Energy Balance Closure and Thermophysical Property Uncertainty in Spent NiMo and NiMoV Catalyst Recovery: Heat Effects, Thermal Integration, and Predictive Reliability—A Critical Review

Spent nickel–molybdenum (NiMo) and nickel–molybdenum–vanadium (NiMoV) hydroprocessing catalysts combine valuable metals with oils, coke, sulfides, and complex oxide supports. Their recovery routes integrate thermal pretreatment, oxidative or alkaline roasting, aqueous separation, and product finishing, but energy claims are often incomparable because boundaries, reference states, thermophysical assumptions, and unmeasured heat losses differ. This critical review develops a property-consistent framework for steady-state and transient energy-balance closure, evaluates sensible and latent heat and reaction enthalpy contributions, and connects thermal integration to uncertainty-aware route assessment. The review critically evaluates a predominantly 2020–2026 bibliography supplemented with a directly relevant route model and foundational reconciliation literature; evidence is evaluated by relevance and transferability rather than assumed uniform quality. The proposed framework distinguishes metered utilities, calculated stream enthalpies, reaction heat, and residual losses; specifies minimum reporting data for solids, gases, and aqueous streams; and integrates reconciliation, sensitivity analysis, and uncertainty propagation. The principal conclusion is that credible energy comparisons require closed elemental and phase inventories, consistent enthalpy reference states, and explicit uncertainty intervals before heat recovery or route superiority can be claimed.