METHOD FOR PRODUCING C2-C4 OLEFINS FROM METHANOL AND ETHANOL

Abstract

The invention relates to a method for producing C2-C4 olefins from methanol and ethanol, said method having the steps of: A) feeding a methanol- and optionally ethanol-containing feed flow A into a dimethyl ether fixed-bed reactor and catalytically reacting methanol to form dimethyl ether, wherein a product flow A1 containing dimethyl ether, methanol, ethanol and steam is obtained; B) mixing the flow A1 with at least one hydrocarbon return flow R containing C2-C6 hydrocarbons and catalytically reacting the mixture in an olefin fixed-bed reactor to form a raw product flow B containing C2-C4 olefins, C5-C6 hydrocarbon and C7+ hydrocarbons; C) cooling the raw product flow B, wherein a hydrocarbon raw product flow C is obtained; D) separating the hydrocarbon raw product flow C in a propylene-containing value product flow, optionally an ethylene-containing value product flow, a butene-containing value product flow, at least one C5-C6 hydrocarbon-containing return flow and at least one C6+ hydrocarbon-containing auxiliary product flow; E) returning a part of the C2-C4 olefins and at least a part of the C5-C6 hydrocarbons as one or more hydrocarbon return flows in step B); F) recovering a propylene-containing value product flow, an ethylene-containing value product flow and optionally a butene-containing value product flow; G) discharging the C6+ hydrocarbon-containing auxiliary product flow; characterised in that the flow A, in relation to methanol and ethanol, contains <1 wt. % or 30 to 50 wt. % ethanol, wherein, in relation to 100 wt. % of the C2-C4 olefins recovered as value products, 30 to 60 wt. % ethylene, 30 to 60 wt. % propylene, and 0 to 30 wt. % butene are recovered as value products, and, in relation to the C2-C4 olefins contained in the raw product flow B, 0 to 40% of the ethylene, 40 to 90% of the propylene, and 0 to 100% of the butene are fed back in step B), or the flow A, in relation to methanol and ethanol, contains 1 to 30 wt. % ethanol, wherein, in relation to 100 wt. % of the C2-C4 olefins recovered as value products, 0 to 20 wt. % ethylene, 70 to 100 wt. % propylene, and 1 to 20 wt. % butene are recovered as value products, and, in relation to the 40 C2-C4 olefins contained in the raw product flow B, 0 to 100% of the ethylene, 0 to 20% of the propylene and 40 to 100% of the butene are fed back in step B).

Claims

1.-3. (canceled)

4. A process for preparing C.sub.2-C.sub.4 olefins from methanol and ethanol, comprising the steps of: A) feeding a feed stream A comprising methanol, with or without ethanol, into a dimethyl ether fixed bed reactor and catalytically converting methanol to dimethyl ether to obtain a product stream A1 comprising dimethyl ether, methanol, ethanol and water vapor; B) mixing stream A1 with at least one hydrocarbon recycle stream R comprising C.sub.2-C.sub.6 hydrocarbons and catalytically converting it in an olefin fixed bed reactor to a crude product stream B comprising C.sub.2-C.sub.4 olefins, C.sub.5-C.sub.6 hydrocarbon and C.sub.7 hydrocarbons; C) cooling crude product stream B to obtain a hydrocarbon crude product stream C; D) separating hydrocarbon crude product stream C into a propylene-comprising product of value stream, optionally an ethylene-comprising product of value stream, at least one C.sub.5-C.sub.6 hydrocarbon-comprising recycle stream, and at least one by-product stream comprising C.sub.6 hydrocarbons; E) recycling a portion of the C.sub.2-C.sub.4 olefins and at least a portion of the C.sub.5-C.sub.6 hydrocarbons as one or more hydrocarbon recycle streams into step B); F) obtaining a propylene-comprising product of value stream, an ethylene-comprising product of value stream, and optionally a product of value stream comprising butenes; G) discharging the by-product stream comprising C.sub.6 hydrocarbons; wherein stream A, based on methanol and ethanol, comprises <1% by weight or 30% to 50% by weight of ethanol, where, based on 100% by weight of the C.sub.2-C.sub.4 olefins obtained as products of value, 30% to 60% by weight of ethylene, 30% to 60% by weight of propylene and 0% to 30% by weight of butenes are obtained as products of value, and, based on the C.sub.2-C.sub.4 olefins present in crude product stream B, 0% to 40% of the ethylene, 40% to 90% of the propylene and 0% to 100% of the butenes are recycled into step B), or stream A, based on methanol and ethanol, comprises 1% to 30% by weight of ethanol, where, based on 100% by weight of the C.sub.2-C.sub.4 olefins obtained as products of value, 0% to 20% by weight of ethylene, 70% to 100% by weight of propylene and 1% to 20% by weight of butenes are obtained as products of value, and, based on the C.sub.2-C.sub.4 olefins present in crude product stream B, 0% to 100% of the ethylene, 0% to 20% of the propylene and 40% to 100% of the butenes are recycled into step B).

