Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Abstract: Naphtha was steamcracked over ZSM-5 zeolites modified by both calcium and magnesium cations in a fixed-bed quartz reactor. Calcium and magnesium cations with a constant proportion were simultaneously impregnated into the fresh ZSM-5 zeolite with Si/Al ratio 140 (mol/mol). After drying and calcination, the modified zeolites were ground into 20~40 mesh for use. Reaction conditions were: temperature 700°c, W/O (w/w) =1.1, WHSV 12h. It was found that Si/Al ratios of the modified ZSM-5 zeolites incresed with the decrease of the impregnated metal contents. And all modified zeolites had higher Si/Al ratios than the fresh one. The total acid amounts of the modified zeolites raised with the Si/Al ratios when the Si/Al ratios were less than 200.86, then dropping and rising again. However, B/L values had no obvious tendency with Si/Al ratios of the modified zeolites. It was also found that gas yields and C2+ C3+ C4 yields basically went up with the increase of Si/Al ratios of the modified zeolites. And a maxium also appeared when the Si/Al ratio was 200.86. Meanwhile, it was found that BTX yields basically raised with the gas yields except the Si/Al ratio with 200.86, when a minimum was seen. In addition, it was found a distinct difference of C5+ product distributions between the modified zoelites and the fresh one. Obviously, the diffenrence was an appearance of the modified function on the steam cracking. As above, it was obtained a direction to the preparation of modified ZSM-5 zeolites with Ca and Mg through the comparison of the characterization results with the steamcracking ones. Also it was acqiured the modification function of the Ca and Mg on the ZSM-5. INTRODUCTION Naphtha steamcracking is an important way to produce ethylene now. Due to the increasing need to propylene, the catalytic steamcracking naphtha has been developed. Usually, the catalysts are focused on the modified MFI zeolites. And the objective of the modification is to change the acidic properties of the original zeolites. In the paper, double alkali-earth metals, calcium and magnesium, were used to modify the ZSM-5 zeolite. Preparation of catalysts The original ZSM-5 zeolite, with Si/Al ratio 140 (mol/mol), was produced by Hunan Jianchang Petrochemical Co., Ltd, China, and marked as ZRP140. The original zeolites were modified by a series of calcium and magnesium elements, with a certain proportion, through ion-exchange+immersion. After drying and calcination, the modified zeolites were ground into 20~40 mesh. Analysis of products The industrial naphtha was provided by Yanshan Chemical Industrial Factory, SINOPEC. The tail gas was routinely analyzed by GC. The liquid products and Yanshan naphtha were qualitatively and quantitatively analyzed by GC-MS. The components of Yanshan naphtha were listed as Table 1. (Table in full paper) Catalytic steamcracking of naphtha The catalytic steamcracking of naphtha was performed in a quartz reactor. The catalyst loading was 1g, reaction temperature 700°C, water/oil (w/w) 1.1, WHSV 12h.
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (1.00)
- Energy > Oil & Gas > Downstream (1.00)
Abstract: Alkylation of isobutane with n-butene is one of the important routes to provide high octane components that can substitute aromatic molecules in gasoline. Traditionally, this route is catalyzed by sulfuric and hydrofluoric acid. Solid acid catalysts have been explored frequently, but have not been commercially implemented to date. This is related to the necessity of frequent regenerations, complex handling of solid catalysts in a liquid-solid system and inherent differences in the reactivity towards n-butene and isobutane. The main drawback in the use of solid catalysts for isobutane alkylation is their rapid deactivation, which so far has prevented their industrial application. Over the last years, significant progress has been made in this field, leading to the successful development of alkylation technology on a pilot stage. Insight into surface chemistry, the advances in catalyst preparation and the integration with novel reactor technology led to remarkable progress. Catalysts, which surpass the lifetime of sulfuric acid by three orders of magnitude, show potential for economic feasibility based on frequent mild regenerations. This progress has been made possible by enhancing the key quality of the solid catalysts, which is the hydride transfer between the surface bound species and the isobutane. The lecture will review the potential and limitations of current chemical and engineering concepts and will give an outlook to new developments in isobutane alkylation. INTRODUCTION The alkylate produced from isobutane/butene alkylation is an excellent blending component for gasoline. In 2005 the worldwide alkylation capacity amounted to approximately 2 million bpd and it is expected to grow further Figure 1. In fact, due to increasingly strict legislation, the concentration of alkenes and aromatics in the gasoline will be more and more limited in the next years. Additionally, methyl-tertiary-butyl ether (MTBE), a high-octane-number oxygenate, is likely to be prohibited as a gasoline compound. (Figure in full paper) Currently, only liquid acid-catalyzed processes are operated on an industrial scale with approximately equal market shares for processes using sulfuric and hydrofluoric acid. Both of these catalysts suffer from serious disadvantages. Anhydrous HF is a corrosive and highly toxic liquid with a boiling point close to room temperature. Therefore, refineries with HF alkylation plants are under pressure to install expensive mitigation systems minimizing the dangers of HF leaks. Moreover, authorities in many industrialized countries have ceased to license new HF alkylation plants. Sulfuric acid is also a corrosive liquid, but not volatile, making its handling easier. Its major disadvantage is the high acid consumption in the alkylation process, which can be as much as 70–100 kg of acid/ton of alkylate. The spent acid contains water and heavy hydrocarbons and has to be regenerated, usually by burning. The cost of such a regenerated acid is about 2–3 times the market price for freshly produced sulfuric acid [2]. In the last 30 years considerable efforts have been made to replace the existing liquid catalysts by solid materials, which are environmentally benign and easier to handle. Among them the most promising candidates seem to be zeolites.
- North America > United States (0.46)
- Europe (0.28)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (1.00)
- Energy > Oil & Gas > Downstream (1.00)