Oganic Sulfides Hydroconversion Catalyst

1. Features and Scope of Application
Some catalysts used in hydrocarbon-based large-scale ammonia plants is sensitive to sulfur compounds and prone to be poisoned and deterioration in activity when sulfur content in feed gas exceeds certain value. Cobalt molybdenum hydroconversion catalyst and zinc oxide are usually used for desulfurization of feed gases or oils.
T201 hydroconversion catalyst, with high organic sulfur conversion capability, is applicable to hydroconversion of feed gases for large-scale ammonia plants. It can bring down organic sulfur in feed gases to less than 0.1 ppm.

Main hydroconversion reactions involved are as follows:
RSH+H2 = RH+H2S

R1SSR2+3H2 = R1H+R2H+H2S

R1SR2+2H2 = R1H+R2H+H2S

C4H4S+4H2 = C4H10+H2S

COS+H2 = CO+H2S here R=alkyl groups.
This product is also applicable to organic sulfur hydro conversion of light oils or gaseous hydrocarbons in petro-chemistry.
The hydrogenation reactions take place at 350-400° C. Initial temperature is usually controlled at 350-380° C. If sulfur concentration in feed oil stays below a certain limit ( I. G., 0.2ppm) for long term, "Sulfur discharge" phenomenon will take place. Therefore, for two-section oil hydrogenation system, operating temperature in 1st section should be such that ensures sulfur concentration of 2_10ppm in effluent naphtha, so as to maintain the catalyst in 2ND section in sulfided state.

5. Loading
(1). Clean the reactor of any debris and screen the catalyst of any powder before loading. Operators working inside the reactor should stand on a broad wooden plate without stepping directly on the catalyst.
(2). Install inert balls at the top and bottom of the reactor. The catalyst particles are separated from the inert balls by stainless wire net of smaller mesh size than the catalyst.
(3). Use a funnel connected by a S-type cloth tube to drop the catalyst slowly and evenly from a maximum height of 1.2m to the reactor while holding lower end of the tube to prevent breakage of the particles.
(4). The loading operators should not stand directly on the catalyst bed during loading.

6. Start-up and Catalyst Presulfiding
Purge the system with nitrogen or other gases and then warm up the catalyst bed with nitrogen, hydrogen-nitrogen or natural gas. Warming-up procedure: 30~50° C/h to 120° C, keep at 120° C for 2 h, and then 30~50° C/h to 220° C. Then carry out presulfiding while warming up.
Usually presulfiding is not necessary for first-time use of the catalyst when using natural gas, associated gas or light naphtha as feedstock, since inorganic sulfur in the gaseous feed may fulfill sulfiding gradually during operation. However, in the case of treating hydrocarbons with high and/or complicated sulfur, presulfiding is need for first-time use to attain higher hydrogenation activity. Sulfur absorbed amounts to about 5% of total weight of the catalyst at the end of presulfiding.

Presulfiding can be done in following two ways:
(1)Adding CS2 into nitrogen or hydrogen
Add CS2 into feed gas (hydrogen-nitrogen or hydrogen) after warming up to 220° C. Carry out presulfiding while warming up at 20° C/h till operating temperature. Presulfiding can be considered complete when sulfur-containing gas equivalent to theoretical sulfur adsorbent capacity of the catalyst is added.

(2)Adding CS2 into light oil(preferably light naphtha)
Pass sulfiding medium into catalyst bed when bed temperature reaches 220° C. Keep on sulfiding while warming up at 20° C/h till operating temperature. Presulfiding can be considered complete when sulfiding medium equivalent to theoretical sulfur absorption capacity of the catalyst is added. Then raise pressure to operation condition, shift to hydrocarbon feed and adjust temperature, LHSV and hydrogen/oil, and and gradually proceed to normal full load operation.