New progress in R&D of lower olefin synthesis

This paper gives a brief review of R&D researches for light olefin synthesis directly and indirectly from synthesis gas in the Dalian Institute of Chemical Physics (DICP). The first pilot plant test was on methanol to olefin (MTO) reaction and was finished in 1993, which was based on ZSM-5-type catalyst and fixed bed reaction. In the meantime, a new indirect method designated as SDTO (syngas via dimethylether to olefin) was proposed. In this process, metal-acid bifunctional catalyst was applied for synthesis gas to dimethylether(DME) reaction, and modified SAPO-34 catalyst that was synthesized by a new low-cost method with optimal crystal size was used to convert DME to light olefin on a fluidized bed reactor. The pilot plant test on SDTO was performed and finished in 1995. Evaluation of the pilot plant data showed that 190-200 g of DME were yielded by single-pass for each standard cubic meter of synthesis gas. For the second reaction, 1.880 tons of DME or 2.615 tons of methanol produced 1 ton of light olefins, which constitutes of 0.533 ton of ethylene, 0.349 ton of propylene and 0.118 ton of butene. DICP also paid some attention on direct conversion of synthesis gas to light olefins. A semi-pilot plant test (catalyst 1.8 1) was finished in 1995 with a CO conversion > 70% and a C(2)(=)-C(4)(=) olefin selectivity 71-74% in 1000 h. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

Validity ranges of interfacial wave theories in a two-layer fluid system

In the present paper, we endeavor to accomplish a diagram, which demarcates the validity ranges for interfacial wave theories in a two-layer system, to meet the needs of design in ocean engineering. On the basis of the available solutions of periodic and solitary waves, we propose a guideline as principle to identify the validity regions of the interfacial wave theories in terms of wave period T, wave height H, upper layer thickness d(1), and lower layer thickness d(2), instead of only one parameter-water depth d as in the water surface wave circumstance. The diagram proposed here happens to be Le Mehautes plot for free surface waves if water depth ratio r = d(1)/d(2) approaches to infinity and the upper layer water density rho(1) to zero. On the contrary, the diagram for water surface waves can be used for two-layer interfacial waves if gravity acceleration g in it is replaced by the reduced gravity defined in this study under the condition of sigma = (rho(2) - rho(1))/rho(2) -> 1.0 and r > 1.0. In the end, several figures of the validity ranges for various interfacial wave theories in the two-layer fluid are given and compared with the results for surface waves.