CN1772719A

CN1772719A - Self-heating reforming method used for acetic acid and methyl alcohol integhal production

Info

Publication number: CN1772719A
Application number: CN 200410095782
Authority: CN
Inventors: D·M·蒂埃博
Original assignee: Acetex Cyprus Ltd
Current assignee: Acetex Cyprus Ltd
Priority date: 2004-11-12
Filing date: 2004-11-12
Publication date: 2006-05-17

Abstract

One integral great capacity 1,000-20,000 MTPD methanol and 300-6,000 MTPD acetic acid producing system is disclosed. The synthetic gas is produced through auto thermal reforming of natural gas, and natural gas, oxygen and circular CO2 are fed to the auto thermal reformer (ATR). Partial synthetic gas is fed to the CO2 eliminator to obtain circular CO2 and fed to cooling box to obtain hydrogen flow and CO flow. The rest synthetic gas, the hydrogen flow and CO2 are fed to the methanol synthesizer to produce methanol. Methanol and CO are fed to the acetic acid synthesizer to produce acetic acid, and acetic acid is then fed to the VAM synthesizer. Oxygen for the ATR and the VAM may be provided with one common air separator, and some other equipment, such as water vapor generator, may be further integrated into the said apparatus.

Description

Autothermal reforming process for the integrated production of acetic acid and methanol

Technical Field

The present invention relates generally to an improvedprocess for the production of methanol, acetic acid, and other chemicals such as Vinyl Acetate Monomer (VAM) from natural gas. The improved process combines a carbon monoxide separation apparatus with a methanol synthesis plant for large scale methanol and acetic acid production using a single-train process.

Background

Methanol is a major raw chemical. The primary uses of methanol include the manufacture of acetic acid, formaldehyde and methyl-tertiary-butyl ether. In the next decade, worldwide demand for methanol is expected to grow because new uses for methanol, such as converting methanol to gas (Mobil MTG process), converting methanol to light olefins (MTO process of UOP and Norsk Hydro), using methanol for power generation, and using methanol for fuel cells, will be commercialized. The development of these applications is clearly associated with the cost of methanol production. The invention can build high-efficiency single-line equipment and convert natural gas into methanol in large quantity at lower cost.

The use of carbonylation catalysts to produce acetic acid from carbon monoxide and methanol is well known in the art. Representative references disclosing this and similar processes include Carlin et al, U.S. Pat. No. 1,961,736(Tennessee Products), Paulik et al, U.S. Pat. No. 3,769,329(Monsanto), Marston et al, U.S. Pat. No. 5,155,261(Reilly Industries), Garland et al, U.S. Pat. No. 5,672,743(BP Chemicals), Joensen et al, U.S. Pat. No. 5,728,871(Haldor Topsoe), Denis et al, U.S. Pat. No. 5,773,642(Acetex Chimie), Hinnenkamp et al, U.S. Pat. No. 5,817,869(Quantum Chemical company), Ditzel et al, U.S. Pat. Nos. 5,877,347 and 5,877,348(BPChemicals), Denis et al, U.S. Pat. No. 5,883,289(Acetex Chimie), and Sunley et al, U.S. Pat. No. 5,883,295 (BPs), the contents of each of which are incorporated herein byreference.

The basic feedstocks for acetic acid manufacture are typically carbon monoxide and methanol. In a typical acetic acid production plant, methanol is imported and carbon monoxide is produced in situ, usually by reforming natural gas or another hydrocarbon with steam and/or carbon dioxide, due to difficulties in its transport and storage. In view of this, attention has recently been paid to the construction of an integrated facility for producing methanol and acetic acid. The major cost of a new acetic acid manufacturing facility is the investment in equipment required to produce carbon monoxide. It is highly desirable that this investment can be reduced considerably or at least significantly.

The basic raw materials for vinyl acetate monomer manufacture are ethylene, acetic acid and oxygen. Carbon dioxide, an undesirable by-product of the reaction, is formed and must be removed from the recycled ethylene. The major cost of new synthesis gas, methanol, acetic acid and acetic acid derivatives such as VAM manufacturing facilities is the investment in the required equipment. Other major costs include operating costs (including raw material costs). There is a need to reduce these investment and operating costs.