5. The process according to claim 4, wherein steps A) to D) comprise the following steps A1), A2), B1), B2), C1), C2) and D): A1) feeding a feed stream A comprising methanol and ethanol into a dimethyl ether fixed bed reactor and catalytically converting methanol to dimethyl ether to obtain a product stream A1 comprising dimethyl ether, methanol, ethanol and water vapor; A2) mixing at least a portion of product stream A1 with at least one hydrocarbon recycle stream R comprising C.sub.2-C.sub.6 hydrocarbons and a water vapor stream to obtain a second feed stream A2; B1) heating the second feed stream A2 in one or more heat exchangers to a temperature in the range from 430 to 500 C. and feeding it into an olefin fixed bed reactor, where the heating may also precede the mixing of individual substreams to give the feed stream A2 in step A2; B2) catalytically converting feed stream A2 at a temperature in the range from 430 520 C. to a crude product gas stream B comprising ethylene, propylene, butenes, further C.sub.2-C.sub.6 hydrocarbons, C.sub.7.sup.+ hydrocarbons, methanol and water vapor; C1) cooling crude product gas stream B in one or more heat exchangers to a temperature in the range from 170 to 220 C. by heat exchange with feed stream A2; C2) cooling crude product gas stream B to a temperature in the range from 30 to 60 C. by contacting with at least one water-containing quench circulation stream K, with condensation of water and methanol, to obtain a water- and methanol-depleted hydrocarbon crude product gas stream C2; D) separating hydrocarbon crude product gas stream C into a propylene-comprising product of value stream, optionally an ethylene-comprising product of value stream, a butene-comprising product of value stream, at least one recycle stream comprising C.sub.5-C.sub.6 hydrocarbons, and at least one by-product stream comprising C.sub.6.sup.+ hydrocarbons.

6. The process according to claim 4, wherein step D) comprises steps D1) to D7): D1) compressing hydrocarbon crude product gas stream C to obtain a liquid hydrocarbon stream D11 comprising propylene and C.sub.4, C.sub.5 and C.sub.6.sup.+ hydrocarbons, and an ethane-, ethene- and propylene-comprising gaseous hydrocarbon stream D12; D2) separating water from the liquid hydrocarbon stream D11 by phase separation to obtain a liquid hydrocarbon stream D21; D3) separating a propylene-comprising stream D31 from the liquid hydrocarbon stream D21 to obtain a stream D32 comprising C.sub.4, C.sub.5 and C.sub.6.sup.+ hydrocarbons; or separating a stream D31 comprising propylene and C.sub.4 hydrocarbons to obtain a stream D32 comprising C.sub.4, C.sub.5 and C.sub.6.sup.+ hydrocarbons; D4) separating a by-product stream D41 comprising C.sub.6.sup.+ hydrocarbons from the stream D32 comprising C.sub.4, C.sub.5 and C.sub.6.sup.+ hydrocarbons to obtain a stream D42 comprising C.sub.4, C.sub.5 and C.sub.6 hydrocarbons; stream D41 optionally comprises aromatic C.sub.6 hydrocarbons, and stream D42 aliphatic C.sub.6 hydrocarbons; D5) separating a propylene-comprising stream D51 from the ethane-, ethene- and propylene-comprising gaseous hydrocarbon stream D12 to obtain an ethane- and ethene-comprising stream D52; D6) separating a stream D61 comprising butenes from the stream D42 comprising C.sub.4, C.sub.5 and C.sub.6 hydrocarbons to obtain a stream D62 comprising C.sub.5 and C.sub.6 hydrocarbons; and or separating a propylene-comprising stream D63 from stream D31 to obtain a stream D64 comprising butenes; D7) obtaining at least one recycle stream R from one or more of the streams selected from stream D42 comprising C.sub.4, C.sub.5 and C.sub.6 hydrocarbons, stream D62 comprising C.sub.5 and C.sub.6 hydrocarbons, the propylene-comprising stream D31, the propylene-comprising stream D51, the propylene-comprising stream D63, stream D61 comprising butenes, stream D64 comprising butenes, and the ethane- and ethene-comprising stream D52.

