Method for starting up a fischer tropsch process

Abstract

The invention relates to a method to start up a Fischer-Tropsch process. A catalyst with a latent activity is used. The catalyst comprises titania, cobalt, promoter, and chlorine. The catalyst comprises more than 0.7 and less than 4 weight percent of the element chlorine, calculated on the total weight of the catalyst.

Claims

1. A method to start up a Fischer-Tropsch process comprising the steps of: (a) providing a reactor with a Fischer-Tropsch catalyst that comprises: titania at least 5 weight percent cobalt calculated on the total weight of the catalyst in the range of between to 0.1 to 15 weight percent promoter, whereby the promoter comprises manganese, rhenium, Group 8-10 noble metals, or mixtures thereof; and more than 0.7 and less than 4, weight percent of the element chlorine, calculated on the total weight of the catalyst, (b) providing syngas to the reactor, and (c) providing the following process conditions in the reactor: a temperature in the range from 150 to 350° C., a pressure in the range from 5 to 150 bar absolute, and a gaseous hourly space velocity in the range from 500 to 10000 Nl/l/h.

2. The method according to claim 1, wherein the catalyst is fixed in the reactor.

3. The method according to claim 1, wherein at least 25 weight % of the catalyst comprises particles having a particle size of at least 1 mm.

Description

EXPERIMENTAL

(1) Measurement Method; Activity

(2) Catalytic activities can be measured, for example, in a model Fischer-Tropsch reactor. The catalytic activities measured may be expressed as space time yield (STY) or as an activity factor, whereby an activity factor of 1 corresponds to a space time yield (STY) of 100 g/l.Math.hr at 200° C.

(3) Sample Preparation

(4) Fixed bed particles were prepared as follows. Mixtures were prepared containing titania powder, cobalt hydroxide, manganese hydroxide, water and several extrusion aids. The mixtures were kneaded. The mixtures were shaped using extrusion. The extrudates were dried and calcined. The obtained catalysts contained about 20 wt % cobalt and about 1 wt % of manganese.

(5) A part of the catalyst particles was used as reference (Comparative Examples). As one or more of the ingredients used comprised chlorine or chlorine components, the Comparative Examples comprised a very small amount of chlorine. Several batches were prepared, with slightly different properties.

(6) The comparative examples and the examples according to the invention were tested under different conditions. The experimental data can be compared per measurement set as presented below.

Examples A1-A3

(7) A base catalyst was prepared. The fixed bed catalyst particles of the base catalyst comprised 20 wt % cobalt and 1.1 wt % manganese on titania.

(8) A part of the fixed bed particles of the base catalyst was impregnated with an aqueous cobalt chloride solution (CoCl2). During the impregnation 3 wt % of the element chlorine was added, calculated on the total weight of the dry catalyst. After the impregnation the catalyst particles were dried in air at 70° C. for 4 hours. In a subsequent final drying step in air, parts of the chorine impregnated catalyst particles were subjected to different final drying temperatures. After the final drying the chlorine content was determined by microcoulometry.

(9) The catalyst particles were reduced with hydrogen at 280° C. for 18 hours, followed by a reduction with hydrogen at 290° C. for 2 hours.

(10) The performance of each of the different samples prepared was tested using the following conditions in a Fischer-Tropsch reactor: a H2/CO ratio of 1.11, 25% N2, 60 bar, and 215° C. The selectivity of each of the samples was determined at 30% CO conversion after 60-100 hours time on stream. The base catalyst was used for a comparative example. Example A1 is an example according to the present invention.

Examples B1-B3

(11) A base catalyst was prepared. The fixed bed catalyst particles of the base catalyst comprised 20 wt % cobalt and 1.1 wt % manganese on titania.

(12) A part of the fixed bed particles of the base catalyst was impregnated with an aqueous cobalt chloride solution (CoCl2). In order to reach a target chloride content of 6 wt %, impregnation was carried out in 2 consecutive steps with drying for 4 hours at 70° C. in air after both steps. In a subsequent final drying step in air, parts of the chorine impregnated catalyst particles were subjected to different final drying temperatures and drying times. After the final drying the chlorine content was determined by XRF. The performance of each of the different samples prepared was tested as described for the previous examples.

(13) The test results of the examples are summarized in Table 1.

(14) TABLE-US-00001 TABLE 1 Final Cl Cl drying content added step after Act. C5+ CO2 (wt (° C./ drying Act. change select. select. Sample %) hrs) (wt %) factor 5-100 hrs (%) (%) Base 0 None 0.07 1.42 −6% 88.9 2.4 cat. A1 3 140/1 2.15 0.73 1% 93.1 0.6 A2 3 300/1 0.53 1.45 −3% 90.2 1.2 A3 3 450/1 0.13 NA NA NA NA B1 6 140/1 3.3 0.57 16% 94.9 0.4 B2 6 140/4 2.9 0.67 21% 94.7 0.4 B3 6 550/2 0.07 NA NA NA NA

(15) From these experiments is clear that the addition of a small amount of chlorine results in a higher selectivity towards C5+ hydrocarbons.

(16) It is further visible that the amount of chlorine can be adjusted by means of the drying temperature and/or drying time.

(17) A relatively high amount of chlorine, 2.15 wt %, resulted in a relatively high selectivity towards C5+ hydrocarbons. The activity of this catalyst was relatively low, but the overall performance of this catalyst was fine due to the high selectivity towards C5+ hydrocarbons. Moreover, this reduced activity is highly advantageous at the start-up of a Fischer-Tropsch process.

(18) Additionally, it is clear that the low activity of the catalyst with the high amount of chlorine started to recover during test run hours 50-100.