Differences between the liquid-phase process and the dry gas process for producing styrene

The purity of styrene products is the same; it’s just that the processes used to produce ethylbenzene differ

Is the purity of products produced using dry gas lower? Not at all; we use dry gas to produce ethylbenzene, and the purity of styrene can reach 99.9%

The purity is fine, but could the level of impurities present affect the quality of the polystyrene products produced downstream?

Is there anyone interested in the “Aromatics production via catalytic dry gas aromatization in oil refining” project?

Different processes yield different results. The final production costs also vary

Dry gas method, A-SM styrene – xylene levels are too high! ! ! ! !

Could someone explain to me the principle behind the process for producing ethylbenzene from dry gas, or send me some relevant materials? Thank you

The impurities are different; ethylbenzene produced from pure ethylene is diethylbenzene, which tends to polymerize, while ethylbenzene produced from catalytic dry gas is propylbenzene

Xylene levels are too high; polymerization does not occur easily during styrene polymerization, resulting in slightly lower quality!

The production of ethylbenzene from dry gas involves four process steps: propylene removal, hydrocarbonation and dehydrocarbonation reactions, absorption and benzene recovery, and ethylbenzene separation. 1 Depropyleneation: The catalytic dry gas coming from outside the boundary zone enters the catalytic dry gas wash tank (D-101), where water washing is used to remove ethanolamine, a desulfurization agent that may be present in the catalytic dry gas, thereby preventing poisoning and deactivation of the hydrocarbonation catalyst. The catalytic dry gas coming out of the catalytic dry gas washing tank passes through the catalytic dry gas heat exchanger (E-101) to exchange heat with the depropylene catalytic dry gas at the top of the propylene absorber (C-101); after that, it is cooled to 15°C in the catalytic dry gas subcooler (E-102) before entering the bottom of the propylene absorber. The depropylene catalytic dry gas, after propylene has been absorbed by the absorbent, is cooled to around 35°C in a catalytic dry gas heat exchanger before being sent to the dehydrogenation reactor (R-101A/B). The absorbent in the propylene absorption tower is a dehydrogenation material, whose main component is diethylbenzene. The rich absorbent from the bottom of the propylene absorption tower passes through the lean-liquid to rich-liquid heat exchanger (E-103) before entering plate 16 in the middle of the desorption tower (C-102); the bottom of the desorption tower is heated to 257°C using a heat carrier. The bottom liquid from the desorption tower is pumped by the absorbent circulation pumps (P-102A/B/C) and cooled to 40°C in the lean-liquid to rich-liquid heat exchanger; it is then subcooled to 15°C in the lean-liquid subcooler (E-104) before entering the top of the propylene absorption tower. The gas at the top of the desorption tower is partially condensed at 165°C by the steam generator (E-106) and enters the desorption tower reflux tank (D-102); the condensed liquid is pumped back to the top of the desorption tower by the desorption tower reflux pumps (P-103A/B). The gas discharged from the desorption reflux tank is cooled to 10°C by the desorption tower top gas cooler (E-107) and the desorption tower top gas subcooler (E-108), before entering the desorption tower top gas liquid separation tank (D-103). The condensed liquid is sent back to the desorption reflux tank by the desorption tower top condensate pump (P-104A/B), while the non-condensable, propylene-rich catalytic dry gas is sent to the catalytic units outside the boundary area or discharged through the pipeline network. 2 Hydrocracking and dehydrocracking reactions: The recycled benzene coming from the 11th plate side stream of the recycled benzene column (C-104) is transported to the recycled benzene tank (D-105) by the recycled benzene column side stream extraction pumps (P-111A/B). Then, a portion of it is sent to the dehydrocracking reaction feed tank (D-106) by the recycled benzene pumps (P-106A/B), while most of it is heated to 250°C through the fresh benzene-recycled benzene heat exchanger (E-115), the reaction product-recycled benzene heat exchanger (I) (E-111), and the reaction product-recycled benzene heat exchanger (II) (E-110), before entering the recycled benzene heater (F-102). The recycled benzene exiting the heater reaches 348°C and then enters the top of the hydrocracking reactor (R-101A/B). The depropylene catalytic dry gas from the top of the propylene absorber enters the hydrocarbonation reactor in four streams. The temperature of the reaction products exiting the bottom of the hydrocarbonation reactor is 360°C; it is cooled to 159°C through Reactor Products-Cycle Benzene Heat Exchanger (1) and Reactor Products-Cycle Benzene Heat Exchanger (2), before entering the Reactor Products-Benzene Column Feed Heat Exchanger (E-112) where it is partially condensed at 127°C. The condensate is then transported by the Reactor Products Intermediate Condensate Pumps (P-107A/B) as feed for the benzene