WO1995021146A1

WO1995021146A1 - Removal of carbon monoxide from hydrocarbon streams

Info

Publication number: WO1995021146A1
Application number: PCT/US1995/001634
Authority: WO
Inventors: David Rosenfeld. Daniel
Original assignee: Exxon Chemical Patents Inc.
Priority date: 1994-02-07
Filing date: 1995-02-07
Publication date: 1995-08-10
Also published as: AU1873195A

Abstract

A process for removing carbon monoxide from contaminated hydrocarbon feeds to below 1 ppb is disclosed. The process involves low temperature, liquid phase contact of the contaminated feed with a copper containing or copper/manganese dioxide-containing sorbent. Removal of arsenic-containing contaminates to below 2 ppb is also disclosed.

Description

REMOVAL OF CARBON MONOXIDE FROM HYDROCARBON STREAMS

The present invention relates to a process for the removal of carbon monoxide from hydrocarbon streams. Additionally, certain other contaminants may also be simultaneously removed.

The presence of trace contaminants such as carbon monoxide and/or arsenic compounds in hydrocarbon streams proves detrimental where these streams or cuts thereof are to be used as feed material in polymerization processes or in reforming processes. For example, carbon monoxide present in olefin feedstreams tends to deactivate transition metal (Ziegler/Natta) catalysts used to polymerize these olefins. The presence of carbon monoxide and/or arsenic compounds in feedstreams used in reforming processes tends to more quickly deactivate noble metal catalysts, e.g., platinum, which catalyze aromatization reactions in such processes.

The presence of these contaminants has long been recognized as detrimental in such polymerization and reforming processes and various techniques have been developed to reduce the content of one or both of them. For example, US-A-3,676,516 discloses a process for reducing the level of carbon monoxide present in propylene or ethylene feedstreams to a level of 0.2 parts per million (ppm) or lower by passing the feedstream in the gaseous state over a catalyst bed comprising copper oxide supported on an alumina or talc. The copper oxide is at least partially reduced such that 20 to 90 weight % of the copper of the copper oxide remains in the cupric or two valent state.

Similarly, US-A-3, 549,719 discloses a process for removing contaminants such as carbon dioxide from alpha olefin feedstreams down to levels of 0.2 ppm or less by passing the olefins in the gaseous state and at elevated temperatures over a catalyst mass comprising a mixture of copper oxide and Zinc oxide.

It is also known in the art that the content of arsenic-containing compounds, e.g., arsine, present in hydrocarbon feedstreams may be reduced to levels of 0.05 ppm or less by contacting the feedstream with a readily reducible metal oxide, e.g., ferric, cupric or nickel oxide, to oxidize the arsine into a water soluble compound, and removing the water soluble arsenic compound by a water wash. Such a process is disclosed in US-A- 2,778,779.

Analogous processes are disclosed in US-A-3,789,581 and US-A- 3,812,653, which disclose the removal of arsenic from hydrocarbon feedstreams by passing the hydrocarbons in the gaseous state through a sorbent comprising 1-30% by weight of reduced copper oxide on a suitable refractory metal oxide support such as alumina. The use of various metallic oxides for the separation of carbon monoxide and/or arsine from other gases dates back to the early part of the twentieth century. For example, US-A-1 ,519,470 discloses a combination of copper and copper oxide impregnated on a charcoal carrier as an effective sorbent for arsine when arsine-containing gases such as ammonia or acetylene are passed through the sorbent. US-A-1 ,418,246 additionally teaches that carbon monoxide may be separated from hydrogen by passing a gaseous mixture of contaminated hydrogen and oxygen through a catalyst based on copper oxide or a mixture of copper oxide and manganese dioxide. The catalyst facilitates the conversion of carbon monoxide to carbon dioxide in the presence of oxygen.

JP 57-77,627 discloses the removal of arsenic contained in a hydrocarbon by treating the contaminated hydrocarbon with an oxidation catalyst in the gaseous phase to absorb and oxidize the arsenic at a temperature of 45°C. The catalyst is preferably manganese oxide and/or copper oxide. The hydrocarbon stream comprises propylene and propane. However, the removal of the carbon monoxide contaminant is neither disclosed nor suggested. Additionally, the simultaneous removal of both carbon monoxide and arsine is neither disclosed nor suggested.

