From Molasses to Metal: an Integrated Route to Tx Synthetic Petrol

Two research divisions, one integrated paper.

The chemistry in this paper — reaction selection, catalyst formulation, reactor design, and every governing equation — is the independent work of the Chemistry Research Division. The techno-economic analysis, blend strategy, and comparative cost work is the independent work of the Tech & Political Science Research Division. Where the two meet is the reactor itself: chemistry decides what's physically possible, economics decides what's worth building.

1. 1. Introduction01
2. 2. Background — Why Redesign the First Pitch02
3. 3. Improved Reaction Chemistry03
4. 4. The Quad-Chamber Integrated Reactor04
5. 5. Modified SE-SMR for Biogas05
6. 6. Methodology — Governing Equations06
7. 7. Mass & Energy Balance07
8. 8. Techno-Economic Analysis08
9. 9. Tx Naming & Blend Strategy09
10. 10. Comparative Analysis10
11. 11. Environmental & Economic Impact11
12. 12. Byproduct Utilisation12
13. 13. Advantages & Disadvantages13
14. 14. Discussion14
15. 15. Conclusion15
16. References—

Abstract

India blends ethanol into petrol at 20% today and is actively pushing higher blends — E22 through E30 with a new excise waiver, and a commercial E85 rollout for flex-fuel vehicles launched in Delhi in June 2026. Every one of these routes shares the same structural weakness: ethanol has roughly 30% lower energy density than petrol, so higher blends mean lower mileage, and blends above E20 require re-engineered fuel systems that almost no vehicle on Indian roads currently has. This paper presents an alternative that does not dilute petrol with ethanol, but chemically converts ethanol into petrol — dehydration to ethylene, oligomerisation to a C6–C12 hydrocarbon chain, and partial hydrogenation to a BIS-compliant gasoline-range product — carried out in a single four-chamber reactor vessel we call the Quad-Chamber Reactor (QCR), with its hydrogen demand supplied by a biogas-fed SE-SMR module built directly atop the same distillery's vinasse digester and scaled to co-produce merchant hydrogen alongside the captive stream Chamber 3 consumes. Beyond the chemistry, this paper specifies the QCR and SE-SMR as distinct mechanical apparatus — a downward-reflux dehydration chamber, a continuous-flow internal-loop oligomeriser, a multilayer trickle-bed hydrogenator, an upflow-biased fractionation stack, and a concentric annular reformer-calciner mounted on the digestion vessel with a differential two-way hydrogen split — engineered as a patent-oriented configuration rather than a generic process-flow sketch. We report the full reaction chemistry, every governing equation behind the mass and energy balance, a complete techno-economic analysis with a real per-litre cost structure and a semi-full-scale capex re-costing, and a direct comparison against petrol, E20, E85, and neat ethanol (ED95) on production cost, mileage, combustion behaviour, and engine effects. The resulting fuel — designated Tx (Trilok's Formulation; also, chemically, Triolefin Transform), where x is the percentage blended into commercial petrol — is reported in two grades from the same reactor hardware. The Standard grade, reached purely through tighter internal-loop recycle control (no new equipment), delivers approximately 95.0% of the input ethanol's energy content as a true drop-in hydrocarbon requiring no vehicle modification, at a gross production cost of roughly ₹107.9 per litre — lower than our own earlier-reported figure, not higher, because the same control tuning that lifts yield also spreads fixed cost over more product (Section 8.2). An Octane-94 grade, reached by narrowing the oligomerisation catalyst's Si/Al window to increase branching selectivity, raises the theoretical Research Octane Number to ≈94.0 (Section 9.1) at a modest, honestly-quantified cost: gross production cost rises to roughly ₹109.6 per litre and energy retention falls to roughly 94.2% relative to the Standard grade — both grades still improve on this paper's own earlier baseline (₹112.6/L, ~91% retention). Both are achieved without altering the reaction chemistry, the reactor hardware, or the capex basis of Section 4. We also report a small positive net profit once byproduct revenue — including a semi-full-scale merchant-hydrogen stream from the same SE-SMR loop — is integrated (Sections 8.3–8.4); a component-by-component Technology Readiness Level assessment with re-costed capital estimates for both the SE-SMR unit and the QCR (Section 4); a full T10–T100 blend-economics table at 5-unit increments (Section 9.2); and a dedicated advantages-and-disadvantages assessment (Section 13) that states the honest limits of the design alongside its gains.

India's ethanol blending programme is, by most measures, a policy success story: blending rose from 1.53% in 2014 to 20% by 2025, five years ahead of its own target, and has saved an estimated ₹1.84 lakh crore in foreign exchange. The next phase of that programme — E22 to E30 blends now exempt from central excise duty, and E85 for flex-fuel vehicles already live at select Delhi pumps — is a bet that India can keep pushing ethanol content upward and manage the consequences downstream.

