The effect of phosphate on the hydrodenitrogenation activity and selectivity of alumina-supported sulfided Mo, Ni, and Ni-Mo catalysts

Al2O3-supported Mo, Ni, Ni---Mo, and Rh catalysts, prepared by sequential aqueous impregnation and in situ sulfidation, were investigated in the hydrodenitrogenation (HDN) of quinoline at 643 K and 3 MPa and in the hydrodesulfurisation (HDS) of thiophene at 673 K and 0.1 MPa. The Ni and Mo catalysts had a very low conversion of quinoline to hydrocarbons which improved only slightly in the presence of phosphate. The Rh catalysts had a high conversion and a high selectivity for propylcyclohexane and showed no deactivation with time. The addition of Ni to MO/Al2O3 and of phosphate to Ni---Mo/Al2O3 and Rh/Al2O3 catalysts increased the HDN conversion significantly. The selectivity for propylbenzene and the apparent HDN activation energy increased with increasing P-loading. Ni increased the thiophene conversion of Mo/Al2O3, but phosphate had almost no influence on the HDS activity of Ni---Mo/Al2O3 and Rh/Al2O3. The effect of phosphate is due to a combination of structural and catalytic factors. Phosphate improves the activity by inducing the formation of the type II Ni---Mo---S structure, but also, especially at high Ni loading, lowers the activity by inducing a decrease in the dispersion of the Ni---Mo---S phases and a segregation of Ni3S2. Phosphate also promotes the S- and N-elimination reactions, but this only has an influence on the overall catalyst activity if the preceding hydrogenation reactions are not rate determining

In situ poisoning of the thiophene hydrodesulfurization activity of carbon-supported transition metal sulfide catalysts by phosphorus

Carbon-supported transition metal sulfide catalysts, prepared by pore volume impregnation of an activated carbon support with aqueous solutions of first, second and third row transition metal salts (Group V-VIII), drying and in situ sulfidation, were tested in thiophene hydrodesulfurization (723 K, 0. 1 MPa). In the poisoning experiments a bed of phosphorus compound-containing carbon was placed upstream of the catalyst bed. Under the sulfiding and reaction conditions the phosphorus compound was volatilized and transported to the catalyst bed where it could affect the catalytic properties of the active metal sulfide phase. This poisoning effect was different for the thiophene conversion to hydrocarbons and butene hydrogenation, and depended on the transition metal sulfide. Group VIII transition metal Sulfides were rather resistant towards the poisoning by the phosphorus compound. Only the hydrodesulfurization activity of the carbon-supported nickel catalyst was promoted in the presence of phosphorus. This beneficial effect of phosphorus on nickel might atso explain the gain in activity for the commercial Al2O3-supported Ni-Mo-P catalysts

Understanding the Influence of Ethnicity and Socioeconomic Factors on Graft and Patient Survival After Kidney Transplantation

Background Studies on the influence of socioeconomic factors and ethnicity on the results of kidney transplantation have led to various outcomes. In this study, we analyzed the influence of a combination of these factors on graft and patient survival in a population of kidney transplant recipients. Methods This retrospective study included all 1,338 patients who received a kidney transplant between 2000 and 2011 (825 living, 513 deceased donor transplantations). Both clinical and socioeconomic variables were studied. Clinical variables were recipient age, gender, ethnicity, original disease, maximum and current panel reactive antibodies, ABO blood type, retransplants, pretreatment, time on dialysis, comorbidity, transplant year, total number of HLA mismatches, donor type (living or deceased), age and gender, and calcineurin inhibitor treatment. Each recipient's postal code was linked to a postal code area information database to extract information on housing value, income, percentage non-Europeans in the area, and urbanization level. Results In multivariable analysis, graft survival censored for death was significantly influenced by recipient age, maximum panel reactive antibodies, HLA mismatches, donor type, donor age, and calcineurin inhibitor treatment. Patient survival was significantly influenced by recipient age, comorbidity, transplant year, and donor type. Socioeconomic factors and ethnicity did not have a significant influence on graft and patient survival. Conclusions Though ethnicity and socioeconomic factors do not influence survival after kidney transplantation, the favorable influence of living donor type is of paramount importance. As non-Europeans and patients with unfavorable socioeconomic variables less often receive a living donor kidney transplant, their survival may be unfavorable after all

A High Comorbidity Score Should Not be a Contraindication for Kidney Transplantation

Background. Currently, potential kidney transplant patients more often suffer from comorbidities. The Charlson Comorbidity Index (CCI) was developed in 1987 and is the most used comorbidity score. We questioned to what extent number and severity of comorbidities interfere with graft and patient survival. Besides, we wondered whether the CCI was best to study the influence of comorbidity in kidney transplant patients. Methods. In our center, 1728 transplants were performed between 2000 and 2013. There were 0.8% cases with missing values. Nine pretransplant comorbidity covariates were defined: cardiovascular disease, cerebrovascular accident, peripheral vascular disease, diabetes mellitus, liver disease, lung disease, malignancy, other organ transplantation, and human immunodeficiency virus positivity. The CCI used was unadjusted for recipient age. The Rotterdam Comorbidity in Kidney Transplantation score was developed, and its influence was compared to the CCI. Kaplan-Meier analysis and multivariable Cox proportional hazards analysis, corrected for variables with a known significant influence, were performed. Results. We noted 325 graft failures and 215 deaths. The only comorbidity covariate that significantly influenced graft failure censored for death was peripheral vascular disease. Patient death was significantly influenced by cardiovascular disease, other organ transplantation, and the total comorbidity scores. Model fit was best with the Rotterdam Comorbidity in Kidney Transplantation score compared to separate comorbidity covariates and the CCI. In the population with the highest comorbidity score, 50% survived more than 10 years. Conclusions. Despite the negative influence of comorbidity, patient survival after transplantation is remarkably good. This means that even patients with extensive comorbidity should be considered for transplantation

Transplantation Results of Completely HLA-Mismatched Living and Completely HLA-Matched Deceased-Donor Kidneys Are Comparable

Background Human leukocyte antigen (HLA) mismatches are known to influence graft survival in deceased-donor kidney transplantation. We studied the effect of HLA mismatches in a population of recipients of deceased-donor or living-donor kidney transplantations. Methods All 1998 transplantations performed in our center between 1990 and 2011 were included in this retrospective cohort study. Four different multivariable Cox proportional hazard analyses were performed with HLA mismatches as continuous variable, as categorical variable (total number of HLA mismatches), as binary variable (zero vs. nonzero HLA mismatches), and HLA-A, -B, and -DR mismatches included separately. Results Nine hundred ninety-one patients received a deceased-donor kidney and 1007 received a living-donor kidney. In multivariable Cox analysis, HLA mismatches, recipient age, current panel-reactive antibodies, transplant year, donor age, calcineurin inhibitor treatment, and donor type were found to have a significant and independent influence on the risk of graft failure, censored for death. Variables representing the total number of HLA-A, -B, and -DR mismatches had a significant and comparable influence in all analyses. Conclusions The influence of HLA mismatches on death-censored graft survival holds true for both deceased- and living-donor kidney transplantation. However, the relative risk of death-censored graft failure of a 2-2-2 mismatched living-donor kidney is comparable with that of a 0-0-0 mismatched deceased-donor kidney