For methanol production, it has been determined that autothermal reforming is an economical method of producing syngas for large capacity syngas plants, since significant capital investment can be saved by not constructing a large main reformer or multiple partial oxidation reactors. However, in any case, it has the disadvantage that not all carbon molecules are used up, resulting in a large amount of CO₂Is not advantageous. In fact, the syngas needs to be conditioned at the outlet of the autothermal reformer, as denoted by SN ═ H [ ("H ═ H₂-CO₂)/(CO+CO₂)]Is less than 2, typically 1.7 and 1.9. The goal is to obtain an optimum syngas ratio, which is between 2.0 and 2.1, to supplement the methanol synthesis cycle. Lee et al, in U.S. patent 5,180,570, disclose an integrated process for making methanol and ammonia so as to approximate the stoichiometric conditions in the methanol reaction cycle. McShea, III et al, in U.S. Pat. No. 4,927,857, disclose a catalyst for autothermal reforming and a process for obtaining stoichiometric syngas by controlling the steam to carbon ratio and the oxygen to carbon ratio. Banquy, in U.S. Pat. nos. 4,888,130 and 4,999,133, discloses a process suitable for the production of methanol on a very large scale, wherein synthesis gas is produced with a composition close to the stoichiometric composition required for methanol production by using a combination of a main steam reformer and an autothermal reactor. In a paper published at the 2000 world methanol conference (11.8-10.2000) held by Copenhagen, denmark, Streb indicated that methanol production plants are of very large capacityA special process flow design is required. Streb suggested that pure autothermal reforming could be used when the feed was light natural gas, but he emphasized that CO suppression may be required at stoichiometric ratios less than 2₂The transformation of (3).

In us patent 6,495,609, Searle discloses the introduction of CO in the manufacture of ethylene oxide from ethylene₂Recycled to the methanol synthesis reactor. In U.S. patent 6,444,712, Janda discloses the introduction of CO₂Recycled back to the reformer or methanol synthesis cycle in order to control the SN to 1.6-2.1. Both Searle and Janda demonstrated that SN can be controlled by using steam and a partial oxidation reformer. Typically, the SN of the syngas generated by the steam reformer is greater than 2.8, while the SN of the syngas generated by the partial oxidation reformer is in the range of 1.4 to 2.1.

Disclosure of Invention

It has now been found that by incorporating an acetic acid production plant which consumes carbon monoxide for the carbonylation of especially a methanol gas stream, a general plant using an autothermal reformer can be adapted to the production of methanol. Carbon monoxide is separated from a portion of the reformer effluent, and CO is recovered₂Recycled to the reformer and the hydrogen is returned to the methanol synthesis. The amount of reformer effluent from which CO is recovered is balanced to yield the desired SN for the make-up syngas for the methanol cycle.

The present invention combines a methanol synthesis process with an acetic acid process. The present invention utilizes a carbon monoxide separation device located in front of the methanol reactor to adjust the SN of the remaining syngas to 2.0-2.1, preferably close to 2.05. The present invention provides a process for making methanol, acetic acid, and optionally vinyl acetate monomer, and the like. The present invention also finds that it is possible to reduce the capital costs by combining the production processes of these compounds in a specific way into an integrated, single line process.

In one embodiment of the present invention, there is provided a process for producing methanol and acetic acid, characterized by integrating the steps of: autothermal reforming a stream of hydrocarbon, such as natural gas, with oxygen, steam and carbon dioxide to produce a synthesis gas stream; separating a portion of from 5% to less than 50%, preferably from 5% to 40%, more preferably from 10% to 30%, still more preferably from 15% to 25% of said synthesis gas stream into a carbon dioxide rich stream, a hydrogen rich stream, a carbon monoxide rich stream and a methane rich stream; optionally using the methane-rich gas stream as fuel; recycling the carbon dioxide rich gas stream to the autothermal reforming step; compressing at least 50% up to 95%, preferably 60-95%, more preferably 70-90%, still more preferably 75-85% of the remainder of the synthesis gas stream with at least a portion of the hydrogen rich stream, feeding a make-up gas stream having an SN of 2.0-2.1, preferably 2.04-2.06, to a methanol synthesis cycle to obtain a methanol product; acetic acid is synthesized from at least a portion of the methanol product and the carbon monoxide rich gas stream.