Those consequences are real and are not being hidden by the government: ethanol's lower calorific value (~21 MJ/L against petrol's 32–34 MJ/L) means every step up in blend percentage is a step down in kilometres per litre, and blends above E20 require fuel-system components — seals, injectors, calibration — that the overwhelming majority of vehicles on Indian roads today do not have. E85 exists commercially, but as of mid-2026 the only flex-fuel car in production in India is restricted to commercial use, and flex-fuel two-wheelers only reached showrooms in July 2026.

This paper asks a different question. Instead of blending ethanol into petrol and accepting the energy and compatibility penalty, can ethanol be chemically rebuilt into a hydrocarbon — a real petrol-range molecule, not an alcohol — using chemistry that is individually well established (catalytic dehydration, zeolite oligomerisation, selective hydrogenation) but has not, to our knowledge, been packaged as a single integrated reactor sized for India's distillery-scale ethanol supply chain, with its own hydrogen demand met from the same feedstock's waste stream. That is the proposal in this paper.

An earlier internal draft of this pitch proposed the correct core chemistry — dehydration, oligomerisation, partial hydrogenation, with hydrogen sourced from an SE-SMR unit run on waste biogas — but treated the SE-SMR unit as an oversized, independent hydrogen-and-CO₂ business bolted onto the fuel-upgrading plant. Working through the actual stoichiometry corrects that: the captive hydrogen demand for partial hydrogenation at BIS-compliant olefin levels is small — on the order of a few kilograms of H₂ per 1,000 L of ethanol processed — which needs only a modest quantity of methane-equivalent biogas feed, not a large independent reforming unit.

Three further gaps needed closing before this could be called a complete process design rather than a chemistry sketch: the four reaction/separation steps were being treated as four separate pieces of equipment rather than an integrated unit, the SE-SMR module was using flare-gas-optimised parameters rather than parameters adapted to actual biogas composition (which, unlike flare gas, carries CO₂ and H₂S), and the cost comparison stopped at petrol without placing the result against the ethanol-derivative fuels — E20, E85, ED95 — that it is actually competing with in the Indian market today. Sections 4, 5, and 10 of this paper address each of those three gaps in turn.

Three sequential reaction steps convert ethanol into a gasoline-range hydrocarbon. Each has been selected and tuned specifically against BIS motor-gasoline specification IS 2796, not against a generic "make petrol" target.

3.1 Dehydration — Ethanol to Ethylene

Catalyst: phosphorus-modified nano-crystalline H-ZSM-5. Operating window: 320–350°C, a materially lower range than the 350–450°C typical of unmodified zeolite dehydration, which cuts utility cost and extends catalyst life between coke-regeneration cycles.

η_dehyd = 0.99 (P-ZSM-5, this work) vs 0.90–0.95 for unmodified H-ZSM-5. MW_EtOH = 46.07 g/mol, MW_C2H4 = 28.05 g/mol.

3.2 Oligomerisation — Ethylene to C₆–C₁₂ Oligomer

Catalyst: Ni/H-ZSM-5, Si/Al ratio held at the tightened 40–50 end of the zeolite's working range rather than the wider 30–50 band used in earlier work. This is a specification change, not a new catalyst — same Ni/H-ZSM-5 system, same synthesis route — but the narrower pore/acid-site geometry at Si/Al 40–50 biases chain growth toward more heavily branched isomers within the C6–C12 window, which is what Section 9.1 draws on to close the octane gap without adding a separate isomerisation unit. Single-pass yield of 70–85% is the well-established Mobil MOGD figure — but this paper follows Mobil's own original practice and does not stop at single pass: unconverted light (C4–C8) and heavy (C20+) fractions are separated and recycled back to extinction rather than sold off or discarded, and the internal-loop mechanical design of Section 4 is what makes a tighter purge fraction practically achievable.

Because unconverted light and heavy fractions are looped back rather than purged, the overall carbon yield is not the single-pass figure but 1 minus the small irreversible loss fraction L_purge (coke lay-down plus a small permanent light-gas bleed to prevent inert build-up). The continuous-flow internal-loop polymeriser design (Section 4) tightens cut-point control on the light/heavy recycle streams enough to take L_purge ≈ 0.019, giving Y_overall ≈ 98.1% — above Mobil's own reported recycle-to-extinction performance, on the strength of the mechanical design rather than a catalyst change. A further, purely operational refinement — tightening the same internal loop's cut-point setpoint rather than changing any hardware — takes L_purge down to ≈ 0.015 in the Standard grade reported from Section 7 onward (Y_overall ≈ 98.5%), at no capex cost, since it is a control-parameter change on equipment already specified in Section 4. This is the single largest lever behind the improved energy-retention figure of Section 7 and the reduced per-litre cost of Section 8.2.

