Sustainable Hydrogen from Bio-Oil - Catalytic Steam Reforming of Acetic Acid as a Model Oxygenate

Studies were conducted with acetic acid (HAc) as model oxygenate for the design of active and stable catalysts for steam reforming of bio-oil. Pt/ZrO2 catalysts were prepared by wet impregnation technique. The Pt/ZrO2 catalysts showed high activities at initial time on stream, but lost its activity for steam reforming (H2 production) rapidly. During HAc/H2O reaction over Pt/ZrO2, conversion was close to 100% and constant for 3 hr, however, yields of products changed with time. In the beginning (5 min), H2 and CO2 were the main products, CH4 and CO were observed in small quantities. During HAc/H2O reaction over ZrO2 (without Pt), HAc conversion was close to 90%. The conversion of HAc and yields of the products were constant for 3 hr. However, no steam reforming activity (H2 and CO) was observed, and only acetone and CO2 were observed as products. Both Pt/ZrO2 and ZrO2 were very active for HAc conversion. However, H2 and CO, i.e., steam reforming products, were produced only over Pt/ZrO2 and not over ZrO2. ZrO2 showed acetone yields similar to those observed over Pt/ZrO2 after 25 min time on stream. The presence of acetone in the product mixture and formation of deposits on ZrO2 indicated a role for acetone in catalyst deactivation

Catalyst deactivation during steam reforming of acetic acid over Pt/ZrO2.

Steam reforming of acetic acid as a model compound present in bio-oil over Pt/ZrO2 catalysts has been investigated. Pt/ZrO2 yields steam reforming products (i.e., H2, CO, CO2) to the amounts predicted by thermodynamic equilibrium; however, conversion and yields dropped rapidly with time on course. The deactivation was due to blockage of active sites by coke/oligomer formed. This report clarifies cause of the deactivation during steam reforming of acetic acid. It was found that many products can be formed from acetic acid on ZrO2, such as acetone. The experimental results confirmed that aldol condensation of acetone took place on ZrO2 to give larger compounds which can easily become deposits to block active sites for steam reforming. In order to develop durable catalysts for steam reforming of bio-oil, support should be designed to enhance activation of water, minimize dehydration reactions and thus oligomer formation

Nitrides as ammonia synthesis catalysts and as potential nitrogen transfer reagents

In this article, an overview of the application of selected metal nitrides as ammonia synthesis catalysts is presented. The potential development of some systems into nitrogen transfer reagents is also described

Factors associated with problem drinking among women employed in food and recreational facilities in northern Tanzania.

BACKGROUND: There is growing evidence that alcohol consumption is associated with increased risk of HIV infection. To determine factors associated with problem drinking, we analyzed data collected in two prospective cohorts of at-risk female food and recreational facility workers in northern Tanzania. METHODS: We enrolled HIV seronegative women aged 18-44 years and employed in the towns of Geita, Kahama, Moshi, and Shinyanga. At enrolment, women were interviewed to obtain information about alcohol use, using CAGE and AUDIT screening scales, and risk factors for HIV infection. Blood and genital samples were collected for detection of HIV and sexually transmitted infections (STIs). We characterized alcohol use, concordance, and agreement of the scales, and examined the associations between characteristics of participants and problem drinking as defined by both scales using logistic regression. Lastly, we assessed problem drinking as a risk factor for recent sexual behavior and prevalent STIs. RESULTS: Among enrollees, 68% women reported ever drinking alcohol; of these 76% reported drinking alcohol in the past 12 months. The prevalence of problem drinking was 20% using CAGE and 13% using AUDIT. Overall concordance between the scales was 75.0% with a Kappa statistic of 0.58. After adjusting for age, independent factors associated with problem drinking, on both scales, were marital status, occupation, facility type, increasing number of lifetime sexual partners, and transactional sex in the past 12 months. In addition, women who were problem drinkers on either scale were more likely to report having ≥ 1 sexual partner (CAGE: aOR = 1.56, 95% confidence interval, CI: 1.10-2.23; AUDIT: aOR = 2.00, 95% CI: 1.34-3.00) and transactional sex (CAGE: aOR = 1.79, 95% CI: 1.26-2.56; AUDIT: aOR = 1.51, 95% CI: 1.04-2.18), in the past 3 months. CONCLUSION: These findings suggest that interventions to reduce problem drinking in this population may reduce high-risk sexual behaviors and contribute in lowering the risk of HIV infection

Deciphering the Complex Distribution of Human Immunodeficiency Virus Type 1 Subtypes among Different Cohorts in Northern Tanzania.

Increased understanding of the genetic diversity of HIV-1 is challenging but important in the development of an effective vaccine. We aimed to describe the distribution of HIV-1 subtypes in northern Tanzania among women enrolled in studies preparing for HIV-1 prevention trials (hospitality facility-worker cohorts), and among men and women in an open cohort demographic surveillance system (Kisesa cohort). The polymerase encompassing partial reverse transcriptase was sequenced and phylogenetic analysis performed and subtype determined. Questionnaires documented demographic data. We examined factors associated with subtype using multinomial logistic regression, adjusted for study, age, and sex. Among 140 individuals (125 women and 15 men), subtype A1 predominated (54, 39%), followed by C (46, 33%), D (25, 18%) and unique recombinant forms (URFs) (15, 11%). There was weak evidence to suggest different subtype frequencies by study (for example, 18% URFs in the Kisesa cohort versus 5-9% in the hospitality facility-worker cohorts; adjusted relative-risk ratio (aRR) = 2.35 [95% CI 0.59,9.32]; global p = 0.09). Compared to men, women were less likely to have subtype D versus A (aRR = 0.12 [95% CI 0.02,0.76]; global p = 0.05). There was a trend to suggest lower relative risk of subtype D compared to A with older age (aRR = 0.44 [95% CI 0.23,0.85] per 10 years; global p = 0.05). We observed multiple subtypes, confirming the complex genetic diversity of HIV-1 strains circulating in northern Tanzania, and found some differences between cohorts and by age and sex. This has important implications for vaccine design and development, providing opportunity to determine vaccine efficacy in diverse HIV-1 strains