The process may also include combining a hydrogen-containing stream and a natural gas feed containing higher hydrocarbons to form a hydrocarbon-containing feed stream, and contacting the feed stream with a hydrogenation catalyst at a hydrogenation temperature to produce a pretreated gas stream having a low level of higher hydrocarbons.

The method may include supplying a purge gas stream from the methanol synthesis step to the pre-reformer, the fuel and/or the separation step. In the latter case, the inert gas is purged from the methane-rich gas stream system as a tail gas after recovery of CO and hydrogen from, for example, a cold box.

Preferably, the process uses a single autothermal reformer capable of producing 1,000-20,000 metric tons/day of methanol and 300-6,00 metric tons/day of acetic acid.

The method also includes feeding the carbon dioxide gas stream and/or a carbon dioxide gas stream from an associated process into the methanol synthesis cycle. For example, the associated processes use acetic acid as a reactant, methanol product as a reactant, a portion of the oxygen from a conventional air separation unit, a common piece of equipment (utility), or a combination thereof. At least a portion of the acetic acid produced may be fed to a Vinyl Acetate Monomer (VAM) synthesis cycle in the associated process for reaction with ethylene and oxygen to produce VAM. The carbondioxide-rich gas stream from the VAM synthesis cycle may be fed to a methanol synthesis cycle.

The feed gas stream may also be pretreated by hydrogenation to use a lower steam to carbon ratio while avoiding soot formation in the autothermal reformer and corresponding facilities. In this process, a hydrogen-rich gas stream is added to a feed gas stream containing higher hydrocarbons (2 or more carbon atoms), the resulting mixture is contacted with a hydrogenation catalyst at a hydrogenation temperature, and the hydrogenated mixture is fed to an autothermal reformer with steam and oxygen to form synthesis gas. The hydrogen-rich stream is preferably a purge gas or a portion thereof from a methanol synthesis cycle receiving synthesis gas or a portion thereof. Preferably, the hydrogen-rich stream is added to the methane at a rate to provide at least a stoichiometric amount of hydrogen for the hydrogenation of the higher hydrocarbons. Preferably, the hydrogenation temperature is 300-550 ℃. In this embodiment, the apparatus and substance comprises: a feed gas comprising higher hydrocarbons; a pre-hydrogenation reactor containing a hydrogenation catalyst (typically using a base metal such as platinum, palladium, cobalt, molybdenum, nickel or tungsten supported on alumina or zeolite as the catalyst) for converting the higher hydrocarbons to form a gas stream having a low content of higher hydrocarbons; an autothermal reformer for reacting the low-level higher hydrocarbon gas stream with steam and oxygen to form a synthesis gas stream; a methanol synthesis cycle for reacting hydrogen from the synthesis gas stream with carbon monoxide to form methanol; a purge gas stream from the methanol synthesis cycle; and a line for feeding a portion of the purge gas stream to the pre-hydrogenation reactor.

Since the hydrogenation reaction is exothermic, the hydrogenation process can be carried out in one or several reactors, optionally with intermediate cooling means. This hydrogenation step is particularly suitable for use with autothermal reformers having a low steam to carbon ratio in the feed.

Drawings

FIG. 1 is a simplified block flow diagram of one embodiment of the present invention process for making methanol, acetic acid and vinyl acetate monomers using an autothermal reformer for making syngas.

Detailed Description

The apparatus used in the process of the present invention may be a new apparatus, but may also be a retrofit of an existing apparatus for the manufacture of methanol, acetic acid and/or VAM.