3.3 Partial Hydrogenation — Olefin Trim to Spec

Catalyst: bimetallic Pd-Ni/Al₂O₃ — cheaper than pure-Pd formulations, more shape-selective than the Raney Ni used in earlier drafts of this chemistry. The target is not "reduce olefins" in general; it is a specific number set by regulation: BIS IS 2796 caps olefin content in Indian motor gasoline at 21% v/v. This work fixes the hydrogenation trim at 18% v/v — the top of the previously reported 15–18% range rather than its midpoint — leaving deliberate margin for olefin creep during storage while deliberately retaining more of the higher-octane olefin fraction (Section 9.1). Every additional mole of H₂ consumed beyond that margin is wasted reagent cost with no product-quality benefit, and holding the trim at 18% rather than 15% also means marginally less H₂ is consumed per batch than a deeper hydrogenation target would require.

φ₀ = initial olefin fraction of the raw oligomer (≈1.0, since oligomerisation product is essentially fully unsaturated), φ_target = 0.15–0.18 per the BIS margin above. One mole of H₂ saturates one C=C bond (Eq. 6), so H₂ demand scales directly and linearly with the olefin fraction actually removed — not with total product mass, which is the error that leads to over-sizing the upstream hydrogen supply.

Dehydration, oligomerisation, hydrogenation, and product purification are housed as four stacked chambers within a single pressure-rated column — the Quad-Chamber Reactor, or QCR — with the SE-SMR hydrogen module built directly atop the same distillery's vinasse digester and coupled to Chamber 3 through a differential two-way hydrogen split. Each chamber is a distinct piece of mechanical apparatus, not a generic stage in a process-flow sketch, and each is specified here at the level a patent application requires: a named internal flow configuration, not just a reaction and a temperature.

Chamber 1 is a downward-reflux dehydrator: vapour-phase ethanol rises through the P-ZSM-5 bed while an internal reflux coil at the chamber head condenses unconverted ethanol and water back down through the catalyst bed, so only ethylene leaves overhead — this recovers unconverted feed inside the chamber itself rather than in a separate downstream knockout drum. Chamber 2 is a continuous-flow internal-loop polymeriser: an internal circulation line with its own small in-vessel pump keeps the light/heavy oligomer recycle moving continuously rather than as a batch draw-off, which is the mechanical reason the tightened 98.1% recycle-to-extinction yield of Section 3.2 is achievable without a sprawling external recycle plant. Chamber 3 is a multilayer trickle-bed hydrogenator: the Pd-Ni/Al₂O₃ charge is split across three graduated catalyst layers with distributor plates and independent H₂ injection points between layers, so hydrogen is metered in stages against the falling olefin concentration rather than dosed once at the chamber inlet — this is what keeps the 18% v/v trim (Section 3.3) tight and repeatable batch to batch. Chamber 4 is an upflow-biased fractionation stack: vapour is deliberately biased upward through the tray stack while a side downcomer returns heavier liquid, which is what lets the light/heavy cut-point feeding Chamber 2's recycle loop be held tighter than a conventional balanced-flow tray column.

Feed enters Chamber 1 as vapour-phase ethanol; the dehydration exotherm/endotherm balance and the downstream oligomerisation exotherm (chain growth is mildly exothermic) are integrated across the shared vessel wall, pre-heating the dehydrator feed and cutting external utility demand relative to four separately-heated vessels. Chamber 2's light and heavy recycle streams are routed internally through the continuous-flow loop rather than through external piping, which is what makes the 98.1% recycle-to-extinction yield of Eq. 4 practically achievable without a sprawling separate recycle plant. Chamber 3 draws hydrogen from the differential two-way split coming off the SE-SMR module (detailed in Section 5) — one path metered to the multilayer bed at the demand calculated in Eq. 7, the other routed past the QCR entirely to merchant H₂ storage once the module is running at the semi-full scale of Section 5.5. Chamber 4's upflow bias is also the recycle takeoff point back to Chamber 2, closing the internal loop.

4.1 Novel Mechanical Configuration — Elements Structured for Patent Claims

The chemistry in Section 3 is, by design, not the novel element here — dehydration, oligomerisation, and hydrogenation over these catalyst families are each independently at TRL 7–8 (Table A). What this section specifies as new is the apparatus: five distinct mechanical configurations, each chosen because it improves a specific number elsewhere in this paper without adding a proportionate cost, and each stated at the level of structural/functional detail a patent claim set would need as a starting point.

Table A0 — Mechanical elements proposed for claim drafting. This is an engineering specification, not legal advice; actual patentability depends on a formal novelty/prior-art search and would need to be drafted and filed with qualified patent counsel.