Despite these developments, it would be extremely advantageous to provide a process which does not require the feedstream to be in the gaseous phase for the removal of carbon monoxide or carbon monoxide and arsenic from hydrocarbon feeds down to levels of less than 5 parts per billion (ppb), preferably less than 1 ppb, since the presence of any level of carbon monoxide and/or arsenic contaminant in hydrocarbon feeds will ultimately prove detrimental in catalytic polymerization and reforming as described above. SUMMARY OF THE INVENTION

The present invention provides for a process for the removal of carbon monoxide contaminants from hydrocarbon feedstreams down to levels below 5 parts per billion (ppb), preferably below 1 ppb, wherein the feedstream is contacted in the liquid phase with a sorbent comprising a copper-containing compound. The sorbents contain either dispersed zero valent copper, a dispersed mixture of zero valent and 1 valent copper, a dispersed mixture of zero valent copper, 1 valent copper and manganese dioxide or a dispersed mixture of 2 valent copper and manganese dioxide, The contact occurs at a temperature of less than about 40°C.

In one embodiment, the hydrocarbon feedstream comprises a hydrocarbon having from 1 to about 16 carbon atoms, and preferably comprises an alpha-monoolefm having from 2-4 carbon atoms. Even more preferably, the hydrocarbon stream comprises propylene, ethylene, or mixtures thereof.

In another embodiment, the process also provides the ancillary benefit of removing arsenic-containing compounds, e.g., arsine, from the hydrocarbon feedstream down to levels below about 5 ppb, preferably below about 2 ppb. In still another embodiment, the feedstream has an initial content of carbon monoxide in excess of 5 parts per billion, and optionally, may have an initial content of arsine in excess of 2 parts per billion.

In the various embodiments, the copper-containing sorbent comprises copper in a reduced state, and may further comprise manganese dioxide or zinc oxide.

In still another embodiment, sorbent comprises non-reduced copper oxide mixed with manganese dioxide.

In all embodiments, the copper content of the sorbent ranges from about 5 to about 90% by weight. The sorbent may also comprise other metal oxides in admixture with the copper-containing compound, such as magnesium oxide, ferric oxide, cobalt oxide, zinc oxide, barium oxide, nickel oxide, lead oxide, chromium oxide and/or mixtures thereof.

The sorbent is dispersed on a refractory metal oxide carrier or binder, preferably alumina. The process is conducted under conditions of pressure such that contact of the hydrocarbon feedstream with the sorbent occurs in the liquid phase, even where the hydrocarbons are normally gaseous.

DETAILED DESCRIPTION OF THE INVENTION

Hydrocarbon streams which may be treated in accordance with this invention include normally gaseous or liquid hydrocarbons which are contaminated with carbon monoxide or mixtures of carbon monoxide and arsenic-containing compounds. These streams include normally gaseous C2 to C4 alpha-monoolefins such as ethylene and propylene, as well as liquid straight or branched chain monoolefins having from 5 to 16 carbon atoms such as hexene, octene, decene and the like.

The hydrocarbon stream may also comprise straight or branched chain Ci to C16 alkanes, more particularly C5 to Cβ alkane cuts which are intended to be subjected to reforming aromatization reactions.

The sorbent material with which the hydrocarbon feed is contacted in accordance with this invention comprises a dispersed copper compound containing copper in the valence state zero (copper metal), optionally mixed with manganese dioxide; mixed copper in the valence state zero and 1 (cuprous), optionally mixed with manganese dioxide; and cupric copper in the valence state 2 mixed with manganese dioxide.

Where the copper compound is present in the sorbent in the below 2 valent state, it is conveniently prepared in highly dispersed form by forming a mixture of copper oxide, optional additional metal oxides and a refractory metal oxide, adding water to form a paste, forming the paste into pellets, drying the pellets, subjecting the pellet mixture to conditions of high temperature in excess of 100°C, and contacting the pellets with a reducing gas such as hydrogen or carbon monoxide until essentially all of the copper oxide is reduced to copper metal or to a mixture containing at least about 10% by weight copper metal and the balance cuprous oxide. Alternatively, cuprous copper in the form of cuprous salts may be mixed with or precipitated within the refractory metal oxide and reduced as set forth above. Where the copper compound is present in the sorbent in the cupric state, it is most conveniently prepared by forming a mixture of copper oxide, manganese dioxide, optional additional metal oxides and optional refractory metal oxide, forming the mixture into dried pellets as above and calcining the pellets in an inert or oxygen-containing atmosphere at temperatures in the range of from about 200° to 800°C.