Natural gas 102 is provided as a fuel 103 for the plant as well as a feed gas for the synthesis. The natural gas used for synthesis is combined with a hydrogen rich gas stream and fed to a conventional desulfurization unit 104 and, optionally, to an adiabatic catalytic pre-reformer 106 with steam 108. The prereformer may be used to reduce soot formation in a subsequent ATR in which the natural gas contains a quantity of hydrocarbons containing two carbon atoms and higher hydrocarbons. The air is compressed in a compressor 115 and then sent to an Air Separation Unit (ASU)116, which is operated in a conventional manner to obtain an oxygen stream 114. Oxygen 114 from the ASU 116 and recycled CO-rich₂Is fed to the effluent 112 of the pre-reformer. A mixture of prereformed natural gas, carbon dioxide, and, optionally, steam, along with oxygen, is introduced into an autothermal reformer 118, which is catalytically reformed using conventional autothermal reforming equipment and catalyst systems, to produce a syngas stream 120. The syngas 120 is cooled and separated from the condensed liquid water in a conventional manner.

A portion of the syngas stream 120 is sent via line 119 to CO₂In the removal device 122, the aforementioned CO is generated₂A gas stream 110 is recycled. The amount of syngas added to stream 119 is determined primarily by the amount of CO required for acetic acid synthesis, but will comprise at least 5% and up to 50%, preferably 5-40%, more preferably 10-30%, still more preferably 15-25% of stream 120. The production of methanol and acetic acid should make full use of the H produced₂CO and CO₂Preferably, the yield of methanol is 1,000-20,000 metric tons/day,the yield of acetic acid was 300-6,000 metric tons/day. For a given methanol production there is an optimum acetic acid production when the SN meets the target SN value, e.g., 2.05. If more acetic acid is produced relative to methanol produced, more hydrogen is produced than is required for methanol synthesis, e.g., SN may be too high or excess hydrogen is fed into the fuel. Of course, excess hydrogen can also be balanced to some extent if there is carbon dioxide that can be fed in. If less acetic acid is produced, there is a deficiency of hydrogen, e.g., SN will be too low. If the total methanol and acetic acid production is increased, the process capacity limit of one ASU is exceeded, requiring a second investment to build another ASU. On the other hand, if the total production is reduced, economies of scale are lost and the investment cost per unit production is increased.

CO₂The removal device 122 may use conventional CO₂Removal method and apparatus for removing CO₂For example, solvent absorption followed by desorption. Optionally, all or a portion of the methanol synthesis recycle purge stream 124 may also be fed to CO via line 119₂And (4) removing the device.

CO₂Removal unit producing rich CO₂And substantially no CO in the gas stream 110₂CO/H of₂The combined gas stream 128. Will be rich in CO₂Is introduced into a syngas stream 112 located before the autothermal reformer 118. All or a portion of the CO from the VAM synthesis process, or from any other related process, or combination thereof, via line 126 can be used₂With CO enrichment from 122₂Is mixed and subjected to said autothermal reformingLine 110 before vessel 118.

Separation means 130, preferably comprising molecular sieves and a conventional cold box, separates stream 128 into at least a CO-rich stream 135 and a H-rich stream₂But may also include small amounts of one or more of the residual gases or tail gases of the mixed hydrogen, methane and CO used as fuel or output via line 134. The separation device 130 may be, for example, a partial condensation tank having two columns. The CO-rich stream 135 may be fed to an acetic acid synthesis plant136, as described in detail below. If the nitrogen content of the feed natural gas is too high, a column for nitrogen removal may be added and CO with a purity greater than 97% may be sent to the acetic acid synthesis unit.

The remaining syngas from line 120, CO from stream 126₂And hydrogen from stream 131, are compressed in compressor 138 to the pressure of methanol synthesis and then fed as make-up gas stream 123 to methanol synthesis unit 140 using a methanol synthesis cycle and catalytic methanol synthesis reactor as is well known in the art. The purge stream 124 from the synthesizer 140 may be recycled to the CO₂The removal device 122 is as described above. The purge stream 124 is required to prevent the accumulation of inert gases such as argon and methane in the methanol synthesis cycle, as is well known. In CO₂The purge gas is processed in the removal device 122 andthe cold box 130 with recycling of CO from the purge gas₂CO and hydrogen while suppressing the ingress of inert gases into the residual gas stream 134. The methanol product may be purified using distillation apparatus 142 or other conventional means. Purified methanol is output as product via line 144 or a portion thereof can be supplied to the acetic acid synthesis unit 136 via line 145.

