A PROCESS FOR SELECTIVELY REMOVING DIOLEFINS FROM A GAS STREAM

Abstract

In a process for hydrotreatment of a gas stream containing both olefins and diolefins as well as organic sulfur compounds, the gas stream is introduced into a pre-treatment reactor, where diolefins are reacted with hydrogen in the presence of a supported Mo-catalyst not containing Co or Ni, whereby the diolefins are substantially converted to olefins. Then the gas stream is introduced into a hydrotreater reactor having a higher inlet temperature than the pre-treatment reactor, in which the gas stream is reacted with hydrogen in the presence of a hydrotreating catalyst under hydrodesulfurisation process conditions, whereby the olefins are substantially converted to paraffins and the organic sulfur compounds are converted to H.sub.2S, which is removed by subjecting the hydrotreated gas to a chemisorption or physisorption treatment.

Claims

1. A process for hydrotreatment of a gas stream containing both olefins and diolefins as well as organic sulfur compounds, said process comprising: introducing the gas stream into a pre-treatment reactor, where diolefins are reacted with hydrogen in the presence of a supported Mo-catalyst not containing Co or Ni at a temperature of 140-180 C., a pressure of 3-45 barg and a gaseous hourly space velocity up to 22500 NL/kg/h, whereby the diolefins are substantially converted to olefins, introducing the gas stream, now depleted in diolefins, into a hydrotreater reactor having a higher inlet temperature than the pre-treatment reactor, in which the gas stream is reacted with hydrogen in the presence of a hydrotreating catalyst under hydrodesulfurisation process conditions, whereby the olefins are substantially converted to paraffins and the organic sulfur compounds are converted to H.sub.2S, and subjecting the hydrotreated gas to a chemisorption or physisorption treatment to remove the H.sub.2S.

2. Process according to claim 1, wherein the gas stream is a fuel gas stream.

3. Process according to claim 1, wherein the gas stream has a diolefin content between 2 ppmv and 2 vol %.

4. Process according to claim 1, wherein the supported Mo-catalyst has a Mo content of 0.1 to 20 wt %.

5. Process according to claim 1, wherein the catalyst support is selected from alumina, silica, titania and combinations thereof.

6. Process according to claim 1, wherein the gas stream contains olefins up to a level of 20 vol %.

7. Process according to claim 6, wherein the gas stream has an olefin content of 1-15 vol %.

8. Process according to claim 1, wherein the gaseous hourly space velocity in the pretreatment reactor is between 500 and 10000 NL/kg/h.

9. Process according to claim 8, wherein the gaseous hourly space velocity in the pretreatment reactor is between 1000 and 7000 NL/kg/h.

Description

EXAMPLE

[0027] A simulated fuel gas containing 325 ppmv 1,3-butadiene, 1.3% ethane and 1.3% propene was passed over a catalyst bed of an alumina-supported catalyst containing Mo, but not containing Ni or Co, at a gaseous hourly space velocity of 22472 Nl/kg/h.

[0028] The detailed gas composition is given in Table 1 below.

TABLE-US-00001 TABLE 1 Detailed gas composition component concentration H.sub.2 14.9 vol % C.sub.2H.sub.4 1.3 vol % C.sub.3H.sub.6 1.3 vol % CO 0.8 vol % CO.sub.2 0.6 vol % H.sub.2S 1.0 vol % N.sub.2 79.5 vol % H.sub.2O 0.7 vol % 1,3-butadiene 325 ppmv

[0029] The operating conditions are given in Table 2 below.

TABLE-US-00002 TABLE 2 Operating conditions Pressure 20-40 barg Temperature 140-220 C. Catalyst load 4.45 g Flow 100 Nl/h

[0030] The measured conversions of 1.3-butadiene and olefins (ethene and propene) at a pressure of 20/40 barg for a temperature of 140-220 C. are shown in the figure. The butadiene is primarily converted to the corresponding olefin. It was found that the selectivity of the conversion of butadiene to butenes was above 85% at all conditions tested.