Estimation of activation energies during hydrodesulfurization of middle distillates

Hydrodesulfurization (HDS) of different petroleum distillates was carried out in a batch reactor using commercial CoMo catalyst and reaction conditions similar to industrial practice. Various experiments (agitation, particle size and amount of catalyst tests) were conducted with different hydrocarbon feeds to assure the operation under kinetic regime. Reaction orders and activation energies for each feed were determined by two approaches (linear and non-linear regressions). Both kinetic parameters (n and E_A) were found to follow a direct relationship with sulfur content in the feed. Reaction orders ranged between 1.96 and 3.36 and activation energies from 21.49 to 41.96 kcal/mol, which were within the range of those reported in the literature. High values of reaction order were attributed to contributions of HDS reaction of each individual compound exhibiting very different reaction rate constants.     

Monetary Policy Under Time-Varying Uncertainty Aversion

In this paper we develop a framework to analyze the optimal policy of an inflation-targeting monetary authority that is not fully confident about its model and the degree of mistrust changes over time as the structure of the economy changes. These changes can include structural breaks as well as price, output or real exchange shocks. We use robust control to denote the degree of uncertainty aversion of the policy maker and a Markov chain to capture the time-varying nature of the uncertainty aversion. We find that in general a more aggressive interest rate policy is the optimal response to: (i) more uncertainty aversion and (ii) higher likelihood that the uncertainty aversion may appear in the future. Moreover, we find that the policy maker’s welfare decreases when there is an increase in uncertainty aversion. However, the transition probabilities in the Markov-chain have ambiguous effects on the policy maker expected losses.     

The role of kinetics and hydrocarbon distribution in the multiplicities of a two-bed catalytic distillation column for deep hydrodesulfurization

The Damköhler number (Da) is used to research the physical mechanisms leading to multiplicities and the effect of the hydrocarbon distribution on a light gasoil (LGO) deep hydrodesulfurization (HDS) two-bed catalytic distillation column. In doing so, three hydrocarbon mixtures are studied: a real LGO fraction, a synthetic gas oil mixture (SGO), and hexadecane (n-C₁₆). The parametric planes, Da(RR) and Da(B), were obtained for the three mixtures as a function of the reflux ratio, RR, and the bottom flow rate, B. The total sulfur regions (C_s) with respect to Da and RR, and Da and B, were also obtained. RR and B were chosen as bifurcation parameters, since they are frequently used for column operation.Results show that this system is controlled kinetically because the operating point and the multiplicity region lay on the kinetically controlled region (Da ? 1). Results also show that the hydrocarbon distribution plays an important role in the occurrence of multiplicities, as well as exhibiting the importance of choosing a realistic gasoil fraction during process design and lab scale experiments.     

Robust Control: A Note on the Response of the Control to Changes in the “Free” Parameter Conditional on the Character of Nature

In this paper an analytical framework similar to a robust control problem was developed for the one-state, one-control variable model to examine the response of the control to changes in the free parameter. However, in contrast to Gonzalez and Rodriguez (2003), the sign multiplying the free parameter in the criterion function of the min–max problem is positive. We find that this set up corresponds to the case where nature is benevolent while the problem posed by Gonzalez and Rodriguez (2003) corresponds to a malevolent nature. We show that for the benevolent case, the solution is a minimum giving way to an ordinary control problem. In addition, the left side of the discontinuity in Gonzalez and Rodriguez (2003) corresponds to the benevolent case.The opinions contained in this note are exclusively of the authors and do not represent either those of the Sociedad Hipotecaria Federal or Bank of Mexico.     

Robust Control: A Note on the Timing of Model Uncertainty

In this note a one-state, one-control variable quadratic linear problem with robust control and discount factor is developed to examine the optimal response of the first-period control to changes in future model uncertainty. A change in future model uncertainty has an effect on the optimal first-period control response going in the same direction as the one caused by an equal size change in current model uncertainty. However, both analytical and numerical results show that such effect is much lower than the one derived from a change in current model uncertainty. Moreover, such effect is even much lower as the change in model uncertainty moves farther away into the future. Finally, the infinite horizon result confirms the reinforcing nature of the effects on the optimal first-period control response of current and future changes in model uncertainty.The author thanks P. Ruben Mercado, David A. Kendrick and an anonymous referee for useful comments on earlier versions of this note. This research work was completed while the author was working at the Centro de Investigación y Docencia Económicas (CIDE) in Mexico City. The content of this note is only responsibility of the author. Any opinions expressed here in no way reflect comments nor suggestions made by the Board of Governors or any other member of the Bank of Mexico.     

Neural network rule extraction for gaining insight into the characteristics of poverty

Neural Computing and Applications - Nearly one in five families in the country was poor in 2012, according to the Philippine Statistics Authority. While this proportion is lower than the...     

Antiphospholipid Antibodies and Lipids in Hematological Malignancies

One of the main groups of lipids is phospholipids, which are mainly involved in forming cell membranes. Neoplastic processes such as cell replication have increased lipid synthesis, making tumor cells dependent on this synthesis to maintain their requirements. Antiphospholipid antibodies attack phospholipids in the cell membranes. Three main types of antiphospholipid antibodies are recognized: anti-β2 glycoprotein I (anti-β2GP-I), anticardiolipin (aCL), and lupus anticoagulant (LA). These types of antibodies have been proven to be present in hematological neoplasms, particularly in LH and NHL. This review on antiphospholipid antibodies in hematological neoplasms describes their clinical relationship as future implications at the prognostic level for survival and even treatment.