The acetic acid synthesis unit 136 forms acetic acid from the CO from stream 135 and the methanol from stream 145 using conventional acetic acid production equipment and processes that are well known to those skilled in the art and/or commercially available, for example, according to one or more of the above-mentioned patents relating to acetic acid production. For example, a conventional BP/Monsanto process can be used, or a modified BP/Monsanto process utilizing BP-Positive technology (iridium catalyst), Celanese Low Water technology (rhodium-lithium acetate catalyst), Millennium Low Water technology (rhodium-phosphorus oxide catalyst) and/or Dual Process methanol carbonylation-methyl formate isomerization. The reaction generally comprises: methanol, methyl formate, or a combination thereof is reacted in the presence of a reaction mixture comprising carbon monoxide, water, a solvent, and a catalyst system comprising at least one halogenation promoter and at least one compound of rhodium, iridium, or a combination thereof. Preferably, the water content of the reaction mixture is up to 20% by weight. When the reaction is a simple carbonylation, the preferred water content in the reaction mixture is about 14 to about 15 weight percent. When the reaction is a low water carbonylation, the preferred water content in the reaction mixture is from about 2 to about 8 weight percent. When the reaction is methyl formate isomerization or a combination of isomerization and methanol carbonylation, the reaction mixture preferably has a water content of at least greater than 0wt.% and up to 2 wt.%. The reaction is generally continuous. Acetic acid product is obtained via line 146.

Optionally, a portion of the acetic acid from line 146 can be sent via line 147 to produce CO as a byproduct₂Such as a conventional Vinyl Acetate (VAM) synthesis plant 148. The acetic acid reacts with the ethylene input via line 150 and at least a portion of the oxygen 114 from the air separation unit 116. In a conventional VAM distillation unit 156, the liquid product gas stream 152 is distilled to output substantially pure (commercial specification) VAM via line 158. Carbon dioxide byproduct from VAM synthesis plant is passed over conventional CO₂The removal system 154 is separated from the reactor effluent gas and recycled to the methanol synthesis cycle via line 126. For example, conventional (preferably cryogenic) air separation 116 can be used to obtain oxygen in line 114 to supply the VAM synthesis unit 148 and the requirements of the autothermal reformer 118.

The manufacture of VAM is accomplished by acetoxylation of ethylene, mainly according to the following reaction:

major by-product CO₂Produced by the following reaction:

the selectivity of the process is about 7-8 mass% CO₂. A VAM plant producing about 100,000 metric tons/year (MTY) requires about 35,000MTY of ethylene and produces 5,000-10,000MTY of CO₂。

Optionally, the apparatus 160 (which typically includes a water vapor system) is provided in an integrated systemCooling systems, air compressors, etc.), such a large supply system of integrated equipment offers the advantage of economies of scale relative to each individual device. It is noted that the steam produced from the waste heat recovered from the ATR118, methanol synthesis unit 140, acetic acid synthesis unit 136 and/or VAM synthesis unit 148, or any other associated integrated unit, may be used to feed a boiler feed water pump, a fresh water cooling water pump, a seawater cooling water pump, a natural gas compressor, the ASU compressor 115, the pre-reformer 106, the ATR118, the CO compressor 115, the pre-reformer 106, the CO synthesis unit 148, or any other associated integrated unit₂A removing device 122, a supplementary compressor 138, a methanol synthesis gas circulating compressor and the like. Unlike the general case (excess steam generation by steam reforming), the integrated system of the present invention does not output steam, which is advantageous. If desired, an auxiliary boiler may provide additional steam to the process.

Example 1: in this example, the values of flow, composition and other properties are two significant digits unless otherwise noted. Unless otherwise stated, flow rates are in standard cubic meters per hour (Nm)³In mol%/h), the composition. FIG. 1 shows a MeOH/AcOH/VAM manufacturing process according to an embodiment of the invention to produce 5,088 metric tons/day (MTPD) of methanol and 20,000Nm³Flow scheme for CO for acetic acid synthesis. At 190,000Nm³Per supplying natural gas 102 as fuel 103 for the plant (16,000 Nm)³H) and process feed gas (175,000)Nm³H). A portion of the methanol synthesis recycle purge gas (8,300 Nm) was combined with natural gas having a composition of about 89.5% methane, 5% ethane, 1.0% propane, 0.5% butanes and heavier hydrocarbons, 4.0% nitrogen³H) combined and then fed to the desulfurizer 104 for removal of sulfur compounds. For the combined gas stream (183,000 Nm)³H) desulfurization, followed by reaction with steam (180,000 Nm)for the prereformer 106³H) combined to give 380,000Nm³The reaction mixture was 1.8% nitrogen and 2.3% CO₂An effluent of less than 0.1% CO, 6% hydrogen, less than 44% water vapor, 46% methane.