Description

EXAMPLES

[0063] The below ranges 1-4 of the composition of feed stream (ethanol content), crude product stream (ratios of C.sub.2/C.sub.3 olefins and C.sub.4/C.sub.3 olefins) and product of value obtained (proportions of C.sub.2, C.sub.3 and C.sub.4 olefins) were simulated by calculation. Figures in weight ratios.

[0064] In order to ascertain the preferred ranges, catalytic experiments were conducted on a laboratory scale, on the basis of which the expected conversions and mass flow rates in an industrial process with a preliminary reactor, tray reactors and separation section were calculated. Optimization of this system led to the in ranges 1-4 that are specified in table 1. Table 2 shows the relevant flow rates for example points determined in ranges 1 and 2. Similar example values for ranges 3 and 4 are listed in table 3. The addition of ethanol in each case allows minimization of the relative recycle stream (Recycle) and the relative by-product stream, and hence improvement of the energy efficiency and mass efficiency of the process.

TABLE-US-00001 TABLE 1 Ratio of Proportion Proportion C.sub.2/C.sub.3 Ratio of of of olefins in C.sub.4/C.sub.3 recycled recycled Proportion the olefins olefin in olefin of recycled product in the the over- in the olefin in of value product of value all C.sub.2 olefin overall C.sub.3 olefin the overall C.sub.4 olefin [00001]$\frac{\mathrm{EtOH}}{\mathrm{EtOH}+\mathrm{MeOH}}$ Range 1 0.8-1.2 0-0.7 0-0.4 0.4-0.9 0-1 Range 2 0.8-1.2 0-0.7 0-0.4 0.4-0.9 0-1 0.3-0.5 Range 3 .sup.0-0.2 0.01-0.2 0-1 1 0-0.6 Range 4 .sup.0-0.2 0.01-0.2 0-1 1 0-0.6 0.01-0.3

[0065] The results of the simulations are collated in tables 2 and 3. All figures in weight ratios.

TABLE-US-00002 TABLE 2 0 0.5 [00002]$\frac{\mathrm{EtOH}}{\mathrm{EtOH}+\mathrm{MeOH}}$ Product Recycle By-products Product Recycle By-products Rel. mass flow 1.0 3.73 1.88 1.0 0.63 0.53 MeOH EtOH DME 0.01 0.01 0.02 H.sub.2O H.sub.2 CO.sub.2 CH.sub.4 0.02 0.01 C.sub.2H.sub.4 0.39 0.41 C.sub.3H.sub.6 0.41 0.39 0.41 0.66 C.sub.4H.sub.8 0.20 0.12 0.18 0.03 C.sub.5H.sub.10 0.01 0.02 0.02 0.02 C.sub.6-C.sub.8 olefins 0.01 0.01 0.02 0.03 C.sub.2H.sub.6 0.08 0.04 C.sub.3H.sub.8 0.20 0.11 0.11 0.13 C.sub.4H.sub.10 0.18 0.16 0.02 0.19 C.sub.5H.sub.12 0.05 0.11 0.07 0.08 C.sub.6-C.sub.8 0.03 0.06 0.06 0.08 paraffins Aromatics 0.42 0.39

TABLE-US-00003 TABLE 3 0 0.21 [00003]$\frac{\mathrm{EtOH}}{\mathrm{EtOH}+\mathrm{MeOH}}$ Product Recycle By-products Product Recycle By-products Rel. mass flow 1.0 1.09 0.65 1.0 1.02 0.56 MeOH EtOH DME 0.02 0.02 0.01 0.02 H.sub.2O H.sub.2 CO.sub.2 CH.sub.4 0.01 0.01 C.sub.2H.sub.4 0.02 0.15 0.03 0.23 C.sub.3H.sub.6 0.85 0.86 C.sub.4H.sub.8 0.13 0.18 0.11 0.16 C.sub.5H.sub.10 0.01 0.02 0.01 0.02 C.sub.6-C.sub.8 olefins 0.01 0.02 0.01 0.03 C.sub.2H.sub.6 0.36 0.07 0.34 0.07 C.sub.3H.sub.8 0.10 0.12 C.sub.4H.sub.10 0.16 0.18 0.14 0.17 C.sub.5H.sub.12 0.07 0.12 0.06 0.10 C.sub.6-C.sub.8 0.04 0.06 0.04 0.07 paraffins Aromatics 0.39 0.39