Carrier supports which may be present in the sorbents of this invention include a large class of refractory metal oxides having a high surface area and an affinity for the copper compound. Preferred carriers include aluminum oxide, silica, natural or synthetic zeolites, silica-alumina gel, clay minerals, zinc oxide and the like. Carbon may also be used as a support material. Preferred materials have a surface area greater than 100 m2/g, preferably greater than 200 m2/g.

Where the copper compound is present in the sorbent in the 2 valent (non-reduced) state, it is ineffective in removing carbon monoxide in hydrocarbon streams to levels below about 1 ppb unless combined with manganese dioxide. The reason for this is not clearly understood, but the combination of cupric copper and manganese dioxide appears to work synergistically with respect to absorption of carbon monoxide, as well as arsine. The cupric copper and manganese dioxide may also be used in combination of one or more of the other difficult-to-reduce metal oxides set forth above. The content of copper (0, 1 or 2 valent form) present in the sorbent will generally range from about 5 to about 90% by weight, with the balance of the sorbent composed of the one or more difficult-to-reduce metal oxides and/or refractory metal oxides set forth above. Preferably the sorbent contains at least about 10% by weight of copper. Where present in the sorbent, the refractory metal oxide may be present at a level ranging from about 5 to about 95% by weight, more preferably at a level of from about 10 to about 60% by weight. The difficult-to-reduce metal oxides may be present in the sorbent generally at levels ranging from about 1 to about 60% by weight, more preferably from about 10 to about 50% by weight. Sorbents of the present invention are particularly effective for removing carbon monoxide from normally gaseous alpha monoolefin feedstreams which contain carbon monoxide at levels in excess of 5 ppb, i.e., levels of from about 25 to about 100,000 ppb. In the preferred mode, the contaminated feedstream, e.g., propylene is passed through a bed of sorbent particles packed in a suitable reactor under conditions of pressure and temperature such that the feedstream is maintained in the liquid phase. Advantageously the process is conducted at temperatures below 40°C, or at ambient temperatures in the range of from about 0 to 30°C. This avoids the need to heat the feedstream to high temperatures which can lead to quicker deactivation of the sorbent or the development of unwanted side reactions in the feedstream. Pressures may range from atmospheric up to about 8.3 KPag (1200 psig). Where the feedstream material is normally liquid at 40°C and atmospheric pressure, then no additional pressure is required. Where the feedstream is normally gaseous at these conditions, then pressure is required. Preferred pressures for normally gaseous feedstreams range from about 4.8 to about 8.3 KPag (700 to 1200 psig). The preferred rate of feed of the hydrocarbon through the sorbent may range from about 0.5 to about 10 volumes of hydrocarbon per volume of packed sorbent per hour.

The effectiveness of any particular sorbent for the removal of contaminants from the contaminated hydrocarbon feedstream is measured as the time of passage of the feedstream through the sorbent until the effluent contains a break-through level of contaminant. For the purposes of this invention, the preferred break-through level of carbon monoxide is 1 ppb and for arsine is 2 ppb. Thus, the efficiency and effectiveness of the sorbent is measured as the amount of running time during which the sorbent removes essentially all of the contaminant up to the point where the contaminant is detected in the effluent at the break-through level. Once the break-through level is achieved, the process is discontinued and the sorbent is either discarded or regenerated. Regeneration may be accomplished by calcining the sorbent at temperatures in excess of 200°C in the presence of an oxygen-containing gas, followed by reduction where the sorbent contains less than 2 valent copper as described above. The following examples are illustrative of the invention.

EXAMPLES 1-8

A series of sorbents were evaluated for their effectiveness and efficiency in removing carbon monoxide and in some cases arsine from a propylene feedstream. Propylene was introduced into a 12" pipe reactor having an inside diameter of 1/2" which was packed with 20-40 mesh size pellets of the various sorbents set forth in Table I. The sorbent weight packed in the reactor ranged from about 4.2 to about 7.7 grams depending on the density and particle size of the pellets. The liquid propylene was contacted with the sorbent at various temperatures indicated in Table I at a flow rate of 3.0 volumes of propylene per volume of sorbent per hour and under a pressure averaging from about 5.3 to 5.9 KPag (775 to 850 psig).