Desulfurized natural gas effluent (380,000 Nm) in line 112³H) and a channelLine 110 feeds a gas stream containing 98% CO₂And less than 1% each of CO, hydrogen, steam and methane₂(12,000Nm³H) into the autothermal reformer 118. ATR118 Re-consumption 110,000Nm³H water vapor and consumes 99,000Nm from line 114³Oxygen (containing 0.5% argon), yielding 580,000Nm³H contains 9% CO₂23% CO, 65% hydrogen, 1.2% nitrogen and an effluent of water vapour, methane and argon each less than 1% (the composition of which is dried).

125,000Nm³The dried effluent from the ATR118 (about 22% of the ATR118 effluent) is fed to the CO₂Removing the device 122. Rich in CO₂Has been described above, CO₂The gas flow at a low content is 112,000Nm³H, the composition of the gas stream is: 25% CO, 72% hydrogen, 1% methane, 1.3% nitrogen, and less than 1% each of argon and methane, the gas stream being fed into the cold box 130.

The cold box 130 is a condensation cold box that removes nitrogen, yielding 20,000Nm³A stream 131 of 98% CO and less than 1% each of hydrogen, nitrogen, argon and methane; 4,700Nm³A tail gas stream 134 containing 26% CO, 36% hydrogen, 23% methane, 15% nitrogen and less than 1% argon; and 87,000Nm³A stream 128 of 90% hydrogen, 9% CO and less than 1% each of nitrogen, argon and methane.

The remaining portion of stream 120, along with the major portion of stream 131, is compressed into stream 123, which has a flow rate of 541,000Nm³H is 69% hydrogen, 21% CO, 8.4% CO₂1.0% methaneand less than 1% each of make-up gases of water vapor, nitrogen and argon (SN ═ 2.04) were fed to the methanol synthesis unit 140. The device 140 generates the aforementioned purge gas stream 124; 248,000kg/h containing 17.5% water, 1.6% CO₂And less than 1% each of CO, hydrogen, argon and methane; and 212,000kg/h of commercially pure methanol in streams 144 and 145.

Stream 145 26,000kg/h methanol are fed to acetic acid synthesis unit 136 (stream 145 reacts with CO fed via line 135 in a classical Monsanto process) to yield 49,000kg/h of distilled, commercially available glacial acetic acid having a purity greater than 99.85% by weight.

A portion of the acetic acid from line 146 was fed at a rate of 22,000kg/h to a VAM synthesis unit 148 where it was mixed with 10,000Nm³Polymerization grade ethylene (containing more than 99.9% ethylene and less than 0.1% impurities) via line 150 and 6,000Nm³The oxygen from the air separation unit 116 reacted to provide 31,000kg/h of a commercial VAM product gas stream 152 having a purity in excess of 99.9 wt.%. VAM manufacture is accomplished primarily by acetoxylation of ethylene. Purity over 98% CO₂CO of₂The gas flow rate is 1,400Nm³Produced from CO₂Recycled in the removal system 154.

In this example, CO₂The gas stream is not recycled to the methanol synthesis cycle via line 126. Optionally, the CO delivered via line 127 can be used instead or in addition₂Make-up total CO required via line 126₂。

The steam balance for this exemplary process requires a high pressure steam assisted boiler that produces 180MT/h steam at 101bar and 500 ℃. Carbon efficiencies not calculated for acetic acid synthesis 136 and VAM synthesis 148 (including VAM distillation 156 and CO₂System 154) is approximately 82%.

