Periodic operation pilot-scale reactors

Several pilot plants have been built to test periodic flow direction reversal. Pilot-scale reactors with bed diameters from 1.6 to 2.8 m were operated with flow reversal for several years. The units, described by Bunimovich et al. (1984,1990) and Matros and Bunimovich (1996), handled 600 to 3000 m3/h and operated with cycle periods of 15 to 20 min. Table VIII shows the performance of these plants for different feeds and potassium oxide promoted vanadia catalysts. The SVD catalyst was granular the IK-1-4 was in the form of 5 (i.d.) x 10-mm cylinders, while the SYS catalyst was... 

OS 39] ]R 25] ]P 27] A 24 h run of a pilot-scale micro reactor for azo pigment production was performed using a diazo suspension [55], At the end of this period, the pressure loss of the micro reactor increased exponentially. Special means were developed to prevent clogging and unstable operation. By partial removal of the deposits, the pressure loss was brought back to normal. 

The viscosity of the mixture was adjusted by the addition of approximately 50 % of toluene. The pilot plant consist of oxo-reactor and the membrane unit, which was directly connected to the reactor. Standard plate modules from Dow (Type DDS 30-4.5) were used. The conditions of the membrane separation were overflow 200 1/h, separation temperature 40 °C, transmembrane pressure 1 MPa. The unit was continuously operated over a period of 12 weeks. No decrease of activity of the catalyst was observed. In order to obtain a dialdehyde selectivity > 90 %, the Rh concentration must be increased to 100 ppm. Most of the loss of ligand was due to traces of oxygen, which could not excluded totally on pilot scale. 

The 2" phase (2006-2009) R D activities undertake a SI process optimization and the performance tests of various chemical reactors selected for the SI cycle. The 2" phase research covers a dynamic code development for the SI process, a construction of a lab. scale( l 000 NL/h) SI process, and integrated operations of the process at prototypical pressures. On the other hand, conceptual and basic designs of a pilot scale( 100 Nm /li) SI process and its equipment will also be carried out according to the optimized process established from the theoretical evaluation using a commercial-base computer code and the experiences of the lab. scale construction and operations. Preliminary performance tests of the equipment, mechanical devices, and accessories for the pilot scale SI process should be carried out to obtain the design basis. Not only the several catalysts based on non-noble metals required for section II in the SI cycle but also a membrane for the separation of the hydrogen required for section III will be developed during the 2" phase research period. 

The pilot plant was operated smoothly without any problems for a period of 24 h to obtain 14.7 kg of the product (92% yield). It should also be emphasized that the industrial-scale production, which has been carried out using a batch reactor (10 m ), was accomplished by numbering-up only four microflow systems of the present scale. The use of microflow systems should lead to a significant decrease in investment compared with current batch process. 

Industrial interest in soluble polymer-bound catalysts has been closely linked to the development of ultrafiltration membranes with sufficient long-term stability in organic solvents. Membranes fulfilling these requirements were prepared first in the late 1980s. Today, solvent-stable flat sheet membranes and membrane modules are available from several suppliers. As for the viability of ultrafiltration in organic solvents, rhodium-catalyzed hydroformylation of dicydopentadiene with continuous catalyst recovery and recycling has been demonstrated successfully on a pilot plant scale over an extended period of time [5]. The synthesis of other fine chemicals by asymmetric reduction and other reactions has also been carried out in continuously operated membrane reactors (also cf Section 7.5) [6-9]. The extent of commercial interest in catalysts bound to soluble polymers appears to fluctuate at intervals. Amongst other factors, the price of precious metals can be a driver. 

The fixed bed of ARGE and the entrained bed reactors were steadily optimized and modernized to present-day technology. The three-phase FT processes were realized only in pilot and demonstration plants. They had actually no chance to prove their effectivity and superiority over a longer period of operation and were not optimized in larger-scale equipment. Although the three-phase processes were a full success from an engineering point of view they were a failure in view of the economic requirements in those days. 

Moreover, the study of pilot reactor performance data is very important in the understanding of the long-term stabiUty of an industrial catalyst. Plant operation often requires a catalyst lifetime of four years without losing too much PA yield during this period of time. PHTHALIMAX , for example, loses about 0.5-1% PA yield per year. To study aging, catalysts are subjected to special stress tests on the bench-scale, as well as pilot units under high temperature and load conditions for... 

The areas of reactor design and operation involve a combination of applied science and art. The amount of published material in these areas is quite limited and this fact is another reason for using a pilot plant which is similar to the potential commercial process in the development period. Even under such conditions the scale-up problems can be quite significant. 

---