column (C-104). The non-condensable gas is cooled to 15°C via the reaction product condenser (E-113) and the reaction product subcooler (E-114), before entering the hydrocarbonization off-gas absorption tower (C-103). The dehydrogenation feed coming from the top of the polyethylbenzene tower (C-108) has a temperature of 122°C; it is pumped by the dehydrogenation feed pump (P-120) and heated to 210°C in the circulating absorbent-dehydrogenation feed heat exchanger (E-124) before entering the dehydrogenation reaction feed tank. In the dehydrogenation reaction feed tank, the temperature of the dehydrogenation reaction feed is 158°C; it is pressurized to 4.0 MPaG by the dehydrogenation reaction feed pump, and then heated to 260°C by the dehydrogenation reaction feed heater (E-116) before entering the bottom of the dehydrogenation reaction reactor (R-102). The dehydrogenation products coming out of the top of the dehydrogenation reactor enter the circulating benzene column. 3 Absorption and benzene recovery: The recycled absorbent from the bottom of the ethylbenzene distillation column (C-106) is cooled to 15°C in the recycled absorbent subcooler (E-126) before being fed into the top of the hydrocarbonation off-gas absorption column (C-103). The liquid-phase reaction products from the reaction product condensation cooler and the gas-phase reaction products from the reaction product subcooler enter the bottom of the hydrocarbonation off-gas absorption tower respectively. The hydrocarbonated exhaust gas at the top of the absorption tower is discharged into the fuel gas pipeline network. The liquid from the hydrocarbonation off-gas absorption tower bottom is pumped by pump P-109; it is heated after heat exchange in the reaction product-benzene tower feed heat exchanger (E-112), and then sent together with the intermediate reaction product condensate from pump P-107 and the hydrocarbonation reaction products from reactor R-102 to plate 52 of the recycle benzene tower (C-104). Fresh benzene from the fresh benzene pump (P-105) is heated to 127°C in the fresh benzene-circulating benzene heat exchanger (E-115) before entering plate 7 of the circulating benzene column (C-104). The reboiler of the recycle benzene column (E-118A/B) is heated with steam at 3.5 MPaG. The vapor generator at the top of the recycle benzene column (E-117) produces steam at 0.21 MPaG, which is used as process steam for the styrene plant. The aftercooler at the top of the recycle benzene column (E-133) generates hot water at 120°C for use in the lithium bromide refrigeration unit. The non-condensable gas from the top of the recycle benzene tower is sent to the fuel gas separator tank (D-116) after benzene is recovered through non-aromatic removal. The recycle benzene taken from plate 11 of the recycle benzene tower is transported to the recycle benzene tank (D-105) using the benzene tower side-line pump (P-111). The circulating benzene tower bottom stream is sent to plate 60 of the ethylbenzene distillation tower (C-106). 4 Ethylbenzene separation: The reboiler (E-122) at the bottom of the ethylbenzene distillation column (C-106) is heated with steam at 3.5 MPaG, while the steam generator at the top of the ethylbenzene distillation column produces steam at 0.21 MPaG, which is used as process steam for the styrene plant. A portion of the material pumped by the ethylbenzene distillation reflux pump is taken as ethylbenzene product; after being cooled in the ethylbenzene product cooler (E-123), it is sent to the ethylbenzene product tanks (D-110A/B), and following analysis, to the ethylbenzene storage tanks in the ethylbenzene tank area (T-702A/B). The bottom liquid from the ethylbenzene distillation tower is pumped by the bottom pump of that tower; part of it is sent to plate 11 of the propylbenzene tower, while the other part is cooled through the circulating absorbent–dehydrogenation feed heat exchanger (E-124), the circulating absorbent cooler (E-125), and the circulating absorbent subcooler (E-126) before being sent to the hydrogenation off-gas absorption tower (C-103). The reboiler (E-128) at the bottom of the cumene tower (C-107) is heated with steam at 3.5 MPaG, while the steam generator (E-117) at the top of the cumene tower produces steam at 0.21 MPaG, which is used as process steam for the styrene plant. A portion of the material pumped by the cumene reflux pump is separated as a cumene fraction; after being cooled in the cumene fraction cooler (E-123), it is sent to the cumene intermediate tank (D-112). The cumene tower bottom liquid is pumped by the cumene tower bottom pump (P-118) to the middle section of the polyethylbenzene tower. The polyethylbenzene tower (C-108) operates under negative pressure; the reboiler at the bottom of the tower (E-131) is heated using a heat carrier, while the condenser at the top of the tower (E-130) generates hot water at 120°C for use in the lithium bromide refrigeration unit. The dehydrogenation feed produced at the top of the polyethylbenzene tower is transported by a dehydrogenation feed pump; after being heated to 210°C in the circulating absorbent-dehydrogenation feed heat exchanger (E-124), it enters the dehydrogenation feed tank (D-106).