DD250226A3 - METHOD FOR PRODUCING MOLECULAR SHAPING BODIES - Google Patents

Abstract

The invention relates to a process for the preparation of molecular sieve shaped bodies of the type NaCaA, which find in the art for selective adsorption and separation processes. In order to produce molecular sieves having uniform mechanical and adsorptive characteristics by pressing a molecular sieve clay / liquid mixture (pregranulate), the moisturized mass used for the deformation must have a plasticity characteristic in the range of 300 to 500 Ncm.

Description

Characteristic of the known technical solutions

It is known to produce molecular sieve shaped articles by granulation of molecular sieve-binder mixtures in cylindrical form, the predominant clays being used as binders.

The Molekularsiebformkörper used in technical adsorption plants must meet minimum requirements with respect to mechanical stresses. To avoid malfunctions, the compressive strengths of the cylindrical moldings should be above 10 MPa and abrasion resistance below 15 mass% (according to standard DDR TGL 22309). In the granulation process, a homogenized mixture of molecular sieve and binder is transferred in a known manner with the addition of granulation liquid in a plastic state, whereby it is possible, for example, to produce molecular sieve granules by means of screw presses.

The plastic molecular sieve pellets are converted in the further technological sequence by drying and annealing in solid shaped bodies. So far, the granulation process over the moisture content of the molecular sieve-binder mass to be deformed (Vergranulat) was controlled. In practice, it has been shown that in this procedure, quality variations in the mechanical and adsorptive properties in the final product occur.

Object of the invention

The aim of the invention is to ensure consistent quality parameters in the production of molecular sieve moldings of the NaCaA type.

Explanation of the essence of the invention

The object of the invention is to develop a process for the production of molecular sieve shaped articles of the NaCaA type with constant mechanical and adsorptive code numbers. It has been found through studies on plasticized molecular sieve clay mixtures (pregranules) that there is a connection between the plasticity of the pregranules and the mechanical and adsorptive characteristics of the molecular sieve shaped bodies.

The literature (Ullmanns Enc. D.Techn. Chemie, 5, 1980, p. 762ff.) Cites rheological test methods for viscosity and plasticity determination which are intended to characterize the properties of intermediate and end products of various preparation processes. DD-PS 119089 describes the modification of a measuring arrangement for determining the viscosity of resinous media, which is based on the principle of the rotational viscometer. These test methods are not applicable to plasticized molecular sieve clay mixtures (Vorgranulate), since the technological conditions of the production of the deformable molecular sieve mass, such as efficiency of the mixing process, temperature influence, homogeneity of the starting materials and swelling capacity of the clay binder can not be detected as time-dependent processes in their complexity ,

The technological conditions based on the complex detection of the time-dependent influencing factors have an effect on the mechanical and adsorptive properties of the solid end product formed after drying and annealing of the moist granules.

To produce molecular sieve moldings of constant quality by shaping zeolitic molecular sieves with the addition of clay-like binders, the moisturized molecular sieve-binder mixtures used for shaping must have a plasticity-defining torque in the range from 300 to 500 N cm. The measurement of the torque can preferably be carried out with a Brabender Plasti-Corder.

In the method according to the invention first molecular sieve and clay binders are to be mixed homogeneously in an aggregate. Thereafter, the mixture is converted by the addition of water with the addition of a plasticizer in a plastic state (pre-granules). If the desired plasticity of the pregranules is reached, the liquid addition is terminated. The clay-bonded Molekularsiebformkörper produced by deformation of the invention plasticized molecular sieve-binder mixtures have a consistent product quality in terms of abrasion and compressive strengths and adsorptive indices, so that malfunctions due to mechanical destruction of the granules are avoided in adsorption.

As a further advantage turns out that with the torque measurement is a method with which a process control to comply with the intended for the deformation plasticity of the wet molecular sieve-binder mixtures can be ensured.

embodiment

A mixture consisting of 78 wt .-% NaCaA zeolite powder, 22 wt .-% clay and 2 wt .-% PVA additive (based on the glow loss Zeoiith and clay) is homogenized with a vortex mixer and with addition of water in a wet plastic state defined moisture content transferred. Subsequently, using a Plasti-Corder from Brabender, the torque of the moisturized mixtures is determined, whereby the following measuring conditions are to be observed:

- Measuring range to be set: 0-1 000 N -cm

- measuring chamber: roller kneader type W30 (kneading chamber volume approx. 30 ml)

- Speed: 30 rpm

- duration of measurement: at least 15 minutes

- Sample amount: 28g (± 0.1g). The remaining amount of the wet-plasticized molecular sieve-clay mixture is shaped with a technical extrusion press into strand granules of 3 mm diameter. The strand pellets produced in this way receives after drying at about 110 ⁰ C its final mechanical strength by annealing at 600 ⁰ C for 6 hours.

The table compares the torques of the wet-plasticized molecular sieve clay mixture, the strength characteristics of the strand granules produced by deformation from the mixtures, and the n-pentane retention volume determined by gas chromatography.

Table:

moisture content torque Druckfe Mahlabneb n-pentane (Loss on ignition) stigkeit Ret. vol. (Wt .-%) (N-cm) (MPa) (Wt .-%) (Ml / g) 32.6 253 7.9 17.8 33.1 270 11.2 12.4 130.2 34.2 309 15.4 7.5 126.7 35.2 355 16.9 6.4 127.0 36.3 438 18.3 5.2 128.4 37.5 473 17.6 4.3 118.5 38.4 456 15.1 6.0 117.8 39.4 363 13.4 7.2 118.0 40.6 211 10.7 8.9 109.0 41.3 118 8.6 9.8

The strand granules produced according to the invention have uniform mechanical and adsorptive properties. The minimum requirements for the compressive strength are significantly exceeded and fell below the Mahlabrieb. As the measurements of the n-pentane retention volumes illustrate, a dependence of the dynamic adsorption behavior on the moisture content of the plastic mass in the granules produced according to the invention can not be demonstrated. If, on the other hand, the claimed plasticity range falls short as a result of an increased moisture content of the plastic mass, as the decrease in the n-pentane retention volume documents, the dynamic adsorption behavior of the granules is negatively influenced.

In the case of deformation of wet-plasticized molecular sieve-binder mixtures with plasticity indexes in the range of 300 to 500 .mu.m, maximum throughput rates are achieved with screw presses.

Claims (1)

Process for the preparation of molecular sieve molds of the NaCaA type with uniform mechanical and adsorptive characteristics by mixing zeolite NaCaA and clay binders in the powdery state, plasticizing by adding water in the presence of a plasticizer, shaping into pellets, drying and annealing, characterized in that the zeolite Clay mixture is added as long as the plasticized mixture has reached a torque in the range 300 to 500 N cm. Field of application of the invention The invention relates to a process for the preparation of molecular sieve shaped articles of the NaCaA type which are used in the art for selective adsorption and separation processes. Molecular sieves are all inorganic zeolitic products.