Example 2: in this example, the conditions are the same as in the previous example, except that the CO from the VAM process is used₂Via line 126 to the methanol synthesis unit. To adjust SN to the optimum value of 2.05, 131,000Nm is used here³The effluent from the ATR118 is sent to CO₂A removal unit 122 and a CO separation unit 130 and a hydrogen rich stream from the cold box 130 is fed via 131 to the methanol synthesis cycle. Since in this example the entire hydrogen rich stream is fed to the methanol synthesis cycle, a Pressure Swing Adsorption (PSA) unit is also used to produce a purified hydrogen stream. Under normal operating fluctuations, a portion of the purified hydrogen stream may optionally be introduced into the methanol synthesis unit to adjust SN.

Then, the CO production was increased to 21,000Nm³H, yield of acetic acidThe increase was 5% to 51MT/h, at which point the methanol yield was 5,105 MTPD.

In the foregoing, the invention has been described in conjunction with specific embodiments for purposes of illustration and not limitation. Various modifications and alterations of this invention are contemplated as would occur to one skilled in the art. All such modifications and variations are intended to be included herein within the scope and spirit of this disclosure as expressed in the following claims.

Claims

1. A process for the manufacture of methanol and acetic acid, characterized in that it comprises the integrated steps of:

autothermal reforming the hydrocarbon gas stream with oxygen, steam and carbon dioxide to produce a synthesis gas stream;

separating a portion of the synthesis gas stream into a carbon dioxide rich stream, a hydrogen rich stream and a carbon monoxide rich stream;

recycling the carbon dioxide rich gas stream to the autothermal reforming step;

compressing the remaining portion of the synthesis gas stream with at least a portion of the hydrogen-rich stream and supplying a make-up gas stream having an SN of 2.0 to 2.1 to the methanol synthesis cycle to produce a methanol product;

synthesizing acetic acid from at least a portion of said methanol product and said carbon monoxide rich gas stream.

2. The method of claim 1, further comprising:

combining the hydrogen-containing stream and the higher hydrocarbon-containing feed natural gas to form a hydrocarbon-containing feed gas stream;

the feed gas stream is contacted with a hydrogenation catalyst at a hydrogenation temperature to produce a pretreated gas stream low in higher hydrocarbons.

3. The method of claim 1, wherein the portion of the synthesis gas stream that is separated into the carbon dioxide rich stream, the hydrogen rich stream and the carbon monoxide rich stream comprises from 5% to 50% of the synthesis gas stream and the remainder comprises from 50% to 95% of the synthesis gas stream.

4. The method of claim 1, wherein the portion of the synthesis gas stream that is separated into the carbon dioxide rich stream, the hydrogen rich stream and the carbon monoxide rich stream comprises from 5% to 40% of the synthesis gas stream and the remainder comprises from 60% to 95% of the synthesis gas stream.

5. The method of claim 1, wherein the portion of the synthesis gas stream that is separated into the carbon dioxide rich stream, the hydrogen rich stream and the carbon monoxide rich stream comprises from 10% to 30% of the synthesis gas stream and the remainder comprises from 70% to 90% of the synthesis gas stream.

6. The method of claim 1, wherein the portion of the synthesis gas stream that is separated into the carbon dioxide rich stream, the hydrogen rich stream, and the carbon monoxide rich stream comprises from 15% to 25% of the synthesis gas stream, and the remainder comprises from 75% to 85% of the synthesis gas stream.

7. The method of claim 1, wherein the SN is 2.04-2.06.

8. The method of claim 1, further comprising fueling a purge gas stream from the methanol synthesis cycle to the separating step, the reforming step, or a combination thereof.

9. The method of claim 1 further comprising supplying the portion of the hydrogen-enriched gas stream from the separating step to a pre-reformer.

10. The method of claim 1, wherein the purge gas stream from the methanol synthesis step is purified in a PSA unit to produce a purified hydrogen stream.

11. The method of claim 10, wherein a portion of the purified hydrogen stream is introduced into the methanol synthesis cycle and the SN of the feed gas stream is adjusted.

12. The method of claim 1, wherein the methanol production is 1,000-20,000 metric tons/day.

13. The process of claim 1, wherein the acetic acid production is 300-6,000 metric tons/day.

14. The method of claim 1, wherein the reforming step uses a single-train autothermal reformer.

15. The method of claim 1, further comprising feeding an input of carbon dioxide into the methanol synthesis cycle.

16. The method of claim 15 wherein the input carbon dioxide gas stream is fed into the methanol synthesis cycle from an associated process.

