Hybrid Process for o‐ and p‐Xylene Production in Aromatics Plants

Abstract

A new hybrid process for the production of o-and p-xylene is proposed to replace the traditional plant of aromatics in refineries. The proposed process comprises a simulated moving bed (SMB) unit and two crystallizers. The SMB technology as the first unit of the suggested process is applied for the separation of xylene isomers and was investigated by simulation of an industrial size unit, using experimentally measured adsorption equilibrium data on MIL-53(Al)-shaped material. The separation of p-xylene from o-xylene with m-xylene as desorbent is the key characteristic of this method. An industrial-scale SMB unit could provide extract and raffinate streams with very high purities.

Intensified p-Xylene Production Process through Toluene and Methanol Alkylation

“…inlet methanol-outlet methanol z = 100 inlet methanol     (11) Subject to a set of constraints as follows:…”

“…[1][2][3][4] The demand of p-xylene in the world has been greatly increasing in recent years, especially from China. 5 P-xylene is mainly produced by selective toluene disproportionation [6][7][8] , C8 aromatic isomerization 9 , and adsorptive separation or crystallization from other xylene isomers [10][11] . Although these methods produce high-purity p-xylene, relatively high cost is required because of either expensive raw materials in selective toluene disproportionation or low selectivity of p-xylene in C8 aromatic isomerization.…”

Crystal engineering of a rectangular sql coordination network to enable xylenes selectivity over ethylbenzene

“…Further, formation of eutectics handicaps crystallisation as a purication tool. 2 Distillation is only somewhat feasible for OX removal as it has a relatively high boiling point of 144 C (PX: 138 C, MX: 139 C and EB: 136 C). 3 In this context, adsorption based technology involving physisorbents is recognised as offering the potential for reducing the energy footprint of C8 purication.…”

“…Separation of C8 aromatics, p -xylene (PX), m -xylene (MX), o -xylene (OX) and ethylbenzene (EB), represents one of the seven industrially critical separation processes “ to change the world ”. 1 Whereas C8 aromatic mixtures have utility as anti-knocking additives in gasoline and as solvents for synthetic chemistry, each of the pure isomers are individually relevant: 2 PX is used to manufacture polyethylene terephthalate (PET) and polybutylene terephthalate (PBT); MX is the precursor for isophthalic acid and isophthalic nitrite; OX is converted to phthalic anhydride, an intermediate to coatings and plasticisers; EB is a petrochemical intermediate in production of the resin monomer styrene by dehydrogenation. EB also has utility in the pharmaceutical industry, e.g.…”

“…Further, formation of eutectics handicaps crystallisation as a purification tool. 2 Distillation is only somewhat feasible for OX removal as it has a relatively high boiling point of 144 °C (PX: 138 °C, MX: 139 °C and EB: 136 °C). 3 …”