PTQ Q2 2022 Issue

activity. The simplicity of this pro- cess generates significant capital cost savings when compared to liquid catalyst technologies. K-SAAT technology offers a step change in sustainability of alkyla- tion processes. The process generates no liquid wastes and has 25% lower carbon emissions than the closest viable alternative. It produces a sul- phur-free alkylate product and gen- erates no SOx emissions. The catalyst itself is safe to handle and environ- mentally benign, eliminating health, safety, and environmental hazards from liquid catalyst spills (see Figure 9 ). The K-SAAT process offers Indian refiners an opportunity to produce alkylate at lower cost and higher quality without the health, safety, and environmental impact of liquid alkylation catalysts. With the like- lihood of a 95 RON standard being adopted in the coming years, now is the time for Indian refiners to add alkylation capacity. Off-gas to alkylate K-SAAT offers a further source of value to refiners through its unique ability to alkylate ethylene to isooc- tane (liquid acids form stable esters with ethylene and are thus unable to alkylate it) in a single reactor stage, opening an opportunity to generate high octane alkylate from low-value off-gas. Refinery off-gases from the fluid catalytic cracking (FCC) unit and coker are normally routed to the refinery fuel gas system to recover limited value in the form of process heating. However, K-SAAT with integrated ethylene recovery from dry gas produces high octane, low RVP, alkylate with more than double the yield of conventional dry gas to liquid technologies. This scheme uti- lises more moderate ethylene recov- ery conditions than typical ethylene recovery units to reduce energy con- sumption and deliver greater eco- nomic value, while making better use of valuable natural resources. Conclusions The Indian gasoline market is under- going a period of rapid growth and change. As a consequence, Indian refiners started importing a lighter crude slate to meet growing gasoline

Isobutane recycle

K-SAAT reactors A + B Alkylation

LPG feed (Olen + isobutane)

Distillation

K-SAAT reactor C Regeneration

Hydrogen

Alkylate product

Figure 8 K-SAAT solid acid alkylation process

acid and HF, but many of the same or similar issues can be associated with this solution. Ionic liquids are classed as salts that are liquid at low temperature. Ionic liquids for alky- lation require hydrogen chloride (HCl), to be added as a co-catalyst. Organic chlorides and HCl in the reactor effluent are carried over to the fractionation section, meaning that extensive chloride management, rather than fluoride management as in HF alkylation, is required to prevent corrosion in downstream equipment and engines. To achieve reasonable alkylate octane rating, ionic liquid alkylation requires low reaction temperatures, using ener- gy-intensive refrigeration, and a feed rich in 2-butenes, making a selective hydrogenation unit highly recommended for 1-butene isomer- isation. Due to the unit complexity and metallurgy requirements, ionic liquid alkylation units are capital intensive. In addition, a recent paper published in Renewable & Sustainable Energy Reviews concluded that “cur- rent ionic liquids are not eco-friendly compounds”. 13 Solid acid catalysis has long been recognised as the ultimate solution in alkylation technology offering a simpler, safer, and more sustain- able process. The main barrier to success of solid acid catalysts has been the high rate of catalyst deac- tivation by oligomerisation, leading to a short and impractical alkylation cycle length. However, the ExSact catalyst, developed by Exelus Inc., has overcome this limitation with a catalyst offering unparalleled alky - lation performance and a 24-hour alkylation cycle length. The cata- lyst is zeolite based and free from precious metals, lowering the costs

K-SAAT alkylate properties

Feed

RON

MON

Ethylene

99 92 99 97 93

95 90 95 93 89

Propylene (70% C 3 =) MTBE raffinate

FCC BBF Amylenes

Table 1

compared to previous-generation solid acid catalysts. It is selective to high octane trimethylpentanes, surpassing liquid acids for alkylate quality. Through rigorous testing on various feedstocks, and evidence from a commercial-scale unit, the catalyst robustness has been demonstrated through hundreds of regeneration cycles. ExSact is offered exclusively as a proprietary catalyst in KBR’s solid acid alkylation technology (K-SAAT). The superior catalyst per- formance allows a simple fixed-bed reactor design to be implemented (see Figure 8 ), with the reactors oper- ating above ambient temperature. The catalyst is regenerated in-situ by circulating hot hydrogen through the offline reactor to strip oligomers from the catalyst and restore full

Figure 9 ExSact alkylation catalyst

20 PTQQ 2 2022