17. The method of claim 16, wherein the associated process uses acetic acid as a reactant, uses a methanol product as a reactant, uses a portion of the oxygen from a common air separation plant, shares common equipment, or combinations thereof.

18. The method of claim 17, further comprising:

providing at least a portion of the acetic acid produced to a Vinyl Acetate Monomer (VAM) synthesis cycle in the associated process;

the portion of the acetic acid is combined with the ethylene feed and oxygen to produce vinyl acetate monomer.

19. The method of claim 18, wherein the data is derived fromCO-rich of the VAM synthesis cycle₂Is fed into the methanol synthesis cycle.

20. The method of claim 1, wherein the separating step produces an inert gas rich tail gas stream.

21. A process for the manufacture of methanol and acetic acid, characterized in that it comprises the integrated steps of:

combining a hydrogen-containing gas stream with a feed natural gas comprising higher hydrocarbons to form a hydrogen-containing feed steam;

contacting the hydrogen-containing feed stream with a hydrogenation catalyst at a hydrogenation temperature to eliminate the low-level, pretreated gas stream of higher hydrocarbons;

autothermal reforming said pretreated gas stream with oxygen, steam and carbon dioxide to eliminate the synthesis gas stream;

recycling the carbon dioxide rich gas stream to the autothermal reforming step;

recovering a purge gas stream from the methanol synthesis cycle;

22. The method of claim 21, wherein the portion of the synthesis gas stream that is separated into the carbon dioxide rich stream, the hydrogen rich stream, and the carbon monoxide rich stream comprises 5% to 50% of the synthesis gas stream, and the remainder comprises 50% to 95% of the synthesis gas stream.

23. The method of claim 21, wherein the portion of the synthesis gas stream that is separated into the carbon dioxide rich stream, the hydrogen rich stream, and the carbon monoxide rich stream comprises 5% to 40% of the synthesis gas stream, and the remainder comprises 60% to 95% of the synthesis gas stream.

24. The method of claim 21, wherein the portion of the synthesis gas stream that is separated into the carbon dioxide rich stream, the hydrogen rich stream, and the carbon monoxide rich stream comprises from 10% to 30% of the synthesis gas stream, and the remainder comprises from 70% to 90% of the synthesis gas stream.

25. The method of claim 21, wherein the portion of the synthesis gas stream that is separated into the carbon dioxide rich stream, the hydrogen rich stream, and the carbon monoxide rich stream comprises from 15% to 25% of the synthesis gas stream, and the remainder comprises from 75% to 85% of the synthesis gas stream.

26. The method of claim 21, further comprising fueling a purge gas stream from the methanol synthesis cycle, feeding the purge gas stream to the separating step, the reforming step, or a combination thereof.

27. The method of claim 21, further comprising supplying a portion of the hydrogen-enriched gas stream from the separation step to a pre-reforming step.

28. The method of claim 21, wherein the purge gas stream from the methanol synthesis step is purified in a PSA unit to produce a purified hydrogen stream.

29. The process of claim 28 wherein a portion of said purified hydrogen stream is introduced into said methanol synthesis cycle and the SN of said feed gas stream is adjusted.

30. The method ofclaim 21, wherein the SN is 2.04-2.06.

31. The method of claim 21, wherein the methanol production is 1,000-20,000 metric tons/day.

32. The method of claim 21, wherein the acetic acid production is 300-6,000 metric tons/day.

33. The method of claim 21, wherein the reforming step uses a single-train autothermal reformer.

34. The method of claim 21, further comprising:

providing at least a portion of the acetic acid produced to a Vinyl Acetate Monomer (VAM) synthesis cycle in an associated process;

35. The method of claim 34, wherein the associated process uses acetic acid as a reactant, uses a methanol product as a reactant, uses a portion of the oxygen from a common air separation unit, shares common equipment, or combinations thereof.

36. The method of claim 34, wherein the CO-rich from the VAM synthesis cycle is introduced₂Is fed into the methanol synthesis cycle.