Juan Conesa | University of Alicante / Universidad de Alicante (original) (raw)

Papers by Juan Conesa

The constant increase in the production of electronic devices implies the need for an appropriate... more The constant increase in the production of electronic devices implies the need for an appropriate management of a growing number of waste electrical and electronic equipment. Thermal treatments represent an interesting alternative to recycle this kind of waste, but particular attention has to be paid to the potential emissions of toxic by-products. In this study, the emissions from thermal degradation of printed circuit boards (with and without metals) have been studied using a laboratory scale reactor, under oxidizing and inert atmosphere at 600 and 850 °C. Apart from carbon oxides, HBr was the main decomposition product, followed by high amounts of methane, ethylene, propylene, phenol and benzene. The maximum formation of PAHs was found in pyrolysis at 850 °C, naphthalene being the most abundant. High levels of 2-, 4-, 2,4-, 2,6- and 2,4,6-bromophenols were found, especially at 600 °C. Emissions of PCDD/Fs and dioxin-like PCBs were quite low and much lower than that of PBDD/Fs, due to the higher bromine content of the samples. Combustion at 600 °C was the run with the highest PBDD/F formation: the total content of eleven 2,3,7,8-substituted congeners (tetra- through heptaBDD/Fs) was 7240 and 3250 ng WHO2005-TEQ/kg sample, corresponding to the sample with and without metals, respectively.

A study of the thermal degradation of TBBPA has been carried out in the present work to assess th... more A study of the thermal degradation of TBBPA has been carried out in the present work to assess the emission of pollutants under different operating conditions. The analysis, identification and quantification of gases, semivolatiles (bromophenols, polycyclic aromatic hydrocarbons and others) and polybrominated dibenzo-p- dioxins and dibenzofurans (PBDD/Fs) have been done. A special effort has been made to identify brominated compounds in the combustion gases.

On the basis of laboratory experiments with model mixtures (active carbon+CuBr2 at different load... more On the basis of laboratory experiments with model mixtures (active carbon+CuBr2 at different loads), this work studies the formation of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) by de novo synthesis. For the different samples, the temperature of the maximum carbon oxidation rate was determined by thermogravimetric analysis, and a kinetic model was proposed for the degradation of the materials in an oxidizing atmosphere (synthetic air). The effect of the addition of different amounts of CuBr2 was studied, finding that its presence accelerates the degradation of the carbonaceous structure in the presence of oxygen. The thermal degradation of the samples in air is satisfactorily described by a first-order single-reaction model. In addition, combustion runs of one of the mixtures (consisting of activated carbon+50 wt % CuBr2, pyrolyzed at 700 °C) were performed in a quartz horizontal laboratory furnace. The analysis of the emissions and the solid residue proved the formation of brominated dioxins and furans at 300, 400, and 500 °C, with a maximum yield at 300 °C (91.7 ng/g of total PBDD/Fs) and a higher bromination degree with increasing temperature.

Journal of Analytical and Applied Pyrolysis, 2014

The present work has two dimensions: analytical and environmental. On the one hand we proved that... more The present work has two dimensions: analytical and environmental. On the one hand we proved that thermogravimetric analysis can be used to perform fast characterization of oil refinery sludge. To this end, thermogravimetric curves were deconvoluted by using autocatalytic kinetics to take into account acceleratory phases in a thermal degradation performed in oxygen-containing atmosphere or at high heating rates. Based on thermogravimetric results, oil refinery sludge was modeled in terms of various fractions (pseudo-components) which degrade as major oil cuts. On the other hand, as an alternative to landfill, we have seen that Soxhlet extraction allows recovery almost half of the weight of sludge as a mixture of hydrocarbons, similar to gas-oil, which burns without residue. This ensures both, waste inerting and significant reduction in sludge volume.

Fuel, 2010

Compost from vegetable residues is usually used as an organic amendment to soil; however, their t... more Compost from vegetable residues is usually used as an organic amendment to soil; however, their thermal degradation characteristics show that it could be used as raw material in air gasification facilities. According to the obtained data, hydrogen production ...

J Anal Appl Pyrol, 2004

The pyrolysis and combustion of solid residues from olive oil processing were studied by dynamic ... more The pyrolysis and combustion of solid residues from olive oil processing were studied by dynamic TG–DTG at heating rates between 5 and 20 °C min−1 at atmospheric pressure. Two different atmospheres were used: on the one hand, an inert atmosphere (He) in order to study the pyrolysis of the material, and on the other hand an oxidative atmosphere (He:O2 in different ratios) to study its combustion. Pyrolysis follows a two parallel and independent fractions model, with kinetic parameters typical of holocelulose (12%) and lignin (48%). Combustion adds a third reaction to the model, which is cocurrent, due to the combustion does not start until the main devolatilization is finished, attaining kinetic parameters and reaction orders typical of a gasification reaction.