The various sorbents used in the Examples were as follows:

Sorbent A - A sorbent comprising a mixture of copper oxide (35 wt%), zinc oxide (35 wt%) and alumina (30 wt%), commercially available from the Katalco Corporation under the trade designation KATALCOR 53- 1.

Sorbent B - A sorbent comprising a mixture of copper oxide (66 wt%) dispersed in zinc oxide (33 wt%) commercially available from United Catalyst Corporation under the trade designation UClTM C-61-3.

Sorbent C - A sorbent comprising a mixture of copper oxide (82 wt%) and alumina (8 wt%) commercially available from Mallinckrodt Inc. under the trade designation CALSICATTM E-408-TU.

Sorbent D - A sorbent comprising a mixture of copper oxide (16 wt%), manganese dioxide (29 wt%) and alumina (55 wt%) commercially available from United Catalyst Corporation under the trade designation UClTM 3522.

Sorbent E - A sorbent comprising a mixture of copper oxide (47 wt%), manganese dioxide (4 wt%) and chromium oxide (49 wt%) commercially available from Mallinckrodt, Inc. under the trade designation CALSICATTM E-118-TU. Sorbent F - A sorbent comprising copper oxide (13 wt%) on carbon

(87 wt%) commercially available from United Catalyst Corporation under the trade designation UClTM C8-7-01.

TABLE 1

*NT - not tested

** Arsine content in feed = 10-20 ppb.

R = Reduced

NR = Not Reduced Table 1 also indicates whether the sorbent was evaluated in the reduced (R) or non-reduced (NR) form. The reduced sorbents were obtained by packing the pellets in a tubular reactor, heating the sorbent in the reactor at a rate of about 60°C per hour to a temperature of about 165 °C under flowing nitrogen, introducing from about 1-2% by volume of hydrogen gas into the nitrogen stream, increasing the heat at the rate of about 60°C per hour until a bed temperature of about 210°C is reached, and continuing reduction under these conditions for a period of about 12 hours. Reduction is essentially complete when the inlet and outlet hydrogen concentrations differ by no more than 0.2%. The reduced sorbent is then cooled under nitrogen and is ready for use.

This process reduces all or a substantial content of the cupric oxide to the metallic or zero valent form, with some content of partially reduced cuprous oxide remaining in the sorbent, depending on the time and severity of the reduction.

All sorbents which may have been allowed to absorb atmospheric moisture were dried immediately prior to use such as by passing heated nitrogen gas through the catalyst bed at a temperature of 100°C for a period of time sufficient to evaporate all removable moisture. Quantities of carbon monoxide (CO) present in the initial and effluent feedstream as shown in Table 1 were measured on a volume basis using a gas chromatograph connected to a Model RGD-2 detector marketed by Trace Analytical of Stanford, California. This unit is capable of detecting carbon monoxide levels at + 1 ppb. Arsine analysis was carried out using an MDA Scientific, Inc. Model 8500 Process Gas Analyzer with a tape chemcassette.

In Example 1, two separate runs (1a and 1b) were made using a propylene feed containing the two indicated different levels of CO. The non-reduced sorbent was poor in removing CO in each case as evidenced by an immediate break-through of CO above the 1 ppb level.

In Example 2, four separate runs were made using a reduced version of the same sorbent as Example 1. In run 2(a) the sorbent effectively removed 55 ppb CO for greater than 12 days, after which the run was terminated; in run 2(b), 350 ppb CO was removed for greater than 8 days; in run 2(c), 700 ppb CO was removed for 28 days (after which break through of CO at 1 ppb occurred); in run 2(d), the sorbent proved only moderately effective where the feed contained 20,000 ppb CO, with an immediate breakthrough of CO at the 5 ppb level.

Examples 3(a) and 3(b) demonstrates the efficacy of a different reduced sorbent based on CuO/ZnO. Examples 4(a), 4(b) and 4(c) once again demonstrate the need to use a copper sorbent in the reduced form. The data shows that a non- reduced CUO/AI2O3 sorbent works poorly in removing as little as 10 ppb CO, even at higher contact temperatures.