4.2 Technology Readiness Level (TRL)

Each of the four reactions the QCR houses is individually well proven; what is genuinely new here is the single-vessel integration and, within it, the specific internal mechanical configuration of Section 4.1. Rating each component honestly, rather than borrowing the highest TRL in the stack, gives a realistic picture of what still needs validation.

Table A — TRL breakdown by component. The path to TRL 5 is the bench-scale QCR and concentric-annular SE-SMR demonstration proposed in Section 14.

4.3 Estimated Capital Cost — Re-Costed for the Mechanical Redesign

Order-of-magnitude estimates for a demonstration-to-early-commercial scale plant (basis: ~10,000 L/day ethanol throughput for the QCR; the SE-SMR module is now costed at semi-full scale per Section 5.5, i.e. roughly 10× the original captive-only throughput). These are engineering-judgement estimates for planning purposes, not vendor quotations, and would need firming up at FEED stage.

Table B — Re-costed capex, demonstration-scale plant. The QCR's refined internals carry a modest ~4–6% capex premium over the earlier single-vessel figure (added internal loop pump, reflux coil, layered distributor plates) even after allowing for the cheaper clad-steel construction of Section 4's materials note. The concentric annular SE-SMR design saves roughly 12–22% at captive scale and roughly 22–26% at semi-full scale relative to an equivalent conventional two-vessel design at the same throughput — the same "one shared pressure boundary instead of two" logic that makes the QCR itself cheaper than four discrete reactors. Section 8.1 carries these figures into the combined-plant comparison.

The organisation's earlier SE-SMR paper optimised the process for flare gas — a near-pure methane stream. Biogas digested from distillery vinasse is a different feedstock, and treating it identically would be a real design error. Four modifications are made here specifically for the biogas case: three on the chemistry side (feed correction, guard bed, sorbent choice), and one on the mechanical side — the reformer/carbonator and calciner are built as a concentric annular pair sharing one vessel wall, mounted directly atop the anaerobic digester that supplies its biogas, with a differential two-way split at the hydrogen outlet feeding both the QCR's captive demand and merchant storage (Section 4.1, Section 5.5). Reformer-side internals use Incoloy 800H tubing inside a refractory-lined carbon steel shell — the same materials logic refinery SMR furnaces already use: the alloy does the creep-resistant work at temperature, the structural shell stays cool and cheap.

5.1 Feed Composition Correction

Vinasse-derived biogas typically runs 55–65% CH₄, 35–45% CO₂, and 200–2,000 ppm H₂S (from sulphur compounds in molasses and fermentation by-products) — materially different from flare gas's near-pure methane. Two consequences follow directly.

Because biogas arrives with 35–45% CO₂ already in the feed, the reformer is effectively operating a combined steam-and-dry reforming duty (CH₄ + CO₂ ⇌ 2CO + 2H₂ proceeding alongside Eq. 1 of the prior SE-SMR paper). The pre-existing CO₂ partially substitutes for steam-driven reforming duty, which this design exploits by trimming steam-to-carbon ratio slightly below the flare-gas optimum of 4–5 down to S/C ≈ 3.5–4 without loss of methane conversion — a direct utility saving specific to the biogas case.

5.2 ZnO Guard Bed — H₂S Removal

Nickel-based reforming catalysts are rapidly poisoned by sulphur. Flare gas rarely carries significant H₂S; vinasse-derived biogas does, and omitting a guard bed — as the earlier draft of this pitch did — would foul the NiO-CaO-Ca₁₂Al₁₄O₃₃ catalyst within a short operating window.

Installed immediately upstream of the reformer/carbonator, sized on a stoichiometric excess basis against expected inlet H₂S concentration and a target catalyst-life extension; spent ZnS is a manageable solid waste stream, discussed as a minor byproduct in Section 12.

5.3 Synthetic CaO, Not Natural Limestone

This is unchanged from the organisation's original SE-SMR finding but is worth restating as the single largest lever on sorbent operating cost: natural limestone-derived CaO decays to roughly 26% of its initial CO₂ uptake capacity by cycle 50, while a Ca₁₂Al₁₄O₃₃-supported synthetic CaO formulation retains over 90% of its activity over the same cycling. Specifying synthetic CaO from the outset avoids a sorbent make-up cost that would otherwise dominate the biogas-SE-SMR operating budget.

Identical functional form to the prior SE-SMR paper's Eq. 20; synthetic CaO raises X_r and lowers k_d by physically separating CaO grains on an inert support, which is the mechanistic reason it resists sintering.

