RESUMO
Herein, the hydrothermal stability of amorphous silica-alumina (ASA) is investigated under conditions relevant for the catalytic conversion of biomass, namely in liquid water at 200 °C. The hydrothermal stability of ASA is much higher than that of pure silica or alumina. Interestingly, the synthetic procedure used plays a major role in its resultant stability: ASA prepared by cogelation (CG) lost its microporous structure, owing to hydrolysis of the siloxane bonds, but the resulting mesoporous material still had a considerable surface area. ASA prepared by deposition precipitation (DP) contained a silicon-rich core and an aluminum-rich shell. In hot liquid water, the latter structure was transformed into a layer of amorphous boehmite, which protected the particle from further hydrolysis. The surface area showed relatively minor changes during the transformation. Independent of the synthetic method used, the ASAs retained a considerable concentration of acid sites. The concentration of acid sites qualitatively followed the changes in surface area, but the changes were less pronounced. The performance of different ASAs for the hydrolysis of cellobiose into glucose is compared.
Assuntos
Óxido de Alumínio/química , Dióxido de Silício/química , Catálise , Celobiose/química , Glucose/química , Temperatura Alta , Hidrólise , Porosidade , Propriedades de Superfície , Água/químicaRESUMO
OBJECTIVE: The study aimed to assess psychiatric morbidity in stable chronic respiratory disorders and to examine the pattern of psychiatric illness in specific respiratory disorders in Northern India. METHODS: All consecutive patients with stable chronic respiratory illnesses who attended the respiratory disease clinic were recruited in the study. Their healthy attendants were interviewed as a control group. The research clinician, trained in the use of the Global Mental Health Assessment Tool, Primary Care Version (GMHAT/PC), interviewed all the participants. The respiratory consultant made the respiratory illness diagnosis. The data were analyzed comparing the patient and the control group by using relative risk and adjusted odds ratios. RESULTS: Of 391 patients with respiratory illness, 44.8% had a mental illness identified by GMHAT/PC interview compared with 24.3% of 177 attendants (controls). Anxiety (20.6%), depression (13.2%) and obsessive compulsive disorders (4.6%) were the most frequently identified mental disorders in the respiratory disease group. Chronic obstructive pulmonary disease and bronchial asthma when combined with rhinitis had a significantly higher prevalence of comorbid mental illness than those illnesses alone. CONCLUSION: Patients with chronic respiratory illness have high mental health comorbidity. Physicians and practitioners can be trained to identify mental illness using computer-assisted tools such as GMHAT/PC (which is easy to use by clinicians and well accepted by patients). A holistic approach of providing care to such patients may improve their overall outcome and quality of life.