We develop a model for analyzing the sovereign debt crises of 2010–2012 in the Eurozone. The gove... more We develop a model for analyzing the sovereign debt crises of 2010–2012 in the Eurozone. The government sets its expenditure-debt policy optimally. The need to sell large quantities of bonds every period leaves the government vulnerable to self-fulfilling crises in which investors, anticipating a crisis, are unwilling to buy the bonds, thereby provoking the crisis. In this situation, the optimal policy of the government is to reduce its debt to a level where crises are not possible. If, however, the economy is in a recession where there is a positive probability of recovery in fiscal revenues, the government may optimally choose to “gamble for redemption,” running deficits and increasing its debt, thereby increasing its vulnerability to crises.

_________________________________________________________________ In 1975 hours worked per adult ... more _________________________________________________________________ In 1975 hours worked per adult were higher in Spain than in the US, one decade later they were 40 percent smaller. This paper quantitatively assesses the impact of the evolution of TFP and taxes on the evolution of aggregate hours worked in Spain. Solow decomposition shows that the sharp decrease in hours worked per adult is responsible for the negative comovement of TFP and output per adult. We show that as much as 80 percent of the decrease in hours worked can be accounted for by the evolution of taxation in an otherwise standard neoclassical growth model. Finally, we provide a comparison with the experience of France over the same period and show that the model fits well the French experience over the same time period.

Two years after the rescue package for Greece provided by the European Union and the Internationa... more Two years after the rescue package for Greece provided by the European Union and the International Monetary Fund in May 2010, sovereign debt crises continue to threaten a growing number of countries in the eurozone. We develop a theory for analyzing these crises based on the research of Cole and Kehoe (1996, 2000) and Conesa and Kehoe (2012). In this theory, the need to frequently sell large quantities of bonds leaves a country vulnerable to sovereign debt crisis. This vulnerability provides a strong incentive to the country’s government to run surpluses to pay down its debt to a level where a crisis is not possible. ; A deep and prolonged recession, like those currently afflicting many eurozone countries, creates a conflicting incentive, however, to “gamble for redemption”—to bet that the recession will soon end, to sell more bonds in order to smooth government spending, and, if indeed the economy recovers, to reduce debt. Under some circumstances, this policy is the best that a go...

This paper is a primer on the great depressions methodology developed by Cole and Ohanian (1999, ... more This paper is a primer on the great depressions methodology developed by Cole and Ohanian (1999, 2007) and Kehoe and Prescott (2002, 2007). We use growth accounting and simple dynamic general equilibrium models to study the depression that occurred in Finland in the early 1990s. We find that the sharp drop in real GDP over the period 1990-93 was driven

Journal of Environmental Management, 2015

The catalytic hydrodechlorination (HDC) of high concentrations of trichloroethylene (TCE) (4.9 mo... more The catalytic hydrodechlorination (HDC) of high concentrations of trichloroethylene (TCE) (4.9 mol%, 11.6 vol%) was studied over 1%Pd, 1%Rh and 0.5%Pd-0.5%Rh catalysts supported on CeO2 under conditions of room temperature and pressure. For this, a one-phase system of NaOH/2-propanol/methanol/water was designed with molar percentages of 13.2/17.5/36.9/27.6, respectively. In this system, the alcohols delivered the hydrogen required for the reaction through in-situ dehydrogenation reactions. PdRh/CeO2 was the most active catalyst for the degradation of TCE among the evaluated materials, degrading 85% of the trichloroethylene, with alcohol dehydrogenation rates of 89% for 2-propanol and 83% for methanol after 1 h of reaction. Fresh and used catalysts were characterized by Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), and Thermogravimetric analysis (TGA). These results showed important differences of the active phase in each catalyst sample. Rh/CeO2 had particle sizes smaller than 1 nm and the active metal was partially oxidized (Rh(0)/Rh(+δ) ratio of 0.43). This configuration showed to be suitable for alcohols dehydrogenation. On the contrary, Pd/CeO2 showed a Pd completed oxidized and with a mean particle size of 1.7 nm, which seemed to be unfavorable for both, alcohols dehydrogenation and TCE HDC. On PdRh/CeO2, active metals presented a mean particle size of 2.7 nm and more reduced metallic species, with ratios of Rh(0)/Rh(+δ) = 0.67 and Pd(0)/Pd(+δ) = 0.28, which showed to be suitable features for the TCE HDC. On the other hand, TGA results suggested some deposition of NaCl residues over the catalyst surfaces. Thus, the new reaction system using PdRh/CeO2 allowed for the degradation of high concentrations of the chlorinated compound by using in situ hydrogen liquid donors in a reaction at room temperature and pressure.