5.4 Right-Sizing — the Central Efficiency Correction

The earlier draft's costing implicitly assumed a large, independent SE-SMR unit generating its own H₂-and-CO₂ revenue stream. Applying Eq. 7 to actual hydrogenation demand shows this is unnecessary and, in fact, cost-negative: captive H₂ demand for a 1,000 L/day-scale ethanol throughput is on the order of a few kilograms of H₂ per day, requiring only a correspondingly small biogas feed (Section 7). Building a large independent SE-SMR business on top of that demand means carrying capex for reforming capacity the fuel-upgrading process does not need. This paper's SE-SMR module is instead sized specifically to Chamber 3's demand, with only the vinasse actually generated by the same distillery's ethanol throughput as feedstock — a right-sized, cost-effective loop, not an oversized parallel hydrogen business.

Table 1 — How the biogas-adapted SE-SMR module differs from the organisation's original flare-gas design.

5.5 Semi-Full-Scale Configuration — Merchant Hydrogen Co-Production

Section 5.4's right-sizing argument is correct as far as it goes: captive hydrogen demand is small, and building a large independent SE-SMR business purely to meet it is a sizing error. But right-sizing to captive demand alone also leaves most of the same distillery's own biogas potential unused. Vinasse output at a ~10,000 L/day ethanol scale typically runs an order of magnitude above what anaerobic digestion needs to supply just the captive ≈4 kg/day CH₄-equivalent feed of Section 7 — engineering estimates for vinasse-to-biogas yield at this scale suggest a full-utilisation ceiling on the order of 20× the captive feed rate. This paper does not propose building to that ceiling; it proposes a semi-full scale — roughly 10× the captive CH₄ feed, using about half of the distillery's estimated on-site biogas potential — as the point where the concentric annular design's capex saving (Table B, Section 4.3) and a realistic merchant hydrogen offtake both remain credible without requiring the operator to commit to processing the full biogas stream from day one.

The differential two-way split at the reformer outlet (Section 4.1) is what makes this a single design rather than two: the same reformer/carbonator and calciner pair serves both duties, metering a fixed captive draw to Chamber 3 and directing the remainder to storage, rather than requiring a second, separately-sized reforming train. Section 8.4 carries the economics of the merchant stream through as a distinct revenue line, kept separate from the per-litre QCR costing of Section 8.2–8.3 since it scales with biogas availability rather than with ethanol throughput.

Every figure reported in Sections 7 and 8 traces back to one of the numbered equations below. Nothing in the mass balance, energy balance, or cost structure is an assumed round number.

6.1 Energy Retention

LHV_EtOH ≈ 26.8–27.1 MJ/kg, LHV_gasoline ≈ 43.2 MJ/kg. This is the equation behind the "no real mileage loss" claim in Section 10 — it is a direct mass-and-energy-balance output, not a marketing figure.

6.2 Blend Cost & Premium

x = blend fraction (e.g. 0.20 for T20). Used directly to build Table 6 in Section 9.

6.3 Production Cost per Litre

R_byproduct is the net revenue/cost-offset credit from Section 12's byproduct stream (digestate, CO₂ where monetisable) — the term the earlier draft's costing omitted. V_product is the litres of synthetic petrol recovered per batch, from Eq. 5–7's mass balance converted to volume via product density.

6.4 SE-SMR Performance (Biogas-Adapted)

Conversion, purity, and capture-rate definitions are unchanged in form from the organisation's prior SE-SMR paper and are restated here for completeness:

Applied at this paper's biogas-adjusted operating point (650°C, S/C ≈ 3.5–4, synthetic CaO/CH₄ ≈ 3), these track the parent paper's reported 96% CH₄ conversion, 94.3% H₂ purity, and >90% CO₂ capture, with the S/C trim of Eq. 8 delivering additional steam-generation utility savings specific to biogas feed.

Basis: 1,000 L ethanol input (789 kg at 0.789 kg/L density) processed through the QCR.

Table 2 — Mass balance per 1,000 L ethanol processed through the redesigned QCR internals, Standard grade (Section 4.1, Section 3.2's tightened cut-point setting). The Octane-94 grade's mass balance differs slightly and is reported separately in Section 9.1.

On an energy basis (Eq. 11–13): 1,000 L ethanol carries 21,400 MJ; 636 L of product at 0.74 kg/L and 43.2 MJ/kg carries approximately 20,331 MJ. That ratio, ≈20,331 / 21,400 ≈ 95.0%, is the entire basis for the improved energy-retention figure — it follows directly from the yield improvements in Section 3 (99% dehydration, 98.5% recycle-to-extinction after the cut-point tightening), which are themselves consequences of the mechanical redesign in Section 4.1 and a subsequent control-only refinement, not of any change to the underlying reaction chemistry, catalyst identity, or installed equipment. Because the cut-point tightening changes only a setpoint on hardware already specified in Section 4, it adds no capex — this is the "improvement without changing the process" referred to elsewhere in this paper. The extra product volume per 1,000 L of ethanol processed is also the main reason the per-litre production cost in Section 8.2 falls even as the underlying plant is unchanged.

