DD154009A1 - METHOD FOR PRODUCING HIGH-ABRASIVE, DUST-FREE ZEOLTHIAN GRANULES - Google Patents

Abstract

The invention relates to the production of highly abrasion-resistant, dust-free, bound with kaolinitisches clay NaA zeolite granules. They are obtained by mixing the zeolite powder with clay, granulation, annealing, recrystallization and renewed annealing, the recrystallization according to the invention being carried out in the crystallization mother liquor obtained during the preparation of the NaA zeolite.

Description

VEB CHEMICAL COMPANY BITTERFELD Bitterfeld, 31. 10.

2101

Process for the preparation of highly abrasion-resistant, dust-free zeolitic granules

Usefulness . he invention d

The invention relates to a process for the preparation of clay-bound molecular sieve granules having improved strength and adsorption properties.

Characteristic of the known technical solution

Areas of application for zeolitic molecular sieves are primarily selective separation and adsorption processes. The use of zeolitic molecular sieves in industrial plants is generally carried out in the form of granules, which are produced by deformation of molecular sieve with a binder, mainly clay (DE-AS 1 040 005, DE-AS 1 055 515). The molecular sieve clay granules obtain their strength through the annealing process.

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The mechanical properties of the molecular sieve clay granules achieved under these conditions are insufficient for use in moving beds or in fluidized bed processes. The inadequate strength of the granules leads to an increased attack of abrasion and dust, which has a negative effect on the technological process.

Furthermore, the addition of about 20 % clay causes a reduction in the adsorption capacity of the molecular sieve clay granules o

Several methods for increasing the mechanical strength and the adsorption capacity of the molecular sieve clay granules are already known.

According to DE-OS 2 446 974, zeolite X powder and metakaolin powder are processed into shaped bodies; followed by the hydrothermal conversion of the major portion of the metakaolin in asn shaped bodies in zeolite X. For this, the mixture is added a solution of NaOH to provide the necessary for the conversion of metakaolin to zeolite X S ₂ 0th The excess HapO is eliminated by Ya ash. The addition of the ITaOH solution and an additional washing step after ITachkristallisation makes the process more expensive. According to DE-AS 1 203 238 Na zeolite A is processed with 15% binder to give moldings. The granulate is treated with a solution of alumina and ITaOH 24 hours in the cold and for 5 hours at 80 ⁰ C. -This results in hard granules with very good adsorption capacity.

By providing a solution of alumina and HaOH and by the Uachkristallisation in the cold and at 80 ⁰ G, a higher cost is recorded.

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According to DE-AS 1,567,557 powdered Zeolite A with 10 to 25% of powdered kaolin is mixed, with the addition of deformed UaOH into granules and crystallized for 24 hours at 90 ⁰ C. The added kaolin converts to zeolite A mn.

According to DE-PS 1 567 568 abrasion-resistant zeolites are prepared by mixing shaped bodies of calcined clay with an alkaline solution and hydrothermal conversion.

The provision of the HaOH solution for deformation and crystallization causes additional costs.

Aim of the invention;

The aim of the invention is the production of highly abrasion-resistant, dust-free zeolitic granules with high mechanical strength and improved adsorption-kinetic properties at low cost.

Presentation of the invention

It has been found that strength and static adsorption capacity of clay-molded molecular sieves can be substantially improved by post-crystallization in the crystallization mother liquor (by-product of molecular sieve synthesis). The recrystallization of the annealed at 550 ⁰ C molecular sieve clay granules is carried out in a closed system under hydrothermal conditions at a temperature of 70 to 80 ⁰ C for 1 to 8 hours, preferably 5 to 8 hours. The optimum binder content of kaolinitonen clays is 30 to 40% by mass.

This method enables effective use of the previous waste product, the crystallization mother liquor. Furthermore, by the

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Addition of 30 to 40% by mass of the kaolinitic clay, instead of previously 20 %, allows a saving in high-quality molecular sieve. The relatively high proportion of kaolinitic clay has been at least partially converted into metakaolin in the pre-annealed molecular sieve granules.