Transplantation Proceedings, 2005

Recent studies have demonstrated some association between the renin-angiotensin system (RAS) acti... more Recent studies have demonstrated some association between the renin-angiotensin system (RAS) activity and the development and progression of different entities as diabetes mellitus (DM) or chronic allograft nephropathy. To investigate these associations, we studied some gene polymorphisms of RAS in a group of renal transplant recipients. We retrospectively analyzed 42 patients who underwent a primary renal transplantation for 2 years. A subgroup of 23 patients (55%) was diagnosed with postransplant DM in accordance with American Diabetes Association 2001 criteria. We studied two RAS gene polymorphisms: the angiotensin-converting enzyme insertion/deletion (ACE I/D) and angiotensinogen (AGTM235T). Genotyping was performed by DNA purification and amplification with a polymerase chain reaction technique. The distributions of genotypes were ACE DD, ID, II: 33%, 48%, 19%; and AGT TT, MT, MM: 15%, 45%, 40%, respectively. We observed a progressive loss in renal function measured by creatinine clearance (Cockroft) in D-allele carriers (DD+ID) between the first and the second transplantation year: 65.3 +/- 4.3 vs 59.8 +/- 4.6 mL/min (P = 0.02); that was not seen in II patients: 68.8 +/- 4.6 vs 68.4 +/- 4 mL/min (P = 0.87). Fifty percent of D-allele carriers developed DM vs 25% of non-D-allele carriers (P = 0.19). Eighty-three percent of homozygous patients for the AGT-TT allele developed DM vs 35% of non TT patients (P = 0.04). There were no significant differences regarding recipient demographic characteristics, type of donor, number and severity of acute rejections, and immunosuppressant treatment between the groups. In conclusion, ACE D-allele seems to be associated with a poorer kidney graft long-term outcome. ACE D and AGT T alleles may be implicated in glucose metabolism disorders after transplantation.

Transplantation Proceedings, 2007

Since calcineurin inhibitors (CNI) have been introduced, they have become the cornerstone of immu... more Since calcineurin inhibitors (CNI) have been introduced, they have become the cornerstone of immunosuppression for renal transplant patients, but their cardiovascular and neurological toxicities, and primarily their renal toxicity, have brought about an increased effort to find combinations of immunosuppressants that are either CNI-free or that use minimum doses of these drugs. The weight of immunosuppression therefore lies with drugs that have a better toxicity profile. The POP observational transverse study including 213 renal transplant patients was designed to study CNI minimization strategies. The mean time of transplant evolution to the time of reduction was 9.9 +/- 11.8 months. The acute rejection rate to the start of reduction was 9.4%. Almost all the patients were undergoing treatment with CNI + mycophenolate mofetil (MMF) + steroids in the immediate posttransplantation period. When reduction was chosen, all patients were undergoing treatment with MMF (mean dose at the start of reduction = 1490.7 +/- 478.0 mg/d). Among the cohort, 66.7% of patients were being treated with tacrolimus (mean C0 levels 13.3 +/- 6.6 ng/mL) and 33.3% with cyclosporine (mean C0 levels 192.2 +/- 94.0 ng/mL; mean C2 levels 1097.5 +/- 457.6). The main reasons for withdrawal were nephrotoxicity (55.9% of the cases), as well as prevention of adverse effects (21.6%). The mean target CNI dose reduction was 41.4% +/- 21.45% in the tacrolimus group and 28.6 +/- 10.0% in the cyclosporine group. In conclusion, CNI toxicity, primarily renal toxicity, makes reduction of these drugs based on the use of full MMF doses an alternative to manage renal transplant patients.

Thermochimica Acta, 1995

The kinetics of the thermal decomposition of cellulose in nitrogen were studied using dynamic TG ... more The kinetics of the thermal decomposition of cellulose in nitrogen were studied using dynamic TG at heating rates between 5 and 50 K min-]. The most widely used models found in the literature which are usually applied in isothermal conditions were tested. Important differences were found between models that take into account the formation of an activated cellulose and those that assume the direct decomposition of cellulose to char, tar and gases. The best agreement between experimental and calculated values was found with models which consider the formation of activated cellulose and take into account the different behaviour at low and high temperatures.

The Journal of Physical Chemistry A, 2008

The effect of sodium hydroxide on the-liquid phase hydrodechlorination (LPHDC) of polychlorinated... more The effect of sodium hydroxide on the-liquid phase hydrodechlorination (LPHDC) of polychlorinated dibenzo- p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) over 2% Pd/gamma-Al 2O 3 was evaluated. Reactions were carried out using 2-propanol both as a hydrogen donor and as a solvent. Fresh and used catalyst samples were characterized by BET, hydrogen chemisorption, TEM/EDS, XPS, and TPR. When the reaction mixture contained no NaOH, active-phase leaching and Pd-C formation were observed even after 10 min of reaction. Therefore, sodium hydroxide appears to be required to maintain surface metal clusters on the support and avoid binding of carbon species to the active metal. On the other hand, excess NaOH in the reaction mixture led to deposition of organic and inorganic solid residues on the catalyst surface, blocking the active sites. Under the conditions of this study, the addition of 30 mg of NaOH maintained the basicity of the system and diminished deposition of solid residues on the catalyst samples, and almost 100% detoxification was reached after a 3 h reaction.

American Economic Review, 2014

ABSTRACT In January 1995, US President Bill Clinton organized a bailout for Mexico that imposed p... more ABSTRACT In January 1995, US President Bill Clinton organized a bailout for Mexico that imposed penalty interest rates and induced the Mexican government to reduce its debt, ending the debt crisis. Can the Troika (European Commission, European Central Bank, and International Monetary Fund) organize similar bailouts for the troubled countries in the eurozone? Our analysis suggests that debt levels are so high that bailouts with penalty interest rates could induce the eurozone governments to default rather than reduce their debt. A resumption of economic growth is one of the few ways that the eurozone crises can end.