Browse Prior Art Database

Nitriding of a Fischer-Tropsch catalyst

IP.com Disclosure Number: IPCOM000029503D
Publication Date: 2004-Jul-01

Publishing Venue

The IP.com Prior Art Database

Abstract

A process for preparing a Fischer- Tropsch hydrocarbon synthesis catalyst by reducing a precursor to the catalyst with hydrogen in a first pretreatment step, and nitriding the reduced catalyst with NH3 and no H2 in a second step. The use of the catalyst in a process for producing higher paraffins, alcohols and olefins selectively, by reacting hydrogen with carbon monoxide in the presence of a catalyst substantially as described herein above. In a preferred embodiment of the invention there is provided a process for producing linear paraffins, alcohols and olefins selectively.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 17% of the total text.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BACKGROUND OF THE INVENTION

THIS invention relates to catalysts for use in the conversion of synthesis gas (CO and H2) to alcohols and olefins.

International patent publication no. WO 01/89689 discloses an iron-based Fischer-Tropsch catalyst composition wherein the iron phase is ferrihydrite.  The catalyst composition includes structural promoters which may be selected from manganese or chromium or a mixture thereof and chemical promoters selected from magnesium zinc, copper and alkaline or alkali earth metals.  The catalyst is best bound to a refractory oxide support such as silica.  According to the specification, the catalyst composition produces significant yield of higher paraffins, olefins and alcohols. 

International Patent Publication No. WO 03/043734 also discloses an iron-based Fischer-Tropsch catalyst composition wherein the iron phase is ferrihydrite.  According to the specification of this application, the catalyst composition includes alumina as a structural promoter.  The use of alumina as the structural promoter increases the activity and selectivity of the catalyst for higher paraffins, olefins and alcohols (compared to the catalyst described in WO 01/89689) by 1.5 to 3 times.

International Patent Publication No. WO 01/49809 teaches the enhancement or improvement of the performance of active hydrocarbon synthesis catalyst, including a Fischer-Tropsch type of hydrocarbon synthesis catalyst, by contacting the catalyst with a reducing gas comprising a mixture of hydrogen and ammonia, at conventional catalyst reduction conditions, effective to form an active catalyst, and to hydrocarbon synthesis conditions using the enhanced catalyst.

It is an object of this invention to provide an improved catalyst with increased activity and selectivity towards alcohols and olefins.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a process for preparing a Fischer- Tropsch hydrocarbon synthesis catalyst by reducing a precursor to the catalyst with hydrogen in a first pretreatment step, and nitriding the reduced catalyst with NH3 and no H2 in a second step.

The precursor to the catalyst is preferably pretreated in the first step with H2  at a temperature of 240ºC - 400ºC, preferably at a temperature not above 300ºC.

In the nitriding step, the precursor to the catalyst is preferably nitrided with a gas containing NH3 and no H2 at a temperature of 240ºC to 400ºC, preferably at a temperature not below 300ºC.

Typically, the Fischer-Tropsch catalyst is an iron-based catalyst precursor wherein the main iron phase is ferrihydrite.  The catalyst may be supported on a refractory oxide support such as silica or alumina.

By "iron-based" is meant that Fe makes up at least 30% (by mass) of the composition.  The term "the main iron phase is ferrihydrite" means that at least 75% of the iron phase is ferrihydrite, as determined by X-ray diffraction using Co K alpha radiation.  The preferred catalyst compos...