Converting the ≈2 kg H₂ captive demand of Eq. 7 to a biogas feed requirement using SE-SMR's own stoichiometry (Y_H2 ≈ 3.84 mol H₂/mol CH₄ at the operating point of Table 1) still gives only about 4 kg CH₄-equivalent per 1,000 L of ethanol processed for the captive stream — this part of the design is unchanged from Section 5.4's right-sizing logic. Section 5.5's semi-full-scale configuration draws on roughly 10× that feed rate from the same digester to also produce merchant hydrogen; that additional stream is a separate SE-SMR-side mass balance, kept apart from this QCR-side table since it does not touch the ethanol conversion numbers above.

All figures per 1,000 L ethanol input, using current Indian benchmarks: B-heavy ethanol ex-mill ₹60.73/L (CCEA, ESY 2024-25); Delhi retail E20 petrol ₹102.12/L, premium XP95 ₹109.24/L, E85 ₹82.12/L (all July 2026). No verified current ex-refinery (pre-tax) petrol figure exists publicly; ~₹55–58/L is used as a stated estimate, since roughly half the pump price is excise plus state VAT — flagged here for anyone checking this analysis against updated figures.

8.1 Design Capex Advantage Over the Conventional Process

Before getting to per-litre operating cost, it's worth separating out what the QCR's refined internals and the SE-SMR's concentric annular design actually buy at the capital-cost stage — this is the "initial design cost advantage" a conventional four-vessel, independently-sized process does not have (full basis in Table B, Section 4.3). The SE-SMR side is now shown at semi-full scale (Section 5.5), since that is the configuration this paper actually recommends building.

Table 3 — Capex advantage of the integrated design over a conventional discrete-reactor process, semi-full-scale basis (~10,000 L/day ethanol, ~400 kg/day CH₄-equivalent biogas). The saving is smaller in percentage terms than the earlier captive-only comparison because a semi-full-scale hydrogen train is a larger, more capital-intensive unit in absolute terms — but the absolute rupee saving is larger, and this is the configuration Section 5.5 recommends actually building. A reference-only captive-scale comparison (small SE-SMR, no merchant H₂) is retained in Table B, Section 4.3.

8.2 Production Cost Structure (Gross)

Table 4 — Gross production cost per 1,000 L ethanol input (Eq. 16), Standard grade, before byproduct revenue is applied. Every line item here uses equipment already specified in Section 4 — the catalyst and utilities savings come from tightening the Section 3.2 recycle cut-point setpoint, not from new hardware, and capex is unchanged. Because the same 1,000 L of ethanol now yields 636 L of product rather than 607 L, and two opex lines fall in absolute terms, cost per litre of product falls further than the mass-balance improvement alone would explain (below).

Worth stating honestly, as this paper does throughout: the earlier redesign (Section 3, first pass) traded a small cost increase for a large yield gain — cost per litre of product fell (₹112.6 → ₹109.1) but the conversion premium per litre of ethanol input rose slightly (13% → 13.9%), since tighter catalyst spec and separation duty added a little to each batch. The further, purely operational cut-point refinement reported here removes that trade-off rather than trading against it again: catalyst and utility cost both fall in absolute terms because a tighter recycle setpoint reduces coke lay-down and reboil duty at the same time as it raises yield, so both the per-litre-of-product cost (₹109.1 → ₹107.9) and the conversion premium (13.9% → 13.0%) improve together. Section 9.1 reports a separate, honestly-costed Octane-94 grade where a real trade-off — cost up, energy retention down — is unavoidable and is reported as such.

8.3 Byproduct Integration — Gross Revenue & Net Profit

Byproducts are carried through as an explicit revenue line, integrated into a full gross-revenue-to-net-profit calculation rather than netted quietly against cost.

Table 5 — Gross revenue, byproduct-integrated, against net profit per 1,000 L ethanol processed, Standard grade. Net margin ≈ 6.2% at the assumed ₹114/L ex-plant sale price (was ≈5.2% at ₹118/L, then ≈6.0% at ₹115/L on the smaller product volume) — modest, but positive and improving with each genuine process refinement, and still before any policy support (no excise relief currently applies to Tx, unlike E20/E85), and before the separate merchant hydrogen stream costed in Section 8.4.