Example 5(a) shows that a reduced version of the same sorbent employed in Example 4 is quite effective in removing CO. The catalyst also effectively removed arsine to below 2 ppb for 86 days, after which the test was terminated without breakthrough occurring. Run 5(b) shows that this sorbent effectively removed about 18,000 ppb of CO from the propylene for 31 days, after which break through at 1 ppb occurred. In Example 6, a non-reduced sorbent analogous to that used in

Example 1 was employed, except that ZnO was replaced by Mnθ2- This non-reduced sorbent proved effective in removing 45 ppb of CO from the feed for 70 days, after which break-through at 1 ppb took place. The sorbent also removed arsine to below 2 ppb for 182 days, after which the run was terminated.

In Example 7, a reduced version of the sorbent of Example 6 was used. This sorbent effectively removed CO for 84 days, after which the run was terminated, and arsine to below 2 ppb for 84 days, after which the run was terminated, with no breakthrough in either case. In Example 8, a non-reduced CuO/Mnθ2/Cr 03 sorbent was used.

This sorbent was effective in the removal of CO and arsine for 44 days, after which the run was terminated. Example 9 demonstrates again that a non-reduced CuO on a different support, i.e., carbon, is ineffective in the removal of CO, although effective in the removal of arsine. These data clearly demonstrate the effectiveness of the liquid phase, low contact temperature process for removing either carbon monoxide or carbon monoxide and arsine from hydrocarbon feeds using reduced copper-containing sorbents and reduced or non-reduced sorbents containing both copper and manganese dioxide.

Claims

1. A liquid phase low temperature contact process for reducing the carbon monoxide or the carbon monoxide and the arsine contaminant content of a hydrocarbon feedstream comprising contacting the feedstream in the liquid phase with a copper- containing sorbent consisting of sorbents containing dispersed zero valent copper, sorbents containing a dispersed mixture of zero valent and 1 valent copper, sorbents containing a dispersed mixture of zero valent copper, 1 valent copper and manganese dioxide or sorbents containing a dispersed mixture of 2 valent copper and manganese dioxide, wherein the contact occurs at a temperature of less than about 40°C, and wherein the feedstream has a content of carbon monoxide after contact with the sorbent of less than 5 parts per billion.

2. The process of Claim 1, wherein the hydrocarbon feedstream comprises a hydrocarbon having from 1 to about 16 carbon atoms, preferably an alpha-monoolefin having from 2-4 carbon atoms.

3. The process of Claim 1 or 2, wherein the contact occurs at pressures within the range of from 4.8 to 8.3 KPag (700 to 1200 psig).

4. The process of any of the preceding claims, wherein the feedstream has an initial content of carbon monoxide in excess of 5 parts per billion, and optionally, an initial content of arsine in excess of 2 parts per billion.

5. The process of any of the preceding claims, wherein the content of carbon monoxide in the feedstream after contact with the sorbent is less than about 1 part per billion.

6. The process of Claim 5, wherein the content of arsine in the feedstream after contact with the sorbent is less than about 2 parts per billion.

7. The process of any of the preceding claims, wherein the copper- containing sorbent comprises copper in a reduced state.

8. The process of Claim 7, wherein the copper-containing sorbent further comprises manganese dioxide.

9. The process of Claim 7, wherein the copper-containing sorbent further comprises zinc oxide.

10. The process of Claim 1 - 6, wherein the copper-containing sorbent comprises non-reduced copper oxide mixed with manganese dioxide.

11. The process of any of the preceding claims, wherein the copper- containing sorbent is dispersed in a refractory metal oxide carrier.

12. The process of Claim 11 , wherein the refractory metal oxide carrier is alumina.

13. The process of any of the preceding claims, wherein the copper content of the sorbent ranges from about 5 to about 90% by weight.

14. The process of Claims 2 - 13, wherein the olefin is propylene, ethylene, or mixtures thereof.

15. The process of any of the preceding claims, wherein the copper- containing sorbent further comprises magnesium oxide, ferric oxide, cobalt oxide, zinc oxide, barium oxide, nickel oxide, lead oxide, chromium oxide and/or mixtures thereof.