, due to the good strength and impermeability of their concretions; the SPG slurries require easy steps and a low grouting pressure in construction. The promotion and application of the proposed SPG materials will definitely bring good economic and social benefits, owing to the huge demand for high-performance grouting materials at home and abroad.
Keywords
Grouting Material; Weathered Granite; Orthogonal Test; Permeability
ZHANG YICHAO, WANG YING, ZHOU JINGHAI, KANG TIANBEI, WANG QINGHE
Abstract
Phosphogypsum is a byproduct of the manufacture of phosphoric acid by dehydrating process. The discarded phosphogypsum not only occupies considerable land resource, but also leads to serious environmental contamination. In order to improve the utilization rate of phosphogypsum, hemihydrate phosphogypsum was used as raw materials for manufacturing energy efficiency wall materials in this paper. Comparing with the conventional structure, the optimized structure was designed based on energy efficiency wall materials. The heat transfer of optimized structure was simulated to evaluate the energy efficiency of wall. The results show that the prepared material has suitable setting time, compressive strength and low thermal conductivity. Two-dimensional heat transfer coefficient of thermal bridge is decreased by 18.5%, and the average heat transfer coefficient of wall structure is decreased by 13.9%. The optimized structure can effectively improve the thermal insulation properties of walls.
Keywords
Hemihydrate phosphogypsum, vitrified microsphere, energy efficiency wall materials, heat transfer characteristic
LIGIA TODAN, DOREL CRIŞAN, NICOLAE DRĂGAN, DANIELA C. CULIȚĂ, CRINU CIUCULESCU, SANDA MARIA DONCEA
Abstract
In this paper the adsorption of pyridine, a toxic pollutant, on naturally occurring clay, namely bentonite, was studied at a basic pH and room temperature. Sodium saturated bentonite as well as modified with a cationic surfactant were used and the results compared. The influence of contact time and of the initial pollutant concentration on the pyridine uptake was determined by GC-MS. The adsorbents were characterized before and after being in contact with the pyridine solution by BET specific surface area and porosity, XRD and FTIR analysis.
The hydroxyl groups of bentonite in contact with pyridine solution led to protonated pyridine forms which can be responsible for hydrogen bonds formation and electrostatic interactions with the clay and for surfactant removal. Chemical adsorption prevailed over the partition/physical adsorption in both cases and the process followed the pseudo-second-order kinetics with the Freundlich isotherm model representing well the equilibrium adsorption data. The equilibrium adsorptive efficiency was 82.88% for the surfactant modified bentonite and 97.82% for sodium bentonite, the latter being a better alternative for sequestering pyridine from solution.
Keywords
bentonite, infrared spectroscopy, X-ray diffraction, kinetics, pyridine adsoption