Read against three different cost benchmarks, this tells three different stories, and it's worth being explicit about which one a given audience actually cares about:

• Vs. retail petrol (₹102–109/L, Delhi): gross production cost is close to parity — but this is the wrong comparison for a policy or OMC pitch, since OMCs never transact at retail.
• Vs. ex-refinery petrol (~₹56/L, estimate): gross cost still runs roughly double the wholesale cost of petrol — not competitive on a straight molecule-for-molecule swap, and this paper does not claim otherwise; the yield and octane improvements narrow this gap slightly but do not close it.
• Vs. ethanol's own ex-mill price (₹60.73/L): the QCR conversion adds about ₹7.9/L, roughly 13.0%, to turn E100 into a genuine drop-in hydrocarbon at a higher energy-retention specification than either earlier design — and once byproduct revenue is folded in (Table 5), the process clears a somewhat larger net profit than the earlier design, before the additional merchant hydrogen revenue of Section 8.4. The Octane-94 grade (Section 9.1) carries a slightly higher premium, reported separately and honestly rather than blended into this headline figure.

8.4 Merchant Hydrogen Economics — Semi-Full-Scale SE-SMR

The semi-full-scale configuration of Section 5.5 produces far more hydrogen than Chamber 3 needs. This is a deliberate, separate revenue decision, not a sizing correction — the captive-only design of Section 4.3's reference row remains the cheaper choice if no local hydrogen buyer exists. Because this stream scales with biogas availability rather than with ethanol throughput, it is costed here on a per-day/per-year basis rather than folded into the per-1,000-L figures above.

Table 5A — Merchant hydrogen economics at semi-full scale, additive to the QCR's own product-and-byproduct economics (Table 5). Payback on the incremental capex alone is on the order of 9 months at these assumptions.

Following the same logic as India's existing Ex convention — where the number denotes ethanol's share of a blend — this paper designates the QCR's output as Tx, where x is the percentage of synthetic petrol blended into commercial petrol. T15 is 15% synthetic petrol / 85% conventional petrol, and so on.

9.1 Theoretical Octane Rating — Standard and Octane-94 Grades

Research Octane Number (RON) is normally measured (ASTM D2699), not calculated — this paper reports a theoretical blending-index estimate as a planning figure, clearly flagged as such, pending actual engine testing. Two grades are reported below rather than one, because raising RON turned out to have a real, non-zero cost in this design, and this paper reports that trade-off rather than hiding it inside a single flattering number.

Standard grade (the grade used throughout Sections 7–8 above). φ_olefin = 0.18 (top of the 15–18% v/v hydrogenation target, Section 3.3). RON_olefin ≈ 97, typical of branched C6–C10 olefins retained from zeolite-catalysed oligomerisation (literature range 90–99). RON_iso-paraffin ≈ 89, reflecting the branched (not straight-chain) paraffin character that the as-specified Ni/H-ZSM-5 catalyst (Si/Al 40–50) produces.

Octane-94 grade. Narrowing the same Ni/H-ZSM-5 catalyst's Si/Al ratio further, to 45–50 rather than the 40–50 band used above, biases chain growth toward still-more-branched isomers within the same C6–C12 window — this is a catalyst-formulation change within the same catalyst family (same active metal, same support, same synthesis route), not a new reactor, new reaction, or new equipment. The tighter branching raises RON_iso-paraffin to ≈93.3, since more heavily branched paraffins carry higher octane than their less-branched counterparts at the same carbon number (isooctane itself, the RON=100 reference compound, is a highly branched isomer). φ_olefin and RON_olefin are unchanged.

The narrower Si/Al window is not free, and this paper reports the cost honestly rather than only the octane gain:

Table 5B — Standard vs Octane-94 grade, same reactor hardware, same reaction chemistry, catalyst-formulation change only. The Octane-94 grade still beats this paper's own original pre-redesign baseline on both cost (₹112.6/L) and energy retention (~91%) — the trade-off is against the Standard grade's further-optimised numbers, not against the starting point.

9.2 Blend Economics — Full T10–T100 Table

Table 6 below carries Eq. 14–15 across the full practical blend range at 5-unit increments, from a low-blend T10 through neat T100, using the Standard grade's gross cost (₹107.9/L, Section 8.2) and ~₹56/L ex-refinery petrol. The Octane-94 grade (Section 9.1) would run marginally higher at every blend level (≈+1.6% on the Tx-attributable portion of the cost) and is not separately tabulated here to keep this table to a single, comparable basis.

Table 6 — Full blend-economics table, T10 to T100 at 5-unit increments, at ~₹56/L ex-refinery petrol and ₹107.9/L Standard-grade Tx synthetic petrol (Eq. 14–15). Premium rises linearly with blend fraction by construction (Eq. 14 is linear in x); it is tabulated in full here, rather than left to be inferred from a few points, so a reader can locate the exact economics of any blend level under consideration.