The hydrothermal treatment in the crystallization mother liquor converts a portion of the activated binder (metakaolin) into zeolite crystallite, resulting in a close intertwining of the molecular sieve primary agglomerates.

The result is a highly abrasion-resistant, dust-free granules with increased capacity. The nachkristallisierten zeolite granules at 500 to 550 ⁰ C are to be activated for technical use.

The following examples are intended to illustrate the nature of the invention without, however, limiting it.

embodiments

example 1

HaA zeolite and kaolinitic clay are mixed in proportions of 80:20, 70:30 and 60:40 and formed into 3μ extruded granules. 4 g each of the strand granules annealed at 550 ° C. are introduced into a vessel with in each case 30 ml of crystallization mother liquor and recrystallized in the closed state at 75 ° C. for 1 to 8 hours. Subsequently, the crystallization mother liquor is separated and the dried strand pellets annealed at 500 to 550 ⁰ C. The pressure resistance values obtained, the water vapor adsorption capacity, the dust content and the ammonia retention volume determined by gas chromatography are summarized below as a function of the binder content and the postcrystallization time (Table 1).

2101

Tab. 1

Binding agent content Post-crystallization time (h) 2 Compressive strength 2 Water vapor - adsorption capacity Dust content Reten- tion volume (ml 20 - 406.14 18,00 0.17 418.4 20 1 624.30 16.00 0.00 248.1 3 716.34 18.75 0.00 342.0 5 737.09 18.55 0.00 331.2 8th 714.40 18.85 0.00 386.0 30 - 557.80 17.10 0.01 385.0 30 1 785.50 17.00 0.00 239.7 3 822.47 17.30 0.00 ' 320.6 5 862.37 19.30 0.00 380.5 8th 1,006.81 19.30 0.00 376.3 40 - 783.90 14,60 345.2 40 1 755.71 15,30 - 254.8 3 652.76 15,10 - 283.2 5 901.85 16,80 - 320.4 8th 864.23 17.80 - 356.2 example

ITaA zeolite and a kaolinitic clay are mixed in a weight ratio of 70:30 and processed into pellets and annealed at 550 ^° C. 35 g of the spherical granules thus obtained are mixed with 60 ml of crystallization mother liquor. Further processing and recrystallization are carried out as described under Example 1.

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The following summary shows the abrasion, the water vapor adsorption capacity, the dust content and the retention volume for ammonia as a function of the post-crystallization time (Table 2).

Tab. 2

Frak To- 15 From 2.5 water dust Reten tion crystallize 15 1 rubbed 1.0 steam - proportion of tions (Mm) sations- 3 1.0 adsorptive volume Time 5 (*) 1.0 tionska- \ / OJ (ml 1.6-3, (H) 8th 1.0 capacity (%) NH ₃ / g) 1.6-3, 16,80 0.55 242.2 13.10 0.20 130.6 18,10 0.13 196.2 18.30 0.19 211.3 18,90 0.19 229.5

Examples 1 and 2 clearly show that a substantial pressure is hard igkeitserhöhung achieved by a post-crystallization in the crystallization mother liquor at 75 ⁰ C after 1 hour. Uachkristallisationszeiten of 5 and 8 · hours cause a further strength increase and a significant increase in the water vapor adsorption capacity.

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Claims (3)

- 7 - 2101 Invention claim 1. A process for producing highly abrasion-resistant, dust-free zeolitic granules by mixing HaA ~ zeolite powder with kaolinitic clay in the amount ratio of 70 to 60: 30 to 40, granulation, annealing at 500 to 550 ⁰ C, post-crystallisation and re-annealing at 500 to 550 ⁰ C, characterized in that the Nachkristallisation in the at , Preparation of the HaA-zeolite resulting crystallization mother liquor is made. 2. The method according to item 1, characterized in that the ITachkristallisierung takes place at a temperature between 70 and 80 ⁰ C. 3 · Method according to items 1 and 2, characterized in that the ITachkristallisierung in a period of 1 to 8 hours, preferably 5 to 8 hours, takes place.