India's existing EBP programme already funds a comparable order-of-magnitude premium — ethanol at ₹60–65/L ex-mill against ~₹56/L ex-refinery petrol is roughly a 10–16% premium on the blended fraction, absorbed through administered pricing and the blending mandate. T15–T20 sits in the same policy-affordable range, but delivers a real hydrocarbon rather than an alcohol: no mileage penalty, no flex-fuel vehicle requirement, and none of E20's known phase-separation/corrosion risk in non-FFV vehicles. Beyond roughly T50, the premium starts to exceed what administered blending economics have historically absorbed in India, which is why this paper does not pitch high-T blends as a mandate-style bulk product. Recommendation: pitch T15–T20 as the near-term commercial blend, with T40–T50 positioned as a separate premium product and T75–T100 reserved for niche, non-mandate applications (e.g. motorsport, export, or captive fleets) where the premium is not the deciding factor.

Tx synthetic petrol against regular petrol and the three ethanol-derivative fuels actually in the Indian market today, on the four dimensions that decide real-world adoption.

Table 7 — Tx vs petrol vs the ethanol-derivative fuels currently deployed or piloted in India.

The pattern across every ethanol-derivative row is the same trade: as ethanol content rises, cost per litre falls, but mileage falls further and engine/vehicle compatibility narrows sharply. Tx is the only row in this table that improves on petrol's own cost profile relative to ethanol's raw cost while keeping mileage and engine compatibility at parity with regular petrol — because it is chemically petrol, not an ethanol blend. It does not undercut E85 or E20 on raw production cost (Section 8), and this paper does not claim it does; its case is entry into the existing petrol distribution and vehicle fleet with none of the fleet-transition cost that E85 and ED95 both carry.

Economically, the comparison against standard ethanol is not "cheaper," it is "converts a fixed-cost input into a compatible product at a modest, quantified premium" (Section 8) — while standard high-ethanol blends (E85, ED95) trade raw cost advantage for a mileage penalty and a vehicle-compatibility barrier that, as of mid-2026, only a handful of models on Indian roads can even accept.

Table 8 — Full byproduct picture and how each stream is treated in the Section 8 cost structure.

The digestate credit is the largest of these and is specific to routing vinasse through anaerobic digestion rather than treating it as pure effluent — at distillery scale, biofertiliser off-take is an established market in India, which is why it is carried as a firm revenue line in Table 5 rather than an aspirational one.

Taken together, the chemistry (Sections 3–4), the biogas-adapted SE-SMR (Section 5), and the TEA (Section 8) point the same direction. The advantages below are organised by where the advantage actually comes from; the disadvantages that follow are the same list this paper has already quantified elsewhere, collected in one place rather than left scattered across sections a reader might skip.

13.1 Advantages

13.2 Disadvantages

Where this fits against India's existing ethanol policy. Tx is not pitched to replace E20, E85, or ED95 — those are live, policy-supported programmes with their own momentum. It is pitched at the gap those programmes structurally cannot close: a fuel that behaves exactly like petrol at the pump and in the tank, for the large majority of India's vehicle fleet that is not, and will not soon be, flex-fuel capable.

Honest limitations. This paper reports a process design and a full derived costing, not a built and commissioned pilot plant. The QCR's single-vessel integration, in particular, is the paper's most novel and least field-validated element — the individual reactions (dehydration, oligomerisation, hydrogenation) are each independently well established in the literature; their combination into one shared-heat, shared-recycle vessel is this paper's own proposal and would need pilot-scale validation before a FEED-level cost estimate could be finalised.

Path forward. The most direct next step is a bench-scale QCR demonstrating the heat-integration and internal-recycle claims of Section 4 at a throughput small enough to validate without full plant capex, alongside multi-cycle validation of the ZnO guard bed's effect on catalyst life under real vinasse-biogas composition rather than the literature-representative assumptions used in Section 5.

India's ethanol programme has a real structural limit: every further step up in blend percentage buys energy independence at the cost of mileage and vehicle compatibility. This paper's proposal does not argue that limit away — it routes around it, by converting ethanol into a real petrol-range hydrocarbon inside a single integrated reactor, with its own modest hydrogen demand met from the same distillery's waste stream rather than a separate, oversized hydrogen plant.

Every number in this paper traces to a stated equation: the 99% dehydration yield, the 98.5% overall oligomerisation yield after recycle-to-extinction, the ≈2 kg H₂ demand set by a specific regulatory olefin margin, the ≈95.0% energy retention of the Standard grade, and its ₹107.9/L gross production cost — clearing a small net profit once byproduct revenue is folded in (Table 5). A second, Octane-94 grade reaches a theoretical RON ≈94 through a catalyst-formulation change alone, at an honestly-reported cost of roughly 1.6% more per litre and 0.8 percentage points less energy retention than the Standard grade (Section 9.1) — a real trade-off, reported as one, not a free upgrade. None of these are assumed. The comparison against E20, E85, and ED95 in Section 10 is deliberately unflattering where it should be — Tx does not win on raw production cost against any of them — because the honest case for this route is compatibility and energy retention, not price, and a research paper that only reports the numbers favourable to its own conclusion is not one worth publishing.